Thermoplastic elastomer composition

Abstract

To provide a thermoplastic elastomer composition having excellent flexibility, mechanical properties, thermal strain resistance (compression set resistance properties at high temperatures), bleeding resistance, ease of preparation and moldability as well as excellent grease resistance.SOLUTION: There is provided a thermoplastic elastomer composition which comprises (a) 100 pts.mass of a copolymer rubber of an unsaturated nitrile and a conjugated diene, (b) 15 to 150 pts.mass of a polypropylene-based resin, (c) 20 to 160 pts.mass of a softener, (d) 5 to 80 pts.mass of a hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene compound and (e) 0.1 to 0.6 pt.mass of an organic peroxide, wherein the block copolymer (d) is composed of (d-1) 40 to 70 mass% of a hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene compound and (d-2) 30 to 60 mass% of an amine-modified hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene compound and the sum of the component (d-1) and the component (d-2) is 100 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoplastic elastomer composition, and more particularly to a thermoplastic elastomer composition that is useful as a material for automobile parts, particularly automobile parts such as packings and seals. [Background technology]

[0002] In recent years, thermoplastic elastomers, which are soft materials with rubber elasticity that do not require a vulcanization process and have moldability and material recyclability similar to thermoplastic resins, have been widely used as alternatives to vulcanized rubber in fields such as automobile parts, home appliance parts, electric wire coatings, medical parts, and miscellaneous goods.

[0003] For example, polyester-based thermoplastic elastomers are excellent in mechanical properties such as strength and flexural fatigue resistance, thermal properties such as cold resistance and heat resistance, and oil resistance, and are used in automobile constant velocity joint boots, etc. However, compared with conventional vulcanized rubber, polyester-based thermoplastic elastomers have problems such as being expensive, needing to be dried before molding, insufficient properties such as flexibility, weather resistance, compression set resistance, and hydrolysis resistance, and having a high specific gravity.

[0004] Furthermore, polystyrene-based thermoplastic elastomers such as hydrogenated styrene-butadiene block copolymers and hydrogenated styrene-isoprene block copolymers are widely used because of their excellent flexibility, rubber elasticity at room temperature, heat aging resistance (thermal stability), weather resistance, and moldability. Therefore, as a means of improving the above-mentioned problems of TPEE, materials obtained by dynamically crosslinking compositions containing hydrogenated styrene-butadiene block copolymers have been proposed (e.g., Patent Documents 1 to 5).

[0005] Many thermoplastic elastomer compositions obtained by dynamically crosslinking polyolefin resins or polyolefin copolymer rubbers are also known. For example, an elastomer composition obtained by dynamically crosslinking an ethylene copolymer resin such as ethylene-vinyl acetate copolymer with a rubber such as halogenated butyl rubber (Patent Document 6) and a dynamically vulcanized thermoplastic elastomer composition containing a polyolefin such as ethylene-vinyl acetate copolymer, a monoolefin rubber such as EPDM, a conjugated diene polymer such as nitrile rubber, and a process oil have been proposed (Patent Document 7).

[0006] Furthermore, the present applicant has also developed an alternative material to vulcanized rubber and has proposed a specific thermoplastic elastomer composition containing a copolymer rubber of an unsaturated nitrile and a conjugated diene, which has excellent hot oil resistance (oil resistance at high temperatures) and heat distortion resistance (compression set resistance at high temperatures) (Patent Document 8). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 59-6236 [Patent Document 2] Japanese Patent Application Publication No. 63-57662 [Patent Document 3] Special Publication No. 3-49927 [Patent Document 4] Special Publication No. 3-11291 [Patent Document 5] Special Publication No. 6-13628 [Patent Document 6] Japanese Patent Application Publication No. 61-26641 [Patent Document 7] Japanese Patent Application Publication No. 9-291176 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-060757 Summary of the Invention [Problem to be solved by the invention]

[0008] The materials proposed in the above Patent Documents 1 to 5 have a poor balance between flexibility and resistance to compression set at high temperatures, particularly at 100°C or higher, and oil resistance, and also have problems such as low mechanical strength, and are not satisfactory as materials to replace vulcanized rubber.

[0009] Furthermore, the elastomer composition proposed in Patent Document 6 is excellent in heat shrinkage resistance and molding processability, but is poor in balance between flexibility and resistance to compression set at high temperatures and oil resistance, and is therefore not satisfactory as a material to replace vulcanized rubber. Furthermore, the dynamically vulcanized thermoplastic elastomer composition proposed in Patent Document 7 is very soft, but is poor in molding processability and has insufficient resistance to compression set at high temperatures and oil resistance.

[0010] Furthermore, the thermoplastic elastomer compositions proposed so far have the problem that when a molded product thereof is immersed in machine oil such as grease at high temperatures, the compounded oil contained in the thermoplastic elastomer composition elutes into the machine oil, causing the dimensions of the molded product to shrink, making them unsuitable for use as automotive parts such as packings and seals (i.e., use in an environment where they come into contact with machine oil at high temperatures). Therefore, in order to expand the applications of thermoplastic elastomers, there is a demand for materials that have properties equal to or better than those of vulcanized rubber and also have excellent grease resistance.

[0011] Therefore, an object of the present invention is to provide a thermoplastic elastomer composition that is excellent in flexibility, mechanical properties, heat distortion resistance (compression set resistance at high temperatures), bleeding resistance, ease of composition preparation, and moldability, as well as in grease resistance. [Means for solving the problem]

[0012]

[0003] After extensive research, the present inventors have discovered that a thermoplastic elastomer composition containing a copolymer rubber of an unsaturated nitrile and a conjugated diene, a polypropylene resin, a softener, a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound, and an organic peroxide in specified proportions, can be obtained by amine-modifying the hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound in a specific proportion, thereby achieving a thermoplastic elastomer composition having properties equivalent to or superior to those of vulcanized rubber and also having excellent grease resistance. The present invention is based on this discovery. The gist of the present invention is as follows:

[0013] [1] (a) 100 parts by mass of a copolymer rubber of an unsaturated nitrile and a conjugated diene; (b) 15 to 150 parts by mass of a polypropylene-based resin; (c) 20 to 160 parts by mass of a softener; (d) 5 to 80 parts by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound; and (e) Organic peroxide 0.1~0.6 parts by mass; Including, The (d) block copolymer is (d-1) 40 to 70% by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound; and (d-2) 30 to 60 mass% of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound modified by amine; wherein the sum of the component (d-1) and the component (d-2) is 100% by mass. A thermoplastic elastomer composition comprising: [2] The softener (c) is (c-1) 20 to 60 mass% of a non-aromatic rubber softener; and (c-2) polyester plasticizer 80 to 40 mass%; wherein the sum of the component (c-1) and the component (c-2) is 100% by mass. [1] The thermoplastic elastomer composition according to the present invention. [3] The thermoplastic elastomer composition according to [1] or [2], wherein the (a) copolymer rubber of unsaturated nitrile and conjugated diene has a content of structural units derived from unsaturated nitrile of 30 to 50 mass % and a content of structural units derived from conjugated diene of 50 to 70 mass %. [4] A method for producing the thermoplastic elastomer composition according to any one of [1] to [3], Mixing the components (a) to (e) and, if desired, components other than the components (a) to (e), A method for producing a thermoplastic elastomer composition, characterized by melt-kneading at a temperature equal to or higher than the one-minute half-life temperature of the (e) organic peroxide. [5] A molded article made of the thermoplastic elastomer composition according to any one of [1] to [3]. [6] The molded article according to [5], which is an automotive component selected from the group consisting of packings and seals. [7] A method for producing the molded article according to [5] or [6], [4] A step of preparing a thermoplastic elastomer composition by the method described in [4]; and a step of processing the thermoplastic elastomer composition into a molded article; A method for producing a molded article, comprising: [Effects of the Invention]

[0014] According to the present invention, it is possible to realize a thermoplastic elastomer composition that is excellent in flexibility, mechanical properties, heat distortion resistance, bleeding resistance, ease of composition preparation, and moldability, as well as in grease resistance. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Thermoplastic elastomer composition] The thermoplastic elastomer composition according to the present invention contains, as essential components, a copolymer rubber of an unsaturated nitrile and a conjugated diene (hereinafter sometimes referred to as "component (a)"), a polypropylene resin (hereinafter sometimes referred to as "component (b)"), a softener (hereinafter sometimes referred to as "component (c)"), a hydrogenated product of a block copolymer of an aromatic vinyl compound and a conjugated diene compound (hereinafter sometimes referred to as "component (d)"), and an organic peroxide (hereinafter sometimes referred to as "component (e)"). Each component constituting the thermoplastic elastomer composition according to the present invention will be described below.

[0016] <Component (a): Unsaturated nitrile and conjugated diene copolymer rubber> The thermoplastic elastomer composition of the present invention contains, as component (a), a copolymer rubber of an unsaturated nitrile and a conjugated diene. Component (a) plays an important role in heat distortion resistance. Component (a) is not particularly limited, and can be a copolymer obtained by copolymerizing any unsaturated nitrile and any conjugated diene by a known method such as emulsion polymerization. If desired, other monomers besides the unsaturated nitrile and conjugated diene may also be used.

[0017] Unsaturated nitriles are polymerizable monomers having a polymerizable carbon-carbon double bond and a nitrile group (cyano group) in one molecule. Examples of unsaturated nitriles include (meth)acrylonitrile compounds such as acrylonitrile, methacrylonitrile, α-ethyl acrylonitrile, methyl α-isopropyl acrylonitrile, and methyl α-n-butyl acrylonitrile; cyano group-containing (meth)acrylic acid ester compounds such as 2-cyanoethyl (meth)acrylate, 2-(2-cyanoethoxy)ethyl (meth)acrylate, 3-(2-cyanoethoxy)propyl (meth)acrylate, 4-(2-cyanoethoxy)butyl (meth)acrylate, and 2-[2-(2-cyanoethoxy)ethoxy]ethyl (meth)acrylate; fumaronitrile; and 2-methylene glutaronitrile. These can be used alone or in combination. Among these, acrylonitrile is preferred.

[0018] In this specification, the term "(meth)acrylate" encompasses acrylate and methacrylate, and the term "(meth)acrylonitrile" encompasses acrylonitrile and methacrylonitrile.

[0019] The content of structural units derived from unsaturated nitriles in component (a) (hereinafter sometimes abbreviated as "nitrile content") is not particularly limited, but from the viewpoint of heat distortion resistance, it is preferably 25% by mass or more, more preferably 30% by mass or more. From the viewpoint of flexibility, it is preferably 70% by mass or less, more preferably 50% by mass or less. The nitrile content is further preferably 30 to 50% by mass. When the nitrile content is within the above range, a thermoplastic elastomer composition having an excellent balance between flexibility and heat distortion resistance can be obtained.

[0020] Conjugated dienes are polymerizable monomers having a structure in which two carbon-carbon double bonds are connected by one carbon-carbon single bond. Examples of conjugated dienes include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and chloroprene (2-chloro-1,3-butadiene), and these can be used alone or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferred.

[0021] The content of structural units derived from conjugated dienes in component (a) (hereinafter sometimes abbreviated as "diene content") is not particularly limited, but from the viewpoint of flexibility, it is preferably 30% by mass or more, more preferably 50% by mass or more, and from the viewpoint of grease resistance, it is preferably 75% by mass or less, more preferably 70% by mass or less.

[0022] The copolymer rubber of unsaturated nitrile and conjugated diene of component (a) may contain other constituent monomers than those mentioned above, and any monomer can be used without any particular limitation as long as it is copolymerizable with the saturated nitrile and conjugated diene. Examples of other monomers include alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2- Examples of the polymerizable compound include alkoxyalkyl (meth)acrylate compounds such as methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 3-ethoxypropyl (meth)acrylate; polymerizable compounds having a carboxyl group and a carbon-carbon double bond such as acrylic acid, methacrylic acid, itaconic acid, and β-carboxyethyl (meth)acrylate; and aromatic vinyl compounds such as styrene. These may be used alone or in combination of two or more.

[0023] The content of structural units derived from other monomers in component (a) is usually 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less, from the viewpoint of the balance between flexibility and heat distortion resistance.

[0024] Examples of the copolymer rubber of unsaturated nitrile and conjugated diene of component (a) include acrylonitrile-butadiene copolymer rubber (NBR), acrylonitrile-butadiene-isoprene copolymer rubber (NBIR), acrylonitrile-isoprene copolymer rubber (NIR), acrylonitrile-butadiene-butoxyacrylate copolymer rubber, acrylonitrile-butadiene-acrylic acid copolymer rubber, and acrylonitrile-butadiene-methacrylic acid copolymer rubber, and one or a mixture of two or more of these can be used. Among these, acrylonitrile-butadiene copolymer rubber (NBR) is preferred from the viewpoint of grease resistance.

[0025] From the viewpoints of flexibility and moldability, component (a) preferably has a Mooney viscosity (ML(1+4)100°C) of 20 to 120, more preferably 40 to 100, measured in accordance with JIS K6300-1-2013 using an L-shaped rotor with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100°C.

[0026] <Component (b): Polypropylene resin> The thermoplastic elastomer composition of the present invention contains a polypropylene resin as component (b), which controls the fluidity of the composition during melt-kneading and provides the function of improving the dispersion of rubber components such as component (a) in the composition.

[0027] Examples of component (b) include propylene homopolymers; copolymers (including block copolymers and random copolymers) of propylene with small amounts of other α-olefins (e.g., ethylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene); and the like, and one or a mixture of two or more of these can be used.

[0028] From the viewpoint of moldability, the component (b) preferably has a melt mass flow rate of 0.1 to 100 g / 10 min, measured in accordance with JIS K 7210-1999 under conditions of 230° C. and 21.18 N.

[0029] From the viewpoint of heat distortion resistance, component (b) has a peak top melting point of preferably 150°C or higher, more preferably 160°C or higher, of the peak appearing on the highest temperature side in a second melting curve (a melting curve measured during the final heating process) measured using a DSC differential scanning calorimeter according to a program that involves holding at 230°C for 5 minutes, cooling to -10°C at 10°C / min, holding at -10°C for 5 minutes, and heating to 230°C at 10°C / min. There is no particular upper limit to the peak top melting point, but since it is a polypropylene-based resin, it is at most 167°C. As the DSC differential scanning calorimeter, for example, a Diamond manufactured by PerkinElmer Japan Co., Ltd. can be used.

[0030] The amount of component (b) blended is 15 parts by mass or more, preferably 25 parts by mass or more, per 100 parts by mass of component (a) from the viewpoints of mechanical properties and ease of preparation of the composition. From the viewpoints of flexibility and heat distortion resistance, it is 150 parts by mass or less, preferably 120 parts by mass or less, and more preferably 30 to 100 parts by mass. By blending component (b) in the above range, a thermoplastic elastomer composition having an excellent balance between flexibility and heat distortion resistance can be obtained.

[0031] <Component C: Softener> The thermoplastic elastomer composition of the present invention contains a softener as component (c). Component (c) plays an important role in improving the balance between flexibility and heat distortion resistance. Any softener used in thermoplastic elastomer compositions can be used as component (c) without limitation. However, in the present invention, from the viewpoints of flexibility, heat distortion resistance, bleed resistance, and grease resistance, it is preferable to use a non-aromatic rubber softener (hereinafter sometimes referred to as "component (c-1)") and a polyester plasticizer (hereinafter sometimes referred to as "component (c-2)").

[0032] The non-aromatic rubber softener of component (c-1) is a non-aromatic mineral oil (a hydrocarbon compound derived from petroleum, etc.) or synthetic oil (a synthetic hydrocarbon compound), and is usually liquid, gel-like, or gum-like at room temperature. Here, "non-aromatic" means that for mineral oils, they are not classified as aromatic in the classification below (the number of aromatic carbon atoms is less than 30%). For synthetic oils, this means that they do not use aromatic monomers.

[0033] Mineral oils used as rubber softeners are mixtures of one or more of paraffin chains, naphthenic rings, and aromatic rings. They are classified as follows: those with 30 to 45% naphthenic ring carbon atoms are called naphthenic; those with 30% or more aromatic carbon atoms are called aromatic; and those that are neither naphthenic nor aromatic and have 50% or more paraffin chain carbon atoms are called paraffinic.

[0034] Examples of component (c-1) include paraffinic mineral oils such as linear saturated hydrocarbons, branched saturated hydrocarbons, and derivatives thereof; naphthenic mineral oils; and synthetic oils such as hydrogenated polyisobutylene, polyisobutylene, and polybutene. Among these, paraffinic mineral oils are preferred from the viewpoint of compatibility, and paraffinic mineral oils with a small number of aromatic carbon atoms are more preferred. Furthermore, from the viewpoint of handleability, those that are liquid at room temperature are preferred. As component (c-1), one or a mixture of two or more of these can be used. Commercially available non-aromatic rubber softeners may be used, and examples thereof include the isoparaffinic hydrocarbon oil "NA Solvent (trade name)" manufactured by Nippon Oil & Fats Corporation, n-paraffinic process oils "PW-90 (trade name)" and "PW-380 (trade name)" manufactured by Idemitsu Kosan Co., Ltd., synthetic isoparaffinic hydrocarbon "IP-Solvent 2835 (trade name)" manufactured by Idemitsu Petrochemical Co., Ltd., and n-paraffinic process oil "Neothiosol (trade name)" manufactured by Sanko Chemical Industry Co., Ltd.

[0035] From the viewpoints of heat resistance and handleability, component (c-1) preferably has a dynamic viscosity at 37.8°C of 20 to 1000 cSt. From the viewpoint of handleability, the pour point is preferably -10 to -15°C. From the viewpoint of safety, the flash point (COC) is preferably 170 to 300°C. In this specification, the dynamic viscosity can be measured by a standard method in accordance with JIS K 2283:2000. The pour point can be measured by a standard method in accordance with JIS K 2269:1987. The flash point (COC) can be measured by a standard method in accordance with JIS K 2265:2007.

[0036] The polyester plasticizer of component (c-2) is a synthetic compound that has a polar group in its molecule and is liquid at room temperature. It is distinguished from component (c-1) in that it has a polar group but is not a hydrocarbon compound.

[0037] Examples of component (c-2) include polyester-based plasticizers that use polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-hexanediol, 1,6-hexanediol, and neopentyl glycol, dibasic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, and terephthalic acid, and optionally a monohydric alcohol or monocarboxylic acid as a stopper. These may be used alone or in combination. Among these, adipic acid-based polyester plasticizers are preferred.

[0038] The mass average molecular weight (Mw) of component (c-2) is usually 900 or more, preferably 1000 or more, from the viewpoint of grease resistance. From the viewpoint of grease resistance, a larger mass average molecular weight is preferable. On the other hand, from the viewpoint of ease of preparation of the composition, Mw is usually 3000 or less, preferably 2000 or less. In this specification, the mass average molecular weight refers to the polystyrene-equivalent mass average molecular weight (Mw) determined from a differential molecular weight distribution curve (hereinafter sometimes abbreviated as "GPC curve") measured by gel permeation chromatography (hereinafter sometimes abbreviated as "GPC").

[0039] In the present invention, component (c) preferably comprises 20 to 60 mass% of (c-1) a non-aromatic rubber softener and 80 to 40 mass% of (c-2) a polyester plasticizer. Here, the sum of components (c-1) and (c-2) is 100 mass%. By having component (c-1) at 60 mass% or less, more preferably 40 mass% or less (component (c-2) at 40 mass% or more, more preferably 60 mass% or more), a thermoplastic elastomer composition with good bleed resistance is easily obtained. Furthermore, by having component (c-1) at 20 mass% or more, more preferably 30 mass% or more (component (c-2) at 80 mass% or less, more preferably 70 mass% or less), a thermoplastic elastomer composition with good grease resistance is easily obtained. By ensuring that the ratio of component (c-1) to component (c-2) is within the above range, it is possible to obtain a thermoplastic elastomer composition that has an excellent balance of flexibility, heat distortion resistance, bleed resistance, and grease resistance.

[0040] The amount of component (c) is 20 parts by mass or more, preferably 40 parts by mass or more, per 100 parts by mass of component (a), from the viewpoints of flexibility and heat distortion resistance, and 160 parts by mass or less, preferably 120 parts by mass or less, from the viewpoints of heat distortion resistance, mechanical properties, bleeding resistance, and ease of preparation of the composition.

[0041] <Component (d): Hydrogenated block copolymer of aromatic vinyl compound and conjugated diene compound> The thermoplastic elastomer composition of the present invention contains a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound as component (d), which plays an important role in improving grease resistance and mechanical properties.

[0042] In the present invention, component (d) comprises 40 to 70% by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound (hereinafter sometimes referred to as "component (d-1)") and 30 to 60% by mass of an amine-modified hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound (hereinafter sometimes referred to as "component (d-2)"). The sum of components (d-1) and (d-2) is 100% by mass. By having component (d-1) at 70% by mass or less, more preferably 60% by mass or less (component (d-2) at 30% by mass or more, more preferably 40% by mass or more), a thermoplastic elastomer composition with good bleed resistance is easily obtained. Furthermore, by having component (d-1) at 40% by mass or more, more preferably 50% by mass or more (component (d-2) at 60% by mass or less, more preferably 50% by mass or less), a thermoplastic elastomer composition with good grease resistance is easily obtained. When the ratio of component (d-1) to component (d-2) is within the above range, a thermoplastic elastomer composition having an excellent balance of flexibility, grease resistance, and bleeding resistance can be obtained.

[0043] The hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound, component (d-1), is at least one selected from the group consisting of a block copolymer of an aromatic vinyl compound and a conjugated diene compound and a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound. Component (d-1) is distinguished from component (a) in that it does not use an unsaturated nitrile as a monomer. Component (d-1) serves to improve grease resistance and mechanical properties.

[0044] The aromatic vinyl compound is a polymerizable monomer having a polymerizable carbon-carbon double bond and an aromatic ring. Examples of the aromatic vinyl compound include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, and p-tert-butylstyrene, and these can be used alone or in combination of two or more. Among these, styrene is preferred.

[0045] Examples of the conjugated diene include the compounds mentioned above in the description of component (a), and one or more of them can be used in combination. Among these, 1,3-butadiene and isoprene are preferred.

[0046] From the viewpoints of grease resistance and mechanical properties, the block copolymer of an aromatic vinyl compound and a conjugated diene compound is preferably a block copolymer consisting of two or more polymer blocks A mainly composed of an aromatic vinyl compound and one or more polymer blocks B mainly composed of a conjugated diene compound. Examples of block copolymers include those having structures such as ABA, BABA, and ABABA.

[0047] The content of structural units derived from the aromatic vinyl compound in the block copolymer of an aromatic vinyl compound and a conjugated diene compound is preferably 5 to 60 mass %, more preferably 20 to 50 mass %, from the viewpoints of mechanical properties and grease resistance.

[0048] The polymer block A is a polymer block consisting of only an aromatic vinyl compound or a copolymer block of an aromatic vinyl compound and a conjugated diene compound. When the polymer block A is a copolymer block, the content of structural units derived from the aromatic vinyl compound in the polymer block A is usually 50% by mass or more, and from the viewpoints of mechanical properties and grease resistance, it is preferably 70% by mass or more, and more preferably 90% by mass or more. The distribution of structural units derived from the conjugated diene compound in the polymer block A is not particularly limited and can be any distribution. When there are two or more polymer blocks A, they may have the same structure or different structures.

[0049] The polymer block B is a polymer block consisting of only a conjugated diene compound or a copolymer block of an aromatic vinyl compound and a conjugated diene compound. When the polymer block B is a copolymer block, the content of structural units derived from the conjugated diene compound in the polymer block B is usually 50% by mass or more, and from the viewpoints of flexibility and mechanical properties, it is preferably 70% by mass or more, more preferably 90% by mass or more. The distribution of structural units derived from the aromatic vinyl compound in the polymer block B is not particularly limited and can be any distribution. The bonding mode between the conjugated diene compounds (hereinafter sometimes abbreviated as microstructure) is not particularly limited and can be any distribution. When there are two or more polymer blocks B, they may have the same structure or different structures.

[0050] The block copolymer of an aromatic vinyl compound and a conjugated diene compound has a number average molecular weight of preferably 5,000 to 1,500,000, more preferably 10,000 to 550,000, and even more preferably 100,000 to 400,000, from the viewpoint of grease resistance and mechanical properties. The molecular weight distribution (mass average molecular weight / number average molecular weight) is preferably 10 or less, from the viewpoint of mechanical properties.

[0051] The molecular chain structure of the block copolymer of an aromatic vinyl compound and a conjugated diene compound may be linear, branched, radial, or any combination thereof.

[0052] Examples of block copolymers of aromatic vinyl compounds and conjugated diene compounds include styrene-butadiene-styrene block copolymers (SBS) and styrene-isoprene-styrene block copolymers (SIS), and these can be used alone or in combination of two or more.

[0053] The block copolymer of an aromatic vinyl compound and a conjugated diene compound is not particularly limited, and may be one obtained by copolymerizing any aromatic vinyl compound with any conjugated diene by a known method such as the method described in JP-B-40-023798.

[0054] The hydrogenated product of the block copolymer of an aromatic vinyl compound and a conjugated diene compound can be obtained by adding hydrogen to the carbon-carbon double bonds in the block copolymer of the aromatic vinyl compound and a conjugated diene compound to convert them into carbon-carbon single bonds. The hydrogenation can be carried out by a known method, for example, by hydrogenation in an inert solvent using a hydrogenation catalyst.

[0055] The hydrogenation rate of the hydrogenated product (the ratio of the number of bonds that have become carbon-carbon single bonds due to hydrogenation to the number of carbon-carbon double bonds in the block copolymer of an aromatic vinyl compound and a conjugated diene compound before hydrogenation) is not particularly limited, but from the viewpoint of bleeding resistance, it may be usually 50% or more, preferably 70% or more, and more preferably 90% or more.

[0056] When the conjugated diene polymer block of the hydrogenated product is a butadiene polymer block, the microstructure may have 1,2-bonds in an amount of preferably 20 to 50 mass %, more preferably 25 to 45 mass %, from the viewpoint of flexibility.Furthermore, from the viewpoint of heat aging resistance and weather resistance, the 1,2-bonds may be selectively hydrogenated.

[0057] When the conjugated diene polymer block of the hydrogenated product is a copolymer block of isoprene and butadiene, the microstructure may have a 1,2-bond content of preferably less than 50%, more preferably less than 25%, and even more preferably less than 15%, from the viewpoints of heat aging resistance and weather resistance.

[0058] When the conjugated diene polymer block of the hydrogenated product is an isoprene polymer block, the 1,4-bond content of the microstructure may be preferably 70 to 100 mass % from the viewpoint of flexibility, and the hydrogenation rate is preferably 90 mass % or more from the viewpoint of bleeding resistance.

[0059] The content of structural units derived from aromatic vinyl compounds in the hydrogenated product is preferably 5 to 70 mass %, more preferably 20 to 50 mass %, from the viewpoint of grease resistance and mechanical properties. The number average molecular weight of the hydrogenated product is preferably 150,000 or more, more preferably 200,000 or more, from the viewpoint of bleed resistance. From the viewpoint of compatibility, it is preferably 500,000 or less, more preferably 400,000 or less.

[0060] Examples of hydrogenated block copolymers of aromatic vinyl compounds and conjugated diene compounds include styrene-ethylene-butene copolymer (SEB), styrene-ethylene-propylene copolymer (SEP), styrene-ethylene-butene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), and styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS). These can be used alone or in combination. Among these, styrene-ethylene-butene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), and styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS) are preferred from the viewpoints of flexibility, grease resistance, and heat distortion resistance.

[0061] The hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound, component (d-2), modified by amine, is a compound in which an amine compound is copolymerized (usually graft copolymerized) with the hydrogenated copolymer of an aromatic vinyl compound and a conjugated diene compound, component (d-1), described above. Component (d-2) functions to improve grease resistance.

[0062] Component (d-2) can be obtained by reacting any component (d-1) with any amine compound by a known method. For example, a method of melt-kneading any component (d-1) with any amine compound in the presence of an organic peroxide can be mentioned. Examples of the amine compound to be used include aliphatic amine compounds, aromatic amine compounds, and heterocyclic amine compounds.

[0063] Examples of the aliphatic amine compound include aliphatic primary amine compounds, aliphatic secondary amine compounds, aliphatic tertiary amine compounds, and aliphatic polyamine compounds (aliphatic amine compounds having two or more amine groups in one molecule), and these may be used alone or in combination of two or more.

[0064] Examples of the aliphatic primary amine compound include saturated aliphatic primary amine compounds such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, tert-butylamine, pentylamine, isopentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, and cyclohexylamine; and unsaturated aliphatic primary amine compounds such as dodecenylamine, octadecenylamine, and docosenylamine; and the like, and these may be used alone or in combination of two or more.

[0065] Examples of the aliphatic secondary amine compound include saturated aliphatic secondary amine compounds such as dimethylamine, diethylamine, diisobutylamine, and dicyclohexylamine; and unsaturated aliphatic secondary amine compounds, and these may be used alone or in combination of two or more.

[0066] Examples of the aliphatic tertiary amine compound include saturated aliphatic tertiary amine compounds such as trimethylamine, triethylamine, triethanolamine, tributylamine, N,N-diisopropylethylamine, and N,N-dimethylcyclohexylamine; unsaturated aliphatic tertiary amine compounds such as N,N-dimethyloctadecenylamine; and the like, and these may be used alone or in combination of two or more.

[0067] Examples of the aliphatic polyamine compound include ethylenediamine, hexamethylenediamine, and N,N,N',N'-tetramethylethylenediamine, and one or more of these may be used in combination.

[0068] Examples of aromatic amine compounds include anilines (aniline and its derivatives) and arylalkylamine compounds, and these may be used alone or in combination of two or more.

[0069] Examples of the anilines include primary amine aniline compounds such as aniline, toluidine, xylidine, anisidine, phenetidine, 4-ethylaniline, 2-ethylaniline, and 4-isopropylaniline; secondary amine aniline compounds such as N-methylaniline, N-ethylaniline, and N-isopropylaniline; and tertiary amine aniline compounds such as N,N-dimethylaniline, N,N-diethylaniline, and N,N-diisopropylaniline, and these may be used alone or in combination of two or more.

[0070] Examples of arylalkylamine compounds include arylalkyl primary amine compounds such as benzylamine, 1-phenylethylamine, and 2-phenylethylamine; arylalkyl secondary amine compounds such as N-methylbenzylamine; and arylalkyl tertiary amine compounds such as N,N-diethylbenzylamine, and the like, and these may be used alone or in combination of two or more.

[0071] Examples of heterocyclic amines include pyrrolidine, piperidine, piperazine, imidazole, 2-thienylamine, and 2-thienylmethylamine, and these may be used alone or in combination of two or more.

[0072] The amount of the amine compound may be typically 0.01 parts by mass or more, preferably 0.05 parts by mass or more, relative to 100 parts by mass of component d-2. On the other hand, from the viewpoint of suppressing gel formation and maintaining good coatability, the amount may be typically 20 parts by mass or less, preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less.

[0073] The content of component (d) in the thermoplastic elastomer composition of the present invention is 5 to 80 parts by mass, based on 100 parts by mass of component (a), and from the viewpoints of flexibility and grease resistance, it is preferably 15 parts by mass or more, and from the viewpoints of mechanical properties, bleeding resistance, and ease of preparation of the composition, it is preferably 60 parts by mass or less.

[0074] <Component (e): Organic peroxide> The thermoplastic elastomer composition of the present invention contains an organic peroxide as component (e). Component (e) is a compound in which one or two hydrogen atoms of hydrogen peroxide are substituted with organic free radicals. Because of the peroxide bond in its molecule, it generates radicals during melt-kneading, which then undergo a chain reaction to crosslink components (a) and (d). At the same time, it decomposes component (b) and controls the fluidity of the composition during melt-kneading, thereby improving the dispersion of the rubber component.

[0075] Examples of component (e) 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, and these may be used alone or in combination of two or more. Among these, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane and 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3 are preferred from the viewpoints of odor, coloring, and scorch safety.

[0076] The amount of component (e) blended is 0.1 parts by mass or more, preferably 0.2 parts by mass or more, per 100 parts by weight of component (a) from the viewpoint of grease resistance. Furthermore, from the viewpoint of mechanical properties, it is 0.6 parts by mass or less, preferably 0.4 parts by mass or less. The amount of component (e) blended is more preferably 0.2 to 0.4 parts by mass. By blending component (e) in the above range, a thermoplastic elastomer composition having an excellent balance between flexibility and grease resistance can be obtained.

[0077] <Other ingredients> In addition to the above-described components (a) to (e), the thermoplastic elastomer composition of the present invention may contain heat stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, crystal nucleating agents, antiblocking agents, sealability improvers, release agents such as stearic acid and silicone oil, lubricants such as polyethylene wax, colorants, and foaming agents (organic and inorganic), as long as the object of the present invention is not impaired. There are no particular restrictions on the additives mentioned above, and known additives can be used. For example, phenol-based antioxidants, phosphite-based antioxidants, thioether-based antioxidants, and the like can be used as antioxidants.

[0078] [Method of producing thermoplastic elastomer composition] The transparent thermoplastic elastomer composition of the present invention can be produced by adding the above components (a) to (e) and any optional components used as desired simultaneously or in any order, and melt-kneading them using any melt-kneader.

[0079] The melt-kneading method is not particularly limited, and commonly known methods can be used. For example, a single-screw extruder, twin-screw extruder, roll, Banbury mixer, or various kneaders can be used. For example, the above operation can be performed continuously by using a twin-screw extruder, Banbury mixer, pressure kneader, or the like with an appropriate L / D ratio. The melt-kneading temperature can be appropriately set depending on the blending ratio of each component. From the viewpoint of ensuring that component (e) functions reliably, it is preferable to perform the melt-kneading for 1 minute or more at a temperature equal to or higher than the 1-minute half-life temperature of component (e). It is more preferable to perform the melt-kneading for 2 minutes or more at a temperature equal to or higher than the 1-minute half-life temperature of component (e). Furthermore, from the viewpoints of mechanical properties, manufacturability of the composition, and injection moldability, the melt-kneading temperature may usually be 240°C or lower, preferably 220°C or lower.

[0080] [Molded product] The transparent thermoplastic elastomer composition of the present invention can be pelletized by any method and then molded into any article by any method, such as hot cutting, strand cutting, and underwater cutting.

[0081] [Application] Due to the properties described above, the transparent thermoplastic elastomer composition of the present invention can be suitably used for automobile parts, home appliance parts, electric wire coatings, medical parts, footwear, miscellaneous goods, etc. It is particularly useful as a material for automobile parts such as fuel tubes, diaphragms, boots for joints, packings, seals, etc. [Example]

[0082] Next, the embodiments of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0083] In this specification, the manufacturing methods, evaluation methods and raw materials of the test specimens used in the examples and comparative examples are as follows.

[0084] <Evaluation method> (1) Hardness Each composition shown in Tables 1 and 2 was used to prepare a 6.3 mm thick cylindrical press sheet conforming to JIS K 6253 using an extrusion molding machine, and this was used as a test specimen. The durometer hardness, Type A (Shore A), of the obtained test specimen was measured using a durometer (Auto Durometer P-2, manufactured by Kobunshi Keiki Co., Ltd.). The measurement results are shown in Tables 1 and 2. The hardness is preferably 45-90, and more preferably 55-80.

[0085] (2) Mechanical properties (tensile strength and tensile elongation) A 1 mm thick press sheet conforming to JIS K 6251-2010 was prepared using an extrusion molding machine from each composition shown in Tables 1 and 2, and No. 3 dumbbells were punched out from the press sheet to serve as test pieces, which were then measured at a tensile speed of 500 mm / min. The measurement results are shown in Tables 1 and 2. The tensile strength is preferably 3.0 MPa or more, more preferably 5.0 MPa or more, and the tensile elongation is preferably 150% or more, more preferably 200% or more.

[0086] (3) Heat-resistant grease (grease resistance at high temperatures) Using each composition shown in Tables 1 and 2, pressed sheets (2 mm thick) and extruded tapes (22 mm wide, 1 mm thick) were prepared in accordance with JIS K 6258-2016 and used as test specimens. The test specimens were immersed in Multemp WR194 (lithium-based grease, manufactured by Kyodo Yushi Co., Ltd.) at a temperature of 115°C for 240 hours, after which the change (rate) in physical properties was measured. The change (rate) in physical properties measured included hardness change and dimensional change rate. The dimensional change rate was the dimensional change rate in the width direction of the extruded tape. The measurement results are shown in Tables 1 and 2. The hardness change is preferably 0 or less, more preferably -2 or less. The dimensional change rate is preferably 0% or more, more preferably 2% or more.

[0087] (4) Compression set (compression set at high temperatures) Using each composition shown in Tables 1 and 2, a cylindrical press sheet having a thickness of 6.3 mm was prepared in accordance with JIS K 6262-2003 to serve as a test specimen. The test specimen was subjected to a compressive strain equivalent to 25% of its thickness, held at 70°C for 22 hours, and then released. After 1 hour, the compression set rate (%) was measured. The measurement results are shown in Tables 1 and 2. The range of the compression set is preferably 70% or less, and more preferably 60% or less.

[0088] (5) Bleeding resistance After the heat resistance grease property evaluation in (3) above was carried out, the surface of the test piece was visually observed and evaluated according to the following criteria. ○: No bleeding is observed on the sheet surface △: Slight bleeding is observed on the sheet surface ×: Significant bleeding occurs on the sheet surface The evaluation results are shown in Tables 1 and 2 below.

[0089] (6) Ease of preparation of the composition Each composition shown in Tables 1 and 2 was melt-kneaded using an apparatus equipped with a twin-screw extruder and a strand-cutting type granulator at an extruder outlet temperature of 180°C, and the manufacturability was evaluated according to the following criteria. ○: Strands can be pulled stably △: Strands are occasionally unstable ×: Strands are not stable The evaluation results are shown in Tables 1 and 2 below.

[0090] (7) Moldability Each composition shown in Tables 1 and 2 was extruded using a 20 mm single-screw extruder at a die outlet temperature of 200°C to form a sheet having a thickness of 1 mm and a width of 22 mm. The sheet was then observed for take-up properties (draw-down properties), contamination at the lip opening, and the presence or absence of residual material (eye oil), and evaluated according to the following criteria. ○: No problems at all △: A little bit of eye oil is seen on the lip ×: Problems with take-up and / or eye oil adhesion observed on lip opening The evaluation results are shown in Tables 1 and 2 below.

[0091] <Materials used> Component (a): Unsaturated nitrile and conjugated diene copolymer rubber (a-1) Acrylonitrile-butadiene copolymer rubber "PNC-48 (product name)" manufactured by JSR Corporation, nitrile content 30% by mass, Mooney viscosity (ML (1 + 4) 100℃) 60 (a-2) Acrylonitrile-butadiene copolymer rubber "PN-30A (product name)" manufactured by JSR Corporation, nitrile content 35% by mass, Mooney viscosity (ML(1+4)100℃) 56 (a'-1) Chlorinated butyl rubber "CHLOROBUTYL1066 (product name)" manufactured by JSR Corporation, specific gravity 0.92, Mooney viscosity (ML(1+8)125℃) 38, chlorine content 1.2% by mass

[0092] Component (b): Polypropylene resin (b-1) Polypropylene resin SunAllomer Co., Ltd. "PX600N (product name)", melt mass flow rate (230℃, 21.2N) 7.5g / 10min

[0093] Ingredient (c): Softener (c-1) Paraffin oil "Diana Process Oil PW-380 (product name)" manufactured by Idemitsu Kosan Co., Ltd., paraffin content 73% by mass, naphthene content 27% by mass (c-2) Polyester plasticizer ADEKA Cizer PN-230 (trade name), molecular weight 2000, manufactured by ADEKA Corporation

[0094] Component (d): Hydrogenated block copolymer of aromatic vinyl compound and conjugated diene compound (d-1) Styrene-ethylene-ethylene-propylene-styrene copolymer "SEPTON4077 (product name)" manufactured by Kuraray Co., Ltd. (d-2) Amine-modified styrene-ethylene-butene-styrene block copolymer "Tuftec MP10 (product name)" manufactured by Asahi Kasei Corporation. (d'-2) Maleic anhydride-modified styrene-ethylene-butene-styrene block copolymer "Tuftec M1913 (product name)" manufactured by Asahi Kasei Corporation

[0095] Component (e): Organic peroxide (e) 2,5-dimethyl-2,5-di(t-butylperoxy)hexane "Perhexa 25B (product name)" manufactured by Nippon Oil & Fats Co., Ltd., 1-minute half-life temperature 179°C

[0096] The above-mentioned raw materials were mixed according to the composition shown in Table 1, and melt-kneaded at a kneading temperature of 180° C. using a twin-screw extruder with an L / D of 47 (TEX28, manufactured by The Japan Steel Works, Ltd.), and pelletized. The pellets thus obtained were used to prepare test pieces for the evaluations (1) to (7) described above. The numerical values ​​for the compositions in the tables represent parts by mass.

[0097] [Table 1]

[0098] [Table 2]

[0099] As is clear from the evaluation results shown in Tables 1 and 2, the thermoplastic elastomer compositions of the present invention (Examples 1 to 20) are very flexible and have excellent grease resistance and heat distortion resistance. They are also excellent in mechanical properties, bleeding resistance, ease of composition preparation, and extrusion moldability. On the other hand, it can be seen that the thermoplastic elastomer compositions of Comparative Examples 1 to 11 are insufficient in at least one of flexibility, grease resistance, heat distortion resistance, mechanical properties, bleeding resistance, ease of preparation of the composition, and extrusion moldability.

Claims

1. (a) 100 parts by mass of a copolymer rubber of an unsaturated nitrile and a conjugated diene; (b) 15 to 150 parts by mass of a polypropylene resin; (c) softener: 20 to 160 parts by mass; (d) 5 to 80 parts by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound; and (e) organic peroxide 0.1 to 0.6 parts by mass; Including, The (d) block copolymer is (d-1) 40 to 70% by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound; and (d-2) 30 to 60% by mass of a hydrogenated block copolymer of an aromatic vinyl compound and a conjugated diene compound modified by an amine; wherein the sum of the component (d-1) and the component (d-2) is 100% by mass. A thermoplastic elastomer composition comprising:

2. The (c) softener is (c-1) 20 to 60 mass% of a non-aromatic rubber softener; and (c-2) polyester-based plasticizer 80 to 40% by mass; wherein the sum of the component (c-1) and the component (c-2) is 100% by mass. The thermoplastic elastomer composition according to claim 1.

3. 3. The thermoplastic elastomer composition according to claim 1, wherein the copolymer rubber (a) of an unsaturated nitrile and a conjugated diene has a content of structural units derived from an unsaturated nitrile of 30 to 50% by mass and a content of structural units derived from a conjugated diene of 50 to 70% by mass.

4. A method for producing the thermoplastic elastomer composition according to any one of claims 1 to 3, comprising: Mixing the components (a) to (e) and, if desired, components other than the components (a) to (e), A method for producing a thermoplastic elastomer composition, characterized by melt-kneading at a temperature equal to or higher than the one-minute half-life temperature of the (e) organic peroxide.

5. A molded article made of the thermoplastic elastomer composition according to any one of claims 1 to 3.

6. The molded article according to claim 5, which is an automotive part selected from the group consisting of packings and seals.

7. A method for producing the molded article according to claim 5 or 6, comprising the steps of: Preparing a thermoplastic elastomer composition by the method of claim 4; and a step of processing the thermoplastic elastomer composition into a molded article; A method for producing a molded article, comprising:

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