Catalyst system for uretdione dispersions

Abstract

The present invention relates to a catalyst system comprising: A) at least one compound selected from azoles, oxazoles, thiazoles, benzotriazole, benzimidazole, benzoxazole and salts thereof; B) at least one acid catcher, which contains at least one epoxy group; and C) at least one catalyst containing an N,N,N′-trisubstituted amidine structure with an amidine group content of from 12.0 to 47.0 wt %, calculated as CN2 with molecular weight=40. The invention also relates to a kit which comprises the catalyst system of the present invention and an aqueous uretdione dispersion having an acid number of from 1 to 100 KOH/g and additionally at least one carboxyl group. The invention further relates to a method for producing a polyurethane layer using the catalyst system of the present invention and said uretdione dispersion, and to the obtained polyurethane layer, and to the use of the catalyst system for curing aqueous acidic uretdione dispersions and/or for the production of paints or coatings.

1 : A catalyst system comprising
 A) at least one compound selected from the group consisting of azoles, oxazoles, thiazoles, benzotriazole, benzimidazole, benzoxazole, and salts thereof;   B) at least one acid scavenger containing at least one epoxy group; and   C) at least one catalyst containing an N,N,N′-trisubstituted amidine structure and having an amidine group content of 12.0 to 47.0% by weight calculated as CN2 with molecular weight=40.   
     
     
         2 : The catalyst system as claimed in  claim 1 , wherein the at least one compound A) is selected from pyrazole, imidazole, 1,2,3-triazole, 1,2,4-triazole, benzotriazole, and salts thereof. 
     
     
         3 : The catalyst system as claimed in  claim 1 , wherein the at least one acid scavenger B) is selected from aliphatic or aromatic alcohols, diols, polyols, ethers and acids containing at least one epoxy group. 
     
     
         4 : The catalyst system as claimed in  claim 1 , wherein the at least one catalyst containing an N,N,N′-trisubstituted amidine structure and having an amidine group content of 12.0 to 47.0% by weight calculated as CN2, molecular weight=40, C) is selected from optionally substituted amidine bases bearing alkyl, aralkyl or allyl radicals, wherein the CN double bond of the amidine structure is both part of an open-chain molecule and an element of a cyclic or bicyclic system, or else may be positioned exocyclically on a ring system, or any desired mixtures of such amidines. 
     
     
         5 : The catalyst system as claimed in  claim 1 , wherein A) and B) are present in a mass ratio of 1:1 to 10:1 and/or A) and C) are present in a mass ratio of 0.5:1 to 5:1 and/or B) and C) are present in a mass ratio of 1:1 to 1:10. 
     
     
         6 : A kit comprising the catalyst system as claimed in  claim 1  and an aqueous uretdione dispersion wherein the dispersion has an acid value of 1 to 100 mg KOH/g and at least one carboxyl group. 
     
     
         7 : The kit as claimed in  claim 6 , wherein the equivalents ratio of uretdione to hydroxy groups is 0.5:1 to 1:0.5. 
     
     
         8 : A process for producing a polyurethane layer comprising the steps of
 i) providing an aqueous uretdione dispersion having an acid value of 1 to 100 mg KOH/g and having at least one carboxyl group;   ii) adding the catalyst system as claimed in  claim 1  to produce a mixture;   iii) applying the mixture obtained in ii to a substrate);   iv) drying the mixture from step iii), and   v) curing the mixture from step iv) by heating to 120° C. for up to 180 minutes.   
     
     
         9 : A polyurethane layer, obtained by the process as claimed in  claim 8 . 
     
     
         10 : In a process for curing aqueous uretdione dispersions having an acid value of 1 to 100 mg KOH/g and having at least one carboxyl group, or for producing paints or coatings the improvement comprising including the catalyst system as claimed in  claim 1 .