JP2008037933A - Sealing material and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recyclable sealing material exhibiting excellent heat resistance, oil resistance and compression set at a high temperature such as 150°C. <P>SOLUTION: The sealing material comprises a thermoplastic elastomer composition molded in a temperature range from melting point of a thermoplastic polyester resin to a decomposition starting temperature of an acrylic rubber, wherein the thermoplastic elastomer composition is obtained by subjecting a raw material composition comprising a component (A) of the acrylic rubber, a component (B) of the thermoplastic polyester resin, a component (C) of a graft copolymer or its precursor comprising an olefin-based copolymer segment and a vinyl-based copolymer segment, and in some cases a component (D) of a plasticizer, component (E) of an antioxidant, ultraviolet ray stabilizer, a processing aid, a coloring agent or pigment, and component (F) of filler, flame retardant, to a dynamic crosslinking in the presence of 0.05-5 part.mass of a cross linking agent per 100 part.mass of the component (A). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sealing material formed by using a thermoplastic elastomer composition having excellent characteristics such as heat resistance, oil resistance and compression set, and can be used particularly as an automobile part, an industrial part, etc., and recycled. It is related with the sealing material which can be used, and its manufacturing method.

  As a sealing material, vulcanized rubber has been mainly used from a general material to a material that requires characteristics such as heat resistance, oil resistance, and compression set used for automobile parts. The sealing material using vulcanized rubber requires a rubber kneading step and a vulcanization step, and thus the manufacturing process is complicated. Once vulcanized rubber cannot be re-formed by heating, the recyclability is poor. Had drawbacks. In recent years, thermoplastic elastomers that do not require a vulcanization process and have the same level as thermoplastic resins in terms of molding processability and recyclability have been widely used in automotive interior and exterior parts and in the electrical field as an alternative to vulcanized rubber. Has come to be used.

In such a flow, an attempt has been made to replace the sealing material with a thermoplastic elastomer. For example, an olefinic thermoplastic elastomer obtained by melt-kneading an acrylic rubber, a graft copolymer consisting of an olefinic copolymer segment and a vinylic copolymer segment, a crosslinking agent, and a cocrosslinking agent is used. Such a sealing material is known (see, for example, Patent Document 1).
In addition, a sealing material molded using a thermoplastic elastomer made of a graft copolymer of a thermoplastic polymer mainly composed of an acrylate ester and an aromatic polyester oligomer is known. (For example, see Patent Document 2).

JP 2004-002651 A (pages 20 to 23) JP-A-7-138556 (pages 5-7)

However, the sealing material described in Patent Document 1 has resulted in insufficient heat resistance and oil resistance because the graft copolymer melts at a high temperature of 150 ° C.
On the other hand, the sealing material described in Patent Document 2 has insufficient oil resistance and compression set because a thermoplastic polymer mainly composed of an acrylate ester is not crosslinked.
Therefore, at present, a sealing material made of a thermoplastic elastomer having excellent heat resistance, oil resistance and compression set even at a high temperature of 150 ° C. is not disclosed. Therefore, an object of the present invention is to provide a sealing material capable of exhibiting excellent heat resistance, oil resistance and compression set at a high temperature of 150 ° C., and a method for producing the same.

In order to achieve the above object, the sealing material of the first invention in the present invention comprises the following component (A), component (B), component (C), component (D), component (E) and component Using a thermoplastic elastomer composition obtained by dynamically crosslinking a raw material composition comprising (F) by adding 0.05 to 5 parts by mass of a crosslinking agent per 100 parts by mass of component (A), heat It is characterized in that it is molded in a temperature range from the melting point of the plastic polyester resin to the decomposition start temperature of the acrylic rubber.
Component (A): Acrylic rubber formed by copolymerizing a monomer mixture containing an acrylic ester as a main component and containing an epoxy group-containing monomer in an amount of 0.5 to 15% by mass, comprises component (A) and component (B). ) In a total of 100 parts by mass, 50 to 85 parts by mass.
Component (B): 15 to 50 parts by mass of the thermoplastic polyester resin in a total of 100 parts by mass of component (A) and component (B).
Component (C): an olefin copolymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer mixture containing an acrylate ester, 1 to 35 parts by mass per 100 parts by mass in total of the component (A) and the component (B) of the graft copolymer or the precursor thereof in which the segment forms a dispersed phase in the matrix phase formed by the other segment .
Component (D): The plasticizer is 60 parts by mass or less per 100 parts by mass of the component (A).
Component (E): One or more other additives selected from the group consisting of antioxidants, ultraviolet stabilizers, processing aids, colorants and pigments are 5 parts by mass or less per 100 parts by mass of component (A).
Component (F): One or more other additives selected from the group consisting of fillers and flame retardants are 70 parts by mass or less per 100 parts by mass in total of component (A), component (B) and component (C).

The sealing material of the second invention is characterized in that, in the first invention, the component (D) is trimellitic acid esters or polyesters.
The manufacturing method of the sealing material of the third invention is characterized in that it is molded using the thermoplastic elastomer composition of the first or second invention by an injection molding method, an extrusion molding method or a press molding method.

According to the present invention, the following effects can be exhibited.
In the sealing material of the first invention, the sealing material formed from the thermoplastic elastomer composition can exhibit excellent heat resistance, oil resistance and compression set at a high temperature of 150 ° C. It can be recovered after use and used again as a raw material for formation, that is, recycled.

  In the sealing material of the second invention, the plasticizer exhibits heat resistance, and at the same time, a good plasticizing effect can be exhibited. Therefore, any of the effects of the first invention can be exhibited, and the heat resistance is particularly excellent.

  In the manufacturing method of the sealing material of the third invention, a sealing material having a simple manufacturing process and an excellent appearance of the molded product in addition to the effects of the first invention can be obtained.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
In the sealing material of the present embodiment, the raw material composition containing the following component (A), component (B), component (C) and component (D) is added to 0.05 parts by mass of component (A). It is molded from a thermoplastic elastomer composition obtained by dynamic crosslinking with -5 parts by mass of a crosslinking agent. Here, the sealing material is a soft rubber material that requires airtightness as typified by packing and gasket.
Component (A): Acrylic rubber formed by copolymerizing a monomer mixture containing an acrylic ester as a main component and containing an epoxy group-containing monomer in an amount of 0.5 to 15% by mass, comprises component (A) and component (B). ) In a total of 100 parts by mass, 50 to 85 parts by mass.
Component (B): 15 to 50 parts by mass of the thermoplastic polyester resin in a total of 100 parts by mass of component (A) and component (B).
Component (C): an olefin copolymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer mixture containing an acrylate ester, 1 to 35 parts by mass per 100 parts by mass in total of the component (A) and the component (B) of the graft copolymer or the precursor thereof in which the segment forms a dispersed phase in the matrix phase formed by the other segment .
Component (D): The plasticizer is 60 parts by mass or less per 100 parts by mass of the component (A).

Next, each of these components will be described in order.
[Component (A) Acrylic rubber]
Acrylic rubber is a component for exerting flexibility, heat resistance and oil resistance in a sealing material obtained by molding a thermoplastic elastomer composition. The acrylic rubber is obtained by copolymerizing a monomer mixture containing an acrylic ester as a main component and 0.5 to 15% by mass of an epoxy group-containing monomer.
As acrylic acid ester which is the main component constituting acrylic rubber, acrylic acid alkyl ester and acrylic acid alkoxy ester are preferable, and one or more of these are appropriately selected and used.

  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 alkyl acrylate 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 ester of acrylic acid include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, and 2-butoxyethyl acrylate. Among these, from the viewpoint that excellent oil resistance can be exhibited, acrylic acid alkoxyalkyl esters having 2 to 4 carbon atoms in the alkyl group are preferable, and 2-methoxyethyl acrylate is particularly preferable.

  The acrylic ester content in the acrylic rubber is preferably 85 to 99.5% by mass. When this content is less than 85% by mass, the molding processability of the thermoplastic elastomer composition is lowered, a sealing material having a good appearance cannot be obtained, and the content of acrylic ester is 99.5. When it exceeds mass%, the acrylic rubber is not sufficiently crosslinked and the compression set of the sealing material tends to be inferior.

  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 compression set of the sealing material obtained from the thermoplastic elastomer composition is inferior, and 15% by mass. If it exceeds 1, the acrylic rubber is excessively crosslinked, so that the molding processability of the thermoplastic elastomer composition is lowered, and a sealing material having a good appearance cannot be obtained.

  Further, for the purpose of improving physical properties such as flexibility, moldability, oil resistance, etc., other copolymerizable monomers can be blended and copolymerized in the monomer mixture. Examples of such copolymerizable monomers include methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate; methacrylic acid alkoxyalkyl esters such as methacrylic acid-2-methoxyethyl and methacrylic acid-2-ethoxyethyl; Carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, and maleic acid; Hydroxyl group-containing monomers such as (meth) acrylic acid-2-hydroxyethyl and (meth) acrylic acid-2-hydroxypropyl; 2 -Active chlorine-containing monomers such as chloroethyl vinyl ether, vinyl monochloroacetate, and allyl chloroacetate; Fluorine-based (meth) such as (meth) acrylic acid trifluoromethyl methyl, (meth) acrylic acid-2-trifluoromethyl ethyl Acrylic ester; styrene, α-methylstyrene, etc. Aromatic vinyl compounds; Vinyl nitriles such as acrylonitrile and methacrylonitrile; Vinyl amides such as acrylamide, methacrylamide and N-methylol acrylamide; α-olefins such as ethylene, propylene and isobutene; Conjugated dienes such as butadiene, isoprene and chloroprene Difunctional (meth) acrylates, trifunctional (meth) acrylates, vinyl acetate, vinyl chloride and the like.

  The content of these copolymerizable monomers in the monomer mixture is preferably 40% by mass or less, and more preferably 30% by mass or less. When this content exceeds 40% by mass, the balance of physical properties such as heat resistance, oil resistance, molding processability, and low temperature characteristics of the acrylic rubber may be impaired.

The glass transition temperature (Tg) of component (A) acrylic rubber 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 sealing material formed from the thermoplastic elastomer composition may not be able to withstand practical use.
The content of the component (A) acrylic rubber contained in the thermoplastic elastomer composition is 50 to 85 parts by mass, preferably 60 to 75 parts by mass, out of a total of 100 parts by mass of the component (A) and the component (B). It is necessary to have an excellent balance between compression set and moldability. When the acrylic rubber content is less than 50 parts by mass, the compression set of the sealing material formed from the thermoplastic elastomer composition is inferior, and when it exceeds 85 parts by mass, the molding processability of the thermoplastic elastomer composition is impaired. Therefore, it is inappropriate.

[Component (B) Thermoplastic polyester resin]
The thermoplastic polyester resin of component (B) is a component for improving the molding processability of the thermoplastic elastomer composition and exhibiting the heat resistance and oil resistance of the molded sealing material. Such thermoplastic polyester resins include all thermoplastic saturated polyester resins having an ester bond in the main chain. The thermoplastic polyester resin can be obtained by a known method such as polycondensation of dicarboxylic acid and dihydroxy (diol), polycondensation of oxycarboxylic acid, polycondensation of dicarboxylic acid, dihydroxy (diol) and oxycarboxylic acid. It can be either a homopolyester or a copolyester. One or more of these thermoplastic polyester resins are used in appropriate combination.

  The thermoplastic polyester resin may be non-crystalline, but is preferably crystalline because it is excellent in 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 component (B) thermoplastic polyester resin contained in the thermoplastic elastomer composition is 15 to 50 parts by mass, preferably 25 to 40 parts by mass in 100 parts by mass in total of the component (A) and the component (B). It is necessary to have an excellent balance between compression set and moldability. 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 compression set of the sealing material obtained from the thermoplastic elastomer composition is low. It is inappropriate because it is damaged.

[Component (C) Graft copolymer]
The component (C) graft copolymer exhibits compatibility (affinity) with the component (A) acrylic rubber and the component (B) thermoplastic polyester resin, and the function of the component (A) and the function of the component (B). It is a component for fully exhibiting the above and developing 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 mixture containing an acrylate ester. A graft copolymer in which a segment forms a dispersed phase in a matrix phase formed by the other segment.

  The olefin copolymer 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- Vinyl acetate-maleic anhydride copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid-n-butyl copolymer, ethylene-ethyl acrylate-glycidyl methacrylate copolymer Polymer, maleic anhydride modified ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-dimethylaminomethyl methacrylate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol copolymer Combined ethylene oxide adduct, ethylene-acrylic Copolymer, ethylene - methacrylic acid copolymer, ethylene - acrylic acid copolymer or ethylene - sodium intermolecular methacrylic acid copolymer, intermolecular bonded ionomer, and the like with a metal ion such as zinc.

  The proportion of the polar monomer in the olefin copolymer segment is preferably 10 to 50 parts by mass and more preferably 15 to 40 parts by mass in 100 parts by mass of ethylene and the polar monomer. When the proportion of the polar monomer is less than 10 parts by mass, the graft copolymer has high hardness and low oil resistance, so that the flexibility and oil resistance of the sealing material obtained from the thermoplastic elastomer composition are impaired. There is. On the other hand, when the polar monomer exceeds 50 parts by mass, the graft copolymer is flexible and excellent in oil resistance, but has poor mechanical strength. Therefore, the tensile strength of the sealing material obtained from the thermoplastic elastomer composition is low. Mechanical properties such as strength and elongation decrease.

  The vinyl copolymer segment is formed from a vinyl monomer mixture containing an acrylate ester. The vinyl copolymer segment is compatible with the component (A) acrylic rubber to improve the molding processability of the thermoplastic elastomer composition and the appearance of the sealing material, and further improve the mechanical properties of the sealing material. Can do.

  The acrylic ester contained in the vinyl copolymer segment is preferably an alkyl acrylate in terms of excellent compatibility with acrylic rubber. 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, particularly preferred from the viewpoint of oil resistance and compatibility with the component (A) acrylic rubber is an acrylic acid having 2 to 4 carbon atoms in an alkyl group such as ethyl acrylate and acrylic acid-n-butyl. It is an alkyl ester.

  The acrylic ester contained in 100 parts by mass of the vinyl copolymer segment is preferably 20 to 100 parts by mass, and more preferably 30 to 100 parts by mass or more. When the acrylic acid ester is less than 20 parts by mass, the compatibility between the graft copolymer and the acrylic rubber cannot be sufficiently obtained. Therefore, the sealing material formed from the thermoplastic elastomer composition is deteriorated in mechanical strength or appearance. Deterioration occurs and is not preferable.

  The vinyl copolymer segment can be formed by copolymerizing one or more vinyl monomers in addition to the acrylate ester. Examples of the copolymerizable vinyl monomer include methacrylic acid alkyl esters such as methyl methacrylate and ethyl methacrylate; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and the like. (Meth) acrylic acid alkoxyesters; epoxy group-containing monomers such as glycidyl (meth) acrylate, vinyl glycidyl ether, allyl glycidyl ether; carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid and maleic acid Body; hydroxyl group-containing monomers such as (meth) acrylic acid-2-hydroxyethyl and (meth) acrylic acid-2-hydroxypropyl; styrene, methylstyrene, dimethylstyrene, ethylstyrene, isopropylstyrene, chlorostyrene, etc. Aromatic vinyl compounds; α-methylstyrene α- ethylstyrene, etc. α- substituted styrene; acrylonitrile, vinyl nitriles such as methacrylonitrile, and the like. These vinyl monomers are preferably 0 to 80 parts by mass, and more preferably 0 to 70 parts by mass 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. When the number average degree of polymerization is less than 5, it is possible to improve the moldability of the thermoplastic elastomer composition, but the heat resistance and oil resistance are reduced, or the compatibility with the component (A) acrylic rubber is reduced. Decreases and the appearance of the sealing material molded from the thermoplastic elastomer composition 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 content of the olefin copolymer 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 ratio of the vinyl copolymer segment is the remainder obtained by removing the olefin copolymer segment from the graft copolymer, and is usually 5 to 95 parts by mass, preferably 10 to 80 parts by mass, and most preferably 15 to 15 parts by mass. 70 parts by mass. When the proportion of the olefin copolymer segment is less than 5 parts by mass or the proportion of the vinyl copolymer segment exceeds 95 parts by mass, the moldability of the thermoplastic elastomer composition becomes insufficient. On the other hand, when the proportion of the olefin copolymer segment exceeds 95 parts by mass, or when the proportion of the vinyl copolymer segment is less than 5 parts by mass, the compatibility with the component (A) acrylic rubber becomes low. The mechanical properties and appearance of the sealing material obtained from the thermoplastic elastomer composition tend to deteriorate.

  As described above, the graft copolymer is a multilayer 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 component (C) graft copolymer and the component (A) acrylic rubber is lowered, and the thermoplastic elastomer composition The mechanical properties and appearance of the sealing material obtained from the above 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 graft efficiency is high, and there is no secondary aggregation of the vinyl copolymer segment due to heat, so that the component (C) graft copolymer can be used as the component (A) acrylic rubber or component. (B) It is easy to mix with the thermoplastic polyester resin.
Below, the manufacturing method of such a graft copolymer is demonstrated. An olefin copolymer formed from ethylene and a polar monomer suspended in water is a vinyl monomer mixture containing an acrylate ester, represented by the following general formula (1) or (2) One or a mixture of radically polymerizable organic peroxides and a radical polymerization initiator are impregnated. Thereafter, the vinyl monomer and the radical polymerizable organic peroxide are copolymerized in an olefin copolymer formed from ethylene and a polar monomer to obtain a grafted precursor.

  The grafting precursor is a vinyl copolymer of a vinyl monomer mixture containing an acrylate ester and a radical polymerizable organic oxide in an olefin copolymer particle formed from ethylene and a polar monomer. A structure in which coalescence is dispersed. In the graft precursor, a copolymer of a vinyl monomer and a radical polymerizable organic peroxide dispersed therein contains 0.003 to 0.73% by mass as an active oxygen amount. It is preferable. 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, when it exceeds 0.73 mass%, since the production | generation of a gel increases in the case of grafting, it is unpreferable. 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 component (C) graft copolymer can be obtained by melt-kneading the grafted precursor under heating. By heating during melt-kneading, the peroxide bond in the vinyl copolymer is cleaved, and the generated radicals perform a hydrogen abstraction reaction on the olefin copolymer, and the graft copolymer is converted into a graft copolymer by the subsequent grafting reaction. Manufactured. 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 kneading temperature is less than 100 ° C., the melting is incomplete or the melt viscosity is too high, so that the mixing becomes insufficient and phase separation or delamination of the graft copolymer appears, which is not preferable. On the other hand, when it exceeds 300 ° C., decomposition or gelation tends to occur during grafting, which is not preferable.

  The component (C) graft copolymer thus obtained has its olefin copolymer segment oriented in the component (B) thermoplastic polyester resin (showing compatibility), and the vinyl copolymer segment as the component. (A) It is considered that it is oriented to 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 content of the component (C) graft copolymer contained in the thermoplastic elastomer composition is 1 to 35 parts by mass, preferably 100 parts by mass in total of component (A) acrylic rubber and component (B) thermoplastic polyester resin. Is 2 to 25 parts by mass. When the content of the graft copolymer is less than 1 part by mass, the effect of improving the molding processability is insufficient, the appearance of the molded sealing material is inferior, and when it is more than 35 parts by mass, it is obtained from the thermoplastic elastomer composition. The heat resistance, oil resistance, and compression set of the resulting sealing material are impaired.

[Component (D) Plasticizer]
A plasticizer is blended in the thermoplastic elastomer composition in order to obtain the flexibility of the sealing material. Examples of the plasticizer include phthalic acid esters, adipic acid esters, azelaic acid esters, sebacic acid esters, phosphoric acid esters, trimellitic acid esters, polyesters, or a mixture thereof. The specific advantage of including a plasticizer is that the processability of the thermoplastic elastomer composition, the flexibility of the sealing material, 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, problems occur such as cracks in the molded sealing material and a decrease in sealing performance, resulting in a decrease in heat resistance as the sealing material. To do.
Therefore, as the plasticizer blended in the thermoplastic elastomer composition, those having high heat resistance and low volatility are preferable.

Such preferred plasticizers include trimellitic acid esters or polyesters. Examples of trimellitic esters include tri-2-ethylhexyl trimellitic acid, tri-n-octyl trimellitic acid, triisononyl trimellitic acid, triisodecyl trimellitic acid, and the like. Examples of polyesters include adipic acid polyester, sebacic acid polyester, trimellitic acid polyester, pyromellitic acid polyester, polyether ester, polyether polyester, and the like. These plasticizers can be used alone or in combination of two or more.
The compounding quantity of a plasticizer is 60 mass parts or less per 100 mass parts of component (A) acrylic rubber, and it is preferable that it is 5-50 mass parts. When the blending amount of the plasticizer exceeds 60 parts by mass, the plasticizer bleeds out or the mechanical strength of the sealing material obtained from the thermoplastic elastomer composition is greatly reduced.

[Component (E) Antioxidant, UV stabilizer, processing aid, colorant, pigment]
In the thermoplastic elastomer composition, in addition to the above components, one or more other additives selected from the group consisting of antioxidants, ultraviolet stabilizers, processing aids, colorants and pigments are used as component (A) 100. It mix | blends suitably at 5 mass parts or less per mass part. Examples of such additives include phenol-based and amine-based antioxidants, ultraviolet stabilizers such as hindered amines, processing aids such as stearic acid, and colorants and pigments such as titanium dioxide.

[Ingredient (F) Filler, Flame Retardant]
Further, in the thermoplastic elastomer composition, one or more other additives selected from the group consisting of a filler (reinforcing agent) and a flame retardant are further added as component (A), component (B) and component (C). Is suitably blended at 70 parts by mass or less per 100 parts by mass in total. Examples of such additives include fillers (reinforcing agents) such as carbon black, white carbon, clay and talc, and flame retardants such as magnesium hydroxide.

[Crosslinking agent]
The crosslinking agent used for forming a crosslinked structure in the thermoplastic elastomer composition has a function of crosslinking the acrylic rubber by covalently bonding with an epoxy group of the acrylic rubber. Examples of such cross-linking agents include polyamines, polyols, polycarboxylic acids, acid anhydrides, organic carboxylic acid ammonium salts, dithiocarbamates, etc. Among them, particularly preferred cross-linking agents are polycarboxylic acids or acid anhydrides. is there.

  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 the crosslinking agent to select, it is 0.05-5 mass parts with respect to 100 mass parts of component (A) acrylic rubber, Preferably it sets in the range of 0.1-2 mass parts. Is done. When the amount of the crosslinking agent used is less than 0.05 parts by mass, the crosslinking is insufficient and the sealing material obtained from the thermoplastic elastomer composition results in lack of heat resistance, oil resistance and compression set. On the other hand, when the amount exceeds 5 parts by mass, the thermoplastic elastomer composition is excessively crosslinked, so that a sealing material with good moldability and good appearance cannot be obtained.

[Thermoplastic elastomer composition]
The thermoplastic elastomer composition is produced by performing dynamic crosslinking with a crosslinking agent on the raw material composition containing the components. Here, dynamic cross-linking involves melting component (A) acrylic rubber, component (B) thermoplastic polyester resin, component (C) graft copolymer and component (D) plasticizer at a temperature higher than the melting point of the thermoplastic polyester resin. It means kneading and crosslinking the epoxy group of acrylic rubber under high shear during kneading.
As an apparatus for performing dynamic crosslinking, 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.
Usually, the dynamically crosslinked acrylic rubber is finely dispersed in the matrix phase of the thermoplastic polyester resin. By forming such a phase structure (sea-island structure), the elastomer composition can exhibit thermoplasticity despite the acrylic rubber being crosslinked.
Therefore, the thermoplastic elastomer composition is processed 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. Rework can be performed.

  When producing a thermoplastic elastomer composition, a grafting precursor can be used instead of a graft copolymer. 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 during melt kneading. The cross-linking agent is simultaneously added to the kneader together with component (A) acrylic rubber, component (B) thermoplastic polyester resin, component (C) graft copolymer or grafting precursor and component (D) plasticizer, or appropriate addition It can be added by the procedure to effect dynamic crosslinking. 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.

  Generally, it is preferable that various additives are sufficiently mixed (blended) in the raw material composition before adding the crosslinking agent. This is because even when various additives are added during the crosslinking reaction or after the reaction is completed, they are often not sufficiently dispersed in the raw material composition. Therefore, it is preferable to add various other additives before the crosslinking reaction starts, that is, at the beginning or as early as possible of the kneading, and after sufficiently mixing in the raw material composition, the crosslinking agent is added. 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.

[Sealant]
The sealing material of this embodiment is obtained by molding the thermoplastic elastomer composition under a certain temperature condition. As a molding method for obtaining the sealing material, an injection molding method, an extrusion molding method or a press molding method is adopted, and each molding method can be molded according to a conventional method. The molding may be performed directly so as to have the shape of the sealing material, or may be punched out after being molded into a sheet shape and processed into a final shape sealing material.

  Regardless of the molding method, the temperature at which the sealing material is molded is preferably a temperature range from the melting point of the thermoplastic polyester resin to the decomposition start temperature of the acrylic rubber. A range of 100 to 350 ° C. corresponding to this temperature range is appropriate. This temperature is more preferably 150 to 300 ° C, particularly preferably 180 to 280 ° C. The sealing material thus obtained can be recovered after use and used again as a raw material for molding, that is, can be recycled.

As a sealing material of this embodiment, it can be used as a motion seal such as a static seal such as an O-ring, each ring, and a gasket, an oil seal, a mechanical seal, and a gland packing. Among these sealing materials, it is preferably used as automobile parts, industrial parts and the like that are particularly required to have heat resistance, oil resistance and compression set.
This is because the thermoplastic elastomer composition exhibits excellent resistance in a severe heat resistance and oil resistance test of, for example, 150 to 180 ° C. and 1000 hours, and is excellent in compression set at 150 ° C.

  Examples of automotive seal materials include door seals, dust seals, trunk lid seals, hood seals, window seals, crankshaft seals, valve stem seals, mission oil seals, power steering oil seals, air conditioning seals, rocker cover gaskets, Examples thereof include an oil filter seal ring, an oil pan packing, a head cover packing, and a cylinder liner packing.

Now, operations and effects of the present embodiment will be described together below.
The thermoplastic elastomer composition is a raw material composition comprising an acrylic rubber as component (A), a thermoplastic polyester resin as component (B), a graft copolymer as component (C), and a plasticizer as component (D). It is prepared by dynamic crosslinking with a crosslinking agent. The resulting thermoplastic elastomer composition has a structure in which the component (B) thermoplastic polyester resin serves as a matrix, and the component (A) acrylic rubber is finely dispersed in the matrix.

  Furthermore, the component (C) graft copolymer exists so as to be compatible (affinity) with the component (A) and the component (B), and each component is stably held in that state. Therefore, it is presumed that the function of the component (A) and the function of the component (B) are fully expressed, and that their effects are enhanced by synergism. The sealing material obtained from the thermoplastic elastomer composition can exhibit excellent heat resistance, oil resistance and compression set at a high temperature of 150 ° C. or higher (for example, 150 to 180 ° C.). Moreover, although the acrylic rubber is crosslinked, the elastomer composition has excellent moldability and flexibility because it has thermoplasticity.

  -When the said component (D) plasticizer is trimellitic acid ester or polyester, these plasticizers can show heat resistance, and can express a favorable plasticization effect. Therefore, the moldability, flexibility and oil resistance can be further improved while maintaining the heat resistance of the sealing material.

-The above sealing material can be used suitably for the sealing material for motor vehicles, and the above-mentioned effect can be exhibited in those uses.
In addition, by heating the sealing material, the thermoplastic polyester resin of the component (B) constituting the matrix is melted and can be molded again, thereby exhibiting recyclability. For example, scrap generated in the manufacturing process of sealing materials using thermoplastic elastomer compositions and products after use can be easily reprocessed using conventional molding methods and molding equipment, and are excellent in recyclability. ing.

Hereinafter, although the embodiment will be described more specifically with reference to examples and comparative examples, the present invention is not limited to these 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, a thermometer, a cooler, a dropping device and a nitrogen gas inlet tube was charged with 1000 g of ion-exchanged water, 10 g of sodium dodecyl sulfate, 0.5 g of sodium hydrogen sulfite, 0.005 g of ferrous sulfate, and sodium ethylenediaminetetraacetate 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) which contains 4 mass% of GMA. This acrylic rubber (A-1) had a glass transition temperature (Tg) of -27 ° C.

[Synthesis Example 2, Production of Acrylic Rubber (A-2)]
4% by mass of GMA is contained 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)]
GMA was prepared 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% 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% by weight of GMA is contained 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.

[Synthesis Example 5, production of grafted 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. 700 g of ethylene-ethyl acrylate copolymer (trade name: NUC6570, 75 parts by mass of ethylene, 25 parts by mass of ethyl acrylate, manufactured by Nihon Unicar Co., Ltd.) was added to this and stirred and dispersed. As a polymerization initiator, 2 g of benzoyl peroxide (trade name: Nyper BW, manufactured by NOF Corporation), 6 g of tert-butylperoxymethacryloyloxyethyl carbonate, and a vinyl monomer mixture (acrylic acid-n-butyl) A monomer mixture consisting of 300 g) of 150 g and 150 g of 2-hydroxypropyl methacrylate was charged into the autoclave.

  Next, the autoclave was heated to 60 to 65 ° C. and stirred for 2 hours to impregnate the ethylene-vinyl acetate copolymer with the polymerization initiator, the radical polymerizable organic peroxide and the vinyl monomer. . 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 multilayer 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 Graft Copolymer (C-2))
A grafting precursor 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 n-butyl acrylate, 100 g of glycidyl methacrylate and 50 g of styrene. The obtained grafting precursor was a multilayer structure in which true spherical resins having an average particle size of 0.3 to 0.5 μm were uniformly dispersed. The grafted precursor (C-2) was obtained by extruding this grafted precursor by a Laboplast mill single screw extruder (Toyo Seiki Seisakusho Co., Ltd.) at 180 ° C. and a rotation speed of 100 rpm to cause a grafting reaction. . This graft copolymer was a multilayer structure in which a true spherical resin having an average particle size of 0.3 to 0.4 μm was uniformly dispersed.

[Synthesis Example 7 (Production of Grafting Precursor (C-3))
A grafting precursor was obtained in the same manner as in Synthesis Example 5 except that the olefin copolymer segment was changed to polyethylene (trade name: Sumikasen G401, manufactured by Sumitomo Chemical Co., Ltd.). The obtained grafting precursor was a multilayer structure in which true spherical resins having an average particle size of 0.3 to 0.5 μm were uniformly dispersed.

[Synthesis Example 8 (Production of Grafting Precursor (C-4))
A grafted precursor 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 was a multilayer structure in which a true spherical resin having an average particle size of 0.5 to 0.6 μm was uniformly dispersed.

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 2002 (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-S (Adipic acid polyester, manufactured by Dainippon Ink & Chemicals, Inc.)
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), non-flex DCD (amine-based antioxidant, manufactured by Seiko Chemical Co., Ltd.)

[Evaluation of thermoplastic elastomer composition]
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 240 ° 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.
(Compression set)
In accordance with JIS K 6262, compression set (%) after 22 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.

[Example 1]
65 parts by mass of acrylic rubber A-1 of Synthesis Example 1, 35 parts by mass of Duranex 600JP, 5 parts by mass of grafted precursor C-1 of Synthesis Example 5, 23 parts by mass of Adekasizer C8, Irganox 1010 Were added to a pressure kneader heated to 250 ° C. at a ratio of 0.5 part by mass and 1 part by mass of non-flex DCD. Then, melt kneading was performed at a rotational speed of 42 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 weight 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 a kneader, put into a kneader ruder, extruded into a strand at 230 ° C., cooled and cut to obtain pellets of a thermoplastic elastomer composition. Using this, the pellets were molded from a pellet into a 2 mm-thick sealing material sheet with a 240 ° C. hot press, and the various evaluations described above were performed. Table 1 shows the composition and evaluation results of the thermoplastic elastomer composition.
Further, a sealing material was obtained by punching the sheet into an annular shape having an outer diameter of 115 mm and an inner diameter of 95 mm.

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

Example 8
An O-ring having an outer diameter of 70 mm and an inner diameter of 59 mm was molded from the pellets of the thermoplastic elastomer composition obtained in Example 2 using an injection molding machine (Nissei Plastic Industry Co., Ltd.) at a molding temperature of 260 ° C. The obtained O-ring was flexible and excellent in appearance.

[Comparative Examples 1 to 10]
A thermoplastic elastomer composition and a sealing material were produced in the same manner as in Example 1 at the blending ratio shown in Table 2. Table 2 shows the blending ratio of each component and the results of various evaluations.

(Summary)
As shown in Table 1, in Examples 1 and 2, sealing materials having different hardnesses could be obtained depending on the blending ratio of various materials. These sealing materials had excellent heat resistance, oil resistance and compression set at a high temperature of 150 ° C. In Example 3, as a result of changing the types of the acrylic rubber and the plasticizer in Example 1, the heat resistance, oil resistance, and compression set were all good as in Example 1. In Example 4, as a result of changing the types of acrylic rubber, thermoplastic polyester resin and plasticizer in Example 2, the heat resistance, oil resistance and compression set were all good as in Example 2.

  In Example 5, as a result of changing the type of the graft copolymer in Example 3, the heat resistance, oil resistance, and compression set were all good as in Example 3. In Example 6, as a result of increasing the contents of the graft copolymer and the plasticizer in Example 3, the heat resistance, oil resistance, and compression set were all good as in Example 3. In Example 7, as a result of changing the types and contents of acrylic rubber, thermoplastic polyester resin, and plasticizer in Example 3, the heat resistance, oil resistance, and compression set were all good as in Example 3. It was.

  As shown in Table 2, when the amount of GMA in the acrylic rubber is too small (0.3% by mass) in the monomer mixture (Comparative Example 1), the tensile strength and compression set are inferior. It was. When the amount of GMA in the acrylic rubber is an excess amount of 16% by mass in the monomer mixture (Comparative Example 2), the molding processability is poor and the evaluation sealing material sheet is cracked, and various evaluations are made. Could not do.

When the blending amount of the acrylic rubber was made too small and at the same time the blending amount of the thermoplastic polyester resin was made excessive (Comparative Example 3), the hardness was remarkably increased even in a region where the sealing material could not be used. When the blending amount of the acrylic rubber was excessive and the blending amount of the thermoplastic polyester resin was too small (Comparative Example 4), the molding processability was inferior as in Comparative Example 2. 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 a decrease in the oil resistance of the sealing material.
When the polar monomer is not contained in the olefin copolymer segment of the grafting precursor (Comparative Example 5) or when the acrylic ester is not contained in the vinyl copolymer segment (Comparative Example 6), The compatibility between the acrylic rubber and the thermoplastic polyester was lowered, and the tensile strength, elongation and compression set of the sealing material were lowered.

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 cross-linking agent was too small (Comparative Example 9), the cross-linking was insufficient, and the tensile strength and compression set were inferior. When the blending amount of the crosslinking agent was excessive (Comparative Example 10), the crosslinking of the acrylic rubber proceeded excessively, resulting in poor molding processability, and the evaluation sealing material sheet could not be produced.
The sealing material obtained by the present invention is not only excellent in heat aging resistance and oil resistance at high temperatures (150 ° C.), but also clearly has good compression set at high temperatures, particularly automobile parts and industrial parts. It can be used as such.

It should be noted that the present embodiment can be implemented with the following modifications.
-According to the purpose, each component of component (A) acrylic rubber, component (B) thermoplastic polyester resin, and component (C) graft copolymer is blended in appropriate combination, and a thermoplastic elastomer composition The sealing material formed from can be prepared.
Furthermore, the technical idea grasped from the embodiment will be described below.
The sealing material according to claim 1 or 2, wherein the crosslinking 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 sealing material can be improved.

The sealing material according to claim 1 or 2, wherein the raw material composition contains an antioxidant. When comprised in this way, the oxidation deterioration of a sealing material 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 component (A) acrylic rubber has 2 to 4 carbon atoms in the alkyl group, and the acrylic acid alkoxyalkyl ester has 2 to 4 carbon atoms in the alkyl group. The sealing material according to claim 1 or 2. 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 the sealing material formed from a thermoplastic elastomer composition can be improved.

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

Claims (3)

A raw material composition composed of the following component (A), component (B), component (C), component (D), component (E) and component (F) is added to a composition of 0.000 per 100 parts by mass of component (A). Sealing material molded in a temperature range from the melting point of the thermoplastic polyester resin to the decomposition start temperature of the acrylic rubber, using a thermoplastic elastomer composition obtained by dynamically cross-linking by adding 5 to 5 parts by mass of a crosslinking agent .
Component (A): Acrylic rubber formed by copolymerizing a monomer mixture containing an acrylic ester as a main component and containing an epoxy group-containing monomer in an amount of 0.5 to 15% by mass, comprises component (A) and component (B). ) In a total of 100 parts by mass, 50 to 85 parts by mass.
Component (B): 15 to 50 parts by mass of the thermoplastic polyester resin in a total of 100 parts by mass of component (A) and component (B).
Component (C): an olefin copolymer segment formed from ethylene and a polar monomer, and a vinyl copolymer segment formed from a vinyl monomer mixture containing an acrylate ester, 1 to 35 parts by mass per 100 parts by mass in total of the component (A) and the component (B) of the graft copolymer or the precursor thereof in which the segment forms a dispersed phase in the matrix phase formed by the other segment .
Component (D): The plasticizer is 60 parts by mass or less per 100 parts by mass of the component (A).
Component (E): One or more other additives selected from the group consisting of antioxidants, ultraviolet stabilizers, processing aids, colorants and pigments are 5 parts by mass or less per 100 parts by mass of component (A).
Component (F): One or more other additives selected from the group consisting of fillers and flame retardants are 70 parts by mass or less per 100 parts by mass in total of component (A), component (B) and component (C). The sealing material according to claim 1, wherein the component (D) is trimellitic acid esters or polyesters. A method for producing a sealing material, wherein the thermoplastic elastomer composition according to claim 1 or 2 is molded by an injection molding method, an extrusion molding method or a press molding method.