JPS6140241B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing chloroprene rubber in which mold contamination (hereinafter referred to as mold contamination) is extremely less likely to occur when chloroprene rubber is molded and vulcanized using a mold. Chloroprene rubber has the high elasticity required for practical use.
In order to satisfy properties such as high strength and stability, additives such as vulcanization aids, anti-aging agents, fillers, and softeners are blended, and the product is then molded and vulcanized for practical use. When performing mold vulcanization using a mold in this process,
With conventional chloroprene rubber, the additives blended into the rubber migrate to the surface and stain the mold, and the stain remains on the mold even after the vulcanizate is removed.
If it is continued to be used as is, the vulcanized rubber will lose its luster and cause cracks due to contaminants that have accumulated in the mold. Therefore, in order to avoid this, it is necessary to frequently clean the mold, which reduces work efficiency. A method for solving this mold contamination problem is proposed in Japanese Patent Publication No. 49-37118. According to the publication, at least 60% of chloroprene is added in the presence of specified amounts of the following three components: rosin acid soap/alkali salt of higher saturated or unsaturated fatty acids/sodium salt of the condensation product of formaldehyde and naphthalene sulfonic acid. It is disclosed that chloroprene rubber with improved mold contamination can be obtained by polymerizing at a high polymerization rate. The present invention differs from this in that chloroprene or a mixture of monomers copolymerizable with it up to 50% by weight, 0.5 to 5% by weight of its resin acid derivative and 0.1 to 10% by weight of the following general formula (However, in the formula, R is a hydrogen atom, a lower alkyl group, X is a hydrogen atom, a lower alkyl group, a halogen atom, or a hydroxyl group, Y is a hydrogen atom, potassium, sodium, or quaternary ammonium, and n is 10 to 20,000
is an integer. This is a method for producing chloroprene rubber with extremely low tendency to mold mold contamination by polymerizing it in an alkaline aqueous emulsion in the presence of polystyrene sulfonic acid or its derivatives represented by (). The method of using styrene sulfonic acid or its derivatives together with an emulsifier such as a resin acid derivative in the emulsion polymerization of chloroprene has already been reported in Japanese Patent Publication No. 53
-Disclosed in Publication No. 4031. however,
The styrene sulfonic acid and its derivatives are not polymers but monomers, and cannot be expected to have the effect of improving mold contamination as in the present invention. In the present invention, various resin acid derivatives that are commonly used in the polymerization of chloroprene, such as unmodified rosin, disproportionated rosin, hydrogenated rosin, and their alkali metal salts, can be used, but the amount As mentioned above, the amount is 0.5 to 5% by weight, preferably 1.0 to 3.0% by weight, based on chloroprene or the mixture of monomers copolymerizable with it. If this amount is less than 0.5% by weight, the stability of the emulsion will be poor, and if it exceeds 5% by weight, mold contamination is likely to occur. Examples of polystyrene sulfonic acid or its derivatives include poly-p-styrene sulfonic acid or its sodium salt, potassium salt, quaternary ammonium salt, poly-α-methyl-p-sodium styrene sulfonate, poly-o-chloro- p-
Average degree of polymerization as described above for styrene sulfonic acid, etc.
The number ranges from 10 to 20,000, preferably from 50 to 1,000, and the amount is from 0.1 to 10% by weight, preferably from 1 to 5% by weight, based on chloroprene or the mixture of monomers copolymerizable therewith. If this amount is less than 0.1% by weight, the effect on mold contamination will be small;
Moreover, if the amount exceeds 10% by weight, the viscosity of the polymerized chloroprene latex becomes too thick, which is not preferable. In some cases, higher saturated or unsaturated fatty acids such as stearic acid and oleic acid may be used together with these drugs. Polymerization is carried out by a conventional chloroprene emulsion polymerization method, except that a specified amount of the above-mentioned drug is used. Chloroprene is used alone, and if necessary, monomers copolymerizable with it, such as 1-chlorobutadiene, 2, 3-dichlorobutadiene, butadiene,
Those containing up to 50% by weight of 2-cyanobutadiene, styrene, acrylonitrile, alkyl methacrylate, alkyl acrylate, etc. can be used. As the molecular weight regulator, for example, alkyl mercaptan, alkyl xanthogen disulfide, etc., and as the radical initiator, any commonly used ones such as potassium persulfate and alkyl hydroperoxide can be used. The polymerization is carried out at a temperature of 0 to 100°C, preferably 5 to 60°C, in the presence of said defined amount of drug.
This is carried out until a conversion of 60% is reached, and then a conventional polymerization inhibitor such as t-butylcatechol or phenothiazine is added to stop the polymerization. The remaining monomers are removed by, for example, high temperature and reduced pressure treatment, and the resulting polychloroprene latex is then frozen, coagulated, washed with water, and dried to obtain solid chloroprene rubber. The present invention will be explained in further detail by way of Examples below. In addition, unless otherwise specified, parts represent parts by weight. Example 1 Using an autoclave with a 10 stirrer, chloroprene monomer (including 2,3-dichloro-1,3-butadiene) and other agents were charged according to the recipe shown in Table 1, and persulfuric acid was added as a catalyst. Continuously add 0.5% aqueous solution of potassium for 40 min under nitrogen stream
Polymerization was carried out at ℃. At a polymerization conversion rate of 70%, t-butylcatechol and phenothiazine were added.
An emulsion containing 0.01 part was added to stop the polymerization, and then unreacted monomers were removed by a steam flash method. Next, a 10% acetic acid aqueous solution was added to this latex to adjust the pH to 5.8, and the polymer was separated on a freezing roll, washed with water, and dried to obtain solid chloroprene rubber.

[Table] Polymer No. is a control chloroprene rubber that does not use sodium polystyrene sulfonate. Mooney viscosity of produced chloroprene rubber ML ₁₊₄
(100℃) were as follows.

[Table] Next, using chloroprene rubber of each polymer number, the following chemicals were mixed at 50°C on a roll with a diameter of 10 inches. Compounded chemical rubber 100 parts Stearic acid 0.5 MgO 4 Carbon black (SRF) 40 Process oil 10 ZnO 5 2-mercaptoimidazoline 1 Each of the obtained compounds was vulcanized continuously for a total of 100 times using one mold. . Vulcanization conditions are
It was heated at 220°C for 10 minutes. The contamination status of the mold after 100 vulcanizations was as follows.

[Table] In the case of control polymer No., a large amount of compounded chemicals adhered to the mold, contaminating the mold significantly, but when sodium polystyrene sulfonate was used, the compounded chemicals adhered to the mold to a large extent. The amount of adhesion was reduced, and almost no adhesion was observed, especially in the case of polymer No., and it was possible to continue using the mold as it was. Example 2 Using the same equipment as in Example 1, chloroprene monomer and other chemicals were charged according to the formulation shown in Table 2, and polymerization, isolation, and drying were carried out in the same manner as in Example 1 to produce solid chloroprene rubber. I got it.

[Table] Polymer No. is a control chloroprene rubber that does not use sodium poly α-methyl-p-styrene sulfonate. Polymer No. Mooney viscosity of produced chloroprene rubber ML ₁₊₄
(100℃) were as follows.

[Table] Next, using chloroprene rubber of each polymer number,
The chemicals were blended in the same manner as in Example 1, and the blend was subjected to continuous 100 vulcanizations. The contamination status of the mold after 100 vulcanizations was as follows.

[Table] As described above, it is clear that the present invention prevents mold contamination more significantly than the conventional method.

Claims (1)

[Claims] 1. Chloroprene or a mixture of monomers copolymerizable with it up to 50% by weight, 0.5 to 5% by weight of its resin acid derivative and 0.1 to 10% by weight of the following general formula: (However, in the formula, R is a hydrogen atom, a lower alkyl group, X is a hydrogen atom, a lower alkyl group, a halogen atom, or a hydroxyl group, Y is a hydrogen atom, potassium, sodium, or quaternary ammonium, and n is 10 to 20,000
is an integer. ) A method for producing chloroprene rubber, which comprises polymerizing it in an alkaline aqueous emulsion in the presence of polystyrene sulfonic acid or a derivative thereof.