GB856326A - Process for drying olefin polymers - Google Patents

Abstract

A process for drying solid aliphatic olefin polymers which have been prepared in the presence of a liquid solvent and which polymers have been separated in the solid state from the major portion of said solvent, comprising drying said polymer by evaporation at a temperature below the softening temperature of said polymer to 95-98% solids, and heating the thus partially dried polymer to at least the softening temperature thereof but below the temperature at which decomposition of said polymer takes place in an extruder-dryer so as to reduce the volatile matter associated with said polymer to not more than 0,05% and recovering a substantially dry polymer from said extruder-dryer. The olefin polymer may be produced by the low-pressure process, e.g. using a supported chromium oxide catalyst, and the drying is applicable to polymers mixed with both hydrocarbon polymerization solvent and water such as are obtained after initial separation from the polymerization mixture, e.g by steam stripping. The polymer may be derived from a 1-olefin such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene or alkyl substituted derivatives of these. The drying below the softening temperature may be carried out using an apparatus such as an apron drier or steam tube. A continuous polymer recovery system is described. Specifications 790,195 and 804,641 are referred to.