| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for separating and purifying a trimer or tetramer of a cyclic phosphonitrilic acid ester from a phosphonitrilic acid ester. SOLUTION: A phosphonitrilic acid ester produced by reacting phosphonitrile dichloride with a phenol and/or an alcohol is purified by recrystallization using a nitrile compound as the recrystallization solvent. The trimer or tetramer of cyclic phosphonitrilic acid ester is separated and purified by precipitating the trimer, or telramer by recrystallization. COPYRIGHT: (C)2007,JPO&INPIT
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