| 摘要 |
Powdered polymers are prepared by a process which comprises contacting an olefinically unsaturated monomer with a free radical initiator in a reaction zone at elevated pressure, withdrawing the resulting polymerized product from the reaction zone and reducing the pressure to atmospheric, admixing the polymerized product with at least 10 weight per cent based on the monomer fed to the reaction zone after withdrawal of the polymerized product from the reaction zone and before reducing the pressure, the temperature of the alkanol being at least 100 DEG C. below that of the polymerization reaction. Proportions of 10 to 90 weight per cent of the alkanol may be added at - 70 DEG to +60 DEG C. when the reaction is effected at 150 DEG to 250 DEG C. Specified alkanols are methanol, ethanol, n-propanol, isopropanol, n-butanol, t.-butanol or hexanol. The olefinically unsaturated monomer may be ethylene and/or vinyl fluoride, and the ethylene may be copolymerized with other olefinically unsaturated compounds many of which are listed. Apparatus suitable for carrying out the process of the invention, in which quenching is effected in a cylindrical chamber in the product flow line into which the alkanol is introduced through a plurality of tangentially disposed entry ports fed from a surrounding annulus, is described and illustrated. In examples, ethylene polymerized in the presence of oxygen, and vinyl fluoride and ethylene copolymerized in the presence of di-t.-butyl peroxide are quenched with methanol. The products may be used in rotational moulding and in fluidized bed and spray coating. |
