Aliphatic polyester coating compositions containing tetramethyl cyclobutanediol

Abstract

Disclosed are aliphatic polyester resins containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol and solvent borne, thermosetting coating compositions prepared therefrom. The aliphatic polyesters exhibit good hardness and flexibility when formulated into thermosetting coatings compositions.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 12 / 367,190, 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 aliphatic, curable polyesters for solvent-borne, thermosetting coating compositions. More particularly, this invention pertains to curable polyesters containing 2,2,4,4-tetramethyl-1,3-cyclobutanediol and high-solids, solvent-borne thermosetting coating compositions prepared from these polyesters. These polyesters can be used in blends with acrylic resins or serve as the primary film former in a coating formulation.BACKGROUND OF THE INVENTION[0003]Solvent-borne, polyester thermosetting coatings that exhibit high hardness are desirable. Coatings with high hardness typically exhibit high gloss, good distinctness of image (DOI), fast dry-times, scratch, stain, chemical, and humidity resistance, and outdoor du...

AI Technical Summary

Benefits of technology

This patent describes a coating made from aliphatic polyester resins that have high gloss, good hardness, flexibility, solvent and chemical resistance, and good gloss retention during UV and humidity exposure. The coating can be used in various applications such as automotive, aerospace, and construction. When blended with thermosetting acrylic resins, the aliphatic polyesters display good solubility, compatibility, viscosity reduction, and high Tg retention.

Problems solved by technology

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

Unfortunately, poor solvent solubility and compatibility with acrylic resins often are observed as CHDM content is increased in the polyester resin formulation.

The amount of CHDM that can be incorporated into the resin formulation, therefore is limited.

Poor resin solubility often manifests itself over time by phase separation, precipitation of the resin from solution, and the development of hazy to opaque resin solutions.

These characteristics are undesirable and limit the storage stability of the resin solution and the coatings formulated from these solutions.

Such coatings, for example, may experience a viscosity increase, phase separation, agglomeration of ingredients, etc., that result in an undesirable higher application viscosity, poor appearance and poor mechanical properties of the cured film.

Although TSA resins exhibit many desirable properties, they often lack flexibility and require more solvent in the coating formulation to achieve a practical application viscosity.

The higher solvent requirement for TSA resins makes it difficult to achieve high solids coatings with reduced VOC content as mandated by various federal and state air quality organizations.

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.