Rhodia Chimie

Fr&eacute;d&eacute;ric Amiche

Adrien Dromard

A method for preparing hollow particles comprising a dense silica shell, by precipitating active silica from an aqueous alkaline metal silicate on a core constituted in a material other than silica and by eliminating the material without destroying the silica shell. The particles are used as insulating materials; as hollow fillers for polymers, building materials, rubber, paper, paint; as absorbing agents; as toothpaste abrasives or additives; as support for the absorption and/or graining out active matter, the liberation of the active matter being effected by the destruction of the silica core by mechanical rupture or by dissolving the silica shell in a basic medium or by diffusion; as sun screening agents or sun screening agent supports or for the formulation of liquid matter in solid form.

Method for preparing hollow silica particles

The invention discloses an abrasive precipitation silica useable in toothpaste compositions, said silica having a BET specific surface ranging from 15 to 300 m,/g, a DOP oil absorption ranging from 40 to 160 ml/g, a median particle diameter of at least 10 &mgr;m, generally ranging from 12 to 30 &mgr;m, a particle cohesion factor of at least 85% about for a median particle diameter ranging from 12 to 20 &mgr;m. Method for preparing silica by reacting an alkaline metal silicate with an acidifying agent, to form a silica slurry, separating and optionally drying the recuperated silica suspension, the operation for forming the slurry being effected according to the following steps: a first step consisting in using one initial heel solution constituted of water, an electrolyte salt of the alkaline or alkaline-earth metal group and optionally of one acidobasic agent; a second step consisting in introducing the silicate and the acidifying agent, the reaction medium pH remaining constant from 4 to 7 and particularly from 5.8 to 6.7; and a third optional step, consisting in acidifying the reaction medium until a silica slurry with a pH of less than 6 and particularly of 4 is obtained. The silica is useful in toothpaste compositions. Toothpaste compositions containing the said silica are also disclosed.

Growing community of inventors

Vaucresson, France

Frédéric Amiche

Growing community of inventors

Vaucresson, France

Fr&eacute;d&eacute;ric Amiche

Frédéric Amiche