| abstract |
The present invention relates to aqueous polyurethane dispersions, to processes for their preparation, to products comprising them, and to their use for coating compositions, impregnating compositions, adhesives or sealants. The aqueous polyurethane dispersion comprises a polyurethane obtained by reacting a system comprising the following components: A1) at least one polyisocyanate having an isocyanate functionality of at least 2; A2) at least two different polytetramethylene ether glycols A2a) and A2b), wherein A2a) has a number average molecular weight of up to 1500 g/mol and A2b) has a number average molecular weight of more than 1500 g/mol; and A3) at least one anionic or potentially anionic hydrophilic agent having a number average molecular weight of 32 g/mol to 400 g/mol and containing hydroxyl and carboxyl functions; B) at least one amino-functional anionic or potentially anionic hydrophilic agent; and C) at least one amino-functional compound having a number average molecular weight of 32 g/mol to 400 g/mol and containing no hydrophilic groups; wherein the ratio of the number average molecular weight of A2a) to the number average molecular weight of A2b) is from 1:9 to less than 1:1, and the weight of A3) amounts to 20% to 70% of the weight of the hydrophilic agent of the system, wherein the The hydrophilic agents are components A3 and B. |