| 摘要 |
PROBLEM TO BE SOLVED: To provide a protective colloid agent enabling stable emulsion polymerization of an ethylenic unsaturated monomer and producing an emulsion polymerization product having excellent fluidity, particle size distribution and mechanical stability. SOLUTION: A protective colloid agent containing a vinylpyrrolidone-modified polyvinyl alcohol obtained by the graft polymerization of vinylpyrrolidone to a polyvinyl alcohol is used in the emulsion polymerization of one or more kinds of ethylenic unsaturated monomers selected from acrylate monomers, styrenic monomers and diene monomers. The vinylpyrrolidone-modified polyvinyl alcohol preferably contains 5-95 wt.% vinylpyrrolidone unit and has a saponification degree of≥10 mol% and a viscosity of≥1.5 mPas as a 4% aqueous solution. The modified polyvinyl alcohol can be produced by adding vinylpyrrolidone to a polyvinyl alcohol solution and carrying out graft-polymerization by using hydrogen peroxide or an organic peroxide as a polymerization initiator. COPYRIGHT: (C)2007,JPO&INPIT
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