A silica-based particle dispersion including a silica-based particle group and a high polishing rate and high surface precision is achieved to a silica-based substrate or a NiP-plated substrate to be polished or the like. A silica-based particle dispersion containing a group including irregularly-shaped and non-irregularly-shaped silica-based particles, wherein the irregularly-shaped silica-based particles each have a plurality of small holes thereinside and a covering silica layer which covers the core, and the silica-based particle group satisfies [1]-[3]. [1] Having an average particle size (D.sub.1) of 100-600 nm, and a particle size (D.sub.2) of 30-300 nm in terms of specific surface area. [2] An irregular-shape degree D (D=D.sub.1/D.sub.3) represented by the average particle size (D.sub.1) and a projected area-equivalent particle size (D.sub.3) being in the range of 1.1-5.0. [3] When waveform separation is performed on a volume-reference particle size distribution, a multi-peak distribution in which three or more peaks are detected.

A porous silica particle with the small specific surface area and large pore volume, which is contained as the scrubbing agent in the cleansing cosmetics is provided. The porous silica particle has high collapsibility, and therefore the damage of the skin can be prevented. A porous silica particle according to the present invention has: an average circularity of 0.1 to 0.5; a pore volume of 0.1≦Pv<1.0 ml/g; a specific surface area of 5 to 60 m.sup.2/cm.sup.3; a median size of 100 to 1000 μm; a ratio of a maximum particle diameter to the median size, of 3.0 or less; and a median size of 5 to 40 μm and a maximum particle diameter of 15 to 200 μm, after rubbing for 30 seconds with a load of 1.0 to 1.4 KPa.

A process of preparing precipitated silica is disclosed. Said process comprises of reacting an aqueous solution of a metal silicate with a mineral acid in the presence of a surfactant solution comprising gelatin and C8-C20 sulfosuccinate blend, at a reaction temperature in a range of about 70 to 100° C. with constant stirring such that a reaction mixture having a pH of about 10.Math.0.3 is obtained; optionally, allowing the reaction mixture to age at a temperature in a range of about 70 to 100° C. for a time period in range of 10 to 100 minutes; adjusting the pH of the reaction mixture to about 4, followed by aging said mixture at a temperature in a range of about 70 to 100° C. for a time period in a range of 10 minutes to 2 hours; and recovering the precipitated silica from the reaction mixture.

A process of preparing precipitated silica is disclosed. Said process comprises of reacting an aqueous solution of a metal silicate with a mineral acid in the presence of a surfactant solution comprising gelatin and C8-C20 sulfosuccinate blend, at a reaction temperature in a range of about 70 to 100° C. with constant stirring such that a reaction mixture having a pH of about 10.Math.0.3 is obtained; optionally, allowing the reaction mixture to age at a temperature in a range of about 70 to 100° C. for a time period in range of 10 to 100 minutes; adjusting the pH of the reaction mixture to about 4, followed by aging said mixture at a temperature in a range of about 70 to 100° C. for a time period in a range of 10 minutes to 2 hours; and recovering the precipitated silica from the reaction mixture.

The present invention provides highly dispersible precipitated silica having improved structure and properties for use as reinforcing filler in elastomeric compositions and method of preparation thereof. The present invention further provides an alkaline silicate solution having reduced dielectric constant by digesting biogenic silica source with alkaline solution such that soluble organic compounds present in the biogenic silica source leach into the alkaline silicate solution. The alkaline silicate solution obtained as above is then acidified with a mineral acid under particular conditions of pH, temperature, time etc. to obtain the highly dispersible precipitated silica of the present invention.

The present invention provides highly dispersible precipitated silica having improved structure and properties for use as reinforcing filler in elastomeric compositions and method of preparation thereof. The present invention further provides an alkaline silicate solution having reduced dielectric constant by digesting biogenic silica source with alkaline solution such that soluble organic compounds present in the biogenic silica source leach into the alkaline silicate solution. The alkaline silicate solution obtained as above is then acidified with a mineral acid under particular conditions of pH, temperature, time etc. to obtain the highly dispersible precipitated silica of the present invention.

A precipitated silica having an SiOH.sub.isolated absorbance ratio of greater than or equal to 1.5, a silanol group density of 1 to 3.0 SiOH/nm.sup.2, a modified tapped density of 1 to 50 g/l, and a pH of 3-5, when measured as a aqueous suspension of 5.00 g of the precipitated silica in 100 ml. of deionized water allows preparation of storage-stable RTV-1 silicone rubber formulations without stabilizer. A process for preparing the precipitated silica and its use in thickening sealants is provided.

A precipitated silica having an SiOH.sub.isolated absorbance ratio of greater than or equal to 1.5, a silanol group density of 1 to 3.0 SiOH/nm.sup.2, a modified tapped density of 1 to 50 g/l, and a pH of 3-5, when measured as a aqueous suspension of 5.00 g of the precipitated silica in 100 ml. of deionized water allows preparation of storage-stable RTV-1 silicone rubber formulations without stabilizer. A process for preparing the precipitated silica and its use in thickening sealants is provided.

The invention relates to a novel method of preparing silicas and to highly-structured silicas having the following characteristics: a specific surface area CTAB (S.sub.CTAB) of between 40 and 525 m.sup.2/g; a specific surface area BET (S.sub.BET) of between 45 and 550 m.sup.2/g; an object size distribution width Ld ((d84−D16)/d50), which is measured by XDC particle size analysis after deagglomeration with ultrasound, of at least 0.91; and a pore-size distribution such that ratio V(d5−d50)/V(d5−d100) is at least 0.66. The invention also relates to the use of said silicas as polymer reinforcing fillers.

The invention relates to a novel method of preparing silicas and to highly-structured silicas having the following characteristics: a specific surface area CTAB (S.sub.CTAB) of between 40 and 525 m.sup.2/g; a specific surface area BET (S.sub.BET) of between 45 and 550 m.sup.2/g; an object size distribution width Ld ((d84−D16)/d50), which is measured by XDC particle size analysis after deagglomeration with ultrasound, of at least 0.91; and a pore-size distribution such that ratio V(d5−d50)/V(d5−d100) is at least 0.66. The invention also relates to the use of said silicas as polymer reinforcing fillers.