High solids polyurethane-urea dispersions having improved storage stability

US6084051A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Harald Blum · Wachtendonk, DE
• Wieland Hovestadt · Leichlingen, DE
• Lothar Kahl · Bensberg, DE
• Douglas A. Wicks · Mount Lebanon, US

Key dates

• Filing date: May 25, 1999
• Grant date: Jul 4, 2000
• Expiry date: May 25, 2019

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C09D175/06
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

The present invention relates to aqueous polyurethane-urea dispersions having a resin solids content of at least 35 wt. % and a pH of at least 7.5 which are prepared by PA1 a) forming an isocyanate-terminated prepolymer by reacting a difunctional polyol having a molecular weight of 500 to 6000, a low molecular weight alcohol, a diisocyanate and/or triisocyanate and an isocyanate-reactive compound which has an acid group, PA1 b) neutralizing 65% to 95% of the acid groups prior to dispersing the prepolymer in water, PA1 c) dispersing the neutralized prepolymer in water, PA1 d) chain extending the isocyanate groups with water to form a polyurethane-urea, and PA1 e) after completion of the chain extending reaction adding additional neutralizing agent to provide a total amount of neutralizing agent that is sufficient to neutralize at least 115% of the acid groups of component D), wherein the polyurethane-urea contains 1.0 to 4.0%, based on resin solids, of the isolated urea groups. The present invention also relates to a process for the preparation of these polyurethane-urea dispersions and to their use in coating compositions.