JPH061884A - Vulcanization accelerator composition - Google Patents

Abstract

PURPOSE:To obtain the title compsn. excellent in vulcanization characteristics, including resistances to scorch and blooming, and in storage stability by compounding tetrakis(2-ethylhexyl)thiuram disulfide as a component of the compsn. CONSTITUTION:The title compsn. is prepd. by compounding 5-90wt.% tetrakis(2- ethylhexyl)thiuram disulfide, 5-80wt.% sulfenamide accelerator, 0-80wt.% accelerator other than the foregoing two accelerators and other than a thiuram accelerator, and 5-60wt % at least one rubber ingredient other than the foregoing three ingredients and/or rubbery polymer. The compsn. has a good storage stability and gives a rubber compd. which is scorch-resistant, has a good vulcanization rate, and gives a vulcanizate excellent in physical propeties and free from appearance defect due to blooming.

Description

Detailed Description of the Invention

[0001]

The present invention relates to (1) tetrakis (2-ethylhexyl) thiuram disulfide 5 to 90% by weight (2) sulfenamide vulcanization accelerator 5 to 80% by weight (3) above (1) , A vulcanization accelerator other than (2) and a vulcanization accelerator other than a thiuram-based vulcanization accelerator 0 to 80% by weight (4) One or more rubber compounding agents other than the above (1) to (3) And / or 5 to 60% by weight of rubber-like polymer. The present invention relates to a mixed vulcanization accelerator composition comprising the above (1) to (4) and having excellent storage stability and vulcanization characteristics.

[0002]

2. Description of the Related Art Conventionally, a vulcanization accelerator is generally used in a rubber vulcanization system using sulfur or an organic vulcanizing agent as a vulcanizing agent. In order to add various characteristics to the physical properties of vulcanized rubber,
There are more than one kind of combination. In particular, the sulfur vulcanization system of EPDM is disclosed in JP-B-56-262 because of the characteristic vulcanization behavior of unvulcanized rubber and blooming of the obtained vulcanized rubber.
A complicated combination of several vulcanization accelerators as shown in Japanese Patent No. 60 is usually performed, which makes it difficult to measure and manage the inventory of vulcanization accelerators, and to control the process of unvulcanized rubber. It significantly affects the quality control of vulcanized rubber.

In order to solve these problems, some mixed vulcanization accelerators have been proposed and put on the market, but the problem that scorch occurs during storage and processing of unvulcanized rubber and it becomes impossible to produce a rubber product. There is. As a solution to this, a sulfenamide-based vulcanization accelerator is required to maintain scorch resistance, but when mixed with a thiuram-based vulcanization accelerator represented by tetramethylthiuram disulfide, tetraethylthiuram disulfide, etc. This is a problem because they react with each other during storage to cause decomposition.

As a method of suppressing this decomposition reaction, a method of using an aromatic acid anhydride such as phthalic anhydride as a stabilizer is proposed in Japanese Patent Publication No. 1-24299. But,
This method has the drawbacks of reducing the vulcanization rate and deteriorating the productivity because an aromatic acid anhydride such as phthalic anhydride is added as a stabilizer. In order to improve the vulcanization rate, it can be improved by increasing the addition amount of a thiuram-based vulcanization accelerator represented by tetramethylthiuram disulfide, tetraethylthiuram disulfide, etc.
The scorch resistance is reduced, and the vulcanized rubber causes remarkable blooming, which causes poor appearance. Therefore, from the economical viewpoint in the rubber industry, the scorch resistance is good, the vulcanization speed and the physical properties of the vulcanized rubber are good, the appearance of the vulcanized rubber does not deteriorate due to blooming, and the storage stability is good. There is a strong demand for sulfur accelerators.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention A vulcanized rubber which has good scorch resistance, good vulcanization speed and physical properties of vulcanized rubber, does not cause a bad appearance of vulcanized rubber due to blooming, and has good storage stability. It is to provide a sulfur accelerator composition to the art.

[0006]

[Means for Solving the Problems] As a result of diligent studies to solve the above problems, the present inventors have found that tetrakis (2
-Ethylhexyl) thiuram disulfide is a reduction in scorch resistance found in general-purpose general thiuram vulcanization accelerators such as tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, and tetrabutyl thiuram disulfide, and mixed sulfenamide-based addition agents. Without degrading storage stability due to decomposition reaction with a vulcanization accelerator, etc., without causing poor appearance of vulcanized rubber due to blooming,
It was found that the vulcanization rate was improved, and based on these findings,

(1) Tetrakis (2-ethylhexyl)
Thiuram disulfide 5 to 90% by weight (2) Sulfenamide-based vulcanization accelerator 5 to 80% by weight (3) Vulcanization accelerator other than the above (1) and (2), and other than thiuram-based vulcanization accelerator Vulcanization accelerator of 0 to 80% by weight (4) One or more rubber compounding agents other than the above (1) to (3) and / or 5 to 60% by weight of rubber-like polymer (1) to (4) The mixed vulcanization accelerator composition consisting of
Surprisingly, it did not cause a decomposition reaction during storage and had good storage stability. When this composition was used as a vulcanization accelerator, not only did it exhibit scorch resistance and a good vulcanization rate, but it was obtained. The inventors have found that the vulcanized rubber also has satisfactory physical properties and that the appearance of the vulcanized rubber due to blooming is not poor, and the present invention has been completed.

The vulcanization-accelerating effect of tetrakis (2-ethylhexyl) thiuram disulfide has been reported [Journal of the Rubber Society of Japan, Vol. 45, No. 8, 745 (1972)], as well as other vulcanization. Although it is commonly used in combination with a vulcanization accelerator, by using tetrakis (2-ethylhexyl) thiuram disulfide found in the present invention as one component of the mixed vulcanization accelerator composition, Regarding the fact that a mixed vulcanization accelerator composition having scorch resistance and storage stability, as well as a satisfactory vulcanization rate and causing no poor appearance of the vulcanized rubber due to blooming can be obtained, there have been reported examples. I can't find it.

The rubber which is the object of the mixed vulcanization accelerator composition according to the present invention is a natural rubber, isoprene rubber, butadiene rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, ethylene / propylene / diene terpolymer rubber. (EPDM), isoprene / isobutylene rubber, and other diene rubbers alone, or blended rubbers of two or more of these rubbers, but are not limited thereto. Among these rubbers, particularly preferable rubbers are EPDM and blend rubbers of EPDM and other diene rubbers.

The mixing ratio of the (1) tetrakis (2-ethylhexyl) thiuram disulfide component in the mixed vulcanization accelerator composition according to the present invention is 5 to 90% by weight, preferably 10 to 90% by weight. . If the mixing ratio is less than 5% by weight, a sufficient vulcanization accelerating effect cannot be obtained, and
If the amount exceeds 5% by weight, the vulcanization accelerating effect is not obtained as much as the mixed amount, which is economically disadvantageous and is not preferable.

Examples of the (2) sulfenamide-based vulcanization accelerator in the mixed vulcanization accelerator composition according to the present invention include N-cyclohexyl-2-benzothiazolyl sulfenamide and N-oxydiethylene-2-. Benzothiazolyl sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N, N-dicyclohexyl-2-benzothiazolyl sulfenamide, N, N-diethyl-
Examples thereof include 2-benzothiazolylsulfenamide, but the invention is not limited thereto. Particularly preferred is N-cyclohexyl-2-benzothiazolylsulfenamide. The mixing ratio of the sulfenamide vulcanization accelerator component is 5 to 80% by weight, preferably 10 to 50% by weight. The mixing ratio is 5% by weight
If the amount is less than 80% by weight, the scorch resistance and the vulcanization rate are not sufficient, and if the amount exceeds 80% by weight, the scorch resistance and the vulcanization rate are not improved as much as the mixed amount, which is economically disadvantageous and is not preferable.

(3) In the mixed vulcanization accelerator composition according to the present invention, as the vulcanization accelerator other than the above (1) and (2), and as the vulcanization accelerator other than the thiuram-based vulcanization accelerator, Thiazole vulcanization accelerator, dithiocarbamate vulcanization accelerator,
Examples thereof include, but are not limited to, aldehyde / ammonia vulcanization accelerators, thiourea vulcanization accelerators, and guanidine vulcanization accelerators. Particularly preferred are dithiocarbamate vulcanization accelerators, such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc N-ethyl-N-phenyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, Examples thereof include zinc dibenzyldithiocarbamate, sodium diethyldithiocarbamate, sodium dibutyldithiocarbamate, copper dimethyldithiocarbamate, ferric dimethyldithiocarbamate and tellurium diethyldithiocarbamate. The mixing ratio of the vulcanization accelerator other than the above (1) and (2) and the vulcanization accelerator component other than the thiuram-based vulcanization accelerator is 0 to 80% by weight, preferably 0 to 60%. % By weight. If the mixing ratio exceeds 80% by weight, the characteristics of scorch resistance and non-blooming property may not be sufficiently exhibited, which is not preferable.

(4) In the mixed vulcanization accelerator composition according to the present invention, (4) one or more rubber compounding agents and / or rubber-like polymers other than the above (1) to (3) are calcium carbonate, clay. , Inorganic fillers and fillers such as silica, organic fillers and fillers such as carbon black, paraffin-based, naphthene-based and aromatic-based oils, polybutene, ester-based softeners, plasticizers, waxes, stearic acid Examples thereof include higher fatty acids, ethylene / propylene / diene terpolymer rubber (EPDM), styrene / butadiene rubber, ethylene vinyl acetate (EVA), and the like, but are not limited thereto. The mixing ratio of at least one rubber compounding agent and / or rubber-like polymer component other than the above (1) to (3) is 5 to 60% by weight, preferably 5 to 50% by weight. If the mixing ratio exceeds 60% by weight, the vulcanization accelerator component in the mixed vulcanization accelerator composition according to the present invention decreases, which is uneconomical and not preferable. Hereinafter, the effects of the present invention will be described with reference to Examples, but the claims of the present invention are not limited to the modes of the Examples.

[0014]

【Example】

Example 1 Production Example of Mixed Vulcanization Accelerator Composition (1) Carplex ^# 67 in 10 L small dash kneader
(Shionogi Pharmaceutical Co., Ltd. product name of silica-based reinforcing agent) 24
0 g, tetrakis (2-ethylhexyl) thiuram disulfide 280 g, Noxceller CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide Ouchi Shinko Chemical Industry Co., Ltd. trade name) 360 g, and Noxceler ZT
120 g of C (Zinc dibenzyldithiocarbamate, trade name of Ouchi Shinko Kagaku Kogyo Co., Ltd.) was sequentially added, and the mixture was stirred for 5 minutes. This was designated as Inventive Example 1. Inventive Examples 2 to 10 and Comparative Examples 1 to 9 were produced in the same proportions as in Inventive Example 1 below, at the mixing ratios shown in Table 1.

Invention Example 11 Preparation of mixed vulcanization accelerator composition
Example (2) Mitsui EPT 4021 (Mitsui Petrochemical Industry Co., Ltd. EP ) on 600 ml Labo Plastmill ( manufactured by Toyo Seiki Co., Ltd.)
DM brand name) 60 g was added, followed by tetrakis (2-ethylhexyl) thiuram disulfide 140.
g, NOXCELLER CZ 180g, NOXCELLER ZTC 6
After charging 0 g and 60 g of Carplex ^# 67,
The mixture was kneaded for about 5 minutes, taken out from the mixer, then formed into a sheet by a roll mill, and then pelletized with a diameter of 5 mm to obtain a pale yellowish white rubber compound. This pale yellow-white rubber compound was designated as Inventive Example 11.

Example 2 Storage stability test of mixed vulcanization accelerator composition Inventive Example 1 of mixed vulcanization accelerator composition prepared in Example 1
10 and Comparative Examples 1 to 9, 20 g each, diameter 10c
The mixture was taken in a glass petri dish of m, and the appearance of each mixed vulcanization accelerator composition was visually observed in a constant temperature bath at 40 ° C. and the change with time depending on the presence or absence of decomposition products was tested. Regarding the presence or absence of decomposition products, 10 mg of each mixed vulcanization accelerator composition aged with time was sampled, dissolved in 1 ml of chloroform, and subjected to thin layer chromatography (developing solution: benzene / hexane / methanol / ethyl acetate). = 5
At 0/50/2 / 0.5), the presence or absence of decomposition products was tested by comparison with the same mixed vulcanization accelerator composition before aging. The results are shown in Table 1. However, with respect to Inventive Example 11, 20 g of the rubber compound in pellet form was used to test the same aging change as described above. Furthermore, the presence or absence of the same decomposition products as described above was tested using 20 mg of the rubber compound in the form of pellets that had been aged. These results are also shown in Table-1.
It was shown to.

[0017]

[Table 1]

[Table 2]

Example 3 Vulcanization Properties of Mixed Vulcanization Accelerator Composition By the same method as Example 1 of the present invention, Example 1 of the present invention shown in Table 3 was used.
2-15 and the mixed vulcanization accelerator composition of Comparative Examples 10-13 were produced, and the predetermined heat treatment of Table-3 was performed. Then, based on the formulation of Table-2, a masterbatch was prepared by a known kneading method with an 8-inch test roll, the masterbatch was divided into eight equal parts, and the invention examples 12 to 12 shown in Table-3 were prepared.
The unvulcanized rubber compositions were prepared by kneading the compounding amounts of the mixed vulcanization accelerator compositions of 15 and Comparative Examples 10 to 13. For these unvulcanized rubber compositions, a rheometer test at a test temperature of 160 ° C. (using a rheometer 100 manufactured by Monsanto Co., Ltd. is used) in accordance with the Japan Rubber Association Standard Standard SRIS 3102-1977 (vulcanization test method by a vulcanization tester). ) Was done. Furthermore, these unvulcanized rubber compositions were vulcanized by a press at 160 ° C. for 30 minutes to prepare respective vulcanized rubber compositions. These vulcanized rubber compositions were left standing at room temperature (23 ° C.) and humidity of 50%, and a visual observation test of vulcanized rubber was conducted. The respective results are shown in Table-3.

[0019]

[Table 3]

[Table 4]

[0020]

[Effect] From the results shown in Tables 1 and 3, the mixed vulcanization accelerator composition using the general-purpose thiuram-based vulcanization accelerators (TT, TET and TBT) as one component shows the appearance and the presence or absence of decomposition products. The storage stability is significantly impaired by the test [Comparative Examples 1 to 9], and blooming is observed on the surface of the vulcanized rubber [Comparative Examples 10 to 13], whereas the mixed vulcanization using EHT as a component. The accelerator composition had good storage stability [Invention Examples 1 to 11], no blooming was observed on the vulcanized rubber surface, good scorch resistance (rheometer test t '(10)), and vulcanization rate. (Rheometer test tΔ80) is also excellent [Invention Examples 12 to 1]
5], the mixed vulcanization accelerator composition of the present invention is suitable for the rubber industry.

Front page continued (72) Inventor Masaki Ohara 7-4 Nihonbashi Kobunecho, Chuo-ku, Tokyo Inside Ouchi Shinko Chemical Industry Co., Ltd. (72) Yoshiko Yamamoto 7-4 Nihonbashi Kobune-cho, Chuo-ku, Tokyo Uchi Shinko Chemical Industry Co., Ltd.

Claims (1)

[Claims] (1) Tetrakis (2-ethylhexyl)
Thiuram disulfide 5 to 90% by weight (2) Sulfenamide-based vulcanization accelerator 5 to 80% by weight (3) Vulcanization accelerator other than the above (1) and (2), and other than thiuram-based vulcanization accelerator Vulcanization accelerator of 0 to 80% by weight (4) One or more rubber compounding agents other than the above (1) to (3) and / or 5 to 60% by weight of rubber-like polymer (1) to (4) A mixed vulcanization accelerator composition which is excellent in storage stability and vulcanization characteristics.