Akzo Nobel N.v.

Akzo Nobel Chemicals International B.v.

Swegon Operations Ab

Akzo Nobel Pulp and Performance Chemicals Ab

Freddie Hansson

Marek T Tokarz

Michael Persson

Joakim Carlén

Erik Sanne

Glenn Mankin

Annika Viola Pal

Lars Lindahl

Joakim Carlen

Marek Tokarz

The present invention relates to a silica sol having a pH above about 10, molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, concentration of soluble silica above about 3000 mg SiO2/l, and S-value of from about 18 to about 40%. The invention further relates to a process for producing a silica sol which comprises acidifying an aqueous alkali metal silicate solution to a pH of from 1 to 4 to form an acid sol, alkalizing the acid sol by addition of aqueous alkali metal silicate solution to obtain an intermediate sol and interrupt the addition of aqueous alkali metal silicate solution when the intermediate sol has reached a pH of from about 5 to about 8, stirring the intermediate sol for a time period of from about 10 to about 6000 seconds without addition of aqueous alkali metal silicate solution, alkalizing the intermediate sol by addition of aqueous alkali metal silicate solution to obtain a silica sol having a pH above about 10 and molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, and optionally adding an aluminum compound to the acid sol, intermediate sol or silica sol. The invention further relates to a silica sol obtainable by the process of the invention. The invention further relates to the use of the silica sol as a flocculating agent, in water purification and in producing paper and board. The invention further relates to a process for producing paper and board which comprises: (i) providing an aqueous suspension comprising cellulosic fibers; (ii) adding to the suspension one or more drainage and retention aids comprising the silica sol; and (iii) dewatering the obtained suspension to provide a sheet or web of paper or board.

Silica sol

The invention relates to a sol containing silica-based particles having an axial ratio of at least about 10 and specific surface area of at least about 600 m2/g. The invention further relates to a sol containing silica-based particles having an axial ratio of at least about 10 and S-value up to about 25. The invention further relates to a sol containing silica-based particles having an axial ratio of at least about 10 and a specific surface area of at least about 400 m2/g, wherein the silica-based particles are surface-modified. The invention further relates to a sol containing silica-based particles having a viscosity of at least 50 cP and silica content of at least about 3% by weight, wherein the silica-based particles have a specific surface area of at least about 400 m2/g. The invention further relates to a process for producing the aqueous silica-based sol according to the invention, a sol containing silica-based particles obtainable by the process, use of the sol containing silica-based particles as a flocculating agent. The invention further relates to a process for producing paper in which the sol containing silica-based particles is used as a drainage and retention aid.

Silica-based sols

The invention relates to a process for producing aqueous silica-based sols which comprises providing a cationic ion exchange resin having at least part of its ion exchange capacity in hydrogen form; bringing said ion exchange resin in contact with an aqueous alkali metal silicate to form an aqueous slurry; adjusting the pH of the aqueous slurry and separating the ion exchange resin from the aqueous slurry, as well as the silica-based sols obtained by the process; the invention also relates to silica-based sols obtained by the process, as well as a process for producing paper which comprises providing an aqueous suspension comprising cellulosic fibres; 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 and their production and use

The invention relates to a process for producing aqueous silica-based sols which comprises providing a cationic ion exchange resin having at least part of its ion exchange capacity in hydrogen form; bringing said ion exchange resin in contact with an aqueous alkali metal silicate to form an aqueous slurry; adjusting the pH of the aqueous slurry and separating the ion exchange resin from the aqueous slurry, as well as the silica-based sols obtained by the process. The invention also relates to silica-based sols obtained by the process, as well as a process for producing paper which comprises providing an aqueous suspension comprising cellulosic fibres; 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.

Growing community of inventors

Kungälv, Sweden

Freddie Hansson