GB650002A - New or improved resinous polyesters and method for their manufacture - Google Patents

Abstract

Polyesters are produced by heating a mixture of a dialkyl carbonate in which the alkyl groups contain 1 to 6 carbon atoms and pentaerythritol, di-pentaerythritol, or a higher polypentaerythritol in the presence of an alkali metal alkoxide as catalyst with continuous distillation from the reaction mixture of the saturated monohydric aliphatic alcohol produced by the reaction. Preferably the reaction mixture contains at least as many moles of dialkyl carbonate per mole of pentaerythritol, dipentaerythritol, or polypentaerythritol as there are primary alcoholic groups in the molecule of the latter reagent. It is preferred to react pentaerythritol or di-pentaerythritol with four or six molar proportions respectively of the di-alkyl carbonate. The heating may be continued until as many molar proportions of saturated alcohol are distilled from the reaction mixture as there are primary aliphatic alcohol groups in the molecule of pentaerythritol, or stopped in which case the products contain unesterified alcoholic hydroxyl groups and may be reacted further, e.g. with di-isocyanates. In examples: (1) pentaerythritol (1 mole) and diethyl carbonate (8 moles) are heated together with a solution of sodium ethoxide until 4 moles of ethyl alcohol has distilled off, glacial acetic acid is added, and the solution distilled, leaving a syrup soluble in acetone, chloroform, toluene, ethyl acetate, butyl acetate, and mixtures of alcohols and aromatic hydrocarbons. Films of the product mixed with nitrocellulose on heating become hard and insoluble; (2) similar procedure to (1) is followed using dipentaerythritol (1 mole), diethyl carbonate (12 moles) and distilling off 6 moles of alcohol; (3) a syrupy resinous polyester containing about 5.5 per cent free hydroxyl groups is prepared by reacting pentaerythritol (1 mole), diethyl carbonate (5 moles) until 3.1 moles of alcohol has distilled off. The product is mixed with hexamethylene di-isocyanate and baked at 100 DEG C. to form an insoluble film. The cyclic carbonate of 3 : 3-dimethylol-oxa-cyclobutane and diethyl carbonate are produced by treating the product of (1) with sodium ethoxide, heating it until it gels, and then heating the resulting solid in vacuo at 200 DEG C.ALSO:Diethyl carbonate and the cyclic carbonate of 3 : 3-dimethyl-oxacyclobutane are obtained on heating with sodium ethoxide until solid, and then in vacuo at 200 DEG C., the syrupy polyester obtained by reacting pentaerythritol and diethyl carbonate in the presence of an alkali metal alkoxide (see Group p IV (a)).