Coating compositions containing acrylic and aliphatic polyester blends

Abstract

Disclosed are solvent borne thermosetting coating compositions containing curable, aliphatic polyesters, acrylic copolymers, crosslinkers, and nonaqueous solvents. The aliphatic polyesters contain 2,2,4,4-tetramethyl-1,3-cyclobutanediol. Blends of acrylic copolymers with these aliphatic polyesters exhibit good compatibility, viscosity reduction, and good Tg retention. Coating compositions formulated from these blends exhibit high gloss, hardness with flexibility; solvent and chemical resistance; and outdoor durability.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation U.S. patent application Ser. No. 12 / 367,151, filed on Feb. 6, 2009, the disclosure of which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]This invention pertains to thermosetting coating compositions. More particularly, this invention pertains to thermosetting coating compositions comprising a curable, aliphatic polyester containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol, a thermosetting acrylic copolymer, a crosslinker, and a solvent.BACKGROUND OF THE INVENTION[0003]Acrylics and polyesters are common types of resins used in the manufacture of solvent borne thermosetting coatings. Acrylics are known for their excellent hardness, fast dry times, scratch, stain, chemical, and humidity resistance, and outdoor durability. They can be formulated to a very high glass transition temperature (Tg) and exhibit excellent light stability and hydrolysis resistance. Acrylic coatings,...

AI Technical Summary

Benefits of technology

[0017]Coatings formulated from these aliphatic polyester / TSA blends can exhibit high gloss, distinctness of image and reflectivity; good hardness with good flexibility; solvent and chemical resistance; and good gloss retention during UV and humidity exposure for good outdoor durability. These coatings are useful as factory and field-applied coatings for auto OEM, auto refinish, transportation, aerospace, maintenance, marine, machinery and equipment, general metal, appliance, metal furniture, plastic, and building / construction applications.

Problems solved by technology

Acrylic coatings, however, often lack flexibility and require high levels of solvent in the coating formulation to achieve a practical application viscosity.

The high solvent requirement for acrylics makes it difficult to satisfy VOC (volatile organic compound) content regulations as mandated by various federal and state air quality organizations.

Polyesters, however, typically do not weather as well as acrylics.

Coatings made from aliphatic polyesters are generally flexible but tend to be soft, resulting in poor resistance to solvents and chemicals, poor humidity resistance and poor outdoor durability.

Unfortunately, the glass transition temperature (“Tg”) of the blend frequently decreases significantly as the polyester content increases.

The lower Tg of the blend has an adverse impact on the desirable characteristics that the TSA resin imparts to the coating.