Dimer fatty acid/polyesterdiol reaction product and use thereof in coating materials

Abstract

The present invention relates to a dimer fatty acid/polyesterdiol reaction product which is preparable by reacting (a) dimer fatty acids with (b) at least one polyesterdiol of the general structural formula (I) where R is a divalent radical comprising 2 to 10 carbon atoms, R 1 and R 2 independently of one another are straight-chain or branched alkylene radicals having 2 to 10 carbon atoms, X and Y independently of one another are O, S or NR 3 , in which R 3 is hydrogen or an alkyl radical having 1 to 6 carbon atoms, and m and n are selected accordingly such that the polyesterdiol possesses a number-average molecular weight of 450 to 2200 g/mol, where components (a) and (b) are used in a molar ratio of 0.7/2.3 to 1.3/1.7 and the resulting dimer fatty acid/polyesterdiol reaction product possesses a number-average molecular weight of 1500 to 5000 g/mol and an acid number <10 mg KOH/g. The invention further relates to a pigmented aqueous basecoat material which comprises this dimer fatty acid/polyesterdiol reaction product, and also to the use of said dimer fatty acid/polyesterdiol reaction product in pigmented aqueous basecoat materials. It relates, further, to a method for producing multicoat paint systems, and also to the multicoat paint systems producible by means of said method. The present invention relates, furthermore, to the refinishing of defects on multicoat paint systems.

1 . A dimer fatty acid/polyesterdiol reaction product preparable by reacting
 (a) dimer fatty acids with   (b) at least one polyesterdiol of the general structural formula (I)   
       
         
           
           
               
               
           
         
         where 
         R is a divalent organic radical comprising 2 to 10 carbon atoms, 
         R 1  and R 2  independently of one another are straight-chain or branched alkylene radicals having 2 to 10 carbon atoms, 
         X and Y independently of one another are O, S or NR 3 , in which R 3  is hydrogen or an alkyl radical having 1 to 6 carbon atoms, and 
         m and n are selected accordingly such that the polyesterdiol possesses a number-average molecular weight of 450 to 2200 g/mol, 
         where components (a) and (b) are used in a molar ratio of 0.7/2.3 to 1.3/1.7 and the resulting dimer fatty acid/polyesterdiol reaction product possesses a number-average molecular weight of 1500 to 5000 g/mol and an acid number <10 mg KOH/g. 
       
     
     
         2 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , wherein the dimer fatty acids consist of at least 90 wt % of dimeric molecules, less than 5 wt % of trimeric molecules, and less than 5 wt % of monomeric molecules and of other byproducts. 
     
     
         3 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , wherein the dimer fatty acids are prepared from linolenic, linoleic and/or oleic acid and consist of ≧98 wt % of dimeric molecules, ≦1.5 wt % of trimeric molecules, and ≦0.5 wt % of monomeric molecules and of other byproducts. 
     
     
         4 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , wherein
 R is a divalent aliphatic radical comprising 2 to 6 carbon atoms,   R 1  and R 2  independently of one another are straight-chain or branched alkylene radicals having 5 and/or 6 carbon atoms,   X and Y independently of one another are O or NH, and   m and n are selected accordingly such that the polyesterdiol possesses a number-average molecular weight of 500 to 1400 g/mol.   
     
     
         5 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , wherein components (a) and (b) are used in a molar ratio of 0.9/2.1 to 1.1/1.9. 
     
     
         6 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , which possesses a number-average molecular weight of 1200 to 4000 g/mol. 
     
     
         7 . The dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 , which possesses an acid number of <5 mg KOH/g. 
     
     
         8 . A pigmented aqueous basecoat material which comprises at least one dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1 . 
     
     
         9 . The pigmented aqueous basecoat material as claimed in  claim 8 , wherein the sum total of the weight-percentage fractions of all dimer fatty acid/polyesterdiol reaction products, based on the total weight of the pigmented aqueous basecoat material, is 0.1 to 30 wt %. 
     
     
         10 . The pigmented aqueous basecoat material as claimed in  claim 8 , which comprises as further binder at least one polyurethane resin. 
     
     
         11 . A method for improving adhesion comprising incorporating the dimer fatty acid/polyesterdiol reaction product as claimed in  claim 1  into a pigmented aqueous basecoat material. 
     
     
         12 . A method for producing a multiple-coat paint system, where
 (1) a pigmented aqueous basecoat material is applied to a substrate,   (2) a polymer film is formed from the coating material applied in stage (1),   (3) a clearcoat material is applied to the resulting basecoat film, and subsequently   (4) the basecoat film is cured together with the clearcoat film,   
       wherein a pigmented aqueous basecoat material as claimed in  claim 8  is used in stage (1). 
     
     
         13 . The method as claimed in  claim 12 , wherein said substrate from stage (1) is a multicoat paint system which possesses defects. 
     
     
         14 . A multicoat paint system producible by the method as claimed in  claim 12 . 
     
     
         15 . A multicoat paint system producible by the method as claimed in  claim 13 .