US 12,195,344 B2Granted

Charge-reversed silica sol

AssigneeNouryon Chemicals International B. V.

InventorAnders Törncrona

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Abstract

A process for producing a charge-reversed aqueous silica sol includes: (a) providing a slurry of an acidic cation-exchange solid in an aqueous liquid; (b) providing a starting aqueous silica sol with an alkaline pH and including a monovalent cation(s); (c) contacting the slurry with the starting sol; (d) separating the acidic cation-exchange solid from the mixture (c) to leave a decationised aqueous silica sol with an acidic pH and a reduced monovalent cation(s) content compared to the starting sol; and (e) contacting the decationised sol with a compound(s) including a modifying element(s) that can adopt a +3 or +4 oxidation state to produce a charge-reversed aqueous silica sol whose silica particles include the modifying element(s) on their surface. The S-value of the starting sol is from about 10 to about 50%, and the surface area of colloidal silica particles in the starting sol is at least about 500 m2 g−1.

Claims7

Dependent claims

A process for producing a charge-reversed aqueous silica sol comprising the steps of:

(a) providing a slurry of an acidic cation-exchange solid in an aqueous liquid;
(b) providing a starting aqueous silica sol with an alkaline pH and comprising one or more monovalent cations and colloidal silica particles;
(c) contacting the slurry of (a) and the aqueous silica sol of (b) to form a mixture;
(d) removing the acidic cation-exchange solid from the mixture resulting from (c) to leave a decationised aqueous silica sol with an acidic pH and a reduced content of monovalent cations compared to the starting aqueous silica sol;
and
(e) contacting the decationised aqueous silica sol with one or more compounds comprising one or more modifying elements that is capable of adopting a +3 or +4 oxidation state to produce a charge-reversed aqueous silica sol whose silica particles comprise the one or more modifying elements on a surface of the silica particles;
wherein the starting aqueous silica sol has an S-value of from about 10 to about 50%, and the colloidal silica particles in the starting aqueous silica sol have a surface area of at least about 500 m2g−1.

4 more elements

Dependencies are inferred from the claim text.