FR2189451A1 - Powdered polyurethane resin - by emulsifying one reagent in organic nonsolvent contg surface active polymer, and adding second - Google Patents

Abstract

Polyurethane resins are prepd. directly in finely divided form from an org. polyisocyanate and an org. cpd. contg. at least two groups having active H atoms by (a) emulsifying one of the reagents with a surface active polymer in the form of small droplets in a continuous phase consisting of an org. liquid which is inert towards the reagent, less polar than the reagent, and a nonsolvent for the first reagent, and the solid reaction pdt. (b) introducing a second reagent which reacts with the first reagent, (c) reacting the reagents at their interface with energetic agitation to form small particles of polyurethane which can be separated from the inert liquid by sedimentation and (d) separating the particles from the inert liquid. The molecules of the surface active polymer have a molt. wt. of at least 2000 and polar groups which associate with the surfaces of the droplets of the insoluble reagent and with the particles of solid reaction pdt. and less polar groups which are solvated by the inert org. liquid to ensure a total association between the less polar groups and the solid reaction pdt. The intensity of agitation, the amount of polar and less polar groups of the surface active agent and the quilibrium between the polarities of these groups and the polarities of the insoluble reagent and the reaction ptd. are coordinated so that at least 95 wt. % of the emulsified droplets have a diameter of 1-300 mu esp. 5-75 mu the association between the surface active agent and the reaction pdt maintaining the surface active agent on the surface of the pdt. particles to avoid agglomeration of the particles.