| 摘要 |
Low M.W. polyesters or copolyesters are continuously produced by ester interchange of at least one ester of a dicarboxylic and a low M.W. alcohol with at least one diol while maintaining a ratio of one mol of said ester of a dicarboxylic acid to more than 2 mols of said diol, in the presence of an ester interchange and a precondensation catalyst and subsequent precondensation in thin layers, the primary ester interchange being carried out in a reaction tube provided with a heating jacket over its whole length, at a temperature below the B.P. of the diol and under a pressure slightly higher than atmospheric pressure in such a way that the average residence time of the ester interchange product in the reaction tube is less than 30 minutes, and the precondensation being subsequently carried out under sub-atmospheric pressure at a temperature above the B.P. of the diol in a falling film evaporator, the residence time of the precondensation product in the falling film evaporator being less than 3 mins. The dicarboxylic acid ester may be an ester of terephthalic acid, isophthalic acid, sebacic acid or adipic acid with an aliphatic alcohol of 1-6 C. The diol may be ethylene glycol or 1: 4 dimethylol cyclohexane. The interchange catalyst may be (CH3COO)2Ca(CH3COO)2Mn or (CH3COO)2Zn and the precondensation catalyst Sb2O3.ALSO:Low M.W. polyesters or copolyesters are continuously produced by ester interchange of at least one ester of a dicarboxylic and a low M.W. alcohol with at least one diol while maintaining a ratio of one mol of said ester of a dicarboxylic acid to more than 2 mols of said diol, in the presence of an ester interchange and a precondensation catalyst and subsequent precondensation in thin layers, the primary ester interchange being carried out in a reaction tube provided with a heating jacket over its whole length, at a temperature below the B.P. of the diol and under a pressure slightly higher than atmospheric pressure in such a way that the average residence time of the ester interchange product in the reaction tube is less than 30 minutes, and the precondensation being subsequently carried out under sub-atmospheric pressure at a temperature above the B.P. of the diol in a falling film evaporator, the residence time of the precondensation product in the falling film evaporator being less than 3 minutes. The dicarboxylic acid ester may be ester of terephthalic acid, isophthalic acid, sebacic acid or adipic acid with an aliphatic alcohol of 1-6 C. The diol may be ethylene glycol or 1:4-dimethylol cyclohexane. The interchange catalyst may be (CH3COO)2Ca, (CH3COO)2Mn or (CH3COO)2Zn and the precondensation catalyst Sb2O3. |
