JPH0881585A - Rubber composition and method for vulcanizing rubber - Google Patents

Abstract

PURPOSE: To increase the rate of vulcanization at a low temperature, improve the physical properties and prevent the formation of a carcinogenic nitrosoamine by incorporating a specified amine salt and a vulcanization accelerator based on a sulfenamide into a diene rubber. CONSTITUTION: 100 pts.wt. diene rubber is kneaded with 0.5-5 pts.wt. total of 2-mercaptobenzothiazole, a salt of an amine of NHR1 R2 (wherein R1 and R2 are each H, a 1-18C noncyclic aliphatic group or an 8C or lower alicyclic group, except for the case where both of them are H at the same time) and at least one vulcanization accelerator based on benzothiazole and a sulfenamide, and if necessary, a filler, a vulcanization accelerator aid, a vulcanizing agent, etc., at 110-140 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition of a diene rubber material, which is characterized by a vulcanization accelerator to be compounded therein, while avoiding deterioration of rubber physical properties and vulcanization speed. The present invention relates to a rubber composition and a rubber vulcanization method capable of performing vulcanization at a vulcanization temperature lower than usual.

[0002]

2. Description of the Related Art A heat energy is required for molding and vulcanizing rubber, and the reduction of the heat energy is one of the items to be considered as a part of total cost reduction.
Generally, when vulcanization is carried out at a low vulcanization temperature, the vulcanization rate and physical properties are lowered. As a method for dealing with this, it is not possible to obtain a particular effect by simply increasing the blending amount of the vulcanization accelerator, and furthermore, it is not economical.

As one method for solving these problems, a thiuram-based vulcanization accelerator represented by tetramethylthiuram disulfide and a dithiocarbamate-based vulcanization accelerator represented by zinc dimethyldithiocarbamate are used alone. Or the method of using together is mentioned. However, since most of these vulcanization accelerators are compounds that are the subject of the carcinogenic nitrosamine problem, which has become a concern in recent years as a hygiene problem, their use is shunned.

[0004]

DISCLOSURE OF THE INVENTION The present invention discloses a rubber vulcanizing system capable of sufficiently obtaining physical properties even when vulcanized at a temperature lower than usual. Another object of the present invention is to provide a rubber composition capable of adjusting the vulcanization time without adversely affecting the rubber physical properties and the vulcanization rate. Further, in particular, the present invention discloses a vulcanization system that does not affect the physical properties of rubber even if it is a vulcanization system that does not produce carcinogenic nitrosamines.

[0005]

Means for Solving the Problems As a result of earnest studies on a vulcanization accelerator in order to achieve the above object, the present inventors have found that
By using a sulfenamide-based vulcanization accelerator and an amine salt of 2-mercaptobenzothiazole in combination, physical properties do not deteriorate even when vulcanization is performed at a temperature lower than usual, and further, physical properties and vulcanization speed It was found that it is possible to adjust only the scorch time without adversely affecting the.

The structure of the present invention is as follows. That is, the rubber composition of the present invention contains 2-mercaptobenzothiazole and NHR per 100 parts by weight of the diene rubber.
₁ R ₂ (provided that R ₁ and R ₂ are each a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, or a cycloaliphatic group having up to 8 carbon atoms, and R ₁ and R ₂ are hydrogen at the same time. It is not an atom) and a salt with an amine represented by the following formula and a sulfenamide vulcanization accelerator represented by the following chemical formula 1 are used in combination. The total amount of the amine salt of mercaptobenzothiazole and the sulfenamide accelerator is 0.5 to 5.0.
Parts by weight.

[0007]

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(Wherein R ₃ and R ₄ are each a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, a cycloaliphatic group having up to 8 carbon atoms, or R ₃ and R ₄ are oxygen. Represents a group forming a heterocycle containing atoms, and R ₃ and R ₄ are not hydrogen atoms at the same time)

The above rubber composition can be produced by a conventional kneading method using a mixer or a kneader. At this time, if necessary, a filler such as carbon black, a vulcanization accelerating aid such as stearic acid or zinc oxide, a vulcanizing agent such as sulfur, and other additives may be added depending on the purpose of use.

Examples of the amine of the compound represented by the amine salt of mercaptobenzothiazole include methylamine, dimethylamine, cyclohexylamine, and the like, but primary amines such as cyclohexylamine and tert-butylamine which do not produce nitrosamine. Specific examples are amines and secondary amines such as dicyclohexylamine, diphenylamine, dibenzylamine, and di-2-ethylhexylamine that are not subject to carcinogenic nitrosamine problems.

Examples of the benzothiazole / sulfenamide-based vulcanization accelerator include morpholinothiobenzothiazole, N, N-diethylbenzothiazyl-2-sulfenamide and the like, but particularly carcinogenic nitrosamines are produced. N-cyclohexylbenzothiazyl-
2-sulfenamide, N-tert-butylbenzothiazyl-2-sulfenamide, N, N-dicyclohexylbenzothiazyl-2-sulfenamide and the like are preferably exemplified.

When the total amount of both is less than 0.5 parts by weight, the vulcanization rate is remarkably lowered and the practicality is poor. On the other hand, if 5.0 parts by weight or more is added, no particular effect can be expected, which is economically unfavorable. Further, from the viewpoint of safety of scorch during rubber processing, it is preferable to avoid adding more than 5.0 parts by weight.

[0013]

EXAMPLES Examples will be described in detail below, but the present invention is not limited thereto. The compounding ratio of the rubber composition excluding the vulcanization accelerator is shown below, and Tables 1 and 2 show the compounding ratio of the vulcanization accelerator and the test results. The data of the tensile test described as the test result here is JIS K6301.
It was obtained by measuring in accordance with the "tensile test" in (Vulcanized rubber physical test method).

Natural rubber 100 HAF carbon black 50 naphthenic process oil 5 stearic acid 1 zinc white 5 sulfur yellow 1.5 vulcanization accelerator

[0015]

[Table 1]

[0016]

[Table 2]

Explanation of abbreviations Sansel CM N-cyclohexylbenzothiazyl-2-sulfenamide trade name (manufactured by Sanshin Chemical Industry Co., Ltd.) Sanseller NS N-tert butylbenzothiazyl-2-sulfenamide trade name (Manufactured by Sanshin Chemical Industry Co., Ltd.) Sansera HM 2-mercaptobenzothiazole cyclohexylamine salt (manufactured by Sanshin Chemical Industry Co., Ltd.) M-TBA 2-mercaptobenzothiazole tert-butylamine salt Sancellar MA 2-mercaptobenzothiazole Trade name of dicyclohexylamine salt (manufactured by Sanshin Chemical Industry Co., Ltd.) M-DOA 2-mercaptobenzothiazole di-2-ethylhexylamine salt product name of Sansera M2-mercaptobenzothiazole (manufactured by Sanshin Chemical Industry Co., Ltd.) Sun cellar DM dibenzo Trade name of thiazyl disulfide (manufactured by Sanshin Chemical Industry Co., Ltd.)

Although the rubber compositions having the compositions of Examples 1 to 5 shown in Table 1 have sufficient vulcanization rates and physical properties and have different vulcanization times (t ₉₀ ) respectively, There is almost no difference in the vulcanization rate (t ₉₀ -t ₁₀ ) and the maximum torque value. Also, there is almost no difference in the measured values of the tensile test. On the other hand, Comparative Examples 1 to 4 in Table 2 are the same as those in Examples 1 to 4 described above.
It can be seen that the vulcanization rate and the physical properties tend to be lower than those of No. 5. A large change was observed in the vulcanization speed, maximum torque, and physical property values with changes in the vulcanization accelerator.
As can be seen, it is impossible to adjust the vulcanization time while maintaining the vulcanization speed and maximum torque.

Comparing Examples 1 to 5 with Comparative Examples 5 and 6, Examples 1 to 5 have a sufficient vulcanization rate and rubber physical properties although the vulcanization temperature is low. From this, it is clear that the blending of Examples 1 to 5 makes it possible to reduce the thermal energy during the vulcanization and molding of rubber.

[0020]

As described above, according to the present invention, by using a specific amine salt of 2-mercaptobenzothiazole and a sulfenamide-based accelerator in combination,
Sufficient vulcanization rate and physical properties can be obtained even by vulcanization at a temperature lower than usual. Not only that, by changing the combined ratio of these two types of vulcanization accelerators, it becomes possible to adjust the vulcanization rate without affecting the physical property values, which is sufficiently applicable in practical situations. Moreover, since it is possible to select a compounding system that does not generate carcinogenic nitrosamine, it is possible to contribute to hygiene of the rubber industry.

Claims (10)

[Claims] 1. With respect to 100 parts by weight of the diene rubber, 2-
Mercaptobenzothiazole and NHR ₁ R ₂ (however, R
₁ and R ₂ respectively represent a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, and a cycloaliphatic group having up to 8 carbon atoms, and R ₁ and R ₂ are simultaneously hydrogen atoms. A) and a benzothiazole / sulfenamide-based vulcanization accelerator of one kind or two or more kinds, and the amine salt of 2-mercaptobenzothiazole and benzothiazole. A rubber composition, characterized in that the total amount with the sulfenamide vulcanization accelerator is 0.5 to 5 parts by weight. 2. The amine constituting the amine salt of 2-mercaptobenzothiazole according to claim 1 is any one of cyclohexylamine, tert-butylamine, dicyclohexylamine and di-2-ethylhexylamine. Rubber composition. 3. The benzothiazole / sulfenamide vulcanization accelerator according to claim 1, wherein cyclohexylbenzothiazyl-2-sulfenamide, N-tert-butylbenzothiazyl-2-sulfenamide, A rubber composition, which is any one of N, N-dicyclohexylbenzothiazyl-2-sulfenamide. 4. The amine constituting the amine salt of 2-mercaptobenzothiazole according to claim 1 is any one of cyclohexylamine, tert-butylamine, dicyclohexylamine, and di-2-ethylhexylamine. Sulfenamide vulcanization accelerators include cyclohexylbenzothiazyl-2-sulfenamide, N-tert-butylbenzothiazyl-2-sulfenamide, N, N-dicyclohexylbenzothiazyl-
A rubber composition which does not produce a carcinogenic nitrosamine, which is any one of 2-sulfenamide. 5. 2-Mercaptobenzothiazole and NH
R ₁ R ₂ (wherein R ₁ and R ₂ represent a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, and a cyclic aliphatic group having 8 carbon atoms, respectively, R ₁ , R ₂ Is not a hydrogen atom at the same time), and one or more kinds of benzothiazole / sulfenamide vulcanization accelerators are used in combination with the diene rubber. A method for vulcanizing a diene rubber, characterized by: 6. The amine constituting the amine salt of 2-mercaptobenzothiazole according to claim 5 is any one of cyclohexylamine, tert-butylamine, dicyclohexylamine and di-2-ethylhexylamine, and benzothiazole -Sulfenamide vulcanization accelerators include cyclohexylbenzothiazyl-2-sulfenamide, N-tert-butylbenzothiazyl-2-sulfenamide, N, N-dicyclohexylbenzothiazyl-2-sulfene A method for vulcanizing a diene rubber that does not produce a carcinogenic nitrosamine, which is characterized by being any of amides. 7. The method for vulcanizing a rubber according to claim 5, wherein the vulcanization temperature is 110 to 140 ° C. 8. A 2-mercaptobenzothiazole and NHR ₁ R ₂ (provided that R ₁ and R ₂ are each a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, and up to 6 carbon atoms). A salt with an amine represented by a cycloaliphatic group, wherein R ₁ and R ₂ are not hydrogen atoms at the same time) B Any one or two benzothiazole / sulfenamide vulcanization accelerators As described above, the method for vulcanizing a diene rubber, which is characterized in that A and B are mixed and used. 9. 2-Mercaptobenzothiazole and NH
R ₁ R ₂ (wherein R ₁ and R ₂ represent a hydrogen atom, an acyclic aliphatic group having 1 to 18 carbon atoms, and a cyclic aliphatic group having 8 carbon atoms, respectively, R ₁ , R ₂ Is not a hydrogen atom at the same time), and a benzothiazole / sulfenamide vulcanization accelerator.
A vulcanization accelerator for rubber, which is composed of one kind or a mixture of two or more kinds. 10. A vulcanization accelerator for rubber, which is obtained by mixing a cyclohexylamine salt of 2-mercaptobenzothiazole and cyclohexylbenzothiazyl-2-sulfenamide.