Patent ID: 11958980
Assignee: RHODIA OPERATIONS
Field: Macromolecular chemistry, polymers (Chemistry)
Classification: CPC C | IPC C

Claim 8:
9. A process for preparing the precipitated silica of claim 1, which comprises the steps of:
(i) providing a starting solution with a pH of between 2.0 and 5.0;
(ii) simultaneously adding a silicate and an acid to said starting solution to result in a reaction medium having a pH, such that the pH of the resulting reaction medium is maintained between 2.0 and 5.0;
(iii) stopping the addition of the acid, while continuing the addition of the silicate to the reaction medium until a pH value of the reaction medium of between 7.0 and 10.0 is obtained;
(iv) simultaneously adding the silicate and the acid to the reaction medium obtained in (iii), such that a pH value of the reaction medium is maintained between 7.0 and 10.0; and
(v) stopping the addition of the silicate while continuing the addition of the acid to the reaction medium until a pH value of the reaction medium of less than 6.0 is reached and a silica suspension is obtained;
wherein a total amount of at least one alkali metal alkyl siliconate is metered into the reaction medium in at least one of steps (i) or (ii), with the proviso that said metering of the total amount of the alkali metal alkyl siliconate into the reaction medium in at least one of steps (i) or (ii) takes place before 50% of a total amount of the silicate is added to the reaction medium.