Thermoplastic polyester elastomer resin foam molded article and method for producing same

Abstract

To provide a thermoplastic polyester elastomer resin foam molding which is excellent in light weight property and high expansion property while being flexible and having a low repulsion elastic modulus.SOLUTION: A resin foam molding is formed from a thermoplastic polyester elastomer resin composition obtained by blending 20-95 mass% of a polyester block copolymer (A) composed of a high melting point crystalline segment composed of a crystalline aromatic polyester unit and a low melting point polymer segment composed of an aliphatic polyether unit, and 5-80 mass% of a core-shell copolymer (B) having a polymer obtained by emulsion polymerization of butylacrylate, an alkyl (meth)acrylate having an alkyl group having 1 to 4 carbon atoms, a vinyl cyanide compound, a maleic acid monoalkyl ester and a crosslinking agent as a core, and a polymer obtained by polymerization of styrene, vinyl cyanide and a crosslinking agent as a shell, and has a density of less than 0.70 g / cm3 and an expansion ratio of 2.0 or more and a repulsion elastic modulus of 60% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foam molded article made from a thermoplastic polyester elastomer resin. [Background technology]

[0002] Polyester block copolymers, which have crystalline aromatic polyester units as hard segments and aliphatic polyether units such as poly(alkylene oxide) glycol or aliphatic polyester units such as polylactone as soft segments, are excellent in many respects, including moldability, impact resistance, elastic recovery, flexibility, and other mechanical properties, as well as heat resistance. Because of their excellent balance of these properties (moldability, mechanical properties, and heat resistance), their applications have expanded to include industrial materials such as sheets, films, and fibers, as well as automobiles and electrical and electronic parts.

[0003] For shock absorbing and vibration isolating applications, materials that are flexible, have low impact resilience, and have excellent shock absorbing properties are required. In addition, since sound absorption properties may be required depending on the location of use of the shock absorbing and vibration isolating materials, excellent sound absorption properties are also desirable.

[0004] Theoretically, polyester block copolymers can be made more flexible by increasing the mass ratio of the soft segment, but at the same time, the impact resilience increases. Furthermore, the surface Shore D hardness of 30 is the limit of flexibility, and in terms of flexibility, they are positioned as the hardest elastomers among engineering plastic elastomers and general-purpose elastomers, which limits their application.

[0005] Furthermore, in recent years, efforts have been made to reduce the weight of resin parts, and one of the means for achieving this reduction is the use of foamed molded articles.

[0006] Conventionally, a method of using an inert gas in a supercritical state as a physical blowing agent has been proposed as a method for obtaining foamed bodies of polyester block copolymers, and it has become possible to obtain foamed molded bodies with excellent lightness and a high expansion ratio (for example, Patent Documents 1 and 2). Patent Documents 1 and 2 disclose foamed molded bodies with excellent lightness and a high expansion ratio, which are obtained by impregnating a low-hardness polyester elastomer with an inert gas in a supercritical state. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6380638 [Patent Document 2] Patent No. 6358368 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the compositions of Patent Documents 1 and 2 use a polyester elastomer with a high mass ratio of soft segments, so the resulting foamed molded article has a high rebound resilience, making it difficult to obtain a flexible foamed molded article with a high expansion ratio and a rebound resilience of less than 60%.

[0009] As a result of intensive research into achieving the above object, the present inventors have succeeded in obtaining a thermoplastic polyester elastomer resin foam molded article with a high expansion ratio that is flexible, has a low rebound resilience, and is lightweight, by controlling the mass ratio of each component in a composition in which a specific polyester block copolymer is simultaneously blended with a core-shell copolymer, the core of which is a polymer mainly composed of butyl acrylate or a mixture of butyl acrylate and 2-ethylhexyl acrylate and obtained by emulsion polymerization of a specific group of compounds, and the shell is a polymer mainly composed of an aromatic vinyl compound and a vinyl cyanide compound and obtained by polymerization of a specific compound. [Means for solving the problem]

[0010] That is, the present invention constitutes [1] to [6]. [1] A polyester block copolymer (A) mainly composed of a high-melting crystalline segment (a-1) consisting mainly of a crystalline aromatic polyester unit and a low-melting polymer segment (a-2) consisting mainly of an aliphatic polyether unit and / or an aliphatic polyester unit, is mixed with 20 to 95% by mass of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1), at least one compound (b-2) selected from an alkyl acrylate having an alkyl group of 1 to 4 carbon atoms and an alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms, a vinyl cyan compound (b-3), and a copolymer represented by the following structural formula (I): and a core-shell copolymer (B) having a core formed by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5), and a shell formed by polymerization of an aromatic vinyl compound (b-6), a vinyl cyan compound (b-3), and a crosslinking agent (b-5). The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5), and the shell is a polymer obtained by further polymerizing an aromatic vinyl compound (b-6), a vinyl cyan compound (b-3), and a crosslinking agent (b-5). The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5), and the shell is a polymer obtained by ... The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5), and the shell is a polymer obtained by polymerizing an aromatic vinyl compound (b-6), a vinyl cyan compound (b-3), and a crosslinking agent (b-5). The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5). The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5). The core-shell copolymer (B) is a polymer obtained by emulsion polymerization of an aromatic vinyl compound (b 3 A thermoplastic polyester elastomer resin foam molded article having an expansion ratio of 2.0 or more and a rebound resilience of 60% or less. [2] The thermoplastic polyester elastomer resin foam molded article according to [1], wherein the foam cells have an average cell diameter of 10 to 600 μm. [3] The thermoplastic polyester elastomer resin foam molded article according to [1] or [2], characterized in that the surface hardness measured according to the method described in JIS K7215 is 90A or less. [4] A method for producing a thermoplastic polyester elastomer resin foam molded article according to any one of [1] to [3], comprising: injecting the thermoplastic polyester elastomer resin composition in a molten state together with a chemical foaming agent (E) and / or an inert gas (D) in a supercritical state into a cavity of a mold consisting of a fixed mold and a movable mold that can move forward and backward to any position, and then moving the movable mold in the mold opening direction to expand the volume of the cavity and cause foaming. [5] A method for producing a thermoplastic polyester elastomer resin foam molded article according to [4], characterized in that the thermoplastic polyester elastomer resin composition in a molten state is injected and filled together with an inert gas (D) in a supercritical state. [6] The method for producing a foamed molded article of a thermoplastic polyester elastomer resin according to [4] or [5], wherein the inert gas (D) is nitrogen. [Effects of the Invention]

[0011] The thermoplastic polyester elastomer resin foam molded article of the present invention is not only lightweight but also flexible and exhibits a low rebound resilience. Furthermore, despite a high expansion ratio, it has a uniform foaming state and exhibits high heat resistance, water resistance, sound absorption properties, and molding stability, making it possible to provide a thermoplastic polyester elastomer resin foam molded article that can be used in parts that require high reliability. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will now be described.

[0013] The thermoplastic polyester elastomer resin foam molded article of the present invention comprises 20 to 95 mass % of a polyester block copolymer (A) having as its main components a high-melting-point crystalline polymer segment (a-1) mainly composed of a crystalline aromatic polyester and a low-melting-point polymer segment (a-2) mainly composed of an aliphatic polyether unit and / or an aliphatic polyester unit, and a mixture of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1), at least one compound (b-2) selected from an alkyl acrylate having an alkyl group of 1 to 4 carbon atoms and an alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms, a vinyl cyan compound ( a core-shell copolymer (B) having a core formed by emulsion polymerization of a vinyl monoalkyl ester compound (b-4) represented by the following structural formula (I) and a crosslinking agent (b-5), and a shell formed by polymerization of an aromatic vinyl compound (b-6), a vinyl cyan compound (b-3) and the crosslinking agent (b-5); and 5 to 80 mass % of a core-shell copolymer (B) having a core formed by emulsion polymerization of a vinyl monoalkyl ester compound (b-5) represented by the following structural formula (I) and a crosslinking agent (b-6), and 0 to 40 mass % of a hydrogenated styrene block copolymer (C) comprising at least one vinyl aromatic compound polymer block (c-1) and at least one conjugated diene block (c-2), the core-shell copolymer (B) having a core formed by emulsion polymerization of a vinyl monoalkyl ester compound (b-4) represented by the following structural formula (I) and a crosslinking agent (b-5), and 3 The thermoplastic polyester elastomer resin foam molded article is characterized by having an expansion ratio of 2.0 or more and a rebound resilience of 60% or less.

[0014] The polyester block copolymer (A) used in the present invention mainly comprises a high-melting crystalline segment (a-1) composed mainly of crystalline aromatic polyester units and a low-melting polymer segment (a-2) composed mainly of aliphatic polyether units and / or aliphatic polyester units. The high-melting crystalline polymer segment (a-1) 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 aromatic dicarboxylic acids 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.

[0015] The high-melting-point crystalline polymer segment (a-1) mainly uses an aromatic dicarboxylic acid, but if necessary, a portion of the aromatic dicarboxylic acid may be substituted with an alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, or 4,4'-dicyclohexyldicarboxylic acid, or an aliphatic dicarboxylic acid such as adipic acid, succinic acid, oxalic acid, sebacic acid, dodecanedioic acid, or dimer acid. Of course, ester-forming derivatives of dicarboxylic acids, such as lower alkyl esters, aryl esters, carbonate esters, and acid halides, may also be used.

[0016] Preferred diols include diols having a molecular weight of 400 or less, such as aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, and decamethylene glycol; alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, and tricyclodecane dimethanol; and aromatic diols such as xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4′-dihydroxy-p-terphenyl, and 4,4′-dihydroxy-p-quarterphenyl. These diols may also be used in the form of ester-forming derivatives, such as acetylated forms and alkali metal salts.

[0017] Two or more of these dicarboxylic acids and their derivatives or diol components may be used in combination.

[0018] The most preferred example of the high melting point crystalline polymer segment (a-1) is polybutylene terephthalate derived from terephthalic acid and / or dimethyl terephthalate and 1,4-butanediol.

[0019] The low-melting polymer segment (a-2) of the polyester block copolymer (A) used in the present invention is an aliphatic polyether and / or an aliphatic polyester. Examples of aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, ethylene oxide adducts of poly(propylene oxide) glycol, and copolymers of ethylene oxide and tetrahydrofuran. Examples of aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprylolactone, and polybutylene adipate. Among these aliphatic polyethers and / or aliphatic polyesters, poly(tetramethylene oxide) glycol, an ethylene oxide adduct of poly(propylene oxide) glycol, poly(ε-caprolactone), polybutylene adipate, etc. are preferred in view of the elastic properties of the resulting polyester block copolymers, and among these, an ethylene oxide adduct of poly(propylene oxide) glycol is particularly preferred.

[0020] The copolymerization amount of the low melting point polymer segment (a-2) in the polyester block copolymer (A) used in the present invention is usually 10 to 90 mass%, preferably 15 to 85 mass%, and more preferably 20 to 80 mass%. In particular, if it is 10 mass% or less, flexibility is insufficient, and if it is 90 mass% or more, crystallinity is low and moldability is poor.

[0021] Two or more types of polyester block copolymers having different compositions may also be used in combination.

[0022] The polyester block copolymer (A) used in the present invention can be produced by any known method, such as a method of transesterifying a lower alcohol diester of a dicarboxylic acid, an excess amount of a low-molecular-weight glycol, and a low-melting polymer segment component in the presence of a catalyst, followed by polycondensation of the resulting reaction product, a method of esterifying a dicarboxylic acid, an excess amount of a glycol, and a low-melting polymer segment component in the presence of a catalyst, followed by condensation of the resulting reaction product, a method of randomizing a high-melting crystalline segment by transesterification, a method of linking a high-melting crystalline segment and a low-melting polymer segment with a chain linking agent, or, when poly(ε-caprolactone) is used for the low-melting polymer segment, an addition reaction of ε-caprolactone monomer to the high-melting crystalline segment.

[0023] The core-shell copolymer (B) used in the present invention is a core-shell copolymer having a core polymer obtained by emulsion polymerization of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1), at least one compound (b-2) selected from alkyl acrylates having an alkyl group of 1 to 4 carbon atoms and alkyl methacrylates having an alkyl group of 1 to 4 carbon atoms, a vinyl cyanide compound (b-3), a maleic acid monoalkyl ester compound (b-4) represented by the following structural formula (I), and a crosslinking agent (b-5), and a shell polymer obtained by further polymerizing an aromatic vinyl compound (b-6), the vinyl cyanide compound (b-3), and the crosslinking agent (b-5).

[0024] Examples of the acrylic acid ester having an alkyl group with 1 to 4 carbon atoms and the methacrylic acid ester having an alkyl group with 1 to 4 carbon atoms (b-2) that constitute the core of the core-shell copolymer (B) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate, with methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate being preferred.

[0025] [ka]

[0026] (In the formula, the substituent R represents a saturated aliphatic hydrocarbon group having 10 to 24 carbon atoms, an unsaturated aliphatic hydrocarbon group, or an aromatic hydrocarbon group.) The vinyl cyanide compound (b-3) constituting the core-shell copolymer (B) used in the present invention can be acrylonitrile, methacrylonitrile, etc. The vinyl cyanide compound (b-3) used in the core and the vinyl cyanide compound (b-3) used in the shell can be the same or different, but if they are the same, the core-shell copolymer (B) can be easily obtained.

[0027] The maleic acid monoalkyl ester compound (b-4) constituting the core-shell copolymer (B) used in the present invention is represented by the structural formula (I) above. Examples of saturated aliphatic hydrocarbon groups include lauryl, undecanyl, myristyl, palmityl, heptadecanyl, stearyl, arachidyl, and behenyl groups. Examples of unsaturated aliphatic hydrocarbon groups include palmitoleic, heptadecenyl, oleyl, eicosenyl, erucyl, linoleic, and linolenic groups. Examples of aromatic hydrocarbon groups include phenylpropane, phenylsulfone, xylyl, and naphthyl groups. Examples of alkali metals include sodium and potassium.

[0028] Examples of the crosslinking agent (b-5) constituting the core-shell copolymer (B) used in the present invention include diacrylates and / or triacrylates of polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,4-butanediol, and glycerin, dimethacrylates and / or trimethacrylates of similar polyhydric alcohols, and aromatic divinyl compounds such as divinylbenzene and divinyltoluene. The crosslinking agent (b-5) used for the core and the crosslinking agent (b-5) used for the shell may be the same or different, but if they are the same, the core-shell copolymer (B) can be easily obtained.

[0029] Examples of the aromatic vinyl compound (b-6) constituting the core-shell copolymer (B) used in the present invention include styrene, α-methylstyrene, o-methylstyrene, m-methoxystyrene, and N,N-dimethyl-p-aminostyrene.

[0030] The copolymerization amount of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1) constituting the core-shell copolymer (B) used in the present invention is preferably 40 to 80% by mass per 100% by mass of the core-shell copolymer (B). If the copolymerization amount of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1) is less than 40% by mass, the flexibility of the core-shell copolymer (B) is insufficient, and the objective of the present invention to produce a flexible thermoplastic polyester elastomer resin foam molded article cannot be fully achieved. Furthermore, if the copolymerization amount of butyl acrylate alone or a mixture of 2-ethylhexyl acrylate (b-1) exceeds 80% by mass, the stickiness of the core-shell copolymer (B) becomes significant, resulting in a sticky thermoplastic polyester elastomer resin foam molded article of the present invention, which fails to achieve the desired improved handleability and pleasant feel.

[0031] In the butyl acrylate alone or the mixture (b-1) of butyl acrylate and 2-ethylhexyl acrylate that constitutes the core-shell copolymer (B) used in the present invention, the amount of 2-ethylhexyl acrylate is preferably 40% by mass or less. If the amount of 2-ethylhexyl acrylate exceeds 40% by mass, the core-shell copolymer (B) becomes significantly tacky, and the thermoplastic polyester elastomer resin foam molded article of the present invention becomes tacky, making it impossible to achieve the desired improved handleability and pleasant feel to the touch.

[0032] The shell constituting the core-shell copolymer (B) used in the present invention is preferably obtained by polymerizing 6 to 20 parts by weight of an aromatic vinyl compound (b-6), 3 to 12 parts by weight of a vinyl cyan compound (b-3), and 0.05 to 1 part by weight of a crosslinking agent (b-5) per 100 parts by weight of the core polymer. If the amount of aromatic vinyl compound (b-6) or vinyl cyan compound (b-3) constituting the shell polymer is low, the dispersion of the core-shell copolymer (B) in the polyester block copolymer (A) is poor, resulting in a significant decrease in the strength of the thermoplastic polyester elastomer resin foam molded article. Furthermore, if the amount of aromatic vinyl compound (b-6) or vinyl cyan compound (b-3) constituting the shell polymer is high, the flexibility of the core-shell copolymer (B) is insufficient, preventing the flexible thermoplastic polyester elastomer resin foam molded article, which is the objective of the present invention.

[0033] Two or more types of core-shell copolymers (B) having different compositions may be used in combination.

[0034] The core-shell copolymer (B) used in the present invention can be produced by a known two-step reaction. For example, butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1), at least one compound selected from alkyl acrylates and alkyl methacrylates with alkyl groups having 1 to 4 carbon atoms (b-2), a vinyl cyanide compound (b-3), a monoalkyl maleate (b-4), and a crosslinking agent (b-5) are placed in a reaction vessel together with a solvent such as water, a surfactant such as sodium alkylbenzenesulfonate, and a radical initiator such as di-t-butyl peroxide, and emulsion polymerization is carried out at a predetermined temperature to produce a core polymer latex. The desired core-shell copolymer can be obtained by further reaction with the core polymer latex in the reaction vessel, followed by the addition of an aromatic vinyl compound (b-6), a vinyl cyanide compound (b-3), and a crosslinking agent (b-5). The resulting latex of the core-shell copolymer (B) is added with a coagulant such as calcium chloride, and then washed and dried to isolate the core-shell copolymer (B).

[0035] The hydrogenated styrene-butadiene block copolymer (C) used in the present invention is a hydrogenated styrene-butadiene block copolymer, and the styrene-butadiene block copolymer is a diblock copolymer, triblock copolymer, radial block copolymer, or the like, each of which is composed of a styrene block and a butadiene block.

[0036] At least one vinyl aromatic compound polymer block (c-1) of the hydrogenated styrene block copolymer (C) used in the present invention is a block polymerized from styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, pt-butylstyrene, o-ethylstyrene, o,p-dichlorostyrene, etc., and among these, styrene is preferably used.

[0037] At least one conjugated diene block (c-2) of the hydrogenated styrene block copolymer (C) used in the present invention is a block polymerized from butadiene, isoprene, butadiene / isoprene copolymer, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene, or the like, and among these, styrene-butadiene block copolymers, styrene-isoprene block copolymers, and styrene-isoprene / butadiene block copolymers are preferably used.

[0038] The hydrogenated styrene block copolymer (C) may be modified with an unsaturated carboxylic acid or its anhydride, or an epoxy group-containing monomer. Specific examples include modified styrene-hydrogenated butadiene diblock copolymers and modified styrene-hydrogenated butadiene-styrene triblock copolymers (modified styrene-ethylene-butylene-styrene block copolymers: modified SEBS).

[0039] Furthermore, two or more types of hydrogenated styrene-butadiene block copolymers (C) having different compositions may be used.

[0040] The blending ratios of the respective components in the thermoplastic polyester elastomer resin composition of the present invention are 20 to 95% by mass, more preferably 20 to 90% by mass, preferably 25 to 85% by mass, and even more preferably 30 to 80% by mass of the polyester block copolymer (A), 5 to 80% by mass, preferably 5 to 75% by mass of the core-shell copolymer (B), and 0 to 40% by mass, preferably 0 to 25% by mass of the hydrogenated styrene block copolymer (C). The hydrogenated styrene block copolymer (C) is an optional component.

[0041] If the content of the polyester block copolymer (A) is less than 20% by mass, the melt tension of the thermoplastic polyester polymer decreases, and the cells tend to break, resulting in the formation of coarse cells. If the content exceeds 95% by mass, flexibility is lost.

[0042] If the core-shell copolymer (B) is less than 5% by mass, sufficient flexibility cannot be obtained. If it exceeds 80% by mass, the melt tension of the thermoplastic polyester polymer decreases, making the bubbles more likely to break and forming coarse cells.

[0043] When the hydrogenated styrene block copolymer (C) is used, if it exceeds 40% by mass, the melt tension of the thermoplastic polyester polymer decreases, and the cells tend to break, resulting in the formation of coarse cells.

[0044] In the thermoplastic polyester elastomer resin composition of the present invention, the surface hardness measured according to the method described in JIS K7215 is preferably 90A or less, more preferably 80A or less.

[0045] The thermoplastic polyester elastomer of the present invention may optionally contain or exclude any of the following, provided that the properties of the thermoplastic polyester elastomer are not impaired: known hindered phenol-based, phosphite-based, thioether-based, aromatic amine-based antioxidants; benzophenone-based, benzotriazole-based, hindered amine-based light stabilizers; epoxy compounds; isocyanate compounds; colorants; dyes; pigments; ultraviolet screeners; glass fiber; carbon fiber; potassium titanate fiber; fillers;

[0046] The thermoplastic polyester elastomer resin foam molded article of the present invention is obtained using the thermoplastic polyester elastomer resin composition of the present invention described above. The thermoplastic polyester elastomer resin foam molded article of the present invention has a non-foamed skin layer on the surface and a foamed layer on the inner layer. Because the non-foamed skin layer and the foamed layer are formed from the thermoplastic polyester elastomer resin composition of the present invention described above, the article has a foam structure with uniform and fine foam cells, and exhibits excellent lightness, low resilience, and flexibility. The foamed layer is composed of a resin continuous phase and independent foam cells. Here, the resin continuous phase refers to the non-void portion formed by the cured polyester elastomer resin composition.

[0047] The diameter (cell diameter) of the foam cells of the thermoplastic polyester elastomer resin foam molded article of the present invention varies in properties depending on the size, as long as it is uniform and without variation. A smaller cell diameter is advantageous for achieving flexibility and low impact resilience, and specifically, an average cell diameter of 10 to 600 μm is preferred. If the average cell diameter is less than 10 μm, the internal pressure of the foam molded article will be low, resulting in insufficient pressure during the formation of the non-foamed skin layer, and this will tend to result in poor appearance, such as sink marks. On the other hand, if the average cell diameter exceeds 600 μm, the tensile strength will be low and the mechanical properties will tend to be poor.

[0048] The density (apparent density) of the thermoplastic polyester elastomer resin foam molded article of the present invention is 0.70 g / cm 3 The density of a typical polyester elastomer is approximately 1.0 to 1.4 g / cm 3 Therefore, it can be said that the foamed molded article of the present invention is sufficiently lightweight. 3 If it exceeds this, sufficient flexibility is not obtained.

[0049] The thermoplastic polyester elastomer resin expansion molded article of the present invention is characterized in that its rebound resilience is 60% or less, more preferably 50% or less. If the rebound resilience exceeds 60%, the rebound force is large and sufficient impact absorption cannot be obtained.

[0050] The thermoplastic polyester elastomer resin foam molded article of the present invention is characterized by having foam cells and an expansion ratio of 2.0 or more. If the expansion ratio is less than 2.0, the foam molded article will have insufficient low-resilience modulus and light weight. An expansion ratio of 4 or more is more preferable. Furthermore, from the viewpoint of extensibility for forming the edge surface of the foam molded article faithfully to the mold, an expansion ratio of 6 or less is preferable.

[0051] The thermoplastic polyester elastomer resin foam molded article of the present invention preferably has a normal incidence sound absorption coefficient at the sound absorption peak frequency (hereinafter sometimes referred to as "peak frequency sound absorption coefficient") of 0.3% or more, more preferably 0.4% or more, even more preferably 0.5% or more, and particularly preferably 0.6% or more, measured in the frequency range of 0.4 kHz to 5.0 kHz, which is the main frequency range that generally causes noise problems, according to a method in accordance with JIS A1405 (2007). The peak frequency sound absorption coefficient can be measured, for example, using a normal incidence sound absorption coefficient measurement system, WinZacMTX, manufactured by Nihon Onkyo Engineering Co., Ltd.

[0052] The sound absorption peak frequency is preferably 0.4 kHz to 4.0 kHz, more preferably 0.4 kHz to 3.5 kHz, even more preferably 0.4 kHz to 3.0 kHz, particularly preferably 0.4 kHz to 2.5 kHz, and most preferably 0.4 kHz to 2.0 kHz. The thermoplastic polyester elastomer resin expansion molded product of the present invention preferably has the sound absorption peak frequency in the low frequency range.

[0053] Here, the expansion ratio in the present invention is calculated from the density of the thermoplastic polyester elastomer resin composition before foaming / the density of the thermoplastic polyester elastomer resin foam-molded product. The density of the thermoplastic polyester elastomer resin composition before foaming and the density of the thermoplastic polyester elastomer resin foam-molded product can be determined according to ASTM D792.

[0054] The foaming method for the foamed molded article of the present invention is not particularly limited, but a foaming method in which a resin composition is impregnated with a high-pressure gas and then the pressure is reduced (the pressure is released) is preferred. Among these, a method in which a foamed molded article is obtained by melt-mixing a foaming agent and the polyester elastomer resin composition of the present invention and then injection-molding the mixture to expand the volume of the cavity is preferred, as this molding method is advantageous in terms of molding cycle time, cost, and homogeneous foaming.

[0055] Specifically, a molten thermoplastic polyester elastomer resin composition is injected into a cavity formed by a mold consisting of multiple clamped fixed molds and a movable mold that can move forward and backward to any position, together with a chemical foaming agent (E) and / or a supercritical inert gas (D), to fill the cavity, and once a non-foamed skin layer is formed, at least one movable mold is moved in the mold opening direction to expand the cavity volume and cause foaming, thereby obtaining a thermoplastic polyester elastomer resin foam molded article. Among these, the use of a supercritical inert gas (D) is preferred.

[0056] The distance traveled in the mold opening direction is the core-back amount, and adjusting the core-back amount allows for the desired thickness of the foamed molded article to be adjusted. Furthermore, during foam molding, the molding temperature, cooling time, the time from when the thermoplastic polyester elastomer resin composition is filled into the mold cavity until it is core-backed (core-back delay time), and the time from the start of core-backing to its completion (core-back transition time) can be appropriately adjusted depending on the material to obtain an optimal foamed molded article. The thermoplastic polyester elastomer resin composition for foam molding, the chemical blowing agent (E) and / or the supercritical inert gas (D) can be mixed in the plasticization zone of the injection molding machine before filling the cavity.

[0057] The chemical foaming agent (E) that can be used to obtain the foamed molded article of the present invention is added to the molten resin in the resin melting zone of the molding machine as a gas component or source of gas that becomes foam nuclei. Specifically, the chemical foaming agent (E) may be inorganic compounds such as ammonium carbonate and sodium bicarbonate, or organic compounds such as azo compounds, sulfohydrazide compounds, nitroso compounds, and azide compounds.

[0058] Examples of the azo compounds include diazocarbonamide (ADCA), 2,2-azoisobutyronitrile, azohexahydrobenzonitrile, and diazoaminobenzene, among which ADCA is preferred. Examples of the sulfohydrazide compounds include benzenesulfohydrazide, benzene-1,3-disulfohydrazide, diphenylsulfone-3,3-disulfonhydrazide, and diphenyloxide-4,4-disulfonhydrazide. Examples of the nitroso compounds include N,N-dinitrosopentaethylenetetramine (DNPT), and examples of the azide compounds include terephthalazide and p-tert-butylbenzazide.

[0059] Chemical blowing agents (E) produce a variety of gases. For example, diazocarbonamide (ADCA) produces mainly nitrogen, carbon monoxide, and carbon dioxide as thermal decomposition products, along with trace amounts of ammonia gas. Biurea, cyanuric acid, and urazole may also remain as decomposition residues. These thermal decomposition products and decomposition residues can be identified using pyrolysis gas chromatography, infrared spectroscopy, and mass spectrometry.

[0060] When using a chemical blowing agent (E), the chemical blowing agent (E) can be used as a blowing agent masterbatch based on a thermoplastic resin having a melting point lower than the decomposition temperature of the thermally decomposable blowing agent to ensure uniform dispersion in the thermoplastic polyester elastomer of the present invention. The base thermoplastic resin is not particularly limited as long as it has a melting point lower than the decomposition temperature of the chemical blowing agent (E), and examples include polystyrene (PS), polyethylene (PE), and polypropylene (PP). In this case, the blending ratio of the chemical blowing agent (E) to the thermoplastic resin is preferably 10 to 100 parts by mass of the thermally decomposable blowing agent per 100 parts by mass of the thermoplastic resin. If the chemical blowing agent (E) is used in an amount less than 10 parts by mass, the amount of masterbatch relative to the thermoplastic polyester elastomer of the present invention may be too large, potentially resulting in a deterioration in physical properties. If the amount exceeds 100 parts by mass, masterbatch formation becomes difficult due to issues with the dispersibility of the chemical blowing agent (E).

[0061] Other additives can be used with these chemical foaming agents (E) as needed. For example, to stabilize and uniformly fine the cells in the foamed molded article, organic acids such as citric acid, which promote gas generation, and metal salts of organic acids such as sodium citrate can be used or added in combination. Nucleating agents such as inorganic fine particles such as talc and lithium carbonate can also be added. Particularly preferred are sodium bicarbonate, a combination of sodium bicarbonate and sodium citrate, and a combination of sodium bicarbonate and citric acid.

[0062] The amount of the chemical blowing agent (E) in the thermoplastic polyester elastomer resin composition of the present invention is preferably 1.0 to 5.0 parts by mass, and more preferably 1.0 to 3.5 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin composition. If the amount of the chemical blowing agent (E) is 1.0 part by mass or less, foaming performance may be poor, while if it exceeds 5.0 parts by mass, the amount of foaming gas becomes excessive, and the bubbles tend to interfere with each other, resulting in the formation of open cells, which may result in a non-uniform foam.

[0063] The supercritical inert gas (D) is not particularly limited as long as it can be dissolved in the thermoplastic polyester elastomer resin composition and is inactive, but carbon dioxide and nitrogen are preferred from the standpoints of safety and cost. The supercritical inert gas (D) is preferably used in an amount of 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, per 100 parts by mass of the thermoplastic polyester elastomer resin composition.

[0064] The supercritical inert gas (D) is preferably impregnated into the molten thermoplastic polyester elastomer resin composition in a kneader. Examples of methods include injecting the gaseous supercritical inert gas (D) directly or under pressure or pressure into the kneader, or injecting the liquid supercritical inert gas (D) into the kneader using a plunger pump or the like. When impregnating the thermoplastic polyester elastomer resin with the supercritical inert gas (D), the gas pressure is maintained at or above the critical pressure of the supercritical inert gas (D) to be impregnated, at least until the thermoplastic polyester elastomer resin composition is filled into the mold. To further improve the impregnation rate, the gas pressure is preferably 1 MPa or higher, more preferably 5 MPa or higher.

[0065] As the supercritical inert gas (D), carbon dioxide or nitrogen can be used alone, but a mixture of carbon dioxide and nitrogen may also be used. Nitrogen tends to be suitable for forming finer closed cells in thermoplastic polyester elastomer compositions, while carbon dioxide is suitable for achieving a higher expansion ratio because it allows for a larger amount of gas to be injected.

[0066] As the inert gas (D) in a supercritical state used in the present invention, nitrogen is more preferred from the viewpoint of forming closed cells having uniform and preferable cell diameters of 10 to 600 μm.

[0067] To inject the molten thermoplastic polyester elastomer composition into the cavity together with the chemical blowing agent (E) and / or the inert gas (D) in a supercritical state, the molten thermoplastic polyester elastomer composition and the chemical blowing agent (E) and / or the inert gas (D) in a supercritical state may be mixed in the plasticizing zone of the injection molding machine. When using a chemical blowing agent (E), it is desirable to mix it with the thermoplastic polyester elastomer pellets in advance.

[0068] When supercritical carbon dioxide and / or nitrogen are used, for example, a method can be employed in which gaseous carbon dioxide and / or nitrogen are injected into the injection molding machine directly from a gas cylinder or after being pressurized by a booster pump. The carbon dioxide and / or nitrogen must be in a supercritical state inside the injection molding machine from the viewpoint of solubility, permeability, and diffusibility in the molten thermoplastic polyester elastomer composition.

[0069] Here, the term "supercritical state" refers to a state in which, when the temperature and pressure of a substance that exists in a gas phase and a liquid phase are increased, the distinction between the gas phase and the liquid phase can be eliminated within a certain temperature and pressure range, and the temperature and pressure at this time are called the critical temperature and critical pressure. That is, in a supercritical state, a substance has the properties of both a gas and a liquid, and the fluid that occurs in this state is called a critical fluid. Such a critical fluid has a higher density than a gas and a lower viscosity than a liquid, and therefore has the property of being extremely easy to diffuse within a substance. [Example]

[0070] The effects of the present invention will be explained below with reference to examples. In the examples, all parts are by mass unless otherwise specified. The physical properties shown in the examples were measured as follows.

[0071] [Density (Apparent Density)] The obtained foamed molded article was cut into a rectangular parallelepiped, the dimensions of which were measured with a vernier caliper, and the mass was measured with an electronic balance and calculated using the following formula. Density (g / cm 3) = mass of specimen / volume of specimen.

[0072] [Expansion ratio] The density of the thermoplastic polyester elastomer resin foam molded product sample was divided by the density of the thermoplastic polyester elastomer resin composition, and the value rounded to one decimal place was used as the expansion ratio. The density of the thermoplastic polyester elastomer resin composition before foaming and the density of the thermoplastic polyester elastomer resin foam molded product were determined according to ASTM D792.

[0073] [Average cell diameter] Observations were made using a JEOL scanning electron microscope (FE-SEM). 100 voids (foam cells) were randomly selected, and the equivalent circle diameter of adjacent foam cells was measured with a vernier caliper. The average of these 100 voids was calculated, and this was repeated at three random locations within the foamed molded sample. The average of these three average values ​​was then used as the average cell diameter.

[0074] [Tensile strength] The obtained foamed molded sample was cut into a JIS K7113 No. 2 dumbbell test piece shape using a punching blade, and measurements were carried out in accordance with JIS K7113 (1995 edition).

[0075] [Rebound elasticity] The obtained foamed molded samples were cut into 8 x 50 mm strips and measured in accordance with BS903. Using a Tripso type rebound resilience tester, a hammer was dropped onto the test piece from a specified angle and the maximum rebound angle was read. Three measurements were taken, and the median value was calculated to calculate the rebound resilience.

[0076] [Sound absorption peak frequency and peak frequency sound absorption coefficient] The obtained foamed molded articles were cut into circular shapes with a diameter of 39.5 mm using a punching blade, and the normal incidence sound absorption coefficient in the frequency range of 0.4 kHz to 5.0 kHz was measured for each of Examples 1 to 8 and Comparative Examples 1 to 4 using a normal incidence sound absorption coefficient measurement system, WinZacMTX, manufactured by Nippon Engineering Co., Ltd., in accordance with JIS A1405 (2007). The lowest frequency peak was taken as the sound absorption peak, and this frequency was read as the sound absorption peak frequency. The normal incidence sound absorption coefficient at this sound absorption peak frequency was taken as the peak frequency sound absorption coefficient.

[0077] [Compounds used in the examples] [Production of Thermoplastic Polyester Elastomer (A-1)] 273 parts of dimethyl terephthalate, 120 parts of 1,4-butanediol, and 723 parts of poly(tetramethylene oxide) glycol with a number-average molecular weight of approximately 2000 were charged into a reaction vessel equipped with a helical ribbon impeller, along with 3 parts of titanium tetrabutoxide and 3 parts of trimellitic anhydride, and heated at 210°C for 2 hours and 30 minutes, distilling 95% of the theoretical amount of methanol out of the system. After adding 0.5 parts of "Irganox" 1330 (a hindered phenol-based antioxidant manufactured by Ciba-Geigy), the reaction mixture was heated to 245°C, and the pressure in the system was reduced to 27 Pa over 50 minutes. Polymerization was carried out under these conditions for 1 hour and 50 minutes. The resulting polymer was extruded into water in the form of strands and cut into pellets.

[0078] [Production of Thermoplastic Polyester Elastomer (A-2)] 340 parts of terephthalic acid, 100 parts of isophthalic acid, 394 parts of 1,4-butanediol, and 495 parts of poly(tetramethylene oxide) glycol with a number-average molecular weight of approximately 1400 were charged into a reaction vessel equipped with a helical ribbon impeller along with 2 parts of titanium tetrabutoxide. The mixture was heated at 190-225°C for 3 hours to carry out an esterification reaction while distilling off the reaction water. After adding 0.5 parts of "Irganox" 1098 (a hindered phenol antioxidant manufactured by Ciba-Geigy), the reaction mixture was heated to 245°C, and the pressure in the system was reduced to 27 Pa over 50 minutes. Polymerization was carried out under these conditions for 2 hours and 45 minutes. The resulting polymer was extruded into water in the form of strands and cut into pellets.

[0079] [Production of Thermoplastic Polyester Elastomer (A-3)] 348 parts of terephthalic acid, 340 parts of 1,4-butanediol, and 645 parts of poly(tetramethylene oxide) glycol with a number-average molecular weight of approximately 1400 were charged into a reaction vessel equipped with a helical ribbon impeller along with 0.2 parts of titanium tetrabutoxide. The mixture was heated at 190-225°C for 3 hours to carry out an esterification reaction while distilling off the reaction water. After adding 0.5 parts of "Irganox" 1098 (a hindered phenol-based antioxidant manufactured by Ciba-Geigy), the reaction mixture was heated to 245°C. The pressure in the system was then reduced to 27 Pa over 50 minutes, and polymerization was carried out under these conditions for 2 hours and 45 minutes. The resulting polymer was extruded into water in the form of strands and cut into pellets.

[0080] [Preparation of core-shell copolymer (B)] A reactor was charged with 37.3 kg of water, 0.46 kg of hexadecyl maleate, 0.16 kg of a 50% aqueous solution of potassium hydroxide, 0.031 kg of sodium dodecylbenzenesulfonate, 9 kg of butyl acrylate, 2.6 kg of methyl acrylate, 1.3 kg of acrylonitrile, 0.19 kg of 1,4-butanediol dimethacrylate, 0.039 kg of t-dodecyl mercaptan, and 0.029 kg of potassium persulfate. The mixture was reacted at 60°C for 2 hours and 30 minutes to obtain a latex of the core polymer. Furthermore, 301.7 kg of styrene, 0.74 kg of acrylonitrile, 0.025 kg of divinylbenzene, and 0.005 kg of t-dodecyl mercaptan were added to the reactor, and the reaction was continued to obtain the core-shell copolymer (B). The resulting latex of the core-shell copolymer (B) was then broken down by salting out, washed, dried, and powdered.

[0081] [Hydrogenated styrene block copolymer (C)] Hydrogenated styrene-butadiene-styrene block copolymer (SEBS) "Tuftec" H1272 manufactured by Asahi Kasei Corporation.

[0082] [Supercritical inert gas (D)] nitrogen.

[0083] [Chemical foaming agent (E)] Sankyo Kasei Co., Ltd.'s "Cellmic Masterbatch" 1023 (containing 30% by mass of the thermal decomposition type foaming agent azodicarbonamide (ADCA)).

[0084] Examples 1 to 8, Comparative Examples 1 to 4 According to the compounding compositions shown in Table 1, various components were melt-kneaded with a thermoplastic polyester elastomer using a twin-screw extruder, and then pelletized to obtain pellets of Examples 1-8 and Comparative Examples 1-4.

[0085] Next, a foam molded article was produced using the mold expansion method described above. The mold used was a flat plate production mold consisting of a fixed mold and a movable mold, which could form a cavity with a width of 150 mm, a length of 150 mm, and a thickness of 2 mm when clamped, and which could form a cavity with the same width and length but a thickness of 2 mm + the core-back amount (mm) when cored back in the mold opening direction.

[0086] Specifically, using a Japan Steel Works, Ltd. J110AD-180H-MuCell injection molding machine, pellets of the resulting thermoplastic polyester elastomer were mixed with a chemical blowing agent (E) and / or a supercritical inert gas (nitrogen gas) (D) in the plasticizing zone of the injection molding machine. The mixture was then injected into a mold controlled at a surface temperature of 50°C. After the non-foamed skin layer was formed by external injection pressure and internal foaming pressure, the operating mold was moved in the mold opening direction by the core-back distance (mm) listed in Table 1 to expand the cavity volume and produce a foamed molded article. The properties of the resulting foams were investigated, and the results are shown in Table 1. The chemical blowing agent (E) was dry-blended with the pellets in advance, and the supercritical inert gas (nitrogen gas) (D) was injected into the injection molding machine by pressurizing gaseous nitrogen from a gas cylinder using a booster pump.

[0087] [Table 1]

[0088] From the above results, the thermoplastic polyester elastomers shown in Examples 1 to 8 have a density of 0.70 g / cm 3 It is highly lightweight with a surface hardness of less than 75A, is flexible, and has a rebound resilience of less than 60%.

[0089] Comparative Examples 1 and 2, which are thermoplastic polyester elastomer resin expansion molded articles constituted only of polyester block copolymer (A), have high impact resilience.

[0090] Furthermore, in Comparative Example 3, in which the part by mass of the core-shell copolymer (B) was large, a foamed molded article with a high expansion ratio exceeding 2.0 could not be obtained. In Comparative Example 4, in which the part by mass of the hydrogenated styrene block copolymer (C) was large, the average cell diameter became large, and a foamed molded article with the target average cell diameter could not be obtained.

[0091] Furthermore, in all of Examples 1 to 8 and Comparative Examples 1 and 2, the sound absorption peak frequency was 0.4 kHz to 5.0 kHz, and the peak frequency sound absorption coefficient was 0.3% or more. It can be seen that, compared to Comparative Examples 1 and 2, which are thermoplastic polyester elastomer resin foam molded articles composed only of polyester block copolymer (A), Examples 1 to 4 and Example 7, which are composed of polyester block copolymer (A) and core-shell copolymer (B), and Examples 5 to 8, which are composed of polyester block copolymer (A), core-shell copolymer (B), and hydrogenated styrene block copolymer (C), show no significant differences in sound absorption peak frequency or peak frequency sound absorption coefficient. Comparative Example 3 has a low expansion ratio, resulting in a high proportion of the skin layer inside the foam molded article, and therefore a low peak frequency sound absorption coefficient of 0.3% or less. Furthermore, Comparative Example 4, due to its large cell diameter, exhibited a low peak frequency sound absorption coefficient of 0.3% or less.

Claims

1. The polyester block copolymer (A) mainly comprises a high-melting crystalline segment (a-1) composed of a crystalline aromatic polyester unit and a low-melting polymer segment (a-2) composed of an aliphatic polyether unit and / or an aliphatic polyester unit, and the polyester block copolymer (A) is mixed with 20 to 95% by mass of butyl acrylate alone or a mixture of butyl acrylate and 2-ethylhexyl acrylate (b-1), at least one compound (b-2) selected from an alkyl acrylate having an alkyl group of 1 to 4 carbon atoms and an alkyl methacrylate having an alkyl group of 1 to 4 carbon atoms, a vinyl cyan compound (b-3), and a copolymer represented by the following structural formula (I): and a thermoplastic polyester elastomer resin composition comprising 5 to 80 mass% of a core-shell copolymer (B) having a core formed by emulsion polymerization of a maleic acid monoalkyl ester compound (b-4) and a crosslinking agent (b-5), and a shell formed by polymerization of an aromatic vinyl compound (b-6), a vinyl cyan compound (b-3), and a crosslinking agent (b-5); and 0 to 40 mass% of a hydrogenated styrene block copolymer (C) comprising at least one vinyl aromatic compound polymer block (c1) and at least one conjugated diene block (c2), the copolymer having foam cells and a density (apparent density) of 0.70 g / cm. ３ 1. A thermoplastic polyester elastomer resin foam molded article having an expansion ratio of 2.0 or more and a rebound resilience of 60% or less.

2. 2. The thermoplastic polyester elastomer resin foam molded article according to claim 1, wherein the foam cells have an average cell diameter of 10 to 600 μm.

3. 3. The thermoplastic polyester elastomer resin foam molded article according to claim 1, wherein the surface hardness measured in accordance with the method described in JIS K7215 is 90A or less.

4. 4. A method for producing the thermoplastic polyester elastomer resin foam molded article according to claim 1, comprising: injecting the thermoplastic polyester elastomer resin composition in a molten state together with a chemical foaming agent (E) and / or an inert gas (D) in a supercritical state into a cavity of a mold comprising a fixed mold and a movable mold that can move forward and backward to any position, and then moving the movable mold in a mold opening direction to expand the volume of the cavity and cause foaming.

5. 5. The method for producing a thermoplastic polyester elastomer resin foam molded article according to claim 4, wherein the thermoplastic polyester elastomer resin composition in a molten state is injected and filled together with an inert gas (D) in a supercritical state.

6. 6. The method for producing a foamed molded article of a thermoplastic polyester elastomer resin according to claim 4, wherein the inert gas (D) is nitrogen.

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