Process for the preparation of low molecular weight polyesters from

Abstract

The present invention provides a process for the preparation of low molecular weight polyesters directly from hydroxypivaldehyde. The process comprises reacting dry hydroxypivaldehyde with a diester, a multifunctional ester, a diacid, a polyester, or a mixture thereof at a temperature of about 100.degree. C. to 230.degree. C. in the presence of a transesterification catalyst. Optionally, modifying glycols, triols, or polyols may also be added. Suitable catalysts include tetraisopropyl titanate, dibutyltin oxide, lithium hydroxide, and lithium alkoxide, with tetraisopropyl titanate being especially preferred. The reaction is preferably accomplished in two stages by heating the reaction mixture to about 130.degree. C. for about three hours and subsequently heating the reaction mixture to about 190.degree.-230.degree. C. until the reaction is essentially complete. In an especially preferred embodiment, the low molecular weight polyesters are produced by the reaction of hydroxypivaldehyde with a diester such as dimethyl adipate, dimethyl cyclohexane-1,4-dicarboxylate, and dimethyl terephthalate. The low molecular weight polyester product typically exhibits a molecular weight of about 400-2000 and a hydroxyl number of about 100-300.