JPH0119687B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a chloroprene rubber vulcanization composition containing a 2-iminocycloalkyldithiocarboxylic acid derivative as a vulcanization accelerator for chloroprene rubber (hereinafter abbreviated as "CR"). In general, compared to other diene rubbers, CR has
It is widely agreed that it has excellent ozone resistance, heat resistance, weather resistance, and oil resistance, and for this reason, it is used in large quantities as a so-called durable rubber for industrial parts. However, in order to maximize the characteristics of CR, various additives play a large role, and in particular, the method of using the vulcanization accelerator plays a large role. This effect is partly due to the fact that CR has fewer types of vulcanization accelerators than other diene rubbers. For example, in diene rubber, the vulcanization accelerators include thiazole compounds (2-meltocaptobenzothiazole, dibenzothiazolyl disulfide, etc.) and sulfenamide compounds (N-cyclohexyl-2-benzothiazolyl sulfene). amide, N-oxydiethylene-2-benzothiazolylsulfenamide, etc.), guanidine compounds (1,3-diphenylguanidine, 1,3-
di-o-tolylguanidine, etc.), thiuram compounds (tetramethylthiuram disulfide, tetramethylthiuram monosulfide, etc.), and dithioate compounds (zinc dimethyldithiocarbamate, sodium diethyldithiocarbamate, etc.). whereas it is spread over the things of
Vulcanization accelerators in CR have so far been
One type of thiourea compounds (ethylenethiourea, diethylthiourea, etc.) is most effectively used. However, since the oil shock in 1971,
The energy and resource conservation movement is gaining momentum around the world.
For this reason, there is an urgent need for countermeasures in the rubber industry as well. Among these measures, as an energy saving measure, there is a demand for high-speed vulcanization that shortens the vulcanization time in order to shorten the process time, and in particular to save energy during the vulcanization process. Generally, high-speed vulcanization is carried out using two methods: raising the vulcanization temperature and using a vulcanization accelerator that has the ability to accelerate vulcanization, but for the reason of energy saving mentioned above, vulcanization is performed without raising the vulcanization temperature A method as described above is desired which can save time. Further, as a resource saving measure, especially with the development of the automobile industry, there is a demand for higher durability of rubber parts. For this reason, rubber parts require more sophisticated processing, and as the processing process inevitably becomes more complex, it is necessary to heat the unvulcanized rubber before it is placed in a calendar or extruder, or during the extruder. There is a strong desire for scorch stability of unvulcanized rubber against heat generation in unvulcanized rubber. For these purposes, diethylthiourea (hereinafter abbreviated as "EUR") is usually used as a vulcanization accelerator with ultra-fast vulcanization accelerating power.
When using EUR, the vulcanization time is considerably shortened, but the unvulcanized rubber causes "scorching" during the processing process, leading to destruction of the processing machine and interruption of the vulcanization process. are forced to do so. For this purpose, dibenzothiazolyl disulfide and tetramethylthiuram disulfide are generally used as scorch inhibitors.
Lowers the crosslink density and lowers the tensile stress (Kennari Goda, Synthetic Rubber Processing Technology Complete Book, Chloroprene Rubber, Taiseisha Co., Ltd., October 1972)
Published on March 20th, pages 24-25). Furthermore, although a scorch inhibitor has been proposed in Japanese Patent Application Laid-Open No. 55-135147, it is not satisfactory. Furthermore, the use of such scorch inhibitors is uneconomical. Therefore, there is a need for a vulcanization accelerator that essentially stabilizes scorch during processing and has ultra-fast vulcanization accelerating properties during vulcanization. An object of the present invention is to develop and provide a chloroprene vulcanization accelerator that should meet such demands. In order to achieve the above object, the inventors conducted intensive research and found that the 2-iminocycloalkyldithiocarboxylic acid derivative has a significantly faster vulcanization rate than EUR, which conventionally has ultra-fast vulcanization accelerating properties, and has a faster vulcanization rate during processing. It was discovered that the scorch stability was also significantly more stable than that of EUR, and this invention was completed based on this knowledge. The gist of this invention is 2-- expressed by the following general formula [] or [].
A chloroprene rubber vulcanization composition comprising one or more iminocycloalkyldithiocarboxylic acid derivatives as a vulcanization accelerator. General formula [] [However, R ¹ is hydrogen, an alkyl group having 1 to 3 carbon atoms, or a cyclopentyl group, R ² is hydrogen, an alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or a cyclohexyl group, and R ³ is hydrogen, a methyl group, n represents ammonia, and n represents an integer of 2 to 3. ] General formula [ ] [However, R ⁴ represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or a cyclohexyl group. ] A detailed and specific explanation of the constituent elements of this invention will be described below. The 2-iminocycloalkyldithiocarboxylic acid derivative used as the vulcanization accelerator for chloroprene rubber according to the present invention can be produced by a known synthesis method described below. The following are representative examples. That is, as those belonging to the general formula [], 2-iminocyclopentanedithiocarboxylic acid, 2-methyliminocyclopentanedithiocarboxylic acid, 2-ethyliminocyclopentanedithiocarboxylic acid, 2-
sec-butyliminocyclopentanedithiocarboxylic acid, 2-methyliminocyclopentanedithiocarboxylic acid methyl ester, 3-methyl-2-iminocyclopentanedithiocarboxylic acid, 3-methyl-2-cyclohexaniminodithiocarboxylic acid,
Examples include 2-methyliminocyclohexanedithiocarboxylic acid, 2-ethyliminocyclohexanedithiocarboxylic acid, and 2-n-propyliminocyclohexanedithiocarboxylic acid, but are not limited to these compounds. Also, as those belonging to the above general formula [], bis(2-iminocyclopentylthiocarbonyl) disulfide, bis(2-methyliminocyclopentylthiocarbonyl) disulfide, bis(2-ethyliminocyclopentylthiocarbonyl) disulfide, bis( 2-n-propyliminocyclopentylthiocarbonyl) disulfide, bis(2-sec-butyliminocyclopentylthiocarbonyl) disulfide, bis(2-cyclopentyliminocyclopentylthiocarbonyl) disulfide, bis(2-cyclohexyliminocyclopentylthiocarbonyl) disulfide, etc. However, it is not limited to these compounds. Furthermore, it is preferable that a compound having a small molecular weight is economical because it requires a small amount to be added. Compounds belonging to the above general formula [] are Naoaki Fukuda, Kenichi Arai, Tatsuo Takeshima: Synthesis Vol. 7, Page 566, 1980 [Naoaki Fukuda, Kenichi Arai, Tatsuo
Takeshima: Synthesis, vol. 7566 (1980)], it can be easily produced according to the following reaction formula. That is, an example of the production of 2-methyliminocyclopentanedithiocarboxylic acid will be shown. Under ice cooling, add 8.4 g (0.1 mol) of cyclopentanone and 15.5 g of carbon disulfide to a 300 ml four-necked flask.
[0.1 x 1.5 mol], then add 15.5 g of 40% monomethylamine aqueous solution [0.1 x 2.0 mol] and 60 ml of water.
After reacting for 2 hours at below 10℃, add 2N hydrochloric acid 57
Added ml. The resulting powder was filtered, washed with water, and then recrystallized from acetone to obtain the desired product as a yellow-red powder. Yield 68%, melting point 124~125℃ (literature value: 125~
(126°C) Furthermore, the esterified product of the target product [A] in the above reaction formula (1) can be easily produced according to the general esterification reaction described below. That is, a production example of 2-methyliminocyclopentanedithiocarboxylic acid methyl ester will be shown. Pour 100 ml of water and 2.6 g (0.06 mol) of sodium hydroxide into a 200 ml four-necked flask, and add 2.
-Methyliminocyclopentanedithiocarboxylic acid
After adding and dissolving 10.4 g [0.06 mol], 7.6 g [0.06 mol] dimethyl sulfate was added under ice cooling (10-20°C).
was added dropwise and stirred for 5 hours. The generated precipitate was filtered, washed with water, and then recrystallized from isopropyl alcohol to obtain the desired product as a yellow-red powder. Yield 74.9
%, melting point 142-144℃ (Literature value: 143-144℃) On the other hand, the compounds belonging to the above general formula [] are Naoaki Fukada, Kenichi Arai, Tatsuo Takeshima: Synthesis Volume 7, Page 566
1980 [Naoaki Fukada, Kenichi Arai,
Tatsuo Takeshima: Synthesis, vol.7, 566
(1980)] and can be easily produced according to the following reaction formula. That is, a production example of bis(2-methyliminopentylthiocarbonyl) disulfide) is shown. Under ice cooling, 8.4 g [0.1 mol] of cyclopentanone and 11.4 g [0.1 mol] of carbon disulfide were placed in a 300 ml four-necked flask.
x 1.5 mol] and 0.56 g [0.1 x 0.18 mol] of sulfur, and further 12.8 g [0.1 40% monomethylamine].
x 1.7 mol] and 62.4 ml of water were added, stirred at below 10°C for 8 hours, and after reaction, the mixture was left to stand for 1 day and night, and 55.6 ml of 2N hydrochloric acid was added. The resulting powder was filtered, washed with water, and then recrystallized from an aniline/ethanol mixed solvent to obtain the desired product as a yellow powder. Yield 51.0%, melting point 177.3-180.5°C (literature value: 179-180°C) The characteristic values of the 2-iminocycloalkyldithiocarboxylic acid derivative according to this invention are shown in Table 1-
1. Shown in Table-1-2.

【table】

[Table] dec.: Indicates decomposition.

【table】

[Table] Next, embodiments of the present invention will be described. The chloroprene rubber vulcanized composition of this invention is manufactured according to conventional rubber processing methods. and,
When the 2-iminocycloalkyldithiocarboxylic acid derivative according to this invention is added to CR as a vulcanization accelerator, the amount added is per 100 parts by weight of CR.
The amount is 0.1 to 3 parts by weight, preferably 0.3 to 1.5 parts by weight.
In this case, if it is less than 0.1 part by weight, the vulcanization rate will drop significantly and it is not practical. On the other hand, if 3 parts by weight or more is added, the scorch speed increases, but the vulcanization rate does not increase, which is uneconomical. In addition, the chloroprene rubber vulcanization composition of the present invention contains metal oxides such as zinc oxide, magnesium oxide, and lead oxide, as well as commonly used vulcanization accelerators for diene rubber, anti-aging agents, and fillers. , pigments, plasticizers, and other compounding agents, and sulfur can also be used. Furthermore, the method of using the 2-iminocycloalkyldithiocarboxylic acid derivative according to the present invention as a vulcanization accelerator is no different from that of conventional vulcanization accelerators for chloroprene rubber. Therefore, conventionally
Vulcanization can be carried out using methods commonly used in the CR vulcanization process, such as press vulcanization, in-die extension vulcanization, and vulcanization machines. Next, the effects of this invention will be described. The 2-iminocycloalkyldithiocarboxylic acid derivative according to the present invention is particularly effective as an ultra-fast vulcanization accelerator among ordinary thiourea compound vulcanization accelerators in terms of vulcanization temperature and in combination with other vulcanization accelerators. The scorch stability (scorch time) according to the Mooney scorch test is 50~
The remarkable feature is that the vulcanization time (t' _c (90)) was shortened by 10 to 50% in the rheometer vulcanization test. Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples, but the invention is not limited thereto. Example 1 Measurement of scorch time and vulcanization time of unvulcanized composition A compound according to the present invention or a comparative compound was used as a test vulcanization accelerator according to a conventional rubber processing method based on the formulation shown in Table 2 below. Knead the specified amount using a kneading roll machine, and according to JIS K6300,
The scorch time was measured using an L-type rotor and a test temperature of 125°C. Furthermore, the Japan Rubber Association standards
Rheometer vulcanization test (Toyo Seiki testing machine, die diameter 30 mm, amplitude angle 3°, frequency
6cpm, test temperature 150℃ ₎
(90)) was measured. The results are shown in Table-3.

【table】

【table】

[Table] As can be seen from the above examples, when the 2-iminocycloalkyldithiocarboxylic acid derivative according to the present invention is used as a vulcanization accelerator for CR,
This is not found in conventionally known vulcanization accelerators.
It is clear that this is a vulcanization accelerator that has scorch stability and has ultra-fast vulcanization accelerating properties.

Claims (1)

[Claims] 1. 2 represented by the following general formula [] or []
- A chloroprene rubber vulcanization composition containing one or more iminocycloalkyldithiocarboxylic acid derivatives as a vulcanization accelerator. General formula [] [However, R ¹ is hydrogen, an alkyl group having 1 to 3 carbon atoms, or a cyclopentyl group, R ² is hydrogen, an alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or a cyclohexyl group, and R ³ is hydrogen, a methyl group, n represents ammonia, and n represents an integer of 2 to 3. ] General formula [ ] [However, R ⁴ represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, or a cyclohexyl group. ]