JPH06256572A - Nbr composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition capable of preventing nitrosamine from occurring in producing rubber products by adding tetrakis(2-ethylhexyl) thiuram disulfide and a vulcanization accelerator to an acrylonitrile-butadiene copolymer rubber (NBR). CONSTITUTION:This NBR composition is obtained by blending (A) 100 pts.wt. acrylonitrile.butadiene copolymer rubber (NBR) with (B) 0.5-10 pts.wt. tetrakis(2- ethylhexyl)thiuram disulfide and (C) one or more vulcanization accelerators such as benzothiazole-based, sylfenamide-based, dithiocarbamate-based, guanidine- based, aldehyde.ammonia-based, aldehyde.amine-based, thiourea-based, xanthate- based and dithiophosphate-based vulcanization accelerators in an amount so as to provide 1-10 pts.wt. total amount of the vulcanization accelerators. This composition is capable of preventing nitrosamine which is a carcinogenic substance from occurring in a working environment related to the production of rubber products.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition comprising NBR. More specifically, N for the purpose of preventing the generation of nitrosamine in a work environment related to rubber product manufacturing, etc.
BR composition.

[0002]

2. Description of the Related Art NBR is widely used for packings, hoses, belts, rubber footwear and the like.
When producing these NBR rubber products, vulcanization accelerators such as benzothiazole-based, sulfenamide-based, thiuram-based, dithiocarbamate-based and thiourea-based vulcanization accelerators [hereinafter, referred to as “accelerator” for short] depending on the purpose. To do. ] Are typically used in various combinations.

TRGS 552 (Technical Regulations for Hazardous Substances, Nitrosamines) 1988 in Old West Germany
It was enforced on July 11, 2014, and the guidance value of nitrosamine concentration of 2.5 μg / m ³ was set in the work environment related to rubber. From 1991, the value changed to 1 μg / m ³ .

The formation of nitrosamines from thiuram accelerators, which are considered to be one of the sources of these nitrosamines, is as follows.

[Chemical 1] [K. G. Ashnoss et. al. ，
Plastics a-nd Rubber Pros
sing and Appl. , 4 , 74 (198
4)], for details, refer to [Dr. W. Hofma
nn Co., Ltd. Impex Chemical Kenshin Hiroyuki (Translation), Polymer Digest, January 1991, P. 65].

The nitrosamines measured in the rubber relation specified in the above rules are N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, N-nitrosopiperidine, N-nitrosomethylphenylamine, N -Nitrosoethylphenylamine and N-nitrosomorpholine, which are related to general-purpose accelerators, have been attracting attention in recent years to the domestic rubber industry.

Recently, in the rubber industry in Japan, the improvement of 3K has been sought, and in return, the improvement of the working environment and the enforcement of the above rules strongly demand the prevention of nitrosamine generation in the working environment. do it,
Even if nitrosamine is produced, it is a non-carcinogenic amine [N-Nitroso Compounds: O
ccurrence and Biological
Effects, I-international Ag
energy for Research onCance
r Lyon (1982), Proceedings
of the VIth International
Symposium on N-Ni-troso C
opensounds in Tokyo, 28
Se-ptember-1 October 198
1, P. [231] and a combination of an accelerator in which nitrosamine does not volatilize when used in a rubber, or a combination of only an accelerator in which nitrosamine does not volatilize when used in a rubber,
There has been a strong demand for an NBR crude product having a vulcanization rate and vulcanization properties equal to or higher than those of conventional accelerator blends.

[0007]

PROBLEM TO BE SOLVED BY THE INVENTION Even if nitrosamine is produced, it is used as a rough combination of an accelerator that uses a non-carcinogenic amine and an accelerator that does not volatilize nitrosamine when used in rubber, or in rubber. The purpose of the present invention is to provide to the art an NBR crude product having a vulcanization rate and vulcanization properties equivalent to or higher than the vulcanization properties and vulcanization physical properties by a conventional accelerator combination, in which only accelerating agents that do not cause nitrosamine to volatilize in such a case are combined. .

[0008]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that tetrakis (2-ethylhexyl) thiuram disulfide [hereinafter referred to as "TOT"] per 100 parts by weight of NBR. Is abbreviated. ] 0.5-10
Parts by weight, and selected from benzothiazole-based, sulfenamide-based, dithiocarbamate-based, guanidine-based, aldehyde / ammonia-based, aldehyde / amine-based, thiourea-based, xanthate-based and dithiophosphoric acid-based accelerators When the total amount of the one or more accelerators is 1 to 10 parts by weight, the vulcanized product does not volatilize nitrosamine, and the vulcanization speed and the vulcanized physical properties equivalent to or higher than those of the conventional compounding are obtained. Succeeded in obtaining a rubber composition comprising NBR, and based on this finding, completed the present invention.
However, the dithiocarbamate-based accelerator is zinc dibenzyldithiocarbamate, and the thiourea-based accelerator is N,
N'-diphenylthiourea, N, N'-diethylthiourea, and the sulfenamide-based accelerator is N-cyclohexyl-2-benzothiazolyl sulfenamide, N
-Tert-butyl-2-benzothiazolyl sulfenamide and N, N-dicyclohexyl-2-benzothiazolyl sulfenamide.

According to the results carried out by the present inventors, no nitrosamine was detected in the NBR vulcanizate based on the combination of the claims of the present invention containing the thiuram accelerator TOT according to the present invention. . The finding that nitrosamine was not detected in this vulcanized product was never found in the past, and this result is exemplified in the section of Examples. The effect of TOT on vulcanization has already been reported [Journal of the Japan Rubber Association, Vol. 45, August issue, 745].
(1972)], but the EPDM / NBR blend rubber has a slow vulcanization rate and is difficult to put into practical use, and this report does not mention that nitrosamine is volatilized from the vulcanized product. Not not. An additional characteristic of the NBR composition according to the present invention is that the scorch stability during processing is superior to conventional formulations.

The main constituent of the rubber composition of the present invention is N
As the BR, any commercially available NBR can be used. Examples of the benzothiazole accelerator according to the present invention include 2-mercaptobenzothiazole, dibenzothiazyl disulfide, zinc salt of 2-mercaptobenzothiazole and cyclohexylamine salt of 2-mercaptobenzothiazole. Examples of the guanidine-based accelerator according to the present invention include 1,3-diphenylguanidine, di-o-tolylguanidine, 1-o-tolylbiguanide, and di-o-tolylguanidine salt of dicatecholborate. Examples of the accelerator according to the present invention include hexamethylenetetramine (aldehyde / ammonia type accelerator), n-butyraldehyde aniline (aldehyde / amine type accelerator), zinc butylxanthogenate, zinc isopropylxanthogenate (xanthogenate type accelerator). Agent).

Examples of the dithiophosphoric acid accelerator according to the present invention include bis (diisopropyl) thiophosphoryl disulfide, bis (diisopropyl) thiophosphoryl monosulfide and zinc o, o-di-butyldithiophosphate. it can. The amount of TOT according to the present invention is 0.5 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of NBR. Sulfurization rate is slow and there is no use effect,
If the amount is more than 10 parts by weight, the vulcanization rate is not high for the amount, which is economically disadvantageous.

Among the benzothiazole-based, sulfenamide-based, dithiocarbamate-based, guanidine-based, aldehyde / ammonia-based, aldehyde / amine-based, thiourea-based, xanthate-based and dithiophosphate-based accelerators according to the present invention, The total amount of the selected one or more accelerators is 1 to 10 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of NBR, but the amount is 1 part by weight. If it is less than 10%, the vulcanization rate is hardly increased compared with the case where TOT is used alone, and there is no effect in use.
If the amount is more than parts by weight, bloom may occur in the vulcanized product in some cases, which makes it difficult to use.

The rubber composition according to the present invention includes vulcanization accelerators such as stearic acid and zinc oxide, vulcanizing agents such as sulfur, carbon black, calcium carbonate, titanium dioxide, clay, talc, alumina and silica. The above-mentioned filler, processability softening agent, antioxidant, and rubber compounding agent such as resin can be appropriately compounded as necessary. Hereinafter, the effects of the present invention will be shown in Examples, but the claims of the present invention are not limited to the embodiments.

[0014]

【Example】

Practical example 1. An unvulcanized rubber composition was prepared by a known kneading method using an 8-inch roll in accordance with the formulation shown in Table-1, and the unvulcanized rubber composition was equally divided into 10 parts and described in Table-2. The vulcanization accelerator based on the sample number of No. 2 was kneaded by the same method as above to prepare unvulcanized rubber compositions for each sample shown in Table 2. The Mooney scorch test (JIS K630
0)) and a rheometer test [according to SRIS (Japan Rubber Association Standard Standard) 3102-1977 (vulcanization test method using a vulcanization tester)], and then pressing the unvulcanized rubber composition relating to each sample. At 160 ° C. for 15 minutes, a vulcanized product was prepared and subjected to a tensile test (JIS K 63
01), Bloom test at room temperature (visual observation)
Was done. Furthermore, nitrosamines volatilized and generated from those vulcanizates are [M. Lh-eureux et. a
l. , Kautsch. Gummi Kunsts
t. , 43 , 107 (1990)]. The results are shown in Table-2.

[0015]

[Table 1]

[0016]

[Table 2]

[Table 2]

[0017]

【effect】

(1) In the results shown in Table 2, nitrosamine was not detected in the TOT-containing NBR vulcanizate (Example) according to the present invention. (2) In the results shown in Table 2, the TOT-containing NBR compositions (Examples) according to the present invention show no significant difference in vulcanization rate at vulcanization temperature and tensile properties of vulcanizates in comparison with Comparative Examples. (3) In the results shown in Table-2, no bloom is observed in the TOT-containing NBR composition according to the present invention (Example) in comparison with Comparative Example, and the scorch stability during processing is excellent. From the above results, it is considered that the NBR composition according to the present invention is useful in the rubber industry.

Claims (4)

[Claims] 1. An acrylonitrile-butadiene copolymer rubber [hereinafter, abbreviated as "NBR"]. ] With respect to 100 parts by weight, tetrakis (2-ethylhexyl) thiuram disulfide 0.5 to 10 parts by weight, benzothiazole type, sulfenamide type, dithiocarbamate type, guanidine type, aldehyde / ammonia type, aldehyde / amine -Based, thiourea-based, xanthate-based, and dithiophosphoric acid-based vulcanization accelerators, the total amount of one or more selected vulcanization accelerators is 1 to 10 parts by weight, and the NBR composition is characterized. object. 2. The N according to claim 1, wherein the dithiocarbamate vulcanization accelerator is zinc dibenzyldithiocarbamate.
BR composition. 3. The NBR composition according to claim 1, wherein the thiourea vulcanization accelerator is N, N'-diphenylthiourea or N, N'-jetylthiourea. 4. A sulfenamide vulcanization accelerator is N-cyclohexyl-2-benzothiazolyl sulfenamide,
The NBR according to claim 1, which is N-tert-butyl-2-benzothiazolyl sulfenamide and N, N-dicyclohexyl-2-benzothiazolyl sulfenamide.
Composition.