Abstract: A process for the preparation of a meso/racemic-(bis(indenyl)ethane zirconium dichloride compound comprising (a) reacting zirconium tetrachloride with the solid reaction product of the bis(indenyl)ethane ligand with an alkyllithium in a solvent as reaction medium and (b) recovering a solid mixture of lithium chloride and meso/racemic composition of (bis(indenyl)ethane) zirconium dichloride, characterized in that the solvent used as reaction medium in a reaction (a) is an ether, pentane or a mixture thereof.

Abstract: A process for producing a chromium-based catalyst for the production of polyethylene, the process comprising the steps of providing a catalyst support selected from silica, silica-titania and silica-zirconia; reacting the support with one of an aluminium alkyl compound or a chromium salt compound selected from at least one of chromium (III) acetylacetonate, chromium (III) acetate, chromium (III) oxalate and chromium (III) stearate; and thereafter reacting the support with the other of the aluminium alkyl compound or the chromium salt to produce a chromium-impregnated catalyst having a silica-alumina support, the catalyst composition comprising from 0.4 to 1.5 wt % chromium, based on the weight of the chromium-based catalyst and the alumina in the silica-containing support comprising from 0.5 to 4 wt % aluminium in the chromium-based catalyst.

Abstract: High-solids air-drying or semi-drying alkyd paints essentially comprise, as binder, a conventional air-drying or semi-drying long-oil or medium-oil alkyd resin, and as reactive diluent an oligomer of polyol, polyisocyanate and unsaturated fatty acids. Use of the oligomer as reactive diluent is also claimed.

Abstract: Bridged metallocenes of Group IVb metals provide improved results when the bridge comprises a neutral electron-donor substituent of general formulaR'"Z R"".sub.jwhereinR'" is a rigid unsaturated hydrocarbon radical between Z and the bridge, such that Z is separated from the bridge by 2 to 5 carbon atomsZ is nitrogen, phosphorus, oxygen or sulphur,R"" is H or an alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl having a maximum of 15 carbon atoms, each R"" being the same or different,j is 1 when Z=O or S and 2 when Z=N or P.

Abstract: Process for the preparation of polyethylene by the homopolymerization of ethylene or by the copolymerization of ethylene and of at least one alpha-olefinic comonomer containing from 3 to 10 carbon atoms, in two reactors for loop polymerization in liquid phase which are connected in series in the presence of a chromium catalyst, in which ethylene and the chromium catalyst are first introduced into the first reactor at a temperature of 95 to 110.degree. C. to produce an ethylene homopolymer of low molecular weight of a melt index MI.sub.2 of at least 1 g/10 minutes and in which the ethylene homopolymer thus obtained is next transferred into the second reactor to which ethylene and optionally the alpha-olefinic comonomer is added, at a temperature of 80 to 90.degree. C. to obtain an ethylene copolymer of high molecular weight.

Abstract: A process for eliminating color from vinyl aromatic/conjugated diene copolymers which process comprises treating the copolymers with a monocarboxylic acid having the general formula R--COOH, where R is a hydrocarbon radical comprising 2 to 4 carbon atoms and R further comprises linear or branched aliphatic radicals, cycloaliphatic radicals, alkenic radicals, aromatic radicals or alkylaromatic radicals.

Abstract: Powder compositions comprising about 5-15 wt % of PVdF-compatible thermoplastic resin, about 50-90 wt % of a thermosetting binder system, about 0-35 wt % of pigments and about 0-3 wt % of leveling agent are disclosed which are particularly suitable for use as primers with a later application of a pigmented PVdF-based top coating. Preferred compositions are based on an epoxy system containing about 8 wt % of PVdF or acrylic thermoplastic resin, 5-25 wt % of pigments and 0.7-1 wt % of leveling agent.

Abstract: An elastomer is blended with bitumen, an alkaline compound is then added which is soluble in the bitumen, and to this mixture is added 0.01 to 0.1% by weight of a mixture of vulcanizing agents comprising elemental sulphur and a sulphur-containing derivative of the form: ##STR1## where R.sub.1 and R.sub.2 are C.sub.1 to C.sub.4 alkyl radicals or, together R.sub.1 and R.sub.2 have the formula ##STR2## and where M, which is optional, is Zn, Ba or Cu.

Abstract: Sulphur-containing hydrocarbon feedstocks are desulphurized prior to being subjected to steam cracking in the presence of one or more thiohydrocarbons wherein the sulphur is part of aromatic heterocycles, preferably thiophene and/or benzothiophene. Optimum results are obtained in terms of the combination of reduced coking rate and reduced carbon monoxide formation.

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, fluordised before or during the activation step, and reduced, the first and second chromium-based catalysts having a pore volume difference of at least O.8 cc/g.

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.

Abstract: Bridged metallocenes of Group IVb metals provide improved results when the bridge comprises a neutral electron-donor substituent of general formulaR'" Z R"".sub.jwhereinR'" is a rigid unsaturated hydrocarbon radical between Z and the bridge, such that Z is separated from the bridge by 2 to 5 carbon atomsZ is nitrogen, phosphorus, oxygen or sulphur,R"" is H or an alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl having a maximum of 15 carbon atoms, each R"" being the same or different,j is 1 when Z=O or S and 2 when Z=N or P.

Abstract: Process for reducing the wax content of wax-containing hydrocarbon feedstocks to produce middle distillate products including low freeze point jet fuel and/or low pour point and low cloud point diesel fuel and heating oil. The process involves contacting the feedstock with a hydrocracking catalyst containing a carrier, at least one hydrogenation metal component of Group VIB and Group VIII metals, and a large pore zeolite such as a Y type zeolite, in a hydrocracking zone in the presence of hydrogen at elevated temperature and pressure, and contacting the entire effluent from the hydrocracking zone with a dewaxing catalyst containing a crystalline, intermediate pore size molecular sieve selected from metallosilicates and silicoaluminophosphates in a hydrodewaxing zone in the presence of hydrogen at elevated temperature and pressure.

Abstract: Powder compositions comprising about 5-15 wt % of PVdF-compatible thermoplastic resin, about 50-90 wt % of a thermosetting binder system, about 0-35 wt % of pigments and about 0-3 wt % of leveling agent are disclosed which are particularly suitable for use as primers with a later application of a pigmented PVdF-based top coating. Preferred compositions are based on an epoxy system containing about 8 wt % of PVdF or acrylic thermoplastic resin, 5-25 wt % of pigments and 0.7-1 wt % of leveling agent.

Abstract: The present invention relates to the production of high density polyethylene homopolymers or copolymers having a broad and monomodal molecular weight distribution wherein the polymerization process is conducted in the presence of supported metallocene-alumoxane catalysts wherein the metallocene is bridged, comprises at least a hydrogenated indenyl or fluorenyl and a metal M which may be Ti, Zr or Hf, wherein a plurality of conformers of the metallocene are formed and isolated on the support by reaction of the metallocene with the alumoxane and depositing the product formed on the support at a temperature in the range 85.degree. C. to 110.degree. C.

Abstract: Silicalite to be used as catalyst in the isomerization of olefins is pretreated by passing steam thereon at a temperature of 300 to 750.degree. C. Particularly, isobutene is selectively produced by isomerization of n-butenes.

Abstract: Bituminous compositions modified with self-adhesive cold-application polymers generally used for manufacturing of watertight panels, said compositions comprising a mixture containing a rubbery styrene-diene polymeric mixture, one or more tackifying resins, and bitumen.

Abstract: Medium-chain olefins containing as impurities 2-alkyl substituted isomers having a close boiling point are purified by (i) passing over a solid acid catalyst under mild conditions to selectively double-bond isomerise said impurities, and (ii) separating said isomerised olefins by distillation.

Abstract: The present invention relates to polypropylene fibers and nonwoven fabrics produced from spunlaid or staple fibers having improved natural bulk. Said polypropylene fibers are made of a blend of sPP and iPP.

Abstract: A improved process is provided for the alkylation of aromatic compounds under at least partial liquid phase conditions, and in the presence of a zeolite-type alkylation/transalkylation catalyst. In accordance with the present process, a diluted aromatic hydrocarbon feedstock containing C.sub.5 -C.sub.7 olefins is brought into contact with a diluted olefinic feedstream in the presence of the alkylation/transalkylation catalyst. Prior to contact with the olefinic feedstream, C.sub.5 -C.sub.7 olefins present in the aromatic hydrocarbon feedstock are selectively hydrogenated.