New pathways were explored to make aqueous polyurethane dispersions without the co-solvent nmethylpyrolidone (NMP). This includes methods to process these materials with alternate cosolvents as well as with co-solvents that can be removed from the product during processing. Chemical modifications of the polyurethane were investigated in order to use these alternative processes.
New co-solvent free polyurethane dispersions, useful as coatings for wood floors, have been developed using an alternative process. These materials have outstanding properties, are low odor, and free of NMP.
NMP has been the solvent of choice for the widely used prepolymer mixing process (PMP) for aqueous polyurethane dispersion (PUD) synthesis. This solvent reduces the prepolymer viscosity during the production steps to enabling smooth handling and dispersing of the prepolymer. This is due to the good solubilizing characteristics of NMP for organic materials and its water solubility. Furthermore NMP supports the coalescence of the dispersion particles when the dispersion is applied to a substrate.