| 摘要 |
PROBLEM TO BE SOLVED: To provide a process that can efficiently produce a phosphonitric acid ester having high purity, a low acid value, without occurrence of side reactions, for example, hydrolysis, crosslinking and the like. SOLUTION: A cyclic or linear phosphonitrile dihalide represented by the formula ((n) is an integer of >=3; Xs are identical or different and represent halogen atoms) is allowed to react with an alkali metal salt of a compound selected from alcohols, thiols, phenols, and thiophenols to produce the objective phosphonitric acid ester. In this case, the alkali metal salt is prepared by mixing a hydroxyl group- or thiol group-bearing compound with an alkali metal compound in an organic solvent or in the absence of solvent and subjecting them to the azeotropic dehydration. The reaction in the organic solvent is carried out, as the reaction mixture is maintained its temperature in a higher boiling point range from the azeotropic point of the organic solvent and water to the boiling point of the organic solvent or of water. In the case of no solvent, the reaction temperature is maintained at 40-200 deg.C and the amount of water in the reaction system is retained to <=10 wt.% based on the whole weight of the reaction system.
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