GB738509A - New mixed esters - Google Patents

Abstract

Polyesters are prepared by heating a substance of the formula <FORM:0738509/IV (a)/1> (see Group IV (b)) wherein R is an alkyl radical. The alcohol ROH formed during polymerization is preferably more volatile than ethylene glycol. Specified esters are methyl, isopropyl and n-butyl b -hydroxyterephthalates. The polymers are obtained by heating, under reduced pressure if necessary, until filaments drawn from the melt may be cold or hot drawn to give strong fibres. Glycols, or derivatives such as ethylene glycol diacetate, or dithiols whereby sulphur linkages are introduced into the polymer, may be added to the reaction mixture, as well as ester-interchange and polycondensation catalysts. In example (4) a mixture of methyl b -hydroxyethylterephthalate, ethylene glycol and zinc acetate is heated to remove methanol, and then heated under reduced pressure until a fibre-forming polymer is obtained.ALSO:Mixed esters of terephthalic acid of the general formula <FORM:0738509/IV (b)/1> wherein R is an alkyl radical, are prepared by reacting a monoalkyl ester of terephthalic acid with ethylene oxide, in the presence or absence of a solvent or diluent such as water, or an p organic liquid such as tertiary butanol or xylene. Pressures up to 50 pounds per square inch and temperatures up to 100 DEG C. are satisfactory. Catalysts such as sulphuric acid, arylsulphonic acids, hydroxides and salts of alkali or alkaline earth metals, or ammonium salts may be used. The preferred esters, which are used in the manufacture of fibre-forming polymers (see Group IV (a)) are those in which the alkyl radical contains less than five carbon atoms, especially where R is methyl. Specified esters are methyl, isopropyl and n-butyl b -hydroxyterephthalates. In examples (1) methyl b -hydroxyethyl terephthalate is prepared from mono-ethyl-terephthalate and ethylene oxide using caustic soda as catalyst; methyl b -hydroxyethyl terephthalate is prepared by passing ethylene oxide into a mixture of monomethyl terephthalate and methyl p-toluate at 150 DEG C. using sodium metal as catalyst; (3) ethyl b -hydroxyethyl terephthalate is prepared by passing ethylene oxide into ethyl hydrogen terephthalate at 170 DEG C. using sodium metal as catalyst, and extracting the product with benzene.