The present invention relates to colloidal silicas having a low S-value and a high solids content, the preparation thereof, and the use thereof in the production of paper. When used in the production of paper, the colloidal silicas of the invention exhibit good retention and drainage performance so that they can be used in lower amounts compared to conventional colloidal silicas. The present invention also relates to an apparatus and a method for producing such activated colloidal silicas.

A solid composite material combining: an inorganic pigment in the form of discrete particles each comprising a colored core and a coating adapted to allow light to pass through and a matrix based on metalloid or metal oxide, said matrix being adapted to allow light to pass through.

A method of preparing silica composite particles includes preparing an alkali catalyst solution containing an alkali catalyst at a concentration of from 0.6 mol/L to 0.85 mol/L, in a solvent containing alcohol; and supplying, into the alkali catalyst solution, (i) a mixed solution of tetraalkoxysilane and an organic titanium compound in which an organic group is coupled to a titanium atom through oxygen, and (ii) an alkali catalyst. The mixed solution is supplied at a supply amount of from 0.001 mol/(mol.Math.min) to 0.01 mol/(mol.Math.min) relative to the alcohol, and the alkali catalyst is supplied at a supply amount of from 0.1 mol to 0.4 mol, relative to 1 mol of a total supply amount of the tetraalkoxysilane and the organic titanium compound supplied per one minute.

Precipitated silica having a BET specific surface area in the range of from 35-700 m.sup.2/g, a CTAB specific surface area in the range of from 30 to 400 m.sup.2/g, and a content of polycarboxylic acid and/or carboxylate groups, expressed as total carbon content, of at least 0.15 wt %

A precipitated silica having a CTAB specific surface in the range of from 50 to 300 m.sup.2/g; a BET/CTAB specific surface ratio equal to or greater than 1.3 and comprising at least one polycarboxylic acid.

The invention relates to a novel process for preparing a precipitated silica, in which: a silicate is reacted with an acidifying agent, so as to obtain a suspension of precipitated silica, said suspension of precipitated silica is filtered, so as to obtain a filter cake, said filter cake is subjected to a liquefaction operation comprising the addition of an aluminum compound, after the liquefaction operation, a drying step is performed, characterized in that at least one polycarboxylic acid is added to the filter cake, during or after the liquefaction operation.

The invention also relates to novel precipitated silicas and to uses thereof.

A solid composite material (16) combining: an inorganic pigment (10) in the form of discrete particles each comprising a colored core and a coating adapted to allow light to pass through; and a matrix (12) based on metalloid or metal oxide, said matrix being adapted to allow light to pass through.

Disclosed in certain embodiments are polymer compositions comprising a hybrid metal oxide particles and methods of preparing the same. In at least one embodiment, hybrid metal oxide particles comprise a continuous matrix of a first metal oxide having embedded therein an array of metal oxide particles comprising a second metal oxide. In at least one embodiment, the hybrid metal oxide particles are substantially non-porous.

The invention relates to a process for the preparation of a novel precipitated silica, wherein: a silicate is reacted with an acidifying agent, so as to obtain a silica suspension; said silica suspension is filtered, so as to obtain a filter cake; said filter cake is subjected to a liquefaction operation, in the absence of an aluminium compound; wherein a mixture of polycarboxylic acids is added to the filter cake, during or after the liquefaction operation. It also relates to novel precipitated silicas and to their uses.

The invention relates to a process for the preparation of a novel precipitated silica, wherein: a silicate is reacted with an acidifying agent, so as to obtain a silica suspension; said silica suspension is filtered, so as to obtain a filter cake; said filter cake is subjected to a liquefaction operation, optionally in the presence of an aluminium compound; wherein at least one polycarboxylic acid is added to the filter cake, during or after the liquefaction operation. It also relates to a novel precipitated silica and to its uses.