JP2002265688A - Environmentally friendly chloroprene rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an environmentally friendly CR composition exhibiting rubber characteristics equivalent to those of conventional SBR compositions by using a vulcanization promoter generating no nitrosamine. SOLUTION: This environmentally friendly SBR composition is characterized by being obtained by compounding a CR composition with, as a vulcanizing system, 0.1-5 pt(s).wt. of at least one vulcanizing agent selected from the group consisting of zinc oxide and magnesium oxide and 0.1-5 pt(s).wt. of a tetrakis(alkyl)thiuram disulfide each based on 100 pts.wt. of the rubber component of the above CR composition. Because of compounding a specified amount of the tetrakis(alkyl)thiuram disulfide as the vulcanization promoter of the vulcanization system, there are such advantages that the CR after vulcanized generates no toxic nitrosamine and causes no deterioration of its rubber characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an environmental protection CR (chloroprene rubber: the same applies hereinafter) composition, and more particularly to an environmental protection CR composition which does not generate nitrosamine and has good rubber properties.

[0002]

2. Description of the Related Art In recent years, interest in protecting the global environment has been increasing, and the use of environmental pollutants has become stricter worldwide. Nitrosamines are mentioned as one of such environmental pollutants. This nitrosamine is known to be generated by certain vulcanization accelerators, antioxidants, and scorch inhibitors added to the rubber composition. These additives are necessary additives in order to improve the rubber properties. Selection of additives that do not generate nitrosamine, and a rubber composition that can obtain the same rubber properties as the conventional ones by using the additives. Is needed. In particular, rubber used for industrial parts such as automobiles (for example, O-rings, hoses, diaphragms for fuel pumps, and other diaphragms) has strict performance requirements, demands the best rubber properties, and is environmentally friendly, such as nitrosamines. There is an increasing need to avoid pollutants.

[0003] The present invention has been made in view of the above-mentioned problems. Particularly, attention is paid to a vulcanization accelerator, and a vulcanization accelerator which does not generate nitrosamine is used to exhibit rubber properties equivalent to those of the conventional rubber. It is an object of the present invention to provide an environmentally friendly CR composition.

[0004]

Means for Solving the Problems In order to achieve the above object, the environmental protection CR composition according to the present invention is added to the rubber component of the CR composition and to the rubber component of the chloroprene rubber composition as a vulcanization system in an amount of 100 parts by weight. On the other hand, 0.1 to 5 parts by weight of one or more vulcanizing agents selected from the group consisting of zinc oxide and magnesium oxide, and 0.1 to 5 parts by weight of tetrakis (alkyl) thiuram disulfide of the following formula (1) It is characterized by being added.

[0005]

Embedded image (1) (where R is the same or different alkyl group having 5 or more carbon atoms)

According to the present invention, since a predetermined amount of tetrakis (alkyl) thiuram disulfide is added as a vulcanization accelerator, no harmful nitrosamine is produced in the vulcanized chloroprene rubber, and the rubber properties are deteriorated. There is an advantage that it does not.

More specifically, the CR composition used as the base material of the present invention comprises a CR, a process oil, an antioxidant, a plasticizer, a filler such as carbon black, zinc oxide, and the like. Can be added. In the present invention, it is possible not to add a plasticizer. Plasticizers, especially dioctyl phthalate, are substances whose addition is restricted as environmental hormones.However, in the environmental protection CR composition of the present invention, the above-mentioned plasticizers, especially dioctyl phthalate, are not added. Both
There is an advantage that good characteristics can be obtained.

[0008] The vulcanizing system according to the present invention uses at least one selected from the group consisting of zinc oxide and magnesium oxide as a vulcanizing agent, and uses the following tetrakis (alkyl) thiuram disulfide as a vulcanizing accelerator. I have. In the following chemical formula, R represents the same or different alkyl group having 5 or more carbon atoms, and is preferably a 2-ethylhexyl group. The tetrakis (alkyl) disulfide is less volatile and not react with NO _x in the atmosphere,
Does not produce harmful nitrosamines.

[0009]

Embedded image (1)

In the present invention, ethylenethiourea can be further added as a vulcanization accelerator. Ethylenethiourea also does not generate nitrosamines. Ethylenethiourea is added to reduce the amount of tetrakis (alkyl) thiuram disulfide described above. That is, by adding this ethylenethiourea as a vulcanization accelerator, it is possible to reduce the amount of tetrakis (alkyl) thiuram disulfide to be added, and it is possible to maintain rubber properties particularly well.

In the above-described vulcanizing system, zinc oxide, magnesium oxide and the like can be used as a vulcanizing agent. Such a vulcanizing agent is preferably added in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the rubber component of CR. 0.1
If the amount is less than 10 parts by weight, the CR may not be sufficiently vulcanized. On the other hand, if the amount is more than 20 parts by weight, there may be a disadvantage that the processability of the rubber deteriorates.

The vulcanization accelerator tetrakis (alkyl)
Thiuram disulfide preferably has a rubber content of 10
The amount is preferably 0.1 to 5 parts by weight with respect to 0 parts by weight.
If the amount is less than 0.1 part by weight, the CR may not be sufficiently vulcanized, while if it exceeds 5 parts by weight, the properties of the rubber may be impaired.

It is preferable to add 1 to 5 parts by weight of ethylenethiourea as a vulcanization accelerator added together with the above-mentioned tetrakis (alkyl) thiuram disulfide to 100 parts by weight of the rubber component of CR. If it is less than 1 part by weight, the effect of promoting vulcanization is small, while if it exceeds 5 parts by weight, rubber properties may be impaired.

An embodiment of the present invention will be described below.

[0015]

EXAMPLES The compositions shown in the following table were prepared, and rubber properties were measured after vulcanization. Formulation (parts by weight) Example Comparative Example CR 100 100 Antioxidant 11 1 Wax 11 1 Adeka fatty acid 1 1 Fatty acid ester 3 3 (Processing aid) Magnesium oxide 12 12 Rosin 0.8 0.8 (Processing aid) FAF Carbon 42 42 Dioctyl phthalate-2 tetramethylthiuram disulfide-0.6 Tetrakis (2-ethylhexyl) thiuram disulfide 0.3-(parts by weight)

[0016] In addition to the above formulation, zinc oxide 5
2 parts by weight of ethylene thiourea (vulcanization accelerator) were added to each part and vulcanized to produce CR, and the rubber properties were measured. The results are shown in Table 1 below.

[0017]

[Table 1]

Further, as a result of measuring the generation amount of harmful nitrosamine, the CR of the example was not detected, and the CR of the comparative example was not detected.
Is 1 to 1.16 μg / kg (vulcanized rubber), indicating that the generation amount of nitrosamine is significantly suppressed.

As is clear from Table 1 above, the environmental protection CR composition according to the present invention has almost the same rubber properties as the conventional one, and can minimize the generation of harmful nitrosamines.

[0020]

As described above, according to the present invention,
Since a predetermined amount of tetrakis (alkyl) thiuram disulfide was added as a vulcanization accelerator, the vulcanized CR
Harmful nitrosamines are not produced, and the rubber properties are not reduced.

Claims (5)

[Claims] 1. A chloroprene rubber composition comprising, as a vulcanization system, at least one vulcanizing agent selected from the group consisting of zinc oxide and magnesium oxide with respect to 100 parts by weight of a rubber component of the chloroprene rubber composition. An environmental protection chloroprene rubber composition comprising 5 parts by weight, and 0.1 to 5 parts by weight of tetrakis (alkyl) thiuram disulfide of the following formula (1). Embedded image (1) (where R is the same or different alkyl group having 5 or more carbon atoms) 2. The environmental protection chloroprene rubber composition according to claim 1, wherein the tetrakis (alkyl) thiuram disulfide is tetrakis (2-ethylhexyl) thiuram disulfide. 3. The environment-protecting chloroprene rubber composition according to claim 1, wherein ethylenethiourea is added to the vulcanization system. 4. The addition amount of the ethylene thiourea is based on 100 parts by weight of a rubber component of the chloroprene rubber composition.
The environmental protection chloroprene rubber composition according to claim 3, wherein the amount is 0.1 to 5 parts by weight. 5. The environmentally-friendly chloroprene rubber composition according to claim 1, wherein the plasticizer does not contain dioctyl phthalate.