GB765501A - Improvements in or relating to polymerization of ethylene propylene and isobutylene - Google Patents

Abstract

<PICT:0765501/IV(a)/1> Ethylene, propylene and isobutylene are polymerized in the presence of a free-radical catalyst at a pressure above 500 atmospheres in a plurality of stages, e.g. in a plurality of reaction vessels, in which a sufficient quantity of free-radical catalyst to polymerize only a portion of the monomer is added prior to each stage and the product from each stage is deactivated and the polymer recovered at the reaction pressure. Deactivation may be effected by reducing the temperature, e.g. 10 DEG to 100 DEG C. below the reaction temperature, or by adding a more reactive monomer such as propylene, styrene, vinyl chloride, butadiene, butene, isobutylene, acrylonitrile or substances containing secondary or tertiary hydrogen. The polymer may be collected after each stage or after the final stage. Catalysts such as oxygen, benzoyl, acetyl, acetyl-benzoyl, di-t.-butyl, potassium, zinc, lauryl, succinyl, m-bromobenzoyl, urea, and cyclohexanone peroxides, t.-butyl, di-isopropylbenzene, and p-methane hydroperoxides, a -a 1-azo-bis-isobutyronitrile, peracetic and persuccinic acids, alkaline earth metal persulphates, perborates, perchlorates, dialkyl peroxy dicarbonates, ascaridole, nitric acid, manganese dioxide, tetraphenyl tin, tetraethyl lead and Grignard-type compounds may be used and polymerization effected in a liquid medium, e.g. water, benzene, toluene, chlorobenzene, 2,2,4-dimethylpentane, methyl t.-butyl ether, t.-butyl alcohol, pentamethylethylene, methyl pivalate and pivaloin. In an example ethylene containing oxygen as catalyst is compressed to 1500 atmospheres in a compressor 30, heated to 210 DEG C., 60, and passed to a reactor 10, cooled to 120 DEG C., 40, and the polymer separated in 70. Unpolymerized ethylene is heated in a second vessel 60, additional oxygen added and passed to a second reactor 12 at 210 DEG C. The cycle may be repeated to obtain the desired conversion and yield a product of uniform molecular weight suitable for films, moulded products and structural forms.