Aqueous polysiloxane-polyurethane dispersion, its preparation and use in coatings

摘要

Aqueous polysiloxane/polyurethane dispersions, where the polyurethane is partially neutralized with bases and is a reaction product of (a) linear polydimethylsiloxanediol, linear polyol, an acid component, a low molecular component, hydrophilic ethylene oxide units, and a polyisocyanate component are new. Aqueous polysiloxane/polyurethane (PS/PUR) dispersions, of acid number 5-100 mg KOH/g solid, OH group content 0.25-6.5 wt.%, urethane group content (calculated as NH-CO-O) 2.0-25.0 wt.% relative to the PS/PUR solids, where the polyurethane is partially neutralized with bases and is a reaction product of (wt.%):(a) at least one linear polydimethylsiloxanediol of molecular weight 1500-10,000 (3-25), (b) at least one linear polyol selected from:(i) an OH group containing polycarbonate of molecular weight 400-6000, (ii) an OH group containing, polyetherpolyol of molecular weight 350-3500, (iii) an ester group containing, by hydrogenation of carboxyl groups to OH groups, alkoxylation of the carboxyl groups, or ester interchange of carboxyl groups with low molecular diols of dimer fatty acid containing polyester polyols, and (iv) OH group containing linear polyester polyols of molecular weight 500-4000, (c) at least one acid component, consisting of:(i) hydroxycarboxylic acids, (ii) amino carboxylic acids, (iii) aminosulfonic acids, and (iv) alkali salts of these acids, (d) at least one low molecular component (0-20) consisting of at least one of at least two OH and/or amino group containing compounds of molecular weight 60-300, (e) at least one hydrophilic ethylene oxide unit (5-50) with a mono or multihydric alcohol of molecular weight 350-3000, (f) at least one polyisocyanate component (5-50) consisting of at least one organic polyisocyanate of molecular weight 168-1000, where at least 50 wt.% of the polyisocyanate component is a diisocyanate of molecular weight 168-300, where the total of the wt.% amounts add up to 100 wt.%. Independent claims are included for: (1) a process for preparation of an aqueous polysiloxane/polyurethane by:preparation of an isocyanate functional prepolymer (1) from components a-c and d and g, where the NCO/OH ratio = 1.8:1 to 3.0:1, and the prepolymer thus obtained is reacted with component (d) to give an isocyanate functional polymer (II), where the NCO/OH ratio 1.2:1 to 1.6:1, and by reaction of a further polyol as component (b) and/or (d) to a final OH-group containing PS/PUR polymer, which is dispersed by addition of water in the presence of neutralization agent; (2) an aqueous coating agent, optionally containing conventional additives and aids, which as binder a combination of (A) a polyol component with (B) a crosslinking resin selected from melamine resins, optionally hydrophilically modified polyisocyanates with free isocyanate groups, where the polyol component A contains 25-100 wt.% OH groups carrying PS/PUR dispersed in water and 0-85 wt.% of other binders different from PS/PUR binder;a polyol component A containing 80-100 wt.% of OH-group containing PS/PUR dispersed in water and 0-20 wt.% of other binders different from PS/PUR.