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2K waterborne clearcoat—a competition between crosslinking and side reactions

Authors
Journal
Progress in Organic Coatings
0300-9440
Publisher
Elsevier
Publication Date
Volume
45
Identifiers
DOI: 10.1016/s0300-9440(02)00052-8
Keywords
  • Waterborne
  • Clearcoat
  • Refinish
  • Analytical Data
  • Urea
  • Urethane
Disciplines
  • Chemistry
  • Communication
  • Physics

Abstract

Abstract The combination of OH-functional polymers with di- or trifunctional polyisocyanates is widely used as crosslinking chemistry in high-performance two component clearcoats. This curing chemistry had always been limited by strong side reactions. Thus use of solvents in formulation was limited to non-OH-/NH-functional components. Some years ago Bayer came up with the strange idea to formulate 2K isocyanate waterborne paints. They carried out a lot of investigations to establish the proportion of crosslinking and side reactions. Nevertheless the formulation of two-component waterborne PUR paint remains a highly sophisticated task. This presentation shows the basic evaluation carried out and communicated by Bayer [Aqueous two-component polyurethane systems for coatings, in: Proceedings of the IUPAC Symposium, Warsaw, July 2000; Aqueous 2-Pack Polyurethane Coatings for Automotive Refinish and Transportation, Bayer Publication; Prog. Org. Coat. 40 (2000) 99] and additional experiences we have gathered in DuPont Performance Coatings [DE 19 607 672, EP 654 051, EP 654 053, EP 654 055, EP 358 979, EP 542 105, EP 578 940, EP 669 352, EP 751 179, EP 469 389, EP 456 210, etc.]. The focus of DuPont experiments is on a high-performance waterborne clearcoat system for car refinish. Especially, the demands of refinish customers have led us to focus on miscibility, sprayability and pot life issues. Kinetic as well as thermodynamic effects are discussed. Finally, a formulation is described which fulfils most of our customer needs.

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