LOW VISCOSITY UNSATURATED POLYESTER RESINS

摘要

A low viscosity unsaturated polyester resin for making products, optionally reinforced with glass fibers is described, which comprises an alkyd prepared by esterification of maleic anhydride and/or acid and/or fumaric acid in association with isophtalic acid, with one or more glycols, essentially comprising dipropylene glycol, and further comprises 25-40% by weight of the total resin of an ethylenically unsaturated monomer copolymerizable with the alkyd essentially chosen among styrene and vinyl toluene, the alkyd having a molecular weight/double bond factor between 300 and 390 and an amount of free functional groups between 50 and 85 mg of KOH per g of alkyd inclusive. The products obtainable from said resin are also described. The resin has a better behaviour in processing has lower heat development and shrinkage than the comparable prior art resins while the mechanical properties of the finished products are very good.