Process for the preparation of precipitated silica, new precipitated silicas containing zinc and their use for the reinforcement of elastomers

A process for preparing precipitated silica comprising reacting a silicate with an acidifying agent to produce a suspension of precipitated silica and, then, separating and drying the suspension to obtain the precipitated silica as a dried product, wherein the precipitation is carried out by the steps comprising:

• (i) forming an initial base stock comprising a silicate and an electrolyte, the silicate concentration (expressed as SiO.sub.2) in said initial base stock being lower than about 100 g/l and the electrolyte concentration in said initial base stock being lower than about 17 g/l,
• (ii) adding the acidifying agent to said base stock until a pH value of the reaction mixture of at least 7 is obtained, and
• (iii) adding simultaneously additional acidifying agent and silicate to said base stock in which a suspension having a solids content of not more than 24% by weight is dried, wherein said process further comprises one of the following two operations (a) or (b):
• (a) adding at least one zinc compound and then a basic agent to the base stock after stage (iii), said separation comprising a filtration to obtain a cake and disintegration of the cake, said disintegration being optionally performed in the presence of at least one aluminum compound B, or
• (b) adding simultaneously additional silicate and at least one zinc compound to the base stock after stage (iii), and said separation comprising a filtration to obtain a cake and the disintegration of the cake, the disintegration being optionally performed in the presence of at least one aluminum compound.