Microcapsules

Details Microcapsules Microcapsules

1991-12-09

1994-07-26

Lovering, Richard D.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Biocides; animal or insect repellents or attractants

71DIG1, 264 43, 264 433, 264 47, 424457, 424497, 42840221, 504112, 504300, 514963, A01N 2528, A01N 3718, B01J 1318

Patent

active

053325842

ABSTRACT:
A process is disclosed for the microencapsulation of a substantially water-insoluble liquid material within a porous shell to effect a slow rate of release of said material through said shell which comprises (a) providing an organic solution comprising said material and an etherified urea-formaldehyde prepolymer dissolved therein in which from about 50% to about 98% of the methylol groups of said prepolymer have been etherified with a C.sub.4 -C.sub.10 alcohol; (b) creating an emulsion of said organic solution in an continuous phase aqueous solution comprising water and a surfaceactive agent, wherein said emulsion comprises discrete droplets of said organic solution dispersed in said continuous phase aqueous solution, there being formed thereby an interface between the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and (c) causing in situ self-condensation and curing of said ureaformaldehyde prepolymers in the organic phase of said discrete droplets adjacent to said interface by simultaneously heating said emulsion to a temperature between about 20.degree. C. to about 100.degree. C., and adding to said emulsion an acidifying agent and maintaining said emulsion at a pH of between about 0 to about 4 for a sufficient period of time to allow substantial completion of in situ condensation of said resin prepolymers to convert the liquid droplets of said organic solution to capsules consisting of solid permeable polymer shells enclosing said liquid material.
Also disclosed are the microcapsules formed by the above-described process.

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