WATER-BASED OR WATER-DILUTIVE BLOCKED POLYISOCYANATE AND ITS USE FOR FORMING VIRTUALLY LOW-THERMALLY YELLOWING TRANSPARENT POLYURETHANE COATING FILM

摘要

PROBLEM TO BE SOLVED: To obtain the subject blocked polyisocyanate exhibiting high resistance to overbaking effect and a relatively low baking temperature, and useful for water-based baking lacquers, incorporated with each specific amount of isocyanurate group, blocked isocyanurate group and hydrazide group in the molecule. SOLUTION: This blocked polyisocyanate is obtained by reaction between a polyisocyanate prepared from an isocyanurate group R1 -bearing diisocyanate, a monofunctional reversible isocyanate blocking agent, a mono- or bifunctional stabilizing component bearing 1-2 hydrazide group(s) R2 , a nonionic/hydrophilic structural component containing side chain or terminal hydrophilic mono- or bifunctional polyether chain-contg. compound, a (potential) anionic structural component containing a compound bearing isocyanate group and saltforming group, an aliphatic polyamine bearing 2-3 amino groups, and a polyhydric alcohol. bearing 2-4 OH groups. This blocked polyisocyanate contains =2wt.%, 5-11wt.% and 0.1-3wt.% of R1 , blocked isocyanate group and R2 , respectively.