JP7555096B2 - Cellulose fiber composition and method for producing the same, and method for producing a cellulose fiber composite composition - Google Patents

Description

The present invention relates to a cellulose fiber composition that exhibits high dispersibility and reinforcing effect in thermoplastic resins and rubbers, and a method for producing the same. The present invention also relates to a method for producing a cellulose fiber composite composition that has excellent mechanical properties and uses the cellulose fiber composition.

Cellulose fibers are inexpensive and have excellent mechanical properties and recyclability, so there are studies underway to develop technology to use them as reinforcing materials for thermoplastic resins and rubber, which are molding materials.
Cellulose fibers are usually handled in a wet state due to moisture absorption during storage and the use of water in processing steps such as pretreatment. Therefore, when cellulose fibers are combined with hydrophobic molding materials, it is necessary to remove the water. However, there is a problem that the hydroxyl groups of the cellulose fibers form hydrogen bonds during the water removal process, causing the fibers to strongly aggregate together. Strongly aggregated cellulose fibers do not disperse uniformly in the molding material, and instead cause the mechanical properties of the molded body to deteriorate.
Methods have been disclosed for improving the dispersibility of cellulose fibers in molding materials by preventing the aggregation of the cellulose fibers to achieve desired mechanical properties.

In Patent Document 1, a wetting agent selected from polyethylene glycol and/or polyhydric alcohol having an average molecular weight of 90 to 40,000 is added to a composite material containing fibers to prevent fiber aggregation and improve fiber dispersibility. However, the fiber dispersibility is insufficient, and the wetting agent, which acts as a plasticizer, is difficult to remove, so the effect of improving mechanical properties is insufficient.

In Patent Document 2, an aqueous suspension of cellulose is immersed in an excess of organic solvent and filtered, the water is removed to give cellulose swollen with the organic solvent, and the organic solvent is then removed to obtain a highly dispersible form of cellulose that does not aggregate or solidify. However, as the organic solvent is required in an amount of several tens to several hundreds of times the amount of cellulose and there are many work steps, a more efficient processing method is needed.

Patent Document 3 discloses that by preparing a resin composition containing a thermoplastic resin, cellulose nanofibers, a specific surface modifier, and a certain amount of an aprotic solvent with a boiling point of 100°C or higher, a sufficient amount of cellulose can be finely dispersed in the resin composition to achieve the desired mechanical properties of the resin molded body, thereby obtaining high mechanical properties and thermal properties. However, with this method, the cellulose nanofibers, surface modifier, and aprotic solvent are diluted in the thermoplastic resin, so the effect of inhibiting the aggregation of the cellulose nanofibers is insufficient, and as a result, the effect of improving the physical properties of the resulting resin molded body is not sufficient.

Special Publication No. 2015-532344 JP 2011-6551 A JP 2020-7492 A

The present invention aims to provide a cellulose fiber composition that is highly dispersible in thermoplastic resins and rubbers, which are molding materials, and has an excellent reinforcing effect on molded articles, a method for producing the same, and a method for producing a cellulose fiber composite composition that gives molded articles excellent mechanical properties.

As a result of extensive research to solve the above problems, the inventors discovered that by making a cellulose fiber composition by incorporating a small amount of a specific organic solvent into cellulose fibers, the dispersibility in thermoplastic resins and rubbers is improved, resulting in excellent reinforcing effects for molded articles, and thus completed the present invention.

That is, the present invention provides
<1> A cellulose fiber composition comprising 80 to 98 mass% of cellulose fibers (A), 1 to 20,000 ppm of an organic solvent (B), and the remainder being other components (C), wherein the organic solvent (B) satisfies the following conditions (1) to (4):
(1) The boiling point is 125 to 300°C.
(2) The solubility in 100 g of water at 25° C. is 5 g or more.
(3) The surface tension at 25°C is 20 to 36 mN/m.
(4) It does not have an active proton.
<2> The organic solvent (B) is at least one selected from the group consisting of (poly)ethylene glycol dialkyl ethers and (poly)propylene glycol dialkyl ethers,
The cellulose fiber composition according to <1>, characterized in that the alkyl group constituting the alkyl ether has 1 to 4 carbon atoms.
<3> The cellulose fiber composition according to <1>, wherein the cellulose fiber (A) is a cellulose fiber acylated with a carboxylic acid anhydride (D).
<4> A method for producing a cellulose fiber composition comprising 80 to 98 mass% of cellulose fibers (A), 1 to 20,000 ppm of an organic solvent (B), and the remainder being other components (C), wherein the organic solvent (B) satisfies the following conditions (1) to (4):
(1) The boiling point is 125 to 300°C.
(2) The solubility in 100 g of water at 25° C. is 5 g or more.
(3) The surface tension at 25°C is 20 to 36 mN/m.
(4) It does not have an active proton.
<5> A method for producing a cellulose fiber composite composition, comprising kneading the cellulose fiber composition according to any one of <1> to <3> with a thermoplastic resin and/or rubber (E) in a ratio of cellulose fiber (A):thermoplastic resin and/or rubber (E)=0.05 to 60:40 to 99.95 mass%.
It is.

According to the present invention, a cellulose fiber composition that has excellent reinforcing effects for thermoplastic resins and/or rubber can be obtained, and a cellulose fiber composite composition using the cellulose fiber composition is molded into a molded article that has excellent mechanical properties.

The following describes an embodiment of the present invention in detail. Note that the following description is an example of an embodiment of the present invention, and is not intended to be limiting.

<Cellulose fiber composition>
The cellulose fiber composition of the present invention comprises cellulose fibers (A), an organic solvent (B), and other components (C).

<Cellulose fiber (A)>
The cellulose fiber (A) may be any fiber containing cellulose, and the origin of the cellulose is not particularly limited, but examples thereof include fibers derived from plants such as wood, bamboo, hemp, jute, kenaf, cotton, and beet, mercerized cellulose fibers, regenerated cellulose fibers such as rayon and lyocell, and cellulose fibers produced by organisms such as microorganisms and sea squirts. Among these, preferred is wood, such as Sitka spruce, cedar, cypress, pine, eucalyptus, and acacia. In addition, paper and waste paper obtained from these raw materials that have been defibrated are also suitable for use as cellulose fibers. One or more types of cellulose fibers can be used in combination.

Pulp, which is one of the cellulose fibers obtained from fibers derived from the above plants, can be obtained by pulping cellulose fibers chemically, mechanically, or by using a combination of both. Examples of such pulps include chemical pulp (unbleached kraft pulp (UKP), bleached kraft pulp (BKP), sulfite pulp (SP)), semi-chemical pulp (SCP), chemi-ground pulp (CGP), chemi-mechanical pulp (CMP), groundwood pulp (GP), refiner mechanical pulp (RMP), thermo-mechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP). Among these pulps, unbleached kraft pulp (NUKP) or bleached kraft pulp (NBKP) derived from coniferous trees, which have high fiber strength, are particularly preferred.

The cellulose fiber (A) may be a cellulose fiber modified with a compound reactive to hydroxyl groups on the surface of the cellulose fiber. Examples of compounds reactive to hydroxyl groups on the surface of the cellulose fiber include carboxylic acid anhydrides, compounds having an isocyanate group, and epoxy compounds. Among the cellulose fibers modified with these compounds, cellulose fibers acylated with carboxylic acid anhydrides (D) are preferred because they have superior dispersibility and affinity to thermoplastic resins and/or rubbers (E) compared to unmodified cellulose fibers, and can further improve the mechanical properties when the cellulose fiber composite composition is molded into a molded product.

The carboxylic acid anhydride (D) is not particularly limited as long as it is a compound capable of acylating the cellulose fiber (A), but at least one selected from the group consisting of acetic anhydride, propionic anhydride, butyric anhydride, polybasic acid anhydrides having 6 to 50 carbon atoms, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, and maleic anhydride-modified diene polymers is preferred, and at least one selected from the group consisting of acetic anhydride, polybasic acid anhydrides having 6 to 50 carbon atoms, and maleic anhydride-modified diene polymers is more preferred.

There are no particular limitations on the polybasic acid anhydride having 6 to 50 carbon atoms, but those having 8 to 40 carbon atoms are preferred, those having 12 to 30 carbon atoms are more preferred, and those having 15 to 24 carbon atoms are most preferred.

The diene polymer that is the main component of the maleic anhydride modified diene polymer is not particularly limited, but specific examples include polyisoprene, polybutadiene, styrene-butadiene copolymer, polychloroprene, acrylonitrile-butadiene copolymer, (meth)acrylic acid (ester)-butadiene copolymer, isobutene-isoprene copolymer, vinylpyridine-butadiene copolymer, vinylpyridine-styrene-butadiene copolymer, and polynorbornene. Diene polymers also include those in which other monomers are used in combination, and these can be used alone or in combination of two or more. Polyisoprene and polybutadiene are preferred, and polybutadiene is more preferred. The polymerization method for the diene polymer is not particularly limited, and the diene monomer may contain a 1,2-addition component in addition to a 1,4-addition component during polymerization, resulting in the presence of a vinyl group in the side chain.

The cellulose fiber (A) content of the cellulose fiber composition must be 80 to 98% by mass. When producing a cellulose fiber composite composition, the content is preferably 90 to 98% by mass in order to efficiently knead a sufficient amount of cellulose fiber (A) with the thermoplastic resin and/or rubber (E). The cellulose fiber (A) used in the cellulose fiber composition may be previously finely divided.

<Organic Solvent (B)>
The organic solvent (B) must satisfy the following conditions (1) to (4).
(1) The boiling point is 125 to 300°C.
(2) The solubility in 100 g of water at 25° C. is 5 g or more.
(3) The surface tension at 25°C is 20 to 36 mN/m.
(4) It does not have an active proton.

Typically, during the drying process of cellulose fibers that contain water, an attractive force is generated between the cellulose fibers due to the surface tension of the water (Campbell effect), and the cellulose fibers approach each other during the drying process, and the hydroxyl groups form hydrogen bonds, causing the cellulose fibers to aggregate.
In the present invention, by preparing a cellulose fiber composition in which water contained in the cellulose fibers is replaced with an organic solvent (B) satisfying the above conditions (1) to (4) before kneading the cellulose fibers (A) with a thermoplastic resin and/or rubber (E), aggregation of the cellulose fibers (A) can be effectively reduced and dispersibility in the thermoplastic resin and/or rubber (E) can be improved. Although the mechanism by which the effect of the present invention is exerted by adding the organic solvent (B) is not clear, it is presumed that the organic solvent (B) is water-soluble and therefore has the effect of replacing water having a high surface tension to reduce the Campbell effect, and that the organic solvent (B) remains even after dehydration due to its higher boiling point than water, thereby relaxing the hydrogen bonds between the hydroxyl groups of the cellulose fibers (A).

The boiling point of the organic solvent (B) at normal pressure must be 125 to 300°C. If the boiling point of the organic solvent (B) is less than 125°C, the organic solvent (B) will be removed together with the water in the process of removing the water after mixing the cellulose fibers (A) dissolved by adding water with the organic solvent (B). As a result, the water present between the cellulose fibers (A) is not sufficiently replaced by the organic solvent (B) and no organic solvent (B) remains, making it impossible to prevent the aggregation of the cellulose fibers (A). The boiling point of the organic solvent (B) is preferably 140 to 260°C, more preferably 150 to 240°C.

The organic solvent (B) must have a solubility of 5 g or more in 100 g of water at 25°C. If the solubility is less than 5 g or more, the organic solvent will not be absorbed into the cellulose fibers (A) containing water, and aggregation of the cellulose fibers (A) cannot be prevented. The organic solvent (B) preferably has a solubility of 10 g or more in 100 g of water at 25°C, and more preferably 20 g or more.

The surface tension of the organic solvent (B) at 25°C must be 20 to 36 mN/m. If the surface tension exceeds 36 mN/m, even if the water present between the cellulose fibers (A) is replaced with the organic solvent (B), the organic solvent (B) will exhibit the Campbell effect, causing the hydroxyl groups to form hydrogen bonds with each other, resulting in strong aggregation of the cellulose fibers (A). As a result, good dispersibility and reinforcing properties in thermoplastic resins and/or rubbers cannot be obtained. The surface tension of the organic solvent (B) at 25°C is preferably 20 to 35 mN/m, more preferably 20 to 34 mN/m.

The organic solvent (B) does not have an active proton. If the organic solvent (B) has an active proton, it will not be able to relax the hydrogen bonds formed between the hydroxyl groups of the cellulose fibers (A), resulting in insufficient inhibition of aggregation of the cellulose fibers (A).

In addition to satisfying the above conditions (1) to (4), the organic solvent (B) preferably has an ether bond from the viewpoint of affinity with the cellulose fibers (A) and surface tension, and more preferably does not have a nitrogen atom or a sulfur atom. From the viewpoint of preventing aggregation of the cellulose fibers (A) and taking into consideration the solubility in water and boiling point, a particularly preferred organic solvent (B) is at least one selected from the group consisting of (poly)ethylene glycol dialkyl ethers and (poly)propylene glycol dialkyl ethers, in which the number of carbon atoms in the alkyl group constituting the alkyl ether is 1 to 4.

Preferred organic solvents (B) include (poly)ethylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, and polyethylene glycol dimethyl ether. Also, (poly)propylene glycol dialkyl ethers such as dipropylene glycol dimethyl ether and tripropylene glycol dimethyl ether.

By containing the organic solvent (B) in the cellulose fiber composition, the dispersibility of the cellulose fiber (A) in the thermoplastic resin and/or rubber (E) is improved when producing a cellulose fiber composite composition, and as a result, the cellulose fiber (A) can exhibit a high reinforcing effect. The content of the organic solvent (B) in the cellulose fiber composition needs to be 1 to 20,000 ppm. The amount of the organic solvent (B) contained in the cellulose fiber composition is measured using a gas chromatograph GC-2014 manufactured by Shimadzu Corporation.
If the organic solvent (B) content of the cellulose fiber composition is less than 1 ppm, the effect of improving the dispersibility of the cellulose fiber (A) as described above cannot be expected. If the organic solvent (B) content of the cellulose fiber composition is more than 20,000 ppm, the excess organic solvent (B) functions as a plasticizer during kneading with the thermoplastic resin and/or rubber (E), and the mechanical properties of the cellulose fiber composite composition are reduced. The organic solvent (B) content is preferably 5 to 19,000 ppm, more preferably 25 to 18,000 ppm, and most preferably 50 to 16,000 ppm. Since the presence of an excess of organic solvent (B) is accompanied by the risk of fire or explosion, it is preferable to keep the content to the minimum level at which the effects of the present invention can be fully obtained.

In order to grasp the dispersibility of the cellulose fiber composition in the thermoplastic resin and/or rubber (E), the amount of fiber aggregates contained in the cellulose fiber composition serves as a guide, and the smaller this amount is, the better the dispersibility tends to be.
The fiber aggregates in the cellulose fiber composition are preferably 30% by mass or less, more preferably 25% by mass or less, based on the cellulose fiber composition. It is possible to mechanically crush cellulose fibers (A) containing more than 30% by mass of fiber aggregates to reduce the fiber aggregates to 30% by mass or less. However, the cellulose fibers (A) obtained by such a process do not exhibit appropriate dispersibility, and the reinforcing effect of the thermoplastic resin and/or rubber (E) is inferior.
In the present invention, the fiber agglomerate refers to an agglomerate of a cellulose fiber composition that cannot pass through a metal sieve having an opening of 600 μm and a metal wire diameter of 400 μm.

<Other Components (C)>
The other component (C) is a distillable component other than the cellulose fibers (A) and the organic solvent (B), such as water that remains after not being completely removed during the production of the cellulose fiber composition. The content of the other component (C) in the cellulose fiber composition is the remainder obtained by subtracting the total of (A) and (B) from 100% by mass, where the total of (A) to (C) is taken as 100% by mass. It is preferable that the content of the other component (C) is as small as possible from the viewpoints of the dispersibility of the cellulose fibers (A) in the thermoplastic resin and/or rubber (E) during the production of the cellulose fiber composite composition and the contribution to improving the mechanical properties of the cellulose fibers (A).

The cellulose fiber composition of the present invention can be produced, for example, by adding an organic solvent (B) to cellulose fibers (A) in a wet state containing water, and heating under reduced pressure while stirring to distill off the water and organic solvent (B) until the content of cellulose fibers (A) in the cellulose fiber composition is 80% by mass or more. The amount of organic solvent (B) used is not particularly limited, but from the viewpoints of work efficiency and energy efficiency, it is preferable to use 7 to 50,000 parts by mass of organic solvent (B) per 100 parts by mass of cellulose fibers (A), more preferably 10 to 10,000 parts by mass, even more preferably 12 to 1,000 parts by mass, and most preferably 15 to 500 parts by mass.

<Method of producing cellulose fiber composite composition>
The cellulose fiber composite composition can be obtained by kneading the cellulose fiber composition with a thermoplastic resin and/or a rubber (E).

<Thermoplastic resin and/or rubber (E)>
The thermoplastic resin and/or rubber (E) is not particularly limited as long as it can be used as a molding material. In the present invention, the thermoplastic resin refers to a resin that softens when heated, and means a thermoplastic plastic or a thermoplastic elastomer (a polymer that exhibits rubber-like elasticity is called an elastomer). In addition, the rubber refers to a thermosetting resin (a resin that has the property of hardening by a chemical reaction when heat is applied) that is classified as an elastomer. Furthermore, in the present invention, the "thermoplastic resin and/or rubber (E)" is either a "thermoplastic resin", "rubber", or a "mixture of a thermoplastic resin and a rubber". The thermoplastic resin and/or rubber (E) may be used alone or in combination of two or more kinds.

Examples of thermoplastic resins include various polyolefins such as polyethylene and polypropylene; various polyamides such as polyamide 11 and polyamide 12; various polyesters such as polybutylene succinate and polylactic acid; various poly(meth)acrylates such as polymethyl methacrylate and polyethyl methacrylate; various polyethers such as polyoxymethylene; various polycarbonates such as polypropylene carbonate and polycarbonate diol; polystyrene; petroleum resins, coumarone resins; terpene resins; rosin resins; polyvinyl alcohol; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyurethane; polyvinyl chloride; and the like. Examples of thermoplastic elastomers include ester-based elastomers such as styrene-based elastomers and block copolymers of polybutylene terephthalate and polybutylene glycol; polyurethane elastomers; and polyamide elastomers. Among these, polyolefins, polystyrenes, ethylene-vinyl acetate copolymers, styrene-based elastomers, and ester-based elastomers are preferred, with polyolefins being particularly preferred.

Examples of rubber include rubber containing a diene compound in the raw material monomer, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluororubber, and modified products thereof. Among these, rubber containing a diene compound in the raw material monomer and modified products thereof are preferred. Examples of rubber containing a diene compound in the raw material monomer include natural rubber, synthetic polyisoprene, polychloroprene, polybutadiene, styrene-butadiene copolymer, styrene-isoprene copolymer, isobutylene-isoprene copolymer, styrene-isoprene-butadiene copolymer, acrylonitrile-butadiene copolymer, ethylene-propylene-diene copolymer, ethylene-butene-diene copolymer, ethylene-hexene-diene copolymer, ethylene-octene-diene copolymer, and modified products thereof. In particular, ethylene-propylene-diene copolymer is preferred.

From the viewpoint of moldability and mechanical properties, the cellulose fiber composite composition preferably contains cellulose fiber (A): thermoplastic resin and/or rubber (E) in a ratio of 0.05-60:40-99.95% by mass. It is more preferable that the cellulose fiber (A): thermoplastic resin and/or rubber (E) ratio be 0.1-55:45-99.9% by mass, and even more preferable that the cellulose fiber (A): thermoplastic resin and/or rubber (E) ratio be 0.5-51:49-99.5% by mass.

As a kneading method, a known kneading device can be used, such as a Labo Plastomill manufactured by Toyo Seiki Co., Ltd., a roll mill manufactured by Yasuda Seiki Seisakusho Co., Ltd., or a twin-screw extruder manufactured by Technovel Co., Ltd. The temperature during kneading is not particularly limited, but it is preferable to melt and knead the cellulose fiber (A) at a temperature equal to or higher than the melting point of the thermoplastic resin and/or rubber (E) used, since the fiber diameter of the cellulose fiber (A) becomes finer and the cellulose fiber (A) is more uniformly dispersed in the thermoplastic resin and/or rubber (E) and a higher reinforcing effect is exhibited.

The fact that the cellulose fibers (A) have been finely divided by melt kneading can be confirmed by forming the cellulose fiber composite composition into a thin film having a thickness of 0.1 mm and visually observing the thin film. In the present invention, the cellulose fibers (A) are considered to have been finely divided when they can no longer be visually recognized in the thin film.

The cellulose fiber composite composition of the present invention may contain other additives as long as they do not impair the effects of the present invention. Examples of other additives include stabilizers, compatibilizers, foaming assistants, inorganic fillers, and pigments. Stabilizers are used to prevent deterioration of the quality of the cellulose fiber (A) during storage and processing, and examples of such stabilizers include antioxidants, metal deactivators, ultraviolet absorbers, quenchers, light stabilizers, flame retardants, and antistatic agents.

The cellulose fiber composite composition of the present invention can be suitably used in fields requiring functions such as weight reduction, heat insulation, soundproofing, insulation, and shock absorption, and can be effectively used by molding it into parts suited to the intended use, for example, transportation equipment, electrical appliances, seals and packing materials, printing equipment, musical instruments, copying equipment, medical supplies, footwear, sporting goods, building materials, office supplies, heat insulation materials, sound absorbing materials, miscellaneous goods, containers, clothing, etc.

The following describes examples of the present invention. Note that the present invention is not limited to these examples.

The boiling points, solubility in 100 g of water (25°C), surface tension (25°C), and presence or absence of active protons of the organic solvents used in the examples are shown in Table 1.

In the table, "any ratio" means that the material can be mixed with water in any ratio.
The abbreviations in Tables 1 and 2 below represent the following solvents.
DEGDM: diethylene glycol dimethyl ether DEGDE: diethylene glycol diethyl ether DEGBM: diethylene glycol butyl methyl ether DPGDM: dipropylene glycol dimethyl ether EGMAc: ethylene glycol methyl ether acetate PEGDM: polyethylene glycol dimethyl ether ... manufactured by Toho Chemical Industry Co., Ltd., Hisorb (registered trademark, hereinafter sometimes abbreviated) MPM, average number of repeating units of glycol unit: 4.4
AC: Acetone EG: Ethylene glycol PGDM: Propylene glycol dimethyl ether DEGDB: Diethylene glycol dibutyl ether NMP: N-methyl-2-pyrrolidone DEGB: Diethylene glycol monobutyl ether

The evaluation method is as follows.
(1) Confirmation of the progress of the modification reaction The progress of the modification reaction was observed using a Fourier transform infrared spectrometer "Spectrum One" manufactured by Perkin Elmer Co., Ltd. Specifically, it was confirmed that the peak intensity derived from the stretching vibration of the carbonyl carbon and oxygen of the ester bond generated at 1650 to 1750 cm ^-1 increased as the modification reaction progressed.
(2) Measurement of non-volatile content The non-volatile content was measured using an infrared moisture meter (manufactured by Kett Electric Laboratory Co., Ltd.: "FD-620"). The set temperature was 150°C.
(3) Measurement of fiber aggregate content in cellulose fiber composition 4.0 g of the cellulose fiber composition was placed on a metal sieve with a mesh size of 600 μm and a metal wire diameter of 400 μm, and after vacuuming from below, the mass of the cellulose fiber composition that did not pass through the sieve and remained was divided by 4.0 g to measure the fiber aggregate content in the cellulose fiber composition. A fiber aggregate content in the cellulose fiber composition of 30 mass% or less is considered to be at a practical level.
(4) Measurement of flexural modulus The cellulose fiber composite composition was formed into a bar-shaped test piece as described in JIS standard K7171 using an injection molding machine, and the flexural modulus was measured in accordance with JIS K7171 using a universal material testing machine "Tensilon (registered trademark) RTM-50" manufactured by Orientec Co., Ltd. The flexural modulus is a mechanical property that indicates the hardness of a material, and a practical level is 2.5 GPa or more.
(5) Measurement of 50% modulus The sheeted cellulose fiber composite composition was crosslinked with peroxide and punched out to prepare a test piece with a length of 70 mm, a width of 5 mm, and a thickness of 1 mm. The 50% modulus of the obtained test piece was measured by a tensile test using a universal material testing machine "Tensilon (registered trademark) RTM-50" manufactured by Orientec Co., Ltd. The 50% modulus is a mechanical property that indicates the hardness of a material, and a practical level is 1.0 MPa or more.
(6) Evaluation of fiber diameter of cellulose fiber (A) in cellulose fiber composite composition 1.0 g of the cellulose fiber composite composition was formed into a thin film with a thickness of 0.1 mm, and the thin film was visually observed to evaluate whether the fiber diameter of the cellulose fiber (A) was fine or not. When the fiber diameter was so small that the cellulose fiber (A) was not visible in the thin film, it was judged as fine (good), and when the cellulose fiber (A) was visible, it was judged as not fine (fair).
(7) Measurement of Content of Organic Solvent (B) The amount of organic solvent (B) contained in the cellulose fiber composition was measured using a gas chromatograph GC-2014 manufactured by Shimadzu Corporation.

[Production of cellulose fiber composition]
(Production Example 1)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of water-containing bleached softwood kraft pulp (hereinafter referred to as NBKP) (100.0 parts by mass of nonvolatile content, where all nonvolatile content is cellulose fiber (A), the same applies below) and 100.0 parts by mass of diethylene glycol dimethyl ether were mixed, and the mixture was heated at 120°C for 3 hours under a vacuum of -0.090 MPa or less while stirring to distill off the water and organic solvent, thereby obtaining a cellulose fiber composition (X-1). The composition of the cellulose fiber composition (X-1) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Example 2)
500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol diethyl ether were mixed in a reaction vessel equipped with a stirrer, a thermometer, and a distiller, and the mixture was heated at 130°C for 6 hours under a vacuum of -0.090 MPa or less while stirring to distill off the water and organic solvent, thereby obtaining a cellulose fiber composition (X-2). The composition of the cellulose fiber composition (X-2) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Examples 3 to 5, 7)
Cellulose fiber compositions X-3 to X-5, and X-7 were obtained in the same manner as in Production Example 2, except that the organic solvent (B) was changed to one shown in Table 1. The compositions of the cellulose fiber compositions (X-3 to X-5, X-7) and the contents of fiber aggregates in the cellulose fiber compositions are shown in Table 2.

(Production Example 6)
500.0 parts by mass of water-containing bleached softwood kraft pulp (hereinafter referred to as NBKP) (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of polyethylene glycol dimethyl ether (Hisorb MPM manufactured by Toho Chemical Industry Co., Ltd.) were mixed in a reaction vessel equipped with a stirrer, a thermometer, and a distiller, and heated at 130°C for 46 hours at a vacuum degree of -0.090 MPa or less while stirring to distill off the water and organic solvent, thereby obtaining a cellulose fiber composition (X-6). The composition of the cellulose fiber composition (X-6) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Example 8)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol dimethyl ether were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 600.0 parts by mass of acetic anhydride was added and reacted at 100 ° C. under normal pressure for 14 hours, and then heated at 130 ° C. at a vacuum of -0.090 MPa or less for 12 hours while stirring to distill off water and organic solvents to obtain a cellulose fiber composition (X-8). The composition of the cellulose fiber composition (X-8) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Example 9)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol diethyl ether were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 25.0 parts by mass of hexadecenyl succinic anhydride was added and reacted at 90 ° C. under normal pressure for 2 hours to form a covalent bond with the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off water and organic solvents. Then, 10 parts by mass of water was added to obtain a cellulose fiber composition (X-9). The composition of the cellulose fiber composition (X-9) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Example 10)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol diethyl ether were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 40.0 parts by mass of maleic anhydride-modified polybutadiene (Total Cray Valley, Ricon (registered trademark; hereinafter, may be abbreviated) 130MA8) was added and reacted at normal pressure for 2 hours at 100 ° C. to form a covalent bond with the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off the water and organic solvent to obtain a cellulose fiber composition (X-10). The composition of the cellulose fiber composition (X-10) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Production Example 11)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatiles), 15.0 parts by mass of diethylene glycol diethyl ether, and 40.0 parts by mass of maleic anhydride-modified polybutadiene (Ricon130MA8) were mixed, and the system was kept at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, and then reacted at 100 ° C. under normal pressure for 2 hours to covalently bond the maleic anhydride-modified polybutadiene to the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off the water and solvent to obtain a cellulose fiber composition (X-11). The composition of the cellulose fiber composition (X-11) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 1)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) was heated at 130°C for 6 hours under a vacuum of -0.090 MPa or less while stirring, thereby distilling off the water to obtain a cellulose fiber composition (x-1). The composition of the cellulose fiber composition (x-1) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 2)
The cellulose fiber (x-1) was pulverized in a food processor to adjust the content of fiber aggregates to 5% by mass, thereby obtaining a cellulose fiber composition (x-2). The composition of the cellulose fiber composition (x-2) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative production examples 3, 4, 6, 8)
Cellulose fiber compositions x-3, x-4, x-6, and x-8 were obtained in the same manner as in Production Example 2, except that the organic solvent (B) was changed to one shown in Table 2. The compositions of the materials (x-3, x-4, x-6, and x-8) and the content of fiber aggregates in the cellulose fiber compositions are shown in Table 2.

(Comparative Production Example 5)
500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of ethylene glycol were mixed in a reaction vessel equipped with a stirrer, a thermometer, and a distiller, and heated at 130°C for 24 hours under a vacuum of -0.090 MPa or less while stirring to distill off the water and organic solvent, thereby obtaining a cellulose fiber composition (x-5). The composition of the cellulose fiber composition (x-5) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 7)
500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol dibutyl ether were mixed in a reaction vessel equipped with a stirrer, a thermometer, and a distiller, and the mixture was heated at 130°C for 20 hours under a vacuum of -0.090 MPa or less while stirring to distill off the water and organic solvent, thereby obtaining a cellulose fiber composition (x-7). The composition of the cellulose fiber composition (x-7) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 9)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatiles) and 100.0 parts by mass of diethylene glycol diethyl ether were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 25.0 parts by mass of hexadecenyl succinic anhydride was added and reacted at 90 ° C. under normal pressure for 2 hours to form a covalent bond with the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off the water and solvent, and 25 parts by mass of water was added to obtain a cellulose fiber composition (x-9). The composition of the cellulose fiber composition (x-9) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 10)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatiles) and 100.0 parts by mass of N-methylpyrrolidone were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 40.0 parts by mass of maleic anhydride-modified polybutadiene (Ricon130MA8) was added and reacted at 100 ° C. under normal pressure for 2 hours to form a covalent bond with the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off the water and solvent to obtain a cellulose fiber composition (x-10). The composition of the cellulose fiber composition (x-10) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

(Comparative Production Example 11)
In a reaction vessel equipped with a stirrer, a thermometer, and a distiller, 500.0 parts by mass of NBKP containing water (100.0 parts by mass of nonvolatile content) and 100.0 parts by mass of diethylene glycol monobutyl ether were mixed, and the system was maintained at 40 ° C. at a vacuum of -0.090 MPa or less for 3 hours, after which 40.0 parts by mass of maleic anhydride-modified polybutadiene (Ricon130MA8) was added and reacted at 100 ° C. under normal pressure for 2 hours to form a covalent bond with the cellulose fibers, and the mixture was heated at 130 ° C. at a vacuum of -0.090 MPa or less for 6 hours while stirring to distill off the water and solvent to obtain a cellulose fiber composition (x-11). The composition of the cellulose fiber composition (x-11) and the content of fiber aggregates in the cellulose fiber composition are shown in Table 2.

[Production and evaluation of cellulose fiber composite composition]
<Cellulose fiber composite composition using polypropylene as thermoplastic resin and/or rubber (E)>
Example 1
52 parts by mass of the cellulose fiber composition (X-1) (50 parts by mass as cellulose fiber (A)) and 50 parts by mass of maleated polypropylene (Toyobo Co., Ltd., Toyo Tac (registered trademark, hereinafter sometimes abbreviated) PMA H-1000P) were melt-kneaded at 170°C in a Labo Plastomill (Toyo Seiki Co., Ltd.), and 150 parts by mass of polypropylene (Prime Polypro (registered trademark, hereinafter sometimes abbreviated) J108M) was added and melt-kneaded at 190°C to obtain a cellulose fiber composite composition containing 20% by mass of cellulose fiber. Table 3 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A): thermoplastic resin and/or rubber (E) ratio, and the flexural modulus when made into a test piece.

(Examples 2 to 9, Comparative Examples 1 to 8)
Cellulose fiber composite compositions containing 20 mass% of cellulose fiber were obtained in the same manner as in Example 1, except that the type and amount of cellulose fiber composition (50 parts by mass of cellulose fiber (A)) were changed as shown in Table 3. Table 3 shows the raw material charge composition ratio, cellulose fiber (A):thermoplastic resin and/or rubber (E) ratio, and flexural modulus when made into test specimens for each cellulose fiber composite composition.

(Reference example)
Polypropylene (Prime Polypro J108M) was used as it was as a reference example. The flexural modulus of the test piece of the reference example not containing the cellulose fiber (A) is shown in Table 3.

In Table 3, MPP refers to maleated polypropylene (Toyotac PMA H-1000P, manufactured by Toyobo Co., Ltd.).

<Cellulose fiber composite composition using rubber as thermoplastic resin and/or rubber (E)>
Example 10
10 parts by mass of cellulose fiber composition (X-2) (10.0 parts by mass as cellulose fiber (A)), 5.0 parts by mass of zinc oxide, 1.0 parts by mass of stearic acid, 100.0 parts by mass of ethylene-propylene-diene copolymer (manufactured by JSR Corporation, EP24), 10.0 parts by mass of ethylene-propylene-diene copolymer (manufactured by Mitsui Chemicals, Inc., X-3012P), and 2.0 parts by mass of dicumyl peroxide were kneaded in a roll mill at 25 ° C., and the resulting rubber sheet was crosslinked at 170 ° C. for 20 minutes to obtain a peroxide crosslinked rubber containing 7.8% by mass of cellulose fiber (A). Table 4 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A): thermoplastic resin and / or rubber (E) ratio, and the 50% modulus when made into a test piece.

(Examples 11 to 13)
A peroxide-crosslinked rubber containing 7.8 mass% of cellulose fiber (A) was obtained in the same manner as in Example 10, except that the type and amount of cellulose fiber composition (10.0 parts by mass of cellulose fiber (A)) was changed as shown in Table 4. Table 4 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A):thermoplastic resin and/or rubber (E) ratio, and the 50% modulus when made into a test specimen.

(Example 14)
12 parts by mass of cellulose fiber (X-10) (10.0 parts by mass as cellulose fiber (A)) and 10.0 parts by mass of ethylene-propylene-diene copolymer (X-3012P) were melt-kneaded at 100°C in a Labo Plastomill to obtain a primary kneaded product. 5.0 parts by mass of zinc oxide, 1.0 parts by mass of stearic acid, 100.0 parts by mass of ethylene-propylene-diene copolymer (EP24), and 2.0 parts by mass of dicumyl peroxide were further added to this primary kneaded product and kneaded at 25°C in a roll mill, and the obtained rubber sheet was crosslinked and molded at 170°C for 20 minutes to obtain a peroxide-crosslinked rubber containing 7.8% by mass of cellulose fiber (A). Table 4 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A): thermoplastic resin and/or rubber (E) ratio, and the 50% modulus when the test piece was made.

(Comparative Example 9)
10 parts by mass of the cellulose fiber composition (x-1) (10.0 parts by mass as cellulose fiber (A)), 5.0 parts by mass of zinc oxide, 1.0 parts by mass of stearic acid, 100.0 parts by mass of ethylene-propylene-diene copolymer (EP24), 10.0 parts by mass of ethylene-propylene-diene copolymer (X-3012P), and 2.0 parts by mass of dicumyl peroxide were kneaded in a roll mill at 25°C, and the resulting rubber sheet was crosslinked and molded at 170°C for 20 minutes to obtain a peroxide-crosslinked rubber containing 7.8% by mass of cellulose fiber (A). Table 4 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A): thermoplastic resin and/or rubber (E) ratio, and the 50% modulus when made into a test piece.

(Comparative Examples 10 to 12)
A peroxide-crosslinked rubber containing 7.8 mass% of cellulose fiber (A) was obtained in the same manner as in Comparative Example 9, except that the type and amount of cellulose fiber composition (10.0 parts by mass of cellulose fiber (A)) was changed as shown in Table 4. Table 4 shows the raw material charge composition ratio of the cellulose fiber composite composition, the cellulose fiber (A):thermoplastic resin and/or rubber (E) ratio, and the 50% modulus when made into a test specimen.

(Reference example)
A kneaded material of 100.0 parts by mass of ethylene-propylene-diene copolymer (EP24) and 10.0 parts by mass of ethylene-propylene-diene copolymer (X-3012P) was used as a reference example. The 50% modulus of the test piece of the reference example not containing cellulose fiber (A) is shown in Table 4.

Table 5 shows the evaluation results of the fiber diameter of the cellulose fiber (A) contained in the cellulose fiber composite composition of Example 12 kneaded by a roll mill and the cellulose fiber composite composition of Example 14 melt-kneaded in the primary kneaded product by a Labo Plastomill.

Comparing Examples 1 to 9 with Comparative Examples 1 to 8, and comparing Examples 10 to 14 with Comparative Examples 9 to 12, it is clear that cellulose fiber compositions that satisfy the conditions of the present invention efficiently reinforce thermoplastic resins and rubbers and exhibit excellent mechanical properties.

From Example 3 and Comparative Example 7, it can be seen that the solubility of the organic solvent (B) in 100 g of water at 25°C must be 5 g or more.

From Example 1 and Comparative Examples 3 and 6, it can be seen that when the boiling point of the organic solvent (B) is high, the dispersibility of the cellulose fiber (A) increases and the mechanical properties are also improved.

From Examples 2, 8-9, 10, and 11-13, it can be seen that when the cellulose fiber (A) is acylated with a carboxylic anhydride (D), the mechanical properties are superior compared to when it is not acylated.

Example 12 and Comparative Example 12 show that the organic solvent (B) must not have an active proton.

From Examples 12 and 14, it can be seen that in the production of a cellulose fiber composite composition, the fiber diameter of the cellulose fiber (A) contained in the cellulose fiber composite composition is sufficiently fined by melt-kneading the cellulose fiber composition with a thermoplastic resin and/or rubber (E), resulting in superior mechanical properties.

Claims (4)

The cellulose fiber composition comprises 80 to 98 mass% of cellulose fibers (A), 1 to 20,000 ppm of an organic solvent (B), and the remainder being other components (C), characterized in that the organic solvent (B) satisfies the following conditions (1) to (4), is at least one selected from the group consisting of (poly)ethylene glycol dialkyl ethers and (poly)propylene glycol dialkyl ethers, and the number of carbon atoms in the alkyl group constituting the alkyl ether is 1 to 4 .
(1) The boiling point is 125 to 300°C.
(2) The solubility in 100 g of water at 25° C. is 5 g or more.
(3) The surface tension at 25°C is 20 to 36 mN/m.
(4) It does not have an active proton. The cellulose fiber composition according to claim 1, characterized in that the cellulose fiber (A) is a cellulose fiber acylated with a carboxylic acid anhydride (D). A method for producing a cellulose fiber composition comprising 80 to 98 mass% cellulose fibers (A), 1 to 20,000 ppm of an organic solvent (B), and the remainder being other components (C), wherein the organic solvent (B) satisfies the following conditions (1) to (4) , is at least one selected from the group consisting of (poly)ethylene glycol dialkyl ethers and (poly)propylene glycol dialkyl ethers, and the alkyl group constituting the alkyl ether has 1 to 4 carbon atoms .
(1) The boiling point is 125 to 300°C.
(2) The solubility in 100 g of water at 25° C. is 5 g or more.
(3) The surface tension at 25°C is 20 to 36 mN/m.
(4) It does not have an active proton. A method for producing a cellulose fiber composite composition, comprising kneading the cellulose fiber composition according to any one of claims 1 to 2 with a thermoplastic resin and/or rubber (E) in a ratio of cellulose fiber (A):thermoplastic resin and/or rubber (E) = 0.05 to 60:40 to 99.95 mass%.