Fumed silanized and ground silica

Abstract

The invention relates to a hydrophobic fumed silica which is obtained by grinding a fumed silica which, as a result of silanization, has trimethylsilyl groups fixed on the surface; and to coating formulations comprising this silica.

1 . A process, comprising: grinding a fumed silica which has trimethylsilyl groups fixed on the surface thereof, thereby obtaining fumed silanized silica. 
     
     
         2 . The process according to  claim 1 , wherein the grinding comprises grinding the fumed silica with a pin mill or an air-jet mill. 
     
     
         3 . The process according to  claim 1 , wherein the fumed silanized silica has a lower grindometer value than the unground silica. 
     
     
         4 . The process according to  claim 1 , wherein the fumed silanized silica has a tamped density of from 10 to 100 g/l. 
     
     
         5 . The process according to  claim 1 , wherein the fumed silanized silica has a tamped density of from 15 to 65 g/l. 
     
     
         6 . The process according to  claim 1 , wherein the fumed silanized silica has a specific BET surface area of from 200 to 250 m 2 /g. 
     
     
         7 . The process according to  claim 1 , wherein the fumed silanized silica has a specific BET surface area of from 210 to 225 m2/g. 
     
     
         8 . The process according to  claim 1 , wherein the fumed silanized silica has a specific BET surface area of from 215 to 220 m 2 /g. 
     
     
         9 . The process according to  claim 1 , wherein the fumed silanized silica has a mean particle size of from 3.5 to 8.5 μm. 
     
     
         10 . The process according to  claim 1 , wherein the fumed silanized silica has a pH in the range of 6.5 to 8.0. 
     
     
         11 . The process according to  claim 1 , wherein the fumed silanized silica has an agglomerate strength of less than 25 mm. 
     
     
         12 . The process according to  claim 1 , wherein the fumed silanized silica has an agglomerate strength of less than 20 mm. 
     
     
         13 . A coating formulation comprising a hydrophobic fumed silica obtained by grinding a fumed silica which has trimethylsilyl groups present on the surface thereof. 
     
     
         14 . The coating formulation according to  claim 13 , wherein the ground silica the hydrophobic fumed silica has a lower grindometer value than the unground silica. 
     
     
         15 . The coating formulation according to  claim 13 , wherein the hydrophobic fumed silica has a tamped density of from 10 to 100 g/l. 
     
     
         16 . The coating formulation according to  claim 13 , wherein the hydrophobic fumed silica has a tamped density of from 15 to 65 g/l. 
     
     
         17 . The coating formulation according to  claim 13 , having, at a 20° reflectometer value of 85 to 90, a blackness value M y  of at least 280. 
     
     
         18 . The coating formulation according to  claim 13 , wherein the hydrophobic fumed silica is present in the coating formulation in an amount of from 0.5 to 15% by weight, relative to the total weight of the coating formulation. 
     
     
         19 . The coating formulation according to  claim 13 , further comprising
 5.0 to 99.5% by weight of solids of a polymer component or of a mixture of two or more physically or chemically crosslinking polymer components,   0 to 99.5% by weight of a low molecular weight component which functions as a solvent or of a mixture of such low molecular weight components, or   a combination thereof.   
     
     
         20 . The coating formulation according to  claim 13 , further comprising a binder, which is a polymer or copolymer of (meth)acrylic acid and an ester thereof, which optionally has a further functional group, with an olefinically unsaturated compound, 
     
     
         21 . The coating formulation according to  claim 20 , where the olefinically unsaturated compound comprises styrene, a polyetherpolyol, a polyesterpolyol, a polycarbonatepolyol, a polyurethanepolyol, an epoxy resin, and a fatty acid-modified alkyd resin prepared by polycondensation. 
     
     
         22 . A process, comprising: grinding a fumed silica which has trimethylsilyl groups fixed on the surface thereof, thereby obtaining a ground hydrophobic fumed silanized silica, wherein the ground hydrophobic fumed silanized silica has:
 a tamped density of from 10 to 65 g/l;   a specific BET surface area of from 210 to 225 m 2 /g; and   a grindometer value of 12 μm or less for a dispersion time of 30 minutes or a value of less than 10 μm for a dispersion time of 60 minutes.