| 摘要 |
Acrylonitrile is polymerized alone or together with a copolymerizable monomer in an aqueous medium having a pH value below 7 with the aid of a free-radical forming substance or redox system in the presence of an aqueous dispersion of a polymer and a complex former for heavy metals and, if necessary, in the presence of colourless or substantially colourless water-soluble polyvalent metal salts and/or heavy metal ions, e.g. those of divalent iron and copper. Comonomers specified for use with the acrylonitrile are methyl acrylate, methacrylic esters, styrene, styrene sulphonic acid, acrylic acid, vinyl and vinylidene chlorides and vinyl acetate. Catalysts specified are dialkyl and diacyl peroxides, hydrogen peroxide, alkyl and aryl hydroperoxides, azodiisobutyronitrile and redox systems based on persulphates and sulphur compounds of low oxidation stages. As a complex former for heavy metals there is specified ethylene diamine tetraacetic acid. As the polymer dispersion there is preferably used a dispersion of a copolymer of acrylonitrile with a comonomer of the type specified above, particularly styrene sulphonic acid. Water-soluble polyvalent metal salts specified are the chlorides, sulphates and nitrates of calcium, magnesium, alum and zinc and potash alum. The various components of the polymerization system may be added gradually during the course of the reaction. The Specification describes also the preparation of a copolymer dispersion by polymerizing acrylonitrile with the sodium salts of o- and p-styrene sulphonic acids in an aqueous medium having a pH of 2,5 in the presence of potassium persulphate and sodium pyrosulphite.
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