Patent ID: 6548619
Filing Date: 2003-04-15
Classification: B01J,B29B,C08G,C08J

Abstract:
A process for the production of particles from a solution or melt of a heat-activatable polyurethane which comprises the reaction product of:a) a crystallizing oligomeric dihydroxy compound, b) optionally an amorphous oligomeric dihydroxy compound in an amount by weight which is less than the amount of component a), c) an aromatic and/or aliphatic diisocyanate and d) optionally a low molecular weight difunctional chain extender, optionally in admixture with e) a light stabilizer, antioxidant, powdering agent or a polyfunctional cross-linking compound, â€ƒwhich comprises: i) dissolving a compressible auxiliary agent at a pressure of between 50 and 1000 bar into a conveyable solution or melt of a heat-activatable polyurethane having a polyurethane content of between 40 and 100 wt. % and a solvent content of 0 to 60 wt. % to obtain a mixture of polyurethane, compressible auxiliary agent and optionally solvent, ii) optionally adjusting of the temperature of the resulting mixture to a temperature of from 40Â° K below to 150Â° K above the crystallite melting point of the polyurethane, iii) expanding the mixture by means of an expansion device into a container, while adjusting the temperature in the container to at least 5Â° K below the softening temperature of the polyurethane to maintain the open jet particles in a form in which they do not agglomerate, and iv) separating the formed particles from the stream of decompressed compressible auxiliary agent and optionally solvent.