Fire retardant polyester resins

Claim 1

A process for making a fire retardant infusible cured polyester bromine-containing resin comprising the steps of: initially forming a bromine containing polyester resin having ester groups derived from an ethylenically unsaturated dicarboxylic acid or acid anhydride in the polyester chain by simultaneously mixing and reacting a. polyhydric alcohol selected from the group consisting of aliphatic glycols having from 2 to 10 carbon atoms and aliphatic glycol ethers having from 4 to 20 carbon atoms; b. an ethylenically unsaturated dicarboxylic acid or acid anhydride selected from the group consisting of maleic acid, maleic anhydride, fumaric acid, itaconic acid, and mixtures thereof, and c. a 4,5-dibromohexahydrophthalic compound selected from 4,5-dibromohexahydrophthalic anhydride and 4,5-dibromohexahydrophthalic dicarboxylic acid at a temperature of from about 100°C to about 175°C to form a product having an acid number within the range of about 0 to 40 mg. KOH/g., wherein the dicarboxylic acid or anhydride (b) and the 4,5-dibromohexahydrophthalic compound (c) are collectively employed in an amount such that there is approximately one hydroxyl equivalent based on the polyhydric alcohol (a) per carboxyl equivalent and wherein the 4,5-dibromohexahydrophthalic compound (c) is present in an amount of from about 5 to about 25 mole percent of the total dicarboxylic acids (b) and (c); mixing the resulting polyester resin with a cross linking agent which is a polymerizable monomer having terminal ethylenic unsaturation; and, curing the resultant mixture to produce said fire retardant infusible cured polyester.