Thermoplastic resin composition and pellet mixture

Abstract

The present invention provides: a thermoplastic resin composition which is capable of improving impact resistance while maintaining flexural strength when formed into a molded article; and a pellet mixture which is suitable for use for the production of the composition.　The present invention specifically provides a thermoplastic resin composition which contains a thermoplastic resin (A), cellulose-based fibers (B), and reinforcing fibers (C). The reinforcing fibers (C) are other than the cellulose-based fibers (B), and the average fiber length of the reinforcing fibers (C) is 500 μm or more and 1,200 μm or less.

Description

Thermoplastic resin composition and pellet mixture

[0001] The present invention relates to a thermoplastic resin composition, and more particularly to a fiber-reinforced thermoplastic resin composition in which a thermoplastic resin is blended with a cellulosic fiber and a reinforcing fiber.

[0002] Fiber-reinforced thermoplastic resin compositions are lightweight and high-strength, and are therefore used in place of metal materials in fields such as automobile parts, aircraft interior parts, electronic devices, household appliances, and construction materials. In particular, from the perspective of reducing the weight of structures, natural fiber-reinforced thermoplastic resin compositions using cellulose-based fibers, which have a low specific gravity among fibers, have been proposed (see Patent Documents 1 to 10). Such natural fiber-reinforced thermoplastic resin compositions have attracted attention as materials using natural fibers in line with recent efforts to address environmental issues.

[0003] JP 2016-176052 A JP 2019-6997 A JP 2019-147861 A JP 2024-63851 A JP 2021-36024 A JP 2024-82928 A JP 2021-84999 A International Publication No. 2023 / 037937 JP 2022-147464 A JP 2010-155970 A

[0004] Patent Document 1 discloses a fiber-reinforced resin composition containing chemically modified cellulose nanofibers. However, this fiber-reinforced resin composition has a problem of low impact resistance. Patent Document 2 discloses a fiber-reinforced resin composition using a combination of chemically modified microfibrillated cellulose-based fibers and an inorganic filler such as glass fibers, but the improvement in impact resistance is insufficient. Furthermore, Patent Document 3 discloses a composition using a combination of cellulose fibers having an aspect ratio of 30 or more and a filler having an aspect ratio of 10 or more, but does not consider impact resistance.

[0005] Patent Documents 4 to 7 describe compositions containing a polyamide resin and a cellulose-based fiber, but further improvements in impact resistance and bending strength are required. Patent Document 8 discloses a polyamide resin composition containing a polyamide resin and a fibrous reinforcing filler selected from glass fiber, carbon fiber, cellulose fiber, etc. However, Patent Document 8 does not consider impact resistance.

[0006] Patent Document 9 discloses a resin composition containing a thermoplastic resin and reinforcing fibers, the reinforcing fibers including organic fibers such as cellulose fibers and carbon fibers, but does not consider bending strength. Patent Document 10 discloses a thermoplastic resin composition containing first pellets containing a thermoplastic resin and cellulose fibers, and second pellets that are glass fiber bundles containing a thermoplastic resin and glass fibers having a length of 4 to 15 mm, the glass fibers being integrated by the thermoplastic resin, but further improvements in impact resistance and bending strength are required.

[0007] An object of the present invention is to provide a thermoplastic resin composition that can improve impact resistance while maintaining bending strength when formed into a molded article, and a pellet mixture that is suitably used for producing the composition.

[0008] The present inventors have conducted extensive research to solve the above problems and have found that a thermoplastic resin composition using a combination of reinforcing fibers having a specific average fiber length and cellulosic fibers can improve the impact resistance of the resulting molded article while maintaining the bending strength.

[0009] The present invention relates to the following items [1] to

[19] . [1] A thermoplastic resin composition comprising a thermoplastic resin (A), a cellulose-based fiber (B), and a reinforcing fiber (C), wherein the reinforcing fiber (C) is other than the cellulose-based fiber (B), and the average fiber length of the reinforcing fiber (C) is 500 μm or more and 1200 μm or less. [2] The thermoplastic resin composition according to [1], wherein the reinforcing fiber (C) is at least one selected from the group consisting of glass fiber and carbon fiber. [3] The thermoplastic resin composition according to [1] or [2], wherein the average fiber diameter of the cellulose-based fiber (B) is 4 nm to 1000 μm and the average fiber length of the cellulose-based fiber (B) is 100 nm to 10,000 μm. [4] The thermoplastic resin composition according to any one of [1] to [3], wherein the degree of modification of hydroxyl groups with substituents of the cellulose-based fiber (B) is 0 to 2.55. [5] The thermoplastic resin composition according to any one of [1] to [4], wherein the cellulose-based fiber (B) contains acetylated cellulose. [6] The thermoplastic resin composition according to any one of [1] to [5], wherein, based on 100% by mass of the thermoplastic resin composition, the content of the cellulose-based fiber (B) is 1 to 40% by mass, the content of the reinforcing fiber (C) is 1 to 40% by mass, and the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is 10 to 60% by mass. [7] The thermoplastic resin composition according to any one of [1] to [6], wherein, based on 100% by mass of the thermoplastic resin composition, the content of the cellulose-based fiber (B) is 3 to 25% by mass, the content of the reinforcing fiber (C) is 4 to 16% by mass, and the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is 7 to 41% by mass. [8] The thermoplastic resin composition according to any one of [1] to [7], wherein the mass ratio (B) / (C) of the cellulose-based fiber (B) to the reinforcing fiber (C) is 0.3 to 15. [9] The thermoplastic resin composition according to any one of [1] to [8], wherein the thermoplastic resin (A) comprises a polyamide resin (a).

[10] The thermoplastic resin composition according to [9], wherein the polyamide resin (a) is an aliphatic polyamide resin.

[11] The polyamide resin (a) is selected from the group consisting of polybutyrolactam (polyamide 4), polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polytetramethylene sebacamide (polyamide 410), polypentamethylene adipamide (polyamide 56), polypentamethylene sebacamide (polyamide 510), polypentamethylene dodecamide (polyamide 512), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), The thermoplastic resin composition according to [9] or

[10] , which is at least one homopolymer selected from the group consisting of polyhexamethylene dodecamide (polyamide 612), polynonamethylene dodecamide (polyamide 912), polydecamethylene sebacamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyundecane amide (polyamide 11), and polydodecanamide (polyamide 12), and / or a copolymer using several raw material monomers forming these.

[12] A molded article comprising the thermoplastic resin composition according to any one of [1] to

[11] .

[13] The molded article according to

[12] , which is an automobile part or a sliding material member.

[14] A pellet mixture comprising first pellets containing a first thermoplastic resin (a1) and a cellulosic fiber (B); and second pellets containing a second thermoplastic resin (a2) and a reinforcing fiber (C), wherein the reinforcing fiber (C) is other than the cellulosic fiber (B), and the average fiber length of the reinforcing fiber (C) is 5 mm or more and 20 mm or less.

[15] The pellet mixture according to

[14] , wherein the second pellets are cylindrical, elliptical cylindrical, or rectangular prism-shaped, and the reinforcing fiber (C) is arranged substantially parallel to the length direction of the pellets.

[16] In 100% by mass of the first pellets, the first thermoplastic resin (a1) is 50 to 99% by mass, and the cellulosic fiber (B) is 1 to 50% by mass; in 100% by mass of the second pellets, the second thermoplastic resin (a2) is 1 to 80% by mass, and the reinforcing fiber (C) is 20 to 99% by mass; in 100% by mass of the molded product after heat-molding the pellet mixture, the first thermoplastic resin (a1) and the second thermoplastic resin (a2) are 40 to 90% by mass in total, 1 to 40% by mass of cellulose-based fiber (B), and 1 to 40% by mass of reinforcing fiber (C), and the total of 10 to 60% by mass of cellulose-based fiber (B) and reinforcing fiber (C) is the pellet mixture according to

[14] or

[15] .

[17] The pellet mixture according to

[14] or

[15] , further comprising a third pellet containing a third thermoplastic resin (a3), wherein the first pellet contains 50 to 99% by mass of the first thermoplastic resin (a1) and 1 to 50% by mass of cellulose-based fiber (B) in 100% by mass of the first pellet; and the second pellet contains 1 to 80% by mass of the second thermoplastic resin (a2) and 20 to 99% by mass of reinforcing fiber (C), and the pellet mixture is heated and molded into a molded product. 100% by mass of the first thermoplastic resin (a1), the second thermoplastic resin (a2) and the third thermoplastic resin (a3) ​​contain a total of 40 to 90% by mass, 1 to 40% by mass of cellulose-based fiber (B), and 1 to 40% by mass of reinforcing fiber (C), and the total of the cellulose-based fiber (B) and the reinforcing fiber (C) is 10 to 60% by mass. A pellet mixture.

[18] A method for producing a molded article according to

[12] or

[13] , comprising heat-molding the pellet mixture according to any one of

[14] to

[17] .

[19] A method for producing a molded article according to

[18] , wherein the heat-molding is carried out by injection molding.

[0010] According to the present invention, it is possible to provide a thermoplastic resin composition that can improve impact resistance while maintaining bending strength when formed into a molded article, and a pellet mixture that is suitably used for producing the composition.

[0011] In this specification, the content of each component in a composition refers to the total amount of the components when the composition contains multiple substances corresponding to each component, unless otherwise specified. In this specification, the term "thermoplastic resin composition" refers to a composition containing at least a thermoplastic resin, and includes any form such as pellets, sheets, strands, chips, and molded articles formed by various methods. The terms "pellets" and "molded articles" each refer to one of the forms that a thermoplastic resin composition can take. The thermoplastic resin composition and pellet mixture according to the present invention will be described in detail below.

[0012] [Thermoplastic resin composition] The thermoplastic resin composition contains a thermoplastic resin (A), a cellulose-based fiber (B), and a reinforcing fiber (C), wherein the reinforcing fiber (C) is other than the cellulose-based fiber (B), and the average fiber length of the reinforcing fiber (C) is 500 μm or more and 1200 μm or less.

[0013] <Thermoplastic Resin (A)> The thermoplastic resin (A) is not particularly limited, and examples thereof include polyamide resins, polyolefin resins, polystyrene resins, polyester resins, polyether resins, polysulfone resins, polythioether resins, polyketone resins, polynitrile resins, poly(meth)acrylate resins, polyvinyl resins, cellulose resins, polycarbonate resins, polyimide resins, polyurethane resins, fluorine-containing resins, and other thermoplastic resins. The thermoplastic resin (A) may be used singly or in combination of two or more.

[0014] From the viewpoint of moldability, the content of the thermoplastic resin (A) in 100% by mass of the thermoplastic resin composition is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 90% by mass, and particularly preferably 68 to 82% by mass. The content of the thermoplastic resin (A) in 100% by mass of the thermoplastic resin composition can also be 59 to 93% by mass or 64 to 86% by mass.

[0015] <<Polyamide Resin (a)>> From the viewpoint of moldability, the thermoplastic resin (A) preferably contains a polyamide resin (a). The lower limit of the content of the polyamide resin (a) in 100% by mass of the thermoplastic resin (A) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The upper limit of the content of the polyamide resin (a) in 100% by mass of the thermoplastic resin (A) is 100% by mass. The specific content of the polyamide resin (a) in 100% by mass of the thermoplastic resin composition is preferably 20 to 90% by mass, more preferably 40 to 90% by mass, even more preferably 60 to 90% by mass, and particularly preferably 68 to 82% by mass. Furthermore, the content of the polyamide resin (a) in 100% by mass of the thermoplastic resin composition can also be 59 to 93% by mass or 64 to 86% by mass.

[0016] From the viewpoint of molding processability, the polyamide resin (a) is preferably an aliphatic polyamide resin. The aliphatic polyamide resin may be an aliphatic homopolyamide resin or an aliphatic copolymer polyamide resin. The lower limit of the content of the aliphatic polyamide resin in 100% by mass of the thermoplastic resin (A) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The upper limit of the content of the aliphatic polyamide resin in 100% by mass of the thermoplastic resin (A) is 100% by mass.

[0017] (Aliphatic homopolyamide resin) The aliphatic homopolyamide resin refers to a polyamide resin in which the monomer component constituting the aliphatic polyamide resin is a single type. The aliphatic homopolyamide resin may be composed of at least one of a lactam and an aminocarboxylic acid which is a hydrolyzate of the lactam, or may be composed of a combination of aliphatic diamine and aliphatic dicarboxylic acid. Here, when the monomer components constituting the aliphatic polyamide resin are a combination of aliphatic diamine and aliphatic dicarboxylic acid, the combination of one aliphatic diamine and one aliphatic dicarboxylic acid is considered to be one type of monomer component.

[0018] Examples of the aliphatic homopolyamide resin include an aliphatic homopolyamide resin made from an aliphatic diamine and an aliphatic dicarboxylic acid, and an aliphatic homopolyamide resin made from a lactam or an aminocarboxylic acid.

[0019] Examples of the monomer component constituting the aliphatic homopolyamide resin include a combination of an aliphatic diamine having 2 to 20 carbon atoms, preferably 4 to 12 carbon atoms, and an aliphatic dicarboxylic acid having 2 to 20 carbon atoms, preferably 6 to 12 carbon atoms; a lactam or aminocarboxylic acid having 4 to 12 carbon atoms, preferably 6 to 12 carbon atoms; and the like.

[0020] Examples of aliphatic diamines include ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,8-octanediamine, and 2,2,4 / 2,4,4-trimethylhexamethylenediamine. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedionic acid, dodecanedionic acid, tridecanedionic acid, tetradecanedionic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, and derivatives thereof.

[0021] Examples of combinations of aliphatic diamines and aliphatic dicarboxylic acids include a combination of hexamethylenediamine and adipic acid, a combination of hexamethylenediamine and azelaic acid, a combination of hexamethylenediamine and sebacic acid, a combination of hexamethylenediamine and dodecanedioic acid, a combination of nonamethylenediamine and dodecanedioic acid, a combination of decamethylenediamine and sebacic acid, a combination of decamethylenediamine and dodecanedioic acid, and a combination of dodecamethylenediamine and dodecanedioic acid, and equimolar salts of these combinations are preferably used.

[0022] Examples of lactams include α-pyrrolidone, δ-valerolactam, ε-caprolactam, ω-enantholactam, ω-octalactam, undecanelactam, and laurolactam. From the viewpoint of productivity, the lactam is preferably ε-caprolactam, undecanelactam, or laurolactam. Examples of aminocarboxylic acids include γ-aminobutyric acid, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

[0023] Specific examples of the aliphatic homopolyamide resin include polyamide 4, polyamide 6, polyamide 7, polyamide 8, polyamide 9, polyamide 11, polyamide 12, polyamide 46, polyamide 410, polyamide 412, polyamide 56, polyamide 59, polyamide 510, polyamide 512, polyamide 66, polyamide 69, polyamide 610, polyamide 611, polyamide 612, polyamide 96, polyamide 99, polyamide 910, polyamide 912, polyamide 106, polyamide 109, polyamide 1010, polyamide 1012, polyamide 126, polyamide 129, polyamide 1210, polyamide 1212, and polyamide 122.

[0024] From the viewpoint of productivity, the aliphatic homopolyamide resin is preferably one or more selected from the group consisting of polyamide 4, polyamide 6, polyamide 46, polyamide 410, polyamide 56, polyamide 510, polyamide 512, polyamide 66, polyamide 69, polyamide 610, polyamide 612, polyamide 912, polyamide 1010, polyamide 1012, polyamide 1212, polyamide 11, and polyamide 12, and polyamide 6 and / or polyamide 66 are particularly preferred.

[0025] The aliphatic homopolyamide resin may be one type or a combination of two or more types.

[0026] (Aliphatic copolyamide resin) The aliphatic copolyamide resin refers to a polyamide resin in which two or more types of monomer components constituting the aliphatic polyamide resin are combined. The aliphatic copolyamide resin is a copolymer of two or more types selected from the group consisting of a combination of an aliphatic diamine and an aliphatic dicarboxylic acid, a lactam, and an aminocarboxylic acid. Here, the combination of an aliphatic diamine and an aliphatic dicarboxylic acid is considered to be one type of monomer component, with one type of aliphatic diamine and one type of aliphatic dicarboxylic acid being combined.

[0027] Examples of the aliphatic diamine include the same as those exemplified as raw materials for the aliphatic homopolyamide resin.

[0028] Examples of the aliphatic dicarboxylic acid include the same as those exemplified as raw materials for the aliphatic homopolyamide resin.

[0029] Examples of lactams include those exemplified as raw materials for aliphatic homopolyamide resins, and examples of aminocarboxylic acids include those exemplified as raw materials for aliphatic homopolyamide resins.

[0030] These aliphatic diamines, aliphatic dicarboxylic acids, lactams and aminocarboxylic acids may be used alone or in combination of two or more.

[0031] Specific examples of aliphatic copolyamide resins include polyamide 6 / 66, polyamide 6 / 69, polyamide 6 / 610, polyamide 6 / 611, polyamide 6 / 612, polyamide 6 / 11, polyamide 6 / 12, polyamide 6 / 66 / 12, polyamide 6 / 66 / 610, and polyamide 6 / 66 / 612.

[0032] Among these, at least one selected from the group consisting of polyamide 6 / 66, polyamide 6 / 12 and polyamide 6 / 66 / 12 is preferred, and at least one selected from the group consisting of polyamide 6 / 66 and polyamide 6 / 66 / 12 is more preferred.

[0033] The aliphatic copolyamide resin may be one type or a combination of two or more types.

[0034] (Preferred embodiment of polyamide resin (a)) Among them, from the viewpoint of moldability, the polyamide resin (a) is preferably polybutyrolactam (polyamide 4), polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polytetramethylene sebacamide (polyamide 410), polypentamethylene adipamide (polyamide 56), polypentamethylene sebacamide (polyamide 510), polypentamethylene dodecamide (polyamide 512), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), poly The polymer is preferably at least one homopolymer selected from the group consisting of nonamethylene dodecamide (polyamide 912), polydecamethylene sebacamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyundecaneamide (polyamide 11), and polydodecanamide (polyamide 12), and / or a copolymer using several of the raw material monomers that form these. The polymer is more preferably polycaproamide (polyamide 6) or polyhexamethylene adipamide (polyamide 66), and particularly preferably polycaproamide (polyamide 6).

[0035] (Other Polyamide Resins) The polyamide resin (a) may contain other polyamide resins in addition to aliphatic homopolyamide resins and aliphatic copolymer polyamide resins. Examples of other polyamide resins include polyamide resins that are copolymers having an alicyclic group, an aromatic group, or the like in the main chain or side chain. The other polyamide resin is preferably, for example, a copolymer polyamide resin containing at least two aromatic monomer components. The other polyamide resins may be one type or a combination of two or more types.

[0036] (Method for producing polyamide resin (a)) Examples of an apparatus for producing polyamide resin (a) include known polyamide production apparatuses such as a batch reaction vessel, a single-vessel or multi-vessel continuous reaction vessel, a tubular continuous reaction vessel, and kneading reaction extruders such as a single-screw kneading extruder and a twin-screw kneading extruder. As the polymerization method, known methods such as melt polymerization, solution polymerization, and solid-phase polymerization can be used, and polymerization can be carried out by repeating operations such as normal pressure, reduced pressure, and increased pressure. These polymerization methods can be used alone or in appropriate combination.

[0037] <<Polyolefin Resin>> Examples of polyolefin resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-high-molecular-weight polyethylene (UHMWPE), polypropylene (PP), polybutene (PB), polymethylpentene (TPX), etc. The polyolefin resin may be modified with a functional group such as a carboxyl group and its salt, an acid anhydride group, or an epoxy group.

[0038] <<Polystyrene-based Resin>> Examples of polystyrene-based resins include polystyrene (PS), syndiotactic polystyrene (SPS), methyl methacrylate / styrene copolymer (MS), methyl methacrylate / styrene / butadiene copolymer (MBS), etc. The polystyrene-based resin may be modified with a functional group such as a carboxyl group and its salt, an acid anhydride group, or an epoxy group.

[0039] <<Polyester-Based Resin>> Examples of polyester-based resins include polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), poly(ethylene terephthalate / ethylene isophthalate) copolymer (PET / PEI), polytrimethylene terephthalate (PTT), polycyclohexanedimethylene terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyarylate (PAR), liquid crystal polyester (LCP), polylactic acid (PLA), and polyglycolic acid (PGA).

[0040] <<Polyether Resin>> Examples of polyether resins include polyacetal (POM) and polyphenylene ether (PPO).

[0041] <<Polysulfone Resin>> Examples of polysulfone resins include polysulfone (PSU), polyethersulfone (PESU), and polyphenylsulfone (PPSU).

[0042] <<Polythioether Resin>> Examples of polythioether resins include polyphenylene sulfide (PPS) and polythioether sulfone (PTES).

[0043] <<Polyketone Resin>> Examples of polyketone resins include polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretheretherketone (PEEEK), polyetheretherketoneketone (PEEKK), polyetherketoneketoneketone (PEKKK), and polyetherketoneetherketoneketone (PEKEKK).

[0044] <<Polynitrile Resin>> Examples of polynitrile resins include polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, acrylonitrile / butadiene / styrene copolymer (ABS), and acrylonitrile / butadiene copolymer (NBR).

[0045] <<Poly(meth)acrylate Resin>> Examples of poly(meth)acrylate resins include polymethyl methacrylate (PMMA) and polyethyl methacrylate (PEMA).

[0046] <<Polyvinyl Resin>> Examples of polyvinyl resins include polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, and vinylidene chloride / methyl acrylate copolymer.

[0047] <<Cellulose-Based Resin>> Examples of the cellulose-based resin include cellulose acetate and cellulose butyrate.

[0048] <<Polycarbonate-Based Resin>> Examples of polycarbonate-based resins include polycarbonate (PC).

[0049] <<Polyimide Resin>> Examples of polyimide resins include thermoplastic polyimide (TPI), polyetherimide, polyesterimide, polyamideimide (PAI), and polyesteramideimide.

[0050] <<Polyurethane Resin>> Examples of polyurethane resins include polyurethane (PU) and polyurethane elastomer.

[0051] <<Fluorine-based resins>> Examples of fluorine-based resins include polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polytetrafluoroethylene (PTFE), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer (THV), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride / perfluoro(alkyl vinyl ether) copolymer, tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA), tetrafluoroethylene / hexafluoropropylene / perfluoro(alkyl vinyl ether) copolymer, and chlorotrifluoroethylene / perfluoro(alkyl vinyl ether) / tetrafluoroethylene copolymer (CPT).

[0052] <Cellulosic fiber (B)> Cellulosic fiber (B) refers to a fiber composed of at least one polymer selected from the group consisting of cellulose, holocellulose, and lignocellulose. By including the cellulosic fiber (B) in the thermoplastic resin composition, the mechanical strength of a molded article obtained from the thermoplastic resin composition can be improved. The cellulosic fiber (B) may be used alone or in combination of two or more.

[0053] The raw material for the cellulosic fiber (B) is preferably pulp obtained from natural plants such as wood, bamboo, hemp, jute, kenaf, cotton, bagasse, straw, beet, agricultural waste, waste paper, or textile fabric. Pulp is separated plant fibers contained in plants such as wood, and contains cellulose, hemicellulose, holocellulose, and / or lignocellulose.

[0054] Preferred examples of wood materials for pulp include wood derived from conifers or broad-leaved trees such as Sitka spruce, pine (such as Abies sachalinensis and red pine), cedar, cypress, eucalyptus, and acacia. Examples of waste paper materials for pulp include deinked waste paper, recycled corrugated paper, magazines, and copy paper. Pulp may or may not contain lignin. Pulp materials may be used singly or in combination of two or more.

[0055] Pulp can be obtained by treating the above pulp raw materials by mechanical pulping, chemical pulping, a combination of mechanical and chemical pulping, etc. Examples of such pulps include various kraft pulps (softwood unbleached kraft pulp (NUKP), softwood oxygen-bleached kraft pulp (NOKP), and softwood bleached kraft pulp (NBKP)); mechanical pulps (MP) such as groundwood pulp (GP), refiner GP (RGP), thermomechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP); and the like.

[0056] The cellulosic fiber (B) may be a chemically modified cellulosic fiber in which some of the hydroxyl groups of the polysaccharides and lignin in cellulose, holocellulose, and / or lignocellulose have been substituted with functional groups. Such chemically modified cellulosic fibers may be prepared by chemically modifying some of the hydroxyl groups of cellulosic pulp and then defibrating the pulp, or by chemically modifying some of the hydroxyl groups of the cellulosic pulp after defibrating the pulp. From the viewpoints of the defibration ability, heat resistance, and compatibility with the thermoplastic resin (A), the cellulosic fiber (B) is preferably a chemically modified cellulosic fiber. Chemically modified cellulosic fibers may be used alone or in combination of two or more.

[0057] In the cellulosic fiber (B), the degree of modification with hydroxyl group substituents is preferably 0 to 2.55, more preferably 0.40 to 2.00, and particularly preferably 0.60 to 1.00. The lower limit of the modification degree is preferably 0 or more, more preferably 0.30 or more, even more preferably 0.35 or more, even more preferably 0.40 or more, and particularly preferably 0.60 or more. The upper limit of the modification degree is preferably 2.55 or less, more preferably 2.52 or less, even more preferably 2.00 or less, even more preferably 1.80 or less, and particularly preferably 1.00 or less. Here, the degree of modification with hydroxyl group substituents is the average number of substituted hydroxyl groups per repeat unit of the residue of the cellulosic fiber (B). When the cellulosic fiber (B) is composed entirely of cellulose, the repeat unit is a glucopyranose residue, and the number of hydroxyl groups per unit is 3, so the upper limit of the modification degree is 3. The degree of modification can be adjusted by adjusting the amount of the compound having a substituent, the reaction temperature, the reaction time, and the like.

[0058] The degree of modification by the substituent of the hydroxyl group was determined by elemental analysis, neutralization titration, FT-IR, and two-dimensional NMR ( １ H and １３ The analysis can be carried out by various analytical methods such as C-NMR.

[0059] The substituent on the hydrogen atoms of the chemically modified cellulose-based fiber is preferably at least one selected from the group consisting of acyl groups such as acetyl, propionyl, butyryl, and isobutyryl; carboxyalkyl groups and their salts; carboxyalkylcarbonyl groups and their salts; and 3-carboxypropenoyl groups and their salts. The number of carbon atoms in the substituent is preferably 2 to 6, and more preferably 2 to 4. Examples of salts include alkali metal salts such as lithium, sodium, and potassium; divalent metal salts such as calcium, barium, zinc, and copper; trivalent metal salts such as aluminum; primary to quaternary ammonium salts; and salts with polyamines. From the perspective of ease of production, the substituent is preferably an acetyl group or a propionyl group, with an acetyl group being particularly preferred. That is, it is particularly preferred that the cellulose-based fiber (B) contains acetylated cellulose.

[0060] (Method for producing acylated cellulose fibers) Hereinafter, a method for acylating cellulose fibers will be described. Acylated cellulose fibers can be produced by a method of acylating hydroxyl groups (such as hydroxyl groups of cellulose, hemicellulose, and lignin) present on the fiber surface or amorphous portion of a raw material cellulose pulp and then defibrating the resulting material; or a method of defibrating the cellulose pulp and then acylating some of the hydroxyl groups of the cellulose fibers. It is preferable that the acylation be carried out by acylating hydroxyl groups present on the fiber surface or amorphous portion of the cellulose pulp, such as hydroxyl groups of cellulose, hemicellulose, and lignin, so as not to destroy the cellulose crystalline structure present in the raw material cellulose pulp.

[0061] For example, cellulosic fibers can be acylated by the method described in JP 2016-176052 A. Specifically, the raw material cellulosic pulp is suspended in an anhydrous aprotic polar solvent capable of swelling the raw material, such as N-methylpyrrolidone or N,N-dimethylformamide, and acylated in the presence of a base with a carboxylic acid anhydride (acetic anhydride, propionic anhydride, etc.) or acid chloride having the corresponding acyl group. Preferred bases used in this acylation reaction include pyridine, N,N-dimethylaniline, sodium carbonate, sodium bicarbonate, and potassium carbonate. The acylation reaction is preferably carried out with stirring, for example, at room temperature to 100°C.

[0062] (Degree of acylation of acylated cellulose-based fibers) The degree of acylation (degree of substitution, DS) of the sugar chain hydroxyl groups of acylated cellulose-based fibers is the degree of modification of the hydroxyl groups by the substituent when the substituent is an acyl group, and is the average number of hydroxyl groups substituted with acyl groups per repeating unit of the residue of the cellulose-based fiber (B). When the acylated cellulose-based fibers are composed entirely of cellulose, the repeating units are glucopyranose residues, and the number of hydroxyl groups per unit is 3, so the upper limit of the degree of substitution (DS) is 3.

[0063] On the other hand, when the cellulosic fiber is lignocellulose, the lignocellulose contains hemicellulose and lignin in addition to cellulose. The number of hydroxyl groups in the xylose residues in xylan or the galactose residues in arabinogalactan contained in hemicellulose is 2, and the number of hydroxyl groups in standard lignin residues is also 2. Therefore, the number of hydroxyl groups in these residues is less than 3. Therefore, the upper limit of the degree of substitution (DS) in lignopulp is less than 3, and is approximately 2.7 to 2.8, depending on the contents of hemicellulose and lignin contained in the lignopulp.

[0064] Furthermore, when the cellulosic fiber is holocellulose, since holocellulose contains hemicellulose as well as cellulose, the average number of hydroxyl groups in the repeating unit is less than 3, and the upper limit of the degree of substitution is also less than 3.

[0065] The degree of substitution (DS) of the acylated cellulose-based fiber, more specifically, the acetylated cellulose-based fiber, is preferably 0 to 2.55, more preferably 0.30 to 2.55, even more preferably 0.35 to 2.52, even more preferably 0.40 to 1.80, and particularly preferably 0.60 to 1.00. The lower limit of the degree of substitution (DS) is preferably 0 or more, more preferably 0.30 or more, even more preferably 0.35 or more, even more preferably 0.40 or more, and particularly preferably 0.60 or more. The upper limit of the degree of substitution (DS) is preferably 2.55 or less, more preferably 2.52 or less, even more preferably 2.00 or less, even more preferably 1.80 or less, and particularly preferably 1.00 or less. The degree of substitution (DS) can be adjusted by adjusting the amount of acylating agent, reaction temperature, reaction time, etc.

[0066] The degree of substitution (DS) was determined by elemental analysis, neutralization titration, FT-IR, and two-dimensional NMR ( １ H and １３ C) and other analytical methods.

[0067] (Method for defibrating cellulosic fibers (B)) Unmodified or chemically modified cellulosic fibers can be defibrated, for example, by preparing the cellulosic fibers as a suspension or slurry and using known means such as mechanical grinding or beating using a refiner, a high-pressure homogenizer, a grinder, a multi-shaft kneader such as a single-shaft or double-shaft kneader, a bead mill, or the like.

[0068] When preparing a thermoplastic resin composition using chemically modified cellulose-based fibers, it is preferable to chemically modify some of the hydroxyl groups of the cellulose-based pulp, and then melt and knead the chemically modified pulp with a thermoplastic resin in a single- or multi-screw kneader, preferably a multi-screw kneader, under heating. According to this method, the chemically modified pulp is defibrated and microfibrillated by the shear force during kneading, allowing the chemically modified cellulose-based fibers to be uniformly dispersed in the thermoplastic resin. The resulting melt-kneaded mixture of thermoplastic resin (A) and cellulose-based fiber (B) can be added with reinforcing fiber (C) and any other component (D), and further melt-kneaded to form a thermoplastic resin composition. Alternatively, after defibrating the cellulose-based pulp, some of the hydroxyl groups can be chemically modified to prepare chemically modified cellulose-based fibers. The resulting cellulose-based fiber (B) can then be separately melt-kneaded with thermoplastic resin (A), reinforcing fiber (C), and any other component (D) to form a thermoplastic resin composition.

[0069] (Average Fiber Diameter and Average Fiber Length of Cellulosic Fiber (B)) From the viewpoint of improving the bending strength and impact resistance of molded articles obtained from the thermoplastic resin composition, the average fiber diameter (fiber width) of the cellulose fiber (B) is preferably 4 nm to 1,000 μm, more preferably 50 nm to 200 μm, even more preferably 0.15 μm to 50 μm, and particularly preferably 1 μm to 50 μm. Furthermore, the average fiber length of the cellulose fiber (B) is preferably 100 nm to 10,000 μm, more preferably 0.5 μm to 1,000 μm, and even more preferably 1 μm to 1,000 μm. The fiber length and fiber diameter of the cellulose fiber (B) can be measured from the image obtained by observing the cellulose fiber (B) using an electron microscope, optical microscope, digital microscope, or the like. The average fiber length and average fiber diameter of the cellulose fiber (B) are the average values ​​of the measured fiber lengths and fiber diameters obtained by observing 100 or more cellulose fibers (B). Here, the average fiber length and average fiber diameter refer to the average fiber length and average fiber diameter of the cellulose-based fibers (B) in the thermoplastic resin composition. When the fiber length and fiber diameter of the cellulose-based fibers do not change during the production of the thermoplastic resin composition, the average fiber length and average fiber diameter are the average fiber length and average fiber diameter of the cellulose-based fibers used as raw materials. Specific methods for measuring the average fiber length and average fiber diameter of the cellulose-based fibers (B) include, for example, the following: (1) Dissolve the thermoplastic resin (A) in the thermoplastic resin composition in a solvent to separate the cellulose-based fibers (B) in the resin composition. (2) Obtain an image of the cellulose-based fibers (B) obtained in (1) by observing them with a microscope, randomly select 100 or more fibrous particles from the obtained image, determine the major axis and minor axis of each fibrous particle, calculate the arithmetic average of the major axes to obtain the average fiber length, and calculate the arithmetic average of the minor axes to obtain the average fiber diameter. The major axis is the length of the longest part of the fibrous particle, and the minor axis is the length of the thickest part in the direction perpendicular to the major axis.Even if the defibration of the cellulose-based fibers (B) is insufficient and the resin composition contains fibers having a fiber diameter greater than the above range after defibration, such cellulose-based fibers (B) are included in the present invention as long as the object of the present invention is achieved.

[0070] The content of the cellulose fiber (B) in 100% by mass of the thermoplastic resin composition is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, even more preferably 3 to 25% by mass, and particularly preferably 10 to 20% by mass. If the content of the cellulose fiber (B) is less than the above range, the mechanical properties tend to be inferior, and if it is more than the above range, the moldability tends to be inferior.

[0071] <Reinforcing fiber (C)> The thermoplastic resin composition contains reinforcing fiber (C) having an average fiber length of 500 μm or more and 1200 μm or less. The reinforcing fiber (C) is a fiber other than the cellulose-based fiber (B). The average fiber diameter of the reinforcing fiber (C) is preferably 4 μm or more and 20 μm or less. Here, the average fiber length and average fiber diameter refer to the average fiber length and average fiber diameter of the reinforcing fiber (C) in the thermoplastic resin composition. Note that, for the reinforcing fiber (C), when the cross section when cut along a plane perpendicular to the length direction is not circular, the fiber diameter of the reinforcing fiber (C) means the circle-equivalent diameter. When the reinforcing fiber (C) is glass fiber, at least a portion of the glass fiber may be broken during the production process of the thermoplastic resin composition and the molded product, resulting in an average fiber length smaller than that of the raw glass fiber. In molded articles obtained from thermoplastic resin compositions, it is believed that the fiber length of the reinforcing fibers (C) actually present in the thermoplastic resin composition constituting the molded article contributes to improving mechanical properties such as bending strength and impact resistance, so the average fiber length of the reinforcing fibers (C) is defined as above. The same applies to the average fiber diameter of the reinforcing fibers (C). Note that fibers with too small a fiber length are thought to contribute little to improving mechanical properties such as bending strength and impact resistance when molded into a molded article, so in this specification, 1,000 fibers were randomly selected from fibers with a fiber length of 10 μm or more, and the average fiber length was determined. The reinforcing fibers (C) may be used alone or in combination of two or more types.

[0072] In this specification, when the reinforcing fiber (C) is glass fiber, the method for measuring the average fiber length is as follows. First, for a thermoplastic resin composition or a molded article thereof, the resin is dissolved using a solvent such as an acid or alkali that dissolves the thermoplastic resin but not the glass fiber, and the glass fiber is extracted. The obtained glass fiber is observed using image analysis software to measure the fiber length of the glass fiber. The average fiber length is the average value of the fiber length of the glass fiber. There are no particular limitations on the image analysis software as long as it can measure the fiber length, and an example is A-zo-kun, an image analysis software manufactured by Asahi Kasei Engineering Corporation. The average fiber diameter of the reinforcing fiber (C) can also be measured in the same manner. Even when the reinforcing fiber (C) is other than glass fiber, the average fiber length and average fiber diameter can be determined by the same method.

[0073] By including reinforcing fibers (C) having an average fiber length of 500 μm or more and 1200 μm or less in the thermoplastic resin composition, the impact resistance of the molded article obtained from the thermoplastic resin composition can be significantly improved while maintaining the bending strength. If the average fiber length of the reinforcing fibers (C) is less than 500 μm, the impact resistance of the molded article obtained from the thermoplastic resin composition cannot be improved. During molding such as injection molding, the orientation direction of the reinforcing fibers (C) changes depending on the flow (direction) of the resin. However, if the average fiber length of the reinforcing fibers (C) exceeds 1200 μm, the difference in the reinforcing effect between the orientation direction of the reinforcing fibers (C) and the direction perpendicular thereto becomes large, which tends to make the design of the molded article difficult. The average fiber length of the reinforcing fibers (C) is 500 μm or more and 1200 μm or less, preferably 550 μm or more and 1100 μm or less, and particularly preferably 600 μm or more and 1000 μm or less.

[0074] From the viewpoint of improving impact resistance while maintaining the bending strength when formed into a molded article, the average fiber diameter of the reinforcing fibers (C) is preferably 4 μm or more and 20 μm or less, more preferably 5 μm or more and 18 μm or less, and particularly preferably 6 μm or more and 16 μm or less.

[0075] The reinforcing fiber (C) may be either an inorganic filler or an organic filler. The reinforcing fiber (C) is preferably at least one selected from the group consisting of glass fiber and carbon fiber, and more preferably glass fiber.

[0076] The reinforcing fibers (C) may be surface-treated with a surface treatment agent. Furthermore, to improve workability, the reinforcing fibers (C) may be converged or granulated with the surface treatment agent. Even when the reinforcing fibers (C) are converged or granulated with a surface treatment agent, the average fiber length and average fiber diameter of the reinforcing fibers (C) refer to the average fiber length and average fiber diameter of the reinforcing fibers (C) in the thermoplastic resin composition. Examples of surface treatment agents include various coupling agents such as silane coupling agents, titanium-based coupling agents, aluminum-based coupling agents, and zirconia-based coupling agents; water glass, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, starch, polyvinyl alcohol, acrylic resins, epoxy resins, phenolic resins, polyvinyl acetate, polyurethane resins, epoxy compounds, isocyanate compounds, colloidal silica, colloidal alumina, fatty acids, surfactants, etc. The surface treatment agents may be used alone or in combination of two or more.

[0077] The surface treatment agent may be applied to the reinforcing fibers (C) in advance, dried, and subjected to a surface treatment or a convergence treatment, or may be added simultaneously with the reinforcing fibers (C) during the preparation of the resin composition. When a thermoplastic resin (A), cellulosic fibers (B), reinforcing fibers (C), and other components (D) are blended and melt-kneaded to produce a thermoplastic resin composition, the reinforcing fibers (C) in the resin composition may remain as they are, may be completely dissolved into individual particles, or may be partially dissolved with some remaining as they are; or the dissolved individual particles may be further pulverized.

[0078] The raw material reinforcing fibers (C) may have an average fiber diameter of 4 to 25 μm. For example, when the raw material is glass fiber, the average fiber diameter is preferably 4 to 25 μm, more preferably 6 to 23 μm, and even more preferably 10 to 23 μm, from the viewpoint of the bending strength and impact resistance of the molded product.

[0079] The glass fibers as raw materials may be used alone or in combination of two or more types. Two or more types of glass fibers having different average fiber diameters may be used. An example of a combination of glass fiber diameters is a combination of (C1) glass fibers having an average fiber diameter of 6 to 11 μm and (C2) glass fibers having an average fiber diameter of 13 to 25 μm.

[0080] The average fiber length (cut length) of the raw material glass fibers is not particularly limited, and chopped strands cut to 1 mm to 50 mm can be used. From the viewpoint of making the average fiber length of the glass fibers in the thermoplastic resin composition and in the molded product 500 μm or more and 1200 μm or less, the average fiber length of the raw material glass fibers is preferably 5 mm to 20 mm, more preferably 7 mm to 15 mm, and even more preferably 8 mm to 12 mm. The average fiber length of the raw material glass fibers is, for example, a value obtained by measuring the fiber lengths of the raw material glass fibers using image analysis software and averaging the measured values.

[0081] Glass fibers are commercially available, and for example, ECS 03T-249H, ECS 03T-275H manufactured by Nippon Electric Glass Co., Ltd. can be used.

[0082] Examples of carbon fibers include polyacrylonitrile (PAN)-based carbon fibers made from PAN fibers, pitch-based carbon fibers made from petroleum tar or petroleum pitch, vapor-grown carbon fibers made from hydrocarbons, and graphitized fibers thereof. Of these carbon fibers, PAN-based carbon fibers are preferably used because of their excellent balance between strength and elastic modulus.

[0083] Furthermore, as the reinforcing fiber (C), a form in which continuous reinforcing fibers such as glass fibers or carbon fibers are composited with the thermoplastic resin (A) so that they are the same length and in the same direction in the pellet can also be used. When using such composite reinforcing fibers (C), it is preferable because it is easy to control the average fiber length of the reinforcing fibers (C) to 500 μm or more and 1200 μm or less. The average fiber length of the reinforcing fibers (C) in the composite form is preferably 5 mm to 20 mm, preferably 6 mm to 15 mm, and more preferably 7 mm to 12 mm. Furthermore, the average fiber diameter of the reinforcing fibers (C) in the composite form is preferably 4 to 20 μm, more preferably 5 to 18 μm, even more preferably 6 to 17 μm, and particularly preferably 6 to 16 μm.

[0084] Such composite reinforcing fibers (C) are commercially available, and examples thereof include Plastron (registered trademark) PP-GF20-01, PP-GF30-01, PP-GF40-01, PP-GF50-01, PP-GF40-02, PP-CF40-11 (L8), PA6-GF60-01 (L9), PA6-CF40-01 (L9), PAX-GF60-02 (L9), PAX-CF40-02 (L9), PA9T-GF50-01 (L9), PA9T-CF40-01 (L9), and the like, manufactured by Polyplastics Co., Ltd.

[0085] The content of the reinforcing fiber (C) in 100% by mass of the thermoplastic resin composition is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, even more preferably 3 to 30% by mass, and particularly preferably 4 to 16% by mass. If the content of the reinforcing fiber (C) is less than the above range, the mechanical properties tend to be inferior, and if it is more than the above range, molding processability tends to be difficult.

[0086] The total content of the cellulose-based fiber (B) and the reinforcing fiber (C) in 100% by mass of the thermoplastic resin composition is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 10 to 40% by mass, and even more preferably 18 to 32% by mass. The total content of the cellulose-based fiber (B) and the reinforcing fiber (C) in 100% by mass of the thermoplastic resin composition can also be 7 to 41% by mass or 14 to 36% by mass. If the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is less than the above range, the mechanical properties tend to be poor, and if it is greater than the above range, molding processability tends to be difficult.

[0087] From the viewpoint of improving the bending strength and impact resistance of a molded article obtained from the thermoplastic resin composition, the mass ratio (B) / (C) of the cellulosic fiber (B) to the reinforcing fiber (C) is preferably 0.3 to 15, more preferably 0.5 to 8.0, and even more preferably 0.9 to 3.1.

[0088] <Other Components (D)> The thermoplastic resin composition may contain, as optional components, appropriate functionalizing agents such as dyes, pigments, plasticizers, antioxidants, heat resistance agents, foaming agents, weather resistance agents, crystal nucleating agents, crystallization accelerators, mold release agents, lubricants, antistatic agents, flame retardants, flame retardant assistants, and colorants, depending on the purpose, etc. The content of the other components (D) in 100% by mass of the thermoplastic resin composition is preferably 0.01 to 1% by mass, and more preferably 0.05 to 0.5% by mass.

[0089] [Method for producing thermoplastic resin composition] The method for producing the thermoplastic resin composition is not particularly limited. For example, the following production methods 1 and 2 can be applied as the method for producing the thermoplastic resin composition.

[0090] (Production Method 1) A thermoplastic resin composition can be obtained by melt-kneading a thermoplastic resin (A), a cellulose-based fiber (B), a reinforcing fiber (C), and other components (D) in a kneader. Examples of kneaders include single-screw or twin-screw extruders, Banbury mixers, kneaders, mixing rolls, and the like. For example, a twin-screw extruder can be used to blend all raw materials and then melt-knead them; a portion of the raw materials can be blended, melt-kneaded, and then the remaining raw materials can be blended and melt-kneaded; or a portion of the raw materials can be blended, and then the remaining raw materials can be mixed using a side feeder during melt-kneading. The thermoplastic resin composition can be in the form of pellets or the like. The thermoplastic resin composition obtained in this way can be used as a raw material for molded articles by injection molding, extrusion molding, blow molding, rotational molding, etc.

[0091] (Production Method 2) Pellets containing a thermoplastic resin (A) and a cellulosic fiber (B), and pellets containing a thermoplastic resin (A) and a reinforcing fiber (C) are prepared in advance, and these pellets are blended as a raw material and can be used as a raw material for a molded product by injection molding, extrusion molding, blow molding, rotational molding, or the like. When producing pellets, a method similar to Production Method 1 can be used. From the viewpoints of defibration, productivity, and moldability, it is more preferable to produce pellets containing a thermoplastic resin (A) and a cellulosic fiber (B) by feeding the thermoplastic resin (A) and the cellulosic fiber (B) into a twin-screw extruder or the like and melt-kneading them. Pellets can also be produced by passing a resin-impregnated fiber bundle of cellulosic fiber through a pelletizer, but this method generally results in the cellulosic fiber being too long, making it unsuitable for molding fine shapes, and therefore it is preferable to adopt the melt-kneading method described above.

[0092] Specifically, the following method is preferably employed. First, first pellets containing a first thermoplastic resin (a1) and cellulosic fibers (B) are prepared. Second pellets containing a second thermoplastic resin (a2) and reinforcing fibers (C) are prepared. Optionally, third pellets containing a third thermoplastic resin (a3) ​​are prepared. The first, second, and third pellets may each contain other components (D). The first and second pellets thus obtained, and optionally the third pellets and other components (D), are separately or simultaneously introduced into various molding machines such as injection molding machines, extrusion molding machines, blow molding machines, and rotary molding machines, and molded to obtain a thermoplastic resin composition, or directly a molded product. Alternatively, the first and second pellets, and optionally the third pellets and other components (D), are separately or simultaneously introduced into a kneader and melt-kneaded to obtain a thermoplastic resin composition. The kneader exemplified in Production Method 1 can be used. The thermoplastic resin composition can be in the form of pellets or the like. Alternatively, the first and second pellets, and optionally the third pellets and other components (D), may be uniformly dry-blended to a specific ratio using, for example, a tumbler, a mixer, etc. to prepare a pellet mixture, which may then be subjected to molding, melt-kneading, etc. Among these, the method of molding the pellet mixture is preferred from the viewpoint of miniaturizing and uniformly dispersing the cellulosic fibers (B) in the thermoplastic resin composition and setting the average fiber length and average fiber diameter of the reinforcing fibers (C) in the thermoplastic resin composition within the desired ranges.

[0093] [Pellet Mixture] The pellet mixture used in the above-mentioned manufacturing method 2 includes first pellets containing a first thermoplastic resin (a1) and a cellulosic fiber (B); and second pellets containing a second thermoplastic resin (a2) and a reinforcing fiber (C), wherein the reinforcing fiber (C) is other than the cellulosic fiber (B), and the average fiber length of the reinforcing fiber (C) is preferably 5 mm or more and 20 mm or less. The first and second pellets are different from each other. The first pellets preferably do not contain the reinforcing fiber (C). The second pellets preferably do not contain the cellulosic fiber (B). The first and second pellets may each be one type or a combination of two or more types.

[0094] The pellet mixture may further include third pellets containing a third thermoplastic resin (a3). The third pellets are different from the first and second pellets. The third pellets preferably do not contain the cellulosic fiber (B) or the reinforcing fiber (C). The third pellets may be one type or a combination of two or more types.

[0095] The first thermoplastic resin (a1) and the second thermoplastic resin (a2) may be the same or different resins. From the viewpoint of improving the compatibility between the thermoplastic resins and improving the mechanical properties of the resulting molded product, it is preferable that the first thermoplastic resin (a1) and the second thermoplastic resin (a2) are the same type of resin. The third thermoplastic resin (a3) ​​may be the same or different from the first thermoplastic resin (a1) and the second thermoplastic resin (a2), but is preferably the same type of resin. The resins exemplified in the section <Thermoplastic resin (A)> can be used as the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3). The first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3) ​​may each be used alone or in combination of two or more.

[0096] In the present invention, two or more resins corresponding to the polyamide resin (a) are the same type of resin. For example, polyamide 6 and polyamide 66 are the same type of resin. The same applies to polyolefin-based resins, polystyrene-based resins, polyester-based resins, polyether-based resins, polysulfone-based resins, polythioether-based resins, polyketone-based resins, polynitrile-based resins, poly(meth)acrylate-based resins, polyvinyl-based resins, cellulose-based resins, polycarbonate-based resins, polyimide-based resins, polyurethane-based resins, and fluorine-based resins. From the viewpoint of moldability, it is preferable that the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the optional third thermoplastic resin (a3) ​​are all polyamide resins (a), and preferably aliphatic polyamide resins. The polyamide resin (a) is preferably at least one homopolymer selected from the group consisting of polyamide 4, polyamide 6, polyamide 46, polyamide 410, polyamide 56, polyamide 510, polyamide 512, polyamide 66, polyamide 69, polyamide 610, polyamide 612, polyamide 912, polyamide 1010, polyamide 1012, polyamide 1212, polyamide 11, and polyamide 12, and / or a copolymer using several raw material monomers that form these, more preferably polyamide 6 or polyamide 66, and particularly preferably polyamide 6.

[0097] (Production of Pellets) The pellets can be obtained, for example, by extruding the resin composition constituting the pellets in the form of strands from an extruder or the like, and cutting the strands with a cutter having a rotary blade.

[0098] The pellets may have a shape such as a sphere, a rectangle, a spheroid, a shape slightly deformed from an exact spheroid, a cylindrical shape with a circular, elliptical, or polygonal cross section. The first and third pellets are preferably spherical, spheroidal, or cylindrical with a circular, elliptical, or polygonal cross section. The second pellet is preferably cylindrical with a circular, elliptical, or polygonal cross section, i.e., a circular cylinder, an elliptical cylinder, or a rectangular cylinder.

[0099] When the cross section of the pellet is circular, its diameter is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.0 to 3.5 mm. When the cross section of the pellet is elliptical, its major axis is preferably 1 to 5 mm, more preferably 2 to 4 mm, and even more preferably 2.0 to 3.5 mm. Furthermore, when the cross section of the pellet is elliptical, its minor axis is preferably 1 to 3 mm, and even more preferably 2 to 3 mm. The ratio of the major axis to the minor axis (major axis / minor axis) is not particularly limited, but is preferably 1 to 4. The major axis and minor axis of the pellet can be controlled, for example, by adjusting the diameter of the nozzle of the extruder or the like to change the diameter of the strand. When the cross section of the pellet is polygonal, examples of the polygon include a triangle, a rectangle, a pentagon, and a hexagon. In these polygons, the lengths of the sides may be the same or different.

[0100] The length of the pellets is not particularly limited, but is preferably 2 to 4 mm, more preferably 2.5 to 4.0 mm, for the first and third pellets, and is preferably 5 to 20 mm, more preferably 6 to 15 mm, and even more preferably 7 to 12 mm, for the second pellet.

[0101] (First pellets) From the viewpoint of melt stability and molding processability during the production of the first pellets, the content of the first thermoplastic resin (a1) is preferably 50 to 99% by mass, more preferably 50 to 95% by mass, and even more preferably 60 to 90% by mass, based on 100% by mass of the first pellets. Similarly, the content of the cellulosic fiber (B) is preferably 1 to 50% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, based on 100% by mass of the first pellets.

[0102] From the viewpoint of molding processability, the content of the other component (D) is preferably 0 to 30% by mass, and more preferably 0 to 10% by mass, based on 100% by mass of the first pellets.

[0103] From the viewpoint of mechanical properties and molding processability, the content of the first pellets is preferably 30 to 70 mass%, more preferably 35 to 65 mass%, and even more preferably 40 to 60 mass%, based on 100 mass% of the pellet mixture.

[0104] (Second pellet) In the second pellet, the average fiber length of the reinforcing fiber (C) is preferably 5 mm or more and 20 mm or less, preferably 6 mm or more and 15 mm or less, and more preferably 7 mm or more and 12 mm or less. When the average fiber length of the reinforcing fiber (C) in the second pellet is within the above range, it is easy to set the average fiber length of the reinforcing fiber (C) in the thermoplastic resin composition or molded product obtained by hot molding the pellet mixture to a range of 500 μm or more and 1200 μm or less, and the impact resistance can be improved while maintaining the bending strength of the thermoplastic resin composition or molded product.

[0105] In the second pellets, the average fiber diameter of the reinforcing fibers (C) is preferably 4 μm or more and 20 μm or less, more preferably 5 μm or more and 18 μm or less, and even more preferably 6 μm or more and 16 μm or less. When the average fiber diameter of the reinforcing fibers (C) in the second pellets is within the above range, it is easy to set the average fiber diameter of the reinforcing fibers (C) in the thermoplastic resin composition or molded article obtained by hot molding the pellet mixture, etc., to the range of 4 μm or more and 20 μm or less, and the impact resistance can be improved while maintaining the bending strength of the thermoplastic resin composition or molded article.

[0106] In order to improve the bending strength and impact resistance, the average fiber length of the reinforcing fibers (C) in the thermoplastic resin composition or molded article is set to a range of 500 μm to 1200 μm, and the second pellets are preferably cylindrical, elliptical cylindrical, or prismatic, and the reinforcing fibers (C) are preferably arranged substantially parallel to the length direction of the pellets. In the present invention, the length direction of the cylindrical, elliptical cylindrical, or prismatic pellets refers to the direction perpendicular to the cross section of a circle, ellipse, or prismatic shape.

[0107] When the second pellets are cylindrical, elliptical, or rectangular, the length of the pellets is preferably 5 mm to 20 mm, more preferably 6 mm to 15 mm, and even more preferably 7 mm to 12 mm. In addition, it is preferable that the lengths of the reinforcing fibers (C) in the second pellets are approximately the same.

[0108] Pellets in this form are commercially available, for example, the aforementioned Plastron (registered trademark) manufactured by Polyplastics Co., Ltd.

[0109] From the viewpoint of improving the bending strength and impact resistance of the resulting thermoplastic resin composition or molded article, the content of the second thermoplastic resin (a2) is preferably 1 to 80% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass, based on 100% by mass of the second pellets. Similarly, the content of the reinforcing fiber (C) is preferably 20 to 99% by mass, more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass, based on 100% by mass of the second pellets.

[0110] From the viewpoint of molding processability, the content of the other component (D) is preferably 0 to 10% by mass, and more preferably 0 to 5% by mass, based on 100% by mass of the second pellets.

[0111] From the viewpoint of the bending strength, impact resistance, and moldability of the resulting thermoplastic resin composition or molded article, the content of the second pellets is preferably 5 to 70 mass%, more preferably 6 to 60 mass%, and even more preferably 7 to 30 mass%, based on 100 mass% of the pellet mixture.

[0112] (Third pellets) The pellet mixture may optionally contain third pellets. The third pellets contain a third thermoplastic resin (a3). The content of the third thermoplastic resin (a3) ​​is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 99 to 100% by mass, based on 100% by mass of the third pellets.

[0113] From the viewpoint of molding processability, the content of the other component (D) is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, and even more preferably 0 to 1 mass%, based on 100 mass% of the third pellets.

[0114] The content of the third pellets is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 43% by mass or less, based on 100% by mass of the pellet mixture.

[0115] The pellet mixture may contain other component (D) in addition to the first pellets, second pellets, and third pellets.

[0116] (Pellet mixture) When the pellet mixture contains the first and second pellets but does not contain the third pellet, the molded product after heat-molding the pellet mixture contains 40 to 90 mass% of the first thermoplastic resin (a1) and the second thermoplastic resin (a2) in total, 1 to 40 mass% of the cellulose-based fiber (B), and 1 to 40 mass% of the reinforcing fiber (C), and the total of the cellulose-based fiber (B) and the reinforcing fiber (C) is preferably 10 to 60 mass%.

[0117] The total content of the first thermoplastic resin (a1) and the second thermoplastic resin (a2) is preferably 40 to 90 mass%, more preferably 50 to 90 mass%, even more preferably 60 to 90 mass%, and particularly preferably 68 to 82 mass%, based on 100 mass% of the molded product obtained after the pellet mixture is heat-molded. By setting the total content of the first thermoplastic resin (a1) and the second thermoplastic resin (a2) within the above range, the moldability of the thermoplastic resin composition is improved.

[0118] When the pellet mixture further contains a third pellet in addition to the first and second pellets, the molded product after heat-molding the pellet mixture preferably contains a total of 40 to 90 mass% of the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3), 1 to 40 mass% of the cellulose-based fiber (B), and 1 to 40 mass% of the reinforcing fiber (C), and a total of 10 to 60 mass% of the cellulose-based fiber (B) and the reinforcing fiber (C).

[0119] The total content of the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3) ​​is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 90% by mass, and particularly preferably 68 to 82% by mass, of the molded product obtained by heat-molding the pellet mixture. Furthermore, the total content of the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3) ​​of the molded product obtained by heat-molding the pellet mixture can also be 59 to 93% by mass or 64 to 86% by mass. By setting the total content of the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3) ​​within the above range, the molding processability of the thermoplastic resin composition is improved.

[0120] Regardless of the presence or absence of third pellets, the content of the cellulose fiber (B) is preferably 1 to 40 mass%, more preferably 2 to 30 mass%, even more preferably 3 to 25 mass%, and particularly preferably 10 to 20 mass%, of 100 mass% of the molded article obtained after the pellet mixture is heat-molded. By setting the content of the cellulose fiber (B) within the above range, the molding processability of the pellet mixture is improved, and the mechanical properties of the resulting molded article are improved.

[0121] Regardless of the presence or absence of the third pellet, the content of the reinforcing fiber (C) is preferably 1 to 40% by mass, more preferably 2 to 35% by mass, even more preferably 3 to 30% by mass, and particularly preferably 4 to 16% by mass, based on 100% by mass of the molded article after the pellet mixture is heat-molded. By setting the content of the reinforcing fiber (C) within the above range, the molding processability of the pellet mixture is improved, and the mechanical properties of the resulting molded article are improved.

[0122] Regardless of the presence or absence of the third pellet, the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 10 to 40% by mass, and even more preferably 18 to 32% by mass, of the molded article 100% by mass after the pellet mixture is heated and molded. Furthermore, the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) of the molded article 100% by mass after the pellet mixture is heated and molded can also be 7 to 41% by mass or 14 to 36% by mass. By setting the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) within the above range, the molding processability of the pellet mixture is improved, and the mechanical properties of the resulting molded article are improved.

[0123] Regardless of the presence or absence of the third pellets, the mass ratio (B) / (C) of the cellulose-based fiber (B) to the reinforcing fiber (C) in 100% by mass of the molded article after heat-molding the pellet mixture is preferably 0.3 to 15, more preferably 0.5 to 8.0, and even more preferably 0.9 to 3.1. By setting the mass ratio of the cellulose-based fiber (B) to the reinforcing fiber (C) within the above range, the bending strength and impact resistance of the obtained molded article are improved.

[0124] Regardless of the presence or absence of the third pellets, the content of the other component (D) is preferably 0.01 to 1 mass%, more preferably 0.05 to 0.5 mass%, based on 100 mass% of the molded product obtained by heat-molding the pellet mixture.

[0125] Examples of the thermoforming method include blend molding and melt kneading, with blend molding being preferred. Examples of blend molding include injection molding, extrusion molding, blow molding, and rotational molding, with injection molding being particularly preferred from the viewpoint of the degree of freedom in the shape of the molded product. The heating temperature is preferably in the range of the melting point of the thermoplastic resin mainly used plus 10 to 70°C, and more preferably in the range of 20 to 60°C. Another aspect of the present invention is a method for producing a molded product, which includes thermoforming a pellet mixture. From the viewpoint of the degree of freedom in the shape of the molded product, it is preferred that the thermoforming be performed by injection molding.

[0126] [Uses of Thermoplastic Resin Composition and Pellet Mixture] The thermoplastic resin composition and pellet mixture can be suitably used for producing molded articles by injection molding, extrusion molding, blow molding, rotational molding, etc. Another aspect of the present invention is a molded article comprising the thermoplastic resin composition.

[0127] In particular, thermoplastic resin compositions and pellet mixtures have good injection moldability and can be suitably used for producing injection-molded articles. There are no particular limitations on the method for producing injection-molded articles, and known methods can be used. For example, a method conforming to ISO 294-1 can be taken into consideration. Yet another aspect of the present invention is a method for producing a molded article, comprising the step of molding a thermoplastic resin composition or a pellet mixture by injection molding to obtain a molded article.

[0128] Applications of the molded articles include, but are not limited to, automotive parts such as spoilers, air intake ducts, intake manifolds, resonators, fuel tanks, gas tanks, hydraulic oil tanks, fuel filler tubes, fuel delivery pipes, and various other hoses, tubes, and tanks; interior and exterior materials, sliding materials, and the like (e.g., gears, pulleys, cams, bearings, cable housings, and the like) for transport vehicles such as trains, ships, and airplanes; housings, structural materials, and internal parts for electrical appliances such as personal computers, televisions, and telephones; building materials; mechanical parts such as power tool housings and pipes; electric and electronic parts such as tanks, tubes, hoses, and films; household and office supplies; building material-related parts; furniture parts; etc. Among these, the thermoplastic resin composition is preferably used for automotive parts or sliding material members because of its excellent calcium chloride resistance.

[0129] Furthermore, because the thermoplastic resin composition has excellent gas barrier properties, it is suitable for use in molded articles that come into contact with high-pressure gas, such as tanks, tubes, hoses, films, etc. The type of gas is not particularly limited and examples include hydrogen, nitrogen, oxygen, helium, methane, butane, propane, etc., with gases having low polarity being preferred, and hydrogen, nitrogen, and methane being particularly preferred.

[0130] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0131] The analytical and physical property measurement methods used in the examples and comparative examples, as well as the materials used in the examples and comparative examples, are shown below.

[0132] The properties of the thermoplastic resin composition were measured by the following methods.

[0133] [Preparation of Test Pieces] Using the pellet mixtures of the Examples and Comparative Examples, test pieces having a thickness of 4 mm were prepared in accordance with ISO 294-1 using an injection molding machine SE100D-C160S manufactured by Sumitomo Heavy Industries, Ltd.

[0134] [Average fiber length of glass fibers] A sample of approximately 4 mm x 4 mm cut from the test piece prepared by the above method was immersed in 95% by mass sulfuric acid for 16 hours to dissolve the thermoplastic resin in the sample, precipitate the glass fibers, and extract the glass fibers. The extracted glass fibers were photographed using a microscope capable of taking images. The photographed images were observed using A-zo-kun, an image analysis software manufactured by Asahi Kasei Engineering Corporation, and 1,000 fibers were randomly extracted from fibers with a fiber length of 10 μm or more. These were analyzed to determine the fiber length of the glass fibers. The average fiber length of the glass fibers was calculated as the average value of the fiber lengths of the glass fibers.

[0135] [Average Fiber Length and Average Fiber Diameter of Cellulosic Fiber (B)] A sample of approximately 4 mm x 4 mm cut from the test piece prepared by the above method was immersed in hexafluoroisopropanol to dissolve the thermoplastic resin in the sample and separate the cellulose fibers. The obtained cellulose fibers were observed under an optical microscope to obtain images. The observation magnification was set so that the number of fibers in one image was 100 or more. Using the obtained images, the major and minor diameters of 100 or more randomly selected fibrous particles were determined. The arithmetic average of the major diameters was calculated as the average fiber length, and the arithmetic average of the minor diameters was calculated as the average fiber diameter.

[0136] [Flexural Strength] Tests were conducted in accordance with the test method described in ISO 178 at room temperature (23°C) and 50% relative humidity using 4 mm thick test pieces at a bending speed of 2 mm / min. The average value of the flexural strength was calculated for five test pieces (n = 5). A flexural strength of 160 MPa or more was determined to be excellent.

[0137] [Charpy impact strength] Tests were conducted in accordance with the test method described in ISO 179 / 1eA at room temperature (23°C) and 50% relative humidity using notched test pieces with a thickness of 4 mm. The average value of the Charpy impact strength was calculated for 10 test pieces (n = 10). If the Charpy impact strength was 5.0 kJ / m ２ If the value was equal to or greater than this, it was determined that the impact resistance was excellent.

[0138] [Materials used in Examples and Comparative Examples] Thermoplastic resin (A): Polyamide 6 (A-1) (manufactured by UBE Co., Ltd., relative viscosity 2.64)

[0139] Cellulosic fiber (B) Cellulosic fiber (B-1) (Degree of modification by hydroxyl group substituents (degree of acetylation): 0.86. Produced in accordance with the method described in the examples of JP 2016-176052 A using cellulosic fibers having an average fiber length of 4 mm and an average fiber diameter of 35 μm.) Cellulosic fiber (B-2) (Degree of modification by hydroxyl group substituents (degree of acetylation): 0. Cellulosic fibers having an average fiber length of 4 mm and an average fiber diameter of 35 μm) Here, the degree of acetylation means the degree of modification by acetyl groups, which are substituents of hydroxyl groups, in cellulosic fiber (B).

[0140] Reinforced fiber-containing thermoplastic resin (AC-1) Reinforced fiber-containing thermoplastic resin (AC-1) (manufactured by Polyplastics Co., Ltd., Plastron (registered trademark) PA6-GF60-01 (L9), long fiber glass reinforced polyamide 6 resin pellets (glass fibers are aligned parallel to the length direction of the pellets), glass fiber content 60 mass%, glass fiber length 9 mm (catalog value), glass fiber diameter 16 μm, cylindrical pellets) Hereinafter, the glass fiber contained in (AC-1) is referred to as (C-1).

[0141] Glass fiber (C-2) (manufactured by Nippon Electric Glass Co., Ltd., ECS03T-249H, glass fiber diameter 10.5 μm, glass fiber length 3 mm (glass fiber diameter and glass fiber length are catalog values))

[0142] [Production of Cellulose-Based Fiber-Containing Thermoplastic Resin (AB-1)] Polyamide 6 (A-1) was preliminarily mixed with cellulose-based fiber (B-1), and the mixture was fed into a twin-screw melt kneader (manufactured by Coperion Co., Ltd., model ZSK, cylinder diameter 32 mm, L / D 48), melt-kneaded at a cylinder temperature of 230°C to 250°C, and the molten resin was extruded in the form of strands, which were then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of cellulose-based fiber-containing thermoplastic resin (AB-1) with a polyamide 6 (A-1) / cellulose-based fiber (B-1) ratio of 70 / 30% by mass (solid content ratio).

[0143] [Production of Cellulose-Based Fiber-Containing Thermoplastic Resin (AB-2)] Polyamide 6 (A-1) was pre-mixed with cellulose-based fiber (B-2), and the mixture was fed into a twin-screw melt kneader (manufactured by Coperion Co., Ltd., model ZSK, cylinder diameter 32 mm, L / D 48), melt-kneaded at a cylinder temperature of 230°C to 250°C, and the molten resin was extruded into a strand shape, which was then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of cellulose-based fiber-containing thermoplastic resin (AB-2) with a polyamide 6 (A-1) / cellulose-based fiber (B-2) ratio of 70 / 30% by mass (solid content ratio).

[0144] [Production of Reinforcing Fiber-Containing Thermoplastic Resin (AC-2)] Polyamide 6 (A-1) was pre-mixed with glass fiber (C-2), fed to a twin-screw melt kneader (manufactured by Coperion Co., Ltd., model ZSK, cylinder diameter 32 mm, L / D 48), melt-kneaded at a cylinder temperature of 260 ° C. to 280 ° C., and the molten resin was extruded in the form of a strand, which was then introduced into a water tank, cooled, cut, and vacuum-dried to obtain pellets of reinforcing fiber-containing thermoplastic resin (AC-2) with a polyamide 6 (A-1) / glass fiber (C-2) ratio of 70 / 30% by mass.

[0145] Example 1 Production of pellet mixture (A1) Three types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-1) / reinforcing fiber-containing thermoplastic resin (AC-1) / polyamide 6 (A-1) = 50.0 / 8.3 / 41.7 mass% so that the content of cellulose fiber (B-1) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-1) was 5.0 mass%, to obtain a pellet mixture (A1).

[0146] Example 2 Production of pellet mixture (A2) Three types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-1) / reinforcing fiber-containing thermoplastic resin (AC-1) / polyamide 6 (A-1) = 50.0 / 16.6 / 33.4 mass% so that the content of cellulose fiber (B-1) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-1) was 10.0 mass%, to obtain a pellet mixture (A2).

[0147] Example 3 Production of pellet mixture (A3) Three types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-1) / reinforcing fiber-containing thermoplastic resin (AC-1) / polyamide 6 (A-1) = 50.0 / 24.9 / 25.1 mass% so that the content of cellulose fiber (B-1) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-1) was 14.9 mass%, to obtain a pellet mixture (A3).

[0148] Example 4 Production of pellet mixture (A4) Three types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-2) / reinforcing fiber-containing thermoplastic resin (AC-1) / polyamide 6 (A-1) = 50.0 / 24.9 / 25.1 mass% so that the content of cellulose fiber (B-2) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-1) was 14.9 mass%, to obtain a pellet mixture (A4).

[0149] Comparative Example 1 Production of Pellet Mixture (CA1) Three types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-1) / reinforcing fiber-containing thermoplastic resin (AC-2) / polyamide 6 (A-1) = 50.0 / 16.7 / 33.3 mass% so that the content of cellulose fiber (B-1) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-2) was 5.0 mass%, to obtain a pellet mixture (CA1).

[0150] Comparative Example 2 Production of Pellet Mixture (CA2) Two types of pellets were mixed in a ratio of 50.0 / 50.0 mass% of cellulose-based fiber-containing thermoplastic resin (AB-1) / reinforcing fiber-containing thermoplastic resin (AC-2) so that the content of cellulose-based fiber (B-1) in the pellet mixture was 15.0 mass% and the content of glass fiber (C-2) was 15.0 mass%, to obtain a pellet mixture (CA2).

[0151] Comparative Example 3 Production of Pellet Mixture (CA3) Two types of pellets were mixed in a ratio of cellulose fiber-containing thermoplastic resin (AB-1) / polyamide 6 (A-1) = 50.0 / 50.0 mass% so that the content of cellulose fiber (B-1) in the pellet mixture was 15.0 mass%, to obtain a pellet mixture (CA3).

[0152] The formulations and evaluation results of the examples and comparative examples are shown in Table 1.

[0153]

[0154] As is clear from Table 1, the thermoplastic resin compositions of Examples 1 to 4 containing reinforcing fibers (C) having an average fiber length of 500 μm or more and 1200 μm or less exhibited remarkably excellent impact resistance while maintaining the bending strength when molded into articles. On the other hand, the thermoplastic resin compositions of Comparative Examples 1 and 2, which used reinforcing fibers having an average fiber length of less than 500 μm, had good bending strength but poor impact resistance. The thermoplastic resin composition of Comparative Example 3, which did not use reinforcing fibers (C) and contained only cellulosic fibers (B), exhibited poor bending strength and impact resistance.

[0155] The thermoplastic resin composition of the present invention can improve impact resistance while maintaining flexural strength when molded into a molded article, and can be suitably used for a variety of parts, particularly automobile parts.

Claims

1. A thermoplastic resin composition comprising a thermoplastic resin (A), a cellulosic fiber (B), and a reinforcing fiber (C), wherein the reinforcing fiber (C) is other than the cellulosic fiber (B), and the average fiber length of the reinforcing fiber (C) is 500 μm or more and 1200 μm or less.

2. The thermoplastic resin composition according to claim 1, wherein the reinforcing fiber (C) is at least one selected from the group consisting of glass fiber and carbon fiber.

3. The thermoplastic resin composition according to claim 1 or 2, wherein the cellulosic fiber (B) has an average fiber diameter of 4 nm to 1,000 μm and an average fiber length of 100 nm to 10,000 μm.

4. The thermoplastic resin composition according to claim 1 or 2, wherein the degree of modification of the hydroxyl groups of the cellulose-based fiber (B) with substituents is 0 to 2.

55.

5. The thermoplastic resin composition according to claim 1 or 2, wherein the cellulosic fiber (B) contains acetylated cellulose.

6. The thermoplastic resin composition according to claim 1 or 2, wherein, in 100% by mass of the thermoplastic resin composition, the content of the cellulose-based fiber (B) is 1 to 40% by mass, the content of the reinforcing fiber (C) is 1 to 40% by mass, and the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is 10 to 60% by mass.

7. The thermoplastic resin composition according to claim 1 or 2, wherein, in 100% by mass of the thermoplastic resin composition, the content of the cellulose-based fiber (B) is 3 to 25% by mass, the content of the reinforcing fiber (C) is 4 to 16% by mass, and the total content of the cellulose-based fiber (B) and the reinforcing fiber (C) is 7 to 41% by mass.

8. The thermoplastic resin composition according to claim 6, wherein the mass ratio (B) / (C) of the cellulosic fiber (B) to the reinforcing fiber (C) is 0.3 to 15.

9. The thermoplastic resin composition according to claim 1 or 2, wherein the thermoplastic resin (A) comprises a polyamide resin (a).

10. The thermoplastic resin composition according to claim 9, wherein the polyamide resin (a) is an aliphatic polyamide resin.

11. The polyamide resin (a) is selected from the group consisting of polybutyrolactam (polyamide 4), polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polytetramethylene sebacamide (polyamide 410), polypentamethylene adipamide (polyamide 56), polypentamethylene sebacamide (polyamide 510), polypentamethylene dodecamide (polyamide 512), polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelamide (polyamide 69), polyhexamethylene sebacamide (polyamide 610), ), polyhexamethylene dodecamide (polyamide 612), polynonamethylene dodecamide (polyamide 912), polydecamethylene sebacamide (polyamide 1010), polydecamethylene dodecamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyundecane amide (polyamide 11), and polydodecanamide (polyamide 12), and / or a copolymer using several of the raw material monomers forming these homopolymers.

12. A molded article comprising the thermoplastic resin composition according to claim 1 or 2.

13. The molded article according to claim 12, which is an automobile part or a sliding member.

14. A pellet mixture comprising: first pellets comprising a first thermoplastic resin (a1) and a cellulosic fiber (B); and second pellets comprising a second thermoplastic resin (a2) and a reinforcing fiber (C); wherein the reinforcing fiber (C) is other than the cellulosic fiber (B), and the average fiber length of the reinforcing fiber (C) is 5 mm or more and 20 mm or less.

15. The pellet mixture according to claim 14, wherein the second pellets are cylindrical, elliptical cylindrical, or rectangular prism-shaped, and the reinforcing fibers (C) are arranged substantially parallel to the length of the pellets.

16. The pellet mixture according to claim 14, wherein 100% by mass of the first pellets contain 50 to 99% by mass of a first thermoplastic resin (a1) and 1 to 50% by mass of cellulosic fiber (B); 100% by mass of the second pellets contain 1 to 80% by mass of a second thermoplastic resin (a2) and 20 to 99% by mass of reinforcing fiber (C); and 100% by mass of a molded product obtained by heat-molding the pellet mixture contains 40 to 90% by mass of the first thermoplastic resin (a1) and the second thermoplastic resin (a2) in total, 1 to 40% by mass of cellulosic fiber (B), and 1 to 40% by mass of reinforcing fiber (C), and 10 to 60% by mass of the cellulosic fiber (B) and the reinforcing fiber (C).

17. The pellet mixture according to claim 14 or 15, further comprising third pellets containing a third thermoplastic resin (a3), wherein 100% by mass of the first pellets contain 50 to 99% by mass of the first thermoplastic resin (a1) and 1 to 50% by mass of the cellulosic fiber (B); 100% by mass of the second pellets contain 1 to 80% by mass of the second thermoplastic resin (a2) and 20 to 99% by mass of the reinforcing fiber (C); and after heat-molding the pellet mixture, 100% by mass of a molded product contains 40 to 90% by mass of the first thermoplastic resin (a1), the second thermoplastic resin (a2), and the third thermoplastic resin (a3) ​​in total, 1 to 40% by mass of the cellulosic fiber (B), and 1 to 40% by mass of the reinforcing fiber (C), and the pellet mixture contains 10 to 60% by mass of the cellulosic fiber (B) and the reinforcing fiber (C).

18. A method for producing a molded article according to claim 12, comprising hot molding the pellet mixture according to claim 14 or 16.

19. The method for producing a molded article according to claim 18, wherein the thermoforming is carried out by injection molding.

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