JP2000351889A - Thermoplastic elastomer composition and joint boot made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermoplastic elastomer composition which has improved softness and compression set and has good low-temperature properties without detriment to its inherent mechanical properties and resistances to heat and oil by compounding a composition containing a thermoplastic copolyester elastomer with a specified amount of a composition containing an acrylic rubber. SOLUTION: A composition containing a thermoplastic copolyester elastomer (A) in an amount of 30-90 pts.wt. is compounded with 10-70 pts.wt. composition containing an acrylic rubber (B). Ingredient A used contains high-melting-point crystalline polymer hard segments containing crystalline aromatic polyester and low-melting-point polymer soft segments containing aliphatic polyester units and/or aromatic polyester units containing aliphatic polyester, and the molar ratio of polyol residues of the hard segments to that of the soft segments is 1/(1.5 or higher but lower than 4.0). Ingredient B used contains at least 25 wt.% units derived from an alkyl acrylate having a 3-18C alkyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to joint boots having improved flexibility, compression set and low-temperature properties without impairing the excellent mechanical properties, heat resistance and oil resistance of a thermoplastic elastomer composition. Regarding a joint boot made of a thermoplastic elastomer composition, more specifically,
For example, the present invention relates to a thermoplastic elastomer composition for joint boots which is preferably used for a constant velocity joint of an automobile.

[0002]

2. Description of the Related Art Bellows-shaped joint boots are mounted on joints of automobiles and industrial machines in order to hold grease sealed therein or to prevent dust and the like. Conventionally, such a joint boot has been made of rubber such as chloroprene rubber (CR). However, in recent years, it has become desirable to reduce the weight of automobiles, and by using a thermoplastic copolyester elastomer that is higher in strength than rubber, the thickness of joint boots has been reduced to reduce the weight of joint boots. I have.

[0003] However, since the thermoplastic copolyester elastomer has a large compression set, it is necessary to increase the tightening force of the metal fittings of the joint portion, and since it is a hard resin, it is not flexible and the mounting of the joint boot is not easy. Also, since the yield elongation is small, if the number of bellows on the boots is increased so that the boots have elasticity, the mold releasability from the mold is deteriorated at the time of molding the joint boots, and abnormal noise due to the contact of the bellows is generated. was there.

[0004] In order to solve these problems,
JP-A-5-125263, JP-A-6-14547
No. 7, JP-A-7-97507 proposes a thermoplastic copolyester elastomer composition in which a rubber composition is mixed with a thermoplastic copolyester elastomer. However, these thermoplastic copolyester elastomer compositions cannot be said to have sufficient flexibility and durability required for joint boots, and require further improvement.

[0005]

Accordingly, the present invention solves the problems of flexibility and compression set without deteriorating the mechanical properties, heat resistance and oil resistance of a thermoplastic elastomer composition, and provides good low-temperature properties. It is an object to provide a thermoplastic elastomer composition for joint boots.

[0006]

According to a first aspect of the present invention, there is provided:
(I) at least an acrylic thermoplastic resin composition 30 to 90 parts by weight containing one thermoplastic copolyester elastomer and (ii) acrylic acid and the alkyl component contains an alkyl ester portion of the C ₃ -C ₁₈ 25% by weight or more A thermoplastic composition comprising 10 to 70 parts by weight of a rubber composition containing a rubber, wherein the thermoplastic copolyester elastomer (i) comprises a high-melting crystalline polymer hard segment containing a crystalline aromatic polyester, and an aromatic containing an aliphatic polyether. A low-melting-point polymer soft segment containing an aromatic and / or aliphatic polyester unit (as a main constituent), and the molar ratio of the polyol residue of the hard segment to the polyol residue of the soft segment is: 1: 1.
5 or more and less than 4.0 (hereinafter referred to as thermoplastic elastomer composition 1).
Also referred to as).

A second aspect of the present invention is to provide a rubber composition containing (i) a thermoplastic resin composition containing at least one thermoplastic copolyester elastomer in an amount of 30 to 90 parts by weight and (ii) an ethylene component-containing rubber. 70 parts by weight,
The thermoplastic copolyester elastomer (i) comprises a high-melting crystalline polymer hard segment containing a crystalline aromatic polyester and a low-melting polymer containing an aromatic and / or aliphatic polyester unit containing an aliphatic polyether. A thermoplastic elastomer composition containing a combined soft segment and a molar ratio of the polyol residue of the hard segment to the polyol residue of the soft segment being 1: 1.5 or more and less than 4.0. (Hereinafter, also referred to as thermoplastic elastomer composition 2).

[0008] In the first or second embodiment of the present invention,
A thermoplastic elastomer composition in which at least a part of a rubber component in the rubber composition is crosslinked and dispersed as a dispersed phase in a matrix phase of a thermoplastic resin composition containing a thermoplastic copolyester elastomer is preferable. Further, the thermoplastic elastomer composition of the first or second embodiment of the present invention is preferably a thermoplastic elastomer composition further containing 0.5 to 20 parts by weight of a slidability imparting agent.

In the second embodiment of the present invention, it is preferable that the rubber composition containing a rubber containing an ethylene component contains at least 50% by weight of a rubber component having a glass transition point at -25 ° C. or less. In the first or second embodiment of the present invention, when the rubber composition is crosslinked, a thermoplastic elastomer composition crosslinked with a crosslinking agent other than an organic peroxide is preferred.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The thermoplastic elastomer composition for a joint boot according to the present invention comprises a thermoplastic resin composition containing a thermoplastic copolyester elastomer in an amount sufficient to provide thermoplasticity, and a rubbery elasticity. At least in part, comprises a blend with a rubber composition containing a vulcanized acrylic rubber or a rubber containing an ethylene component, wherein the thermoplastic copolyester elastomer component forms a continuous phase (matrix phase), wherein It refers to the presence of at least partially vulcanized acrylic rubber or ethylene component-containing rubber as a discontinuous phase (dispersed phase). In addition, what is called a salami structure in which a thermoplastic resin is further dispersed in the discontinuous phase (rubber phase) may be used.

FIG. 1 shows the shape of a general resin boot. Currently, the commercially available joint boot material is a single thermoplastic copolyester elastomer.
The strength of the thermoplastic copolyester elastomer alone
Although there is elongation, since the yield elongation is smaller than that of rubber, in order to use the material within the yield elongation range, measures such as increasing the number of bellows from the aspect of structural design and making the peaks 1 and valleys 2 deeper have been taken. It has come to have the bellows part 3 shown in FIG. When the thermoplastic elastomer composition comprising the thermoplastic resin composition containing the thermoplastic copolyester elastomer of the present invention and the rubber composition containing the acrylic rubber or the rubber containing an ethylene component is used as a joint boot material, it is compared with the current material. As a result, the number of peaks can be reduced and the height of the peaks can be reduced as compared with the current joint boot shape. Thereby, abnormal noise due to contact between the peaks can be reduced. Further, since the thermoplastic elastomer composition of the present invention is also excellent in compression set properties, by changing the fastening fitting between the boot and the shaft to a simple one, weight reduction and cost reduction can be achieved, and flexible. Therefore, attachment can be easily performed.

First, a first embodiment of the present invention will be described. Hereinafter, the thermoplastic elastomer composition 1 of the present invention will be described.
Will be described. The thermoplastic copolyester elastomer contained in the thermoplastic resin composition (i), which is the first component of the thermoplastic elastomer composition 1 of the present invention, is a multi-block copolymer having a polyester and a polyether as main repeating units. In the present invention, a high melting point crystalline polymer hard segment containing a crystalline aromatic polyester and a low melting point weight containing an aromatic and / or aliphatic polyester unit containing an aliphatic polyether are used. And a combined soft segment. The thermoplastic copolyester elastomer of the thermoplastic elastomer composition 1 of the present invention is a multi-block copolymer having a polyester and a polyether as main repeating units, and is a high-melting crystalline polymer containing a crystalline aromatic polyester. A low-melting polymer soft segment containing an aromatic and / or aliphatic polyester unit containing an aliphatic polyether; and a polyol residue of the hard segment and a polyol residue of the soft segment. Is 1: 1.5 or more and less than 4.0.

The high-melting crystalline polymer hard segment containing a crystalline aromatic polyester of the thermoplastic copolyester elastomer used in the present invention is mainly composed of an aromatic dicarboxylic acid or an ester-forming derivative thereof, and a diol or an ester-forming derivative thereof. It is a polyester formed from a sex derivative. As aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-
Dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid, 4,4 ′
-Diphenyl ether dicarboxylic acid, 5-sulfoisophthalic acid, sodium 3-sulfoisophthalate and the like. Although an aromatic dicarboxylic acid is mainly used, if necessary, a part of the aromatic dicarboxylic acid is replaced with 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid,
It may be substituted with an alicyclic dicarboxylic acid such as 4,4'-dicyclohexyldicarboxylic acid or an aliphatic dicarboxylic acid such as adipic acid, succinic acid, oxalic acid, sebacic acid, decanedicarboxylic acid, or dimer acid. Of course, ester-forming derivatives of dicarboxylic acids, for example, lower alkyl esters, aryl esters, carbonates, acid halides and the like can be equally used.

Examples of the diol include diols having a molecular weight of 400 or less, for example, aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, decamethylene glycol, and the like. Alicyclic diols such as 1,1-cyclohexanedimethanol, 1,4-dicyclohexanedimethanol, tricyclodecanedimethanol, xylylene glycol,
Bis (p-hydroxy) diphenyl, bis (p-hydroxyphenyl) propane, 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane, bis [4-
(2-hydroxy) phenyl] sulfone, 1,1-bis [4- (2-hydroxyethoxy) phenyl] cyclohexane, 4,4′-dihydroxy-p-terphenyl,
Aromatic diols such as 4,4'-dihydroxy-p-quarterphenyl are preferred, and such diols can also be used in the form of an ester-forming derivative, for example, an acetyl form or an alkali metal salt. These dicarboxylic acids and their derivatives or diol components may be used in combination of two or more. And the most preferred example of the high melting crystalline polymer segment is terephthalic acid and / or polybutylene terephthalate derived from dimethyl terephthalate and 1,4-butanediol.

The low-melting-point polymer soft segment constituting the thermoplastic copolyester elastomer of the present invention contains aromatic and / or aliphatic polyester units containing an aliphatic polyether. Examples of the aliphatic polyether include poly (ethylene oxide) glycol, poly (propylene oxide) glycol, poly (tetramethylene oxide) glycol, poly (hexamethylene oxide) glycol, a copolymer of ethylene oxide and propylene oxide, and poly (propylene oxide). Examples include an ethylene oxide addition polymer of glycol, and a copolymer of ethylene oxide and tetrahydrofuran. By containing such an aliphatic polyether, it is possible to impart rubber elasticity to the thermoplastic copolyester elastomer,
Flexibility can be improved without impairing the mechanical properties of the thermoplastic elastomer composition.

Examples of the aromatic polyester include the same as the above-described crystalline aromatic polyester of the high-melting crystalline polymer hard segment. Further, as the aliphatic polyester, poly (ε-caprolactone), polyenantholactone, polycaprylolactone,
And polybutylene adipate. Among those containing aromatic and / or aliphatic polyester units containing these aliphatic polyethers, poly (tetramethylene oxide) glycol and poly (propylene oxide) glycol are considered from the elastic properties of the obtained polyester block copolymer. Ethylene oxide adduct, poly (ε-
Caprolactone), polybutylene adipate and the like are preferred.

The copolymerization amount of the low-melting-point polymer soft segment in the thermoplastic copolyester elastomer used in the present invention is determined by the molar ratio of the polyol residue of the hard segment to the polyol residue of the soft segment.
1: 1.5 or more and less than 4.0, preferably 1: 1.6 to
3.5. If the soft segment ratio is less than 1: 1.5, the effect of improving flexibility cannot be obtained. If the soft segment ratio is 1: 4.0 or more, physical properties such as mechanical strength are reduced and durability of the joint boot is deteriorated. . Further, the thermoplastic resin composition (i) containing at least one thermoplastic copolyester elastomer may contain a thermoplastic resin other than the thermoplastic copolyester elastomer, as appropriate. It is preferred that the content be 50% by weight or more.

The acrylic rubber used in the rubber composition (ii), which is the second component of the thermoplastic elastomer composition 1 of the present invention, contains acrylic acid and 25 alkyl ester moieties having a C ₃ -C ₁₈ alkyl moiety. Examples of the crosslinkable rubber containing at least% by weight include a copolymer rubber with polyacrylonitrile containing acrylate and / or methacrylate as a copolymerization component. The (meth) acrylate copolymer includes (1) an alkyl (meth) acrylate and / or an alkoxy-substituted alkyl (meth) acrylate, and other copolymerizable ethylenically unsaturated monomers as required. Is a multi-component copolymer rubber obtained by polymerizing The acrylic acid and the alkyl component make up at least 25% by weight, preferably 40 to 60% by weight of the C _{3 to} C ₁₈ alkyl ester moiety.
The low-temperature properties of the thermoplastic elastomer composition can be improved by containing the same by weight.

In the acrylic rubber of the present invention, a crosslinkable rubber having an acrylic group and an epoxy group as a main chain or a side chain in a molecule can be used. For example, acrylate and / or methacrylate containing an epoxy group can be used together. Copolymer rubber containing as a polymerization component can be mentioned.
The epoxy group-containing (meth) acrylate copolymer or the epoxy group-containing (meth) acrylate copolymer rubber used in the present invention can be obtained by using the above-mentioned (1) alkyl (meth) acrylate and / or (meth) acrylic acid. It is obtained by polymerizing an alkoxy-substituted alkyl ester, (2) an epoxy group-containing monomer, and, if necessary, (3) another ethylenically unsaturated monomer copolymerizable with these (1) and (2). It is a multi-component copolymer rubber.

The alkyl (meth) acrylate (1) used in the production of the (meth) acrylate copolymer rubber has the following formula:

[0021]

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(Wherein R ₁ is an alkyl group having 1 to 18 carbon atoms, and R ₂ represents hydrogen or a methyl group). Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and n- Pentyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-methylpentyl (meth) acrylate, n-octyl (meth) acrylate, 2-
Ethylhexyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, n-octadecyl (meth) acrylate, and the like, among which ethyl (meth) acrylate, n-propyl (meth) acrylate, Preferred are n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-octyl (meth) acrylate.

The alkoxy-substituted alkyl (meth) acrylate (1) has the following formula:

[0024]

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Wherein R ₃ is hydrogen or a methyl group, R ₄ is an alkylene group having 1 to 18 carbon atoms, and R ₅ is a hydrogen or methyl group.
Represents an alkyl group). Specific examples of the alkoxy-substituted alkyl (meth) acrylate include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2- (n-propoxy) ethyl (meth) acrylate, 2- ( n-butoxy) ethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 2- (n-propoxy) propyl (meth) acrylate, 2- (n-butoxy) propyl ( (Meth) acrylate and the like. R ₁ , R ₄ or R ₅ in the alkyl (meth) acrylate and the alkoxy-substituted alkyl (meth) acrylate is C ₃
It is necessary that the acrylic rubber contains at least 25% by weight of an alkyl ester moiety of ~ ₁₈ .

Examples of the epoxy group-containing monomer used for producing the epoxy group-containing (meth) acrylate copolymer rubber include allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, and the compounds shown below (in each formula). , Wherein R ₆ represents hydrogen or a methyl group).

[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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If necessary, the monomer to be copolymerized with the alkyl (meth) acrylate or the alkoxy-substituted alkyl (meth) acrylate (1) and the monomer containing an epoxy group may be 2-cyanoethyl (meth) A) cyano-substituted alkyl (meth) acrylates such as acrylate, 3-cyanopropyl (meth) acrylate and 4-cyanobutyl (meth) acrylate; amino-substituted alkyl (meth) acrylates such as diethylaminoethyl (meth) acrylate; Fluorine-containing (meth) such as 1-trifluoroethyl (meth) acrylate
Acrylates, hydroxy-substituted alkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, alkyl vinyl ketones such as methyl vinyl ketone, vinyl or allyl ethers such as vinyl ethyl ether, allyl methyl ether, styrene, α-methyl styrene,
Examples include vinyl aromatic compounds such as chlorostyrene and vinyl toluene, vinyl nitriles such as acrylonitrile and methacrylonitrile, vinyl amides such as acrylamide, methacrylamide, and N-methylol acrylamide, and ethylene, propylene, and vinyl acetate. Acrylic rubber used in the present invention is preferably an acrylic rubber alkyl moiety and acrylic acid is from alkyl esters of C ₃ -C _18, such as butyl acrylate, propyl acrylate, dodecyl acrylate,
Hexadecyl acrylate is contained in an amount of 25% by weight or more, more preferably 30 to 60% by weight.

Specific components of the acrylic rubber include:
From the viewpoint of heat resistance, a copolymer rubber composed of ethyl acrylate alone as the alkyl (meth) acrylate or alkoxyalkyl (meth) acrylate and glycidyl methacrylate as the epoxy group-containing monomer is exemplified. From the viewpoint of properties, a copolymer rubber composed of ethyl acrylate, butyl acrylate and methoxyethyl acrylate as alkyl (meth) acrylate or alkoxyalkyl (meth) acrylate and glycidyl methacrylate as an epoxy group-containing monomer Are preferably exemplified. Further, in terms of the balance between heat resistance and cold resistance, it is preferable to select the type and amount of the alkyl (meth) acrylate or the alkoxyalkyl (meth) acrylate. In addition, the epoxy group-containing monomer component is used for the crosslinking reaction of the epoxy group in the crosslinking of the copolymer rubber, and is usually 1 to 20% by weight, preferably 1.5 to 15% by weight, more preferably , 2-1
The one containing 0% by weight is suitably used in the vulcanization reactivity dynamically performed during kneading of the thermoplastic elastomer composition of the present invention described later.

The thermoplastic elastomer composition 1 of the present invention
Can be obtained by mixing a thermoplastic resin composition (i) containing a thermoplastic copolyester elastomer and a rubber composition (ii) containing an acrylic rubber, with component (i): component (ii) = 30 to 90 parts by weight: 70 to 10 parts by weight. Parts by weight, preferably component (i): component (ii) = 30 to 80 parts by weight: 70 to 20 parts by weight. If the amount of the component (i) is too large, the flexibility is impaired, which is not preferable. If the amount is too small, the mechanical strength is reduced. It is not preferable to further increase the amount of the rubber composition because the rubber phase becomes a matrix phase and the fluidity at the time of extrusion or the like is impaired.

The rubber composition need not be crosslinked, but it is desirable that at least a part of the rubber composition is crosslinked in order to improve compression set characteristics, mechanical characteristics and oil resistance.
Examples of the crosslinking agent for the rubber composition include a crosslinking agent compound having at least one of a carboxyl group and a carboxylic anhydride group as a carboxyl group in the molecule, or an organic peroxide. Typical examples of such a crosslinking agent compound include, for example, the following compounds.

The crosslinking agent of the present invention is not particularly limited as long as it is a compound having two or more carboxyl groups and / or one or more carboxylic anhydride groups in the molecule. Preferably, aliphatic, cycloaliphatic and aromatic polycarboxylic acids, their (partial) carboxylic anhydrides, and (partial) esterified products of these compounds with (poly) alkylene glycols are used. As the crosslinking agent, those having a molecular weight of 5,000 or less are preferable.

Specific examples of the aliphatic polycarboxylic acid include:
Examples include succinic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, dodecenylsuccinic acid, and butanetetracarboxylic acid. Specific examples of the alicyclic polycarboxylic acid include cyclopentane dicarboxylic acid, cyclopentane tricarboxylic acid, cyclopentane tetracarboxylic acid, cyclohexane dicarboxylic acid, cyclohexane tricarboxylic acid, methyl cyclohexane dicarboxylic acid, tetrahydrophthalic acid, endomethylene tetrahydrophthalic acid And methylendomethylenetetrahydrophthalic acid.
Specific examples of the aromatic polycarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, and pyromellitic acid. Specific examples of (partial) carboxylic acid anhydrides include (partial) carboxylic acid anhydrides of these polycarboxylic acids. The preferred amount of the crosslinking agent compound is 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight, per 100 parts by weight of the rubber composition containing the acrylic rubber.

As the organic peroxide-based crosslinking agent,
Benzoyl peroxide, t-butyl hydroperoxide, 2,4-dichlorobenzoyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethylhexane-2, 5-
Di (peroxyl benzoate) and the like are exemplified. It is preferable that the amount is, for example, 1 to 15 parts by weight based on 100 parts by weight of rubber. The acrylic rubber dispersed phase is cross-linked by adding such a cross-linking agent compound, whereby the mechanical strength is improved, and the set resistance and the oil resistance are improved. However, the organic peroxide-based crosslinking agent decomposes the thermoplastic copolyester elastomer and deteriorates the physical properties. It is important to knead the mixture and reduce the chance of contact with the thermoplastic copolyester elastomer. Preferably, use of an aliphatic polycarboxylic acid is desirable.

Next, a second embodiment of the present invention will be described. In the second embodiment of the present invention, (i) the thermoplastic copolyester elastomer which is the first component of the thermoplastic elastomer composition 2 has the same meaning as described in the first embodiment.

The rubber composition (iii) containing a rubber containing an ethylene component, which is the second component of the thermoplastic elastomer composition 2 of the present invention, will be described below. The ethylene component-containing rubber of the present invention is a rubber containing an ethylene chain in its main chain, for example, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM),
Ethylene-acrylate copolymer rubber (AEM),
Examples include ethylene-vinyl acetate copolymer rubber (EVA), ethylene-ethyl acrylate copolymer rubber (EEA), chlorosulfonated polyethylene (CSM), and chlorinated polyethylene (CM).

The ethylene-acrylate copolymer rubber (AEM) is a rubber obtained by radical copolymerization of ethylene and an alkyl acrylate, and has a good heat resistance, a good balance of oil resistance, and a main chain. It has excellent low temperature characteristics by containing an ethylene chain. Examples of the alkyl acrylate include those exemplified for the alkyl (meth) acrylate (1) used in the aforementioned (meth) acrylate copolymer rubber. Among these,
Preferred are methyl acrylate, ethyl acrylate and methyl methacrylate. As the ethylene-acrylate copolymer rubber (AEM), preferably, ethylene-methyl acrylate copolymer rubber (EMA), ethylene-ethyl acrylate copolymer rubber (EEA), and ethylene-methyl methacrylate copolymer rubber (EMMA). The ethylene content in the ethylene acrylic acid copolymer rubber is preferably from 10 to 85 mol%, and from 50 to 70 mol%.
A range of 1% is more preferred. If it is less than 10 mol%, the flexibility at low temperature is inferior, and if it exceeds 85 mol%,
This is because oil resistance and grease resistance deteriorate. Such ethylene-acrylate copolymer rubber (AEM)
As, VamacD manufactured by DuPont-Mitsui Polychemicals Co., Ltd. obtained by copolymerizing ethylene and methyl acrylate,
VamacDLS.

Further, the ethylene-acrylate copolymer rubber (AEM) is preferably a multi-component copolymer obtained by copolymerizing ethylene and an alkyl acrylate with a crosslinking monomer. Examples of the crosslinkable monomer include those containing an epoxy group or a carboxyl group. This is because the use of such a crosslinkable monomer has the effect of strengthening the interface between the thermoplastic copolyester elastomer (i) forming the continuous phase and the ethylene-containing rubber. The crosslinkable monomer is preferably from 0.05 to 5 mol%, more preferably from 0.1 to 3 mol%, based on the sum of the moles of ethylene acrylate and the other alkyl ester of acrylic acid.

The ethylene-acrylate copolymer rubber (AEM) obtained by copolymerizing a crosslinkable monomer containing an epoxy group includes, for example, a copolymer of an epoxy group-containing crosslinkable monomer, ethylene, and methyl acrylate. Esprene E manufactured by Sumitomo Chemical Co., Ltd. obtained by polymerization
MA2752 (trade name). Further, as the ethylene-acrylate copolymer rubber obtained by copolymerizing a crosslinkable monomer having a carboxyl group, Mitsui obtained by copolymerizing a crosslinkable monomer having a carboxyl group, ethylene, and methyl acrylate Vamac G (trade name) manufactured by Dupont Polychemicals, Bomac L
S (product name).

Ethylene-vinyl acetate copolymer rubber (EV
M) is a rubber obtained by subjecting ethylene and vinyl acetate to radical polymerization at high temperature and high pressure, and has excellent heat aging resistance.
The ethylene content of the ethylene-vinyl acetate copolymer rubber is 6
The range is preferably 5 to 95 mol%, more preferably 80 to 90 mol%. If it is less than 65 mol%, flexibility at low temperature is lacking, and if it exceeds 95 mol%, oil resistance and grease resistance are poor.

The ethylene-propylene-diene copolymer rubber (EPDM) is a copolymer rubber composed of ethylene, propylene and diene. Propylene content is 10 ~
It is preferably 70 mol%, and 15 to 50 mol%
Is more preferable. The diene component is, for example, ethylidene norbornene, dicyclopentadiene, 1,4-
Hexadiene is mentioned. Among them, ethylidene norbornene having a high crosslinking rate is preferable. The amount of the diene component is
The iodine value is preferably from 3 to 25, and more preferably from 5 to 20.

Among them, ethylene-acrylate copolymer rubber (AEM), a multipolymer of ethylene-acrylate copolymer rubber (AEM) for copolymerizing the above-mentioned crosslinkable monomer, ethylene-vinyl acetate copolymer rubber (EVM), ethylene-propylene-diene copolymer rubber (EPDM) has strength, weather resistance, heat resistance, low-temperature properties,
It is preferable because it has excellent grease resistance. These may be used alone or in combination of two or more. Further, they can be used in combination with other rubber components. As the other rubber component, the above-mentioned acrylic rubber and acrylonitrile-butadiene rubber (NBR) are preferable. In this case, the rubber containing the ethylene component is preferably contained in a weight ratio of 50% by weight or more to the total rubber component, and It is more preferable that the content be not less than% by weight.

The rubber composition containing the ethylene component-containing rubber of the present invention preferably contains a rubber component having a glass transition point (Tg) at -25 ° C. or lower by 50% by weight or more, more preferably 60% by weight or more. If the rubber component is a single component,
The glass transition point is fixed to one. On the other hand, when the rubber composition is composed of a plurality of rubber components, a plurality of glass transition points are observed, and a glass transition point unique to each rubber component included in the composition appears. In the present invention, when using a plurality of rubber components in which a plurality of glass transition points are observed, -25 ° C
Below, a rubber component having a glass transition point is 50% in the composition.
It is preferably contained in an amount of at least 60 wt%, more preferably at least 60 wt%.

The thermoplastic elastomer composition 2 of the present invention
Converts a thermoplastic resin composition (i) containing a thermoplastic copolyester elastomer and a rubber composition (ii) containing a rubber containing an ethylene component into components (i): component (ii) = 30 to 90.
Parts by weight: 70 to 10 parts by weight, preferably 50 to 80 parts by weight of component (i): component (ii): 50 to 20 parts by weight. If the amount of component (i) is too large, the flexibility and compression set characteristics are impaired, which is not preferable. Conversely, if the amount is too small, the mechanical strength decreases. Oil resistance of the thermoplastic elastomer composition of the present invention is based on JIS K6258,
JIS No. After immersion in the three oils at 120 ° C. for 70 hours, the volume change rate is desirably 100% or less. It is not preferable to further increase the amount of the rubber composition because the rubber phase becomes a matrix phase and the fluidity at the time of extrusion or the like is impaired.

The rubber composition need not be crosslinked, but it is desirable that at least a part of the rubber composition is crosslinked in order to improve compression set characteristics, mechanical characteristics and oil resistance.
As the crosslinking agent (vulcanizing agent) for the rubber composition, a general rubber vulcanizing agent is used in addition to the same ones as those described for the thermoplastic elastomer composition 1.

Specific examples of the sulfur vulcanizing agent used as the rubber vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, alkylphenol disulfide and the like. Is exemplified. When this sulfur-based vulcanizing agent is used, the amount used is preferably, for example, 0.5 to 4 phr (parts by weight per 100 parts by weight of the rubber component, the same applies hereinafter).

Further, as a phenol resin-based vulcanizing agent, bromide of an alkylphenol resin, tin chloride,
A mixed crosslinking system containing a halogen donor such as chloroprene and an alkylphenol resin is exemplified. When this phenolic resin-based vulcanizing agent is used, the amount used is preferably, for example, an amount of 1 to 20 phr.

Other vulcanizing agents include zinc white (about 5 phr), magnesium oxide (about 4 phr), litharge (about 10 to 20 phr), p-quinone dioxime, p-dibenzoylquinone dioxime, Examples thereof include chloro-p-benzoquinone, poly-p-dinitrosobenzene (about 2 to 10 phr), and methylene dianiline (about 0.2 to 10 phr).

Further, a vulcanization accelerator may be added to the composition of the present invention, if necessary. As the vulcanization accelerator used, aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram,
A general vulcanization accelerator such as a dithionate salt or a thiourea may be used, for example, in an amount of about 0.5 to 2 phr.

As specific examples, the aldehyde / ammonia vulcanization accelerator includes hexamethylenetetramine;
Examples of the guanidine vulcanization accelerator include diphenylguanidine and the like; examples of the thiazole vulcanization accelerator include dibenzothiazyl disulfide (DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt and the like; Examples of the amide-based vulcanization accelerator include cyclohexylbenzothiazylsulfenamide (CB)
S), N-oxydiethylenebenzothiazyl-2-sulfenamide, Nt-butyl-2-benzothiazolesulfenamide, 2- (dimorpholinyldithio)
Benzothiazole and the like; tetramethylthiuram disulfide (TMT) as a thiuram-based vulcanization accelerator;
D), tetraethylthiuram disulfide, tetramethylthiuram monosulfide (TMTM), dipentamethylenethiuram tetrasulfide, and the like; as the dithioate-based vulcanization accelerator, Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn -Ji-
n-butyldithiocarbamate, Zn-ethylphenyldithiocarbamate, Tc-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate, pipecoline pipecolyldithiocarbamate, etc .; as thiourea-based vulcanization accelerators, Ethylenethiourea, diethylthiourea and the like; each disclosed. As a vulcanization accelerator, a general rubber auxiliary agent can be used in combination.
hr), stearic acid, oleic acid, and Zn salts thereof (about 2 to 4 phr) can be used.
Further, among the above-mentioned compounds, the organic peroxide-based crosslinking agent decomposes the thermoplastic copolyester elastomer, and therefore, it is preferable to use another crosslinking agent.

The thermoplastic elastomer composition 1 or 2 of the present invention may further contain a slidability imparting agent.
This slidability-imparting agent forms a surface layer having good lubricity by lowering the surface tension of the thermoplastic elastomer composition. As a result, it is possible to suppress abnormal noise and heat generated due to friction of the bellows portions of the joint boot. Specific examples of the slidability-imparting agent include silicone-based and fluorine-based agents, and those generally used as lubricants for resin materials. Specifically, dimethylpolysiloxane, dimethyltrimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, etc .; modified polysiloxane such as epoxy-modified, carboxy-modified, alcohol-modified; polytetrafluoroethylene, tetrafluoroethylene-
Perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-ethylene copolymer, polychlorotrifluoroethylene, Polyvinylidene fluoride,
Polyvinyl fluoride and the like. Examples of the lubricant include hydrocarbon waxes, higher fatty acids, fatty acid amides, fatty acid alcohol esters, and the like. These may be used alone or in combination of two or more. Further, an inorganic material may be used as the slidability imparting agent. Although the inorganic slidability imparting agent is not particularly limited, a surfactant such as an organosiloxane; ethylene tetrafluoride powder, molybdenum disulfide, graphite, spheroidal graphite, short fibers, and ultrafine fibers are preferably used.

The amount of the slidability-imparting agent is 0.5 parts by weight per 100 parts by weight of the thermoplastic resin elastomer composition 1 or 2.
To 20 parts by weight, preferably 1.0 to 5 parts by weight in consideration of the balance between the physical properties of the molded article and the sliding effect.
If the content of the slidability-imparting agent is less than 0.5 part by weight, the slidability will be insufficient, and if it exceeds 20 parts by weight, the physical properties of the joint boot will be reduced.

The thermoplastic elastomer composition 1 or 2 may be added with a reinforcing agent or a filler in order to improve fluidity, heat resistance, physical strength, cost, etc. within a range not to impair the object of the present invention. , A necessary amount of a compounding agent such as a softening agent, an anti-aging agent, and a processing aid, which is added to a usual composition.

When the specific thermoplastic resin and the rubber composition have different chemical compatibility, it is preferable to use a suitable compatibilizing agent as the third component to compatibilize the two.
By mixing the compatibilizer into the system, the interfacial tension between the thermoplastic resin and the rubber composition is reduced, and as a result, the particle diameter of the rubber composition forming the dispersion layer becomes fine, so that both components are dispersed. The properties will be more effectively expressed. As such a compatibilizer generally a thermoplastic resin component, a copolymer having a structure of both or one of the rubber components, or an epoxy group capable of reacting with the thermoplastic resin component or the rubber component,
The copolymer may have a structure having a carboxyl group, a carbonyl group, a halogen atom, an amino group, an oxazoline group, a hydroxyl group, and the like. These may be selected depending on the types of the thermoplastic resin component and the rubber component to be mixed, and commonly used ones include styrene-ethylene-butylene-styrene-based block copolymer (SEBS) and its maleic acid-modified product, EPDM, EPM and their maleic acid-modified products, EPDM / styrene or EPDM /
An acrylonitrile graft copolymer and its maleic acid-modified product, styrene / maleic acid copolymer, maleic acid or epoxy-modified ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate, reactive phenoxine, and the like can be given. The amount of such a compatibilizer is not particularly limited, but is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the polymer component (total of thermoplastic resin and rubber).

The method for producing the thermoplastic elastomer composition 1 or 2 used in the present invention is a method in which a thermoplastic resin component containing a thermoplastic copolyester elastomer and a rubber composition containing an acrylic rubber or a rubber containing an ethylene component are used in advance. Melt and kneaded with a kneading extruder etc., continuous phase (matrix phase)
By dispersing the rubber composition as a dispersed phase (domain) in a thermoplastic resin that forms Next, in order to vulcanize the rubber composition, a vulcanizing agent (including a vulcanization accelerator or a vulcanization accelerator) is added under kneading, and the rubber composition is dynamically vulcanized. Further, various compounding agents for the thermoplastic resin or the rubber composition may be added during the kneading, but it is preferable to mix them beforehand before the kneading. At this time, a vulcanizing agent may be mixed in the rubber composition in advance, and vulcanization may be simultaneously performed during kneading of the thermoplastic resin and the rubber composition. The kneading machine used for kneading the thermoplastic resin and the rubber composition is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a twin-screw kneading extruder and the like can be used. Among them, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the rubber composition and for dynamic vulcanization of the rubber composition. Further, two or more types of kneaders may be used to knead sequentially.

By utilizing such a production method, the obtained thermoplastic elastomer composition 1 or 2 is obtained by vulcanization wherein at least a part thereof becomes a thermoplastic resin phase which becomes a continuous phase and at least a part thereof becomes a discontinuous phase. Since the rubber phase is in a finely dispersed state, this thermoplastic elastomer composition shows the same behavior as the vulcanized rubber, and at least the continuous phase is a thermoplastic resin phase. Processing according to the plastic resin is possible.

Such a thermoplastic elastomer composition comprises at least a part of a thermoplastic resin as a continuous phase and at least a part of a rubber composition as a discontinuous phase, and comprises a vulcanized rubber composition which is a discontinuous phase. The particle diameter is preferably 20 μm or less, and more preferably 0.1 to 10 μm.

The kneading conditions and the type and amount of vulcanizing agent (including vulcanization accelerator or vulcanization accelerator) used, the vulcanization conditions (temperature, etc.) are determined by the type of rubber composition to be added, What is necessary is just to determine suitably according to the compounding quantity of a rubber composition, and it does not specifically limit.

The conditions for melt kneading are preferably, for example, a kneading temperature of 180 to 300 ° C., but there is no particular limitation as long as the temperature is equal to or higher than the melting temperature of the thermoplastic copolyester elastomer component. The shear rate during kneading is 50
0 to 8000 sec ^-1 , especially 500 to 5000 sec
It is preferably ^-1 . The residence time of the entire melt kneading is 3
The residence time (vulcanization time) after adding the vulcanizing agent is preferably from 0 seconds to 10 minutes and from 15 seconds to 5 minutes. Here, the residence time in the part where dynamic vulcanization is performed is calculated by multiplying the total volume of the part where dynamic vulcanization is performed by the filling factor and dividing the result by the volume flow rate.

It should be noted that the thermoplastic elastomer is produced by the above-mentioned method.
-When producing composition 1 or 2, use thermoplastic copolyester.
Thermoplastic resin composition containing terelastomer and acrylic
Viscosity during melt-kneading of rubber or ethylene component-containing rubber composition
Degree and volume fraction are related to each other, and the normal kneading temperature
180-300 ° C, shear rate 500-8000 sec ^-1
In the range, it is preferable to satisfy the relationship of the following formula. 0.25 ≦ φ₁≦ 0.90, preferably 0.30 ≦ φ₁
≦ 0.80 0.10 ≦ φ_Two≦ 0.75, preferably 0.20 ≦ φ_Two
≦ 0.70 φ₁+ Φ_Two= 1.0 η_Two/ Η₁<4.0, preferably <3.7 (η₁/ Η_Two) (Φ_Two/ Φ₁) <1.0 where η₁: Viscosity of the thermoplastic resin composition during melt-kneading η_Two： Viscosity of the rubber composition during melt-kneading φ₁: Volume fraction of thermoplastic resin composition φ_Two: Represents the volume fraction of the rubber composition. By kneading within the range of the above formula, the kneading property is
Stabilize, widely control the rubber ratio, preferably high rubber ratio
Heat that is flexible and has high elongation at break
A plastic elastomer composition can be obtained.

Here, the melt viscosity means an arbitrary temperature and the melt viscosity of the components during kneading, and the melt viscosity of each polymer material depends on the temperature, the shear rate (sec ⁻¹ ) and the shear stress. For this purpose, the stress and shear rate of the polymer material are generally measured at an arbitrary temperature in a molten state flowing in the thin tube, particularly at a temperature range during kneading, and the melt viscosity is measured by the following equation (1). The melt viscosity was measured using a capillary rheometer Capillograph 1C manufactured by Toyo Seiki Co., Ltd.

[0071]

(Equation 1)

The joint boot of the present invention is obtained by molding the above-mentioned thermoplastic elastomer composition of the present invention using a mold. As a molding method, extrusion molding, injection molding, or the like can be used, but it is preferable to use injection molding because crosslinking and molding can be performed simultaneously. The thickness of the joint boots is 0.6
To 1.5 mm, preferably 0.8 to 1.1 mm.
The shape is a flat cylindrical shape so that both ends can be attached to other parts such as a shaft, the center is a hollow housing,
The side surface has a bellows shape composed of two or more peaks. As in the conventional product shown in FIG. 1, both ends have relatively small openings at one end because they are attached to a small-diameter shaft, and relatively large openings at the other end because they are attached to a large-diameter shaft or other members. Have.

The molded joint boots are attached by covering the outer diameter of the shaft with both ends thereof and tightening the band with a band from above. For example, in the case of an automobile, the small mounting portion is fixed to the drive shaft with a band, and the large diameter mounting portion is fixed to the joint outer ring with a band. Rotational force from the drive shaft is transmitted to a wheel-side shaft via a constant velocity joint ball. Since the shaft on the wheel side is displaced relative to the drive shaft,
The change in the angle and the change in the angular velocity are absorbed by the joint boot, and the bellows portion of the boot expands and contracts accordingly. The band is usually made of metal, and the thickness of SUS or brass is 0.6 ~
It is 1.2 mm, preferably 0.8 to 1.0 mm, and has a structure that can be tightened with screws or a clamp structure having hooks and tunnels.

[0074]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited to the following Examples. <Preparation of Thermoplastic Copolyester Elastomer> The preparation of a thermoplastic copolyester elastomer is generally known, and can be synthesized, for example, by the method described in JP-B-49-31558. Dimethyl terephthalate, 1,4-butanediol, polytetramethylalene glycol (PTMG) were used as raw materials, and tetra-n-butyl titanate was used as a catalyst. The temperature was raised to 250 ° C. for 100 minutes while stirring them. . Thereafter, the pressure was gradually reduced to 0.1 mmHg for 10 minutes to carry out polycondensation. After reacting under reduced pressure for 120 minutes, the mixture was extruded into water. Further, it was extruded with a rubber pelletizer and pelletized. The resulting thermoplastic copolyester elastomer has a hard segment of terephthalic acid / 1,4-
The butanediol copolymer and the soft segment were terephthalic acid / tetramethylene glycol copolymer, and the molecular weight was 26,000. The molar ratio between the polyol residue of the hard segment and the polyol residue of the soft segment was adjusted by changing the amount of 1,4-butanediol and the molecular weight and amount of PTMG, and the obtained thermoplastic copolyester elastomer was obtained. The molar ratio of the polyol residues of 1 to 5 is shown in Table 1 below.

[0075]

[Table 1]

(Examples 1 to 8 and Comparative Examples 1 to 6) <Preparation of Thermoplastic Elastomer Composition 1> The acrylic rubber (ACM) shown in Table 2 was mixed at the blending amount (parts by weight) shown in Table 3 below. Pour into a Banbury mixer and set the initial temperature to 50
After kneading at 4 ° C. for 4 minutes, the mixture was released to prepare rubber compounds 1 to 3. Next, the rubber compound was pelletized with a rubber pelletizer. The obtained rubber compound, the previously produced thermoplastic copolyester elastomer, the compatibilizer, and the slidability-imparting agent were dry-blended at the weight ratios shown in Table 4 below, and were biaxially set at 230 ° C. and a shear rate of 1000 sec ^−1. It was introduced from the first inlet of the kneader. After the rubber component and the resin component were well kneaded, a crosslinking agent was charged from the second charging port to perform dynamic crosslinking, thereby producing a thermoplastic elastomer composition for joint boots. The obtained thermoplastic elastomer composition was pelletized, dried sufficiently, and then formed into a sheet having a thickness of 2 mm by injection molding at 240 ° C., and subjected to the following material property tests. The results are shown in Table 4 below.

JIS A (type A) hardness: JIS K
6253. Tensile strength (MPa), elongation at break (%): JISK62
51. After oil immersion, strength retention (%): In JIS No. 3 oil,
The tensile strength after immersion at 120 ° C. for 70 hours was measured, and the retention rate with respect to the initial state was shown. After immersion in grease, strength retention (%): After immersion in No. 2 grease at 120 ° C. for 70 hours, the tensile strength was measured, and the retention from the initial state was determined. Compression set (%): D according to JIS K6251
A sample having a predetermined shape was prepared under the same molding conditions as the hardness measurement sample, and the compression set (%) after 25% compression at 100 ° C. for 70 hours was measured. Low temperature embrittlement (-50 ° C): Based on JIS K6261,
The low-temperature embrittlement at −50 ° C. was evaluated. When the sample was not broken at −50 ° C., the sample was rated as ○, and when the sample was broken, ×.

[0078]

[Table 2]

[0079]

[Table 3]

Further, pellets of the thermoplastic elastomer composition obtained above were injection-molded using a boot mold to form a joint boot having a thickness of 1.0 mm. Further, a joint boot composed of only the thermoplastic polyester elastomer (Comparative Example 2) was molded in the same manner, and the following evaluation was performed. The results are shown in Table 4 below.

Boot assemblability: The workability when assembling the produced boots using a band was evaluated as follows. ○: Easy to tighten with bare hands, no problem in sealability △: Tightened with a crimping jig, no problem in sealability ×: Tightening with bare hands or crimping jigs impossible Boot durability test: Constant speed boots It was mounted on a joint, sealed with grease, and rotated at a working angle of 30 degrees and 1000 rpm (times / minute) for 300 hours. Looseness of metal fittings after durability test: After the above boot durability test,
も の indicates that the metal fitting did not loosen, and x indicates that the metal fitting loosened. Abnormal noise: In the above-mentioned boot durability test, ○ indicates that no abnormal noise was generated due to contact with the bellows portion, Δ indicates that a slight noise was generated, and X indicates that a large noise was generated.

[0082]

[Table 4]

[0083]

[Table 5]

In Comparative Example 1, there was a problem in the assemblability of the joint boot because the amount of the rubber composition was too small, and in Comparative Example 2, the amount of the rubber composition was too large and the thermoplastic copolyester elastomer and the rubber composition were mixed. The sea-island structure was reversed and biaxial kneading was not possible. In Comparative Example 3, since using the acrylic rubber acrylic acid and the alkyl component contains no C ₃ alkyl ester moiety -C ₁₈ or 25 wt%, cold resistance had decreased. Further, Comparative Example 4,
5 is a thermoplastic thermoplastic copolyester elastomer in which the molar ratio of the polyol segment of the hard segment to the soft segment is less than 1: 1.5 (the number of soft segments is small) and 1: 4 or more. : 1.5
If it is smaller, the assemblability of the joint boot is poor (Comparative Example 4), and if it is 1: 4 or more, the durability of the boot itself is inferior (Comparative Example 5). In Comparative Example 6, since only the thermoplastic copolyester elastomer containing no rubber was used, the hardness was too large and the assemblability of the joint boot was poor, and the compression set was large. I have. On the other hand, the compositions and the joint boots used in Examples 1 to 8 all obtained good results such as boot assemblability, low-temperature characteristics, and durability.

(Examples 9 to 19, Comparative Examples 7 to 13) Thermoplastic Elastomer Composition 2 An ethylene component-containing rubber having the composition shown in Table 6 was charged into a Banbury mixer and kneaded at an initial temperature of 50 ° C. for 4 minutes.
Release, rubber blends 4 to 12 were prepared, and the previously prepared thermoplastic copolyester elastomer, compatibilizer, and slidability imparting agent were dry-blended according to the blend shown in Table 6, and the same as thermoplastic elastomer composition 1. And subjected to dynamic crosslinking to produce a thermoplastic elastomer composition 2 for joint boots. The obtained thermoplastic elastomer composition 2 was subjected to a material property test in the same manner as in the thermoplastic elastomer composition 1. The glass transition temperatures of rubber compounds 4 to 12 and the strength retention after heat deterioration of Examples 9 to 19 and Comparative Examples 7 to 13 were evaluated as follows.

Glass transition temperature: About 1 for rubber compounding 4-10
0 mg was collected and measured at a heating rate of 2 ° C./min by DSC. After heat resistance deterioration, strength retention (%): After leaving in an oven at 120 ° C. for 70 hours, it was taken out, tensile strength was measured, and the retention with respect to the initial state was determined. The results are shown in Tables 7 and 8.

[0087]

[Table 6]

[0088]

[Table 7]

[0089]

[Table 8]

In Comparative Example 7, since the amount of the rubber composition was too small, the assemblability of the joint boot was poor, and the metal fittings became loose after the durability test. On the other hand, in Comparative Example 8, the amount of the rubber composition was too large to be kneaded. In Comparative Example 9, the hardness of the joint boot was large due to too few polyol residues of the soft segment relative to the hard segment of the thermoplastic elastomer 1, and the metal fittings became loose. In Comparative Example 10, the hardness of the joint boot was low due to too many polyol residues in the soft segment, and the durability was poor. In Comparative Example 11, when acrylonitrile-butadiene rubber (NBR) was used as the rubber component, the heat deterioration resistance was poor. Further, when hydrogenated NBR (HNBR) is used (Comparative Example 12), the low-temperature characteristics deteriorate. On the other hand, in all of the compositions of the examples, favorable results such as boot assemblability, low-temperature characteristics, and durability were obtained.

[0091]

As described above, according to the present invention,
By using a thermoplastic elastomer composition joint boot containing a specific thermoplastic copolyester elastomer and an acrylic rubber or a rubber containing an ethylene component,
The problems of flexibility and compression set can be solved and good low-temperature properties can be obtained without impairing the mechanical properties, heat resistance and oil resistance of the thermoplastic elastomer composition.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the shape of a general resin boot.

[Explanation of symbols]

 1 Mountains 2 Valleys 3 Bellows

Claims (7)

[Claims] (I) a thermoplastic resin composition containing at least one thermoplastic copolyester elastomer;
0 parts by weight and (ii) acrylic acid and the alkyl moiety is C ₃ ~
The thermoplastic copolyester elastomer (i), comprising 10 to 70 parts by weight of a rubber composition containing an acrylic rubber containing at least 25% by weight of a _C18 alkyl ester moiety;
Contains a high melting crystalline polymer hard segment containing a crystalline aromatic polyester, and a low melting polymer soft segment containing an aromatic and / or aliphatic polyester unit containing an aliphatic polyether, A thermoplastic elastomer composition, wherein the molar ratio between the polyol residue of the hard segment and the polyol residue of the soft segment is 1: 1.5 or more and less than 4.0. 2. A thermoplastic resin composition comprising (i) at least one thermoplastic copolyester elastomer.
0 parts by weight and (iii) 10 to 70 parts by weight of a rubber composition containing an ethylene component-containing rubber, wherein the thermoplastic copolyester elastomer (i) is a high-melting crystalline polymer hard containing a crystalline aromatic polyester. And a low-melting polymer soft segment containing an aromatic and / or aliphatic polyester unit containing an aliphatic polyether, and a mole of a polyol residue of the hard segment and a mole of a polyol residue of the soft segment. A thermoplastic elastomer composition having a ratio of 1: 1.5 or more and less than 4.0. 3. The rubber component in the rubber composition according to claim 1, wherein at least a part of the rubber component is cross-linked and dispersed as a dispersed phase in a matrix phase of the thermoplastic resin composition containing the thermoplastic copolyester elastomer. 3. The thermoplastic elastomer composition according to 2. 4. The thermoplastic elastomer composition according to claim 1, further comprising 0.5 to 20 parts by weight of a slidability imparting agent. 5. The thermoplastic composition according to claim 2, wherein the rubber composition (iii) containing the ethylene component-containing rubber contains at least 50% by weight of a rubber component having a glass transition point at -25 ° C. or lower. Elastomer composition. 6. The thermoplastic elastomer composition according to claim 3, wherein the rubber composition is crosslinked using a crosslinking agent other than an organic peroxide. 7. A joint boot comprising the thermoplastic elastomer composition according to claim 1.