JP2014193959A - Plant fiber-containing resin composition and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a plant fiber-containing resin composition which is simple and efficient and has reduced environmental load.SOLUTION: A method of producing a plant fiber-containing resin composition is characterized by melt-kneading A) a thermoplastic resin, B) a plant fiber composition and C) a plant fiber modifier to form a composite material. The plant fibers in B) the plant fiber composition meet the conditions: 1 the average fiber length being 0.1-0.7 mm and 2 the average fiber width being 2-15,000 nm.

Description

  The present invention relates to a resin composition containing cellulose nanofibers (fine fibrous cellulose) and a thermoplastic resin, and a method for producing the resin composition. More specifically, the present invention relates to a resin composition in which cellulose nanofibers are highly dispersed in a thermoplastic resin and a method for producing the same.

  For the purpose of expanding the use application of thermoplastic resins, a method of combining various fibrous fillers with thermoplastic resins is widely used. As an example, there is a fiber-containing resin composition in which glass fiber and carbon fiber are contained in a thermoplastic resin. A lightweight, high-strength thermoplastic resin reinforced by various fibers is used for automobiles, houses, and household appliances. It is used in a wide range of fields. However, carbon fibers are difficult to burn, and glass fibers are non-flammable and thus have the disadvantage of being unsuitable for thermal recycling. In addition, since carbon fiber is expensive, there is a problem that it is difficult to adapt to general-purpose use.

  Other fibrous fillers include polyester fibers and polyamide fibers. The thermoplastic resin composition reinforced with these fibers is light in weight and excellent in thermal recyclability, but has a drawback that the mechanical strength reinforcing effect is not sufficient. Further, as another fibrous filler, there is an aramid fiber, and a thermoplastic resin reinforced by this is lightweight and has a high mechanical strength reinforcing effect and is also suitable for thermal recycling. It has low defects and has drawbacks such as impact resistance.

The market demands a fibrous filler that has a high mechanical strength reinforcing effect, is lightweight, has excellent thermal recyclability, and can be manufactured at low cost. In recent years, cellulose fibers obtained from plant fibers have attracted attention and have been studied as fibrous fillers having these characteristics. Since the raw material of cellulose fiber is a plant, its resource reserves are enormous, its price is relatively low, and it is excellent in thermal recycling.
Furthermore, in recent years, nanotechnology aimed at obtaining physical properties different from the bulk level by making the material a nanometer size has attracted attention, and cellulose fibers have also been studied. For example, the width of cellulose fibers used in paper is mostly 10 to 50 μm, but cellulose nanofibers obtained by refining cellulose fibers to 1/100 to 1/1000 (microfibrils) It has been found that strength and dimensional stability are improved because the number of fibers is dramatically increased at the same mass compared to cellulose used in paper. This is presumably because the characteristics of the high elastic modulus and low thermal expansion coefficient of the original cellulose fiber were sufficiently exhibited. Thus, utilization to the resin which utilized the characteristic of the fine fibrous cellulose is anticipated.
However, due to its high hydrophilicity, cellulose fibers are difficult to disperse in thermoplastic resins, particularly highly hydrophobic olefin resins. In addition, even if cellulose refined into nanofibers is used, cellulose fibers reaggregate when mixed with resin, and coarse cellulose aggregates are generated, which improves mechanical properties. In addition to suppressing the development of advantages obtained by mixing cellulose fibers such as lowering of the coefficient of thermal expansion and thermal expansion coefficient, it also gives other disadvantages such as reduced impact resistance and reduced transparency There is a point.
Various improvements have been made with the aim of enjoying the advantages of compounding these cellulose nanofibers and eliminating the drawbacks.

For example, in Patent Document 1, it is not a method of dispersing cellulose nanofibers in a resin, but fine cellulose fibers are made into a nonwoven fabric, impregnated with epoxy resin or polycarbonate resin, and then dried or cooled after defoaming. Thus, a method of compounding with a resin is disclosed. However, even if we intend to apply this technology to compounding with olefinic resins, it takes a lot of heat energy to dissolve the olefinic resin in a solvent or impregnate it into a cellulose nonwoven fabric as a melt. Therefore, it is difficult industrially. Further, even when heated to a high temperature and dissolved in a solvent or melted, there is a problem that they are not substantially impregnated into cellulose fibers.
Further, in Patent Documents 2 to 4, a method of performing surface modification with various fiber modifiers in advance after the cellulose is refined or before being refined and then mixed with a thermoplastic resin is disclosed. Both methods require a special process such as solvent replacement for the surface modification treatment of cellulose and pretreatment, and there is a problem that the process becomes complicated and the production cost increases.

  Patent Document 2 discloses that the elastic modulus of a composite film with cellulose acetate is improved by performing in advance a surface modification treatment for introducing an acetyl group into cellulose fibers. In addition, the cellulose acetate currently disclosed by patent document 2 is a thing with high affinity with a cellulose fiber from the first, and it is difficult to apply this technique to resin with low affinity with a cellulose.

In Patent Document 3, it is produced by introducing a carboxylic acid into a cellulose molecule by reacting a hydroxyl group of cellulose nanofiber with a polybasic anhydride, and further mixing the cellulose fiber into which the carboxylic acid is introduced with a resin. Further, a plant fiber-containing resin composition is disclosed. According to the method disclosed in Patent Document 3, by introducing carboxylic acid into cellulose nanofiber, it has a chemical interaction with a resin having a functional group capable of reacting with carboxylic acid (for example, epoxy resin). This makes it possible to increase the dispersibility of the cellulose nanofibers in the resin.
However, it is necessary to disperse cellulose nanofibers in an aprotic solvent or a ketone-based solvent in the step of reacting the hydroxyl group of cellulose nanofiber with an anhydrous polybasic acid, which increases the production cost and the process is complicated. In addition, the environmental load due to the discharge of these solvents into the environment becomes a problem.

In Patent Document 4, a carboxylic acid is introduced into cellulose molecules by a method such as reacting a hydroxyl group of cellulose with a polybasic anhydride, and cellulose fibers into which the carboxylic acid has been introduced are made into fine fibers, and further resin and A method for compounding a plant fiber-containing resin composition characterized by mixing is disclosed. However, the plant fiber-containing resin composition that can be produced by the method disclosed in Patent Document 4 includes a step of reacting a polybasic acid half-esterified cellulose with a raw material of cellulose nanofibers contained therein, and the polybasic A step of microfibrating acid half-esterified cellulose, a step of adding a swelling agent to refined polybasic acid half-esterified cellulose to form a cellulose slurry, and a step of mixing polybasic acid half-esterified cellulose with resin This requires a complicated process, which leads to an increase in manufacturing costs.
On the other hand, as a method for producing a paper-containing resin composition in which a waste paper pulverized product and a resin raw material are mixed, Patent Document 5 discloses that a waste paper pulverized product made of bleached kraft pulp is esterified with maleic anhydride and then pulped with magnesium oxide. It is disclosed that, after neutralizing the organic acid generated by thermal decomposition of the resin, it is melt kneaded with polypropylene to improve the dispersibility of the paper in the polypropylene and improve the fluidity of the resin composition.
However, Patent Document 5 shows a case in which a pulverized material of paper is used as a raw material, and the content of the pulverized material of paper exceeds 50% by mass of the entire resin composition, and in this case, As in the present invention, the mechanical strength reinforcing effect obtained by microfibrillation of cellulose fibers does not appear, and it is difficult to use as a highly effective fibrous filler. The main purpose of Patent Document 5 is to provide a resin composition having high fluidity and moldability even when the blending ratio of paper in the resin composition is high. There is no suggestion or disclosure about the case of using as a highly effective fibrous filler.

JP 2006-316253 A Japanese National Patent Publication No. 11-513425 JP 2012-229350 A JP 2009-293167 A Japanese Patent No. 4994249

  In view of the conventional problems described above as the background art, the present invention is a simple and efficient method that does not depend on any conventional method including each problem, and has a low environmental load, and contains plant fibers. It is an object of the present invention to provide a method for producing a resin composition, and a plant fiber-containing resin composition having high plant fiber dispersibility and free of coarse plant fiber aggregates.

As a result of conducting various studies to solve the above-mentioned problems, the present inventors have surprisingly found that plant fiber is a simple and efficient method that has not been envisaged in the past, and that has a low environmental impact. Plant fiber-containing resin composition that is dispersed in a resin composition in a sufficiently refined state and in which coarse plant fiber aggregates are not present is possible. It has been found that the fiber-containing resin composition is free of plant fiber aggregates and has both high mechanical properties and impact resistance, and has led to the creation of the present invention.
That is, the present invention melt-kneads a thermoplastic resin, a plant fiber composition containing cellulose nanofibers, and a plant fiber modifier without using cellulose nanofibers that have been surface-treated with a plant fiber modifier in advance. In the same melt-kneading process, the process of chemically modifying the plant fiber in the plant fiber composition by the plant fiber modifier to increase the dispersibility of the fiber and the process of dispersing the modified plant fiber in the thermoplastic resin The plant fiber-containing resin composition having high fiber dispersibility can be provided by a method that is simpler and less burdensome on the environment than conventional techniques.

The present invention includes the following aspects.
[1] A method for producing a resin composition comprising combining A) a thermoplastic resin, B) a plant fiber composition, and C) a plant fiber modifier while melt-kneading, wherein B ) A method for producing a plant fiber-containing resin composition, wherein the plant fiber in the plant fiber composition satisfies the following conditions.
1. Average fiber length is 0.1-0.7mm
2. Average fiber width is 2 to 15000 nm
[2] A step of compounding B) a plant fiber in the plant fiber composition and C) a plant fiber modifier in the molten A) thermoplastic resin, and B) converting the plant fiber in the plant fiber composition into A ) The method for producing a vegetable fiber-containing resin composition according to [1], comprising at least a step of dispersing in a thermoplastic resin.
[3] C) A functional group selected from plant acid modifiers selected from acids, acid anhydrides, alcohols, halogenating reagents, silane compounds, isocyanate group-containing compounds, amino group-containing compounds, cyclic amide compounds, and cyclic ester compounds. The method for producing a plant fiber-containing resin composition according to [1] or [2], wherein the compound is a contained compound.
[4] Production of a plant fiber-containing resin composition according to any one of [1] to [3], wherein the plant fiber modifier is a compound containing a carboxylic acid or an acid anhydride. Method.
[5] The method for producing a plant fiber-containing resin composition according to any one of [1] to [4], wherein the A) thermoplastic resin is an olefin resin.
[6] Any one of [1] to [5], wherein the plant fiber in the plant fiber composition is 0.1 to 100 parts by mass with respect to 100 parts by mass of A) the thermoplastic resin. The manufacturing method of the vegetable fiber containing resin composition of description.
[7] Any of [1] to [6], wherein C) the plant fiber modifier is 0.1 to 100 parts by mass with respect to 100 parts by mass of B) plant fiber in the plant fiber composition. The manufacturing method of the vegetable fiber containing resin composition of crab.
[8] B) The method for producing a plant fiber-containing resin composition according to any one of [1] to [7], wherein the plant fiber in the plant fiber composition has been defibrated.
[9] A) The thermoplastic resin is any one of an ethylene homopolymer, a copolymer of ethylene and α-olefin, and a copolymer of ethylene, a vinyl group and a monomer having a polar group. The manufacturing method of the plant fiber containing resin composition in any one of [1]-[8].
[10] The method for producing a plant fiber-containing resin composition according to any one of [1] to [9], wherein the plant fiber composition is a cellulose web (cellulose / emulsion web).

[11] A plant fiber-containing resin composition comprising A) a thermoplastic resin, B) a plant fiber composition, and C) a plant fiber modifier, and B) a part or all of hydroxyl groups of the plant fiber composition Is a plant fiber-containing resin composition characterized in that C) is chemically modified by a plant fiber modifier, and B) the plant fiber contained in the plant fiber composition satisfies the following conditions: A vegetable fiber-containing resin composition in which cellulose nanofibers are dispersed in a resin composition, and coarse aggregates are substantially not found.
1. Average fiber length is 0.0001 to 0.7 mm
2. Average fiber width is 2 to 15000 nm
[12] C) A functional group selected from plant acid modifiers selected from acids, acid anhydrides, alcohols, halogenating reagents, silane compounds, isocyanate group-containing compounds, amino group-containing compounds, cyclic amide compounds, and cyclic ester compounds. The plant fiber-containing resin composition according to [11], which is a compound containing the plant fiber.
[13] The vegetable fiber-containing resin composition according to [11] or [12], wherein the A) thermoplastic resin is an olefin resin.
[14] Any one of [11] to [13], wherein B) the plant fiber in the plant fiber composition is 0.1 to 100 parts by mass with respect to 100 parts by mass of A) the thermoplastic resin. The plant fiber-containing resin composition described in 1.
[15] Any of [11] to [14], wherein C) the plant fiber modifier is 0.1 to 100 parts by mass with respect to 100 parts by mass of B) plant fiber in the plant fiber composition. A vegetable fiber-containing resin composition according to claim 1.

  The method for producing a plant fiber-containing resin composition of the present invention is a method that is simple and efficient and has a low environmental load.

3 is an electron micrograph of a plant fiber-containing resin composition of Example 3. 2 is an electron micrograph of a plant fiber-containing resin composition of Comparative Example 1.

"Plant fiber-containing resin composition"
<Thermoplastic resin>
The thermoplastic resin is not particularly limited. For example, olefin resin, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, poly (meth) acrylic acid alkyl ester polymer, (meth) acrylic acid alkyl ester copolymer Polymer, styrene-acrylonitrile copolymer, styrene- (meth) acrylic acid alkyl ester copolymer, polyester resin (for example, polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polybutylene succinate, unsaturated polyester, etc.), Polyurethane, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, polyisoprene, polychloroprene, styrene-butadiene-methyl methacrylate copolymer, saponified polyvinyl alcohol, ethylene -Saponified product of vinyl acetate copolymer (EVOH), polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polystyrene, styrene-acrylic copolymer, acrylic resin, ABS resin, polyhydroxybutyrate, polyethylene adipate, polycaprolactone, nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, nylon 610, polyamide resins such as polymetaxylylene adipamide, polycarbonate, polyacetal, polyphenylene oxide, fluorine resin, and the like. These thermoplastic resins may be used alone or in combination of two. Among these, olefin resin, polyamide resin, polyester resin, polycarbonate, polystyrene, and polyacetal are preferably selected, and olefin resin is more preferably selected.

  As the olefin-based resin, an ethylene homopolymer, an α-olefin having 3 to 20 carbon atoms, obtained by a high-pressure radical polymerization method, a high-medium-low pressure method using a Ziegler-type, Phillips type or single-site catalyst, and other known methods. An α-olefin homopolymer obtained by polymerizing a monomer selected from ethylene, a copolymer obtained by copolymerizing two or more monomers selected from ethylene and an α-olefin having 3 to 20 carbon atoms, ethylene And a vinyl monomer containing a polar group. Among these, an ethylene homopolymer, a copolymer of ethylene and an α-olefin having 3 to 20 carbon atoms, or a copolymer of ethylene and a vinyl monomer containing a polar group is preferable.

  An ethylene homopolymer is obtained by polymerizing ethylene alone, and an α-olefin homopolymer is obtained by polymerizing a monomer selected from α-olefins having 3 to 20 carbon atoms. Examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and 1-dodecene. Preferred homopolymers include ethylene homopolymer, propylene homopolymer, 1-butene homopolymer, 1-hexene homopolymer, 1-octene homopolymer, 1-dodecene homopolymer and the like. More preferred are ethylene homopolymers and propylene homopolymers.

  The copolymer obtained by copolymerizing two or more types of monomers selected from ethylene and an α-olefin having 3 to 20 carbon atoms is two or more types selected from ethylene and an α-olefin having 3 to 20 carbon atoms. If it is a copolymer obtained by superposing | polymerizing the monomer of, it will not specifically limit. Two or more types of monomers may be used for the polymerization. A copolymer of two or more types of monomers selected from ethylene and an α-olefin having 3 to 20 carbon atoms preferably includes ethylene, and further includes one or more α-olefins having 3 to 20 carbon atoms. It is a copolymer. More preferred is a copolymer which contains ethylene essential and further contains at least one α-olefin having 3 to 10 carbon atoms. A copolymer that contains ethylene in an essential manner and contains one or more α-olefins selected from propylene, 1-butene, 1-hexene, and 1-octene can be more preferably used.

A copolymer of a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms and a vinyl monomer containing a polar group includes a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms, The copolymer is not particularly limited as long as it is a copolymer obtained by polymerizing a vinyl monomer containing a polar group.
The monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms may be one type or two or more types, and the vinyl monomer containing a polar group may be one type or two or more types. . Furthermore, even if two types of monomers are used for the polymerization of a copolymer of a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms and a vinyl monomer containing a polar group, the number of the monomers is three or more. There may be. A copolymer of a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms and a vinyl monomer containing a polar group is preferably a copolymer of ethylene and a vinyl monomer containing a polar group. .

  A vinyl monomer containing a polar group used for copolymerization of a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms and a vinyl monomer containing a polar group is a monomer containing a carboxylic acid group or an acid anhydride group. At least one selected from (a), an ester group-containing monomer (b), a hydroxyl group-containing monomer (c), an amino group-containing monomer (d), a silane group-containing monomer (e), and a glycidyl group-containing monomer (f) Monomer.

Examples of the carboxylic acid group or acid anhydride group-containing monomer (a) include acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, and bicyclo [2 , 2,1] hept-2-ene-5,6-dicarboxylic acid and the like, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic acid Acid anhydride, 3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, tetracyclo [6. 2. 1. 1 ^{3, 6} . 0 ^{2, 7} ] Dodeca-9-ene-4,5-dicarboxylic acid anhydride, unsaturated carboxylic acid anhydrides such as 2,7-octadien-1-ylsuccinic acid anhydride, etc. Ester group-containing monomer (b) Examples thereof include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate and the like, and particularly preferred is methyl acrylate.
Examples of the hydroxyl group-containing monomer (c) include hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.
Examples of the amino group-containing monomer (d) include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, cyclohexylaminoethyl (meth) acrylate, and allylamine.
Examples of the silane group-containing monomer (e) include unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetylsilane, and vinyltrichlorosilane.
Examples of the glycidyl group-containing monomer (f) include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 2-methylallyl glycidyl ether, styrene-p-glycidyl ether, 1,2-epoxy-9-decene, 4-hydroxybutyl acrylate glycidyl. Examples include ether and 1,2-epoxy-4-vinylcyclohexane.

  The production method of the olefin-based resin is not particularly limited. For example, a known high-pressure radical polymerization method such as a tubular method or an autoclave method, a high-medium-low pressure method using a Ziegler-type, Phillips type or single-site catalyst, and other known methods. Can be manufactured by.

  The method for producing a copolymer of a monomer selected from ethylene and an α-olefin having 3 to 20 carbon atoms and a vinyl monomer containing a polar group is not particularly limited. For example, it is based on a high-pressure radical polymerization process. Polymerization (for example, the method described in Japanese Patent No. 2792982 and JP-A-3-229713), a method in which the polar group of the polar group-containing monomer is masked with organoaluminum at the time of polymerization and the masking is removed after copolymerization (for example, patent No. 4672214 No., method described in Japanese Patent No. 3603785 No.), a method of modifying a double bond portion of an olefin copolymer having a double bond in a molecular chain (for example, JP 2005-97587 A, JP-A-2005-97588, JP-A-2006-131707, JP-A-2009-155655 A method described in JP 2009-155656 A), a method of polymerizing a polar group-containing olefin copolymer in the presence of a catalyst in which a specific ligand is coordinated to a transition metal (for example, JP 2010-202647 A). And the method described in JP 2010-150532 A, JP 2010-150246 A, and JP 2010-260913 A).

  The olefin resin may have a polar group-containing monomer added thereto by graft modification. Examples of the graft modification method include a method of reacting a polymer grouped resin component with a polar group-containing monomer for graft modification in an extruder or in a solution in the presence of a radical generator.

  Examples of the radical generator include organic peroxides, dihydroaromatic compounds, dicumyl compounds and the like. Examples of the organic peroxide include hydroperoxide, dicumyl peroxide, t-butylcumyl peroxide, dialkyl (allyl) peroxide, diisopropylbenzene hydroperoxide, dipropionyl peroxide, dioctanoyl peroxide, and benzoyl. Peroxide, peroxysuccinic acid, peroxyketal, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane , T-butyloxyacetate, t-butylperoxyisobutyrate and the like. Examples of the dihydroaromatic compound include dihydroquinoline or a derivative thereof, dihydrofuran, 1,2-dihydrobenzene, 1,2-dihydronaphthalene, 9,10-10 dihydrophenanthrene, and the like. Examples of the dicumyl compound include 2,3-dimethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-diphenylbutane, 2,3-diethyl-2,3-di (p-methylphenyl) butane, 2,3-diethyl-2,3-di (p-bromophenyl) butane and the like can be mentioned.

Examples of the polar group-containing monomer used for graft modification include a carboxylic acid group or acid anhydride group-containing monomer (a), an ester group-containing monomer (b), a hydroxyl group-containing monomer (c), and an amino group-containing monomer (d). And silane group-containing monomer (e), glycidyl group-containing monomer (f), and the like.
Examples of the carboxylic acid group- or acid anhydride group-containing monomer (a) include α, β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, and itaconic acid, or anhydrides thereof, acrylic acid, methacrylic acid, furan Examples thereof include unsaturated monocarboxylic acids such as acid, crotonic acid, vinyl acetate and pentenoic acid.
Examples of the ester group-containing monomer (b) include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate.
Examples of the hydroxyl group-containing monomer (c) include hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate.
Examples of the amino group-containing monomer (d) include aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, cyclohexylaminoethyl (meth) acrylate, and the like.
Examples of the silane group-containing monomer (e) include unsaturated silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetylsilane, and vinyltrichlorosilane.
Examples of the glycidyl group-containing monomer (f) include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, 2-methylallyl glycidyl ether, and styrene-p-glycidyl ether.

<Plant fiber composition>
The plant fiber composition of the present invention is not particularly limited as long as it contains vegetable fiber as a main component, and examples thereof include pulp, paper, vegetable fiber woven fabric, plant fiber nonwoven fabric, and powdered cellulose. The plant fiber composition may contain a fiber dispersion resin in addition to the plant fiber.

(Plant fiber)
The type of plant fiber is not particularly limited, and examples thereof include wood fiber manufactured from wood, non-wood fiber manufactured from herbs, and the like.
Wood fibers include chemical pulp fibers obtained by digesting conifers and hardwoods using the craft method, sulfite method, soda method, polysulfide method, etc., mechanical pulp fibers that have been pulped by mechanical force such as refiners and grinders, and after pretreatment with chemicals. And semi-chemical pulp fibers pulped by mechanical force, or waste paper pulp fibers. These can be used in an unbleached (before bleaching) or bleached (after bleaching) state, respectively.
Examples of non-wood fibers include fibers obtained by pulping cotton, manila hemp, flax, straw, bamboo, bagasse, kenaf, and the like in the same manner as wood pulp.

Among the plant fibers, fine fibers that are aggregates of cellulose molecules having an average fiber width of 2 to 15000 nm measured by a method described later and having a crystal structure of type I (parallel chain) are preferable. If the average fiber width is 2 nm or more, it is possible to suppress dissolution as water as cellulose molecules in water, so that physical properties (strength, rigidity, dimensional stability) as fine fibers can be easily expressed. When the average fiber width is 15000 nm or less, the width is remarkably narrower than the fiber width of fibers contained in normal papermaking pulp, and the characteristics different from those of normal papermaking pulp are exhibited.
The average fiber width of the fine fibers is preferably 2 to 12000 nm, and more preferably 20 to 12000 nm. In addition, in terms of operability such as drainage in the step of papermaking the mixed dispersion described later, the average fiber width of the fine fibers is preferably 200 to 12000 nm.
When the average fiber width of the fine fibers is within the above range, it is not necessary that all the fine fibers are within the above fiber width range, and some of the fine fibers may have a fiber width that exceeds the upper limit or less than the lower limit. It may be. That is, thick fibers and thin fibers may be mixed.

The average fiber width is measured as follows. An aqueous suspension of fibers having a concentration of 0.05 to 0.1% by mass is prepared, and the suspension is appropriately diluted and then cast on a carbon film-coated grid that has been subjected to a hydrophilic treatment. To do. Observation with an electron microscope image is performed at a magnification according to the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies the above conditions. In this way, at least three sets of images of the surface portion that do not overlap each other are observed, and the width of the fiber intersecting with the straight line X and the straight line Y is read for each image. In this way, at least 20 × 2 × 3 = 120 fiber widths are read. The fiber width in the present invention is an average value of the fiber widths read in this way.

The fine fibers preferably have an average fiber length measured by the method described later of 0.01 to 3.0 mm, more preferably 0.05 to 1.5 mm, and 0.1 to 0. 7 mm is more preferable. If the average fiber length of the fine fibers is equal to or greater than the lower limit, the strength of the plant fiber-containing resin composition can be more easily improved due to the reinforcing effect of the fibers. In the melt-kneading step of mixing and kneading a composite sheet containing a thermoplastic resin and a thermoplastic resin, the dispersibility of the fine fibers is improved, and the strength of the plant fiber-containing resin composition is easily improved.
The average fiber length was determined by measuring the length weighted average fiber length using a Kajaani fiber length measuring instrument (FS-200 type) manufactured by Kajaani Automation.
In addition, as the miniaturization progresses, fibers having a narrow width and a short length may not be measured with a Kajaani fiber length measuring instrument. Therefore, an optical microscope, a scanning microscope (SEM), and a transmission electron microscope (TEM) were appropriately selected according to the length of the fiber, and the fiber length was observed and measured. The fiber length was measured by selecting 20 or more fibers from the obtained photograph.

  The axial ratio (major axis / minor axis) of the fine fibers in the present invention is preferably in the range of 20 to 10,000. If the axial ratio is less than 20, it may be difficult to form a composite sheet. If the axial ratio exceeds 10,000, the viscosity of the fiber slurry may be too high. Further, when the axial ratio is in the range of 20 to 1000, it is possible to suppress a decrease in drainage in the step of papermaking the mixed dispersion described later. The axial ratio in this invention is the value calculated | required with the average fiber width calculated | required by the average fiber length measured using the Kajaani fiber length measuring device (FS-200 type | mold) of Kajaani Automation, and electron microscope observation.

  The proportion of B) plant fiber in the plant fiber-containing resin composition in the plant fiber-containing resin composition is preferably 0.1 to 100 parts by mass with respect to 100 parts by mass of A) thermoplastic resin. It is more preferably 5 to 80 parts by mass, and further preferably 1 to 50 parts by mass. If it is lower than this range, the reinforcing effect of the plant fiber is not sufficient, and if it is higher than this range, the fluidity of the plant fiber-containing resin composition is lowered, and molding processing is difficult.

(Fiber dispersion resin)
The fiber-dispersing resin plays a role of enhancing the dispersibility of the plant fibers in the thermoplastic resin when the plant fiber-containing resin composition is produced.
The fiber dispersion resin is not particularly limited, and examples thereof include olefin resins, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, poly (meth) acrylic acid alkyl ester polymers, and (meth) acrylic acid alkyl ester copolymers. Polymer, styrene-acrylonitrile copolymer, styrene- (meth) acrylic acid alkyl ester copolymer, polyester (for example, polyethylene terephthalate, polybutylene terephthalate, etc.), polyurethane, natural rubber, styrene-butadiene copolymer, acrylonitrile- Examples thereof include butadiene copolymers, polyisoprene, polychloroprene, styrene-butadiene-methyl methacrylate copolymers, and saponified ethylene-vinyl acetate copolymers. These fiber dispersion resins may be used alone or in combination of two kinds.

  The resin for dispersing fibers is preferably A) a resin having high compatibility with the thermoplastic resin, for example, A) a resin having the same monomer unit as the monomer unit constituting the thermoplastic resin. If the resin for dispersing fibers is highly compatible with A) the thermoplastic resin, the dispersibility of the plant fibers in the thermoplastic resin can be further improved, and the strength can be further improved.

(Content ratio)
The plant fiber content in the plant fiber-containing resin composition is preferably 1 to 100 parts by mass, more preferably 5 to 70 parts by mass, and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of the thermoplastic resin. More preferably, it is a part. If the content of the plant fiber is not less than the lower limit, the strength can be sufficiently improved, and if the content is not more than the upper limit, the plant-containing resin composition can be easily produced, and a decrease in toughness is suppressed. it can.
The content of the fiber dispersing resin is preferably 1 to 500 parts by mass, more preferably 10 to 100 parts by mass, and still more preferably 15 to 70 parts by mass with respect to 100 parts by mass of the plant fiber. . If the content of the fiber dispersion resin is equal to or higher than the lower limit value, a sufficiently high strength can be ensured. If the content of the fiber dispersion resin is equal to or lower than the upper limit value, the plant fiber-containing resin composition is obtained. Easy to manufacture.

(Method for producing plant fiber composition)
Next, an embodiment of the method for producing the plant fiber composition of the present invention will be described.
The manufacturing method of the vegetable fiber composition of this embodiment is a method which has a slurry preparation process, an emulsion preparation process, a mixing process, and a sheet | seat preparation process, and manufactures a vegetable fiber composition.

[Slurry preparation process]
A slurry preparation process is a process of preparing the fiber slurry containing a vegetable fiber. Here, the fiber slurry is a liquid in which plant fibers are dispersed in a dispersion medium. As the dispersion medium, water, an organic solvent, or the like can be used, but water is preferable.
The solid content concentration of the fiber slurry is preferably 0.1 to 10.0% by mass, and more preferably 0.5 to 5.0% by mass. If the solid content concentration of the fiber slurry is equal to or higher than the lower limit value, a composite sheet that sufficiently contains plant fibers can be easily produced in the sheet preparation step described later. Can be secured.
The fiber slurry may contain known papermaking chemicals such as a sizing agent and a paper strength enhancer, if necessary.

Specifically, in the slurry preparation step, plant raw materials such as conifers, hardwoods, and grasses are processed into fibers, that is, pulped, and diluted with a dispersion medium to obtain a fiber slurry. When the plant fiber is made into a fine fiber, the fiber is processed into a fine fiber to obtain a fiber slurry.
When obtaining fine fibers, it is preferable to use wood-based cellulose fibers obtained from conifers or hardwoods as plant materials. Wood-based cellulose fibers are aggregates of microfibril fibers composed of single nanofibers having a diameter of 2 to 4 nm (diameters of several μm to several tens of μm, fiber lengths of 0.1 mm to several mm). Therefore, the fine fiber obtained from wood-based cellulose can easily control the fiber diameter and fiber length depending on the degree of chemical treatment and mechanical treatment.
When obtaining wood-based cellulose fibers, pulp can be pulped using softwood chips, hardwood chips, or wood powder obtained by pulverizing these chips. A chip having a thickness of 2 mm to 8 mm is preferable. Wood flour can be obtained by sun drying or forcibly drying with a drier so that the moisture content of the chips is 10% by mass or less, and then pulverizing. Here, the particle diameter of the wood powder is preferably 0.1 mm to 1 mm.
Various pulps can be used as the raw material cellulose fiber. Pulp is pulp obtained by mechanical methods (ground wood pulp, refiner ground pulp, thermomechanical pulp, semichemical pulp, chemiground pulp, etc.), or pulp obtained by chemical methods (craft pulp, sulfite pulp) Etc.). Moreover, you may use a pulp individually by 1 type or in combination of 2 or more types.

  Fine fiber processing methods for obtaining fine fibers include known pulverizers and paper beating machines such as grinders (stone mill type pulverizers), high-pressure homogenizers, ultrahigh-pressure homogenizers, high-pressure collision type pulverizers, and disk type refiners. And a method of refining cellulosic fibers by wet pulverization or dry pulverization using a mechanical action such as a conical refiner, an ultrasonic homogenizer, a ball mill, a bead mill, a roll mill, a jut mill, a turbo mill, an atomizer, or a cutter mill.

  When obtaining fine fibers, a pretreatment such as a chemical modification treatment, a degreasing treatment, a delignification treatment, and a dehemicellulose treatment can be performed before the fine fiberization treatment in order to facilitate the fine formation.

In addition to the above pretreatment, before the fine fiber treatment, beating treatment, chemical modification treatment such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation treatment, ozone treatment, Kraft treatment, sulfite treatment, bleaching treatment, and enzyme treatment may be performed.

[Emulsion preparation process]
The emulsion preparation step is a step of preparing a resin emulsion containing a fiber dispersion resin. Here, the resin emulsion is a liquid in which resin particles for fiber dispersion are emulsified and dispersed in a dispersion medium.
The average particle diameter of the resin particles for fiber dispersion is preferably in the range of 0.001 to 100 μm, and more preferably in the range of 0.01 to 1.0 μm. The average particle diameter in the fiber dispersion resin particles is a value measured by measuring with a laser diffraction particle size distribution measuring device, for example, LA920 manufactured by Horiba, Ltd.
The average particle size of the resin emulsion is preferably large in consideration of yield and dehydration properties, but if it is too large, the uniformity of the sheet and the optical properties may be lowered.
In addition, the ionicity of the resin emulsion is appropriately selected from cationic, anionic, and nonionic properties due to characteristics such as operability in the process of making the mixed dispersion and paper plant-containing resin composition. can do.

  Moreover, it is preferable that the solid content concentration of a resin emulsion is 20-60 mass%, and it is more preferable that it is 30-60 mass%. If the solid content concentration of the resin emulsion is equal to or higher than the lower limit value, it is possible to easily produce a composite sheet sufficiently containing a fiber dispersing resin in the sheet preparation step described later. Can be secured.

  Emulsions can be prepared by emulsion polymerization of the monomer constituting the fiber dispersion resin in the presence of a surfactant in a dispersion medium (polymerization method), and the fiber dispersion resin and surfactant are added to the dispersion medium. And a method of stirring (post-emulsification method).

Specifically, the polymerization method is a method in which a monomer constituting the fiber dispersion resin is radically polymerized in a dispersion medium in the presence of a polymerization initiator, a chain transfer agent, and a surfactant.
In that case, it is preferable that the usage-amount of surfactant is the range of 0.1-6 mass% with respect to all the monomers. If the amount of the surfactant used is equal to or greater than the lower limit, sufficient polymerization stability can be ensured, aggregates are not easily generated during the reaction, and if the amount is equal to or smaller than the upper limit, the emulsion has a moderate particle size. It becomes.

As the surfactant, any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used. These surfactants may be used alone or in combination of two kinds.
Specific examples of anionic surfactants include potassium oleate, sodium laurate, sodium todecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylallyl. Examples include sodium ether sulfate, sodium polyoxyethylene dialkyl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl allyl ether phosphate, and the like.
Specific examples of the cationic surfactant include alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, acylaminoethyldiethylammonium salt, acylaminoethyldiethylamine salt, alkylamidopropyldimethylbenzylammonium salt, alkylpyridinium Quaternary ammonium salts such as salts, alkylpyridinium sulfates, stearamide methylpyridinium salts, alkylquinolinium salts, alkylisoquinolinium salts, fatty acid polyethylene polyamides, acylaminoethylpyridinium salts, acylcoraminoformylmethylpyridinium salts , Stearooxymethylpyridinium salt, fatty acid triethanolamine, fatty acid triethanolamine formate, trioxyethylene Ester-linked amines such as fatty acid triethanolamine, cetyloxymethylpyridinium salt, p-isooctylphenoxyethoxyethyldimethylbenzylammonium salt, ether-bonded quaternary ammonium salts, alkylimidazolines, 1-hydroxyethyl-2-alkylimidazolines, Complexed amines such as 1-acetylaminoethyl-2-alkylimidazoline, 2-alkyl-4-methyl-4-hydroxymethyloxazoline, polyoxyethylene alkylamine, N-alkylpropylenediamine, N-alkylpolyethylenepolyamine, N- Examples thereof include amine derivatives such as alkyl polyethylene polyamine dimethyl sulfate, alkyl biguanide, and long chain amine oxide.
Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, oxyethylene-oxypropylene block copolymer, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester and the like.
Further, in combination with the above-mentioned emulsifier, a relatively low molecular weight polymer compound having an emulsifying and dispersing ability, for example, polyvinyl alcohol, and modified products thereof, polyacrylamide, polyethylene glycol derivatives, and neutralization of polycarboxylic acid copolymers You may add a thing, casein, etc.

The density | concentration of the monomer at the time of superposition | polymerization is about 30-70 mass% normally, Preferably it is about 40-60 mass%.
As a polymerization initiator used in the polymerization, a peroxide compound or an azo compound can be used.
Peroxide compounds include benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, paramentane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, dicumyl Examples include peroxide, cyclohexane peroxide, succinic peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide, and the like.
As the azo compound, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2- Methylpropionitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl) azo ] Formamide, dimethyl 2,2′-azobis (2-methylpropionate), 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2,4,4-trimethylpentane) 2,2′-azobis {2-methyl-N- [1,1′-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azobis {2- (2-imidazoline-2 Yl) propane] dihydrochloride, 2,2′-azobis {2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis {2- [1- (2-hydroxy Ethyl) -2-imidazolin-2-yl) propane]} dihydrochloride, 2,2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis (2 -Methylpropionamidine) dihydrochloride, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate, and the like.

  Examples of the dispersion medium include water or an organic solvent, or a mixed solvent of water and an organic solvent. Here, as the hydrophilic organic solvent, ethers such as tetrahydrofuran, dioxane and dimethoxyethane, ketones such as methyl ethyl ketone, methyl isobutyl ketone and acetone, aromatics such as toluene, benzene and chlorobenzene, dichloromethane, 1,1, Examples include halogenated hydrocarbons such as 2-trichloroethane and dichloroethane, alcohols such as isopropanol, ethanol, methanol, and methoxyethanol, and ethyl acetate.

As monomers, ethylene, propylene, styrene, vinyl chloride, vinylidene chloride, vinyl acetate, (meth) acrylic acid alkyl ester, unsaturated carboxylic acid, (meth) acrylonitrile, (meth) acrylamide, butadiene, isoprene, chloroprene At least one selected from the group consisting of:
Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic acid. Examples include octyl, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like.
Further, as (meth) acrylic acid alkyl ester, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, polyethylene glycol (meth) acrylate, 2-hydroxy-3 -Phenoxypropyl (meth) acrylate, glycenol mono (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate , Dipropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane At least 1 such as tra (meth) acrylate, divinylbenzene, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and the like Seeds can also be used.
Examples of the unsaturated carboxylic acid include (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, monoalkylmaleic acid, monoalkylfumaric acid and the like.

  Examples of chain transfer agents include mercaptans such as n-dodecyl mercaptan, octyl mercaptan, t-butyl mercaptan, thioglycolic acid, thiomalic acid, thiosalicylic acid, sulfides such as diisopropylxanthogen disulfide, diethylxanthogen disulfide, diethylthiuram disulfide, and iodoform. And the like, diphenylethylene, p-chlorodiphenylethylene, p-cyanodiphenylethylene, α-methylstyrene dimer, sulfur and the like can be used.

  It is preferable to add a polymerization inhibitor after completion of the polymerization. Examples of the polymerization inhibitor include phenothiazine, 2,6-di-t-butyl-4-methylphenol, 2,2′-methylenebis (4-ethyl-6-t-butylphenol), tris (nonylphenyl) phosphite, 4 , 4′-thiobis (3-methyl-6-tert-butylphenol), N-phenyl-1-naphthylamine, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2-mercaptobenzimidazole, hydroquinone N, N-diethylhydroxylamine and the like can be used.

The polymerization reaction is usually performed at a reaction temperature of about 40 to 95 ° C., preferably about 60 to 90 ° C. for 1 to 10 hours, preferably about 4 to 8 hours.
Monomer addition method includes batch addition method, divided addition method, continuous addition method, monomer tap method for adding non-emulsified monomer, monomer pre-emulsion tap method for adding emulsified monomer, etc. It can be done by the method. A monomer pre-emulsification tapping method is preferred by a continuous addition method.

Next, a method for obtaining a resin emulsion by the post-emulsification method will be described.
The post-emulsification method is a method in which a fiber dispersion resin is dispersed in a dispersion medium using a dispersant such as a surfactant or a protective colloid agent.
As an apparatus used in the post-emulsification, any of high shear mixers such as homomixers, kneaders, colloid mills, and homogenizers, and extruders used for melt kneading of resins such as twin screw extruders are preferably used. These may be batch or continuous.
The post-emulsification process is not particularly limited. A method of heating and melting a fiber dispersion resin, mixing a dispersant, mixing with a heat dispersion medium, and rapidly stirring with a high shear stirrer to form an emulsion. The fiber dispersion resin is dissolved in an organic solvent in advance, mixed with a heat dispersion medium mixed with a dispersant, emulsified with a high shear stirrer, and then the organic solvent is removed. For fiber dispersion using a twin screw extruder A method of continuously emulsifying the resin by heating and melting, supplying a dispersant and a heat dispersion medium from the middle of the extruder, and kneading strongly can be suitably used. These methods are disclosed in JP-A-57-61035 and JP-A-56-2149.

  As the dispersant for post-emulsification, various surfactants in the polymerization method can be suitably used. The amount of the dispersant is preferably 0.1 to 20 parts by mass, more preferably 2 to 15 parts by mass with respect to the fiber dispersion resin. If the amount of the dispersant is equal to or more than the lower limit, the average particle diameter of the resin emulsion is reduced, and physical properties such as sheet uniformity and optical properties can be improved. Also, the emulsion stability of the resin emulsion itself, long-term Storage stability can be improved. On the other hand, if the amount of the dispersant is not more than the above upper limit value, the reinforcing effect by the plant fiber can be surely exhibited.

As the resin to be emulsified by the post-emulsification method, any of the aforementioned fiber dispersion resins is preferably used. However, the post-emulsification method is a process of finely dispersing in a dispersion medium. Since it is necessary to vigorously stir with the dispersion medium in the molten state, it is preferable that the melting point is low. Specifically, the melting point of the linear dispersion resin is preferably 170 ° C. or lower, and more preferably 100 ° C. or lower in that it can be mixed with hot water under atmospheric pressure. In order to disperse the fiber dispersion resin having a melting point exceeding 170 ° C. in a molten state with the heat dispersion medium, it must be mixed and stirred at a high temperature and a high pressure, and a large-scale production facility corresponding to a higher pressure is required. I need.
From the above, among the fiber dispersion resins described above, olefin resins having a melting point of 35 to 170 ° C are preferable, and those having a temperature of 45 to 101 ° C are more preferable.
Further, although the fiber dispersion resin can be used even if it is water-soluble, it is more preferably a water-insoluble resin that is easily separated from water from the viewpoint of dehydration in the sheet preparation process.

Moreover, a water-soluble or aqueous polyurethane emulsion is mentioned as a resin emulsion obtained by post-emulsification. As an example, a relatively low to medium molecular weight range heat-reactive polyurethane emulsion using a blocked isocyanate group may be mentioned. Another example is a relatively high molecular weight thermoplastic polyurethane emulsion mainly composed of a linear structure.
These can be obtained by introducing a hydrophilic group such as anion, cation or nonion into the polyurethane skeleton and self-emulsifying or dispersing, or by adding the above surfactant to polyurethane and forcibly dispersing in water. .

[Mixing process]
The mixing step is a step of mixing the fiber slurry and the resin emulsion to prepare a mixed dispersion. By this step, it is presumed that part or all of the plant fiber can be coated with the fiber dispersing resin.
Examples of the mixing method include a method in which the fiber slurry and the resin emulsion are put in a container and the mixture is stirred using a stirrer such as a homomixer, and the method in which the fiber slurry and the resin emulsion are passed through a line mixer.

  The mixing ratio of the fiber slurry and the resin emulsion is preferably such that the mixing amount of the fiber dispersing resin is 1 to 500 parts by mass, more preferably 10 to 100 parts by mass with respect to 100 parts by mass of the plant fiber. The ratio which becomes 15-70 mass parts is further more preferable. If the ratio of the resin emulsion is equal to or higher than the lower limit, the dispersibility of the plant fibers in the thermoplastic resin is further improved in the obtained plant fiber-containing resin composition, and a sufficiently high strength can be ensured. On the other hand, if the ratio of the resin emulsion is less than or equal to the above upper limit value, the peelability of the composite sheet is improved and the productivity is further increased in the sheet preparation process described later.

  For the mixed dispersion, publicly known and publicly available papermaking chemicals can be appropriately used. Examples of the papermaking chemicals include various chemicals such as paper strength agents, wet strength agents, retention agents, coagulants, filtering agents, bulking agents, viscosity modifiers, and antifoaming agents.

[Sheet preparation process]
The sheet preparation step is a step of preparing a composite sheet that is contained in a mixed state of plant fibers and fiber dispersion resin from the mixed dispersion. In this embodiment, a composite sheet is produced by papermaking of the mixed dispersion.

In the sheet manufacturing process in the present embodiment, a known continuous paper making apparatus used when manufacturing general paper can be used.
A known continuous papermaking machine comprises a dewatering section with a wire part, a squeezing section with a press part, and a drying section with a dryer part. In this specification, “dehydration” means not only removing water but also removing an organic solvent, and “squeezing” means not only squeezing water but also squeezing the organic solvent. Including.

As the dewatering section, a known dewatering method which is usually used in the production of paper such as long net paper can be used.
As a wire used at the time of spin-drying | dehydration, the wire applied with general papermaking can be used. Specific examples include metal wires such as stainless steel and bronze and plastic wires such as polyester, polyamide, polypropylene, and polyvinylidene fluoride. Moreover, you may use membrane filters, such as a cellulose acetate base material, as a wire.
The opening of the wire is preferably 0.2 to 200 μm, and more preferably 0.4 to 100 μm. If the mesh opening is equal to or greater than the lower limit, a sufficient dehydration rate can be obtained, and if the mesh is equal to or smaller than the upper limit, the yield of fine fibrous cellulose is increased.

As the squeezed section, a known method of dewatering with a roll press or a shoe press can be used.
As the drying section, a known method used in paper production can be employed. For example, a method using a drying device such as a cylinder dryer, a Yankee dryer, hot air drying, or an infrared heater can be used.

The basis weight of the composite sheet is preferably 1.0~1000g / ^{m 2,} more preferably 5.0~500g / ^{m 2,} more preferably 10.0~100g / ^{m 2.} If the basis weight of the composite sheet is equal to or greater than the lower limit value, sufficient sheet strength can be ensured, and continuous production is facilitated. If the basis weight is equal to or less than the upper limit value, the dehydration time is shortened and the composite sheet productivity is increased. .

  The thickness of the composite sheet is preferably 1-1000 μm, more preferably 5.0-500 μm, and even more preferably 10.0-100 μm. If the thickness of the composite sheet is equal to or greater than the lower limit value, sufficient sheet strength can be secured and continuous production is facilitated. If the thickness is equal to or less than the upper limit value, the dehydration time is shortened and the composite sheet productivity is increased. .

In the sheet preparation step, the obtained composite sheet can be pulverized to obtain a fine pulverized sheet. By pulverizing the composite sheet, the plant fibers can be more easily dispersed in the thermoplastic resin, and the strength of the resulting plant fiber-containing resin composition can be further improved.
In pulverization, it is preferable to pulverize to the extent that the shape of the microfiber after the microfibrillation treatment is not impaired. In the pulverization, a known pulverizer such as a sample mill, a hammer mill, a turbo mill, an atomizer, a cutter mill, a bead mill, a ball mill, a roll mill, or a jet mill can be used. Further, it may be shredded with a shredder.
Preferably the area of the sheet pulverized product is 0.1~2500mm ^2, more preferably 0.2~1000mm ^2.
Even if the area of the pulverized product is less than the lower limit value or more than the upper limit value, the mixture with the thermoplastic resin may be non-uniform in the melt-kneading step described later, and supply to the melt-kneading apparatus Can be difficult.

  After pulverization, the shape and size of the pulverized product may be sieved with a screen. Sifting facilitates uniform mixing with the thermoplastic resin. The aperture of the screen used for sieving is appropriately selected according to the type and shape of the thermoplastic resin.

<Plant fiber modifier>
The C) plant fiber modifier in the present invention is a compound having at least one functional group capable of reacting with a hydroxyl group present on the surface of the cellulose fiber, and re-aggregates the cellulose fiber when complexed with the thermoplastic resin. A compound containing an isocyanate group, a compound containing an epoxy group, a compound containing an amino group, an acid, an acid anhydride, an alcohol, a silane compound, a halogenating reagent, a cyclic ester compound, a cyclic amide 1 type, or 2 or more types chosen from the group which consists of a compound etc. are mentioned. When combining 2 or more types, two or more different functional groups can be introduced into the cellulose fiber. Among these plant fiber modifiers, halogenated reagents, compounds containing acid anhydride groups, compounds containing epoxy groups, silane compounds, cyclic amide compounds, and cyclic ester compounds are preferred. Among these, C) a plant fiber modifier that exhibits a gaseous or liquid form at the kneading temperature selected in the melt-kneading step is more preferable from the viewpoint of easy contact with the hydroxyl group of the plant fiber. .

  Examples of the acid include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, palmitic acid, stearic acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, behenic acid, Saturated fatty acids such as oleic acid, erucic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, norbornene dicarboxylic acid, bicyclo Carboxylic acids such as [2,2,1] hept-2-ene-5,6-dicarboxylic acid, carboxylic acids having different functional groups in addition to carboxylic acid groups such as ω-aminocarboxylic acid It is done.

An acid anhydride refers to a compound having an acid anhydride formed by dehydration condensation from two oxo acids, more preferably two carboxyl groups. For example, an acid anhydride having a cyclic structure formed by dehydration condensation of a compound having two or more carboxylic acids in the molecule, an oxo acid, and more preferably a plurality of molecules having a carboxyl group may undergo dehydration condensation. The acid anhydride etc. which are produced | generated are illustrated. Examples of acid anhydrides having a cyclic structure include maleic anhydride, itaconic anhydride, citraconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, succinic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, 3, 6-epoxy-1,2,3,6-tetrahydrophthalic anhydride, tetracyclo [6. 2. 1. 1 ^{3, 6} . 0 ^{2, 7} ] Dodeca-9-ene-4,5-dicarboxylic anhydride, 2,7-octadien-1-yl succinic anhydride, alkyl or alkenyl succinic anhydride and the like. In addition, acid anhydrides produced by dehydration condensation of a plurality of molecules having a carboxyl group include hexanoic anhydride, acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, octanoic anhydride, glutaric acid Examples include anhydrides, hexanoic anhydrides, and acid anhydrides produced by dehydration condensation of a plurality of different compounds having a carboxyl group, so-called mixed acid anhydrides (for example, acetic acid propionic acid anhydrides) It may be.

  Examples of the halogenating reagent include hexanoyl halide, heptanoyl halide, octanoyl halide, nonanoyl halide, decanoyl halide, lauroyl halide, palmitoyl halide, stearoyl halide and the like.

  Examples of the alcohol include pentanol, hexanol, heptanol, octanol, nonanol, decanol, dodecanol, cetanol, octadecanol, lauryl alcohol, cetyl alcohol, stearyl alcohol and the like.

  Examples of the compound containing an isocyanate group include pentyl isocyanate, hexyl isocyanate, cyclopentyl isocyanate, cyclohexyl isocyanate, and the like.

  Examples of the compound containing an epoxy group include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, p- (tert-butyl) phenyl glycidyl ether, 2,6-dibromophenyl glycidyl ether, resorcinol diglycidyl ether, neopentyl glycol. Diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycidyl acrylate, glycidyl methacrylate, 2-methylallyl glycidyl ether, styrene-p-glycidyl ether, 4-hydroxybutyl acrylate glycidyl ether, 1,2-epoxy-9- Examples include decene, butyl glycidyl ether, and glycidol.

  Compounds containing amino groups include octylamine, stearylamine, laurylamine, oleylamine, distearylamine, myristylamine, cetylamine, oleylamine, behenylamine, oleylpropylenediamine and other fatty acid amines, cyclohexylamine, dimethylaminocyclohexane, aniline , Saturated or unsaturated alicyclic amines such as chloroaniline, aminobenzenesulfonic acid, nitroaniline, nitrosoaniline, methylnitrosoaniline, N-methylaniline and their derivatives, monoethanolamine, diethanolamine, triethanolamine, phenylethanolamine , Naphthylethanolamine, methyldiethanolamine, aminophenol, aminoalcohols such as aminobenzoic acid, ethylene dia , Compounds having multiple amino groups such as hexamethylenediamine, alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, leucine, isoleucine, lysine, methionine, phenylalanine, proline, serine, threonine, Examples include amino acids such as tryptophan, tyrosine, and valine, methylamine, dimethylamine, ethylamine, diethylamine, and allylamine.

  The silane compound is a compound mainly containing methoxysilane or ethoxysilane. Specific examples include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltri. Methoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N 2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-chloropropyltrimethoxy Silane, 3-ureidopropyltriethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, n-octyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetraethoxysilane, tetra Methoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexyltrimethyl Kishishiran, decyl trimethoxysilane, etc., and more preferably, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane. These compounds may be monomers, but one or more of the monomers may form an oligomer.

  The cyclic ester compound is a compound having a lactone structure in the molecular structure. The lactone structure is a cyclic structure formed by atoms constituting an ester group, and is a structure in which a hydroxyl group and a carboxyl group are dehydrated and condensed. Examples of the cyclic ester compound include α-lactone, β-lactone, γ-lactone, δ-lactone, and ε-lactone. More specifically, α-acetolactone, α-angelica lactone, ε-caprolactone, δ-valerolactone, β-propiolactone, γ-butyrolactone, γ-crotonolactone, γ-pentanolactone, γ-dodeca Nolactone, γ-hexanolactone, DL-lactide, D-mannonic acid δ-lactone, 2-furanone, pentano-4-lactone and the like.

  The cyclic amide compound is a compound having a lactam structure in the molecular structure. The lactam structure is a cyclic structure formed by atoms including nitrogen atoms constituting the amide group, and is a structure in which a carboxyl group and an amino group are dehydrated and condensed. Cyclic amide compounds include ω-lactams having a main ring of 4 to 12 carbon atoms, and more specifically α-lactams, β-lactams, γ-lactams, δ-lactams, ε-lactams, and the like. It is done. Among them, γ-butyrolactam, ε-caprolactam, ω-enantolactam, ω-caprolactam, ω-laurolactam, ω-heptalactam, ω-octalactam, ω-undecalactam, and ω-laurolactam are further included. preferable.

  The content of the C) plant fiber modifier in the plant fiber-containing resin composition is preferably 0.1 to 200 parts by mass, and 1 to 150 parts per 100 parts by mass of the plant fiber in the plant fiber composition. It is more preferable that it is a mass part, and it is further more preferable that it is 2-100 mass parts. If it is lower than this range, the modification amount of the plant fiber is too small, and not only the dispersibility of the plant fiber in the thermoplastic resin is bad, but also the mechanical properties are lowered. If it is higher than this range, the residue of the plant fiber modifier in the resin composition is increased, which not only deteriorates the mechanical properties, but also causes odor and discoloration of the resin.

<Other ingredients>
In order to add other functions to the plant fiber-containing resin composition of the present invention without departing from the gist of the function of the composition of the present invention, an antioxidant, an ultraviolet absorber, a lubricant, an antistatic agent, You may mix | blend additives, such as a coloring agent, a pigment, a crosslinking agent, a foaming agent, a nucleating agent, a flame retardant, and a filler.

  Various resin modifiers and the like may be blended with the plant fiber-containing resin composition of the present invention within a range not departing from the gist of the function of the composition of the present invention. Examples of other components include butadiene rubber, isobutylene rubber, isoprene rubber, natural rubber, nitrile rubber, and petroleum resin, and these may be used alone or in a mixture.

<Plant fiber aggregate>
When coarse aggregates derived from plant fibers are present in the plant fiber-containing resin composition, even if the majority of the microfibrillated plant fibers are present, the tensile breaking elongation and impact resistance of the resin composition are high. descend. This is because coarse agglomerates become the starting point of fracture and stress concentrates.
The confirmation of the presence of coarse particles in the plant fiber-containing resin composition and the measurement of dimensions can be carried out by direct observation with an optical microscope. For example, when the plant fiber is cellulose and the thermoplastic resin is a polyolefin resin, the resin composition molded body containing the fiber is processed into a thin section using a razor, a microtome, etc., and this is processed with an optical microscope. By observing it, it is possible to confirm the presence and size of coarse aggregates of cellulose fibers. At that time, if cellulose fibers are dyed with iodine solution or the like, the observation becomes easier.
The coarse aggregate of plant fiber refers to a coarse aggregate that satisfies both the fiber length and fiber width dimensions described below. That is, if the length of the aggregate is 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less, the decrease in impact resistance of the plant fiber-containing resin composition is small. When the width of the aggregate is 80 μm or less, preferably 60 μm or less, more preferably 45 μm or less, and even more preferably 30 μm or less, the impact resistance of the plant fiber-containing resin composition is less deteriorated. That is, an aggregate having a length longer than 300 μm and a width greater than 80 μm is a coarse aggregate. For example, even if the fiber length is longer than 300 μm, if the fiber width is 80 μm or less, preferably 60 μm or less, more preferably 45 μm or less, and even more preferably 30 μm or less, the decrease in impact resistance is small. Further, the minimum fiber length and the minimum fiber width of the aggregate are not observed with an optical microscope. This is because the measurement limit of the optical microscope is affected by the wavelength of light, and for example, observation of 1 μm or less is substantially difficult. Therefore, although the minimum range of the size of the aggregate cannot be determined, theoretically, the minimum width of the plant fiber, for example, about 4 nm is the minimum width in the case of cellulose fiber. Even when the fiber length is 300 μm or more, the impact resistance of the resin composition containing the fiber width does not decrease as long as the fiber width is not observable with an optical microscope.

"Manufacture of plant fiber-containing resin composition"
(Melting and kneading process)
The melt-kneading step is a step in which A) a thermoplastic resin, B) a plant fiber composition, and C) a plant fiber modifier are combined while being melt-kneaded. The melt-kneading process mainly consists of two processes. That is, B) a step of combining a plant fiber in a plant fiber composition and C) a plant fiber modifier, and B) a step of dispersing the plant fiber in the plant fiber composition in A) a thermoplastic resin. is there. These steps may be performed simultaneously, or may be performed in an appropriate order.

As the melt-kneading apparatus, a known kneading apparatus such as a single-screw extruder, a twin-screw extruder, a twin-screw kneader, a kneader, a Banbury mixer, a reciprocating kneader (BUSS KNEADER), a roll kneader, or the like can be used. . Of these, a single screw extruder, a twin screw extruder, a twin screw kneader, a Banbury mixer, and a reciprocating kneader are preferable in consideration of productivity and workability. When selecting a melt-kneading apparatus, a plant fiber-containing resin composition having a higher dispersibility and a substantial absence of coarse agglomerates is more effective when an apparatus having a high hermeticity inside the kneader is selected. Can be manufactured. That is, when the plant fiber is modified with C) the plant fiber modifier, modification can be performed more efficiently if the leakage of the C) plant fiber modifier is less from the inside of the extruder.
Specific examples of the melt-kneading method include the following methods. In advance, A) thermoplastic resin, B) plant fiber composition and C) plant fiber modifier are uniformly mixed with a tumbler mixer, super mixer, super floater, Henschel mixer, etc. A method in which the mixture is put into a screw extruder and melt kneaded, and A) a thermoplastic resin and B) a plant fiber composition are melt kneaded with a single screw extruder or a twin screw extruder. A method of adding a plant fiber modifier and melt-kneading again with a single screw extruder or a twin screw extruder, A) a thermoplastic resin and C) a plant fiber modifier with a single screw extruder or a twin screw extruder A method in which B) a plant fiber composition is further added to the kneaded material obtained by melt-kneading and the mixture is melt-kneaded again with a single-screw extruder or a twin-screw extruder, using a twin-screw extruder. Kneading thermoplastic resin and B) plant fiber composition In the middle of the extruder, C) a method of adding a plant fiber modifier and further melt-kneading, using a twin screw extruder, A) a thermoplastic resin and C) a plant fiber modifier are first kneaded, Examples thereof include B) a method of adding a plant fiber composition and further melt-kneading. In order to enhance the dispersibility of the plant fiber, the resin composition in which the plant fiber is combined may be melt-kneaded in a further step. Even if coarse fiber aggregates exist in the plant fiber composition used as a raw material, the coarse fiber aggregates are re-defibrated during the melt-kneading process, and the plant fiber-containing resin composition is substantially Coarse aggregates are not present. A) Opening of vents and deaeration to remove moisture and other volatiles generated from thermoplastic resins and plant fiber compositions, and residual volatile components when volatile C) plant fiber modifiers are used. Equipment may be used.

  The temperature at the time of melt kneading in the production of the plant fiber-containing resin composition is appropriately set according to the melting temperature of the thermoplastic resin, and is, for example, in the range of 70 to 300 ° C. In particular, when an olefin resin is used as the thermoplastic resin, the kneading temperature is in the range of 70 ° C to 300 ° C, preferably in the range of 80 ° C to 250 ° C, more preferably in the range of 85 ° C to 230 ° C, and more preferably 90 ° C. The range of ° C to 200 ° C is good. Below this range, the resin to be kneaded does not melt and is virtually impossible to manufacture. If this range is exceeded, the A) thermoplastic resin and B) plant fiber composition used for production are damaged by heat, resulting in molecular chain breakage, oxidative degradation, modification, and the like, resulting in a decrease in mechanical properties. Without any unpleasant odor or discoloration.

  The melt kneading time in the production of the plant fiber-containing resin composition is preferably longer from the viewpoint of the chemical reaction between C) the plant fiber modifier and B) the plant fiber in the plant fiber composition. It is set as appropriate. For example, when a batch-type kneader such as a Banbury mixer is used, if it is within the range of 1 to 100 minutes, both plant fiber modification and productivity can be achieved, but productivity must be taken into consideration. For example, the manufacturing can be performed even in a longer time. Further, for example, when a continuous kneader such as a single screw extruder, a twin screw extruder, a reciprocating kneader (BUSS KNEADER) is used, if the residence time is within a range of 1 to 20 minutes, Although it is possible to achieve both plant fiber modification and productivity, if the productivity is not taken into consideration, the production is possible even in a longer time.

  In the following, the present invention will be described in detail by way of examples and comparative examples, and the rationality and significance of the configuration of the present invention and the prior art by comparing the data of each preferred example and the comparison between each example and each comparative example. Demonstrate excellence against

(Manufacture of plant fiber composition fibers)
[Fiber slurry]
Softwood bleached kraft pulp (manufactured by Oji Paper Co., Ltd., Canada Standard Freeness (CSF) 550 ml measured according to JIS P8121) was beaten using a double disc refiner made by Kumagai Rika Kogyo. The average fiber length of the fibers contained in the fiber water slurry was 0.66 mm, and the average fiber width was 300 nm.

[Resin emulsion]
The resin emulsion was produced according to the method described in JP-A-2007-326913. The raw materials are an ethylene-methyl acrylate-maleic anhydride copolymer (trade name: Lexpearl ET, grade: ET330H) manufactured by Nippon Polyethylene Co., Ltd., a cationic polymer surfactant, and water.
Specifically, the ethylene-methyl acrylate-maleic anhydride copolymer is continuously supplied from the hopper of the same direction rotating meshing twin screw extruder at a rate of 100 parts by mass / hour, and provided in the vent portion of the extruder. From a supply port, an aqueous solution of a cationic polymer surfactant having a solid content of 35% by mass at a rate of 26.8 parts by mass / hour (the solid content is 8 parts by mass / hour) is a gear pump (discharge pressure 3 Kg / cm 2 G). ) And continuously extruding at a heating temperature of 110 ° C. The cationic polymer surfactant used here was produced according to the method described in 2007-326913.
The resin emulsion used was an ethylene-methyl acrylate-maleic anhydride copolymer dispersed in water with an average particle size of 1 μm. This resin emulsion has a non-volatile component of 45.3% and a pH of 4.6.
The average particle diameter was measured according to the method described in JP 2011-46776 A. Specifically, the median diameter in the volume distribution was measured using a laser diffraction particle size distribution analyzer SALD-2000 series manufactured by Shimadzu Corporation under the condition of refractive index: 1.50-0.20i.
The nonvolatile component was measured according to the method described in JP 2011-46776 A. Specifically, about 1 g of an aqueous emulsion sample was precisely weighed and dried with a hot air circulating dryer at 105 ° C. for 3 hours, then allowed to cool in a desiccator, and its mass was measured. Minutes were calculated.
Nonvolatile content [%] = (mass of sample after drying / mass of sample before drying) × 100
The pH of the resin emulsion was measured according to JIS Z8802 “pH measurement method”.

[Production of plant fiber composition (B-1)]
70 parts of the fiber slurry (in terms of solid content) and 30 parts of the resin emulsion (in terms of solid content) were mixed.
While stirring this mixed slurry, 46 ppm of cationic polymer retention agent ND-200C (manufactured by Hymo) was added, and 46 ppm of anionic polymer retention agent FA-230 (manufactured by Hymo) was further added.
Next, the mixed dispersion liquid was subjected to suction paper dehydration on a double woven plastic wire manufactured by Nippon Filcon Co., Ltd. to obtain a water-containing web composed of fine fibrous cellulose and a resin emulsion. The water-containing web was dried using a cylinder roll to obtain a sheet-like plant fiber-containing composition (B-1) having a basis weight of 30.8 g / m ² .

(Example 1) Production of plant fiber-containing resin composition (D-1) Linear low density polyethylene (manufactured by Nippon Polyethylene Co., Ltd., trade name: F30HG, described as “LLDPE” in the table) 5.0 kg, plant After sufficiently mixing 365 g of the fiber composition (B-1) and 12.5 g of maleic anhydride (manufactured by NOF Corporation, trade name: SY-A) with a Henschel mixer, the set temperature is 160 ° C. using a 50 mm single screw extruder. The kneading was carried out at a rotational speed of 80 times / min, and the strand discharged from the die was processed into a pellet shape. The obtained pellets were kneaded for 10 minutes at a preset temperature of 160 ° C. and a rotational speed of 75 revolutions / minute using a Laboplast mill mixer (manufactured by Toyo Seiki Seisakusho, roller mixer R60). After kneading, the kneaded product was recovered from the mixer to obtain a plant fiber-containing resin composition (D-1).

(Example 2) Production of plant fiber-containing resin composition (D-2) A plant fiber-containing resin composition (D-2) was produced in the same manner as in Example 1, except that the amount of maleic anhydride added was changed to 50 g. )

(Example 3) Production of plant fiber-containing resin composition (D-3) A plant fiber-containing resin composition (D-3) was produced in the same manner as in Example 1 except that the amount of maleic anhydride added was changed to 125 g. )

(Comparative Example 1) Production of plant fiber-containing resin composition (D-4) A plant fiber-containing resin composition (D-4) was obtained in the same manner as in Example 1 except that maleic anhydride was not added.

<Evaluation>
For each example, the tensile properties and coarse aggregates were evaluated by the following methods. The evaluation results are shown in Table 1.

[Measurement of tensile yield strength and tensile fracture elongation]
○ Preparation method of tensile test sample The pellets of each example and each comparative example were put into a hot press mold having dimensions of 150 mm x 150 mm and a thickness of 2 mm, and preheated for 5 minutes in a hot press machine having a surface temperature of 190 ° C. The resin was melted by repeating pressurization and decompression, and the residual gas in the molten resin was degassed, and further pressurized at 4.9 MPa and held for 5 minutes. Thereafter, the plate was gradually cooled at a rate of 10 ° C./min with a pressure of 4.9 MPa applied, and the molded plate was taken out of the mold when the temperature dropped to near room temperature. The obtained molded plate was conditioned for 48 hours or more in an environment of temperature 23 ± 2 ° C. and humidity 50 ± 5 ° C. The pressed plate after the state adjustment was punched into the shape of No. 2 test piece described in JIS K 7113-1995 to obtain a tensile test sample.
Tensile test conditions Tensile yield strength and tensile elongation at break were measured according to JIS K 7113-1995 using the above test pieces. Tensilon (model: RTG-1250) manufactured by A & D Co., Ltd. was used as a tensile tester. The tensile speed was 50 mm / min.

[Measurement of tensile impact strength]
Preparation method of tensile impact strength test sample The pellets of each example and each comparative example were placed in a hot press mold having dimensions of 50 mm × 60 mm and a thickness of 1 mm, and preheated for 5 minutes in a hot press machine having a surface temperature of 190 ° C. Thereafter, the resin was melted by repeating pressurization and decompression, and the residual gas in the molten resin was deaerated, and further pressurized at 4.9 MPa and held for 5 minutes. Thereafter, the plate was gradually cooled at a rate of 10 ° C./min with a pressure of 4.9 MPa applied, and the molded plate was taken out of the mold when the temperature dropped to near room temperature. The obtained molded plate was conditioned for 48 hours or more in an environment of temperature 23 ± 2 ° C. and humidity 50 ± 5 ° C. A test piece having the shape of ASTM D1822 Type-S was punched out of the press plate after the state adjustment to obtain a tensile impact strength test sample.
-Tensile impact strength test conditions Tensile impact strength was measured using the above test piece with reference to method B of JIS K 7160-1996. The only difference from JIS K 7160-1996 is the shape of the test piece. Regarding other measurement conditions, etc., the test was carried out by a method according to JIS K 7160-1996.

[Observation of coarse aggregates of plant fibers]
A molded plate of the plant fiber-containing resin composition was prepared in the same manner as in the above [Measurement of tensile impact strength]. A steel knife (manufactured by Microtome Laboratories Co., Ltd., model number: T-40) was attached to a rotary microtome (manufactured by Japan Microtome Laboratories Co., Ltd.), and the molded plate was processed into thin sections having a thickness of about 10 μm. Thereafter, the thin section was stained with iodine solution (manufactured by Kanto Chemical Co., Inc.) having a concentration of 0.05 mol / l. Only cellulose was colored by dyeing. The stained thin section was fixed on a slide glass using liquid paraffin (manufactured by Kanto Chemical Co., Inc.) and a cover glass. The thin slice fixed on the slide glass was observed with an optical microscope equipped with a 20 × objective lens and a 20 × eyepiece lens, and a photograph with a field of view of about 460 μm × 370 μm was taken. As a specific example, the photograph of the vegetable fiber containing resin composition of Example 3 is shown in FIG. 1, and the photograph of the vegetable fiber containing resin composition of the comparative example 1 is shown in FIG. For the same sample, five photographs were taken at different observation locations at random, and the largest aggregate size was defined as the aggregate size. The aggregate size was a fiber length of 300 μm or more, and a fiber width. When both of 60 μm or more were satisfied, it was defined that coarse aggregates were present in the plant fiber-containing resin composition.

[Consideration of results of Examples and Comparative Examples]
Examples 1-3 are plant fiber containing LLDPE compounded in a range of 5 parts by mass to 50 parts by mass with respect to 100 parts by mass of cellulose fiber and 5 parts by mass of maleic anhydride with respect to 100 parts by mass of cellulose fiber. It is a resin composition. Compared with these examples and Comparative Example 1 in which maleic anhydride is not added, although the tensile yield strength is comparable, the tensile elongation at break and the tensile impact strength are excellent. That is, if a plant fiber-containing resin composition produced by the method of the present invention using maleic anhydride as a plant fiber modifier, the plant fiber-containing resin maintains a good balance of strength, tensile fracture elongation, and impact resistance. It was shown that the composition can be manufactured. Further, it was shown that the plant fiber-containing resin composition having the plant fiber dispersibility within the range of the present invention can maintain the strength, tensile fracture elongation, and impact resistance in a well-balanced manner.

  The significance and rationality of the configuration of the present invention (invention specific matter) and the superiority over the prior art are clarified by the good results of each of the above examples and the comparison with each comparative example.

  Since the plant fiber-containing resin composition obtained by the production method of the present invention has high strength and impact resistance, personal computers, mobile phones, portable terminals and other information equipment, home appliance housings, stationery, office equipment, It can be suitably used for furniture, sports equipment, automobile interior and exterior materials, aircraft interior materials, parts for transportation equipment, building materials, and the like. Moreover, since this vegetable fiber containing resin composition is excellent also in electrical insulation, it can be used conveniently also for an electric equipment, an electronic device, and a communication apparatus.

Claims (15)

A method for producing a resin composition comprising combining A) a thermoplastic resin, B) a plant fiber composition, and C) a plant fiber modifier while melt-kneading, and B) a plant fiber A method for producing a plant fiber-containing resin composition, wherein the plant fiber in the composition satisfies the following conditions.
1. Average fiber length is 0.1-0.7mm
2. Average fiber width is 2 to 15000 nm   In the molten A) thermoplastic resin, B) a step of compounding the plant fiber in the plant fiber composition with C) a plant fiber modifier; B) the plant fiber in the plant fiber composition is A) thermoplastic The method for producing a plant fiber-containing resin composition according to claim 1, comprising at least a step of dispersing in a resin.   C) Compound in which the plant fiber modifier contains a functional group selected from an acid, an acid anhydride, an alcohol, a halogenating reagent, a silane compound, an isocyanate group-containing compound, an amino group-containing compound, a cyclic amide compound, and a cyclic ester compound The method for producing a plant fiber-containing resin composition according to claim 1, wherein the method is a plant fiber-containing resin composition.   The method for producing a plant fiber-containing resin composition according to any one of claims 1 to 3, wherein the plant fiber modifier is a compound containing a carboxylic acid or an acid anhydride.   A) A thermoplastic resin is an olefin resin, The manufacturing method of the vegetable fiber containing resin composition as described in any one of Claims 1-4 characterized by the above-mentioned.   The plant fiber in the plant fiber composition is 0.1 to 100 parts by mass with respect to 100 parts by mass of A) the thermoplastic resin, according to any one of claims 1 to 5. A method for producing a plant fiber-containing resin composition.   B) The plant fiber modifier is 0.1 to 200 parts by mass with respect to 100 parts by mass of the plant fiber in the plant fiber composition, according to any one of claims 1 to 6. Of producing a vegetable fiber-containing resin composition.   B) The method for producing a plant fiber-containing resin composition according to any one of claims 1 to 7, wherein the plant fiber in the plant fiber composition has been defibrated.   A) The thermoplastic resin is any one of an ethylene homopolymer, a copolymer of ethylene and an α-olefin, and a copolymer of ethylene, a vinyl group and a monomer having a polar group, The manufacturing method of the vegetable fiber containing resin composition as described in any one of Claims 1-8.   B) The method for producing a plant fiber-containing resin composition according to any one of claims 1 to 9, wherein the plant fiber composition is a cellulose web (cellulose / emulsion web). A plant fiber-containing resin composition comprising A) a thermoplastic resin, B) a plant fiber composition, and C) a plant fiber modifier, wherein B) part or all of the hydroxyl groups of the plant fiber composition are C) A plant fiber-containing resin composition that is chemically modified with a plant fiber modifier, and further B) the plant fiber contained in the plant fiber composition satisfies the following conditions: A vegetable fiber-containing resin composition in which cellulose nanofibers are dispersed and coarse aggregates are substantially not found.
1. Average fiber length is 0.0001 to 0.7 mm
2. Average fiber width is 2 to 15000 nm   C) Compound in which the plant fiber modifier contains a functional group selected from an acid, an acid anhydride, an alcohol, a halogenating reagent, a silane compound, an isocyanate group-containing compound, an amino group-containing compound, a cyclic amide compound, and a cyclic ester compound The plant fiber-containing resin composition according to claim 11, wherein   The plant fiber-containing resin composition according to claim 11 or 12, wherein A) the thermoplastic resin is an olefin resin.   The plant fiber in B) plant fiber composition is 0.1-100 mass parts with respect to 100 mass parts of A) thermoplastic resins, It is characterized by the above-mentioned. A plant fiber-containing resin composition.   B) The plant fiber modifier is 0.1 to 200 parts by mass with respect to 100 parts by mass of the plant fiber in the plant fiber composition, according to any one of claims 11 to 14. Plant fiber-containing resin composition.