JPH0322892B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel acrylic rubber and a method for producing the same, and more particularly, the present invention relates to a new acrylic rubber and a method for producing the same, and more particularly, the present invention relates to an acrylic rubber containing a carboxyl group-containing unsaturated monomer unit and an epoxy group-containing unsaturated monomer unit as crosslinking monomer units. This invention relates to rubber and its manufacturing method. Acrylic rubber is an elastic body containing acrylic ester as a main component, and is generally known as a rubber with excellent heat resistance, oil resistance, etc. However, since the main chain of the rubber molecule does not have a double bond, it has conventionally been carried out to copolymerize a monomer having an active group that serves as a crosslinking point. Copolymerized halogen-containing monomers such as 2-chloroethyl vinyl ether, vinyl chloroacetate, allyl chloroacetate, vinylbenzyl chloride, 5-chloroacetoxymethyl-2-norbornene, etc. as crosslinking points, glycidyl acrylate, glycidyl methacrylate ,
Copolymerizers of epoxy group-containing monomers such as allyl glycidyl ether, or copolymerizers of carboxyl group-containing unsaturated monomers such as acrylic acid, methacrylic acid, and maleic acid have traditionally been used. There is. For acrylic rubber copolymerized with such crosslinking monomers, amines, ammonium salts, metal soaps, sulfur, etc. are usually used as crosslinking agents, but the vulcanization rate is slow and it is difficult to achieve optimal vulcanized physical properties. In order to obtain a vulcanized product having the above-mentioned properties, it is necessary to carry out a long heat treatment after vulcanization. Therefore, eliminating the need for this long heat treatment or shortening the treatment time would be of great industrial benefit, and the development of such an acrylic rubber is eagerly awaited. Various attempts have been made to more effectively vulcanize acrylic rubber, such as a method of using a halogen-containing unsaturated monomer and a carboxyl group-containing unsaturated monomer in combination (Japanese Patent Publication No. 56-25943). Although it has been proposed, it has drawbacks such as vulcanization being too fast and scorch occurring during the processing process, so it is not practically satisfactory. Against this background, the present inventors conducted various studies to develop an acrylic rubber that does not require substantially post-vulcanization heat treatment, and found that an epoxy group-containing unsaturated monomer and a carboxyl The present invention was developed based on the knowledge that a vulcanizate having an appropriate vulcanization rate and excellent vulcanization properties can be obtained by copolymerizing a predetermined proportion of a group-containing unsaturated monomer. . The purpose of the present invention is to avoid the need for long-term heat treatment after vulcanization, which is a disadvantage of conventional acrylic rubber, without impairing the characteristics of acrylic rubber such as heat resistance, oil resistance, weather resistance, and ozone resistance. The purpose of the present invention is to provide a new acrylic rubber with low compression set and a good balance between cold resistance and oil resistance, and a method for producing the same. The object of the present invention is to (1) contain 30 to 89.8% by weight of at least one monomer of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, (2) an alkoxy group having 1 to 4 carbon atoms and At least one alkoxy acrylate having ~4 alkylene groups10
~60% by weight, (3) epoxy group-containing unsaturated monomer 0.1
~5% by weight, (4) carboxyl group-containing unsaturated monomer
0.1 to 5% by weight, (5) ethylenically unsaturated monomer 0 to
Achieved by producing and using acrylic rubber, which is a random copolymer with 30% by weight as a constituent unit, is substantially free of branching, and has a Mooney viscosity (ML ₁₊₄ , 100℃) of 10 or more. . Monomer component (1) constituting the acrylic rubber of the present invention
Examples of the alkyl acrylate having an alkyl group having 1 to 8 carbon atoms include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and octyl acrylate. Ethyl acrylate, propyl acrylate, preferably having an alkyl group having 2 to 4 carbon atoms;
butyl acrylate, etc. The content in acrylic rubber is 30-89.8% by weight. If it is less than 30% by weight, the resulting acrylic rubber will have poor elasticity and strength, and if it exceeds 89.8% by weight, the balance between cold resistance and oil resistance will be poor. Preferably it is 40 to 80% by weight. Examples of the alkoxyalkyl acrylate having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms as the constituent monomer component (2) of the acrylic rubber of the present invention include methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, Examples include butoxyethyl acrylate, methoxyethoxyethyl acrylate, and the like.
The content of these alkoxy acrylates in acrylic rubber is 10 to 60, considering the balance between cold resistance and oil resistance.
% by weight, preferably 20-50% by weight. Examples of the epoxy group-containing unsaturated monomer of the constituent monomer component (3) of the acrylic rubber of the present invention include vinyl glycidyl ether, allyl glycidyl ether, methallyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate. Preferred are glycidyl methacrylate and allyl glycidyl ether. The content of these epoxy group-containing unsaturated monomers in acrylic rubber is
It is 0.1 to 5% by weight. If the amount is less than 0.1% by weight, the resulting acrylic rubber will have a slow vulcanization rate, and a practically satisfactory vulcanizate cannot be obtained. Moreover, when the amount exceeds 5% by weight, the vulcanization rate of the resulting acrylic rubber becomes faster and it becomes easier to harden during processing. Preferably it is 0.5 to 3% by weight. The carboxyl group-containing unsaturated monomers of the constituent monomer component (4) of the acrylic rubber of the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, 2-norbornene-5-carboxylic acid, and cinnamic acid. Examples include acids, monomethyl maleate, and the like.
Preferred are acrylic acid and methacrylic acid. The content of these carboxyl group-containing monomers is 0.1~
It is 5% by weight. If the amount is less than 0.1% by weight, the resulting acrylic rubber will have a slow vulcanization rate, and a practically satisfactory vulcanizate cannot be obtained. Moreover, when the amount exceeds 5% by weight, the vulcanization rate of the resulting acrylic rubber becomes faster and it becomes easier to harden during processing. Preferably it is 0.2 to 3% by weight. The ethylenically unsaturated monomer as the constituent monomer component (5) of the acrylic rubber of the present invention is used to adjust the strength and oil resistance of the obtained acrylic rubber as necessary, and the content is preferably 30% by weight or less. is 2 to 20% by weight. Such monomers include styrene, α-
Examples include aromatic vinyl compounds such as methylstyrene, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, and unsaturated amide compounds such as acrylamide, methacrylamide, and N-methyl methacrylolamide. The acrylic rubber of the present invention can be obtained by polymerizing a mixture of the above-mentioned monomers in a predetermined proportion using a commonly used radical initiator. Except for the epoxy group-containing unsaturated monomer, the amount of each of the monomers used during polymerization is approximately the same as the content in the resulting acrylic rubber, so the ratio of the monomers used is determined by the amount contained in the acrylic rubber. It may be the same as the composition ratio. However, some epoxy group-containing unsaturated monomers have low copolymerizability with other monomers, and in order to contain them in the acrylic rubber in a predetermined amount, it is necessary to use an excessive amount. In order to make the amount of the monomer unit in the acrylic rubber 0.1 to 5% by weight, the monomer needs to be used in an amount of 0.1 to 20% by weight (based on the total monomer mixture). The acrylic rubber of the present invention can be easily produced by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization using a predetermined proportion of the monomer mixture using a commonly used radical initiator. However, emulsion polymerization is particularly suitable. The polymerization can be carried out batchwise or by adding one or more component monomers continuously or intermittently during the polymerization. The polymerization temperature is in the range of -10°C to 100°C, preferably 2 to 80°C. Commonly used radical initiators include, but are not limited to, organic and inorganic peroxides, inorganic persulfates, organic hydroperoxides, azo compounds, or known redox catalyst systems. When producing by emulsion polymerization, anionic, cationic or nonionic surfactants and other auxiliary materials for polymerization are used, but it goes without saying that these substances are not limited in any way in the present invention. stomach. After the completion of polymerization, the acrylic rubber of the present invention is isolated from the polymerization system by a conventional coagulation method, for example, by adding a coagulant such as hydrochloric acid or a polyvalent metal salt, followed by washing and drying steps to obtain a solid acrylic rubber. The acrylic rubber of the present invention is mixed with various compounding agents (vulcanizing agents, reinforcing agents, fillers, processing aids, anti-aging agents, etc.) commonly used in the rubber industry in a conventional mixer such as a roll or Banbury mixer. be able to. The acrylic rubber of the present invention includes, for example, quaternary ammonium salts, quaternary phosphonium salts, guanidines,
It can be easily vulcanized with alkali metal salts of weak organic acids. The acrylic rubber of the present invention not only does not require long-term heat treatment after vulcanization, but its vulcanized product has extremely excellent compression set properties, and has a good balance between heat resistance, weather resistance, ozone resistance, cold resistance, and oil resistance. It is an excellent acrylic rubber with a smooth texture. The acrylic rubber vulcanizate of the present invention is useful in many fields requiring heat resistance, oil resistance, weather resistance, and ozone resistance. Such uses include a variety of rubber products such as gaskets, hoses, conveyor belts, packing, oil seals, and valve seats. The chemical structure and composition of the acrylic rubber of the present invention is
The epoxy group content is determined from the ¹³ C-nuclear magnetic resonance spectrum, and the epoxy group content is determined by dissolving a predetermined amount of the sample in methyl ethyl ketone, reacting the excess amount with hydrochloric acid, and neutralizing and titrating the remaining hydrochloric acid. Further, the carboxyl group content can be determined by dissolving the sample in acetone and then directly performing neutralization titration. Next, the present invention will be specifically explained with reference to Examples. Example 1 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, put () into a flask, adjust the pH of the mixture in the flask to 7, bring the temperature inside the system to 5°C while stirring, degas,
After repeating nitrogen substitution to sufficiently remove oxygen from the system, () was added to initiate polymerization. Polymerization is approx.
It was completed in 16 hours. Polymerization conversion was within the range of 95-99%. After the polymerization was completed, 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 dodecylbenzenesulfonate 20g Sodium naphthalene sulfonate 10g Sodium sulfate 3g Ethylenediaminetetraacetic acid tetrasodium salt
0.2g Sodium ethylenediaminetetraacetate ferric salt 0.005g Monomer mixture (Table 1) 1000g () Na ₂ S ₂ O ₄ 0.2g Sodium formaldehyde sulfoxylate
0.2g P-menthane hydroperoxide 0.1g

[Table] The composition of the acrylic rubber thus obtained was determined by the method described in the detailed description of the invention. ^13C for determination of ethyl acrylate, butyl acrylate, methoxyethyl acrylate, and acrylonitrile
- Determined from each NMR chemical shift. The result is second
Shown in the table. Chemical shift (ppm, TMS standard) (solvent: _CDCl3 ) _70.17 ( _O- ^* _CH2CH2OCH3 )
Methoxyethyl acrylate 64.42 (O- ^* CH ₂ CH ₂ ...) Butyl acrylate 60.47 (O- ^* CH ₂ CH ₃ ) Ethyl acrylate 28.21 (- ^* CH ₂ -CH-) Acrylotrile

【table】

[Table] These 10 types of acrylic rubber were prepared according to the formulations in Table 3 using open rolls under cooling, then press vulcanized at 170°C for 20 minutes, and then further placed in a gear oven. Heat treatment was performed at 150°C for 4 hours and at 150°C for 16 hours. The properties of these vulcanizates were measured according to JISK-6301, and the results are shown in Table 4. Further, FIG. 1 shows the vulcanization behavior of the inventive example, and FIG. 2 shows the vulcanization behavior of the comparative example using an oscillating disk rheometer (manufactured by Toyo Seiki Co., Ltd.).

【table】

【table】

[Table] As is clear from FIGS. 1 and 2, the acrylic rubber according to the prior art was vulcanized "sloppily" (Experiment No. 8) or vulcanized too quickly (Experiment No. 9,
10) In contrast, the acrylic rubber of the present invention (experiment numbers 1 to 6) has a practical vulcanization rate and exhibits flat vulcanization. Furthermore, as shown in Table 4, the acrylic rubber according to the prior art is
Vulcanization at 170°C for 20 minutes alone will result in an inferior compression set value, making it unusable and requires long heat treatment. However, the acrylic rubber of the present invention has no permanent compression set after vulcanization at 170°C for 20 minutes. Since the value falls within the practical range, there is virtually no need for heat treatment, resulting in significant energy savings and productivity improvements. It also has an excellent balance between cold resistance and oil resistance. Comparative example experiment number 10
Although it has relatively excellent compression set properties, it vulcanizes too quickly to be practical. From these results, the acrylic rubber of the present invention has the advantages of conventional acrylic rubber, such as heat resistance, oil resistance,
It eliminates the need for long-term heat treatment after vulcanization, which is a disadvantage of conventional acrylic rubber, without impairing weather resistance, ozone resistance, or cold resistance, and has a low compression set, a good balance between cold resistance and oil resistance. It can be seen that this is an excellent acrylic rubber. Example 2 Acrylic rubber was obtained by the method of Example 1 except that the composition of the monomer mixture used was shown in Table 5. The composition of the obtained acrylic rubber was determined in the same manner as in Example 1. The results are shown in Table 6.

【table】

[Table] Vulcanized products of these six types of acrylic rubber were prepared in the same manner as in Example 1 using the same formulation as in the columns of "Invention Examples 1 to 7, 11 to 13" in Table 3, and the vulcanized physical properties were The results shown in Table 7 were obtained.

[Table] From the results in Table 7, it can be seen that the acrylic rubber of the present invention requires only a short heat treatment after vulcanization, and
From the comparison with Experiment Nos. 11 to 13, it can be seen that this is an excellent acrylic rubber with a good balance of cold resistance and oil resistance.

[Brief explanation of drawings]

FIG. 1 shows the vulcanization behavior of the acrylic rubber of the present invention of Example 1, and FIG. 2 shows the vulcanization behavior of the acrylic rubber of the comparative example of Example 1. All numbers in the figure represent experiment numbers.

Claims (1)

[Scope of Claims] 1 (1) 30 to 89.8% 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% 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) Containing epoxy groups 0.1 to 5% by weight of an unsaturated monomer, (4) 0.1 to 5% by weight of an unsaturated monomer containing a carboxyl group, and (5) 0 to 5% of an ethylenically unsaturated monomer copolymerizable with each of the above monomers. It is a random copolymer containing 30% by weight as a constituent unit, contains virtually no branches, and has a Mooney viscosity (ML ₁₊₄ , 100
Acrylic rubber with a temperature of 10°C or higher. 2 (1) at least one monomer selected from alkyl acrylates having an alkyl group of 1 to 8 carbon atoms, (2) an alkoxy group having 1 to 4 carbon atoms, and At least one monomer selected from alkoxyalkyl acrylates in which the alkylene group has 1 to 4 carbon atoms, (3) an epoxy group-containing unsaturated monomer, and (4) a carboxyl group-containing unsaturated monomer. (5) Radical copolymerization using predetermined proportions of ethylenically unsaturated monomers that can be copolymerized with each of the above monomers, and as needed. The amount is (1) 30-89.8% by weight, (2)
10 to 60% by weight, (3) 0.1 to 5% by weight, (4) 0.1 to 5% by weight, and (5) 0 to 30% by weight, and has a Mooney viscosity (ML ₁₊₄ , 100°C) of 10 or more. A method for producing acrylic rubber, characterized in that it is made into a copolymer.