PROCESS FOR PREPARING A BIODEGRADABLE WATER-DISPERSIBLE AROMATIC-ALIPHATIC COPOLYESTER AND AQUEOUS DISPERSION THEREOF

摘要

The invention relates to a process for preparing a biodegradable aromatic-aliphatic copolyester and to an aqueous dispersion thereof employed in encapsulating fertilizer granules aiming at the controlled release of nutrients. According to the invention, the process consists in the degrading trans-esterification of a polyethylene terephthalate waste, in the presence of at least two oxyalkylene diols, one of which is isosorbite, and the diesters thereof with 5-sodium sulphonate isophthalic acid, esterification of the glycolysis products with an aliphatic dicarboxylic acid with 4...6 carbon atoms, polycondensation of reaction products at temperatures of 220...265°C and under vacuum of 5...10 mmHg, at the most, resulting in a copolyester having an inherent viscosity of 0.20...0.40 dl/g and a temperature of transition to the glass phase of at least 30°C, which, at a temperature of 85...90°C forms with water, without co-solvent or surface-active agent admixture, dispersions that contain up to 35% copolyester, which are capable of generating biodegradable films, upon water removal, by evaporation.