Abstract: A process for the continuous manufacture of homopolymers of an ethylene monomer and copolymers of an ethylene monomer with at least one .alpha.-olefin containing 3 to 8 carbon atoms. The monomers and a catalytic system are introduced into a first stage reactor to form a reaction medium for polymerizing the monomers. During a first stage, when the polymerization is substantially complete, a first compound, which is capable of reducing a transition metal of the catalytic system, is introduced into the reaction medium.

Abstract: A catalyst system for use in the polymerization of ethylene under high pressure and temperature containing an alkyl-aluminum or alkylsiloxalane activator and a compound of the formula:(TiCla) (MgCL.sub.2).sub.y (AlCl.sub.3)z (RMgCl).sub.bin whicha is from 2 to 3;y is 2 or more;z is from 0 to 1/3;b is from 0 to 1; andR is an aliphatic or aromatic hydrocarbon radical.

Abstract: A modified copolymer of ethylene and of at least one .alpha.-olefin having from 3 to 12 carbon atoms, comprising from 0.5 to 10 mole percent of units derived from the .alpha.-olefin, wherein the measured limiting viscosity of the copolymer is between 1.5 and 10 times the limiting viscosity of the copolymer calculated from the molecular weight distribution of the copolymer. Process for producing these copolymers employing at least one free-radical initiator.

Abstract: A process for polymerizing ethylene under high pressure and temperature in at least one reactor having at least one reaction zone. A catalyst system is used that comprises (a) an activator selected from trialkylaluminums, hologenodialkylaluminums, and alkylsiloxalanes, (b) a halogen compound of a transition metal of groups IV to VI A, and (c) a complexing agent that is injected into the reactor in such a manner that its concentration in the reactor may be adjusted independently from the concentration of (b). The complexing agent may be selected from silicone oils and from compounds having the formula X(OR).sub.n, wherein X is hydrogen or a metal, n is the valence of X, and R is an alkyl radical of up to 20 carbon atoms.

Abstract: Ethylene is polymerized, in the presence of hydrogen, at a temperature of 180.degree. to 340.degree. C and a pressure of 200 2,500 bars with a Ziegler catalyst in a stirred reactor having at least one first reaction zone and at least one second reaction zone. The reaction mixture is fed to a separator at a pressure of 80 to 400 bars. The improvement results from partially liquifying at least a part of the gas coming from the separator at a temperature of -50.degree. to +20.degree. C, releasing the pressure to a value of 10 to 60 bars, separating the partially liquified gas into a gas phase and a liquid phase, and recycling the gas phase to the second reaction zone and the liquid phase to the first reaction zone. The resulting polymer has a low melt index, a high polydispersity index, and superior physical properties compared to polymers prepared by conventional processes.

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.