| 摘要 |
In the manufacture of highly polymeric polymethylene terephthalates by effecting esterinterchange between a dialkyl terephthalate and a glycol of formula HO(CH2)nOH, where n is 2-10, in presence of an alkaline earth metal compound and subjecting to the product to polycondensation in presence of a polycondensation catalyst, the alkaline earth metal compound is converted wholly or in part to a phosphorus acid salt of that metal which is catalytically inert and which is soluble in the polycondensation reaction mixture and in the final polymer. The resulting polymers have improved clarity and films made therefrom have improved friction characteristics. The conversion of the alkaline earth metal compound is effected by adding at the beginning or during the early stage of the reaction phosphoric acid, hypophosphorous acid, phosphorous acid or a trialkyl phosphite (e.g. triphenyl phosphite). The alkaline earth metal compound acting as ester-interchange catalyst may be calcium acetate, calcium benzoate, calcium salicylate, calcium borate or strontium acetate and the polycondensation catalyst may be litharge, germanium oxide or an antimony compound (e.g. antimony oxide). Examples describe the manufacture of polyethylene terephthalates from ethylene glycol and dimethyl terephthalate or a mixture of dimethyl terephthalate and dimethyl isophthalate. |
