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Solvent-Free and M-Pyrol-Free PUDs

SpecialChem / Jun 21, 2004

Polyurethane dispersions (PUDs) are the polymers of choice for demanding applications. These waterborne polymers are low in VOCs and can be formulated to be in compliance with most federal, state and local emission control laws. One source of the low VOC content is a small amount of cosolvent that is introduced as a processing aid and has a side benefit of coalescing the particles in the dispersion into a smooth, continuous elastomeric film. The requirements of a cosolvent are many (Table 1). M-Pyrol" [N-Methyl-2-Pyrrolidone (NMP)] has been the cosolvent of choice because it meets all the requirements. In addition, it is a good coalescent and has the ability to behave as both catalyst and surfactant1 (Figure 1). However, NMP is not a low-cost solvent. It has a strong tendency to oxidize when in contact with oxidizing reagents and/or strong acids. When subjected to a high-temperature environment (>100 deg C) for more than two hours, discoloration was often experienced. NMP is capable of dissolving or swelling a wide spectrum of protective gears in an industrial environment.

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