JP6361399B2 - Thermoplastic elastomer - Google Patents

Description

  The present invention relates to a thermoplastic elastomer obtained by dynamically crosslinking a mixture containing acrylic rubber and thermoplastic polyolefin in the presence of a crosslinking agent.

  In recent years, as an alternative to vulcanized rubber, thermoplastic elastomers that do not require a vulcanization process and have the same moldability as thermoplastic resins have been used in fields such as automobiles, electrical / electronics, medical, food, and daily necessities. Widely used. In particular, in a field where sealability is required, a thermoplastic elastomer of a type in which a mixture containing rubber and a thermoplastic resin is dynamically cross-linked in the presence of a cross-linking agent is used.

  As this kind of thermoplastic elastomer, for example, there is Patent Document 1 below. The thermoplastic elastomer of Patent Document 1 is a mixture of a polyamide polymer or a polyester polymer with an acrylic rubber having at least one selected from the group consisting of a halogen-containing group, an epoxy group or a carboxyl group as a crosslinkable group, Dynamically crosslinked. The acrylic rubber here is a copolymer having a structural unit derived from an alkyl acrylate ester and a structural unit derived from a polyfunctional monomer, and a gel content of 30% by weight or more is uniformly dispersed. Thus, by mixing acrylic rubber particles with the polyamide polymer or polyester polymer, the acrylic rubber particles can be finely dispersed in the polyamide polymer matrix or polyester polymer matrix. It is said that a thermoplastic elastomer having excellent oil resistance and tensile strength can be obtained.

International Publication No. 2005/030869

  However, in patent document 1, the gel part exists uniformly from the surface layer part of an acrylic rubber particle to the inside. In this case, although the acrylic rubber particles can be finely dispersed in the polyamide polymer or polyester polymer matrix, the interface strength between the polyamide polymer or polyester polymer and the acrylic rubber particle surface is low, so that the heat obtained Not only is there a limit to the tensile strength of the plastic elastomer, it has the problem of insufficient tensile elongation.

  Then, this invention solves the said subject, Comprising: The core layer comprised from the core layer of the inner-layer part which contains a gel part and has a crosslinkable group, and the shell layer of the surface layer part which does not contain a gel part An object of the present invention is to provide a thermoplastic elastomer having excellent tensile strength and tensile elongation by using an acrylic rubber having a shell structure.

The present invention is as follows .
(A) A mixture containing 100 parts by mass of acrylic rubber and (B) 15 to 70 parts by mass of thermoplastic polyolefin, (A) 0.1 to 5 parts by mass of (C) crosslinker A method for producing a thermoplastic elastomer by dynamically crosslinking in the presence of a thermoplastic elastomer,
(A) Acrylic rubber has a core-shell structure,
The core layer is
(A-1) 70-100 parts by mass of at least one selected from an alkyl acrylate monomer or an alkoxyalkyl acrylate monomer;
(A-2) 0-30 parts by mass of an unsaturated nitrile monomer;
(A-3) 0.1-3 parts by mass of a polyfunctional monomer having a carbon-carbon double bond in the side chain with respect to 100 parts by mass in total of (a-1) and (a-2) ,
(A-4) A monomer having at least one selected from the group consisting of a chlorine group, an epoxy group and a carboxyl group, which is a crosslinkable group, is added to 100 parts by mass of (a-1) and (a-2). In contrast, 0.1 to 3 parts by mass
Including
The shell layer does not include a polyfunctional monomer having a carbon-carbon double bond in the side chain,
(A-5) 70-100 parts by mass of at least one selected from an alkyl acrylate monomer or an alkoxyalkyl acrylate monomer;
(A-6) A method for producing a thermoplastic elastomer containing 0 to 30 parts by mass of an unsaturated nitrile monomer

  (A) The core layer of acrylic rubber is (a-1) + (a-2) = 100 parts by mass, (a-1) is 70 to 100 parts by mass, and (a-2) is 0 to 30 parts by mass. Including. Moreover, 0.1-3 mass parts of (a-3) and 0.1-3 mass parts of (a-4) are included with respect to a total of 100 mass parts of (a-1) and (a-2). .

  On the other hand, the shell layer of (A) acrylic rubber is (a-5) + (a-6) = 100 parts by mass, (a-5) is 70 to 100 parts by mass, and (a-6) is 0 to 30. Including parts by mass.

  The thermoplastic elastomer of the present invention is a mixture containing 100 parts by mass of (A) and 15 to 70 parts by mass of (B), and (C) is 0.1 to 5 parts by mass with respect to 100 parts by mass of (A). It is dynamically crosslinked under the existing conditions.

  In the present invention, “OO to XX” indicating a numerical range means to include the lower limit numerical value (OO) and the upper limit numerical value (XX). That is, if it is accurately described, it will be “XX or more and XX or less”.

  According to the present invention, the core layer of (A) acrylic rubber has a gel content because it includes (a-3) the polyfunctional monomer having a carbon-carbon double bond in the side chain. Thereby, the uniform dispersibility of an acrylic rubber can be ensured. Furthermore, since (a-4) the monomer containing a crosslinkable group is included, the tensile strength of the thermoplastic elastomer obtained can be improved. On the other hand, since the shell layer does not contain a polyfunctional monomer having a carbon-carbon double bond in the side chain, no gel content is generated in the shell layer. Thereby, the interface strength of thermoplastic polyolefin and acrylic rubber particle becomes high, and the tensile strength and tensile elongation of the thermoplastic elastomer obtained can be improved more.

  Hereinafter, the present invention will be described in detail. The thermoplastic elastomer of the present invention has a so-called sea-island structure in which (A) acrylic rubber is finely dispersed in (B) thermoplastic polyolefin.

≪ (A) Acrylic rubber≫
(A) Acrylic rubber is a component that acts as a soft segment in a thermoplastic elastomer and mainly imparts flexibility, elasticity, sealing properties, heat resistance, oil resistance, and the like. In addition, the acrylic rubber (A) of the present invention has a core-shell structure constituted by a core layer containing a gel component inside and a shell layer covering the core layer and not containing a gel component.

<Core layer>
The core layer includes (a-1) at least one selected from an alkyl acrylate monomer or an alkoxy alkyl ester monomer, (a-2) an unsaturated nitrile monomer, and (a-3). 1) a monomer having at least one selected from a polyfunctional monomer having a carbon-carbon double bond in the side chain and a chlorine group, an epoxy group or a carboxyl group which is a crosslinkable group in the side chain; Including the body.

(A-1)
Examples of the alkyl acrylate monomer include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and n-acrylate. Examples include pentyl, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, and 2-ethylhexyl acrylate. Among these, an acrylic acid alkyl ester monomer having 2 to 4 carbon atoms in the alkyl group is particularly preferable because it can exhibit excellent flexibility and oil resistance.

  As the acrylic acid alkoxyalkyl ester monomer, an acrylic acid alkoxyalkyl ester monomer having an alkyl group having 2 to 4 carbon atoms is preferable. Specific examples include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, and the like. Among these, 2-methoxyethyl acrylate is particularly preferable in that it can exhibit excellent oil resistance.

  In the core layer, the content of (a-1) is preferably 70 to 100 parts by mass with respect to 100 parts by mass in total with (a-2) described later. If content of (a-1) is less than 70 mass parts, the softness | flexibility etc. of a thermoplastic elastomer will fall. On the other hand, when the content of (a-1) exceeds 100 parts by mass, the content of (a-4) described later becomes relatively small, and crosslinking of acrylic rubber does not proceed sufficiently, and the resulting thermoplasticity The tensile strength of the elastomer is reduced.

(A-2)
Examples of the unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, ethacrylonitrile, α-chloroacrylonitrile, α-fluoroacrylonitrile and the like. These can use only 1 type and can also use 2 or more types together.

  In the core layer, the content of (a-2) is preferably 0 to 30 parts by mass with respect to 100 parts by mass in total with (a-1). That is, (a-2) is not an essential component and may not necessarily be contained in the core layer. (A-2) When the unsaturated nitrile monomer is contained, oil resistance is improved. However, when the content of (a-2) exceeds 30 parts by mass, the flexibility and the like of the resulting thermoplastic elastomer tend to be lowered.

(A-3)
Examples of the polyfunctional monomer having a carbon-carbon double bond in the side chain include divinylbenzene, 1,3,5-trivinylbenzene, diallyl phthalate, diallyl fumarate, trimethylolpropane triacrylate, and ethylene glycol. Examples include dimethacrylate, allyl methacrylate, and dicyclopentenyl acrylate. These can use only 1 type and can also use 2 or more types together.

  In the core layer, the content of (a-3) is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass in total of (a-1) and (a-2). When the content of (a-3) is less than 0.1 parts by mass, the polyfunctional monomer for gelation is reduced, and (A) the gelation of acrylic rubber does not proceed sufficiently. Excellent tensile strength cannot be obtained. On the other hand, when the content of (a-3) exceeds 3 parts by mass, the polyfunctional monomer for gelation increases, and (A) the acrylic rubber is excessively gelled. Workability is reduced.

(A-4)
(A-4) has a chlorine group, an epoxy group, or a carboxyl group in the side chain as a functional group for crosslinking. Examples of the chlorine group-containing monomer include 2-chloroethyl vinyl ether, chloromethyl styrene, vinyl chloroacetate and the like.

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate, vinyl glycidyl ether, and allyl glycidyl ether. In addition, (meth) acrylic acid means both acrylic acid and methacrylic acid.

  The carboxyl group-containing monomer means a vinyl monomer having a carboxyl group in the molecule. Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acryloxypropionic acid, citraconic acid, fumaric acid, itaconic acid, crotonic acid, maleic acid or esters thereof, maleic anhydride and derivatives thereof. Can be mentioned. Each of these monomers can be used alone or in combination of two or more.

  In the core layer, the content of (a-4) is preferably 0.1 to 3 parts by mass with respect to 100 parts by mass in total of (a-1) and (a-2). When the content of (a-4) is less than 0.1 part by mass, (A) the acrylic rubber is not sufficiently crosslinked, and an excellent tensile strength cannot be obtained in the thermoplastic elastomer. On the other hand, if the content of (a-4) exceeds 3 parts by mass, (A) the acrylic rubber is excessively crosslinked, so that the molding processability of the thermoplastic elastomer is lowered.

<Shell layer>
The shell layer includes (a-5) at least one selected from an acrylic acid alkyl ester monomer or an acrylic acid alkoxyalkyl ester monomer, and (a-6) an unsaturated nitrile monomer. However, unlike the core layer, a polyfunctional monomer having a carbon-carbon double bond in the side chain is not included. Therefore, when acrylic rubber is polymerized, no gel content is generated in the shell layer.

(A-5 / a-6)
For (a-5) and (a-6), the same type of monomer as (a-1) and (a-2) of the core layer may be used.

In the shell layer, the contents of (a-5) and (a-6) may be in the same ranges as (a-1) and (a-2) of the core layer, respectively. Specifically, with respect to a total of 100 parts by mass of (a-5) and (a-6), 70 to 100 parts by mass of (a-5) and 0 to 30 parts by mass of (a-6) are contained. It is preferable.
[Acrylic rubber polymerization]

  The acrylic rubber having a core-shell structure can be obtained by a method in which the core layer is polymerized first and the monomer of the shell layer is subsequently added when the polymerization conversion rate becomes a certain level or more. Specifically, first, a mixture containing (a-1), (a-3), (a-4), and (a-2) as necessary is copolymerized in the presence of a radical polymerization initiator. To form a core layer. Subsequently, in the state in which the core layer is dispersed, (a-5) is added as it is, and (a-6) is added as necessary, and the copolymer is copolymerized again in the presence of a radical polymerization initiator. A shell layer is formed to cover the layer. As the polymerization method, known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be used, and emulsion polymerization is particularly preferable.

  Examples of the emulsifier used in the emulsion polymerization include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant. Usually, anionic surfactants are frequently used. For example, long chain fatty acid salts having 10 or more carbon atoms, rosin acid salts and the like are used. Specific examples include capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, and potassium and sodium salts of stearic acid. These emulsifiers may use only 1 type and can also use 2 or more types together.

  Examples of the radical polymerization initiator include hydroperoxide, inorganic peroxide, azo compound and the like. Examples of the hydroperoxide include t-butyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and the like. Examples of inorganic peroxides include potassium persulfate and ammonium persulfate. Moreover, the redox catalyst which combined these peroxide and ferrous sulfate can also be used. Examples of the azo compound include azobisisobutyronitrile, 2,2′-azobis (2- (2-imidazolin-2-yl) propane) dihydrochloride, and the like. These radical polymerization initiators may be used alone or in combination of two or more. (A) A chain transfer agent can also be used to adjust the molecular weight of the acrylic rubber. Examples of the chain transfer agent include alkyl mercaptans, carbon tetrachloride, thioglycols, diterpenes, terpinolene, and γ-terpinenes. These chain transfer agents can be used alone or in combination of two or more.

  (A) When the acrylic rubber is copolymerized, the polymerization may be started by batch charging each monomer, emulsifier, radical polymerization initiator, etc. into the reaction vessel, or continuously or intermittently as the reaction continues. You may add to. Polymerization can be carried out at 0 to 100 ° C., preferably 0 to 80 ° C., using a reactor from which oxygen has been removed, such as nitrogen substitution. The polymerization method may be a continuous method or a batch method. The polymerization time is about 0.01 to 30 hours, preferably about 1 to 10 hours. (A) After completion of polymerization of acrylic rubber (after completion of polymerization of the core-shell structure), the reaction product (latex) is put into an aqueous solution of an inorganic salt such as sodium chloride or calcium chloride to be coagulated, washed with water and dried. Thus, an acrylic rubber having a core-shell structure is obtained.

≪ (B) Thermoplastic polyolefin≫
(B) The thermoplastic polyolefin is a component that acts as a hard segment in the thermoplastic elastomer and mainly improves the molding processability and heat resistance of the thermoplastic elastomer. Examples of the thermoplastic polyolefin (B) include α-olefin polymers or copolymers. Examples of the α-olefin include ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. Only one type of thermoplastic polyolefin may be used, or two or more types may be used in combination.

  (B) The thermoplastic polyolefin may be non-crystalline, but is preferably crystalline from the viewpoint of tensile strength and heat resistance. Moreover, 100 degreeC or more is preferable and melting | fusing point is 150-250 degreeC more preferably. Examples of the thermoplastic polyolefin include polypropylene, polymethylpentene, a copolymer of propylene and another α-olefin, and polyethylene. Among these, polypropylene, polymethylpentene, and polyethylene are preferable, and polypropylene and polymethylpentene are more preferable.

  (B) Content of thermoplastic polyolefin shall be 15-70 mass parts with respect to 100 mass parts of (A) acrylic rubber. (B) When the content of the thermoplastic polyolefin is less than 15 parts by mass, the molding processability of the thermoplastic elastomer tends to be lowered. On the other hand, when it exceeds 70 mass parts, it exists in the tendency for the softness | flexibility of a thermoplastic elastomer to fall.

≪ (C) Crosslinking agent≫
(C) The cross-linking agent is added to cross-link (A) acrylic rubber, and has a function of cross-linking acrylic rubber by covalently bonding with chlorine group, epoxy group or carboxyl group of acrylic rubber. . For example, polyamine, polycarboxylic acid, polyepoxide, polyol, acid anhydride, organic carboxylic acid ammonium salt, dithiocarbamate and the like can be mentioned.

  Examples of polyamines include hexamethylene diamine, hexamethylene diamine carbamate, N, N′-dicinnamylidene-1,6-hexane diamine, 4,4′-methylenebis (cyclohexylamine) carbamate, 4,4′-methylenedianiline, 4,4′-oxyphenyldiphenylamine, m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis (o-chloroaniline), 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4, 4 ′-(m-phenylenediisopropylidene) dianiline, 4,4 ′-(p-phenylenediisopropylidene) dianiline, 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 4,4 '-Diaminobenzanilide, 4,4' Bis (4-aminophenoxy) biphenyl, m- xylylenediamine, p- xylylenediamine, hexamethylenediamine - cinnamaldehyde adduct and hexamethylenediamine - dibenzoate salt, and the like.

  Examples of the polycarboxylic acid include succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, dodecenylsuccinic acid, butanetetracarboxylic acid, cyclopentanedicarboxylic acid, cyclopentanetricarboxylic acid, cyclopentane Examples include pentanetetracarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanetricarboxylic acid, phthalic acid, trimellitic acid, trimesic acid, and pyromellitic acid. Examples of the acid anhydride include acid anhydrides of the above polycarboxylic acids.

  (C) The amount of the crosslinking agent used is preferably as small as possible. When the amount of the crosslinking agent used is large, the molding processability and flexibility of the resulting thermoplastic elastomer are lowered. Specifically, it is 0.1 to 5 parts by mass with respect to 100 parts by mass of (A) acrylic rubber.

  (C) When using a crosslinking agent, a crosslinking accelerator or a crosslinking aid can also be used. Examples of the crosslinking accelerator include sulfenamide compounds, thiazole compounds, guanidine compounds, aldehyde amines or aldehyde-ammonia compounds, imidazoline compounds, thiourea compounds, thiuram compounds, dithioate compounds, Examples thereof include xanthate compounds. Examples of the sulfenamide compound include N-cyclohexyl-2-benzothiazolylsulfenamide, N-oxydiethylene-2-benzothiazolylsulfenamide, N, N-diisopropyl-2-benzothiazolylsulfene. Examples include amides. Examples of thiazol compounds include 2-mercaptobenzothiazol, 2- (2 ′, 4′-dinitrophenyl) mercaptobenzothiazol, and 2- (4′-morpholinodithio) benzothiazol. And dibenzothiazyl disulfide. Examples of the guanidine compound include diphenyl guanidine, diorthotolyl guanidine, diorthonitrile guanidine, orthonitrile biguanide, diphenyl guanidine phthalate and the like. Examples of the aldehyde amine or aldehyde-ammonia compound include acetaldehyde-aniline reactant, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde ammonia, and the like. Examples of the imidazoline compound include 2-mercaptoimidazoline. Examples of the thiourea compound include thiocarbanilide, diethylthiourea, dibutylthiourea, trimethylthiourea, diortholylthiourea and the like. Examples of thiuram compounds include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetraoctylthiuram disulfide, pentamethylenethiuram tetrasulfide and the like. Examples of the dithioate-based compound include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc di-n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate. And tellurium dimethyldithiocarbamate. Examples of the xanthate compound include zinc dibutylxanthate. These crosslinking accelerators may be used alone or in combination of two or more.

  Examples of the crosslinking aid include quinone dioxime compounds, methacrylate compounds, allyl compounds, maleimide compounds, and the like. Examples of the quinone dioxime compound include p-quinone dioxime. Examples of the methacrylate compound include polyethylene glycol dimethacrylate. Examples of allylic compounds include diallyl phthalate and triallyl cyanurate. Examples of maleimide compounds include m-phenylene bismaleimide. These crosslinking aids may be used alone or in combination of two or more.

≪Other additives≫
In addition, (A) acrylic rubber has a plasticizer, a softening agent, a filler, a reinforcing agent, a metal oxide, an anti-aging agent, a processing aid, a flame retardant, or an ultraviolet absorber within a range that does not impair the effects of the present invention. Other additives such as an agent can also be added. As each of the other additives, only one kind of the specific materials shown below may be used, or two or more kinds may be used in combination.

  Examples of the plasticizer include phthalic acid esters, fatty acid esters, trimellitic acid esters, adipic acid polyesters, polyether esters, epoxidized soybean oil, and the like. Examples of the phthalic acid esters include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, dioctyl phthalate, butyl octyl phthalate, di (2-ethylhexyl) phthalate, diisooctyl phthalate, diisodecyl phthalate, and the like. Examples of fatty acid esters include dimethyl adipate, diisobutyl adipate, di (2-ethylhexyl) adipate, diisooctyl adipate, diisodecyl adipate, octyl decyl adipate, di (2-ethylhexyl) azelate, diisooctyl azelate, diisobutyl aze Rate, dibutyl sebacate, di (2-ethylhexyl) sebacate, diisooctyl sebacate and the like. Examples of trimellitic acid esters include trimellitic acid isodecyl ester, trimellitic acid octyl ester, trimellitic acid n-octyl ester, trimellitic acid isononyl ester, and the like.

Examples of the softener include petroleum-based softeners, vegetable oil-based softeners, subs, and the like. Examples of petroleum softeners include aromatic, naphthenic, and paraffinic softeners. Examples of plant softeners include castor oil, cottonseed oil, rapeseed oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut oil, and wax. Examples of the sub include a black sub, a white sub, and a dark blue sub.

  Examples of fillers include silica, heavy calcium carbonate, pepper, light calcium carbonate, ultrafine activated calcium carbonate, special calcium carbonate, basic magnesium carbonate, kaolin clay, calcined clay, pyroflight clay, and silane-treated clay. , Synthetic calcium silicate, synthetic magnesium silicate, synthetic aluminum silicate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, kaolin, sericite, talc, fine talc, wollastonite, zeolite, zonotonite, asbestos, PMF (Processed Mineral Fiber), sepiolite, potassium titanate, elastadite, gypsum fiber, glass balun, silica balun, hydrotalcite, fly ash balun, shirasu balun, carbo System balun, alumina, barium sulfate, aluminum sulfate, calcium sulfate, molybdenum disulfide, and the like.

  Examples of the reinforcing agent include SAF carbon black, ISAF carbon black, HAF carbon black, FEF carbon black, GPF carbon black, SRF carbon black, FT carbon black, MT carbon black, acetylene carbon black, ketjen black and the like. .

  Examples of the metal oxide include zinc white, activated zinc white, surface-treated zinc white, zinc carbonate, composite zinc white, composite active zinc white, surface-treated magnesium oxide, magnesium oxide, calcium hydroxide, ultrafine calcium hydroxide, Lead monoxide, red lead, white lead, etc. are mentioned.

  Antiaging agents include, for example, naphthylamine, diphenylamine, p-phenylenediamine, quinoline, hydroquinone derivative, mono, bis, tris, polyphenol, thiobisphenol, hindered phenol, phosphite Imidazole, nickel dithiocarbamate, phosphoric acid and the like.

  Examples of the processing aid include stearic acid, oleic acid, lauric acid, zinc stearate, calcium stearate, potassium stearate, sodium stearate, stearylamine and the like.

  Moreover, rubber other than (A) acrylic rubber can also be mix | blended with the thermoplastic elastomer of this invention as a rubber component. Examples thereof include styrene-butadiene copolymer rubber, butadiene rubber, isoprene rubber, butadiene-isoprene copolymer rubber, styrene-butadiene-isoprene copolymer rubber, acrylonitrile-butadiene copolymer rubber, butyl rubber, natural rubber, chloroprene rubber and the like.

[Synthesis of thermoplastic elastomer]
The thermoplastic elastomer is obtained by dynamically cross-linking a molten mixture containing (A) 100 parts by mass of acrylic rubber and (B) 15 to 70 parts by mass of thermoplastic polyolefin in the presence of (C) a cross-linking agent. Dynamic crosslinking means that crosslinking proceeds while kneading a mixture containing (A) acrylic rubber and (B) thermoplastic polyolefin.

  The melt kneading of (A) acrylic rubber and (B) thermoplastic polyolefin is higher than the melting point of (B) thermoplastic polyolefin, (A) about the decomposition start temperature of acrylic rubber, specifically 100 to 300 ° C, Preferably it may carry out at 130-270 degreeC, More preferably, it may carry out at 150-250 degreeC.

  For kneading a mixture containing (A) acrylic rubber and (B) thermoplastic polyolefin, continuous extruders such as single screw extruders, twin screw extruders, twin screw rotor type extruders, pressure kneaders and Banbury mixers are used. A closed kneader such as a Brabender mixer can be used. Usually, the dynamically crosslinked (A) acrylic rubber is finely dispersed in the matrix phase of the thermoplastic polyolefin. By forming such a phase structure, the elastomer has thermoplasticity (fluidity) even though (A) the acrylic rubber is crosslinked. Therefore, the thermoplastic elastomer can be molded into a predetermined shape by a known thermoplastic resin molding method such as an extrusion molding method, an injection molding method, a blow molding method, or a compression molding method.

  The thermoplastic elastomer of the present invention has good oil resistance and heat resistance, and is excellent in tensile strength, tensile elongation, sealability and the like. Therefore, the thermoplastic elastomers are oil cooler hose, air duct hose, power steering hose, control hose, intercooler hose, torque converter hose, oil return hose, heat-resistant hose and other various hose materials, fuel hose materials, bearing seals, bulk stems. It can be suitably used for sealing materials such as seals, various oil seals, O-rings, packings, gaskets, various diaphragms, rubber plates, belts, oil level gauges, hose masking, piping insulation materials, rolls, etc. it can.

  Hereinafter, although the specific Example of this invention is described, this invention is not limited to this.

<(A) Polymerization of acrylic rubber>
200 parts by weight of water, 1 part by weight of sodium lauryl sulfate, 0.01 part by weight of ferrous sulfate, 0.03 part by weight of sodium ethylenediaminetetraacetate, 0.05 part by weight of sodium hydroxymethanesulfinate dihydrate were replaced with nitrogen. The material shown in Table 1 as a monomer for core was added dropwise with 0.1 parts by mass of p-menthane hydroperoxide over 2 hours, and the reaction temperature was 30 ° C. Was emulsion polymerized. When the polymerization conversion rate reached 100%, the material shown in Table 1 as a shell monomer was added dropwise over 30 minutes together with 0.1 part by mass of p-menthane hydroperoxide at the ratio shown in Table 1, and the reaction temperature Emulsion polymerization was performed at 30 ° C.

  The obtained reaction product (latex) was dropped into a 1% calcium chloride aqueous solution to coagulate the acrylic rubber. After sufficiently washing this coagulated product with water, it is dried at 80 ° C. for 24 hours, whereby (A) acrylic rubbers A-1 to A-5 (for examples) and A′-1 to A′-5 (comparative examples). Obtained).

The numerical values shown in Table 1 are parts by mass, and the specific names of the materials shown in Table 1 are as follows: EA: ethyl acrylate BA: butyl acrylate MEA: 2-methoxyethyl acrylate AN: acrylonitrile AMA : Allyl methacrylate DCPA: Dicyclopentenyl acrylate VCAc: Monochlorovinyl acetate GMA: Glycidyl methacrylate MBM: Mono n-butyl maleate

<Synthesis of thermoplastic elastomer>
The materials shown in Table 2 are used as (A) acrylic rubber and (B) thermoplastic polyolefin in the amounts shown in Table 2, and they are put into a Banbury mixer set at a temperature of 200 ° C. and a blade rotation speed of 100 rpm, and the torque becomes constant. Until kneading. Next, (C) the materials shown in Table 2 as the cross-linking agent were added in the amount shown in Table 2 and kneaded until the torque became constant, and thermoplastic elastomers (Examples 1 to 7, Comparative Examples 1 to 5) were added. Synthesized.

  The obtained thermoplastic elastomers of Examples and Comparative Examples were taken out from the Banbury mixer and compressed into a pancake by a cooling press. Subsequently, it was molded into a sheet having a thickness of 2 mm by a press heated to 200 ° C., and its mechanical properties (tensile strength, tensile elongation, hardness), heat resistance and oil resistance were measured.

In addition, the numerical value shown in Table 2 is a mass part, and the specific name of the material shown in Table 2 is as follows.
PP: polypropylene PMP: polymethylpentene PE: polyethylene HMDAC: hexamethylenediamine carbamate MXDA: m-xylylenediamine

Moreover, the measuring method of each physical property is as follows.
<Tensile strength / elongation>
Based on JIS K 6251, tensile strength (MPa) and tensile elongation (%) were measured at a test speed of 500 mm / min.
<Hardness>
In accordance with JIS K 6253, the hardness was measured with a spring hardness tester A type.
<Heat resistance>
In accordance with JIS K 6257, the tensile strength (MPa) and tensile elongation (%) after the test piece was left in a gear oven set at 120 ° C. for 70 hours were measured, and the rate of change in tensile strength (%) and tensile strength were measured. The percent change in elongation was calculated.
<Oil resistance>
In accordance with JIS K 6258, the mass (g) after being left in a gear oven set at 120 ° C. for 70 hours with the test piece immersed in IRM903 test oil was measured, and the mass change rate was calculated (%). .

  From the result of Table 2, since Examples 1-7 used the acrylic rubber of the core-shell structure comprised from the core layer which contains a gel part and has a crosslinkable group, and the shell layer which does not contain a gel part, Not only the tensile strength and tensile elongation were excellent, but also the hardness was excellent. In Examples 1 to 6, since polypropylene or polymethylpentene was used as the thermoplastic polyolefin, it was particularly excellent in tensile strength and heat resistance. Since Example 1, Example 3, Example 6, and Example 7 used the acrylic rubber containing an unsaturated nitrile monomer, they were particularly excellent in oil resistance.

  On the other hand, Comparative Example 1 does not have a shell layer and has a gel content in the entire acrylic rubber, and Comparative Example 2 includes a gel content in the shell layer as well as the core layer. It was inferior. On the other hand, Comparative Example 3 does not have a gel content in the core layer and has a gel content in the shell layer, Comparative Example 4 does not have a shell layer and the entire acrylic rubber has no gel content, and Comparative Example 5 Since neither the core layer nor the shell layer has a gel content, the tensile elongation was inferior.

Claims (1)

(A) A mixture containing 100 parts by mass of acrylic rubber and (B) 15 to 70 parts by mass of thermoplastic polyolefin. (A) 0.1 to 5 parts by mass of (C) cross-linking agent A method for producing a thermoplastic elastomer by dynamically crosslinking in the presence of a thermoplastic elastomer,
(A) Acrylic rubber has a core-shell structure,
The core layer is
(A-1) 70-100 parts by mass of at least one selected from an alkyl acrylate monomer or an alkoxyalkyl acrylate monomer;
(A-2) 0-30 parts by mass of an unsaturated nitrile monomer;
(A-3) 0.1-3 parts by mass of a polyfunctional monomer having a carbon-carbon double bond in the side chain with respect to 100 parts by mass in total of (a-1) and (a-2) ,
(A-4) A monomer having at least one selected from the group consisting of a chlorine group, an epoxy group and a carboxyl group, which is a crosslinkable group, in a total of 100 parts by mass of (a-1) and (a-2). In contrast, 0.1 to 3 parts by mass ,
The shell layer does not include a polyfunctional monomer having a carbon-carbon double bond in the side chain,
(A-5) 70-100 parts by mass of at least one selected from an alkyl acrylate monomer or an alkoxyalkyl acrylate monomer;
(A-6) A method for producing a thermoplastic elastomer , comprising 0 to 30 parts by mass of an unsaturated nitrile monomer.