Adhesive filled with surface-treated chalk and soot

Abstract

The invention relates to an adhesive composition containing a special silane cross-linking polymer and fine-particle coated calcium carbonate and soot. 20 to 50 ml of fine-particle coated calcium carbonate and soot are provided for every 100 g of polymer, and the volume ratio of fine-particle coated calcium carbonate and soot is between 70:30 and 30:70. The inventive adhesive composition is characterized by having good mechanical properties, a high electrical volume resistance and a good applicability.

1 . An adhesive composition comprising at least one silane-crosslinking polymer, fine-particle coated calcium carbonate, and soot, characterized in that 
 a) the at least one silane-crosslinking polyurethane polymer is constructed in accordance with the following formula (I):                          where R 1  stands for an alkyl group having 2 to 8 carbon atoms, linear or branched,    R 2  stands for an alkyl radical having 1 to 8 carbon atoms,    R 3  stands for an alkyl radical having 1 to 5 carbon atoms,    a stands for 0 or 1,    Z stands for a sulfur or an NR 4 , where R 4  stands for a hydrogen atom or an organic radical, for example, an alkyl group or an aryl group having 1 to 20 carbon atoms, or a compound having ester groups such as, for example, a moiety of the formula (II)                          where R 5  stands for an alkyl group having 1 to 8 carbon atoms,    n denotes a number from 2 to 4,    and A stands for a radical of a polyurethane prepolymer with the functionality n,    b) the fine-particle coated calcium carbonate, is a calcium carbonate coated with fatty acid, especially stearate, and having a particle size of from 0.05 to 1 micron and a density of approximately 2.6-2.7 g/ml, and    c) the soot is soot with a density of approximately 1.8 g/ml, in particular soot having a large surface area,    there being from 20 to 50 ml of fillers b)+c) per 100 g polymer a), and the volume ratio of b) to c) being between 70/30 and 30/70.    
     
     
         2 . The adhesive composition according to  claim 1 , characterized in that A stands for a polyurethane radical obtainable by reacting commercially customary polyols with an excess of commercially customary polyisocyanates, the average molecular weight of A usually being in the range from 500 to 100 000 g/mol, and A containing at least n urethane groups.  
     
     
         3 . The adhesive composition according to  claim 1  or  2 , characterized in that A denotes a radical of the formula (III)  
       
         
           
           
               
               
           
         
         where Q stands for an aromatic, aliphatic or cycloaliphatic radical which represents in particular a polyisocyanate, with special preference a commercially customary diisocyanate, following elimination of two or more isocyanate groups, and  
         P stands for a radical which represents a polyoxyalkylene-polyol or polyalkyldiene-polyol, in particular a commercially customary polyol, following elimination of at least two OH groups,  
         X denotes a radical of the formula (IV)  
         
           
             
             
                 
                 
             
           
         
         where m independently of one another denotes 0 to 5 and where  
         Q has the abovementioned definition and where  
         P 1 =P or denotes P(X) u , with the proviso that not more than one P 1  is P(X) u  and where  
         u=1 or 2, and where  
         the average molecular weight of A is preferably in the range from 500 to 100 000 g/mol,  4 . The adhesive according to one of  claims 1  to  3 , characterized in that the radical A has a funtionality n=2 and can be depicted by formula (V)  
         
           
             
             
                 
                 
             
           
         
         where Q stands for a radical which represents an aliphatic, cycloaliphatic or aromatic polyisocyanate following elimination of at least 2 isocyanate groups, in particular a dissocyanate, following elimination of both isocyanate groups, and  
         P stands for a radical which represents a polyalkyldiene- or polyoxyalkylene-polyol following elimination of at least 2 of OH groups, in particular a diol, following elimination of both OH groups, and  
         m=0 to 5.  
       
     
     
         5 . The adhesive according to one of the preceding claims, characterized in that Q is the radical which remains following elimination of 2 isocyanate groups from one of the isocyanates from the following group: 
 2,4- and 2,6-toluene diisocyanate, 4,4′- and 2,4′-diphenylmethane diisocyanate, isophorone diisocyanate, 2,2,4- and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, m- and p-tetramethylxylylene diisocyanate, the isomers of 4,4′- or 2,4′-dicyclohexylmethane diisocyanate, polymers or oligomers of these isocyanates, and mixtures of two or more of the stated isocyanates.    
     
     
         6 . The adhesive according to one of the preceding claims, characterized in that P is the radical that remains following the elimination of at least two OH groups from a polyol from the following group: 
 polyetherpolyols, which are the polymerization product of ethylene oxide, propylene oxide or butylene oxide or mixtures thereof, or hydroxy-terminated polybutadiene polymers, especially polyols having an OH functionality of from 1.8 to 3 and a molecular weight from 500 to 20 000 g/mol.    
     
     
         7 . The adhesive according to one of the preceding claims, characterized in that it further comprises one or more of the following constituents: 
 plasticizers, especially organic esters and polybutenes, solvents, further organic or inorganic fillers, such as other calcium carbonates, kaolines, aluminas, silicas, fibers, pigments, thickeners, heat stabilizers or UV stabilizers, adhesion promoters, dryers, catalysts.    
     
     
         8 . A process for preparing an adhesive α-cording to one of the preceding claims, characterized in that the at least one silane-terminated polyurethane prepolymer is prepared by reacting—in a first step—polyols with an excess of polyisocyanate to give a prepolymer having isocyanate end groups and in that these isocyanate end groups are subsequently reacted with at least one organofunctional silane containing an isocyanate-reactive group, whereupon the prepolymer thus obtained is subsequently mixed in the absence of moisture with soot dried beforehand and with fine-particle coated calcium carbonate dried beforehand.  
     
     
         9 . The process according to  claim 8 , characterized in that the organofunctional silane is a compound with the formula (VI)  
       
         
           
           
               
               
           
         
         where R 1 , R 2 , R 3  and a have a definition described above and Y stands for —SH or —NH 2  or —NHR 4 , and R 4  likewise has the definition described above, especially aminosilane containing as R 4  the following moiety  
         
           
             
             
                 
                 
             
           
         
         where R 5  stands for an alkyl group having 1 to 8 carbon atoms.  
       
     
     
         10 . The process according to  claim 8  or  9 , characterized in that the polyol- and the isocyanate are reacted at temperatures of from 50 to 100° C., using where appropriate suitable catalysts as well, the isocyanate component being employed in excess, and where this polyurethane prepolymer having isocyanate end groups is subsequently reacted with the organofunctional silanes stoichiometrically or in a slight excess.