Abstract: A process for producing an olefin polymer in a slurry polymerisation process is disclosed, in which the process is operating at a temperature of 90° C. to 107° C. and utilising a chromium catalyst having an activity of at least 1,000 g polymer/g catalyst/hour on a support having a pore volume of at least 1.3 cm3/g, comprising adding to the polymerisation mixture from 0.1 to 100 ppm by weight of an anti-static agent, wherein the resulting polymer has a particle size distribution such that less than 8 vol %, preferably less than 5 Vol % of the polymer particles have an average diameter of 125 ?m or less.

Abstract: The invention relates to a polymer of ethylene which has a ?o/?2 ratio of at least 13; and a high load melt index HLMI lower than 8 g /10 min, and a value of tan ? at ?/?c=0.01 of less than 1.3, where ? is G?/G?, ? is the frequency at which G? and G? are measured and we is the frequency at which G?=G?, and G and G? are respectively the elastic modulus and viscous modulus, both measured in Pa at 190° C.; a process for making the polymer using a catalyst comprising chromium supported on a silica-titania support is also described.

Abstract: The invention relates to a polymer of ethylene which has a ?o/?2 ratio of at least 13; and a high load melt index HLMI lower than 8 g/ 10 min, and a value of tan ? at ?/?c=0.01 of less than 1.3, where ? is G?/G?, ? is the frequency at which G? and G? are measured and we is the frequency at which G?=G?, and G and G? are respectively the elastic modulus and viscous modulus, both measured in Pa at 190° C.; a process for making the polymer using a catalyst comprising chromium supported on a silica-titania support is also described.

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: 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.

Abstract: Process for the production of a microspheroidal powder of low dispersity, according to which a hydrogel is prepared, an aqueous suspension of the ground hydrogel is subjected to atomisation in a stream of gas, gelled particles containing moisture are collected from the atomisation, the particles are brought into contact with an organic liquid in order to remove at least some of the moisture and the particles are then subjected to drying. The process applies to the production of silica powders intended to serve as support for chromium oxide catalysts which may contain titanium oxide and are suitable for the polymerisation of ethylene.

Abstract: Process for the production of a microspheroidal powder of low dispersity, according to which a hydrogel is prepared, an aqueous suspension of the ground hydrogel is subjected to atomisation in a stream of gas, gelled particles containing moisture are collected from the atomisation, the particles are brought into contact with an organic liquid in order to remove at least some of the moisture and the particles are then subjected to drying.The process applies to the production of silica powders intended to serve as support for chromium oxide catalysts which may contain titanium oxide and are suitable for the polymerisation of ethylene.

Abstract: Process for the polymerization of alpha-olefins in the presence of a catalyst, including providing monodisperse microspheroidal particles by spraying an electrostatically charged gellable liquid material (L) through a spraying orifice and into a chamber, so as to produce macrodrops which break up into microdrops which fall in the chamber and within which gelling is produced after spraying; providing a catalyst for the polymerization of alpha-olefins which contains chromium and which is supported on the monodisperse microspheroidal particles; and polymerizing alpha-olefins in the presence of the catalyst.

Abstract: Process for obtaining monodisperse microspheroidal particles, comprising spraying an electrostatically charged gellable liquid material through a spraying orifice and into a chamber, so as to produce macrodrops which break up into microdrops which fall in the chamber and within which gelling is produced after spraying. The microspheroidal particles thus obtained can be collected on a solid surface or preferably in a liquid medium and find application in the manufacture of silica-based microspheroidal particles. These microspheroidal particles can be employed as catalyst supports for alpha-olefin polymerization.