LOW SURFACE ENERGY POLYISOCYANATES AND THEIR USE IN TWO-COMPONENT COATING COMPOSITIONS

The present invention is directed to a polyisocyanate mixture i) having a monomeric diisocyanate content of less than 3% by weight, ii) having a urethane group content of more than 50 equivalent %, based on the total equivalents of urethane and allophanate groups, and iii) containing siloxane groups (calculated as SiO, MW 44) in an amount of 0.002 to 50% by weight, wherein the preceding percentages are based on the solids content of the polyisocyanate mixture and wherein the siloxane groups are incorporated by reacting a) an isocyanate group from a polyisocyanate adduct containing at least 60% by weight, based on the total weight of the polyisocyanate adduct, of a polyisocyanate adduct which is prepared from 1,6-hexamethylene diisocyanate, contains isocyanurate, iminooxadiazine dione and/or uretdione groups and has a viscosity at 25°C and 100% solids of less than 2000 mPa.s, with b) a compound containing one or more hydroxyl groups directly attached to a carbon atom and one or more siloxane groups to form urethane groups. The present invention also relates to the use of this polyisocyanate mixture, optionally in blocked form, as an isocyanate component in two- component coating compositions.