JPH0148296B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vulcanizable epoxy group-containing acrylic rubber composition. Acrylic rubber has no double bonds in its main chain, so it inherently has excellent weather and heat resistance, but it cannot be vulcanized with sulfur or cheap vulcanizing agents commonly used in diene rubbers. , acrylic rubber containing epoxy groups has been put into practical use. Various methods of vulcanizing acrylic rubber containing epoxy groups have been proposed, such as the
Publication No. 39181 discloses a vulcanization system using an alkali metal salt of an organic carboxylic acid, sulfur or a sulfur donor, and a nitrogen-containing compound selected from ureas, thioureas, imidazolines, and amino acids. However, this vulcanization system does not provide sufficient compression set and heat resistance. The present inventors have discovered a vulcanization system for epoxy group-containing acrylic rubber that eliminates these drawbacks, and have completed the present invention. According to the present invention, 1 to 10 parts by weight of a guanidine compound, or 1 to 10 parts by weight of a guanidine compound and less than 0.1 part by weight of sulfur, or 1.5 parts by weight of a sulfur compound, per 100 parts by weight of acrylic rubber containing an epoxy group. A vulcanizable rubber composition is provided comprising: The acrylic rubber containing an epoxy group used in the present invention can be obtained by copolymerizing an alkyl acrylate and/or an alkyl acrylate derivative with a compound containing an epoxy group, or by copolymerizing an alkyl acrylate and/or an alkyl acrylate derivative and a compound other than the acrylate thereof. It can be obtained by copolymerizing an unsaturated monomer and a compound containing an epoxy group. Examples of alkyl acrylates used include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-hexyl acrylate, n-octyl acrylate, and 2-ethylhexyl acrylate, and examples of alkyl acrylate derivatives include methoxyethyl acrylate. , alkoxyalkyl acrylates, alkylthioalkyl acrylates, and cyanoalkyl acrylates, such as methoxymethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, methoxyethoxyethyl acrylate, and ethoxyethoxyethyl acrylate. Alkyl acrylate and/or alkyl acrylate derivative is 40-99% based on the total monomers.
Weight percent is preferred. Examples of compounds containing epoxy groups include glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether. The preferred amount of the epoxy group-containing compound used is 1 to 5% by weight, particularly preferably 1.5 to 3% by weight, based on the total monomers. In copolymerization, if there are few compounds containing epoxy groups, there is a risk that the resulting copolymer will not have enough vulcanization points and will not be able to obtain the degree of vulcanization required to obtain the desired physical properties. When the amount of compounds containing epoxy groups is large, the elongation at break of the vulcanizate tends to decrease significantly. Further, the acrylic rubber used in the present invention may be a product obtained by copolymerizing an alkyl acrylate and/or an alkyl acrylate derivative with a compound containing an epoxy group and one or more other unsaturated monomers. Preferred unsaturated monomers used in the copolymerization include vinyl carboxylate and ethylene. Examples of vinyl carboxylates include vinyl acetate, vinyl propionate, vinyl butyrate, and the like. The preferred amount of these comonomers to be used is 0 to 59
Weight%. Acrylonitrile is also preferred, and the preferred amount for copolymerization is 0 to 20% by weight. Specific examples of the acrylic rubber used in the present invention include copolymers of a compound containing an epoxy group and one or more monomers shown below. That is, copolymers with ethyl acrylate, copolymers with n-butyl acrylate, copolymers with methoxyethyl acrylate, copolymers with ethoxyethyl acrylate,
Copolymers of methyl acrylate and n-butyl acrylate, copolymers of ethyl acrylate and n-butyl acrylate, copolymers of n-butyl acrylate and methoxyethyl acrylate, copolymers of n-butyl acrylate and ethoxyethyl acrylate copolymers with methyl acrylate, ethyl acrylate and n-butyl acrylate; copolymers with methyl acrylate, n-butyl acrylate and methoxyethyl acrylate; copolymers with methyl acrylate, n-butyl acrylate and ethoxyethyl acrylate; Copolymers, copolymers with ethyl acrylate, n-butyl acrylate and methoxyethyl acrylate, copolymers with ethyl acrylate, n-butyl acrylate and ethoxyethyl acrylate, copolymers with n-butyl acrylate and acrylonitrile, A copolymer with methoxyethyl acrylate and acrylonitrile, a copolymer with n-butyl acrylate and vinyl acetate,
Copolymer of methoxyethyl acrylate and vinyl acetate, methyl acrylate, copolymer of n-butyl acrylate and vinyl acetate, ethyl acrylate, copolymer of n-butyl acrylate and vinyl acetate, methyl acrylate, methoxyethyl acrylate and copolymers with vinyl acetate, ethyl acrylate, methoxyethyl acrylate and copolymers with vinyl acetate, copolymers with methyl acrylate and ethylene, ethyl acrylate, copolymers with vinyl acetate and ethylene, n-butyl Acrylate, copolymer with vinyl acetate and ethylene, methoxyethyl acrylate, copolymer with vinyl acetate and ethylene, ethyl acrylate, methoxyethyl acrylate,
Copolymer with vinyl acetate and ethylene, n-butyl acrylate, methoxyethyl acrylate,
Examples include, but are not limited to, copolymers with vinyl acetate and ethylene. In addition, commercially available products such as "Toacron AR-601" manufactured by Toa Paint Co., Ltd., "Noxtite PA-301" manufactured by Nippon Oil Seal Co., Ltd., and "Nitsupol AR-32" manufactured by Nippon Zeon Co., Ltd. can also be used. The rubber composition of the present invention contains a guanidine compound as a vulcanizing agent. The guanidine compounds used in the present invention are usually commercially available as vulcanization accelerators for diene rubbers, and typical examples include:
Diphenylguanidine, di-o-tolylguanidine, 1-o-tolyl biguanide and salts thereof,
For example, there is di-o-tolylguanidine salt of dicatechol borate. The guanidine compound is blended in an amount of 1 to 10 parts by weight, preferably 3 to 7 parts by weight, per 100 parts by weight of the epoxy group-containing acrylic rubber. If the guanidine compound is less than 1 part by weight,
It is not possible to impart sufficient heat resistance and low compression set to the vulcanizate, and if the amount exceeds 10 parts by weight, the tackiness of the composition increases, making it difficult to roll when adding various rubber chemicals to the composition. becomes difficult. According to the present invention, by blending 1 to 10 parts by weight of a guanidine compound to 100 parts by weight of acrylic rubber containing an epoxy group, the resulting composition can undergo a vulcanization process normally carried out in the rubber industry. After that, a so-called post-vulcanization is performed in which the material is exposed to high-temperature air for a certain period of time, thereby obtaining a vulcanized material having the desired performance. The vulcanizate has low compression set and good heat resistance. Furthermore, the composition of the present invention can also contain sulfur or a sulfur compound in addition to the guanidine compound in the vulcanization system. The addition of sulfur or sulfur compounds can improve the tensile properties of the vulcanizate before post-vulcanization. When adding sulfur, per 100 parts by weight of acrylic rubber containing epoxy groups.
It should be limited to less than 0.1 part by weight; if it exceeds 0.1 part by weight, the effect of improving the compression set of the vulcanizate will decrease. In addition, sulfur compounds that can be added together with guanidine compounds are those that can be produced as free sulfur by decomposition, such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and tetramethylthiuram monosulfide. It is commonly used as a vulcanization accelerator for diene-based rubbers such as hydride, dipentamethylenethiuram tetrasulfide, dibenzothiazyl sulfide, 2-(4′-morpholinodithio)benzothiazole, and dithiodimorpholine. Things can be mentioned. Furthermore, as the sulfur compound, those containing free sulfur or sulfur compounds as impurities, such as sub-sulfur compounds, are also effective. When adding a sulfur compound, it should be limited to 1.5 parts by weight or less per 100 parts by weight of acrylic rubber containing an epoxy group. If it exceeds 1.5 parts by weight, vulcanization of the vulcanizate will be incomplete, so it is preferably 1 part by weight or less, and particularly preferably 0.5 parts by weight or less if emphasis is placed on compression set of the vulcanizate. The rubber composition of the present invention can be vulcanized in principle by any vulcanization operation normally used in the rubber industry, such as press vulcanization, steam vulcanization, and molten salt vulcanization. The temperature and time do not require any specific conditions, except that the vulcanizate must be able to maintain its own shape in the post-vulcanization step described below. For example, preferred vulcanization conditions are a vulcanization temperature of 140 to 170°C and a vulcanization time of 10 to 60 minutes, and in the case of injection molding, a temperature of 180 to 220°C and 0.5 to 2 minutes. After the vulcanization process, the vulcanizate is then subjected to heat treatment using heated air, a so-called post-vulcanization process, before it can exhibit its desired performance. The conditions for post-vulcanization are usually
2-24 hours at 130-180℃ is the most common, but
Depending on the productivity and required performance of the vulcanizate, the time may be increased or decreased or the post-vulcanization temperature may be increased or decreased. Furthermore, the rubber composition of the present invention can naturally contain various additives such as fillers and plasticizers that are commonly used in the rubber industry, if necessary. This will be explained below using examples. The epoxy group-containing acrylic rubber used in the examples was manufactured as follows. Production of acrylic rubber containing epoxy groups: Polyvinyl alcohol in an autoclave of 40
530g, sodium acetate 21.6g, sodium formaldehyde sulfoxylate (Rongalitz) 32.4g, sodium salt of ethylenediaminetetraacetic acid 1.08g and ferrous sulfate 0.54g and water 15614g
was added and dissolved, vinyl acetate (see Table 1) was added thereto and stirred, and after purging the space inside the autoclave with nitrogen, 1800 g of ethylene monomer was injected under pressure. Then, the pressure was 50Kg/cm ² and the polymerization temperature was 55℃.
While maintaining the temperature of The solution was added dropwise to promote polymerization. After the polymerization was completed, unreacted monomers were removed, a 3% by weight aqueous borax solution was added to coagulate the polymer, and after dehydration, the polymer was cut into pieces and washed with water. This polymer was dried on two rolls at 120-130°C. The dried polymers were used as Elastomers 1 and 2 in Examples. The amounts of various substances added to the autoclave are shown in Table 1.

[Table] Examples 1 to 4, Comparative Example 1 Using an 8-inch mixing roll, the formulations shown in Table 2 were made. After dispensing the compound to a thickness of 2.4 mm, it was press-cured at 170°C for 20 minutes, and then
It was post-vulcanized for 8 hours in a gear oven at 150°C. The vulcanizate was subjected to a tensile test, hardness test, and compression set test in accordance with JIS K6301.
It was also heat aged in a gear oven and subjected to a tensile test and hardness test. The results are shown in Table 2.

[Table] Examples 5 to 8, Comparative Examples 2 to 3 Elastomer 1 was used and the amount of diorthotolylguanidine added was varied as shown in Table 3. The mixture was vulcanized in the same manner as in Example 1, and the physical properties of the vulcanized product were measured. The results are shown in Table 3.

[Table] Examples 9 to 16, Comparative Example 4 Elastomer 1 was used and the amounts of diphenylguanidine and sulfur compound added were varied as shown in Table 4. The mixture was vulcanized in the same manner as in Example 1, and the physical properties of the vulcanized product were measured. The results are shown in Table 4.

【table】

[Table] Examples 17 to 19, Comparative Examples 5 to 7 Elastomer 2 was used and the amounts of diphenylguanidine and sulfur added were varied as shown in Table 5. After the blend was separated in the same manner as in Example 1, it was vulcanized and the physical properties of the vulcanized product were measured.

【table】

【table】

Claims (1)

[Claims] 1 1 to 10 parts by weight of a guanidine compound per 100 parts by weight of acrylic rubber containing an epoxy group,
or 1 to 10 parts by weight of a guanidine compound and sulfur
A vulcanizable rubber composition containing less than 0.1 part by weight or 1.5 parts by weight or less of a sulfur compound.