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 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.

It is provided a method for obtaining mesoporous silica particles with surface functionalisation comprising the steps of a) providing solutions of at least three precursors; wherein the pH of the mixture is adjusted to a range between 2 and 8 in a buffered system; b) Mixing the precursor solutions thereby allowing a reaction to take place at a temperature between 20 and 60° C., whereby surface functionalized mesoporous silica particles as solid reaction product are formed; c) Separating the surface functionalized mesoporous silica particles from the reaction mixture by centrifugation or filtration; d) Removing any pore structure directing agent present in the pores of the formed surface functionalized mesoporous silica particles by ultrasonication; e) followed by separation by centrifugation or filtration, washing and drying of the surface functionalized mesoporous silica particles.

It is provided a method for obtaining mesoporous silica particles with surface functionalisation comprising the steps of a) providing solutions of at least three precursors; wherein the pH of the mixture is adjusted to a range between 2 and 8 in a buffered system; b) Mixing the precursor solutions thereby allowing a reaction to take place at a temperature between 20 and 60° C., whereby surface functionalized mesoporous silica particles as solid reaction product are formed; c) Separating the surface functionalized mesoporous silica particles from the reaction mixture by centrifugation or filtration; d) Removing any pore structure directing agent present in the pores of the formed surface functionalized mesoporous silica particles by ultrasonication; e) followed by separation by centrifugation or filtration, washing and drying of the surface functionalized mesoporous silica particles.

Silica particles having a d50 median particle size of at least 6 μm, a ratio of (d90−d10)/d50 from 1.1 to 2.4, a RDA at 20 wt. % loading from 40 to 200, and a sphericity factor (S80) of at least 0.9, are disclosed, as well as methods for making these silica particles, and dentifrice compositions containing the silica particles.

The present invention pertains to a hydrous silica for rubber-reinforcing filler, having a BET specific surface area ranging from 230 to 350 m.sup.2/g; the volume average particle diameter (D50) measured by the laser diffraction method after dispersing 50 ml of a hydrous silica slurry adjusted to 4% by weight with an ultrasonic homogenizer having an output of 140 W for 10 minutes is 3.0 μm or less; and the top 10% of particles (D90) in the particle size distribution is 10.0 μm or less. This invention provides a hydrous silica capable of further improving reinforcing properties of a rubber, particularly the wear resistance by improving dispersibility of the hydrous silica in the rubber in addition to rubber reinforcing properties obtained by a high BET specific surface area.

Precipitated silicas having, a N-cetyl-N,N,N-trimethylammonium bromide (CTAB) surface area ≤115 m.sup.2/g, a dioctyl adipate (DOA) absorption ≥130 ml/(100 g), a RoTap for >300 μm of ≥86%, and a pore volume distribution of V (d5−d50)/V (d5−d100)<0.66. A method of producing the precipitated silicas.

Precipitated silicas having, a N-cetyl-N,N,N-trimethylammonium bromide (CTAB) surface area ≤115 m.sup.2/g, a dioctyl adipate (DOA) absorption ≥130 ml/(100 g), a RoTap for >300 μm of ≥86%, and a pore volume distribution of V (d5−d50)/V (d5−d100)<0.66. A method of producing the precipitated silicas.

Silica particles having a d50 median particle size from 8 to 20 μm, a sphericity factor (S.sub.80) of at least 0.9, a BET surface area from 0.1 to 8 m.sup.2/g, a total mercury intrusion pore volume from 0.35 to 0.8 cc/g, and a loss on ignition from 3 to 7 wt. %, are disclosed, as well as methods for making these silica particles, and dentifrice compositions containing the silica particles.

The invention relates to the use of carboxylic acid during the preparation of precipitated silica or a suspension of precipitated silica and to the precipitated silicas thus obtained, particularly with low water uptake, which can be used, for example, as a reinforcing filler in silicon matrices.