Water-based coating compositions and systems with improved sag resistance and related methods

Abstract

The present invention provides a system for monitoring and controlling an industrial paint operation, where a five-sided intermodal shipping container is painted with a water-based coating composition. The system includes a paint application system, a drying system with a chamber configured to handle one or more intermodal shipping containers, and modules for monitoring and controlling the application of paint and the drying of the applied paint.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)[0001]This application is a continuation in part of U.S. patent application Ser. No. 13 / 717,221, filed Dec. 17, 2012, which is a continuation of PCT Application No. PCT / US2011 / 057010, filed 20 Oct. 2011, which claims priority to U.S. Provisional Application Ser. No. 61 / 450,481, filed 8 Mar., 2011.FIELD OF THE INVENTION[0002]The present invention relates to water-based coating systems and methods used to form protective coatings on substrates and in particular metal containing substrates. More particularly, the present invention relates to coating compositions, methods, and coating systems involving an aqueous coating composition. These coatings are typically used as a primer coat (also referred to as a base coat) or as a direct-to-metal coat (“DTM”), wherein the aqueous coating composition preferably has a sufficiently high loading of one or more clay anti-sag agents (hereinafter “CAS agents”), and / or the coating is applied in a controlled hu...

AI Technical Summary

Benefits of technology

[0019]Increasing the levels of CAS agents beyond conventional levels for use in a humid drying environment can be counterintuitive for several reasons. For example, conventional wisdom holds that the viscosity will increase when excessive amounts of CAS agents are used to a degree such that the release of water from the composition may be inhibited and the dry time will thereby be undesirably increased. As yet another example, increasing the levels of CAS agents beyond conventional levels (e.g., above one pound of CAS agent per 100 pounds (0.12 kg of CAS agents per 100 L) of aqueous coating composition) is counterintuitive because hydrophilic clay-based materials are hygroscopic and they may further inhibit the release of water from the composition and thereby increase dry time to an undue degree.

[0020]Surprisingly, increasing the level of CAS agents beyond conventional levels prevents undue sagging in a humid environment, yet allows water to be released from the coating and does not impact dry time to an undue degree.

[0021]In addition to controlling sag resistance using specific agents or thickeners, it is possible to improve sag resistance of the primer composition using other types of thickeners or rheology agents, if the system used to apply and dry / cure the coating includes measures to control humidity. By controlling the humidity conditions in the spray booth when the coating is applied, and in the oven during drying / cure of the coating, a wet film of the coating is allowed to dry uniformly in a way that eliminates problems associated with sag caused by high humidity environments (i.e. the shear forces acting on a wet film applied to a vertically positioned substrate).

Problems solved by technology

If a conventional drying chamber is used to dry shipping containers to which a water-based paint has been applied, the paint on the container does not adequately dry in a reasonable amount of time, which increases operating costs and adversely affects the appearance of the painted container.

It is typically not cost-effective to extend the length of the drying chamber or significantly increase the air flow capacity of the system that applies the heated air to the drying chamber.

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