JPS62926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a novel sulfur-vulcanizable acrylic rubber, and more particularly relates to (1) at least one alkyl acrylate whose alkyl group has 1 to 8 carbon atoms; 30 to 89.5 parts by weight of the monomer, (2) 1 to 4 alkoxy groups
carbon atoms, and the alkylene group is 1 to 4
At least one monomer selected from alkoxyalkyl acrylates having 5 carbon atoms
10 to 60 parts by weight, (3) 0.5 to 10 parts by weight of at least one of the monomers represented by the general formula (), (In the formula, R ₁ is hydrogen or a methyl group, R ₂ and
R ₃ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms) (4) Relating to a method for producing sulfur-vulcanizable acrylic rubber by radical copolymerizing with 30 parts by weight or less of acrylonitrile. It is something. Acrylic rubber is an elastic material whose main component is acrylic ester, and is generally known as a rubber with excellent heat resistance and oil resistance, but because it does not have a double bond in the main chain of the rubber molecule, it is generally It is well known that these are copolymerized monomers having active groups that serve as crosslinking points. Monomer components that serve as crosslinking points include 2-chloroethyl vinyl ether, vinyl chloroacetate,
Halogen monomers such as allyl chloroacetate, vinylbenzyl chloride, and 5-chloroacetoxymethyl-2-norbornene, and epoxy monomers such as allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate have been commonly used. . Acrylic rubber containing such crosslinking components cannot be vulcanized with ordinary sulfur or sulfur-containing organic compound-vulcanization accelerator systems, and cannot be vulcanized with amines, ammonium salts,
Metallic soaps such as sulfur are generally used as crosslinking agents, but they have the drawback of slow vulcanization speed and the need for long heat treatment after vulcanization to obtain optimal vulcanization properties. Furthermore, the use of amines and ammonium salts has the disadvantage that they generate odor during vulcanization, and that the final product cannot be used for medical or food purposes due to hygiene reasons. Furthermore, acrylic rubbers that use halogen monomers as crosslinking monomers have problems in that they corrode molds during vulcanization and corrode metals in contact with the product. In order to improve these drawbacks, acrylic rubbers containing dicyclobentadiene, methylcyclopentadiene, ethylidenenorbornene, putadiene, allyl acrylate, 2-putenyl acrylate, etc. as crosslinking monomer components have also been developed. However, the vulcanization rate is not sufficient and the heat resistance and compression set resistance are poor, so that a product that is fully satisfactory for practical use has not yet been obtained. As a result of various studies to improve the above-mentioned drawbacks, the present inventors found that (1) at least one monomer of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms;
30 to 89.5 parts by weight, (2) at least one alkoxyalkyl acrylate having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms10
~60 parts by weight, (3) General formula () (In the formula, R ₁ is hydrogen or a methyl group, R ₂ and
0.5 to 10 parts by weight of at least one of alkenyl acrylates and alkenyl methacrylates (R ₃ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms); (4) 0 to 10 parts by weight of acrylonitrile; The inventors have discovered that an acrylic rubber that is sulfur-vulcanizable and has well-balanced practical properties can be obtained by radically polymerizing a monomer mixture consisting of 30 parts by weight, leading to the present invention. Therefore, the purpose of the present invention is to improve the vulcanization speed, which is a disadvantage of conventional acrylic rubber, compared to diene rubber, without impairing the heat resistance, oil resistance, weather resistance, ozone resistance, etc., which are the characteristics of conventional acrylic rubber. It is an object of the present invention to provide a new sulfur-vulcanizable acrylic rubber that has been improved to the same extent, has a small compression set, does not require long-term heat treatment after vulcanization, and has a good balance between cold resistance and oil resistance. Examples of the alkyl acrylate having an alkyl group having 1 to 8 carbon atoms as component (1) used in the present invention include methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, hexyl acrylate, cyclohexyl acrylate,
Examples include octyl acrylate. Preferred are ethyl acrylate, propyl acrylate, butyl acrylate, etc. having an alkyl group having 2 to 4 carbon atoms. The amount used is 30~ in the monomer mixture
89.5 parts by weight are used. If the amount is less than 30 parts by weight, the resulting acrylic rubber will have poor elasticity and strength. Examples of the alkoxyalkyl acrylate having an alkyl group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms as component (2) used in the present invention include methoxymethyl acrylate, methoxyethyl acrylate, and ethoxyethyl acrylate. . The amount of these alkoxyalkyl acrylates used is 10 to 60 parts by weight, preferably 20 to 50 parts by weight. Examples of alkenyl acrylate and/or alkenyl methacrylate as component (3) used in the present invention include 3-methyl-2-putenyl acrylate, 3-methyl-2-heptenyl acrylate,
3-methyl-2-hexenyl acrylate, 3-
Examples include ethyl-2-heptenyl acrylate, 3-ethyl-2-hexenyl acrylate, and their corresponding methacrylates. Other binary copolymers with alkyl acrylates such as allyl acrylate and ethyl acrylate using 2-butenyl acrylate are known (US Pat. No. 3,476,722), but even if sulfur vulcanization is performed, conventional Similar to acrylic rubber (using halogen monomers, epoxy monomers, etc. as crosslinking points), not only does it require a long heat treatment after vulcanization, but the resulting vulcanizate also has properties that are sufficient for practical use. I don't have it. Also, acrylic rubber made by copolymerizing allyl methacrylate/alkyl acrylate/acrylonitrile, etc. is also known (Japanese Patent Publication No. 47-7893).
Similar to the above, it does not have characteristics that can be used practically. Alkenyl acrylate used in the present invention,
The amount of alkenyl methacrylate is 0.5 to 10 parts by weight. If the amount is less than 0.5 parts by weight, the vulcanization rate of the resulting acrylic rubber will be extremely slow. Moreover, when the amount exceeds 10 parts by weight, the resulting acrylic rubber vulcanizate has a significantly increased hardness and a significant decrease in strength and elongation.
Preferably it is 2 to 6 parts by weight. Component (4) acrylonitrile used in the present invention is used to adjust the strength and oil resistance of the acrylic rubber obtained, and the amount used is 30 parts by weight or less, preferably 2 to 20 parts by weight. The acrylic rubber according to the present invention can be easily produced using known polymerization methods such as emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization using the monomer mixture using a commonly used radical initiator. can.
The polymerization can be carried out batchwise or by adding one or more component monomers continuously or intermittently during the polymerization. The polymerization temperature ranges from -10°C to 100°C, preferably from 2 to 80°C. The acrylic rubber obtained in this way can be easily vulcanized with a sulfur vulcanization system commonly used for diene rubbers, and the acrylic rubbers that are unavoidable in the vulcanization of ordinary acrylic rubbers that have halogen and epoxy components as crosslinking points Not only does it not require extremely long heat treatment after vulcanization, but the vulcanizate has excellent heat resistance, weather resistance,
It is an excellent acrylic rubber with a good balance of ozone resistance, cold resistance, and oil resistance. Furthermore, the acrylic rubber of the present invention is an acrylic rubber that has significantly improved heat resistance and compression set properties, which are disadvantages of known acrylic rubbers that can be vulcanized with sulfur. In addition to the vulcanization system, the acrylic rubber of the present invention may optionally contain compounding agents such as reinforcing agents, fillers, plasticizers, and anti-aging agents that are generally used for rubber. The acrylic rubber vulcanizate obtained by the present invention is useful in many fields requiring heat resistance, oil resistance, weather resistance, and ozone resistance. Such uses include various rubber products such as gaskets, hoses, conveyor belts, packing, oil seals, and valve seats. Next, the present invention will be specifically explained with reference to Examples. Example The monomer mixture shown in Table 1 was polymerized according to the following polymerization recipes () and () in two separable flasks equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a pressure reducing device. Prior to polymerization, the pH of the mixture in the flask was adjusted to 7, the temperature in the system was brought to 5°C while stirring, degassing and nitrogen substitution were repeated, and oxygen in the system was sufficiently removed. was added to initiate polymerization. Polymerization was completed in about 16 hours. Polymerization conversion was within the range of 95-99%. After polymerization,
The polymerization product was salted out, thoroughly washed with water, and then dried in a vacuum dryer to obtain the desired acrylic rubber. (Polymerization recipe) () Water 1000g Sodium dodecylbenzene sulfonate 20g Sodium naphthalene sulfonate 10g Sodium sulfate 3g Ethylenediaminetetraacetic acid tetrasodium salt 0.2g Ethylenediaminetetraacetic acid sodium salt-ferric salt 0.005g Monomer mixture (ferric salt) Table) 1000g () Na ₂ S ₂ O ₄ 0.2g Sodium formaldehyde sulfoxylate 0.2g P-menthane hydroperoxide 0.1g

【table】

[Table] Compounds of the eight types of acrylic rubber thus obtained were prepared using oven rolls under cooling according to the formulations in Table 2, and then press vulcanization was performed at 160°C for 20 minutes, and then further gear vulcanization was performed. Heat treatment was carried out in an oven at 150°C for 4 hours and at 150°C for 16 hours. The properties of these vulcanizates were measured according to JIS K-6301. The obtained physical properties are shown in Table 3. Further, FIG. 1 shows the vulcanization behavior of Experiment No. 1 of the present invention example and Comparative Examples 7 and 8 using an oscillating disk rheometer (manufactured by Toyo Seiki Co., Ltd.).

【table】

【table】

[Table] As is clear from Figure 1, the acrylic rubber obtained by the present invention has a "sloppy" texture compared to ordinary acrylic rubber.
Although it undergoes vulcanization, it exhibits flat vulcanization similar to diene rubber. Therefore, as shown in Table 3, conventional acrylic rubber requires long heat treatment at 150°C for 16 hours after vulcanization, but the acrylic rubber of the present invention requires extremely short heat treatment of only 4 hours. Not only does it provide a vulcanizate with properties equivalent to those of conventional acrylic rubber, but it also significantly improves heat resistance and compression set, which are shortcomings of known sulfur-vulcanizable acrylic rubber. It also has an excellent balance between hardness and oil resistance. From these results, according to the present invention, the vulcanization speed, which is the disadvantage of conventional acrylic rubber, can be improved by diene without impairing the advantages of conventional acrylic rubber, such as heat resistance, oil resistance, weather/ozone resistance, and cold resistance. It can be seen that an acrylic rubber can be obtained that can be improved to the same level as other rubbers, has a low compression set, and has a good balance between cold resistance and oil resistance.

[Brief explanation of the drawing]

FIG. 1 shows the vulcanization behavior of the formulations of Experiment Nos. 1, 7, and 8 on an oscillating disc rheometer. The vertical axis is torque (Kg・
cm), and the horizontal axis represents vulcanization time (minutes).

Claims (1)

[Scope of Claims] 1 (1) 30 to 89.5 parts by weight of at least one monomer selected from alkyl acrylates having an alkyl group of 1 to 8 carbon atoms, (2) an alkoxy group of 1 to 8 carbon atoms; 10 to 60 parts by weight of at least one monomer selected from alkoxyalkyl acrylates having ~4 carbon atoms and an alkylene group having 1 to 4 carbon atoms, (3) general formula 0.5 to 10 parts by weight of at least one of the monomers represented by (), (In the formula, R ₁ is hydrogen or a methyl group, R ₂ and
(R ₃ may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms) (4) A sulfur-vulcanizable product characterized by radical copolymerization with 0 to 30 parts by weight of acrylonitrile. Method of manufacturing acrylic rubber. 2 The monomer represented by the general formula () is 3-methyl-2-butenyl acrylate or 3-methyl-
The manufacturing method according to claim 1, which is 2-butenyl methacrylate. 3. The manufacturing method according to claim 1, wherein the radical copolymerization is carried out in an aqueous medium.