Metal decorating and aqueous coating composition comprising copolymer and aminoplast

Abstract

Abstract Aqueous resinous compositions having an alkaline pH for application to metal sheets and curing the same prior to shaping the metals to achieve metal decoration are disclosed. By "decorating" is meant applying synthetic resinous coatings to the metal followed by a severe mechanical forming operation such as the formation of screw-threaded bottle caps. The composition is thermosettable and comprises (A) an addition copolymer of certain monomers and (B) a water-soluble urea-formaldehyde reaction product or a water-soluble methanol or ethanol ether thereof. The copolymer contains small amounts of carboxyl and amide and/or hydroxyl functionality. The weight ratio of (A) to (B) is from 35:65 to 65:35, and the solids content is between 40 and 80 percent. The coating composition has properties which similar previously known aqueous compositions lack, an important one being that the composition may be direct-roller coated onto the substrate without fouling the coating roller with a partially dried accumulation of the coating composition. The coated panels having a wet coating may be placed directly into the curing oven without blistering, avoiding the necessity of a preliminary low temperature drying step and freedom from patterning. The proportions of functional monomers are critical as are the ratios of the addition copolymer to the urea-formaldehyde adduct. Other critical properties are the minimum film-forming temperature (MFT) of the composition which can be no higher than about 15°C. and the glass transition temperature (Tg) of the addition copolymer which must be below 0° C., preferably below -15° C.

Inventors

• 👤 Richard Martorano
• 👤 William H. Brendley, Jr.
• 👤 Thomas H. Haag

Bibliographic Details