Use of comb polymers for controlling the rheology of mineral binder compositions

Abstract

A comb polymer is used for increasing the flow rate and/or reducing the viscosity of a mineral binder composition, where the comb polymer has a main chain including acid groups and there are pendent chains linked to the main chain, and where the average number-average molar mass of all of the pendent chains is from 120 to 1000 g/mol and the molar ratio of the acid groups to the side chains is in the range from 0.5 to 2.

1 . A comb polymer used for increasing the flow rate and/or for reducing the viscosity of a mineral binder composition, the comb polymer having a main chain comprising acid groups, and side chains being attached on the main chain, with the number-average molecular weight (M n ) of all side chains being 12 0-1000 g/mol, and with the molar ratio of the acid groups to the side chains being in the range of 0.5-2. 
     
     
         2 . The comb polymer as claimed in  claim 1 , wherein the side chains are bonded to the main chain via ester, ether, amide and/or imide groups. 
     
     
         3 . The comb polymer as claimed in  claim 1 , wherein the number-average molecular weight (M n ) of the side chains is in the range of 250-800 g/mol. 
     
     
         4 . The comb polymer as claimed in  claim 1 , wherein at least 50 mol % of the side chains consist of polyalkylene oxide side chains. 
     
     
         5 . The comb polymer as claimed in  claim 4 , wherein a fraction of ethylene oxide units in the polyalkylene oxide side chains, based on all alkylene oxide units present in the side chains, is more than 90 mol %. 
     
     
         6 . The comb polymer as claimed in  claim 1 , wherein the side chains have no hydrophobic groups. 
     
     
         7 . The comb polymer as claimed in  claim 1 , wherein in the comb polymer comprises or consists of the following structural subunits:
 a) a mole fractions of a structural subunit S1 of the formula (I)   
       
         
           
           
               
               
           
         
         b) b mole fractions of a structural subunit S2 of the formula (II) 
       
       
         
           
           
               
               
           
         
         c) optionally c mole fractions of a structural subunit S3 of the formula (III) 
       
       
         
           
           
               
               
           
         
         d) optionally d mole fractions of a structural subunit S4 of the formula (IV) 
       
       
         
           
           
               
               
           
         
       
       where
 R 1 , in each case independently of any other, 
 
       is —COOM, —SO 2 —OM, —O—PO(OM) 2  and/or —PO(OM) 2 ,
 R 2 , R 3 , R 5 , R 6 , R 9 , R 10 , R 13  and R 14 , in each case independently of one another, are H or an alkyl group having 1 to 5 carbon atoms, 
 R 4 , R 7 , R 11  and R 15 , in each case independently of one another, are H, —COOM or an alkyl group having 1 to 5 carbon atoms, 
 M, independently of any other, is H + , an alkali metal ion, an alkaline earth metal ion, a di- or trivalent metal ion, an ammonium ion or an organic ammonium group, 
 m is 0, 1 or 2, 
 p is 0 or 1, 
 R 8  and R 12 , in each case independently of one another, are a C 1  to C 20  alkyl, cycloalkyl or alkylaryl group or are a group of the formula -[AO] n —R a ,
 where A is C 2  to C 4  alkylene, R a  is H, a C 1  to C 20  alkyl, cyclohexyl or alkylaryl group, 
 and n is 2-250, 
 
 R 16 , independently of any other, is NH 2 , —NR b R c  or —OR d NR e R f , where R b  and R c , independently of one another, are
 a C 1  to C 20  alkyl, cycloalkyl, alkylaryl or aryl group, 
 or are a hydroxyalkyl group or are an acetoxyethyl (CH 3 —CO—O—CH 2 —CH 2 —) or a hydroxyisopropyl (HO—CH(CH 3 )—CH 2 —) or an acetoxyisopropyl (CH 3 —CO—O—CH(CH 3 )—CH 2 —) group; 
 
 or R b  and R c  together form a ring of which the nitrogen is a part, in order to construct a morpholine or imidazoline ring; 
 R d  is a C 2 -C 4  alkylene group, 
 R e  and R f  each independently of one another are a C 1  to C 20  alkyl, cycloalkyl, alkylaryl or aryl group or a hydroxyalkyl group, 
 and where a, b, c and d are mole fractions of the respective structural subunits S1, S2, S3, and S4, where 
 
       a/b/c/d=(0.1-0.9)/(0.1-0.9)/(0-0.8)/(0-0.8). 
     
     
         8 . The comb polymer as claimed in  claim 7 , wherein R 1  is COOM; R 2  and R 5 , independently of one another, are H, —CH 3  or mixtures thereof; R 3  and R 6 , independently of one another, are H or CH 3 ; and R 4  and R 7 , independently of one another, are H or COOM. 
     
     
         9 . The comb polymer as claimed in  claim 7 , wherein R 8  is -[AO] n —R a , A is C 2  alkylene, and R a  is H or a C 1  alkyl group, and where n is 2-30. 
     
     
         10 . The comb polymer as claimed in  claim 7 , wherein m is 0 and p is 1 and also R 2  and R 5  are each mixtures of 40-60 mol % H and 40-60 mol % —CH 3 . 
     
     
         11 . The comb polymer as claimed in  claim 1 , wherein the comb polymer is used with a fraction of 0.01-10 wt % based on the binder content. 
     
     
         12 . The comb polymer as claimed in  claim 1 , wherein the mineral binder composition is a mortar composition or concrete composition. 
     
     
         13 . The comb polymer as claimed in  claim 1 , wherein the mineral binder composition comprises fine-grain material. 
     
     
         14 . A self-compacting concrete comprising at least one comb polymer as described in  claim 1 . 
     
     
         15 . A molding obtainable by curing a self-compacting concrete as claimed in  claim 14  after addition of water.