Novel Polyol Dispersions with End of Usable Pot-life Indicator

摘要

Decreasing Volatile Organic Compound (VOC) emissions of coatings has been a progressive effort for scientists active in the coatings industry. To this end, the industry has sought to employ a variety of innovative approaches to improve the performance of waterborne dispersions and facilitate the replacement of solvent-borne with waterborne coatings without performance penalties. However, significant challenges still remain especially in industrial coatings, which demand much higher performance. Performance in industrial coatings is strongly coupled with the presence of a thermoset network formed via a crosslinking mechanism. Ambient cure waterborne two-component coatings with poly isocyanates (PIC) provide the opportunity to create high performance thermoset coatings. An appropriate polymer design should enable waterborne technology to achieve comparable performance to that of a solventborne system at a lower hydroxyl value and VOC demand. However, formulation with waterborne polyols remains a highly sophisticated task. Introduction of water reducible PICs was the first step toward more robust formulas. An outstanding challenge is the lack of a discernible pot-life marker in waterborne systems. In this contribution we describe recent BASF efforts to address the shortcomings of waterborne 2 pack urethane coatings. We sought commercially viable routes to produce dispersions that can provide an end of pot-life indicator in the same manner as their solventborne counterparts. Joncryl OH 8314 is a newly developed acrylic polyol dispersion with 70 mg KOH/g hydroxyl value (2.1 wt% OH) and provides an end of pot-life signal via viscosity increase when formulated with a PICs. Joncryl OH 8314 allows low VOC formulations of two-pack topcoats and direct to metal (DTM) coatings with provide superior chemical resistance, good appearance, hardness, humidity and corrosion resistance.