Patent Title: ENCAPSULATION BY INTERFACIAL POLYCONDENSATION
Number/Link: US3577515
Applicant/Assignee: Pennwalt Corp.
Publication date: 4-05-1971
“Gist”: Interfacial polycondensation on the surface of emulsified droplets.
Why it is interesting: Micro-sized droplets are encapsulated with a polymeric film or ‘skin’ formed by an interfacial polycondensation reaction. The idea is both very clever and simple: one reaction component is dissolved in a liquid which is then dispersed in another -immiscible- liquid. The second reaction component is then added to the continuous phase resulting in a polycondensation reaction at the surface of the droplets, encapsulating these with a polymeric film. For example a solution of a polyisocyanates in an organic solvent can be dispersed in water (to a desired droplet size) after which a water soluble diol or diamine is added resulting in a polyurethane or polyurea film encapsulating the solvent droplets. Microcapsules are now common and used in may applications like cosmetics, phase change materials, e-paper, self-healing coatings etc.
Figure illustrating the process
Innovation in Polyurethanes 