Verfahren zur Verbesserung der Eigenschaften von Linearpolyolefinen

摘要

Linear polyolefines which have been prepared by the polymerization of olefines containing two to four carbon atoms using as catalysts heavy metals of Group IV(a), V(a), or VI(a) of the Mendelleeff Periodic System are simultaneously purified and thermally degraded by dissolving or swelling the polyolefine in an inert organic solvent and heating the solution in the presence of oxygen or oxygen-supplying compounds for 15 to 200 minutes at a temperature between 70 DEG and 240 DEG C. Optionally the heat-treatment may be effected in the presence of 2 to 20% of water and in the presence of such an amount of an alkaline compound that the pH in the aqueous solution after the heat-treatment step is 6 to 7. Substances which have a large internal surface on to which impurities are absorbed may be added to the polymers before, during, or after the heat-treatment. Suitable substances are carbon, aluminium oxide, bleaching earths, and kieselguhr. The linear polymers may be polyethylene, polypropylene, or copolymers of ethylene and/or propylene and/or butene-1. Specified solvents are tetra- or decahydro-naphthalene, cyclohexane, benzene, toluene, xylene, and ethylbenzene. The oxygen-supplying compounds may be peroxides. Alkaline compounds which may be included in the heat-treatment step are ammonia, sodium, potassium, or calcium hydroxide, hydroxylamine or aniline.