| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for inhibiting polymerization of (meth)acrylic acid and an ester effective in both vapor and liquid phases where, because of using non metal compound, waste liquid treatment can be made easily. SOLUTION: This method is characterized by comprising using, in a refining column, a combination of N-nitrosophenylhydroxylamine or salt thereof with an N-oxyl compound, an N-hydroxy-,2,2,6,6-tetramethylpiperidine compound and a 2,2,6,6-tetramethylpiperidine compound. In this method, N- nitrosophenylhydroxylamine or a salt thereof rises inside a refining column under splitting part thereof to effectively inhibit polymerization of (meth)acrylic acid or the like. The above polymerization in both vapor and liquid phases can be inhibited more effectively by the combined use of the compounds mentioned above.
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