Thermoplastic polyester elastomer resin composition

Abstract

The present invention aims to provide a thermoplastic polyester elastomer resin composition characterized by excellent flexibility, a smooth texture, excellent bleed resistance, a white appearance, and superior aesthetic qualities. [Solution] The present invention is a thermoplastic polyester elastomer resin composition characterized by containing 40 to 74% by mass of a polyester block copolymer (A) whose main components are a high-melting-point crystalline polymer segment (a) mainly composed of crystalline aromatic polyester units and a low-melting-point polymer segment (b) mainly composed of aliphatic polyether units and / or aliphatic polyester units, and 26 to 60% by mass of a core-shell type rubber (B) obtained by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber, wherein the content of the softener is 0.0 to 5.0 parts by mass per 100 parts by mass of the polyester block copolymer (A).

Description

Technical Field

[0001] The present invention relates to a thermoplastic polyester elastomer resin composition.

Background Art

[0002] Polyester block copolymers having a crystalline aromatic polyester unit as a hard segment and an aliphatic polyether unit such as poly(alkylene oxide) glycol as a soft segment are excellent in mechanical properties such as strength, impact resistance, elastic recovery, flexibility, and low-temperature and high-temperature characteristics, and are also thermoplastic and easy to mold. Therefore, they are widely used in fields such as automobiles, electrical and electronic parts, and consumer goods.

[0003] For materials used in parts that directly touch human skin, such as interior trim materials and consumer goods, a smooth touch is preferred, and at the same time, flexibility is also required.

[0004] In theory, polyester block copolymers can be softened by increasing the weight ratio of the soft segment, but their characteristic good moldability (curing rate, mold release property) and heat resistance rapidly decrease. In fact, a surface Shore D hardness of 30 is the limit, and the flexibility is positioned as the hardest elastomer among polyolefin-based elastomers and general-purpose elastomers, and its application development is restricted. As a conventional technique for improving the flexibility of polyester block copolymers, blending thermoplastic resins, elastomers, and plasticizers that are more flexible than the polyester block copolymer has been tried many times.

[0005] For example, a thermoplastic polyester resin composition (see, for example, Patent Document 1) in which a core-shell copolymer in which a polymer mainly composed of styrene and acrylonitrile copolymerizes as a shell with a core polymer mainly composed of butyl acrylate is blended with a polyester block copolymer has been proposed.

[0006] Furthermore, thermoplastic polyester resin compositions containing polyester block copolymers, core-shell copolymers, and ester compounds have been proposed (see, for example, Patent Document 2).

[0007] On the other hand, conventional techniques for improving the smooth texture of polyester block copolymers include adding silicone oil as a lubricant, and incorporating a copolymer (for example, a silicone-modified acrylic resin) that combines a structural part with good compatibility with the resin component and a structural part that improves sliding properties.

[0008] For example, a thermoplastic polyester resin composition has been proposed that combines a polyester block copolymer and a core-shell copolymer, with the addition of silicone oil (see, for example, Patent Document 3).

[0009] Furthermore, thermoplastic polyester resin compositions have been proposed in which a silicone-modified (meth)acrylic polymer is blended with a polyester block copolymer (see, for example, Patent Document 4), and thermoplastic polyester resin compositions have been proposed in which a silicone-acrylic copolymer is blended with a polyester block copolymer (see, for example, Patent Document 5). [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2000-302940 [Patent Document 2] Japanese Patent Publication No. 2018-150525 [Patent Document 3] Japanese Patent Application Publication No. 10-219036 [Patent Document 4] Japanese Patent Publication No. 2016-079228 [Patent Document 5] International Publication No. 2022 / 131340 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, Patent Document 1 had the problem of insufficient smooth texture and low whiteness, resulting in poor color development when colored. Patent Document 2 had the problem of insufficient smooth texture and ester compounds bleeding out, resulting in poor appearance. Patent Document 3 had the problem of insufficient flexibility and whiteness, and silicone oil bleeding out. Patent Documents 4 and 5 had the problem of low whiteness, resulting in poor color development when colored.

[0012] The present invention aims to solve the problems of the prior art described above, and provides a thermoplastic polyester elastomer resin composition characterized by excellent flexibility, a smooth texture, excellent bleed resistance, a white appearance, and good aesthetics. [Means for solving the problem]

[0013] As a result of diligent research to achieve the above objectives, the inventors of the present invention discovered that the above objectives can be effectively achieved by blending a specific amount of a particular core-shell type rubber into a polyester block copolymer, and thus arrived at the present invention.

[0014] In other words, the embodiments of the present invention are as follows. (1) A thermoplastic polyester elastomer resin composition characterized by containing 40 to 74% by mass of a polyester block copolymer (A) whose main components are a high-melting-point crystalline polymer segment (a) mainly composed of crystalline aromatic polyester units and a low-melting-point polymer segment (b) mainly composed of aliphatic polyether units and / or aliphatic polyester units, and 26 to 60% by mass of a core-shell type rubber (B) obtained by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber, wherein the content of the softening agent is 0.0 to 5.0 parts by mass per 100 parts by mass of the polyester block copolymer (A). (2) The thermoplastic polyester elastomer resin composition described in (1), wherein the hardness measured by durometer A in accordance with JIS K7215 is 50A to 90A. (3) The thermoplastic polyester elastomer resin composition according to (1) or (2), wherein the color tone L value measured using a 2 mm thick test piece is 80 or higher and the yellowness YI value is 10 or lower. (4) The thermoplastic polyester elastomer resin composition according to (1) or (2), wherein the coefficient of dynamic friction measured using a textured urethane contactor on a 125 mm × 75 mm × 2 mm thick rectangular injection-molded test piece obtained by injection molding the thermoplastic polyester elastomer resin composition is 0.6 or less, with a load of 100 g and a speed of 10 mm / sec. (5) A molded article comprising the thermoplastic polyester elastomer resin composition described in any of (1) to (4). [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a thermoplastic polyester elastomer resin composition that is excellent in flexibility, has a smooth texture, has excellent bleed resistance, has a white color, and has excellent appearance. [Modes for carrying out the invention]

[0016] The present invention will be described in detail below.

[0017] The thermoplastic polyester elastomer resin composition of the present invention contains 40 to 74% by mass of a polyester block copolymer (A) (hereinafter sometimes referred to as polyester block copolymer (A)) whose main components are a high-melting-point crystalline polymer segment (a) mainly composed of crystalline aromatic polyester units and a low-melting-point polymer segment (b) mainly composed of aliphatic polyether units and / or aliphatic polyester units, and 26 to 60% by mass of a core-shell type rubber (B) (hereinafter sometimes referred to as core-shell type rubber (B)) obtained by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber, and is characterized in that the content of the softener is 0.0 to 5.0 parts by mass per 100 parts by mass of polyester block copolymer (A).

[0018] The polyester block copolymer (A) used in the present invention mainly comprises a high melting point crystalline polymer segment (a) mainly composed of a crystalline aromatic polyester unit and a low melting point polymer segment (b) mainly composed of an aliphatic polyether unit and / or an aliphatic polyester unit as main components. The high melting point crystalline polymer segment (a) is a polyester formed mainly from an aromatic dicarboxylic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracene dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, and sodium 3-sulfoisophthalate. Although mainly an aromatic dicarboxylic acid is used, if necessary, a part of the aromatic dicarboxylic acid may be replaced with an alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, 4,4'-dicyclohexyldicarboxylic acid, or an aliphatic dicarboxylic acid such as adipic acid, succinic acid, oxalic acid, sebacic acid, dodecanedioic acid, and dimer acid. Ester-forming derivatives of dicarboxylic acids, such as lower alkyl esters, aryl esters, carbonates, and acid halides, can of course be used equivalently.

[0019] Specific examples of diols include aliphatic diols with a molecular weight of 400 or less, such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, decamethylene glycol, etc., alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, tricyclodecanedimethanol, and aromatic diols such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxy)diphenylpropane, 2,2'-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4'-dihydroxy-p-terphenyl, and 4,4'-dihydroxy-p-quarterphenyl. Such diols can also be used in the form of ester-forming derivatives, such as acetylated derivatives and alkali metal salts.

[0020] These dicarboxylic acids, their derivatives, diol components, and their derivatives may be used in combination of two or more types. A preferred example of a high-melting-point crystalline polymer segment (a) is a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol. Alternatively, a structure consisting of a polybutylene terephthalate unit derived from terephthalic acid and / or dimethyl terephthalate and a polybutylene isophthalate unit derived from isophthalic acid and / or dimethyl isophthalate and 1,4-butanediol is also preferably used.

[0021] The low-melting polymer segment (b) of the polyester block copolymer (A) used in the present invention is an aliphatic polyether and / or an aliphatic polyester. Specific examples of this aliphatic polyether include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(trimethylene ether) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, a copolymer of ethylene oxide and propylene oxide, an ethylene oxide adduct of poly(propylene oxide) glycol, and a copolymer of ethylene oxide and tetrahydrofuran. Among these, poly(tetramethylene oxide) glycol and / or an ethylene oxide adduct of poly(propylene oxide) glycol and / or a copolymer of ethylene oxide and tetrahydrofuran are preferred. Specific examples of the aliphatic polyester include poly(ε-caprolactone), poly(enantholactone), polycapryllactone, polybutylene adipate, polyethylene adipate, and the like. Among these, poly(tetramethylene oxide) glycol and / or an ethylene oxide adduct of poly(propylene oxide) glycol and / or a copolymer of ethylene oxide and tetrahydrofuran are preferred. Also, the number average molecular weight of these low-melting polymer segments (b) is preferably about 300 to 6000 in the copolymerized state.

[0022] The mass ratio (a / b) of the high-melting crystalline polymer segment (a) and the low-melting polymer segment (b) of the polyether ester block copolymer (A) used in the present invention is preferably 50 / 50 to 20 / 80% by mass, more preferably 40 / 60 to 20 / 80% by mass.

[0023] The polyester block copolymer (A) used in the present invention can be produced by known methods. Specific examples include, for example, a method in which a lower alcohol diester of a dicarboxylic acid, an excess amount of low molecular weight glycol, and a low melting point polymer segment component are transesterified in the presence of a catalyst, and the resulting reaction product is polycondensed; and a method in which a dicarboxylic acid, an excess amount of glycol, and a low melting point polymer segment component are esterified in the presence of a catalyst, and the resulting reaction product is polycondensed.

[0024] The core-shell type rubber (B) used in the present invention is obtained by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber. Specifically, it is a core-shell type rubber in which a composite rubber containing polyorganosiloxane and polyalkyl (meth)acrylate serves as the core, and a vinyl polymer composed of one or more vinyl monomer units serves as the shell.

[0025] The polyorganosiloxane constituting the composite rubber is preferably a polymer containing dimethylsiloxane units as constituent units. The dimethylsiloxane units constituting the polyorganosiloxane are preferably cyclic organosiloxanes with 3 to 7 membered rings, such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, and octaphenylcyclotetrasiloxane. These monomer components may be used individually or in combination of two or more.

[0026] Furthermore, the polyorganosiloxane may be crosslinked with a siloxane-based crosslinking agent. Examples of siloxane-based crosslinking agents include trifunctional or tetrafunctional silane-based crosslinking agents such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, and tetrabutoxysilane.

[0027] The polyalkyl (meth)acrylate constituting the composite rubber is preferably a polymer containing alkyl (meth)acrylate units and polyfunctional alkyl (meth)acrylate units as constituent components. Examples of alkyl (meth)acrylates include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate, and alkyl methacrylates such as hexyl methacrylate, 2-ethylhexyl methacrylate, and n-lauryl methacrylate. These monomer components may be used individually or in combination of two or more. Examples of polyfunctional alkyl (meth)acrylates include allyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, triallyl cyanurate, and triallyl isocyanurate. These monomer components may be used individually or in combination of two or more.

[0028] Composite rubber has a structure in which polyorganosiloxane and polyalkyl (meth)acrylate are intertwined in a way that prevents them from separating. Core-shell type rubber can be obtained by graft copolymerization of one or more vinyl monomers in the presence of composite rubber. Graft copolymerization can be carried out using any of the following methods: bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. The copolymerization method can be single-stage or multi-stage grafting, but emulsion polymerization is preferred because it allows for easier control of productivity and particle size.

[0029] Specific examples of vinyl monomer components that can be graft copolymerized with composite rubber include aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; (meth)acrylic acid ester compounds such as methyl methacrylate, ethyl methacrylate, and 2-ethylhexyl methacrylate; acrylic acid ester compounds such as methyl acrylate, ethyl acrylate, and butyl acrylate; and epoxy group-containing (meth)acrylic acid ester compounds such as glycidyl (meth)acrylate. These monomer components may be used individually or in combination of two or more.

[0030] Examples of such core-shell type rubber (B) include "Metablen® SX-005" manufactured by Mitsubishi Chemical Corporation and "KaneAce® MR-01" manufactured by Kaneka Corporation.

[0031] The core-shell type rubber (B) used in the present invention preferably has a weight loss rate of less than 3.3% when measured using a thermogravimetric analyzer at a heating rate of 10°C / min from room temperature to 250°C, and more preferably less than 3.2%. If the weight loss rate is 3.3% or more, it may be undesirable because it may lead to increased gas generation during the production of the thermoplastic polyester elastomer resin composition or during molding, and may also increase the degree of contamination of the equipment and molds used.

[0032] The thermoplastic polyester elastomer resin composition of the present invention comprises 40 to 74% by mass of the above-mentioned polyester block copolymer (A) and 26 to 60% by mass of core-shell type rubber (B), preferably comprising 40 to 70% by mass of polyester block copolymer (A) and 30 to 60% by mass of core-shell type rubber (B), more preferably comprising 45 to 65% by mass of polyester block copolymer (A) and 35 to 55% by mass of core-shell type rubber (B), and particularly preferably comprising 50 to 60% by mass of polyester block copolymer (A) and 40 to 50% by mass of core-shell type rubber (B).

[0033] If the polyester block copolymer (A) is less than 40% by mass, the mechanical properties and moldability of the polyester elastomer are impaired, which is undesirable. If it exceeds 74% by mass, the flexibility is insufficient, which is undesirable. If the core-shell type rubber (B) is less than 26% by mass, the flexibility and smooth feel are insufficient, which is undesirable. If it exceeds 60% by mass, the moldability is impaired, which is undesirable. By blending polyester block copolymer (A) and core-shell type rubber (B) in specific amounts, a thermoplastic polyester elastomer resin composition with excellent flexibility and a smooth feel can be obtained.

[0034] There are no limitations on the method of mixing the polyester block copolymer (A) and core-shell type rubber (B) of the present invention. One example is a method of mixing (A) and (B) together. Known methods such as a Banbury mixer or an extruder can be used as the kneading method.

[0035] The thermoplastic polyester elastomer resin composition of the present invention may contain a softening agent (C). Examples of softening agents (C) include phthalate ester compounds, phosphate ester compounds, trimellitic acid ester compounds, fatty acid ester compounds, polyether ester compounds, benzoate ester compounds, and hydrocarbon rubber softening agents.

[0036] The content of the softening agent (C) is 0.0 to 5.0 parts by mass, preferably 0.0 to 3.0 parts by mass, more preferably 0.0 to 1.0 parts by mass, and particularly preferably 0.0 parts by mass, per 100 parts by mass of polyester block copolymer (A).

[0037] If the content of the softening agent (C) exceeds 5.0 parts by mass, it is undesirable because it can cause blooming or a decrease in mechanical strength.

[0038] The thermoplastic polyester elastomer resin composition of the present invention preferably contains an antioxidant (D). The antioxidant (D) is a compound that prevents the decomposition of the thermoplastic polyester elastomer resin composition due to heat, light, oxygen, etc. Examples of antioxidants (D) include one or more selected from the group consisting of aromatic amine antioxidants, hindered phenol antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0039] Specific examples of aromatic amine antioxidants include phenylnaphthylamine, 4,4'-dimethoxydiphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and 4-isopropoxydiphenylamine, but among these, the use of diphenylamine compounds is preferred.

[0040] Specific examples of hindered phenol antioxidants include 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butylphenol, 2,6-di-t-butyl-p-cresol, hydroxymethyl-2,6-di-t-butylphenol, 2,6-di-t-α-dimethylamino-p-cresol, 2,5-di-t-butyl-4-ethylphenol, 4,4'-bis(2,6-di-t-butylphenol), 2,2'-methylene-bis-4-methyl-6-t-butylphenol, and 2,2'-methylene-bis(4-ethyl-6-t-butylphenol). ), 4,4'-methylene-bis(6-t-butyl-o-cresol), 4,4'-methylene-bis(2,6-di-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-cyclohexylphenol), 4,4'-butylidene-bis(3-methyl-6-t-butylphenol), 4,4'-thiobis(6-t-butyl-3-methylphenol), bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide, 4,4'-thiobis(6-t-butyl-o-cresol), 2,2'-thiobis(4-methyl-6-t-butylphenol (Nol), 2,6-bis(2'-hydroxy-3'-t-butyl-5'-methylbenzyl)-4-methylphenol, diethyl ester of 3,5-di-t-butyl-4-hydroxybenzenesulfonic acid, 2,2'-dihydroxy-3,3'-di(α-methylcyclohexyl)-5,5'-dimethyl-diphenylmethane, α-octadecyl-3(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate, 6-(hydroxy-3,5-di-t-butylanilino)-2,4-bis-octyl-thio-1,3,5-triazine, hexamethyl Glycol-bis[β-(3,5-di-t-butyl-4-hydroxyphenol)propionate], N,N'-hexamethylene-bis(3,5-di-t-butyl-4-hydroxyhydrocinnamic acid amide), 2,2-thio[diethyl-bis-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate], dioctadecyl ester of 3,5-di-t-butyl-4-hydroxybenzenephosphonic acid, tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,3,5-trimethyl-2,4,Examples include 6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,1,3-tris(2-methyl-4-hydroxy-5-di-t-butylphenyl)butane, tris(3,5-di-t-butyl-4-hydroxyphenyl)isocyanurate, and tris[β-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl-oxyethyl]isocyanurate. Among these, the use of those with a molecular weight of 500 or more, such as tetrakis[methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, is particularly preferred.

[0041] Sulfur-based antioxidants are compounds containing sulfur, such as thioethers, dithioates, mercaptobenzimidazoles, thiocarbanilides, and thiodipropion esters. Among these, the use of thiodipropion ester compounds is particularly preferred.

[0042] Phosphorus-based antioxidants are compounds containing phosphorus, such as phosphoric acid, phosphorous acid, hypophosphorous acid derivatives, phenylphosphonic acid, polyphosphonates, dialkylpentaerythritol diphosphite, and dialkylbisphenol A diphosphite. Among these, it is preferable to use compounds that have both phosphorus and sulfur atoms in their molecule, or compounds that have two or more phosphorus atoms in their molecule.

[0043] The content of the antioxidant (D) is 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, and more preferably 0.1 to 1.5 parts by mass, per 100 parts by mass of the total of the polyester block copolymer (A) and the core-shell type rubber (B).

[0044] If the antioxidant (D) content is less than 0.01 parts by mass, the degree to which the desired improvement effect can be obtained is small, and if it exceeds 5 parts by mass, blooming may occur or the mechanical strength may decrease, which is undesirable.

[0045] The thermoplastic polyester elastomer resin composition of the present invention may contain, as necessary and within limits that do not impair its purpose, additives and reinforcing agents such as ultraviolet absorbers, light stabilizers, antistatic agents, lubricants, sliding agents, nucleating agents, dyes, pigments, flame retardants, mold release agents, glass fibers, metal fibers, carbon fibers, and metal flakes.

[0046] The thermoplastic polyester elastomer resin composition of the present invention preferably has a hardness of 50A to 90A, more preferably 55A to 85A, even more preferably 60A to 80A, and particularly preferably 65A to 75A, as measured according to JIS K7215. If the hardness exceeds 90A, the flexibility is insufficient, and if it is less than 50A, the smooth texture is insufficient, which may be undesirable.

[0047] The thermoplastic polyester elastomer resin composition of the present invention preferably has a tensile breaking strength of 7.0 MPa or higher, and more preferably 8.0 MPa or higher, when measured according to JIS K7113. If the tensile breaking strength is less than 7.0 MPa, the strength of the thermoplastic polyester elastomer resin composition is insufficient and therefore undesirable.

[0048] The thermoplastic polyester elastomer resin composition of the present invention preferably has a tensile elongation at break of 300% or more, and more preferably 400% or more, when measured according to JIS K7113. If the tensile elongation at break is less than 300%, the elongation as a thermoplastic polyester elastomer resin composition is insufficient and therefore undesirable.

[0049] The thermoplastic polyester elastomer resin composition of the present invention preferably has a tensile modulus of 10 MPa or more, and more preferably 12 MPa or more, when measured according to JIS K7113. If the tensile modulus is less than 10 MPa, the modulus of elasticity as a thermoplastic polyester elastomer resin composition is insufficient and therefore undesirable.

[0050] The thermoplastic polyester elastomer resin composition of the present invention preferably has a static friction coefficient of 1.1 or less, more preferably 1.0 or less, and even more preferably 0.9 or less. If the static friction coefficient exceeds 1.1, it may be undesirable because it does not provide a sufficiently smooth feel.

[0051] The thermoplastic polyester elastomer resin composition of the present invention preferably has a dynamic friction coefficient of 0.6 or less, more preferably 0.5 or less, and even more preferably 0.4 or less. If the dynamic friction coefficient exceeds 1.0, it may be undesirable because it does not provide a sufficiently smooth feel.

[0052] The thermoplastic polyester elastomer resin composition of the present invention preferably has a color tone L value of 80 or higher, more preferably 84 or higher, even more preferably 88 or higher, and particularly preferably 92 or higher, as measured by a colorimeter. If the color tone L value is less than 80, the whiteness is insufficient, and the color may not be vivid when colored, which is undesirable.

[0053] The thermoplastic polyester elastomer resin composition of the present invention preferably has a yellowness YI value of 10 or less, more preferably 8 or less, even more preferably 5 or less, and particularly preferably 3 or less, as measured by a colorimeter. If the yellowness YI value exceeds 10, the yellowness is high and may not result in vivid color development during coloring, which is undesirable.

[0054] The melt viscosity index (MFR) of the thermoplastic polyester elastomer resin composition of the present invention refers to the value measured according to ASTM D1238 at a measurement temperature of 220°C and a measurement load of 10.0 kg. The MFR of the thermoplastic polyester elastomer resin composition of the present invention is preferably 5 to 100 g / 10 min, more preferably 10 to 75 g / 10 min, and even more preferably 15 to 50 g / 10 min. If the MFR is less than 5 g / 10 min, the fluidity is low and the moldability is insufficient, and if it exceeds 100 g / 10 min, burrs are likely to form during injection molding and the moldability is insufficient, which may be undesirable.

[0055] The thermoplastic polyester elastomer resin composition of the present invention preferably has a flexural modulus of 60 MPa or less, more preferably 40 MPa or less, and even more preferably 20 MPa or less, when measured at 23°C according to ASTM D790. If the flexural modulus at 23°C exceeds 60 MPa, the flexibility of the thermoplastic polyester elastomer resin composition becomes insufficient, which is undesirable. The thermoplastic polyester elastomer resin composition of the present invention preferably has a flexural modulus of 500 MPa or less, more preferably 250 MPa or less, and even more preferably 100 MPa or less, when measured at -40°C according to ASTM D790. If the flexural modulus at -40°C exceeds 500 MPa, the flexibility of the thermoplastic polyester elastomer resin composition becomes insufficient, which is undesirable.

[0056] The thermoplastic polyester elastomer resin composition of the present invention preferably has a dimensional change rate of 15% or less, more preferably 13% or less, and even more preferably 11% or less after immersion in oleic acid for 20 days. A dimensional change rate exceeding 15% may be undesirable because it can lead to significant dimensional changes due to oils and greases when used in environments where it comes into direct contact with human skin.

[0057] The thermoplastic polyester elastomer resin composition of the present invention can be molded into a thermoplastic polyester elastomer article using commonly used molding machines such as injection molding, extrusion molding, blow molding, compression molding, extrusion film deposition, T-die film deposition, and calender film deposition.

[0058] Furthermore, composite molded articles consisting of the thermoplastic polyester elastomer resin composition of the present invention and a rigid resin can be obtained using methods such as two-color molding, co-extrusion molding, and insert molding. The rigid resin is not particularly limited, but examples include polycarbonate resin, ABS resin, and PBT resin. The thermoplastic polyester elastomer resin composition of the present invention exhibits excellent adhesion to these rigid resins.

[0059] The thermoplastic polyester elastomer molded articles of the present invention are not particularly limited in their applications, but can be found in fields such as automobiles, construction, furniture, electronic and electrical equipment, precision instruments, robots, sports, clothing, healthcare, office supplies, and general consumer goods. They are particularly suitable for use in products that come into direct contact with human skin. Specific examples include automotive interior materials such as instrument panels, armrests, and door trims; wallpaper, flooring, handrails, elbow rests, seat cushions; home appliances; smartphone cases; tuff covers; remote controls; earphones; headphones; mice; keyboards; game device surfaces; robot surfaces; clothing; buttons; zippers; belts; musical instruments; handrails; wallets; watches; toys; writing instruments; styluses; cosmetic containers; and hairbrushes. [Examples]

[0060] The effects of the present invention will be explained below with reference to examples. In the examples, percentages and parts are all based on mass unless otherwise specified. Furthermore, the characteristics shown in the examples were measured as follows.

[0061] [Hardness (Durometer A)] The hardness was measured using a durometer A in accordance with JIS K7215.

[0062] [Melting point measurement] Using a DSC Q100 manufactured by T.A. Instruments, the melting point was measured by heating from room temperature to 240°C at a heating rate of 10°C / min. Furthermore, after holding at 240°C for 3 minutes, the crystallization temperature was measured by cooling to 40°C at a cooling rate of 10°C / min.

[0063] [Tensile properties] Measurements were taken using JIS No. 2 injection-molded test specimens in accordance with JIS K7113.

[0064] [Coefficient of dynamic friction] The coefficient of kinetic friction was measured under the following conditions. <Measurement conditions> Load: 100g Speed: 10mm / sec Dynamic friction analysis range: 5mm-25mm Testing equipment: Friction testing machine (manufactured by Trinity Labs) Test environment: 23℃ × 50%RH Test specimen: Square plate injection molded test specimen (125mm x 75mm x 2mm thickness) Test method: In the above test environment, the test specimen was fixed to the above testing machine, a textured urethane contact was placed in the center of the test specimen, a weight of the above load was placed on it, and the above range was measured at the above speed.

[0065] [Tactile evaluation (smoothness)] The tactile sensation of the surface of the square plate injection-molded test specimen obtained above, when slid with the pad of the index finger, was evaluated according to the following criteria. The evaluation was performed by 10 people, and the average score of the 10 evaluations was used as the evaluation score. 4 points: Good (I strongly feel the smooth texture) 3 points: Good (feels smooth and dry) 2 points: Poor (doesn't feel smooth) 1 point: Defective (does not feel smooth at all) [Color tone L value] In accordance with JIS Z8722, L*, a*, and b* were measured using an SM-T colorimeter (light source: C, field of view: 2 degrees) manufactured by Suga Test Instruments Co., Ltd. The value of L* was defined as the color tone L value.

[0066] [Yellowness YI value] In accordance with JIS Z8722, the yellowness YI value was measured using an SM-T colorimeter manufactured by Suga Test Instruments Co., Ltd. (light source: C, field of view: 2 degrees).

[0067] [Bleed resistance] Using black-colored rectangular injection-molded test specimens (125mm x 75mm x 2mm thick), the specimens were left for 500 hours at a temperature of 85°C and a relative humidity of 95%. After this, the surface of the specimens was visually inspected for the presence of powder, oil, or other deposits.

[0068] [Melting Viscosity Index (MFR)] In accordance with ASTM D1238, the thermoplastic polyester elastomer resin compositions of the following examples and comparative examples were measured at 220°C and under a load of 10 kg.

[0069] [Flexural modulus] Measurements were taken using injection-molded test specimens in accordance with ASTM D790, under atmospheric conditions of 23°C and -40°C.

[0070] [Oleic acid swelling resistance] Using JIS No. 2 injection-molded test specimens, they were immersed in oleic acid at room temperature for 20 days, and then the dimensions in the flow direction were measured and the dimensional change rate was calculated.

[0071] [Reference example] [Production of polyester block copolymer (A-1)] 234 parts terephthalic acid, 228 parts 1,4-butanediol, and 754 parts poly(tetramethylene oxide) glycol with a number average molecular weight of approximately 2000 were charged together with 0.2 parts titanium tetrabutoxide in a reaction vessel equipped with a helical ribbon-type stirring blade. The mixture was heated at 190-225°C for 3 hours, and the esterification reaction was carried out while distilling off the reaction water from the system. After adding 0.5 parts "Irganox" 1330 (a hindered phenol antioxidant manufactured by BASF) to the reaction mixture, the temperature was raised to 245°C, and then the pressure in the system was reduced to 0.2 mmHg over 50 minutes. Under these conditions, melt polycondensation was carried out for 3 hours and 30 minutes. The resulting polyester elastomer was extruded in strand form into water and cut to form pellets.

[0072] [Production of polyester block copolymer (A-2)] 348 parts terephthalic acid, 151 parts 1,4-butanediol, and 576 parts poly(tetramethylene oxide) glycol with a number average molecular weight of approximately 1400 were charged together with 0.5 parts titanium tetrabutoxide and 0.2 parts mono-n-butyl-monohydroxytin oxide in a reaction vessel equipped with a helical ribbon-type stirring blade. The mixture was heated at 190-225°C for 3 hours, and the esterification reaction was carried out while distilling off the reaction water from the system. 2.0 parts titanium tetrabutoxide were added to the reaction mixture, and 0.5 parts "Irganox" 1098 (a hindered phenol antioxidant manufactured by Ciba-Geigy) were added. The temperature was then raised to 245°C, and the pressure in the system was reduced to 0.2 mmHg over 50 minutes. Under these conditions, melt polycondensation was carried out for 2 hours and 45 minutes. The resulting polyester elastomer was discharged in strand form into water and cut into pellets.

[0073] [Production of polyester block copolymer (A-3)] 420 parts terephthalic acid, 196 parts 1,4-butanediol, and 480 parts poly(tetramethylene oxide) glycol with a number average molecular weight of approximately 1400 were charged together with 0.3 parts titanium tetrabutoxide and 0.2 parts mono-n-butyl-monohydroxytin oxide in a reaction vessel equipped with a helical ribbon-type stirring blade. The mixture was heated at 190-225°C for 3 hours, and the esterification reaction was carried out while distilling off the reaction water. 2.0 parts titanium tetrabutoxide were added to the reaction mixture, and 0.5 parts "Irganox" 1098 (a hindered phenol antioxidant manufactured by Ciba-Geigy) were added. The temperature was then raised to 245°C, and the pressure in the system was reduced to 0.2 mmHg over 50 minutes. Under these conditions, melt polycondensation was carried out for 2 hours and 45 minutes. The resulting polyester elastomer was extruded in strand form into water and cut into pellets.

[0074] [Core-shell type rubber (B)] (B-1) As a core-shell type rubber formed by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber, Mitsubishi Chemical's "Metablen" SX-005 was used. The weight loss rate at 250°C was 3.16%. (B-2) As a core-shell type rubber formed by graft polymerization of vinyl monomers onto acrylic rubber, Synthomer's "SaniGum" P95 was used.

[0075] [Softener (C)] (C) Tri-2-ethylhexyl trimellitate was used as a softening agent.

[0076] [Antioxidant (D)] (D-1) As a phenolic antioxidant, BASF's "Irganox" 1010 was used. (D-2) As a phosphoric acid-based antioxidant, Clariant Japan's "HOSTANOX" P-EPQ was used.

[0077] [Examples 1-7] and [Comparative Examples 1-4] The polyester block copolymers (A-1), (A-2), (A-3) obtained in the reference example, core-shell type rubber (B), softener (C), and antioxidant (D) were dry-blended in the mixing ratios (mass%) shown in Table 1, and then melt-kneaded at 180°C to 220°C using a twin-screw extruder with a diameter of 45 mm and a three-thread screw type to form pellets. After drying these pellets at 80°C for 5 hours, JIS No. 2 dumbbell test specimens measuring 125 mm (length) x 75 mm (width) x 2 mm (thickness) and rectangular plate test specimens measuring 125 mm (length) x 75 mm (width) x 2 mm (thickness) were injection molded using an electric injection molding machine (NEX-1000) manufactured by Nissei Plastic Industrial Co., Ltd., at a cylinder temperature of 210°C and a mold temperature of 50°C (mold cavity surface). The results of the characteristics investigated for each test are shown in Table 1.

[0078] [Table 1]

[0079] Based on the above results, the thermoplastic polyester elastomer resin compositions of the present invention, which are compounded with a polyester block copolymer (A) and a specific core-shell type rubber (B) as shown in Examples 1 to 7, exhibit excellent flexibility, a smooth feel, bleed resistance, and whiteness.

[0080] On the other hand, the thermoplastic polyester elastomer resin compositions of Comparative Examples 1 to 4, which did not satisfy the conditions of the present invention, were inferior in any of the following: flexibility, smooth texture, bleed resistance, or whiteness.

[0081] Comparative Examples 1 and 2, in which a polyester block copolymer (A-1) was blended with a core-shell type rubber (B-2) which is not a core-shell type rubber formed by graft polymerization of vinyl monomers into a silicone / acrylic composite rubber, lacked a smooth feel and had a low color tone L value, making them undesirable. Comparative Example 3, in which a polyester block copolymer (A-3) was blended with a core-shell type rubber (B-2) which is not a core-shell type rubber formed by graft polymerization of vinyl monomers into a silicone / acrylic composite rubber, lacked flexibility and a smooth feel, making it undesirable. Comparative Example 4, in which a polyester block copolymer (A-1) was blended with a core-shell type rubber (B-1) formed by graft polymerization of vinyl monomers into a silicone / acrylic composite rubber, but a softener (C) was further added at a rate of 10 parts by mass per 100 parts by mass of polyester block copolymer (A), lacked a smooth feel and had poor bleed resistance, making it undesirable.

Claims

1. A thermoplastic polyester elastomer resin composition characterized by containing 40 to 74% by mass of a polyester block copolymer (A) whose main components are a high-melting-point crystalline polymer segment (a) mainly composed of crystalline aromatic polyester units and a low-melting-point polymer segment (b) mainly composed of aliphatic polyether units and / or aliphatic polyester units, and 26 to 60% by mass of a core-shell type rubber (B) obtained by graft polymerization of vinyl monomers onto a silicone / acrylic composite rubber, wherein the content of the softener is 0.0 to 5.0 parts by mass per 100 parts by mass of the polyester block copolymer (A).

2. The thermoplastic polyester elastomer resin composition according to claim 1, wherein the hardness measured by durometer A in accordance with JIS K7215 is 50A to 90A.

3. The thermoplastic polyester elastomer resin composition according to claim 1 or 2, wherein the color tone L value measured using a 2 mm thick test piece is 80 or higher, and the yellowness YI value is 10 or lower.

4. The thermoplastic polyester elastomer resin composition according to claim 1 or 2, wherein the coefficient of dynamic friction measured on a 125 mm × 75 mm × 2 mm thick rectangular plate test piece obtained by injection molding the thermoplastic polyester elastomer resin composition is 0.6 or less, using a textured urethane contactor at a load of 100 g and a speed of 10 mm / sec.

5. A molded article comprising the thermoplastic polyester elastomer resin composition according to any one of claims 1 to 4.

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