GB744975A - Improvements in the preparation of linear polyesters of sulphonyl dibenzoic acids - Google Patents

Abstract

Linear polyesters are made either (a) by reacting a sulphonyl dibenzoic acid, an alkyl or a beta-hydroxyethyl diester thereof with an alpha - omega straight chain polymethylene glycol or an ester thereof, if desired in presence of another dicarboxylic acid, e.g. adipic, succinic, sebacic, phthalic, terephthalic, fumaric, maleic or itaconic acid or in presence of diethylene glycol or (b) by heating a beta-hydroxyethyl diester of a sulphonyl dibenzoic acid either alone or with a dicarboxylic acid, e.g. one of those specified above. The sulphonyl dibenzoic acids have the formula <FORM:0744975/IV(a)/1> wherein the carboxyl groups are attached to the benzene nuclei in positions either meta or para to the sulphone group, and wherein the benzene nuclei may contain alkyl substituents. Specified polymethylene glycols are ethylene, propylene, butylene and hexylene glycol. The polyesters have high melting points (above 200 DEG C.) and may be used in the manufacture of sheets, films, coatings, fibres, threads, filaments and moulding plastics. Polyesterification is normally effected by heating at 180-230 DEG C. for about 2-5 hours, then at about 240-290 DEG C. for about 1/2 -2 hours and finally under vacuum (less than 10 mm. of Hg pressure) at 240-290 DEG C. for about 3-8 hours. Catalysts, e.g. alkali or alkaline earth metals or their hydroxides or alkoxides may be used. Examples disclose polyesters obtained by reacting: (4) and (5) the butyl diester of p:p1-sulphonyl dibenzoic acid, ethylene glycol and diethylene glycol; (6) the ethyl diester of m:m1-sulphonyl dibenzoic acid and butylene glycol; (7) the beta-hydroxyethyl diester of p:p1-sulphonyl dibenzoic acid and adipic acid. Specification 620,494 is referred to.ALSO:Sulphonyl dibenzoic acids of formula <FORM:0744975/IV(a)/1> wherein the carboxyl groups are attached to the benzene nuclei in positions either meta or para to the sulphone group, and wherein the benzene nuclei may contain alkyl substituents are made by oxidizing the corresponding meta- or para-dimethyl diphenyl sulphone in the presence of a cobalt or manganese catalyst in a solvent which is substantially inert to oxidation and which contains a lower aliphatic aldehyde as an oxidation promoter, at a temperature of 70-120 DEG C. Specified catalysts are cobalt and manganese acetate; specified solvents are dioxane, acetic acid, propionic acid and butyric acid, and specified aldehydes are acetaldehyde, propionaldehyde, isobutyraldehyde and n-butyraldehyde. Preferably the catalyst is suspended in the solvent, the mixture heated and a mixture of oxygen and aldehyde vapours passed into the mixture. When using a cobalt catalyst, the colour of the solution changes from pink to dark green showing that the catalyst has been activated. Then a solution of the dimethyl diphenyl sulphone is added while the introduction of aldehyde and oxygen is continued. The lower alkyl diesters or the beta-hydroxyethyl diesters of the above acids may be prepared by refluxing the acid with a large excess of lower alcohol or ethylene glycol for a long time. Preferably the beta-hydroxy-ethyl diester is prepared by reacting the acid with ethylene oxide at 80-150 DEG C. in presence of a tertiary amine catalyst (many specified). The reaction is preferably effected in an unreactive liquid medium, e.g. a lower alkanol or 1 : 4-dioxane at 100-200 lb./sq. in. Any mono-ester obtained in the reaction product may be removed by washing with a dilute alkaline solution.