Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
2007-01-30
2007-01-30
Halpern, Mark (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S158000, C162S168300, C162S175000, C162S181700, C423S335000, C516S079000, C516S080000, C516S081000
Reexamination Certificate
active
10007885
ABSTRACT:
An aqueous sol containing silica-based particles which has an S-value within the range of from 10 to 45%, a viscosity within the range of from 5 to 40 cP, and a molar ratio of SiO2to M2O, where M is alkali metal or ammonium, within the range of from 10:1 to 40:1, or a silica content of at least 10% by weight. The invention further relates to a process for the production of silica-based particles comprising the steps of: (a) acidifying an aqueous silicate solution to a pH of from 1 to 4 to form an acid sol; (b) alkalising the acid sol at an SiO2content within the range of from 4.5 to 8% by weight to; (c) allowing particle growth of the alkalised sol for at least 10 minutes, or heat-treating the alkalised sol at a temperature of a least 30° C.; and then (d) alkalising the obtained sol to a pH of at least 10.0. The invention further relates to silica-based particles obtainable by the process, the use of the silica-based particles as drainage and retention aids in the production of paper as well as a process for the production of paper from an aqueous suspension containing cellulosic fibers, and optional filler, in which silica-based particles and at least one charged organic polymer are added to the cellulosic suspension.
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Dahlgren Maj-Lis
Persson Michael
Tokarz Marek
Akzo Nobel N.V.
Burke Michelle J.
Halpern Mark
Morriss Robert C.
Parker Lainie E.
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