JPH0136483B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for obtaining a polymer by radical polymerization reaction of α-chloroacrylonitrile. Specifically, the present invention relates to a method for producing colorless poly-α-chloroacrylonitrile or a copolymer of α-chloroacrylonitrile and other olefin copolymerizable monomers by radical polymerization reaction. Limer containing α-chloroacrylonitrile is
Because it contains nitrile and Cl groups on its main chain, it has many uses as a flame-retardant resin, as a raw material for polarizing films, and as a pyroelectric polymer. However, conventional polymerization methods only yield colored polymers. In this regard, it is known that a particular polymerization method, namely polymerization in the presence of sodium phosphate, results in significantly less colored polymers (UK Patent 741236). However, in order to obtain a white polymer by this method, it is necessary to polymerize at a low temperature, and therefore the reaction rate is slow, making it extremely unsatisfactory as an industrial production method. As a result of various studies, the present inventors have found that by using a specific polymerization method, white poly-α-chloroacrylonitrile or α-chloroacrylonitrile and other monomers can be produced in industrially satisfactory yield. The present invention was completed based on the discovery that a copolymer can be obtained. That is, the present invention relates to a method for producing a polymer containing α-chloroacrylonitrile as a constituent monomer by a radical polymerization reaction, in which an inorganic acid, an organic sulfone is used in the presence of a carboxylic acid using a water-soluble radical polymerization initiator, and a water-soluble radical polymerization initiator is used. This is a method for polymerizing α-chloroacrylonitrile, which is characterized in that it is carried out in an aqueous medium at 70°C or lower in the absence of other acids such as. An object of the present invention is to provide a method for efficiently producing color-free α-chloroacrylonitrile or a copolymer of α-chloroacrylonitrile and other olefins. In the method of the present invention, the polymerization reaction is carried out in an aqueous medium, and the mixing ratio of monomers and water is preferably 0.5 to 20 times the weight of water relative to the total amount of monomers, particularly preferably 2 It is preferable to use ~10 times the weight of water. If it is less than 0.5 times the weight, the polymerization reaction will not proceed uniformly and a uniform polymer will not be obtained, and if it is more than 20 times the polymerization rate will be slow, the yield will be low, and the polymerization time will be too long, making it impractical. . In order to improve the dispersion of monomers and polymers during polymerization, it is more preferable to use a known dispersant. For example, gelatin, starch, methyl cellulose,
Carboxymethylcellulose, polyvinyl alcohol, and polyacrylic acid can be added in an amount of 0.05 to 5% by weight based on water. In the present invention, it is essential to have an organic acid present in the polymerization system, and a white polymer cannot be obtained without the presence of the organic acid. As the organic acid in the present invention,

A carboxylic acid having a hydrocarbyl group represented by the formula is used, and specific examples include formic acid, acetic acid, propionic acid, oxalic acid, benzoic acid, and polyacrylic acid. The amount of organic acid used is usually 0.001 to 1% by weight based on the total amount of water, and if it is too small, it will not be effective, and if it is too large, the effect will not change much. By adding an organic acid, the pH in the polymerization system usually becomes 1 to 5. As the radical polymerization initiator in the present invention,
Various known water-soluble radical polymerization initiators can be used, but preferred examples include persulfate salts alone such as potassium persulfate, sodium persulfate, and ammonium persulfate, or electron-donating salts of these salts and hydrogen sulfite. Examples include so-called Redox-based initiators. The polymerization reaction of the present invention is carried out at 70°C or lower. If the temperature exceeds 70°C, the polymer will become colored and the object of the present invention will not be met. Furthermore, if a conventional radical polymerization initiator is simply used, the polymerization rate will be slow at low temperatures, making it impractical. Regarding the relationship between reaction temperature and water-soluble radical polymerization initiator, it is sufficient to use persulfate alone at temperatures higher than 55°C, but when the polymerization reaction is carried out at temperatures lower than 55°C, oversulfate is sufficient. It is preferable to choose a Redox system containing sulfate in order to shorten the polymerization time. The amount of the polymerization initiator used in the present invention is not particularly limited as long as it is within the usual range, and is, for example, about 0.01 to 5% by weight based on the total amount of the polymer. The present invention uses not only α-chloroacrylonitrile alone but also other copolymerizable monomers such as styrene monomers, acrylic acid or acrylic acid ester monomers, and other radically polymerizable monomers. Applicable to copolymerization reactions. The present invention has great industrial significance as it is possible to obtain a copolymer containing α-chloroacrylonitrile as a constituent monomer without coloration. The present invention will be explained in more detail below with reference to Examples. Examples 1 to 3 and Comparative Examples 1 to 4 50 ml of ion-exchanged water was placed in a 200 ml glass polymerization container.
ml and dissolved 0.1 g of polyvinyl alcohol as a dispersant while blowing nitrogen gas. α
-10 g of chloroacrylonitrile monomer and the acid compounds shown in Table 1 were added, and the temperature was raised to 60°C with stirring. After a further 30 minutes, 0.1 g of potassium persulfate was added.
Stirring was carried out under a nitrogen atmosphere for 7 hours, and after the reaction was completed, the temperature of the mixture was lowered to room temperature, and then filtered to obtain a solid substance, which was washed with water and methanol and dried under reduced pressure to obtain a white polymer. . The results are also shown in Table 1.

【table】

[Table] Example 4 In Example 1, 5.5 g of α-chloroacrylonitrile was used instead of α-chloroacrylonitrile.
and methyl-α-chloroacrylic acid ester 4.5g
Polymerization was carried out in the same manner as in Example 1 except that a monomer mixture of
g was obtained. Comparative Example 5 Under the experimental conditions of Example 1, only the temperature was 80
When the temperature was changed to .degree. C. and polymerization was carried out, an orange colored polymer was obtained in a yield of 85%. Comparative Example 6 Polymerization was carried out in exactly the same manner as in Example 1, except that 0.1 g of benzoyl oxide was used instead of potassium persulfate as a radical polymerization initiator, and a light brown polymer was obtained. was obtained with a yield of 38%. Note that the molecular weight of the polymer was 50,000.

Claims (1)

[Claims] 1. A method for producing a polymer containing α-chloroacrylonitrile as a constituent monomer by a radical polymerization reaction, in which an inorganic acid, 70°C in aqueous medium in the absence of other acids such as organic sulfonic acids
A method for polymerizing α-chloroacrylonitrile, characterized by carrying out the following steps. 2 Carboxylic acid is formic acid, acetic acid, propionic acid,
The method for polymerizing α-chloroacrylonitrile according to claim 1, which is oxalic acid, benzoic acid, polyacrylic acid, or a mixture thereof. 3. The method for polymerizing α-chloroacrylonitrile according to claim 1 or 2, wherein the water-soluble radical polymerization initiator is a persulfate.