JPS6228802B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses a specific emulsifier and a sparingly soluble phosphate in combination with a monomer mixture containing aromatic vinyl monomers and vinyl cyanide monomers as main components, and superimposes polymerization as a polymerization initiator. This invention relates to a method for producing a copolymer whose polymerization rate is stabilized by using a sulfate. Conventionally, a monomer mixture containing aromatic vinyl monomers and vinyl cyanide monomers as main components was used as a polymerization initiator to form an aqueous system using a compound containing persulfate and an alkali metal sulfonate base as an emulsifier. When emulsion polymerization is carried out, runaway reactions tend to occur during the induction period before the start of polymerization, and it is difficult to obtain a uniform polymerization rate, so this method is not suitable for industrial production. Various methods have been proposed to improve such non-uniform polymerization rates.
For example, there are methods such as controlling the polymerization temperature, or changing the type and/or amount of the polymerization initiator added. However, the method of controlling the polymerization temperature is complicated and requires a lot of effort, and the method of changing the type and/or amount of the polymerization initiator added is not sufficient to obtain a uniform polymerization rate. In order to solve these drawbacks, the present inventor conducted extensive research and found that the inventors used a small amount of poorly soluble phosphate in combination with an emulsifier containing an alkali metal sulfonate base, and also used a persulfate as a polymerization initiator. The present invention was achieved by discovering a method for producing a copolymer with a uniform polymerization rate from a monomer mixture containing aromatic vinyl monomers and vinyl cyanide monomers as main components. The present invention uses a monomer mixture containing 50 to 80% by weight of an aromatic vinyl monomer, 15 to 40% by weight of a vinyl cyanide monomer, and 0 to 30% by weight of a vinyl monomer copolymerizable with these monomers. Part by weight as polymerization initiator
0.001-0.3 parts by weight of persulfate, 0.5-0.5 parts by weight of compounds containing alkali metal sulfonate bases as emulsifiers
It is characterized by carrying out aqueous emulsion polymerization at a temperature of 40 to 120°C in the presence of 5 parts by weight and 0.001 to 0.3 parts by weight of a poorly soluble phosphate. In the present invention, additives such as a molecular weight regulator, an emulsification aid, or a lubricant may be added to the polymerization system. The present invention is particularly characterized by the addition of a sparingly soluble phosphate, and examples of the sparingly soluble phosphate include calcium phosphate, magnesium phosphate, barium phosphate, and the like. The amount of the poorly soluble phosphate added is 0.001 to 0.3 parts by weight, particularly preferably 0.01 to 0.05 parts by weight, per 100 parts by weight of the monomer mixture. By adding a small amount of poorly soluble phosphate in this way, a uniform polymerization rate can be obtained, making reaction control much easier, and the resulting copolymer has excellent quality, especially improved color tone. It has a big effect. Examples of the aromatic vinyl monomer used in the present invention include styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, and halogen-substituted styrene. As vinyl cyanide monomers, acrylonitrile, methacrylonitrile, α
-chloroacrylonitrile, etc. Specific examples of vinyl monomers that can be copolymerized with aromatic vinyl monomers and vinyl cyanide monomers include acrylic esters such as methyl acrylate and ethyl acrylate, and methacrylic acids such as methyl methacrylate and ethyl methacrylate. Examples include one of various conventionally known vinyl monomers such as ester, acenaphthylene, maleimide, N-alkyl substituted maleimide, N-aromatic substituted maleimide, and mixtures thereof. Typical examples of persulfate polymerization initiators used in the present invention are ammonium persulfate, sodium persulfate, and potassium persulfate. Examples of emulsifiers that can be used include alkali metal salts of alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate and potassium dodecylbenzenesulfonate, and sodium alkylnaphthalenesulfonates. In the present invention, the polymerization temperature is operated at 40-120℃, but if the polymerization temperature is too low, the polymerization rate will be slow and the productivity of the copolymer will be reduced, and if it is too high, the polymerization system will be under high pressure, and special equipment will be required. 55 for requiring
~80°C is particularly preferred. The weight of water used as a medium for emulsion polymerization is based on 100 parts by weight of the monomer mixture.
The amount is preferably 100 to 500 parts by weight, but if the amount of water is too small, it will be difficult to remove the polymerization heat, and if it is too large, the production efficiency of the copolymer will decrease, so the amount is preferably 150 to 250 parts by weight. EXAMPLES The present invention will be specifically explained below using Examples, but these are not intended to limit the scope of the present invention. Example 1 The substances shown in Table 1 were charged into a glass autoclave equipped with a stirrer while blowing nitrogen gas.

[Table] After raising the temperature of the autoclave to 65°C, 10 ml of a 1% potassium persulfate aqueous solution was added to initiate polymerization, and 5 ml of a potassium persulfate aqueous solution of the same concentration was added 6 hours after the start of polymerization. In addition, several ml of the emulsion was collected from the autoclave in order to observe changes in the polymerization rate over time. Polymerization was stopped 12 hours after the start of polymerization. A small amount of hydroquinone was added as a polymerization inhibitor to each sampled emulsion, and the solid content was measured by evaporation to dryness.
The polymerization rate was calculated from this, and the results are shown in Table 2. For comparison, the same procedure as in Example 1 was carried out except that calcium phosphate was not added.

[Table] Example 2 The substances shown in Table 3 were charged into the autoclave used in Example 1 while blowing nitrogen.

[Table] After raising the temperature of the autoclave to 70℃,
18 ml of a 1% aqueous solution of potassium persulfate was added to initiate polymerization, and 6 hours later, 10 ml of an aqueous solution of potassium persulfate of the same concentration was added. The other operations were the same as in Example 1. The results are shown in Table 5. Example 3 The same procedure as in Example 1 was carried out except that the same amount of barium phosphate was used in place of the calcium phosphate used in Example 1. The results are shown in Table 5. Examples 4 and 5 Example 2 except that the monomers shown in Table 4 were used.
The same operation was performed. The results are shown in Table 5.

【table】

[Table] Example 6 Example 2 except that the monomers shown in Table 6 were used.
The same operation was performed. The results are shown in Table 7.

【table】

【table】

Claims (1)

[Scope of Claims] 1. Monomers containing 50 to 80% by weight of aromatic vinyl monomers, 15 to 40% by weight of vinyl cyanide monomers, and 0 to 30% by weight of vinyl monomers copolymerizable with these monomers. 100 parts by weight of the mixture, 0.001 to 0.3 parts by weight of persulfate, and 0.5 parts by weight of a compound containing an alkali metal sulfonic acid base.
A process for producing a thermoplastic resin, characterized by carrying out aqueous emulsion polymerization at a temperature of 40 to 120°C in the presence of ~5 parts by weight and 0.001 to 0.3 parts by weight of a poorly soluble phosphate. 2 The aromatic vinyl monomer is styrene and/or α
- methylstyrene, and the vinyl cyanide monomer is acrylonitrile and/or methacrylonitrile. 3. The method according to claim 1, wherein the compound containing an alkali metal sulfonate base is an alkali metal salt of an alkyl-substituted aromatic sulfonate. 4. The manufacturing method according to claim 1, wherein the poorly soluble phosphate is calcium phosphate. 5. The manufacturing method according to claim 1, wherein the persulfate is potassium persulfate.