JP7154798B2 - Composite and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite and a method for producing the same.

Cellulose is a major component of the cell walls of plant cells and plant fibers, and is a natural polymer in which a large number of β-glucose molecules are linearly polymerized through glycosidic bonds, so it has a low environmental load. In this cellulose fiber, single cellulose nanofibers with a width of 3 to 4 nm, which are basic units, are bundled to form cellulose nanofibers with a width of 10 to 20 nm, which are basic units in the cell wall. It has a structure in which a bundle of several tens of μm is formed.

In recent years, it has been found that these cellulose nanofibers have excellent properties such as high elastic modulus, high strength, low linear expansion coefficient, and gas barrier properties. Therefore, research and development are being carried out with various applications such as resin reinforcing materials, paint additives, films, and thickeners.

As a method for producing cellulose nanofibers, there is a method of mechanical defibration using a high-pressure dispersing device or a grinder, and a simple mechanical defibration method using a kneader after chemically hydrophilizing the pulp with a cationizing agent. Examples include a method of fibrillating, a method of partially oxidizing using a TEMPO catalyst or the like to facilitate chemical fibrillation, and the like.

By the way, cellulose nanofibers are rarely used alone, and are generally used in combination with an organic component or an organic solvent. Since cellulose constituting cellulose nanofibers has a large number of hydroxyl groups of glucose molecules, there is a problem that hydrogen bonding between hydroxyl groups easily occurs, and as a result, aggregation of cellulose nanofibers easily occurs. Moreover, as described above, since cellulose has a large number of hydroxyl groups on its surface, it is extremely hydrophilic and has the problem of lacking affinity with hydrophobic organic solvents.

In other words, cellulose nanofibers exist stably in water, but it is difficult to combine (especially melt-knead) with hydrophobic or hydrolyzable polymers in a state containing a large amount of water. On the other hand, when it dries, it agglomerates and becomes remnants in the polymer, resulting in deterioration of properties.

In order to solve this problem, methods of hydrophobizing cellulose nanofibers have also been investigated, but most methods involve substituting the hydroxyl groups of cellulose nanofibers with hydrophobic substituents by chemical techniques. In addition to being costly, such a method has problems such as inability to completely suppress aggregation due to hydrogen bonding because only a part of the hydroxyl groups are substituted.

Although the same problem exists in ordinary cellulose fibers, it can be said that the problem appears remarkably in cellulose nanofibers, in which a large number of hydroxyl groups are exposed on the surface relative to the weight.

In view of the above circumstances, the object of the present invention is to improve the strength of a resin composition by hydrophobizing cellulose by a method other than substituting the hydroxyl groups of cellulose with hydrophobic substituents. To provide a complex capable of

The present inventors have made intensive studies to achieve the above object. It was found that a composite having performance equal to or higher than that of the composite can be obtained. The inventors of the present invention conducted further studies based on such knowledge, and completed the present invention.

Specifically, the present invention provides the following complexes.
Section 1.
cellulose and a coating partially or entirely on the surface of the cellulose;
The composite, wherein the coating contains a fluorene compound having a plurality of hydroxyl groups.
Section 2.
Item 2. The composite according to Item 1, wherein the fluorene compound has a molecular weight of 500 or less.
Item 3.
Item 3. The complex according to item 1 or 2, wherein the fluorene compound is represented by the following general formula (1).

（式中、環Ｚは芳香族炭化水素環、Ｒ^１は任意の置換基又は水素原子、Ｒ^２はアルキレン基、Ｒ^３は任意の置換基又は水素原子、ｋは０～４の整数、ｍは０又は１の整数、ｎは０以上の整数を表わす。）

(Wherein, ring Z is an aromatic hydrocarbon ring, R ¹ is an optional substituent or a hydrogen atom, R ² is an alkylene group, R ³ is an optional substituent or a hydrogen atom, k is an integer of 0 to 4, m represents an integer of 0 or 1, and n represents an integer of 0 or more.)

Section 4.
In the above formula (1), ring Z is a benzene ring or naphthalene ring, R1 is a hydrogen atom, R2 is a methylene group, m is 0 or 1, R3 is a methyl group, hydrogen or hydroxyl, n is 0, 1 or 2. Item 4. The complex according to any one of Items 1 to 3.
Item 5.
Item 5. The composite according to any one of Items 1 to 4, wherein the fluorene compound is a diol or a diphenol.
Item 6.
The fluorene compound is selected from the group consisting of bisphenolfluorene (BPF), biscresolfluorene (BCF), bisphenoxyethanolfluorene (BPEF), bisnaphtholfluorene (BNF), bisxylenolfluorene (BXF), and biscatecholfluorene (BCAF). Item 6. The complex according to any one of Items 1 to 5, which is one or more selected.
Item 7.
Item 7. The composite according to any one of Items 1 to 6, wherein the cellulose is cellulose nanofibers having a diameter of 3 to 1000 nm.
Item 8.
Item 8. The composite according to any one of items 1 to 7, containing 2 to 100 parts by mass of the fluorene compound with respect to 100 parts by mass of the cellulose.
Item 9.
A composition comprising the complex according to any one of Items 1 to 8 in an organic solvent.
Item 10.
Item 10. The composition according to Item 9, wherein the organic solvent has a boiling point of 110°C or higher.
Item 11.
Item 11. The composition according to Item 9 or 10, wherein the organic solvent does not have a hydroxyl group.
Item 12.
Item 12. The composition according to any one of items 9 to 11, further comprising water, wherein the content of water in the composition is 10% by mass or less based on 100% by mass of the composition.
Item 13.
A resin composition comprising the composite according to any one of Items 1 to 8 and a resin.
Item 14.
Item 14. The resin composition according to Item 13, wherein the resin is at least one selected from the group consisting of polyester-based resins, polyamide-based resins, and polycarbonate-based resins.
Item 15.
14. The resin composition according to claim 13, wherein the resin is one or more selected from the group consisting of biomass plastics and microbial plastics.
Item 16.
Item 13. Item 13, wherein the resin is one or more selected from the group consisting of polylactic acid, polyamide 4, polyamide 11, polybutylene succinate, polyhydroxybutyrate, and copolymers containing these structures. of the resin composition.
Item 17.
Item 14. The resin composition according to Item 13, wherein the resin is one or more selected from the group consisting of polyethylene, polypropylene, and copolymers having these structures.
Item 18.
A method for producing a composite comprising cellulose and a coating provided on part or all of the surface of the cellulose, the coating comprising a fluorene compound having a plurality of hydroxyl groups, comprising:
A production method comprising a step 1 of adding a coating-forming solution containing the fluorene compound and an organic solvent to the cellulose.
Item 19.
The coating-forming solution further contains water,
Item 19. The manufacturing method according to Item 18, comprising a step 2 of removing water in the coating forming solution by heating and/or reducing pressure after the step 1.

INDUSTRIAL APPLICABILITY According to the composite of the present invention, it is possible to provide a composite capable of improving the strength of the resin composition without chemically modifying the cellulose surface.

(1. Complex)
The composite of the present invention is characterized by comprising cellulose and an aromatic epoxy resin layer partially or entirely covering the surface of the cellulose.

(1.1. Cellulose)
A wide range of known celluloses can be used as the cellulose, and there is no particular limitation. In addition, any of plant-derived cellulose, animal-derived cellulose, and bacterial-derived cellulose can be suitably used. These may be used individually by 1 type, and may be used in combination of 2 or more types.

Examples of plant-derived cellulose include cellulose derived from broad-leaved trees (eucalyptus, poplar, etc.), cellulose derived from conifers (pine, fir, cedar, cypress, etc.), and cellulose derived from herbs (straw, bagasse, reeds, kenaf, abaca, sisal, etc.). , and seed hair fibers (such as cotton). The raw material pulp may be a mechanical pulp obtained by mechanically treating wood chips, a chemical pulp obtained by chemically removing non-cellulose components from wood chips, or a dissolved pulp obtained by removing non-cellulose components and refining them. Pulp may also be used.

In addition, cellulose derived from animals such as sea squirt, cellulose derived from bacteria such as nata de coco, and the like can be used. Moreover, such cellulose does not necessarily have to consist of only pure cellulose components, and non-cellulose components may accompany cellulose as the main component. Of course, the cellulose may consist only of pure cellulose components.

The main non-cellulose component associated with cellulose is not particularly limited, and can be appropriately selected according to the application of the composite. Examples include hemicellulose and lignin. The more hemicellulose is, the easier it is to defibrate during the production of cellulose nanofibers, but the resulting resin composition tends to have a lower elastic modulus. The larger the amount of lignin, the more difficult it is to defibrate during the production of cellulose nanofibers.

It is preferable that the cellulose is defibrated so that part or all of it becomes cellulose nanofibers.

Also, the ratio of the pure cellulose component in the cellulose may be appropriately set according to the use of the composite. For example, when the composite is used for the purpose of resin reinforcement, the pure cellulose component ratio is 70% by mass in 100% by mass of cellulose fiber in order to effectively utilize the strength characteristics of the cellulose component. 80% by mass or more is more preferable. The upper limit of the cellulose ratio can be 100% by mass. In this specification, the cellulose ratio is defined as the ratio of a pure cellulose component in which β-glucose molecules are linearly polymerized through glycosidic bonds to 100% by mass of the entire cellulose.

The degree of polymerization of cellulose contained in cellulose may also be appropriately set according to the use of the composite. The lower the degree of polymerization of cellulose contained in cellulose, the easier it is for cellulose to defibrate. On the other hand, the higher the degree of polymerization of the pure cellulose component contained in the cellulose, the higher the modulus of elasticity of the composite and composition. In order to obtain a high-strength resin composition, it is preferable to use cellulose with a degree of polymerization of 500 or more, and more preferably cellulose with a degree of polymerization of 600 or more. Although the upper limit of the degree of polymerization of cellulose is not particularly limited, it is preferably 100,000, for example.

As for the crystallinity of the pure cellulose component contained in the cellulose, the lower the crystallinity, the easier it is to defibrate. In order to obtain a high-strength composition, the crystallinity of the pure cellulose component contained in the cellulose is preferably 60% or more, more preferably 70% or more. Although the upper limit of the crystallinity of the pure cellulose component is not particularly limited, it is preferably 99%, more preferably 98%, for example. The crystalline structure of cellulose includes type I, type II, type III, and type IV. Among them, from the viewpoint of resin reinforcement, cellulose with a type I crystal structure having a high elastic modulus is preferred. preferable.

Cellulose fibers contained in pulp usually have a diameter of 10 to 100 μm in many cases, but the cellulose used in the present invention is preferably finely divided into fibers having a diameter of 1 to 10 μm in circumferential cross section. Fibers are more preferred. More specifically, cellulose nanofibers with a diameter of 3 to 1000 nm are more preferred, and cellulose nanofibers with a diameter of 3 to 100 nm are even more preferred. However, not all of them need to be miniaturized, and they may be partly miniaturized. In this specification, the diameter of a cellulose fiber is defined as the median diameter obtained by observing 50 or more randomly extracted cellulose nanofibers with an SEM.

In general, cellulose is considered to be ideally finely divided and ideally dispersed without impairing the length, crystallinity, and degree of polymerization, so that the resulting resin composition exhibits strength. However, in practice, it is assumed that the finer and longer the nanofibers are, the more they aggregate and the strength of the resin composition cannot be obtained. In addition, since miniaturization to nanosize may cause a decrease in the length of nanofibers, crystallinity, and degree of polymerization, the appropriate degree of miniaturization differs depending on the purpose and the means for miniaturization.

As a method for refining cellulose, a wide range of known methods can be employed, and there is no particular limitation. Specifically, physical methods such as a high-pressure homogenizer method, underwater collision method, grinder method, ball mill method, and biaxial kneading method may be used. method can be used. Generally, physical methods yield nanofibers with a diameter of 10 to 1000 nm, while chemical methods can yield thinner cellulose nanofibers with a diameter of 3 to 10 nm. On the other hand, the smaller the diameter and the larger the aspect ratio, the higher the strength and other physical properties of the resulting resin composition can be expected. It may not be possible.

(1.2. Coating)
The coating is provided partially or entirely on the cellulose surface for the purpose of imparting hydrophobicity to the cellulose.

The coating includes a fluorene compound having multiple hydroxyl groups. When such a fluorene compound is not contained, a large number of hydrogen bonds are formed between the cellulose and the fluorene compound in the cellulose, and the complex tends to aggregate. In addition, an unintended crosslinked structure is likely to be formed during the production of the composite.

A fluorene compound having a hydroxyl group may have an alcoholic hydroxyl structure in which a hydroxyl group is bonded to an aliphatic structure, or a phenolic structure in which a hydroxyl group is bonded to an aromatic structure. That is, it may be a diol or a diphenol.

In order to improve the elastic modulus and heat resistance of the resulting resin composition, and to improve compatibility with the resin, the molecular weight of the fluorene compound is preferably 1000 or less, preferably 500 or less. is more preferred.

More specifically, the structural formula of such a fluorene compound is preferably represented by the following general formula.

（式中、環Ｚは芳香族炭化水素環、Ｒ^１は任意の置換基又は水素原子、Ｒ^２はアルキレン基、Ｒ^３は任意の置換基又は水素原子、ｋは０～４の整数、ｍは０又は１の整数、ｎは０以上の整数を表わす。）

(Wherein, ring Z is an aromatic hydrocarbon ring, R ¹ is an optional substituent or a hydrogen atom, R ² is an alkylene group, R ³ is an optional substituent or a hydrogen atom, k is an integer of 0 to 4, m represents an integer of 0 or 1, and n represents an integer of 0 or more.)

In addition, because it has heat resistance, in the above formula (1), the ring Z is a benzene ring or a naphthalene ring, R ¹ is a hydrogen atom, R ² is a methylene group, m is 0 or 1, R ³ is a methyl group, Hydrogen or hydroxyl, n is preferably 0, 1 or 2.

More specifically, the fluorene compound represented by the above formula (1) is bisphenol fluorene (BPF), biscresol fluorene (BCF), bisphenoxyethanol fluorene (BPEF), bis It is preferably one or more selected from the group consisting of naphtholfluorene (BNF) and bisxylenolfluorene (BXF).

The content of the fluorene compound in the composite is preferably 2 to 100 parts by mass, more preferably 5 to 75 parts by mass, based on 100 parts by mass of cellulose (in terms of solid components). By adopting such a configuration, it is possible to achieve aggregation prevention by inhibiting hydrogen bonding of cellulose nanofibers and modification of the resin by the fluorene compound.

The thickness of the coating is also not particularly limited, and is preferably 1 to 1000 nm, for example.

The coating is selected from the group consisting of epoxy resins, epoxy resin curing agents, epoxy resin curing accelerators, inorganic metal oxides, and carbon materials in addition to the above fluorene compounds, depending on the intended use of the composite and resin composition. One or more additives may also be included.

The composite of the present invention as described above can be obtained, for example, by dissolving a fluorene compound in an organic solvent, adding cellulose thereto, and kneading the mixture.

(2. Composition)
The composition of the invention preferably comprises the complex of the invention in an organic solvent.

(2.1. Organic solvent)
As the organic solvent, it is possible to employ a wide range of known organic solvents. It is preferable to employ an organic solvent having a temperature of ℃ or higher. On the other hand, it is preferable to use an organic solvent having a boiling point of 250° C. or less from the viewpoint of making it possible to easily remove such an organic solvent.

In addition, when kneading with a hydrolyzable resin in a state containing an organic solvent, for the reason of avoiding alcoholysis, when kneading with a hydrolyzable resin is assumed, an organic solvent having no hydroxyl group is used. Preferably a solvent is employed.

More specifically, organic solvents include both alcohol-based, ketone-based, glycol-based, lactone-based, lactam-based, amide-based, sulfoxide-based, and ether-based solvents that have affinity for both water and epoxy. It is preferred to use a solvent organic solvent. Considering that the composition is kneaded while the solvent remains, the group consisting of ketones, glycols having etherified ends and no hydroxyl groups, lactones, lactams, amides, and sulfoxides. It is preferable to use one or more selected organic solvents.

(2.2. Water)
The composition may further contain water in addition to the organic solvent to prevent aggregation of cellulose. The content of water is preferably 0.1 to 10% by mass based on 100% by mass of the composition. However, in the resin composition described later, when combining with a non-hydrolyzable resin such as polyolefins such as polyethylene and polypropylene, or when combining with a highly hydrophobic resin, it is preferable to remove water as much as possible. The less or no water, the better the dispersibility of the composite in polyolefins or hydrophobic resins, and the better physical properties can be obtained.

(3. Resin composition)
A resin composition containing the composite of the present invention and a resin is also preferable. Such a resin composition is superior in strength and elastic modulus after curing to a resin composition containing no composite.

(3.1. Resin)
As the resin to be used, it is preferable to use one or more selected from the group consisting of polyester-based resins, polyamide-based resins, and polycarbonate-based resins because of good compatibility with the fluorene compound. Moreover, it is preferable to use one or more selected from the group consisting of biomass plastics and microbially produced plastics because it is preferable to increase the biomass ratio from the viewpoint of environmental friendliness.

Rubber or thermoplastic elastomers may be used because they take advantage of the high modulus of cellulose. Examples of rubbers include diene rubbers, olefin rubbers, acrylic rubbers, butyl rubbers, epichlorohydrin rubbers, silicone rubbers, polysulfide rubbers, and fluororubbers. is preferred. Examples of thermoplastic elastomers include styrene, olefin, ester, urethane, amide, polyvinyl chloride, and fluorine, and olefin, ester, and amide are preferred from the viewpoint of compatibility.

More specifically, one or more selected from the group consisting of polylactic acid, polyamide 4, polyamide 11, polybutylene succinate, polyhydroxybutyrate, and copolymers containing these structures can be used. preferable.

Preferred diene rubbers are styrene-butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber and acrylonitrile-butadiene rubber. Preferred olefin rubbers are ethylene-propylene rubber and ethylene-propylene-diene rubber.

The thermoplastic elastomer preferably has a polyethylene structure, a polypropylene structure, a butadiene structure, a polyethylene terephthalate structure, a polyamide 6 structure, a polyamide 66 structure, a polyamide 11 structure, a polyamide 12 structure, and a styrene-ethylene-butylene-styrene copolymer. , a styrene-butadiene-styrene copolymer, and a styrene-butylene-butadiene-styrene copolymer, while having an olefin structure or a diene structure, they may contain a styrene structure of another system.

In addition, for the purpose of reducing the weight of the resin composition, it is also preferable to use one or more selected from the group consisting of polyethylene, polypropylene, and copolymers having these structures.

The resin composition of the present invention is composed of an organic solvent and a composite, and the resin is mixed with the composition described above, and the organic solvent and water are volatilized (evaporated) by heating and drying. ,Obtainable. Here, when using a resin that does not hydrolyze (or hardly hydrolyzes) such as polyethylene, polypropylene, and copolymers having these structures as the resin, the resin composition I prefer to get things. By adopting such a method, it is possible to reduce the interaction between the fluorene compound and cellulose based on the good affinity between cellulose and water.

(4. Manufacturing method of composite)
The method for producing a composite of the present invention is a method for producing a composite having cellulose and a coating provided partially or entirely on the surface of the cellulose, wherein the cellulose is coated with the fluorene compound and an organic solvent. It is characterized by having a step 1 of adding the contained coating forming solution.

As for the cellulose, the fluorene compound, and the organic solvent, those described above can be used.

As a method of adding the coating-forming solution containing the fluorene compound and the organic solvent to the cellulose, it is preferable to mix all of them. A more specific mode of such mixing operation may be melt-kneading or mixing via an organic solvent. Among them, by adopting melt-kneading, not only can productivity be improved, but also the dispersibility of the composite can be improved.

When cellulose nanofibers are used as cellulose, the fluorene compound may be added before or after defibration of cellulose. When added before defibration, the cellulose nanofibers can be efficiently coated. A fluorene compound does not necessarily have to be highly water-soluble.

Moreover, the coating-forming solution may further contain water, and after the step 1, a step 2 of removing water from the coating-forming solution by heating and/or reducing pressure may be performed.

A known method can be widely adopted for the heating operation, and there is no particular limitation. Specifically, it is possible to adopt a heating method using a stationary hot air dryer, a vacuum dryer, a rotary evaporator, or a mixing dryer (conical dryer, Nauta dryer, etc.). . The temperature condition for heating is preferably set to 40 to 200°C, more preferably set to 60 to 150°C.

As for the depressurization operation, it is possible to employ a wide range of known methods, and there is no particular limitation. Specifically, the pressure may be reduced using a device such as an oil pump, an oilless pump, an aspirator, or the like. The pressure condition in the decompression operation is preferably set to 0.00001 to 0.05 MPa, more preferably 0.00001 to 0.03 MPa.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to such examples, and can of course be embodied in various forms without departing from the gist of the present invention.

EXAMPLES Hereinafter, embodiments of the present invention will be described more specifically based on Examples, but the present invention is not limited to these.

(Example 1)
1800 g of cyclohexanone and 15 g of bisphenoxyethanolfluorene (BPEF) (cellulose nanofiber A fluorene compound (50 parts by mass per 100 parts by mass) was added, and after stirring, the pressure was reduced at 80° C. to obtain 150 g of a wet composite. Thereafter, 150 g of the composite and 255 g of polypropylene (Novatec BC06C, manufactured by Nippon Polypropylene) were melt-kneaded at 220° C. using a twin-screw extruder (15 mmφ, L/D=30, manufactured by Technovel) to obtain 250 g of a compound. The resulting compound was dried at 80°C for 24 hours, and then molded using an injection molding machine (Shinko Cellvic, C, MOBILE-0813) into a length of 75 mm, parallel width of 5 mm, and parallel length of 35 mm. Dumbbell specimens with a thickness of 2 mm were molded.

(Example 2)
A test piece was obtained in the same manner as in Example 1, except that 15 g of bisphenoxyethanolfluorene (BPEF) was changed to 15 g of bisnaphtholfluorene (BNF).

(Example 3)
A test piece was obtained in the same manner as in Example 1, except that 15 g of bisphenoxyethanol fluorene (BPEF) was changed to 15 g of biscresol fluorene (BCF).

(Example 4)
A test piece was obtained in the same manner as in Example 3, except that 15 g of bis-cresol fluorene (BCF) was changed to 7.5 g of bis-cresol fluorene (BCF) (25 parts by mass of the fluorene compound relative to 100 parts by mass of cellulose nanofibers). rice field.

(Comparative example 1)
PP (Nippon Polypro: Novatec BC06C) was melt-kneaded using a twin-screw extruder, dried at 80°C for 24 hours, and then molded into a dumbbell test piece using an injection molding machine.

(Comparative example 2)
1800 g of cyclohexanone was added to 30 g of cellulose nanofibers containing 50% or more of fibers with a diameter of 100 nm or less (150 g of water wet matter with a solid content of 20% by weight), which had been defibrated by a grinder method, and the pressure was reduced at 80°C after stirring. 150 g of wet cellulose were obtained. 150 g of the composite containing 30 g of the cellulose and 270 g of PP (Nippon Polypropylene: Novatec BC06C) were kneaded at 220° C. to obtain 250 g of a compound. Thereafter, a test piece was obtained in the same manner as in Example 1.

(Comparative Example 3)
An experiment was conducted in the same manner as in Example 1, except that 15 g of bisphenoxyethanolfluorene (BPEF) was changed to 15 g of tannic acid, which is an aromatic compound having multiple hydroxyl groups.

(Comparative Example 4)
An experiment was conducted in the same manner as in Example 1, except that 15 g of bisphenoxyethanol fluorene (BPEF) was changed to 15 g of tilabazole D-818M, which is a filler dispersion accelerator in PP.

(Tensile strength, tensile elasticity test)
A tensile test was performed on the obtained test pieces of each example and comparative example using a universal material testing machine (Instron 5567) at an ambient temperature of 23 ° C. and a tensile speed of 10 mm / min n = 5. Elastic modulus was calculated. The results obtained are shown in Table 1 below.

As shown in Table 1, it was confirmed that the test pieces of each example were superior in strength to the test pieces of each comparative example.

Claims (1)

A method for producing a composite comprising cellulose and a coating provided on part or all of the surface of the cellulose, the coating comprising a fluorene compound having a plurality of hydroxyl groups, comprising:
step 1 of adding a coating-forming solution containing the fluorene compound, an organic solvent and water to the cellulose;
A production method characterized by comprising, after the step 1, a step 2 of removing water in the coating molding solution by heating at a temperature of 40 to 80° C. and/or reducing pressure.