Patent GB-837064-A (GB)
Title: Improvements in or relating to the manufacture of polyolefins
Inventor: REAY WALTER HARKNESS
IPC: C08F6/02
Filed: 1958-04-23
Abstract: Products of low-pressure catalytic olefin polymerization processes are worked up to remove catalyst elements by processes comprising supplying an "impure polyolefin slurry" to a vessel having an agitator and at or near the bottom a plurality of filter elements through which liquid can be supplied and withdrawn, withdrawing solvent from the vessel through the filter elements, washing the polyolefin by supplying a wash liquid to the vessel through the filter elements and agitating, and withdrawing the supernatant liquid from the vessel through the filter elements. In a modification a "polymerization product" is fed to the vessel together with a liquid reagent to decompose the catalyst. "Polymerization product" is defined as the catalyst-containing polyolefin slurry resulting from a polymerization process, which may have been concentrated, e.g. by settling or centrifuging, or washed, e.g. with iso-octane.  "Impure polyolefin slurry" is the slurry obtained by treating a "polymerization product" with a liquid reagent to decompose the catalyst, with or without separation of a liquid phase comprising said reagent. Polymerization may be effected using catalysts formed by mixing (A) a compound of a metal of Group IVa, Va, VIa, VIIa or VIII of the Periodic Table after Mendeleeff with (B) a Group I, II or III metal e.g. zinc or aluminium or an alloy thereof; an organo-metallic compound or hydride of a Group I, II or III metal, tin or lead; or an organic compound of boron or addition complex thereof.  Examples of these catalysts are described in Specifications 799,392, 799,823 and 801,031.  Polymerization may be effected in inert organic solvents, e.g. iso-octane and light petroleum distillates.  The liquid reagent may be an alcohol, e.g. methanol, ethanol, propanol or butanol, and may contain a small amount of mineral acid, e.g. hydrochloric acid.  The wash liquid may be an inert organic solvent such as that used in the polymerization process, and may contain an alcohol.  The liquid for second and subsequent washings preferably contains a small amount of acid, e.g. hydrochloric, phosphoric, sulphuric, acetic, oxalic, citric and tartaric acids.  After withdrawing the wash liquid the polyolefin may be slurried in an aqueous liquid and withdrawn from the vessel.  The aqueous liquid may be water, or dilute solutions of wetting agents, e.g. octyl phenol-ethylene oxide condensates, sodium or potassium hydroxide or carbonate, complexing agents, e.g. sodium citrate, ammonium hydroxide or carbonate and amines, e.g. methylamine or ethylamine.  The aqueous slurry may be steam-stripped as described in Specification 801,554 and, after separating the aqueous phase, extruded into strips or rods in a devolatilizing extruder.  Colouring matter and anti-corrosive agents, e.g. polymeric glycidyl polyethers, and acid accepters, e.g. calcium oxide, calcium hydroxide or sodium carbonate, may be added to the polymer prior to treatment in the devolatilizing extruder.  In an example ethylene is polymerized in the presence of a catalyst formed by mixing titanium tetrachloride with aluminium diethyl monochloride.