JP2018044115A - Thermoplastic elastomer composition - Google Patents

Abstract

An object of the present invention is to provide a thermoplastic elastomer composition having excellent moldability and excellent flexibility, oil resistance and compression set resistance, and a molded article obtained by using the thermoplastic elastomer composition. A thermoplastic elastomer composition containing a core-shell rubber having a shell layer containing a (meth) acrylic polymer, an acrylic rubber crosslinked by a crosslinking agent, and a thermoplastic elastomer composition obtained by using the thermoplastic elastomer composition Molded body. [Selection diagram] None

Description

  TECHNICAL FIELD The present invention relates to a thermoplastic elastomer composition used for electrical and electronic parts, automotive parts, sealing materials, packing, vibration damping members, tubes, and the like, and a molded body obtained by thermoforming the thermoplastic elastomer composition. . More specifically, a thermoplastic elastomer composition suitable for a sealant, packing, tube, and the like for automobile engines and the like that are particularly required to have heat resistance and oil resistance, and a molded article obtained using the thermoplastic elastomer composition About.

  Acrylic rubber and acrylic thermoplastic elastomer are excellent in heat resistance and oil resistance, and are widely used for automotive parts, sealing materials, packing, tubes and the like.

  Conventionally, acrylic rubber has been used as a crosslinked product through a vulcanization process from the viewpoint of heat resistance, but the heating temperature in the vulcanization process is high and the holding time is required for a long time. Absent. In addition, an acrylic thermoplastic elastomer having excellent molding fluidity has, for example, a (meth) acrylic block polymer having a glass transition point of 100 ° C. or higher and an acrylic block polymer having a glass transition point of less than 0 ° C., Although it is used as a block copolymer, its physical properties are inferior to those of a crosslinked acrylic rubber when it is used in a compression set and particularly in a high temperature environment.

  Patent Document 1 discloses a thermoplastic elastomer composition comprising (A) a thermoplastic copolyester elastomer and a crosslinked (B) core-shell type rubber, and a structure in which crosslinked rubber particles are dispersed in a copolyelastomer matrix. It is described that a composition excellent in flexibility, tensile permanent elongation, and compression set resistance can be obtained.

  Patent Document 2 discloses a composition comprising 5 to 95 parts by weight of an acrylic block copolymer (A) and 95 to 5 parts by weight of a core / shell type graft copolymer as an extender. As the shell-type graft copolymer, one having a shell mainly composed of a polymer grafted with a methacrylic acid ester monomer on a core which is a crosslinked rubber mainly composed of an acrylate ester is disclosed.

Japanese Patent Laid-Open No. 5-25374 JP 2005-8861 A

However, Patent Document 1 discloses that the use of polycarboxylic acid as a cross-linking agent can improve rubber elasticity with high stress. However, acrylic rubber tends to have residual stress when it is thermoformed. While the stress may be released and the molded body may be deformed, the method using the copolyester elastomer as disclosed in Patent Document 1 does not solve this problem of moldability.
Further, Patent Document 2 does not disclose that the acrylic block copolymer (A) is cross-linked, and those not cross-linked in this way have insufficient oil resistance.

  An object of the present invention is to provide a thermoplastic elastomer composition excellent in moldability and excellent in flexibility, oil resistance and compression set resistance, and a molded article obtained by using the thermoplastic elastomer composition. .

The present invention
[1] A core-shell rubber having a shell layer containing a (meth) acrylic polymer, a thermoplastic elastomer composition containing an acrylic rubber cross-linked with a cross-linking agent, and [2] the thermoplastic as described in [1] above The present invention relates to a molded article made of an elastomer composition.

  The thermoplastic elastomer composition of the present invention is excellent in moldability and excellent in flexibility, oil resistance and compression set resistance as a material for a molded body.

The thermoplastic elastomer composition of the present invention (hereinafter also referred to as the composition of the present invention) contains a core shell rubber having a shell layer containing a (meth) acrylic polymer, and an acrylic rubber crosslinked with a crosslinking agent. .
In the composition of the present invention, the core-shell rubber is easily compatible with acrylic rubber in the shell layer, and the flexibility and permanent compression resistance of the composition are improved by mixing with the acrylic rubber. Acrylic rubber, on the other hand, has excellent oil resistance, and mixing with the core-shell rubber facilitates stress relaxation during melt-kneading and thermoforming, and can suppress deformation after molding due to residual stress. Product formability is improved. Furthermore, since the acrylic rubber is crosslinked, the concentration of the crosslinked rubber component in the composition increases, and as a result, the compression set resistance is further improved.

  The core-shell rubber in the present invention is a polymer particle having a core-shell structure composed of a core layer (innermost layer) and a shell layer covering the core layer. The shell layer may consist of a plurality of layers.

  The core layer is preferably a rubber-like elastic body. Examples of the monomer that imparts rubber-like elasticity to the core layer include (meth) acrylic acid ester monomers, silicone monomers, and styrene monomers. , Nitrile monomers, conjugated diene monomers and the like.

Examples of (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. And (meth) acrylic acid alkyl ester having 1 to 22 carbon atoms in the alkyl group.
Examples of the silicone monomer include dimethylsiloxane and phenylmethylsiloxane.
Examples of the styrene monomer include styrene and α-methylstyrene.
Examples of nitrile monomers include acrylonitrile and methacrylonitrile.
Examples of the conjugated diene monomer include butadiene and isoprene.

  The core layer may be a polymer of the monomer or a copolymer, but from the viewpoint of improving oil resistance, heat resistance, and weather resistance, a (meth) acrylic acid ester based monomer Polymer rubber ((meth) acrylic rubber), silicone monomer polymer rubber (silicone rubber), and (meth) acrylic acid ester monomer and silicone monomer copolymer rubber ( It is preferable to include at least one selected from the group consisting of (meth) acrylic / silicone rubber. Of these, a core containing polymer rubber ((meth) acrylic rubber) of (meth) acrylic acid ester monomer as a main component (60% by mass or more, preferably 80% by mass or more) is more preferable. In particular, a polymer rubber of a (meth) acrylic acid ester monomer having a main component (45% by mass or more, preferably 65% by mass or more) of a (meth) butyl acrylate monomer unit is flexible. It is preferable because it is excellent.

  Further, the core layer may be a crosslinked rubber obtained by copolymerizing the monomer with a crosslinkable monomer such as divinylbenzene, allyl acrylate, or butylene glycol diacrylate.

  From the viewpoint of flexibility, the glass transition temperature of the core layer is preferably 0 ° C. or lower, more preferably −100 to −5 ° C., further preferably −90 to −7 ° C., and further preferably −40 to −7 ° C. is there.

  The shell layer includes a (meth) acrylic polymer from the viewpoint of affinity with acrylic rubber. Note that “(meth) acryl” includes acrylic, methacrylic, or both.

  Examples of the (meth) acrylic polymer monomer include (meth) acrylic acid ester monomers and (meth) acrylonitrile. In the present invention, (meth) acrylic acid ester monomers are preferred. . Examples of the (meth) acrylic acid ester monomers include alkyl acrylates having 1 to 22 carbon atoms in the alkyl group such as methyl (meth) acrylate and ethyl (meth) acrylate.

  In the (meth) acrylic polymer, monomers such as styrene and α-methylstyrene may be used as long as the effects of the present invention are not impaired.

  Furthermore, a monomer having a reactive functional group such as glycidyl (meth) acrylate and maleic anhydride may be used for the (meth) acrylic polymer.

  The content of the (meth) acrylic acid ester monomer is preferably 30% by mass or more, more preferably 50% by mass or more, and still more preferably 60% in the total amount of monomers constituting the (meth) acrylic polymer. It is at least 70% by mass, more preferably at least 70% by mass.

  The content of the (meth) acrylic polymer in the shell layer is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and further preferably 100% by mass. Examples of the polymer other than the (meth) acrylic polymer include an acryl-styrene copolymer, an acryl-acrylonitrile copolymer, and an acryl-styrene-acrylonitrile copolymer.

  In the core-shell rubber, the mass ratio of the core layer to the shell layer (core layer / shell layer) is not particularly limited, but is preferably 0.05 to 5, more preferably 0.25 to 4, more preferably from the viewpoint of flexibility and moldability. Is 0.7 to 3.0, more preferably 1.0 to 2.0.

  Examples of commercially available core shell rubber include “Paraloid (registered trademark)” manufactured by Rohm and Haas, “Metablene (registered trademark)” manufactured by Mitsubishi Rayon Co., Ltd., and “Kaneace® (registered trademark) manufactured by Kaneka Corporation. ) "," STAPHYLOID (registered trademark) "manufactured by Aika Industry Co., Ltd.," Paraface (registered trademark) "manufactured by Kuraray Co., Ltd., etc., and two or more of these may be used. .

  The content of the core-shell rubber is preferably 4.5 to 94% by mass, more preferably 10 to 80% by mass in the composition of the present invention.

  Acrylic rubber is a polymer in which an acrylic ester is contained in a monomer, and is provided with rubber elasticity by the acrylic ester. In the present specification, “acrylic rubber” refers to an uncrosslinked acrylic rubber before being crosslinked unless otherwise specified.

  As the acrylate ester, non-crosslinkable monomers such as an alkyl acrylate ester and an alkoxyalkyl acrylate ester are preferable, and two or more of these may be used. In the present invention, an alkyl acrylate ester is more preferable. .

  The greater the number of carbon atoms in the alkyl group of the acrylic acid alkyl ester, the greater the flexibility, and the smaller the carbon number, while the smaller the number tends to increase the oil resistance, so it can be selected according to the desired physical properties. From the viewpoint of providing a balance that is easy to use in general applications, it is preferably 1 to 12, more preferably 1 to 8. Specific examples of the alkyl group of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, -n-propyl acrylate, -n-butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate. In the present invention, since the acrylic rubber is crosslinked by a crosslinking agent, when the alkyl group having a relatively large number of carbon atoms in the alkyl group is selected, the flexibility and elongation are high. On the other hand, it is possible to obtain a special effect that oil resistance and compression set resistance are hardly lowered.

  Examples of the alkoxyalkyl acrylate include methoxyethyl acrylate, ethoxyethyl acrylate, methoxyethoxyethyl acrylate, and the like.

  The acrylic rubber is crosslinked with a crosslinking agent in the composition of the present invention. Therefore, the acrylic rubber has a functional group for forming a crosslinked structure, and examples of the functional group include an epoxy group, a carboxy group, and an active chlorine-containing group. Among these, an epoxy group and A carboxy group is preferred, and an epoxy group is more preferred.

Accordingly, in addition to the acrylic ester, the acrylic rubber has a functional monomer for forming a crosslinked structure, such as a non-conjugated diene, a carboxy group-containing monomer, an epoxy group-containing monomer, an active hydrogen. Atom-containing monomers are used.
Non-conjugated dienes include alkylidene norbornene such as 4-methyl-1,4-hexadiene and ethylidene norbornene.
Examples of the carboxy group-containing monomer include (meth) acrylic acid.
Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.
Examples of the active hydrogen atom-containing monomer include 2-chloroethyl vinyl ether, vinyl benzyl chloride, vinyl chloroacetate and the like.

Examples of the monomer other than the acrylic acid ester and the functional monomer for forming the crosslinked structure include, for example, ethylene, propylene, isobutene as a monomer that imparts rubber elasticity to the copolymer together with the acrylic acid ester. And conjugated dienes such as butadiene, isoprene, chloroprene and the like.
Other copolymerizable monomers include ethylenically unsaturated nitriles such as styrene and acrylonitrile substituted with substituents such as styrene, lower alkyl, lower alkoxy, halogen and vinyl, and alkyl groups such as methyl methacrylate. Examples thereof include alkyl methacrylates having about 1 to 8 carbon atoms, tetrahydrobenzyl methacrylate, divinylbenzene and the like.

  As a suitable acrylic rubber, a copolymer of an acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms and an epoxy group or carboxy group-containing monomer (acrylic acid alkyl ester: 90 to 99.95 mol%, epoxy Group or carboxy group-containing monomer: 0.05 to 10 mol%), a copolymer of acrylic acid alkyl ester having 1 to 8 carbon atoms of alkyl and ethylene and an epoxy group or carboxy group-containing monomer (acrylic acid) Alkyl ester: 10 to 89.95 mol%, ethylene: 10 to 80 mol%, epoxy group or carboxy group-containing monomer: 0.05 to 10 mol%) and the like.

The Mooney viscosity (ML _{1 + 4} ) at 100 ° C. of the acrylic rubber in the present invention is preferably 10 to 150, more preferably 10 to 120, still more preferably 15 to 80. Mooney viscosity is defined by JIS K6300 and can be used as an index of melt fluidity related to moldability. Mooney viscosity varies depending on various factors such as composition and molecular weight, but the smaller the viscosity, the better the melt fluidity, while the larger the viscosity, the higher the strength of the composition.

  The glass transition temperature of the acrylic rubber is preferably −10 to 10 ° C., more preferably −90 to 0 ° C., and further preferably −40 to −10 ° C.

  The content of the acrylic rubber is preferably 2.6 to 95.2% by mass, more preferably 20 to 90% by mass in the composition of the present invention.

  From the viewpoint of moldability, the mass ratio of the core shell rubber to the acrylic rubber (core shell rubber / acrylic rubber) in the composition of the present invention is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, More preferably, it is 15 / 85-85 / 15.

  The crosslinking agent is preferably a compound having a functional group capable of reacting with a functional group for forming a crosslinked structure of acrylic rubber. It is preferable to have two or more functional groups in one molecule.

  Examples of the functional group possessed by the crosslinking agent include an amino group, an acid anhydride group, a carboxy group, an isocyanate group, an epoxy group, and a phenolic hydroxyl group.

  Examples of the crosslinking agent containing an amino group include aliphatic diamines such as trimethylhexamethylenediamine, ethylenediamine, hexamethylenediamine carbamate, and 1,4-diaminobutane; fats such as triethylenetetramine, pentaethylenehexamine, and aminoethylethanolamine. Aromatic polyamines such as phenylenediamine, 4,4′-methylenedianiline, toluenediamine, and diaminoditolylsulfone.

  Examples of the crosslinking agent having an acid anhydride group include trimellitic anhydride and pyromellitic anhydride.

  Examples of the crosslinking agent having a carboxy group include low molecular weight polycarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, cyanuric acid, and butanetetracarboxylic acid, polymer polycarboxylic acids obtained by polymerizing these carboxylic acids, and phenols. And the like.

  In the crosslinking agent having an acid anhydride group or carboxy group, a compound having an acid anhydride group or carboxy group is preferable from the viewpoint of hardly causing coloration due to heat, and foaming and bad odor are caused by degassing during the reaction. From the viewpoint of difficulty, a high molecular weight polycarboxylic acid is preferable. Among polymer carboxylic acids, those having a plurality of carboxy group-containing side chains in the polymer main chain are superior in that they do not cause coloring or degassing, and those containing a polyacrylic acid derivative in the main chain are acrylic. It is particularly excellent in terms of good mixing with rubber.

  The weight average molecular weight of the polymer polycarboxylic acid is preferably 500 to 200,000, more preferably 1000 to 100,000.

  The content of the polymer polycarboxylic acid is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 98% by mass or more in the crosslinking agent.

  Examples of the crosslinking agent having an isocyanate group include diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

  Examples of the crosslinking agent having an epoxy group include bisglycidyl compounds such as bisphenol A type epoxy resins and cresol novolac type epoxy resins.

  Examples of the crosslinking agent having a phenolic hydroxyl group include phenol resins such as resol type phenol resins and novolak type phenol resins, vinyl phenol resins such as polyvinyl phenol resins and vinyl copolymers thereof.

  A known crosslinking accelerator may be used in combination with these crosslinking agents.

  As a crosslinking agent suitable for acrylic rubber having an epoxy group, a crosslinking agent containing an amino group, a crosslinking agent having an acid anhydride group, a crosslinking agent having a carboxy group, a crosslinking agent having a phenolic hydroxyl group, and the like are preferable.

  Examples of the crosslinking agent suitable for the acrylic rubber having a carboxy group include an amino group-containing crosslinking agent. Among the crosslinking agents containing an amino group, hexamethylenediamine and 4,4'-methylenedianiline are preferable, and 4,4'-methylenedianiline is more preferable. These crosslinking agents are preferably used together with a crosslinking accelerator such as 1,3-diphenylguanidine.

  Examples of the crosslinking agent suitable for the acrylic rubber having an amino group include a crosslinking agent having an epoxy group. Of the crosslinking agents having an epoxy group, a bisglycidyl compound is preferred.

  The amount of the crosslinking agent is preferably 0.1 to 12 parts by mass, more preferably 0.2 to 8 parts by mass, and still more preferably 0.5 to 7 parts by mass with respect to 100 parts by mass of the acrylic rubber.

It is preferable that the composition of the present invention further contains a plasticizer having a low solubility parameter. By using the plasticizer together with the core-shell rubber, the plasticizer is taken into the core layer of the core-shell rubber, and the oil resistance is further improved while maintaining the hardness. The solubility parameter (SP value) of the plasticizer is preferably 18.7 (J / cm ³ ) ^1/2 or less, more preferably 18.5 (J / cm ³ ), from the viewpoint of compatibility with the core layer of the core-shell rubber. ^1/2 or less, more preferably 18.3 (J / cm ³ ) ^1/2 or less, from the viewpoint of oil resistance, preferably 17.0 (J / cm ³ ) ^1/2 or more, more preferably 17.5 (J / cm cm ³ ) ^1/2 or more, more preferably 18.2 (J / cm ³ ) ^1/2 or more.

  As the plasticizer having the SP value, phthalic acid plasticizer, aliphatic ester plasticizer, trimellitic acid plasticizer, pyromellitic acid plasticizer, phosphate ester plasticizer, epoxy plasticizer, high Examples thereof include molecular plasticizers, and two or more of these may be used.

  Examples of the phthalic acid plasticizer include diisodecyl phthalate (DIDP) and diundecyl phthalate (DUP).

  Aliphatic ester plasticizers include di-2-ethylhexyl adipate (DOA), diisodecyl adipate, dibutyl adipate, dibutyl diglycol adipate, di-2-ethylhexyl azelate, dibutyl sebacate, di-sebacate Examples include 2-ethylhexyl (DOS).

  Examples of trimellitic acid plasticizers include trimellitic acid trialkyl esters such as trioctyl trimellitic acid, tridecyl trimellitic acid, and triisodecyl trimellitic acid.

  Examples of the pyromellitic acid plasticizer include pyromellitic acid-di-2-ethylhexyl.

  Examples of the phosphate plasticizer include tributyl phosphate, tri-2-ethylhexyl phosphate, tricresyl phosphate, and tributoxyethyl phosphate.

  Examples of the epoxy plasticizer include epoxidized soybean oil.

  Examples of the polymer plasticizer include chlorinated paraffin, polyester polymer plasticizer, and polyether polymer plasticizer.

  The number average molecular weight of the polymer plasticizer is preferably 300 or more, more preferably 500 or more from the viewpoint of suppressing bleed out, and preferably 10,000 or less, more preferably 5,000 or less from the viewpoint of flexibility. The number average molecular weight of the polymer plasticizer is measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as an eluent, and the number average molecular weight is calculated from the measurement result of polystyrene (PS) molecular weight standard. .

  The viscosity of the plasticizer at 25 ° C. is preferably 10 to 10,000 mPa · s, more preferably 20 to 8,000 mPa · s, and still more preferably 50 to 6,000 mPa · s, from the viewpoint of compatibility with the core layer of the core-shell rubber. More preferably, it is 100 to 3,000 mPa · s.

  The greater the plasticizer content, the more flexible the composition becomes. However, when the amount that the core-shell rubber cannot absorb is added, bleeding out from the composition becomes easier. From these viewpoints, the content of the plasticizer is preferably 1 to 100 parts by mass, more preferably 5 to 70 parts by mass, and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of the core-shell rubber.

  The content of the plasticizer in the composition of the present invention is preferably 0.05 to 49% by mass, more preferably 0.1 to 40% by mass.

  From the viewpoint of heat resistance, the composition of the present invention preferably further contains at least one crystalline elastomer selected from polyester elastomers and polyamide elastomers. When an acrylic rubber having a crosslinking point functional group (functional group for forming a crosslinked structure) is used, it is generated by a reaction between a molecular terminal functional group of the crystalline elastomer and a rubber crosslinking point functional group of the acrylic rubber. A strong interface is formed by the graft of acrylic rubber and crystalline elastomer, and heat resistance and mechanical strength are further improved.

  In the present invention, a polyester-based elastomer is preferable from the viewpoint of easily balancing the flexibility and heat resistance.

  The polyester-based elastomer and the polyamide-based elastomer are preferably a block copolymer including a hard segment and a soft segment block from the viewpoint of achieving both heat resistance and flexibility.

  As the hard segment of the polyester elastomer, a polyester block is preferable, and a crystalline polyester block formed by a condensation reaction of an aromatic dicarboxylic acid compound and an alkylene glycol having 2 to 6 carbon atoms is preferable. Examples of the aromatic dicarboxylic acid compound include terephthalic acid, isophthalic acid, alkyl esters of these acids, and anhydrides. Examples of the alkylene glycol having 2 to 6 carbon atoms include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, and the like.

  The melting point of the block constituting the hard segment is preferably higher than 160 ° C., more preferably 160 to 300 ° C., further preferably 170 to 290 ° C., from the viewpoint of heat resistance.

  Examples of the soft segment of the polyester-based elastomer include a polyester-type polymer block, a polyether-type polymer block, and a polycarbonate-type polymer block. Among these, a polyester-type polymer block is preferable from the viewpoint of heat aging resistance.

  Examples of the polyester type polymer block include polycaprolactone, polyenane lactone, polycaprylolactone, polyalkylene ester formed by condensation reaction of an aliphatic dicarboxylic acid compound and an aliphatic diol, and the like. Examples of the polyalkylene ester formed by the condensation reaction of an aliphatic dicarboxylic acid compound and an aliphatic diol include polybutylene adipate.

  From the viewpoint of flexibility, the glass transition temperature of the block constituting the soft segment is preferably less than 0 ° C, more preferably -100 to -5 ° C, and further preferably -80 to -10 ° C.

  The number average molecular weight of the blocks constituting the soft segment is preferably 400 to 6000, more preferably 500 to 4000, from the viewpoint of flexibility.

  As the polyamide-based elastomer, a block copolymer including a hard segment made of polyamide and a soft segment made of polyether is preferable.

  The mass ratio of the hard segment to the soft segment (hard segment / soft segment) in the polyester elastomer and the polyamide elastomer is preferably 20/80 to 90/10, more preferably 30/70 to 85/15.

  The melting point of the crystalline elastomer is preferably 160 to 300 ° C, more preferably 170 to 290 ° C, and still more preferably 180 to 280 ° C, from the viewpoint of heat resistance and prevention of thermal decomposition.

  The bending elastic modulus of the crystalline elastomer is preferably 10 to 1000 MPa, more preferably 50 to 900 MPa, and still more preferably 80 to 800 MPa from the viewpoint of the flexibility of the composition.

  Commercially available crystalline elastomers include "Perprene (registered trademark) P" and "Perprene S" (trade name, manufactured by Toyobo Co., Ltd.), "Hytrel (registered trademark)" (trade name, manufactured by Toray DuPont Co., Ltd.) , “Lomod (registered trademark)” (trade name, manufactured by Nippon GE Plastics Co., Ltd.), “Nichigo Polyester (registered trademark)” (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), “Nouvelain (registered trademark)” ( Teijin Kasei Co., Ltd. product name). Commercially available polyamide-based elastomers include “Pebax (registered trademark)” (trade name, manufactured by Arkema Co., Ltd.), “Daiamide (registered trademark)” (trade name, manufactured by Daicel-Evonik Co., Ltd.), “UBESTA (registered trademark)”. "XPA" (trade name, manufactured by Ube Industries, Ltd.), "Novamid (registered trademark)" (trade name, manufactured by DSM Corporation), "Glorel (registered trademark)" (trade name, manufactured by Toyobo Co., Ltd.), "Grillon" (Registered trademark) "(trade name, manufactured by Ms Chemie Japan Co., Ltd.) and the like.

  The crystalline elastomer has a high melting point and usually phase-separates from the core shell rubber and acrylic rubber, which are essential constituents of the present invention. Therefore, if there is too much crystalline elastomer, the crystalline elastomer is transformed into the sea phase, core shell rubber and acrylic rubber. It tends to have a sea-island structure with rubber as an island phase, and the whole composition tends to be hard. Therefore, from the viewpoint of improving the heat resistance without impairing the flexibility of the composition by making the crystalline elastomer into a co-continuous phase or an island phase having a sea-island structure, the content of the crystalline elastomer is the core-shell rubber and the acrylic. The amount is 5 to 80 parts by mass, preferably 10 to 70 parts by mass with respect to 100 parts by mass of the total amount of rubber.

  Further, the content of the crystalline elastomer in the composition of the present invention is preferably 1 to 70% by mass, more preferably 10 to 60% by mass.

  The composition of the present invention is obtained by kneading a raw material mixture under heating conditions. The acrylic rubber is preferably crosslinked by blending a crosslinking agent, and more preferably dynamically crosslinked by a crosslinking agent. Therefore, the composition of the present invention is prepared by heating a raw material mixture containing at least an additive such as a core-shell rubber, an acrylic rubber, a crosslinking agent, and, if necessary, a plasticizer, a crystalline elastomer, and other additives. Those obtained by kneading under conditions are preferred.

  Other additives to be blended as necessary in the composition of the present invention include fillers such as calcium carbonate, talc, silica and glass fiber, known flame retardants, stabilizers such as antioxidants, colorants, Examples include lubricants.

  The heating temperature at the time of kneading is preferably kneaded at a temperature of 170 to 300 ° C. from the viewpoint of dynamically crosslinking the acrylic rubber with a crosslinking agent.

  For kneading, a kneader or a general melt extruder can be used, and it is preferable to use a single screw extruder for improving the kneading state. As for the supply to the extruder, various components may be directly supplied to the extruder, a mixture of various components using a mixing device such as a Henschel mixer in advance may be provided from one hopper, or two hoppers. Each of the components may be charged and used while being quantified with a screw or the like under the hopper.

  The composition of the present invention is not only used by directly molding the product obtained by kneading into a molded product, but before forming into a molded product to be used as a final product, depending on the purpose, Intermediate products such as sheets can be used. For example, it is melt-mixed by an extruder, extruded into a strand, and cut into pellets such as a cylindrical shape and a rice grain by a cutter while cooling in cold water. The obtained pellets can be usually formed into a predetermined sheet-like molded product or a molded product by a molding method such as injection molding, extrusion molding, or press molding.

  The A hardness of the composition of the present invention is preferably 95 or less, more preferably 10 to 90, and still more preferably 20 to 80, from the viewpoint of flexibility.

  The D hardness of the composition of the present invention is preferably 60 or less, more preferably 1 to 55, and still more preferably 5 to 45, from the viewpoint of flexibility.

  A molded body is obtained by appropriately heat-molding the composition of the present invention according to a conventional method.

  Although the temperature at the time of heat molding is not particularly limited, it is usually preferably about 150 to 300 ° C. from the viewpoint of moldability.

  Any molding machine capable of melt-molding the composition can be used for an apparatus used for producing a molded body using the composition of the present invention. Examples thereof include a kneader, an extrusion molding machine, an injection molding machine, a press molding machine, a blow molding machine, and a mixing roll.

  The molded product obtained by molding the thermoplastic elastomer composition of the present invention can be suitably used in the vicinity of automobile engines and high temperature equipment sealing materials, packings, tubes, and the like that require high heat resistance and oil resistance.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Various physical properties of the raw materials used in Examples and Comparative Examples were measured by the following methods.

<Core shell rubber>
(Monomer composition)
Using a gas chromatograph mass spectrometer (Gas Chromatograph 7890A manufactured by Agilent Technologies, Jms-Q1000GC K9 manufactured by JEOL Ltd.), the sample is thermally decomposed at 550 ° C., and mass analysis of the pyrolyzate is performed. Thus, the monomer composition is analyzed. However, since the content of the silicone component is not detected by this measurement method, the monomer composition in the table is a value excluding the silicone component.

[Glass transition temperature of core layer (Tg)]
A batch kneader “Plastograph EC50 type” (manufactured by Brabender) heated to 180 ° C. is charged with 50 g of core-shell rubber and kneaded at 60 r / min for 10 minutes to obtain a molten resin. Then, the core-shell rubber kneaded material heated to 180 ° C was heated to 180 ° C using a heat press device "TB-50-2" (manufactured by Toho Machinery Co., Ltd., 50t hydraulic press). In a mold with a width of 100 mm and a length of 150 mm, pressurize at 5 MPa and heat for 2 minutes, sandwich the whole mold with a water-cooled cooling plate and apply a cooling press process at 5 MPa for 3 minutes to produce a press sheet.
A test piece of 12mm width x 30mm length is cut from the press sheet, and the dynamic viscoelasticity measuring device (TA Instruments RSA-II type) torsion mode (10gf load), frequency 10Hz, heating rate Measure the viscoelastic properties of each sample at the setting of 5 ℃ / min and temperature -80 ～ 150 ℃.
Tg is the peak value of loss tangent (Tanδ) in viscoelasticity measurement. In core shell rubber, Tg of core layer and Tg of shell layer are generally observed from low temperature side. Observe as Tg.

<Acrylic rubber>
(Monomer composition)
Using a gas chromatograph mass spectrometer (Gas Chromatograph 7890A manufactured by Agilent Technologies, Jms-Q1000GC K9 manufactured by JEOL Ltd.), the sample is thermally decomposed at 550 ° C., and mass analysis of the pyrolyzate is performed. Thus, the monomer composition is analyzed.

[Mooney viscosity]
Measure Mooney viscosity (ML _{1 + 4} ) after 1 minute of preheating at 100 ° C and 4 minutes after starting rotation in accordance with the method specified in JIS K6300.

[Glass transition temperature (Tg)]
The Tg of the homopolymer of the constituent monomer component is calculated by weighted averaging according to the composition.

<Crosslinking agent>
[Weight average molecular weight of polymer polycarboxylic acid]
Gel permeation chromatography (GPC) is measured using tetrahydrofuran (THF) as an eluent, and the weight average molecular weight is calculated from the measurement result of polystyrene (PS) molecular weight standard.

[Acid value]
In accordance with JIS K2501, the crosslinking agent is dissolved in a titration solvent in which xylene and dimethylformamide are mixed in an equal ratio, titrated with a 0.1 mol / L potassium hydroxide / ethanol solution by potentiometric titration, and the end point of the potassium hydroxide solution The acid value is calculated from the titration amount until.

<Plasticizer>
[SP value]
The SP value can be directly measured by a cloud point method, but it is generally accepted to be estimated from the molecular structure, and “Polymer Engineering and Science” 14 (2), 147, written by RFFedors. Calculated by the calculation method described in (1974). Specifically, the SP value ((cal / cm ³ ) ^1/2 ) is calculated by the calculation method shown in the following formula (1), and 1 (cal / cm ³ ) ^{1/2 is set} to 2.05 (J / cm ³ ) Convert to ^1/2 .

δ: SP value ((cal / cm ³ ) ^1/2 )
ΔE _vap : Heat of molar evaporation of each atomic group (cal / mol)
V: molar volume of each atomic group (cm ³ / mol)

〔viscosity〕
Measured at 25 ° C using a B-type viscometer in accordance with JIS Z8803.

<Crystalline elastomer>
[Melting point]
Using a differential scanning calorimetry (DSC) apparatus, the melting peak temperature obtained by raising the temperature at 10 ° C./min according to the method specified in JIS K 7121 is defined as the melting point. When a plurality of melting peaks appear, the melting peak appearing at a lower temperature is taken as the melting point.

(Flexural modulus)
In accordance with ASTM D790 standard, a test piece of 127mm x 12.7mm and thickness 3.2mm obtained by injection molding was placed at a temperature of 23 ° C and a relative humidity of 50% for 40 hours and then 1.4mm / min using an autograph. A vertical displacement is applied at a speed, and the flexural modulus is calculated from the load-deflection curve.

Examples 1-20 and Comparative Examples 1-7
[Production of thermoplastic elastomer composition (press sheet)]
A batch type kneader “Plastograph EC50 type” (made by Brabender Co., Ltd.) heated to 180 ° C. is charged with a total of 54 g of raw material components having the composition ratios (mass ratios) shown in Tables 6 to 11, and rotated at 60 r / min. The mixture was melt kneaded at 180 to 210 ° C. In a kneading time of 10 minutes, the entire kneaded material in a molten state was taken out and cooled at room temperature (25 ° C.) to obtain a composition.
Each composition was heated to 180 ° C in a mold with a thickness of 2mm x width 100mm x length 150mm using the "TB-50-2" (manufactured by Toho Machinery Co., Ltd., 50t hydraulic press). Then, pressurizing at 5 MPa and heating for 2 minutes, sandwiching the whole mold with a water-cooled cooling plate, and performing a cold press process at 5 MPa for 3 minutes, a press sheet was produced.

  The thickness x width x length of the press sheet thus obtained was measured and recorded. The moldability of the composition is greatly influenced by the melt flowability and the stress strain relaxation rate. First, if the fluidity is good, the hot-pressed composition should reach the corners of the mold to obtain a molded product according to the dimensions of the mold, and if the fluidity is poor, the molded product will be It will be out of the dimensions of the formwork. Further, if stress strain remains in the molded product, the molded product taken out from the mold is deformed with the release. Among the components of the composition of the present invention, acrylic rubber has a very slow stress relaxation and a low glass transition temperature. Therefore, after molding, the stress is gradually released, and the molded product is deformed. Therefore, this degree of deformation was used as an evaluation of formability. Measure the maximum thickness (easy to measure) of 10 molded products that were removed from the mold and left to stand at 23 ° C for 24 hours, and calculate the average value. Then, the moldability was evaluated according to the following evaluation criteria. The results are shown in Tables 6-11.

[Evaluation criteria for formability]
A: The thickness of the molded product is 1.8 mm or more and 2.6 mm or less. ○: The thickness of the molded product exceeds 2.6 mm and 3.0 mm or less. X: The thickness of the molded product exceeds 3.0 mm.

  The detail of the raw material component used by the Example and the comparative example is shown to Tables 1-5.

  The following evaluation was performed about the composition obtained by the Example and the comparative example. The results are shown in Tables 6-11.

(1) Flexibility [A hardness]
The press sheet was allowed to stand in a constant temperature and humidity chamber (temperature 23 ° C., relative humidity 50%) for 24 hours or more to stabilize the state of the sheet. Three press sheets with a thickness of 2 mm were stacked, and the A hardness was measured according to JIS K7215 “Plastic Durometer Hardness Test Method”.

[D hardness]
Similarly to the A hardness, the D hardness was measured according to JIS K7215 “Plastic Durometer Hardness Test Method”.

(2) Mechanical strength (tensile fracture stress and tensile fracture strain)
A No. 3 test piece (length 20 mm) described in JIS K7113 was prepared from the press sheet using a die cutting machine, and a tensile tester (Autograph AG-50kND type) manufactured by Shimadzu Corporation was used. The test piece was pulled at a speed of 200 mm / min in a temperature environment of ° C. The stress at break (MPa) and elongation (the length of the test piece at break (mm) / 20 (mm) × 100,%) were recorded as the tensile fracture stress and tensile fracture strain, respectively.

(3) Compression set resistance (compression set)
A circular sample having a diameter of 29 mm and a thickness of 2 mm was punched from the press sheet using a circular punching blade having a diameter of 29 mm. Measure the compression set (CS) in a 24-hour environment at 70 ° C using a test piece adjusted to a thickness of 12.5mm by stacking six round samples and compressing them to a thickness of 12.5mm. did. The compression set is preferably 90% or less, more preferably 60% or less.

(4) Oil resistance (swelling rate)
In accordance with JIS K6258, the press sheet was immersed in IRM903 oil manufactured by Nippon San Oil Co., Ltd. at 70 ° C for 24 hours, and the mass of the press sheet before and after immersion was measured. Previous mass × 100,%) was calculated. When the test piece did not swell at all with oil, it was 0%, and the larger the swelling, the larger the number. Therefore, the swelling ratio was 0% or more, and the smaller the value, the better the oil resistance. The swelling rate is preferably 20% or less, and more preferably 15% or less.

From Table 6, the core-shell rubber of Comparative Example 2 has good moldability but insufficient oil resistance. The crosslinked acrylic rubber of Comparative Example 3 has good flexibility and oil resistance but lacks moldability. I understand that When the core shell rubber, the acrylic rubber and the crosslinking agent are used in combination in Example 1, not only the flexibility, oil resistance, and moldability are all well balanced but also the compression set resistance is a comparative example. It is superior to any of 1-3, and it can be seen that the composition of the present invention exhibits an unexpected effect.
Table 7 shows the results when the type of the core-shell rubber is changed. Compared with Example 2 and Comparative Example 4 in which the core layer / shell layer is low with (meth) acrylic rubber, the core layer / shell layer is 1 In Examples 3 and 4 in which the core layer exceeding the core shell rubber of acrylic rubber is used, it can be seen that the effect of improving the compression set resistance against the corresponding Comparative Examples 5 and 6 is greater. In comparison between Example 5 and Comparative Example 7 in which the core layer of the core-shell rubber is acrylic / silicone rubber, the oil resistance is greatly improved.
From Table 8, it can be seen that moldability, compression set resistance, and oil resistance are improved by increasing the amount of the crosslinking agent. Furthermore, the flexibility tends to decrease by increasing the amount of the crosslinking agent, but from the comparison between Example 10 and Example 11, butyl acrylate (alkyl group having 4 carbon atoms as the alkyl group) is used as a non-crosslinkable monomer. It can be seen that, when an acrylic rubber containing an acrylic acid alkyl ester) is used, good flexibility can be maintained even in a blend with an increased amount of the crosslinking agent.
From Table 9, it can be seen from the comparison between Example 1 and Examples 12 and 13 that the use of the polymer crosslinking agent improves the compression set resistance and mechanical strength.
From Table 10, it can be seen that the more core-shell rubber, the better the moldability, and the more acrylic rubber, the more flexible.
From Table 11, it can be seen from the comparison between Example 1 and Example 18 that oil resistance is improved by using a plasticizer. Moreover, it turns out that oil resistance is further improved by combining Example 19 and 20 and using a plasticizer and a crystalline elastomer together.

  The thermoplastic elastomer composition of the present invention is used for various molded products such as electrical and electronic parts, automotive parts, sealing materials, packings, vibration damping members, and tubes.

Claims (7)

  A thermoplastic elastomer composition containing a core-shell rubber having a shell layer containing a (meth) acrylic polymer, and an acrylic rubber crosslinked with a crosslinking agent.   The thermoplastic elastomer composition according to claim 1, wherein the mass ratio of the acrylic rubber before being crosslinked with the core shell rubber (core shell rubber / acrylic rubber) is 5/95 to 95/5.   The thermoplastic elastomer composition according to claim 1 or 2, wherein the amount of the crosslinking agent is 0.1 to 12 parts by mass with respect to 100 parts by mass of the acrylic rubber before being crosslinked.   The thermoplastic elastomer composition according to any one of claims 1 to 3, wherein the crosslinking agent contains a high-molecular polycarboxylic acid. The thermoplastic elastomer composition according to any one of claims 1 to 4, further comprising a plasticizer having a solubility parameter of 18.7 (J / cm ³ ) ^1/2 or less.   Furthermore, the thermoplastic elastomer composition in any one of Claims 1-5 containing the at least 1 sort (s) of crystalline elastomer chosen from the polyester-type elastomer and the polyamide-type elastomer.   The molded object which consists of a thermoplastic-elastomer composition in any one of Claims 1-6.