GB550837A - Process for the preparation of condensation products of hydroxyacetic acids - Google Patents

Abstract

550,837. Condensation products of hydroxyacetic acids. DU PONT DE NEMOURS & CO., E. I. July 23, 1941, No. 9291. Convention date, July 24, 1940. [Class 2 (iii)] [Also in Group V] Condensation products of hydroxyacetic acid useful in baking powder compositions are obtained by heating hydroxyacetic acid or a partially dehydrated product thereof under atmospheric or higher pressure until not more than 25 per cent. of the initial combined water in the hydroxyacetic acid remains and then heating under vacuum to remove the major portion of the residual combined water and the volatile low molecular weight substances. Preferably the first stage is carried out by heating to 180‹-230‹ C., and the second stage between 210‹-250‹ C. at a pressure of between 5 and 100 mm. The first stage may be carried out under pressures up to 10 or more atmospheres, if desired in the presence of an acidic catalyst, e.g. phosphoric, sulphuric or p-toluenesulphonic acids. The second stage is preferably carried out whilst introducing an inert fluid, e.g., nitrogen, hydrogen, carbon dioxide, benzene or toluene, and towards the end a dehydrating agent, e.g. phosphorus pentoxide or calcium oxide may be added. Starting materials in addition to aqueous solutions of hydroxyacetic acid of all strengths including the partially dehydrated acid such as 110 per cent. hydroxyacetic acid are diglycollide, hydroxyacetic anhydride and esters such as methyl hydroxyacetate (which latter may first be hydrolyzed with water and the product concentrated under atmospheric pressure). ). In the Specification as open to inspection under Sect. 91 the ability of the product to liberate acid slowly in the presence of water and give carbon dioxide in the presence of a carbonate or bicarbonate at high temperatures is described. It may be employed in making gaseous cellular products such as soap, cement, plaster, rubber and plastics. This subjectmatter does not appear in the Specification as accepted.