Process for the produciton of metal oxide and metalloid oxide dispersions

Abstract

Process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m 2 /g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the following steps:—water, which is optionally adjusted to pH values of between 2 and 4 by adding acids, is circulated from a receiving vessel via a rotor/stator machine, and—metal oxide or metalloid oxide powder is introduced, using a feed device, into the shear zone between the slots in the rotor teeth and the stator slots, continuously or discontinuously and with the rotor/stator machine running, in a quantity such that a predispersion with a solids content of between 20 and 40 wt. % results, and, after all the metal oxide powder or metalloid oxide powder has been added,—the feed device closes and shearing continues in such a way that the shear rate is in the range of between 10000 and 40000 s −1 , and—then, by dilution, the predispersion is adjusted to the desired solids content of the dispersion while maintaining the dispersing conditions.

1 . A process for the production of an aqueous dispersion of pyrogenically produced metal oxide and metalloid oxide powders with a BET surface area of between 5 and 600 m 2 /g, with a metal oxide or metalloid oxide content in the dispersion of between 5 and 25 wt. %, comprising the steps: 
 water, which is optionally adjusted to pH values of between 2 and 4 by adding acids, is circulated from a receiving vessel via a rotor/stator machine, and    metal oxide or metalloid oxide powder is introduced, using a feed device, into the shear zone between the slots in the rotor teeth and the stator slots, continuously or discontinuously and with the rotor/stator machine running, in a quantity such that a predispersion with a solids content of between 20 and 40 wt. % results, and, after all the metal oxide powder or metalloid oxide powder has been added,    the feed device closes and shearing continues in such a way that the shear rate is in the range of between 10000 and 40000 s −1 , and    then, by dilution, the predispersion is adjusted to the desired solids content of the dispersion while maintaining the dispersing conditions.    
     
     
         2 . The process according to  claim 1 , wherein the metal oxide or metalloid oxide powder is a silica powder, an alumina powder, a silica powder doped with alumina or a silicon-aluminium mixed oxide powder.  
     
     
         3 . The process according to  claim 1 , wherein bases or acids are added to the dispersion and/or predispersion.  
     
     
         4 . The process according to  claim 1 , wherein cationic polymers and/or aluminium salts are added to the dispersion and/or predispersion.  
     
     
         5 . The process according to  claim 1 , wherein a surface-active substance is added to the dispersion and/or predispersion.  
     
     
         6 . The process according to  claim 1 , wherein a preservative is added to the dispersion and/or predispersion.