Reversible Microcapsule Filter Cake
The invention teaches a method of efficiently dewatering a microcapsule slurry to form a water re-suspendable filter cake of microcapsules. The process comprises providing an aqueous slurry of microcapsules dispersed in an aqueous solution; adding an agglomeration agent and dispersing the agglomeration agent into the aqueous slurry; adjusting the pH to a pH level sufficient to agglomerate the dispersed microcapsules; and filtering the aqueous slurry of microcapsules by gravity, vacuum or pressure filtration to thereby form a filter cake of dewatered microcapsules. The agglomeration agent is sodium polyphosphate, sodium tetrapolyphosphate, sodium hexametaphosphate, and/or sodium tripolyphosphate; or with anionic microcapsules or coatings even alkaline earth metal salts such as magnesium chloride, calcium chloride or barium chloride, or even aluminum salt such as aluminum chloride.
1 . A filter cake formed by dewatering a microcapsule slurry to form a water re-suspendable filter cake of microcapsules comprising:
providing an aqueous slurry of microcapsules dispersed in an aqueous solution, wherein the microcapsules are cationic microcapsules having an acrylate wall;
adding an agglomeration agent selected from an alkali metal polyphosphate or an alkaline earth metal polyphosphate and dispersing the agglomeration agent into the aqueous slurry of microcapsules;
adjusting the pH of the aqueous slurry of microcapsules to at least a pH of 5 to agglomerate the dispersed microcapsules;
centrifuging or filtering the aqueous slurry of microcapsules by gravity, vacuum, or pressure filtration to form a filter cake of dewatered microcapsules.
2 . A slurry of microcapsules formed by resuspending the filter cake of claim 1 into an aqueous solution; and
filtering the aqueous slurry of microcapsules by gravity, vacuum, centrifuging or pressure filtration to form a filter cake of dewatered microcapsules.
3 . A filter cake formed by:
dewatering a microcapsule slurry to form a water resuspendable filter cake of microcapsules comprising:
providing an aqueous slurry of microcapsules dispersed in an aqueous solution wherein the microcapsules are cationic microcapsules having an acrylate wall;
adding an agglomeration agent selected from an alkali metal polyphosphate or an alkaline earth metal polyphosphate to the aqueous slurry of microcapsules;
dispersing the agglomeration agent into the aqueous slurry; and adjusting the pH of the slurry of microcapsules in a range from 4 to 10 to agglomerate the dispersed microcapsules; and
centrifuging or filtering the aqueous slurry of microcapsules by gravity, vacuum or pressure filtration to form a filter cake of dewatered microcapsules.
4 . A slurry of microcapsules formed by resuspending the filter cake of claim 3 into an aqueous solution.