Abstract: (I) The (co)polymerisation of ethylene is carried out in at least one reaction zone (R) under high pressure, at 150.degree.-320.degree. C.; (II) the reaction product is routed into a zone (S), under an intermediate pressure P, for separation of the (co)polymer, in the molten state, from the unreacted (co)monomer(s), or the reaction product is routed into a first separation zone (S1), under an intermediate pressure (P1); the (co)polymer issuing from (S1) is then routed into a second separation zone (S2), under a pressure P2<P1; (III) the (co)polymer is routed into a zone (SF), under low pressure, for final separation of the (co)polymer from the residual gases. Let-down zones (D), (D1) and (D2) are provided along the path of the (co)polymer between the zones (S) and (SF), (S1) and (S2), and (S2) and (SF) respectively, the grafting monomer or monomers being introduced on-line, in the path of the (co)polymer, at at least one point located at the level of the zone (D) or at at least one zone (D1, D2).

Abstract: (I) The (co)polymerisation of ethylene is carried out in at least one reaction zone (R) under high pressure, at 150.degree.-320.degree. C.; (II) the reaction product is routed into a zone (S), under an intermediate pressure P, for separation of the (co)polymer, in the molten state, from the unreacted (co)monomer(s), or the reaction product is routed into a first separation zone (S1), under an intermediate pressure (P1); the (co)polymer issuing from (S1) is then routed into a second separation zone (S2), under a pressure P2<P1; (III) the (co)polymer is routed into a zone (SF), under low pressure, for final separation of the (co)polymer from the residual gases. Let-down zones (D), (D1) and (D2) are provided along the path of the (co)polymer between the zones (S) and (SF), (S1) and (S2), and (S2) and (SF) respectively, the grafting monomer or monomers being introduced on-line, in the path of the (co)polymer, at at least one point located at the level of the zone (D) or at at least one zone (D1, D2).

Abstract: Polyolefin rubber which is an ethylene/propylene and/or 1-butene copolymer, which has a melt index of 0.3 to 15 dg/min and a relative density of 0.860 to 0.885, comprising 74-91 mol % of units derived from ethylene and 9-26 mol % of units derived from propylene and/or from 1-butene, characterised by a crystalline melting point J of 100.degree. to 125.degree. C. The process for obtaining this rubber consists in copolymerising, at a temperature of 150.degree.-300.degree. C. and at a pressure of 400-2000 bars, a gas stream containing 15-42% by vol. of ethylene and 58-85% by vol. of propylene and/or 1-butene, in the presence of a Ziegler-type catalyst system comprising at least one compound of a transition metal of groups IVB, VB, VIB and VIII of the Periodic Classification, and at least one organoaluminium compound and, if appropriate, in the presence of at least one chain transfer agent.

Abstract: Aromatic hydrocarbon resins having a number-average molecular weight of 500-2,500 and containing, in particular, units derived from styrene and/or from its higher homologs, are acylated with vinylketone groups RR'C.dbd.CR"--CO-- grafted onto the aromatic nuclei of the said resin, said resin further containing from 10 to 90 mol %, and preferably from 30 to 60 mol %, of units derived from indene and/or from its higher homologs, and containing from 0.02 to 0.07 grafted vinylketone group per aromatic nucleus.The resultant acylated resins are either polymerized anionically to polymers having a weight-average molecular weight ranging from 10.sup.4 to 2.10.sup.7, or are copolymerized with a living polymer such as polymethyl methacrylate.

Abstract: Aromatic hydrocarbon resins having a number-average molecular weight of 500-2,500 and containing, in particular, units derived from styrene and/or from its higher homologs, are acylated with vinylketone groups RR'C.dbd.CR"--CO-- grafted onto the aromatic nuclei of the said resin, said resin further containing from 10 to 90 mol %, and preferably from 30 to 60 mol %, of units derived from indene and/or from its higher homologs, and containing from 0.02 to 0.07 grafted vinylketone group per aromatic nucleus.The resultant acylated resins are either polymerized anionically to polymers having a weight-average molecular weight ranging from 10.sup.4 to 2.10.sup.7, or are copolymerized with a living polymer such as polymethyl methacrylate.