Process for producing a crosslinked cellulose ether

A process for producing a water soluble, nonionic crosslinked cellulose ether comprising the steps of:

• (a) contacting at least one cellulose material with at least one alkalization reagent to form an activated cellulose material;
• (b) contacting the activated cellulose material of step (a) with at least one etherification reagent to form an uncrosslinked cellulose ether, wherein the uncrosslinked cellulose ether forms at a pressure of greater than or equal to 1,000 kilopascals;
• (c) subjecting the uncrosslinked cellulose ether of step (b) to a step selected from:
• (ci) a washing step and a granulating step, wherein the washing step and the granulating step are performed simultaneously and wherein the washing step comprises washing with water at a temperature of greater than 90° C.;
• or
• (cii) a washing step and a granulating step, wherein the washing step is a step separate from the granulating step;
• wherein the washing step comprises washing with water at a temperature of greater than 90° C.;
• and wherein the washing step and the granulating step are performed separately in a stepwise procedure;
• or
• (ciii) a washing step only, wherein the washing step comprises washing with water at a temperature of greater than 90° C.;
• or
• (civ) a granulating step only, wherein the granulating step is carried out at a pressure of less than 500 kilopascals;
• and
• (d) adding at least one crosslinking agent to the uncrosslinked cellulose ether such that the at least one crosslinking agent and the uncrosslinked cellulose ether form a water soluble, nonionic, crosslinked cellulose ether;
• wherein the crosslinking agent is added to the process:
• (di) during the washing step (ci) while washing with water at a temperature of greater than 90° C. and during the granulating step (ci);
• or
• (dii) during the washing step (cii) while washing with water at a temperature of greater than 90° C. and during the granulating step (cii);
• or
• (diii) only during the washing step (cii) while washing with water at a temperature of greater than 90° C.;
• or
• (div) only during the granulating step (cii);
• or
• (dv) during the washing step (ciii) while washing with water at a temperature of greater than 90° C.;
• or
• (dvi) during the granulating step (civ);
• wherein the at least one crosslinking agent of step (d) is a diglycidylether type crosslinking agent having the following chemical Structure (I):
• where n is from 3 to 25, and
• wherein the at least one crosslinking agent is added in the addition step (d) at a concentration of from 0.0001 moles of the crosslinking agent per moles of anhydroglucose units of the cellulose ether to 0.05 moles of the crosslinking agent per moles of anhydroglucose units of the cellulose ether.