JPH0762029A - Method for producing sulfur-modified chloroprene polymer - Google Patents

Abstract

(57) [Summary] [Structure] 0.1 to 100% by weight of a polymer obtained by aqueous emulsion polymerization of chloroprene or a mixture of chloroprene and a monomer copolymerizable therewith in the presence of sulfur.
A method for producing a sulfur-modified chloroprene polymer, which comprises adding 3.0% by weight of at least one tetraalkyl thiuram disulfide having an alkyl group having 8 or more carbon atoms to deflocculate. [Effect] Obtained by peptization by adding tetraalkyl thiuram disulfide, which has been used conventionally, without producing a nitrosamine compound having strong mutagenicity that may adversely affect the health of workers. A sulfur-modified chloroprene polymer having excellent storage stability, flex resistance and heat aging resistance comparable to that of a conventional sulfur-modified chloroprene polymer is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses tetraalkylthiuram disulfide having an alkyl group having 8 or more carbon atoms which does not form a nitrosamine compound showing strong mutagenicity, as a peptizing agent to obtain conventional sulfur. The present invention relates to a method for producing a sulfur-modified chloroprene polymer having excellent storage stability, bending resistance, and heat aging resistance comparable to a modified chloroprene polymer.

[0002]

2. Description of the Related Art It is known that a sulfur-modified chloroprene polymer can be obtained by polymerizing chloroprene in the presence of sulfur in an aqueous emulsion containing an emulsifier and an initiator.

Generally, this polymerization reaction is carried out at a polymerization conversion rate of 60% or more, and the obtained polymer becomes a benzene-insoluble high-viscosity polymer having poor processability. Therefore, this polymer is used as a sulfur-containing compound such as tetraethyl disulfide. It has been practiced to peptize with a compound and cleave the polysulfide bond in the polymer until the polymer has a viscosity that makes it easy to process.

The deflocculated polymer latex is frozen and coagulated by a conventional method to separate the polymer, and then dried to produce a sulfur-modified chloroprene polymer.

The conventionally used alkyl group is methyl,
Risk of formation of nitrosamine compounds with strong mutagenicity in calendars, salt baths, high-frequency equipment, extruders, extruders, mold vulcanization workshops, inspection rooms, and product storage rooms in tetraalkyl thiuram disulfides such as ethyl. Therefore, the effect on the health of workers is a problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a tetraalkyl group having an alkyl group having 8 or more carbon atoms which does not form a nitrosamine compound having a strong mutagenicity which may adversely affect the health of workers. An object of the present invention is to provide a sulfur-modified chloroprene polymer having excellent storage stability, flex resistance and heat aging resistance, which is not inferior to the conventional sulfur-modified chloroprene polymer, by using alkyl thiuram disulfide as a peptizer.

[0007]

The inventors of the present invention have completed the present invention as a result of earnest research to solve these problems all at once. That is, the present invention is 0.1 to 3.0 wt% relative to 100 wt% of a polymer obtained by aqueous emulsion polymerization of chloroprene or a mixture of chloroprene and a monomer copolymerizable therewith in the presence of sulfur. % Of an alkyl group having 8 or more carbon atoms, at least one tetraalkyl thiuram disulfide is added for deflocculation, which is a method for producing a sulfur-modified chloroprene polymer.

The present invention will be described in more detail below.

In the aqueous emulsion polymerization of the present invention, chloroprene alone or a mixture of chloroprene and a monomer copolymerizable therewith is used as a raw material.

As the copolymerizable monomer, for example, 2,3
-Dichlorobutadiene-1,3, butadiene-1,3,
2-Cyanobutadiene-1,3,1-chlorobutadiene-1,3, styrene, acrylonitrile, methyl methacrylate, methacrylic acid, acrylic acid and the like can be mentioned.

These monomers are usually used in the range of 0 to 20% by weight based on the total monomer composition.

The polymerization is carried out by a known method. A monomer in which a predetermined amount of sulfur (usually 0.1 to 2.0% by weight based on chloroprene) is dissolved and an aqueous emulsion containing an emulsifier are mixed and stirred. Then, the catalyst liquid is added at a temperature of 0 to 60 ° C. and a pH of the polymerization system of 7 to 13.

Examples of emulsifiers include higher fatty acids, resin acids, disproportionated abietic acid, long-chain alkyl sulfonic acids,
Any one of water-soluble salts such as condensates of naphthalene sulfonic acid and formaldehyde, especially so-called anionic surfactants such as alkali metal salts and nonionic surfactants such as polyoxyethylene nonylphenyl ether
More than one seed is used.

As the catalyst for initiating the polymerization, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide and the like are used.

The polymerization is carried out up to a polymerization conversion rate of about 60 to 90%, and then a small amount of a polymerization inhibitor is added to terminate the polymerization.

Examples of the polymerization inhibitor include thiodiphenylamine, 4-t-butylcatechol, 2,2'-methylenebis-4-methyl-6-t-butylphenol,
A water-soluble salt of dialkyldithiocarbamic acid or the like is added in an amount of 0.01 to 2.0% by weight based on the polymer.

The polymer thus obtained is then deflocculated at a temperature of 5 to 60 ° C. until an aqueous emulsion of tetraalkyldisulfide is added and the polymer reaches the desired viscosity range.

As the tetraalkyl thiuram disulfide used in the peptization reaction, one having an alkyl group having 8 or more carbon atoms is used. For example, tetraoctyl thiuram disulfide <tetranonyl thiuram disulfide <tetradecanyl thiuram disulfide <tetrakis (2-ethylhexyl) thiuram disulfide.

These are 0.1% based on 100% by weight of the polymer.
It is used in the range of up to 3.0% by weight, but if it is less than this range, the Mooney viscosity of the obtained polymer becomes too high,
If too much, it will be too low.

Then, the deflocculated polymer latex is
The unreacted monomer is removed and collected by a steam stripping method under reduced pressure, and then frozen and coagulated according to a conventional method to separate and dry the polymer to obtain the target sulfur-modified chloroprene polymer.

[0021]

EXAMPLES Next, the present invention will be specifically described by way of examples, but the present invention is not limited to these.

Unless stated otherwise, parts and% are by weight.

Example 1 A monomer mixture having the following composition and an emulsified aqueous solution were mixed and stirred, and the temperature was kept at 40 ° C.

Monomer mixture part Chloroprene 100 2,6-t-butyl-p-cresol 0.01 Sulfur 0.6 Emulsified aqueous solution part Disproportionated sodium salt of abietic acid 5.0 Condensation of naphthalene sulfonic acid and formaldehyde Sodium salt of product 0.7 Sodium hydroxide 0.2 Sodium orthophosphate 0.3 Water 130 A polymerization catalyst having the following composition was added at a constant rate by a pump to carry out polymerization.

Polymerization catalyst part potassium persulfate 1.0 anthraquinone-β-sodium sulfonate 0.01 water 30 Polymerization was carried out by adding a polymerization catalyst until the specific gravity of the latex reached 1.075 at 40 ° C. Polymerization conversion rate about 84
%) To terminate the polymerization by adding a polymerization terminator having the following composition.

Polymerization terminator part Dimethylammonium dimethyldithiocarbamate 0.3 Water 4.0 Then, a deflocculant having the following composition was added and deflocculated at 40 ° C. for 5 hours.

Peptizer Part tetrakis (2-ethylhexyl) thiuram disulfide 1.6 thiodiphenylamine 0.01 2,6-di-t-butyl-p-cresol 0.05 toluene 6.0 sodium lauryl sulfate 0.2 water 6.0 The deflocculated latex was recovered by removing unreacted chloroprene by steam stripping under reduced pressure, adjusted to pH 6.0 with acetic acid, frozen and dried by a conventional method, and then the polymer was dried to obtain sulfur. A modified chloroprene polymer was obtained.

The results are summarized in Table 1.

Next, this sulfur-modified chloroprene polymer was stored at 100 ° C. for 3 days and 7 days, and then JISK630 was used.
The Mooney viscosity was measured according to 0 and its storage stability was investigated. The results are shown in Table 2.

Further, in order to measure the physical properties of the sulfur-modified chloroprene polymer vulcanizate, ASTM D3190
According to -73, 100 parts of polymer, 30 parts of SRF carbon,
0.5 parts of stearic acid, 4.0 parts of magnesium, 5.0 parts of zinc white, and 2.0 parts of Doshiba D (phenyl-β-naphthylamine) were blended on a roll and heated at a temperature of 150 ° C. for 20 minutes. Sulfur was prepared and its tensile properties were measured according to JIS K6301.

Further, this vulcanized product was further heat-treated in a gear oven at a temperature of 120 ° C. for 96 hours and then its tensile properties were measured to perform a heat aging test.

The results are shown in Table 3.

Example 2 A sulfur-modified chloroprene polymer was obtained by the same procedure as in Example 1, except that tetraoctyl disulfide was used instead of tetrakis (2-ethylhexyl) thiuram disulfide in the peptization solution. .

Then, the physical properties of this product and the vulcanized product thereof were measured in the same manner as in Example 1.

The results are shown in Tables 1-3.

Example 3 A sulfur-modified chloroprene polymer was obtained in the same manner as in Example 1, except that tetranonyl thiuram disulfide was used instead of tetrakis (2-ethylhexyl) thiuram disulfide in the peptizer. .

Then, the physical properties of this product and the vulcanized product of this product were measured in the same manner as in Example 1. The results are shown in Table 1
3 shows.

Example 4 A sulfur-modified chloroprene polymer was prepared in the same manner as in Example 1 except that tetradecanyl thiuram disulfide was used instead of tetrakis (2-ethylhexyl) thiuram disulfide in the peptizer. Got

Then, the physical properties of this product and the vulcanized product thereof were measured in the same manner as in Example 1 and the results are shown in Table 1.
~ 3.

Comparative Example A A sulfur-modified chloroprene polymer was obtained in the same manner as in Example 1, except that the peptizing solution having the following composition was used.

Peptization Part Tetraethylthiuram disulfide 1.6 Thiodiphenylamine 0.01 2,6-Di-t-butyl-p-cresol 0.05 Toluene 6.0 Sodium lauryl sulfate 0.2 Water 6.0 Then The physical properties of the product and the vulcanized product thereof were measured in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

From Table 2, it is clear that the storage stability of the sulfur-modified chloroprene polymer obtained in the present invention is as excellent as that of the tetraethylthiuram disulfide of Comparative Example A alone.

According to Table 3, the vulcanized product of the polymer obtained by the present invention has good tensile properties as in the case of tetraethyl thiuram disulfide alone, and has an excellent rate of change in heat aging properties. . Therefore, a sulfur-modified chloroprene polymer obtained by using a tetraalkylthiuram disulfide having an alkyl group having 8 or more carbon atoms which does not form a nitrosamine compound showing strong mutagenicity according to the present invention is a conventional sulfur-modified chloroprene polymer. It has excellent storage stability, tensile properties, and heat aging resistance comparable to polymers.

[0047]

INDUSTRIAL APPLICABILITY The sulfur-modified chloroprene polymer produced by the method of the present invention can be used conventionally without producing a nitrosamine compound having a strong mutagenicity which may adversely affect the health of workers. It has excellent storage stability, flex resistance and heat aging resistance comparable to conventional sulfur-modified chloroprene polymers obtained by adding and peptizing tetraalkyl thiuram disulfide.

Claims (1)

[Claims] 1. 0.1% based on 100% by weight of a polymer obtained by aqueous emulsion polymerization of chloroprene or a mixture of chloroprene and a monomer copolymerizable therewith in the presence of sulfur.
A method for producing a sulfur-modified chloroprene polymer, which comprises adding at least one tetraalkyl thiuram disulfide having an alkyl group having 8 to 3.0% by weight of a carbon number of ˜3.0% by weight to deflocculate.