Granular masterbatch for fiber-reinforced resin composition, fiber-reinforced resin composition, fiber-reinforced resin molded article, and methods for manufacturing the same

Abstract

To provide a granular masterbatch that allows easy production of a fiber-reinforced resin molded article exhibiting excellent flexural modulus.SOLUTION: A granular masterbatch for a fiber-reinforced resin composition, characterized by containing a modified plant fiber (A) and a thermoplastic resin fiber (B).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a granular masterbatch for a fiber-reinforced resin composition containing plant fibers, a fiber-reinforced resin composition, a fiber-reinforced resin molded product, and methods for producing the same. [Background technology]

[0002] Fiber-reinforced plastics are lightweight and have excellent mechanical strength, so they are used in automotive exterior panels and interior materials, electrical equipment housings, building materials, etc., in order to reduce greenhouse gas emissions, and are expected to be one of the means to build a decarbonized society. In particular, increasing the strength of fiber-reinforced plastics and their efficient production can reduce the amount of plastic and energy used, and are therefore expected to be one of the means to efficiently reduce greenhouse gas emissions.

[0003] Plant fibers such as cellulose fibers are known as fibers used in such fiber-reinforced plastics. However, even if plant fibers are mixed directly with resin, it is difficult to uniformly disperse the plant fibers in the resin, making it difficult to sufficiently improve the mechanical properties of resin molded articles. Furthermore, in conventional fiber-reinforced plastics, pre-fine plant fibers such as microfibrillated cellulose are used to highly disperse the plant fibers. However, the fine plant fibers have hydrophilic surfaces, making it difficult to uniformly disperse them directly in hydrophobic resins. Therefore, it is necessary to subject the surfaces of the fine plant fibers to hydrophobic treatment. Because such fine plant fibers with hydrophobic surfaces are expensive, there is a need to develop a method for obtaining fiber-reinforced resin molded articles with excellent mechanical properties at lower cost.

[0004] Japanese Patent Laid-Open Publication No. 2023-47589 (Patent Document 1) discloses a microfiber cellulose solid obtained by compression molding a mixture containing resin powder and microfiber cellulose, and also describes that the use of this microfiber cellulose solid improves the productivity of the kneading process. However, even when this microfiber cellulose solid is used, the dispersibility of the cellulose fibers is not necessarily high, and the mechanical properties of the resulting fiber-reinforced resin molding are not necessarily sufficient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-47589 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the problems associated with the above-described conventional techniques, and aims to provide a granular masterbatch that can easily produce a fiber-reinforced resin molded product having an excellent flexural modulus, a fiber-reinforced resin composition and a fiber-reinforced resin molded product using the masterbatch, and methods for producing the same. [Means for solving the problem]

[0007] As a result of extensive research to achieve the above object, the inventors discovered that fiber-reinforced resin moldings with excellent flexural modulus can be easily obtained by using a granular masterbatch containing modified plant fibers and thermoplastic resin fibers, and thus completed the present invention.

[0008] That is, the present invention provides the following aspects. [1] A granular masterbatch for a fiber-reinforced resin composition, comprising modified plant fibers (A) and thermoplastic resin fibers (B). [2] The granular masterbatch according to [1], wherein the thermoplastic resin fiber (B) is at least one selected from the group consisting of polyolefin-based resin fibers and polyester-based resin fibers. [3] The modified plant fiber (A) is a plant fiber (A') modified with at least one modifier (C) selected from the group consisting of silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers. [1] The granular masterbatch according to [2]. [4] The granular masterbatch according to any one of [1] to [3], further comprising at least one of a compatibilizer (D) and a binder resin (E). [5] A mixing step of obtaining a mixture (α) of plant fibers (A') and thermoplastic resin fibers (B); a modification step of modifying the plant fibers (A') in the mixture (α) with a modifying agent (C) to obtain a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B); A method for producing a granular masterbatch for a fiber-reinforced resin composition, comprising: [6] The method for producing a granular masterbatch according to [5], wherein in the mixing step, the plant fibers (A') and the thermoplastic resin fibers (B) are wet-mixed, and then the solvent is removed to obtain the solid mixture (α) containing the plant fibers (A') and the thermoplastic resin fibers (B). [7] The method for producing a granular masterbatch according to [5], wherein in the mixing step, the plant fibers (A') and the thermoplastic resin fibers (B) are dry-mixed to obtain the solid mixture (α). [8] The method for producing a granular masterbatch according to [6] or [7], wherein in the modification step, the solid mixture (α) is pulverized to obtain a granular mixture (α), and then the plant fibers (A') in the granular mixture (α) are modified with a modifying agent (C) to obtain the granular masterbatch. [9] The method for producing a granular masterbatch according to [6] or [7], wherein in the modification step, the plant fibers (A') in the solid mixture (α) are modified with a modifying agent (C) to obtain a solid mixture (β) containing the modified plant fibers (A) and the thermoplastic resin fibers (B), and then the solid mixture (β) is pulverized to obtain the granular masterbatch.

[10] The method for producing a granular masterbatch according to any one of [5] to [9], wherein the modifier (C) is at least one selected from the group consisting of silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers.

[11] The method for producing a granular masterbatch according to any one of [5] to

[10] , wherein the granular masterbatch contains at least one of a compatibilizer (D) and a binder resin (E).

[12] A fiber-reinforced resin composition containing modified plant fibers (A), thermoplastic resin fibers (B), and a diluent resin (F).

[13] A fiber-reinforced resin molding obtained by molding the fiber-reinforced resin composition according to

[12] .

[14] A method for producing a fiber-reinforced resin molded body, comprising mixing the granular masterbatch according to any one of [1] to [4] and a granular or powdery diluent resin (F) in a molding machine, and molding the resulting mixture to obtain a fiber-reinforced resin molded body.

[15] A method for producing a fiber-reinforced resin molded body, comprising melt-kneading the granular masterbatch according to any one of [1] to [4] and a granular or powdery diluent resin (F), and feeding the resulting molten mixture into a molding machine to mold it, thereby obtaining a fiber-reinforced resin molded body. [Effects of the Invention]

[0009] According to the present invention, it is possible to easily obtain a fiber-reinforced resin molded product having an excellent flexural modulus. Furthermore, according to the present invention, it is possible to mix the masterbatch and the diluent resin without melt-kneading, i.e., to mix them on a machine, thereby reducing production costs and easily producing a fiber-reinforced resin molded product having an excellent flexural modulus. Furthermore, by wet-mixing plant fibers and thermoplastic resin fibers when preparing the masterbatch, it is possible to easily obtain a fiber-reinforced resin molded product having an excellent flexural strength, and by dry-mixing, it is possible to easily obtain a fiber-reinforced resin molded product having an excellent Charpy impact strength. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on preferred embodiments thereof.

[0011] First, each component used in the present invention will be described.

[0012] (A) Modified plant fibers and (A') plant fibers: The modified plant fibers (A) used in the present invention are plant fibers (A') whose surfaces have been hydrophobically modified with a modifier (C) or the like, as described below. The plant fibers (A') are not particularly limited as long as they can be used in fiber-reinforced plastics, and examples include cellulose-based fibers (cellulosic fibers), such as wood fibers, seed fibers, bast fibers, leaf vein fibers (vascular fibers), fruit fibers, and stem fibers. These plant fibers may be used as they are, or may be pulped (from which lignin and hemicellulose have been removed). That is, the plant fibers (A') may contain lignin (e.g., lignocellulosic fibers) or may not contain lignin (e.g., pulp).

[0013] Examples of the wood fibers include coniferous fibers and broad-leaved fibers. Examples of the seed fibers include cotton, kapok, and burdock. Examples of the bast fibers include ramie, flax, jute, hemp, paper mulberry, mitsumata, gampi, kenaf, and mulberry. Examples of the leaf vein fibers include sisal, Manila hemp, pineapple, New Zealand hemp, Sansevieria hemp, banana, and agave. Examples of the fruit fibers include coconut coir and oil palm coir. Examples of the stem fibers include sugarcane bagasse, bamboo, rice straw, wheat straw, reeds, palm, napier grass (elephant grass), switchgrass, miscanthus (Japanese silvergrass), and erianthus.

[0014] The pulp may be a chemical pulp (CP) or a mechanical pulp (MP). Examples of chemical pulp include kraft pulp (KP), sulfide pulp (SP), and alkaline pulp (AP). Examples of mechanical pulp include ground pulp (GP), refiner ground pulp (RGP), thermo-mechanical pulp (TMP), and chemi-thermo-mechanical pulp (CTMP). Furthermore, the pulp may be bleached with chemicals (BP) or unbleached (UP).

[0015] Pulps derived from wood fibers (wood pulps) include, but are not limited to, softwood bleached chemical pulps (NBCPs) such as softwood bleached kraft pulp (NBKP), softwood unbleached chemical pulps (NUCPs) such as softwood unbleached kraft pulp (NUKP), hardwood bleached chemical pulps (LBCPs) such as hardwood bleached kraft pulp (LBKP), and hardwood unbleached chemical pulps (LUCPs) such as hardwood unbleached kraft pulp (LUKP).

[0016] Furthermore, the pulp may be dry pulp or never-dry pulp. The never-dry pulp is pulp that has never been dried and remains wet, and is not particularly limited, but examples include unbleached pulp (for example, never-dry pulp in NUCP such as NUKP or LUCP such as LUKP) obtained by boiling raw material chips with chemicals to break down the chip fibers during the pulp production process, washing the broken down fibers to remove lignin and foreign matter, and then decomposing the remaining lignin with oxygen, or pulp that has been bleached with chemicals (for example, never-dry pulp in NBCP such as NBKP or LBCP such as LBKP).

[0017] The plant fibers (A') may be either pulverized (pulverized plant fibers) or not pulverized (non-pulverized plant fibers), but non-pulverized plant fibers are preferred from the viewpoint of low cost. Even when non-pulverized plant fibers are used as the plant fibers (A'), according to the present invention, a large amount of the plant fibers (A') can be uniformly dispersed in the diluent resin (F) described below, making it possible to easily obtain a fiber-reinforced resin molding having excellent flexural modulus and flexural strength. The average fiber diameter of the plant fibers (A') is not particularly limited, but is preferably 0.1 to 60 μm, and more preferably 10 to 30 μm from the viewpoint of non-pulverized plant fibers.

[0018] These plant fibers (A') may be used alone or in combination of two or more.

[0019] (B) Thermoplastic resin fiber: The thermoplastic resin fiber (B) used in the present invention is mixed with the modified plant fiber (A) to form a granular masterbatch, which allows a large amount of the modified plant fiber (A) to be uniformly dispersed in the diluent resin (F) described below. Examples of such thermoplastic resin fibers include polyolefin resin fibers and polyester resin fibers. Examples of polyolefin resin fibers include polyethylene fibers, polypropylene fibers, and ethylene-propylene copolymer fibers. Examples of polyester resin fibers include polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polytrimethylene terephthalate fibers. These thermoplastic resin fibers (B) may be used alone or in combination of two or more. Among these thermoplastic resin fibers (B), polyester resin fibers are preferred, and polyethylene terephthalate fibers are more preferred, from the viewpoint of improving mechanical properties (e.g., flexural modulus and flexural strength in the case of wet mixing).

[0020] The fineness of the thermoplastic resin fibers (B) is preferably 0.01 to 5 dtex, more preferably 0.05 to 3 dtex, from the viewpoint of obtaining a granular masterbatch in which the modified plant fibers (A) and the thermoplastic resin fibers (B) are uniformly mixed. The average fiber length of the thermoplastic resin fibers (B) is preferably 1 to 50 mm, more preferably 3 to 40 mm, from the viewpoint of obtaining a granular masterbatch in which the modified plant fibers (A) and the thermoplastic resin fibers (B) are uniformly mixed.

[0021] (C) Denaturant: The modifier (C) used in the present invention is used to modify the surface of the plant fiber (A') to make it hydrophobic. By appropriately hydrophobizing the surface of the plant fiber (A'), the dispersibility of the modified plant fiber (A) in the diluent resin (F), which will be described later, is improved. Examples of such modifiers (C) include silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers. These modifiers (C) may be used alone or in combination of two or more.

[0022] Examples of the silane coupling agent include those disclosed in JP-A-2008-266630. Specifically, the silane coupling agent is a silane coupling agent represented by the following formula (I): R 1 -(CH2) n -Si(OR 2 )3(I) (In the formula, R 1 represents an amino group, a mercapto group, a glycidoxy group, an acryloxy group, or a methacryloxy group, and R 2 represents a methyl group or an ethyl group, and n is an integer of 1 to 3. Among these silane coupling agents, silane coupling agents having an amino group or a mercapto group are preferred, silane coupling agents having an amino group are more preferred, and 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane are even more preferred.

[0023] Examples of carboxylic acids include aliphatic monocarboxylic acids, aromatic monocarboxylic acids, aliphatic polycarboxylic acids, aromatic polycarboxylic acids, rosin acid, and derivatives thereof. Examples of aliphatic monocarboxylic acids include propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, nonanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, acrylic acid, oleic acid, linoleic acid, and linolenic acid. Examples of aromatic monocarboxylic acids include benzoic acid and salicylic acid. Examples of aliphatic polycarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, eicosanedioic acid, itaconic acid, fumaric acid, maleic acid, octyl succinic acid, dodecyl succinic acid, tridecenyl succinic acid, tetrahexadecyl succinic acid, hexadecyl succinic acid, octadecyl succinic acid, pentenyl succinic acid, hexenyl succinic acid, octenyl succinic acid, decenyl succinic acid, undecenyl succinic acid, dodecenyl succinic acid, tridecenyl succinic acid, tetradecenyl succinic acid, hexadecenyl succinic acid, octadecenyl succinic acid, and iso-octadecenyl succinic acid. Examples of aromatic polycarboxylic acids include phthalic acid (1,2-benzenedicarboxylic acid), isophthalic acid (1,3-benzenedicarboxylic acid), terephthalic acid (1,4-benzenedicarboxylic acid), pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), and trimesic acid (1,3,5-benzenetricarboxylic acid). Examples of rosin acids include abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, and dehydroabietic acid. Examples of rosin acid derivatives include condensates of the rosin acid, acrylic acid-modified rosin acid, fumaric acid-modified rosin acid, maleic anhydride-modified rosin acid, phenolized rosin acid, and rosin acid-modified phenolic resins.

[0024] Examples of polyamines include aliphatic polyamines, aromatic polyamines, etc. Examples of aliphatic polyamines include polyethyleneimine, poly(trimethyleneimine), poly(aminomethylethylene), poly(aminoethylene), poly(meth)acrylic acid amino alkylene amide (a polymer in which a carboxylic acid of polyacrylic acid or polymethacrylic acid forms an amide bond with one amino group of an alkylenediamine), etc. Examples of aromatic polyamines include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl 1,3-bis(4-aminophenoxy)benzene, resorcinol bis(4-aminophenyl) ether, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis(4-aminophenyl)sulfone, and 2,2'-dimethylbiphenyl-4,4'-diamine.

[0025] Examples of alkenyl succinic anhydrides include compounds having a skeleton derived from an olefin having 4 to 30 carbon atoms and a maleic anhydride skeleton. Specific examples include pentenyl succinic anhydride, hexenyl succinic anhydride, octenyl succinic anhydride, decenyl succinic anhydride, undecenyl succinic anhydride, dodecenyl succinic anhydride, tridecenyl succinic anhydride, hexadecenyl succinic anhydride, and octadecenyl succinic anhydride. These alkenyl succinic anhydrides can be used alone, or two or more can be used in combination from the viewpoint of being able to control properties such as hydrophobicity and water resistance.

[0026] Examples of alkyl ketene dimers include alkyl ketene dimers having 8 to 30 carbon atoms, such as decyl ketene dimer, dodecyl ketene dimer, tetradecyl ketene dimer, hexadecyl ketene dimer, stearyl ketene dimer, and eicosyl ketene dimer. Among these alkyl ketene dimers, alkyl ketene dimers having 10 to 26 carbon atoms are preferred because they have an appropriate melting point. These alkyl ketene dimers may be used alone or in combination of two or more.

[0027] (D) Compatibilizer: The compatibilizer (D) used in the present invention has affinity for both the modified plant fiber (A) and the diluent resin (F) described below, and improves the dispersibility of the modified plant fiber (A) in the diluent resin (F). Examples of such compatibilizers (D) include acid anhydride-modified polyolefins, graft products of polyolefins with other polymers, and graft products of acrylic polymer chains with affinity for polyolefins with acrylic polymer chains with affinity for celluloses. These compatibilizers (D) may be used alone or in combination.

[0028] Examples of acid anhydride-modified polyolefins include maleic anhydride-modified polyolefins (i.e., polyolefins in which maleic anhydride is grafted into the polyolefin molecule and / or to the molecular terminal, or copolymers of maleic anhydride and olefins) and hydrolysates thereof (i.e., polyolefins in which the acid anhydride group in the maleic anhydride-modified polyolefin has been hydrolyzed). Examples of maleic anhydride-modified polyolefins include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-modified polybutene, maleic anhydride-modified polypentene, and maleic anhydride-modified polyhexene.

[0029] Examples of grafted products of polyolefins and other polymers include copolymers of polyolefins such as polyethylene, polypropylene, and polybutene with polyvinyl acetate (PVAc), poly(meth)acrylic acid, or poly(meth)acrylate.

[0030] Examples of grafted products of acrylic polymer chains having an affinity for polyolefins and acrylic polymer chains having an affinity for cellulose include block copolymers having a resin affinity segment and a cellulose affinity segment, as described in Japanese Patent No. 6234037.

[0031] (E) Binder resin: The binder resin (E) used in the present invention improves the adhesion between the modified plant fiber (A) and the diluent resin (F) described below. Examples of such binder resins (E) include vinyl acetate resins, polyvinyl alcohol, polyvinyl acetal, phenolic resins, and melamine resins. These binder resins (E) may be used alone or in combination of two or more.

[0032] (F) Dilution resin: The diluent resin (F) used in the present invention is the base resin for the fiber-reinforced resin composition and fiber-reinforced resin molded article of the present invention. Examples of such diluent resin (F) include thermoplastic resins such as polyolefins, polyamides, aliphatic polyesters, aromatic polyesters, polyacetals, polycarbonates, polystyrenes, acrylonitrile-butadiene-styrene copolymers (ABS resins), polycarbonate-ABS alloys (PC-ABS alloys), cellulose-based resins, polylactic acid (PLA), polyhydroxybutyrate (PHBT), polyhydroxyhexanoate (PHAT), copolymers of polyhydroxybutyrate and polyhydroxyhexanoate (PHBH), polybutylene succinate (PBS), modified polyphenylene ether (m-PPE), and polyvinyl chloride. Specific examples of polyolefins include polyethylene (such as low-density, medium-density, high-density, or linear low-density polyethylene), polypropylene, ethylene-propylene copolymers, and terpolymers such as ethylene-propylene-butene-1.

[0033] In addition, styrene-based thermoplastic elastomers such as SBS (styrene-butadiene-styrene) and SEBS (styrene-ethylene-butylene-styrene) can also be used as diluents. SEBS can also be used to improve the impact resistance of polypropylene.

[0034] These diluent resins (F) may be used alone or in combination of two or more. Among these diluent resins (F), polyolefin, polyamide, aliphatic polyester, aromatic polyester, polyacetal, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin), polycarbonate-ABS alloy (PC-ABS alloy), cellulose-based resin, polylactic acid (PLA), polyhydroxybutyrate (PHBT), polyhydroxyhexanoate (PHAT), copolymer of polyhydroxybutyrate and polyhydroxyhexanoate (PHBH), polybutylene succinate (PBS), and modified polyphenylene ether are preferred from the viewpoints of thermal stability and strength properties. Poly(m-PPE) is preferred, and from the viewpoints of environmental conservation, thermal stability, strength properties, and lightweight molded articles, biomass-derived polyethylene, biomass-derived polypropylene, a copolymer of biomass-derived ethylene and biomass-derived propylene, a copolymer of at least one of biomass-derived ethylene and biomass-derived propylene with a petrochemical-derived olefin, polylactic acid (PLA), polyhydroxybutyrate (PHBT), polyhydroxyhexanoate (PHAT), a copolymer of polyhydroxybutyrate and polyhydroxyhexanoate (PHBH), and polybutylene succinate (PBS) are more preferred.

[0035] (Other ingredients) Other components used in the present invention include fillers, solvents, various additives, and the like.

[0036] Examples of fillers include talc, clay, zeolite, aluminum oxide, calcium carbonate, titanium oxide, silica, magnesium oxide, mica, etc. These fillers may be used alone or in combination of two or more. By incorporating such fillers, the modified plant fibers (A) in the fiber-reinforced resin composition are more easily dispersed during melt-kneading, improving the dispersibility of the modified plant fibers (A).

[0037] The solvent is used to dissolve the modifier (C). This allows the plant fibers (A'), the thermoplastic resin fibers (B), and the modifier (C) to be uniformly mixed, resulting in a granular masterbatch in which the modified plant fibers (A) and the thermoplastic resin fibers (B) are uniformly mixed. Examples of such solvents include tripropylene glycol and polyethylene glycol.

[0038] Examples of the various additives include antioxidants, surfactants, plasticizers, antistatic agents, ultraviolet absorbers, colorants, and deodorants.

[0039] [Granular masterbatch for fiber-reinforced resin composition and method for producing the same] Next, the granular masterbatch for a fiber-reinforced resin composition of the present invention and its manufacturing method will be described. The granular masterbatch for a fiber-reinforced resin composition of the present invention contains the modified plant fiber (A) and the thermoplastic resin fiber (B). By using such a granular masterbatch, the modified plant fiber (A) can be uniformly dispersed in the diluent resin (F), making it possible to easily obtain a fiber-reinforced resin molded product having excellent flexural modulus and flexural strength. In the granular masterbatch, the content of the thermoplastic resin fiber (B) is preferably 1 to 300 parts by mass, more preferably 5 to 200 parts by mass, even more preferably 8 to 100 parts by mass, and particularly preferably 10 to 80 parts by mass, per 100 parts by mass of the plant fiber (A') in the modified plant fiber (A).

[0040] The granular masterbatch of the present invention preferably contains the compatibilizer (D). This improves the dispersibility of the modified plant fibers (A) in the diluent resin (F), making it possible to easily obtain a fiber-reinforced resin molding with excellent mechanical properties. The content of the compatibilizer (D) in the granular masterbatch is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, per 100 parts by mass of the plant fibers (A') in the modified plant fibers (A).

[0041] The granular masterbatch of the present invention preferably contains the binder resin (E). This improves adhesion between the modified plant fibers (A) and the diluent resin (F), making it possible to easily obtain a fiber-reinforced resin molding with excellent mechanical properties. In the granular masterbatch, the content of the binder resin (E) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the plant fibers (A') in the modified plant fibers (A).

[0042] Furthermore, the granular masterbatch of the present invention may contain other components such as the filler, the solvent, and the various additives (e.g., antioxidants, surfactants, plasticizers, antistatic agents, ultraviolet absorbers, colorants, and deodorizers).

[0043] There are no particular limitations on the method for producing such a granular masterbatch of the present invention. For example, a method of mixing the plant fiber (A') (the modified plant fiber (A)) that has been previously modified with the modifying agent (C) with the thermoplastic resin fiber (B) may be employed. However, from the viewpoint of easily producing a granular masterbatch in which the modified plant fiber (A) and the thermoplastic resin fiber (B) are uniformly mixed, it is preferable to employ the following method.

[0044] That is, the method for producing the granular masterbatch of the present invention includes the following steps: a step (mixing step) of obtaining a mixture (α) of the plant fibers (A') and the thermoplastic resin fibers (B); a step (modification step) of modifying the plant fibers (A') in the mixture (α) with the modifying agent (C) to obtain a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B); A method comprising the steps of:

[0045] Each step of the method for producing a granular masterbatch of the present invention will be described below.

[0046] [Mixing process] In the mixing step, the plant fibers (A') and the thermoplastic resin fibers (B) may be wet-mixed or dry-mixed, but wet-mixing is preferred from the viewpoint of improving the bending strength of the resulting fiber-reinforced resin molding, and dry-mixing is preferred from the viewpoint of improving the Charpy impact strength. In the case of wet-mixing, a solid mixture (α) containing the plant fibers (A') and the thermoplastic resin fibers (B) is obtained by subsequent desolvation, while in the case of dry-mixing, a solid mixture (α) containing the plant fibers (A') and the thermoplastic resin fibers (B) is obtained as is.

[0047] The wet mixing method may be, for example, a method in which a suspension of the plant fibers (A') and a suspension of the thermoplastic resin fibers (B) are mixed in a predetermined ratio, and the resulting mixed suspension is desolvated to produce a solid (e.g., sheet-like) mixture (α). The solvent (dispersion medium) used in the suspension may be water or an organic solvent, but water is preferred from the viewpoint of environmental load.

[0048] Furthermore, as a dry mixing method, a method of directly mixing the plant fibers (A') and the thermoplastic resin fibers (B) in a predetermined ratio to produce a granular mixture (α) may be employed. However, from the viewpoint of obtaining a granular masterbatch in which the modified plant fibers (A) and the thermoplastic resin fibers (B) are more reliably dispersed, a method of laminating a sheet of the plant fibers (A') and a sheet of the thermoplastic resin fibers (B) in a predetermined ratio to produce a composite sheet (sheet-like mixture (α)), or a method of drawing, roving, and finely spinning a sliver of the plant fibers (A') and a sliver of the thermoplastic resin fibers (B) in a predetermined ratio to produce a composite yarn (string-like mixture (α)), is preferred.

[0049] [Modification step] In the modification step, when the mixture (α) obtained in the mixing step is granular, the granular mixture (α) is mixed with the modifying agent (C) to modify (hydrophobize) the plant fibers (A') in the granular mixture (α) to be hydrophobic, thereby obtaining a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B).

[0050] Furthermore, when the mixture (α) is in a solid form other than granular (for example, a sheet or string form), the other solid mixture (α) may be pulverized to obtain the granular mixture (α), and the granular mixture (α) may then be mixed with the modifying agent (C) to hydrophobize the plant fibers (A') in the granular mixture (α), thereby obtaining a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B). Alternatively, the other solid mixture (α) may be impregnated with the modifying agent (C) to hydrophobize the plant fibers (A') in the other solid mixture (α), thereby obtaining another solid mixture (β) containing the modified plant fibers (A) and the thermoplastic resin fibers (B), and the other solid mixture (β) may then be pulverized to obtain a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B).

[0051] In the method for producing a granular masterbatch of the present invention, the resulting granular masterbatch may contain the compatibilizer (D) and / or the binder resin (E), as needed. Furthermore, the other components, such as the filler, the solvent, and the various additives (e.g., antioxidants, surfactants, plasticizers, antistatic agents, UV absorbers, colorants, and deodorizers), may also be contained. These components may be mixed with the plant fibers (A') and the thermoplastic resin fibers (B) in the mixing step, or may be added to the mixture (α) together with the modifier (C) and mixed in the modification step.

[0052] [Fiber reinforced resin composition] Next, the fiber-reinforced resin composition of the present invention will be described. The fiber-reinforced resin composition of the present invention contains the modified plant fiber (A), the thermoplastic resin fiber (B), and the diluent resin (F). This fiber-reinforced resin composition can be prepared by mixing the granular masterbatch of the present invention with the diluent resin (F). The fiber-reinforced resin composition prepared in this manner has the modified plant fiber (A) uniformly dispersed in the diluent resin (F), and can easily form a fiber-reinforced resin molding having excellent flexural modulus and flexural strength.

[0053] In the fiber-reinforced resin composition, the content of the thermoplastic resin fiber (B) is preferably 1 to 300 parts by mass, more preferably 5 to 200 parts by mass, even more preferably 8 to 100 parts by mass, and particularly preferably 10 to 80 parts by mass, relative to 100 parts by mass of the plant fiber (A') in the modified plant fiber (A). The total amount of the thermoplastic resin fiber (B) and the diluent resin (F) is preferably an amount such that the content of the plant fiber (A') in the fiber-reinforced resin composition is 1 to 50% by mass, more preferably an amount such that the content is 5 to 40% by mass, and even more preferably an amount such that the content is 10 to 30% by mass.

[0054] The fiber-reinforced resin composition of the present invention preferably contains the compatibilizer (D). This improves the dispersibility of the modified plant fibers (A) in the diluent resin (F), making it possible to easily obtain a fiber-reinforced resin molding with excellent mechanical properties. The compatibilizer (D) may be one that is contained in the granular masterbatch or may be one that is added when preparing the fiber-reinforced resin composition. In the fiber-reinforced resin composition, the content of the compatibilizer (D) is preferably 1 to 50 parts by mass, more preferably 3 to 30 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the plant fibers (A') in the modified plant fibers (A).

[0055] Furthermore, the fiber-reinforced resin composition of the present invention preferably contains the binder resin (E). This improves adhesion between the modified plant fiber (A) and the diluent resin (F), making it possible to easily obtain a fiber-reinforced resin molding with excellent mechanical properties. The binder resin (E) may be one that is contained in the granular masterbatch or may be one that is added when preparing the fiber-reinforced resin composition. In the fiber-reinforced resin composition, the content of the binder resin (E) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the plant fiber (A') in the modified plant fiber (A).

[0056] The fiber-reinforced resin composition of the present invention may also contain other components such as the filler, the solvent, and the various additives (for example, antioxidants, surfactants, plasticizers, antistatic agents, UV absorbers, colorants, and deodorizers). These other components may be those contained in the granular masterbatch or may be those added when preparing the fiber-reinforced resin composition.

[0057] [Fiber-reinforced resin molded body and its manufacturing method] Next, the fiber-reinforced resin molding of the present invention and its manufacturing method will be described. The fiber-reinforced resin molding of the present invention is obtained by molding the fiber-reinforced resin composition of the present invention. This fiber-reinforced resin molding has the modified plant fiber (A) uniformly dispersed in the diluent resin (F), and has excellent flexural modulus and flexural strength.

[0058] In the fiber-reinforced resin molding, the total amount of the thermoplastic resin fiber (B) and the diluent resin (F) is preferably an amount such that the content of the plant fiber (A') in the fiber-reinforced resin molding is 1 to 50 mass%, more preferably an amount such that the content of the plant fiber (A') in the fiber-reinforced resin molding is 5 to 40 mass%, and even more ...30 mass%.

[0059] Furthermore, the fiber-reinforced resin molding of the present invention preferably contains the compatibilizer (D). This improves the dispersibility of the modified plant fibers (A) in the diluent resin (F), thereby improving mechanical properties. The compatibilizer (D) may be one that was contained in the granular masterbatch, or may be one that was added when preparing the fiber-reinforced resin composition. In the fiber-reinforced resin molding, the content of the compatibilizer (D) is preferably 1 to 50 parts by mass, more preferably 3 to 30 parts by mass, and even more preferably 5 to 20 parts by mass, per 100 parts by mass of the plant fibers (A') in the modified plant fibers (A).

[0060] Furthermore, the fiber-reinforced resin molding of the present invention preferably contains the binder resin (E). This improves adhesion between the modified plant fibers (A) and the diluent resin (F), thereby improving mechanical properties. The binder resin (E) may be one that was contained in the granular masterbatch, or may be one that was added when preparing the fiber-reinforced resin composition. In the fiber-reinforced resin molding, the content of the binder resin (E) is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 2 parts by mass, per 100 parts by mass of the plant fibers (A') in the modified plant fibers (A).

[0061] The fiber-reinforced resin molding of the present invention may also contain other components such as the filler, the solvent, and the various additives (for example, antioxidants, surfactants, plasticizers, antistatic agents, ultraviolet absorbers, colorants, and deodorizers). These other components may be those contained in the granular masterbatch or may be those added when preparing the fiber-reinforced resin composition.

[0062] The method for producing such a fiber-reinforced resin molding of the present invention is not particularly limited, and for example, a method (first production method) in which the granular masterbatch of the present invention and the granular or powdery diluent resin (F) are mixed in a molding machine (mixing step), and the resulting mixture (fiber-reinforced resin composition of the present invention) is molded (molding step) to obtain a fiber-reinforced resin molded product; The granular masterbatch of the present invention and the granular or powdery diluent resin (F) are dry-blended as necessary, and then melt-kneaded [melt-kneading step]. The resulting melt-kneaded product (melt-kneaded product of the fiber-reinforced resin composition of the present invention) is then charged into a molding machine and molded [molding step] to obtain a fiber-reinforced resin molded product [second manufacturing method]. Examples include:

[0063] Among these methods for producing fiber-reinforced resin moldings, the first method in which the plant fibers (A') are mixed on a molding machine (without melt-kneading) is preferred, from the viewpoint of minimizing damage to the plant fibers (A') and improving the flexural modulus and flexural strength.

[0064] In the method for producing a fiber-reinforced resin molded body of the present invention, the mixing method and mixing conditions in the mixing step, the melt-kneading method and melt-kneading conditions in the melt-kneading step, and the molding method and molding conditions in the molding step are not particularly limited, and known methods and conditions can be adopted depending on the resin to be used, etc.

[0065] In the method for producing a fiber-reinforced resin molding of the present invention, the resulting fiber-reinforced resin molding may contain the compatibilizer (D) and / or the binder resin (E), if necessary. Furthermore, the other components, such as the filler, the solvent, and the various additives (e.g., antioxidants, surfactants, plasticizers, antistatic agents, UV absorbers, colorants, and deodorizers), may also be contained. These components may be mixed with the granular masterbatch and the granular or powdered diluent resin (F) in the mixing step, melt-kneaded with the granular masterbatch and the granular or powdered diluent resin (F) in the melt-kneading step, or fed into a molding machine together with the mixture or the melt-kneaded product in the molding step. However, from the viewpoint of uniform mixing, mixing in the mixing step and / or the melt-kneading step is preferred. [Example]

[0066] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0067] (Comparative Example 1) Polypropylene (PP) pellets (Novatec BC03B, manufactured by Japan Polypropylene Corporation) were placed in an injection molding machine (J75EII-P, manufactured by The Japan Steel Works, Ltd.) and injection molded under conditions of a clamping force of 75 tons, a cylinder temperature of 190°C, and a mold temperature of 40°C to obtain a polypropylene molded article (multipurpose test piece (JIS K7139 Type A1), 170 mm x 10 mm x 4 mm thick). Both ends of this polypropylene molded article were cut to prepare rectangular test pieces (JIS K7139, 80 mm x 10 mm x 4 mm thick).

[0068] Example 1 <Preparation of Granular Masterbatch> Cotton linters (manufactured by Azumi Filter Paper Co., Ltd.) were suspended in water to a plant fiber concentration of 0.5% by mass to prepare a water suspension of plant fibers. Furthermore, polypropylene (PP) fibers (manufactured by Daiwabo Co., Ltd., "PZ", fineness: 2.2 dtex, cut length: 5 mm) were suspended in water as thermoplastic resin fibers (B) to a PP fiber concentration of 0.5% by mass to prepare a water suspension of PP fibers.

[0069] The aqueous suspension of the plant fiber and the aqueous suspension of the PP fiber were mixed in a mass ratio of plant fiber:PP fiber = 70:30, and the resulting mixed aqueous suspension was filtered through a 70-mesh filter to produce a water-containing sheet on the filter. This water-containing sheet was then sandwiched between nonwoven fabrics and press-dehydrated to obtain a sheet-like mixture (moisture content: approximately 50 mass%) containing the plant fiber and the PP fiber.

[0070] This sheet mixture was placed in a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd., model: FM20C, capacity: 20 liters), and then water was added in an amount equal to the amount of the sheet mixture. The sheet mixture was then pulverized at a rotation speed of 2000 rpm for 2 minutes to obtain a granular mixture. To this granular mixture, a silane coupling agent (3-aminopropyltriethoxysilane (APTES), manufactured by Momentive Performance Materials Japan, LLC) was added as a modifier (C) in a ratio of 1 part by mass per 100 parts by mass of plant fiber in the sheet-like mixture, and a maleic anhydride-modified polypropylene (MAPP, manufactured by Toyobo Co., Ltd., "TOYOTAC H1000P") was added as a compatibilizer (D) in a ratio of 20 parts by mass per 100 parts by mass of plant fiber in the sheet-like mixture. The mixture was stirred for 5 minutes, and then a vinyl acetate resin (PVAc, manufactured by Konishi Co., Ltd., polyvinyl acetate emulsion) was added as a binder resin (E) in a ratio of 0.4 parts by mass per 100 parts by mass of plant fiber in the sheet-like mixture. The mixture was stirred for 1 minute and pelletized using a compression granulator to obtain a granular masterbatch (moisture content: approximately 70% by mass) containing the plant fiber modified with the silane coupling agent (modified plant fiber), the PP fiber, the MAPP, and the vinyl acetate resin.

[0071] <Production of fiber-reinforced resin molded body> The granular masterbatch was dried for 16 hours at 90° C. The dried granular masterbatch was dry-mixed with polypropylene (PP) pellets (Novatec BC03B, manufactured by Japan Polypropylene Corporation) as a diluent resin (F) so that the plant fiber content was 20% by mass in terms of solid content after drying.

[0072] The resulting mixture was placed in an injection molding machine ("J75EII-P" manufactured by The Japan Steel Works, Ltd.) and injection molded under conditions of a clamping force of 75 tons, a cylinder temperature of 190°C, and a mold temperature of 40°C to obtain a fiber-reinforced polypropylene molded article (multipurpose test piece (JIS K7139 Type A1), 170 mm x 10 mm x 4 mm thick). Both ends of this fiber-reinforced polypropylene molded article were cut to prepare rectangular test pieces (JIS K7139, 80 mm x 10 mm x 4 mm thick).

[0073] Example 2 A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the PP fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that the amount of vinyl acetate resin used as the binder resin (E) was changed to 1 part by mass per 100 parts by mass of plant fiber in the sheet-like mixture. Further, a fiber-reinforced polypropylene molded body (multipurpose test piece (JIS K7139 Type A1), 170 mm x 10 mm x 4 mm thick) and a strip test piece (JIS K7139, 80 mm x 10 mm x 4 mm thick) were produced.

[0074] (Comparative Example 2) A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that the PP fiber was not mixed in. Further, a fiber-reinforced polypropylene molded body (multipurpose test piece (JIS K7139 Type A1), 170 mm x 10 mm x 4 mm thick) and a strip test piece (JIS K7139, 80 mm x 10 mm x 4 mm thick) were produced.

[0075] Example 3 A granular masterbatch (moisture content: approximately 70% by mass) containing modified plant fibers, the PP fibers, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that softwood bleached kraft pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) was used instead of cotton linter. Furthermore, a fiber-reinforced polypropylene molded body (multipurpose test piece (JIS K7139 Type A1), 170 mm × 10 mm × 4 mm thick) and a strip test piece (JIS K7139, 80 mm × 10 mm × 4 mm thick) were produced.

[0076] (Comparative Example 3) A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 3, except that the PP fiber was not mixed in. Further, a fiber-reinforced polypropylene molded body (multipurpose test piece (JIS K7139 Type A1), 170 mm x 10 mm x 4 mm thick) and a strip test piece (JIS K7139, 80 mm x 10 mm x 4 mm thick) were produced.

[0077] Example 4 A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the PP fiber, the MAPP, and the vinyl acetate resin, prepared in the same manner as in Example 1, was dry-mixed with polypropylene (PP) pellets (Novatec BC03B, manufactured by Japan Polypropylene Corporation) as a diluent resin (F) so that the plant fiber content was 20% by mass in terms of solid content after drying.

[0078] The resulting mixture was placed in a twin-screw kneader ("Tex30α" manufactured by The Japan Steel Works, Ltd., L / D=45) and melt-kneaded for 2 minutes while removing moisture at a kneading temperature of 170°C and a discharge rate of 6 kg / hour.

[0079] The obtained molten kneaded pellets were placed in an injection molding machine ("J75EII-P" manufactured by The Japan Steel Works, Ltd.) and injection molded under the conditions of a clamping force of 75 tons, a cylinder temperature of 190°C, and a mold temperature of 40°C to obtain a fiber-reinforced polypropylene molded body (multipurpose test piece (JIS K7139 Type A1), 170 × 10 × 4 mmt). Both ends of this fiber-reinforced polypropylene molded body were cut to prepare rectangular test pieces (JIS K7139, 80 mm × 10 mm × 4 mm thick).

[0080] Example 5 A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the PP fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that the mass ratio of the plant fiber to the PP fiber was changed to plant fiber:PP fiber = 90:10. A fiber-reinforced polypropylene molded article (multipurpose test piece (JIS K7139 Type A1), 170 mm × 10 mm × 4 mm thick) and a strip test piece (JIS K7139, 80 mm × 10 mm × 4 mm thick) were produced in the same manner as in Example 4, except that this granular masterbatch was used.

[0081] Example 6 A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the PET fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that polyethylene terephthalate (PET) fiber (Tetron TA04PN, manufactured by Teijin Limited, 0.1 dtex, cut length: 3 mm) was used instead of the PP fiber in a mass ratio of plant fiber:PET fiber = 7:3. A fiber-reinforced polypropylene molded article (multipurpose test piece (JIS K7139 Type A1), 170 mm × 10 mm × 4 mm thick) and a strip test piece (JIS K7139, 80 mm × 10 mm × 4 mm thick) were prepared in the same manner as in Example 4, except that this granular masterbatch was used.

[0082] Comparative Example 4 A granular masterbatch (moisture content: approximately 70% by mass) containing the modified plant fiber, the MAPP, and the vinyl acetate resin was prepared in the same manner as in Example 1, except that the PP fiber was not mixed in. A fiber-reinforced polypropylene molded article (multipurpose test piece (JIS K7139 Type A1), 170 mm × 10 mm × 4 mm thick) and a strip test piece (JIS K7139, 80 mm × 10 mm × 4 mm thick) were produced in the same manner as in Example 4, except that this granular masterbatch was used.

[0083] (Comparative Example 5) Polypropylene (PP) pellets (Novatec BC08F manufactured by Japan Polypropylene Corporation) were placed in an injection molding machine (NP7 type manufactured by Nissei Plastic Industrial Co., Ltd.) and injection molded under the following conditions: clamping force: 7 tons, cylinder temperature: 190°C, mold temperature: 35°C, to obtain a polypropylene molded article (strip test piece (JIS K7139), 80 mm x 10 mm x 4 mm thick).

[0084] Example 7 <Preparation of Granular Masterbatch> Bleached cotton (Marusan Sangyo Co., Ltd.), which was made by degreasing and bleaching cotton, was slivered using a carding machine (Platt Saco Lowell (UK) Ltd.) to produce vegetable fiber slivers. Also, polypropylene (PP) fiber (2.2 dtex, fiber length 38 mm) was slivered using a carding machine (Platt Saco Lowell (UK) Ltd.) to produce PP fiber slivers as thermoplastic resin fiber (B).

[0085] The plant fiber sliver and the PP fiber sliver were mixed using a drawing frame (manufactured by Hara Loom Works, Ltd.), a spinning frame (manufactured by O-M Ltd.), and a winding machine (manufactured by Shinko Kikai Co., Ltd.) so that the mass ratio of the plant fiber to the PP fiber was plant fiber:PP fiber = 65:35, to produce a composite yarn (string-like mixture) containing the plant fiber and the PP fiber.

[0086] In addition, a silane coupling agent (3-aminopropyltriethoxysilane (APTES) manufactured by Tokyo Chemical Industry Co., Ltd.) in an amount equivalent to 20 parts by mass per 100 parts by mass of plant fiber in the composite yarn was diluted four times with a solution of ethanol:water (4:1) to prepare a solution containing the silane coupling agent as a modifier (C).

[0087] The entire amount of the ethanol solution containing the silane coupling agent was absorbed into the composite yarn, which was then air-dried for 24 hours and further dried at 110°C for 2 hours in a fan oven to produce a composite yarn containing the plant fiber modified with the silane coupling agent (modified plant fiber) and the PP fiber. This composite yarn was cut to a length of approximately 15 mm to obtain a granular masterbatch containing the modified plant fiber and the PP fiber.

[0088] <Production of fiber-reinforced resin molded body> The granular masterbatch was dry-mixed with polypropylene (PP) pellets (Novatec BC08F manufactured by Japan Polypropylene Corporation) as a diluent resin (F), and maleic anhydride-modified polypropylene (MAPP, Toyotack H1000P manufactured by Toyobo Co., Ltd.) as a compatibilizer (D) in a mass ratio of plant fiber:MAPP:PP (including PP fiber) = 20:4:76.

[0089] The resulting mixture was placed in an injection molding machine (Nissei Plastic Industrial Co., Ltd., "NP7 Type") and injection molded under the conditions of a clamping force of 7 tons, a cylinder temperature of 190°C, and a mold temperature of 35°C to obtain a fiber-reinforced polypropylene molded article (strip test piece (JIS K7139), 80 mm x 10 mm x 4 mm thick).

[0090] (Comparative Example 6) A string-like yarn was produced using only the plant fiber sliver, without using the PP fiber sliver. A granular masterbatch of the modified plant fiber was prepared in the same manner as in Example 7, except that the entire amount of the ethanol solution of the silane coupling agent was absorbed into a yarn consisting of only the plant fiber sliver instead of the composite yarn (string-like mixture). A fiber-reinforced polypropylene molded article (strip test piece (JIS K7139), 80 mm x 10 mm x 4 mm thick) was then produced.

[0091] <Bending test> The molded articles obtained in the Examples and Comparative Examples were subjected to a bending test in accordance with JIS K7171. Specifically, the rectangular test specimens (JIS K7139, 80 mm x 10 mm x 4 mm thick) obtained in the Examples and Comparative Examples were left to stand for two days in an atmosphere of 23°C and 50% relative humidity, and then subjected to a bending test using a universal testing machine (Instron "3365") at a support distance of 64 mm and a test speed of 10 mm / min to measure the flexural modulus and flexural strength. The results are shown in Tables 1 and 2.

[0092] <Charpy impact test> The molded articles obtained in the examples and comparative examples were subjected to a Charpy impact test in accordance with JIS K7111-1. Specifically, the strip test pieces (JIS K7139, 80 mm x 10 mm x 4 mm thick) obtained in the examples and comparative examples were attached to a Charpy impact tester ("DG-CB" manufactured by Toyo Seiki Co., Ltd.), and the Charpy impact test was performed under the condition of a hammer weight of 4 J. The results are shown in Tables 1 and 2.

[0093] [Table 1]

[0094] [Table 2] As shown in Tables 1 and 2, when a masterbatch containing modified plant fiber and PP fiber or PET fiber was used (Examples 1 to 7), the obtained fiber-reinforced polypropylene moldings were found to have superior flexural modulus and flexural strength compared to the polypropylene moldings (Comparative Examples 1 and 5).

[0095] On the other hand, when a masterbatch containing no PP fibers or PET fibers was used (Comparative Examples 2 to 4 and 6), the resulting fiber-reinforced polypropylene moldings were superior in flexural modulus and flexural strength compared to the polypropylene moldings (Comparative Examples 1 and 5). However, when the components other than the PP fibers and PET fibers were the same, the masterbatch preparation method (wet mixing or dry mixing) was the same, and the method of mixing the masterbatch with the diluent resin was the same (Comparative Example 2 and Examples 1 to 2, Comparative Example 3 and Example 3, Comparative Example 4 and Examples 4 to 6, Comparative Example 6 and Example 7), it was found that the fiber-reinforced polypropylene moldings obtained in Comparative Examples 2 to 4 and Comparative Example 6 were inferior in flexural modulus compared to the fiber-reinforced polypropylene moldings obtained in Examples 1 to 7.

[0096] Furthermore, as shown in Table 1, when a masterbatch was prepared by wet mixing, and the components other than the PP fiber and PET fiber were the same and the method of mixing the masterbatch with the diluent resin was the same (Examples 1 to 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Examples 4 to 6 and Comparative Example 4), it was found that when a masterbatch containing PP fiber or PET fiber was used (Examples 1 to 6), the obtained fiber-reinforced polypropylene molded body was superior not only in flexural modulus but also in flexural strength and Charpy impact strength, compared to when a masterbatch not containing PP fiber or PET fiber was used (Comparative Examples 2 to 4).

[0097] Furthermore, as shown in Table 1, when the masterbatch and diluent resin were mixed in a molding machine (Example 1), the resulting fiber-reinforced polypropylene molding was superior in flexural modulus, flexural strength, and Charpy impact strength compared to when the masterbatch and diluent resin were melt-mixed and then molded (Example 4). This is thought to be because molding the masterbatch and diluent resin without melt-mixing them in advance reduced damage to the plant fibers due to mixing and kneading, allowing the reinforcement provided by the plant fibers to be fully exerted.

[0098] Furthermore, as shown in Table 1, when cotton linter was used as the plant fiber (Example 1), the resulting fiber-reinforced polypropylene molding was found to have superior flexural modulus and flexural strength compared to when softwood bleached kraft pulp (NBKP) was used (Example 3).

[0099] Furthermore, as shown in Table 1, when PET fiber was used as the thermoplastic resin fiber (Example 6), the obtained fiber-reinforced polypropylene molding was found to be superior in flexural modulus, flexural strength, and Charpy impact strength compared to when PP fiber was used (Example 4).

[0100] Furthermore, as shown in Table 2, when a masterbatch containing PP fibers was used in preparing a masterbatch by dry mixing, the fiber-reinforced polypropylene molding obtained in Example 7 was superior not only in flexural modulus and flexural strength but also in Charpy impact strength compared to the polypropylene molding in Comparative Example 5, and was also superior in flexural modulus and Charpy impact strength compared to the molding in Comparative Example 6 that did not contain PP fibers or PET fibers. [Industrial Applicability]

[0101] As described above, according to the present invention, a fiber-reinforced resin molded product having an excellent flexural modulus can be easily obtained. Furthermore, according to the present invention, the masterbatch and the diluent resin can be mixed without melt-kneading, i.e., on-machine mixing can be performed, thereby reducing production costs and easily producing a fiber-reinforced resin molded product having an excellent flexural modulus. Furthermore, when preparing the masterbatch, wet mixing of plant fibers and thermoplastic resin fibers can easily produce a fiber-reinforced resin molded product having an excellent flexural strength, and dry mixing can easily produce a fiber-reinforced resin molded product having an excellent Charpy impact strength.

[0102] Therefore, the fiber-reinforced resin molding of the present invention is useful as a material to replace glass fiber-reinforced plastics in the fields of automobiles, home appliances, construction, industrial machinery, etc.

Claims

1. A granular masterbatch for a fiber-reinforced resin composition, comprising modified plant fibers (A) and thermoplastic resin fibers (B).

2. 2. The granular masterbatch according to claim 1, wherein the thermoplastic resin fiber (B) is at least one selected from the group consisting of polyolefin-based resin fibers and polyester-based resin fibers.

3. The modified plant fiber (A) is a plant fiber (A') modified with at least one modifier (C) selected from the group consisting of silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers. The granular masterbatch described in claim 1 is characterized in that the modified plant fiber (A) is a plant fiber (A') modified with at least one modifier (C) selected from the group consisting of silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers.

4. The granular masterbatch according to claim 1, further comprising at least one of a compatibilizer (D) and a binder resin (E).

5. a mixing step of obtaining a mixture (α) of plant fibers (A′) and thermoplastic resin fibers (B); a modification step of modifying the plant fibers (A') in the mixture (α) with a modifying agent (C) to obtain a granular masterbatch containing the modified plant fibers (A) and the thermoplastic resin fibers (B); A method for producing a granular masterbatch for a fiber-reinforced resin composition, comprising:

6. 6. The method for producing a granular masterbatch according to claim 5, wherein in the mixing step, the plant fibers (A') and the thermoplastic resin fibers (B) are wet-mixed, and then the solvent is removed to obtain the solid mixture (α) containing the plant fibers (A') and the thermoplastic resin fibers (B).

7. The method for producing a granular masterbatch according to claim 5, characterized in that in the mixing step, the plant fibers (A') and the thermoplastic resin fibers (B) are dry-mixed to obtain the solid mixture (α).

8. 8. The method for producing a granular masterbatch according to claim 6 or 7, characterized in that in the modification step, the solid mixture (α) is pulverized to obtain a granular mixture (α), and then the plant fiber (A') in the granular mixture (α) is modified with a modifier (C) to obtain the granular masterbatch.

9. 8. The method for producing a granular masterbatch according to claim 6 or 7, characterized in that in the modification step, the plant fibers (A') in the solid mixture (α) are modified with a modifying agent (C) to obtain a solid mixture (β) containing the modified plant fibers (A) and the thermoplastic resin fibers (B), and then the solid mixture (β) is pulverized to obtain the granular masterbatch.

10. The method for producing a granular masterbatch according to claim 5, characterized in that the modifier (C) is at least one selected from the group consisting of silane coupling agents, carboxylic acids, polyamines, alkenyl succinic anhydrides, and alkyl ketene dimers.

11. 6. The method for producing a granular masterbatch according to claim 5, wherein the granular masterbatch contains at least one of a compatibilizer (D) and a binder resin (E).

12. A fiber-reinforced resin composition comprising modified plant fibers (A), thermoplastic resin fibers (B), and a diluent resin (F).

13. A fiber-reinforced resin molding obtained by molding the fiber-reinforced resin composition according to claim 12.

14. The granular masterbatch according to any one of claims 1 to 4 and a granular or powdery diluent resin (F) are mixed in a molding machine, and the resulting mixture is molded to obtain a fiber-reinforced resin molded body. A method for producing a fiber-reinforced resin molded body.

15. The granular masterbatch according to any one of claims 1 to 4 and a granular or powdery diluent resin (F) are melt-kneaded, and the resulting molten mixture is placed in a molding machine and molded to obtain a fiber-reinforced resin molded body. A method for producing a fiber-reinforced resin molded body.

Images