JPH0710933A - Acrylic copolymer rubber and its composition - Google Patents

Abstract

PURPOSE:To obtain an acrylic copolymer rubber which has satisfactory resistance to both oil and cold and has high heat resistance. CONSTITUTION:This copolymer rubber is prepared by copolymerizing 5 to 40wt.% of (A) (meth)acrylic ester shown by the formula (1), CH2=CR<1>-COO-CH2 CH2-O[COR<2>O]nH, (R<1> is H or a methyl group; R<2> is a 3-20C alkylene group; (n) is a positive integer of 1 to 20), 10 to 90wt.% of (B-1) alkyl acrylate with a 1-20C alkyl group and/oralkoxy-substd. alkyl acrylate and 0 to 40wt.% of (B-2) other menomers copolymerizable with (A) and (B-1), and has a glass transition temp. (Tg) of below --30 deg.C and a Mooney viscosity (ML1+4, 100 deg.C) of higher than 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic copolymer rubber having excellent heat resistance, oil resistance and cold resistance for use in industrial materials.

[0002]

2. Description of the Related Art Conventionally, natural rubber, styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), butyl rubber (IIR), rubber as an industrial material mainly for automobile parts, Acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), ethylene-propylene-diene ternary copolymer rubber (EPDM) and acrylic rubber (ACM)
Are known. In particular, acrylic rubber has an excellent balance between heat resistance and cost, and the demand for improving the heat resistance of automobile rubber materials has been increasing in recent years, resulting in growing demand.

However, it is inferior in cold resistance to the conventionally used NBR, which is one of the drawbacks of the acrylic rubber. Generally, there is a method of using a low temperature plasticizer to improve the cold resistance of the rubber material. In this method, the plasticizer is almost extracted when immersed in engine oil etc. Will return to. Also,
The deterioration of heat resistance cannot be ignored.

In order to improve the cold resistance of acrylic rubber, the polymer composition and the composition are mainly changed. In order to improve the cold resistance of the acrylic rubber, a method of copolymerizing a monomer capable of lowering the glass transition point of the acrylic rubber with an acrylate ester is used. As the monomer, n-butyl acrylate or a combination of n-butyl acrylate and methoxyethyl acrylate is used. However, although the cold resistance is improved, the oil resistance and heat resistance are reduced.

As a method for improving cold resistance without impairing oil resistance and heat resistance, a (meth) acrylic acid ester of a monovalent saturated alcohol ε-caprolactone adduct is used as a component to be copolymerized with acrylic rubber. A method of copolymerization is known. As these methods, JP-A-63-63
JP-A No. 268717 discloses a method of copolymerizing with ethyl acrylate, and JP-A No. 160008 describes a method of copolymerizing with an acrylate ester and a crosslinkable monomer. In the description of Japanese Patent No. 264612 in 1988, a method of copolymerizing with an acrylic ester and vinyl chloroacetate is known. However, the method using a (meth) acrylic acid ester of an ε-caprolactone adduct of a monovalent saturated alcohol increases as the copolymerization amount increases,
Although the glass transition temperature is lowered, the physical properties at low temperature are deteriorated and the heat resistance and oil resistance are not satisfied.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and provides an acrylic copolymer rubber having satisfactory oil resistance and cold resistance at the same time and having good heat resistance. The purpose is to do.

[0007]

Means for Solving the Problems As a result of intensive studies for solving these objects, the present inventors have found that (A) general formula (1) CH ₂ ═CR ¹ —COO—CH ₂ CH ₂ —O [ COR ² O] _n
H (wherein R ¹ is a hydrogen atom or a methyl group, R ² is a carbon atom of 3
~ 20 alkylene group, n represents an integer of 1 to 20) represented by (meth) acrylic acid ester 5 to 40 wt%,
(B-1) 10 to 90% by weight of alkyl acrylate and / or alkoxy-substituted alkyl acrylate having an alkyl group having 1 to 20 carbon atoms, (B-2) (A),
(B-1) having a polymerization composition of 0 to 40% by weight of another monomer copolymerizable with, and having a glass transition temperature (Tg) of -30 ° C.
Below, Mooney viscosity (ML1 + 4, 100 ° C) is 1
An acrylic copolymer rubber of 5 or more, and 0.1 parts by weight of a crosslinking agent to 100 parts by weight of these acrylic copolymer rubbers.
The problem was solved by using an acrylic copolymer rubber composition containing 10 to 10 parts by weight.

Explaining the (meth) acrylic acid ester represented by the general formula (1) which is the component (A) used in the present invention, R ¹ is a hydrogen atom or a methyl group,
It is preferably a hydrogen atom. R ² is an alkylene group having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms. n is 1-2
It is 0, preferably 1-10. The following compounds may be mentioned as specific examples of the (meth) acrylic acid ester represented by the general formula (1).

[0009] CH ₂ = CH over COO chromatography CH ₂ CH ₂ over _{OCOC 3 H 6 OH CH 2 =} CH over COO chromatography CH ₂ CH ₂ over _{OCOC 4 H 8 OH CH 2 =} CH over COO chromatography CH ₂ CH ₂ over OCOC ₅ H ₁₀ OH CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₃ H
₆ O] ₂ H CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₄ H
₈ O] ₂ H CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₅ H
₁₀ O] ₂ H CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₅ H
₁₀ O] ₃ H CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₅ H
₁₀ O] ₄ H CH ₂ = CH-COO-CH ₂ CH ₂ -O [COC ₅ H
₁₀ O] ₅ H CH ₂ = C (CH ₃ ) -COOCH ₂ CH ₂ -O [COC _{3
H 6 O] 2 H CH 2} = C (CH 3) over COOCH ₂ CH ₂ over O [COC _{4
H 8 O] 2 H CH 2} = C (CH 3) over COOCH ₂ CH ₂ over O [COC ₅
H ₁₀ O] ₂ H

The useful copolymer rubber of the present invention can be obtained by copolymerizing the (meth) acrylic acid ester (1) of the component (A) of the present invention with the other monomer described below. The content of the (meth) acrylic acid ester in the copolymer rubber of the present invention is 5 to 40% by weight, preferably 10 to 30% by weight. When it is 5% by weight or less, the effects of cold resistance and oil resistance are small, If it is 40% by weight or more, the tensile strength is lowered.

The component (B-1) of the present invention has 1 to 1 carbon atoms.
Specific examples of the alkyl acrylate having 20 alkyl groups and / or the alkoxy-substituted alkyl acrylate include the following compounds. As the alkyl acrylate, methyl (meth) acrylate,
Examples thereof include ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and hexyl (meth) acrylate. Examples of the alkoxy-substituted alkyl acrylate include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate,
2-Butoxyethyl (meth) acrylate and the like can be mentioned.

The content of the component (B-1) in the copolymer rubber of the present invention is from 10 to 90% by weight. When it exceeds 90%, the component (A) becomes small, and the balance of cold resistance, heat resistance and oil resistance becomes insufficient.

(A) which is the component (B-2) of the present invention,
Examples of the other monomer copolymerizable with (B-1) include cyclic and unsaturated monomers excluding the alkyl acrylate and the alkoxy-substituted alkyl acrylate of the component (B-1), for example, (meth) acryl. Cyclohexyl acid, benzyl (meth) acrylate, dimethyl itaconate, diethyl fumarate, di-n-butyl maleate, carboxylic acid esters such as perfluoroalkyl (meth) acrylate, vinyl acetate, vinyl propionate, vinyl caproate, etc. Vinyl cyanide compounds such as carboxylic acid vinyl ester, (meth) acrylonitrile, α-methylacrylonitrile, styrene, ethylene, vinyl chloride,
Examples thereof include vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene and the like.

As the other monomer, the following monomers that can be used as crosslinking points of the copolymer (hereinafter referred to as "crosslinkable monomer") can also be copolymerized. Examples of such monomers are 1) Diene monomer 2) Unsaturated group-containing unsaturated carboxylic acid ester 3) Epoxy group-containing vinyl monomer 4) Reactive halogen atom-containing vinyl monomer

Here, as the 1) diene monomer, for example, butadiene, ethylidene norbornene, isoprene,
Examples of piperylene, divinylbenzene, vinylcyclohexene, chloroprene, methylbutadiene, cyclopentadiene, methylpentadiene, dimethylvinylstyrylsilane and the like 2) unsaturated group-containing unsaturated carboxylic acid ester include ethylene glycol di (meth) acrylate and propylene. Glycol di (meth) acrylate, dihydrodicyclopentadienyloxyethyl (meth) acrylate, vinyl (meth) acrylate, dimethylvinylmethacryloxymethylsilane, etc., 3) The epoxy group-containing vinyl monomer is, for example, glycidyl. (Meth) acrylate, allyl glycidyl ether, etc.

4) Examples of the vinyl monomer containing a reactive halogen atom include 2-chloroethyl vinyl ether, vinyl chloroacetate, allyl chloroacetate and chloromethylstyrene. The above copolymerizable monomers are
These may be used alone or in combination of two or more.

The content of the crosslinkable monomer as the component (B-2) in the copolymer rubber of the present invention is 0.1 to 10% by weight, preferably 0.1 to 5% by weight. If it is less than 1% by weight, the tensile strength of the obtained copolymer rubber is inferior, while that of 10% by weight
If it exceeds, elongation tends to decrease.

The method of copolymerizing the acrylic copolymer rubber of the present invention can be easily produced by ordinary emulsion polymerization, suspension polymerization, bulk polymerization or solution polymerization in the presence of a radical polymerization initiator. it can. As an emulsifier for producing a copolymer rubber by an emulsion polymerization method, an anionic or nonionic surfactant may be used alone or as a mixture, and various dispersants may be used. Examples of these emulsifiers include alkyl sulfates,
Alkylaryl sulfonates, salts of higher fatty acids, such as polyoxyethylene alkyl ether sulfate ester salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene oxypropylene block polymers, etc. To be The copolymerization reaction can be carried out under the conditions of temperature of 100 to 200 ° C, preferably 0 to 60 ° C.

Examples of the radical initiator for initiating the polymerization include organic peroxides such as benzoyl peroxide, cumene hydroperoxide and paramenthane hydroperoxide, organic peroxides such as hydroperoxide and t-butyl hydroperoxide. Examples include hydroperoxides, azo compounds represented by azobisisobutyronitrile, inorganic persulfates such as potassium persulfate and ammonium persulfate, and redox catalysts represented by a combination of organic peroxide and iron sulfate. . These radical initiators are usually added in an amount of 0.01 to
2% by weight is used.

The molecular weight regulator is used as necessary, and specific examples thereof include tododecyl mercaptan, dimethylxanthogen sulfide and the like.

The polymerization reaction is terminated by adding a reaction terminator such as N, N-diethylhydroxyamine after the predetermined polymerization conversion rate is reached, and then the unreacted unit amount in the obtained latex. Remove the body by steam distillation,
After adding antioxidants such as phenols and amines, and coagulating the latex by a usual coagulation method, for example, aluminum sulfate aqueous solution, calcium chloride aqueous solution, sodium chloride aqueous solution, ammonium salt aqueous solution and the like are mixed with the metal salt aqueous solution, A copolymer rubber can be obtained by drying.

When a copolymer rubber is produced by suspension radical polymerization, a saponification product of polyvinyl alcohol or the like is added as a dispersant, and an oil-soluble radical initiator such as azobisisobutyronitrile or benzoyl peroxide is added. It is possible to obtain a copolymer rubber by carrying out polymerization using the above and removing water after completion of the polymerization. Further, in the case of producing a copolymer rubber by solution radical polymerization, a generally known method can be adopted. The polymerization method may be either continuous or batch.

The glass transition temperature (T
g) is -30 ° C or lower, preferably -40 ° C or lower.
If it is less than -30 ° C, the cold resistance becomes poor. The Mooney viscosity (ML1 + 4, 100 ° C.) of the copolymer rubber of the present invention is 15 or more,
It is preferably from 15 to 100, and when it is less than 15, the tensile strength of the copolymer rubber is inferior, and when it exceeds 100, the processability may be deteriorated, which is not preferable.

The acrylic copolymer rubber of the present invention can be vulcanized by a generally known vulcanization method by adding a vulcanization accelerator, a crosslinking agent and the like. As the cross-linking agent, the following can be selected depending on the type of the (B-2) cross-linking monomer used for the copolymerization.

That is, when the crosslinkable monomer is 1) a diene monomer and / or an unsaturated group-containing carboxylic acid ester, sulfur, an organic sulfur-containing compound, or an organic peroxide is used as a crosslinking agent. To be Further, as a crosslinkable monomer, 2)
When an epoxy group-containing vinyl monomer is used, polyamine, polyamide, sulfonamide, dithiocarbamate, ammonium organic carboxylate or the like is used as a crosslinking agent.

Further, when 4) a vinyl monomer containing a reactive halogen atom is used as the crosslinkable monomer, metal soap, organic carboxylic acid ammonium salt, polyamine, polycarbamate, trithiocyanuric acid and the like are used as the crosslinker. Used as.

Among these crosslinking agents, as the sulfur, any of powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur and highly dispersible sulfur can be used. The organic sulfur-containing compound is a compound that releases active sulfur by thermal dissociation, and examples thereof include tetramethylthiuam disulfide and 4,4-dithiomorpholine which are thiuram accelerators.

As the organic peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, 2,
5-dimethyl-2,5- (t-butylperoxy) hexane, 1,3-bis (t-butylperoxyisopropyl) benzene, dicumyl peroxide, dibutyl peroxide, 1,1-di-t-butylperoxy-3,3
3,5-Trimethylcyclohexane, t-butylcumyl peroxide, t-butylperoxy-isopropyl carbonate and the like are used.

Examples of polyamines include triethylenetetramine, methylenedianiline, diethylenetriamine and the like. Examples of the metal soap include sodium stearate and potassium stearate.

As the organic carboxylic acid ammonium salt,
Examples thereof include ammonium benzoate and ammonium adipate.

Examples of dithiocarbamic acid include hexamethylenediamine carbamate and zinc dimethyldithiocarbamate.

A cross-linking aid may be added to these cross-linking agents in order to shorten the cross-linking time, lower the cross-linking temperature, and improve the performance of the cross-linked product. For example, when sulfur is used as a cross-linking agent, thiazoles such as mercaptobenzothiazole, thiurams such as tetramethylthiuram disulfide, guanidines such as diphenylguanidine, dithiocarbamate salts such as zinc dimethyldithiocarbamate, etc. It can be effectively used as an agent.

When an organic peroxide is used as a crosslinking agent, ethylene glycol dimethacrylate, 1,3
-Butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol di Acrylate 2,
2'-bis (4-methacryloyldiethoxyphenyl)
Propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate,

Pentaerythritol triacrylate,
Divinylbenzene, N, N'-methylenebisacrylamide, p-quinonedioxime, p, p'-dibenzoylquinonedioxime, triazinedithiol, triallyl cyanurate, triallyl isocyanurate, bismaleimide, high vinyl content Silicone oil, etc.
It can be effectively used as a crosslinking aid.

When metal soap is used as a crosslinking agent, for example, sulfur or dipentamethylene thiuram tetrasulfide can be effectively used as a crosslinking aid. When an amine is used as a cross-linking agent, for example, diphenylguanidine and diorsotolylguanidine can be effectively used as a cross-linking aid. When trithiocyanuric acid is used as a crosslinking agent, dithiocarbamate, metal oxide, alkali metal salt of organic carboxylic acid, dicyandiamide and aluminum-containing compound can be effectively used as a crosslinking aid.

The compounding amount of these cross-linking agents in the rubber composition of the present invention is usually 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer rubber. If it is less than 1 part by weight, the crosslinking hardly proceeds, while if it exceeds 10 parts by weight, the physical properties of the obtained copolymer rubber composition are impaired, which is not preferable. The copolymer rubber of the present invention is
In addition to the cross-linking agent, various compounding agents are further added, if necessary, and they are mixed by using an ordinary mixer such as a two-roll or Banbury mixer.

Among the compounding agents, examples of the filler include carbon black, and white fillers such as silica, calcium carbonate, talc and magnesium carbonate. Among the compounding agents, examples of dispersants include higher fatty acids and metal salts or amide salts thereof; examples of plasticizers include phthalic acid derivatives, adipic acid derivatives, polyether esters; examples of softening agents include lubricating oils,
Process oils, castor oils; Antiaging agents include, for example, amines such as 4,4- (α, α'-dimethylbenzyl) diphenylamine and imidazoles such as 2,2'-methylenebis (4-methyl-6-t-butylphenol) In addition, pigments, cross-linking accelerators, flame retardants, foaming agents, scorch inhibitors, tackifiers, lubricants and the like may be optionally added.

The rubber composition containing the copolymer rubber of the present invention as the main component thus obtained can be formed into a crosslinked product by molding and crosslinking under ordinary conditions for producing a crosslinked rubber. That is, after molding, it is usually 1 at 150 to 180 ° C.
Primary cross-linking under heat and pressure of 50 to 150 kg / cm ² for 0 to 60 minutes, and if necessary, at 150 to 180 ° C. for 1
Secondary cross-linking can be performed for up to 20 hours to give a cross-linked product having excellent heat resistance, cold resistance, and oil resistance. The rubber cross-linked product thus obtained can be used in industrial applications such as rolls and hoses for automobiles such as seals, packings and hoses.

[0039]

EXAMPLES The present invention will now be described in more detail based on examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

In the examples, parts and% are based on weight unless otherwise specified. In the examples, the methods for measuring various properties of the copolymer rubber and the crosslinked product are as follows. Quantitative determination of vinyl chloroacetate The chlorine content in the polymer was measured and determined by fluorescent X-ray. It was determined by dissolving the quantitative polymer of allyl glycidyl ether in chloroform and measuring the epoxy equivalent by acetic acid method.

Determination of acrylic acid ester in copolymer rubber
The amount of acrylic acid ester such as ethyl acrylate and n-butyl acrylate was determined from ¹³ C-nuclear magnetic resonance spectrum. The glass transition temperature (Tg ) was measured and determined by a differential scanning calorimeter (DSC). Properties of cross-linked product A rubber sheet or block was prepared from a composition containing an acrylic copolymer rubber, and cross-linked for a predetermined time using a cross-linking press machine. Further, if necessary, a gear open was used for further crosslinking for a predetermined time. The obtained crosslinked sheet or block is molded with a dumbbell cutter, and JIS K
According to 6301, heat resistance, cold resistance, compression set and oil resistance were measured.

(Examples 1 to 6, Comparative Examples 1 to 3 (Production of Acrylic Copolymer Rubber)) 100 parts of monomer mixture, 4 parts of sodium lauryl sulfate, 0.25 part of p-menthane hydroperoxide. 0.01 part of ferrous sulfate, 0.025 part of sodium ethylenediaminetetraacetate and 0.04 part of sodium formaldehyde sulfoxylate were charged into a nitrogen-substituted autoclave, and the conversion rate of the monomer was 90 at a reaction temperature of 30 ° C. The reaction was stopped until the content reached%, and 0.5 part of N, N-diethylhydroxylamine was added to stop the reaction.

Next, the reaction product was taken out and steam was blown into it to remove unreacted monomers. The rubber latex thus obtained is added to a 0.25% calcium chloride aqueous solution to coagulate, and the coagulated product is thoroughly washed with water and kept at about 90 ° C. for 3 hours.
Copolymer A corresponding to Example 1 was obtained after drying for an hour.
The composition of copolymer A is shown in Table 1.

Copolymer rubbers B to J were produced in the same manner. Then, to 100 parts of each of the obtained copolymer rubbers, MA
F carbon black (60 parts), stearic acid (1 part), the vulcanization accelerator and the cross-linking agent shown in Table 2 were added according to the type of the cross-linkable monomer used in the production of each copolymer rubber, and after mixing with a roll, Crosslinking was performed at 170 ° C. for 20 minutes to produce a crosslinked sheet and block. This crosslinked sheet and block
Further cross-linking in open at 175 ° C. for 4 hours. The obtained crosslinked sample is in accordance with JIS K6301
Tensile strength characteristics, heat resistance, oil resistance, and cold resistance were measured.
The results are shown in Table 2.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

EFFECT OF THE INVENTION The acrylic copolymer rubber composition of the present invention has a higher oil resistance than the conventional acrylic rubber composition.
It can be seen that the balance of cold resistance is very good.

Claims (2)

[Claims] 1. (A) General formula (1) CH ₂ ═CR ¹ —COO—CH ₂ CH ₂ —O [COR ² O] _n
H (wherein R ¹ is a hydrogen atom or a methyl group, R ² is a carbon atom of 3
To an alkylene group of 20 to 20, n is an integer of 1 to 20), and 5 to 40% by weight of a (meth) acrylic acid ester, (B-1) an alkyl acrylate having an alkyl group of 1 to 20 carbon atoms, and Glass transition temperature having a polymerization composition of 10 to 90% by weight of an alkoxy-substituted alkyl acrylate and / or 0 to 40% by weight of another monomer copolymerizable with (B-2) (A) and (B-1). (Tg) is -30 ° C or lower, and Mooney viscosity (ML1 +
4, 100 ℃) 15 or more acrylic copolymer rubber. 2. An acrylic copolymer rubber composition comprising 100 parts by weight of the acrylic copolymer rubber according to claim 1 and 0.1 to 10 parts by weight of a crosslinking agent.