To obtain an aqueous solution of a polymer in a relatively short polymerization time and at a high conversion rate which can be used as it is without solvent substitution or the like by polymerizing at least two monomers selected from 4 water soluble amide monomers in water using a water soluble polymerization initiator.
Monomers to be use are represented by formula I to IV (wherein R1 to R8 are each H or a 1-3C hydrocarbon; and (m) and (n) are each 1 to 3). The water may be distilled water or deionized water and it is preferable to remove oxygen dissolved in water before polymerization. The polymerization initiator is preferably a water soluble azo-based polymerization initiator and pH of the polymerization solution is preferably adjusted at 6.5 to 10. The polymerization is conducted by firstly adding the polymerization initiator to the polymerization solution dissolving the whole monomer represented by formula I and a part of a monomer to be copolymerized, and then adding the residual monomer gradually to the polymerization reaction system. The polymerization temperature is preferably in the range from a temperature lower than a lower critical consolute temperature by 20°C corresponding to a concentration of the produced polymer in water to the lower critical consolute temperature.
TOYAMA MASAYUKI
NISHIDA KOJI
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