GB634609A - Improvements in the production of polyesters - Google Patents

Abstract

Polyesters are prepared by heating an excess over 2 moles. of a halogen hydrin of a volatile glycol with a mol. of a salt of a strong base with a dicarboxylic acid which is a p : p1-dicarboxy derivative of a benzene compound or of a compound containing two benzene rings linked together directly or through carbon, oxygen or sulphur atoms, separating the halide salt of the strong base, if desired working up the reaction product to form the pure bis-glycol ester of the dicarboxylic acid, and finally heating, preferably at 220-280 DEG C. under high vacuum, to produce a polymer. Suitable dicarboxylic acids include terephthalic acid, 2 : 51-dichlorterephthalic acid, 4 : 41 - dicarboxy - diphenyl, 4 : 41-dicarboxy-3 : 31-dimethyl-diphenyl, a : o -bis-(paracarboxy-phenyl)-alkanes and a : o -bis - (paracarboxyphenoxy) - alkanes. Suitable halogen hydrins are o -hydroxyalkyl chlorides and bromides. Propylene chlorhydrin is also suitable. The step of heating to produce the polyester is conveniently carried out in the presence of an ester exchange catalyst such as alkali metal, magnesium or tin. The polymers may be drawn out into filaments and may be used with sulphonamide, phenolic, urea and thiourea plasticizers. In examples: (1), (2) and (3) terephthalic acid dissolved in aqueous sodium hydroxide is heated with ethylene chlorhydrin, in the presence of a small quantity of sodium iodide, the bis-b -hydroxyethyl terephthalate is isolated and is heated in the presence of metallic magnesium to give a filament forming polymer; and (4) crude bis-b -hydroxyethyl terephthalate is formed as in (1) and is converted directly to the polyester without being isolated.ALSO:Bis-glycol esters of dicarboxylic acids which are p : p1-dicarboxy derivatives of compounds containing a single benzene ring or of compounds containing two benzene rings linked together directly or through carbon, oxygen or sulphur atoms, e.g. terephthalic acid, 2 : 5-dichloroterephthalic acid, 4 : 41 - dicarboxy - diphenyl, 4 : 41 - dicarboxy - 3 : 31 - dimethyl-diphenyl, a : o - bis - (paracarboxyphenyl) - alkanes and a : b -bis-(paracarboxyphenoxy)-alkanes are prepared by heating the sodium or other salt of the dicarboxylic acid and a strong base with an excess over two molecules of the halogen hydrin of the glycol, separating the sodium halide or other halide salt and isolating the ester formed. Suitable halogen hydrins are o -hydroxyalkyl bromides or chlorides, but propylene chlorhydrin may also be used. In examples: (1) and (2) terephthalic acid dissolved in aqueous caustic soda is heated with ethylene chlorhydrin in the presence of a small quantity of sodium iodide to give bis-b -hydroxyethyl terephthalate; and (4) the reaction of (1) is repeated and the crude ester is converted directly to a polyester.