| 摘要 |
In a process for making polyesters by effecting a transesterification reaction between a dialkyl ester of a dicarboxylic acid and then polycondensing the product, a gallium compound is used as catalyst for the polycondensation reaction. As additional catalyst for the transesterification reaction there is preferably used a compound of manganese, zinc, magnesium, calcium or cadmium. Specified metal compounds are the alkyls, alkoxides, iodides, carbonates, oxides, hydrated oxides, hydroxides or lower alkanoic acid salts (e.g. the basic acetate, the propionate or the butyrate of gallium or the acetates of the other metals). Gallium may also be used as the amino-halide of formula GaX3.nNH3, where X is Cl, Br or I and n is 1 to 14. Less preferred additional catalysts are litharge, magnesium titanium butoxides or alkali metals, e.g. in the form sodium acetate, lithium hydride or potassium ethoxide. Also present during the polyesterification may be stabilizers, antioxidants or pigments, e.g. diethyl hydrogen phosphate, butylated hydroxytoluene or titanium dioxide. The dicarboxylic acid is preferably aromatic (e.g. terephthalic or isophthalic) or a mixture thereof with an aliphatic dicarboxylic acid. The glycol may be ethylene glycol, a polymethylene glycol, 2:2:4:4-tetramethyl - 1:3 - cyclobutanediol or 1:4 - cyclohexanedimethanol. The final stage of the polyesterification may be effected in liquid or solid phase. Examples describe the manufacture of polyethylene terephthalate by reacting dimethyl terephthalate with ethylene glycol.ALSO:A polyesterification catalyst consists of a mixture of a compound of gallium and one or more compounds of manganese, zinc, magnesium, calcium or cadmium. The mixture preferably contains 0,2-5 atoms of gallium for each atom of the other metal. Specified metal compounds are the alkyls, alkoxides, iodides, carbonates, oxides, hydrated oxides, hydroxides or lower alkanoic acid salts (e.g. the basic acetate, the propionate or the butyrate of gallium or the acetates of the other metals). Gallium may also be used as the amino-halide of formula GaX3,nNH3 where X is Cl, Br or I and n is 1-14. |
