Thermosetting polyester coating compositions containing tetramethyl cyclobutanediol

A thermosetting coating composition, comprising:

• (A). about 50 to about 90 weight percent, based on the total weight of (A) and (B), of at least one curable polyester, comprising
• i. diacid residues, comprising about 20 to 100 mole percent, based on the total moles of diacid residues, of the residues of isophthalic acid;
• ii. diol residues, comprising about 10 to 100 mole percent, based on the total moles of diol residues, of the residues of 2,2,4,4-tetramethyl-1,3-cyclobutanediol;
• and
• iii. about 2 to about 40 mole percent of the residues of at least one polyol, based on the total moles of diol and polyol residues;
• wherein said curable polyester has a number average molecular weight of about 500 to about 10,000 daltons, a glass transition temperature of about −35° C., to about 50° C., a hydroxyl number of about 20 to about 300 mg KOH/g of polyester, and an acid number of 0 to about 80 mg KOH/g of polyester;
• (B). about 10 to about 50 weight percent, based on the total weight of (A) and (B), of a crosslinker comprising at least one compound reactive with a carboxylic acid or a hydroxyl group;
• (C). about 10 to about 60 weight percent, based on the total weight of (A), (B), and (C), of at least one nonaqueous solvent.

A process for the preparation of a curable polyester, comprising:

• heating a mixture comprising
• i. a diol component comprising about 10 to 100 mole percent of 2,2,4,4-tetramethyl-1,3-cyclobutanediol, based on the total moles of diol component;
• ii a diacid component comprising about 20 to about 80 mole percent of isophthalic acid and about 80 to about 20 mole percent of adipic acid, each based on the total moles of diacid component;
• iii. about 2 to about 40 mole percent of a polyol component, based on the total moles of diol and polyol components;
• and
• iv. a catalyst
• at a temperature of about 150 to about 250° C. while recovering water from said mixture to produce a curable polyester having number average molecular weight of about 500 to about 10,000 daltons, a glass transition temperature of about −35° C. to about 50° C., a hydroxyl number of about 20 to about 300 mg potassium hydroxide/g of polyester, or an acid number of 0 to about 80 mg potassium hydroxide/g of polyester.