JP2002265736A - Acrylic rubber composition and vulcanizate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic rubber vulcanizate which is excellent in tensile strength and resistances to heat and oil and has a low compression set. SOLUTION: An acrylic rubber composition comprising (A) 80-99 wt.% carboxylated acrylic rubber and (B) 1-20 wt.% epoxidized olefin/vinyl ester copolymer is vulcanized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vulcanizate having excellent tensile strength, heat resistance and oil resistance and low compression set, and an acrylic rubber composition as a material thereof.

[0002]

2. Description of the Related Art Acrylic rubber has excellent heat resistance.
It is widely used in automobile-related fields. But,
Recently, there has been a demand for an acrylic rubber having better performance, and studies for improvement have been made, and a method of blending an ethylene-vinyl acetate copolymer with the acrylic rubber has been proposed.

For example, as a material for obtaining a vulcanizate excellent in processability and vulcanization moldability and excellent in mechanical properties and oil resistance of a vulcanizate, 10 to 90 parts by weight of an acrylic rubber and a vinyl acetate unit content of 50% are used. % By weight or more of ethylene-vinyl acetate copolymer 9
It has been proposed to use a composition consisting of 0 to 10 parts by weight (JP-A-55-98236), but even if this composition was vulcanized, the heat resistance was insufficient.

[0004] Further, as a material for obtaining a vulcanizate having excellent tensile strength and hardness, an ethylene-vinyl acetate copolymer obtained by grafting ethyl acrylate and a vulcanizable point monomer capable of sulfur vulcanization, and vinyl chloroacetate are included. It has been proposed to use a composition that is a blend of a polyacrylate elastomer (JP-A-59-93744), but the heat resistance of the vulcanized product was still insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an acrylic rubber composition which is excellent in tensile strength, heat resistance and oil resistance and is used as a material for a vulcanizate having a small compression set.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies and found that the above-mentioned compound is obtained by blending an epoxy group-containing olefin-vinyl ester copolymer with a carboxyl group-containing acrylic rubber. The inventors have found that the object can be achieved, and have completed the present invention based on the knowledge.

Thus, according to the present invention, an acrylic rubber composition comprising 80 to 99% by weight of a carboxyl group-containing acrylic rubber (A) and 1 to 20% by weight of an epoxy group-containing olefin-vinyl ester copolymer (B) And a vulcanized product obtained by vulcanizing the acrylic rubber composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The carboxyl group-containing acrylic rubber (A) used in the present invention has a carboxyl group in the molecule, preferably 5 × 10 ^-4 to 4 × 10 ^-1 ephr, more preferably 2.5 × 10 ^-1 ephr. It is an acrylic rubber containing from × 10 ^{-3 to} 2 × 10 ^-1 ephr, particularly preferably from 5 × 10 ^-3 to 1 × 10 ^-1 ephr. If the number of carboxyl groups is too small, the vulcanized product may not be sufficiently vulcanized, so that the shape of the vulcanized product may not be maintained.

The carboxyl group can be introduced by copolymerization of a monomer containing the carboxyl group or by carrying out a post-modification reaction on an acrylic rubber containing no carboxyl group. Hereinafter, an acrylic rubber (A) produced by copolymerization of a (meth) acrylate monomer (a) and an ethylenically unsaturated monomer (b) having a carboxyl group will be described below as an example. explain.

The (meth) acrylic acid ester monomer (a) used in the polymerization is not particularly limited, but may be either (meth) acrylic acid alkyl ester monomer (a-1) alone or (meth) acrylic acid. It is preferable to use the acid alkyl ester monomer (a-1) and the (meth) acrylic acid alkoxyalkyl ester monomer (a-2) in combination.
The monomer (a) unit content in the acrylic rubber (A) is preferably from 80 to 99.9% by weight, more preferably from 90 to 9% by weight.
It is 9.5% by weight, particularly preferably 95 to 99% by weight. If the amount of the monomer (a) is too small, the vulcanizate may lose rubber elasticity. On the other hand, if the amount is too large, the content of the carboxyl group may decrease and vulcanization may not be sufficiently performed.

The alkyl (meth) acrylate monomer (a-1) preferably has 1 to 8 carbon atoms in the alkyl group, more preferably 2 to 4 carbon atoms. Monomer (a-
Specific examples of 1) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic. Isobutyl acid, n-hexyl (meth) acrylate, 2- (meth) acrylate
Examples include ethylhexyl and cyclohexyl (meth) acrylate. Monomer (a-1) and monomer (a-2)
Is used together with the monomer (a-) in the acrylic rubber (A).
1) The unit content is preferably 30 to 96.9% by weight,
It is more preferably 60 to 95.5% by weight, particularly preferably 75 to 94% by weight. If the content is too low, the heat resistance is poor, and elongation or the like may be reduced after heat load. If the content is too high, the vulcanized product may have poor oil resistance or poor cold resistance.

The alkoxyalkyl (meth) acrylate monomer (a-2) preferably has 2 to 16 carbon atoms, more preferably 2 to 8 carbon atoms in the alkoxyalkyl group. Specific examples of the monomer (a-2) include (meth)
Methoxymethyl acrylate, ethoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate,
2-Ethoxyethyl (meth) acrylate, 2-propoxyethyl (meth) acrylate, 2- (meth) acrylate
Butoxyethyl, 3-methoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate and the like are exemplified. When the monomer (a-1) and the monomer (a-2) are used in combination, the monomer (a-2) unit content in the acrylic rubber (A) is preferably 3 to 50% by weight, It is more preferably 4 to 30% by weight, particularly preferably 5 to 20% by weight.

Examples of the ethylenically unsaturated monomer (b) having a carboxyl group include carboxylic acid monomers such as acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid, fumaric acid and citraconic acid; Butenedioic acid monoalkyl ester monomers such as monomethyl, monoethyl maleate, mono-n-butyl maleate, monomethyl fumarate, monoethyl fumarate, and mono-n-butyl fumarate; and the like. The carboxyl group may be a carboxylic anhydride group, and specific examples of the carboxylic anhydride monomer include maleic anhydride and citraconic anhydride. Among these, a monoalkyl butenedionate monomer is preferable, and in particular, monoethyl maleate, mono-n-butyl maleate, monoethyl fumarate, and mono-n-butyl fumarate have 2 to 2 carbon atoms.
Those having 4 alkyl groups are preferred. The monomer (b) unit content in the acrylic rubber (A) is preferably 0.1%.
1 to 20% by weight, more preferably 0.5 to 10% by weight,
Particularly preferably, it is 1 to 5% by weight.

The acrylic rubber (A) may be one obtained by copolymerizing another copolymerizable monomer within a range that does not substantially impair the effects of the present invention. Such monomers include acrylonitrile, methacrylonitrile, ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, butyl vinyl ether,
Styrene, α-methylstyrene, isoprene, butadiene, chloroprene, piperylene, dicyclopentadiene, norbornene, ethylidene norbornene, hexadiene, norbornadiene, divinylbenzene, ethylene glycol diacrylate, propylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate And the like.

The Mooney viscosity (ML) of the acrylic rubber (A)
_{(1 + 4} , 100 ° C.) is preferably 10 to 70, more preferably 15 to 65, and particularly preferably 20 to 60.
If the Mooney viscosity is too low, the moldability and the mechanical strength of the vulcanizate may be poor, and if it is too large, the moldability may be poor.

Epoxy group-containing olefin used in the present invention
-The vinyl ester copolymer (B) is an olefin monomer
(C) unit and vinyl ester monomer (d) unit
It is a copolymer containing epoxy group as a constitutional unit.
You. The epoxy group content is preferably 1 × 10^-2~ 5x
10^-1ephr, more preferably 2 × 10^-2~ 3 × 10
^-1ephr, particularly preferably 3 × 10^-2~ 1 × 10^-1e
phr. If the epoxy group content is too low,
Insufficient tensile strength due to difficulty in co-vulcanization with ril rubber (A)
If the amount is too large, on the contrary, the vulcanization moldability is inferior. Epoki
The method of introducing a di-group is based on the method of combining monomer (c) and monomer (d).
In the method of modifying the copolymer and introducing it, the monomer (c) and the
And epoxy group copolymerizable with monomer (d)
A method in which the vinyl monomer (e) is copolymerized and introduced may be used.
No. Hereinafter, the monomer (c), the monomer (d) and the monomer
An example of a method in which (e) is copolymerized to introduce an epoxy group
I will explain it.

The olefin monomer (c) is preferably an α-olefin monomer, and specific examples thereof include ethylene, propylene, 1-butene and 1-pentene.
Of these, ethylene is preferred. Examples of the vinyl ester monomer (d) include vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, and vinyl stearate. Of these, vinyl acetate is preferable. Examples of the epoxy group-containing vinyl monomer (e) include glycidyl (meth) acrylate and allyl glycidyl ether, and glycidyl methacrylate is preferred.

In the olefin-vinyl ester copolymer (B) containing an epoxy group, the unit content of the monomer (c) is preferably 50 to 90% by weight, more preferably 60 to 89% by weight, and particularly preferably 70 to 90% by weight. And the monomer (d) unit content is preferably 1 to 50% by weight, more preferably 2 to 40% by weight, and particularly preferably 3 to 30% by weight.
%, And the unit content of the monomer (e) is preferably 5 to 30% by weight, more preferably 8 to 25% by weight, and particularly preferably 10 to 20% by weight. If the amount of the monomer (c) is too small, the tensile strength of the vulcanized molded product of the blend becomes low. If the amount of the monomer (d) is too small, the oil resistance is poor, and if it is too large, the tensile strength of the vulcanized molded article of the blend becomes low. If the monomer (e) unit is too small,
If the tensile strength is too low, the vulcanizability of the blend is poor if it is too high.

The melt flow rate of the olefin-vinyl ester copolymer (B) measured at 190 ° C. is preferably 1 to 25 g / 10 min, more preferably 3 to 20 g / 10 min, and particularly preferably 5 to 15 g.
/ 10 min. If the melt flow rate is too low, the kneading operation may be difficult, and if it is too high, it may be difficult to mix uniformly with the acrylic rubber.

The acrylic rubber composition of the present invention comprises 80 to 99% by weight of the acrylic rubber (A), preferably 85 to 98% by weight, more preferably 90 to 97% by weight, and the copolymer (B) 20 to 1%. %, Preferably 15 to 2% by weight, more preferably 10 to 3% by weight. If the acrylic rubber (A) is too small, heat resistance and oil resistance are inferior, and the compression set becomes large. If it is too large, the tensile strength is insufficient.

When vulcanizing the acrylic rubber composition of the present invention, a vulcanizing agent is blended. As the vulcanizing agent, a polyvalent amine vulcanizing agent is preferable. Examples of the polyvalent amine vulcanizing agent include an aliphatic polyvalent amine vulcanizing agent and an aromatic polyamine vulcanizing agent. As the aliphatic polyamine vulcanizing agent, hexamethylene diamine, hexamethylene diamine carbamate,
N, N′-dicinnamylidene-1,6-hexanediamine and the like, and as the aromatic polyamine vulcanizing agent,
4,4'-methylenedianiline, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4 '
-Diaminodiphenyl ether, 4,4 '-(m-phenylenediisopropylidene) dianiline, 4,4'-
(P-phenylenediisopropylidene) dianiline,
2,2′-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminobenzanilide,
4,4′-bis (4-aminophenoxy) biphenyl,
m-xylylenediamine, p-xylylenediamine,
Examples thereof include 1,3,5-benzenetriamine and 1,3,5-benzenetriaminomethyl. Of these, aromatic polyamine vulcanizing agents are preferred. The compounding amount of the polyvalent amine vulcanizing agent is based on 100 parts by weight of the total amount of the acrylic rubber (A) and the olefin-vinyl ester copolymer (B).
Preferably 0.05 to 10 parts by weight, more preferably 0.1 to 10 parts by weight.
It is 1 to 5 parts by weight, particularly preferably 0.2 to 3 parts by weight.

A vulcanization accelerator may be used together with the vulcanizing agent. The vulcanization accelerator has a base dissociation constant of 1 at 25 ° C. in water.
0 ^-12 to 10 ^+6, which is substantially the same as that of the acrylic rubber (A).
A base or a conjugate base which does not react with a carboxyl group or an epoxy group of the olefin-vinyl ester copolymer (B) is preferable, and a guanidine compound, an imidazole compound, a quaternary onium salt, a tertiary amine compound, a tertiary phosphine compound, Examples thereof include an alkali metal salt of a weak acid. Examples of the guanidine compound include 1,3-diphenylguanidine, 1,3-diortitolylguanidine, and the like. Examples of the imidazole compound include 2-methylimidazole and 2-phenylimidazole. Examples of the quaternary onium salt include tetra n-butylammonium bromide and octadecyltri n-butylammonium bromide. Examples of the tertiary amine compound include triethylenediamine and 1,8-diaza-bicyclo [5.4.0] undecene-7. Examples of the tertiary phosphine compound include triphenylphosphine and tri-p-tolylphosphine. Examples of the alkali metal salt of a weak acid include inorganic weak salts such as sodium and potassium phosphates and carbonates, and organic weak salts such as stearates and laurates. The compounding amount of the vulcanization accelerator is acrylic rubber (A)
And preferably 0.1 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, per 100 parts by weight of the total amount of the copolymer (B) and
Parts by weight, particularly preferably 0.3 to 10 parts by weight.

In the acrylic rubber composition, if necessary,
As long as the effects of the present invention are not substantially impaired, reinforcing agents, fillers, anti-aging agents, light stabilizers, anti-scorch agents, vulcanization retarders, plasticizers, processing aids, lubricants, adhesives, lubricants And additives such as a flame retardant, a fungicide, an antistatic agent, a coloring agent, a coupling agent, and a foaming agent.

The acrylic rubber composition may be, if necessary, a rubber other than the acrylic rubber (A), an elastomer, a resin other than the copolymer (B), as long as the effects of the present invention are not substantially impaired. May be further compounded. For example, natural rubber, acrylic rubber other than acrylic rubber (A), rubber such as polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber; olefin-based elastomer, styrene-based elastomer, vinyl chloride-based elastomer, polyester-based Elastomers such as elastomers, polyamide elastomers, polyurethane elastomers, and polysiloxane elastomers; resins such as polyolefin resins, polystyrene resins, polyacrylic resins, polyphenylene ether resins, polyester resins, and polycarbonate resins; be able to.

In preparing the acrylic rubber composition,
Appropriate mixing methods such as roll mixing, Banbury mixing, screw mixing, and solution mixing are used. The order of blending is not particularly limited, but after sufficiently mixing components that are not easily decomposed by heat, components that are easily reacted or decomposed by heat, such as a vulcanizing agent and a vulcanization accelerator, are mixed in as short a time as possible. do it.

The method for molding the acrylic rubber composition is not particularly limited. Any method such as compression molding, injection molding, transfer molding, or extrusion molding can be used. Further, the vulcanization method may be selected as required according to the shape of the vulcanized product, and may be any of a method of performing molding and vulcanization simultaneously or a method of performing vulcanization after molding.

When the acrylic rubber composition of the present invention contains a vulcanizing agent, a vulcanized product can be obtained by heating. The heating temperature is preferably 130 to 220 ° C or higher,
More preferably, the temperature is from 140 ° C to 200 ° C, and the vulcanization time is preferably from 30 seconds to 5 hours. As a heating method, a method used for vulcanization of rubber, such as press heating, steam heating, oven heating, and hot air heating, may be appropriately selected. Further, after vulcanizing once, vulcanization may be performed after heating for a long time in order to securely vulcanize the inside of the vulcanized product. Post-vulcanization varies depending on the heating method, vulcanization temperature, shape and the like, but is preferably performed for 1 to 48 hours. A heating method and a heating temperature may be appropriately selected.

[0028]

The vulcanizates obtained according to the present invention have excellent tensile strength, heat resistance and oil resistance and low compression set.

Taking advantage of this property, the acrylic rubber composition of the present invention can be used for sealing materials, gasket materials, cushioning materials in a wide range of fields such as electronics and electric fields in addition to transportation machines such as automobiles and general equipment. It is useful as a material, protective material, wire covering material, industrial belts, hoses, rolls and the like.

[0030]

EXAMPLES The present invention will be specifically described below with reference to Comparative Examples and Examples. The parts and percentages relating to the monomer composition of the rubber and the composition of the composition are based on weight.

Examples 1 to 3, Comparative Examples 1 to 5 Acrylic rubbers 1 to 3, ethylene-vinyl acetate copolymer 1
To 2 are shown in Table 1, and carbon black (MAF,
50 parts of Tokai Carbon, Seast 116), 2 parts of stearic acid, lubricant (manufactured by Dainippon Ink and Chemicals, Greg G)
-8205) 1 part, antioxidant (4,4'-bis (α,
2 parts of α-dimethylbenzyl) diphenylamine) are kneaded at 50 ° C. using a Banbury, and then, at 60 ° C., using an open roll, a polyamine vulcanizing agent, an organic peroxide vulcanizing agent, triazine Vulcanizing agent, vulcanization accelerator 1-2
Was added and kneaded to prepare an acrylic rubber composition.

The acrylic rubber 1 has an ethyl acrylate unit content of 48% and an n-butyl acrylate unit content of 50%.
%, Mono-n-methyl fumarate unit content 2%, carboxy group content 7 × 10 ⁻³ ephr, Mooney viscosity (M
L _{1 + 4} , 100 ° C.) 33, which corresponds to the acrylic rubber (A). The acrylic rubber 2 has an ethyl acrylate unit content of 58%, an n-butyl acrylate unit content of 40%, a mono-n-methyl fumarate unit content of 2%, a carboxy group content of 7 × 10 ⁻³ ephr, Mooney It has a viscosity (ML _{1 + 4} , 100 ° C.) of 45 and corresponds to the acrylic rubber (A). The acrylic rubber 3 has an ethyl acrylate unit content of 48%, an n-butyl acrylate unit content of 30%, and a 2-methoxyethyl acrylate unit content of 2%.
It has a 0% content, a vinyl chloroacetate unit content of 2%, and a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 40, does not contain a carboxyl group, and does not correspond to the acrylic rubber (A).

The ethylene-vinyl acetate copolymer 1 had an ethylene unit content of 83%, a vinyl acetate unit content of 5%, a glycidyl methacrylate unit of 12%, an epoxy group content of 8 × 10 ^-2 ephr, and a melt flow rate. 7g / 1
0 min (manufactured by Sumitomo Chemical Co., Ltd., Bond First, grade 7B), which corresponds to the olefin-vinyl ester copolymer (B). The ethylene-vinyl acetate copolymer 2 has a melt flow rate of 8 g / 10 min.
Is a commercially available product containing no epoxy group (Ultracene, manufactured by Tosoh Corporation) and does not correspond to the olefin-vinyl ester copolymer (B).

The Mooney viscosity is 100 ° C. according to JIS K6300, and the melt flow rate is
Measured at 190 ° C. according to K6730.

The polyvalent amine vulcanizing agent is hexamethylene diamine carbamate, and the organic peroxide vulcanizing agent is 1,1.
3-bis (t-butylperoxyisopropyl) benzene 40% product (manufactured by Hercules, Vul-cup-40)
KE) and the triazine vulcanizing agent is 2,4,6-trimercapto-s-triazine. Further, the vulcanization accelerator 1 is 1,3-dioltolyl guanidine, and the vulcanization accelerator 2 is zinc dibutyldithiocarbamate.

The acrylic rubber composition was molded and vulcanized by pressing at 170 ° C. for 20 minutes to obtain a 15 cm × 15 cm ×
A 2 mm test piece was prepared and, for post vulcanization, 17
It was left at 0 ° C. for 4 hours. Using this test piece, JIS
According to K6301, the tensile strength, elongation and hardness were measured as the normal physical properties of the vulcanized product.

The heat resistance was evaluated according to JIS K6257.
In air at 175 ° C. for 70 hours, and the rate of change in tensile strength, the rate of change in elongation, and the change in hardness of the vulcanizate after heat load were measured.

Evaluation of oil resistance is based on JIS K6258.
Using an IRM903 test oil, a 70-hour oil immersion test was performed in an environment at 150 ° C. to measure the volume change rate.

The compression set of the vulcanizate is determined according to JIS K6
According to H.262, it was measured at a compression ratio of 25% and a compression condition of 175 ° C. and 70 hours. Diameter 29.0mm, thickness 1
A 2.5 mm test piece was press vulcanized at 170 ° C. for 20 minutes, and then left for 4 hours in an environment of 170 ° C. to perform secondary vulcanization.

Table 1 shows the measurement results and the judgment results.

[0041]

[Table 1]

A vulcanizate having a larger amount of the olefin-vinyl ester copolymer than the acrylic rubber (A) is inferior in heat resistance and oil resistance and has a large compression set (Comparative Example 1). A vulcanizate using an ethylene-vinyl acetate copolymer containing no epoxy group is inferior in tensile strength (Comparative Example 2). When an acrylic rubber composition using an olefin-vinyl ester copolymer containing no epoxy group is vulcanized with an organic peroxide, the tensile strength is poor and the compression set is large (Comparative Example 3). On the other hand, when a composition using an acrylic rubber containing no carboxyl group is vulcanized with an organic peroxide, the tensile strength is also inferior, the compression set is also large, and the heat resistance and oil resistance are inferior (Comparative Example). 4). When a composition using an acrylic rubber containing no carboxyl group is vulcanized with a triazine vulcanizing agent, heat resistance is inferior and compression set becomes large (Comparative Example 5).

On the other hand, the vulcanizates of the present invention have excellent normal physical properties, particularly excellent tensile strength, excellent heat resistance and oil resistance, and low compression set (Examples 1 to 5).
3).

Claims (2)

[Claims] 1. Carboxyl group-containing acrylic rubber (A)
An acrylic rubber composition comprising 80 to 99% by weight and 1 to 20% by weight of an epoxy group-containing olefin-vinyl ester copolymer (B). 2. A vulcanizate obtained by vulcanizing the acrylic rubber composition according to claim 1.