Polyester Prepolymers

Abstract

The invention relates to prepolymers containing alkoxysilane groups based on special, low-viscosity polyester polyols, which exhibit particularly high tensile strength, a process for the production thereof and their use as a binder for adhesives, primers or coatings.

1 . Alkoxysilane group-containing polyurethanes of the general formula (I), 
     
       
         
         
             
             
         
       
       in which 
       PIC is a residue of a diisocyanate reduced by the isocyanate groups, 
       PES is a residue of a polyester polyol with 2-3 OH groups, reduced by the OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol, 
       a=0 or 1, 
       b=0 to 5, 
       c=1 or 2, 
       X represents the same or different alkoxy or alkyl residues, which may also be bridged, provided that at least one alkoxy residue is present on each Si atom, 
       Q is a difunctional, linear or branched, aliphatic residue, 
       R denotes either hydrogen or any organic residue which can be bridged with R1 (if present), R always denoting hydrogen when a=0, and 
       R1 denotes either hydrogen or an organic residue which is bridged with R. 
     
   
   
       2 . Alkoxysilane group-containing polyurethanes according to  claim 1 , wherein a=0. 
   
   
       3 . Alkoxysilane group-containing polyurethanes according to  claim 1 , wherein a=1. 
   
   
       4 . Alkoxysilane group-containing polyurethanes according to  claim 3 , wherein R and R1 are bridged as a hydantoin ring. 
   
   
       5 . Alkoxysilane group-containing polyurethanes according to  claim 1 , wherein b=0. 
   
   
       6 . Alkoxysilane group-containing polyurethanes according to  claim 2 , wherein b=0. 
   
   
       7 . Alkoxysilane group-containing polyurethanes according to  claim 3 , wherein b=0. 
   
   
       8 . Alkoxysilane group-containing polyurethanes according to  claim 4 , wherein b=0. 
   
   
       9 . A process for the production of polyurethanes modified with alkoxysilane groups, comprising either
 A) a polyester polyol with 2-3 OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol, is first reacted with an excess of diisocyanate to form an isocyanate-functional polyurethane prepolymer, which is then capped with an aminosilane, or   B) a polyester polyol with 2-3 OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol, is optionally first reacted with a deficiency of diisocyanate to form an OH-functional polyurethane prepolymer and then the OH groups of this prepolymer and/or polyester are capped with an isocyanate-functional alkoxysilane.   
   
   
       10 . The process for the production of polyurethanes modified with alkoxysilane groups according to  claim 9  A), wherein the aminosilane has the general formula (II), 
     
       
         
         
             
             
         
       
       wherein X signifies the same or different alkoxy or alkyl residues, which may also be bridged, provided that one alkoxy residue is present on each Si atom,
 Q is a difunctional, linear or branched aliphatic residue and Z denotes an aliphatic C1-C12 alkoxy residue. 
 
     
   
   
       11 . The process for the production of polyurethanes modified with alkoxysilane groups according to  claim 10 , further comprising cyclocondensation to form a hydantoin. 
   
   
       12 . An adhesive, coating or primer which comprising at least one alkoxysilane group-containing polyurethane according to  claim 1 .