JPH0725972B2 - Heat and oil resistant elastomer composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vulcanizable elastomer obtained by blending a fluorine-containing acrylic elastomer and a fluororubber. More specifically, a vulcanizable elastomer composition having excellent heat resistance and oil resistance, which is composed of an acrylic elastomer and fluororubber that facilitates blending with fluororubber by introducing a fluorine-substituted (meth) acrylic ester Regarding things.

[Prior Art] Although fluororubber is the best as a heat resistant elastomer, it is expensive and difficult to process in the kneading process and the molding and vulcanization process, and the vulcanized compound has a cold resistance due to its physical properties. There are times when you are not satisfied.

In addition, acrylic elastomers are important as heat- and oil-resistant rubber materials because they have a good balance between various properties such as heat resistance, oil resistance, and cold resistance and price, but continuous application temperature of 150 ° C and fluorine 230 ° C, which is the continuous application temperature of rubber
And its application is limited depending on the site of use. In actual industrial applications, especially in automobiles, the environment where heat resistance intermediate between the above application temperatures is required is expanding, and an elastomer material having properties between fluororubber and acrylic elastomer is required. Has been done.

Therefore, in order to obtain an elastomer material having intermediate properties between fluororubber and acrylic elastomer, attempts have been made to blend fluororubber and acrylic elastomer. However, since the kneading is difficult in processing and the affinity of the fluororubber with the acrylic elastomer is poor, there is no practically satisfactory vulcanized product in terms of physical properties, particularly heat resistance.

Further, a method of copolymerizing an acrylate ester and a fluorine-containing monomer has been attempted for the purpose of improving heat resistance, but the heat resistance of the vulcanized compound is not practically satisfactory. For example, JP-B-51-8433 discloses a method for producing an acrylic polymer characterized by copolymerizing an acrylate ester with 1,1, ω-trihydroperfluoroalkyl methacrylate. The heat resistance of the vulcanized compound is not much different from the heat resistance of acrylic elastomers that have been conventionally put into practical use, and it cannot be said to be satisfactory.

[Problems to be Solved by the Invention] An object of the present invention is an elastomer having intermediate heat resistance between fluororubber and an acrylic elastomer, and specifically, the maximum usable maximum temperature of the acrylic elastomer is 15 ° C.
It is an object of the present invention to provide a heat-resistant and oil-resistant elastomer composition, which is widely known above.

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, blended an acrylic elastomer into which a fluorine-substituted (meth) acrylic ester was introduced and a fluororubber. By doing so, it has been found that an elastomer composition having excellent heat resistance and oil resistance, excellent compression set resistance, etc., and well balanced in terms of cold resistance can be obtained, and to complete the present invention. I arrived.

That is, the present invention relates to (A) (a) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and an alkoxyalkyl acrylate having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms. 20-99.4% (wt%, the same applies hereinafter) of at least one acrylate selected from the group consisting of: (b) General formula (I): (In the formula, R is a hydrogen atom or a methyl group, x is 0, 1 or 2, y is 0 or 1, n is 0 or 1, m is an integer of 1 to 12, and A is a hydrogen atom or a fluorine atom.) 40% to 0.5% of at least one fluorine-substituted (meth) acrylic acid ester represented by: (C) one of crosslinking monomers having at least one of chlorine group, epoxy group and carboxyl group, or Two
Fluorine-containing acrylic system consisting of 15 to 0.1% or more and (d) 25 to 0% of a copolymerizable monomer copolymerizable with the monomers of the above (a) component, (b) component and (c) component (B) (a) at least one of hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene and 1-hydropentafluoropropene, and vinylidene fluoride with respect to 100 parts of elastomer (parts by weight; At least one fluororubber selected from the group consisting of a copolymer of (2) and a copolymer of (b) perfluoromethyl vinyl ether or propylene and tetrafluoroethylene 1
The present invention relates to a heat-resistant and oil-resistant elastomer composition containing 50 parts by weight.

[Examples] A vulcanizable fluorine-containing acrylic elastomer (component (A)) used in the present invention was substituted with a specific acrylate ester ((A)-(a) component) and a specific fluorine (meta). ) Monomer ((A)) copolymerized with acrylic acid ester ((A)-(B) component) and further having at least one of a chlorine group, an epoxy group and a carboxyl group in the molecule as a crosslinking point. -(C) component). The elastomer may be copolymerized with another copolymerizable monomer ((A)-(D) component) which is copolymerizable with the above-mentioned monomer as a copolymerization component.

The fluorine-containing acrylic elastomer used in the present invention as described above may be a random copolymer or a block copolymer and is not particularly limited, but the Mooney viscosity (ML _{1 + 4} , 100
C.) of 20 to 60 is preferable. If the Mooney viscosity is less than 20, the rubber composition tends to stick and the kneading workability tends to be impaired due to its tackiness, and it is difficult to obtain an elastomer composition in a uniformly dispersed state with the fluororubber which is the object of the present invention. Become. On the other hand, when the Mooney viscosity exceeds 60, the Mooney viscosity of the compound becomes high, and the moldability tends to be impaired due to insufficient fluidity.

The acrylic acid ester as the component (A)-(a) is at least one acrylic acid ester selected from the group consisting of specific alkyl acrylates and specific alkoxyalkyl acrylates.

The alkyl acrylate is an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms. When the number of carbon atoms exceeds 8, the oil resistance, which is a characteristic of acrylic elastomers, decreases. Specific examples of the alkyl acrylate include, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate,
2-ethylhexyl acrylate and the like can be mentioned.

The alkoxyalkyl acrylate has 1 to 10 carbon atoms.
It is an alkoxyalkyl acrylate having a 4 alkoxy group and an alkylene group having 1 to 4 carbon atoms. If the number of carbon atoms of the alkoxy group or alkylene group exceeds 4, the oil resistance decreases. Specific examples of the alkoxyalkyl acrylate include methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate and butoxyethyl acrylate.

The proportion of the units derived from the alkyl acrylate and the alkoxyalkyl acrylate is 20 to 99.4%, preferably 60 to 98.5% in the fluorine-containing acrylic elastomer. If the ratio is less than 20%, the rubber elasticity of the obtained fluorine-containing acrylic elastomer tends to be impaired, and 99.4%
If it exceeds the above range, sufficient crosslinking density cannot be obtained due to lack of crosslinking monomer, and the vulcanizate will not satisfy the physical properties required for practical use. The affinity of the system elastomer with the fluororubber is insufficient, and the object of the present invention is not satisfied.

The fluorine-substituted (meth) acrylic acid ester as the component (A)-(b) is a component that imparts an affinity to the fluororubber and has the general formula (I): (In the formula, R is a hydrogen atom or a methyl group, x is 0, 1 or 2, y is 0 or 1, n is 0 or 1, m is an integer of 1 to 12, and A is a hydrogen atom or a fluorine atom.) Which is at least one fluorine-substituted (meth) acrylic acid ester selected from the group consisting of fluorine-containing alkyl acrylates, fluorine-containing alkyl methacrylates, fluorine-containing alkoxyalkyl acrylates and fluorine-containing alkoxyalkyl methacrylates.

The fluorine-substituted (meth) acrylic acid ester is
A copolymer having good copolymerizability with the alkyl acrylate and the alkoxyalkyl acrylate of the component (A)-(a) and having an arbitrary ratio can be obtained, and the obtained copolymer is (B).
It has a sufficient affinity with the component fluororubber.

Specific examples of the fluorine-substituted (meth) acrylic acid ester include, for example, 2,2,2-trifluoroethyl acrylate, 2,2,3,3 tetrafluoropropyl acrylate, 1H, 1H, 5H-octafluoropentyl. Acrylate, 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate, 2,2,2-trifluoroethoxymethyl acrylate, 2,2,2-trifluoroethoxyethyl acrylate, 2,2,3,3-tetrafluoro Propoxyethyl acrylate, 2,2,2-trifluoroethyl methacrylate,
2,2,3,3-tetrafluoropropyl methacrylate, 1H,
1H, 5H-octafluoropentyl methacrylate, 1H, 1
Examples include H, 2H, 2H-heptadecafluorodecyl methacrylate.

The ratio of the units derived from the fluorine-substituted (meth) acrylic monomer is 40 to 40 in the fluorine-containing acrylic elastomer.
It is 0.5%, preferably 30 to 5%. If the ratio is less than 0.5%, the fluorine-containing acrylic elastomer obtained has a insufficient fluorine content, and it is difficult to obtain sufficient affinity with the fluororubber. Further, when the ratio exceeds 40%, the rubber elasticity of the fluorine-containing acrylic elastomer is impaired, and it becomes difficult to obtain a high-molecular weight polymer, and the vulcanized product satisfies the physical properties required for practical use. Will not do.

The crosslinking monomer having at least one of a chlorine group, an epoxy group and a carboxyl group of the components (A)-(c) is a component that becomes a crosslinking point during vulcanization.

Specific examples of the chlorine group-containing monomer include allyl chloroacetate, 2-chloroethyl vinyl ether, vinylbenzyl chloride, chloromethylstyrene, vinyl chloroacetate and the like. Of these, vinyl chloroacetate and chloromethylstyrene are preferable from the viewpoint of rapid crosslinking reactivity.

Specific examples of the epoxy group-containing monomer, for example, glycidyl acrylate, glycidyl methacrylate,
Examples include allyl glycidyl ether. Of these, allyl glycidyl ether, which has a relatively rapid crosslinking reaction and good initial vulcanization stability of the compound, is preferable.

Specific examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, 2-acryloyloxyethyl succinate. Acid, 2-acryloyloxyethyl phthalic acid and the like. Of these, monoethyl maleate and monoethyl itaconate, which have good copolymerization reactivity and relatively rapid crosslinking reaction, are preferred.

The crosslinking monomer in the fluorinated acrylic elastomer may be one kind selected from the group of the crosslinking monomers,
Two or more kinds may be used.

The ratio of the units derived from the crosslinking monomer is 15 to 0.1% in the fluorine-containing acrylic elastomer, preferably 5 to 0.5%.
%. If the ratio is less than 0.1%, the crosslinking reaction rate of the obtained fluorine-containing acrylic elastomer becomes slow, and the vulcanized product cannot obtain practically sufficient physical properties. Also
If it exceeds 15%, the crosslink density of the vulcanizate becomes too high and the rubber elasticity is lost.

The copolymerizable monomer that can be used as the component (A)-(D) is not particularly limited, and specific examples thereof include acrylonitrile, methyl methacrylate, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, ethyl vinyl ether, Butyl vinyl ether, divinylbenzene,
Examples thereof include vinyl monomers such as ethylene glycol diacrylate.

The copolymerizable monomer of the component (A)-(d) in the fluorinated acrylic elastomer may be one type or two or more types, and the ratio of units derived from the component is 25. ~ 0
%, Preferably 10-0%. If the proportion exceeds 25%, the rubber elasticity and cold resistance of the vulcanizate are impaired.

The fluorinated acrylic elastomer comprising the above-mentioned component (a), component (b), component (c) and optionally component (d) can be synthesized by various known polymerization methods. From the viewpoint of adjusting the molecular weight, a method of polymerizing the monomer mixture in an emulsion aqueous solution in the presence of an emulsifier, a polymerization initiator and a polymerization regulator is preferable. Of course, the polymerization may be carried out in solution or in bulk, for example by utilizing heat or actinic radiation in the presence or absence of peroxides to induce the polymerization reaction. After polymerization, in the case of suspension polymerization method, salts are added to the copolymerization product to coagulate it, followed by washing with water and drying, or in the case of solution polymerization method, evaporation of the copolymerization product to dryness. The fluorine-containing acrylic elastomer can be obtained by removing the solvent with.

The fluorine-containing acrylic elastomer may be used alone or in combination of two or more.

The specific fluororubber used as the component (B) may be liquid or solid, but the Mooney viscosity (ML _{1 + 4} , 1
It is preferably 90 ° C. or less, and more preferably 60 or less. If the Mooney viscosity exceeds 90, it will be difficult to knead during processing, the dispersibility of the compounding agent will decrease and the physical properties of the vulcanized compound will be insufficient, and the fluorine-containing acrylic elastomer and fluororubber It is difficult to obtain a good dispersion state, and the vulcanized compound is likely to undergo phase separation under practical use conditions, so that it may not satisfy sufficient physical properties.

The fluororubber used in the present invention includes (i) a copolymer of vinylidene fluoride and at least one of hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene and 1-hydropentafluoropropene, and (b) It is at least one selected from the group consisting of copolymers of perfluoromethyl vinyl ether or propylene and tetrafluoroethylene.

Specific examples of the vinylidene fluoride copolymer as the component (B)-(a) include vinylidene fluoride-
Hexafluoropropene copolymer, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-1-hydropentafluoropropene copolymer, etc. To be

Specific examples of the tetrafluoroethylene copolymer of the component (B)-(b) include tetrafluoroethylene-perfluoromethyl vinyl ether copolymer and tetrafluoroethylene-propylene copolymer.

Among these fluororubbers, a vinylidene fluoride-hexafluoropropene copolymer and a vinylidene fluoride-hexafluoropropene-tetrafluoroethylene copolymer are co-crosslinked with the fluorine-containing acrylic elastomer of the component (A). Is preferable because of excellent properties, kneadability and heat resistance of the vulcanized product.

In the composition of the present invention, the fluororubber is blended according to the required heat resistance and the like, but the ratio is 1 to 5 per 100 parts of the fluorine-containing acrylic elastomer.
It is 0 part, preferably 5 to 40 parts. If the amount of fluororubber is less than 1 part, the continuous layer portion of the fluororubber in the composition will be insufficient, and the object of the present invention will not be satisfied. When it exceeds 50 parts, it is difficult to perform the kneading process and the molding vulcanization process, or the cold resistance of the vulcanized compound becomes practically unsatisfactory.

For the vulcanization of the composition of the present invention, a vulcanizing agent generally used for vulcanizing an acrylic elastomer can be used, but a vulcanizing agent capable of co-vulcanizing a fluorine-containing acrylic elastomer and a fluororubber. By selecting the sulfurizing agent, it becomes possible to enhance the bonding between the phases of both components, and more preferable physical properties can be obtained.

For example, for a fluorine-containing acrylic elastomer containing a crosslinking monomer having a chlorine group and a carboxyl group, a polyamine-based vulcanizing agent and / or a trithiocyanuric acid-dithiocarbamic acid metal salt-based vulcanizing agent is used. A diamine compound-based vulcanizing agent is preferable for the fluorine-containing acrylic elastomer containing a crosslinking monomer having an epoxy group.

Specific examples of the polyamine-based vulcanizing agent include, for example, ethylenediamine, hexamethylenediamine, hexamethylenediaminecarbamate, 4,4-bis (aminocyclohexyl) methanecarbamate, N, N′-dicinnamylidene-1,6-hexanediamine. And so on. Of these, N, N'-dicinnamylidene-1,6-hexanediamine is preferred because of its stable initial vulcanizability and easy balance of physical properties of the vulcanizate.

Specific examples of trithiocyanuric acid-dithiocarbamic acid metal salt-based vulcanizing agent dithiocarbamic acid metal salt include
Examples thereof include zinc dimethyldithiocarbamate, iron dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dihexyldithiocarbamate, and zinc dibutyldithiocarbamate. Of these, zinc dibutyldithiocarbamate, which accelerates vulcanization relatively quickly and has stable initial vulcanizability, is preferred.

When vulcanizing fluororubber, it is known to use an acid acceptor to neutralize an acidic substance generated during vulcanization. In the composition of the present invention as well, in order to increase the crosslink density of the compound, and also to accelerate the vulcanization of the fluororubber when co-vulcanizing the fluorine-containing acrylic elastomer and the fluororubber, and control the vulcanization speed of the other side Therefore, it is preferable to use an acid acceptor.

Specific examples of the acid acceptor include magnesium oxide, calcium oxide, zinc white, dibasic lead phosphite, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate and the like. Of these, calcium carbonate is preferred from the viewpoints of rapid vulcanization and stability of initial vulcanization.

The composition of the present invention may generally have a reinforcing agent for an acrylic elastomer, a filler which may be compounded as a filler (for example, carbon black, white carbon, clay, talc, calcium carbonate, or the like) in order to give a more preferable balance of physical properties. Graphite, powdered quartz, etc.)
To 100 parts of fluorine-containing acrylic elastomer
You may mix up to 200 parts. If necessary, an antioxidant, a vulcanization stabilizer, a plasticizer, a processing aid, etc. may be added.

The method for preparing the composition of the present invention is not particularly limited, and for example, other compounding ingredients such as a fluorine-containing acrylic elastomer, fluororubber and a vulcanizing agent are kneaded by a usual rubber kneading machine such as a Banbury, a kneader or a roll. It can be prepared by

The thus obtained elastomer composition of the present invention is usually 140 ° C. or higher, preferably at a temperature of about 170 to 200 ° C. for about 1 to 20 minutes by a molding method such as compression, injection, injection generally used in the rubber industry. Can be vulcanized under the conditions
Even if post-vulcanization is performed, 1-5 at a temperature of 150-180 ° C
It only has to be done for about an hour.

The vulcanized product obtained from the elastomer composition of the present invention exhibits excellent heat resistance, and extremely favorable properties such as good oil resistance and compression set resistance. Moreover, since it is also excellent in the balance of various properties such as weather resistance, ozone resistance, and cold resistance, it is possible to make effective use of these characteristics to make various seals (gaskets, packing, o
-Rings, etc.), various hoses, coating materials, etc., as well as various belts, rolls, etc., and can be effectively used widely.

Next, the present invention will be described more specifically based on production examples and examples, but the present invention is not limited to the production examples and examples. Production Examples 1 to 4 and Comparative Production Examples 1 to 3 (synthesis of acrylic copolymer elastomer) 400 parts of a monomer mixture having the composition shown in Table 1, 4 parts of polyoxyethylene dodecyl ether, and sodium dodecyl sulfate.
1.5 parts and 200 parts of water were stirred and emulsified using a homomixer, charged into a reaction vessel preliminarily charged with 400 parts of water, and nitrogen substitution was sufficiently carried out while stirring while maintaining the liquid temperature at 30 ° C. Then, 0.2 part of cumene hydroperoxide, 0.01 part of ferrous sulfate and 0.2 part of sodium formaldehyde sulfoxylate were sequentially added to start the polymerization reaction and the temperature started to rise. When the temperature of the content liquid reached 50 ° C, the copolymerization reaction was completed by stirring for about 3 hours while maintaining the same temperature. The obtained copolymerized product was heated at about 80 ° C for 15
% Saline solution to coagulate the copolymer, which is washed with water and dried to give a fluorine-containing acrylic elastomer (A) to (D).
And acrylic elastomers (a) to (c) were obtained.

Examples 1 to 6 and Comparative Examples 1 to 7 Fluorine-containing acrylic elastomers (A) to (D) or acrylic elastomers (a) to (c) and compounding agents having compounding recipes shown in Tables 2 to 4 were prepared. The mixture was kneaded with a 6-inch roll for 20 minutes to prepare an acrylic elastomer composition. After aging the prepared composition for 1 day, it was vulcanized under the conditions described in each table to prepare a vulcanized composition. The properties of the obtained vulcanized product were evaluated in accordance with JIS K 6301 "Vulcanized rubber physical test method". The results are shown in Tables 2 to 4.

The following can be seen from the comparison between the results of the examples shown in Tables 2 to 4 and the results of the comparative examples.

(1) From the comparison between Examples 1 and 2 and Comparative Examples 1 to 4,
The composition of the present invention is a composition of acrylic elastomer alone,
As compared with the blend composition of the acrylic elastomer and the fluororubber and the single composition of the fluorine-containing acrylic elastomer, it is found that the heat resistance is excellent as shown in the results of the hot air aging test.

(2) From the comparison between Examples 3 to 5 and Comparative Examples 5 and 6,
It can be seen that the heat resistance is improved by increasing the blending ratio of the fluororubber as shown in the results of the hot air aging test. In addition, it can be seen that the oil resistance is improved from the volume change after JIS No. 3 oil immersion in the thermal lubricating oil immersion test. In addition, it can be seen from the results of the compression set resistance test and the Gehman torsion test that the composition of the present invention has excellent compression set resistance and various properties and low temperature characteristics are well balanced.

(3) From the comparison between Examples 1 to 6 and Comparative Examples 3, 6 and 7, the composition of the present invention has a heat resistance temperature of 15 as compared with the conventional acrylic elastomer as shown in the results of the hot air aging test. It can be seen that the temperature is improved by over ℃.

[Effect of the Invention] The elastomer composition of the present invention has a good affinity for fluororubber of the fluorine-containing acrylic elastomer and is kneaded,
It is possible to produce a vulcanized compound which is easy to be molded and vulcanized, has excellent heat resistance and oil resistance, and is well balanced in other physical properties such as compression set resistance and cold resistance.

Claims (1)

[Claims] 1. (A) (a) Alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and 1 carbon atom.
To at least one acrylate ester selected from the group consisting of alkoxyalkyl acrylates having 1 to 4 alkoxy groups and alkylene groups having 1 to 4 carbon atoms 20
~ 99.4% by weight, (b) general formula (I): (In the formula, R is a hydrogen atom or a methyl group, x is 0, 1 or 2, y is 0 or 1, n is 0 or 1, m is an integer of 1 to 12, and A is a hydrogen atom or a fluorine atom.) 40% to 0.5% by weight of at least one fluorine-substituted (meth) acrylic acid ester represented by: (C) one type of a crosslinking monomer having at least one type of chlorine group, epoxy group and carboxyl group Or 2
15 to 0.1% by weight of a fluorine-containing fluorine-containing monomer, which is 15 to 0.1% by weight and (d) 25 to 0% by weight of a copolymerizable monomer copolymerizable with the monomers of the above (a) component, (b) component and (c) (B) (a) a copolymer of vinylidene fluoride with at least one of hexafluoropropene, tetrafluoroethylene, chlorotrifluoroethylene and 1-hydropentafluoropropene, relative to 100 parts by weight of the acrylic elastomer. And (b) at least one fluororubber selected from the group consisting of copolymers of perfluoromethyl vinyl ether or propylene and tetrafluoroethylene 1
A heat- and oil-resistant elastomer composition containing up to 50 parts by weight.