JP2013194065A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a delay vulcanized rubber composition less liable to cause reversion.SOLUTION: A rubber composition contains, in rubber, sulfur and N,N-diisopropyl-2-benzothiazole sulfenamide and ≤1 pt.wt. of 2-mercaptobenzothiazole and/or di-2-benzothiazolyl disulfide as a vulcanization accelerator, wherein the weight of the N,N-diisopropyl-2-benzothiazole sulfenamide is larger than the sum of the weights of the 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide.

Description

The present invention relates to a rubber composition and a vulcanization method thereof. More specifically, the present invention relates to a rubber composition containing a sulfenamide compound that acts as a vulcanization accelerator without reversion.

Conventionally, as vulcanization accelerators used in rubber products such as tires, N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, N, N-dicyclohexyl are used. Sulfenamide vulcanization accelerators such as 2-benzothiazole sulfenamide are used, and N, N-dicyclohexyl-2-benzothiazole sulfenamide is awarded especially for heavy-duty tires. Yes.

By the way, when a rubber composition mainly composed of a diene rubber is vulcanized at a high temperature with a polysulfide type crosslinking structure using sulfur and a vulcanization accelerator, the reversion phenomenon and heat resistance are poor. This phenomenon is seen. In particular, N, N-dicyclohexyl-2-benzothiazolesulfenamide, which is a slow-acting vulcanization accelerator for heavy-duty tires, exhibits a particularly strong phenomenon of reversion, not only because of its toxicity. In use, attention is required.

Patent Document 1 discloses an example in which N, N-dicyclohexyl-2-benzothiazolesulfenamide is used as a vulcanization accelerator for heavy-duty tires. Patent Document 2 discloses a production example of N, N-diisopropyl-2-benzothiazole sulfenamide used in the present invention.

Published patent publication 2007 No. 217492 Published patent publication No. 215383 in 1986

Among conventional sulfenamide vulcanization accelerators, N, N-dicyclohexyl-2-benzothiazole sulfenamide, which is known as the vulcanization accelerator that gives the slowest effect to the vulcanization reaction, is used for heavy duty tires. Although it is excellent as a sulfur accelerator, its toxicity and reversion phenomenon are problems, and it is used with caution. Therefore, further improvement of the vulcanization accelerator is demanded. An object of the present invention is to provide a vulcanized rubber composition having an improved vulcanization return resistance without changing other physical properties while having a vulcanization retarding effect, and a vulcanization accelerator therefor. .

The present invention essentially includes N, N-diisopropyl-2-benzothiazole sulfenamide, which is one of sulfenamide-based vulcanization accelerators, and includes thiazole-based vulcanization accelerators 2-mercaptobenzothiazole and / or dithiol. The present invention relates to a rubber composition that may contain 2-benzothiazolyl disulfide. Although addition of 2-mercaptobenzothiazole and / or di-2-benzothiazolyl disulfide is not essential, a rubber composition more resistant to reversion is obtained by addition.

The composition of the present invention consists of 100 parts by weight of rubber component, 0.1-5 parts by weight of sulfur, 0.3-3 parts by weight of N, N-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole. And / or di-2-benzothiazolyl disulfide, the sum of the weights of 2-mercaptobenzothiazole and / or di-2-benzothiazolyl disulfide is N, N-diisopropyl-2-benzothiazole sulfenamide Another object of the present invention is to provide a rubber composition comprising a vulcanization accelerator that is present in an amount of 1 part by weight or less under the condition that the weight is less than the weight of the vulcanization system, and a vulcanization system thereof. By this accelerator, a vulcanized rubber composition having improved vulcanization return resistance, which is a conventional problem, can be provided.

The present invention is useful as a reversion-resistant vulcanization accelerator even in a single vulcanization system of N, N-diisopropyl-2-benzothiazole sulfenamide, and in addition to this single system, 2-mercaptobenzothiazole and / or Or, by blending di-2-benzothiazolyl disulfide, the vulcanization rate is the same as that of N, N-dicyclohexyl-2-benzothiazolesulfenamide, and from the viewpoint of vulcanization rate and adhesiveness, It has also been found that an objective rubber composition having a good balance can be obtained, and the present invention has been completed.

Further, the N, N-diisopropyl-2-benzothiazole sulfenamide single system of the present invention or a composite vulcanization accelerator comprising 2-mercaptobenzothiazole and / or di-2-benzothiazolyl disulfide in this single system. Has a vulcanization retarding effect equivalent to that of N, N-dicyclohexyl-2-benzothiazolesulfenamide, and can be suitably used for a rubber composition.

In the vulcanization accelerator of the present invention, 0.3 to 3 parts by weight of N, N-diisopropyl-2-benzothiazolesulfenamide, 2-mercaptobenzothiazole and / or di-2 with respect to 100 parts by weight of the rubber component. -Containing not more than 1 part by weight of benzothiazolyl disulfide, and the weight of N, N-diisopropyl-2-benzothiazole sulfenamide is that of the weight of 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide It must be greater than the sum.

Further, the content of N, N-diisopropyl-2-benzothiazolesulfenamide is preferably 0.5 to 1 part by weight with respect to 100 parts by weight of the rubber component. The weight sum of 2-mercaptobenzothiazole and / or di-2-benzothiazolyl disulfide is 0.8 parts by weight provided that it is smaller than the weight of N, N-diisopropyl-2-benzothiazole sulfenamide. The following is preferred. When the total amount of the vulcanization accelerator is less than 0.3 parts by weight, the vulcanization is not sufficiently performed.

Content of sulfur which is a vulcanizing agent is 0.1-5 weight part with respect to 100 weight part of rubber components, Preferably it is 1-3 weight part. If the sulfur content is less than 0.1 parts by weight, vulcanization will not be sufficiently achieved. On the other hand, if it exceeds 5 parts by weight, the aging performance of the rubber will deteriorate, such being undesirable.

The rubber composition of the present invention is characterized by containing a rubber component, sulfur, and the above single or composite vulcanization accelerator. As the rubber component used in the present invention, natural rubber and / or diene synthetic rubber is used. Specifically, at least one of natural rubber, polyisoprene rubber, styrene-butadiene copolymer, polybutadiene rubber, isoprene rubber, ethylene-propylene-diene copolymer, chloroprene rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber and the like. Can be used.

In addition to the rubber component, sulfur, and vulcanization accelerator, the rubber composition of the present invention can contain a filler usually used in the rubber composition. For example, inorganic filler such as carbon black and silica can be contained. Materials can be included. The total content of these inorganic fillers is 20 parts by weight or more, preferably 30 to 150 parts by weight with respect to 100 parts by weight of the rubber component.

The carbon black used here is not particularly limited, and any carbon black conventionally used as a reinforcing filler for rubber can be selected and used. Examples of carbon black include GPF, FEF, SRF, HAF, ISAF, and SAF. By using carbon black, the effect of improving various physical properties is increased.

Similarly, the silica that can be used here is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Wet silica having excellent properties is preferred. Moreover, it can use together with the said carbon black. When silica is used as the filler, it can contain a silane coupling agent. There is no restriction | limiting in particular as this silane coupling agent, For example, (gamma) -mercaptopropyl triethoxysilane etc. which are conventionally used for the rubber composition can be used.

The rubber composition of the present invention may further contain various chemicals usually used in the rubber industry, such as process oil, anti-aging agent, anti-scorch agent, zinc white, and stearic acid.

According to the present invention, it is possible to obtain a rubber composition excellent in delayed vulcanization property that prevents reversion during vulcanization of diene rubber.

The vulcanization accelerator and rubber composition used in the present invention will be described in further detail based on examples and comparative examples, but the present invention is not limited to these examples.

Rubber test results According to the compounding formulations shown in Tables 1 and 2, they were mixed by a conventional method to obtain a carbon compounded rubber composition. In accordance with JISK6300-2 (unvulcanized rubber physical test method), the rubber composition was measured for vulcanization characteristics using a vibration vulcanization tester. Further, vulcanization characteristics (t10, t90, INDEX evaluation) were measured at 150 ° C. in accordance with JISK6251 (vulcanized rubber physical test method). The results are also summarized in the table.

In this table, vulcanization accelerator 1 is N, N-diisopropyl-2-benzothiazole sulfenamide of the present invention, vulcanization accelerator 2 is di-2-benzothiazolyl disulfide, and vulcanization accelerator 3 is 2. -Mercaptobenzothiazole, vulcanization accelerator 4 is N, N-dicyclohexyl-2-benzothiazole sulfenamide, vulcanization accelerator 5 is N-cyclohexyl-2-benzothiazole sulfenamide, vulcanization accelerator 6 is N -t-Butyl-2-benzothiazole sulfenamide.

Examples 1 to 6, which are rubber compositions containing a sulfenamide vulcanization accelerator within the scope of the present invention, are vulcanization accelerators known as slow-acting accelerators compared to Comparative Examples 2 and 3. It turns out that it has the scorch stability close | similar to this comparative example on the basis of the comparative example 1 which used the agent 4. FIG. Furthermore, it has a higher vulcanization return suppressing effect than that of Comparative Example 1, and exhibits excellent characteristics during high-temperature vulcanization.

As described in the examples, the rubber composition of the present invention is excellent in vulcanization characteristics such as suppressing vulcanization return, and therefore can be suitably used for rubber products such as tires.

Claims (4)

A rubber composition comprising 0.1 to 5 parts by weight of sulfur and 0.3 to 3 parts by weight of N, N-diisopropyl-2-benzothiazolesulfenamide with respect to 100 parts by weight of a rubber component. 0.1 to 5 parts by weight of sulfur, 0.3 to 3 parts by weight of N, N-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole and / or di-per 100 parts by weight of rubber component 1-part by weight of 2-benzothiazolyl disulfide and the weight of N, N-diisopropyl-2-benzothiazole sulfenamide is the weight of 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide A rubber composition that is greater than the sum of The rubber composition according to claim 1 or 2, wherein the rubber component contains at least one of natural rubber and polyisoprene rubber. A method for suppressing reversion of rubber, comprising using the rubber composition according to claim 1.