Hardening accelerator composition containing dispersants

Abstract

A process for the preparation of a hardening accelerator composition by reaction of a water-soluble calcium compound with a water-soluble silicate compound, said reaction being effected in the present of a water-soluble dispersant having at least one polyalkyleneglycol structural unit with a functional group at one end of the polyalkyleneglycol, being able to interact as an anchor group with the surface of cement particles, the hardening accelerator composition and its use.

We claim: 
     
         1 . A process for the preparation of a hardening accelerator composition comprising reacting a calcium compound with a silicon dioxide containing component under alkaline conditions, wherein the reaction is carried out in the presence of an aqueous solution of a water-soluble dispersant comprising at least one polyalkyleneglycol structural unit with a functional group at one end of the polyalkyleneglycol, said functional group capable of interacting as an anchor group with the surface of cement particles. 
     
     
         2 . The process according to  claim 1  wherein the calcium compound is a calcium salt. 
     
     
         3 . The process according to  claim 2  wherein the calcium salt is a water-soluble calcium salt. 
     
     
         4 . The process according to  claim 1 , wherein the molar ratio of calcium from the calcium compound to silicon from the silicon dioxide containing component is from about 0.6 to about 2. 
     
     
         5 . The process of  claim 4 , wherein the molar ratio of calcium from the calcium compound to silicon from the silicon dioxide containing component is from about 1.1 to about 1.8. 
     
     
         6 . The process according to  claim 1 , wherein the functional group being able to interact as an anchor group with the surface of cement particles comprises carboxylate radicals, phosphate radicals, phosphonate radicals, silane radicals, the silane radicals being able to react with water to a silanol compound under alkaline conditions and/or at least 3 hydroxy radicals. 
     
     
         7 . The process according to  claim 6  wherein the at least 3 hydroxy radicals are derived from a sugar compound. 
     
     
         8 . The process according to  claim 1 , wherein the functional group being able to interact as an anchor group with the surface of cement particles comprises at least 5 hydroxy radicals, at least 3 carboxylate radicals, at least 2 phosphonate radicals or at least 2 silane radicals, the silane radicals being able to react with water to a silanol compound under alkaline conditions. 
     
     
         9 . The process according to  claim 1 , wherein the functional group being able to interact as an anchor group with the surface of cement particles contains two phosphonate radicals and is represented by the following general structure (I),
   R—O-(AO) n —CH 2 CH 2 —N—[CH 2 —PO(OM) 2 ] 2   (I)
   
       wherein
 A is the same or different and independently from each other an alkylene with two to 18 carbon atoms, optionally ethylene and/or propylene, further optionally ethylene, 
 n is an integer from 5 to 500, and 
 M is H, an alkali metal, ½ earth alkali metal and/or an amine, and 
 R is H or a saturated or unsaturated hydrocarbon residue. 
 
     
     
         10 . The process according to  claim 9 , wherein n is an integer from 10 to 200. 
     
     
         11 . The process of  claim 10 , wherein n is an integer from 10 to 100. 
     
     
         12 . The process of  claim 9 , wherein R is a C1 to C15 alkyl radical. 
     
     
         13 . The process according to  1 , wherein the polyalkyleneglycol comprises at least 5 repeating units, and contains more than 80 mol-% of ethyleneglycol units, optionally more than 90 mol-% of ethyleneglycol units. 
     
     
         14 . The process of  claim 13 , wherein the polyalkyleneglycol comprises from 10 repeating units to 500 repeating units. 
     
     
         15 . The process of  claim 14 , wherein the polyalkyleneglycol comprises from 10 to 200 repeating units. 
     
     
         16 . The process according to  claim 1 , wherein at the other end of the polyalkyleneglycol structural unit, no group is present, which would be substantially able to interact as an anchor group with the surface of cement particles. 
     
     
         17 . The process according to  claim 1 , wherein the reaction is carried out completely or partially in the presence of an aqueous solution containing a viscosity enhancer polymer, comprising at least one of polysaccharide derivatives or (co)polymers with an average molecular weight M w  higher than 500,000 g/mol, the (co)polymers containing structural units derived (optionally by free radical polymerization) from non-ionic (meth)acrylamide monomer derivatives and/or sulphonic acid monomer derivatives. 
     
     
         18 . The process of  claim 17 , wherein the viscosity enhancer polymer comprises polysaccharide derivatives or (co)polymers with an average molecular weight M w  higher than 1,000,000 g/mol.