Reversible Microcapsule Filter Cake

Abstract

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.

What is claimed is: 
     
         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.