Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Reexamination Certificate
1999-05-10
2001-03-27
Lovering, Richard D. (Department: 1712)
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
C106S484000, C106S486000, C162S181600, C423S330100, C516S110000
Reexamination Certificate
active
06207721
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority from German Application No. DE 198 21 143.0, filed on May 12, 1998, the subject matter of which is hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an aqueous aluminium silicate suspension, a process for its preparation and its use.
2. Background Information
Aluminium silicate, such as, for example, P 820 is described in Ullmanns Enzyklopädie der technischen Chemie [Ullmann's Encyclopaedia of Industrial Chemistry], 4th edition, volume 21, page 467, table 12. It is employed as a pulp filler in papermaking. The printability of newspaper and thin printing paper can be improved by using aluminium silicate. Aluminium silicate is a white powder which is marketed in this form. In papermaking, however, almost all educts are employed in the form of aqueous suspensions. Aluminium silicate therefore has the disadvantage that for its use in papermaking separate devices must be built and used for the processing, because of its pulverulent consistency. This disadvantage can be overcome if the aluminium silicate powder can be employed in papermaking in the form of an aqueous suspension.
SUMMARY OF THE INVENTION
There is therefore the object of converting pulverulent aluminium silicate into an aqueous, storage-stable suspension which has a high solids content and can be used in papermaking.
The invention provides an aqueous aluminium silicate suspension, which is characterized in that, in addition to water, it comprises at least 30 wt. %, preferably at least 35 wt. %, aluminium silicate, 0.1 to 3.0 wt. % aluminium sulfate and 0.1 to 5.0 wt. % surfactants.
In a preferred embodiment of the invention, aluminium silicate P 820 can be employed as the aluminium silicate. Surfactants which can be employed are known nonionic surfactants, such as, for example, polyethylene oxide.
Anionic and/or cationic surfactants can furthermore be employed as surfactants. Such surfactants are, for example, polyacrylates, dodecylbenzenesulfonate and sodium citrate.
In a preferred embodiment, the solids content of the suspension can be 35 to 45 wt. %, in particular 35 to 40 wt. %. The pH of the suspension can be between 4.5 and 9.5, preferably between 5.0 and 8.0.
The invention also provides a process for the preparation of the aluminium silicate suspension, which is characterized in that an aluminium silicate is precipitated by a synthetic route from aluminium sulfate and water-glass and filtered off, the aluminium silicate filter cake is liquefied by stirring and/or subjecting to shear with an aqueous aluminium sulfate solution, at least one surfactant is added, pulverulent aluminium silicate is added to the liquefied aluminium silicate filter cake, while stirring and/or subjecting to shear, and the mixture is optionally stirred and/or subjected to shear once more.
In one embodiment of the invention, the aluminium silicate filter cake can be washed and dried. The resulting aluminium silicate powder can be mixed with an aqueous aluminium sulfate solution, while stirring and/or subjecting to shear, at least one surfactant can be added, further pulverulent aluminium silicate can be added to this suspension, while stirring and/or subjecting to shear, and the mixture can optionally be stirred and/or subjected to shear once more.
The aqueous aluminium silicate suspension according to the invention advantageously has a high solids content. Sedimentation of the solid does not occur even over a relatively long storage time.
Grinding for destructuring is not necessary.
The aqueous aluminium silicate suspension according to the invention can be employed in papermaking.
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Glaum Holger
Schubert Jurgen
Degussa-Huls Aktiengesellschaft
Lovering Richard D.
Pillsbury Madison & Sutro
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