Pyrogenically produced silicon dioxide powder

Abstract

Pyrogenically produced silicon dioxide powder in the form of aggregates of primary particles having a BET surface area of 300±25 m 2 /g, wherein the aggregates display an average surface area of 4800 to 6000 nm 2 , an average equivalent circle diameter (ECD) of 60 to 80 nm and an average circumference of 580 to 750 nm. It is produced by a pyrogenic process in which silicon tetrachloride and a maximum of up to 40 wt. % of a second silicon component comprising H 3 SiCl, H 2 SiCl 2 , HSiCl 3 , CH 3 SiCl 3 , (CH 3 ) 2 SiCl 2 , (CH 3 ) 3 SiCl and/or (n-C 3 H 7 )SiCl 3 are mixed with primary air and a combustion gas and burnt into a reaction chamber, secondary air also being introduced into the reaction chamber, and the feed materials being chosen such that an adiabatic flame temperature of 1390 to 1450° C. is obtained. It can be used as a filler.

1 . A pyrogenically produced silicon dioxide powder comprising aggregates of primary particles having a BET surface area of 300±25 m 2 /g, wherein the aggregates display an average surface area of 4800 to 6000 nm 2 , an average equivalent circle diameter (ECD) of 60 to 80 nm and an average circumference of 580 to 750 nm. 
   
   
       2 . The pyrogenically produced silicon dioxide powder according to  claim 1 , wherein the aggregates display an average surface area of 5000 to 5700 nm 2 , an average equivalent circle diameter of 65 to 75 nm and an average circumference of 600 to 720 nm. 
   
   
       3 . The pyrogenically produced silicon dioxide powder according to  claim 1 , wherein the maximum aggregate diameter is between 100 and 140 nm and the minimum aggregate diameter is between 60 and 90 nm. 
   
   
       4 . The pyrogenically produced silicon dioxide powder according to  claim 2 , wherein the maximum aggregate diameter is between 100 and 140 nm and the minimum aggregate diameter is between 60 and 90 nm. 
   
   
       5 . The pyrogenically produced silicon dioxide powder according to  claim 1 , the chloride content is less than 250 ppm. 
   
   
       6 . The pyrogenically produced silicon dioxide powder according to  claim 2 , the chloride content is less than 250 ppm. 
   
   
       7 . The pyrogenically produced silicon dioxide powder according to  claim 1 , wherein the carbon content is less than 500 ppm. 
   
   
       8 . The pyrogenically produced silicon dioxide powder according to  claim 2 , wherein the carbon content is less than 500 ppm.