| 摘要 |
<p>Cpsns. comprise a mixt. of polyols, and a polyisocyanate (I) chosen from aliphatic diisocyanates of formula: where R2 is lower alkyl, cycloalkyl, alkylidene or cycloalkylidene radicals, R1 and R3 are H or where R4 is alkyl, alkaryl, alkoxyaryl, aryl, aralkyl etc. The mixt. of polyols comprise 50 to 90% wt. of an -OH- modified rigid polyester (II) reacted with isocyanate and having mol. wt. 2500 to 5000 and no. of functional gps. >2.8, and 10 to 50% wt. an OH-contg. flexible polyester (III) having mol. wt. of 500 to 4,000 and having 2 functional gps. The equiv. ratio of NCO:OH is greater than 1:1 but less than 2.5:1. The coatings do not yellow, have good adhesive power and retain shine.</p> |
