JP6211854B2 - Rubber composition and method for improving rubber permanent compression strain - Google Patents

Description

The present invention relates to a composition of a carboxyl group-containing acrylic rubber and a method for improving the permanent compression strain of the rubber. More specifically, the carboxyl group-containing acrylic rubber is an amine salt of hexamethylenediamine carbamate as a crosslinking agent and 2-mercaptobenzothiazole as a vulcanization activator, and the amine is 1,8-diazabicyclo [5.4.0]. Rubber composition containing a salt selected from undecene-7,1,5-diazabicyclo [4.3.0] nonene-5,1,4-diazabicyclo [2.2.2] octane, and improvement of permanent compression strain of the rubber Regarding the method. Hereinafter, in this specification, 1,8-diazabicyclo [5.4.0] undecene-7 is DBU, 1,5-diazabicyclo [4.3.0] nonene-5 is DBN, 1,4-diazabicyclo [2.2.2] octane. May be referred to as DABCO.

Acrylic rubber is obtained by crosslinking an acrylic ester polymer with a co-crosslinking monomer. A particularly important copolymer with 2-chloroethyl vinyl ether is called ACM, and a copolymer with acrylonitrile is called ANM. Yes. The characteristics of ACM are excellent heat resistance, heat aging resistance, and weather resistance, but scorch stability is insufficient, normal tensile strength is low, roll adhesion is large, and cold resistance is insufficient. Is a drawback. Because it has heat resistance and oil resistance, it is used for automobile oil hoses, gaskets, packings, ship-related seals, etc.

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For the crosslinking of these rubbers, basic diphenylguanidine and di (o-tolyl) guanidine are known as vulcanization activators. According to Patent Document 1, at least one vulcanization accelerator selected from non-aromatic amines, amidines such as DBU, and salts thereof is blended with various acrylate rubbers, and guanidine is added. Disclosed mixtures are disclosed.

Similarly, according to Patent Document 1, the sentence number 0005 and after, "If good flex resistance and elongation are required, diphenylguanidine (DPG) or the best compression set is required. , Di-o-tolylguanidine (DOTG) is preferred ", then" systems containing guanidine as a promoter are well known, but these guanidines have been a subject of much public debate about their dangers. In order to improve the permanent compression strain, basic diphenylguanidine and di (o-tolyl) guanidine are known as vulcanization activators, but these guanidine compounds It is understood that there is a problem that its use is limited by hygienic requirements, such as carcinogenicity is estimated.

Although it is disclosed in Patent Document 2 that DBU and DBN act alone or in the form of a salt as a vulcanization activator for acrylic rubber, there is no specific description of the salt. Patent Document 3 discloses an acrylic rubber composition in which an acrylic rubber is blended with a polyamine compound exemplified by hexamethylenediamine carbamate as a crosslinking agent and a diazabicycloalkene exemplified by DBU as a vulcanization activator. Has been.

Further, in claim 2 of Patent Document 4, a carboxylic compound containing a diamine compound as a vulcanizing agent and a guanidine, DBU, DBN or a salt thereof as a vulcanization accelerator is further added to a mercapto-containing acrylic elastomer. An acrylic elastomer composition obtained by blending benzimidazoles is disclosed, and the formation of a salt of mercaptobenzimidazole and DBU is assumed in the system. Patent Document 5 discloses a salt of 2-mercaptobenzothiazole and DBU, which is a requirement of the present invention, and is used for crosslinking of epichlorohydrin rubber.

Published patent publication 2011 No. 52217 Published Patent Publication No. 80488, 1999 Published Patent Publication No. 2008 189733 Japanese Patent Publication No. 3717302 Patent Publication No. 60104, 1986

In the conventional compounding for carboxyl group-containing acrylic rubber, polyamine compound exemplified by hexamethylenediamine carbamate as a crosslinking agent and diazabicycloalkene exemplified by DBU as a crosslinking agent disclosed in Patent Document 2 The acrylic rubber composition has a drawback that the scorch safety is poor. Moreover, since DBU etc. are strong basic liquids, when handling this alone, there existed a difficulty in handling, such as measurement. The object of the present invention is to provide a vulcanization system having equivalent physical properties, particularly in permanent compression strain, without using diphenylguanidine or di (o-tolyl) guanidine which has a problem of toxicity.

The present invention relates to a vulcanization system for carboxyl group-containing acrylic rubber , and improves vulcanization speed and scorch safety without using guanidines whose use is restricted due to hygienic requirements. Constitution is a carboxyl group-containing acrylic rubber , hexamethylenediamine carbamate as a crosslinking agent, and an amine salt of 2-mercaptobenzothiazole as a vulcanization activator, the amine containing a salt selected from DBU, DBN, DABCO It is a rubber composition.

This composition becomes a rubber composition in which the vulcanization rate and permanent compression strain of the carboxyl group-containing acrylic rubber , which are conventional problems, are improved. Incidentally, the patent Salts of 2-mercaptobenzothiazole and DBU in the same configuration as the present invention have been described in the literature 5, the permanent compressive strain resistance and the carboxyl group-containing modified acrylic rubber of the carboxyl group-containing acrylic rubber There are no applicable statements.

In the composition of the present invention, the amount of hexamethylenediamine carbamate is 0.1 to 4 parts by weight, preferably 0.3 to 2 parts by weight, based on 100 parts by weight of rubber. The compounding amount of each salt of DBU, DBN and DABCO of 2-mercaptobenzothiazole is 0.1 to 10 parts by weight, preferably 0.3 to 6 parts by weight based on 100 parts by weight of rubber. When it mixes exceeding 10 weight part, there is no remarkable effect and it is not preferable at the point of cost.

In addition to carbon black and a crosslinking agent, a compounding agent used in the rubber industry can be blended with the rubber composition. Examples of this compounding agent include reinforcing fillers such as silica, non-reinforcing fillers such as calcium carbonate and clay, anti-aging agents such as wax, light stabilizers, scorch inhibitors, plasticizers, tackifiers, Examples include rubber compounding agents such as processing aids, lubricants, lubricants, flame retardants, antistatic agents, colorants, silane coupling agents, and crosslinking retarders. These compounding agents are not particularly limited as long as they do not impair the effects of the present invention, and can be appropriately compounded in amounts according to the compounding purpose.

According to the present invention, a vulcanizate having a high vulcanization rate and excellent permanent compression strain can be obtained in the carboxyl group-containing acrylic rubber .

Examples of the present invention are shown below, but the scope of the present invention is not limited thereto.

Production Example According to the production example of Patent Document 5, DBU salt, DBN salt and DABCO salt of 2-mercaptobenzothiazole were produced. This was subjected to a vulcanization test as described below.

Example of vulcanization test 100 parts of carboxyl group ACM, 50 parts of carbon black FEF and 1 part of stearic acid were mixed with a predetermined part by weight of the above-mentioned chemicals and unvulcanized rubber according to JISK6300-2 (2010). Physical tests were conducted. Moreover, the permanent compression strain test of the vulcanized rubber was implemented according to JISK6262 (2006) under the conditions described in the table. Examples are shown in Table 1 and Comparative Examples are shown in Table 2.

Abbreviations of listed drugs are as follows.
HMDAC: Hexamethylenediamine carbamate M-DBU: DBU salt of 2-mercaptobenzothiazole M-DABCO: DABCO salt of 2-mercaptobenzothiazole M-DBN: DBN salt of 2-mercaptobenzothiazole DOTG: 1,3-di-O -Tolylguanidine MBT: 2-mercaptobenzothiazole CMBT: cyclohexylamine salt of 2-mercaptobenzothiazole DABCO: 1,4-diazabicyclo [2.2.2] octane MBI: 2-mercaptobenzimidazole DBU-BA: DBU salt of benzoic acid

From the examples, the results of vulcanization start-up and compression set tests are all obtained in vulcanization systems in which diamine carbamate is used as the crosslinking agent and DBU salt, DBN salt, DABCO salt of 2-mercaptobenzothiazole is applied as the vulcanization activator. Was good. On the other hand, from Comparative Example 1, a system in which only a diamine carbamate is used as a crosslinking agent and no vulcanization activator is blended is not preferable because the compression set test value is high.

From Comparative Example 2, the vulcanization system using diamine carbamate as the crosslinking agent and 1,3-di-O-tolylguanidine as the vulcanization activator is similar to the present invention. From this, it can be understood that the present invention can provide a vulcanization system free from the toxicity problems of guanidines described above.

From Comparative Example 3, a vulcanization system using diamine carbamate as a cross-linking agent and 2-mercaptobenzothiazole not using a DBU salt as a vulcanization activator, and from Comparative Example 4, diamine carbamate as a cross-linking agent, a vulcanization activator. As the vulcanization system to which 2-mercaptobenzothiazole of cyclohexylamine salt is applied instead of DBU salt, the compression set test value is high, which is not preferable.

From Comparative Example 5, the vulcanization system in which diamine carbamate is used as a crosslinking agent and DBU that is not a 2-mercaptobenzothiazole salt as a vulcanization activator alone is not only a problem of handling as a liquid, but also vulcanization is fast, and scorch properties. There is a problem that.

From the comparative example 6, the result of the compression set test was inferior in the vulcanization system in which diamine carbamate was used as a crosslinking agent and DABCO not a 2-mercaptobenzothiazole salt was applied alone as a vulcanization activator. Therefore, it can be understood that a salt of 2-mercaptobenzothiazole is essential, not a strong base compound alone. From Comparative Example 7, the vulcanization system in which diamine carbamate is applied as a crosslinking agent and 2-mercaptobenzimidazole is applied as a vulcanization activator has a small torque value, and vulcanization performance is not preferable.

From Comparative Example 8, a vulcanization system using diamine carbamate as a crosslinking agent and DBU benzoate as a vulcanization activator is not preferable because the compression set test value becomes high. From Comparative Example 9, the vulcanization system consisting only of 1,3-di-O-tolylguanidine and the vulcanization system consisting only of the DBU salt of 2-mercaptobenzothiazole from Comparative Example 10 did not vulcanize. . It can be understood that diamine carbamate is essential as a crosslinking agent.

The carboxyl group-containing acrylic rubber having the composition of the present invention is vulcanized quickly and excellent in the static characteristics of the rubber, and is particularly effective in terms of the effect of improving the permanent compression strain.

Claims (3)

A carboxyl group-containing acrylic rubber , an amine salt of diamine carbamate as a crosslinking agent and 2-mercaptobenzothiazole as a vulcanization activator, wherein the amine is 1,8-diazabicyclo [5.4.0] undecene-7, 1, A rubber composition comprising a salt which is one or more selected from 5-diazabicyclo [4.3.0] nonene-5,1,4-diazabicyclo [2.2.2] octane. A carboxyl group-containing acrylic rubber , an amine salt of hexamethylenediamine carbamate as a crosslinking agent and 2-mercaptobenzothiazole as a vulcanization activator, wherein the amine is 1,8-diazabicyclo [5.4.0] undecene-7, A rubber composition containing a salt that is one or more selected from 1,5-diazabicyclo [4.3.0] nonene-5,1,4-diazabicyclo [2.2.2] octane. A carboxyl group-containing acrylic rubber , an amine salt of hexamethylenediamine carbamate as a crosslinking agent and 2-mercaptobenzothiazole as a vulcanization activator, wherein the amine is 1,8-diazabicyclo [5.4.0] undecene-7, Permanent compression strain of the rubber comprising one or more salts selected from 1,5-diazabicyclo [4.3.0] nonene-5,1,4-diazabicyclo [2.2.2] octane Improved method.