JP7846313B2 - resin composition - Google Patents

Description

This invention relates to a resin composition containing a styrene-based elastomer.

Thermoplastic elastomers have been used in a wide range of applications because they exhibit rubber elasticity while being melt-molded using the same methods as thermoplastic resins. Known thermoplastic elastomers include styrene-based, olefin-based, polyurethane-based, polyester-based, polyamide-based, acrylic-based, and polyvinyl chloride-based types. Of these, styrene-based elastomers, due to their excellent weather resistance and chemical resistance, have been used in sealing materials, as well as modifiers and additives for various materials.

In resin molded articles, it is necessary to achieve a high degree of balance between various properties desired depending on the application, such as mechanical strength, flexibility, wear resistance, and processability. To improve these properties, it is common practice to incorporate fillers into the resin molded articles. In recent years, with increasing awareness of environmental issues, the use of cellulose, a low-density and renewable material, as a filler in resin molded articles has been explored extensively. Among these, cellulose nanofibers are particularly promising as a filler for resin molded articles because they provide excellent reinforcement per unit of material used when combined with various resins.

Patent Document 1 describes a resin composition comprising a polyamide, an elastomer, and cellulose, wherein at least a portion of the elastomer has an acidic functional group, the polyamide and the elastomer are phase-separated, and more than 50% by mass of the cellulose is present in the polyamide phase.
Patent Document 2 describes a resin composition comprising a polyamide, one or more elastomers selected from the group consisting of aromatic vinyl compound-conjugated diene compound block copolymers and derivatives thereof, and cellulose, wherein the polyamide and the elastomer are phase-separated, and more than 50% by mass of the cellulose is present in the polyamide phase.

Japanese Patent Publication No. 2020-029488 Japanese Patent Publication No. 2022-007985

Among resin molded articles, those primarily composed of styrene-based elastomers, for example, are promising because they exhibit good rubber elasticity and excellent weather resistance and chemical resistance. If styrene-based elastomers can be combined with cellulose nanofibers, in addition to the properties inherent in styrene-based elastomers, properties such as good tensile strength, tensile modulus, and tensile elongation at break can also be imparted. However, since styrene-based elastomers are inherently hydrophobic, while cellulose nanofibers are inherently hydrophilic due to the presence of hydroxyl groups, they tend to be difficult to mix with each other. If the mixing of styrene-based elastomers and cellulose nanofibers in a resin composition is poor, the molded article produced from that resin composition will not exhibit the desired physical properties. Furthermore, when external force is applied to the molded article, voids may form between the styrene-based elastomers and cellulose nanofibers, causing the molded article to whiten. On the other hand, if thorough melt-mixing of styrene-based elastomers and cellulose nanofibers is performed to improve mixing, thermal degradation of the cellulose nanofibers (e.g., discoloration) may occur. The technologies described in Patent Documents 1 and 2 involve dispersing cellulose in polyamide while coexisting with a styrene-based elastomer. However, they do not focus on resin molded articles mainly composed of styrene-based elastomers, and therefore do not address the above-mentioned problems related to the combination of styrene-based elastomers and cellulose nanofibers.

One aspect of the present invention aims to solve the above problems and provide a resin composition, a method for producing the same, and a molded article made by molding the resin composition, which can form a resin molded article that exhibits the advantageous properties inherent in styrene-based elastomers (good rubber elasticity, weather resistance, chemical resistance, etc.), while also being excellent in tensile strength, tensile modulus, and/or tensile elongation at break, and further exhibiting fewer undesirable conditions such as whitening and discoloration.

Furthermore, for a resin molded article containing fillers to exhibit desired properties, it is sometimes important that the fillers are well dispersed within the resin. However, since cellulose is generally hydrophilic due to its hydroxyl groups, it has been proposed to use styrene-based elastomers as additives to well disperse cellulose within the polymer.

Styrene elastomers are soft and possess excellent weather resistance and chemical resistance, making molded articles using styrene elastomers as the main polymer component desirable. However, conventionally, there have been limitations on the applications of resin molded articles using styrene elastomers as the main polymer component. Styrene elastomers generally exhibit tackiness (initial adhesion). Therefore, melt molding of styrene elastomers alone is difficult, and styrene elastomer molded articles tend to stick together, resulting in problems with processability and handling. The technology described in Patent Document 2 attempts to simultaneously achieve the conflicting properties of high toughness and low thermal expansion by using the above-mentioned elastomer in a resin composition containing polyamide and cellulose, but it does not provide a molded article using styrene elastomers as the main polymer component.

Therefore, another aspect of the present invention aims to solve the above problems and provide a resin composition and a method for producing the same, which can form a resin molded article that exhibits the excellent properties inherent in styrene-based elastomers (especially good rubber elasticity, weather resistance, chemical resistance, etc.) while also being excellent in processability and handling, as well as a resin molded article obtained by molding the resin composition.

This disclosure includes the following items:
[Item 1]
A resin composition comprising a thermoplastic elastomer and cellulose nanofibers,
The thermoplastic elastomer comprises an acid-modified styrene elastomer and a styrene elastomer.
A resin composition in which the amount of the thermoplastic elastomer is 60% by mass or more in 100% by mass of the resin composition.
[Item 2]
A resin composition comprising a thermoplastic elastomer and cellulose nanofibers,
The number-average aspect ratio, which is the ratio L/D of the number-average fiber length L to the number-average fiber diameter D of the cellulose nanofibers in the resin composition, is 2 or more and 26 or less.
A resin composition in which the amount of the thermoplastic elastomer is 60% by mass or more in 100% by mass of the resin composition.
[Item 3]
A resin composition comprising a thermoplastic elastomer and cellulose nanofibers,
When the cellulose nanofibers were separated from the resin composition using tetrahydrofuran (THF), the weight increase rate of the cellulose nanofibers was 190% to 600%.
A resin composition in which the amount of the thermoplastic elastomer is 60% by mass or more in 100% by mass of the resin composition.
[Item 4]
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
The resin composition according to any one of items 1 to 3, wherein the total amount of the acid-modified styrene elastomer and the styrene elastomer in 100% by mass of the resin composition is 60% by mass or more.
[Item 5]
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
The resin composition according to any one of items 1 to 4, wherein the acid-modified styrene elastomer and the styrene elastomer are compatible.
[Item 6]
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
The resin composition according to any one of items 1 to 5, wherein the amount of the acid-modified styrene elastomer is 0.5 to 50 parts by mass per 100 parts by mass of the styrene elastomer.
[Item 7]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 6, wherein the amount of the styrene-based elastomer is 0.5 to 250 parts by mass per 1 part by mass of the cellulose nanofiber.
[Item 8]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 7, wherein the amount of the acid-modified styrene elastomer is 0.5 to 45 parts by mass per 1 part by mass of the cellulose nanofiber.
[Item 9]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 8, wherein the amount of the acid-modified styrene elastomer is 0.5% to 50% by mass in 100% by mass of the resin composition.
[Item 10]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 9, wherein the amount of the styrene-based elastomer in 100% by mass of the resin composition is 10% by mass to 98.8% by mass.
[Item 11]
A resin composition according to any one of items 1 to 10, comprising 0.1% to 20% by mass of the cellulose nanofibers.
[Item 12]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 11, wherein the acid modification rate of the acid-modified styrene elastomer is 0.2% by mass to 2.5% by mass.
[Item 13]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 12, wherein the styrene-based elastomer is an unmodified product.
[Item 14]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 13, wherein the acid-modified styrene elastomer is an acid-modified product of a styrene elastomer which is an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated thereof.
[Item 15]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 14, wherein the styrene-based elastomer is an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated product thereof.
[Item 16]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 15, wherein the melt mass flow rate of the styrene-based elastomer at 230°C and 2.16 kg is 20 g/10 min or less.
[Item 17]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 16, wherein the styrene unit ratio of the acid-modified styrene elastomer is 10% to 45% by mass.
[Item 18]
The resin composition includes a styrene-based elastomer as the thermoplastic elastomer,
The resin composition according to any one of items 1 to 17, wherein the styrene unit ratio of the styrene-based elastomer is 10% by mass to 45% by mass.
[Item 19]
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
The resin composition according to any one of items 1 to 18, wherein the ratio of the styrene unit ratio of the styrene-based elastomer to the styrene unit ratio of the acid-modified styrene-based elastomer (styrene ratio of the styrene-based elastomer / styrene ratio of the acid-modified styrene-based elastomer) is 0.3 to 2.5.
[Item 20]
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
The resin composition according to any one of items 1 to 19, wherein the number average molecular weight of the acid-modified styrene elastomer is 10,000 to 500,000, and the number average molecular weight of the styrene elastomer is 10,000 to 500,000.
[Item 21]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 20, wherein the ratio of the styrene unit ratio to the acid modification rate (styrene unit ratio / acid modification rate) in the acid-modified styrene elastomer is 5 to 90.
[Item 22]
The resin composition includes an acid-modified styrene-based elastomer as the thermoplastic elastomer.
The resin composition according to any one of items 1 to 21, wherein the amount of acid-modified groups in the acid-modified styrene elastomer is 0.2% to 5.0% by mass, relative to 100% by mass of the cellulose nanofibers.
[Item 23]
The resin composition according to any one of items 1 to 22, wherein the number-average fiber diameter of the cellulose nanofibers is 2 nm to 1000 nm.
[Item 24]
The resin composition according to any one of items 1 to 23, wherein the thermal decomposition initiation temperature of the cellulose nanofiber is 250°C or higher.
[Item 25]
The resin composition according to any one of items 1 to 24, wherein the specific surface area of the cellulose nanofibers is 10 ^m² /g to 200 ^m² /g.
[Item 26]
A resin composition according to any one of items 1 to 25, further comprising a polyoxyethylene unit-containing polymer.
[Item 27]
A resin composition according to any one of items 1 to 26, further comprising a liquid polymer.
[Item 28]
A method for producing a resin composition according to any one of items 1 to 27,
The resin composition includes, as the thermoplastic elastomer, an acid-modified styrene elastomer and a styrene elastomer.
A method comprising heating and kneading a mixture containing the acid-modified styrene-based elastomer, the styrene-based elastomer, and the cellulose nanofiber.
[Item 29]
The method according to item 28, wherein the weight increase rate of the cellulose nanofibers after heating and kneading compared to the cellulose nanofibers before heating and kneading is 190% to 600%.
[Item 30]
A resin molded article obtained by molding a resin composition described in any one of items 1 to 27.
[Item 31]
A resin molded product as described in item 30, which is a deformed extruded product.
[Item 32]
A method for manufacturing a deformed extruded product,
A method comprising the step of extruding a resin composition described in any one of items 1 to 27 into a deformed shape.
[Item 33]
A 3D printing material comprising a resin composition described in any one of items 1 to 27.
[Item 34]
A 3D printing material as described in item 33, having the form of a filament or powder.
[Item 35]
A molded object obtained by 3D printing a resin composition described in any one of items 1 to 27.
[Item 36]
A molded object formed by 3D printing using a 3D printing material as described in item 33 or 34.
[Item 37]
A method for manufacturing a molded object,
A method comprising the step of fabricating a resin composition described in any one of items 1 to 27 using a 3D printer.
[Item 38]
A method for manufacturing a molded object,
A method comprising the step of fabricating a 3D printing material described in item 33 or 34 using a 3D printer.
[Item 39]
A resin composition comprising a styrene-based elastomer and a tack inhibitor containing cellulose nanofibers.

According to one aspect of the present invention, a resin composition and a method for producing the same, as well as a molded article obtained by molding the resin composition, are provided, which can form a resin molded article that exhibits the advantageous properties inherent in styrene-based elastomers (good rubber elasticity, weather resistance, chemical resistance, etc.), while also being excellent in tensile strength, tensile modulus, and/or tensile elongation at break, and further exhibiting fewer undesirable properties such as whitening and discoloration.

According to another aspect of the present invention, a resin composition and a method for producing the same can be provided, which can form a resin molded article that exhibits the excellent properties inherent in styrene-based elastomers (especially good rubber elasticity, weather resistance, chemical resistance, etc.) while also being excellent in processability and handling, as well as a resin molded article obtained by molding the resin composition.

The following describes exemplary embodiments of the present invention (hereinafter also referred to as "these embodiments"), but the present invention is not limited to these embodiments, and various modifications are possible within the scope of its gist.

≪Resin composition≫
One aspect of the present invention provides a resin composition comprising a thermoplastic elastomer and cellulose nanofibers. In one aspect, the amount of thermoplastic elastomer is 60% by mass or more in 100% by mass of the resin composition. In one aspect, the thermoplastic elastomer comprises a styrene-based elastomer, in one aspect, an acid-modified styrene-based elastomer, in one aspect, a styrene-based elastomer and an acid-modified styrene-based elastomer, and in one aspect, a styrene-based elastomer and an acid-modified styrene-based elastomer.
In one embodiment, the number-average aspect ratio, which is the ratio L/D of the number-average fiber length L to the number-average fiber diameter D of cellulose nanofibers in the resin composition, is between 2 and 26.
In one embodiment, the weight increase rate of cellulose nanofibers when cellulose nanofibers are separated from a resin composition using tetrahydrofuran (THF) is 190% to 600%.

One aspect of the present invention provides a resin composition comprising an acid-modified styrene elastomer, a styrene elastomer, and cellulose nanofibers. In the resin composition according to one aspect, the acid-modified styrene elastomer and the styrene elastomer are miscible without phase separation and are in a continuous phase. In one aspect, the total amount of the acid-modified styrene elastomer and the styrene elastomer is 60% by mass or more of 100% by mass of the resin composition. The styrene elastomer portion in the resin composition contributes to the expression of the good properties inherent in the styrene elastomer, while the acid-modified styrene elastomer portion in the resin composition interposes between the styrene elastomer and the cellulose nanofibers due to its good affinity with both, contributing to the reduction of problems caused by their poor affinity (for example, void generation due to delamination between them).

In one embodiment of the resin composition, it was found that the presence of cellulose nanofibers and an acid-modified styrene elastomer can reduce fuzzing during extrusion molding. As a result, the molded article can exhibit good surface smoothness. The reason why cellulose nanofibers and acid-modified styrene elastomers are excellent at reducing fuzzing is not clear, but it is possible that the cellulose nanofibers and acid-modified styrene elastomers bond through a reaction, and this modifies the surface of the styrene elastomer during molding, resulting in a smoothing effect. Furthermore, adding cellulose nanofibers to the styrene elastomer may also be advantageous in reducing shrinkage during molding, as well as improving the tensile strength, tensile modulus, tensile elongation at break, and/or hardness of the molded article. In one embodiment of the resin composition, it was found that the presence of an acid-modified styrene elastomer in addition to cellulose nanofibers can further improve the tensile strength, tensile modulus, tensile elongation at break, and/or hardness of the molded article, and reduce undesirable conditions such as whitening and discoloration of the molded article. Although not bound by theory, it is believed that the reaction between the hydroxyl groups of cellulose nanofibers and the acid-modified groups of the acid-modified styrene elastomer strengthens the interface between them, making it less likely for delamination to occur between the styrene elastomer, cellulose nanofibers, and acid-modified styrene elastomer when external force is applied to the molded body, and also making it less likely for discoloration to occur due to thermal degradation of the cellulose nanofibers. As a result, the property-improving effect of cellulose nanofibers is well exhibited, the generation of voids in the molded body due to delamination is suppressed, whitening is reduced, and discoloration of the cellulose nanofibers is also suppressed. The resin composition according to one embodiment is excellent in processability and handling while using a styrene elastomer that is excellent in rubber elasticity, weather resistance, chemical resistance, etc., and the property-improving effect of cellulose nanofibers is well exhibited, and furthermore, there are fewer disadvantages such as whitening and discoloration, making it suitable as a substitute for thermoplastic polyurethane elastomer (TPU), for example.

One aspect of the present invention also provides a resin composition comprising a styrene elastomer and a tack inhibitor containing cellulose nanofibers. Styrene elastomers inherently possess good rubber elasticity, weather resistance, chemical resistance, etc., but due to their tackiness, they tend to be difficult to mold and the molded articles are difficult to handle. For example, molding materials with tackiness are difficult to separate from the mold during molding, and if strong force is applied to the molded article to remove it from the mold, it deforms and breaks, making it difficult to obtain a good molded article. Furthermore, when storing molded articles such as pellets, bales, injection molded articles, films, sheets, and filaments with tackiness, the contact points between the molded articles block each other, creating a situation where handling is difficult in all processes. In the resin composition according to one aspect, it has been found that the presence of cellulose nanofibers suppresses tackiness, making molding easier and the molded articles easier to handle. The cellulose nanofibers according to one aspect can function as a tack inhibitor either alone or in cooperation with other components in the resin composition. The reason why cellulose nanofibers are excellent at reducing the tack of styrene-based elastomers is not entirely clear, but it is possible that the fine fibrous structure of cellulose nanofibers contributes to their superior physical entanglement with styrene-based elastomers compared to other fillers (e.g., silica particles, glass fibers, carbon fibers, etc.), resulting in a good tack reduction effect. Cellulose nanofibers are also advantageous because they are softer than, for example, silica particles, glass fibers, carbon fibers, etc., and therefore do not impair the rubber elasticity inherent in styrene-based elastomers. Furthermore, adding cellulose nanofibers to styrene-based elastomers may also be advantageous in reducing shrinkage during molding and improving the tensile strength, tensile modulus, tensile elongation at break, and/or hardness of the molded article. The resin composition according to one embodiment is useful as a soft resin molded article because it has suppressed tackiness and excellent processability and handling properties, even while using a styrene-based elastomer, and is suitable as, for example, a substitute for thermoplastic polyurethane elastomer (TPU).

In one embodiment, the resin composition has a tack strength (hereinafter sometimes simply referred to as tack strength) of 10.0 gf/ ^mm² or less at 23°C, a load of 600 gf, a pressurizing time of 60 seconds, and a release speed of 600 mm/min, as measured by a probe tack test. In one embodiment, the above tack strength may be 9.0 gf/ ^mm² or less, or 7.0 gf/ ^mm² or less, or 5.0 gf/ ^{mm² or} less, or 3.0 gf/ ^mm² or less, or 2.0 gf/ ^mm² or less, or 1.5 gf/ ^mm² or less, or 1.0 gf/ ^mm² or less. From the viewpoint of ease of manufacturing the resin composition, in one embodiment, the above tack strength may be 0.001 gf/ ^mm² or more, or 0.01 gf/mm² or more, or 0.1 gf/ ^mm² or more, or 0.3 gf/ ^mm² or more, or 0.5 gf/ ^mm² or more.

The tack strength of the resin composition according to one embodiment is preferably 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 25% or less, 20% or less, 15% or less, or 10% or less, relative to 100% of the tack strength of a resin composition with the same composition except that it does not contain cellulose nanofibers. From the viewpoint of suppressing tack, a smaller ratio is desirable, but from the viewpoint of ease of manufacturing the resin composition, in one embodiment it may be 0.0001% or more, 0.1% or more, 1% or more, or 3% or more.
The tack strength of the resin composition according to one embodiment may also preferably be as exemplified above, relative to 100% of the tack strength of the styrene-based elastomer contained in the resin composition.

The components of the resin composition will be described below. In this embodiment, the amounts of each component described as values in the resin composition components may be considered as the amounts of each component in the resin composition, and the amounts of each component described as values in the resin composition may be considered as the amounts of each component in the resin composition components.

<Cellulose nanofiber>
Cellulose nanofibers are fibers obtained by finely processing cellulose fiber raw materials through methods such as defibration treatment. Natural cellulose and regenerated cellulose can be used as cellulose fiber raw materials. As natural cellulose, wood pulp obtained from wood species (hardwood or softwood), non-wood pulp obtained from non-wood species (cotton, bamboo, hemp, bagasse, kenaf, cotton linter, sisal, straw, etc.), and cellulose fiber aggregates produced by animals (e.g., sea squirts), algae, and microorganisms (e.g., acetic acid bacteria) can be used. As regenerated cellulose, regenerated cellulose fibers (viscose, cupro, Tencel, etc.), cellulose derivative fibers, and ultrafine threads of regenerated cellulose or cellulose derivatives obtained by electrospinning can be used. Cellulose fiber raw materials that give cellulose nanofibers with a fuzzy surface may be advantageous in terms of tack suppression effect. From this viewpoint, cotton linter and the like are preferred cellulose fiber raw materials.

In one embodiment, defibration is a dry or wet mechanical treatment, preferably a wet treatment in which a slurry obtained by dispersing cellulose fiber raw material in a liquid medium is subjected to mechanical treatment. A single apparatus may be used once or more times for defibration, or multiple apparatuses may be used, each once or more times. The apparatus used for defibration is not particularly limited, but examples include high-speed rotary type, colloid mill type, high-pressure type, roll mill type, ultrasonic type, and high-pressure or ultra-high-pressure homogenizers, refiners, beaters, PFI mills, kneaders, dispersers, high-speed defibration machines, grinders (stone mill type pulverizers), ball mills, vibratory mills, bead mills, conical refiners, disc refiners, single-screw, twin-screw or multi-screw kneaders and extruders.

Cellulose fiber raw materials may be subjected to pretreatment before defibration. Pretreatment can be used to adjust fiber diameter, fiber length, degree of fibrillation, etc., as well as adjust the content of components other than cellulose (acid-insoluble components such as lignin, alkali-soluble polysaccharides such as hemicellulose, etc.), molecular weight, degree of crystallinity, etc.

The pretreatment may, in one embodiment, be one or more selected from chemical treatment, pulverization, grinding, and classification. Chemical treatment is a treatment using chemicals, such as pulverization, bleaching, purification, hydrolysis, enzymatic treatment, regeneration celluloseization, and chemical modification. Pulverization is a dry pulverization of the cellulose fiber raw material. Grinding is a wet pulverization of a slurry obtained by dispersing the cellulose fiber raw material in a liquid medium. Classification is a separation operation to standardize the fiber length of the cellulose fiber raw material, and may be dry classification or wet classification.

Examples of the liquid medium include water and/or other media (e.g., organic solvents, inorganic acids, bases, and/or ionic liquids), and may contain one or more types of media.

Commonly used organic solvents include, for example: alcohols (e.g., methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, ethylene glycol, diethylene glycol, glycerin, etc.); ethers (e.g., propylene glycol monomethyl ether, 1,2-dimethoxyethane, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, etc.); carboxylic acids (e.g., formic acid, acetic acid, lactic acid, etc.); esters (e.g., ethyl acetate, vinyl acetate, etc.); ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, etc.); nitrogen-containing solvents (e.g., dimethylformamide, dimethylacetamide, acetonitrile, etc.); and sulfur-containing solvents (dimethyl sulfoxide). In a typical embodiment, the liquid medium in the slurry is substantially water only.

In one embodiment, the number-average fiber length L of the cellulose nanofibers is preferably 100 nm or more, or 500 nm or more, 1 μm or more, or 5 μm or more, or 10 μm or more, or 20 μm or more, from the viewpoint of exhibiting the physical property improvement effect of the cellulose nanofibers well, and preferably 1000 μm or less, or 800 μm or less, or 500 μm or less, or 400 μm or less, or 300 μm or less, or 200 μm or less, from the viewpoint of well dispersing the cellulose nanofibers in the resin composition.

In one embodiment, the number-average fiber diameter D of the cellulose nanofibers is preferably 2 to 1000 nm from the viewpoint of obtaining a good effect of improving physical properties by the cellulose nanofibers. More preferably, the number-average fiber diameter of the cellulose nanofibers is 4 nm or more, or 5 nm or more, or 10 nm or more, or 15 nm or more, or 20 nm or more, and more preferably 900 nm or less, or 800 nm or less, or 700 nm or less, or 600 nm or less, or 500 nm or less, or 400 nm or less, or 300 nm or less, or 200 nm or less.

The average fiber length (L)/fiber diameter (D) ratio of cellulose nanofibers is preferably 30 or more, or 50 or more, or 80 or more, or 100 or more, or 120 or more, or 150 or more, from the viewpoint of effectively improving the mechanical properties of the rubber composite containing cellulose nanofibers with a small amount of cellulose nanofibers. While there is no particular upper limit, from the viewpoint of ease of handling, it is preferably 5000 or less, or 3000 or less, or 2000 or less, or 1000 or less.

In this disclosure, the fiber length, fiber diameter, and L/D ratio of cellulose nanofibers are values measured using a scanning electron microscope (SEM) by the following procedure. An aqueous dispersion of cellulose nanofibers is replaced with tert-butanol and diluted to 0.001 to 0.1% by mass. The dispersion is then dispersed using a high-shear homogenizer (e.g., IKA product, trade name "Ultra-Turrax T18") under the following conditions: rotation speed 15,000 rpm for 3 minutes. The dispersion is cast onto an osmium-deposited silicon substrate and air-dried. This sample is used as the measurement sample and measured using a high-resolution scanning electron microscope (SEM). Specifically, the length (L) and diameter (D) of 100 randomly selected cellulose nanofibers are measured in an observation field adjusted to the magnification so that at least 100 cellulose nanofibers can be observed, and the ratio (L/D) is calculated. The number average values of these are then taken as the number average fiber diameter L and number average fiber diameter D, and the ratio (L/D) is calculated.

The number-average aspect ratio, which is the ratio L/D of the number-average fiber length L to the number-average fiber diameter D of the cellulose nanofibers in the resin composition, is in one embodiment between 2 and 26. The upper limit of this aspect ratio is not particularly limited, but from the viewpoint of handling, it is preferably 25 or less. The lower limit of this aspect ratio is not particularly limited, but is preferably 5 or more, or 10 or more, or 15 or more. The aspect ratio is a value measured by the method described in the [Examples] section of this disclosure.

Known crystalline forms of cellulose include Type I, Type II, Type III, and Type IV. Among these, Type I and Type II are particularly widely used, while Type III and Type IV, although obtained on a laboratory scale, are not widely used on an industrial scale. The cellulose nanofibers of this disclosure have relatively high structural mobility, and by dispersing these cellulose nanofibers in rubber, a molded article with a lower coefficient of thermal expansion and superior strength and elongation during tensile and bending deformation can be obtained. Therefore, cellulose nanofibers containing cellulose Type I crystals or cellulose Type II crystals are preferred, and cellulose nanofibers containing cellulose Type I crystals and having a crystallinity of 55% or higher are more preferred.

The degree of crystallinity of cellulose nanofibers is preferably 55% or higher. The higher the degree of crystallinity, the higher the mechanical properties (strength, dimensional stability) of the cellulose itself. Therefore, when cellulose nanofibers are dispersed in rubber, the rubber composite tends to have higher strength and dimensional stability. A more preferable lower limit for the degree of crystallinity is 60%, even more preferably 70%, and most preferably 80%. There is no particular upper limit to the degree of crystallinity of cellulose nanofibers; higher is preferable, but from a production standpoint, a preferable upper limit is 99%.

The degree of crystallinity referred to here, when the cellulose nanofiber is a type I cellulose crystal (derived from natural cellulose), can be determined by the Segal method using the following formula from the diffraction pattern (2θ/deg. is 10 to 30) obtained by measuring the sample by wide-angle X-ray diffraction.
Crystallinity (%) = [I ₍₂₀₀₎ - I _(amorphous) ] / I ₍₂₀₀₎ × 100
I ₍₂₀₀₎ : Diffraction peak intensity due to the 200 plane (2θ = 22.5°) in a cellulose type I crystal. I _(amorphous) : Halo peak intensity due to amorphous material in a cellulose type I crystal, at a peak angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°).

Furthermore, if the cellulose is a type II cellulose crystal (derived from regenerated cellulose), the degree of crystallinity can be determined by the following formula using wide-angle X-ray diffraction, based on the absolute peak intensity h0 at 2θ = 12.6°, which is attributed to the (110) plane peak of the type II cellulose crystal, and the baseline peak intensity h1 at this interplanar spacing (the line connecting 2θ = 8° and 15°).
Crystallinity (%) = (h0-h1) /h0 ×100

Furthermore, the degree of polymerization of the cellulose nanofiber is preferably 100 or higher, more preferably 150 or higher, more preferably 200 or higher, more preferably 300 or higher, more preferably 400 or higher, more preferably 450 or higher, preferably 3500 or lower, more preferably 3300 or lower, more preferably 3200 or lower, more preferably 3100 or lower, and more preferably 3000 or lower.

From the viewpoint of processability and mechanical property development, it is desirable to keep the degree of polymerization of cellulose nanofibers within the above-mentioned range. From the viewpoint of processability, it is preferable that the degree of polymerization is not too high, and from the viewpoint of mechanical property development, it is desirable that it is not too low.

The degree of polymerization of cellulose nanofibers refers to the average degree of polymerization measured according to the reduction ratio viscosity method using copper ethylenediamine solution, as described in the confirmation test (3) of the "Fifteenth Revised Japanese Pharmacopoeia Commentary (published by Hirokawa Shoten)".

In one embodiment, the weight-average molecular weight (Mw) of the cellulose nanofiber is 100,000 or more, more preferably 200,000 or more. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw/Mn) is 6 or less, preferably 5.6 or less, or 5.4 or less. A larger weight-average molecular weight means fewer end groups in the cellulose molecule. Also, since the ratio of weight-average molecular weight to number-average molecular weight (Mw/Mn) represents the width of the molecular weight distribution, a smaller Mw/Mn means fewer end groups in the cellulose molecule. Since the end groups of the cellulose molecule are the starting points for thermal decomposition, when the weight-average molecular weight of the cellulose nanofiber is large, and at the same time the width of the molecular weight distribution is narrow, particularly heat-resistant cellulose nanofibers and resin compositions containing cellulose nanofibers can be obtained. From the viewpoint of the availability of cellulose raw materials, the weight-average molecular weight (Mw) of the cellulose nanofiber may be, for example, 600,000 or less, or 500,000 or less, or 400,000 or less. The number-average molecular weight (Mn) of cellulose nanofibers may be, for example, 200,000 or less, 150,000 or less, 100,000 or less, 80,000 or less, or 60,000 or less, from the viewpoint of the availability of cellulose fiber raw materials. The ratio of weight-average molecular weight to number-average molecular weight (Mn) (Mw/Mn) may be, for example, 1.5 or more, 1.7 or more, or 2 or more, from the viewpoint of the ease of manufacturing cellulose nanofibers. Mw can be controlled to the above range by selecting a cellulose raw material having an Mw appropriate for the purpose, and by appropriately performing physical and/or chemical treatments on the cellulose raw material within an appropriate range. Mw/Mn can also be controlled to the above range by selecting a cellulose raw material having an Mw/Mn appropriate for the purpose, and by appropriately performing physical and/or chemical treatments on the cellulose raw material within an appropriate range. In one embodiment, each of the Mw and Mw/Mn of the cellulose raw material may be within the above range.

The weight-average molecular weight and number-average molecular weight of cellulose nanofibers referred to here are values obtained by dissolving cellulose nanofibers in N,N-dimethylacetamide to which lithium chloride has been added, and then determining them by gel permeation chromatography using N,N-dimethylacetamide as the solvent.

The alkali-soluble polysaccharides that cellulose nanofibers may contain include not only hemicellulose but also β-cellulose and γ-cellulose. Alkali-soluble polysaccharides are understood by those skilled in the art as components obtained as the alkali-soluble portion of holocellulose obtained by solvent extraction and chlorine treatment of plants (e.g., wood) (i.e., components obtained by removing α-cellulose from holocellulose). Since alkali-soluble polysaccharides are polysaccharides containing hydroxyl groups and have poor heat resistance, they can decompose when heated, cause yellowing during thermal aging, and reduce the strength of cellulose nanofibers. Therefore, it is preferable to have a low alkali-soluble polysaccharide content in cellulose nanofibers.

In one embodiment, the average content of alkali-soluble polysaccharides in cellulose nanofibers is preferably 20% by mass or less, 18% by mass or less, 15% by mass or less, or 12% by mass or less, based on 100% by mass of cellulose nanofibers, from the viewpoint of obtaining good dispersibility of cellulose nanofibers. The above content may be 1% by mass or more, 2% by mass or more, or 3% by mass or more, from the viewpoint of ease of manufacturing cellulose nanofibers.

The average alkali-soluble polysaccharide content can be determined using the method described in non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000), by subtracting the α-cellulose content from the holocellulose content (Wise method). This method is understood in this industry as a method for measuring hemicellulose content. The alkali-soluble polysaccharide content is calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content is taken as the average alkali-soluble polysaccharide content.

In one embodiment, the average content of acid-insoluble components in cellulose nanofibers is preferably 10% by mass or less, 5% by mass or less, or 3% by mass or less, based on 100% by mass of cellulose nanofibers, from the viewpoint of avoiding a decrease in the heat resistance of cellulose nanofibers and the resulting discoloration. The above content may be 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more, from the viewpoint of ease of manufacturing cellulose nanofibers.

The average acid-insoluble component content is determined using the Claesson method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). This method is understood in this industry as a method for measuring lignin content. After stirring the sample in sulfuric acid solution to dissolve cellulose and hemicellulose, etc., the sample is filtered through glass fiber filter paper, and the resulting residue contains the acid-insoluble components. The acid-insoluble component content is calculated from the weight of these acid-insoluble components. The acid-insoluble component content is measured three times for each sample, and the average of these measurements is taken as the average acid-insoluble component content.

[Chemical modification]
Cellulose nanofibers may be chemically modified cellulose nanofibers (also called chemically modified cellulose nanofibers). Examples of chemically modified cellulose nanofibers include inorganic esters such as nitrate esters, sulfate esters, phosphate esters, silicate esters, and borate esters; organic esters such as acetylated and propionylated products; ethers such as methyl ethers, hydroxyethyl ethers, hydroxypropyl ethers, hydroxybutyl ethers, carboxymethyl ethers, and cyanoethyl ethers; and TEMPO oxides obtained by oxidizing the primary hydroxyl groups of cellulose. Chemically modified cellulose nanofibers may contain one or more types of modifying groups.
In a preferred embodiment, the chemical modification is acylation using an esterifying agent, and particularly preferably acetylation. Preferred esterifying agents are acid halides, acid anhydrides, vinyl carboxylates, and carboxylic acids. Among these esterifying reagents, at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, vinyl acetate, vinyl propionate, vinyl butyrate, and acetic acid, with acetic anhydride and vinyl acetate being particularly preferred from the viewpoint of reaction efficiency. The cellulose nanofibers may be chemically modified with a modifying agent, for example, at the stage of cellulose fiber raw material, during or after the defibration process, or they may be chemically modified during or after the preparation of the slurry as a dispersion, or during or after the drying process.

[Degree of acyl substitution (DS)]
When cellulose nanofibers are chemically modified (for example, by hydrophobicization such as acylation), they tend to disperse well in rubber. On the other hand, when combined with a dispersant, for example, cellulose nanofibers can easily exhibit good dispersibility in rubber even if they are unsubstituted or have a low degree of substitution. When the cellulose nanofibers are esterified cellulose nanofibers, the degree of acyl substitution (DS) is preferably 0.1 or higher, or 0.2 or higher, or 0.25 or higher, or 0.3 or higher, or 0.5 or higher, in order to obtain esterified cellulose nanofibers with a high thermal decomposition onset temperature. Furthermore, since an unmodified cellulose skeleton remains in the esterified cellulose nanofibers, the degree of acyl substitution (DS) is preferably 2.0 or lower, or 1.8 or lower, or 1.5 or lower, or 1.2 or lower, or 1.0 or lower, or 0.8 or lower, or 0.7 or lower, or 0.6 or lower, or 0.5 or lower, in order to obtain esterified cellulose nanofibers that combine high tensile strength and dimensional stability derived from cellulose with a high thermal decomposition onset temperature derived from chemical modification.

The degree of acyl substitution (DS) of chemically modified cellulose nanofibers, when the modifying group is an acyl group, can be calculated from the reflectivity infrared absorption spectrum of esterified cellulose nanofibers based on the peak intensity ratio between the peak derived from the acyl group and the peak derived from the cellulose skeleton. The peak of the C=O absorption band based on the acyl group appears at 1730 ^cm⁻¹ , and the peak of the C-O absorption band based on the cellulose skeleton appears at 1030 ^cm⁻¹ . The DS of esterified cellulose nanofibers is calculated by creating a correlation graph between the DS obtained from solid-state NMR measurements of esterified cellulose nanofibers (described later) and the modification rate (IR index 1030), which is defined as the ratio of the peak intensity of the C=O absorption band based on the acyl group to the peak intensity of the C-O absorption band of the cellulose skeleton chain. The calibration curve of substitution DS calculated from the correlation graph is: DS = 4.13 × IR index (1030).
This can be obtained by using [this method].
IR Index (1030) = H1730 / H1030
In the formulas, H1730 and H1030 represent the absorbances at 1730 ^cm⁻¹ and 1030 ^cm⁻¹ (absorption bands for C-O stretching vibrations of the cellulose backbone chain). However, these values represent the absorbances when the baseline is set to 0, with the baseline being defined as the line connecting 1900 ^cm⁻¹ and 1500 ^cm⁻¹ and the line connecting 800 ^cm⁻¹ and 1500 ^cm⁻¹ , respectively.

The method for calculating the DS of esterified cellulose nanofibers by solid-state NMR involves performing ^13C solid-state NMR measurements on freeze-dried esterified cellulose nanofibers. The DS can be calculated using the following formula, which compares the area intensity (Inf) of the signal attributed to a single carbon atom derived from the modifying group with the total area intensity (Inp) of the signal attributed to the _C1 - _C6 carbon atoms derived from the pyranose ring of cellulose appearing in the range of 50 ppm to 110 ppm.
DS=(Inf)×6/(Inp)
For example, if the modifying group is an acetyl group, you can use the 23 ppm signal assigned to _-CH3 .
The conditions used for ^13C solid-state NMR measurement are, for example, as follows:
Equipment: Bruker Biospin Avance500WB
Frequency: 125.77 MHz
Measurement method: DD/MAS method Waiting time: 75 seconds
NMR sample tube: 4 mm diameter
Total number of times: 640 (approximately 14 hours)
MAS: 14,500Hz
Chemical shift standard: Glycine (External standard: 176.03 ppm)

The thermal decomposition onset temperature ( _TD ) of cellulose nanofibers is preferably, in one embodiment, 200°C or higher, or 210°C or higher, or 220°C or higher, or 230°C or higher, or 240°C or higher, or 250°C or higher, or 260°C or higher, or 270°C or higher, or 275°C or higher, or 280°C or higher, or 285°C or higher, from the viewpoint of achieving the heat resistance and mechanical strength desired for automotive applications and the like. A higher thermal decomposition onset temperature is preferable, but from the viewpoint of ease of manufacturing cellulose nanofibers, it may be, for example, 320°C or lower, or 310°C or lower, or 300°C or lower.

[Temperature at 1% weight loss (T _1% ), 250℃ weight loss rate (T _250℃ )]
The temperature at which cellulose nanofibers lose 1 wt% of their weight (T _1% ) is preferably, in one embodiment, 230°C or higher, or 240°C or higher, or 250°C or higher, or 260°C or higher, or 270°C or higher, or 275°C or higher, or 280°C or higher, or 285°C or higher, or 290°C or higher, from the viewpoint of avoiding thermal degradation during melting and kneading and being able to exhibit mechanical strength. A higher T _1% is preferable, but from the viewpoint of ease of manufacturing cellulose nanofibers, it may be, for example, 330°C or lower, or 320°C or lower, or 310°C or lower.

The weight loss rate (T _{250°C) of cellulose nanofibers at 250°C (T 250°C} ) is preferably, in one embodiment, 15% or less, 12% or less, 10% or less, 8% or less, 6% or less, 5% or less, 4% or less, or 3% or less, from the viewpoint of avoiding thermal degradation during melting and kneading and being able to exhibit mechanical strength. A lower T _250°C is preferable, but from the viewpoint of ease of manufacturing cellulose nanofibers, it may be, for example, 0.1% or more, 0.5% or more, 0.7% or more, or 1.0% or more.

In this disclosure, _TD is a value obtained from a graph in thermogravimetric (TG) analysis, where the horizontal axis is temperature and the vertical axis is weight retention percentage. Starting from the weight of cellulose nanofiber at 150°C (a state in which almost all moisture has been removed) (weight loss of 0 wt%), the temperature is further increased to obtain a straight line passing through the temperature at which the weight loss reaches 1 wt% (T _1% ) and the temperature at which the weight loss reaches 2 wt% (T _2% ). _TD is defined as the temperature at the point where this straight line intersects with a horizontal line (baseline) passing through the starting point of 0 wt% weight loss.

The 1% weight loss temperature (T _1% ) is the temperature at which the weight decreases by 1% by weight, starting from the weight at 150°C, when the heating method _TD described above is continued.

The weight loss rate of cellulose nanofibers at 250°C (T _250°C ) is the weight loss rate when cellulose nanofibers are held at 250°C under a nitrogen flow for 2 hours, as determined by TG analysis. A porous sheet of cellulose nanofibers is heated from room temperature to 150°C at a rate of 10°C/min in a nitrogen flow of 100 ml/min, held at 150°C for 1 hour, then heated from 150°C to 250°C at a rate of 10°C/min, and held at 250°C for 2 hours. The weight W0 at the time of reaching 250°C is taken as the starting point, and the weight W1 after being held at 250°C for 2 hours is calculated using the following formula.
Weight change rate at 250°C (%): (W1 - W0) / W0 × 100

[Porous Sheet]
The measurement of various physical properties of cellulose nanofibers (crystallinity, polymorphism, degree of polymerization, Mw, Mn, Mw/Mn, alkali-soluble content, average acid-insoluble content, T/ _D , T _/1% , T _/250°C , etc.) can vary significantly depending on the form of the measurement sample. To ensure stable and reproducible measurements, a distortion-free porous sheet should be used as the measurement sample. The method for preparing the porous sheet is as follows.

First, a concentrated cake of cellulose nanofibers with a solid content of 10% by mass or more is added to tert-butanol, and then dispersed using a mixer or similar device until no aggregates remain. The concentration is adjusted to 0.5% by mass for every 0.5 g of solid weight of cellulose nanofibers. 100 g of the resulting tert-butanol dispersion is filtered on filter paper. Without removing the filtrate from the filter paper, it is sandwiched between two larger sheets of filter paper, and the edges of the larger sheets are pressed down with weights, and dried in a 150°C oven for 5 minutes. After that, the filter paper is peeled off to obtain a porous sheet with minimal distortion. Sheets with an air permeability resistance R of 100 sec/100 ml or less per 10 g/ ^m² of sheet basis are selected as porous sheets and used as measurement samples.

The air permeability resistance R is measured by first measuring the basis weight W (g/ ^m² ) of a porous sheet sample that has been left standing for one day in an environment of 23°C and 50% RH, and then measuring the air permeability resistance R (sec/100ml) using a Wangyan type air permeability resistance tester (for example, Asahi Seiko Co., Ltd., model EG01). At this time, the value per 10 g/ ^m² basis weight is calculated according to the following formula.
Air permeability resistance per 10 g/ ^m² (sec/100 ml) = R/W × 10

[Specific surface area]
The specific surface area of the cellulose nanofibers is preferably 10 m²/g or more, or 15 m²/g or more, or 20 ^m² /g or more, or 30 ^m² /g or more, or 40 ^m² /g or more, or 50 m²/g or more, in terms of the good color tone of the resin composition due to the high degree of fineness of the cellulose nanofibers, and in terms of the good ^{tack reduction} effect on the styrene-based elastomer. From the viewpoint of ease of manufacturing and handling of cellulose nanofibers, it is preferably ^{200 m² /} g or less, or 170 ^m² /g or less, or 160 ^m² /g or less. The specific surface area is measured using a specific surface area and pore distribution analyzer (e.g., Nova-4200e, manufactured by Quantachrome Instruments). Approximately 0.2 g of the sample is dried under vacuum at 120°C for 5 hours. The amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen is then measured at five points (multi-point method) within a relative vapor pressure (P/P0) range of 0.05 to 0.2. The BET specific surface area ( ^m² /g) is then calculated using the analyzer's program.

Alternatively, the specific surface area of the cellulose nanofibers is preferably 10 ^m² /g or more, or 15 m²/g or more, or 20 m²/g or more, or 30 ^m² /g or more, or 40 ^m² /g or more, or 50 ^m² /g or more, in that the transparency of the resin composition is good due to the high degree of fineness of the cellulose nanofibers, and preferably 200 ^m² /g or less, or ^{170 m² /} g or less, or ^{160 m²} /g or less, in that that is, from the viewpoint of ease of manufacture and handling of cellulose nanofibers. The above range is particularly suitable in embodiments in which a tack inhibitor containing cellulose nanofibers is used. Cellulose nanofibers with a relatively large specific surface area may be advantageous in terms of tack inhibitory effect. From this viewpoint, preferred specific surface areas are 10 ^m² /g or more, or 20 ^m² /g or more, or 30 ^m² /g or more.

Various physical properties of cellulose nanofibers contained in resin compositions, etc. (number-average fiber length, number-average fiber diameter, L/D ratio, degree of crystallinity, crystalline polymorphism, degree of polymerization, Mw, Mn, Mw/Mn, alkali-soluble content, average acid-insoluble content, T/ _D , T/ _1% , T/ _250℃ , DS, specific surface area, etc.) are analyzed by the following method.
The polymer components contained in the resin composition are dissolved in an organic or inorganic solvent capable of dissolving them, the cellulose nanofibers are separated, and after thorough washing with the solvent, the solvent is replaced with tert-butanol. Subsequently, the cellulose nanofiber tert-butanol slurry is analyzed using the same measurement method as described above, and various physical properties of the cellulose nanofibers in the resin composition are calculated.

When cellulose nanofibers are separated from a resin composition using THF, the weight increase rate of the cellulose nanofibers is preferably 190% or more, 250% or more, 300% or more, or 350% or more, from the viewpoint of interfacial strength between the resin and the cellulose nanofibers, and preferably 600% or less, 550% or less, or 500% or less, from the viewpoint of suppressing short fiber formation during kneading. The weight increase rate is the value measured by the method described in the [Examples] section of this disclosure.

In one embodiment, cellulose nanofibers may be provided in the form of a slurry containing a liquid medium, or in the form of a dry material such as particles, a film, or a bulk material. Examples of liquid mediums include water and/or organic solvents having a boiling point, and may contain one or more types of media. The slurry form has a liquid medium content of 50% by mass or more, while the dry material has a liquid medium content of less than 50% by mass. The liquid medium content is measured when heated at 180°C using an infrared heating type moisture meter (e.g., A&D Corporation, product name "MX-50"). In embodiments using a tack inhibitor containing cellulose nanofibers, from the viewpoint of obtaining a better tack inhibitory effect, it is preferable that the cellulose nanofibers mixed with the styrene-based elastomer be in the form of a dry material.

The amount of cellulose nanofibers in 100% by mass of the resin composition is preferably 0.1% by mass or more, or 0.3% by mass or more, or 0.4% by mass or more, or 0.5% by mass or more, or 0.7% by mass or more, or 1.0% by mass or more, from the viewpoint of obtaining the advantages of cellulose nanofibers well, and preferably 20% by mass or less, or 15% by mass or less, or 10% by mass or less, from the viewpoint of the impact resistance of the resin composition. In embodiments using a tack inhibitor containing cellulose nanofibers, the amount of cellulose nanofibers that is particularly preferable from the viewpoint of exhibiting a good tack inhibitory effect is 0.5% by mass or more, or 0.7% by mass or more, or 1.0% by mass or more.

<Thermoplastic elastomer>
In one embodiment, the thermoplastic elastomer includes a styrene-based elastomer, in another embodiment, an acid-modified styrene-based elastomer, in another embodiment, a styrene-based elastomer and an acid-modified styrene-based elastomer, and in another embodiment, a styrene-based elastomer and an acid-modified styrene-based elastomer. In this disclosure, in one embodiment, an elastomer is a substance (specifically, a natural or synthetic polymer) that is elastic at room temperature (23°C). In one embodiment, being elastic means that the storage modulus of elasticity measured by dynamic viscoelasticity measurement at 23°C and 10 Hz is 1 MPa or more and 100 MPa or less. Examples of elastomers that the thermoplastic elastomer may include, in addition to styrene-based elastomers and acid-modified styrene-based elastomers, include one or more selected from natural rubber, conjugated diene compound polymers, aromatic compound-conjugated diene copolymers, hydrogenated aromatic compound-conjugated diene copolymers, polyolefins, polyester elastomers, polyurethane elastomers, polyamide elastomers, and elastomers having a core-shell structure. The amount of thermoplastic elastomer in 100% by mass of the resin composition is preferably 10% by mass or more, or 30% by mass or more, or 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, from the viewpoint of including other components in desired amounts, and preferably 99.5% by mass or less, or 99% by mass or less, or 98% by mass or less, or 95% by mass or less, or 90% by mass or less.
The total ratio of styrene-based elastomer and acid-modified elastomer to 100% by mass of thermoplastic elastomer may, in one embodiment, be 1% by mass or more, 5% by mass or more, 10% by mass or more, 20% by mass or more, 50% by mass or more, or 70% by mass or more, and in one embodiment, it may be 100% by mass.

<Styrene-based elastomers and acid-modified styrene-based elastomers>
A resin composition according to one embodiment includes a styrene elastomer. A resin composition according to one embodiment includes a styrene elastomer and an acid-modified styrene elastomer. In one embodiment, the styrene elastomer is a copolymer of a conjugated diene monomer and an aromatic vinyl monomer. Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene, which may be used individually or in combination of two or more. The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with a conjugated diene monomer. Examples include styrene, m or p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, which may be used individually or in combination of two or more. From the viewpoint of moldability of the resin composition and impact resistance of the molded article, styrene is preferred.

Examples of random copolymers include butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. Regarding the compositional distribution of each monomer in the copolymer chain, examples include perfectly random copolymers with a composition close to statistically random, and tapered random copolymers with a gradient in the compositional distribution. The bonding mode of the conjugated diene polymer, i.e., the composition of 1,4-bonds, 1,2-bonds, etc., may be uniform or different between molecules.

A block copolymer may be a copolymer consisting of two or more blocks. For example, a block copolymer may have a structure such as A-B, A-B-A, A-B-A-B, etc., where block A is an aromatic vinyl monomer and block B is a block of conjugated diene monomer and/or a copolymer of aromatic vinyl monomer and conjugated diene monomer. The boundaries of each block do not necessarily need to be clearly distinguishable; for example, if block B is a copolymer of aromatic vinyl monomer and conjugated diene monomer, the aromatic vinyl monomer in block B may be distributed uniformly or in a tapered manner. Furthermore, block B may have multiple portions where the aromatic vinyl monomer is uniformly distributed and/or distributed in a tapered manner. In addition, block B may have multiple segments with different aromatic vinyl monomer content. When multiple blocks A and block B exist in the copolymer, their molecular weights and compositions may be the same or different.

The styrene-based elastomer may be an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated version thereof. The block copolymer may be a mixture of two or more types in which one or more of the following are different: bond type, molecular weight, aromatic vinyl compound species, conjugated diene compound species, 1,2-vinyl content or the total amount of 1,2-vinyl content and 3,4-vinyl content, aromatic vinyl compound component content, hydrogenation rate, etc.

The styrene-based elastomer may be partially hydrogenated or fully hydrogenated. From the viewpoint of suppressing thermal degradation during processing, the hydrogenation rate of the hydrogenated material is preferably 50% or more, 80% or more, or 98% or more, and from the viewpoint of low-temperature toughness, it is preferably 50% or less, 20% or less, or 0% (i.e., unhydrogenated). Examples of hydrogenated conjugated diene polymers include the hydrogenated conjugated diene polymers exemplified above, and may be, for example, hydrogenated styrene-butadiene copolymers.

In one embodiment, the styrene-based elastomer is not acid-modified. In another embodiment, the styrene-based elastomer may be unmodified.

The acid-modified styrene elastomer may be an acid-modified product of the styrene elastomer exemplified above. In this disclosure, an acid-modified styrene elastomer means that an acidic functional group is added to the molecular skeleton of a styrene elastomer via a chemical bond as an acid-modifying group. In this disclosure, an acidic functional group means a functional group that can react with basic functional groups, etc. Specific examples include hydroxyl groups, carboxyl groups, carboxylate groups, sulfo groups, acid anhydride groups, etc.

The acid modification rate, which is the mass ratio of acid-modified groups in 100% by mass of acid-modified styrene-based elastomer, is preferably 0.2% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1% by mass or more, or 1.5% by mass or more, based on 100% by mass of acid-modified styrene-based elastomer, from the viewpoint of void reduction effect due to good affinity with cellulose nanofibers. From the viewpoint of affinity with styrene-based elastomers, it is preferably 2.5% by mass or less, 2.3% by mass or less, or 2% by mass or less. The acid modification rate is obtained by measuring a calibration curve created using the characteristic absorption band of the acid, after measuring a calibration curve sample that has been pre-mixed with an acidic substance using an infrared absorption spectrum analyzer.

In one preferred embodiment, the acid-modified styrene elastomer is an acid-modified styrene elastomer that is an aromatic vinyl compound-conjugated diene compound copolymer (preferably an aromatic vinyl compound-conjugated diene compound block copolymer) or a hydrogenated thereof. Examples of such acid-modified styrene elastomers include elastomers that are modified products obtained by grafting an α,β-unsaturated dicarboxylic acid or its derivative onto an aromatic compound-conjugated diene copolymer (preferably a block copolymer) or its hydrogenated counterpart in the presence or absence of a peroxide. Specific examples of α,β-unsaturated dicarboxylic acids and their derivatives include maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride, with maleic anhydride being particularly preferred among these. In a preferred embodiment, the acid-modified styrene elastomer is a styrene elastomer modified with an acid anhydride.

From the viewpoint of dispersibility of cellulose nanofibers or compatibility with acid-modified styrene-based elastomers, the styrene-butadiene block copolymer, styrene-ethylene-butadiene block copolymer, styrene-ethylene-butylene block copolymer, styrene-butadiene-butylene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-propylene block copolymer, styrene-isobutylene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-ethylene-butadiene block copolymer, hydrogenated styrene-butadiene-butylene block copolymer, hydrogenated styrene-isoprene block copolymer, and styrene homopolymer (polystyrene) is preferred to be at least one selected from the group consisting of styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer, and polystyrene. From the viewpoint of compatibility with styrene-based elastomers, it is more preferred to be one or more acid-modified products as exemplified above.

The styrene unit ratio of the acid-modified styrene elastomer and the unit ratio of the styrene elastomer are preferably 10% by mass or more, 19% by mass or more, or 29% by mass or more, from the viewpoint of affinity between the acid-modified styrene elastomer and the styrene elastomer, and from the viewpoint of good expression of the advantageous properties inherent in the styrene elastomer, respectively. From the viewpoint of hardness, they are preferably 45% by mass or less, 40% by mass or less, or 35% by mass or less. The styrene unit ratio is a value that can be determined by the following method. Specifically, a predetermined amount of elastomer is dissolved in chloroform and measured using an ultraviolet spectrophotometer (for example, Shimadzu Corporation, UV-2450), and the content of aromatic vinyl monomer units (styrene) is calculated using a calibration curve from the peak intensity of the absorption wavelength (262 nm) caused by the aromatic vinyl compound component (styrene).

The styrene unit ratio of the acid-modified styrene elastomer and the unit ratio of the styrene elastomer are preferably 10 mol% or more, 15 mol% or more, or 20 mol% or more, from the viewpoint of affinity between the acid-modified styrene elastomer and the styrene elastomer, and from the viewpoint of good expression of the advantageous properties inherent in the styrene elastomer, respectively. From the viewpoint of flexibility of the composition, they are preferably 40 mol% or less, 35 mol% or less, 30 mol% or less, or 25 mol% or less. These unit ratios are suitable in embodiments where a tack inhibitor containing cellulose nanofibers is used.
The styrene unit ratio is a value determined by the NMR method.

The ratio of the styrene unit ratio of the styrene-based elastomer to the styrene unit ratio of the acid-modified styrene-based elastomer (styrene ratio of styrene-based elastomer / styrene ratio of acid-modified styrene-based elastomer) is preferably 0.3 or higher, or 0.6 or higher, or 0.9 or higher, from the viewpoint of affinity between the acid-modified styrene-based elastomer and the styrene-based elastomer, and similarly, preferably 2.5 or lower, or 2 or lower, or 1.5 or lower.

In acid-modified styrene elastomers, the ratio of styrene units to the acid modification rate (styrene unit ratio / acid modification rate) is preferably 5 or more, 10 or more, or 20 or more from the viewpoint of affinity with styrene elastomers, and preferably 90 or less, 85 or less, or 80 or less from the viewpoint of affinity with cellulose nanofibers.

With respect to styrene-based elastomers and acid-modified styrene-based elastomers, the amount of vinyl bonds in the conjugated diene bond units in the conjugated diene polymer (e.g., 1,2- or 3,4- bonds of butadiene) is preferably 5 mol% or more, or 10 mol% or more, or 13 mol% or more, or 15 mol% or more, and preferably 80 mol% or less, or 75 mol% or less, or 65 mol% or less, or 50 mol% or less, or 40 mol% or less.
The amount of vinyl bonds in conjugated diene bond units (e.g., the amount of 1,2-bonds in butadiene) can be determined by ^13C -NMR (quantitative mode). Specifically, by integrating the peak areas that appear in ^13C -NMR, a value proportional to the carbon content of each structural unit can be obtained, and as a result, it can be converted to the mass percentage of each structural unit.
Styrene 145-147 ppm
Vinyl 110-116 ppm
Diene (cis) 24-28 ppm
Diene (trans) 29-33 ppm

In a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (hereinafter also referred to as the aromatic vinyl bond amount) may preferably be 5.0% by mass or more and 70% by mass or 10% by mass or more and 50% by mass or less, based on the total mass of the styrene-based elastomer. The aromatic vinyl bond amount can be determined by the ultraviolet absorbance of the phenyl group, and the conjugated diene bond amount can also be determined based on this.

The number-average molecular weight (Mn) of the acid-modified styrene elastomer is preferably 10,000 or more, or 30,000 or more, or 50,000 or more, from the viewpoint of affinity with styrene elastomers, and preferably 500,000 or less, or 250,000 or less, or 200,000 or less, from the viewpoint of affinity with cellulose nanofibers.

The number-average molecular weight (Mn) of the styrene-based elastomer is preferably 10,000 to 500,000, or 40,000 to 250,000, from the viewpoint of achieving both impact strength and fluidity.

In one embodiment, the total amount of acid-modified styrene elastomer and styrene elastomer in 100% by mass of the resin composition is 60% by mass or more, or 65% by mass or more, or 70% by mass or more, or 75% by mass or more. Such a resin composition can exhibit good rubber elasticity, weather resistance, chemical resistance, etc. From the viewpoint of including a desired amount of other components, particularly cellulose nanofibers, the above total amount is 90% by mass or less, or 85% by mass or less, or 80% by mass or less, in one embodiment.

The amount of acid-modified styrene elastomer per 100 parts by mass of styrene elastomer is preferably 0.5 parts by mass or more, or 1 part by mass or more, or 5 parts by mass or more, from the viewpoint of improving the surface smoothness of the molded article and the resistance to whitening during tensile stress (suppression of void formation) of the molded article. From the viewpoint of suppressing discoloration, shrinkage during molding, and/or reduction in hardness caused by a large amount of acid-modified styrene elastomer, it is preferably 50 parts by mass or less, or 40 parts by mass or less, or 30 parts by mass or less.

The amount of acid-modified styrene elastomer per 1 part by mass of cellulose nanofiber is preferably 0.5 parts by mass or more, or 1 part by mass or more, or 5 parts by mass or more, from the viewpoint of improving the surface smoothness of the molded article and the resistance to whitening during tension of the molded article (suppression of void generation), and preferably 45 parts by mass or less, or 40 parts by mass or less, or 35 parts by mass or less, or 30 parts by mass or less, from the viewpoint of suppressing discoloration, shrinkage during molding, and/or decrease in hardness caused by a large amount of acid-modified styrene elastomer. In the resin composition according to one embodiment, the number of acid-modified groups of the acid-modified styrene elastomer can not be excessive compared to the number of hydroxyl groups on the surface portion of the cellulose nanofiber (specifically, the portion that gives surface area in the specific surface area measurement of cellulose nanofiber). The number of hydroxyl groups on the surface portion of the cellulose nanofiber in the resin composition can be calculated from the amount of cellulose nanofiber in the resin composition, the fiber diameter, and the specific surface area. For example, when using an acid-modified substance for the purpose of chemically modifying cellulose nanofibers, an excess amount of the acid-modified substance may be added to the cellulose nanofibers. However, in this embodiment, it may be advantageous to keep the amount of acid-modified styrene elastomer present in the resin composition to the minimum necessary while maintaining the desired affinity with the cellulose nanofibers. From this viewpoint, it is preferable that the amount of acid-modified styrene elastomer be adjusted so as not to be excessive relative to the number of hydroxyl groups in the cellulose nanofibers, and the upper limit amount exemplified above is suitable from this viewpoint.

The amount of acid-modified groups in the acid-modified styrene elastomer relative to 100% by mass of cellulose nanofiber is preferably 0.2% by mass or more, or 0.5% by mass or more, or 0.8% by mass or more, or 1.0% by mass or more, or 1.2% by mass or more, or 1.5% by mass or more, based on 100% by mass of the acid-modified styrene elastomer, from the viewpoint of affinity with cellulose nanofiber. From the viewpoint of suppressing discoloration, shrinkage during molding, and/or hardness reduction caused by the acid-modified styrene elastomer, it is preferably 5.0% by mass or less, or 3.0% by mass or less, or 2.5% by mass or less, or 2.0% by mass or less.

The amount of acid-modified styrene elastomer in 100% by mass of the resin composition is preferably 0.5% by mass or more, or 1% by mass or more, or 5% by mass or more, from the viewpoint of improving the surface smoothness of the molded article and the resistance to whitening during tensile stress (suppression of void formation) of the molded article. From the viewpoint of suppressing discoloration, shrinkage during molding, and/or reduction in hardness caused by a large amount of acid-modified styrene elastomer, it is preferably 50% by mass or less, or 40% by mass or less, or 30% by mass or less. Note that acid-modified styrene elastomer is generally relatively expensive, so reducing the amount used is advantageous from a cost perspective.

In one embodiment, the behavior of the stress-strain curve (e.g., yield behavior) in a tensile test of the resin composition may be controlled according to the desired application of the resin composition by selecting the type and/or amount of acid-modified styrene elastomer.

The amount of styrene-based elastomer per 1 part by mass of cellulose nanofiber is preferably 0.5 parts by mass or more, or 1 part by mass or more, or 5 parts by mass or more, from the viewpoint of obtaining the good rubber elasticity, weather resistance and chemical resistance inherent in styrene-based elastomer, and preferably 250 parts by mass or less, or 200 parts by mass or less, or 150 parts by mass or less, from the viewpoint of improving the surface smoothness and hardness of the molded article.

The amount of styrene-based elastomer in 100% by mass of the resin composition is preferably 10% by mass or more, 20% by mass or more, or 30% by mass or more, from the viewpoint of allowing the advantageous properties inherent in the styrene-based elastomer to be fully exhibited, and preferably 98.8% by mass or less, 90% by mass or less, or 80% by mass or less, from the viewpoint of including other components in desired amounts.

The melt mass flow rate (MFR) of the styrene-based elastomer at 230°C and 2.16 kg is preferably 20 g/10 min or less, or 15 g/10 min or less, or 10 g/10 min or less, or 8 g/10 min or less, or 5 g/10 min or less, from the viewpoint of obtaining good mechanical properties of the resin composition, and preferably 0.1 g/10 min or more, or 0.5 g/10 min or more, or 1.0 g/10 min or more, from the viewpoint of facilitating melt processing.

<Styrene-based elastomers and acid-modified styrene-based elastomers in embodiments using a tack inhibitor containing cellulose nanofibers>
The following describes examples of styrene-based elastomers and acid-modified styrene-based elastomers that are particularly suitable in embodiments using a tack inhibitor containing cellulose nanofibers. In one embodiment, the resin composition contains an acid-modified styrene-based elastomer. It has been found that the presence of an acid-modified styrene-based elastomer in addition to cellulose nanofibers can further improve the tensile strength, tensile modulus, tensile elongation at break, and/or hardness of the molded article, while also reducing undesirable conditions such as whitening and discoloration of the molded article. Although not bound by theory, it is thought that the reaction between the hydroxyl groups of cellulose nanofibers and the acid-modified groups of the acid-modified styrene-based elastomer strengthens the interface between them, making it less likely for delamination to occur between the styrene-based elastomer, cellulose nanofibers, and acid-modified styrene-based elastomer when an external force is applied to the molded article, and also making it less likely for discoloration to occur due to thermal degradation of the cellulose nanofibers. As a result, the property-improving effect of cellulose nanofibers is well exhibited, void generation in the molded article due to delamination is suppressed, whitening is reduced, and discoloration of the cellulose nanofibers is also suppressed. The presence of an acid-modified styrene elastomer in the resin composition is also advantageous in that it further reduces the tackiness caused by the styrene elastomer.

In one embodiment of the resin composition, the acid-modified styrene elastomer and the styrene elastomer are miscible without phase separation and form a continuous phase. In one embodiment of the resin composition, the acid-modified styrene elastomer forms a first phase, and the styrene elastomer forms a second phase separated from the first phase. In one embodiment, the total amount of the acid-modified styrene elastomer and the styrene elastomer is 60% by mass or more of 100% by mass of the resin composition. In one embodiment, the second phase is a continuous phase. In one embodiment, the first phase is a dispersed phase and the second phase is a continuous phase. The dispersed phase may have, for example, a domain size of 20 nm to 10 μm. The domain size can be determined from a scanning electron microscope (SEM) image. Alternatively, in one embodiment, each of the first and second phases may be a continuous phase. Due to the phase separation between the acid-modified styrene elastomer and the styrene elastomer, the styrene elastomer portion in the resin composition contributes to the expression of the inherently good properties of the styrene elastomer, while the acid-modified styrene elastomer portion interposes between the styrene elastomer and cellulose nanofibers due to its good affinity with both, contributing to a further improvement in the property-improving effect of the cellulose nanofibers.

The acid-modified styrene elastomer may be an acid-modified product of the styrene elastomer exemplified above. Preferred examples of acid-modified styrene elastomers are as exemplified above in this disclosure.

The amount of styrene-based elastomer per 1 part by mass of cellulose nanofiber is preferably 0.5 parts by mass or more, or 1 part by mass or more, or 3 parts by mass or more, or 5 parts by mass or more, or 7 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, from the viewpoint of obtaining the good rubber elasticity, weather resistance and chemical resistance inherent in styrene-based elastomer, and preferably 250 parts by mass or less, or 150 parts by mass or less, or 100 parts by mass or less, from the viewpoint of reducing tackiness and improving hardness of the molded article.

The amount of styrene-based elastomer in 100% by mass of the resin composition is preferably 10% by mass or more, or 20% by mass or more, or 40% by mass or more, or 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, from the viewpoint of obtaining the inherent advantages of styrene-based elastomers, and preferably 99.5% by mass or less, or 99% by mass or less, or 98% by mass or less, or 95% by mass or less, or 90% by mass or less, from the viewpoint of including desired amounts of other components.

The melt mass flow rate (MFR) of the styrene-based elastomer at 230°C and 2.16 kg is preferably 20 g/10 min or less, or 15 g/10 min or less, or 10 g/10 min or less, or 8 g/10 min or less, or 5 g/10 min or less, from the viewpoint of obtaining good mechanical properties of the resin composition, and preferably 0.1 g/10 min or more, or 0.5 g/10 min or more, or 1.0 g/10 min or more, from the viewpoint of facilitating melt processing.

The acid modification rate, which is the mass ratio of acid-modified groups in 100% by mass of acid-modified styrene-based elastomer, is preferably 0.2% by mass or more, or 0.5% by mass or more, or 0.8% by mass or more, or 1.0% by mass or more, or 1.2% by mass or more, or 1.5% by mass or more, based on 100% by mass of acid-modified styrene-based elastomer, from the viewpoint of affinity with cellulose nanofibers, and preferably 5.0% by mass or less, or 3.0% by mass or less, or 2.5% by mass or less, or 2.0% by mass or less, from the viewpoint of affinity with styrene-based elastomers.

The ratio of the styrene unit ratio of the styrene-based elastomer to the styrene unit ratio of the acid-modified styrene-based elastomer (styrene ratio of styrene-based elastomer / styrene ratio of acid-modified styrene-based elastomer) is preferably 0.3 or higher, or 0.35 or higher, or 0.4 or higher, from the viewpoint of affinity between the acid-modified styrene-based elastomer and the styrene-based elastomer, and similarly, preferably 4 or lower, or 3 or lower, or 2 or lower.

In acid-modified styrene elastomers, the ratio of styrene units to the acid modification rate (styrene unit ratio / acid modification rate) is preferably 5 or more, or 8 or more, or 12 or more, from the viewpoint of affinity with styrene elastomers, and preferably 90 or less, or 50 or less, or 30 or less, from the viewpoint of affinity with cellulose nanofibers.

The melt mass flow rate (MFR) of the acid-modified styrene elastomer at 230°C and 2.16 kg is preferably 0.1 g/10 min or more, or 0.5 g/10 min or more, or 1.0 g/10 min, from the viewpoint of affinity with the styrene elastomer, and preferably 20 g/10 min or less, or 15 g/10 min or less, or 10 g/10 min or less, or 8 g/10 min or less, or 5 g/10 min or less, from the viewpoint of affinity with cellulose nanofibers.

In one embodiment, the total amount of acid-modified styrene elastomer and styrene elastomer in 100% by mass of the resin composition is 50% by mass or more, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more. Such a resin composition can exhibit good rubber elasticity, weather resistance, chemical resistance, etc. From the viewpoint of including a desired amount of other components, particularly cellulose nanofibers, the above total amount is 99.5% by mass or less, or 99% by mass or less, or 98% by mass or less, or 95% by mass or less, or 90% by mass or less, in one embodiment.

The amount of acid-modified styrene elastomer per 100 parts by mass of styrene elastomer is preferably 0.5 parts by mass or more, or 1 part by mass or more, or 5 parts by mass or more, from the viewpoint of obtaining the advantages of the acid-modified styrene elastomer well, and preferably 100 parts by mass or less, or 50 parts by mass or less, or 20 parts by mass or less, or 10 parts by mass or less, from the viewpoint of suppressing discoloration, shrinkage during molding, and/or decrease in hardness caused by a large amount of acid-modified styrene elastomer.

The amount of acid-modified styrene elastomer per 1 part by mass of cellulose nanofiber is preferably 0.1 parts by mass or more, or 0.3 parts by mass or more, or 0.5 parts by mass or more, or 0.8 parts by mass or more, from the viewpoint of obtaining the advantages of the acid-modified styrene elastomer well, and preferably 45 parts by mass or less, or 30% by mass or less, or 20 parts by mass or less, or 10 parts by mass or less, or 5 parts by mass or less, or 3 parts by mass or less, or 2 parts by mass or less, from the viewpoint of suppressing discoloration, shrinkage during molding, and/or decrease in hardness caused by a large amount of acid-modified styrene elastomer.

The amount of acid-modified styrene elastomer in 100% by mass of the resin composition is preferably 0.5% by mass or more, or 1% by mass or more, or 2% by mass or more, or 3% by mass or more, or 4% by mass or more, from the viewpoint of obtaining the advantages of acid-modified styrene elastomer well. From the viewpoint of suppressing discoloration, shrinkage during molding, and/or reduction in hardness caused by a large amount of acid-modified styrene elastomer, it is preferably 50% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less. Note that acid-modified styrene elastomer is generally relatively expensive, so reducing the amount used is also advantageous from a cost perspective.

The content of styrene-based elastomer in the resin composition components is preferably 10% by mass or more, or 20% by mass or more, and preferably 90% by mass or less, or 85% by mass or less, or 80% by mass or less.

The total content of styrene-based elastomer and acid-modified styrene-based elastomer in the resin composition components is preferably 40% by mass or more, or 45% by mass or more, or 50% by mass or more, and preferably 99% by mass or less, or 95% by mass or less, or 90% by mass or less.

In the resin composition components, the content of acid-modified styrene elastomer relative to 100 parts by mass of the total of styrene elastomer and acid-modified styrene elastomer is preferably 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, and preferably 70 parts by mass or less, or 65 parts by mass or less, or 60 parts by mass or less.

The amount of cellulose nanofibers in the resin composition is preferably 1 part by mass or more, or 2 parts by mass or more, or 3 parts by mass or more, and preferably 70 parts by mass or less, or 65 parts by mass or less, or 60 parts by mass or less, based on 100 parts by mass of the total of the styrene-based elastomer and the acid-modified styrene-based elastomer.

The mass ratio of [cellulose nanofiber] to [total of styrene-based elastomer and acid-modified styrene-based elastomer] in the resin composition components is preferably 1/99 to 60/40, or 2/98 to 50/50, or 3/97 to 40/60.

<Liquid Polymer>
In one embodiment, the resin composition may contain a liquid polymer. A liquid polymer means a polymer that is fluid at 23°C. In one embodiment, the liquid polymer has a glass transition temperature (Tg). In one embodiment, the liquid polymer may be a conjugated diene polymer or a non-conjugated diene polymer. In one embodiment, the liquid polymer is liquid rubber. In this disclosure, liquid rubber means a substance that is fluid at 23°C and forms a rubber elastic body by crosslinking (more specifically vulcanization) and/or chain extension. That is, in one embodiment, the liquid rubber is an uncured product.

Furthermore, having fluidity means, in one embodiment, that a liquid polymer dissolved in cyclohexane is placed in a vial measuring 21 mm in diameter and 50 mm in length at 23°C and then dried. When the vial is filled to a height of 1 mm with the liquid polymer and sealed, and the vial is left upside down for 24 hours, a movement of 0.1 mm or more of the substance in the vertical direction can be observed.

The liquid polymer may have the monomer composition of a general polymer, and is preferably relatively low in molecular weight from the viewpoint of ease of handling and good dispersibility of cellulose nanofibers. In one embodiment, the liquid polymer exhibits a liquid state by having a number-average molecular weight (Mn) of 80,000 or less. Unless otherwise specified, the number-average molecular weight and weight-average molecular weight of the various polymers in this disclosure are values obtained in terms of standard polystyrene using gel permeation chromatography with chloroform as the solvent and a measurement temperature of 40°C.

In one embodiment, the liquid polymer may be combined with cellulose nanofibers to form a masterbatch, and such a masterbatch may be combined with a resin to form the resin composition of the present disclosure.

The number-average molecular weight (Mn) of the liquid polymer is preferably 1,000 or more, or 1,500 or more, or 2,000 or more, from the viewpoint of thermal stability and the effect of improving the dispersibility of cellulose nanofibers in the resin. It is preferably 80,000 or less, or 50,000 or less, or 40,000 or less, or 30,000 or less, or 10,000 or less, in terms of having high fluidity suitable for good dispersion when dispersing cellulose nanofibers in the liquid polymer.

The weight-average molecular weight (Mw) of the liquid polymer is preferably 1,000 or more, 2,000 or more, or 4,000 or more, from the viewpoint of thermal stability and the effect of improving the dispersibility of cellulose nanofibers in the resin. It is preferably 240,000 or less, 150,000 or less, or 30,000 or less, in terms of having high fluidity suitable for good dispersion when dispersing cellulose nanofibers in the liquid polymer.

The ratio (Mw/Mn) of the number-average molecular weight (Mn) to the weight-average molecular weight (Mw) of the liquid polymer is preferably 1.5 or higher, or 1.8 or higher, or 2 or higher, in that the degree of variation in molecular weight allows for a high degree of compatibility of multiple properties (in one embodiment, a high degree of compatibility between good dispersion of cellulose nanofibers in the resin and a good flexural modulus of the resin composition). In that the variation in molecular weight is not excessively large and the desired physical properties of the resin composition can be obtained stably, for example, in terms of compatibility between fluidity and impact resistance, it is preferably 10 or lower, or 8 or lower, or 5 or lower, or 3 or lower, or 2.7 or lower.

Liquid polymers can have good thermal stability. In one embodiment, the thermal decomposition onset temperature ( _TD ) of a liquid polymer is greater than 200°C, or 210°C or higher, or 230°C or higher, or 250°C or higher, or 300°C or higher, from the viewpoint of good thermal stability. A higher thermal decomposition onset temperature is preferable, but in one embodiment, from the viewpoint of the availability of liquid polymers, it may be 500°C or lower, or 450°C or lower, or 400°C or lower.

The glass transition temperature of the liquid polymer is preferably -150°C or higher, or -120°C or higher, or -100°C or higher, in terms of good thermal stability, and preferably 25°C or lower, or 10°C or lower, or 0°C or lower, in terms of good fluidity.

In one embodiment, the liquid polymer comprises a diene polymer, and in another embodiment, a conjugated diene polymer or a non-conjugated diene polymer or hydrogenated thereof. The above polymers or hydrogenated thereof may be oligomers. The monomers constituting the liquid polymer may be unmodified or modified (e.g., acid-modified, hydroxyl-modified, etc.). In one embodiment, the liquid polymer may have reactive groups at both ends (e.g., one or more selected from the group consisting of hydroxyl groups, carboxyl groups, isocyanate groups, thio groups, amino groups, and halo groups), and therefore may be bifunctional. These reactive groups contribute to crosslinking and/or chain extension of the liquid polymer.

[Conjugated diene polymers]
The conjugated diene polymer may be a homopolymer, or a copolymer of two or more conjugated diene monomers, or a copolymer of a conjugated diene monomer and another monomer. The copolymer may be random or block-shaped.

Examples of conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene, which may be used individually or in combination of two or more.

In one embodiment, the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and an aromatic vinyl monomer.
The aromatic vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with a conjugated diene monomer. Examples include styrene, m or p-methylstyrene, α-methylstyrene, ethylstyrene, p-tert-butylstyrene, vinylethylbenzene, vinylxylene, vinylnaphthalene, diphenylethylene, and divinylbenzene, which may be used individually or in combination of two or more. From the viewpoint of moldability of the resin composition and impact resistance of the molded product, styrene is preferred.

Examples of random copolymers include butadiene-isoprene random copolymers, butadiene-styrene random copolymers, isoprene-styrene random copolymers, and butadiene-isoprene-styrene random copolymers. Examples of the compositional distribution of each monomer in the copolymer chain include perfectly random copolymers with a composition close to statistically random, and tapered random copolymers with a gradient in the compositional distribution. The bonding mode of the conjugated diene polymer, i.e., the composition of 1,4-bonds, 1,2-bonds, etc., may be uniform or different between molecules.

A block copolymer may be a copolymer consisting of two or more blocks. For example, a block copolymer may have a structure such as A-B, A-B-A, A-B-A-B, etc., where block A is an aromatic vinyl monomer and block B is a block of conjugated diene monomer and/or a copolymer of aromatic vinyl monomer and conjugated diene monomer. The boundaries of each block do not necessarily need to be clearly distinguishable; for example, if block B is a copolymer of aromatic vinyl monomer and conjugated diene monomer, the aromatic vinyl monomer in block B may be distributed uniformly or in a tapered manner. Furthermore, block B may have multiple portions where the aromatic vinyl monomer is uniformly distributed and/or distributed in a tapered manner. In addition, block B may have multiple segments with different aromatic vinyl monomer content. When multiple blocks A and block B exist in the copolymer, their molecular weights and compositions may be the same or different.

The block copolymer may be a mixture of two or more types in which one or more of the following are different: bond type, molecular weight, aromatic vinyl compound species, conjugated diene compound species, 1,2-vinyl content or the total amount of 1,2-vinyl content and 3,4-vinyl content, aromatic vinyl compound component content, hydrogenation rate, etc.

In conjugated diene polymers, the amount of vinyl bonds in the conjugated diene bond units (e.g., 1,2- or 3,4- bonds of butadiene) is preferably 10 mol% or more and 75 mol% or less, or 13 mol% or more and 65 mol% or less.
The amount of vinyl bonds in conjugated diene bond units (e.g., the amount of 1,2-bonds in butadiene) can be determined by ^13C -NMR (quantitative mode). Specifically, by integrating the peak areas that appear in ^13C -NMR, a value proportional to the carbon content of each structural unit can be obtained, and as a result, it can be converted to the mass percentage of each structural unit.
Styrene 145-147 ppm
Vinyl 110-116 ppm
Diene (cis) 24-28 ppm
Diene (trans) 29-33 ppm

In a copolymer of a conjugated diene monomer and an aromatic vinyl monomer, the amount of aromatic vinyl monomer bonded to the conjugated diene monomer (hereinafter also referred to as the amount of aromatic vinyl bonded) may be preferably 5 mol% to 70 mol%, or 10 mol% to 50 mol%, based on 100% of the total moles of the conjugated diene polymer.

Examples of hydrogenated conjugated diene polymers include those exemplified above, such as hydrogenated butadiene homopolymers, isoprene homopolymers, styrene-butadiene copolymers, and acrylonitrile-butadiene copolymers.

In a preferred embodiment, the liquid polymer is one or more selected from the group consisting of polybutadiene, butadiene-styrene copolymer, polyisoprene, and polychloroprene. These may be derivatives (e.g., maleic anhydride modified, methacrylic acid modified, terminal hydroxyl group modified, hydrogenated, and combinations thereof).

[Non-conjugated diene polymers]
The non-conjugated diene polymer may be a homopolymer, or a copolymer of two or more non-conjugated diene monomers, or a copolymer of a non-conjugated diene monomer and another monomer. The copolymer may be random or block. Examples of non-conjugated diene polymers include olefin polymers (e.g., liquid paraffin), silicone polymers, acrylic polymers, etc. For example, when the liquid polymer is liquid rubber, the non-conjugated diene polymer may be:
Olefin polymers such as ethylene-propylene rubber, ethylene-propylene-diene rubber, ethylene-butene-diene rubber, and ethylene-α-olefin copolymers.
Examples include butyl rubber, brominated butyl rubber, acrylic rubber, fluororubber, silicone rubber, chlorinated polyethylene rubber, epichlorohydrin rubber, α,β-unsaturated nitrile-acrylic acid ester-conjugated diene copolymer rubber, urethane rubber, and polysulfide rubber.

In ethylene-α-olefin copolymers, monomers that can copolymerize with ethylene units include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, or eicosene-1, aliphatic substituted vinyl monomers such as isobutylene, and styrene. Examples include aromatic vinyl monomers such as substituted styrene, vinyl acetate, acrylic acid esters, methacrylic acid esters, glycidyl acrylic acid esters, glycidyl methacrylic acid esters, hydroxyethyl methacrylic acid esters, nitrogen-containing vinyl monomers such as acrylamide, allylamine, vinyl-p-aminobenzene, and acrylonitrile, and dienes such as butadiene, cyclopentadiene, 1,4-hexadiene, and isoprene.

The ethylene-α-olefin copolymer is preferably a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms, more preferably a copolymer of ethylene and one or more α-olefins having 3 to 16 carbon atoms, and most preferably a copolymer of ethylene and one or more α-olefins having 3 to 12 carbon atoms.

From the viewpoint of exhibiting impact resistance, the molecular weight of the ethylene-α-olefin copolymer is preferably 10,000 or more, more preferably 10,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 20,000 to 60,000, as measured by gel permeation chromatography using 1,2,4-trichlorobenzene as a solvent at 140°C with a polystyrene standard.

Furthermore, from the viewpoint of ease of handling during processing, the ethylene unit content of the ethylene-α-olefin copolymer is preferably 30 to 95% by mass relative to the total amount of the ethylene-α-olefin copolymer.

Ethylene-α-olefin copolymers can be manufactured by conventionally known manufacturing methods, such as those described in Japanese Patent Publication No. 4-12283, Japanese Unexamined Patent Publication No. 60-35006, Japanese Unexamined Patent Publication No. 60-35007, Japanese Unexamined Patent Publication No. 60-35008, Japanese Unexamined Patent Publication No. 5-155930, Japanese Unexamined Patent Publication No. 3-163088, and U.S. Patent No. 5,272,236.

In one embodiment, the liquid polymer comprises one or more selected from the group consisting of diene rubber, silicone rubber, urethane rubber, and polysulfide rubber, and hydrogenated versions thereof, and preferably comprises diene rubber.

The viscosity of the liquid polymer at 25°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 200,000 mPa·s or less, from the viewpoint of good dispersion of cellulose nanofibers in the liquid polymer. From the viewpoint of thermal stability, improvement of dispersibility of cellulose nanofibers in the resin, and mechanical properties of the resin composition, it is preferably 100 mPa·s or more, or 300 mPa·s or more, or 500 mPa·s or more.

The viscosity of the liquid polymer at 50°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 200,000 mPa·s or less, or 100,000 mPa·s or less, from the viewpoint of good dispersion of cellulose nanofibers in the liquid polymer and good dispersion of cellulose nanofibers in the resin by heating and kneading. From the viewpoint of thermal stability, improvement of dispersibility of cellulose nanofibers in the resin, and mechanical properties of the resin composition, it is preferably 50 mPa·s or more, or 100 mPa·s or more, or 500 mPa·s or more.

The viscosity of the liquid polymer at 80°C is preferably 1,000,000 mPa·s or less, or 500,000 mPa·s or less, or 250,000 mPa·s or less, or 100,000 mPa·s or less, from the viewpoint of good dispersion of cellulose nanofibers in the liquid polymer and good dispersion of cellulose nanofibers in the resin by heating and kneading. From the viewpoint of thermal stability, improvement of dispersibility of cellulose nanofibers in the resin, and mechanical properties of the resin composition, it is preferably 50 mPa·s or more, or 100 mPa·s or more, or 300 mPa·s or more.

The viscosity of the liquid polymer at 0°C is preferably 2,000,000 mPa·s or less, or 1,000,000 mPa·s or less, or 400,000 mPa·s or less, from the viewpoint of good dispersion of cellulose nanofibers in the liquid polymer. From the viewpoint of thermal stability, improvement of dispersibility of cellulose nanofibers in the resin, and mechanical properties of the resin composition, it is preferably 200 mPa·s or more, or 600 mPa·s or more, or 1,000 mPa·s or more.

It is preferable that the viscosity of the liquid polymer at 80°C, 50°C, 25°C, and 0°C is all within the above range, as this allows for good dispersion of cellulose nanofibers in the liquid polymer over a wide mixing temperature range.

The viscosity of the liquid polymer is measured using a B-type viscometer at a rotation speed of 10 rpm.

In the resin composition, the amount of liquid polymer per 100 parts by mass of styrene-based elastomer is preferably 0.1 parts by mass or more, or 0.3 parts by mass or more, or 0.5 parts by mass or more, or 1.0 part by mass or more, from the viewpoint of obtaining the advantages of the liquid polymer well, and preferably 15 parts by mass or less, or 10 parts by mass or less, or 5 parts by mass or less, from the viewpoint of obtaining the advantages of acid-modified styrene-based elastomer well, or from the viewpoint of obtaining a resin composition that exhibits the inherent physical properties of styrene-based elastomer.

In the resin composition, the amount of liquid polymer per 100 parts by mass of cellulose nanofiber is preferably 5 parts by mass or more, or 10 parts by mass or more, or 20 parts by mass or more, or 30 parts by mass or more, or 40 parts by mass or more, from the viewpoint of obtaining the advantages of the liquid polymer well, and preferably 400 parts by mass or less, or 200 parts by mass or less, or 100 parts by mass or less, from the viewpoint of obtaining good physical properties of the resin composition and the resin molded article.

From the viewpoint of obtaining the advantages of liquid polymers, the content of liquid polymer in the resin composition is preferably 0.1% by mass or more, or 0.3% by mass or more, or 1.0% by mass or more. From the viewpoint of obtaining good physical properties of the resin composition and the resin molded article, it is preferably 20% by mass or less, or 10% by mass or less, or 7% by mass or less, or 5% by mass or less.

<Dispersant>
In one embodiment, the resin composition includes a dispersant. In one embodiment, it is even more preferable, from the viewpoint of more uniformly dispersing cellulose nanofibers in the resin composition, that the dispersant has a hydrophilic segment and a hydrophobic segment within the same molecule (i.e., is an amphiphilic molecule). In a preferred embodiment, the resin composition includes a polyoxyethylene unit-containing polymer.

[Amphiphilic molecules]
In amphiphilic molecules, the hydrophilic segment is the part that exhibits good affinity with cellulose nanofibers by containing a hydrophilic structure. Specifically, the hydrophilic structure includes hydroxyl groups, thiol groups, carboxyl groups, sulfonic acid groups, sulfate ester groups, phosphate groups, boronic acid groups, silanol groups, groups derived from sugars such as sorbitan and sucrose, groups derived from glycerin, groups represented by -OM, -COOM, _-SO₃M , _-OSO₃M , _-HMPO₄ , _{and -M₂PO₄ (} where M represents an alkali metal or alkaline earth metal), as well as primary to tertiary amines and quaternary ammonium salts. Examples of counteranions for the above-mentioned quaternary ammonium salt include one or more hydrophilic groups selected from the group consisting of halogen ions such as hydroxide ions, fluoride ions, chloride ions, bromide ions, and iodide ions, as well as nitrate ions, formate ions, acetate ions, trifluoroacetate ions, p-toluenesulfonate ions, hexafluorophosphates, and tetrafluoroborates.

Examples of hydrophilic segments include polyethylene glycol segments, segments containing repeating units with quaternary ammonium salt structures, polyvinyl alcohol segments, polyvinylpyrrolidone segments, polyacrylic acid segments, carboxyvinyl polymer segments, cationized guar gum segments, hydroxyethylcellulose segments, methylcellulose segments, carboxymethylcellulose segments, and polyurethane soft segments (specifically diol segments). Nonionic polyoxyethylene derivatives are particularly preferred, and the polyoxyethylene chain length of the polyoxyethylene derivative may be 3 or more, or 5 or more, or 10 or more, or 15 or more. While longer chain lengths increase affinity with cellulose nanofibers, from the viewpoint of balancing this with desired properties (e.g., mechanical properties) of the resin molded article, the polyoxyethylene chain length may be 60 or less, or 50 or less, or 40 or less, or 30 or less, or 20 or less.

Examples of hydrophobic segments include segments containing hydrocarbons, segments containing fluorinated carbon, segments containing alkylene oxide units with 3 or more carbon atoms (e.g., PPG blocks), and segments containing polymer structures.
Preferred hydrocarbon segments include alkyl type, alkenyl type, alkyl ether type, alkenyl ether type, alkylphenyl ether type, alkenylphenyl ether type, rosin ester type, bisphenol A type, β-naphthyl type, styrene-phenyl type, and hydrogenated castor oil type. The number of carbon atoms in the alkyl chain or alkenyl chain of the hydrophobic group (in the case of alkylphenyl or alkenylphenyl, the number of carbon atoms excluding the phenyl group) is preferably 2 or more, or 5 or more, or 10 or more, or 12 or more, or 16 or more.
As for the segment having fluorinated carbon, linear or branched alkyl types with 1 to 20 carbon atoms are preferred.
Preferred polymer structures include acrylic polymers, styrene resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, amino acid lactams including ring-opening polymers of lactams, polymers composed of diamines and dicarboxylic acids, polyacetal resins, polycarbonate resins, polyester resins, polyphenylene sulfide resins, polysulfone resins, polyetherketone resins, polyimide resins, fluorine resins, hydrophobic silicone resins, melamine resins, epoxy resins, phenolic resins, and the like.
These hydrophobic segments may have either a linear or branched structure. Furthermore, the hydrophobic segments may have a single-chain structure or a structure of two or more chains, and if they have a structure of two or more chains, they may have multiple types of hydrophobic groups.

The structure of amphiphilic molecules is not particularly limited, but when the hydrophilic segment is A and the hydrophobic segment is B, examples include linear copolymers such as AB-type block copolymers, ABA-type block copolymers, and BAB-type block copolymers; tribranched copolymers containing A and B; tetrabranched copolymers containing A and B; star-shaped copolymers containing A and B; monocyclic copolymers containing A and B; polycyclic copolymers containing A and B; cage copolymers containing A and B; and graft copolymers containing A and B.
When multiple hydrophilic segments are present in a molecule, their molecular structure may be a single type or a combination of two or more types. Similarly, when multiple hydrophobic segments are present in a molecule, their molecular structure may be a single type or a combination of two or more types.

(Surfactants)
Any of the following can be used as the amphiphilic molecule: anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. The dispersant may be a polymeric surfactant, a reactive surfactant, or the like.

Examples of nonionic surfactants include fatty acid dialkanolamides (e.g., lauric acid diethanolamide), polyoxyalkylene fatty acid amides (e.g., polyoxyethylene stearic acid amide), polyoxyalkylene aryl ethers (e.g., polyoxyethylene phenyl ether), polyoxyalkylene alkylaryl ethers (e.g., polyoxyethylene octylphenyl ether), polyoxyalkylene alkyl or alkenyl ethers (e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether), fatty acid esters of polyhydric alcohols (e.g., polyethylene glycol mono or distearate ester, polyethylene glycol mono or dilaurate ester, polyoxyethylene hydrogenated castor oil), glycerin fatty acid esters (e.g., glyceryl monostearate, glyceryl monooleate), sorbitan fatty acid esters (e.g., sorbitan monolaurylate, sorbitan monostearate), and polyoxyethylene-polyoxypropylene block polymers.

Anionic surfactants (emulsifiers) may be carboxylates, sulfonates, sulfate esters, phosphate esters, etc. Examples of carboxylates include aliphatic monocarboxylic acids and alkyl ether carboxylates; examples of sulfonates include dialkyl sulfosuccinates, alkane sulfonates, alkylbenzene sulfonates, and alkylnaphthalene sulfonates; examples of sulfate esters include alkyl sulfates and oil sulfates; and examples of phosphate esters include alkyl phosphates and polyoxyethylene alkyl ether phosphates.

Cationic surfactants include amine salts, amidoamine salts, quaternary ammonium salts, and imidazolinium salts. Specific examples, though not particularly limited, include alkylamine salts, polyoxyethylene alkylamine salts, alkylamidoamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt-type surfactants such as imidazoline, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, alkylpyridinium salts, alkylisoquinolinium salts, and quaternary ammonium salt-type surfactants such as benzethonium chloride.

Examples of amphoteric surfactants include alkylamine oxides, alanines, imidazolinium betaines, amide betaines, and acetate betaine. Specifically, examples include long-chain amine oxides, lauryl betaine, stearyl betaine, laurylcarboxymethylhydroxyethylimidazolinium betaine, lauryldimethylaminoacetic acid betaine, and fatty acid amidopropyldimethylaminoacetic acid betaine.

[Hydrophilic polymer]
In one embodiment, the dispersant is preferably a hydrophilic polymer. In one embodiment, the hydrophilic polymer is a polymer having a hydrophilic group selected from the group consisting of hydroxyl groups, carboxyl groups, amino groups, ammonium groups, sulfonic acid groups, phosphate groups, etc. As the hydrophilic polymer, one or more can be selected from the group consisting of cellulose derivatives (hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, etc.), polyalkylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, carboxyvinyl polymer, cationized guar gum, water-soluble polyurethane, polymers containing quaternary ammonium salt structures, amides, amines, etc. Among these, cellulose derivatives and polyalkylene glycols are more preferred, and polyalkylene glycols are particularly preferred.

The amount of dispersant in the resin composition is preferably 1 part by mass or more, or 3 parts by mass or more, or 5 parts by mass or more, or 10 parts by mass or more, or 15 parts by mass or more, per 100 parts by mass of cellulose nanofiber, and preferably 200 parts by mass or less, or 150 parts by mass or less, or 100 parts by mass or less, or 90 parts by mass or less, or 80 parts by mass or less, or 70 parts by mass or less, or 60 parts by mass or less, or 50 parts by mass or less.

The content of the dispersant in the resin composition components may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more in one embodiment, and may be 40% by mass or less, 35% by mass or less, or 30% by mass or less in one embodiment.

For example, when a preliminary composition containing cellulose nanofibers and an acid-modified styrene elastomer is used in the production of a resin composition, the mass ratio of the preliminary composition to the styrene elastomer in the resin composition components (preliminary composition/styrene elastomer) may, in one embodiment, be 1/99 to 99/1, or 5/95 to 95/5, or 10/90 to 90/10, or 20/80 to 80/20, or 30/70 to 70/30.

[Sulfurizing agents, sulfurizing accelerators]
When the resin composition components include liquid rubber, the resin composition components typically include a vulcanizing agent and may optionally include a vulcanization accelerator. Conventionally known vulcanizing agents and vulcanization accelerators may be appropriately selected depending on the type of liquid rubber in the resin composition components. Examples of vulcanizing agents include organic peroxides, azo compounds, oxime compounds, nitroso compounds, polyamine compounds, sulfur, and sulfur compounds. Examples of sulfur compounds include sulfur monochloride, sulfur dichloride, disulfide compounds, and high-molecular-weight polysulfur compounds.

The amount of vulcanizing agent in the resin composition is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of liquid rubber in the resin composition.

Examples of vulcanization accelerators include sulfenamide-based, guanidine-based, thiuram-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, thiourea-based, and dithiocarbamate-based vulcanization accelerators. Zinc oxide, stearic acid, etc., may also be used as vulcanization aids. The amount of vulcanization accelerator is preferably 0.01 to 20 parts by mass, or 0.1 to 15 parts by mass, per 100 parts by mass of liquid rubber in the resin composition.

[Rubber additives]
The resin composition components may include various conventionally known rubber additives (stabilizers, softeners, antioxidants, etc.). As rubber stabilizers, one or more antioxidants such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, and 2-methyl-4,6-bis[(octylthio)methyl]phenol may be used. As rubber softeners, one or more process oils, extender oils, etc., may be used. However, in one embodiment, the resin composition can form a flexible molded article, and therefore, in one embodiment, the resin composition components may not contain rubber softeners.

While vulcanizing agents, vulcanization accelerators, and rubber additives are typically added during the manufacturing of resin compositions, the manner of addition is not limited thereto.

<Additional components to the resin composition>
The resin composition components may further contain additional components. Examples of additional components include additional polymers, organic or inorganic fillers, heat stabilizers, antioxidants, antistatic agents, colorants, etc. The content ratio of any additional component in the resin composition components is appropriately selected within a range that does not impair the desired effects of the present invention, but may be, for example, 0.01 to 50% by mass, or 0.1 to 30% by mass.

<Manufacturing of resin compositions>
A resin composition according to one embodiment can be produced by mixing composition components which are a mixture containing cellulose nanofibers, an acid-modified styrene elastomer, and a styrene elastomer.
A resin composition according to one embodiment can be produced by mixing a composition component which is a mixture containing a tack inhibitor containing cellulose nanofibers and a styrene-based elastomer.
Mixing is, in one aspect, heating and kneading.
In other words, a method for producing a resin composition according to one embodiment includes a kneading step of heating and kneading a mixture containing a styrene-based elastomer and cellulose nanofibers.

The weight increase rate of cellulose nanofibers after heating and kneading compared to cellulose nanofibers before heating and kneading is preferably 190% or more and 600% or less. From the viewpoint of interfacial strength between the resin and cellulose nanofibers, the weight increase rate is preferably 190% or more, or 250% or more, or 300% or more, or 350% or more, and from the viewpoint of suppressing short fiber formation during kneading, it is preferably 600% or less, or 550% or less, or 500% or less. The weight increase rate is a value measured by the method described in the [Examples] section of this disclosure.

As an example of a method for producing the resin composition, using an acid-modified styrene elastomer is as follows:
(1) A method comprising: a first step of mixing cellulose nanofibers and an acid-modified styrene elastomer to obtain a preliminary composition; and a second step of mixing the preliminary composition with a styrene elastomer to obtain a resin composition.
(2) A method comprising the step of mixing together cellulose nanofibers, an acid-modified styrene elastomer, and a resin composition component containing a styrene elastomer.
These are some examples.
If an acid-modified styrene elastomer is not used, the resin composition components containing cellulose nanofibers and styrene elastomer may be mixed together in the method described in (2) above.
The mixing conditions are not particularly limited, but for example, the components constituting the resin composition may be mixed using stirring means such as a rotation-orbit mixer, planetary mixer, propeller-type agitator, rotary agitator, electromagnetic agitator, open roll, Banbury mixer, kneader, single-screw extruder, or twin-screw extruder to obtain the resin composition. Alternatively, stirring may be performed under heating to efficiently carry out shearing.
In the method described in (1) above, by combining the acid-modified styrene elastomer with cellulose nanofibers in advance, the contact opportunities between the cellulose nanofibers and the styrene elastomer become more appropriate and uniform, which can lead to better improvement in the physical properties of the resin composition.

The cellulose nanofibers used for mixing with acid-modified styrene elastomers or styrene elastomers may be in the form of a dried product containing cellulose nanofibers. In one embodiment, cellulose nanofibers may be mixed with a liquid polymer and/or dispersant in the form of a slurry, and the contained liquid medium may be dried and removed to obtain a dried product containing cellulose nanofibers. In this case, the drying process can be carried out, for example, as follows.

[Drying process]
In one embodiment, a dried body containing cellulose nanofibers can be produced by drying a cellulose nanofiber slurry.
Dryers are not limited to any particular type, but examples include kneaders, planetary mixers, Henschel mixers, high-speed mixers, propeller mixers, ribbon mixers, single-screw or twin-screw extruders, Banbury mixers, freeze dryers, shelf dryers, spray dryers, fluidized bed dryers, drum dryers, etc.

The drying temperature may be, for example, 20°C or higher, 30°C or higher, 40°C or higher, or 50°C or higher, from the viewpoint of forming a dried body containing cellulose nanofibers with excellent powder properties, such as drying efficiency, nanodispersibility of cellulose nanofibers in the resin composition, and macrodispersibility. From the viewpoint of minimizing thermal degradation of cellulose nanofibers and additional components, and from the viewpoint of avoiding excessive pulverization of the dried body containing cellulose nanofibers due to rapid drying of the slurry, the drying temperature may be, for example, 200°C or lower, 180°C or lower, 160°C or lower, 140°C or lower, 120°C or lower, or 100°C or lower.
The drying temperature is the temperature of the heat source in contact with the slurry, and is defined, for example, as the surface temperature of the temperature-controlled jacket of the drying apparatus, the surface temperature of the heating cylinder, or the temperature of the hot air.

The pressure may be either atmospheric pressure or reduced pressure, but from the viewpoint of forming a dried body containing cellulose nanofibers with excellent powder properties such as drying efficiency, nanodispersibility of cellulose nanofibers in the resin composition, and macrodispersibility, it may be -1 kPa or less, -10 kPa or less, -20 kPa or less, -30 kPa or less, -40 kPa or less, or -50 kPa or less. From the viewpoint of avoiding excessive pulverization of the dried body containing cellulose nanofibers due to rapid drying of the slurry, it may be -100 kPa or more, -95 kPa or more, or -90 kPa or more.

The concentration of cellulose nanofibers in the cellulose nanofiber slurry subjected to the drying process is preferably 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more, from the viewpoint of process efficiency during drying. From the viewpoint of avoiding excessive increase in slurry viscosity and solidification due to aggregation, and maintaining good handling properties, it is preferably 50% by mass or less, 45% by mass or less, 40% by mass or less, or 35% by mass or less. For example, cellulose nanofibers are often produced in a dilute dispersion, but the concentration of cellulose nanofibers in the slurry may be adjusted to the above-mentioned preferred range by concentrating such a dilute dispersion. Methods such as suction filtration, pressure filtration, centrifugal deliquidation, and heating can be used for concentration.

In one embodiment, the dried product containing cellulose nanofibers may also contain a liquid polymer and/or a dispersant, which may be added before, during, and/or after drying the cellulose nanofiber slurry.
In one embodiment, the liquid polymer and/or dispersant may be added in a dispersed or dissolved state in water and/or an organic solvent. The organic solvent is not particularly limited, but a solvent in which the liquid polymer and dispersant dissolve is preferred, and examples of water-insoluble solvents include chloroform, toluene, hexane, and cyclohexane.

[Liquid medium content]
The liquid medium content of the dry product containing cellulose nanofibers is preferably 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less, from the viewpoint of workability when kneading with acid-modified styrene elastomer or styrene elastomer. Particularly preferred liquid medium content from the viewpoint of tack suppression effect is 7% by mass or less, 5% by mass or less, or 3% by mass or less. The liquid medium content may be 0% by mass, but from the viewpoint of ease of manufacturing the dry product containing cellulose nanofibers, it may be, for example, 0.1% by mass or more, 1% by mass or more, or 1.5% by mass or more. The liquid medium content is a value measured using an infrared heating type moisture meter.

[Average particle size]
In one embodiment, the average particle size of the dried material containing cellulose nanofibers is preferably 1 μm or more, or 10 μm or more, 50 μm or more, or 100 μm or more, or 200 μm or more, or 500 μm or more, from the viewpoint of ease of manufacture, and preferably 10,000 μm or less, or 5,000 μm or less, or 4,000 μm or less, or 3,000 μm or less, or 2,000 μm or less, from the viewpoint that the dried material containing cellulose nanofibers can easily disintegrate in the resin composition and the cellulose nanofibers can be well dispersed in the resin composition. The above average particle size is a value measured by a dynamic image analysis particle size distribution analyzer (CAMSIZER X2 manufactured by Microtrac).

[Loose bulk density]
In one embodiment, the loosened bulk density of the dry material containing cellulose nanofibers is preferably 0.01 g/cm³ or more, or 0.05 g/cm³ or more, or 0.10 g/cm³ or more, or 0.15 g/ ^cm³ or more, or 0.20 g/cm³ or more, or 0.25 g/ ^cm³ or more, or 0.30 g/ ^cm³ or more, or 0.35 g/ ^cm³ or more, or 0.40 g/ ^cm³ or more, or 0.45 g/ ^cm³ or more, or 0.50 g/ ^cm³ or ^more , from ^the viewpoint of good fluidity and excellent feedability of the dry material containing cellulose nanofibers, and suppression of migration of liquid polymer and/or dispersant to the resin composition. Preferably, the loosened bulk density ^is 0.85 g/cm³ or ^more , from the viewpoint of the dry material containing cellulose nanofibers easily disintegrating in the resin composition so that the cellulose nanofibers can be well dispersed in the resin composition, and from the viewpoint of the dry material containing cellulose nanofibers not being too heavy so as to avoid poor mixing between the dry material containing cellulose nanofibers and the resin composition. It is ³ or less, or 0.80 g/ ^cm³ or less, or 0.75 g/ ^cm³ or less.

[High-density bulk]
In one embodiment, the firm bulk density of the dry material containing cellulose nanofibers is controlled to a range useful for controlling the loose bulk density and compressibility within the scope of the Disclosure, preferably 0.01 g/ ^cm³ or more, or 0.1 g/ ^cm³ or more, or 0.15 g/cm³ or more, or 0.2 g/ ^cm³ or more, or 0.3 g/ ^cm³ or ^more , or 0.4 g/ ^cm³ or more, or 0.5 g/ ^cm³ or more, or 0.6 g/ ^cm³ or more, and preferably 0.95 g/ ^cm³ or less, or 0.9 g/ ^cm³ or less, or 0.85 g/ ^cm³ or less.

[Degree of Compression]
The degree of compression is calculated as follows: degree of compression = (stiff bulk density - loose bulk density) / stiff bulk density. The loose bulk density and stiff bulk density are values measured by the methods described in the [Examples] section of this disclosure.
In one embodiment, the degree of compression represents the degree of bulk reduction. In one embodiment, the degree of compression of the dry material containing cellulose nanofibers is preferably 1% or more, or 5% or more, or 10% or more, or 15% or more, or 20% or more, or 25% or more, in that the fluidity of the dry material containing cellulose nanofibers is not too high. Furthermore, in terms of good fluidity and excellent feedability of the dry material containing cellulose nanofibers, excellent handling (specifically, less prone to scattering, floating, or dust formation), good dispersion of the dry material containing cellulose nanofibers in the resin composition, and suppression of the migration of the dispersant to the resin, the degree of compression is preferably 50% or less, or 45% or less, or 40% or less, or 35% or less, or 30% or less.

The above-mentioned loose bulk density, firm bulk density, and compressibility are measured using a powder tester (model number: PT-X) manufactured by Hosokawa Micron Corporation. The firm bulk density measurement is performed after 180 taps.

As a more specific example of the process sequence, the following can be given when using an acid-modified styrene elastomer:
(i) Prepare a slurry containing cellulose nanofibers and optionally a liquid polymer and/or a dispersant → Dry to prepare a dried body → Prepare a preliminary composition containing the dried body and an acid-modified styrene elastomer → Prepare a resin composition containing the preliminary composition and the styrene elastomer. (ii) Prepare a slurry containing cellulose nanofibers and optionally a liquid polymer and/or a dispersant → Dry to prepare a dried body → Prepare a preliminary composition containing the dried body, an acid-modified styrene elastomer and a styrene elastomer → Prepare a resin composition containing the preliminary composition and the styrene elastomer. (iii) Prepare a slurry containing cellulose nanofibers, an acid-modified styrene elastomer, and optionally a liquid polymer and/or a dispersant → Dry to prepare a dried body → Prepare a resin composition containing the dried body and a styrene elastomer. (iv) Prepare a slurry containing cellulose nanofibers, an acid-modified styrene elastomer, a styrene elastomer, and optionally a liquid polymer and/or a dispersant → Dry to prepare a resin composition.

Furthermore, in embodiments using a tack inhibitor containing cellulose nanofibers, the following can also be mentioned.
(i) Prepare a slurry containing cellulose nanofibers and optionally a liquid polymer and/or a dispersant → Dry to prepare a dried product → Prepare a preliminary composition containing the dried product and an acid-modified styrene elastomer → Prepare a resin composition containing the preliminary composition and the styrene elastomer (ii) Prepare a slurry containing cellulose nanofibers and optionally a liquid polymer and/or a dispersant → Dry to prepare a dried product → Prepare a preliminary composition containing the dried product and an acid-modified styrene elastomer and a styrene elastomer → Prepare a resin composition containing the preliminary composition and the styrene elastomer (iii) Prepare a slurry containing cellulose nanofibers and (iv) Prepare a slurry containing an optional liquid polymer and/or dispersant → Dry to prepare a dried product → Prepare a resin composition containing the dried product, an acid-modified styrene elastomer, and a styrene elastomer. (v) Prepare a slurry containing cellulose nanofibers, an acid-modified styrene elastomer, and an optional liquid polymer and/or dispersant → Dry to prepare a dried product → Prepare a resin composition containing the dried product and a styrene elastomer. (v) Prepare a slurry containing cellulose nanofibers, an acid-modified styrene elastomer, a styrene elastomer, and an optional liquid polymer and/or dispersant → Dry to prepare a resin composition.

A desired molded article may be produced by molding the resin composition alone or together with other components into a desired shape. The method of combining the components and the molding method are not particularly limited and may be selected according to the desired molded article. Molding is usually performed by melt molding, and may be carried out by injection molding, extrusion molding, extruded molded form molding, hollow molding, compression molding, etc.

In one embodiment, the molding method may be for irregular shapes. That is, in one embodiment, the resin molded article of this embodiment may be an irregularly shaped article. Another aspect of the present invention provides a method for manufacturing an irregularly shaped extruded article, which includes a step of extruding the resin composition of this embodiment into an irregular shape.
Known methods can be used for deformed extrusion molding. A specific example of a deformed extrusion molding method is a method in which a resin composition is put into an extruder, kneaded while being heated inside, and extruded from a die for deformed extrusion to obtain an uncooled resin molded body. Then, the uncooled resin molded body is continuously guided to a cooling zone and cooled to obtain a deformed extruded product.

Another method involves performing melt kneading to obtain a resin composition, extruding the die of the kneader as a die for deformed extrusion to obtain an uncooled resin molded body, and then continuously guiding the uncooled resin molded body to a cooling zone to cool it and obtain a deformed extruded product.

The lower limit of the extrusion temperature during shape extrusion is preferably +5°C relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, and more preferably +10°C relative to the glass transition point if it is an amorphous resin. By controlling the lower limit within this range, the productivity of shape extrusion can be improved. The upper limit of the extrusion temperature during shape extrusion is preferably +100°C relative to the melting point if the thermoplastic resin in the resin composition is a crystalline resin, and more preferably +80°C, +70°C, and +60°C relative to the glass transition point if it is an amorphous resin. By controlling the upper limit within this range, the deterioration of cellulose fine fibers can be suppressed, thus maintaining the mechanical properties of the resin composition, and the drawdown of the resin between the shape extrusion die and the cooling zone can be suppressed, resulting in good dimensional accuracy of the shape extruded molded product.

There are no particular restrictions on the cross-sectional shape of the irregularly shaped extruded product, but sheet-like, pipe-like, tubular-like, and angular shapes are preferred. In the case of a sheet-like shape, the sheet thickness can be 0.2 to 50 mm and the sheet width can be 10 to 1500 mm. In the case of a pipe-like or tubular shape, the thickness can be 0.1 to 30 mm and the inner diameter can be 1 to 1000 mm. In the case of an angular shape, the angle of the corner can be 30 to 150 degrees. The minimum radius of curvature on the valley side of the corner can be 0.1 mm.

<Materials for 3D printing>
A preferred application of the resin composition of this embodiment is as a 3D printing material. One aspect of the present invention provides a 3D printing material comprising the resin composition of this embodiment. The 3D printing material may be molded into a desired form selected from various forms such as pellets, filaments, and powders. In one embodiment, the 3D printing material has the form of a filament or powder.

The 3D printing material of this embodiment is advantageous in that, due to its ability to suppress cellulose nanofiber aggregation, it suppresses liquid dripping (drawdown) from the nozzle due to its own weight during 3D printing.

Known methods can be used to mold the resin composition into a 3D printing material of a desired form. For example, the filament may be monofilament or multifilament, but monofilament is preferred due to its ease of molding.

The diameter of the filamentous material is preferably 0.5 to 5.0 mm, more preferably 1.0 to 3.5 mm, and most preferably 1.5 to 3.0 mm. The length of the filamentous material is preferably more than 1 m, more preferably more than 10 m, more preferably more than 100 m, and most preferably more than 300 m. By controlling the shape of the filamentous material within this range, a wide range of applicable 3D printers can be selected, and it becomes possible to appropriately design the printing time, the size of the printed object, and the precision. In one embodiment, the length of the filamentous material may be 20,000 m or less.

In one embodiment, the filamentous molding material can be manufactured by heating and melting a resin composition, passing it through a pore such as a nozzle, cooling it, and winding it. The diameter of the pore can be appropriately selected according to the diameter of the filament and the winding speed, but from the viewpoint of manufacturing efficiency and the frequency of thread breakage defects, it is preferably 0.5 to 10.0 mm, more preferably 0.8 to 5.0 mm, and most preferably 1.0 to 3.0 mm. As for the cooling method, known methods such as air cooling and water cooling can be appropriately selected, but from the viewpoint of preventing water absorption due to the hydrophilicity of cellulose nanofibers, air cooling is preferred. From the viewpoint of manufacturing efficiency and the frequency of thread breakage defects, the winding speed of the filament is preferably 0.1 to 10 m/sec, more preferably 0.15 to 5 m/sec, and most preferably 0.2 to 1 m/sec. The manufacturing apparatus for the filamentous molding material and the manufacturing apparatus for the resin composition may be the same or different.

The particle size, particle shape, and aspect ratio of the powdered 3D printing material can be appropriately selected depending on the 3D printer used. In one embodiment, the particle size is preferably 1 to 10,000 μm, more preferably 10 to 500 μm, and most preferably 30 to 200 μm, from the viewpoint of handling as a 3D printing material and surface smoothness of the printed object. The particle shape may be spherical or irregular, but an irregular shape is preferred from the viewpoint of suppressing voids during printing. The aspect ratio is preferably 1.001 to 3.0, preferably 1.01 to 2.0, and most preferably 1.1 to 1.8, from the viewpoint of suppressing voids by reducing the gaps between particles.

In one embodiment, a powdered molding material can be produced by grinding or reprecipitating a resin composition. The method of grinding the resin composition is not particularly limited, but may include wet grinding, dry grinding, low-temperature grinding, freeze-drying, and heat grinding. A grinding medium may be used for the purpose of controlling the shape of the powdered molding material.

<Sculpture>
One aspect of the present invention provides a molded object formed by 3D printing using a resin composition (e.g., resin composition pellets) or a 3D printing material according to this embodiment. Another aspect of the present invention also provides a method for manufacturing a molded object, which includes the step of 3D printing using a resin composition or a 3D printing material according to this embodiment. Examples of 3D printing methods include fused deposition modeling (FDM), stereolithography (SLA), material jetting, powder bonding, and powder bed fusion. When using a filamentous material, FDM is preferred, and when using a powdered material, powder bonding and powder bed fusion are preferred.

<Applications of 3D printing materials and printed objects>
The molded object can be used as is for various applications, or it can be molded into a desired shape, either alone or in combination with other components, to produce a desired molded product. The method of combining components and the molding method are not particularly limited and may be selected according to the desired molded product. The molding method is not limited to these, but methods such as cutting molding and foam molding can be used. The molded object or molded product is useful as a substitute for steel plates, fiber-reinforced plastics (e.g., carbon fiber reinforced plastics, glass fiber reinforced plastics, etc.), resin composites containing inorganic fillers, etc. Suitable applications for 3D printing materials, molded objects, or molded products include industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

The resulting molded products can be used in a variety of applications, including automotive parts, electrical and electronic components, building materials, household goods, cosmetic and medical components, rails, pipes, sashes, door frames, window frames, handrails, decking materials, fences, and various other building materials.

Specifically, automotive parts include interior components such as inner handles, fuel trunk openers, seat belt buckles, assist wraps, various switches, knobs, levers, and clips; electrical system components such as meters and connectors; in-vehicle electrical and electronic components such as audio equipment and car navigation equipment; metal-contacting components such as window regulator carrier plates; and mechanical components such as door lock actuator components, mirror components, wiper motor system components, and fuel system components.

Electrical and electronic components include parts or components of equipment made of resin molded bodies with numerous metal contacts, such as audio equipment, video equipment, or office automation equipment such as telephones, photocopiers, fax machines, word processors, and computers, as well as parts or components of toys. Specifically, these include chassis, gears, levers, cams, pulleys, and bearings.

Furthermore, it is suitably used in a wide range of everyday life, cosmetic, and medical-related parts, including building materials and plumbing components such as lighting fixtures, doors and windows, pipes, cocks, faucets, and toilet-related equipment parts; fasteners; stationery; lip balm and lipstick containers; washers; water purifiers; spray nozzles; spray containers; aerosol containers; general containers; and syringe needle holders.

Among these, it is more preferably used in gears, which are subjected to high temperatures and heavy loads.

The tensile stress (modulus) (M100) at 100% elongation of the resin composition or resin molded article may, in one embodiment, be 2.0 MPa or more, 3.0 MPa or more, or 4.0 MPa or more, and in one embodiment, it may be 10.0 MPa or less, 9.0 MPa or less, or 8.0 MPa or less.

The tensile stress (M300) of the resin composition or resin molded article at 300% elongation may, in one embodiment, be 3.0 MPa or more, or 5.0 MPa or more, or 6.0 MPa or more, and in one embodiment, it may be 20.0 MPa or less, or 15.0 MPa or less, or 13.0 MPa or less.

The ratio (M300/M100) of the tensile stress at 300% elongation (M300) to the tensile stress at 100% elongation (M100) of the resin composition or resin molded article may, in one embodiment, be 1.3 or more, or 1.4 or more, or 1.5 or more, and in one embodiment, it may be 2.0 or less, or 1.8 or less.

The storage modulus of the resin composition or resin molded article may, in one embodiment, be 2.0 MPa or higher, or 2.5 MPa or higher, and in another embodiment, it may be 4.0 MPa or lower, or 3.5 MPa or lower, or 3.0 MPa or lower.

The loss tangent of the resin composition or resin molded article may, in one embodiment, be 0.18 or less, or 0.15 or less, or 0.10 or less, and in one embodiment, it may be 0.02 or more, or 0.03 or more, or 0.04 or more.
The above storage modulus and loss tangent are values measured using a rheometer in a torsional manner at 50°C and 10Hz.

≪Resin molded product≫
One aspect of the present invention provides a resin molded article obtained by molding the resin composition of this embodiment. The resin molded article may have various shapes. The molded article can be used in a wide range of applications, such as industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing members, containers and packaging members, etc. Examples of applications include automotive parts (e.g., exterior parts such as tires, bumpers, fenders, door panels, various moldings, emblems, engine hoods, wheel caps, roofs, spoilers, various aero parts, and interior parts such as instrument panels, console boxes, and trim), battery parts (automotive secondary battery parts, lithium-ion secondary battery parts, fuel cases for solid methanol batteries, fuel cell piping, etc.), electronic and electrical equipment parts (e.g., various computers and their peripherals, junction boxes, various connectors, various office automation equipment, televisions, video players, disc players, chassis, refrigerators, air conditioners, LCD projectors, etc.), household goods (shoe outsoles, etc.), vibration-damping rubber, conveyor belts, and other molded products.

This disclosure also includes the following items:
≪Item A≫
[Item 1]
A resin composition comprising an acid-modified styrene elastomer, a styrene elastomer, and cellulose nanofibers,
A resin composition in which the total amount of the acid-modified styrene elastomer and the styrene elastomer is 60% by mass or more of the resin composition as 100% by mass.
[Item 2]
The resin composition according to item 1, wherein the acid-modified styrene elastomer and the styrene elastomer are compatible.
[Item 3]
The resin composition according to item 1 or 2, comprising 0.5 to 50 parts by mass of the acid-modified styrene elastomer per 100 parts by mass of the styrene elastomer.
[Item 4]
A resin composition according to any one of items 1 to 3, comprising 0.5 to 250 parts by mass of the styrene-based elastomer per 1 part by mass of the cellulose nanofiber.
[Item 5]
A resin composition according to any one of items 1 to 4, comprising 0.5 to 45 parts by mass of the acid-modified styrene elastomer per 1 part by mass of the cellulose nanofiber.
[Item 6]
A resin composition according to any one of items 1 to 5, comprising 0.5% to 50% by mass of the acid-modified styrene elastomer.
[Item 7]
A resin composition according to any one of items 1 to 6, comprising 10% to 98.8% by mass of the styrene-based elastomer.
[Item 8]
A resin composition according to any one of items 1 to 7, comprising 0.1% to 20% by mass of the cellulose nanofibers.
[Item 9]
The resin composition according to any one of items 1 to 8, wherein the acid modification rate of the acid-modified styrene elastomer is 0.2% by mass to 2.5% by mass.
[Item 10]
The resin composition according to any one of items 1 to 9, wherein the styrene-based elastomer is an unmodified product.
[Item 11]
The resin composition according to any one of items 1 to 10, wherein the acid-modified styrene elastomer is an acid-modified product of a styrene elastomer that is an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated thereof.
[Item 12]
The resin composition according to any one of items 1 to 11, wherein the styrene-based elastomer is an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated product thereof.
[Item 13]
The resin composition according to any one of items 1 to 12, wherein the melt mass flow rate of the styrene-based elastomer at 230°C and 2.16 kg is 20 g/10 min or less.
[Item 14]
The resin composition according to any one of items 1 to 13, wherein the styrene unit ratio of the acid-modified styrene elastomer is 10% by mass to 45% by mass.
[Item 15]
The resin composition according to any one of items 1 to 14, wherein the styrene unit ratio of the styrene-based elastomer is 10% by mass to 45% by mass.
[Item 16]
The resin composition according to any one of items 1 to 15, wherein the ratio of the styrene unit ratio of the styrene-based elastomer to the styrene unit ratio of the acid-modified styrene-based elastomer (styrene ratio of the styrene-based elastomer / styrene ratio of the acid-modified styrene-based elastomer) is 0.3 to 2.5.
[Item 17]
The resin composition according to any one of items 1 to 16, wherein the number average molecular weight of the acid-modified styrene elastomer is 10,000 to 500,000, and the number average molecular weight of the styrene elastomer is 10,000 to 500,000.
[Item 18]
The resin composition according to any one of items 1 to 17, wherein the ratio of the styrene unit ratio to the acid modification rate (styrene unit ratio / acid modification rate) in the acid-modified styrene elastomer is 5 to 90.
[Item 19]
The resin composition according to any one of items 1 to 18, wherein the amount of acid-modified groups in the acid-modified styrene elastomer is 0.2% to 5.0% by mass, relative to 100% by mass of the cellulose nanofibers.
[Item 20]
The resin composition according to any one of items 1 to 19, wherein the number-average fiber diameter of the cellulose nanofibers is 2 nm to 1000 nm.
[Item 21]
The resin composition according to any one of items 1 to 20, wherein the thermal decomposition initiation temperature of the cellulose nanofiber is 250°C or higher.
[Item 22]
The resin composition according to any one of items 1 to 21, wherein the specific surface area of the cellulose nanofibers is 10 ^m² /g to 200 ^m² /g.
[Item 23]
A resin composition according to any one of items 1 to 22, further comprising a polyoxyethylene unit-containing polymer.
[Item 24]
A resin composition according to any one of items 1 to 23, further comprising a liquid polymer.
[Item 25]
A method for producing a resin composition as described in any of items 1 to 24,
A method comprising heating and kneading a mixture containing the acid-modified styrene elastomer, the styrene elastomer, and the cellulose nanofiber.
[Item 26]
A resin molded article obtained by molding a resin composition described in any of items 1 to 24.
[Item 27]
A resin molded product as described in item 26, which is a deformed extruded product.
[Item 28]
A method for manufacturing a deformed extruded product,
A method comprising the step of extruding a resin composition described in any of items 1 to 24 into a deformed shape.
[Item 29]
A 3D printing material comprising a resin composition described in any of items 1 to 24.
[Item 30]
A 3D printing material as described in item 29, having the form of a filament or powder.
[Item 31]
A molded object obtained by 3D printing using a resin composition described in any of items 1 to 24 or a 3D printing material described in item 29 or 30.
[Item 32]
A method for manufacturing a molded object,
A method comprising the step of fabricating a resin composition described in any of items 1 to 24 or a 3D printing material described in item 29 or 30 using a 3D printer.

≪Item B≫
[Item 1]
A resin composition comprising a styrene-based elastomer and a tack inhibitor containing cellulose nanofibers.
[Item 2]
The resin composition according to item 1, comprising 10% by mass or more of the styrene-based elastomer.
[Item 3]
The resin composition according to item 1 or 2, comprising 0.1% to 20% by mass of the cellulose nanofibers.
[Item 4]
A resin composition according to any one of items 1 to 3, further comprising an acid-modified styrene elastomer.
[Item 5]
The resin composition according to any one of items 1 to 4, wherein the styrene-based elastomer is an unmodified product.
[Item 6]
A resin composition according to any one of items 1 to 5, comprising 0.5 to 250 parts by mass of the styrene-based elastomer per 1 part by mass of the cellulose nanofiber.
[Item 7]
The resin composition according to any one of items 1 to 6, wherein the styrene-based elastomer is an aromatic vinyl compound-conjugated diene compound block copolymer or a hydrogenated product thereof.
[Item 8]
The resin composition according to any one of items 1 to 7, wherein the MFR of the styrene-based elastomer at 230°C and 2.16 kg is 20 g/10 min or less.
[Item 9]
The resin composition according to any one of items 1 to 8, wherein the styrene unit ratio of the styrene-based elastomer is 10 mol% to 40 mol%.
[Item 10]
The resin composition according to any one of items 1 to 9, wherein the number average molecular weight of the styrene-based elastomer is 10,000 to 500,000.
[Item 11]
The resin composition according to any one of items 1 to 10, wherein the number-average fiber diameter of the cellulose nanofibers is 2 nm to 1000 nm.
[Item 12]
The resin composition according to any one of items 1 to 11, wherein the thermal decomposition initiation temperature of the cellulose nanofiber is 250°C or higher.
[Item 13]
The resin composition according to any one of items 1 to 12, wherein the specific surface area of the cellulose nanofibers is 10 ^m² /g to 200 ^m² /g.
[Item 14]
A resin composition according to any one of items 1 to 13, further comprising a dispersant.
[Item 15]
The resin composition according to item 14, wherein the dispersant is a polyoxyethylene unit-containing polymer.
[Item 16]
A resin composition according to any one of items 1 to 15, further comprising a liquid polymer.
[Item 17]
A method for producing a resin composition as described in any of items 1 to 16,
A method comprising a kneading step of heating and kneading a mixture containing a styrene-based elastomer and cellulose nanofibers.
[Item 18]
The method according to item 17, wherein the cellulose nanofibers subjected to the kneading step are a dry body with a liquid medium content of 7% by mass or less.
[Item 19]
A resin molded article obtained by molding a resin composition described in any of items 1 to 16.
[Item 20]
A resin molded product as described in item 19, which is a deformed extruded product.
[Item 21]
A method for manufacturing a deformed extruded product,
A method comprising the step of extruding a resin composition described in any of items 1 to 16 into a deformed shape.
[Item 22]
A 3D printing material comprising a resin composition described in any of items 1 to 16.
[Item 23]
A 3D printing material as described in item 22, having the form of a filament or powder.
[Item 24]
A molded object obtained by 3D printing using a resin composition described in any of items 1 to 16 or a 3D printing material described in item 22 or 23.
[Item 25]
A method for manufacturing a molded object,
A method comprising the step of fabricating a resin composition described in any of items 1 to 16 or a 3D printing material described in item 22 or 23 using a 3D printer.

The following describes illustrative embodiments of the present invention with reference to examples, but the present invention is not limited to these examples.

≪Evaluation Method≫
<Acid-modified styrene elastomers and styrene elastomers>
[Acid denaturation rate (maleinization rate)]
The values shown are from the product catalog.

[Styrene unit ratio]
The values shown are from the product catalog.

[MFR at 230°C, 2.16 kg]
The values shown are from the product catalog.

<Liquid Polymer>
[Viscosity at 25°C]
The viscosity of the rubber was measured using a B-type viscometer.

<Cellulose nanofiber>
The following evaluations were conducted on cellulose nanofibers.
[Fabrication of porous sheets]
First, the concentrated cake was added to tert-butanol and then dispersed using a mixer or similar device until no aggregates remained. The concentration was adjusted to 0.5% by mass for every 0.5 g of cellulose nanofiber solids. 100 g of the resulting tert-butanol dispersion was filtered on filter paper. The filtrate was not removed from the filter paper, but sandwiched between two larger sheets of filter paper, and the edges of the larger sheets were pressed down with weights while drying in a 150°C oven for 5 minutes. After that, the filter paper was removed to obtain a porous sheet with minimal distortion. Sheets with an air permeability resistance of 100 sec/100 ml or less per 10 g/ ^m² of sheet basis were selected as porous sheets and used as measurement samples.
After measuring the basis weight W (g/ ^m² ) of the sample, which had been left standing for one day in an environment of 23°C and 50% RH, the air permeability resistance R (sec/100ml) was measured using a Wangyan-type air permeability resistance tester (manufactured by Asahi Seiko Co., Ltd., model EG01). At this time, the value per 10 g/ ^m² basis weight was calculated according to the following formula.
Air permeability resistance per 10 g/ ^m² (sec/100 ml) = R/W × 10

[Weight-average molecular weight (Mw), number-average molecular weight (Mn), and Mw/Mn ratio]
0.88 g of porous sheet was weighed, cut into small pieces with scissors, lightly stirred, and then 20 mL of pure water was added and left for 1 day. Next, the water and solids were separated by centrifugation. Then 20 mL of acetone was added, lightly stirred, and left for 1 day. Next, the acetone and solids were separated by centrifugation. Then 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. After separating the N,N-dimethylacetamide and solids again by centrifugation, 20 mL of N,N-dimethylacetamide was added, lightly stirred, and left for 1 day. The N,N-dimethylacetamide and solids were separated by centrifugation, and 19.2 g of N,N-dimethylacetamide solution, prepared so that lithium chloride was 8 mass percent, was added to the solids, stirred with a stirrer, and visually confirmed to be dissolved. The solution containing dissolved cellulose nanofibers was filtered through a 0.45 μm filter, and the filtrate was used as a sample for gel permeation chromatography. The equipment and measurement conditions used are as follows.
Equipment: Tosoh Corporation HLC-8120
Column: TSKgel SuperAWM-H (6.0 mm I.D. × 15 cm) × 2 Detector: RI detector Eluent: N,N-dimethylacetamide (lithium chloride 0.2%)
Flow rate: 0.6 mL/min Calibration curve: Pullulan equivalent

[Average content of alkali-soluble polysaccharides]
The alkali-soluble polysaccharide content was determined for cellulose nanofibers by subtracting the α-cellulose content from the holocellulose content (Wise method), using the method described in the non-patent literature (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000). The alkali-soluble polysaccharide content was calculated three times for each sample, and the number average of the calculated alkali-soluble polysaccharide content was taken as the average alkali-soluble polysaccharide content of the cellulose nanofibers.

[Average content of acid-insoluble components]
The acid-insoluble components were quantified using the Claesson method described in a non-patent document (Wood Science Experiment Manual, edited by the Japan Wood Research Society, pp. 92-97, 2000) for cellulose nanofibers. Absolutely dried cellulose nanofibers were accurately weighed, placed in a designated container, and 72% by mass concentrated sulfuric acid was added. After pressing the contents uniformly with a glass rod, the mixture was autoclaved to dissolve the cellulose and hemicellulose in the acid solution. After cooling, the contents were filtered through glass fiber filter paper to obtain the acid-insoluble components as residue. The acid-insoluble component content was calculated from the weight of these components, and the number average of the acid-insoluble component content calculated for three samples was taken as the average acid-insoluble component content.

[Crystallization]
X-ray diffraction measurements were performed on the porous sheet, and the degree of crystallinity was calculated using the following formula.
Crystallinity (%) = [I ₍₂₀₀₎ - I _(amorphous) ] / I ₍₂₀₀₎ × 100
I ₍₂₀₀₎ : Diffraction peak intensity at the 200 plane (2θ = 22.5°) in a cellulose type I crystal. I _(amorphous) : Halo peak intensity due to amorphous material in a cellulose type I crystal, at a peak angle 4.5° lower than the diffraction angle of the 200 plane (2θ = 18.0°) (X-ray diffraction measurement conditions).
Device: MiniFlex (manufactured by Rigaku Corporation)
Operation axis 2θ/θ
Radiation source CuKα
Measurement method: Continuous; Voltage: 40kV
Current 15mA
Starting angle 2θ=5°
Ending angle 2θ = 30°
Sampling width 0.020°
Scan speed: 2.0°/min
Sample: A porous sheet is attached to the sample holder.

[Number average fiber diameter]
The concentrated cake was diluted with tert-butanol to 0.01% by mass, dispersed using a high-shear homogenizer (IKA, product name "Ultra-Turrax T18") under the following conditions: rotation speed 15,000 rpm for 3 minutes, cast onto an osmium-deposited silicon substrate, and air-dried. The resulting material was then measured using a high-resolution scanning electron microscope (Hitachi High-Tech Corporation, Regulus 8220). The measurement was performed by adjusting the magnification so that at least 100 cellulose nanofibers could be observed. The diameter (D) of 100 randomly selected cellulose nanofibers was measured, and the number-average fiber diameter was calculated by adding the average of the 100 cellulose nanofibers.

[Aspect Ratio]
The number-average fiber length L, number-average fiber diameter D, and number-average aspect ratio (L/D) of cellulose nanofibers in a resin composition are measured using an optical microscope according to the following procedure. A resin composition prepared by heating and kneading resin and cellulose nanofibers was used as a measurement sample, and the cellulose nanofibers in the resin were measured with an optical microscope while heating to 220°C on a hot stage. Specifically, the length and diameter of 200 randomly selected cellulose nanofibers were measured, and the ratio was calculated. Then, the number-average values of each were taken as the number-average fiber length L and number-average fiber diameter D, and the number-average aspect ratio (L/D) was calculated.

[Specific surface area]
Using a specific surface area and pore distribution analyzer (Nova-4200e, manufactured by Quantachrome Instruments), approximately 0.2 g of a porous sheet was dried under vacuum at 120°C for 5 hours. The amount of nitrogen gas adsorbed at the boiling point of liquid nitrogen was then measured at five points (multi-point method) within the range of relative vapor pressure (P/P ₀ ) between 0.05 and 0.2. The BET specific surface area ( ^m² /g) was then calculated using the analyzer's program.

[Thermal decomposition start temperature ( _TD )]
Thermal analysis of the porous sheet was performed using the following measurement method.
Equipment: Rigaku Thermo Plus EVO2
Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top.
Sample amount: 10 mg
Measurement conditions: In a nitrogen flow of 100 ml/min, the temperature was raised from room temperature to 150°C at a rate of 10°C/min, held at 150°C for 1 hour, and then continued to rise to 450°C at a rate of 10°C/min.
Method for calculating _TD : TD was calculated from a graph with temperature on the horizontal axis and weight retention percentage on the vertical axis. Starting from the weight of the porous sheet at 150°C (when moisture is almost completely removed) (weight loss of 0 wt%), the temperature was further increased to obtain a straight line passing through the temperatures at 1 wt% weight loss and 2 wt% weight loss. The temperature at the point where this straight line intersects with a horizontal line (baseline) passing through the starting point of 0 wt% weight loss was defined as the thermal decomposition onset temperature ( _TD ).

[1wt% weight loss temperature]
The temperature at which a 1 wt% weight loss occurred, used in the calculation of _TD, was defined as the 1 wt% weight loss temperature.

[250℃ weight loss rate]
Equipment: Rigaku Thermo Plus EVO2
Sample: Circular pieces cut from a porous sheet were stacked in aluminum sample pans, with 10 mg of each piece placed on top.
Sample amount: 10 mg
Measurement conditions: In a nitrogen flow of 100 ml/min, the temperature was raised from room temperature to 150°C at a rate of 10°C/min, held at 150°C for 1 hour, then raised from 150°C to 250°C at a rate of 10°C/min, and held at 250°C for 2 hours. The weight W0 at the time of reaching 250°C was used as the starting point, and the weight after holding at 250°C for 2 hours was defined as W1, which was calculated using the following formula.
250℃ weight loss rate (%): (W0-W1)/W0}×100

[Weight increase rate of cellulose nanofibers separated from resin composition using THF]
Separating cellulose nanofibers from a resin composition can be easily performed by methods common to those skilled in the art. The separation was carried out by the following method: Using approximately 1.5 g of fragments of the resin composition, the resin fragments were dissolved in 70 ml of THF, and the soluble components (resin) and insoluble components (cellulose nanofibers and resin adsorbed on the fiber surface) were separated. After filtering the insoluble components through filter paper, the mixture was dried in a vacuum dryer at 80°C for 3 hours to concentrate it, and the weight of the insoluble components was measured. The weight increase rate of cellulose nanofibers was calculated using the following formula. Note that the theoretical weight below is the initial weight of the cellulose nanofibers.
Weight increase rate of cellulose nanofibers (%) = (Weight of insoluble matter - Theoretical weight of cellulose nanofibers contained in the fragment) ÷ Theoretical weight of cellulose nanofibers contained in the fragment × 100

<Resin composition>
[Degree of whitening at fracture (void amount)]
Using specimens tested according to the JIS K-6251 tensile test method, the fracture site (2 mm in the ND direction, 3 mm in the TD direction, and 4 mm in the MD direction) was observed in the MD/TD direction cross-section using X-ray CT.
Equipment: Bruker X-CT Skyscan 1272
<Conditions> Tube voltage: 40kV, Tube current: 100μA, Pixel count: 2k (2452×1640 pixels), Pixel resolution: 2.4μm, Number of integrations: 4, Scan: every 0.4°, Analysis processing: Smoothing (Kuwahara filter 2 pixels)
Next, the observed images were binarized to extract the void areas, and the percentage of the total void volume per unit volume was quantified.

(Conditions for binarizing void areas)
Binarization 0 - 35 (global range: 0 - 255), removal of objects smaller than 4 voxels, and removal of objects larger than 50 pixels in the x and y cross-sections, considering them to be foreign matter or artifacts derived therefrom (evaluation criteria).
Poor: 1% or more Acceptable: 0.5% or more but less than 1% Good: 0.02% or more but less than 0.5% Excellent: Less than 0.02%

[Tensile stress at 400% strain, tensile modulus of elasticity at 50-100% strain, maximum tensile stress, strain]
According to the tensile test method of JIS K-6251, tensile strength, tensile stress at 50% elongation (50% modulus), tensile stress at 100% elongation (100% modulus), and tensile stress at 400% elongation (400% modulus) were measured, and the tensile stress at 400% strain, the tensile modulus of elasticity at 50-100% strain (the value obtained by dividing the increment of 100% modulus relative to 50% modulus by the strain increment (100% - 50%)), the maximum tensile stress, and the strain at fracture were determined.

[Colorability]
The color of the molded dumbbells was visually evaluated.
(Evaluation criteria)
Poor: Caramel colored Acceptable: Light caramel colored Good: Milky white Excellent: White or transparent

[Surface fuzziness of the strand]
The surface condition of the extruded strands was visually evaluated.
(Evaluation criteria)
Poor: No smooth areas, severe surface irregularities. Good: Surface is roughly half smooth and half irregular. Excellent: Slight fuzziness on the surface. Superb: No fuzziness at all.

[Tuckability]
The tack strength was measured using a TAC-II tacking tester manufactured by Resca Corporation. The measurement mode used was Constant Load, which involves pushing the probe up to a set pressure value and continuously controlling the pressure value to be maintained until a set time has elapsed.
Specifically, a stainless steel probe with a flat surface area of 19.625 ^mm² was brought into contact with the surface of the sample under the following conditions: probe movement speed: 120 mm/min, applied pressure (load): 600 gf, and pressurization time: 60 seconds. The probe was then pulled upwards at a probe movement speed (detachment speed): 600 mm/min. The tack peak value on the surface of the resin composition was measured 10 times using a probe tack test, and the average value of the 10 measurements was divided by the area of the probe's flat surface to determine the tack strength. The measurements were performed at 23°C.

[Tensile stress, maximum tensile stress, and strain at 400% strain]
Tensile tests were performed using ISO 37 type 3 specimens at a temperature of 23°C and a relative humidity of 50% at a tensile speed of 5 mm/min. The arithmetic mean of five data points—tensile stress at 400% strain, maximum tensile stress, and strain at fracture—was calculated.

≪Materials used≫
<Styrene-based elastomer>
SEBS, manufactured by Asahi Kasei Corporation, ToughTec H1062, MFR: 4.1 g/10 min (230°C, 2.16 kg)

<Acid-modified styrene elastomer>
Acid-modified styrene elastomer 1: Maleic acid-modified SEBS, manufactured by Asahi Kasei Corporation, ToughTec M1943, MFR: 6.5 g/10 min (230°C, 2.16 kg)
Acid-modified styrene elastomer 2: Maleic acid-modified SEBS, manufactured by Asahi Kasei Corporation, ToughTec M1913, MFR: 6.5 g/10 min (230°C, 2.16 kg)
Acid-modified styrene elastomer 3: Maleic acid-modified SEBS, manufactured by Asahi Kasei Corporation, ToughTec M1911, MFR: 4.2 g/10 min (230°C, 2.16 kg)

<Cellulose nanofiber (unmodified CNF)>
Three parts by mass of cotton linter pulp were immersed in 27 parts by mass of water and dispersed using a pulper. Thirty parts by mass of the pulper-treated cotton linter pulp slurry (of which three parts by mass were cotton linter pulp) were dispersed in water with 170 parts by mass of water (solid content 1.5% by mass), and the aqueous dispersion was beaten for 30 minutes using an SDR14 type laboratory refiner (pressure type disk type) manufactured by Aikawa Iron Works Co., Ltd., with a clearance between disks of 1 mm. Subsequently, the dispersion was thoroughly beaten under conditions where the clearance was reduced to a level close to zero to obtain a beaten aqueous dispersion (solid content concentration: 1.5% by mass). The obtained beaten aqueous dispersion was then subjected to 10 micronization treatments using a high-pressure homogenizer (NSO15H manufactured by Nilo Soavi (Italy)) at an operating pressure of 100 MPa to obtain a cellulose nanofiber slurry (solid content concentration: 1.5% by mass). The mixture was then concentrated to a solid content of 10% by mass using a dehydrator to obtain a cellulose nanofiber cake. The properties of the cellulose nanofiber are as follows.
Weight average molecular weight (Mw): 380000
Number average molecular weight (Mn): 80000
Average content of alkali-soluble polysaccharides: 3.8%
Average content of acid-insoluble components: 3.1%
Crystallinity: 85%
Number-average fiber diameter: 75 nm
Specific surface area: 34m ² /g
Thermal decomposition start temperature (T _D ): 283°C
1wt% weight loss temperature: 297℃
250℃ weight loss rate: 2.8%

<Dispersant>
Polyethylene glycol: PEG6000, manufactured by Sanyo Chemical Industries, Ltd.

<Liquid Polymer>
Liquid polybutadiene: RICON 184, manufactured by Clay Valley, viscosity at 25°C: 75,000 mPa·s

Manufacturing of resin compositions
<Example 1>
Cellulose nanofiber cake, RICON 184, and PEG6000 were blended in a solid weight ratio of 7:4:3. The mixture was stirred in a Kodaira Seisakusho Co., Ltd. planetary mixer (model: ACM-5LVT: paddle type) under the conditions of a jacket temperature of 80°C and 307 rpm, while the pressure was reduced to -90 kPa using a vacuum pump. Vacuum drying was carried out until the product temperature reached 70°C to obtain cellulose nanofiber powder. The obtained cellulose nanofiber powder, SEBS, and acid-modified styrene elastomer 1 were blended in the proportions shown in Table 1. The mixture was melted for 5 minutes at 200°C and 200 rpm using a batch-type twin-screw kneader (DSM Explorer), and test specimens (ISO 37 type 3) were prepared using a dedicated tabletop injection molding machine (DSM) at a mold temperature of 80°C.

<Examples 2-11, Comparative Examples 1-3>
A resin composition was obtained in the same manner as in Example 1, except that the formulation was changed as shown in Table 1.

The resin composition relating to this disclosure can form molded articles with good physical properties and can therefore be suitably applied to a wide range of applications, such as industrial machine parts, general machine parts, automobile, railway, vehicle, ship, and aerospace-related parts, electronic and electrical components, building and civil engineering materials, household goods, sports and leisure goods, wind turbine housing components, containers and packaging components, etc.

Claims (22)

A powder for manufacturing styrene-based elastomer-containing elastomer compositions,
Cellulose nanofibers and
A dispersant containing polyalkylene glycol, which is a hydrophilic polymer ,
Liquid polymer and
A powder containing [something]. The powder according to claim 1, wherein the dispersant is polyalkylene glycol. The powder according to claim 1, wherein the amount of the dispersant is 1 to 200 parts by mass per 100 parts by mass of the cellulose nanofiber. The powder according to claim 1, wherein the amount of the liquid polymer is 5 to 400 parts by mass per 100 parts by mass of the cellulose nanofiber. The powder according to claim 1, wherein the number-average fiber diameter of the cellulose nanofibers is 2 nm to 1000 nm. The powder according to claim 1, wherein the thermal decomposition initiation temperature of the cellulose nanofiber is 250°C or higher. The powder according to claim 1, wherein the specific surface area of the cellulose nanofibers is 10 ^m² /g to 200 ^m² /g. An elastomer composition comprising the powder described in claim 1, an acid-modified styrene-based elastomer, and a styrene-based elastomer. The elastomer composition according to claim 8, wherein the total amount of the acid-modified styrene-based elastomer and the styrene-based elastomer is 60% by mass or more of the elastomer composition as described above. The elastomer composition according to claim 8, wherein the amount of the acid-modified styrene elastomer is 0.5 to 50 parts by mass per 100 parts by mass of the styrene elastomer. The elastomer composition according to claim 8, wherein the acid modification rate of the acid-modified styrene-based elastomer is 0.2% by mass to 2.5% by mass. The elastomer composition according to claim 8, wherein the ratio of the styrene unit ratio of the styrene-based elastomer to the styrene unit ratio of the acid-modified styrene-based elastomer (styrene ratio of the styrene-based elastomer / styrene ratio of the acid-modified styrene-based elastomer) is 0.3 to 2.5. The elastomer composition according to claim 8, wherein the ratio of styrene units to the acid modification rate (styrene unit ratio / acid modification rate) in the acid-modified styrene elastomer is 5 to 90. The elastomer composition according to claim 8, wherein the amount of acid-modified groups in the acid-modified styrene-based elastomer is 0.2% to 5.0% by mass, relative to 100% by mass of the cellulose nanofibers. Cellulose nanofibers and
A dispersant containing polyalkylene glycol, which is a hydrophilic polymer ,
Liquid polymer and
Styrene-based elastomer and
An elastomer composition containing [the specified element]. The elastomer composition according to any one of claims 8 to 15, wherein the amount of the styrene-based elastomer is 0.5 to 250 parts by mass per 1 part by mass of the cellulose nanofiber. The elastomer composition according to any one of claims 8 to 15, comprising 0.1% to 20% by mass of the cellulose nanofibers. The elastomer composition according to any one of claims 8 to 15, wherein the styrene unit ratio of the styrene-based elastomer is 10% to 45% by mass. A method for producing an elastomer composition according to any one of claims 8 to 15,
A method comprising heating and kneading a mixture containing the styrene-based elastomer and the cellulose nanofiber. A molded article obtained by molding an elastomer composition according to any one of claims 8 to 15. A 3D printing material comprising the elastomer composition described in any one of claims 8 to 15. A molded object obtained by 3D printing an elastomer composition according to any one of claims 8 to 15.