A NEW APPROACH TO QUALITY IMPROVEMENT OF UNSATURATED POLYESTER RESIN

To improve the properties of unsaturated polyester resin (UP), we dire cted our attention to control of the molecular weight. The common aver age-number molecular weight (M(n)) of UP is about 3000 or less in the equilibrium state and it becomes a gel on further esterification by in creasing the molecular weight distribution (M(w)/M(n)). The production process for UP with M(n) about 5000 is developed by using a deglycol reaction after normal esterification. By increasing M(n) to about 5000 , the properties of UP, such as boiling water resistance, alkali resis tance, heat distortion temperature, toughness and mechanical strength, are found to be improved. This new process for increasing the molecul ar weight of UP, which improves its properties, will thereby expand it s sales potential.