Allophanate group-containing polyisocyanates improved compatibility with aldimines

A polyisocyanate which

• i) contains 2 to 35% by weight of allophanate groups, based on the weight of the polyisocyanate,
• ii) has a viscosity of less than 3000 mpa.s at 25.degree. C. when measured at a solids content of 100%,
• iii) is based on the reaction product of an aliphatic polyisocyanate with
• 1) 10 to 90 mole percent of a monohydroxy compound and
• 2) 10 to 90 mole percent of a polyhydric alcohol,
• wherein the mole percentages of 1) and 2) add up to 100, and the percentages are based on the total moles of monohydroxy compounds 1) and polyhydric alcohols 2) and
• iv) contains less than 10 mole percent of urethane groups, based on the total moles of urethane groups obtained from monohydroxy compound 1) and polyhydric alcohol 2).

A polyisocyanate mixture which comprises

• A) at least 10% by weight, based on the resin solids of the polyisocyanate mixture, of a polyisocyanate which
• i) contains 2 to 35% by weight of allophanate groups, based on the weight of the polyisocyanate,
• ii) has a viscosity of less than 3000 mpa.s at 25.degree. C. when measured at a solids content of 100%,
• iii) is based on the reaction product of an aliphatic polyisocyanate with
• 1) 10 to 90 mole percent of a monohydroxy compound and
• 2) 10 to 90 mole percent of a polyhydric alcohol, wherein the mole percentages of 1) and 2) add up to 100, and the percentages are based on the total moles of monohydroxy compounds 1) and polyhydric alcohols 2) and
• iv) contains less than 10 mole percent of urethane groups, based on the total moles of urethane groups obtained from monohydroxy compound 1) and polyhydric alcohol 2), and
• B) at least 10% by weight, based on the resin solids of the polyisocyanate mixture, of a polyisocyanate adduct containing isocyanurate, uretdione, biuret and/or urethane groups other than polyisocyanate A).