Abstract: A process for the preparation of polyolefins having a bi- or multimodal molecular weight distribution, the process comprising the steps of: (i) contacting an olefin monomer and a first co-reactant with a catalyst system in a first reaction zone under first polymerization conditions to produce a product comprising a first polyolefin having a first molecular weight distribution; and (ii) contacting an olefin monomer and a second co-reactant with a catalyst system in a second reaction zone under second polymerization conditions to produce a product comprising a second polyolefin having a second molecular weight distribution different from the first molecular weight distribution; wherein the first and second polyolefins are mixed together, wherein one of the co-reactants is hydrogen and the other is a comonomer selected from butene, methylpentene, hexene or octene, and wherein each catalyst system comprises (a) a metallocene catalyst component comprising a bis tetrahydroindenly compound of the general formula (In

Abstract: A process for producing polyolefins having a bimodal molecular weight distribution, the process comprising producing a first polyolefin fraction in the presence of a catalyst in a first loop reactor, and producing a second polyolefin fraction in the presence of the catalyst in a second loop reactor which is serially connected to and downstream of the first loop reactor, the first and second polyolefin fractions being blended in the second loop reactor to form a polyolefin having a bimodal molecular weight distribution, at least the first loop reactor containing a diluent under supercritical conditions which is circulated around the loop of the reactor, and wherein at least the first loop reactor is provided with a fluff concentrating device communicating with the loop and in which polyolefin fluff of the first fraction is concentrated in the supercritical diluent, and polyolefin fluff of the first polyolefin fraction is transferred together with an amount of supercritical diluent from the fluff concentrating

Abstract: Uses of syndiotactic/atactic block polypropylene are provided in which the molecular weight thereof is preferably at least 120 kD. The syndiotactic/atactic block polypropylene may be used as a polypropylene modifier, a component in an adhesive composition, a shock absorber component, a waterproof membrane component, a packaging film or component thereof, a shapable composition component, and an acoustic absorbent material component, a composition for moulding into a footwear component, a bitumen modifier, a compatibiliser, an emulgator or an emulsifier, as a viscosity improver, and as a spilled oil absorber.

Abstract: A process for the preparation of polyethylene resins having a multimodal molecular weight distribution which comprises: (i) contacting ethylene monomer and a comonomer comprising an alpha-olefin having from 3 to 10 carbon atoms with a first catalyst system in a first reactor under first polymerisation conditions to produce a first polyethylene having a first molecular weight, an HLMI of not more than 0.5 g/10 min and a first density of not more than 0.

Abstract: The present invention relates to a chromium/silca-aluminophosphate catalyst, titanated under specific conditions and used for the homopolymerisation or the copolymerisation of ethylene. The polyethylene obtained with this catalyst has a high melt potential and a high shear resistance. The catalyst has a high level of activity.

Abstract: The present invention relates to a chromium/silca-aluminophosphate catalyst, titanated under specific conditions and used for the homopolymerisation or the copolymerisation of ethylene. The polyethylene obtained with this catalyst has a high melt potential and a high shear resistance. The catalyst has a high level of activity.

Abstract: A process for producing a chromium-based catalyst for the production of polyethylene, the process comprising providing a silica support having a surface area of at least 380 m2/g and a pore volume of at least 1.5 ml/g; impregnating the silica support with a liquid including a source of aluminum ions and a source of phosphate ions; neutralizing the resultant impregnated support with a neutralizing agent to provide a pH greater than 7 for the resultant neutralized support whereby aluminum phosphate forms in pores of the silica support; and, at any stage in the method, impregnating the silica support with a chromium component.

Abstract: A blow moulded automobile fuel tank having a wall defining a fuel chamber wherein the minimum wall thickness of the wall is from 2.4 mm to less than 3 mm, the tank being composed of a high density polyethylene having a density of from 0.945 to 0.955 g/cm3, a high load melt index of from 5 to 9.5 g/10 min, the high density polyethylene optionally having a carbon black content of up to 0.5 wt %, and the fuel tank having a fire resistance and an impact resistance both complying with the respective standards defined in ECE 34, ANNEX 5.

Abstract: A process for producing high density polyethylene, the process comprising polymerising ethylene, or copolymerising ethylene and an alpha-olefinic comonomer comprising from 3 to 10 carbon atoms, in the presence of a catalyst system comprising first and second chromium-based catalysts, the first chromium-based catalyst having been reduced and reoxidised and the second chromium-based catalysts having been activated, fluoridised before or during the activation step, and reduced, the first and second chromium-based catalysts having a pore volume difference of at least 0.8 cc/g.

Abstract: A process for producing high density polyethylene in the presence of a metallocene catalyst system in two liquid full loop reactors in series, wherein in a first reactor a first polyethylene product is polymerized substantially by homopolymerization of ethylene and hydrogen, and in a second reactor serially connected to the first reactor downstream thereof a second polyethylene product is copolymerized from ethylene and an alpha-olefinic comonomer comprising from 3 to 8 carbon atoms, and a hydrogenation catalyst is introduced into the reactants downstream of the first reactor, the hydrogenation catalyst comprising a second metallocene catalyst of general formula: Cp2MXn where Cp is a substituted or unsubstituted cyclopentene dienyl group; M is a transition metal from Group IVB of the Periodic Table or vanadium; X is a halogen or a hydrocarbyl group having from 1 to 10 carbon atoms; and n is the valency of the metal M minus 2.

Abstract: A process for reducing the water take up of a vinyl aromatic-conjugated diene polymer when subjected to a humid environment, the process comprising solution polymerising at least one vinyl aromatic hydrocarbon and a conjugated diene in the presence of a catalyst based on an alkali metal to produce alkalimetal derivatives of a vinyl aromatic-conjugated diene polymer and neutralising the derivatives with a C9-C16 alkyl dicarboxylic acid.

Abstract: A process for producing a vinyl aromatic-conjugated diene block copolymer, the process comprising solution polymerising at least one vinyl aromatic hydrocarbon and a conjugated diene in the presence of a catalyst based on an alkali metal to produce copolymer chains which end with an alkali metal and treating the copolymer chains in solution with an alkyl dicarboxylic acid having at least 2 carbon atoms and the acid being in the form of a slurry in an organic liquid with the acid being granulated and having an average granule size of less than 50 microns.

Abstract: A process is disclosed for improving the yield in the production of high octane gasoline after naphtha reforming by utilizing a transalkylation step to upgrade the heavy and light fractions coming from the reforming step.

Abstract: A process for producing a Ziegler-Natta catalyst, the process comprising reacting an organo magnesium compound with a halogenated compound to produce crystalline magnesium halide having an intense diffraction line in an x-ray spectrum thereof at lattice distance within the range of from 2.56 to 3.20 Angstroms and titanating the magnesium halide by mixing the magnesium halide with a titanium compound whereby the titanated magnesium halide hasp in an x-ray spectrum thereof, a halo appearing at a lattice distance within the range from 2.56 to 3.30 Angstroms.

Abstract: A process for producing a polyethylene resin having improved mechanical properties, the process comprising polymerising ethylene in the presence of a chromium-based catalyst to make polyethylene homopolymer in a first polymerisation reactor and in a second polymerisation reactor downstream of the first polymerisation reactor copolymerising ethylene in the presence of the chromium-based catalyst and a co-catalyst from ethylene monomer and comonomer generated in-situ in the second polymerisation reactor to make polyethylene copolymer.

Abstract: A C1 symmetric metallocene compound of general formula R″(CpRb)CP′R′m) MQp for use as a catalyst component in the production of short sequence syndiotactic/isotactic block polyolefins, where Cp is a substituted cyclopentadienyl; each R is independently aryl or hydrocarbyl having 1 to 20 carbon atoms, at least position 3 of Cp is substituted with aryl, at least one other position of Cp is substituted with a non-bulky substituent, and n is an integer in the range from 2 to 4; Cp′ is substituted or unsubstituted fluorenyl; each R′ is independently hydrocarbonyl having 1 to 20 carbon atoms and m is O or an integer in the range from 1 to 8; R″ is a structural bridge to impart stereorigidity between Cp and Cp′; M is a metal from Group IIIB, IVB, VB or VIB; Q is a hydrocarbyl radical having 1 to 20 carbon atoms or a halogen; and p is the valence of M minus 2.

Abstract: A process for producing polyethylene having improved crack resistance, the process comprising copolymerizing ethylene and an alpha-olefinic comonomer comprising from 3 to 8 carbon atoms, in the presence of a chromium-based catalyst in a first reactor, feeding the polyethylene copolymer thereby produced and the chromium-based catalyst to a second reactor, and in the second reactor copolymerizing ethylene and an alpha-olefinic comonomer comprising from 3 to 8 carbon atoms, in the presence of the chromium-based catalyst thereby to produce a second polyethylene product, the first and second polyethylene products forming a combined polyethylene having a monomodal molecular weight distribution.

Abstract: A process for producing medium density polyethylene by copolymerizing ethylene and an alpha-olefinic comonomer comprising from 3 to 10 carbon atoms in the presence of a chromium-based catalyst having a support comprising silica and titania, the catalyst being fluorinated and having been chemically reduced by carbon monoxide, and in the presence of a co-catalyst selected from at least one of an aluminum alkyl and a zinc alkyl to produce a polyethylene copolymer having a density of from 0.930 to 0.945 g/cc and a dispersion index (D) of from 9 to 13.

Abstract: A process of producing polyethylene, the process comprising copolymerizing ethylene and an alpha-olefinic comonomer comprising from 3 to 8 carbon atoms in the presence of a chromium-based catalyst in a main polymerization reactor and, in a gas-phase preliminary reactor upstream of the main polymerization reactor, chemically treating the chromium-based catalyst with at least one treatment agent prior to introduction of the catalyst into the main polymerization reactor and releasing from the preliminary reactor waste gases produced during the chemical treatment.

Abstract: The present invention relates to bituminous compositions used for roofing and waterproofing membranes or material comprising asymmetrical linear polyvinyl aromatic-polydiene block copolymers having improved physical properties over broader ranges of service temperatures than those obtained from bituminous compositions prepared with symmetrical block copolymers of similar type. The asymmetry of the copolymer which is characterised by polyvinyl aromatic endblocks of at least two different molecular weights, one high and one low, ensures improved physical performance to roofing and waterproofing membranes made from such compositions.