JPH0586235A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, composed of a specific copolymer rubber, tetrabenzylthiuram disulfide and zinc dibenzyldithiocarbamate in a specific proportion, having high vulcanization rate and excellent in scorch stability. CONSTITUTION:The objective composition is composed of (A) 100 pts.wt. ethylene-alpha and olefin-nonconjugated diene copolymer rubber (e.g. ethylene-propylene- ethylidenenorbornene copolymer rubber) and (B) a tetrabenzylthiuram disulfide and zinc dibenzyldithiocarbamate in the total amount of the components (B) and (C) of 0.5-5 pts.wt. at (10/90) to (90/10) content ratio of the components (B) to (C).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a rubber composition. More specifically, the present invention has a sufficiently high vulcanization rate required for practical use and is excellent in scorch stability, and controls the characteristic levels of vulcanization rate and scorch stability to the respective required levels. The present invention relates to an ethylene-α-olefin-non-conjugated diene copolymer rubber composition which is capable of producing nitrosamine, which is a chemical substance harmful to the human body, in the vulcanization step or the subsequent treatment step.

[0002]

2. Description of the Related Art Ethylene-.alpha..olefin-non-conjugated diene copolymer rubber has a drawback that its vulcanization rate is slower than that of diene rubber such as natural rubber or styrene-butadiene copolymer rubber. .. In order to solve this drawback, various vulcanization accelerators such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N′-dimethyl-N, N ′ have hitherto been used.
Diphenylthiuram disulfide, dipentamethylene thiuram disulfide, dipentamethylene thiuram tetrasulfide, dipentamethylene thiuram hexasulfide, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate,
Techniques using zinc dipropyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc tellurium diethyldithiocarbamate, and the like have been proposed. However, when these vulcanization accelerators are used, it becomes clear that nitrosamines which are harmful to the human body are produced in the vulcanization step or the subsequent processing steps. TRGS552 (Technische Regeln Fuergefarstoff), which is the technical standard for substances, is also regulated as a hazardous substance. Under such circumstances, thiazole-based, guanidine-based, thiourea-based, sulfenamide-based vulcanization accelerators, etc. have been proposed as vulcanization accelerators that do not produce nitrosamines. However, these vulcanization accelerators have insufficient vulcanization acceleration effect, and particularly when applied to ethylene-α / olefin-non-conjugated diene copolymer rubber, vulcanization operation at high temperature or for a long time Required,
It was inconvenient in industrial practice. By the way, from the viewpoint of industrial use of the rubber composition, in addition to having the above-mentioned sufficiently high vulcanization rate, it is required to have excellent scorch stability, that is, a long scorch time. However, generally having a sufficiently high vulcanization rate and excellent scorch stability are in a trade-off relationship, and a rubber composition excellent in both of these properties,
Moreover, it has been earnestly desired to realize a rubber composition capable of controlling the characteristic levels of vulcanization rate and scorch stability to the respective required levels.

[0003]

In view of the present situation, the problem to be solved by the present invention is to have a sufficiently high vulcanization rate required for practical use, and to have excellent scorch stability and Provided is a rubber composition which can control the characteristic level of scorch stability to a required level and which does not generate nitrosamine, which is a chemical substance harmful to the human body, in a vulcanization step or a subsequent processing step. It depends on what you do.

[0004]

The inventors of the present invention have reached the present invention as a result of extensive studies to solve the above problems.

That is, the present invention comprises ethylene-α-olefin-non-conjugated diene copolymer rubber (A), tetrabenzil thiuram disulfide (B) and zinc dibenzil dithiocarbamate (C), and (A) Ingredient 10
The total amount of the components (B) and (C) per 0 parts by weight is 0.5 to 5 parts by weight, and the ratio of the contents of the components (B) and (C) is 10/90. ~ 90/10
(Weight ratio) of the rubber composition.

The details will be described below. The ethylene-α-olefin-non-conjugated diene copolymer rubber (hereinafter sometimes referred to as “(A) component”) in the present invention is a copolymer composed of ethylene, one or more α-olefins and a non-conjugated diene. It means a polymer, and propylene, 1-butene, 1-pentene, 1-hexene and the like are exemplified as the α-olefin, and dicyclopentadiene, ethylidene norbornene, 1,4-hexadiene and methyltetrahydroindene as the non-conjugated diene. , Methylnorbornene and the like are exemplified.

The rubber composition of the present invention comprises the above-mentioned ethylene
For the α-olefin-non-conjugated diene copolymer rubber (A), tetrabenzil thiuram disulfide (hereinafter,
It may be referred to as "component (B)". ) And zinc dibenzil dithiocarbamate (hereinafter sometimes referred to as “component (C)”). The component (B) and the component (C) used here do not have a risk of producing nitrosamine which is a chemical substance harmful to the human body in the vulcanization step or the subsequent treatment step.

In the present invention, the total content of the components (B) and (C) per 100 parts by weight of the component (A) is 0.5 to 5 parts by weight. When the amount is less than 0.5 part by weight, the vulcanization promoting effect is insufficient, while when the amount exceeds 5 parts by weight, bloom is generated, and the effect due to addition in an increased amount is obtained. It is saturated and economically disadvantageous.

Further, the ratio of the contents of the component (B) and the component (C) is 10/90 to 90/10 (weight ratio).
When the amount of the component (B) is excessive, a sufficient vulcanization rate cannot be obtained, while when the amount of the component (C) is excessive, the scorch stability is poor.

In the present invention, the component (B) and the component (C)
In addition to the components, other vulcanization accelerators that are not regulated as generating nitrosamines by TRGS552 may be used in combination. Examples of such vulcanization accelerators include aldehyde ammonia systems such as hexamethylenetetramine and n-butyraldehydeaniline; guanidine systems such as diphenylguanidine and di-o-tolylguanidine; 2-mercaptobenzothiazole, dibenzothiazyl disulfide or 2- Thiazole compounds such as zinc salts such as mercaptobenzothiazole; N-cyclohexyl-2-benzothiazylsulfenamide, Nt-butyl-2-benzothiazylsulfenamide, N, N'-dicyclohexyl-
Sulfenamide-based compounds such as 2-benzothiazylsulfenamide; thiourea-based compounds such as ethylene thiourea, N, N'-diphenylthiourea and diethyl thiourea; O, O'-di-n-butylphosphorodithioic acid zinc And various vulcanization accelerators such as phosphoric acid.

As explained above, the rubber composition of the present invention does not generate nitrosamine which is a chemical substance harmful to the human body in the vulcanization step or the subsequent treatment, and has a sufficiently high vulcanization rate required for practical use. And has excellent scorch stability. Moreover, in the present invention, which is characterized in that the component (B) and the component (C) are used in combination, the vulcanization is performed by appropriately adjusting the ratios of the component (B) and the component (C) within the scope of the present invention. It is possible to control the level of speed and scorch stability to each required level.

[0012]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples. Examples 1 to 3 and Comparative Examples 1 to 2 The components shown in the formulation (1) of Table 1 were kneaded with a BR type Banbury mixer, and then the obtained kneaded product was subjected to Table 1
The component of the composition (2) was added and kneaded with an open roll having a diameter of 8 inches to obtain a rubber composition. Regarding the obtained rubber composition, the unvulcanized rubber characteristics shown in Table 1 were measured according to JIS K630.
It was measured according to 0. Further, a part of the rubber composition was press-vulcanized at 160 ° C. for 20 minutes. For the obtained vulcanizates, the vulcanized rubber properties shown in Table 1 are measured according to JIS K6
Measured according to 301. The conditions and results are shown in Table 1.

[0013]

[Table 1] Comparative Example Actual Example Comparative Example 1 1 2 3 2 Formulation (1): Parts by weight Component (A) * 1 100 100 100 100 100 FEF Black 150 150 150 150 150 Paraffin oil 100 100 100 100 100 Zinc Hana 5 5 5 5 5 Stearic acid 1 1 1 1 1 Blend (2): parts by weight Component (2) * 2 3.0 2.4 1.5 0.6 0 Component (3) * 3 0 0.6 1.5 2.4 3.0 MBT * 4 1.0 1.0 1.0 1.0 1.0 CBS * 5 1.0 1.0 1.0 1.0 1.0 Sulfur 1.5 1.5 1.5 1.5 1.5 Evaluation results Unvulcanized rubber characteristics Scorch time minutes * 6 11.3 11.0 10.5 10.0 9.7 Optimal vulcanization time minutes * 7 23.9 23.5 22.8 22.2 21.8 Vulcanized rubber characteristics Tensile strength Kgf / cm ² 129 130 131 132 133 Elongation% 350 350 360 360 370 Hardness JIS-A 66 66 66 66 67

* 1 Component (A): ethylene-propylene-ethylidene norbornene copolymer rubber, Mooney viscosity ML _{1 + 4}
121 ° C = 65, ethylene content 70% by weight, iodine value 12 * 2 Component (B): Tetrabenzil thiuram disulfide * 3 Component (C): Zinc dibenzil dithiocarbamate * 4 MBT: 2-Mercaptobenzothiazole * 5 CBS: N-cyclohexyl-2-benzothiazyl sulfenamide * 6 scorch time: t ₅ ML125 ℃ * 7 optimum vulcanization time: t _'c 90 ODR 160 ℃

[0015]

As described above, according to the present invention, a rubber composition having a sufficiently high vulcanization rate required for practical use and excellent scorch stability, and having a vulcanization rate and a scorch stability level are provided. It was possible to provide a rubber composition which can be adjusted to the required level and which does not generate nitrosamine which is a chemical substance harmful to the human body in the vulcanization step or the subsequent processing step. ..

Claims (1)

[Claims] 1. An ethylene-.alpha..olefin-non-conjugated diene copolymer rubber (A), tetrabenzil thiuram disulfide (B) and zinc dibenzil dithiocarbamate (C), and 100 parts by weight of component (A). The total amount of the components (B) and (C) is about 0.5 to
A rubber composition which is 5 parts by weight and the ratio of the contents of the component (B) and the component (C) is 10/90 to 90/10 (weight ratio).