N-methyl pyrrolidone-free polyurethane dispersions based on dimethylol propionic acid

Abstract

The present invention relates to aqueous polyurethane dispersions that are free from N-methylpyrrolidone and other solvents and wherein the polyurethanes are the reaction products of A) a mixture of 25% to 90% by weight of 1-isocyanate-3,3,5,-trimethyl-5-isocyanatomethylcyclohexane (IPDI) and 10% to 75% by weight of 4,4'-diisocyanatodicyclohexylmethane, wherein the preceding percentages are based on the weight of component A), with B) one or more polyols having average molarcular weights (Mn) of 500 to 6000, C) one or more compounds which have at least one OH- or NH-functional group and contain a carboxyl and / or carboxylate group, wherein at least 50 mol % of the acid groups, based on the total moles of acid incorporated into the polyurethane, are incorporated by dimethylolpropionic acid, D) one or more polyols and / or polyamines having average molecular weights (Mn) of below 500, and E) optionally one or more monoalcohols and / or monoamines. The present invention also relates to a process for preparing the aqueous polyurethane dispersions and to the use of the polyurethane dispersions for preparing coatings or adhesives.

Description

technical field

[0001] The invention relates to aqueous polyurethane dispersions which contain dimethylolpropionic acid as hydrophilic agent and which have been prepared without the use of N-methylpyrrolidone, and to them as highly resistant Application of the coating composition. technical background

[0002] In order to reduce the emission of organic solvents, waterborne coating compositions are increasingly being used instead of solventborne systems. An important class of waterborne coating binders are polyurethane dispersions. The advantage of polyurethane dispersions is the combination of important properties such as chemical resistance and mechanical load resistance. The use of polyurethane dispersions is advantageous especially where the coated surface is to be subjected to strong mechanical stress.

[0003] In polyurethane dispersions (PUD), the poorly soluble high-melting compound dimethylolpropionic acid (DMPA) is often used as the hydrophilic component. Howeve...