Classic PU Patent of the Month: Microencapsulation (1963)


 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 1 illustrating the process

Figure illustrating the process


Melt-Dispersed Polymer Polyols


 Number/Link: WO2015/165761  (German)

Applicant/Assignee: BASF

Publication date: 5-11-2015

Gist”: Polymer polyols are prepared by melt-dispersing SAN into a carrier polyol using a specific stabilizer

Why it is interesting: Polymer polyols, or ‘graft polyols’, contain finely dispersed polymeric particles and are especially useful for the production of flexible polyurethane foams.  Usually polymer polyols are produced by in-situ polymerization of styrene-acrylonitrile (SAN)- or polyurea particles in a carrier polyol. In this invention, polymer polyols are prepared by dispersing molten SAN into a carrier polyol using shear mixing and a specific stabilizer.  The stabilizer is a (preferably) comb-shaped polyol-SAN copolymer, and is described in another BASF application: WO2015/165878. The polymer polyols are said to have a fine and uniform particle size distribution, a low viscosity and a high stability against segregation.



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