Unsaturated polyester resin and molding compounds obtained therefrom

Claim 1

A homogeneous, non-separating unsaturated polyester resin, suitable for use in a molding composition, comprising (A) from about 30 to 60% by weight of an unsaturated polyester, (b) from about 10 to 30% by weight of a saturated, liquid polyester as a shrink-reducing or LP additive, (C) from about 30 to 50% by weight of styrene and an effective amount of a polymerization inhibition stabilizer wherein the amounts of (A), (B), and (C) are based on the final resin; and wherein (a) said unsaturated polyester is obtained by polycondensation of (1) a mixture of an alpha, beta olefinically unsaturated C 4 dicarboxylic acid and a saturated, aliphatic C 4 to C 8 alpha, omega dicarboxylic acid and (2) a mixture of 1,2-propylene glycol and ethylene glycol, and wherein said unsaturated polyester has an acid value of from about 5 to 40 mg KOH/g; the molar ratio of said unsaturated dicarboxylic acid to said saturated dicarboxylic acid is from about 4:1 to 8:1; and the molar ratio of said propylene glycol to said ethylene glycol is from about 1:1 to 5:1, respectively; and (b) said saturated polyester is obtained by polycondensation of (1) a saturated, aliphatic C 4 to C 8 alpha, omega dicarboxylic acid, and (2) a mixture of ethylene glycol and a saturated, aliphatic diol having primary hydroxyl groups and having 5 or 6 C atoms in the chain between the hydroxyl groups and 3 methyl side groups, and wherein said saturated polyester has an acid value of from about 15 to 40 and a weight average molecular weight of from about 5000 to 8000, determined by gel permeation chromatographic analysis and the molar ratio of said ethylene glycol to said diol is from about 1:1 to 3:1.