Abstract: The present invention relates to a process for polymerizing or copolymerizing alpha-olefins comprising, on the one hand, a prepolymerization stage by contacting one or more alpha-olefins with a Ziegler catalyst system consisting of a solid catalyst containing essentially atoms of halogen, magnesium and transition metal, and a co-catalyst consisting of an organometallic compound, and, on the other hand, a polymerization or copolymerization stage in a gas phase process by means of a fluidized bed, by contacting one or more alpha-olefins with the prepolymer produced in the first stage, process characterized in that the alpha-olefin prepolymer and polymer or copolymer are in the form of a powder consisting of particles having specific values for the transition metal content and the mean diameter by mass, and characterized in that the particle size distribution of the prepolymer is narrow and easily controlled.

Abstract: The present invention relates to a process for polymerizing or copolymerizing alpha-olefins comprising, on the one hand, a prepolymerization stage by contacting one or more alpha-olefins with a Ziegler catalyst system consisting of a solid catalyst containing essentially atoms of halogen, magnesium and transition metal, and a co-catalyst consisting of an organomatellic compound, and, on the other hand, a polymerization or copolymerization stage in a gas phase process by means of a fluidized bed, by contacting one or more alpha-olefins with the prepolymer produced in the first stage, process characterized in that the alpha-olefin prepolymer and polymer or copolymer are in the form of a powder consisting of particules having specific values for the transition metal content and the mean diameter by mass, and characterized in that the particle size distribution of the prepolymer is narrow and easily controlled.

Abstract: The invention relates to processes and apparatus for the elutriation of particles of a Ziegler-Natta type alpha-olefin polymerization catalyst, based on transition metal compound(s) and preferably also comprising magnesium compounds, by means of an elutriation liquid which is a non-polar liquid, for example a hydrocarbon chemically inert in relation to the catalyst. A preferred process comprises the following stages:preparation of a homogeneous suspension of the catalyst in the elutriation liquid, andelutriation of the catalyst by means of the suspension and the elutriation liquid in one or two elutriation columns (F1),(F2), separating the large and fine catalyst particles respectively.The apparatus comprises a tank (M2) for the preparation of the catalyst suspension and the elutriation column or columns (F1),(F2).

Abstract: The present invention relates to a gas phase process for the (co-)polymerization of alpha-olefins in a fluidized bed, by means of a catalyst system of the Ziegler-Natta type consisting of a catalyst (a) comprising magnesium, halogen and transition metal atoms and a cocatalyst (b) consisting of an organometallic compound. The catalyst system is (i) prepared in a granular form, either fixed on a granular support or converted into a prepolymer, (ii) then subjected to a treatment by a polymerization inhibiting agent in the absence of alpha-olefins, and then (iii) brought into contact with alpha-olefins under (co-)polymerization conditions in the fluidized bed, in the presence of a cocatalyst (c) consisting of an organometallic compound, identical or different from the cocatalyst (b).

Abstract: The invention relates to processes and apparatus for the elutriation of particles of a Ziegler-Natta type alpha-olefin polymerization catalyst, based on transition metal compound(s) and preferably also comprising magnesium compounds, by means of an elutriation liquid which is a non-polar liquid, for example a hydrocarbon chemically inert in relation to the catalyst. A preferred process comprises the following stages:preparation of a homogeneous suspension of the catalyst in the elutriation liquid, andelutriation of the catalyst by means of the suspension and the elutriation liquid in one or two elutriation columns (F1), (F2), separating the large and fine catalyst particles respectively.The apparatus comprises a tank (M2) for the preparation of the catalyst suspension and the elutriation column or columns (F1),(F2).

Abstract: The present invention relates to a process for the preparation of olefins and diolefins by the cracking of hydrocarbons in the presence of steam, consisting in passing a mixture of hydrocarbons and steam flowing in a cracking tube disposed inside a radiation zone of a furnace. The process is characterized in that the mean dwell time of the mixture of flowing in the cracking tube between the inlet and the outlet of the radiation zone is from 300 to 1800 milliseconds, and the reaction volume is greater in the first half of the tube length than in the second one. The present invention relates also to a cracking furnace in which the ratio between the length and the mean diameter of the cracking tube is from 200 to 600, and the tube diameter decreases from the inlet to the outlet of the radiation zone.

Abstract: A process for sealing railroad structures in which the ballast is cleared from the track, the ties are placed on blocks 3, prefabricated concrete elements 6 then being placed under each block, concrete is then poured into the spaces 7 between the prefabricated elements and finally after hardening the tracks are again lowered onto the railroad structure. This relatively simple process sequence includes the use of a synthetic concrete, preferably a synthetic microconcrete, which ensures that due to an extremely intimate connection between the prefabricated elements and the concrete in the spaces between these elements a monolithic layer is obtained.

Abstract: The present invention relates to a process for polymerizing or copolymerizing alpha-olefins comprising, on the one hand, a prepolymerization stage by contacting one or more alpha-olefins with a Ziegler catalyst system consisting of a solid catalyst containing essentially atoms of halogen, magnesium and transition metal, and a co-catalyst consisting of an organomatellic compound, and, on the other hand, a polymerization or copolymerization stage in a gas phase process by means of a fluidized bed, by contacting one or more alpha-olefins with the prepolymer produced in the first stage, process characterized in that the alpha-olefin prepolymer and polymer or copolymer are in the form of a powder consisting of particles having specific values for the transition metal content and the mean diameter by mass, and characterized in that the particle size distribution of the prepolymer is narrow and easily controlled.

Abstract: The invention relates to apparatus for the elutriation of particles of a Ziegler-Natta type alpha-olefin polymerization catalyst, based on transition metal compound(s) and preferably also comprising magnesium compounds, by means of an elutriation liquid which is a non-polar liquid, for example a hydrocarbon chemically inert in relation to the catalyst. The apparatus comprises a tank (M2) for the preparation of the catalyst suspension and the elutriation column or columns (F1), (F2).

Abstract: The invention relates to a process for preparing supported catalysts for the copolymerization of ethylene with higher alpha-olefins, characterized in that a compound of a transition metal of Groups IV, V and VI of the Periodic Table of Elements, used at its maximum valency, is precipitated on to a support of magnesium chloride and possibly aluminum chloride by a reduction reaction in two stages, employing reducing agents selected for the first stage from among alkylaluminum dihalides, and for the second stage from among organo-metallic compounds with a higher reducing power than that of the alkylaluminum dihalides.These catalysts are particularly well suited to the copolymerization in the gas phase of ethylene and higher alpha-olefins.

Abstract: The present invention relates to catalysts for the polymerization and copolymerization of ethylene, characterized in that they comprise a support based on magnesium chloride and possibly on aluminium chloride, of spheroidal shape, having a mean diameter by mass comprised between 10 and 100 microns and with a narrow particle size distribution, such that the ratio of the mean diameter by mass to the mean diameter by number is less than or equal to 3, on which support there has been precipitated a derivative of a transition metal of groups IV, V and VI of the Periodic Table of Elements, and a polymerization process utilizing the said catalysts.

Abstract: An emulsion formed by mixing water with a mixture consisting essentially of an unsaturated polyester resin and an unsaturated monomer, wherein said emulsion is so stable that demulsification does not occur when a setting agent of a kind which sets by hydration thereof is added thereto.