Granulated silica and method for manufacturing the same

Abstract

The present invention provides granulated silica including water-granulated silica powders, each of the silica powders having a primary particle size of 5 to 50 nm and a surface hydrophobized with a silicon atom-containing hydrophobizing agent; the granulated silica having a degree of hydrophobization of 40 or more and a loose bulk density of 150 g/L or more. This provides granulated silica that is excellent in handleability and has good dispersibility.

1 . Granulated silica comprising water-granulated silica powders,
 each of the silica powders having:
 a primary particle size of 5 to 50 nm, and 
 a surface hydrophobized with a silicon atom-containing hydrophobizing agent; 
   the granulated silica having a degree of hydrophobization of 40 or more and a loose bulk density of 150 g/L or more.   
     
     
         2 . The granulated silica according to  claim 1 , wherein the silica powders are powders of wet silica or dry silica. 
     
     
         3 . The granulated silica according to  claim 1 , wherein the silicon atom-containing hydrophobizing agent is at least one member selected from organosilazane compounds, polysilazane compounds, organosilane compounds, and organopolysiloxanes. 
     
     
         4 . The granulated silica according to  claim 2 , wherein the silicon atom-containing hydrophobizing agent is at least one member selected from organosilazane compounds, polysilazane compounds, organosilane compounds, and organopolysiloxanes. 
     
     
         5 . The granulated silica according to  claim 1 , wherein the granulated silica is configured to form a cured material having a total luminous transmittance of 60% or more, the cured material having a thickness of 6 mm and being obtained by curing a resin composition containing the granulated silica. 
     
     
         6 . The granulated silica according to  claim 1 , wherein the granulated silica is configured to form a cured material having a haze value of 40% or less, the cured material having a thickness of 6 mm and being obtained by curing a resin composition containing the granulated silica. 
     
     
         7 . A method for manufacturing granulated silica, comprising:
 a granulation step of granulating silica powders each having a primary particle size of 5 to 50 nm by use of water, and   hydrophobizing each surface of the silica powders with a silicon atom-containing hydrophobizing agent before or simultaneously with the granulation step.   
     
     
         8 . The method for manufacturing granulated silica according to  claim 7 , wherein the silica powders are powders of wet silica or dry silica. 
     
     
         9 . The method for manufacturing granulated silica according to  claim 7 , wherein the silicon atom-containing hydrophobizing agent is at least one member selected from organosilazane compounds, polysilazane compounds, organosilane compounds, and organopolysiloxanes. 
     
     
         10 . The method for manufacturing granulated silica according to  claim 8 , wherein the silicon atom-containing hydrophobizing agent is at least one member selected from organosilazane compounds, polysilazane compounds, organosilane compounds, and organopolysiloxanes. 
     
     
         11 . The method for manufacturing granulated silica according to  claim 7 , wherein the granulation step is performed by use of an agitating granulator. 
     
     
         12 . The method for manufacturing granulated silica according to  claim 7 , further comprising a drying step of removing water used for the granulating after the granulation step. 
     
     
         13 . The method for manufacturing granulated silica according to  claim 8 , further comprising a drying step of removing water used for the granulating after the granulation step. 
     
     
         14 . The method for manufacturing granulated silica according to  claim 9 , further comprising a drying step of removing water used for the granulating after the granulation step. 
     
     
         15 . The method for manufacturing granulated silica according to  claim 11 , further comprising a drying step of removing water used for the granulating after the granulation step. 
     
     
         16 . The method for manufacturing granulated silica according to  claim 12 , further comprising a heat treatment step of heating the granulated silica at a temperature of 150 to 300° C. after the drying step.