Low shrink thermosetting polyesters

In a low-profile molding resin composition for thickening with Group II metal oxides, hydroxides, or alkoxides, the resin system comprising by weight a mixture of (a) at least 25% of a dicyclopentadiene terminated ethylenically unsaturated polyester polymer being the esterification product of an alpha, beta-ethylenically unsaturated dicarboxylic acid, dicyclopentadiene, and glycol, said dicarboxylic acid esterified with about 0.1 to 0.4 moles of dicyclopentadiene per mole of dicarboxylic acid, said polyester produced by first reacting a molar excess of said dicarboxylic acid with said glycol to produce an acid terminated prepolymer and then reacting the dicyclopentadiene with said prepolymer, (b) about 5% to 20% of an acid functional thermoplastic polymer, and (c) about 30% to 60% of an ethylenically unsaturated monomer, the improvement comprising:

• said thermoplastic polymer being a fatty acid modified branched, thermoplastic alkyd condensation polymer, said alkyd being the esterification product of glycol and minor amounts of polyol preferentially esterified with linear saturated dicarboxylic acids having between about 4 to 10 carbon atoms and monocarboxylic fatty acid, said alkyd containing between about 4% to 20% of said fatty acid by weight and having a hydroxyl equivalent branching functionality of between about 2.02 and 2.2.