The present invention related to a hollow silica particle including: a shell layer containing silica; and a space formed inside the shell layer, in which the hollow silica particle has a particle density as measured by a dry pycnometer density measurement using helium gas of 2.00 g/cm.sup.3 or more and a particle density as measured by a dry pycnometer density measurement using oxygen gas of lower than 2.00 g/cm.sup.3.

A method for manufacturing a diatomaceous earth functional filler product with detectable or non-detectable crystalline silica includes the steps of: selecting a diatomaceous earth ore; simultaneously milling and flash-drying the diatomaceous earth ore; beneficiating the milled and flash-dried diamtomaceous earth ore; blending the beneficiated diatomaceous earth ore with a fluxing agent; calcining the blended diatomaceous earth ore and fluxing agent to produce an initial diatomaceous earth powder; air-classifying the initial diatomaceous earth powder to produce a first fraction including the diatomaceous earth functional filler product and a second fraction including coarse particles; further milling the coarse particles to produce additional diatomaceous earth powder; and re-circulating the additional diatomaceous earth powder to blend the additional diatomaceous earth powder with the initial diatomaceous earth powder.

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.

In order to provide a filler composition for fabricating a high-performance filler achieving good productivity while preventing worsening of a working environment and production of a VOC and to provide a filler and a method for producing the filler, a filler composition of the present invention contains wet silica, a polyoxyethylene unsaturated fatty acid ester, and a sulfur-containing silane coupling agent.

Improved silica based matting agents are disclosed. The matting agents are useful in waterborne coatings composition to provide exceptional properties to a wood based substrate. Films resulting on the coated substrate unexpectedly provide improved chemical resistance, thermal stress resistance, weather resistance, and/or film clarity to the surface of a wood substrate. Methods of making and using the matting agents are also disclosed.

Spherically-shaped silica can include a precipitated silica powder having a d.sub.50 particle size selected within a range of greater than 20 m and up to 80 m, a di-octyl adipate oil absorption selected within a range of from 150 ml/100 g to 500 ml/100 g, an average circularity selected within a range of from 0.70 to 1.0, and an angle of repose, of less than 30. A process of preparing spherically-shaped silica powder is also included.

Process for producing fumed silica powder with a decreased silanol group density, comprising subjecting a fumed surface untreated silica powder with a silanol density d.sub.SiOH of at least 1.2 SiOH/nm.sup.2 and a particle size d.sub.90 of not more than 10 ?m, to thermal treatment at a temperature of 350? C. to 1250? C. for 5 min to 5 h, wherein the temperature and the duration of the thermal treatment are chosen so that d.sub.SiOH of the silica is decreased by 10%-70% relative to d.sub.SiOH of the employed thermally untreated silica, wherein the thermal treatment is carried out while the fumed silica powder is in motion, followed by optional surface treatment. Surface unmodified and modified fumed silica powders obtained by this process and the use thereof.

The present invention relates to a spherical silica powder, having a median diameter d50 of 0.5 ?m to 20 ?m, and a product A?d50, which is a product of a specific surface area A (m.sup.2/g) and the median diameter d50 (?m), of 2.7 ?m.Math.m.sup.2/g to 5.0 ?m.Math.m.sup.2/g. The spherical silica powder may have a dielectric loss tangent of 0.0020 or less at a frequency of 1 GHz.

Improved silica based matting agents are disclosed. The matting agents are useful in waterborne coatings composition to provide exceptional properties to a wood based substrate. Films resulting on the coated substrate unexpectedly provide improved chemical resistance, thermal stress resistance, weather resistance, and/or film clarity to the surface of a wood substrate. Methods of making and using the matting agents are also disclosed.

The present invention relates to a method of preparing a high hydrophobic silica aerogel having a low tap density and a hydrophobic silica aerogel prepared thereby. The method of preparing a hydrophobic silica aerogel according to the present invention may have good productivity and economic efficiency, because preparation time is reduced by simultaneously performing surface modification and solvent substitution in a single step, and may control a degree of hydrophobicity of the prepared silica aerogel by controlling a surface modification reaction by including a step of adding ammonium hydroxide. Thus, a hydrophobic silica aerogel having excellent physical properties, such as tap density and specific surface area, as well as high hydrophobicity obtained by controlling the degree of hydrophobicity may be prepared.