Thermoplastic elastomer composition and its use

Abstract

A purpose of the present disclosure is to obtain a thermoplastic elastomer composition exhibiting excellent oil permeability resistance (oil impermeability). The present disclosure relates to a thermoplastic elastomer composition comprising (A) an ethylenic copolymer having a weight average molecular weight of 350,000 or more, (B) a crystalline olefinic polymer, (C) a crosslinking agent, and (D) a plasticizing agent, the composition being characterized in that the amount of (D) plasticizing agent is less than 130 parts by mass relative to 100 parts by mass of (A) the copolymer.

Description

[Technical Field]

[0001] The present disclosure relates to a thermoplastic elastomer composition having good oil permeation resistance (oil impermeability). [Background technology]

[0002] Olefin-based thermoplastic elastomers, which are formed by crosslinking a composition of an ethylene-α-olefin-non-conjugated polyene copolymer, a type of thermoplastic elastomer, with a crystalline olefin polymer, are lightweight and easily recyclable. As such, they are widely used as energy- and resource-saving thermoplastic elastomers, particularly as a substitute for vulcanized rubber, in automobile parts such as hoses, pipes, and boots (blow-molded products) (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-294714 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-202136 Summary of the Invention [Problem to be solved by the invention]

[0004] However, these automobile parts are used in locations that come into contact with engine oil, lubricating oil, grease, etc., and since olefin-based thermoplastic elastomers generally have low oil resistance, further improvement in oil permeation resistance is required even for automobile parts obtained containing the olefin-based thermoplastic elastomers described in Patent Documents 1 and 2. An object of the present disclosure is to obtain a thermoplastic elastomer composition having good oil permeation resistance (oil impermeability). [Means for solving the problem]

[0005] The present disclosure provides an ethylene copolymer (A) having a weight average molecular weight of 350,000 or more; A crystalline olefin polymer (B), a crosslinker (C), and Plasticizer (D) Including, The thermoplastic elastomer composition is characterized in that the content of the plasticizer (D) is less than 130 parts by mass per 100 parts by mass of the copolymer (A). [Effects of the Invention]

[0006] According to the present disclosure, a thermoplastic elastomer composition having good oil permeation resistance (oil impermeability) can be obtained.

[0007] Furthermore, a molded article made from the thermoplastic elastomer composition of the present disclosure has good oil permeation resistance (oil impermeability), and therefore can be suitably used not only in applications in which conventional thermoplastic elastomer compositions are used, but also in applications in which it is difficult to use a molded article made from a conventional thermoplastic elastomer composition, such as automobile parts such as air intake hoses. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments for carrying out the present disclosure will be described. Numerical ranges such as "XX or more and YY or less" or "XX to YY" refer to a range of values ​​including the upper and lower limits, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.

[0009] <Ethylene-based copolymer (A)> The ethylene copolymer (A) (hereinafter, sometimes referred to as "component (A)"), which is one of the components of the thermoplastic elastomer composition of the present disclosure, is a copolymer containing units derived from ethylene and has a weight-average molecular weight (Mw) of 350,000 or more, preferably 420,000 or more, and more preferably in the range of 450,000 to 800,000. The ethylene copolymer (A) can be an ethylene-α-olefin copolymer containing units derived from ethylene and units derived from an α-olefin (e.g., an α-olefin having 3 to 20 carbon atoms). The upper limit of Mw is not particularly limited, but is usually 1,500,000 or less, preferably 1,000,000 or less. If the ethylene polymer has an Mw of less than 350,000, the oil permeation resistance of the molded article obtained from the thermoplastic elastomer composition may not be improved. The Mw of the ethylene copolymer (A) according to the present disclosure is measured by gel permeation chromatography, as described below.

[0010] The ethylene copolymer (A) according to the present disclosure can be obtained, for example, by copolymerizing at least ethylene and an α-olefin. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. Among these, from the viewpoint of imparting flexibility, α-olefins having 3 to 20 carbon atoms are preferred, α-olefins having 3 to 12 carbon atoms are more preferred, propylene, 1-butene, and 1-octene are even more preferred, and propylene is even more preferred.

[0011] When component (A) according to the present disclosure is an ethylene-α-olefin copolymer containing units derived from ethylene and units derived from an α-olefin, the molar ratio of the units derived from ethylene to the units derived from the α-olefin is typically in the range of 40 / 60 to 90 / 10. The lower limit of the molar ratio of the units derived from ethylene to the units derived from the α-olefin is preferably 45 / 55, more preferably 50 / 50, and particularly preferably 55 / 45. The upper limit of the molar ratio is preferably 80 / 20, more preferably 75 / 25, and even more preferably 70 / 30. The molar ratio within the above range is preferable for obtaining a thermoplastic elastomer composition excellent in mechanical strength.

[0012] Component (A) according to the present disclosure can be copolymerized with a monomer having an unsaturated bond (non-conjugated polyene) as needed. Examples of the monomer having an unsaturated bond (non-conjugated polyene) include linear non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene, methyltetrahydroindene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, and 5-isopropyl and trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,5-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene, 4,8-dimethyl-1,4,8-decatriene, and 4-ethylidene-8-methyl-1,7-nonadiene. Among these, linear non-conjugated dienes such as 1,4-hexadiene and cyclic non-conjugated dienes such as 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene are preferred, cyclic non-conjugated dienes are more preferred, and 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene are even more preferred. The monomers having an unsaturated bond (non-conjugated polyenes) can be used alone or in combination of two or more kinds.

[0013] Examples of the copolymer (A) according to the present disclosure include ethylene-propylene-1,4-hexadiene copolymer, ethylene-propylene-5-ethylidene-2-norbornene copolymer, ethylene-propylene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-butene-1,4-hexadiene copolymer, ethylene-1-pentene-1,4-hexadiene copolymer, ethylene-1-hexene-1,4-hexadiene copolymer, ethylene-1-heptene-1,4-hexadiene copolymer, ethylene-1-octene-1,4-hexadiene copolymer, ethylene-1-nonene-1,4-hexadiene copolymer, ethylene-1-decene-1,4-hexadiene ...-octene-1,4-Hexadiene copolymer, Ethylene-1-butene-5-ethylidene-2-norbornene copolymer, Ethylene-1-pentene-5-ethylidene-2-norbornene copolymer, Ethylene-1-hexene-5-ethylidene-2-norbornene copolymer, Ethylene-1-heptene-5-ethylidene-2-norbornene copolymer, Ethylene-1-octene-5-ethylidene-2-norbornene copolymer Ethylene-1-nonene-5-ethylidene-2-norbornene copolymer, Ethylene-1-decene-5-ethylidene-2-norbornene copolymer, Ethylene-1-butene-1-octene-5-ethylidene-2-norbornene copolymer, Ethylene-1-butene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, Ethylene-1-pentene-5-ethylidene-2-no Examples of ethylene-α-olefin-non-conjugated polyene copolymers include ethylene-1-hexene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-heptene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-octene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-nonene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, ethylene-1-decene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer, and ethylene-1-butene-1-octene-5-ethylidene-2-norbornene-5-vinyl-2-norbornene copolymer.

[0014] Examples of the ethylene-α-olefin-non-conjugated polyene copolymer, which is one of the ethylene-based copolymers (A) according to the present disclosure, include ethylene-propylene-non-conjugated diene copolymers manufactured and sold by ExxonMobil Chemical Corporation under the trade name Vistalon 3666 (ethylene-propylene-5-ethylidene-2-norbornene copolymer), by Lion Copolymer under the trade names Royalene 694 and Royalene 677 (ethylene-propylene-5-ethylidene-2-norbornene copolymer), and by LANXESS under the trade names Keltan 4869C, Keltan 5469C, Keltan 5469Q, and Keltan 4969Q (ethylene-propylene-5-ethylidene-2-norbornene copolymer).

[0015] <Crystalline olefin polymer (B)> The crystalline olefin polymer (B), which is one of the components of the thermoplastic elastomer composition of the present disclosure, is a polymer of an α-olefin, and is usually an olefin polymer obtained by polymerizing one or more α-olefins. Examples of such crystalline olefin-containing polymers include ethylene polymers such as ethylene homopolymers and polymers of ethylene and other α-olefins, which are manufactured and sold under names such as high-pressure low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene; propylene polymers such as propylene homopolymers and copolymers of propylene and other α-olefins, which are manufactured and sold under names such as propylene homopolymer (homo PP), propylene random copolymer (random PP), and propylene block copolymer (block PP); 1-butene polymers such as 1-butene homopolymers and copolymers of 1-butene and other α-olefins; and 4-methyl-1-pentene polymers such as 4-methyl-1-pentene homopolymers and copolymers of 4-methyl-1-pentene and other α-olefins. In the present disclosure, a crystalline polymer is a polymer that has a melting point based on crystals at 120°C or higher.

[0016] These α-olefins are preferably α-olefins having 2 to 20 carbon atoms, specifically ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, etc. These α-olefins may be used alone or in combination of two or more kinds. As the crystalline olefin polymer (B), a propylene polymer such as polypropylene can be used, but the present invention is not limited thereto, and any known crystalline olefin polymer can be used.

[0017] <Propylene-based polymer> The propylene-based polymer according to the present disclosure is particularly preferably one or more polymers selected from the group consisting of a propylene homopolymer, a random copolymer of propylene and an α-olefin other than propylene (e.g., a propylene-ethylene random copolymer, a propylene-ethylene-1-butene random copolymer), and a block copolymer of propylene and an α-olefin other than propylene (e.g., a propylene-ethylene block copolymer).

[0018] The crystalline olefin polymer (B) according to the present disclosure preferably has an MFR (JIS K7210 temperature: 230°C, 2.16 kg load) of 0.01 to 3.0 g / 10 min, more preferably 0.1 to 1.0 g / 10 min.

[0019] <Crosslinking agent (C)> The crosslinking agent (C), which is one of the components of the thermoplastic elastomer composition of the present disclosure, is not particularly limited as long as it is a compound that can crosslink the ethylene copolymer (A) and the crystalline olefin polymer (B). Specific examples include organic peroxide-based crosslinking agents and phenolic resin-based crosslinking agents.

[0020] <Organic peroxide crosslinking agent> Specific examples of organic peroxides used as crosslinking agents include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide. Of these, from the viewpoints of odor resistance and scorch stability, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and n-butyl-4,4-bis(tert-butylperoxy)valerate are preferred, and of these, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane and 1,3-bis(tert-butylperoxyisopropyl)benzene are most preferred. In the present disclosure, the organic peroxide is usually used in an amount of 0.05 to 3 parts by mass, preferably 0.1 to 1 part by mass, per 100 parts by mass of the total amount of the ethylene copolymer (A) and the crystalline olefin polymer (B).

[0021] In the crosslinking treatment with an organic peroxide, a crosslinking aid such as sulfur, p-quinone dioxime, p,p'-dibenzoylquinone dioxime, N-methyl-N-4-dinitrosoaniline, nitrosobenzene, diphenyl guanidine, trimethylolpropane, N,N'-m-phenylenedimaleimide, divinylbenzene, or triallyl cyanurate, or a polyfunctional methacrylate monomer such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, or allyl methacrylate; or a polyfunctional vinyl monomer such as vinyl butyrate or vinyl stearate may be blended. By using such compounds, a uniform and mild crosslinking reaction can be expected. The above-mentioned compounds are preferably used in an amount of 0.1 to 2 mass %, particularly 0.3 to 1 mass %, in the thermoplastic elastomer composition, in order to improve the fluidity of the resulting thermoplastic elastomer and prevent changes in physical properties due to thermal history during processing and molding.

[0022] <Phenol resin crosslinking agent> The phenolic resin used as a crosslinking agent is also called a phenolic curative, and refers to a curing agent containing a phenolic curing resin. A preferred example is a phenolic curative system comprising a phenolic curing resin and a cure activator, as disclosed in U.S. Pat. No. 4,311,628. The basic components of the system are prepared by the condensation of substituted phenols (e.g., halogen-substituted phenols, C1-C2 alkyl-substituted phenols) or unsubstituted phenols with aldehydes, preferably formaldehyde, in an alkaline medium, or by the condensation of difunctional phenol dialcohols (preferably C5-C 10Phenol-based curing resins are prepared by condensation of alkyl-substituted dimethylolphenols. Halogenated alkyl-substituted phenol-based curing resins prepared by halogenation of alkyl-substituted phenol-based curing resins are particularly suitable. Phenolic vulcanizing agent systems consisting of a methylolphenol-based curing resin, a halogen donor, and a metal compound are particularly recommended, and details thereof are described in U.S. Pat. Nos. 3,287,440 and 3,709,840. Non-halogenated phenol-based curing resins are used in conjunction with a halogen donor, preferably with a hydrogen halide scavenger. Halogenated phenol-based curing resins, preferably brominated phenol-based curing resins containing 2 to 10 wt.% bromine, do not typically require a halogen donor but are used in conjunction with a hydrogen halide scavenger, such as a metal oxide, for example, iron oxide, titanium oxide, magnesium oxide, magnesium silicate, silicon dioxide, and preferably zinc oxide. The presence of such scavengers promotes the crosslinking of phenolic curative resins, but for rubbers that are not readily vulcanized with phenolic curative resins, the use of both a halogen donor and zinc oxide is desirable. The preparation of halogenated phenolic curative resins and their use in zinc oxide vulcanization systems are described in U.S. Pat. Nos. 2,972,600 and 3,093,613, the disclosures of which, along with those of U.S. Pat. Nos. 3,287,440 and 3,709,840, are incorporated herein by reference. Examples of suitable halogen donors include stannous chloride, ferric chloride, or halogen-donating polymers such as chlorinated paraffins, chlorinated polyethylene, chlorosulfonated polyethylene, and polychlorobutadiene (neoprene rubber). As used herein, the term "activator" means any substance that substantially increases the crosslinking efficiency of phenolic curative resins and includes metal oxides and halogen donors, used alone or in combination. For more information on phenolic vulcanizing agent systems, see "Vulcanization and Vulcanizing Agents" (W. Hoffman, Palmerton Publishing Company). The use of a halogenated phenol-based curing resin as the phenolic resin used as a crosslinking agent eliminates the need for a catalyst, such as a tin chloride catalyst, thereby reducing the environmental impact during production. Furthermore, since the resulting thermoplastic elastomer composition does not contain tin derived from the tin chloride catalyst, deterioration can be prevented when the polyacetal comes into contact with the composition.

[0023] Suitable phenolic curing resins and phenolic resin crosslinkers, such as brominated phenolic curing resins, are commercially available, for example, such phenolic resin crosslinkers may be purchased under the trade names "SP-1045," "CRJ-352," "SP-1055," and "SP-1056" from Schenectady Chemicals, Inc. Similar functionally equivalent phenolic curing resins may also be obtained from other suppliers. The phenolic resin-based crosslinking agent according to the present disclosure generates little decomposition products, and is therefore a suitable crosslinking agent from the viewpoint of preventing fogging. The amount of the phenolic resin-based crosslinking agent according to the present disclosure is usually 0.5 to 10 parts by mass, preferably 0.5 to 7 parts by mass, and more preferably 1 to 7 parts by mass, per 100 parts by mass of the total amount of the ethylene copolymer (A) and the crystalline olefin polymer (B).

[0024] In the crosslinking treatment using a phenolic resin-based crosslinking agent, a crosslinking aid, a polyfunctional methacrylate monomer, or a polyfunctional vinyl monomer may be blended. Preferably, a crosslinking aid such as ZnO is blended. By using such compounds, a uniform and mild crosslinking reaction can be expected. The above-mentioned compounds are preferably used in an amount of 0.1 to 2 mass %, particularly 0.3 to 1 mass %, in the thermoplastic elastomer composition, in order to improve the fluidity of the resulting thermoplastic elastomer and prevent changes in physical properties due to thermal history during processing and molding.

[0025] <Plasticizer (D)> The plasticizer (D), which is one of the components of the thermoplastic elastomer composition of the present disclosure, is not particularly limited, but plasticizers that are usually used in rubber can be used. Specifically, 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; waxes such as tall oil, sab (factice), beeswax, carnauba wax, and lanolin; ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, and lauric acid. Examples of suitable softeners include fatty acids and fatty acid salts such as zinc, naphthenic acid, pine oil, rosin or its derivatives, terpene resins, petroleum resins, coumarone-indene resins, synthetic polymeric substances such as atactic polypropylene, ester-based 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. Of these, petroleum-based softeners, particularly process oil, are preferably used. In the present disclosure, the kinematic viscosity of the plasticizer (D) at 40°C is preferably 95 Pa s or more, and more preferably 100 Pa s or more. By using a plasticizer with the above kinematic viscosity, a thermoplastic elastomer composition having excellent tensile properties can be obtained. The kinematic viscosity of the plasticizer (D) at 40°C was determined in accordance with ASTM D 445 by measuring the time it takes for a certain amount of liquid to flow through a capillary tube and multiplying the outflow time by the viscometer constant.

[0026] The plasticizer (D) contained in the thermoplastic elastomer composition includes not only the so-called plasticizer added to the thermoplastic elastomer composition, but also the oil extended when an oil-extended ethylene copolymer (A) (e.g., oil-extended EPDM, EPT) is used as the ethylene copolymer (A). In other words, the "plasticizer content" in the thermoplastic elastomer composition of the present disclosure is the total amount of the plasticizer added to the thermoplastic elastomer composition and the oil extended in the oil-extended rubber.

[0027] <Thermoplastic elastomer composition> The thermoplastic elastomer composition of the present disclosure comprises the ethylene copolymer (A), the crystalline olefin polymer (B), a crosslinking agent (C), and a plasticizer (D), and the content of the plasticizer (D) is less than 130 parts by mass, preferably 120 parts by mass or less, and more preferably 110 parts by mass or less, per 100 parts by mass of the copolymer (A). The lower limit of the content of the plasticizer (D) is not particularly limited, but is usually 10 parts by mass or more, preferably 40 parts by mass or more, per 100 parts by mass of the copolymer (A). The thermoplastic elastomer composition of the present disclosure contains the crystalline olefin polymer (B), the crosslinking agent (C), and the plasticizer (D) in the above-described ranges in addition to the ethylene copolymer (A), and thereby a molded article having good oil permeation resistance (oil impermeability) can be obtained.

[0028] The present inventors speculate that the reason why a molded article made from the thermoplastic elastomer composition of the present disclosure has excellent oil permeation resistance is as follows. In a molded article made from the thermoplastic elastomer composition of the present disclosure, it is presumed that an island phase containing the ethylene copolymer (A) and a sea phase containing the crystalline olefin polymer (B) constituting the composition are dispersed in the molded article, and that the plasticizer (D) is dispersed (contained) in the island phase containing the ethylene copolymer (A). Furthermore, it is presumed that the sea phase containing the crystalline olefin polymer (B) contains a mixture of amorphous parts and crystalline parts composed of the crystalline olefin polymer (B). It is believed that when oil (e.g., engine oil) is dropped onto a molded article made of the thermoplastic elastomer composition of the present disclosure, the engine oil penetrates the amorphous parts in the sea phase and is absorbed by the ethylene-based copolymer (A) in the island phases. It is also believed that the engine oil that is not absorbed (retained) by the ethylene-based copolymer (A) travels through the amorphous parts in the sea phase and appears on the surface of the molded article. From this oil penetration process, it is believed that the reason why a molded article made of the thermoplastic elastomer composition of the present disclosure has good oil permeation resistance (oil impermeability) is that the ethylene copolymer (A) constituting the thermoplastic elastomer composition of the present disclosure has a weight average molecular weight (Mw) of 350,000 or more, and therefore has a high oil retention capacity (large oil retention amount). On the other hand, if the blending amount of the plasticizer (D) is 130 parts by mass or more in the thermoplastic elastomer composition, there is a risk that the oil permeation resistance (oil impermeability) of the molded article will not be improved.

[0029] The thermoplastic elastomer composition of the present disclosure preferably contains the crystalline olefin polymer (B) in an amount of 20 to 100 parts by mass, more preferably 40 to 60 parts by mass, per 100 parts by mass of the ethylene copolymer (A). When the content of the crystalline olefin polymer (B) is within this range, better oil permeation resistance may be obtained.

[0030] The thermoplastic elastomer composition of the present disclosure may contain components other than the ethylene copolymer (A), the crystalline olefin polymer (B), the crosslinking agent (C), and the plasticizer (D), such as additives such as a heat stabilizer, an antistatic agent, a weather stabilizer, an antioxidant, a reinforcing agent, a filler, a colorant, and a lubricant, as needed, within a range that does not impair the object of the present disclosure.

[0031] <Method of producing thermoplastic elastomer composition> The thermoplastic elastomer composition of the present disclosure is formed by dynamically crosslinking the ethylene copolymer (A) and the crystalline olefin polymer (B) contained in the thermoplastic elastomer composition, whereby at least a portion of the ethylene copolymer (A) and the crystalline olefin polymer (B) contained in the thermoplastic elastomer composition are crosslinked. When performing dynamic crosslinking, it is preferable to dynamically heat treat the composition in the presence of the crosslinking agent (C) or in the presence of the crosslinking agent (C) and the crosslinking coagent. In the present disclosure, "dynamic heat treatment" refers to kneading in a molten state. In addition, with respect to the thermoplastic elastomer composition of the present disclosure, the composition before being dynamically heat-treated may also be referred to as "composition 1," and the composition after being dynamically heat-treated may also be referred to as "composition 2."

[0032] The dynamic heat treatment in the present disclosure is preferably carried out in a closed-type apparatus, and is preferably carried out in an inert gas atmosphere such as nitrogen or carbon dioxide. The heat treatment temperature is in the range of from the melting point of component (A) to 300°C, typically 150 to 270°C, and preferably 170 to 250°C. The kneading time is typically 1 to 20 minutes, and preferably 1 to 10 minutes. The applied shear force, expressed as a shear rate, is typically 10 to 50,000 s -1 , preferably 100 to 10,000 s -1 is in the range.

[0033] In the present disclosure, the timing of adding the plasticizer (D) is not particularly limited, but it is preferable to add it after the completion of dynamic crosslinking. By adding the plasticizer (D) after the completion of dynamic crosslinking, the plasticizer is less likely to remain in the ethylene copolymer (A), and a thermoplastic elastomer composition with excellent oil impermeability can be obtained.

[0034] <Applications of thermoplastic elastomer compositions> The molded article of the present disclosure is made of the thermoplastic elastomer composition of the present disclosure. The thermoplastic elastomer composition of the present disclosure can be molded by various known molding methods, such as extrusion molding, injection molding, compression molding, calendar molding, vacuum molding, press molding, stamping molding, and blow molding. Examples of blow molding include press blow molding, direct blow molding, and injection blow molding. The molded article of the present disclosure has better oil resistance than molded articles made of conventional thermoplastic elastomer compositions, and therefore can be suitably used in applications where it is difficult to use molded articles made of conventional thermoplastic elastomer compositions, such as automobile parts such as air intake hoses. [Example]

[0035] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. "Parts" used in the examples and comparative examples are by mass unless otherwise specified.

[0036] The weight average molecular weight of the ethylene copolymer (A) was measured by the following method. [Weight average molecular weight (Mw)] The weight average molecular weight was measured by gel permeation chromatography under the following conditions: Column: TSKgel GMH6-HT x 2 + TSKgel GMH6-HTL x 2 (Both 7.5mm I.D. x 30cm, manufactured by Tosoh Corporation) Column temperature: 140℃ Mobile phase: o-dichlorobenzene (containing 0.025% BHT) Detector: differential refractometer Flow rate: 1.0mL / min. Sample concentration: 0.1% (w / v) Injection volume: 0.4mL Sampling interval: 0.5 sec. Column calibration: Monodisperse polystyrene (Tosoh Corporation); #3 standard set Molecular weight conversion: PS conversion / standard conversion method

[0037] The melt flow rate (MFR) of the crystalline olefin polymer (B) was measured by the following method. Melt Flow Rate (MFR) Measurement was carried out in accordance with JIS K7210 at a temperature of 230°C under a load of 2.16 kg. In the examples and comparative examples, the following polymers were used as the ethylene copolymer (A) and the crystalline olefin polymer (B).

[0038] [Ethylene-based copolymer (A)] (1) EPT-1 (Vistalon 3666): Ethylene content = 64.0 mass%, ethylidene norbornene content = 4.5 mass%, Mooney viscosity [ML(1+4), 125°C] = 52 MU, Mw = 460,000, oil extension amount = 75 PHR. (2) EPT-2 (Keltan 4869C): Ethylene content = 62 mass%, ethylidene norbornene content = 8.7 mass%, Mooney viscosity [ML(1+4), 125°C] = 48 MU, Mw = 542,000, oil extension amount = 100 PHR. (3) EPT-3 (Mitsui EPT 3072EPM): ethylene content = 64 mass%, ethylidene norbornene content = 5.4 mass%, Mooney viscosity [ML(1+4), 125°C] = 51 MU, Mw = 284,000, oil extension amount = 40 PHR.

[0039] [Crystalline olefin polymer (B)] (1) PP-1 (E111G): Propylene homopolymer commercially available from Prime Polymer Co., Ltd. [Melt flow rate (JIS K7210 temperature: 230°C, 2.16 kg load) = 0.5 g / 10 min (product name Prime Polypro E111G)].

[0040] [Physical properties of thermoplastic elastomer composition and molded product] The physical properties of the thermoplastic elastomer compositions and molded articles in the following examples and comparative examples were evaluated as follows. [Shore A hardness] The obtained thermoplastic elastomer composition pellets 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 produce a 3mm thick pressed sheet. The sheet was measured using a type A measuring instrument in accordance with JIS K6253, and the scale was read immediately after contact with the indenter.

[0041] [Tensile properties] Using a 100t electric automatic press (manufactured by Shoji Co., Ltd.), the obtained pellets of thermoplastic elastomer composition were press-molded at 230°C for 6 minutes, and then cooled and pressed at room temperature for 5 minutes to produce a pressed sheet with a thickness of 2 mm. A No. 3 dumbbell specimen was punched out from the 2 mm thick press sheet produced as described above to obtain a test specimen, and the test specimen was used for measurement according to the method of JIS K6301. Measurement temperature: 23℃ TB: Tensile breaking strength (MPa) EB: Tensile elongation at break (%)

[0042] [Compression set (CS)] Using a 100t electric automatic press (manufactured by Shoji Co., Ltd.), the obtained pellets of thermoplastic elastomer composition were press-molded at 230°C for 6 minutes, and then cooled and pressed at room temperature for 5 minutes to produce a pressed sheet with a thickness of 2 mm. In accordance with JIS K6250, the press sheets having a thickness of 2 mm prepared as described above were laminated together, and a compression set test was carried out in accordance with JIS K6262. The test conditions were as follows: a laminated sheet of 12 mm thickness (four 3 mm thick pieces stacked together) was used, compressed at 25% compression and 70°C for 22 hours, and measurements were taken 30 minutes after strain removal (compression).

[0043] [Oil permeation resistance test] The 2 mm thick press sheet prepared as described above was placed over the opening of a 50 mm inner diameter, 50 mm deep cup containing 5 g of Nissan Motor Co., Ltd. 0w-20 engine oil and fixed in place. The cup was then inverted, and the press sheet was left in contact with the engine oil at 130°C for 72 hours. After this time, the condition of the surface of the press sheet that had not come into contact with the engine oil was evaluated. The evaluation criteria for oil permeation resistance were as follows: ◎: The surface of the press sheet is not shiny and engine oil does not penetrate. Good: There is a shine on the surface of the press sheet, but no engine oil is transmitted through. ×: Shiny surface of the press sheet and engine oil dripping through.

[0044] [Example 1] EPT-1: 175 parts, PP-1: 76 parts, carbon black (PE4993 black MB): 4 parts, crosslinking aid (ZnO): 0.8 parts, crosslinking agent (phenolic resin crosslinking agent SP-1055): 7 parts, and plasticizer (PW-100, kinematic viscosity at 40°C 103.2 cSt): 50 parts, The mixture obtained was dynamically crosslinked using an extruder (product number KTX-46, manufactured by Kobe Steel, Ltd.; cylinder temperatures: C1: 50°C, C2: 50°C, C3: 100°C, C4: 120°C, C5: 120°C, C6: 120°C, C7 to C8: 180°C, C9 to C14: 220°C; die temperature: 250°C; screw rotation speed: 400 rpm; extrusion rate: 100 kg / h) to obtain pellets of a thermoplastic elastomer composition. The physical properties of the resulting thermoplastic elastomer composition were measured by the methods described above, and the results are shown in Table 1.

[0045] [Examples 2 to 6, Comparative Examples 1 to 4] Pellets of the thermoplastic elastomer compositions of Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the components and their blending amounts were changed as shown in Table 1. The physical properties of the resulting thermoplastic elastomer composition were measured by the methods described above, and the results are shown in Table 1.

[0046] Table 1

Claims

1. an ethylene copolymer (A) having a weight average molecular weight of 350,000 or more; a crystalline olefin polymer (B); a crosslinking agent (C), and Plasticizer (D) Including, The crosslinking agent (C) is a phenolic resin-based crosslinking agent, and A thermoplastic elastomer composition characterized in that the content of the plasticizer (D) is less than 130 parts by mass per 100 parts by mass of the copolymer (A).

2. The thermoplastic elastomer composition according to claim 1, wherein the ethylene copolymer (A) has a weight average molecular weight of 420,000 or more.

3. The thermoplastic elastomer composition according to claim 1, wherein the ethylene copolymer (A) is an ethylene-α-olefin-non-conjugated polyene copolymer.

4. The thermoplastic elastomer composition according to claim 1, wherein the ethylene copolymer (A) is an ethylene-propylene-non-conjugated diene copolymer.

5. 2. The thermoplastic elastomer composition according to claim 1, wherein the content of the crystalline olefin polymer (B) is in the range of 20 to 100 parts by mass per 100 parts by mass of the ethylene copolymer (A).

6. 2. The thermoplastic elastomer composition according to claim 1, wherein the crystalline olefin polymer (B) is a crystalline olefin polymer having a melt flow rate measured in accordance with JIS K7210 (temperature: 230°C, 2.16 kg load) in the range of 0.01 to 3.0 g / 10 min.

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

8. The molded article according to claim 7, which is an automobile part.

9. The molded article according to claim 8, wherein the automotive part is an air intake hose.

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