Process for making coated, water-swellable hydrogel microspheres
AssigneeE.I. du Pont de Nemours and Company
InventorsGarret D. Figuly, Henricus Jacobus Cornelis Gommeren, Guangliang Liu
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Abstract
A process for coating water-swellable hydrogel microspheres with various coating materials is described. The coating process described herein is a fluidized bed process, which utilizes inert, cofluidization particles to aid the fluidization of the microspheres. The use of the cofluidization particles increases the efficiency of the coating process and improves the quality of the coating obtained.
Claims13
A process for making coated water-swellable, substantially water-free hydrogel microspheres from starting microspheres having a preselected diameter range from dmin to dmax, and a preselected swell initiation time with a nonvolatile coating material comprising the steps of:
- (a) providing a coating material carrier medium by mixing the coating material with an aqueous medium comprising volatile components;
- (b) providing a dry mixture comprising the starting microspheres and cofluidization particles having a diameter range from Dmin to Dmax, wherein Dmin is at least larger than dmax and a density that allows the dry mixture to form a fluidized bed in step (c);
- (c) exposing the dry mixture to a stream of flowing gas in a chamber at a temperature sufficiently high to evaporate the volatile components of the aqueous medium in a time less than the preselected swell initiation time, thereby forming the fluidized bed comprising the dry mixture;
- (d) atomizing the coating material carrier medium into the chamber containing the fluidized bed for a time sufficient to provide the coated microspheres;
- and
- (e) optionally repeating step (d) one or more times with the same or different coating material carrier medium;
- and
- (f) separating the coated microspheres from the cofluidization particles.
Dependencies are inferred from the claim text.