Water-dispersible, polyester-based coatings formulations and method of making same

Claim 1

The method of making an improved liquid coatings formulation, said method comprising the steps: (a) esterifying a mixture of saturated aliphatic diol and aromatic dicarboxylic acid and/or anhydride thereof, in a mole ratio of diol-to-acid and/or anhydride thereof of about 1.25-1.5:1 at a first elevated temperature until an acid number below about 10 (in mg. of KOH) is obtained on the non-volatile materials so as to form an intermediate reaction product; (b) reacting said intermediate reaction product with an amount of aromatic dicarboxylic acid anhydride sufficient to increase the acid number of the resulting reaction product to about 35-75, said reaction being effected at a second elevated temperature lower than said first elevated temperature but sufficient to effect opening of the ring of said anhydride for esterification of only one carboxyl group thereof, said reaction resulting in a finished polyester resin having a molecular weight of about 700-2,000, an hydroxyl number of about 40-60, said acid number of about 35-75 and reactive pendant carboxyl and hydroxyl groups, said pendant hydroxyl groups being present in a concentration not in excess of about 2 per molecule; and, (c) thereafter mixing said finished polyester resin with solvent comprising water and an aminoplast resin to form an improved liquid coatings formulation.

Claim 2

The method of making an improved liquid coatings formulation, said method comprising the steps: (a) esterifying a mixture of saturated aliphatic diol and aromatic dicarboxylic acid and/or anhydride thereof, in a mole ratio of diol-to-acid and/or anhydride thereof of about 1.25-1.5:1 at a first elevated temperature until an acid number below about 10 (in mg. of KOH) is obtained on the non-volatile materials so as to form an intermediate reaction product; (b) reacting said intermediate reaction product with an amount of aromatic dicarboxylic acid anhydride sufficient to increase the acid number of the resulting reaction product to about 35-75, said reaction being effected at a second elevated temperature lower than said first elevated temperature but sufficient to effect opening of the ring of said anhydride for esterification of only one carboxyl group thereof, said reaction resulting in a finished polyester resin having a molecular weight of about 700-2,000, an hydroxyl number of about 40-60, said acid number of about 35-75 and reactive pendant carboxyl and hydroxyl groups, said pendant hydroxyl groups being present in a concentration not in excess of about 2 per molecule; and, (c) thereafter mixing said finished polyester resin with solvent comprising water and an aminoplast resin to form an improved liquid coatings formulation.