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.

The present invention discloses glycoxy silanes as a source of silica and silica precipitated by advantageous chemical reactions preferably beginning with biogenic silica. Alkoxy COS.sub.1 are hydrolyzed in a controlled fashion to nucleate formation of nanoparticles of silica. The growth rate of the particles is controlled by various parameters such that particles of known sizes, size distributions, specific surface areas and pore sizes and size distributions are recovered.

The present invention discloses glycoxy silanes as a source of silica and silica precipitated by advantageous chemical reactions preferably beginning with biogenic silica. Alkoxy COS.sub.1 are hydrolyzed in a controlled fashion to nucleate formation of nanoparticles of silica. The growth rate of the particles is controlled by various parameters such that particles of known sizes, size distributions, specific surface areas and pore sizes and size distributions are recovered.

The invention relates to a process for producing a paste-like SiO.sub.2 composition using an SiO.sub.2 slip which allows simple intermediate storage and transport conditions without the processability of the slip to give the paste-like SiO.sub.2 composition being impaired thereby. According to the invention, it is for this purpose proposed that a homogeneous SiO.sub.2 base slip be subjected to a drying step to form a dry SiO.sub.2 composition and subsequently be processed further by means of a remoistening step to give the paste-like SiO.sub.2 composition, where the remoistening step comprises the addition of liquid to the dry SiO.sub.2 composition to form a paste-like kneadable SiO.sub.2 composition having a solids content of more than 85% by weight. The invention further relates to the use of a paste-like SiO.sub.2 composition as repair composition.

A method for producing spherical silica particles according to the present disclosure includes: a raw material silica particle preparation step of preparing a liquid dispersion of raw material silica particles from a raw material solution obtained by dissolving silicic acid in a mixed solvent of water and an organic solvent in the presence of a basic substance; and a heating step of heating the liquid dispersion or the raw material silica particles so as to remove an organic substance contained in the liquid dispersion, thereby preparing spherical silica particles. The mixed solvent has a relative permittivity of 21 or higher and 40 or lower, and a quaternary ammonium derived from the basic substance is blended in a blending ratio of 0.3 or higher and 0.8 or lower in terms of molar ratio with respect to a silicon element derived from the silicic acid.

A method for producing spherical silica particles according to the present disclosure includes: a raw material silica particle preparation step of preparing a liquid dispersion of raw material silica particles from a raw material solution obtained by dissolving silicic acid in a mixed solvent of water and an organic solvent in the presence of a basic substance; and a heating step of heating the liquid dispersion or the raw material silica particles so as to remove an organic substance contained in the liquid dispersion, thereby preparing spherical silica particles. The mixed solvent has a relative permittivity of 21 or higher and 40 or lower, and a quaternary ammonium derived from the basic substance is blended in a blending ratio of 0.3 or higher and 0.8 or lower in terms of molar ratio with respect to a silicon element derived from the silicic acid.

A precipitated silica is disclosed. Said precipitated silica has a BET surface area of 165-195 m.sup.2/g; a CTAB surface area of 160-180 m.sup.2/g; a vicinal silanol content of 14 to 21%; a geminal silanol content of 2 to 4%; a total intrusion volume of 2 to 4 mL/g; a pore volume ratio (V2/V1) of 0.45 to 0.7; and a total pore area ranging from 52 to 70 m.sup.2/g.

A precipitated silica is disclosed. Said precipitated silica has a BET surface area of 165-195 m.sup.2/g; a CTAB surface area of 160-180 m.sup.2/g; a vicinal silanol content of 14 to 21%; a geminal silanol content of 2 to 4%; a total intrusion volume of 2 to 4 mL/g; a pore volume ratio (V2/V1) of 0.45 to 0.7; and a total pore area ranging from 52 to 70 m.sup.2/g.