Polyurethane aq dispersion - with excellent film forming props

摘要

The dispersion is prepd. by reacting a polyhydroyl cpd. A of e.g. wt. 250 - 2500 and contg. >2 functional gps., an NCO-gp-blocking cpd. B and an org. diisocyanate C in e.g. ratios satisfying the conditions: 0.5 = nB/(m-2)A =1.5 and 1.5 = C/A =2/3. The obtd. prepolymer is then emulsified and further reacted with a chain extender. Used in coating compsn. for leather, plastics, wood, metals etc. The film has good chemical and mechanical resistance and is easily thermally hardened.