Coating agents having high scratch resistance and weathering stability

Abstract

Disclosed are coating compositions comprising (a) at least one hydroxyl-containing compound (A), (b) at least one compound (B) having isocyanate groups, and (c) at least one catalyst (D) for the crosslinking of silane groups, said catalyst (D) comprising phosphorus. It is an aspect of the disclosed coating compositions that (i) one or more constituents of the coating composition contain hydrolyzable silane groups and (ii) the coating composition can be finally cured to a coating which has statistically distributed regions of an Si—O—Si network.

1 . A coating composition based on aprotic solvents, comprising:
 (a) at least one hydroxyl-containing compound (A),   (b) at least one compound (B) having free and/or blocked isocyanate groups,   (c) at least one catalyst (D) for the crosslinking of silane groups,   where   (i) one or more constituents of the coating composition contain hydrolyzable silane groups and   (ii) the coating composition can be finally cured to a coating which has statistically distributed regions of an Si—O—Si network,   characterized in that   (iii) the catalyst (D) or the catalysts (D) is or are phosphorus-containing and   (iv) one or more constituents of the coating composition comprise between 2.5 and 97.5 mol %, based on the entirety of structural units (II) and (III), of at least one structural unit of the formula (II)
   —N(X—SiR″ x (OR′)3− x ) n (X′—SiR″ y (OR′)3 −y ) m   (II)
 
   where   R′=hydrogen, alkyl or cycloalkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably R′=ethyl and/or methyl   X,X′=linear and/or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, preferably X,X′=alkylene radical having 1 to 4 carbon atoms,   R″=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably R″=alkyl radical, in particular having 1 to 6 carbon atoms,   n=0 to 2, m=0 to 2, m+n=2, and x,y=0 to 2,   and   between 2.5 and 97.5 mol %, based on the entirety of structural units (II) and (III), of at least one structural unit of the formula (III)
   —Z—(X—SiR″ x (OR′)3 −x )  (III),
 
   where   Z=—NH—, —NR—, —O—, with   R=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl,   x=0 to 2, and   X, R′, R″ have the meaning given in formula (II).   
     
     
         2 . The coating composition according to  claim 1 , characterized in that the catalyst (D) is phosphorus- and nitrogen-containing. 
     
     
         3 . The coating composition according to  claim 1 , characterized in that the catalyst (D) or the catalysts (D) is or are selected from the group of substituted phosphonic diesters and/or diphosphonic diesters, of substituted phosphoric monoesters and/or phosphoric diesters, preferably from the group consisting of acyclic phosphoric diesters and/or cyclic phosphoric diesters, and/or the corresponding amine-blocked phosphoric esters. 
     
     
         4 . The coating composition according to  claim 2 , characterized in that the catalyst (D) is blocked with a tertiary amine. 
     
     
         5 . The coating composition according to  claim 1 , characterized in that the catalyst (D) is selected from the group of amine-blocked phosphoric acid ethylhexyl partial esters and amine-blocked phosphoric acid phenyl partial esters, more particularly amine-blocked bis(ethylhexyl) phosphate. 
     
     
         6 . The coating composition according to  claim 1 , characterized in that one or more constituents of the coating composition have at least partly one or more, identical or different structural units of the formula (I)
   —X—Si—R″ x G 3-x   (I)
   where   G=identical or different hydrolyzable groups, more particularly G=alkoxy group (O R′),   X=organic radical, more particularly linear and/or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, very preferably X=alkylene radical having 1 to 4 carbon atoms,   R″=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably R″=alkyl radical, more particularly having 1 to 6 C atoms,   x=0 to 2, preferably 0 to 1, more preferably x=0.   
     
     
         7 . The coating composition according to  claim 1 , characterized in that one or more constituents of the coating composition contain between 5 and 95 mol %, more particularly between 10 and 90 mol %, more preferably between 20 and 80 mol %, and especially between 30 and 70 mol %, based in each case on the entirety of the structural units (II) and (III), of at least one structural unit of the formula (II), and between 5 and 95 mol %, more particularly between 10 and 90 mol %, more preferably between 20 and 80 mol %, and especially between 30 and 70 mol %, based in each case on the entirety of the structural units (II) and (III), of at least one structural unit of the formula (III). 
     
     
         8 . The coating composition according to  claim 1 , characterized in that the structural elements (II) and (III) are present in fractions of 2.5 to 97.5 mol %, preferably of 5 to 95 mol %, more preferably between 10 and 90 mol %, in each case based on the sum of the functional groups critical for crosslinking in the coating composition, formed from the fractions of the hydroxyl and isocyanate groups and from the fractions of the structural elements (II) and (III). 
     
     
         9 . The coating composition according to  claim 1 , characterized in that the coating composition contains less than 6.5% by mass of Si of the structural units (I) and/or (II) and/or (III), preferably not more than 6.0% by mass of Si of the structural units (I) and/or (II) and/or (III), based in each case on the solids content of the coating composition, wherein the structural units (I) have the formula (I)
   —X—Si—R″ x G 3-x   (I)
   where   G=identical or different hydrolyzable groups, more particularly G=alkoxy group (O R′),   X=organic radical, more particularly linear and/or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, very preferably X=alkylene radical having 1 to 4 carbon atoms,   R″=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably   R″=alkyl radical, more particularly having 1 to 6 C atoms,   x=0 to 2, preferably 0 to 1, more preferably x=0.   
     
     
         10 . The coating composition according to  claim 1 , characterized in that the polyisocyanate (B) comprises the structural units (I) or (II) or (III), wherein the structural units (I) have the formula (I)
   —X—Si—R″ x G 3-x   (I)
   where   G=identical or different hydrolyzable groups, more particularly G=alkoxy group (O R′),   X=organic radical, more particularly linear and/or branched alkylene or cycloalkylene radical having 1 to 20 carbon atoms, very preferably X=alkylene radical having 1 to 4 carbon atoms,   R″=alkyl, cycloalkyl, aryl or aralkyl, it being possible for the carbon chain to be interrupted by nonadjacent oxygen, sulfur or NRa groups, with Ra=alkyl, cycloalkyl, aryl or aralkyl, preferably R″=alkyl radical, more particularly having 1 to 6 C atoms,   x=0 to 2, preferably 0 to 1, more preferably x=0.   
     
     
         11 . The coating composition according to  claim 10 , characterized in that, in the polyisocyanate (B),
 between 2.5 and 90 mol % of the isocyanate groups in the core polyisocyanate structure have undergone reaction to structural units (II) and   between 2.5 and 90 mol % of the isocyanate groups in the core polyisocyanate structure have undergone reaction to structural units (III)   and/or the total fraction of the isocyanate groups in the core polyisocyanate structure that have undergone reaction to structural units (II) and/or (III) is between 5 and 95 mol %.   
     
     
         12 . The coating composition according to  claim 10 , characterized in that the core polyisocyanate structure is selected from the group of 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and 4,4′-methylenedicyclohexyl diisocyanate, the biuret dimers of the aforementioned polyisocyanates and/or the isocyanurate trimers of the aforementioned polyisocyanates. 
     
     
         13 . The coating composition according to  claim 1 , characterized in that the polyol (A) comprises at least one poly(meth)acrylate polyol. 
     
     
         14 . A multistage coating method, characterized in that a pigmented basecoat film is applied to an uncoated or precoated substrate and thereafter a film of the coating composition according to  claim 1  is applied. 
     
     
         15 . The multistage coating method according to  claim 14 , characterized in that, following the application of the pigmented basecoat film, the applied basecoat material is first dried at temperatures from room temperature to 80° C. and, following the application of the coating composition according to any one of  claim 1 , the system is cured at temperatures from 30 to 200° C. for a time of 1 min up to 10 h. 
     
     
         16 . The method according to  claim 14 , wherein the method is a method for automotive OEM finishing and automotive refinish. 
     
     
         17 . The coating composition according to  claim 1 , wherein the coating composition is a clearcoat material for automotive OEM finishing and automotive refinish. 
     
     
         18 . The coating composition according to  claim 1 , wherein the coating composition is a transparent clearcoat material for coating transparent plastics substrates.