Abstract: Catalysts for the polymerization of alpha-olefins, which comprise the product of the reaction between:(a) a metalorganic compound of Al;(b) an electron-donor compound reactive towards MgCl.sub.2 but which is not completely complexed with AlEt.sub.3, at the equivalent point of a potentiometric titration under standard conditions;(c) a solid comprising a halogenated Ti compound and an electron-donor belonging to particular classes of compounds and being extractable with AlEt.sub.3 for at least 70% by mols from the solid, the surface area of which after extraction is higher than 20 m.sup.2 /g.The present invention refers to new supported components of catalysts for the polymerization of olefins CH.sub.2 .dbd.CHR, in which R is an alkyl with 1-14 carbon atoms or an aryl, and of mixtures of such olefins with each other and/or with ethylene, and to the catalysts obtained from such components.

Abstract: An inexpensive one-step process is disclosed for producing the lower hydrates of magnesium dihalide by comminuting hydrated magnesium dihalide and anhydrous magnesium dihalide. Also the use of such hydrous magnesium dihalide products in the olefin polymerization catalysts.

Abstract: Components of catalysts for the polymerization of ethylene and of mixtures thereof with other olefins, in the form of emulsions or dispersions, in an inert liquid medium or in an inert gas phase of a liquid phase, comprising a compound of a metal of Groups IV to VI inclusive, of the Mendelyeev Periodic System, or a composition containing such a compound of the Mendelyeev Periodic System, which compound or composition is immiscible with aliphatic hydrocarbons, or which components are obtained from emulsions or dispersions, in an inert liquid medium or in gas phase, of a precursor of the catalyst component which, in the liquid state, is immiscible with the aliphatic hydrocarbons.An object of this invention is to provide new catalyst components for use in the polymerization of ethylene and of mixtures thereof with olefins and the catalysts obtained therefrom.

Abstract: A preactivated catalyst for producing .alpha.-olefin polymers is provided, which is obtained by the steps which comprises:reacting an organoaluminum compound (O-Al.sub.1) with an electron donor (ED.sub.1) to obtain a reaction product (I);reacting (I) with TiCl.sub.4 to obtain a solid product (II);reacting (II) with an electron donor (ED.sub.2) and an electron acceptor to obtain a solid product (III);combining (III) with an organoaluminum compound (O-Al.sub.2) and a reaction product (RP) of an organoaluminum (O-Al.sub.3) with an electron donor (ED.sub.3) (III), (O-Al.sub.2) and (PP) being referred to as catalyst components), and in this combination, subjecting a part or the whole of the catalyst components to polymerization treatment with an .alpha.-olefin at least in the presence of (III) and said (O-Al.sub.2) to obtain a preliminarily activated catalyst; andpolymerizing an .alpha.-olefin in the presence of the catalyst.

Abstract: The present invention relates to catalysts which can be used for the polymerization and copolymerization of propylene with other alpha-olefins, characterized in that they comprise a support containing essentially magnesium chloride and possibly a chlorinated aluminium derivative, and occurring in the form of spheroidal particles having a mean diameter by mass comprised between 10 and 100 microns and a 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, which support has been treated by an electron donor compound chosen from among the aromatic ethers and aromatic acid esters and which when impregnated with titanium tetrachloride comprises 0.5 to 3% of atoms of titanium per atom of magnesium, and process for utilizing the said catalyst.

Abstract: An ethylene polymerization catalyst comprising a supported precursor of vanadium trihalide/electron donor complex and alkylaluminum or boron halides, when combined with alkylaluminum cocatalyst and alkyl halide promoter provides enhanced polymerization and productivity plus superior polyethylene.

Abstract: A catalyst component useful for (co)polymerizing ethylene under high temperatures and pressures comprising the reaction product obtained by treating a magnesium halide supported titanium halide precursor with transition-metal halide or oxyhalide, thoroughly washing the solid reaction product therefrom and prepolymerizing the washed solid product with an alpha-olefin having from 4-12 carbon atoms.

Abstract: A catalytic component for polymerizing olefins comprises a solid support containing magnesium-halogen or manganese-halogen bonds, a transition metal halide of a metal selected from Groups IVB and VB of the periodic table, and electron donors. This catalytic component is obtainable by steps comprising:(a) contacting a mixture comprising a magnesium halide or manganese halide and at least one electron donor with a Ti(OR).sub.4 compound to form a solution, where R is a hydrocarbyl or halogenated hydrocarbyl moiety containing 1 to 20 carbon atoms or a halogen, and(b) reacting the solution with a reagent comprising a transition metal halide selected from Groups IVB and VB of the periodic table,whereby, with a suitable cocatalyst, polyolefin is formed with high activity, showing a high Isotactic Index, and with a narrow range of particle size distribution.

Abstract: An olefin polymerization catalyst prepared by reacting water with a magnesium dihalide in the presence of a phase transfer catalyst and reacting the resulting hydrated magnesium dihalide with reactants including a benzoic acid ester, an alkoxytitanium compound, an organoaluminum halide and a titanium halide.

Abstract: A superior high-rigidity and high-melt-viscoelasticity polypropylene for sheets to be post-processed and for blow molding is provided which polypropylene is produced by subjecting propylene to a multi-stage polymerization into polymer portions of two sections in the presence of a specified Ziegler Natta catalyst, the relationship between the intrinsic viscosities of the polymer portions of the respective sections being regulated within a specified range and also the amount ratio of the polymer portions of the respective sections being regulated.

Abstract: An olefin polymerization and interpolymerization catalyst composition prepared by reacting novel magnesium silylamide compounds with at least one compound of a transition metal selected from Groups IIIB, IVB, VB and VIB of the fourth and fifth periods of the periodic table, and Groups VIIB and VIIIB of the fourth period.

Abstract: A catalyst for polymerizing olefins is the reaction product of (A) the reaction product of (1) the reaction product of (a) an alkyl magnesium compound such as dibutylmagnesium, with (b) an oxygen-containing and/or nitrogen-containing compound such as n-propyl alcohol, or isopropylamine, with (2) a halide source such as titanium tetrachloride or silicon tetrachloride; and (B) a transition metal compound such as titanium tetrachloride and (C) a reducing agent such as triisobutylaluminum.Also disclosed is a non-transition metal containing catalyst support for use in preparing olefin polymerization catalysts.The polymers which are produced in the presence of this catalyst and a cocatalyst such as triethylaluminum have a low catalyst support to transition metal ratio and therefore, the catalyst efficiency based on quantity of polymer per quantity of total catalyst is very high resulting in a polymer having good color and very little, if any, corrosion.

Abstract: A catalyst and its method of preparation and use involving reacting a magnesium dihalide, an alkoxytitanium compound and water, followed by reaction with an organoaluminum compound and then with a halide ion exchanging source.

Abstract: A novel catalyst system for the polymerization of alpha-olefins is provided. The catalyst system is produced by a process comprising heating to an effective temperature for an effective length of time:(i) an organoaluminum containing component comprising an organoaluminum compound and an electron donor compound, e.g. triethyl aluminum and ethyl anisate, and(ii) a titanium halide containing component obtained by contacting a titanium halide compound, e.g. TiCl.sub.4, or complex of the titanium halide compound and an electron donor compound, e.g. TiCl.sub.4.ethylbenzoate, with a support which comprises as the essential support material thereof an anhydrous bihalide of magnesium or manganese in an active state.The combination of effective temperature and effective time is selected to be sufficient to produce a catalyst system having enhanced stereospecificity.

Abstract: A process for producing terpolymers of propylene (as a main monomer), ethylene and another .alpha.-olefin having superior and well-balanced physical properties, almost without forming soluble polymer is provided.This process is characterized by preliminarily activating a catalyst consisting of a titanium trichloride composition and a specified organoaluminum halide, with a small amount of an .alpha.-olefin of 2 to 12 carbon atoms, a trialkylaluminum and an aromatic ester, and copolymerizing specified amounts of propylene, ethylene and an .alpha.-olefin of 4 to 12 carbon atoms in the presence of the preliminarily activated catalyst obtained above.

Abstract: A process for producing a polyolefin, which comprises polymerizing an olefin in the presence of a catalyst system comprising:(a) a solid catalyst component obtained by supporting a titanium compound and/or a vanadium compound on a solid product derived from the reaction of a phenol, an aromatic carboxylate ester, and a solid reaction product of an organomagnesium compound and an aryloxyaluminum compound represented by the general formula Al(OR.sup.1).sub.3, wherein R.sup.1 represents an aryl group having 6 to 20 carbon atoms; and(b) an organoaluminum compound.

Abstract: A process for the stereospecific polymerization of .alpha.-olefins which comprises polymerizing an .alpha.-olefin with a catalyst comprising (A) the reaction product of a magnesium compound and a titanium compound and (B) an organo-aluminum compound. Component (A) is prepared by reacting a (i) magnesium compound of the formula Mg(OR.sup.1).sub.n X.sup.1.sub.2-n wherein R.sup.1 contains from 1 to 10 carbon atoms and is an alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, X.sup.1 is a halogen atom, and n is a real number of from 1.0 to 2.0, with (ii) at least one halogen-containing compound selected from the group consisting of halogenated hydrocarbons, oxygen-containing halogenated hydrocarbons, halogenated thionyls, halogen-containing phosphorus compounds and halogen-containing nitrogen compounds, and (iii) an oxygen-containing titanium compound of the formula Ti(OR.sup.2).sub.4 wherein R.sup.

Abstract: Ethylene copolymers having a density of about 0.91 to 0.94 and a melt flow ratio of about .gtoreq.26 to .ltoreq.40 are readily produced in a low pressure gas phase process at a productivity of .gtoreq.500,000 pounds of polymer per pound of Ti with a catalyst formed from selected organo aluminum compounds and a composition prepared by copulverizing magnesium dihalide with a complex obtained by contacting a titanium compound of the structure Ti(OR).sub.a X.sub.b with an ether, ester, ketone or amine,wherein R is a C.sub.1 to C.sub.14 aliphatic or aromatic hydrocarbon radical, or COR' where R' is a C.sub.1 to C.sub.14 aliphatic or aromatic hydrocarbon radical,X is Cl, Br, I or mixtures thereof, a is 0 or 1, b is 2 to 4 inclusive and a+b=3 or 4.

Abstract: A process is disclosed for producing, in situ and without milling or grinding, an alpha olefin polymerization catalyst component which comprises adding an olefin to a titanium halide and then adding an electron donor to the mixture of the titanium halide and the olefin.

Abstract: Extremely strong, i.e., non-friable TiCl.sub.3 Ziegler-type polymerization catalyst are obtained by prepolymerizing a reduced solid TiCl.sub.3 product with a mixture of propylene and linear C.sub.8 -C.sub.18 alpha-olefin to produce a reduced solid TiCl.sub.3 product containing 5 to 35 weight percent of a copolymer of propylene and C.sub.8 -C.sub.18 alpha-olefin having a ratio of the infrared spectrum of the copolymer at 720 cm.sup.-1 : the infrared spectrum of the copolymer at 975 cm.sup.-1 in the range of 0.04 to 0.20.

Abstract: This invention comprises a catalytic component for polymerizing olefins comprising a solid support containing magnesium-halogen bonds, a transition metal halide of a metal selected from Groups IVB and VB of the periodic table, and an electron donor obtained by the steps comprising:(a) reacting an organometallic compound whose metal comprise members of Groups I to III of the periodic table with an alcohol, ROH, where R is an alkyl, cycloalkyl, or arylalkyl moiety having 1 to 16 carbon atoms, a polysiloxane, and a transition metal halide to form a solid;(b) treating the solid with a transition metal halide optionally in the presence of a polysiloxane to form a treated solid; and(c) reacting the treated solid with an electron donor and a transition metal halide to form the component.

Abstract: A polymer-supported constituent for olefin polymerization catalyst obtained by: mixing in organic solution a chlorine-containing organic polymer and a magnesium compound, removing the solvent, and reacting the resulting magnesium-modified polymer with a titanium halide. An olefin polymerization catalyst is formed by mixing such a polymer-supported constituent with an appropriate organo-metallic compound and optionally also an appropriate selectivity control agent.

Abstract: Catalysts for the polymerization of olefins, comprising the product of the reaction between:(a) an Al-alkyl compound;(b) an electron-donor compound capable of reacting with MgCl.sub.2 but which is not completely complexed with Al-triethyl at the equivalent point of a potentiometric titration under standard conditions and belonging to particular classes of compounds; and(c) a solid comprising a Ti compound having at least a Ti-halogen bond and an electron-donor compound belonging to particular classes of esters, both supported on a Mg halide in active form.

Abstract: An unmilled catalytic component for polymerizing olefins with high activity to yield polymers with high stereoregularity and a narrow particle size distribution with a low weight percentage of small particles comprises a solid, unmilled support containing magnesium-halogen bonds, a transition metal halide of a metal selected from Groups IVB and VB of the periodic table, and electron donors.This catalytic component is obtained by steps comprising:(a) contacting a Mg(OR).sub.2 and/or Mn(OR).sub.2 compound with a Ti(OR).sub.4 compound to comprise a liquid, where R is a hydrocarbyl or halogenated hydrocarbyl moiety containing 1 to 20 carbon atoms or a halogen,(b) reacting the liquid with a fluid comprising a halogenating agent and treatment with an electron donor to form a treated solid, and(c) post-treating the solid with a transition metal halide.

Abstract: A method is disclosed for increasing the productivity of an olefin polymerization catalyst. The catalyst contains an aluminum chloride co-crystallized titanium halide modified with an electron donor containing an ester group. The catalyst component is washed with an olefin and then electron donor is added back to the washed catalyst component, thereby greatly increasing its productivity without significantly adversely affecting the crystallinity of the polymer produced.

Abstract: A method is disclosed for increasing the productivity of an olefin polymerization catalyst. The catalyst contains an aluminum chloride co-crystallized titanium halide modified with an electron donor containing an ester group. The catalyst component is washed with an olefin, thereby greatly increasing its productivity without significantly adversely affecting the crystallinity of the polymer produced.

Abstract: A catalyst useful for polymerizing olefins which comprises a solid catalyst component [A] and an organometallic component [B], the solid catalyst component [A] being obtained by reacting (1) an organometallic compound with (2) a transition metal compound selected from the group consisting of a titanium compound, a vanadium compound, a mixture of a titanium compound and a vanadium compound and a mixture of a titanium compound and a zirconium compound, in the presence of (3) a solid reaction product of (a) an organomagnesium compound of the formulaM.sub..alpha. MgR.sub.p X.sub.q.D.sub.rwherein.alpha., p, q and r each independently is 0 or a number greater than 0,p+q=m.alpha.+20.ltoreq.q/(.alpha.

Abstract: A catalyst component is a transition metal composition which is obtained by reacting together an inert particulate material, an organic magnesium compound, a halogen-containing compound such as carbon tetrachloride or silicon tetrachloride and a specified transition metal compound. The catalyst component obtained can be used, together with an organic metal compound, to give an olefin polymerization catalyst. The catalyst can be used to effect the polymerization of olefin monomers, for example, the copolymerization of ethylene with an alpha-olefin monomer such as butene-1 in a fluidized bed reactor.

Abstract: This invention comprises a catalytic component for polymerizing olefins comprising a siliceous support containing magnesium halide, a transition metal halide, and an electron donor obtained by steps comprising:(a) infusing siliceous oxide with magnesium halide complexed with an alcohol to form a support;(b) reacting the support with an organometallic compound of a metal from Groups I to III of the periodic table to form an intermediate;(c) reacting the intermediate complex with an electron donor to form an intermediary complex; and(d) reacting the intermediary complex with a fluid comprising a transition metal halide.

Abstract: A supported transition metal composition is obtained by suspending a support material in an inert liquid medium, spraying the suspension, collecting a solid material and contacting the sprayed solid with a transition metal compound. The support material may be a metal halide such as magnesium chloride or an inorganic oxide such as silica or alumina. In addition to being contacted with the transition metal compound, the support material may be contacted either before or after the spraying step with other reagents such as organo metallic compounds, halogen compounds, or Lewis Base compounds. The product obtained after contacting with the transition metal compound may be used as a component of a polymerization catalyst system to polymerize an unsaturated monomer such as ethylene or propylene.

Abstract: A solid material which is a transition metal composition, or a support for a transition metal compound, is suspended in a liquid medium, the mixture is subjected to mechanical action and the treated mixture is spray-dried. If the solid is a support material, it is subsequently contacted with a transition metal compound. The mechanical action can be a grinding process or a process providing simultaneous vigorous agitation and a shearing action. The transition metal composition may be used with an organic metal compound to polymerize an unsaturated monomer to give a polymer of good particle form.

Abstract: A titanium containing composition is obtained by contacting a magnesium halide with a non-metallic halide such as thionyl chloride, for example by grinding, and contacting the product with a titanium tetrachloride-containing material, preferably undiluted liquid titanium tetrachloride. The treatment with titanium tetrachloride may be effected by milling or by suspending the solid in the titanium tetrachloride. The solid product can be washed at least once. An ester is preferably contacted with the magnesium halide. The product obtained may be used with an organic metal compound such as aluminum triethyl and preferably a Lewis Base such as ethyl benzoate or an organic silicon compound to give olefin polymerization catalyst. When used to polymerise propylene the product obtained is highly stereoregular and the level of residual catalyst is low.

Abstract: Catalyst-forming components are prepared from(a) a halogenated Ti compound containing at least a Ti-halogen bond;(b) an electron-donor compound free of active hydrogen atoms;and(c) the solid product of the reaction between at least one electron-donor compound containing active hydrogen atoms and a Mg dihalide or a complex thereof with an electron-donor compound free of active hydrogen atoms, obtained by decomposing organic Mg compounds containing at least one Mg-R or Mg-OR group, in which R is an alkyl, aryl, cycloalkyl or alkenyl radical having 1 to 20 carbon atoms, by means of a halogenating agent different from (a).Catalysts for polymerizing olefins and prepared by mixing the aforesaid catalyst-forming components with an organometallic compound of Al are also disclosed.

Abstract: A catalyst and a process for the preparation of homopolymers and copolymers of alpha monoolefins by means of a catalyst system comprising (1) a titanium halide of the formulaTiCl.sub.3 m AlCl.sub.3where m is a number from 0 to 0.5, (2) a coordination complexing agent, the use of which is optional, and (3) an appropriate conventional aluminum-alkyl, the titanium halide (1) and the complexing agent (2), if used, having been milled together before use, wherein the catalyst system employed contains, as a further component (4), a sterically unhindered phenolic compound.

Abstract: A suspension which comprises an inert liquid medium, a solid material, and a transition metal compound is dried using a spray-drying technique. The spray-drying is effected under conditions of temperature and pressure which are such as to cause evaporation of the liquid medium. The solid material is preferably in a finely-divided form. The solid material may consist essentially of a transition metal compound or may be a transition metal compound which is supported on a suitable solid inert matrix material. Alternatively, a suspension of a solid support material in a solution of a transition metal compound may be used. The dried solid is obtained as an agglomerate. The agglomerated solid can be mixed with an organic compound of a non-transition metal to give an olefin polymerization catalyst system.

Abstract: A process for the preparation of the former catalyst component of a catalyst for the polymerization of olefins composed of a titanium-based catalyst component and an organo aluminium compound is disclosed, which process comprises suspending (a) a fatty acid salt of magnesium and (b) dialkoxymagnesium into (c) a liquid halogenated hydrocarbon to form a first suspension, and adding said first suspension to (d) a titanium halide of the general formula: TiX.sub.

Abstract: A novel component of a catalyst for polymerization of olefins, which is highly active, exhibits high stereoregularity and also provides polymers of very uniform particle sizes. The catalyst component is a contact product of the following component A and component B:Component AA solid product obtained by mixing a solution of the following components (1) and (2) and 0.05 to 5 moles of a titanium tetrachloride precipitant per mol of the component (1) in the copresence of the following component (3), thereby to produce a solid product and then washing the solid product to remove a soluble titanium component; (1) a magnesium compound represented by the formula Mg(OR.sup.1).sub.2-n X.sub.n, wherein R.sup.1 is a hydrocarbyl having 1 to 12 carbon atoms, which is an alkyl, an aryl, an aralkyl or a cycloalkyl, or a halo-derivative thereof, X is a halogen, and n is a number satisfying 0<n.ltoreq.2; (2) a titanium compound represented by the formula Ti(OR.sup.2).sub.4 or a polymer thereof, wherein R.sup.

Abstract: A novel catalytic system for polymerizing olefins comprises:(a) a cocatalytic component containing an organometallic compound of Groups I-III of the periodic table, and(b) a catalytic component containing titanium obtained by:(i) copulverizing a substantially anhydrous magnesium compound containing halogen or manganese compound containing halogen with: a phenol, an organic polymer containing silicon, a titanium halide, and an electron-donor compound to produce a copulverized product, and(ii) reacting the copulverized product with a liquid titanium compound containing halogen.The invention also encompasses the novel catalytic component, processes for preparing the catalytic component containing titanium, and the use of the novel catalytic system for polyermizing olefins.

Abstract: An .alpha.-olefin polymerizing catalytic component is obtained by treating, with alcohol and/or phenol, a solid product obtained by allowing an organo-magnesium compound expressed by a generic formula of R'MgX' (wherein R' represents a hydro-carbon group having 1 to 20 carbon atoms and X' a halogen atom selected from the group consisting of chlorine, bromine and iodine or a hydrocarbon group having 1 to 20 carbon atoms) to react with a halogenating agent in the presence of an electron donor; by treating the treated matter with a halogen-containing titanium compound, either after heating under reduced pressure or without such heating; and by treating the product further with a mixture or a complex consisting of an organo-aluminum compound, an organic acid ester and a poly-siloxane. Homo- or co-polymerization of an .alpha.-olefin is carried out in the presence of a catalyst system comprising the catalytic component and an organo-aluminum compound.

Abstract: A catalytic component for polymerization of an .alpha.-olefin is prepared through a process wherein a solid product obtained by allowing an organo-magnesium compound or a mixture of an organo-magnesium compound and an organo-aluminum compound or their reaction product to react, in the presence of an electron donor and an .alpha.-olefin, with a mixture of a halogenating agent other than a halogenated titanium compound and a titanium compound or their reaction product is treated with an alcohol and/or a phenol. The treated product may be further treated with a halogenated titanium compound. Homo- or co-polymerization of an .alpha.-olefin is carried out in the presence of a catalyst composition consisting of the catalytic component and an organo-aluminum compound or with a concomitant electron donor used together with the catalyst composition.

Abstract: New components of catalysts for the polymerization of alpha-olefins, e.g., olefins containing three or more carbon atoms, and mixtures thereof with ethylene, are disclosed, said catalysts comprising a Mg dihalide and, chemically fixed thereto, a Ti compound and an electron-donor compound.

Abstract: A catalytic component for polymerization of an .alpha.-olefin is prepared by allowing an organo-magnesium compound expressed by the generic formula of RMgX (wherein R represents a hydrocarbon group having 1 to 20 carbon atoms and X a halogen atom or a hydrocarbon group having 1 to 20 carbon atoms) to react with carbon tetrahalide in the presence of an electron donor compound to obtain a solid product; by treating the solid product with phenols at 90.degree. to 180.degree. C.; and by further treating the phenol treated solid with a halogenated titanium compound. Homo- or co-polymerization of an .alpha.-olefin is carried out in the presence of a catalyst composition consisting of the catalytic component thus prepared and an organo-aluminum compound.

Abstract: A process for the preparation of the former catalyst component of a catalyst for the polymerization of olefins composed of a titanium-based catalyst component and an organo aluminium compound is disclosed.The former catalyst component can readily be produced by contacting (a) a fatty acid salt of magnesium, (b) an electron donor compound and (c) a titanium halide.In the polymerization of olefins by use of the former catalyst component, both the amount of catalyst residues in the produced polymer and halogen content therein are greatly reduced with high polymerization activity per unit weight of the former catalyst component and with high yield of stereoregular polymer.

Abstract: A Ziegler type supported catalytic component for polymerization of an .alpha.-olefin is prepared by allowing an organo-magnesium compound expressed by a generic formula of R'MgX' (wherein R' represents a hydrocarbon group having 1 to 20 carbon atoms and X' either a halogen atom chosen out of chlorine, bromine and iodine or a hydrocarbon group having 1 to 20 carbon atoms) to react wtih carbon tetrahalide in the presence of an electron donor compound to obtain a solid product through a solid-liquid separation process; by heat treating the separated solid product with a carbon halide; by treating the heat treated solid product with phenols at 90.degree. to 180.degree. C.; and by treating this phenol treated product further with a halogenated titanium compound. Homo- or co-polymerization of an .alpha.-olefin is carried out in the presence or a catalyst composition consisting of the above catalytic component and an organo-aluminum compound. With this catalytic component, stereospecific polymerization of an .alpha.

Abstract: Catalyst compositions suitable for producing ethylene polymers in a low pressure gas phase process are produced by forming a partially activated precursor composition from a magnesium compound, titanium compound, inert carrier material and an organoaluminum activator compound in an electron donor solvent.

Abstract: This invention provides a process for preparing polyolefins using a new catalyst. According to this invention, .alpha.-olefins can be polymerized or copolymerized to have good stereoregularity and at a high activity by the use of such new catalyst. The new catalyst used in this invention consists of [A] a solid component obtained by contacting (1) a magnesium oxide, (2) an aluminum trihalide, (3) a hydroxy compound represented by the general formula ROH wherein R is an organic radical having 1 to 20 carbon atoms and (4) a titanium halide and/or an addition product of a titanium halide and an aromatic carboxylic acid ester, and [B] an organometallic compound and/or an addition product of an organometallic compound and an aromatic carboxylic acid ester; or it consists of the solid component of the above [A], the organometallic compound and/or the addition product of an organometallic compound and an aromatic carboxylic acid ester of the above [B], and [C] an aromatic carboxylic acid ester.