Thermoplastic elastomer composition and molded body comprising said composition

Abstract

The present invention is a thermoplastic elastomer composition containing (a) a thermoplastic elastomer, (b) a polyphenyline ether resin, and (c) a rubber softening agent, wherein: (a) includes (a1) and (a2) at a mass ratio of 90:10 to 45:55, (a1) being a block copolymer comprising a polymer block (X1) and a polymer block (Y1) and having a specific weight average molecular weight and a specific aromatic vinyl compound-derived structural unit content; (a2) is a block copolymer comprising a polymer block (X2) and a polymer block (Y2) and has a specific weight average molecular weight, a specific aromatic vinyl compound-derived structural unit content, and a specific vinyl binding content; the maximum long diameter of (b) dispersed in the matrix phase including (a) is 2 µm or less in a transmission electron microscopic image of the composition; and a JIS K 6253-compliant hardness (A) of the composition is 80 or less.

Description

Thermoplastic elastomer composition and molded article made of said composition

[0001] The present invention relates to a thermoplastic elastomer composition and a molded article made of the thermoplastic elastomer composition.

[0002] Conventionally, vulcanized rubbers such as silicone rubber, butyl rubber, and ethylene propylene diene rubber (EPDM) have been widely used as materials for vibration-damping members used in various industrial equipment, consumer equipment, automobiles, etc. In recent years, the use of styrene-based thermoplastic elastomers has been proposed for the purposes of environmental friendliness and cost reduction, but styrene-based thermoplastic elastomers have the problem of insufficient heat resistance.

[0003] To solve this problem, compositions have been proposed that incorporate polyphenylene ether to enhance heat resistance. For example, Patent Document 1 discloses a heat-resistant, vibration-damping elastomer composition comprising a hydrogenated thermoplastic styrene-based elastomer [I] or an elastomer mixture of a hydrogenated thermoplastic styrene-based elastomer [I] and a hydrogenated thermoplastic styrene-based elastomer [II], a filler, a rubber softener, polyphenylene ether, and polypropylene, and describes that the composition has excellent heat resistance and vibration-damping properties. Furthermore, Patent Document 2 discloses a thermoplastic elastomer composition comprising a hydrogenated block copolymer, a polypropylene-based resin, a polyphenylene ether resin, and a non-aromatic softener, and describes that the resin composition has excellent compression set and permanent elongation set.

[0004] JP 2010-24275 A International Publication No. 2018 / 139122 A

[0005] However, the inventors' investigations have revealed that the heat-resistant, vibration-damping elastomer composition disclosed in Patent Document 1 has poor restoring force and insufficient heat resistance. Furthermore, the thermoplastic elastomer composition disclosed in Patent Document 2 has poor vibration-damping properties and insufficient heat resistance. In view of the problems of the prior art described above, an object of the present invention is to provide a thermoplastic elastomer composition that is excellent in vibration-damping properties, restoring properties, and heat resistance. Another object of the present invention is to provide a thermoplastic elastomer composition that has an appropriate hardness.

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems, and have completed the present invention. That is, the present invention includes the following preferred embodiments: [1] A thermoplastic elastomer composition comprising: (a) a thermoplastic elastomer; (b) a polyphenylene ether resin; and (c) a rubber softener, wherein the thermoplastic elastomer (a) comprises a thermoplastic elastomer (a1) and a thermoplastic elastomer (a2) in a mass ratio of 90:10 to 45:55; the thermoplastic elastomer (a1) is a block copolymer comprising a polymer block (X1) composed of structural units derived from an aromatic vinyl compound and a polymer block (Y1) composed of structural units derived from a conjugated diene compound, and has a weight-average molecular weight of more than 150,000 and not more than 500,000; the content of the structural units derived from the aromatic vinyl compound in the thermoplastic elastomer (a1) is 10 mass% or more based on all structural units constituting the thermoplastic elastomer (a1); The thermoplastic elastomer (a2) is a block copolymer comprising a polymer block (X2) comprising structural units derived from an aromatic vinyl compound and a polymer block (Y2) comprising structural units derived from a conjugated diene compound, and has a weight average molecular weight of 50,000 or more and 150,000 or less, the content of structural units derived from aromatic vinyl compounds in the thermoplastic elastomer (a2) is 2 mass% or more based on all structural units constituting the thermoplastic elastomer (a2), and the total content of 1,2-bond units and 3,4-bond units of structural units derived from conjugated diene compounds in the thermoplastic elastomer (a2) is 50 mol% or more based on all structural units derived from conjugated diene compounds, in a transmission electron microscope image of the thermoplastic elastomer composition, the maximum major axis of the polyphenylene ether resin (b) dispersed in a matrix phase containing the thermoplastic elastomer (a) is 2 μm or less, and three 2 mm thick test pieces obtained by injection molding the thermoplastic elastomer composition at 230°C are stacked and subjected to a JIS K 6253, having a hardness of 80 or less after 3 seconds using a Type A durometer.[2] The composition according to [1] above, wherein the hydrogenation rate of the polymer block (Y2) of the thermoplastic elastomer (a2) is 20% or less. [3] The composition according to [1] or [2] above, wherein the thermoplastic elastomer (a2) has an order-disorder transition temperature of 280°C or less. [4] The composition according to any one of [1] to [3] above, comprising 5 to 100 parts by mass of a polyphenylene ether resin (b) and 50 to 300 parts by mass of a rubber softener (c) per 100 parts by mass of the thermoplastic elastomer (a). [5] The composition according to any one of [1] to [4] above, further comprising a polypropylene (d). [6] The composition according to any one of [1] to [5] above, further comprising an inorganic filler (e). [7] The composition according to any one of [1] to [6], which has a compression set of 50% or less after being subjected to a 25% compressive deformation at 70°C for 22 hours in accordance with JIS K 6262: 2013. [8] A molded article made of the composition according to any one of [1] to [7].

[0007] According to the present invention, it is possible to provide a thermoplastic elastomer composition which is excellent in vibration damping properties, recovery properties and heat resistance, and has an appropriate hardness.

[0008] 1 is a transmission electron microscope image used to determine the maximum major axis of the polyphenylene ether resin (b) of the thermoplastic elastomer composition prepared in Example 2. FIG. 2 is a transmission electron microscope image used to determine the maximum major axis of the polyphenylene ether resin (b) of the thermoplastic elastomer composition prepared in Comparative Example 3.

[0009] The thermoplastic elastomer composition of the present invention comprises: (a) a thermoplastic elastomer; (b) a polyphenylene ether resin; and (c) a rubber softener.

[0010] In a transmission electron microscope image of the thermoplastic elastomer composition of the present invention, the polyphenylene ether resin (b) dispersed in the matrix phase containing the thermoplastic elastomer (a) has a maximum major axis of 2 μm or less. The inventors unexpectedly discovered that by including the components (a) to (c) in the thermoplastic elastomer composition, the polyphenylene ether resin (b) can be dispersed to a higher degree in the thermoplastic elastomer composition than in thermoplastic elastomer compositions of the prior art. As a result, the thermoplastic elastomer composition can exhibit excellent vibration damping, recovery, and heat resistance. In particular, it was surprising that the thermoplastic elastomer composition can exhibit excellent heat resistance despite including a low-molecular-weight thermoplastic elastomer (thermoplastic elastomer (a2)), which is known to have poor heat resistance. Although the reason for this is not clear, the following mechanism of action is thought to be a non-limiting example: as will be described later, a thermoplastic elastomer (a2) having a specific molecular structure and weight-average molecular weight can selectively disperse (become miscible with) the polyphenylene ether resin (b) in the polymer block (X2) of the thermoplastic elastomer (a2) in the thermoplastic elastomer composition. As a result, the compatibility of the polyphenylene ether resin (b) with the polymer block (X2) and the compatibility of the polyphenylene ether resin (b) with the polymer block (X2) and the polymer block (X1) can be improved, i.e., the compatibility of the polyphenylene ether resin (b) with the thermoplastic elastomer (a1) and the thermoplastic elastomer (a2). As a result, it is thought that the obtained thermoplastic elastomer composition is endowed with high heat resistance in addition to excellent vibration damping properties and recovery properties.

[0011] In a transmission electron microscope image of the thermoplastic elastomer composition, the maximum major axis of the polyphenylene ether resin (b) dispersed in the matrix phase is preferably 1 μm or less, more preferably 0.5 μm or less. A smaller maximum major axis of the polyphenylene ether resin (b) indicates a higher degree of dispersion of the polyphenylene ether resin (b), so there is no lower limit for the maximum major axis of the polyphenylene ether resin (b). The lower limit for the maximum major axis of the polyphenylene ether resin (b) dispersed in the matrix phase corresponds to the detection limit in a transmission electron microscope image of the thermoplastic elastomer composition at a magnification of 10,000 times, and is typically 0.0001 μm or more. In a preferred embodiment, the polyphenylene ether resin (b) is dispersed in the matrix phase to such a high degree that it is difficult to clearly identify it as polyphenylene ether resin (b) in a transmission electron microscope image. In this embodiment, the polyphenylene ether resin (b) dispersed in the matrix phase has a maximum major axis of 2 μm or less, preferably 1 μm or less, and more preferably 0.5 μm or less in a transmission electron microscope image. The maximum major axis of the polyphenylene ether resin (b) dispersed in the matrix phase in a transmission electron microscope image of the thermoplastic elastomer composition can be measured by the method described in the Examples below. In a preferred embodiment, the matrix phase contains a rubber softener (c) in addition to the thermoplastic elastomer (a).

[0012] The desired maximum major axis of the polyphenylene ether resin (b) dispersed in the matrix phase can be adjusted to the above upper limit or less by including the specific component (a) and components (b) and (c) in the thermoplastic elastomer composition.

[0013] The thermoplastic elastomer (a) comprises a thermoplastic elastomer (a1) and a thermoplastic elastomer (a2) in a mass ratio of 90:10 to 45:55. If the amount of thermoplastic elastomer (a1) is too large and the mass ratio deviates from the range of 90:10 to 45:55, it is difficult to obtain the desired vibration-damping properties and heat resistance. On the other hand, if the amount of thermoplastic elastomer (a1) is too small and the mass ratio deviates from the range of 90:10 to 45:55, it is difficult to obtain the desired heat resistance. From the viewpoints of vibration damping properties, heat resistance, moldability, and the like, the mass ratio is preferably 90:10 to 50:50, more preferably 90:10 to 55:45, even more preferably 90:10 to 60:40, or preferably 85:15 to 45:55, more preferably 85:15 to 50:50, even more preferably 85:15 to 55:45, particularly preferably 85:15 to 60:40, or preferably 80:20 to 45:55, more preferably 80:20 to 50:50, even more preferably 80:20 to 55:45, particularly preferably 80:20 to 60:40, or preferably 75:25 to 45:55, more preferably 75:25 to 50:50, even more preferably 75:25 to 55:45, and particularly preferably 75:25 to 60:40.

[0014] <Thermoplastic elastomer (a1)> The thermoplastic elastomer (a1) is a block copolymer comprising a polymer block (X1) comprising structural units derived from an aromatic vinyl compound and a polymer block (Y1) comprising structural units derived from a conjugated diene compound. Hereinafter, the thermoplastic elastomer (a1) is also referred to as a "block copolymer (a1)." In this specification, the term "polymer block comprising structural units" means that the structural units are present in the largest amount in the polymer block. The content of the structural units in the polymer block is preferably 70% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, based on the mass of the polymer block, and may even be 100% by mass. For example, "polymer block (X1) composed of structural units derived from an aromatic vinyl compound" means that "structural units derived from an aromatic vinyl compound" are present in the polymer block (X1) in the largest amount, and the content of structural units derived from an aromatic vinyl compound in the polymer block (X1) is preferably 70% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, based on the mass of the polymer block (X1), and may even be 100% by mass. The same applies to the thermoplastic elastomer (a2) described below, etc. The contents of various structural units in the thermoplastic elastomer are as follows: １ It can be determined by H-NMR spectrum or the like.

[0015] The weight-average molecular weight of the block copolymer (a1) is greater than 150,000, preferably 200,000 or greater, and 500,000 or less, preferably 400,000 or less. When the weight-average molecular weight of the block copolymer (a1) is greater than the aforementioned lower limit, or is equal to or greater than the aforementioned lower limit and equal to or less than the aforementioned upper limit, the thermoplastic elastomer composition is likely to be imparted with the desired mechanical properties, flexibility, and vibration-damping properties, as well as a melt viscosity that more suitably disperses the polyphenylene ether resin (b). The weight-average molecular weight of the block copolymer can be calculated by gel permeation chromatography measurement and polystyrene conversion. In the block copolymer (a1), the weight-average molecular weight of the polymer block (X1) is preferably 30,000 to 250,000, more preferably 40,000 to 150,000. In the block copolymer (a1), the weight average molecular weight of the polymer block (Y1) is preferably 120,000 to 400,000, more preferably 150,000 to 350,000.

[0016] From the viewpoints of flexibility and non-stickiness, the block copolymer (a1) preferably has one or more polymer blocks (X1) and one or more polymer blocks (Y1). From the viewpoints of flexibility, heat resistance, and mechanical properties, the block copolymer (a1) preferably has two or more polymer blocks (X1) and one or more polymer blocks (Y1). The bonding mode between the polymer block (X1) and the polymer block (Y1) may be linear, branched, radial, or any combination thereof, but a linear bonding mode is preferred. When the polymer block (X1) is represented by X1 and the polymer block (Y1) is represented by Y1, the block copolymer (a1) may have a diblock structure represented by X1-Y1, a triblock structure represented by X1-Y1-X1, or a (X1-Y1) ｎ and (X1-Y1) ｎ -X1 (where n is an integer of 2 or more), etc. Among these, a triblock structure represented by X1-Y1-X1 is preferred from the viewpoints of heat resistance, mechanical properties, handleability, etc.

[0017] When the block copolymer (a1) has two or more polymer blocks (X1) or two or more polymer blocks (Y1), the polymer blocks (X1) and the polymer blocks (Y1) may have the same or different structures. For example, the two polymer blocks (X1) in the triblock structure represented by X1-Y1-X1 may contain the same or different aromatic vinyl compounds.

[0018] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, vinylnaphthalene, and vinylanthracene. Among these, preferred aromatic vinyl compounds are styrene and styrene derivatives. The aromatic vinyl compounds may be used alone or in combination of two or more.

[0019] The polymer block (X1) may have, in addition to the structural units derived from an aromatic vinyl compound, structural units derived from other copolymerizable monomers. When the polymer block (X1) has, in addition to the structural units derived from an aromatic vinyl compound, structural units derived from other copolymerizable monomers, the content of the structural units derived from other copolymerizable monomers is preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the mass of the polymer block (X1).

[0020] Examples of other copolymerizable monomers include ionically polymerizable monomers such as 1-butene, pentene, hexene, 1,3-butadiene (also simply referred to as "butadiene"), isoprene, and methyl vinyl ether. These other copolymerizable monomers may be used alone or in combination of two or more. When the polymer block (X1) has structural units derived from other copolymerizable monomers in addition to structural units derived from an aromatic vinyl compound, the bonding form thereof may be any of random, tapered, etc.

[0021] The content of structural units derived from aromatic vinyl compounds in block copolymer (a1) is 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less, based on all structural units constituting block copolymer (a1). When the content of structural units derived from aromatic vinyl compounds is at least the above-mentioned lower limit and is at most the above-mentioned upper limit, the thermoplastic elastomer composition is likely to exhibit better flexibility.

[0022] Examples of the conjugated diene compound include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene compound may be used alone or in combination of two or more. From the viewpoint of vibration damping properties, the conjugated diene compound is preferably butadiene, isoprene, or a mixture thereof.

[0023] When the polymer block (Y1) is composed of structural units derived from isoprene, the polymer block (Y1) is preferably composed of a 2-methyl-2-butene-1,4-diyl group [—CH ２ -C(CH ３ )=CH-CH ２ -; 1,4-bond unit], isopropenylethylene group [—CH(C(CH ３ ) = CH ２ )-CH ２ -; 3,4-bond unit] and 1-methyl-1-vinylethylene group [—C(CH ３ ) (CH=CH ２ )-CH ２ -; 1,2-bond unit], or comprises a 2-methyl-2-butene-1,4-diyl group and an isopropenylethylene group, or comprises a 2-methyl-2-butene-1,4-diyl group and a 1-methyl-1-vinylethylene group, or comprises an isopropenylethylene group and a 1-methyl-1-vinylethylene group.

[0024] When the polymer block (Y1) is composed of structural units derived from butadiene, the polymer block (Y1) contains a 2-butene-1,4-diyl group [—CH２ -CH=CH-CH ２ -; 1,4-bond unit] and vinylethylene group [—CH(CH═CH)—CH ２ -; 1,2-bonded units].

[0025] When the polymer block (Y1) is composed of structural units derived from a mixture of isoprene and butadiene, the polymer block (Y1) contains 2-methyl-2-butene-1,4-diyl groups, isopropenylethylene groups, and / or 1-methyl-1-vinylethylene groups derived from isoprene, and 2-butene-1,4-diyl groups and / or vinylethylene groups derived from butadiene.

[0026] The total content of 1,2-bond units and 3,4-bond units of structural units derived from a conjugated diene compound in the thermoplastic elastomer (a1) (hereinafter also referred to as the "vinyl bond content") is preferably 10 mol % or more, more preferably 20 mol % or more, and preferably 50 mol % or less, based on all structural units derived from the conjugated diene compound. When the vinyl bond content in the thermoplastic elastomer (a1) is at least the above-mentioned lower limit and at most the above-mentioned upper limit, an increase in tackiness is suppressed, and a composition with excellent handleability is likely to be obtained.

[0027] The polymer block (Y1) may have, in addition to the structural units derived from a conjugated diene compound, structural units derived from other copolymerizable monomers. When the polymer block (Y1) has, in addition to the structural units derived from a conjugated diene compound, structural units derived from other copolymerizable monomers, the content of the structural units derived from other copolymerizable monomers is preferably 30% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the mass of the polymer block (Y1).

[0028] Examples of other copolymerizable monomers include anionically polymerizable monomers such as aromatic vinyl compounds, such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene, diphenylethylene, 1-vinylnaphthalene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, and 4-(phenylbutyl)styrene. These other copolymerizable monomers may be used alone or in combination of two or more. When the polymer block (Y1) has structural units derived from other copolymerizable monomers in addition to structural units derived from a conjugated diene compound, the bonding form thereof may be any of random, tapered, etc.

[0029] The thermoplastic elastomer (a1) may optionally have one or more functional groups, such as a carboxyl group, a hydroxyl group, an acid anhydride group, an amino group, or an epoxy group, in the molecular chain and / or at the molecular terminal, as long as the effects of the present invention are not impaired.

[0030] From the viewpoint of heat resistance, the block copolymer (a1) is preferably hydrogenated. The hydrogenation rate of the polymer block (Y1) of the block copolymer (a1) is preferably 90% or more, more preferably 95% or more, and particularly preferably 99% or more. The hydrogenation rate is usually 100% or less. The hydrogenation rate of the block copolymer (a1) can be determined by iodine value measurement, infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ It can be measured by spectroscopy (C-NMR) or the like.

[0031] <Method for Preparing Thermoplastic Elastomer (a1)> Examples of the polymerization method for the thermoplastic elastomer (a1) include ionic polymerization methods such as anionic polymerization methods or cationic polymerization methods, single-site polymerization methods, and radical polymerization methods.

[0032] An example of a method for preparing a thermoplastic elastomer (a1) using an anionic polymerization method is shown below. First, an aromatic vinyl compound and a conjugated diene compound are sequentially polymerized in an inert organic solvent such as n-hexane or cyclohexane using an alkyllithium compound or the like as a polymerization initiator, and when the desired molecular structure or molecular weight is reached, an active hydrogen compound such as an alcohol, a carboxylic acid, or water is added to terminate the polymerization, thereby preparing a block copolymer.

[0033] Examples of alkyllithium compounds include alkyllithium compounds in which the alkyl group has 1 to 10 carbon atoms. The alkyllithium compounds may be used alone or in combination of two or more. Methyllithium, ethyllithium, butyllithium, and pentyllithium are particularly preferred. The amount of polymerization initiator, such as an alkyllithium compound, used is determined by the peak-top molecular weight of the desired thermoplastic elastomer (a1). The amount of polymerization initiator per 100 parts by mass of all monomers used in the polymerization is typically 0.01 to 0.2 parts by mass. The polymerization reaction is typically carried out at a reaction temperature of 0 to 80°C for 0.5 to 50 hours.

[0034] In order to make the vinyl bond content of the structural units derived from the conjugated diene compound in the thermoplastic elastomer (a1) preferably 10% or more based on all structural units derived from the conjugated diene compound, it is preferable to use a Lewis base as a co-catalyst during polymerization. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and amine compounds such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. The amount of these Lewis bases used is preferably about 0.1 to 1,000 times the number of moles of lithium in the alkyllithium compound used as the polymerization initiator.

[0035] A preferred method for subjecting the prepared unhydrogenated block copolymer to a hydrogenation reaction is to dissolve the unhydrogenated block copolymer in an inert organic solvent such as n-hexane or cyclohexane, which is inert to the hydrogenation reaction and the hydrogenation catalyst, in the presence of a hydrogenation catalyst, and then react with molecular hydrogen. The prepared block copolymer may be subjected to a hydrogenation reaction in an inert organic solvent in the presence of a hydrogenation catalyst without being isolated, and this hydrogenation method is preferred.

[0036] Examples of hydrogenation catalysts include Raney nickel; heterogeneous catalysts such as metal-supported catalysts in which metals such as Pt, Pd, Ru, Rh, and Ni are supported on carriers such as carbon, alumina, and diatomaceous earth; and Ziegler catalysts consisting of a combination of a transition metal compound and an alkylaluminum compound or alkyllithium compound. The hydrogenation reaction is usually carried out at a hydrogen pressure of 0.1 to 20 MPa and a reaction temperature of 20°C to 250°C for 0.1 to 100 hours. After preparation of the hydrogenated block copolymer, the hydrogenation catalyst is removed by filtration.

[0037] The unhydrogenated block copolymer reaction solution or the hydrogenated block copolymer filtrate (reaction solution) after filtration is heated typically to 40 to 150°C, preferably 60 to 150°C, and a surfactant such as a fatty acid salt or a polyoxyalkylene derivative is added and mixed as needed. Steam stripping is performed by supplying this mixture at a rate of 100 parts by mass / hour into hot water at 80 to 130°C while supplying steam at 1 MPa at a rate of 40 to 60 parts by mass / hour per 100 parts by mass of this mixture. When the inert organic solvent, such as a saturated hydrocarbon, boils or the inert organic solvent forms an azeotrope with water, steam stripping is performed at a temperature from the boiling temperature or the azeotropic temperature to 150°C. Next, the mixture is dehydrated using a compression water wringer to a moisture content of 55% by mass / WB (wet basis, the same applies hereinafter) or less, preferably 45% by mass / WB or less, and then dried at 60 to 100°C using a screw extruder dryer, an expander dryer, a conduction heat transfer dryer, a hot air dryer, or the like, to prepare a powdery thermoplastic elastomer (a1) having a moisture content of 0.1% by mass / WB or less.

[0038] <Thermoplastic elastomer (a2)> The thermoplastic elastomer (a2) is a block copolymer comprising a polymer block (X2) composed of structural units derived from an aromatic vinyl compound and a polymer block (Y2) composed of structural units derived from a conjugated diene compound. Hereinafter, the thermoplastic elastomer (a2) is also referred to as "block copolymer (a2)."

[0039] The weight-average molecular weight of block copolymer (a2) is 50,000 or more, preferably 70,000 or more, and 150,000 or less, preferably 130,000 or less. When the weight-average molecular weight of block copolymer (a2) is at least the above-mentioned lower limit and at most the above-mentioned upper limit, the thermoplastic elastomer composition tends to exhibit excellent recovery and heat resistance. In block copolymer (a2), the weight-average molecular weight of polymer block (X2) is preferably 5,000 to 20,000, more preferably 10,000 to 15,000. In block copolymer (a2), the weight-average molecular weight of polymer block (Y2) is preferably 20,000 to 140,000, more preferably 50,000 to 110,000.

[0040] From the viewpoints of vibration damping property and flexibility, the block copolymer (a2) preferably has one or more polymer blocks (X2) and one or more polymer blocks (Y2). From the viewpoints of vibration damping property, flexibility, heat resistance, and mechanical properties, the block copolymer (a2) preferably has two or more polymer blocks (X2) and one or more polymer blocks (Y2). The bonding mode between the polymer block (X2) and the polymer block (Y2) may be linear, branched, radial, or any combination thereof, but a linear bonding mode is preferred. When the polymer block (X2) is represented by X2 and the polymer block (Y2) is represented by Y2, the block copolymer (a2) may have a diblock structure represented by X2-Y2, a triblock structure represented by X2-Y2-X2, or a (X2-Y2) ｎ and (X2-Y2) ｎ-X2 (where n is an integer of 2 or more), etc. Among these, a triblock structure represented by X2-Y2-X2 is preferred from the viewpoints of not only vibration damping properties but also heat resistance, mechanical properties, handleability, etc.

[0041] When the block copolymer (a2) has two or more polymer blocks (X2) or two or more polymer blocks (Y2), the polymer blocks (X2) and the polymer blocks (Y2) may have the same or different structures. For example, the two polymer blocks (X2) in the triblock structure represented by X2-Y2-X2 may contain the same or different aromatic vinyl compounds.

[0042] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, monofluorostyrene, difluorostyrene, monochlorostyrene, dichlorostyrene, methoxystyrene, vinylnaphthalene, and vinylanthracene. Among these, preferred aromatic vinyl compounds are styrene and styrene derivatives. The aromatic vinyl compounds may be used alone or in combination of two or more.

[0043] The polymer block (X2) may have, in addition to the structural units derived from an aromatic vinyl compound, structural units derived from other copolymerizable monomers. When the polymer block (X2) has, in addition to the structural units derived from an aromatic vinyl compound, structural units derived from other copolymerizable monomers, the content of the structural units derived from other copolymerizable monomers is preferably 10% by mass or less, more preferably 5% by mass or less, based on the mass of the polymer block (X2).

[0044] Examples of other copolymerizable monomers include ionically polymerizable monomers such as 1-butene, pentene, hexene, butadiene, isoprene, and methyl vinyl ether. These other copolymerizable monomers may be used alone or in combination of two or more. When the polymer block (X2) has structural units derived from other copolymerizable monomers in addition to structural units derived from an aromatic vinyl compound, the bonding form thereof may be any of random, tapered, and the like.

[0045] The content of structural units derived from aromatic vinyl compounds in block copolymer (a2) is 2% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less, and particularly preferably 35% by mass or less, based on all structural units constituting block copolymer (a2). When the content of structural units derived from aromatic vinyl compounds is at least the above-mentioned lower limit and is at most the above-mentioned upper limit, the thermoplastic elastomer composition is likely to exhibit higher heat resistance in addition to superior flexibility and vibration damping properties.

[0046] Examples of the conjugated diene compound include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene compound may be used alone or in combination of two or more. From the viewpoint of vibration damping properties, the conjugated diene compound is preferably butadiene, isoprene, or a mixture thereof.

[0047] When the polymer block (Y2) is composed of structural units derived from isoprene, the polymer block (Y2) is preferably composed of a 2-methyl-2-butene-1,4-diyl group [—CH ２ -C(CH ３ )=CH-CH ２ -; 1,4-bond unit], isopropenylethylene group [—CH(C(CH ３ ) = CH ２ )-CH ２ -; 3,4-bond unit] and 1-methyl-1-vinylethylene group [—C(CH ３ ) (CH=CH ２ )-CH ２-; 1,2-bond unit], or comprises a 2-methyl-2-butene-1,4-diyl group and an isopropenylethylene group, or comprises a 2-methyl-2-butene-1,4-diyl group and a 1-methyl-1-vinylethylene group, or comprises an isopropenylethylene group and a 1-methyl-1-vinylethylene group.

[0048] When the polymer block (Y2) is composed of structural units derived from butadiene, the polymer block (Y2) contains a 2-butene-1,4-diyl group [—CH ２ -CH=CH-CH ２ -; 1,4-bond unit] and vinylethylene group [—CH(CH═CH)—CH ２ -; 1,2-bonded units].

[0049] When the polymer block (Y2) is composed of structural units derived from a mixture of isoprene and butadiene, the polymer block (Y2) contains 2-methyl-2-butene-1,4-diyl groups, isopropenylethylene groups, and / or 1-methyl-1-vinylethylene groups derived from isoprene, and 2-butene-1,4-diyl groups and / or vinylethylene groups derived from butadiene.

[0050] The total content (vinyl bond content) of 1,2-bond units and 3,4-bond units of structural units derived from a conjugated diene compound in the thermoplastic elastomer (a2) is 50 mol % or more, preferably 55 mol % or more, and preferably 80 mol % or less, more preferably 70 mol % or less, and even more preferably less than 63 mol %, based on all structural units derived from the conjugated diene compound. When the vinyl bond content in the thermoplastic elastomer (a2) is at least the above-mentioned lower limit and at most the above-mentioned upper limit, the thermoplastic elastomer composition is likely to exhibit higher heat resistance in addition to better vibration damping properties and recovery properties.

[0051] The polymer block (Y2) may have, in addition to the structural units derived from a conjugated diene compound, structural units derived from other copolymerizable monomers. When the polymer block (Y2) has, in addition to the structural units derived from a conjugated diene compound, structural units derived from other copolymerizable monomers, the content of the structural units derived from other copolymerizable monomers is preferably 30% by mass or less, more preferably 10% by mass or less, based on the mass of the polymer block (Y2).

[0052] Examples of other copolymerizable monomers include anionically polymerizable monomers such as aromatic vinyl compounds, such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1,3-dimethylstyrene, diphenylethylene, 1-vinylnaphthalene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, and 4-(phenylbutyl)styrene. These other copolymerizable monomers may be used alone or in combination of two or more. When the polymer block (Y2) has structural units derived from other copolymerizable monomers in addition to structural units derived from a conjugated diene compound, the bonding form thereof may be any of random, tapered, etc.

[0053] The thermoplastic elastomer (a2) may optionally have one or more functional groups, such as a carboxyl group, a hydroxyl group, an acid anhydride group, an amino group, or an epoxy group, in the molecular chain and / or at the molecular terminal, as long as the effects of the present invention are not impaired.

[0054] The unsaturated double bonds of the conjugated diene compound in the thermoplastic elastomer (a2) may be hydrogenated, provided that the objectives of the present invention are not impaired. The hydrogenation rate of the polymer block (Y2) composed of structural units derived from the conjugated diene compound in the thermoplastic elastomer (a2) is preferably 20% or less, more preferably 17% or less, more preferably 14% or less, more preferably 12% or less, more preferably 10% or less, even more preferably 8% or less, even more preferably 6% or less, even more preferably 4% or less, even more preferably 2% or less, and particularly preferably 0% (non-hydrogenated). In a preferred embodiment of the present invention, the polymer block (Y2) of the block copolymer (a2) is non-hydrogenated. When the polymer block (Y2) has a hydrogenation rate of not more than the above-mentioned upper limit or is non-hydrogenated, the compatibility of the polyphenylene ether resin (b) with the polymer block (X2) and the polymer block (X1), particularly with the polymer block (X2), is likely to be improved. As a result, the thermoplastic elastomer composition of the present invention is likely to be imparted with not only superior vibration damping properties and recovery properties but also higher heat resistance. The hydrogenation rate of the polymer block (Y2) of the block copolymer (a2) can be determined by iodine value measurement, infrared spectrophotometer (IR), nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ It can be measured by spectroscopy (C-NMR) or the like.

[0055] In a preferred embodiment of the present invention, the thermoplastic elastomer (a2) has an order-disorder transition temperature (ODTT) of 280°C or less, preferably 270°C or less, and more preferably 260°C or less. When the thermoplastic elastomer (a2) has an order-disorder transition temperature of the aforementioned upper limit or less, the dispersibility of the polyphenylene ether resin (b) in the matrix phase is more likely to be improved, and the thermoplastic elastomer composition of the present invention is more likely to be imparted with higher heat resistance in addition to superior vibration damping and recovery properties. The lower limit of the thermoplastic elastomer (a2) is not particularly limited, but is usually 200°C or higher. The order-disorder transition temperature can be measured by the method described in the Examples below. The order-disorder transition temperature of the thermoplastic elastomer (a2) can be adjusted to be equal to or less than the aforementioned upper limit by adjusting the weight-average molecular weight of the thermoplastic elastomer (a2), the vinyl bond content, and / or the hydrogenation rate of the polymer block (X2).

[0056] <Method for Preparing Thermoplastic Elastomer (a2)> Examples of polymerization methods for the thermoplastic elastomer (a2) include ionic polymerization methods such as anionic polymerization or cationic polymerization, single-site polymerization, and radical polymerization. An example of a method for preparing the thermoplastic elastomer (a2) using anionic polymerization is shown below. First, an aromatic vinyl compound and a conjugated diene compound are sequentially polymerized in an inert organic solvent such as n-hexane or cyclohexane using an alkyllithium compound or the like as a polymerization initiator, and when the desired molecular structure or molecular weight is reached, an active hydrogen compound such as an alcohol, a carboxylic acid, or water is added to terminate the polymerization, thereby preparing a block copolymer.

[0057] Examples of alkyllithium compounds include alkyllithium compounds in which the alkyl group has 1 to 10 carbon atoms. The alkyllithium compounds may be used alone or in combination of two or more. Methyllithium, ethyllithium, butyllithium, and pentyllithium are particularly preferred. The amount of polymerization initiator, such as an alkyllithium compound, used is determined by the peak-top molecular weight of the desired thermoplastic elastomer (a2). The amount of polymerization initiator per 100 parts by mass of all monomers used in the polymerization is typically 0.01 to 0.2 parts by mass. The polymerization reaction is typically carried out at a reaction temperature of 0 to 80°C for 0.5 to 50 hours.

[0058] In order to make the vinyl bond content of the structural units derived from the conjugated diene compound in the thermoplastic elastomer (a2) 50% or more based on all structural units derived from the conjugated diene compound, it is preferable to use a Lewis base as a co-catalyst during polymerization. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, and tetrahydrofuran; glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; and amine compounds such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine. The amount of these Lewis bases used is preferably about 0.1 to 1,000 times the number of moles of lithium in the alkyllithium compound used as the polymerization initiator.

[0059] When the prepared unhydrogenated block copolymer is subjected to a hydrogenation reaction, it may be carried out in the same manner as the hydrogenation reaction in the method for preparing the thermoplastic elastomer (a1). After the preparation of the hydrogenated block copolymer, the hydrogenation catalyst is removed by filtration.

[0060] The reaction solution of the unhydrogenated block copolymer or the filtrate (reaction solution) of the hydrogenated block copolymer after filtration can be heated, steam stripped, dehydrated, and dried in the same manner as in the preparation method of the thermoplastic elastomer (a1), to prepare a powdery thermoplastic elastomer (a2) having a water content of 0.1 mass% / WB or less.

[0061] <Polyphenylene ether resin (b)> The thermoplastic elastomer composition of the present invention can exhibit excellent compression set at high temperatures by containing the polyphenylene ether resin (b). Examples of the polyphenylene ether resin (b) include those represented by the following general formula (1): [In the formula, R １ , R ２ , R ３ and R ４ each independently represents a hydrogen atom, a halogen atom, a hydrocarbon group, a substituted hydrocarbon group, an alkoxy group, a cyano group, a phenoxy group, or a nitro group] can be used.

[0062] In the general formula (1), R １ and R ２ is preferably an alkyl group, more preferably an alkyl group having 1 to 4 carbon atoms, and R ３ and R ４ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0063] Examples of the polyphenylene ether resin (b) include poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene) ether, poly(2,6-dipropyl-1,4-phenylene) ether, poly(2,6-dimethoxy-1,4-phenylene) ether, poly(2,6-dichloromethyl-1,4-phenylene) ether, poly(2,6-dibromomethyl-1,4-phenylene) ether, and poly(2,6-diphenyl-1,4-phenylene) ether. Examples of the polyphenylene ether resin (b) include poly(2,6-ditolyl-1,4-phenylene) ether, poly(2,6-dichloro-1,4-phenylene) ether, poly(2,6-dibenzyl-1,4-phenylene) ether, poly(2-methyl-6-ethyl-1,4-phenylene) ether, poly(2-methyl-6-propyl-1,4-phenylene) ether, poly(2-ethyl-6-propyl-1,4-phenylene) ether, and poly(2,5-dimethyl-1,4-phenylene) ether. The polyphenylene ether resin (b) may be used alone or in combination of two or more. Among these, a particularly preferred polyphenylene ether resin (b) is poly(2,6-dimethyl-1,4-phenylene) ether.

[0064] The polyphenylene ether resin (b) may be modified with a modifying agent having a polar group, such as an acid halide, a carbonyl group, an acid anhydride, an acid amide, a carboxylic acid ester, an acid azide, a sulfone group, a nitrile group, a cyano group, an isocyanate ester, an amino group, an imide group, a hydroxyl group, an epoxy group, an oxazoline group, or a thiol group.

[0065] The number average molecular weight of the polyphenylene ether resin (b) is preferably 1,000 to 100,000, and more preferably 6,000 to 60,000, particularly taking into consideration the balance of various physical properties (heat resistance and compression set).

[0066] The amount of polyphenylene ether resin (b) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 100 parts by mass or less, more preferably 60 parts by mass or less, per 100 parts by mass of thermoplastic elastomer (a). When the amount of polyphenylene ether resin (b) is equal to or greater than the lower limit, the thermoplastic elastomer composition is likely to exhibit excellent compression set at high temperatures. When the amount of polyphenylene ether resin (b) is equal to or less than the upper limit, the thermoplastic elastomer composition is likely to exhibit excellent compression set at high temperatures while maintaining suitable flexibility.

[0067] The polyphenylene ether (b) may be produced by any known method without any particular limitation. Examples of commercially available polyphenylene ether (b) include PPO 640 (product name) manufactured by SABIC Innovative Plastics Japan, LLC, and PX100F manufactured by Mitsubishi Engineering-Plastics Corporation.

[0068] <Rubber Softener (c)> The rubber softener (c) imparts flexibility to the thermoplastic elastomer composition of the present invention. Examples of rubber softeners (c) include paraffinic, naphthenic, or aromatic process oils; phthalic acid derivatives such as dioctyl phthalate or dibutyl phthalate; white oil; mineral oil; liquid cooligomers of ethylene and α-olefins; liquid paraffin; polybutene; low-molecular-weight polyisobutylene; liquid polybutadiene, liquid polyisoprene, liquid polyisoprene / butadiene copolymer, liquid styrene / butadiene copolymer, liquid styrene / isoprene copolymer, and other liquid polydienes or hydrogenated products thereof. The rubber softener (c) may be used alone or in combination of two or more. From the viewpoint of compatibility with the thermoplastic elastomer (a1) and the thermoplastic elastomer (a2), paraffinic process oils, liquid cooligomers of ethylene and α-olefins, or liquid paraffin are preferred.

[0069] The weight average molecular weight of the rubber softener (c) is preferably 700 or more, more preferably 750 or more, and preferably 1500 or less, more preferably 1400 or less. When the weight average molecular weight of the rubber softener (c) is the lower limit or more, the flexibility and mechanical strength are better, and when it is the upper limit or less, the molding processability is better.

[0070] The kinematic viscosity (40°C) of the rubber softener (c) is preferably 80 mm ２ / s or more, more preferably 90 mm ２ / s or more, more preferably 100 mm ２ / s or more, particularly preferably 150 mm ２ / s or more, and even more preferably 200 mm ２ / s or more, preferably 500 mm ２ / s or less, more preferably 400 mm ２ / s or less, more preferably 390 mm ２ When the kinematic viscosity (40°C) of the softener (c) is equal to or higher than the lower limit, the flexibility and non-stickiness are better, and when it is equal to or lower than the upper limit, the molding processability is better. The kinematic viscosity can be measured, for example, according to JIS K 2283.

[0071] The rubber softener (c) can be produced by any known method without any particular limitation on the production method thereof. Examples of commercially available rubber softeners (c) include Diana Process Oil PW series (paraffinic oils) manufactured by Idemitsu Kosan Co., Ltd., Diana Process Oil NR series (naphthenic oils) manufactured by Idemitsu Kosan Co., Ltd., and NOBEL Process Oil AB series (aromatic oils) manufactured by Nikko Oil Products Co., Ltd.

[0072] The amount of rubber softener (c) is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, particularly preferably 70 parts by mass or more, and preferably 300 parts by mass or less, more preferably 200 parts by mass or less, particularly preferably 150 parts by mass or less, per 100 parts by mass of thermoplastic elastomer (a). When the amount of rubber softener (c) is at least the above-mentioned lower limit, the thermoplastic elastomer composition tends to have better flexibility. When the amount of rubber softener (c) is at most the above-mentioned upper limit, the thermoplastic elastomer composition tends to have better mechanical strength.

[0073] <Polypropylene (d)> The thermoplastic elastomer composition of the present invention may further contain polypropylene to impart flexibility. Examples of polypropylene (d) include homopolypropylene, random polypropylene copolymer, and block polypropylene copolymer. Homopolypropylene is preferred from the viewpoint of heat resistance. The polypropylene preferably has a melt flow rate (MFR) at 230°C according to JIS K 7210 of preferably 1 to 100 g / 10 min, more preferably 5 to 85 g / 10 min, and even more preferably 10 to 60 g / 10 min. Such polypropylene is commercially available, and an example of a commercially available product is Prime Polypro J108M (trade name) manufactured by Prime Polymer Co., Ltd. When the thermoplastic elastomer composition of the present invention contains polypropylene (d), the content of polypropylene (d) is preferably 2 to 20 parts by mass, more preferably 3 to 18 parts by mass, and particularly preferably 4 to 15 parts by mass per 100 parts by mass of thermoplastic elastomer (a), from the viewpoint of imparting flexibility without impairing the effects of the present invention (particularly vibration damping and / or recovery).

[0074] <Inorganic Filler (e)> The thermoplastic elastomer composition of the present invention may further contain an inorganic filler, as needed, as long as the effects of the present invention are not impaired. Such inorganic fillers may be those commonly used in the art. Examples of inorganic fillers include calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, magnesium carbonate, glass fiber, and carbon fiber. The inorganic filler (e) may be used alone or in combination of two or more. When the thermoplastic elastomer composition of the present invention contains the inorganic filler (e), the content of the inorganic filler (e) is preferably 10 to 200 parts by mass, more preferably 20 to 150 parts by mass, and particularly preferably 30 to 100 parts by mass, per 100 parts by mass of the thermoplastic elastomer (a), from the viewpoints of flexibility and vibration damping properties.

[0075] <Other Additives> The thermoplastic elastomer composition may contain other additives as needed, as long as the effects of the present invention are not impaired. Examples of such additives include lubricants, flame retardants, antioxidants, heat stabilizers, light resistance agents, weather resistance agents, metal deactivators, UV absorbers, light stabilizers, copper inhibitors, reinforcing agents, antistatic agents, antibacterial agents, mildew inhibitors, dispersants, colorants, polyolefin resins such as polyethylene or polypropylene, rubbers such as isobutylene-isoprene copolymers and silicone rubbers, and thermoplastic resins such as ethylene-vinyl acetate copolymers or ABS resins. The other additives may be used alone or in combination of two or more.

[0076] The lubricant has the effect of improving the fluidity of the thermoplastic elastomer composition and suppressing thermal degradation. Examples of the lubricant include silicone oil; hydrocarbon lubricants such as paraffin wax, microcrystalline wax, and polyethylene wax; butyl stearate, stearic acid monoglyceride, pentaerythritol tetrastearate, and stearyl stearate.

[0077] Examples of the flame retardant include phosphorus-based flame retardants such as triphenylphosphine, triallyl phosphate, aromatic phosphate esters, polyphosphates, red phosphorus, 2-ethylhexyl diphenyl phosphate, and triethyl phosphate; and inorganic flame retardants such as magnesium hydroxide and aluminum hydroxide.

[0078] When the thermoplastic elastomer composition contains other additives, the content of the additives may be any content that allows the additives to exhibit their effects, and can be appropriately selected by a person skilled in the art.

[0079] The thermoplastic elastomer composition may be crosslinked as needed, as long as the effects of the present invention are not impaired. When crosslinking is performed, a crosslinking agent such as a radical generator or sulfur or a sulfur compound may be used, and further, a crosslinking aid may be used as needed.

[0080] Examples of the radical generator include hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, and 2,5-dimethylhexane-2,5-dihydroperoxide; diallyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3; Examples of radical generators include alkyl peroxides; diacyl peroxides such as acetyl peroxide, succinic acid peroxide, and benzoyl peroxide; organic peroxides such as peroxide esters such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, and t-butyl peroxyisopropyl carbonate; and ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; inorganic peroxides such as hydrogen peroxide, persulfates, and metal oxides; azo compounds, mono- and disulfides, metal chelates, and redox initiators. Radical generators may be used alone or in combination of two or more. When a radical generator is used, it is preferably used in an amount of 0.01 to 15 parts by mass, more preferably 0.05 to 10 parts by mass, per 100 parts by mass of the combined total of the thermoplastic elastomer (a1) and the thermoplastic elastomer (a2).

[0081] An example of a crosslinking method using a radical generator is a method in which the thermoplastic elastomer composition and the radical generator are melt-kneaded under heating. The heating temperature is preferably 140 to 230°C, and the melt-kneading can be carried out batchwise or continuously using an apparatus such as an extruder, kneader, roll, or plastograph. The crosslinking reaction proceeds during this melt-kneading step.

[0082] Examples of sulfur compounds include sulfur monochloride and sulfur dichloride. When sulfur or a sulfur compound is used, the amount added is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 10 parts by mass, per 100 parts by mass of the total of the thermoplastic elastomer (a1) and the thermoplastic elastomer (a2). When crosslinking is performed using sulfur or a sulfur compound, it is highly preferable to use a vulcanization accelerator as a crosslinking aid in combination.

[0083] Examples of the vulcanization accelerator include thiazoles such as N,N-diisopropyl-2-benzothiazole-sulfenamide, 2-mercaptobenzothiazole, and 2-(4-morpholinodithio)benzothiazole; guanidines such as diphenylguanidine and triphenylguanidine; aldehyde-amine reaction products or aldehyde-ammonia reaction products such as butyraldehyde-aniline reaction product and hexamethylenetetramine-acetaldehyde reaction product; imidazolines such as 2-mercaptoimidazoline; thiocarbanilide, diethylurea, dibutylthiourea, trimethylthiourea, and the like. Examples of suitable vulcanization accelerators include thioureas such as thiuram monosulfide, tetramethylthiuram disulfide, and pentamethylenethiuram tetrasulfide; thiuram monopolysulfides or polysulfides such as zinc dimethyldithiocarbamate, zinc ethylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate, and tellurium diethyldithiocarbamate; xanthates such as zinc dibutylxanthogenate; organic peroxides; and zinc oxide. These vulcanization accelerators may be used alone or in combination of two or more. When a vulcanization accelerator is used, the amount added is preferably 0.05 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.2 to 10 parts by mass per 100 parts by mass of the combined total of the thermoplastic elastomer (a1) and the thermoplastic elastomer (a2).

[0084] <Method for Producing Thermoplastic Elastomer Composition> The method for producing the thermoplastic elastomer composition is not particularly limited. Examples include a method in which the thermoplastic elastomer (a1), the thermoplastic elastomer (a2), the polyphenylene ether resin (b), the rubber softener (c), and optionally the polypropylene (d), the inorganic filler (e), and / or other additives are premixed and then melt-kneaded using a single-screw extruder, a multi-screw extruder, a Banbury mixer, a heated roll, various kneaders, or the like; and a method in which the thermoplastic elastomer (a1), the thermoplastic elastomer (a2), the polyphenylene ether resin (b), the rubber softener (c), and optionally the polypropylene (d), the inorganic filler (e), and / or other additives are fed into separate feed ports and melt-kneaded. Examples of premixing methods include a method using a mixer such as a Henschel mixer, a high-speed mixer, a V-blender, a ribbon blender, a tumbler blender, or a conical blender. The temperature during melt-kneading can be selected from the range of 200°C to 300°C.

[0085] The thermoplastic elastomer composition of the present invention possesses excellent vibration damping properties, excellent resilience, and excellent heat resistance. The vibration damping properties can be evaluated, for example, by tan δ at 23°C. The tan δ of the thermoplastic elastomer composition at 23°C is preferably 0.15 or more, more preferably 0.17 or more, and particularly preferably 0.20 or more. The resilience can be evaluated, for example, by permanent elongation set. The permanent elongation set of the thermoplastic elastomer composition is preferably 13% or less, more preferably 10% or less, and particularly preferably 7% or less. The heat resistance can be evaluated, for example, by compression set. The permanent elongation set of the thermoplastic elastomer composition is preferably 50% or less, more preferably 45% or less, and particularly preferably 40% or less. In particular, it is preferable for the thermoplastic elastomer composition to satisfy both the above-mentioned ranges for permanent elongation set and the above-mentioned ranges for compression set in terms of the balance of physical properties (resilience and heat resistance). The tan δ, permanent elongation set and permanent compression set at 23° C. of the thermoplastic elastomer composition can be measured by the methods described in the Examples below.

[0086] Three 2 mm thick test pieces obtained by injection molding the thermoplastic elastomer composition at 230°C are stacked on top of each other, and the hardness measured after 3 seconds using a Type A durometer in accordance with JIS K 6253 is preferably 80 or less, more preferably 75 or less, even more preferably 70 or less, and particularly preferably 65 or less. In addition, the hardness is preferably 15 or more, more preferably 20 or more, even more preferably 25 or more, and particularly preferably 30 or more. When the hardness is at least the lower limit and at most the upper limit, the thermoplastic elastomer composition tends to have an excellent balance between strength and vibration damping properties.

[0087] Molded articles can be produced by molding the thermoplastic elastomer composition of the present invention using conventional molding methods such as hot pressing, injection molding, extrusion molding, and calendar molding. Therefore, the present invention also covers molded articles made from the thermoplastic elastomer composition of the present invention. The thermoplastic elastomer composition of the present invention has excellent flowability because the thermoplastic elastomer (a1), an essential component, has excellent absorbency for the softener (c). Therefore, the thermoplastic elastomer composition of the present invention has excellent handleability during melt-kneading and excellent moldability.

[0088] The molded article may have any shape, for example, a sheet, a disk, a cylinder, etc. The molded article may have any size, and the size is determined depending on the application.

[0089] A layer made of a resin composition other than the thermoplastic elastomer composition of the present invention can be bonded to at least a portion of the surface of the molded article of the present invention. Such a layer may be formed alone or in combination of two or more.

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0091] <Evaluation Methods> (1) Weight Average Molecular Weight The weight average molecular weight of the thermoplastic elastomer was determined by gel permeation chromatography under the following measurement conditions, and converted into standard polystyrene. GPC: LC Solution (Shimadzu Corporation) Detector: Differential Refractometer RID-10A (Shimadzu Corporation) Column: Two TSKgel G4000Hxl columns connected in series (Tosoh Corporation) Guard column: TSKguardcolumnHxl-L (Tosoh Corporation) Solvent: Tetrahydrofuran Temperature: 40°C Flow rate: 1 mL / min Concentration: 2 mg / mL

[0092] (2) Content of structural units derived from aromatic vinyl compounds in thermoplastic elastomers. ３ Dissolved in １ H-NMR spectrum measurement was carried out (apparatus: JNM-Lambda 500 manufactured by JEOL Ltd., measurement temperature: 50°C). From the peak area attributable to the aromatic vinyl compound, the content of structural units attributable to the aromatic vinyl compound in the thermoplastic elastomer was calculated.

[0093] (3) The total content of 1,2-bond units and 3,4-bond units of structural units derived from a conjugated diene compound in a thermoplastic elastomer, and the hydrogenation rate of a polymer block composed of structural units derived from a conjugated diene compound in a thermoplastic elastomer. ３ Dissolved in １H-NMR spectrum measurement was carried out (apparatus: JNM-Lambda 500 manufactured by JEOL Ltd., measurement temperature: 50°C). The vinyl bond content (total content of 1,2-bond units and 3,4-bond units) in the thermoplastic elastomer was calculated from the ratio of the total peak area of ​​the structural units derived from isoprene, the structural units derived from butadiene, or the structural units derived from a mixture of isoprene and butadiene to the peak area corresponding to the 1,2-bond units and 3,4-bond units in the structural units of isoprene, the 1,2-bond units in the structural units of butadiene, or the respective bond units in the case of a mixture of isoprene and butadiene. The hydrogenation rate of the polymer block composed of structural units derived from a conjugated diene compound in the thermoplastic elastomer was determined by dissolving the thermoplastic elastomer in CDCl. ３ Dissolved in １ H-NMR spectrum measurement was carried out (apparatus: "ADVANCE 400 Nano bay" (manufactured by Bruker), measurement temperature: 30°C), and the ratio of the total area of ​​the peaks of hydrogenated 1,2-bonds and hydrogenated 3,4-bonds to the total area of ​​all peaks (1,2-bonds, 3,4-bonds) associated with double bonds in the conjugated diene monomer units among the obtained peaks (ratio of the peak area attributable to the residual olefin of isoprene or butadiene to the peak area attributable to ethylene, propylene, butylene, 2-methylbutylene, and 3-methylbutylene) was calculated to determine the ratio.

[0094] (4) TEM Observation Each thermoplastic elastomer composition obtained in the Examples and Comparative Examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet having a thickness of 2 mm. Ten ultrathin sections having a thickness of approximately 150 nm were prepared using a Leica ultramicrotome (model: Ultracut S / FC-S) so that the surface (upper or lower surface) of the obtained sheet served as the observation surface. Each ultrathin section was placed in a copper mesh. ４ Each ultrathin section was stained with a vapor staining solution. ６ A transmission electron microscope (model: HT7700, 3DTEM compatible) manufactured by Hitachi High-Technologies Corporation equipped with an electron gun was used. The accelerating voltage was 100 kV, LaB ６Morphology observation was performed under conditions of an electron beam irradiation dose of 10 μA and an electron beam spot size of 1 μm. An AMT bottom-mount camera (model: XR81B, 8-megapixel camera) was used as the CCD camera for recording images. The maximum diameter of the polyphenylene ether resin (b) in the transmission electron microscope image of each obtained ultrathin section was confirmed, and the maximum diameter of the polyphenylene ether resin (b) in each transmission electron microscope image of the ultrathin section was determined based on the scale attached to the image. The largest maximum diameter of the polyphenylene ether resin (b) among these was used as the maximum diameter of the polyphenylene ether resin (b) in the thermoplastic elastomer composition. When it was difficult to clearly distinguish the polyphenylene ether resin (b) in the transmission electron microscope image, the maximum diameter of the structural unit phase (polymer block X1 and / or polymer block X2) derived from the aromatic vinyl compound was used as the maximum diameter of the polyphenylene ether resin (b) in the thermoplastic elastomer composition. In this case, it is presumed that the phase of the structural units derived from the aromatic vinyl compound contains the polyphenylene ether resin (b).

[0095] (5) Order-Disorder Transition Temperature (ODTT) Each thermoplastic elastomer composition obtained in the Examples and Comparative Examples was compression-molded at 200°C and 1.0 MPa for 3 minutes to obtain a sheet (150 mm long, 150 mm wide, 1 mm thick). Cylindrical test specimens with a diameter of 25 mm and a height of 1 mm were punched out from the sheet. The shear storage modulus G' of each test specimen was measured using an Rheometric Scientific RDA3 viscoelasticity measuring device at temperatures of 100 to 350°C, a frequency of 1 Hz, and a strain of 5% in accordance with JIS K7244-10. The temperature at the intersection of the baseline and the tangent to the point where the shear storage modulus G' began to decrease in the resulting chart was taken as the order-disorder transition temperature.

[0096] (6) Hardness Each thermoplastic elastomer composition obtained in the examples and comparative examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet having a thickness of 2 mm. Three disc-shaped test pieces having a diameter of 120 mm were prepared from the obtained sheet. In accordance with JIS K 6253, the three test pieces were stacked and the hardness was measured. A Type A durometer was used as a hardness tester, and the value after 3 seconds was recorded as the hardness.

[0097] (7) Tan δ at 23°C (Vibration Damping Property) Each thermoplastic elastomer composition obtained in the examples and comparative examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet having a thickness of 2 mm. From the obtained sheet, a disk-shaped test specimen having a diameter of 120 mm was prepared. For the prepared test specimen, the storage modulus (E') and loss modulus (E") were measured using a viscoelasticity measurement analyzer (Reogel-E4000 manufactured by UBM Co., Ltd.) at a frequency of 30 Hz and a heating rate of 3°C / min, and the loss tangent (tan δ = E" / E') was calculated. The change in the value of tan δ with respect to temperature was tracked to determine tan δ at 23°C. Tan δ is used as a measure of vibration damping property, with a higher tan δ value indicating better vibration damping property.

[0098] (8) Permanent Elongation Set (Resilience) Each thermoplastic elastomer composition obtained in the Examples and Comparative Examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet with a thickness of 2 mm. Test specimens were punched out from the obtained sheet using a No. 1 dumbbell so that the measurement direction was the TD direction, and a 4 cm gauge line was drawn on each specimen. The obtained test specimens were stretched 100% for 10 minutes and then allowed to stand for 10 minutes. The distance between the gauge lines was then measured, and the amount of strain was calculated. A smaller value indicates better resilience.

[0099] (9) Compression Set (Heat Resistance) Each thermoplastic elastomer composition obtained in the Examples and Comparative Examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet having a thickness of 2 mm. Six disc-shaped test pieces having a diameter of 120 mm were prepared from the obtained sheet. In accordance with JIS K 6262, the six test pieces were stacked and subjected to a 25% compression deformation at 70°C for 22 hours, after which the compression set was measured. A smaller value indicates better heat resistance.

[0100] (10) Heat Crack Resistance Test (Heat Resistance) Each thermoplastic elastomer composition obtained in the Examples and Comparative Examples was molded at 230°C using an injection molding machine (FE120 manufactured by Nissei Plastic Industrial Co., Ltd.) to obtain a sheet with a thickness of 2 mm. Test specimens were punched out of the obtained sheet using a No. 3 dumbbell so that the measurement direction was the TD direction. The obtained test specimens were stretched 100% and left to stand in an environment at 130°C. The presence or absence of cracks was observed after 8 hours.

[0101] Components Used in the Preparation of Each Thermoplastic Elastomer Composition in the Examples and Comparative Examples: Thermoplastic Elastomer (a1)-1: Preparation of Styrene-Butadiene-Styrene Triblock Copolymer 72 L of cyclohexane as a solvent and 59 mL of sec-butyllithium (10% by mass solution in cyclohexane) as a polymerization initiator were introduced into a nitrogen-purged, dried pressure-resistant vessel, and 99 g of N,N,N',N'-tetramethylethylenediamine as an organic Lewis base was added. Next, 1.84 kg of styrene, 8.57 kg of butadiene, and 1.84 kg of styrene were added in that order to allow polymerization. The resulting polymerization reaction solution was poured into methanol, and the precipitated solid was filtered and dried at 50°C for 20 hours to isolate the triblock copolymer. 10 kg of the resulting triblock copolymer was dissolved in 200 L of cyclohexane, and palladium carbon (palladium loading: 5% by mass) as a hydrogenation catalyst was added in an amount of 5% by mass relative to the copolymer. The reaction was carried out for 5 hours under conditions of a hydrogen pressure of 2 MPa and 150°C. After allowing to cool and releasing the pressure, the palladium carbon was removed by filtration. The filtrate was concentrated and vacuum dried to obtain a hydrogenated styrene-butadiene-styrene triblock copolymer. The properties of the obtained hydrogenated product were as follows: Weight average molecular weight: 280,000 Content of structural units derived from butadiene: 66% by mass Content of structural units derived from styrene: 34% by mass Content of 1,2-bond units and 3,4-bond units in structural units derived from butadiene: 33 mol% Hydrogenation rate of polymer block composed of structural units derived from conjugated diene compound: 99% ODTT: 330°C or higher

[0102] Thermoplastic elastomer (a1)-2 TAIPOL (registered trademark) 6159, manufactured by TSRC Corporation, hydrogenated styrene-butadiene-styrene triblock copolymer Weight average molecular weight: 340,000 Content of structural units derived from butadiene: 68% by mass Content of structural units derived from styrene: 32% by mass Content of 1,2-bond units and 3,4-bond units in structural units derived from butadiene: 33 mol% Hydrogenation rate of polymer block composed of structural units derived from conjugated diene compound: 99% ODTT: 330°C or higher

[0103] Thermoplastic elastomer (a2)-1: Preparation of styrene-isoprene-styrene triblock copolymer. 64 L of cyclohexane as a solvent and 0.20 L of sec-butyllithium (10% by mass solution in cyclohexane) as a polymerization initiator were introduced into a nitrogen-purged, dried pressure vessel, and 0.3 L of tetrahydrofuran (15 times the stoichiometric ratio relative to the lithium atoms in the polymerization initiator) as an organic Lewis base was added. After heating to 50°C, 2.3 L of styrene was added and polymerized for 3 hours. 23 L of isoprene was then added and polymerized for 4 hours. 2.3 L of styrene was then added and polymerized for 3 hours. The resulting reaction solution was poured into 80 L of methanol, and the precipitated solid was collected by filtration and dried at 50°C for 20 hours to obtain a styrene-isoprene-styrene triblock copolymer. The properties of the resulting block copolymer were as follows: Weight average molecular weight: 100,000 Content of structural units derived from isoprene: 80% by mass Content of structural units derived from styrene: 20% by mass Content of 1,2-bond units and 3,4-bond units in structural units derived from isoprene: 60 mol% Hydrogenation rate of polymer block composed of structural units derived from conjugated diene compound: 0% ODTT: 250°C

[0104] Thermoplastic elastomer (a3)-1: Preparation of styrene-isoprene-styrene triblock copolymer 64 L of cyclohexane as a solvent and 0.20 L of sec-butyllithium (10% by mass solution in cyclohexane) as a polymerization initiator were introduced into a nitrogen-purged, dried pressure vessel, and 0.3 L of tetrahydrofuran (15 times the stoichiometric ratio relative to the lithium atoms in the polymerization initiator) as an organic Lewis base was added. After heating to 50°C, 2.3 L of styrene was added and polymerized for 3 hours, followed by the addition of 23 L of isoprene and polymerization for 4 hours, and then 2.3 L of styrene was added and polymerized for 3 hours. The resulting reaction solution was poured into 80 L of methanol, and the precipitated solid was collected by filtration and dried at 50°C for 20 hours to obtain a styrene-isoprene-styrene triblock copolymer. 10 kg of the obtained triblock copolymer was dissolved in 200 L of cyclohexane, and palladium carbon (palladium loading: 5% by mass) was added as a hydrogenation catalyst in an amount of 5% by mass relative to the copolymer, and the reaction was carried out for 10 hours under conditions of a hydrogen pressure of 2 MPa and 150°C. After cooling and releasing the pressure, the palladium carbon was removed by filtration. The filtrate was concentrated and dried in vacuo to obtain a hydrogenated styrene-isoprene-styrene triblock copolymer. The properties of the obtained hydrogenated product were as follows: Weight average molecular weight: 100,000 Content of structural units derived from isoprene: 80% by mass Content of structural units derived from styrene: 20% by mass Content of 1,2-bond units and 3,4-bond units in structural units derived from isoprene: 60 mol% Hydrogenation rate of polymer blocks composed of structural units derived from conjugated diene compounds: 98% ODTT: 300°C

[0105] Thermoplastic elastomer (a4)-1 TAIPOL (registered trademark) 6140, manufactured by TSRC Corporation, hydrogenated product of styrene-butadiene-styrene triblock copolymer, hydrogenation rate of polymer block composed of structural units derived from conjugated diene compound: 95% or more Polyphenylene ether resin (b) PPO 640 (trade name), manufactured by SABIC Innovative Plastics Japan, LLC Rubber softener (c) Diana Process Oil PW-380 (trade name), manufactured by Idemitsu Kosan Co., Ltd., paraffinic oil, kinematic viscosity (40 ° C): 381.6 mm ２ / s, ring analysis paraffin: 73%, ring analysis naphthene: 27%, weight average molecular weight: 1304. Polypropylene (d) Prime Polypro J108M (trade name), homopolypropylene manufactured by Prime Polymer Co., Ltd., MFR (230°C) according to JIS K 7210: 45 g / 10 min. Inorganic filler (e) Softon 1200 (trade name), heavy calcium carbonate manufactured by Bihoku Funka Kogyo Co., Ltd.

[0106] Examples 1 to 9 and Comparative Examples 1 to 6 Using a twin-screw extruder (TEM-26SS-P1, manufactured by Toshiba Machine Co., Ltd.), the components were melt-kneaded at the blending ratios shown in Tables 1 and 2 and extruded into strands at a cylinder temperature of 250°C and a screw rotation speed of 200 rpm. The strand-like extrudate was cut into pellets of the thermoplastic elastomer composition using a pelletizer connected to the twin-screw extruder. In Tables 1 and 2, the blending ratios of components (b) to (e) are shown as parts by mass relative to 100 parts by mass of the thermoplastic elastomer. Each of the resulting thermoplastic elastomer compositions was evaluated. The results are shown in Tables 1 and 2. Transmission electron microscope images used to determine the maximum major axis of the polyphenylene ether resin (b) in the thermoplastic elastomer compositions prepared in Example 2 and Comparative Example 3 are shown in Figures 1 and 2, respectively.

[0107]

[0108]

[0109] It can be seen from Table 1 that the thermoplastic elastomer compositions obtained in Examples 1 to 9 were excellent in vibration damping property, resilience, and heat resistance. In contrast, the thermoplastic elastomer compositions obtained in Comparative Examples 1 to 6 obtained low evaluation results in at least one of vibration damping property, resilience, and heat resistance. In the thermoplastic elastomer compositions of Examples 1 to 9 and Comparative Example 4, the polyphenylene ether resin (b) was dispersed to an extremely high degree in the matrix phase, and it was difficult to clearly identify the polyphenylene ether resin (b) in transmission electron microscope images.

[0110] The thermoplastic elastomer composition of the present invention has excellent vibration-damping properties, recovery properties, and heat resistance. Furthermore, the thermoplastic elastomer composition of the present invention has an appropriate hardness. Therefore, the composition can be suitably used for vibration-damping members and the like that are used to suppress vibrations in home appliances, automobile parts, sporting goods, and the like.

Claims

1. (a) a thermoplastic elastomer; (b) a polyphenylene ether resin, and (c) Rubber softener A thermoplastic elastomer composition comprising: The thermoplastic elastomer (a) comprises a thermoplastic elastomer (a1) and a thermoplastic elastomer (a2) in a mass ratio of 90:10 to 45:55; The thermoplastic elastomer (a1) is a block copolymer consisting of a polymer block (X1) composed of a structural unit derived from an aromatic vinyl compound and a polymer block (Y1) composed of a structural unit derived from a conjugated diene compound, and has a weight average molecular weight of more than 150,000 and not more than 500,000, and the content of the structural unit derived from the aromatic vinyl compound in the thermoplastic elastomer (a1) is 10 mass% or more based on the total structural units constituting the thermoplastic elastomer (a1); The thermoplastic elastomer (a2) is a block copolymer consisting of a polymer block (X2) composed of a structural unit derived from an aromatic vinyl compound and a polymer block (Y2) composed of a structural unit derived from a conjugated diene compound, and has a weight average molecular weight of 50,000 or more and 150,000 or less, the content of the structural unit derived from an aromatic vinyl compound in the thermoplastic elastomer (a2) is 2 mass% or more based on all the structural units constituting the thermoplastic elastomer (a2), and the total content of 1,2-bond units and 3,4-bond units of the structural units derived from a conjugated diene compound in the thermoplastic elastomer (a2) is 50 mol% or more based on all the structural units derived from the conjugated diene compound, In a transmission electron microscope image of the thermoplastic elastomer composition, the polyphenylene ether resin (b) dispersed in a matrix phase containing the thermoplastic elastomer (a) has a maximum major axis of 2 μm or less, The thermoplastic elastomer composition is injection molded at 230°C to obtain three test pieces each having a thickness of 2 mm. The hardness of the test pieces is measured after 3 seconds using a type A durometer in accordance with JIS K 6253 and is 80 or less.

2. The composition according to claim 1, wherein the hydrogenation rate of the polymer block (Y2) of the thermoplastic elastomer (a2) is 20% or less.

3. The composition according to claim 1, wherein the thermoplastic elastomer (a2) has an order-disorder transition temperature of 280° C. or less.

4. The composition according to claim 1, comprising 5 to 100 parts by mass of the polyphenylene ether resin (b) and 50 to 300 parts by mass of the rubber softener (c) relative to 100 parts by mass of the thermoplastic elastomer (a).

5. The composition of claim 1 further comprising a polypropylene (d).

6. The composition of claim 1 further comprising an inorganic filler (e).

7. The composition according to claim 1, wherein the compression set after maintaining a 25% compression deformation at 70°C for 22 hours in accordance with JIS K 6262:2013 is 50% or less.

8. A molded article comprising the composition according to claim 1.