Aqueous Polyurethane Dispersions

摘要

Aqueous polyurethane (PUR) dispersions containing PUR with an OH functionality of 2-6 and a mol. wt. (Mn) of less than 15000, derived from a mixture of polyol, low-mol. wt. diol and ionic group-containing diol in a special mol ratio, plus aliphatic polyisocyanate in a special OH/NCO mol ratio, NCO-reactive amine, water and optionally mono-alcohol. Aqueous polyurethane dispersions containing PUR derived from (a) polyol(s) with a number-average mol. wt. (Mn) of 500-6000, preferably 1000-4000, most preferably 1500-3000, (b) polyol(s), preferably diol(s) with a mol. wt. of less than 500, preferably 61-499, (c) aliphatic polyisocyanate(s), preferably di-isocyanate(s), (d) diol(s) with a mol. wt. of less than 450 containing one or more ionic and/or potentially ionic groups, preferably carboxylic acid or carboxylate group(s), (e) NCO-reactive amine(s) containing 1-6 hydroxyl groups, (f) water and optionally (g) a mono-alcohol. In these compositions the mol ratio of (a):(b + d) = (1:1.5)-(1:4), preferably (1:2)-(1:3) and the mol ratio of (a + b + d):(c) = (1:1.1)-(1:2.5), preferably (1:1.2)-(1:1.7), while the PUR shows an OH functionality of 2-6, preferably 2-4, and an Mn of less than 15000, preferably 2500-10000, most preferably 3000-7000. Independent claims are also included for:- (1) a process for the production of PUR dispersions by reacting components (a), (b), (c), (d) and optionally (g) to an NCO prepolymer and then reacting this with component (e) and water (f) to give a PUR with an OH functionality of 2-6; (2) aqueous PUR systems containing (A) aqueous PUR dispersion(s) as described and (B) water-dispersible aliphatic or cycloaliphatic polyisocyanate(s) with an NCO functionality of at least 2, preferably 2-6, most preferably 2.3-4, in which the ratio of (OH groups in A):(NCO in B) = (1:1)-(1:4), preferably (1:1.2)-(1:3); (3) substrates coated with these PUR systems, especially wood, metal, textiles, paper, plastic and leather; and (4) a process for coating substrates with these aqueous PUR systems.