Thermoplastic elastomer composition and molded article

Abstract

To provide a thermoplastic elastomer composition having excellent flowability, mechanical strength, and oil resistance despite low hardness.SOLUTION: A thermoplastic elastomer composition contains 100 pts.mass of polyolefin-based rubber (A) including ethylene α-olefin copolymer (A1) and ethylene α-olefin nonconjugated polyene copolymer (A2), and 10 to 60 pts.mass of crystalline propylene-based polymer (B), where the content of the ethylene α-olefin copolymer (A1) exceeds 0 mass% and is less than 40 mass% for the total 100 mass% of the content of the ethylene α-olefin copolymer (A1) and the ethylene α-olefin nonconjugated polyene copolymer (A2), the content of the ethylene α-olefin nonconjugated polyene copolymer (A2) exceeds 60 mass% and is less than 100 mass%, and at least a part of which is cross-linked by organic peroxide-based cross-linking agent (C) and phenol resin-based cross-linking agent (D).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic elastomer composition and a molded article containing the same. [Background technology]

[0002] Compositions in which polypropylene is mixed with olefin copolymer rubber are used as thermoplastic elastomers in fields such as automobile parts, home appliance parts, medical device parts, electric wires, and miscellaneous goods. It is known that the formation of a crosslinked structure in thermoplastic elastomers reduces compression set and improves performance such as oil resistance. Thermoplastic elastomers with crosslinked structures can be obtained by subjecting a mixture of olefin copolymer rubber and polypropylene to dynamic heat treatment in the presence of a crosslinking agent.

[0003] For example, a method for producing a thermoplastic elastomer composition by dynamic heat treatment using a phenolic resin crosslinking agent has been proposed (e.g., Patent Document 1). Furthermore, the combined use of multiple crosslinking agents has also been proposed. For example, a method has been proposed in which an olefinic thermoplastic elastomer is pre-crosslinked with an organic peroxide, and then crosslinked with a phenolic resin crosslinking agent (e.g., Patent Document 2). Another method has been proposed in which an olefinic thermoplastic elastomer is pre-crosslinked with a phenolic resin crosslinking agent, and then crosslinked with an organic peroxide (e.g., Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-36143 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-137352 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-24929 Summary of the Invention [Problem to be solved by the invention]

[0005] In fields such as automobile parts, there is a demand for thermoplastic elastomers that are excellent in oil resistance and mechanical strength, as well as low hardness. However, all of the thermoplastic elastomers described in Patent Documents 1 to 3 have high hardness and do not meet such market demands. Furthermore, when a phenolic resin crosslinking agent is used as the crosslinking agent, the melt flow rate (MFR) of the thermoplastic elastomer tends to decrease, resulting in poor processability. An object of the present invention is to provide a thermoplastic elastomer composition that has low hardness but is excellent in flowability, mechanical strength, and oil resistance. [Means for solving the problem]

[0006] As a result of further research, the present inventors have found that the above-mentioned problems can be solved by the following configuration example. In this specification, the numerical range "A to B" indicates A or more and B or less.

[0007] [1] 100 parts by mass of a polyolefin rubber (A) containing an ethylene-α-olefin copolymer (A1) and an ethylene-α-olefin-non-conjugated polyene copolymer (A2); 10 to 60 parts by mass of a crystalline propylene polymer (B); Including, the content of the ethylene-α-olefin copolymer (A1) is more than 0% by mass and less than 40% by mass, and the content of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is more than 60% by mass and less than 100% by mass, relative to 100% by mass of the total content of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin-non-conjugated polyene copolymer (A2); A thermoplastic elastomer composition at least partially crosslinked with an organic peroxide-based crosslinking agent (C) and a phenolic resin-based crosslinking agent (D).

[0008] [2] The thermoplastic elastomer composition according to [1], further comprising 100 to 300 parts by mass of a softener (E).

[0009] [3] The thermoplastic elastomer composition according to claim 1 or 2, wherein the ratio (D / A2) of the content of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) to the content of the phenolic resin-based crosslinking agent (D) is 0.01 to 1.00.

[0010] [4] The thermoplastic elastomer composition according to any one of [1] to [3], wherein the ratio (C / D) of the content of the organic peroxide-based crosslinking agent (C) to the content of the phenolic resin-based crosslinking agent (D) is greater than 0 and not more than 0.5.

[0011] [5] The thermoplastic elastomer composition according to any one of [1] to [4], wherein the content of the organic peroxide-based crosslinking agent (C) is 0.2 to 2.0 parts by mass per 100 parts by mass of the polyolefin-based rubber (A).

[0012] [6] The thermoplastic elastomer composition according to any one of [1] to [5], which satisfies the following requirements (1) and (2): (1) The melt flow rate measured in accordance with ASTM D-1238 at 230°C under a load of 10 kg is 3 to 100 g / 10 min. (2) The Shore A hardness (instantaneous value) measured in accordance with JIS K 6253 is 30 to 70.

[0013] [7] A molded article comprising the thermoplastic elastomer composition according to any one of [1] to [6].

[0014] [8] The molded article according to [7], which is an automobile part.

[0015] [9] The molded article according to [7] or [8], which is a sealing member. [Effects of the Invention]

[0016] According to the present invention, a thermoplastic elastomer composition having low hardness but excellent flowability, mechanical strength and oil resistance can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Thermoplastic elastomer composition> The thermoplastic elastomer composition according to the present invention (hereinafter also referred to as "the composition") contains 100 parts by mass of a polyolefin rubber (A) containing an ethylene-α-olefin copolymer (A1) and an ethylene-α-olefin-non-conjugated polyene copolymer (A2), and 10 to 60 parts by mass of a crystalline propylene polymer (B), and is at least partially crosslinked with an organic peroxide-based crosslinking agent (C) and a phenolic resin-based crosslinking agent (D).

[0018] <Polyolefin rubber (A)> The polyolefin rubber (A) contains an ethylene-α-olefin copolymer (A1) and an ethylene-α-olefin-non-conjugated polyene copolymer (A2).

[0019] The polyolefin rubber (A) is at least partially crosslinked in the composition, and may be completely crosslinked. The timing of crosslinking the polyolefin rubber (A) is not particularly limited. For example, at least a portion of the polyolefin rubber (A) may be (dynamically) crosslinked before mixing with the crystalline propylene polymer (B), or at least a portion of the polyolefin rubber (A) may be (dynamically) crosslinked after or while mixing with the crystalline propylene polymer (B). When the polyolefin rubber (A) has a high degree of crosslinking, the oil resistance and rubber elasticity of the molded article obtained from the composition are good, even if the hardness of the composition is low. In addition, as the degree of crosslinking of the polyolefin rubber (A) increases, the compression set of the molded article produced from the composition tends to decrease. Therefore, the degree of crosslinking of the polyolefin rubber (A) can be estimated from the compression set of the molded article produced from the composition.

[0020] The content of the polyolefin rubber (A) in the composition (when the total of the polyolefin rubber (A), the crystalline propylene polymer (B), the organic peroxide crosslinking agent (C), and the phenolic resin crosslinking agent (D) is taken as 100% by mass) is preferably 62.5 to 91% by mass, more preferably 65 to 84% by mass, even more preferably 67 to 80% by mass, and particularly preferably 68.5 to 75% by mass, because the composition has excellent moldability and the resulting molded article has low hardness but excellent mechanical strength.

[0021] [Ethylene-α-olefin copolymer (A1)] The ethylene-α-olefin copolymer (A1) is not particularly limited as long as it contains structural units derived from ethylene and structural units derived from an α-olefin. The ethylene-α-olefin copolymer (A1) may be synthesized by a conventionally known method of copolymerizing ethylene and an α-olefin, or may be a commercially available product. The ethylene-α-olefin copolymer (A1) contained in the present composition may be one type or two or more types.

[0022] The α-olefin is not particularly limited, but is preferably an α-olefin having 3 to 20 carbon atoms. Specific examples of α-olefins having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene. These α-olefins may be used alone or in combination of two or more. Among these α-olefins, propylene, 1-butene, and 1-octene are preferred, with 1-octene being particularly preferred, from the viewpoints of the degree of crosslinking and dispersibility with the propylene-based polymer. That is, as the ethylene-α-olefin copolymer (A1), an ethylene-propylene copolymer, an ethylene-butene copolymer, and an ethylene-octene copolymer are preferred, with an ethylene-octene copolymer being most preferred.

[0023] The density of the ethylene-α-olefin copolymer (A1) is preferably 0.84 to 0.88 g / cm from the viewpoint of the degree of crosslinking of the composition. 3 , more preferably 0.84 to 0.87 g / cm 3 , and more preferably 0.84 to 0.86 g / cm 3 The content of structural units derived from an α-olefin in the ethylene-α-olefin copolymer (A1) is preferably 1 to 60 wt %, more preferably 10 to 50 wt %, and even more preferably 20 to 45 wt %. The content of ethylene-derived structural units and the content of α-olefin-derived structural units are: 13 The density of ethylene-α-olefin copolymers can be measured by the method described in ASTM D792.

[0024] The ethylene-α-olefin copolymer (A1) preferably has a melt flow rate (hereinafter also referred to as "MFR") of 0.05 to 50 g / 10 min, more preferably 0.1 to 20 g / 10 min, measured at 190°C under a load of 2.16 kg in accordance with the measurement method of ASTM D-1238, in order to improve the fluidity of the composition.

[0025] The ethylene-α-olefin copolymer (A1) forms a crosslinked structure with the organic peroxide-based crosslinking agent (C), but not with the phenolic resin-based crosslinking agent (D). Furthermore, if the polyolefin rubber (A) contains fewer crosslinked structures, the melt fluidity of the composition tends to be less likely to decrease. Therefore, the content of the ethylene-α-olefin copolymer (A1) can be adjusted to reduce the crosslinked structures in the polyolefin rubber (A) within a range that does not excessively reduce the mechanical strength of molded articles obtained from the composition, thereby ensuring the melt fluidity of the composition. The amount of the ethylene-α-olefin copolymer (A1) is more than 0% by mass and less than 40% by mass, preferably 5 to 35% by mass, and more preferably 10 to 30% by mass, relative to 100% by mass of the total amount of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin-non-conjugated polyene copolymer (A2) contained in the polyolefin rubber (A). When the amount of the ethylene-α-olefin copolymer (A1) is within the above range, the composition has excellent moldability, and the obtained molded article has excellent oil resistance and mechanical strength. The polyolefin rubber (A) may contain a polyolefin rubber other than the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin-non-conjugated polyene copolymer (A2). In this case, the amount of the ethylene-α-olefin copolymer (A1) relative to 100% by mass of the polyolefin rubber (A) is preferably more than 0% by mass and less than 40% by mass, more preferably 5 to 35% by mass, and even more preferably 10 to 30% by mass, in order to ensure that the composition has excellent moldability and that the obtained molded article has excellent oil resistance and mechanical strength.

[0026] [Ethylene-α-olefin-non-conjugated polyene copolymer (A2)] The ethylene-α-olefin-non-conjugated polyene copolymer (A2) is not particularly limited as long as it contains ethylene-derived structural units, α-olefin-derived structural units, and non-conjugated polyene-derived structural units. For example, it may be synthesized by a conventionally known method of copolymerizing ethylene, α-olefin, and non-conjugated polyene, or a commercially available product may be used. The ethylene-α-olefin-non-conjugated polyene copolymer (A2) contained in the present composition may be one type or two or more types.

[0027] The α-olefin serving as a structural unit of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is not particularly limited, but is preferably an α-olefin having 3 to 20 carbon atoms. Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene. These α-olefins may be used alone or in combination of two or more. Among these α-olefins, α-olefins having 3 to 20 carbon atoms are preferred, with propylene and 1-butene being more preferred, and propylene being even more preferred, because they are relatively inexpensive raw materials, can be used to obtain an ethylene-α-olefin-non-conjugated polyene copolymer (A2) having excellent mechanical properties, and can be molded into a molded article having excellent rubber elasticity when the composition containing the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is molded. That is, as the ethylene-α-olefin-non-conjugated polyene copolymer (A2), an ethylene-propylene-non-conjugated polyene copolymer and an ethylene-1-butene-non-conjugated polyene copolymer are preferred, and an ethylene-propylene-non-conjugated polyene copolymer is most preferred.

[0028] Non-conjugated polyenes that serve as structural units of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) include cyclic and linear non-conjugated polyenes. Examples of cyclic non-conjugated polyenes include 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinyl-2-norbornene, norbornadiene, and methyltetrahydroindene. Examples of linear non-conjugated polyenes include 1,4-hexadiene, 7-methyl-1,6-octadiene, 8-methyl-4-ethylidene-1,7-nonadiene, and 4-ethylidene-1,7-undecadiene. These non-conjugated polyenes may be used alone or in combination of two or more. Among these non-conjugated polyenes, dicyclopentadiene, 5-vinyl-2-norbornene, and 5-ethylidene-2-norbornene are preferred from the viewpoint of the degree of crosslinking of the present composition, with 5-ethylidene-2-norbornene being more preferred. That is, the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is preferably an ethylene-propylene-5-ethylidene-2-norbornene copolymer.

[0029] The ethylene / α-olefin / non-conjugated polyene copolymer (A2) is obtained by dividing the ethylene / α-olefin ratio by the mass W of the ethylene-derived structural unit [A]. A and the mass W of the structural unit [B] derived from α-olefin B The ratio of [W A / W B ], then [W A / W B ] is preferably in the range of 40 / 60 to 90 / 10. A / W B ] is more preferably 45 / 55 to 80 / 20, further preferably 50 / 50 to 75 / 25, particularly preferably 55 / 45 to 70 / 30, and most preferably 55 / 45 to 68 / 32. The content of ethylene-derived structural units, the content of α-olefin-derived structural units, and the content of non-conjugated polyene-derived structural units are: 13 It can be determined by calculation based on the results of measurements using C-NMR.

[0030] The content of the structural units derived from non-conjugated polyene in the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is an amount that results in an iodine value of preferably 1 to 25, more preferably 5 to 20, and particularly preferably 5 to 15. When the iodine value of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is within the above range, the rubber elasticity and oil resistance of the composition tend to be good. In the ethylene-α-olefin-non-conjugated polyene copolymer (A2), the content of the structural unit [C] derived from the non-conjugated polyene is preferably 0.1 to 10 mass%, more preferably 1.0 to 8.0 mass%, even more preferably 2.0 to 6.0 mass%, and particularly preferably 3.0 to 5.0 mass%, relative to 100 mass% of the total of the structural units [A], [B], and [C]. When the content of the structural unit [C] derived from the non-conjugated polyene is within this range, an ethylene-based copolymer with sufficient crosslinkability and flexibility tends to be obtained. In other words, when the content of the structural unit [C] derived from the non-conjugated polyene is within this range, an ethylene-based copolymer with sufficient crosslinkability and flexibility is obtained, and the rubber elasticity and oil resistance of the composition tend to be good.

[0031] The ethylene-α-olefin-non-conjugated polyene copolymer (A2) preferably has an intrinsic viscosity [η] measured in decalin (decahydronaphthalene) at 135°C of 2.0 to 7.0 dl / g, more preferably 3.0 to 7.0 dl / g, and even more preferably 3.3 to 7.0 dl / g, in order to improve the mechanical strength and oil resistance of the composition. When the ethylene-α-olefin-non-conjugated polyene copolymer (A2) has been oil-extended with an oil extender such as the softener (E) described below, it is degreased before measuring the intrinsic viscosity [η], and the measurement is carried out on the ethylene-α-olefin-non-conjugated polyene copolymer (A2) alone.

[0032] The density of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is preferably 0.80 to 0.89 g / cm 3 and more preferably 0.83 to 0.89 g / cm 3 and more preferably 0.83 to 0.88 g / cm 3 When measuring the density of ethylene-α-olefin-non-conjugated polyene copolymer (A2), if the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is oil-extended, degreasing should be performed before measurement, so that the measurement object is limited to the ethylene-α-olefin-non-conjugated polyene copolymer (A2).

[0033] The ethylene-α-olefin-non-conjugated polyene copolymer (A2) forms a crosslinked structure with both the organic peroxide-based crosslinking agent (C) and the phenolic resin-based crosslinking agent (D). When the crosslinked structure formed by the phenolic resin-based crosslinking agent (D) is contained, the oil resistance and mechanical strength of the composition tend to be improved. The amount of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is more than 60% by mass but less than 100% by mass, preferably 65 to 95% by mass, and more preferably 70 to 90% by mass, relative to the total amount of the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin-non-conjugated polyene copolymer (A2) contained in the polyolefin rubber (A), taken as 100% by mass. When the amount of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) is within the above range, the composition has excellent moldability, and the obtained molded article has excellent oil resistance and mechanical strength. The polyolefin rubber (A) may contain a polyolefin rubber other than the ethylene-α-olefin copolymer (A1) and the ethylene-α-olefin-non-conjugated polyene copolymer (A2). In this case, the amount of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) relative to 100% by mass of the polyolefin rubber (A) is preferably more than 60% by mass and less than 100% by mass, more preferably 65 to 95% by mass, and even more preferably 70 to 90% by mass, in order to ensure that the composition has excellent moldability and that the obtained molded article has excellent oil resistance and mechanical strength.

[0034] <Crystalline propylene polymer (B)> The crystalline propylene polymer (B) is a polymer other than the polyolefin rubber (A). The term "crystalline" means that a melting point (Tm) can be observed in differential scanning calorimetry (DSC).

[0035] The crystalline propylene polymer (B) may be a propylene homopolymer or a copolymer of propylene and a comonomer other than propylene. The structure of the crystalline propylene polymer (B) is not particularly limited, and the propylene-derived structural unit portion may have an isotactic structure, a syndiotactic structure, or an atactic structure. The copolymer may be of any of a random type, a block type, or a graft type. When the crystalline propylene-based polymer (B) is a copolymer, the content of propylene-derived structural units among the structural units constituting the polymer is preferably 70% by mass or more, more preferably 80% by mass or more, since the oil resistance and mechanical strength of the composition are likely to be good.

[0036] The crystalline propylene polymer (B) is preferably a propylene homopolymer or a block copolymer, since this tends to improve the oil resistance and mechanical strength of the composition. Furthermore, a mixture of a propylene homopolymer and a block copolymer may be used as the crystalline propylene polymer (B) from the viewpoint of the oil resistance and mechanical strength of the composition. When a mixture of a propylene homopolymer and a block copolymer is used as the crystalline propylene polymer (B), the proportion of the propylene homopolymer in the crystalline propylene polymer (B) is preferably 5 to 90% by mass, more preferably 5 to 50% by mass, and even more preferably 5 to 40% by mass. Meanwhile, the proportion of the block copolymer in the crystalline propylene polymer (B) is preferably 1 to 90% by mass, more preferably 5 to 90% by mass, and even more preferably 10 to 90% by mass.

[0037] The crystalline propylene polymer (B) may be synthesized by a conventionally known method, or a commercially available product may be used. The crystalline propylene polymer (B) contained in the present composition may be one type or two or more types.

[0038] When the crystalline propylene polymer (B) is a copolymer, the comonomer may be any other monomer copolymerizable with propylene, but is preferably an α-olefin having 2 or 4 to 12 carbon atoms. Specific examples include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene, with ethylene, 1-butene, and 1-octene being preferred. One or more types of comonomers may be used. The content of the structural units derived from the comonomer in the copolymer is preferably 30% by mass or less, more preferably 20% by mass, from the viewpoint of the oil resistance of the composition.

[0039] The melting point of the crystalline propylene polymer (B), measured in accordance with the measurement method of JIS K 7121, is preferably 50 to 170° C., more preferably 70 to 167° C. When the melting point of the crystalline propylene polymer (B) is within the above range, the resulting composition has excellent heat resistance.

[0040] From the viewpoint of fluidity, the crystalline propylene polymer (B) preferably has a melt flow rate (MFR) of 0.1 to 50 g / 10 min, more preferably 0.5 to 30 g / 10 min, as measured at 230°C under a load of 2.16 kg in accordance with the measurement method of ASTM D-1238. When the MFR of the crystalline propylene polymer (B) is within the above range, the resulting composition has excellent fluidity, which is preferred.

[0041] The content of the crystalline propylene polymer (B) in the composition is 10 to 60 parts by mass, preferably 20 to 50 parts by mass, more preferably 25 to 45 parts by mass, and particularly preferably 30 to 40 parts by mass, per 100 parts by mass of the polyolefin rubber (A). When the content of the crystalline propylene polymer (B) in the composition is within the above range, the hardness of the resulting composition is preferably low. Examples of the crystalline propylene polymer (B) include Prime Polypro (trade name) manufactured by Prime Polymer Co., Ltd., Novatec PP (trade name) manufactured by Japan Polypropylene Corporation, polypropylene manufactured by SunAllomer Corporation, polypropylene manufactured by LyondellBasell, polypropylene manufactured by Braskem, and polypropylene manufactured by SCG Chemicals.

[0042] <Organic peroxide crosslinking agent (C)> The organic peroxide crosslinking agent (C) may be either aromatic or aliphatic. The organic peroxide crosslinking agent (C) contained in the composition may be one type or two or more types. Examples of the organic peroxide crosslinking agent (C) include di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, and other dialkyl peroxides; t-butyl peroxybenzoate, t-butyl cumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, and other dialkyl peroxides. peroxyesters such as n-butylperoxyisopropyl monocarbonate, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexyne-3; and diacyl peroxides such as diacetyl peroxide, lauroyl peroxide, dibenzoyl peroxide, p-chlorobenzoyl peroxide, and 2,4-dichlorobenzoyl peroxide. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 are preferred from the viewpoint of the degree of crosslinking of the resulting composition.

[0043] The organic peroxide crosslinking agent (C) preferably has a one-minute half-life temperature of 140 to 230°C, from the viewpoint that the degree of crosslinking and dispersibility of the resulting composition tend to be good. Organic peroxides that satisfy this condition include dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, and 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane; t-butyl peroxybenzoate, t-butylperoxyisopropyl monocarbonate, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexyne-3.

[0044] The content of the organic peroxide crosslinking agent (C) in the composition is preferably 0.2 to 2.0 parts by mass, more preferably 0.3 to 1.8 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of the polyolefin rubber (A). When the content of the organic peroxide crosslinking agent (C) is within the above range, the composition has an excellent balance between the degree of crosslinking and the mechanical strength, which is preferable.

[0045] The ratio (C / D) of the content of the organic peroxide crosslinking agent (C) to the content of the phenolic resin crosslinking agent (D) in the composition is preferably greater than 0 and not greater than 0.5, more preferably 0.10 to 0.40, and even more preferably 0.15 to 0.30. A ratio of the content of the organic peroxide crosslinking agent (C) to the content of the phenolic resin crosslinking agent (D) within the above range is preferred because the composition has an excellent balance between the degree of crosslinking and fluidity. In addition, with the composition, the larger the (C / D) ratio, the greater the MFR value tends to be, and the more fluidity tends to be.

[0046] <Phenol resin-based crosslinking agent (D)> The phenolic resin crosslinking agent (D) is a thermally crosslinkable phenolic resin. Examples of the phenolic resin crosslinking agent include phenolic resins produced by condensation of substituted or unsubstituted phenol with an aldehyde, phenolic resins produced by condensation of bifunctional phenol dialcohols, and halogenated phenolic resins. The substituted phenol is preferably an alkyl group-substituted phenol having 1 to 10 carbon atoms. The aldehyde used in the condensation with the substituted or unsubstituted phenol is preferably formaldehyde.

[0047] For the phenolic resin-based crosslinking agent (D), reference can be made to the descriptions in US Pat. Nos. 3,287,440, 3,709,840 and 4,311,628.

[0048] As the phenolic resin-based crosslinking agent (D), commercially available phenolic resins can be appropriately selected and used. Examples of commercially available products that can be used as the phenolic resin-based crosslinking agent (D) include Tackirol 201 (an alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), Tackirol 250-I (a brominated alkylphenol formaldehyde resin with a bromination rate of 4%, manufactured by Taoka Chemical Co., Ltd.), Tackirol 250-III (a brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), PR-4507 (manufactured by Gunei Chemical Industry Co., Ltd.), Vulkaresat 510E (manufactured by Hoechst), Vulkaresat 532E (manufactured by Hoechst), Vulkaresen E (manufactured by Hoechst), Vulkaresen 105E (manufactured by Hoechst), Vulkaresen 130E (manufactured by Hoechst), Vulkaresol 315E (manufactured by Hoechst), and Amberol Examples of suitable resins include ST 137X (manufactured by Rohm & Haas), Sumilite Resin PR-22193 (manufactured by Sumitomo Durez Co., Ltd.), Symphorm-C-100 (manufactured by Anchor Chem.), Symphorm-C-1001 (manufactured by Anchor Chem.), Tamanol 531 (manufactured by Arakawa Chemical Co., Ltd.), Schenectady SP1059 (manufactured by Schenectady Chem.), Schenectady SP1045 (manufactured by Schenectady Chem.), CRR-0803 (manufactured by UCC), Schenectady SP-1055 (manufactured by Schenectady Chem.), Schenectady SP-1056 (manufactured by Schenectady Chem.), CRM-0803 (manufactured by Showa Union Synthetic Co., Ltd.), and Vulkadu r A (manufactured by Bayer). Among these, brominated alkylphenol formaldehyde resin is preferred from the viewpoint of the degree of crosslinking.

[0049] The content of the phenolic resin crosslinking agent (D) in the composition is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 6 parts by mass, relative to 100 parts by mass of the polyolefin rubber (A). When the content of the phenolic resin crosslinking agent (D) is within the above range, the resulting composition is preferred because it has excellent oil resistance and rubber elasticity.

[0050] The ratio (D / A2) of the content of the phenolic resin-based crosslinking agent (D) to the content of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) in the composition is preferably 0.01 to 1.00, more preferably 0.01 to 0.2, even more preferably 0.02 to 0.08, and particularly preferably 0.03 to 0.06. Here, (D / A2) can approximate the proportion of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) crosslinked with the phenolic resin-based crosslinking agent (D). A ratio of the content of the phenolic resin-based crosslinking agent (D) to the content of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) within the above range is preferred because the resulting composition has excellent oil resistance and rubber elasticity.

[0051] <Other additives> The composition may contain, to the extent that the object of the present invention is not impaired, other thermoplastic resins such as polyolefin resins (excluding the polyolefin rubber (A) and the crystalline propylene polymer (B)), crosslinking aids, activators for the phenolic resin crosslinking agent (D), and resin additives (e.g., slip agents, antioxidants, UV absorbers, light stabilizers, conductivity-imparting agents, antistatic agents, dispersants, flame retardants, antibacterial agents, acid acceptors, softeners (E), fillers, colorants, thermally conductive fillers, etc.). These other additives may be used alone or in combination of two or more.

[0052] When the other additives are contained, the total amount of the other additives in the composition is usually 10% by mass or less, preferably 9% by mass or less, and more preferably 8% by mass or less, relative to 100% by mass of the total of the polyolefin rubber (A) and the crystalline propylene polymer (B).

[0053] [Crosslinking aid] A crosslinking aid can also be used to ensure uniformity in the crosslinking reaction caused by the organic peroxide-based crosslinking agent (C). Specific examples of crosslinking aids include divinyl compounds such as divinylbenzene; oxime compounds such as p-quinone dioxime and p,p'-dibenzoylquinone dioxime; nitroso compounds such as N-methyl-N-4-dinitrosoaniline and nitrosobenzene; maleimide compounds such as trimethylolpropane-N,N'-m-phenylenedimaleimide; and sulfur, diphenyl guanidine, triallyl cyanurate, etc. Other examples of crosslinking aids include polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate; and polyfunctional vinyl monomers such as vinyl butyrate and vinyl stearate.

[0054] [Activator for phenolic resin crosslinker (D)] When the phenolic resin crosslinking agent (D) is not halogenated, it can be used together with an activator. Examples of the activator include halogen donors such as stannous chloride, ferric chloride, chlorinated paraffin, chlorinated polyethylene, and chlorosulfonated polyethylene. When the phenolic resin crosslinking agent (D) is halogenated, the halogen donor need not be used. When a halogen donor is added as an activator together with the phenolic resin-based crosslinking agent (D), the amount of the halogen donor added is such that the ratio of the phenolic resin-based crosslinking agent (D) to the halogen donor ((D) / (halogen donor)) is preferably 1 to 100, more preferably 2 to 50.

[0055] [Acid acceptor] The acid acceptor may be iron oxide, titanium oxide, magnesium oxide, silicon dioxide, zinc oxide, etc. When an acid acceptor is used, the amount of the acid acceptor added is such that the ratio of the phenolic resin crosslinking agent (D) to the acid acceptor ((D) / (acid acceptor)) is preferably 1 to 100, more preferably 2 to 50.

[0056] [Softener (E)] The present composition preferably contains a softener (E) for the purpose of adjusting the flowability and hardness. Specific examples of the softener (E) include petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, polyethylene wax, polypropylene wax, petroleum asphalt, and Vaseline; coal tar-based softeners such as coal tar and coal tar pitch; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, soybean oil, and coconut oil; tall oil; sub(factice); waxes such as beeswax, carnauba wax, and lanolin; ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, and lauric acid. Examples of softeners include fatty acids or fatty acid salts such as zinc phosphate; naphthenic acid; pine oil, rosin or derivatives thereof; synthetic polymer softeners such as terpene resin, petroleum resin, coumarone-indene resin, and atactic polypropylene; ester softeners such as dioctyl phthalate, dioctyl adipate, and dioctyl sebacate; microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, liquid polyisoprene, terminal-modified polyisoprene, hydrogenated terminal-modified polyisoprene, liquid thiokol, and hydrocarbon-based synthetic lubricating oils. Among these, process oil is preferred.

[0057] As described above, the softener (E) may be used, for example, by pre-mixing (oil-extending) with the polyolefin rubber (A), or may be used when preparing the present composition, or may be added later when the components to be blended in the present composition are dynamically heat-treated.

[0058] When the present composition contains a softener (E), the content of the softener in the present composition is preferably 100 to 300 parts by mass, more preferably 120 to 250 parts by mass, and even more preferably 140 to 200 parts by mass, per 100 parts by mass of the polyolefin rubber (A). If the content of the softener (E) is within the above range, the resulting composition tends to have high fluidity and low hardness, which is preferable.

[0059] <Method of manufacturing the present composition> This composition can be produced by mixing polyolefin rubber (A), crystalline propylene polymer (B), organic peroxide crosslinking agent (C), phenolic resin crosslinking agent (D), and, if necessary, other additives described above, and dynamically crosslinking the mixture. In this specification, "dynamic crosslinking" refers to a process of forming a crosslinked structure in at least a part of polyolefin rubber (A) by melt-kneading a mixture containing necessary components such as polyolefin rubber (A) while applying shear force.

[0060] When melt-kneading, it is preferable to use a conventionally known mixing / kneading device such as a Banbury mixer, a mixing roll, a Henschel mixer, a kneader, a single-screw or twin-screw extruder, etc. The order of adding each component when mixing / kneading is not particularly limited, as long as the organic peroxide-based crosslinking agent (C) and the phenolic resin-based crosslinking agent (D) are added simultaneously.

[0061] In this specification, "added simultaneously" means that both the organic peroxide-based crosslinking agent (C) and the phenolic resin-based crosslinking agent (D) are added at a time when the crosslinking reaction by either agent has not substantially occurred. In other words, "added simultaneously" does not include the case where the organic peroxide-based crosslinking agent (C) is added after the crosslinking reaction by the phenolic resin-based crosslinking agent (D) has begun, or the case where the phenolic resin-based crosslinking agent (D) is added after the crosslinking reaction by the organic peroxide-based crosslinking agent (C) has begun. The fact that the crosslinking reaction by the organic peroxide-based crosslinking agent (C) or the phenolic resin-based crosslinking agent (D) has not begun can be confirmed by the fact that the melt viscosity of the mixture has not substantially increased.

[0062] Dynamic crosslinking can provide a composition containing a polyolefin rubber (A) in an at least partially crosslinked state. In this specification, "at least partially crosslinked" refers to a gel content in the range of 30 to 100 mass %, preferably 40 to 100 mass %.

[0063] The dynamic crosslinking is preferably carried out in a non-open type apparatus, and is preferably carried out in an atmosphere of an inert gas such as nitrogen or carbon dioxide. The heating temperature in dynamic crosslinking is usually 125 to 280° C., preferably 145 to 240° C., and the mixing and kneading time is usually 1 to 30 minutes, preferably 3 to 20 minutes. The shear force applied during the mixing and kneading is, for example, a maximum shear rate of 10 to 100,000 sec -1 , preferably 100 to 50,000 seconds -1 , more preferably 1,000 to 10,000 seconds -1 , and more preferably 2,000 to 7,000 seconds -1 Examples of shear forces include:

[0064] As described above, by simultaneously adding the organic peroxide-based crosslinking agent (C) and the phenolic resin-based crosslinking agent (D) to cause dynamic crosslinking, the composition has low hardness and is excellent in all of fluidity, mechanical strength, and oil resistance.

[0065] <Physical properties of the composition> [Shore A hardness] The composition has a Shore A hardness (instantaneous value) of preferably 30 to 70, more preferably 40 to 60, and even more preferably 45 to 55, measured in accordance with JIS K 6253. When the Shore A hardness (instantaneous value) of the present composition is within the above range, it becomes a thermoplastic elastomer composition with low hardness, which meets the market demand, and can be suitably used in applications requiring low hardness, such as sealing materials and hoses. Specifically, the Shore A hardness (instantaneous value) can be measured by the method described in the examples below.

[0066] [MFR] The composition has an MFR of preferably 3 to 100 g / 10 min, more preferably 5 to 80 g / 10 min, and even more preferably 8 to 45 g / 10 min, measured at 230°C under a load of 10 kg in accordance with ASTM D-1238. When the MFR of the composition is within the above range, good moldability is obtained, which is preferred.

[0067] Tensile Breaking Strength (TB) The composition preferably has a tensile break strength (TB) of 1.0 MPa or more, more preferably 1.5 MPa or more, and even more preferably 2.0 MPa or more, measured at 23°C in accordance with JIS K 6301. Since a higher tensile break strength (TB) is preferable, there is no upper limit, but it is usually 40 MPa or less. If the tensile strength at break of the present composition is within the above range, the mechanical properties of the molded article obtained from the present composition will be good, which is preferable. Specifically, the tensile strength at break can be measured by the method described in the examples below.

[0068] [Tensile elongation at break (EB)] The composition preferably has a tensile breaking elongation (EB) of 200% or more, more preferably 300% or more, and even more preferably 350% or more, measured at 23°C in accordance with JIS K 6301. Since a higher tensile breaking elongation (EB) is preferable, there is no particular upper limit, but it is usually 1500% or less. If the tensile elongation at break of the present composition is within the above range, the mechanical properties of the molded article obtained from the present composition will be good, which is preferable. Specifically, the tensile elongation at break can be measured by the method described in the examples below.

[0069] [Compression set (CS)] The present composition preferably has a compression set (CS) of 50% or less, more preferably 45% or less, and even more preferably 40% or less, measured in accordance with JIS K 6262 using a press sheet laminated in accordance with JIS K 6250. Since a lower compression set (CS) is preferable, the lower limit is not particularly limited, but it is usually 5% or more. If the compression set of the present composition is within the above range, the molded article obtained from the present composition will have good sealing properties, which is preferable. Specifically, the compression set can be measured by the method described in the examples below.

[0070] [Oil resistance (volume change rate when immersed in test oil)] The volume change of the present composition when immersed in IRM903 oil at 125°C for 72 hours in accordance with JIS K 6301 is preferably 170% or less, more preferably 160% or less, and even more preferably 150% or less. Since a lower volume change is preferable, the lower limit is not particularly limited, but it is usually 10% or more. If the volume change rate of the present composition is within the above range, the oil resistance of the molded article obtained from the present composition is favorable, which is preferable. Specifically, the volume change rate can be measured by the method described in the examples below.

[0071] <Molded body> The molded article according to the present invention is not particularly limited as long as it contains the composition of the present invention, and is a molded article molded by any known molding method depending on the intended use. Examples of molding methods include press molding, injection molding, extrusion molding, calendar molding, blow molding, vacuum molding, and compression molding.

[0072] The molded article is used in applications requiring low hardness, mechanical strength, and oil resistance, and is preferably used for parts such as engine seals, hoses, etc. The molded article is preferably used for vehicle parts such as automobile parts, but can also be used for other applications such as machine parts and building materials. [Example]

[0073] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0074] <Ingredients> The raw materials used in the following examples and comparative examples are as follows.

[0075] [Ethylene-α-olefin copolymer (A1)] "Copolymer (A1-1)": Non-oil-extended ethylene-octene copolymer rubber, MFR (190°C, 2.16 kg load): 1 g / 10 min, density: 0.86 g / cm 3

[0076] [Ethylene-α-olefin-non-conjugated polyene copolymer (A2)] "Copolymer (A2-1)": oil-extended ethylene-propylene-non-conjugated diene copolymer rubber, ethylene content = 63 mass%, propylene content = 32.5 mass%, non-conjugated diene species: 5-ethylidene-2-norbornene, non-conjugated diene content = 4.5 mass%, non-conjugated diene content (iodine value) = 13, intrinsic viscosity [η] = 3.4 (dl / g), amount of oil extension per 100 parts by mass of rubber component = 40 (PHR) The values ​​for copolymer (A2-1) in Table 1 below indicate the amount of rubber component only, excluding the amount of oil extension. The following softener (E-1) was used to oil extend copolymer (A2-1).

[0077] [Crystalline propylene polymer (B)] "Propylene polymer (B-1)": propylene-ethylene block copolymer, MFR (230°C, 2.16 kg load) = 9 g / 10 min, melting point measured by DSC: 160°C "Propylene polymer (B-2)": Propylene homopolymer, MFR (230°C, 2.16 kg load) = 12 g / 10 min, melting point measured by DSC: 165°C

[0078] [Organic peroxide crosslinking agent (C)] Crosslinking agent (C-1): organic peroxide (2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, trade name: Perhexa 25B, manufactured by NOF Corporation)

[0079] [Phenol resin-based crosslinking agent (D)] Crosslinker (D-1): Brominated alkylphenol formaldehyde resin (product name: SP-1055F, manufactured by Schenectady)

[0080] [Softener (E)] "Softener (E-1)": Paraffin-based process oil (product name: Diana Process Oil (registered trademark) PW-100, manufactured by Idemitsu Kosan Co., Ltd.)

[0081] [Other additives] Crosslinking aid: Divinylbenzene DVB-810 (Nippon Steel Sumikin Chemical Co., Ltd.) Acid acceptor: Zinc oxide (Zinc oxide type 2, manufactured by Hakusui Tech)

[0082] The composition and physical properties of each component used in the examples and comparative examples were measured by the following methods.

[0083] <Mass fraction of constituent units> The mass fraction (mass%) of each structural unit contained in the copolymer (A2-1) is: 13 Specifically, the copolymer (A2-1) obtained using an ECX400P nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd.) under the conditions of a measurement temperature of 120°C, a measurement solvent of orthodichlorobenzene / deuterated benzene = 4 / 1 (volume ratio), and an accumulation number of 8000 times was 13 Calculated from the C-NMR spectrum.

[0084] <Melt flow rate (MFR)> The MFR of the copolymer (A1-1) was measured in accordance with ASTM D-1238 under conditions of 190° C. and a load of 2.16 kg. The MFR of the propylene polymers (B-1) and (B-2) was measured in accordance with ASTM D-1238 under conditions of 230° C. and a load of 2.16 kg.

[0085] <Intrinsic viscosity> The intrinsic viscosity [η] (dl / g) of the copolymer (A2-1) was measured using a fully automatic intrinsic viscometer manufactured by Rigo Co., Ltd. at a temperature of 135° C. and in decalin as a measurement solvent.

[0086] <Melting point> The melting point of the propylene polymer (B-1) was measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121. Specifically, pellets of the propylene polymer (B-1) were heated at 230°C for 10 minutes, then cooled to 30°C at a rate of 10°C / min, held at that temperature for 1 minute, and then heated at a rate of 10°C / min. The temperature at which the maximum amount of absorbed heat was measured in the DSC curve was taken as the melting point. The melting point of the propylene polymer (B-2) was also measured in the same manner.

[0087] <density> The density of the copolymer (A1-1) was measured in accordance with ASTM D1505.

[0088] [Example 1] A raw material was prepared by blending 20 parts by mass of copolymer (A1-1), 80 parts by mass of copolymer (A2-1), 25 parts by mass of propylene-based polymer (B-1), 7 parts by mass of propylene-based polymer (B-2), 0.7 parts by mass of crosslinking agent (C-1) as an organic peroxide crosslinking agent (C), 4 parts by mass of crosslinking agent (D-1) as a phenolic resin-based crosslinking agent (D), and 160.7 parts by mass of softener (E), and further blending 0.5 parts by mass of a crosslinking aid and 1 part by mass of an acid acceptor as other additives.

[0089] The entire amount of the raw materials was kneaded and dynamically crosslinked using an extruder (product number KTX-30, manufactured by Kobe Steel, Ltd.; cylinder temperatures: C1 = 50°C, C2 = 90°C, C3 = 100°C, C4 = 120°C, C5 = 180°C, C6 = 200°C, C7 to C14 = 200°C; die temperature: 200°C; screw rotation speed: 500 rpm; extrusion rate: 40 kg / h), to obtain pellets of a thermoplastic elastomer composition.

[0090] [Examples 2 to 6 and Comparative Examples 1 to 3] Pellets of thermoplastic elastomer compositions were obtained in the same manner as in Example 1, except that the types and amounts of raw materials used were changed as shown in Table 1. The numerical values ​​in the "blending" column in Table 1 indicate parts by mass.

[0091] <MFR of thermoplastic elastomer composition> The melt flow rates of the thermoplastic elastomer compositions obtained in the examples and comparative examples were measured at 230°C under a load of 10 kg in accordance with JIS K 7210. The results are shown in Table 1.

[0092] <Preparation of press sheets and test specimens> Pellets of each of the thermoplastic elastomer compositions obtained in the Examples and Comparative Examples were press-molded at 230°C for 6 minutes using a 100t electric automatic press (manufactured by Shoji Co., Ltd.), and then cooled and pressed at room temperature for 5 minutes to obtain flat pressed sheets with a thickness of 2 mm. Thereafter, a No. 3 dumbbell piece was punched out from the obtained press sheet to prepare a test piece having a thickness of 2 mm.

[0093] <Shore A hardness> Three 2 mm thick pressed sheets prepared by the above method were stacked and used as samples, and the Shore A hardness (instantaneous value) was measured using a durometer in accordance with JIS K 6253. The results are shown in Table 1.

[0094] <Tensile properties> The dumbbell-shaped No. 3 test pieces prepared by the above method were subjected to a tensile test (tensile speed: 500 mm / min, measurement temperature: 23°C) in accordance with JIS K 6301 to measure the tensile strength at break (TB) and tensile elongation at break (EB). The results are shown in Table 1.

[0095] <Compression set (CS)> According to JIS K 6250, six 2 mm thick press sheets were stacked to form a 12 mm thick laminated sheet. According to JIS K 6262, the resulting laminated sheet was compressed by 25% in the longitudinal direction for 22 hours at 70°C. After removal from the compression device, the length of the molded product was measured 30 minutes later, and the compression set was calculated. The results are shown in Table 1.

[0096] <Oil resistance test (volume change rate when immersed in test oil)> Before testing, the pressed sheet (2 mm thick) was cut into a 10 cm square and immersed in IRM903 oil at 125°C for 72 hours according to JIS K6258. The degree of swelling (ΔV) (volume %) was then measured as an indicator of oil resistance. The results are shown in Table 1.

[0097] [Table 1]

[0098] In all of Examples 1 to 6, the compositions had the same hardness, oil resistance, tensile strength at break, and compression set as those in Comparative Example 1, in which crosslinking treatment was performed using only the phenolic resin-based crosslinking agent (D), while the MFR was significantly greater than that of Comparative Example 1. Furthermore, in all of Examples 1 to 6, the compression set was smaller than that of Comparative Example 2, in which crosslinking treatment was performed using only the organic peroxide-based crosslinking agent (C). From these results, it is presumed that the compositions of Examples 1 to 6 have a crosslinked structure derived from the phenolic resin-based crosslinking agent (D), and therefore have better oil resistance, tensile strength at break, and compression set than compositions crosslinked using only the organic peroxide-based crosslinking agent (C).

[0099] Comparing Examples 1, 5, and 6, the MFR of the resulting composition increases as the blending amount of copolymer (A1-1) increases (Example 5 < Example 1 < Example 6). From this result, it is presumed that the melt flowability of this composition was improved by using an ethylene-α-olefin copolymer (A1) that is not crosslinked with the phenolic resin crosslinking agent (D) as part of the polyolefin rubber (A).

[0100] Furthermore, in Example 2, in which the amount of copolymer (A1-1) was less than 40% by mass relative to the total of copolymer (A1-1) and copolymer (A2-1) (100% by mass), the oil resistance was better than in Comparative Example 3, in which the proportion of copolymer (A1-1) was higher. As described above, in all of Examples 1 to 6, thermoplastic elastomer compositions were obtained that had low hardness but excellent flowability, mechanical strength, and oil resistance.

Claims

1. 100 parts by mass of a polyolefin rubber (A) containing an ethylene / α-olefin copolymer (A1) and an ethylene / α-olefin / non-conjugated polyene copolymer (A2); 10 to 60 parts by mass of a crystalline propylene polymer (B); Including, the content of the ethylene / α-olefin copolymer (A1) is 5% by mass or more and less than 40% by mass, and the content of the ethylene / α-olefin / non-conjugated polyene copolymer (A2) is more than 60% by mass and 95% by mass or less, relative to 100% by mass of the total content of the ethylene / α-olefin copolymer (A1) and the ethylene / α-olefin / non-conjugated polyene copolymer (A2); at least a portion of the crosslinked polymer is crosslinked by the organic peroxide-based crosslinking agent (C) and the phenolic resin-based crosslinking agent (D); The thermoplastic elastomer composition has a content of the organic peroxide-based crosslinking agent (C) of 0.5 to 2.0 parts by mass relative to 100 parts by mass of the polyolefin-based rubber (A).

2. The thermoplastic elastomer composition according to claim 1, further comprising 100 to 300 parts by mass of a softener (E).

3. 3. The thermoplastic elastomer composition according to claim 1, wherein a ratio (D / A2) of the content of the ethylene-α-olefin-non-conjugated polyene copolymer (A2) to the content of the phenolic resin-based crosslinking agent (D) is 0.01 to 1.

00.

4. The thermoplastic elastomer composition according to any one of claims 1 to 3, wherein a ratio (C / D) of the content of the organic peroxide-based crosslinking agent (C) to the content of the phenolic resin-based crosslinking agent (D) is greater than 0 and not more than 0.

5.

5. The thermoplastic elastomer composition according to any one of claims 1 to 4, which satisfies the following requirements (1) and (2): (1) The melt flow rate measured in accordance with ASTM D-1238 at 230°C under a load of 10 kg is 3 to 100 g / 10 min. (2) The Shore A hardness (instantaneous value) measured in accordance with JIS K 6253 is 30 to 70.

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

7. The molded article according to claim 6, wherein the molded article is an automobile part.

8. The molded article according to claim 6 or 7, which is a sealing member.

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