GB748583A - Improvements in or relating to process for the production of polymers - Google Patents

Abstract

<PICT:0748583/IV(a)/1> Ethylene and/or propylene, with or without other monomers, is/are polymerized by the process of Specification 748,632, except that an alkali metal hydride is used instead of calcium, strontium or barium carbide and the temperature specified is 75 DEG to 325 DEG C. Additionally, oxides of boron may be present mixed with the catalyst. Monomer from compressor 10 is deoxygenated with metallic copper in chamber 11, dehydrated with alumina, calcium sulphate or silica gel in chamber 12 and decarbonated in chamber 13. It is then passed to absorber 14 and meets via heat exchanger 17, fresh solvent from pump 15 or recycled solvent from line 61. The monomer solution is finally purified in guard chamber 19, e.g. by means of alkali metal, alkaline earth metal, alkali metal hydride or alkaline earth metal hydride, and then passes into the reaction chamber 25 where it is mixed with the metal oxide and hydride already present. Optionally solvent and metal hydride are mixed in chamber 31 and then forced via pump 36 into the reactor. Alternatively the solvent may be purified in chamber 31. Polymerization takes place in reactor 25 and a 2 to 5 per cent solution is obtained. Reactors in parallel or series may be employed to obtain greater control. The upper portion of reactor 25 is a quiescent zone wherein the fine catalyst particles settle so that a clear solution may be drawn off through expansion valve 38 into separator 39, from which unreacted ethylene is discharged via line 40. Hot solvent may be introduced into separator 39 via line 51 in order to prevent separation of polymer. The polymer solution is withdrawn via line 41 into filter 42 wherein residual fine particles are coagulated by ultrasonic vibrators. The polymer solution is then passed into filter 47 and solid polymer is withdrawn at 48 while the solvent is withdrawn via line 49 and may be discharged via 50 or passed into separator 39 or into fractionator 55. Precipitation of polymer in 47 is induced with propane, acetone or alcohols. In fractionator 55 the solvent is vaporized and may be removed via line 57 but is preferably passed via cooler 59, pump 60 and line 61 into absorber 14 to produce a solution of fresh olefin. A portion of the solvent is also passed into absorber 63 wherein it meets recycled gases from separator 39 via compressor 65. The monomer solution from 63 is discharged via lines 67, 23 into reactor 25. Liquid reaction products from 55 may be discharged via line 69 or passed into a second fractionator 71. Alkylates are discharged by line 72 and a portion of these may be passed via line 73 to 42 where the alkylate acts as a solvent. Small portions of grease-like polymers may be removed via line 75. In an alternative procedure the filtered solution from 42 is discharged into hot water, solvent is flashed off, the slurry obtained is concentrated, centrifuged and the polymer obtained then dried.ALSO:Ethylene and/or propylene, with or without other monomers, is/are catalytically polymerized (see Group IV(a)) by the process of Specification 748,632 except that an alkali metal hydride is used instead of calcium, strontium or barium carbide and the temperature is specified as 75 DEG to 325 DEG C. Additionally, oxides of boron may be mixed with the catalyst.