Method of providing cured coating films free of popping defects

Abstract

A method for providing cured coating films free of popping defects. The method requires the application to a substrate of at least 2.0 mils / 50.8 microns of a uncured curable coating composition comprising an anti-popping component (a), a film-forming component (b), and a crosslinking component (c), wherein anti-popping component (a) has from 12 to 72 carbon atoms, is substantially free of any heteroatoms, is not a crystalline solid at room temperature and comprises a mixture of two or more structures selected from the group consisting of aliphatic structures for anti-popping component (a), aromatic-containing structures for anti-popping component (a), cycloaliphatic-containing structures for anti-popping component (a), and mixtures thereof, at least one of the two or more structures being a cycloaliphatic-containing structure or an aromatic-containing structure. The coated uncured substrate is cured to provide a cured film free of popping defects with an average film build of at least 2.0 mils / 50.8 microns.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to coating compositions, especially thermoset coating compositions intended for use in the automotive and / or transportation industries. This application claims priority upon U.S. patent application Ser. No. 09 / 741,511, filed Dec. 19, 2000.[0002] Curable coating compositions, especially thermoset coatings, are widely used in the coatings art. They are often used as topcoats in the automotive and industrial coatings industry. Color-plus-clear composite coatings are particularly useful as topcoats where exceptional gloss, depth of color, distinctness of image, or special metallic effects are desired. The automotive industry has made extensive use of these coatings for automotive body panels. [0003] The effect of the coating process on the environment and the effect of the environment on coatings have increasingly shaped the coatings art in the last few decades. The industry has put considerable effort into developing coatings wi...

AI Technical Summary

Benefits of technology

[0010] Because of the significant losses in time and resources attributable to popping defects, it would be advantageous to provide a method of improving the popping resistance of coating compositions, especially those intended for use in the automotive industry that have desirable etch resistance. At the same time, such method must produce improvements without any decrease in environmental etch resistance or other commercially required performance property.

[0011] It would be particularly desirable to provide a method of improving the popping resistance of coating compositions, especially those intended for use as the clearcoat layer in color-plus-clear composite coatings. SUMMARY OF THE INVENTION

Problems solved by technology

However, it has been difficult to devise environmentally sensitive coatings that simultaneously provided desirable resistance to environmental degradation and superior finished film performance properties.

As a result, these coatings are especially susceptible to a phenomenon known as environmental etch.

It is often difficult to predict the degree of resistance to environmental etch that a high gloss or color-plus-clear composite coating will exhibit.

Many coating compositions known for their durability and / or weatherability when used in exterior paints do not provide the desired level of resistance to environmental etch when used in high gloss coatings such as the clearcoat of a color-plus-clear composite coating.

However, several of these prior art systems are vulnerable to application problems.

For example, many prior art coating compositions show an unacceptable tendency to form popping defects at commercially mandated film builds in commercial application environments.

These popping defects are believed to result from the upward passage of volatile gases from the curing film.

In either case, the presence of these popping or gassing defects often renders the cured surface commercially unacceptable.

Coating compositions used as topcoats are especially vulnerable to this problem due to their higher film build requirements.

Coating composition having poor pop resistance will often show popping defects at the edges of parts where paint collects in film builds thicker than that normally intended.

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