| abstract |
A copolyester is synthesized by reacting a dialkyl ester of an aromatic dicarboxylic acid (e.g., dimethyl terephthalate) with ethylene glycol, low molecular weight poly(ethylene glycol) and a salt of a sulfonic acid-substituted aromatic dicarboxylate (e.g., sodium sulfoisophthalic acid) simultaneously in a first stage reaction in the presence of a phosphite or phosphate stabilizer. The intermediate product of the first stage is further reacted in a second stage in the presence of a polycondensation catalyst to obtain a random copolyester of the desired molecular weight. The copolyester is extruded to form a film which, after orientation and heat setting, has excellent clarity and is useful as a photographic film support. Aqueous processing of the film relaxes any core set or curl. |