| 摘要 |
PROBLEM TO BE SOLVED: To provide a means for suppressing contamination of gel-like matter into a powdery PVP, obtained by drying under heating a PVP aqueous solution obtained by polymerization of N-vinylpyrrolidone and other monomers in an aqueous medium, by a simple and inexpensive technique. SOLUTION: When the PVP aqueous solution is obtained by polymerizing N-vinylpyrrolidone and other monomers in the aqueous medium, a singlet oxygen quencher is caused to exist in the reaction system. Alternatively, ammonia in the PVP aqueous solution is removed by distilling the PVP aqueous solution, obtained by the polymerization, after adding thereto a nonvolatile base. Alternatively, when the obtained PVP aqueous solution is stored, the singlet oxygen quencher is caused to exist in the aqueous solution. COPYRIGHT: (C)2007,JPO&INPIT
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