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Advances in Cationic Polyurethane Dispersions and Blocked Isocyanates for Waterborne Coatings

G. Robert Lomax

Abstract


Cationic polyurethane dispersions can be prepared by incorporating dihydroxyfunctional reagents such as N-methyldiethanolamine into their molecular backbone, and quaternizing the tertiary nitrogen atoms with alkylating agents or strong acids. An alternative method is to use a pre-quaternized monomer, such as N,N-bis(2-hydroxyethyl)-N,N-dimethyl quaternary ammonium methanesulphonate. This paper outlines some latest developments in cationic polyurethane dispersions (PUDs), and of associated blocked isocyanate crosslinkers/adhesion promoters. These latter materials will feature 3,5-dimethylpyrazole (DMP) as a patented, low temperature-unblocking agent. Our R&D emphasis is on optimizing the safety, health and environmental aspects of products for the formulator and end-user.

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