Silica composite particles and method of preparing the same

Abstract

Silica composite particles in which a silica particle surface is sequentially surface-treated with a titanium compound in which an organic group is bonded to a titanium atom through an oxygen atom, and a hydrophobizing agent are provided, in which a titanium content in the silica composite particles measured using fluorescence X-ray is from 0.001% by weight to 10% by weight; a titanium content of a surface layer of the silica composite particles satisfies the following Formula (1); an average particle diameter of the silica composite particles is from 30 nm to 500 nm; and a particle size distribution index of the silica composite particles is from 1.1 to 1.5: 0.6< Y/X <1.8  (1) wherein X represents a titanium content in silica composite particles measured using fluorescence X-ray, and Y represents a titanium content of the silica composite particle surface obtained by XPS measurement.

What is claimed is: 
     
         1 . Silica composite particles in which a silica particle surface is sequentially surface-treated with a titanium compound in which an organic group is bonded to a titanium atom through an oxygen atom, and a hydrophobizing agent, wherein:
 the silica composite particles comprise a center portion and a surface layer;   a titanium content in the silica composite particles measured using fluorescence X-ray is from 0.001% by weight to 10% by weight;   a titanium content of the surface layer of the silica composite particles is larger than a titanium content of the center portion of the silica composite particles and satisfies the following Formula (1):
   0.6< Y/X< 1.8  (1)
 
 wherein in Formula (1), X represents a titanium content (% by weight) in silica composite particles measured using fluorescence X-ray, and Y represents a titanium content (atom %) of the silica composite particle surface layer obtained by XPS measurement; 
   an average particle diameter of the silica composite particles is from 30 nm to 500 nm; and   a particle size distribution index of the silica composite particles is from 1.1 to 1.35, the particle size distribution index being a square root of the value obtained by dividing an 84% diameter by a 16% diameter using a cumulative frequency distribution of a circle-equivalent diameter.   
     
     
         2 . The silica composite particles according to  claim 1 , wherein an average degree of circularity of the silica composite particles is from 0.5 to 0.85. 
     
     
         3 . The silica composite particles according to  claim 1 , wherein the organic group is an alkoxy group. 
     
     
         4 . The silica composite particles according to  claim 3 , wherein the number of carbon atoms in the alkoxy group is 8 or less. 
     
     
         5 . The silica composite particles according to  claim 1 , wherein the titanium compound in which an organic group is bonded to a titanium atom through an oxygen atom is any of tetrabutyl orthotitanate, titanium diisopropoxy bis(acetylacetonate) and titanium isopropoxy bis(ethylacetoacetate). 
     
     
         6 . The silica composite particles according to  claim 1 , wherein the hydrophobizing agent is an organosilicon compound having an alkyl group. 
     
     
         7 . The silica composite particles according to  claim 1 , wherein the hydrophobizing agent is hexamethyldisilazane. 
     
     
         8 . Silica composite particles in which a silica particle surface is sequentially surface-treated with a titanium compound in which an organic group is bonded to a titanium atom through an oxygen atom, and a hydrophobizing agent, wherein:
 the silica composite particles comprise a center portion and a surface layer;   a titanium content in the silica composite particles measured using fluorescence X-ray is from 0.1% by weight to 3% by weight;   a titanium content of the surface layer of the silica composite particles is larger than a titanium content of the center portion of the silica composite particles and satisfies the following Formula (1):
   0.6< Y/X< 1.8  (1)
 
 wherein in Formula (1), X represents a titanium content (% by weight) in silica composite particles measured using fluorescence X-ray, and Y represents a titanium content (atom %) of the silica composite particle surface layer obtained by XPS measurement; 
   an average particle diameter of the silica composite particles is from 100 nm to 250 nm; and   a particle size distribution index of the silica composite particles is from 1.25 to 1.35, the particle size distribution index being a square root of the value obtained by dividing an 84% diameter by a 16% diameter using a cumulative frequency distribution of a circle-equivalent diameter.   
     
     
         9 . The silica composite particles according to  claim 8 , wherein an average degree of circularity of the silica composite particles is from 0.6 to 0.8. 
     
     
         10 . The silica composite particles according to  claim 8 , wherein the organic group is an alkoxy group. 
     
     
         11 . The silica composite particles according to  claim 10 , wherein the number of carbon atoms in the alkoxy group is 8 or less. 
     
     
         12 . The silica composite particles according to  claim 8 , wherein the titanium compound in which an organic group is bonded to a titanium atom through an oxygen atom is any of tetrabutyl orthotitanate, titanium diisopropoxy bis(acetylacetonate) and titanium isopropoxy bis(ethylacetoacetate). 
     
     
         13 . The silica composite particles according to  claim 8 , wherein the hydrophobizing agent is an organosilicon compound having an alkyl group. 
     
     
         14 . The silica composite particles according to  claim 8 , wherein the hydrophobizing agent is hexamethyldisilazane. 
     
     
         15 . A method of preparing the silica composite particles of  claim 1 , the method comprising:
 preparing an alkali catalyst solution in which a first alkali catalyst is contained in a solvent containing alcohol;   supplying a tetraalkoxysilane and a second alkali catalyst into the alkali catalyst solution to form silica particles, the second alkali catalyst being the same as or different from the first alkali catalyst;   adding a mixed solution of alcohol and the titanium compound, in the alkali catalyst solution in which the silica particles are formed, to perform a surface-treatment of the surface of the silica particles by the titanium compound; and   performing a surface-treatment of the surface of the silica particles treated by the titanium compound, with the hydrophobizing agent.   
     
     
         16 . A method of preparing the silica composite particles of  claim 1 , the method comprising:
 preparing an alkali catalyst solution containing a first alkali catalyst at a concentration of from 0.6 mol/L to 0.85 mol/L, in a solvent containing alcohol;   supplying, into the alkali catalyst solution, tetraalkoxysilane at a supply amount of from 0.001 mol/(mol·min) to 0.01 mol/(mol·min) relative to the alcohol, a second alkali catalyst at a supply amount of from 0.1 mol to 0.4 mol, relative to per 1 mol of a total supply amount of the tetraalkoxysilane per one minute, to form silica particles, wherein the second alkali catalyst is the same as or different from the first alkali catalyst;   supplying a mixed solution of alcohol and the titanium compound, in the alkali catalyst solution in which the silica particles are formed, to perform a surface-treatment of the surface of the silica particles by the titanium compound; and   performing a surface-treatment of the surface of the silica particles treated by the titanium compound, with the hydrophobizing agent.   
     
     
         17 . The silica composite particles according to  claim 1 , wherein the titanium compound is titanium diisopropoxy bis(acetylacetonate) or titanium isopropoxy bis(ethylacetoacetate). 
     
     
         18 . The silica composite particles according to  claim 8 , wherein the titanium compound is titanium diisopropoxy bis(acetylacetonate) or titanium isopropoxy bis(ethylacetoacetate). 
     
     
         19 . A method of preparing the silica composite particles of  claim 8 , the method comprising:
 preparing an alkali catalyst solution in which a first alkali catalyst is contained in a solvent containing alcohol;   supplying a tetraalkoxysilane and a second alkali catalyst into the alkali catalyst solution to form silica particles, the second alkali catalyst being the same as or different from the first alkali catalyst;   adding a mixed solution of alcohol and the titanium compound, in the alkali catalyst solution in which the silica particles are formed, to perform a surface-treatment of the surface of the silica particles by the titanium compound; and   performing a surface-treatment of the surface of the silica particles treated by the titanium compound, with the hydrophobizing agent.   
     
     
         20 . A method of preparing the silica composite particles of  claim 8 , the method comprising:
 preparing an alkali catalyst solution containing a first alkali catalyst at a concentration of from 0.6 mol/L to 0.85 mol/L, in a solvent containing alcohol;   supplying, into the alkali catalyst solution, tetraalkoxysilane at a supply amount of from 0.001 mol/(mol·min) to 0.01 mol/(mol·min) relative to the alcohol, a second alkali catalyst at a supply amount of from 0.1 mol to 0.4 mol, relative to per 1 mol of a total supply amount of the tetraalkoxysilane per one minute, to form silica particles, wherein the second alkali catalyst is the same as or different from the first alkali catalyst;   supplying a mixed solution of alcohol and the titanium compound, in the alkali catalyst solution in which the silica particles are formed, to perform a surface-treatment of the surface of the silica particles by the titanium compound; and   performing a surface-treatment of the surface of the silica particles treated by the titanium compound, with the hydrophobizing agent.