GB579882A - Improvements in or relating to the polymerisation of ethylene - Google Patents

Abstract

Ethylene, either alone or mixed with one or more other polymerizable organic compounds, is polymerized at elevated temperature and pressure in the presence of an aqueous medium and an organic per-compound as catalyst, the ethylene being passed under pressure through an aqueous suspension of the catalyst before entering the reaction zone and the polymer or interpolymer continuously withdrawn therefrom. The aqueous medium may contain a surface tension reducing agent or the process may be carried out in the absence of such an agent, as described in Specification 579,883. The resultant suspension of polymer is continuously passed into a region of lower pressure where the unreacted ethylene is separated and passed with fresh ethylene through the catalyst suspension and the polymer separated by filtration. When interpolymerizing ethylene with a liquid unsaturated compound, the latter may be introduced continuously with the aqueous medium, and when with another gas, the gases may be premixed or injected separately. The other polymerizable compounds specified are other mono-olefines, e.g. amylene or butylene; dichloroethylenes, e.g. 1.2-dichloroethylene; 2-chloropropene; tetrafluoroethylene; vinyl ethers, ketones, and esters and other vinyl compounds, e.g. methyl and propyl vinyl ethers, methyl and ethyl vinyl ketones, vinyl chloroacetate, vinyl chloride, vinyl acetate, vinyl propionate, N-vinyl phthalimide; stilbene; styrene; acrylic and methacrylic acids and their amides, nitriles and esters, e.g. methyl, ethyl and propyl acrylates and methacrylates, methylene diacrylate and dimethacrylate, a -haloacrylic acids and esters; esters of crotonic acid, e.g. methyl crotonate; esters of itaconic acid, e.g. diethyl itaconate; dienes, e.g. butadiene, chloro-2-butadiene-1, 3 and isoprene. The aqueous medium may be water alone or mixed with a volatile organic liquid, e.g. iso-octane, toluene, butyl acetate, ethyl ether, n-hexane, cyclohexanone, butanol, methanol, dioxane, m-brom-toluene, petroleum ether or gasoline. Specified catalysts are persuccinic or peracetic acid, an alkali metal persulphate, a perborate, a percarbonate or lauroyl, tetrahydronaphthalene, urea, butyryl, acetyl, benzoyl or acetyl benzoyl peroxide; the persulphates may be used in conjunction with buffering agents such as borax or alkaline phosphates. Surface active agents which may be present during the polymerization are, e.g. starch, the water soluble salts of the higher alkyl sulphates and sulphonates such as sodium tetradecyl and dodecyl sulphate, sodium pentadecane-8-sulphonate, alkali metal salts of sulphonated mineral oils and turkey red oil. In examples: (1) and (2), ethylene under pressure is injected into a heated vessel containing water and benzoyl peroxide, with or without hydrochloric acid to adjust the pH value, and a liquid phase comprising a dispersion of polymer in water is continuously withdrawn from the bottom of the vessel; simultaneously with the withdrawal, fresh water and ethylene charged with benzoyl peroxide are continuously supplied to the vessel. Unreacted ethylene is removed from the top of the vessel, charged with benzoyl peroxide and recirculated. In example (3), the aqueous medium is a mixture of water and isooctane containing the sodium salt of sulphated 9.10-octadecenyl acetate and benzoyl peroxide.