Thermoplastic polyester elastomer resin composition and method for producing same

Abstract

The present invention provides a thermoplastic polyester elastomer resin composition which is lightweight and has excellent surface characteristics, fatigue characteristics and wear characteristics. This thermoplastic polyester elastomer resin composition contains from 0.1 part by mass to 30 parts by mass of (B) cellulose fibers relative to 100 parts by mass of (A) a thermoplastic polyester elastomer wherein a hard segment, which is composed of a polyester that comprises an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituents, and at least one soft segment, which is selected from among an aliphatic polyether, an aliphatic polyester and an aliphatic polycarbonate, are bonded with each other; and the cellulose fibers (B) in this resin composition have an average fiber length of from 100 μm to 2,000 μm, while having an average fiber diameter of from 0.5 μm to 50 μm.

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic polyester elastomer resin composition that has excellent mechanical properties, fatigue properties, wear properties and surface properties while maintaining the performance of an elastomer. [Background technology]

[0002] Thermoplastic polyester elastomers are excellent in injection molding and extrusion molding, and as a material with high mechanical strength, rubber-like properties such as elastic recovery, impact resistance, and flexibility, as well as excellent cold resistance, are used in applications such as automotive parts, electrical and electronic parts, fibers, films, and sports parts.

[0003] However, thermoplastic polyester elastomers alone can sometimes be insufficient in terms of surface properties, fatigue properties, etc., and so composites of elastomers and various inorganic materials are used. On the other hand, resin compositions in which thermoplastic elastomers are reinforced with inorganic fillers such as glass fiber, carbon fiber, talc, and clay have problems such as a high specific gravity and defects in the fillers themselves, which reduce the performance of the elastomer.

[0004] In recent years, cellulose has been attracting attention as a new reinforcing material for resins. It is known that cellulose has high elastic modulus and low coefficient of linear expansion as its single substance properties, and due to these excellent properties, even a small amount of cellulose can be added to enhance the functionality of resins. In addition, cellulose has a true density of 1.6 g / cm 3 and glass fiber (density 2.3 to 2.6 g / cm 3 ) and talc (density 2.7g / cm 3 ) and is a material suitable for weight reduction.

[0005] For example, Patent Document 1 proposes modified nanocellulose obtained by substituting specific substituents for the hydroxyl groups in nanocellulose, and also proposes a resin composition containing this nanocellulose and a resin. While the above document makes it possible to obtain a resin composition exhibiting high tensile strength and elastic modulus, it does not mention surface properties or fatigue properties.

[0006] Furthermore, Patent Document 2 describes that when cellulose raw materials are kneaded in the presence of a resin solution while heating and removing the solvent, a high content of cellulose nanofibers can be uniformly dispersed in the resin; however, like Patent Document 1, this document only mentions mechanical properties.

[0007] Patent Document 3 describes a resin composition that has excellent moldability and mechanical properties by combining cellulose fibers with different fiber diameter to fiber length ratios, but does not mention the effect that the cellulose characteristics themselves in the resin composition have on the properties of the resin composition.

[0008] Furthermore, although Patent Documents 1 to 3 all refer to improving the dispersibility of cellulose and improving the physical properties of general thermoplastic resins, they do not refer to the effects on the suitable cellulose characteristics in elastomer resin compositions or the surface properties and fatigue properties. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6120590 [Patent Document 2] Patent No. 6684371 [Patent Document 3] Patent No. 6419276 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the current state of the prior art, and an object of the present invention is to provide a thermoplastic polyester elastomer resin composition that is lightweight and has excellent surface properties, fatigue properties, and wear properties, and a molded article made of the same. [Means for solving the problem]

[0011] In order to achieve the above object, the present inventors have conducted extensive research into the blending of thermoplastic polyester elastomer and cellulose fiber, and have found that by incorporating a specific amount of cellulose fiber into a thermoplastic polyester elastomer and controlling the average fiber length and average fiber diameter of the cellulose fiber in the resin composition within specific ranges, it is possible to obtain excellent surface properties, fatigue properties, and wear properties while maintaining the properties of the elastomer.

[0012] That is, the present invention comprises the following [1] to [5]. [1] A thermoplastic polyester elastomer resin composition containing 100 parts by mass of a thermoplastic polyester elastomer (A) in which a hard segment made of a polyester having an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components is bonded to at least one soft segment selected from aliphatic polyethers, aliphatic polyesters, and aliphatic polycarbonates, and 0.1 to 30 parts by mass of cellulose fibers (B), wherein the cellulose fibers (B) in the resin composition have an average fiber length of 100 to 2000 μm and an average fiber diameter of 0.5 to 50 μm. [2] The thermoplastic polyester elastomer resin composition according to [1], wherein the content of the cellulose fibers (B) is 1 to 10 parts by mass, and the cellulose fibers in the resin composition have an average fiber length of 100 to 800 μm and an average fiber diameter of 1 to 30 μm. [3] The thermoplastic polyester elastomer resin composition according to [1] or [2], wherein the cellulose fibers (B) are modified cellulose fibers. [4] The thermoplastic polyester elastomer resin composition according to any one of [1] to [3], further comprising a dispersant (C). [5] The thermoplastic polyester elastomer resin composition according to any one of [1] to [4], wherein the resin composition has a tensile elongation of 300% or more as measured in accordance with JIS K6251. [6] A method for producing a thermoplastic polyester elastomer resin composition according to any one of [1] to [5], characterized in that cellulose fibers (B) are dispersed in the thermoplastic polyester elastomer (A) using a twin-screw kneader. [7] A molded article made of the thermoplastic polyester elastomer resin composition according to any one of [1] to [5]. [Effects of the Invention]

[0013] The thermoplastic polyester elastomer resin composition of the present invention and a molded article made thereof are lightweight and exhibit excellent surface properties, fatigue properties, and wear properties. Furthermore, by uniformly dispersing cellulose fibers, even a small amount of the composition can exhibit excellent performance and be molded easily. [Brief explanation of the drawings]

[0014] [Figure 1] 1A is an optical microscope photograph of the press sheet in Example 2, and B is an optical microscope photograph of the press sheet in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Thermoplastic polyester elastomer (A)] The thermoplastic polyester elastomer (A) used in the present invention is composed of hard segments and soft segments bonded together. The hard segments are made of polyester. While common aromatic dicarboxylic acids are widely used as the aromatic dicarboxylic acid constituting the polyester hard segments, it is desirable that the primary aromatic dicarboxylic acid be terephthalic acid or naphthalenedicarboxylic acid (2,6-naphthalenedicarboxylic acid is preferred among isomers). The content of these aromatic dicarboxylic acids is preferably 70 mol% or more, more preferably 80 mol% or more, of the total dicarboxylic acids constituting the polyester hard segments. Other dicarboxylic acid components include aromatic dicarboxylic acids such as diphenyldicarboxylic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and tetrahydrophthalic anhydride; and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, and hydrogenated dimer acid. These can be used in an amount that does not significantly lower the melting point of the resin, and the amount is 30 mol % or less, preferably 20 mol % or less, of the total acid components.

[0016] In the thermoplastic polyester elastomer (A) used in the present invention, the aliphatic or alicyclic diol constituting the polyester of the hard segment is generally a common aliphatic or alicyclic diol, and is not particularly limited, but is preferably an alkylene glycol having 2 to 8 carbon atoms. Specific examples include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. Of these, either ethylene glycol or 1,4-butanediol is preferred.

[0017] As the component constituting the polyester of the hard segment, those comprising butylene terephthalate units (units consisting of terephthalic acid and 1,4-butanediol) or butylene naphthalate units (units consisting of 2,6-naphthalenedicarboxylic acid and 1,4-butanediol) are preferred in terms of physical properties, moldability, and cost performance.

[0018] In addition, when an aromatic polyester suitable as the polyester constituting the hard segment in the thermoplastic polyester elastomer (A) used in the present invention is produced in advance and then copolymerized with the soft segment component, the aromatic polyester can be easily obtained according to a conventional polyester production method. In addition, such a polyester preferably has a number average molecular weight of 10,000 to 40,000.

[0019] The soft segment of the thermoplastic polyester elastomer (A) used in the present invention is at least one selected from aliphatic polyethers, aliphatic polyesters, and aliphatic polycarbonates.

[0020] Examples of aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, poly(trimethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide adducts of poly(propylene oxide) glycol, copolymers of ethylene oxide and tetrahydrofuran, etc. Among these, poly(tetramethylene oxide) glycol and ethylene oxide adducts of poly(propylene oxide) glycol are preferred from the viewpoint of elastic properties.

[0021] Examples of aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprylolactone, polybutylene adipate, etc. Among these, poly(ε-caprolactone) and polybutylene adipate are preferred from the viewpoint of elasticity.

[0022] The aliphatic polycarbonate is preferably composed primarily of aliphatic diol residues having 2 to 12 carbon atoms. Examples of these aliphatic diols include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,9-nonanediol, and 2-methyl-1,8-octanediol. In particular, aliphatic diols having 5 to 12 carbon atoms are preferred in terms of the flexibility and low-temperature properties of the resulting thermoplastic polyester elastomer. These components may be used alone or in combination of two or more types as necessary, based on the examples described below.

[0023] The aliphatic polycarbonate diol having good low-temperature properties and constituting the soft segment of the thermoplastic polyester elastomer (A) used in the present invention preferably has a low melting point (for example, 70°C or less) and a low glass transition temperature. In general, the aliphatic polycarbonate diol made from 1,6-hexanediol used to form the soft segment of the thermoplastic polyester elastomer has a low glass transition temperature of about -60°C and a melting point of about 50°C, resulting in good low-temperature properties. In addition, an aliphatic polycarbonate diol obtained by copolymerizing an appropriate amount of, for example, 3-methyl-1,5-pentanediol with the above aliphatic polycarbonate diol has a slightly higher glass transition temperature than the original aliphatic polycarbonate diol, but has a lower melting point or is amorphous, and therefore corresponds to an aliphatic polycarbonate diol with good low-temperature properties. Furthermore, for example, an aliphatic polycarbonate diol made of 1,9-nonanediol and 2-methyl-1,8-octanediol has a melting point of about 30°C and a glass transition temperature of about -70°C, which are sufficiently low, and therefore corresponds to an aliphatic polycarbonate diol with good low-temperature properties.

[0024] The soft segment of the thermoplastic polyester elastomer (A) used in the present invention is preferably an aliphatic polyether.

[0025] The thermoplastic polyester elastomer (A) used in the present invention is preferably a copolymer primarily composed of terephthalic acid, 1,4-butanediol, and poly(tetramethylene oxide) glycol. Among the dicarboxylic acid components constituting the thermoplastic polyester elastomer (A), terephthalic acid preferably accounts for 40 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. Among the glycol components constituting the thermoplastic polyester elastomer (A), the sum of 1,4-butanediol and poly(tetramethylene oxide) glycol is preferably 40 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

[0026] The number average molecular weight of the poly(tetramethylene oxide) glycol is preferably 500 to 4000. If the number average molecular weight is less than 500, it may be difficult to exhibit elastomeric properties. On the other hand, if the number average molecular weight exceeds 4000, compatibility with the hard segment component may decrease, making it difficult to copolymerize in a block form. The number average molecular weight of the poly(tetramethylene oxide) glycol is more preferably 800 to 3000, and even more preferably 1000 to 2500.

[0027] The thermoplastic polyester elastomer (A) used in the present invention can be produced by any of the following known methods: transesterification of a lower alcohol diester of a dicarboxylic acid, an excess amount of a low-molecular-weight glycol, and a soft segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product; esterification of a dicarboxylic acid, an excess amount of a glycol, and a soft segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product; pre-preparing a hard segment polyester, adding a soft segment component to the polyester, and randomizing the resulting polyester through transesterification; linking the hard and soft segments with a chain linking agent; and, when poly(ε-caprolactone) is used for the soft segment, subjecting the hard segment to an addition reaction with an ε-caprolactone monomer.

[0028] [Cellulose fiber (B)] The cellulose fibers (B) used in the present invention are obtained by mechanically or chemically defibrating raw material fibers. The raw material fibers are not particularly limited, and one or more fibers selected from plant-derived fibers, animal-derived fibers, and microbial-derived fibers can be used.

[0029] The cellulose fibers (B) may be unmodified or at least a part of the functional groups or reactive groups may be modified. Examples of the modification treatment include esterification and etherification.

[0030] In the esterification, an acyl group such as an acetyl group is introduced as a substituent by an esterifying agent. Examples of the esterifying agent include carboxylic acids, carboxylic acid anhydrides, and carboxylic acid halides, with acetic acid, propionic acid, butyric acid, acrylic acid, methacrylic acid, and derivatives thereof being preferred.

[0031] Examples of etherification include alkyl etherification and silyl etherification. Preferred alkyl etherification agents include alkyl halides such as methyl chloride and ethyl chloride, dialkyl carbonates such as dimethyl carbonate and diethyl carbonate, and alkylene oxides such as ethylene oxide and propylene oxide. Preferred silyl etherification agents include alkoxysilanes such as n-butoxytrimethylsilane, tert-butoxytrimethylsilane, sec-butoxytrimethylsilane, isobutoxytrimethylsilane, ethoxytriethylsilane, octyldimethylethoxysilane, and cyclohexyloxytrimethylsilane, alkoxysiloxanes such as butoxypolydimethylsiloxane, disilazanes such as hexamethyldisilazane, tetramethyldisilazane, and diphenyltetramethyldisilazane, silyl halides such as trimethylsilyl chloride and diphenylbutyl chloride, and silyl trifluoromethanesulfonates such as tert-butyldimethylsilyl trifluoromethanesulfonate.

[0032] The cellulose fibers (B) may also contain a dispersant (C). The dispersant (C) may have, for example, a functional group capable of bonding with the hydroxyl groups of the cellulose fibers, or may have a cationic group such as an ammonium, phosphonium, or sulfonium group, or an anionic group such as a carboxyl group, a phosphate group, or a sulfonic acid group.

[0033] The proportion of the dispersant (C) is, for example, 1 part by mass or less, preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and particularly preferably 0.01 to 0.1 parts by mass per 100 parts by mass of the cellulose fibers (B).

[0034] As a method for producing cellulose fiber (B), for example, a method using mechanical shearing may be used, in which pulp or the like is treated with hot water at 100°C or higher to hydrolyze and weaken the hemicellulose portion, and then the pulverized material is defibrated using a pulverizer such as a high-pressure homogenizer, a microfluidizer, a ball mill, or a disc mill.

[0035] Examples of chemical treatment methods include the N-methylmorpholine-N-oxide (NMMO) method, the cuprammonium solution method, and the ionic liquid method.

[0036] The present invention exhibits excellent surface properties and fatigue properties by forming a network of cellulose fibers (B) in a thermoplastic polyester elastomer (A). In the present invention, the amount of cellulose fibers (B) per 100 parts by mass of the thermoplastic polyester elastomer (A) is 0.1 to 30 parts by mass, preferably 0.5 to 25 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 1 to 10 parts by mass. If the amount of cellulose fibers (B) is less than 0.1 part by mass, a cellulose network is not formed, and the effects of improving surface properties, fatigue properties, and wear properties are not achieved. If the amount of cellulose fibers (B) is more than 30 parts by mass, the desired dispersion morphology is not achieved, and there is a concern that the physical properties may deteriorate due to aggregation of the cellulose fibers.

[0037] [Other ingredients] The resin composition of the present invention preferably contains an antioxidant such as an aromatic amine, hindered phenol, sulfur, or phosphorus-based antioxidant, or a light stabilizer such as a hindered amine, benzotriazole, benzophenone, benzoate, triazole, nickel, or salicylic acid-based stabilizer. Two or more of these may be used in combination.

[0038] The blending (content) amount of each of the antioxidants and / or light stabilizers is preferably 0.01 to 3 parts by mass, more preferably 0.05 to 2 parts by mass, and even more preferably 0.1 to 1 part by mass, per 100 parts by mass of the thermoplastic polyester elastomer (A). When two or more types of antioxidants and / or light stabilizers are blended, the upper limit of the total content is preferably 5 parts by mass.

[0039] A crosslinking agent may be blended into the thermoplastic polyester elastomer (A) as needed, provided that the effects of the present invention are not impaired. Such crosslinking agents are not particularly limited as long as they react with the hydroxyl groups and carboxyl groups of the thermoplastic polyester elastomer (A). Examples of such crosslinking agents include epoxy-based crosslinking agents, carbodiimide-based crosslinking agents, isocyanate-based crosslinking agents, acid anhydride-based crosslinking agents, silanol-based crosslinking agents, melamine resin-based crosslinking agents, metal salt-based crosslinking agents, metal chelate-based crosslinking agents, and amino resin-based crosslinking agents. The crosslinking agents may be used alone or in combination of two or more.

[0040] Epoxy crosslinking agents are not particularly limited as long as they are multifunctional epoxy compounds containing two or more epoxy groups (glycidyl groups) per molecule. Specific examples include 1,6-dihydroxynaphthalene diglycidyl ether and 1,3-bis(oxiranylmethoxy)benzene, which contain two epoxy groups; 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and diglycerol triglycidyl ether, which contain three epoxy groups; and 1-chloro-2,3-epoxypropane-formaldehyde-2,7-naphthalenediol polycondensates and pentaerythritol polyglycidyl ether, which contain four epoxy groups. Among these, multifunctional epoxy compounds with heat resistance in the skeleton are preferred. Difunctional or tetrafunctional epoxy compounds with a naphthalene structure as the skeleton, or trifunctional epoxy compounds with a triazine structure as the skeleton, are particularly preferred. Considering the degree of increase in the solution viscosity of the thermoplastic polyester elastomer (A), the effect of efficiently reducing the acid value of the thermoplastic polyester elastomer (A), and the degree of gelation due to aggregation and solidification of the epoxy itself, difunctional or trifunctional epoxy compounds are preferred.

[0041] Specific examples of commercially available epoxy crosslinkers include sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, diglycerol polyglycidyl ethers, and polyethylene glycol diglycidyl ethers. Examples include the epoxy compound "Denacol" (EX-611, EX-614, EX-614B, EX-512, EX-521, EX-421, EX-313, EX-810, EX-830, EX-850, etc.) manufactured by Nagase Chemtec Corporation, diepoxy and polyepoxy compounds (SR-EG, SR-8EG, SR-GLG, etc.) manufactured by Sakamoto Pharmaceutical Co., Ltd., and the epoxy crosslinker "EPICLON" EM-85-75W or CR-5L manufactured by Dainippon Ink Mfg. Co., Ltd.

[0042] Other examples include styrene copolymers containing two or more glycidyl groups per molecule, having a weight-average molecular weight of 4,000 to 25,000, and consisting of 20 to 99% by mass of a vinyl aromatic monomer (X), 1 to 80% by mass of glycidyl (meth)acrylate (Y), and 0 to 79% by mass of a vinyl group-containing monomer other than (X) that does not contain an epoxy group. More preferred are copolymers consisting of 20 to 99% by mass of (X), 1 to 80% by mass of (Y), and 0 to 40% by mass of (Z), and even more preferred are copolymers consisting of 25 to 90% by mass of (X), 10 to 75% by mass of (Y), and 0 to 35% by mass of (Z). Examples of the vinyl aromatic monomer (X) include styrene and α-methylstyrene. Examples of the (Y) glycidyl alkyl (meth)acrylate include glycidyl (meth)acrylate, (meth)acrylic acid esters having a cyclohexene oxide structure, and (meth)acrylic glycidyl ethers. Among these, glycidyl (meth)acrylate is preferred because of its high reactivity. Examples of the (Z) other vinyl group-containing monomers include alkyl (meth)acrylate esters having an alkyl group having 1 to 22 carbon atoms (the alkyl group may be linear or branched), such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, stearyl (meth)acrylate, and methoxyethyl (meth)acrylate; polyalkylene glycol (meth)acrylate esters, alkoxyalkyl (meth)acrylate esters, hydroxyalkyl (meth)acrylate esters, dialkylaminoalkyl (meth)acrylate esters, benzyl (meth)acrylate esters, phenoxyalkyl (meth)acrylate esters, isobornyl (meth)acrylate esters, and alkoxysilylalkyl (meth)acrylate esters. In addition, (meth)acrylamide, (meth)acryldialkylamide, vinyl esters such as vinyl acetate, aromatic vinyl monomers such as vinyl ethers and (meth)allyl ethers, and α-olefin monomers such as ethylene and propylene can also be used as the (Z) other vinyl group-containing monomer. The weight average molecular weight of the copolymer is preferably 4000 to 25000. The weight average molecular weight is more preferably 5000 to 15000. The epoxy value of the copolymer is 400 to 2500 equivalents / 1×10 6 g, and more preferably 500 to 1500 equivalents / 1×10 6 g, and more preferably 600 to 1000 equivalents / 1×10 6 g. As an epoxy-based crosslinking agent that satisfies these conditions, a styrene / glycidyl acrylate copolymer (trade name: ARUFON UG series) manufactured by Toagosei Co., Ltd. can be used.

[0043] The carbodiimide crosslinking agent is not particularly limited as long as it is a polycarbodiimide having two or more carbodiimide groups (-N=C=N- structure) in one molecule, and examples thereof include aliphatic polycarbodiimides, alicyclic polycarbodiimides, aromatic polycarbodiimides, and copolymers thereof. Preferred are aliphatic polycarbodiimide compounds or alicyclic polycarbodiimide compounds.

[0044] Polycarbodiimide compounds can be obtained, for example, by the decarbonation reaction of diisocyanate compounds. Examples of diisocyanate compounds that can be used here include 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, and 1,3,5-triisopropylphenylene-2,4-diisocyanate. These compounds may be used alone or in the form of copolymers of two or more. In addition, a branched structure may be introduced, or a functional group other than a carbodiimide group or an isocyanate group may be introduced by copolymerization. Furthermore, although the terminal isocyanate may be used as it is, the degree of polymerization may be controlled by reacting the terminal isocyanate, or a portion of the terminal isocyanate may be blocked.

[0045] As the polycarbodiimide compound, alicyclic polycarbodiimides derived from dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, etc. are particularly preferred, and polycarbodiimides derived from dicyclohexylmethane diisocyanate or isophorone diisocyanate are particularly preferred.

[0046] From the viewpoints of stability and ease of handling, the polycarbodiimide compound preferably contains 2 to 50 carbodiimide groups per molecule. More preferably, the polycarbodiimide compound contains 5 to 30 carbodiimide groups per molecule. The number of carbodiimide groups in a polycarbodiimide molecule (i.e., the number of carbodiimide groups) corresponds to the degree of polymerization in the case of a polycarbodiimide obtained from a diisocyanate compound. For example, a polycarbodiimide obtained by linking 21 diisocyanate compounds in a chain has a degree of polymerization of 20, and the number of carbodiimide groups in the molecular chain is 20. Polycarbodiimide compounds are usually mixtures of molecules of various lengths, and the number of carbodiimide groups is expressed as an average value. A polycarbodiimide compound having the number of carbodiimide groups within the above range and being solid at around room temperature can be powdered, resulting in excellent workability and compatibility when mixed with the thermoplastic polyester elastomer (A), and is also preferred in terms of uniform reactivity and bleed-out resistance. The number of carbodiimide groups can be measured, for example, by a conventional method (a method of dissolving in an amine and performing back titration with hydrochloric acid).

[0047] The polycarbodiimide compound preferably has an isocyanate group at its terminal, and the isocyanate group content is preferably 0.5 to 4 mass% from the viewpoint of stability and ease of handling. The isocyanate group content is more preferably 1 to 3 mass%. In particular, polycarbodiimides derived from dicyclohexylmethane diisocyanate or isophorone diisocyanate and having an isocyanate group content within the above range are preferred. The isocyanate group content can be measured using a standard method (a method of dissolving in an amine and performing back titration with hydrochloric acid).

[0048] Examples of the isocyanate-based crosslinking agent include the above-mentioned polycarbodiimide compounds containing an isocyanate group and the above-mentioned isocyanate compounds that are raw materials for the polycarbodiimide compounds.

[0049] As the acid anhydride crosslinking agent, a compound containing 2 to 4 anhydrides per molecule is preferred in terms of stability and ease of handling. Examples of such compounds include phthalic anhydride, trimellitic anhydride, and pyromellitic anhydride.

[0050] The amount (content) of the crosslinking agent used is adjusted as appropriate depending on the extrusion conditions, etc., but is, for example, preferably 0.1 to 4.5 parts by mass, more preferably 0.1 to 4 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer (A).

[0051] In addition to the antioxidants, light stabilizers, and crosslinking agents, various additives can be blended into the thermoplastic polyester elastomer (A) used in the present invention depending on the purpose. The types of additives are not particularly limited, and various additives can be used. Specific examples of additives include lubricants, fillers, flame retardants, flame retardant auxiliaries, release agents, antistatic agents, molecular regulators such as peroxides, metal deactivators, organic and inorganic nucleating agents, neutralizing agents, antacids, antibacterial agents, fluorescent brighteners, organic and inorganic pigments, and organic and inorganic phosphorus compounds used to impart flame retardancy or thermal stability. When additives are added, their content (total content when multiple additives are used) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less of the resin composition.

[0052] The composition and composition ratio of the polyester elastomer resin composition used in the present invention can be determined by dissolving a sample in a solvent such as deuterated chloroform and measuring the composition. 1 It can also be calculated from the proton integral ratio in H-NMR.

[0053] The polyester elastomer resin composition of the present invention is characterized by having a tensile elongation of 300% or more, as described in the Examples section below. The tensile elongation is the elongation at break measured in accordance with JIS K6251, as described in the Examples section.

[0054] [Thermoplastic polyester elastomer resin composition] The thermoplastic polyester elastomer resin composition of the present invention can be produced by melt-kneading the components using a conventionally known method. The thermoplastic polyester elastomer (A) and cellulose fibers (B) can be kneaded together without any particular limitation, as long as the thermoplastic polyester elastomer (A) is in a molten state. For example, a mixing roller, a kneader, an extruder, or the like can be used. In the present invention, from the viewpoint of dispersibility of the cellulose fibers (B), a kneader or an extruder capable of applying a particularly high shear force is preferred, and a twin-screw extruder is more preferred.

[0055] The average fiber length of the cellulose fibers (B) in the resin composition is 100 to 2000 μm, preferably 100 to 800 μm, more preferably 200 to 600 μm, and even more preferably 400 to 600 μm. If it is less than 100 μm, sufficient surface properties, fatigue properties, and wear properties cannot be exhibited, and if it exceeds 2000 μm, the fibers tend to become entangled with each other, making it easy for large aggregates to form. The average fiber length is a number-average fiber length measured by the method described in the Examples section below.

[0056] The average fiber diameter of the cellulose fibers in the resin composition is 0.5 to 50 μm, preferably 1 to 30 μm, more preferably 1 to 20 μm, even more preferably 5 to 15 μm, and particularly preferably 6 to 10 μm. If the average fiber diameter is less than 0.5 μm, the fibers tend to become entangled and aggregates tend to form. On the other hand, if it exceeds 50 μm, elongation tends to decrease and defects tend to form in the resin composition. The average fiber diameter is a number-average fiber diameter measured by the method described in the Examples section below.

[0057] By adjusting the average fiber diameter and average fiber length of the cellulose fibers in the thermoplastic polyester elastomer resin composition of the present invention to fall within specific ranges, it is possible to suppress cellulose aggregation and improve surface properties, fatigue properties, and wear properties while maintaining the performance of the elastomer.

[0058] The thermoplastic polyester elastomer resin composition of the present invention can be molded into a molded article by a known molding method. The molding method is not limited to a specific one, and various molding methods such as injection molding, blow molding, extrusion molding, foam molding, profile molding, calendar molding, and the like can be suitably used. Among these, injection molding is preferred. [Example]

[0059] Examples are given below to demonstrate the effects of the present invention, but the present invention is not limited to these examples in any way.

[0060] In the following examples and comparative examples, the following raw materials were used. [Thermoplastic polyester elastomer (A)] (Polyester elastomer A-1) According to the method described in JP-A-9-59491, a thermoplastic polyester elastomer having a soft segment content of 44% by mass was produced using dimethyl terephthalate, 1,4-butanediol, and poly(tetramethylene oxide) glycol having a number average molecular weight of 1,000 as raw materials, and this was designated as polyester elastomer A-1.

[0061] [Cellulose fiber (B)] (Cellulose fiber B-1) The pulp was heated in hot water at 120°C or higher for 3 hours using an autoclave, and the hemicellulose portion was removed. The purified pulp was then squeezed and beaten in heavy water to a solids content of 1.5% by mass to highly shorten and fibrillate the pulp. The pulp was then defibrated in a high-pressure homogenizer at the same concentration to obtain defibrated cellulose with an average fiber diameter of 10 μm and an average fiber length of 1000 μm. (Cellulose fiber B-2) As with the above cellulose fiber B-1, a high-pressure homogenizer was used, and by changing the beating blade and beating time, defibrated cellulose with an average fiber diameter of 10 μm and an average fiber length of 2,800 μm was obtained. (Cellulose fiber B-3) As with the above cellulose fiber B-1, a high-pressure homogenizer was used, and by changing the beating blade and beating time, defibrated cellulose with an average fiber diameter of 200 nm and an average fiber length of 250 μm was obtained. (Cellulose fiber B-4) As with the cellulose fiber B-1, a high-pressure homogenizer was used, and by changing the beating blade and beating time, defibrated cellulose with an average fiber diameter of 100 μm and an average fiber length of 1500 μm was obtained.

[0062] [Average fiber diameter / average fiber length of cellulose fibers used as raw material] The cellulose component was suspended in pure water at a concentration of 1% by mass, and dispersed using a high-shear homogenizer. The resulting aqueous dispersion was diluted with pure water to 0.1-0.5% by mass, cast, air-dried, and photographed using a scanning electron microscope. The cellulose fibers were imaged, and the diameter and length of 50 fibers were measured using analysis software, and the average values were calculated. The fiber diameter was measured at the thickest point of a single fiber. The fiber length of non-straight fibers was measured at multiple points along the length.

[0063] Examples 1 to 6, Comparative Examples 1 to 7 Cellulose fibers were mixed with 100 parts by mass of thermoplastic polyester elastomer according to the formulation shown in Table 1 using a twin-screw extruder, and then pelletized. The length and diameter of the cellulose fibers were adjusted by adjusting the discharge rate and rotation speed during extrusion. Comparative Example 4 was produced by repeating the mixing process in the twin-screw extruder three times. The pellets of this polyester elastomer resin composition were used to perform the following evaluations. The results are shown in Table 1.

[0064] [Average fiber diameter / average fiber length of cellulose fibers in resin composition] A sheet measuring 100 mm wide, 100 mm long, and 50 μm thick was prepared from the pellets using a heat press. Images of the cellulose fibers in the resin composition were photographed using an optical microscope and processed. The diameters and lengths of 50 fibers were measured using analysis software, and the average values were calculated. The fiber diameter was measured at the thickest point of a single fiber. The fiber lengths of non-straight fibers were measured at multiple points along the length.

[0065] [Dispersibility] Sheets measuring 100 mm wide, 100 mm long, and 50 μm thick were prepared from the pellets using a heat press, and the agglomerates on the surface of the sheets were observed. Evaluation was made as follows: no agglomerates or agglomerates with a diameter of less than 100 μm: ◯; agglomerates with a diameter of 100 μm to 300 μm: △; agglomerates with a diameter of more than 300 μm: ×. When multiple agglomerates were present, the largest agglomerate was used for evaluation.

[0066] [Tensile elongation] Measurements were carried out using the method described in JIS K 6251. Test pieces were prepared by punching out a JIS No. 3 dumbbell-shaped specimen parallel to the resin flow direction from an injection-molded product measuring 100 mm in width, 100 mm in length, and 2.0 mm in thickness.

[0067] [Thrust wear resistance] An injection-molded product measuring 50 mm wide, 50 mm long, and 2 mm thick was brought into contact with the end face of a hollow cylindrical mating material made of S-45C, measuring 20 mm in outer diameter, 14.2 mm in inner diameter, and 20 mm in length. A constant load was applied to achieve a surface pressure of 1.0 MPa, and the injection-molded product was rotated at 15 cm / s for 30 minutes, after which the amount of wear was measured.

[0068] [Cyclic fatigue properties] A rectangular test piece, 80 mm long and 10 mm wide, was punched out parallel to the direction of resin flow from an injection molded product with a width of 100 mm, length of 100 mm and thickness of 2.0 mm. Using a Shimadzu Servo Pulser fatigue and durability testing machine, a load was repeatedly applied in tension mode with a frequency of 30 Hz and a grip distance of 30 mm, and the end point was when the amplitude reached ±8 mm. The number of repeated fatigue cycles was 10 7 The load at which this value was reached was measured.

[0069] [Table 1]

[0070] As is clear from Table 1, all of Examples 1 to 6 within the scope of the present invention exhibit excellent surface properties and fatigue properties while maintaining the tensile elongation performance of an elastomer, and also exhibit excellent dispersibility of cellulose fibers in the resin, compared to Comparative Example 1, which does not contain cellulose fibers. In contrast, Comparative Example 2, which contains a low proportion of cellulose fibers in the resin, and Comparative Example 4, which contains short fibers, exhibit excellent dispersibility of cellulose, but are less effective in terms of wear and fatigue properties. Comparative Example 3, which contains a high proportion of cellulose fibers, Comparative Example 5, which contains long fibers, and Comparative Example 6, which contains a small fiber diameter, exhibit excellent wear and fatigue properties, but the cellulose fibers aggregate together, resulting in poor dispersibility. Furthermore, Comparative Example 7, which contains a large fiber diameter, results in reduced elongation and fatigue properties inferior to Example 2.

[0071] The press sheets obtained in Example 2 and Comparative Example 3 were observed using an optical electron microscope. A photograph of Example 2 is shown in Figure 1A, and a photograph of Comparative Example 3 is shown in Figure 1B. Figures 1A and 1B show that in Example 2, the cellulose fibers are uniformly dispersed and form a network in the resin, whereas in Comparative Example 3, aggregates of 300 μm or larger in size are observed, indicating that the dispersion is non-uniform. Industrial Applicability

[0072] The thermoplastic polyester elastomer resin composition of the present invention and a molded article made thereof are lightweight and exhibit excellent surface properties, fatigue properties, and wear properties. Furthermore, by uniformly dispersing cellulose fibers, even a small amount of the composition can exhibit excellent performance and be molded easily.

Claims

1. A thermoplastic polyester elastomer resin composition containing 100 parts by mass of a thermoplastic polyester elastomer (A) in which a hard segment made of a polyester containing an aromatic dicarboxylic acid and an aliphatic and / or alicyclic diol as constituent components is bonded to at least one soft segment selected from aliphatic polyethers, aliphatic polyesters, and aliphatic polycarbonates, and 0.1 to 30 parts by mass of cellulose fibers (B), wherein the cellulose fibers (B) in the resin composition have an average fiber length of 100 to 2000 μm and an average fiber diameter of 0.5 to 50 μm.

2. 2. The thermoplastic polyester elastomer resin composition according to claim 1, wherein the content of the cellulose fibers (B) is 1 to 10 parts by mass, and the cellulose fibers in the resin composition have an average fiber length of 100 to 800 μm and an average fiber diameter of 1 to 30 μm.

3. 3. The thermoplastic polyester elastomer resin composition according to claim 1, wherein the cellulose fibers (B) are modified cellulose fibers.

4. The thermoplastic polyester elastomer resin composition according to any one of claims 1 to 3, further comprising a dispersing agent (C).

5. 5. The thermoplastic polyester elastomer resin composition according to claim 1, wherein the resin composition has a tensile elongation of 300% or more as measured in accordance with JIS K6251.

6. The method for producing a thermoplastic polyester elastomer resin composition according to any one of claims 1 to 5, characterized in that the cellulose fibers (B) are dispersed in the thermoplastic polyester elastomer (A) using a twin-screw kneader.

7. A molded article made of the thermoplastic polyester elastomer resin composition according to any one of claims 1 to 5.

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