| 摘要 |
1,246,064. Solid phase polymerization of polyesters. FARBWERKE HOECHST A.G. 17 Oct., 1969 [19 Oct., 1968], No. 51122/69. Heading C3R. High molecular weight polyesters e.g. polyethylene terephthalate are produced by heating low molecular weight polyesters by means of a high frequency electric field by which the polyester is crystallized and substantially dried at below the polycondensation temperature, followed by a solid phase polycondensation in known manner. The high frequency heating may be performed slowly, e.g. 5-5 mins. or rapidly in stages, e.g. rapidly to 100-180‹ C. followed by heating at a constant temperature in the absence of the field to complete crystallization, followed by an increase to the condensation temperature of about 200-250‹ C. |
