METHOD OF PRODUCING WATER-SOLUBLE AND/OR WATER-DISPERSIBLE COPOLYESTERS Russian patent published in 1998 - IPC

FIELD: polymer copolyesters materials in textile industry. SUBSTANCE: copolyesters for finishing textile threads are prepared by reesterification of dimethylterephthalate and dimethylsulfoaryldicarboxylate with ethylene glycol at ethylene glycol to ester mixture molar ratio (1.8-3.0):1 followed by direct esterification and subsequent polycondensation. Process is conducted at such molar ratio of dimethylterephthalate, dimethylsulfoaryldicarboxylate, and isophthalic acid that copolyester obtained would contain 10-75 mol. % terephthalate units, 15-70 mol.% isophthalate units, and 8-20 mol.% sulfoaryldicarboxylate units. Reesterification is carried out at molar ratio of ethylene glycol to mixture of dimethylterephthalate and dimethylsulfoaryldicarboxylate (1.8-3.5):1, preferably (2.0-3.0):1, and direct esterification at ethylene glycol to isophthalic acid molar ratio (1.8-3.0):1, preferably (2.0-2.8):1. As dimethylsulfoaryldicarboxylate, dimethyl- sodium-5-hydroxysulfonylisophthalate is utilized. Reesterification is carried out at temperature equal or exceeding 130 C, preferably 140- 250 C, in presence of catalyst selected from group including: Mn, Zn, Co, and Ca acetates, butyl titanate, nitrilo-2,2',2"-triethyl titanate, and Ca titanate. Amount of catalyst makes up at least 0.005% based on components' weight, preferably 0.01-2.0%. Direct esterification is carried out in presence of catalyst selected from group at 210-280 C (220-260 C). Amount of esterification catalyst makes up at least 0.005% based on weight of isophthalic acid and ethylene glycol used in esterification step, preferably 0.01-2.0%. Polycondensation is carried out at 230-280 C (240-260 C) in presence of antimony trioxide or germanium dioxide under reduced pressure. EFFECT: copolyesters obtained are less opaque and more stable on storage. 12 cl, 2 tbl