Abstract: The present invention relates to a continuous process for controlling the gas-phase co-polymerisation of olefins in a fluidised bed reactor. The present invention further relates to a method for the continuous gas-phase (co-)polymerisation of olefins in a fluidised bed reactor in the presence of a polymerisation catalyst wherein the density of the polymer powder particles leaving the reactor is maintained constant by controlling the particle size distribution of the polymerisation catalyst. The present invention also relates to a process for controlling the particle size distribution of a polymerisation catalyst in order to achieve the production of a polymer powder of constant density during the continuous gas-phase (co-)polymerisation of olefins in a fluidised bed reactor.

Abstract: Supported ionic metallocene catalyst systems may be prepared by a method comprising the following steps: i) mixing together in a suitable solvent: a) an organometallic compound, and b) an ionic activator comprising a cation and an anion; ii) addition of the mixture from step (i) to a support material; iii) addition of a metallocene complex in a suitable solvent; iv) further addition of an organometallic compound in a suitable solvent; and v) removal of the solvent. The preferred supported catalysts comprise a constrained geometry metallocene complex for example (t-butylamido)(tetramethyl-→5-cyclopentadienyl) dimethyl silanetitanium-→4-1,3-pentadiene and are particularly suitable for the polymerisation of ethylene or the copolymerisation of ethylene and &agr;-olefins having from 3 to 10 carbons in the gas phase.

Abstract: The present invention relates to a continuous process for controlling the gas-phase co-polymerisation of olefins in a fluidised bed reactor. The present invention further relates to a method for the continuous gas-phase (co-)polymerisation of olefins in a fluidised bed reactor in the presence of a polymerisation catalyst wherein the density of the polymer powder particles leaving the reactor is maintained constant by controlling the particle size distribution of the polymerisation catalyst. The present invention also relates to a process for controlling the particle size distribution of a polymerisation catalyst in order to achieve the production of a polymer powder of constant density during the continuous gas-phase (co-)polymerisation of olefins in a fluidised bed reactor.

Abstract: Supported inonic metallocene catalyst prepared by a process comprising the following steps; (i) mixing together in a suitable solvent (a) an metallocene complex, (b) an ionic compound comprising a cation and an anion having up to 100 non-hydrogen atoms and containing at least one substituent comprising a moiety having an active hydrogen, and (c) optionally a support material, (ii) treating the mixture obtained in (i) with an organometallic compound, and (iii) addition of a support material if not added in step (i), and (iv) removing the solvent.

Abstract: Supported ionic metallocene catalyst systems may be prepared by a method comprising the following steps: i) mixing together in a suitable solvent: a) an organometallic compound, and b) an ionic activator comprising a cation and an anion; ii) addition of the mixture from step (i) to a support material; iii) addition of a metallocene complex in a suitable solvent; iv) further addition of an organometallic compound in a suitable solvent; and v) removal of the solvent. The preferred supported catalysts comprise a constrained geometry metallocene complex for example (t-butylamido)(tetramethyl-5-cyclopentadienyl)dimethyl silanetitanium-→4-1,3-pentadiene and are particularly suitable for the polymerisation of ethylene or the copolymerisation of ethylene and &agr;-olefins having from 3 to 10 carbons in the gas phase.

Abstract: The valve device adjustably controls air flow through a mechanical ventilation duct, blocks propagation of flames through the duct, and selectively exhausts smoke through the duct. An air extraction terminal sleeve communicates with the ventilation duct and is provided with an outwardly facing valve seat. A support is mounted in the sleeve inwardly of the valve seat and an elongated guide extends adjustably through the support. An obturator is mounted on the guide outwardly of the support for adjustably controlling the flow area into the terminal sleeve, and includes an outwardly convex dome member fixedly secured to the outer end of the guide, and an inwardly convex valve member having conforming seating engagement with the dome member and arranged to conformingly engage the valve seat to block flow into the terminal sleeve.