Purification and recovery of normally solid polymers

Inorganic solids and/or colour bodies are removed from solid polyolefins by subjecting a solution of the polymer in a dielectric solvent to dielectrophoresis by subjecting the solution to an inhomogeneous electrical field between electrodes having a ratio of surface areas greater than ten with a field strength in the range of 2 to 50 kilovolts per centimetre of distance between electrodes. Specified polyolefins are of ethylene, propylene and their mixtures, preferably prepared by a low-pressure process, e.g. chromium oxide or Ziegler type catalysts. Specified solvents are cyclohexane, an alkyl cyclopentane, heptane, isooctane, decane, benzene, toluene, and xylene. The solution may be kept sufficiently hot during the dielectrophoresis to keep the polymer in solution; the solution may be percolated through solid absorptive material during the dielectrophoresis. Apparatus for carrying out the process is described. Specifications 734,501, 748,634, U.S.A. Specification 2,692,261 and Belgian Specifications 530,617, 533,362, 534,792 and 534,888 are referred to.