Aqueous uretdione group-containing compositions and method for producing same

Abstract

The invention relates to aqueous uretdione group-containing compositions comprising or consisting of (A) at least one uretdione group-containing curing agent based on aliphatic, cycloaliphatic, aliphatic and/or aromatic polyisocyanates which do not contain chemically bonded hydrophilating groups; (B) at least one polyacrylate copolymer; (C) optionally solvents; and (D) optionally auxiliary agents and additives; wherein the quantity ratio of the components (A) and (B) is measured such that the molar ratio of the NCO groups of the curing agent (A), said groups being provided in the form of uretdione, to the NCO reactive groups of the polyacrylate copolymer (B) equals 3.0:0.5 to 0.5:3.0, and A and B are provided as a physical mixture. The invention additionally relates to a method for producing a polyurethane layer using the aqueous uretdione group-containing composition according to the invention, to the polyurethane layer obtained therefrom, and to a substrate which is coated with or adhered to the polyurethane layer.

1 . An aqueous uretdione group-containing compositions comprising:
 (A) at least one uretdione group-containing curing agent based on one or more of aliphatic, cycloaliphatic, araliphatic, and aromatic polyisocyanates that contains no chemically-bonded hydrophilizing groups;   (B) at least one polyacrylate copolymer;   (C) optionally, solvents; and   (D) optionally, auxiliaries and additives;   wherein the quantitative ratio of the at least one uretdione group-containing curing agent (A) and the at least one polyacrylate copolymer (B) is such that the molar ratio of the NCO groups of the curing agent (A) present as uretdione to NCO-reactive groups of the polyacrylate copolymer (B) is 3.0:0.5 to 0.5:3.0, and wherein (A) and (B) are present as a mixture.   
     
     
         2 . The composition as claimed in  claim 1 , wherein the at least one uretdione group-containing curing agent (A) was obtained by reacting a monomeric isocyanate comprising at least one monomeric isocyanate selected from the group consisting of tetramethylene diisocyanate, cyclohexane-1,3-diisocyanate and cyclohexane-1,4-diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, dicyclohexylmethane-2,4′-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, tetramethylxylylene diisocyanate, triisocyanatononane, toluene diisocyanate, diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, triphenylmethane-4,4′-diisocyanate, naphthylene-1,5-diisocyanate, and mixtures thereof. 
     
     
         3 . The composition as claimed in  claim 1 , wherein hydroxyl-containing monomers or polymers are used as starting materials for the at least one uretdione group-containing curing agent (A). 
     
     
         4 . The composition as claimed in  claim 1 , wherein the at least one uretdione group-containing curing agent (A) has a free NCO content of less than 5% by weight and a content of uretdione groups of 1% to 18% by weight—calculated as C 2 N 2 O 2 , molecular weight 84 g/mol. 
     
     
         5 . The composition as claimed in  claim 1 , wherein the aqueous composition has an acid value of 1 to 100 mg KOH/g. 
     
     
         6 . The composition as claimed in  claim 1 , wherein the at least one polyacrylate copolymer is obtained by reacting a mixture of free-radically polymerizable monomers (M), comprising
 (M1) hydroxyl- and carboxyl-free (meth)acrylic esters having C1 to C12 hydrocarbon radicals in the alcohol moiety;   (M2) hydroxyl-functional, free-radically polymerizable monomers;   (M3) carboxyl-functional, free-radically polymerizable monomers;   (M4) optionally, vinyl esters of aliphatic carboxylic acids;   (M5) optionally, at least one cycloaliphatic ester of (meth)acrylic acid and/or vinylaromatics.   
     
     
         7 . The composition as claimed in  claim 1 , wherein the at least one polyacrylate copolymer (B) has an OH content greater than 1% by weight—calculated as OH groups based on the solids content, molecular weight 17 g/mol—and a number-average molecular weight Mn of 500 to 20 000 g/mol. 
     
     
         8 . The composition as claimed in  claim 1 , wherein the solvent is selected from the group consisting of acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, xylene, solvent naphtha, propylene glycol mono-n-butyl ether, dipropylene glycol dimethyl ether, methoxypropyl acetate, dibasic esters, and mixtures thereof. 
     
     
         9 . The composition as claimed in  claim 1 , wherein the auxiliaries and additives are selected from the group consisting of leveling agents, light stabilizers, catalysts, fillers, and pigments or mixtures thereof. 
     
     
         10 . The composition as claimed in  claim 1 , wherein the sum of the proportions by weight of (A), (B), and (D) is 30% to 60% by weight based on the solids content of the total aqueous composition. 
     
     
         11 . A process for producing a polyurethane layer comprising the steps of
 i) providing an aqueous uretdione group-containing composition as claimed in  claim 1 ;   ii) applying to a substrate the composition obtained in i) to produce a mixture;   iii) drying the mixture from step ii), and   iv) curing the mixture from step iii) by heating to from 40° C. to 180° C. for up to 180 minutes.   
     
     
         12 . The process as claimed in  claim 11 , wherein the aqueous uretdione group-containing composition was obtained by mixing the uretdione group-containing curing agent (A) with the at least one polyacrylate copolymer (B) in the absence of water to form a mixture, and subsequently dispersing the mixture with water. 
     
     
         13 . A polyurethane layer obtained by a process as claimed in  claim 11 . 
     
     
         14 . A substrate coated or bonded with the polyurethane layer as claimed in  claim 13 .