Abstract: Ethylene polymer having a die swell ratio (RB) of at least 1.4, a resistance to crazing under stress (ESCR) of at least 55 h and a melt index (MI5) of at least 0.2 g/10 min. Processes for obtaining this ethylene polymer using different catalytic systems, the first based on titanium and zirconium used in a polymerization in two reactors; the second consisting of a mixture of a titanium catalyst and a titanium and zirconium catalyst, used in a polymerization in two reactors; the third based on chromium on a support comprising at least two constituents chosen from silica, alumina and aluminum phosphates, used in a polymerization in a single or in two reactors.

Abstract: A metallocene corresponding to the formula wherein M is a group 4 transition metal, each Y is, independently, selected from the group of halogen, hydrocarbyl and hydrocarbyloxy, R1, R4 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy, R2, R3, R5, R6, R7, R8 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy, with the provision that, respectively, R2 and R3, R5 and R6, R7 and R8 can be linked to each other.

Abstract: A propylene block copolymer comprising(A) 60-90 weight %, based on the total amount of the block copolymer, of a first block of a propylene polymer, optionally containing a small amount of copolymerised ethylene,(B) 40-10 weight %, based on the total amount of the block copolymer, of a second block of an ethylene-propylene copolymer containing 1-10 weight % of ethylene, and the total ethylene content of the block copolymer being within the range of 0.1-2.5%. The weight process for the manufacturing of the propylene block copolymer and use of it for the manufacture of bioriented bottles.

Abstract: A control method for a process of synthesis of at least one chemical product in an equipment comprising at least one reactor (R) which is assimilated to a mixed reactor, in which manipulated variables (GC) allow to act on the course of the process in order to make one or more variables related to the properties of the product and/or to the running of the process, which are called controlled variables (GR).

Abstract: Device for unloading a pressurized vessel, comprising at least two rotary feeders in series, a valve situated between the reactor and the first feeder, and a point of entry for a gas, that is situated between the valve and the reactor.

Abstract: An ethylene-polymer-based composition obtained by mixing, in the melt: 100 parts by weight of an ethylene polymer withfrom 0.0005 to 0.1 part by weight of a compound (a) with the ability to generate free radicals andfrom 0.0005 to 0.1 part by weight of coagent (b) chosen from among the C.sub.3 to C.sub.12 alkenes and the C.sub.5 to C.sub.16 alkadienes.This composition has clearly improved melt strength. It is very suitable for extrusion and rotational molding and in particular for the extrusion of tubes intended for conveying fluids under pressure. The invention also relates to a process for obtaining the composition and using it for the manufacture of shaped articles, and to shaped articles.

Abstract: Novel asymmetric ethylene-bridged metallocenes useful as catalysts in the polymerization of olefins and process for preparing said metallocenes.The novel metallocenes are represented by the general formula: ##STR1## wherein M represents a transition metal selected from titanium, zirconium and hafnium and X and X' represent a halogen atom. Preferably, the transition metal is Zr and the halogen atoms are both chlorine.

Abstract: A metallocene corresponding to the formula ##STR1## wherein M is a group 4 transition metal, each Y is, independently, selected from the group of halogen, hydrocarbyl and hydrocarbyloxy,R.sup.1, R.sup.4 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy,R.sup.2, R.sup.3, R.sup.5, R.sup.6, R.sup.7, R.sup.8 are, independently, selected from the group of hydrogen, hydrocarbyl, hydrocarbyloxy, with the provision that, respectively, R.sup.2 and R.sup.3, R.sup.5 and R.sup.6, R.sup.7 and R.sup.8 can be linked to each other.A process for the preparation of metallocenes comprising the following steps:(a) contacting, in a solvent, a transition metal halide of formula MX.sub.4 with an organometallic compound of formula M'R.sub.

Abstract: Catalytic system which can be used for the polymerisation of .alpha.-olefins comprising:a solid based on complexed titanium trichloride of .delta. crystalline form;an organoaluminium compound;an organic oxygenated silicon compound; characterised in that the organoaluminium compound is a non-halogenated compound.

Abstract: An ethylene polymer having a density greater than 959 kg/m3 and a resistance to slow cracking greater than 23 hours. A composition containing this polymer, hollow bodies obtained using at least one such ethylene polymer, and a process for the manufacture of said polymer.

Abstract: Propylene polymer obtained by melt-blending of:100 parts by weight of polypropylene;from 0.01 to 10 parts by weight of a functional compound (a) comprising at least 2 acrylate groups;at least 0.005 part by weight of a sulphur-containing compound (b) chosen from thiuram sulphides; andfrom 0.01 to 5 parts by weight of a compound (c) capable of generating free radicals.

Abstract: Catalytic system which can be used for the polymerization of .alpha.-olefins comprising:a solid based on complexed titanium trichloride of .delta. crystalline form;an organoaluminium compound;an organic oxygenated silicon compound;characterized in that the organoaluminium compound is a non-halogenated compound.

Abstract: Process for the polymerization of olefins, in which at least one olef in is placed in contact with a catalytic system comprising:(a) a solid catalytic complex based on magnesium, on transition metal and on halogen, and(b) an organometallic compound of a metal from groups IA, IIA, IIB, IIIA and IVA of the Periodic Table,the said solid catalytic complex (a) being prepared by reacting, in a first step, at least one magnesium compound with at least one compound of a transition metal from group IVB or VB of the Periodic Table until a liquid complex is obtained, by treating the said liquid complex, in a second step, using a halogen-containing organoaluminium compound, in order to precipitate the liquid complex as a solid catalytic complex, by separating, in a third step, the solid catalytic complex precipitated and by treating, in a fourth step, the separated solid catalytic complex obtained after the third step using a halogen-containing organoaluminium compound of general formula AlR.sub.n X.sub.3-n.

Abstract: Continous process for grafting a polyolefin within a melt including a polyolefin of linear olefin containing from 2 to 8 carbon atoms, a graftable functional monomer and a radical-generator, in an extruder including at its exit a compression zone followed by a discharge zone, in which at least one antioxidant additive is introduced into the melt not later than before the latter enters the compression zone of the extruder.Stabilized grafted polyolefin obtained by means of this process.

Abstract: Compositions based on propylene polymers (compositions (C)) comprising:from 68 to 80% by weight of a statistical propylene copolymer (copolymer (A)) which contains from 12 to 20% by weight of units derived from 1-butene and from 0 to 2% by weight of units derived from ethylene, andfrom 20 to 32% by weight of a statistical propylene copolymer (copolymer (B)) which contains from 0 to 15% by weight of units derived from 1-butene and from 1 to 8% by weight of units derived from ethylene.

Abstract: Catalyst systems comprising, on the one hand, a catalytic solid based on complexed titanium trichloride and, on the other hand, a nonhalogenated organoaluminium activator. When employed in gas phase olefin polymerisation processes, these catalyst systems make it possible to manufacture a wide range of homopolymers and copolymers (random and block) with an isotacticity index which can be adjusted to very low values and with excellent pourability, even in the case of copolymers of high comonomer content. In the absence of transfer agents they also make it possible to synthesize polymers of very high molecular masses, with an increased activity. These polymerization processes yield particularly advantageous results in the case of propylene.

Abstract: Catalyst systems comprising, on the one hand, a catalytic solid based on complexed titanium trichloride and, on the other hand, a nonhalogenated organolauminium activator.When employed in gas phase olefin polymerization processes, these catalyst systems make it possible to manufacture a wide range of homopolymers and copolymers (random and block) with an isotacticity index which can be adjusted to very low values and with excellent pourability, even in the case of copolymers of high comonomer content.In the absence of transfer agents they also make it possible to synthesise polymers of very high molecular masses, with an increased activity.These polymerization processes yield particularly advantageous results in the case of propylene.

Abstract: Statistical propylene copolymer containing 0.2-0.9% by weight monomeric units derived from ethylene; 13-21% by weight monomeric units derived from .alpha.-olefin having 4-10 carbon atoms, and 78.1-86.8% by weight monomeric units derived from propylene. The copolymer has a melting point of 115-125.degree. C.; a proportion of polymer soluble in boiling heptane greater than or equal to 95% by weight, and a proportion of polymer soluble in cold xylene (25.degree. C.) greater than 40% by weight.

Abstract: Catalyst systems comprising, on the one hand, a catalytic solid based on complexed titanium trichloride and, on the other hand, a nonhalogenated organoaluminium activator. When employed in gas phase olefin polymerization processes, these catalyst systems make it possible to manufacture a wide range of homopolymers and copolymers (random and block) with an isotacticity index which can be adjusted to very low values and with excellent pourability, even in the case of copolymers of high comonomer content. In the absence of transfer agents they also make it possible to synthesize polymers of very high molecular masses, with an increased activity. These polymerization processes yield particularly advantageous results in the case of propylene.

Abstract: A catalyst system for olefin polymerization, including a catalytic solid based on chromium deposited on a support containing silica, alumina and aluminium phosphate and a cocatalyst chosen from organoaluminium compounds. One of the essential characteristics of the invention is the combination of an organoaluminium compound as cocatalyst with a catalytic solid based on chromium deposited on a support containing silica, alumina and aluminium phosphate.