Abstract: A process for the manufacture of radical ethylene terpolymers or copolymers comprising moieties derived from an alkyl (meth)acrylate and/or moieties derived from maleic anhydride by copolymerizing, in the presence of at least one free-radical initiator, a mixture of ethylene, (meth)acrylate and/or maleic anhydride in a device comprising a primary compressor, the delivery pressure of which is between 200 and 300 bars, connected to a secondary compressor which is connected directly to a polymerization reactor, fresh ethylene being fed at the intake of the said primary compressor and said copolymerization being carried out in the said polymerization reactor under a pressure of between 1,000 and 2,500 bars and at a temperature of between 140.degree. and 280.degree. C., wherein the feeding of the (meth)acrylate and/or maleic anhydride into the reactor if effected by introducing maleic anhydride and/or (meth)acrylate at the intake of the secondary compressor.

Abstract: A process for the manufacture of radical ethylene terpolymers or copolymers comprising moieties derived from an alkyl (meth)acrylate and/or moieties derived from maleic anhydride by copolymerizing, in the presence of at least one free-radical initiator, a mixture of ethylene, (meth)acrylate and/or maleic anhydride in a device incorporating a primary compressor, the delivery pressure of which is between 200 and 300 bars, connected to a secondary compressor which is connected directly to a polymerization reactor, fresh ethylene being fed at the intake of the said primary compressor and said copolymerization being carried out in the said polymerization reactor under a pressure of between 1,000 and 2,500 bars and a temperature of between 140.degree. and 280.degree. C., wherein at least one the alkyl (meth)acrylate and/or maleic anhydride is fed directly into the said polymerization reactor.

Abstract: The energy efficiency of a high pressure, high temperature continuous process for the production of polyethylene is improved and residual gases are more completely removed from the product without detriment to product quality by employing an intermediate separator between the first and second separators. The intermediate separator is maintained at a pressure between about 10 and 70 bars, and the second separator is maintained at a pressure between about 1 and 1.5 bars.

Abstract: A process for eliminating low molecular-weight polymers from the recirculating gases of facilities carrying out ethylene polymerization or copolymerization at a pressure of 300 to 2500 bars and a temperature of 130.degree. C. to 350.degree. C., in which facilities the mixture of monomer and polymer leaving the reactor is expanded into a separator operating under a pressure of 50 to 500 bars. The gases are passed, at a temperature at least 20.degree. C. higher than the melting point of the low molecular-weight polymers, through at least one standard cyclone at an inlet velocity between 1 and 10 m/s. The gases are then cooled to a temperature lower than the melting point of the low molecular-weight polymers, and are then passed through at least one heated cyclone at an inlet velocity between 2 and 20 m/s.

Abstract: The present invention relates to a process for the continuous polymerisation and copolymerisation of ethylene under a pressure higher than 500 bars and at temperatures higher than about 160.degree. C in the presence of a catalyst containing a derivative of a transition metal and an organic derivative of aluminium, wherein there is injected into the reaction mixture at the end of reaction at least one alkali metal salt or alkaline earth metal salt of a carboxylic acid, in an amount sufficient to bring about the deactivation of the catalyst, said salt being so chosen that its reaction products with the constituents of the catalyst remain in the polymer.

Abstract: Radical polymerization of ethylene in the presence of an initiator and up to 500 ppm of a cyclic olefin having from 5 to 12 carbon atoms and a ring of 5 to 9 members or styrene and its alkyl homologues.

Abstract: A method for the polymerization or copolymerization of ethylene comprising polymerizing the ethylene at a pressure greater than 500 bars, at a temperature in the range 160.degree. to 280.degree.C and under conditions in which polymerization takes place in a single liquid phase, in the presence of a catalyst system comprisingA. an alkylsiloxalane derivative of the formula, ##EQU1## and B. a halogenated titanium compound of the titanium trichloride type, the Al/Ti ratio between the constituents being between 1 and 10.