Uretdione-containing polyurethane-dispersions comprising hydrophilic groups

Abstract

The present invention relates to a specific uretdione prepolymer, and an aqueous curable composition based on the specific uretdione prepolymer. Furthermore, it pertains to a process for curing said aqueous curable composition, the cured article obtained by this process and additionally to the use of said aqueous composition for coatings, adhesives and/or sealants.

1 . A uretdione prepolymer, which comprises at least one uretdione group, and which is obtained by reacting
 A1) at least one uretdione polyisocyanate having an isocyanate functionality of at least 2.0, wherein said uretdione polyisocyanate is obtained from at least one aliphatic polyisocyanate,   with   A2) at least one polyalkoxy ether derivative comprising at least two —OH groups, which are present on two different non neighboring atoms of the molecule and wherein at least one of the —OH groups is not a terminal —OH group, and   A3) at least one reactant, which comprises at least one Zerewitinoff-active group and being different from A2 or which is H 2 O,   in the presence of at least one catalyst, to obtain the uretdione prepolymer, wherein the prepolymer has an acid number of at most 4 mg KOH/g.   
     
     
         2 . The uretdione prepolymer according to  claim 1 , wherein in a first step, the at least one uretdione polyisocyanate A1 is reacted, with the at least one polyalkoxy ether derivative A2 and in a second step the polymer obtained in the first step is reacted with the at least one reactant A3. 
     
     
         3 . The uretdione prepolymer according to  claim 1 , wherein components A1 to A3 are reacted in a one-step process. 
     
     
         4 . The uretdione prepolymer according to  claim 1 , wherein in a first step, the at least one uretdione polyisocyanate A1 is reacted with the at least one reactant A3 and in a second step the polymer obtained in the first step is reacted in a second step with the at least one polyalkoxy ether derivative A2. 
     
     
         5 . The uretdione prepolymer according to  claim 1 , where-in said uretdione prepolymer is a nonionic prepolymer. 
     
     
         6 . The uretdione prepolymer according to  claim 1 , wherein said uretdione prepolymer exhibits a zeta potential of at least −20 mV. 
     
     
         7 . The uretdione prepolymer according to  claim 1 , wherein said uretdione polyisocyanate A1 is obtained from at least one cycloaliphatic polyisocyanate. 
     
     
         8 . The uretdione prepolymer according to  claim 1 , wherein said uretdione polyisocyanate A1 is prepared from isophorone diisocyanate as the only polyisocyanate. 
     
     
         9 . The uretdione prepolymer according to  claim 1 , wherein compound A2 is selected from compounds of formula (I): 
       
         
           
           
               
               
           
         
         wherein, 
         X is H or alkyl; 
         R is a C 1-4  alkylene group; 
         p is an integer of 2 to 50; 
         in each unit p 
         n is independently 0 or 1 and 
         m is independently 0 or 1, 
         with the proviso that at least one of n or m in each unit p is 1. 
       
     
     
         10 . The uretdione prepolymer according to  claim 1 , wherein compound A3 is selected from the group consisting of at least one polyol, which is different from A2, from polyester polyols, polyether polyols, polyurethane polyols, polyacrylate polyols, polymethacrylate polyols, polycarbonate polyols, and mixtures thereof. 
     
     
         11 . An aqueous, curable composition, comprising:
 the uretdione prepolymer according to  claim 1 , and optionally, at least one compound, which comprises at least one Zerewitinoff-active group and/or   optionally, at least one azolate-compound.   
     
     
         12 . The aqueous, curable composition according to  claim 11 , wherein said uretdione prepolymer is contained in a total amount of 3 to 40 wt. %, based on the total weight of the composition. 
     
     
         13 . The aqueous, curable composition according to  claim 11 , wherein said azolate-compound is selected from the group consisting of at least one triazolate-compound of formula (III) or salts thereof and formula (IV) or salts thereof 
       
         
           
           
               
               
           
         
         wherein, 
         R 1 , R 2 , R 3  and R 4  are independently selected from a hydrogen atom, a halogen atom, a nitro group, a saturated or unsaturated, aliphatic or cycloaliphatic radical, an optionally substituted aromatic group comprising up to 20 carbon atoms and optionally, up to 3 heteroatoms selected from oxygen, sulfur, and nitrogen, an optionally substituted araliphatic group comprising up to 20 carbon atoms and optionally, up to 3 heteroatoms selected from oxygen, sulfur, and nitrogen, 
         and wherein R 3  and R 4  of formula (IV) together with the carbon atoms of the 1,2,3-triazolate five-membered ring form fused rings with 3 to 6 carbon atoms. 
       
     
     
         14 . The aqueous, curable composition according to  claim 13 , wherein said azolate-compound is selected from the group consisting of alkaline metal-1,2,4-triazolate, alkaline metal-1,2,3-triazolate, alkaline metal-benzotriazolate, alkaline earth metal-1,2,4-triazolate, alkaline earth metal-1,2,3-triazolate, and alkaline earth metal-benzotriazolate. 
     
     
         15 . The aqueous, curable composition according to  claim 11 , wherein said at least one compound, which comprises at least one Zerewitinoff-active group is selected from the group consisting of polyester polyols, polyether polyols, polyurethane polyols, polyacrylate polyols, polymethacrylate polyols, polycarbonate polyols, and mixtures thereof. 
     
     
         16 . The aqueous, curable composition according to  claim 11 , wherein said uretdione prepolymer is contained in an amount of 1 to 50 wt. % or said at least one compound, which comprises at least one Zerewitinoff-active group is contained in an amount of 0 to 80 wt.-% or said triazolate-compound is contained in an amount of 0.1 to 10 wt. %, based on the total weight of the composition, respectively. 
     
     
         17 . A process for curing a liquid composition on a substrate, comprising
 a) applying on a substrate an aqueous, curable composition according to  claim 11 ; and   a) exposing the aqueous, curable composition to a temperature of 60° C. to 160° C. to cure said composition.   
     
     
         18 . The cured article obtained by the process according to  claim 17 . 
     
     
         19 . In a process for the production of one of a coating, an adhesive and a sealant, the improvement comprising including the composition according to  claim 11 .