Akzo Nobel N.v.

Nouryon Chemicals International B.v.

Hans-Åke Baltsen

Marek T Tokarz

Jan Nordin

Thomas Christopher Greschik

Marek Tokarz

The present invention relates to a silica-based sol having a concentration of soluble silica of less than about 1000 mg SiO/l, conductivity of at least about 2.0 mS/cm and S-value below about 50%. The invention further relates to a method of producing a silica-based sol comprising subjecting an aqueous alkali metal silicate solution to electrodialysis to form an electrodialyzed sol, and acidifying the electrodialyzed sol to form an acidified sol having a pH in the range of from about 5.0 to about 10. The invention further relates to silica-based sol obtainable by the process and to the use of the silica-based sol as a flocculating agent. The invention further relates to a process for producing paper which comprises providing an aqueous suspension comprising cellulosic fibers, adding to the suspension one or more drainage and retention aids comprising a silica-based sol according to the invention, and dewatering the obtained suspension to provide a sheet or web of paper.

Silica-based sols

The present invention relates to methods of modifying cellulose fibers and of producing paper which methods include providing a pulp suspension of cellulose fibers and adding a cellulose derivative during the bleaching of the cellulose fibers in an acidic bleaching stage.

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Varberg, Sweden

Hans-Åke Baltsen