| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyester generating little mold contamination in molding and residual taste and smell on the molded article and useful for bottle, etc., by treating polyester chip with water having an ammonia nitrogen content and a nitrate nitrogen content maintained below respectively specific levels. SOLUTION: A polyester useful for the molding of film, sheet, etc., is produced by treating polyester chips in a treating tank with water while keeping the ammonia nitrogen content of the treating water to <=0.5 mg/L and the nitrate nitrogen content to <=1 mg/L. The process is preferably carried out by introducing water having an ammonia nitrogen content of 0.01-0.5 mg/L and a nitrate nitrogen content of 0.01-1 mg/L from an outer source. At least one kind of treating water introduced from an outer source and treating water discharged from the treating tank for repeated use is preferably treated by an ion exchange treatment apparatus.
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