Polyurethane coating cure enhancement using zirconium carbonate

Abstract

Zirconiun carbonates can initiate hardening of polyurethane coatings and decrease the coating tack-free time. The decreased tack-free times facilitate earlier application of additional polyurethane layers and earlier return of a coated article to service, and can provide improved floor finishes.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 10 / 756,119, filed Jan. 12, 2004, the disclosure of which is incorporated by reference in its entirety.TECHNICAL FIELD [0002] This invention relates to hardenable polyurethane coatings, to methods for applying polyurethane coatings and to polyurthane coated articles. BACKGROUND [0003] Polyurethane coatings are widely used for applications in which a protective overcoat or film is desired. For example, two-component or so-called “2K” polyurethanes containing a polyol or polyamine first component and a polyisocyanate second component will react when mixed to form a durable film containing polyurethane or polyurea linkages. Unfortunately, 2K polyurethane coatings can have lengthy drying times. If uncatalyzed, the coating can take hours to become tack-free and days to harden completely The hardening rate can be accelerated by adding a suitabl...

AI Technical Summary

Benefits of technology

[0008] We have found that zirconium carbonates can be used to initiate rapid hardening of multicomponent polyurethanes. The hardening effect appears to be generally as rapid as that obtained using dibutyltin dilaurate. When added in au appropriate amount, zirconium carbonates can substantially decrease the coating tack-free time without unduly shortening pot life. Zirconium carbonates can also initiate hardening of a multicomponent polyurethane coating when present in an adjacent non-polyurethane layer, whereas dibutyltin dilaurate does not appear to provide such an effect.

[0009] The present invention provides in one aspect an autohardenable polyurethane coating comprising sufficient zirconium carbonate to decrease the coating tack-free time.

[0010] In another aspect the invention provides a method for applying a polyurethane finish comprising applying to a substrate a layer of an autohardenable polyurethane coating comprising sufficient zirconium carbonate to decrease the coating tack-free time.

[0011] The invention also provides a jobsite-renewable point of use floor finish system comprising a substantially isocyanate-free undercoat, an autohardenable polyurethane topcoat and instructions for jobsite application of the undercoat to a floor and the topcoat to the undercoat, wherein the undercoat or topcoat contain sufficient zirconium carbonate to decrease the topcoat tack-free time.

[0012] The invention provides in another aspect a method for applying a jobsite-renewable finish to a floor comprising applying to the floor a multilayer coating system comprising a layer or layers of a substantially isocyanate-fcc undercoat and a layer or layers of an autohardenable polyurethane topcoat, wherein the undercoat or topcoat contain sufficient zirconium carbonate to decrease the topcoat tack-free time.

Problems solved by technology

Due to their relatively long tack-free times, multiple-component polyurethane coatings can be difficult to apply to flooring.

Following application of the polyurethane coating, the floor cannot be put into service until the hardening process has advanced sufficiently so that the floor can withstand foot traffic.

While hardening of the various layers takes place, the floor is out of service and the finish is susceptible to damage.

Catalysts such as dibutyltin dilaurate can sometimes be employed to reduce coating tack-free times, but this may also undesirably increase cost owing to dibutyltin dilaurate's relatively high price.

However, regulations may limit the use of catalysts based on tin or zinc.

Zirconium carbonates can also initiate hardening of a multicomponent polyurethane coating when present in an adjacent non-polyurethane layer, whereas dibutyltin dilaurate does not appear to provide such an effect.

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