JP2011195629A - Bellows-shaped molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bellows-shaped molded article that is excellent in flexibility, recyclability, and heat resistance and oil resistance at a high temperature.SOLUTION: The bellows-shaped molded article is molded from a thermoplastic elastomer composition, comprising (A) an acrylic rubber, (B) a thermoplastic polyester resin, (C) a graft copolymer comprising an olefin polymer segment and a vinyl copolymer segment, where one segment forms a dispersed phase in a matrix formed of the other segment, or a precursor thereof, (D) a plasticizer and (E) an acrylic polymer processing auxiliary.

Description

  The present invention relates to a bellows molded product using a thermoplastic elastomer excellent in heat resistance and oil resistance, and more particularly to a bellows molded product for an automobile.

  Examples of the bellows molded product that requires heat resistance and oil resistance include a bellows molded product used in an engine room of an automobile. Conventionally, specific cross-linked rubbers such as chloroprene rubber and epichlorohydrin rubber have been used at such sites. However, a bellows molded product using a crosslinked rubber requires a rubber kneading step and a vulcanization step, so the manufacturing process is complicated, and once vulcanized rubber cannot be remolded by heating, making it recyclable. There are shortcomings such as scarcity. Therefore, in recent years, it has been proposed to use a thermoplastic elastomer as a material to replace the crosslinked rubber. Thermoplastic elastomers do not require a vulcanization process and have the same moldability and recyclability as thermoplastic resins, and thus have been widely used in the interior and exterior parts of automobiles and in the electrical field. In such a trend, attempts have been made to substitute thermoplastic elastomers for automobile parts that require heat resistance and oil resistance.

  For example, an air duct hose having a bellows molded product using a thermoplastic elastomer composition comprising 30 to 90% by weight of a thermoplastic copolyester elastomer and 70 to 10% by weight of an epoxy group-containing (meth) acrylate copolymer rubber is known. (See Patent Document 1). In addition, a bellows molded product using a thermoplastic elastomer composition composed of an acrylic rubber, polypropylene, and a compatibilizer is known (see Patent Document 2).

JP-A-6-107804 JP 2008-246916 A

  However, the bellows-molded article molded from the thermoplastic elastomer composition described in Patent Document 1 uses a thermoplastic copolyester elastomer as the thermoplastic component. In addition, it is difficult to use in terms of oil resistance. Moreover, since the thermoplastic elastomer composition described in Patent Document 2 uses polypropylene as the thermoplastic component, it cannot be used at the high temperatures described above. Therefore, at present, a bellows molded product formed of a thermoplastic elastomer exhibiting good heat resistance and oil resistance at high temperatures has not been obtained. Therefore, the object of the present invention is to use a high-melting-point thermoplastic polyester resin as the thermoplastic component, so that heat resistance and oil resistance at high temperatures can be exhibited. By using rubber, in addition to heat resistance and oil resistance, it is possible to give flexibility, and furthermore, bellows molding made of a thermoplastic elastomer having recyclability and excellent in heat resistance and oil resistance Is to provide goods.

  In order to achieve the above object, the bellows molded product of the first invention in the present invention comprises the following component (A), component (B), component (C), component (D) and component (E). It is formed from a thermoplastic elastomer composition.

Component (A): A monomer mixture containing at least one of alkyl acrylate ester and alkoxyalkyl acrylate ester as a main component and containing 0.5 to 15% by mass of an epoxy group-containing monomer is copolymerized. 50 to 85 parts by mass in 100 parts by mass of the total of component (A) and component (B).
Component (B): 15 to 50 parts by mass of the thermoplastic polyester resin in a total of 100 parts by mass of the component (A) and the component (B).

Component (C): an olefin polymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer containing at least an alkyl acrylate, The graft copolymer in which the segment forms a dispersed phase in the matrix phase formed by the other segment or its precursor is 1 to 35 with respect to 100 parts by mass in total of the component (A) and the component (B). Parts by mass.
Component (D): The plasticizer is 60 parts by mass or less with respect to 100 parts by mass of the component (A).
Component (E): 0.5 to 10 parts by mass of acrylic polymer processing aid with respect to 100 parts by mass in total of component (A) and component (B).

  The bellows-molded article of the second invention is formed from a thermoplastic elastomer composition in which the component (D) is selected from trimellitic acid plasticizers, polyester plasticizers, and polyetherester plasticizers in the first invention. It is characterized by that.

  The bellows molded product of the third invention is a thermoplastic comprising the component (A), the component (B), the component (C), the component (D) and the component (E) in the first or second invention. The elastomer composition is formed from a thermoplastic elastomer composition obtained by dynamically crosslinking 0.05 to 5 parts by mass of a crosslinking agent (component (F)) with respect to 100 parts by mass of the component (A). It is characterized by being.

  The bellows molded product of the fourth invention is characterized in that, in any one of the first to third inventions, the thermoplastic elastomer composition is molded by a blow molding method or an injection molding method.

  The bellows molded product of the fifth invention is characterized in that, in any one of the first to third inventions, the thermoplastic elastomer composition is multilayer molded with a thermoplastic resin, a thermoplastic elastomer or a crosslinked rubber. is there.

  The thermoplastic elastomer composition of the present invention is excellent in heat resistance and oil resistance, and is excellent in blow moldability and injection moldability. In addition, since it is excellent in recyclability, it is possible to reduce environmental load and cost. For this reason, the thermoplastic elastomer composition of the present invention is useful for a bellows molded article for automobiles that require high heat resistance and oil resistance.

The bellows-molded article of the present embodiment includes an acrylic rubber as component (A), a thermoplastic polyester resin as component (B), a graft copolymer as component (C) or a precursor thereof, and a plasticizer and component as component (D). It is obtained by molding a thermoplastic elastomer composition comprising the acrylic polymer processing aid (E).
Hereinafter, each component of the thermoplastic elastomer composition will be described in detail.

[Component (A) Acrylic rubber]
The acrylic rubber of component (A) is a component that can exhibit flexibility, heat resistance, and oil resistance in a bellows molded product obtained by molding a thermoplastic elastomer composition. The acrylic rubber is obtained by copolymerizing a monomer mixture containing at least one of alkyl acrylate ester and alkoxyalkyl acrylate ester as a main component and containing 0.5 to 15% by mass of an epoxy group-containing monomer. It is obtained.

  As alkyl acrylates, methyl acrylate, ethyl acrylate, acrylic acid-n-propyl, isopropyl acrylate, acrylic acid-n-butyl, acrylic acid isobutyl, acrylic acid-tert-butyl, acrylic acid-n-pentyl -N-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, and the like. Among these, an acrylic acid alkyl ester having 2 to 4 carbon atoms in the alkyl group is particularly preferable in that it can exhibit excellent flexibility and oil resistance.

  Examples of the alkoxyalkyl acrylate include an alkoxyalkyl acrylate having an alkyl group having 2 to 4 carbon atoms, such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, and 2-butoxyethyl acrylate. Can be mentioned. Among these, 2-methoxyethyl acrylate is particularly preferable in that it can exhibit excellent oil resistance. One or more of these monomers are appropriately selected and used.

  The content of at least one of the acrylic acid alkyl ester and the acrylic acid alkoxyalkyl ester contained in the acrylic rubber is preferably 85 to 99.5% by mass. When this content is less than 85% by mass, physical properties such as flexibility of the bellows molded product obtained from the thermoplastic elastomer composition are lowered, and when it exceeds 99.5% by mass, a relatively epoxy group is contained. It shows a tendency that the content of the monomer is reduced and the acrylic rubber is not sufficiently crosslinked.

  The epoxy group-containing monomer means a vinyl monomer having an epoxy group in the molecule. As this epoxy group-containing monomer, all general epoxy group-containing monomers can be used. Examples thereof include glycidyl acrylate, glycidyl methacrylate, vinyl glycidyl ether, allyl glycidyl ether, and the like. A preferred epoxy group-containing monomer is glycidyl (meth) acrylate. In this specification, acrylic and methacryl are collectively referred to as (meth) acrylic. The content of the epoxy group-containing monomer copolymerized in the acrylic rubber is 0.5 to 15% by mass, preferably 1 to 10% by mass. When the content of the epoxy group-containing monomer is less than 0.5% by mass, the acrylic rubber is not sufficiently crosslinked, and the mechanical strength of the bellows molded product obtained from the thermoplastic elastomer composition is inferior. If it exceeds 50%, the acrylic rubber is excessively cross-linked, so that the molding processability of the thermoplastic elastomer composition is lowered, and a bellows molded product having a good appearance cannot be obtained.

  In addition, for the purpose of improving physical properties such as flexibility, moldability, and oil resistance, methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate; methacrylic acid-2-methoxyethyl, methacrylic acid-2-ethoxyethyl, etc. (Meth) acrylic acid, crotonic acid, maleic acid and other carboxyl group-containing monomers; (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, etc. Hydroxyl group-containing monomers; active chlorine-containing monomers such as 2-chloroethyl vinyl ether, vinyl monochloroacetate and allyl chloroacetate; trifluoromethyl methyl (meth) acrylate, 2-trifluoromethyl (meth) acrylate Fluorine (meth) acrylic esters such as ethyl; Aromatic vinyl compounds such as α-methylstyrene; vinyl nitriles such as acrylonitrile and methacrylonitrile; vinylamides such as acrylamide, methacrylamide and N-methylolacrylamide; α-olefins such as ethylene, propylene and isobutene; butadiene and isoprene Conjugated dienes such as chloroprene; bifunctional (meth) acrylates, trifunctional (meth) acrylates and copolymerizable monomers such as vinyl acetate and vinyl chloride can be copolymerized in acrylic rubber .

  The copolymerization amount of these copolymerizable monomers is preferably 40% by mass or less, and more preferably 30% by mass or less. If the copolymerization amount exceeds 40% by mass, the balance of physical properties such as flexibility, molding processability, oil resistance, and low temperature characteristics of acrylic rubber may be impaired.

  The glass transition temperature (Tg) of the acrylic rubber of component (A) is preferably −15 ° C. or lower, more preferably −20 ° C. or lower. When Tg is higher than −15 ° C., the embrittlement temperature of the thermoplastic elastomer composition becomes high, and the bellows molded product formed of the thermoplastic elastomer may not be able to withstand practical use.

  The content of the acrylic rubber of component (A) contained in the thermoplastic elastomer composition of the present invention is 50 to 85 parts by mass when the total amount of component (A) and component (B) is 100 parts by mass. It is preferable because it is excellent in the balance between moldability and flexibility. When the acrylic rubber content is less than 50 parts by mass, the flexibility of the bellows molded product formed from the thermoplastic elastomer composition is impaired, and when it exceeds 85 parts by mass, the thermoplastic elastomer composition is molded. This is not preferable because the properties are impaired.

[Component (B) Thermoplastic polyester resin]
The thermoplastic polyester resin of component (B) is a component that improves the molding processability of the thermoplastic elastomer composition of the present invention and exhibits the heat resistance and oil resistance of the molded bellows molded product. Such thermoplastic polyester resins include all thermoplastic saturated polyesters having an ester bond in the main chain. The thermoplastic polyester resin can be obtained by a known method such as polycondensation of a dicarboxylic acid component and a dihydroxy component, polycondensation of an oxycarboxylic acid component, or polycondensation of these three components. It may be. The thermoplastic polyester resin is used alone or in combination of two or more.

  The thermoplastic polyester resin may be non-crystalline, but is preferably crystalline because it is excellent in heat resistance and oil resistance. Moreover, it is preferable that melting | fusing point is 100 degreeC or more, and it is most preferable that it exists between 160-280 degreeC at the point which is excellent in the heat resistance and oil resistance in high temperature. Preferable examples of the thermoplastic polyester resin include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate and polybutylene naphthalate.

  The content of the thermoplastic polyester resin of the component (B) contained in the thermoplastic elastomer composition is 15 to 50 parts by mass when the total amount of the component (A) and the component (B) is 100 parts by mass. And, it is preferable because of excellent balance between moldability and flexibility. When the content of the thermoplastic polyester resin is less than 15 parts by mass, the molding processability of the thermoplastic elastomer composition is impaired, and when it exceeds 50 parts by mass, the bellows molded product obtained from the thermoplastic elastomer composition is not preferable. Since flexibility is impaired, it is not preferable.

[Component (C) Graft copolymer]
The graft copolymer of component (C) increases the compatibility (affinity) of the component (A) acrylic rubber and component (B) thermoplastic polyester resin, and the function of component (A) and component (B). It is a component that fully exerts its function and exhibits a synergistic effect. With this graft copolymer, good moldability can be imparted while maintaining the flexibility of the thermoplastic elastomer composition. The graft copolymer is composed of an olefin polymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer containing at least an alkyl acrylate ester, A graft copolymer in which one segment forms a dispersed phase in a matrix phase formed by the other segment.

  The olefin polymer segment is formed from ethylene and a polar monomer, and specific examples thereof include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-glycidyl methacrylate copolymer, ethylene-acetic acid. Vinyl-maleic anhydride copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid-n-butyl copolymer, ethylene-methyl acrylate-glycidyl methacrylate copolymer Polymer, ethylene-ethyl acrylate-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate copolymer, maleic anhydride modified ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methacrylic acid Dimethylaminomethyl copolymer, ethylene-vinyl Of ethylene glycol adduct, ethylene-vinyl alcohol copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer or ethylene-methacrylic acid copolymer Examples include ionomers in which molecules are intermolecularly bonded with metal ions such as sodium and zinc.

  The proportion of the polar monomer in the olefin polymer segment is preferably 5 to 50 parts by mass and more preferably 10 to 40 parts by mass with respect to 100 parts by mass in total of ethylene and polar monomer. A copolymer having a polar monomer ratio of less than 5 parts by mass has high hardness and low oil resistance, so that the flexibility and oil resistance of the bellows molded product obtained from the thermoplastic elastomer composition may be impaired. On the other hand, a copolymer with a polar monomer exceeding 50 parts by mass is excellent in low hardness and oil resistance, but is inferior in mechanical strength. Therefore, the tensile strength and elongation of the bellows molded product obtained from the thermoplastic elastomer composition are low. The mechanical properties such as are reduced.

  The vinyl copolymer segment is formed from a vinyl monomer containing at least an alkyl acrylate ester. The vinyl copolymer segment is compatible with the acrylic rubber of component (A), thereby improving the molding processability of the thermoplastic elastomer composition and the appearance of the bellows molded product, and further improving the mechanical properties of the bellows molded product. Can be improved.

  As alkyl acrylates, methyl acrylate, ethyl acrylate, acrylic acid-n-propyl, isopropyl acrylate, acrylic acid-n-butyl, acrylic acid isobutyl, acrylic acid-tert-butyl, acrylic acid-n-pentyl -N-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, and the like. Among these, an acrylic group having 2 to 4 carbon atoms of an alkyl group such as ethyl acrylate and acrylic acid-n-butyl is particularly preferable in terms of oil resistance and compatibility with the acrylic rubber of component (A). Acid alkyl ester.

  The acrylic acid alkyl ester contained in 100 parts by mass of the vinyl copolymer segment is preferably 20 parts by mass or more, and more preferably 30 parts by mass or more. When the alkyl acrylate is less than 20 parts by mass, the compatibility between the graft copolymer and the acrylic rubber cannot be sufficiently obtained, so that the mechanical strength of the bellows molded product obtained from the thermoplastic elastomer composition is reduced and the appearance is reduced. This is not preferable because of the deterioration.

  The vinyl copolymer segment can be copolymerized with one or more vinyl monomers in addition to the alkyl acrylate ester. Examples of copolymerizable vinyl monomers include, for example, methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate; (meth) acrylic acid-2-methoxyethyl; (meth) acrylic acid-2-ethoxyethyl Epoxy group-containing monomers such as (meth) acrylic acid alkoxyesters, glycidyl (meth) acrylate, vinyl glycidyl ether, allyl glycidyl ether, etc .; carboxyl groups such as (meth) acrylic acid, crotonic acid, maleic acid, etc. Monomer; hydroxyl group-containing monomer such as (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, etc .; styrene, methylstyrene, dimethylstyrene, ethylstyrene, isopropylstyrene, Aromatic vinyl compounds such as chlorostyrene; α-methyl Styrene, alpha-substituted styrenes such as alpha-ethyl styrene; acrylonitrile, vinyl nitriles such as methacrylonitrile, and the like. These vinyl monomers can be copolymerized preferably in an amount of 80 parts by mass or less, more preferably 70 parts by mass or less in 100 parts by mass of the vinyl copolymer segment.

  The number average degree of polymerization of the vinyl copolymer to be the vinyl copolymer segment is usually 5 to 10,000, preferably 10 to 5,000, and most preferably 100 to 2,000. If the number average degree of polymerization is less than 5, it is possible to improve the moldability of the thermoplastic elastomer composition, but the compatibility with the component (A) acrylic rubber is reduced, and the thermoplastic elastomer composition The appearance of the molded bellows molded product tends to deteriorate. On the other hand, when the number average degree of polymerization exceeds 10,000, the melt viscosity increases and the molding processability of the thermoplastic elastomer composition decreases.

  The proportion of the olefin polymer segment contained in 100 parts by mass of the graft copolymer is usually 5 to 95 parts by mass, preferably 20 to 90 parts by mass, and most preferably 30 to 85 parts by mass. Therefore, the proportion of the vinyl copolymer segment is usually 5 to 95 parts by mass, preferably 10 to 80 parts by mass, and most preferably 15 to 70 parts by mass. When the proportion of the olefin polymer segment is less than 5 parts by mass, the molding processability of the thermoplastic elastomer composition becomes insufficient, and when it exceeds 95 parts by mass, the compatibility with the acrylic rubber of component (A) is insufficient. The mechanical properties and appearance of the bellows molded product obtained from the thermoplastic elastomer composition tend to deteriorate.

  As described above, the graft copolymer is a multiphase structure in which one segment forms a dispersed phase in a matrix phase formed by the other segment. One segment forms a dispersed phase as fine particles having an average particle diameter of 0.001 to 10 μm in the other segment. In both cases where the average particle size of the dispersed phase is less than 0.001 μm and more than 10 μm, the compatibility between the graft copolymer of component (C) and the acrylic rubber of component (A) is low, and the thermoplastic elastomer The mechanical properties and appearance of the bellows molded product obtained from the composition tend to deteriorate.

  The grafting method for producing the graft copolymer may be any of generally known chain transfer methods, ionizing radiation irradiation methods, etc., but the method shown below is most preferred. The reason is that the production method is simple, the grafting efficiency is high, the secondary aggregation of the vinyl polymer segment due to heat does not occur, and the graft copolymer of component (C) is used as the acrylic rubber or component of component (A). It is because it becomes easy to mix with the thermoplastic polyester resin of (B).

  Below, the manufacturing method of such a graft copolymer is demonstrated. An olefin polymer formed from ethylene and a polar monomer suspended in water, a vinyl monomer containing a vinyl monomer having at least an alkyl acrylate ester, the following general formula (1) or The radically polymerizable organic peroxide represented by (2) is impregnated with one or a mixture of two or more and a radical polymerization initiator. Thereafter, the vinyl monomer and the radical polymerizable organic peroxide are copolymerized in an olefin polymer formed from ethylene and a polar monomer to obtain a grafted precursor. The graft copolymer can be obtained by melt-kneading this grafted precursor.

  The grafting precursor is composed of an olefin polymer particle formed from ethylene and a polar monomer, a vinyl monomer containing a vinyl monomer having at least an alkyl acrylate ester, and a radical polymerizable organic oxidation. It is a structure in which a copolymer with a product is dispersed. In the grafting precursor, the copolymer of vinyl monomer and radical polymerizable organic peroxide dispersed therein contains 0.003 to 0.73% by mass as active oxygen. Is preferred. When the amount of active oxygen is less than 0.003% by mass, the grafting ability of the grafting precursor is extremely lowered, which is not preferable. On the other hand, if it exceeds 0.73 mass%, gel formation increases during grafting, which is not preferable. In this case, the amount of active oxygen can be obtained by extracting a vinyl copolymer from the grafted precursor by solvent extraction and determining the amount of active oxygen of the vinyl copolymer by iodometry.

  The radical polymerizable organic peroxide is a monomer having an ethylenically unsaturated group and a peroxide bonding group. Preferably, it is a compound represented by the following general formula (1) or (2).

(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 or 2 carbon atoms, R ² is a hydrogen atom or a methyl group, R ³ and R ⁴ are each an alkyl group having 1 to 4 carbon atoms, and R ⁵ is a carbon number 1) An alkyl group of -12, a phenyl group, an alkyl-substituted phenyl group or a cycloalkyl group having 3 to 12 carbon atoms, m is 1 or 2)

(Wherein R ⁶ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ⁷ is a hydrogen atom or a methyl group, R ⁸ and R ⁹ are each an alkyl group having 1 to 4 carbon atoms, and R ¹⁰ is 1 carbon atom) An alkyl group of -12, a phenyl group, an alkyl-substituted phenyl group or a cycloalkyl group having 3 to 12 carbon atoms, n is 0, 1 or 2)

  Examples of the radical polymerizable organic peroxide represented by the general formula (1) include tert-butylperoxyacryloyloxyethyl carbonate, tert-amylperoxyacryloyloxyethyl carbonate, tert-hexylperoxyacryloyloxyethyl carbonate, Examples include tert-butyl peroxymethacryloyloxyethyl carbonate, tert-amyl peroxymethacryloyloxyethyl carbonate, and tert-hexyl peroxymethacryloyloxyethyl carbonate.

  Examples of the radical polymerizable organic peroxide represented by the general formula (2) include tert-butyl peroxyallyl carbonate, tert-amyl peroxyallyl carbonate, tert-hexyl peroxyallyl carbonate, tert-butyl peroxymethallyl carbonate, tert -Amyl peroxymethallyl carbonate, tert-hexyl peroxymethallyl carbonate, etc. are mentioned. Among these, tert-butyl peroxyacryloyloxyethyl carbonate, tert-butyl peroxymethacryloyloxyethyl carbonate, tert-butyl peroxyallyl carbonate or tert-butyl peroxymethallyl carbonate is preferable.

  The graft copolymer of component (C) can be obtained by melt-kneading the grafted precursor. By heating during melt-kneading, the peroxide bond in the vinyl copolymer is cleaved, and the generated radical performs a hydrogen abstraction reaction on the olefin polymer, followed by the grafting reaction to produce the graft copolymer. Is done. Specifically, a Banbury mixer, a Brabender mixer, a pressure kneader, a single screw extruder, a twin screw extruder, a roll or the like is used as a kneader for melt kneading. The kneading temperature is usually in the range of 100 to 300 ° C, preferably 120 to 280 ° C. When the temperature is less than 100 ° C., melting may be incomplete or the melt viscosity may be too high, so mixing is insufficient and phase separation or delamination of the graft copolymer appears, which is not preferable. . On the other hand, when the temperature exceeds 300 ° C., decomposition or gelation tends to occur during grafting, which is not preferable.

  In the graft copolymer of component (C) thus obtained, the olefin polymer segment is oriented to the thermoplastic polyester resin of component (B) (shows compatibility), and the vinyl polymer segment is the component. It is considered that (A) is oriented to the acrylic rubber (shows compatibility). And in a thermoplastic elastomer composition, a component (A) and a component (B) are compatibilized by the component (C), and the function of a component (A) and a component (B) is exhibited synergistically. Guessed.

  The proportion of the graft copolymer of component (C) contained in the thermoplastic elastomer composition is 1 to 35 masses per 100 mass parts in total of the acrylic rubber of component (A) and the thermoplastic polyester resin of component (B). Part. When the proportion of the graft copolymer is less than 1 part by mass, the effect of improving the molding processability is insufficient, and the appearance of the molded bellows molded product tends to be inferior. Since the oil resistance of the obtained bellows molded product is impaired, it is not preferable.

[Component (D) Plasticizer]
The thermoplastic elastomer composition may contain a plasticizer. Plasticizers include phthalic acid, adipic acid, azelaic acid, sebacic acid, phosphoric acid, trimellitic acid, pyromellitic acid, epoxy, polyester or polyether ester, or mixtures thereof. It can be included as a plasticizer. A specific advantage of including a plasticizer is that the processability of the thermoplastic elastomer composition, the flexibility of the bellows molded product, the oil resistance and the cold resistance are improved. On the other hand, when the heat resistance of the plasticizer is low or the volatility is high, the thermoplastic elastomer composition may be adversely affected. That is, deterioration of the thermoplastic elastomer composition due to decomposition of the plasticizer, curing or shrinkage of the thermoplastic elastomer composition due to volatilization of the plasticizer, and the like. When such a thermoplastic elastomer composition deteriorates, cures and shrinks, there is a problem that the molded bellows molded product is cracked or the sealing performance is deteriorated. As a result, the heat resistance as the bellows molded product is generated. Decreases. Therefore, the plasticizer contained in the thermoplastic elastomer composition is preferably a plasticizer having high heat resistance and low volatility. Preferred plasticizers that can be used are trimellitic acid type, polyester type, and polyether ester type. Examples of trimellitic acid include trimellitic acid tri-2-ethylhexyl, trimellitic acid tri-n-octyl, trimellitic acid triisononyl, trimellitic acid triisodecyl, and the like. Examples of polyesters include phthalic acid polyesters, adipic acid polyesters, sebacic acid polyesters, trimellitic acid polyesters, and pyromellitic acid polyesters. Examples of the polyether ester type include polyether polyester type. These plasticizers can be used alone or in combination of two or more.

  It is preferable that the compounding quantity of a plasticizer is 60 mass parts or less with respect to 100 mass parts of acrylic rubber of a component (A). When the compounding amount of the plasticizer exceeds 60 parts by mass, the plasticizer bleeds out, and the mechanical strength of the bellows molded product obtained from the thermoplastic elastomer composition tends to increase.

[Component (E) Acrylic polymer processing aid]
An acrylic polymer processing aid can be added to the thermoplastic elastomer composition. Acrylic polymer processing aids include acrylic acid, methyl acrylate, ethyl acrylate, acrylic acid-n-butyl, acrylic acid isobutyl, acrylic acid ester such as 2-ethylhexyl, methyl methacrylate, methacrylic acid A copolymer having a weight average molecular weight of 400,000 to 5,000,000, mainly composed of a methacrylic acid ester such as ethyl, methacrylic acid-n-butyl, isobutyl methacrylate, or methacrylic acid-2-ethylhexyl. These may be used alone or in combination of two or more. If the weight average molecular weight of the acrylic polymer processing aid is 1,000,000 or more, the die swell of the thermoplastic elastomer composition is increased, and good blow moldability is exhibited, which is preferable.

  The blending amount of the acrylic polymer processing aid is preferably 0.5 to 10 parts by mass with respect to 100 parts by mass in total of the component (A) and the component (B). By adding an acrylic polymer processing aid, it is possible to increase the die swell of the resulting thermoplastic elastomer composition to 1.20 (temperature 260 ° C., shear rate 370 (1 / sec)) or more, Blow moldability is improved. When the ratio of the acrylic polymer processing aid is less than 0.5 parts by mass, there is no effect of increasing the die swell, and good blow moldability cannot be obtained. On the other hand, when the ratio of the acrylic polymer processing aid exceeds 10 parts by mass, the melt viscosity is excessively increased, so that good injection moldability cannot be obtained.

Furthermore, the bellows molded product of the present embodiment is obtained by changing the thermoplastic elastomer composition comprising the component (A), the component (B), the component (C), the component (D), and the component (E) to 100 of the component (A). It is obtained by molding a thermoplastic elastomer composition obtained by dynamic crosslinking with 0.05 to 5 parts by mass of a crosslinking agent (component (F)) with respect to parts by mass.
Hereinafter, the component (F) of the thermoplastic elastomer composition will be described in detail.

[Component (F) Cross-linking agent]
The cross-linking agent used for obtaining the thermoplastic elastomer composition has a function of cross-linking the acrylic rubber by covalently bonding with the epoxy group of the acrylic rubber. As such a crosslinking agent, any crosslinking agent having a functional group that reacts with an epoxy group can be used. For example, polyamine, polyol, polycarboxylic acid, acid anhydride, organic carboxylic acid ammonium salt, dithiocarbamate, block carboxylic acid and the like can be mentioned, among which polycarboxylic acid and acid anhydride are particularly preferable. .

  Specific 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, Examples include cyclopentanetetracarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanetricarboxylic acid, phthalic acid, trimetic acid, trimesic acid, and pyromellitic acid. Specific examples of the acid anhydride include acid anhydrides of these polycarboxylic acids.

  Although the usage-amount of a crosslinking agent changes with kinds of selected crosslinking agent, generally it is set in 0.05-5 mass parts with respect to 100 mass parts of acrylic rubber of a component (A). When the amount of the crosslinking agent used is less than 0.05 parts by mass, sufficient crosslinking is not performed, and the mechanical strength and oil resistance of the bellows molded product obtained from the thermoplastic elastomer composition are reduced, and exceed 5 parts by mass. In this case, since the thermoplastic elastomer composition is excessively crosslinked, good moldability cannot be obtained.

[Other ingredients]
In the thermoplastic elastomer composition, various additives other than the above components can be contained in suitable amounts. Examples of such additives include phenolic and amine antioxidants, hindered amine UV stabilizers, stearic acid, zinc stearate, waxes, low molecular weight polyethylenes, foaming agents, antiblocking agents, and adhesives. Examples thereof include processing aids such as imparting agents, colorants such as titanium dioxide, and pigments. It is preferable that the compounding quantity of an additive is 10 mass parts or less with respect to 100 mass parts of thermoplastic elastomer compositions, respectively. Moreover, fillers represented by carbon black, white carbon, clay, mica, calcium carbonate, talc and the like can be mentioned. The surface of the filler may be subjected to a surface treatment using stearic acid, oleic acid, palmitic acid or a metal salt thereof, paraffin wax, polyethylene wax or a modified product thereof, organic silane, organic borane, organic titanate, etc. preferable. Examples of the flame retardant include inorganic flame retardants represented by magnesium hydroxide and aluminum hydroxide, and organic flame retardants represented by halogen and phosphorus. The blending amount of the filler and the flame retardant is preferably 70 parts by mass or less with respect to 100 parts by mass of the thermoplastic elastomer composition.

[Thermoplastic elastomer composition]
The thermoplastic elastomer composition is produced by melt-kneading the composition comprising the above components. As an apparatus for performing melt kneading, a Banbury mixer, a Brabender mixer, a pressure kneader, a single screw extruder, a twin screw extruder, a roll, or the like can be used. In addition, the dynamic crosslinking by addition of a crosslinking agent includes component (A) acrylic rubber, component (B) thermoplastic polyester resin, component (C) graft copolymer, component (D) plasticizer and component (E ) Of the acrylic polymer processing aid is melt kneaded at a temperature higher than the melting point of the thermoplastic polyester resin, and the epoxy group of the acrylic rubber is crosslinked under high shear during the kneading. Usually, the acrylic rubber thus dynamically crosslinked is finely dispersed in the matrix phase of the thermoplastic polyester resin. By forming such a phase structure, the elastomer composition has thermoplasticity although the acrylic rubber is crosslinked. Therefore, the thermoplastic elastomer composition is processed and reprocessed by a conventional thermoplastic resin molding method (processing technique) such as an extrusion molding method, an injection molding method, a blow molding method, a compression molding method and the like and a molding apparatus. Can do.

  When producing a thermoplastic elastomer composition, not a graft copolymer but a grafted precursor can be used as a material. This is because the grafting precursor undergoes a grafting reaction by melt kneading in the process of producing the thermoplastic elastomer composition, and becomes a graft copolymer. That is, the grafting reaction step and the dynamic crosslinking step can be performed simultaneously by using the grafting precursor. Thus, the method of manufacturing a thermoplastic elastomer composition using a grafting precursor is preferable from the viewpoint of simplification of the manufacturing process.

  The crosslinking reaction proceeds by adding a crosslinking agent of component (F) during melt kneading. Component (F) cross-linking agent includes component (A) acrylic rubber, component (B) thermoplastic polyester resin, component (C) graft copolymer or graft precursor, component (D) plasticizer and Dynamic crosslinking can be carried out by simultaneously charging into the kneader together with the acrylic polymer processing aid of component (E). In many cases, acrylic rubber, thermoplastic polyester resin, graft copolymer or grafting precursor and plasticizer are put into a kneading machine, and after sufficient melting and kneading, a cross-linking agent is added to perform dynamic crosslinking. It is more effective to do it. However, when using a crosslinking agent having a slow reaction rate or a slow-acting crosslinking agent, the crosslinking agent should be added before the acrylic rubber, thermoplastic polyester resin, and graft copolymer are sufficiently melted and kneaded. Can do. When the crosslinking reaction is started by adding a crosslinking agent, the viscosity of the composition increases, and when the viscosity becomes constant, the crosslinking reaction is completed. There are various changes in the viscosity until reaching a constant value. For example, there are cases where the viscosity decreases and reaches a constant value after reaching the maximum value of the viscosity, and continues to increase and reaches a constant value.

  In general, it is preferred that the various additives be thoroughly mixed (blended) in the composition before the cross-linking agent is added. This is because even if various additives are added during the crosslinking reaction or after the reaction is completed, they are often not sufficiently dispersed in the composition. Therefore, it is preferable to add various additives from the beginning or middle of the kneading and add the crosslinking agent after sufficiently mixing in the composition.

The temperature at which melting, mixing and dynamic crosslinking are performed is suitably in the range of 100 to 350 ° C. corresponding to the melting start temperature of the acrylic rubber from the melting point of the thermoplastic polyester resin. This temperature is more preferably 150 to 300 ° C, particularly preferably 180 to 280 ° C.
The resulting thermoplastic elastomer composition has a die swell of 1.20 (temperature 260 ° C., shear rate 370 (1 / sec)) or more, and is excellent in bellows moldability.

[Bellows molding product]
The bellows molded product excellent in heat resistance and oil resistance in the present embodiment is a bellows molded product composed of the thermoplastic elastomer composition. The bellows molded product of the present invention may be a bellows molded product composed of one or more layers using the thermoplastic elastomer composition depending on applications. When the bellows molded product is composed of two or more layers, it is formed from at least one selected from the group consisting of a layer using the thermoplastic elastomer composition and a thermoplastic resin, a thermoplastic elastomer or a crosslinked rubber. One or more layers can be formed in multiple layers to form a bellows molded product made of a laminate. The layer which consists of the said thermoplastic elastomer composition among such laminated bodies may exist in any of an innermost layer, an intermediate | middle layer, an outermost layer, an upper layer part, an intermediate | middle layer part, and a lower layer part. By using a material suitable for each layer forming the laminate, a multilayer bellows molded product having each layer having a desired function can be obtained.

  Examples of the thermoplastic resin include olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-glycidyl methacrylate copolymer; polystyrene Styrene resins such as high impact polystyrene and acrylonitrile-butadiene-styrene copolymer; polyurethane; polyvinyl chloride; polyamide resins such as nylon 6, 66, 11, and 12; polycarbonate; polyester such as polyethylene terephthalate and polybutylene terephthalate Polyacetal resins such as polyoxymethylene; polyphenylene ether; polyvinylidene chloride; polyvinylidene fluoride, polytetrafluoroethylene, and the like.

  Examples of the thermoplastic elastomer include a blend of polypropylene and ethylene-propylene-diene rubber or the like, or an olefinic thermoplastic elastomer such as a rubber component part or a completely crosslinked product; a styrene-butadiene-styrene block copolymer, a styrene-isoprene- Styrene block copolymers, and styrene thermoplastic elastomers such as hydrogenated products thereof; polyvinyl chloride thermoplastic elastomers; polyester thermoplastic elastomers such as block copolymers of crystalline polyester and amorphous polyester; polyamides Polyamide thermoplastic elastomers such as block copolymers with polyester or polyol as soft segment; Polyurethane heat such as copolymers obtained by reaction of polyester or polyether with isocyanate Plastic elastomer and the like.

  Examples of the crosslinked rubber include ethylene-propylene-diene rubber, butadiene rubber, butyl rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber and hydrogenated products thereof, chlorinated polyethylene, chloroprene rubber, chlorosulfonated polyethylene, epichlorohydrin rubber, and acrylic. Examples thereof include rubber, silicon rubber, and fluorine rubber.

  The bellows molded article of the present invention may be a bellows molded article hose or a molded article hose including a bellows part that is excellent in heat resistance and oil resistance using the thermoplastic elastomer composition depending on the application. When it is set as the molded product hose containing a bellows, a tubular part and a bellows part can be suitably selected by the function from the said thermoplastic elastomer composition, the said thermoplastic resin, a thermoplastic elastomer, and crosslinked rubber. In particular, the thermoplastic elastomer composition is preferably used for the bellows portion.

  The bellows molded product of the present embodiment can be molded by normal blow molding or injection molding. Blow molding is performed by melting the thermoplastic elastomer composition to form a parison by extrusion or the like, and then inflating the mold using air or the like on a mold. As the blow molding machine, any molding machine such as an accumulator type, an injection type, a multistage type, or a press blow type can be used, and a press blow type is particularly preferable. Injection molding is performed by melting the thermoplastic elastomer composition and injecting it into a mold set at a predetermined temperature. As the injection molding machine, any molding machine such as a plunger type, a screw type, or a pre-plastic type can be used.

Regardless of the molding method, the temperature at which the bellows molded product is molded is suitably in the range of 100 to 350 ° C. corresponding to the decomposition start temperature of acrylic rubber from the melting point of the thermoplastic polyester resin. This temperature is more preferably 150 to 320 ° C, particularly preferably 200 to 300 ° C.
The bellows molded product thus obtained can be recovered after use and used again as a raw material for molding, and is excellent in recyclability.

  The bellows molded product of the present embodiment includes various industrial vehicles such as automobiles, construction machinery vehicles, agricultural machinery vehicles, and railway vehicles; machine tools, construction machinery, agricultural machinery, mining machinery, industrial robots, chemical plants, and coating machines. It can be used as piping for air, oil, various chemicals, various gases, etc. in the fields of various engineering and mining machines such as chemical transfer machines, food industry machines, hydraulic tools, etc .;

Specific examples of bellows molded products include constant velocity joint boots, dust covers, rack and pinion steering boots, pin boots, piston boots, air duct hoses, air intake hoses, air conditioning hoses, and other automobile boots and hoses; agricultural machinery Boots and hoses for industrial vehicles, boots and hoses for industrial vehicles, boots and hoses for construction machinery, boots and hoses for hydraulic machinery, boots and hoses for pneumatic machinery, boots and hoses for centralized lubricators, boots and hoses for liquid transfer, fire fighting And various industrial boots and hoses such as boots and hoses for liquefied gas, and boots and hoses for transferring various liquefied gases.
Now, operations and effects of the present embodiment will be described together below.

  The thermoplastic elastomer composition is composed of component (A) acrylic rubber, component (B) thermoplastic polyester resin, component (C) graft copolymer, component (D) plasticizer, and component (E) acrylic. It is prepared by melt-kneading a composition comprising a system polymer processing aid. Furthermore, it is also prepared by performing dynamic crosslinking by adding a crosslinking agent. The obtained thermoplastic elastomer composition has a structure in which the thermoplastic polyester resin of component (B) is a matrix and the acrylic rubber of component (A) is dispersed in the matrix. Furthermore, the graft copolymer of component (C) exists so as to be compatible with component (A) and component (B), and the functions of component (A) and component (B) are sufficient. It is thought that these effects are enhanced by synergism. Therefore, although the acrylic rubber is crosslinked, the elastomer composition has thermoplasticity. Therefore, it is excellent in moldability when molding a bellows molded product from a thermoplastic elastomer. Further, the obtained bellows molded product can exhibit excellent heat resistance and oil resistance because each component used is excellent in heat resistance and oil resistance at high temperatures.

  In addition, by heating the bellows molded product, the thermoplastic polyester resin of the component (B) constituting the matrix is melted and can be molded again, thereby exhibiting recyclability. Accordingly, scraps and products generated in the manufacturing process of the bellows molded product using the thermoplastic elastomer composition can be easily reprocessed using a conventional molding method and molding apparatus, and the recyclability is excellent.

  Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples. Synthesis examples of materials used in each example and comparative example are shown below.

[Synthesis Example 1, Production of Acrylic Rubber (A-1)]
A flask equipped with a stirrer, thermometer, cooler, dropping device, nitrogen gas inlet tube, ion-exchanged water 1000 g, sodium dodecyl sulfate 10 g, sodium hydrogen sulfite 0.5 g, ferrous sulfate 0.005 g, ethylenediaminetetraacetate sodium 0 Then, the temperature was raised to 30 ° C. with stirring while blowing nitrogen gas. Thereafter, 5 g of ammonium persulfate was added as a polymerization initiator, and 500 g of a monomer mixture (ethyl acrylate 250 g, acrylic acid-n-butyl 230 g, glycidyl methacrylate (GMA) 20 g) was added dropwise thereto over 3 hours. Thereafter, polymerization was further performed for 3 hours to obtain an emulsion. Next, salting out was performed by dripping this emulsion into 0.5 mass% calcium chloride aqueous solution over 1 hour. And after fully washing with water, it dried at 80 degreeC and obtained the acrylic rubber (A-1) containing 4 mass parts of GMA. The acrylic rubber (A-1) had a Tg of −27 ° C.

[Synthesis Example 2, Production of Acrylic Rubber (A-2)]
4 parts by mass of GMA are included in the same manner as in Synthesis Example 1 except that the composition of the monomer mixture is changed to 250 g of ethyl acrylate, 100 g of acrylic acid-n-butyl, 130 g of 2-methoxyethyl acrylate, and 20 g of GMA. Acrylic rubber (A-2) was produced. The acrylic rubber (A-2) had a Tg of -25 ° C.

[Synthesis Example 3, Production of Acrylic Rubber (A-3)]
In the same manner as in Synthesis Example 1 except that the composition of the monomer mixture was changed to 268.5 g of ethyl acrylate, 100 g of acrylic acid-n-butyl, 130 g of 2-methoxyethyl acrylate, and 1.5 g of GMA, An acrylic rubber (A-3) containing 0.3 part by mass was produced. The acrylic rubber (A-3) had a Tg of -28 ° C.

[Synthesis Example 4, Production of Acrylic Rubber (A-4)]
16 parts by mass of GMA is included in the same manner as in Synthesis Example 1 except that the composition of the monomer mixture is changed to 190 g of ethyl acrylate, 100 g of acrylic acid-n-butyl, 130 g of 2-methoxyethyl acrylate, and 80 g of GMA. Acrylic rubber (A-4) was produced. The acrylic rubber (A-4) had a Tg of -21 ° C.
Table 1 shows the amount of each component of the synthesized acrylic rubber.

[Synthesis Example 5, Production of Grafting Precursor (C-1)]
In a 5-liter stainless steel autoclave, 2000 g of pure water and 2.5 g of polyvinyl alcohol as a suspending agent were dissolved. In this, 700 g of ethylene-glycidyl methacrylate copolymer (LOTADER 8840, 8 parts by mass of glycidyl methacrylate, manufactured by ARKEMA Co., Ltd.) was added and stirred and dispersed. As a polymerization initiator, 2 g of benzoyl peroxide (manufactured by NOF Corporation, Nyper BW), 6 g of tert-butylperoxymethacryloyloxyethyl carbonate, vinyl monomer mixture (acrylic acid-n-butyl 150 g, methacrylic acid) A mixed monomer consisting of 300 g of 2-hydroxypropyl 150 g) was charged into the autoclave. Subsequently, the autoclave is heated to 60 to 65 ° C. and stirred for 2 hours to impregnate the ethylene-glycidyl methacrylate copolymer with the polymerization initiator, the radical polymerizable organic peroxide and the vinyl monomer. It was. Next, the temperature was raised to 80 to 85 ° C. and maintained at that temperature for 6 hours to complete the polymerization, and then washed with water and dried to obtain a grafted precursor (C-1). When this grafted precursor (C-1) was observed with a scanning electron microscope (manufactured by Hitachi, Ltd.), a multiphase structure in which a true spherical resin having an average particle size of 0.3 to 0.5 μm was uniformly dispersed. It was a body.

[Synthesis Example 6, Production of Grafting Precursor (C-2)]
A grafted precursor (C-2) was obtained in the same manner as in Synthesis Example 5 except that the composition of the vinyl monomer mixture was changed to 150 g of styrene and 150 g of 2-hydroxypropyl methacrylate. The obtained grafting precursor (C-2) was a multiphase structure in which a true spherical resin having an average particle size of 0.4 to 0.6 μm was uniformly dispersed.

[Synthesis Example 7, Production of Graft Copolymer (C-3)]
The olefin polymer was changed to an ethylene-ethyl acrylate copolymer (NUC6570, 25 parts by mass of ethyl acrylate, manufactured by Nihon Unicar Co., Ltd.), and the composition of the vinyl monomer mixture was changed to acrylic acid-n-butyl. A grafting precursor was obtained in the same manner as in Synthesis Example 5 except that 150 g, glycidyl methacrylate 100 g and styrene 50 g were changed. The obtained grafting precursor was extruded at 180 ° C. and a rotation speed of 100 rpm by a lab plastmill single screw extruder (Toyo Seiki Seisakusho Co., Ltd.) to cause a grafting reaction, whereby a graft copolymer (C-3) was obtained. Got. This graft copolymer was a multiphase structure in which a true spherical resin having an average particle size of 0.3 to 0.5 μm was uniformly dispersed.
Table 2 shows the amount of each component of the synthesized grafting precursor and graft copolymer.
As other materials, commercially available products described below were used.

  Thermoplastic polyester resin: DURANEX 600JP (polybutylene terephthalate, melting point 205 ° C., manufactured by Wintech Polymer Co., Ltd.), DURANEX 700FP (polybutylene terephthalate, melting point 225 ° C., manufactured by Wintech Polymer Co., Ltd.)

Plasticizer: Adekaizer C8 (Trioctyl trimellitate, manufactured by Asahi Denka Kogyo Co., Ltd.), Polycizer W-230-H (Adipic acid-based polyester, manufactured by Dainippon Ink & Chemicals, Inc.)
Acrylic polymer processing aid: Methabrene P-531A (methacrylic acid copolymer, manufactured by Mitsubishi Rayon Co., Ltd.)
Cross-linking agent: Ricacid BT-W (butanetetracarboxylic acid, manufactured by Shin Nippon Rika Co., Ltd.)

  Antioxidant: Irganox 1010 (hindered phenol-based antioxidant, manufactured by Ciba Specialty Chemicals Co., Ltd.), NOCRACK CD (amine-based antioxidant, manufactured by Ouchi Eshin Co., Ltd.)

[Evaluation of thermoplastic elastomer]
Next, the evaluation method of a thermoplastic elastomer composition is described below. The test piece was formed into a sheet having a thickness of 2 mm by a hot press at 260 ° C. and subjected to various evaluations. Various test methods and conditions are described below. The normal physical properties mean physical properties at normal temperature and normal pressure.
(Tensile test)
Based on JIS K 6251, tensile strength (MPa), 100% stress (MPa), and elongation (%) were measured at a test speed of 500 mm / min.
(Hardness)
In accordance with JIS K 6253, the hardness was measured by a spring hardness tester A type.
(Tear test)
The tear strength (kN / m) was measured at a test speed of 500 mm / min in accordance with JIS K6252.
(Compression set)
According to JIS K 6262, compression set (%) after 72 hours at a temperature of 150 ° C. was measured at a compression rate of 25%.

(Heat-resistant)
In accordance with JIS K 6257, the tensile strength change rate (%), elongation change rate (%), and hardness change amount (point) after being left at 150 ° C. for 1000 hours in a gear type aging tester were measured.
(Oil resistance)
According to JIS K 6258, tensile strength change rate (%), elongation change rate (%), hardness change rate (point) and mass change rate (%) after being immersed in IRM903 oil at 150 ° C. for 1000 hours are measured. did.
(Bending test)
In accordance with JIS K 6260, the number of occurrences of cracks was measured by repeatedly bending the test piece.
(Die swell measurement)
Based on JIS K7199, the value of the die swell was measured at a temperature of 260 ° C. and a shear rate of 370 (1 / sec) using a capillograph (manufactured by Toyo Seiki, CAPILOGRAPH 1B-PMD-C). The die swell was calculated by measuring the diameter of the strand flowing out from the orifice and dividing by the orifice diameter (1 mm).

[Evaluation of bellows molded products]
The evaluation method of the bellows molded product using the thermoplastic elastomer composition is described below.
(Press blow moldability)

  The thermoplastic elastomer composition is formed using a press blow molding machine (PRESSBLOWER DSE 140 manufactured by Osberger) under the molding conditions of a cylinder temperature of 260 ° C., a nozzle temperature of 260 ° C., and a mold temperature of 40 ° C. Molded into a constant velocity joint boot connected by a 1.0 mm thick bellows with five peaks and valleys. Observation of parison flow marks, rough skin, silver stalks (streaks caused by moisture, etc.) and blooming (surface irregularities due to bleed-out) formed in press blow molding, and cracks in parison when inflating parison on mold The moldability was determined by observing the presence or absence of the toner. Moreover, it was evaluated whether the thickness of each mountain valley part of a bellows molded product was settled in 1.0 +/- 0.05mm in all the measurement parts. In the case of having excellent moldability, it was marked as ◯, and in the case where cracks in the parison and poor control of the wall thickness were observed, it was marked as x.

(Injection moldability)
The thermoplastic elastomer composition is made of an injection molding machine (ES600 manufactured by Nissei Plastic Industry Co., Ltd.) under molding conditions of a cylinder temperature of 260 ° C., a nozzle temperature of 260 ° C., and a mold temperature of 50 ° C., and a wall thickness having six peaks and valleys. Molded into a 1.0 mm bellows-like part. It was evaluated whether or not the thickness of each mountain and valley portion of the bellows molded product was within 1.0 ± 0.05 mm at all the measurement sites. In the case of having excellent moldability, it was marked as ◯, and in the case where poor control of the wall thickness was observed, it was marked as x.
(Appearance of bellows molded product)
The surface state of the molded bellows molded product was visually observed, and when the surface was smooth, it was evaluated as ◯, and when an appearance defect such as rough skin was found, it was evaluated as x.

(Assemblyability of bellows molded products)
When the molded bellows molded product is attached to a cylindrical metal member (φ80 mm or φ20 mm), the assembly property of the bellows molded product is judged. If it has an excellent assembly property, ○, if there is a problem with the assembly property X.
(Heat resistance of bellows molded products)
The molded bellows molded product was heat aged at 150 ° C. for 1000 hours in a gear type aging tester, and then the bellows molded product was bent to determine the presence or absence of cracks. When there was no crack, it evaluated as (circle) and when a crack was observed, it evaluated as x.

(Oil resistance of bellows molded products)
After filling the inside of the bellows molded product with IRM903 oil, immediately draining and removing it every 24 hours, the IRM903 oil-removed test piece was placed in a gear type aging tester at 150 ° C. for 1000 hours. After heat aging under the conditions, the bellows molded product was bent to determine the presence or absence of cracks. When there was no crack, it evaluated as (circle) and when a crack was observed, it evaluated as x.
(Cold resistance of bellows molded products)
The bellows molded product was allowed to stand at −40 ° C. for 5 hours and then bent to determine the presence or absence of cracks. When there was no crack, it evaluated as (circle) and when a crack was observed, it evaluated as x.

[Example 1]
70 parts by mass of acrylic rubber A-1 of Synthesis Example 1, 30 parts by mass of Duranex 600 JP, 8 parts by mass of grafting precursor C-1 of Synthesis Example 5, 24 parts by mass of Adekasizer C8, Metabrene P-531A 3 parts by mass, Irganox 1010 0.5 parts by mass, and Nocrack CD 1 part by mass in a pressure kneader heated to 260 ° C. Then, melt kneading was performed at a rotational speed of 32 rpm. All materials were melted and kneaded until the torque showed a constant value by mixing uniformly. When the torque became constant, 0.2 parts by mass of Ricacid BT-W was added as a crosslinking agent, and kneading was continued. It was observed that the torque increased immediately after the cross-linking agent was added, and the kneading was terminated when the torque reached a constant value.

  The obtained thermoplastic elastomer composition was discharged from the kneader, put into a kneader ruder, extruded into a strand at 240 ° C., cooled and cut to obtain pellets of the thermoplastic elastomer composition. Using this, it was formed into a sheet having a thickness of 2 mm by a heating press at 260 ° C., and the various evaluations were performed. Further, bellows molded products were formed from the pellets by the above method, and the various bellows molded products were evaluated. Table 3 shows the blending and evaluation results of the thermoplastic elastomer composition.

[Examples 2 to 7]
A thermoplastic elastomer composition and a bellows-molded article were produced in the same manner as in Example 1 at the blending ratio shown in Table 3. Table 3 shows the blending ratio of each component and the results of various evaluations.

[Comparative Examples 1 to 12]
A thermoplastic elastomer composition and a bellows molded product were produced in the same manner as in Example 1 at the blending ratio shown in Table 4. Table 4 shows the blending ratio of each component and the results of various evaluations.

(Summary)
As shown in Table 3, thermoplastic elastomer compositions having different hardnesses depending on the blending ratio of various materials could be obtained (Examples 1 to 7). These thermoplastic elastomer compositions had excellent heat resistance and oil resistance. Furthermore, since these thermoplastic elastomer compositions exhibited a die swell of 1.20 or more and had good moldability, they could be molded into bellows molded products. The obtained bellows molded product had good appearance, assemblability, heat resistance, and oil resistance.

As shown in Table 4, when the amount of GMA in the acrylic rubber was excessively 0.3 mass% in the monomer mixture (Comparative Example 1), the tensile strength was inferior. Moreover, the molding processability of the bellows molded product was poor, and various evaluations could not be performed. When the amount of GMA in the acrylic rubber was an excess of 16% by mass in the monomer mixture (Comparative Example 2), molding processability was poor and no evaluation could be performed.
When the blending amount of the acrylic rubber was excessive (Comparative Example 3), molding processability was poor and no evaluation could be performed.
When the blending amount of the thermoplastic polyester resin was excessive (Comparative Example 4), the flexibility of the bellows molded product was lowered, and the bending resistance and the assembling property were inferior.
When the graft copolymer is excluded (Comparative Example 5) or when the acrylic copolymer is not contained in the vinyl copolymer segment of the grafting precursor (Comparative Example 6), acrylic rubber and thermoplastic polyester The compatibility of was reduced, and the moldability became poor.

As shown in Table 5, when the blending amount of the grafting precursor was excessive (Comparative Example 7), the test piece collapsed during the oil resistance test as a result of the decrease in the oil resistance of the thermoplastic elastomer composition. did.
When the amount of the plasticizer was excessive (Comparative Example 8), the plasticizer could not be retained in the thermoplastic elastomer composition, and the plasticizer bleeded out.
When the blending amount of the acrylic polymer processing aid was too small (Comparative Example 9), the die swell was low, resulting in poor blow moldability.
When the blending amount of the acrylic polymer processing aid was excessive (Comparative Example 10), the melt viscosity was excessively improved, resulting in poor injection moldability.
When the blending amount of the cross-linking agent was too small (Comparative Example 11), since the cross-linking was insufficient, the tensile strength, compression set, and flex resistance were inferior.
When the blending amount of the crosslinking agent was excessive (Comparative Example 12), the crosslinking of the acrylic rubber proceeded excessively, resulting in poor moldability and no evaluation could be performed.

The bellows molded product obtained by the present invention is not only excellent in heat aging resistance and oil resistance at high temperature (150 ° C.), but also clearly has good compression set at high temperature. It can be used as a component.
It should be noted that the present embodiment can be implemented with the following modifications.

Depending on the purpose, each component of the component (A) acrylic rubber, the component (B) thermoplastic polyester resin, and the component (C) graft copolymer is blended in an appropriate combination, and thermoplasticity A bellows molded article formed from the elastomer composition can be prepared.
Furthermore, the technical idea grasped from the embodiment will be described below.

  The bellows molded product according to claim 1 or 2, wherein the cross-linking agent is a polycarboxylic acid or an acid anhydride. When comprised in this way, in addition to the effect of the invention which concerns on Claim 1 or Claim 2, the bridge | crosslinking function of the acrylic rubber in a bellows molded product can be improved.

  The bellows molded product according to claim 1 or 2, wherein the raw material composition contains an antioxidant. When comprised in this way, the oxidation deterioration of a bellows molded product can be suppressed and the effect of the invention which concerns on Claim 1 or Claim 2 can be improved.

  The acrylic acid alkyl ester of the acrylic rubber of the component (A) has an alkyl group having 2 to 4 carbon atoms, and the acrylic acid alkoxyalkyl ester has an alkyl group having 2 to 4 carbon atoms. The bellows-shaped article according to claim 1 or 2, characterized in that When comprised in this way, in addition to the effect of the invention which concerns on Claim 1 or Claim 2, the softness | flexibility and oil resistance of a bellows molded product formed from a thermoplastic elastomer composition can be improved.

  The graft copolymer of the component (C) is characterized in that the alkyl acrylate ester forming the vinyl copolymer segment is an alkyl group having 2 to 4 carbon atoms. The bellows molded product according to 2. In this case, in addition to the effect of the invention according to claim 1 or 2, the compatibility between the graft copolymer and the acrylic rubber can be enhanced, and the bellows formed from the thermoplastic elastomer composition The appearance and oil resistance of the molded product can be improved.

Claims (5)

A bellows molded product formed from a thermoplastic elastomer composition comprising the following component (A), component (B), component (C), component (D) and component (E).
Component (A): A monomer mixture containing at least one of alkyl acrylate ester and alkoxyalkyl acrylate ester as a main component and containing 0.5 to 15% by mass of an epoxy group-containing monomer is copolymerized. 50 to 85 parts by mass in 100 parts by mass of the total of component (A) and component (B).
Component (B): 15 to 50 parts by mass of the thermoplastic polyester resin in a total of 100 parts by mass of the component (A) and the component (B).
Component (C): an olefin polymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer containing at least an alkyl acrylate, The graft copolymer in which the segment forms a dispersed phase in the matrix phase formed by the other segment or its precursor is 1 to 35 with respect to 100 parts by mass in total of the component (A) and the component (B). Parts by mass.
Component (D): The plasticizer is 60 parts by mass or less with respect to 100 parts by mass of the component (A).
Component (E): 0.5 to 10 parts by mass of acrylic polymer processing aid with respect to 100 parts by mass in total of component (A) and component (B). The thermoplastic elastomer composition according to claim 1, wherein component (D) of the thermoplastic elastomer composition is selected from trimellitic acid plasticizers, polyester plasticizers, and polyether ester plasticizers. Molded bellows molded product. The thermoplastic elastomer composition comprising the component (A), the component (B), the component (C), the component (D) and the component (E) is added in an amount of 0.05 to 100 parts by mass with respect to 100 parts by mass of the component (A). A bellows-molded article formed from the thermoplastic elastomer composition according to any one of claims 1 and 2, which is obtained by dynamic crosslinking with 5 parts by mass of a crosslinking agent (component (F)). . A bellows molded product produced by blow molding or injection molding the thermoplastic elastomer composition according to any one of claims 1 to 3. A bellows-molded article produced by multilayer molding with a thermoplastic resin, a thermoplastic elastomer or a crosslinked rubber using the thermoplastic elastomer composition according to any one of claims 1 to 3.