Abstract: Solid components of catalysts for the (co)polymerization of ethylene, or precursors of such components are prepared by treating an (a) emulsion in a perfluoropolyether of a liquid compound of magnesium, of titanium or of another transition metal, or of solutions thereof, possibly using an electron-donor compound, with (b) a reducing and/or halogenating agent capable of forming an insoluble solid product, after which, if such a product is a precursor of the catalytic component, it is treated with a tetravalent-titanium halide, or with a halide of another transition metal.

Abstract: A catalyst for polymerization of olefins is disclosed which comprises a titanium and/or vanadium compound supported on a silicon and/or aluminum oxide carrier. This carrier has peculiar characteristics including a specified proportion of highly spherical oxide particles, a selected average pore size and a specified proportion of a selected particle size range before and after ultrasonic treatment, whereby there is obtained a catalyst having increased bulk density, narrow particle size distribution and high fluidity.

Abstract: A vanadium-based catalyst is treated with certain oxygen-containing compounds as a means of narrowing and effectively regulating the molecular weight distribution of the polymers produced with the catalyst.

Abstract: A catalyst component for polymerization of olefin, comprising a contact product of a component (A) which is a solid component containing titanium having at least one OR.sup.1 group (where R.sup.1 represents a hydrocarbon residue) and magnesium and a halogen as the essential components; a component (B) which is an acid halide compound; a component (C) which is a compound having an OR.sup.2 group (where R.sup.2 represents a hydrocarbon residue or hydrogen atom); and a component (D) which is a halide compound of silicon. When an olefin is polymerized by use of this as the transition metal component of a Ziegler type catalyst, an olefin polymer with high activity and high I.I and excellent polymer properties can be obtained.

Abstract: A process for producing an alcohol adducted or complexed hydrocarbon soluble magnesium chloride comprising reacting in a hydrocarbon medium a compound selected from magnesium metal, dialkyl magnesium, dialkoxy magnesium and alkoxy magnesium chloride with a dry hydrogen halide and a C.sub.1 to C.sub.10 chloro-alcohol or mixtures of chloro-alcohol and a C.sub.5 to C.sub.18 beta-alkyl substituted alcohol which may optionally contain some C.sub.1 to C.sub.20 primary unsubstituted monohydric alcohol.

Abstract: Catalyst for polymerization of .alpha.-olefines, comprising an organoaluminum compound, an electron donor, as well as a solid catalyst component which is obtained when a compound containing magensium reacts with a titanium halogen compound. A method for producing the catalyst is also provided. The catalyst component is manufactured by reacting with a titanium halogen compound in the presence of an internal electron donor, a solid catalyst component which has been produced by the steps of(a) reacting a magnesium alkyl compound with a chlorinating compound,(b) dissolving the chlorinated magnesium alkyl compound in alcohol, after possible washing,(c) adding into the solution, magnesium silicate which has been calcinated by heating at about 200.degree.-600.degree. C.,(d) adding the mixture obtained in step (c) into a cold medium, to precipitate the magnesium compound into and onto the magnesium silicate carrier, and(e) separating the thus-obtained solid carrier component.

Abstract: A catalyst for olefin polymerization which comprises a combination of:Component which is a solid catalyst component A obtained by contacting a component (i) which is a solid component comprising titanium, magnesium and halogen as essential elements with a component (ii), which is a silicon compound represented by formula: R.sup.1 R.sup.2.sub.3-n Si(OR.sup.3).sub.n where R.sup.1 stands for a branched hydrocarbon radical, R.sup.2 stands for a hydrocarbon radical which is the same as or different from R.sup.1 and n stands for a number satisfying an equation: 1.ltoreq.n.ltoreq.3;Component B which is an organoaluminum compound; andComponent C which is a compound represented by a formula M(OR.sup.4).sub.x R.sup.5.sub.y X.sub.z in which M stands for an element selected from the group consisting of B, Al, C, Si, Sn, P, S, Cl, Br, I, Fe, Ti, V, Zr, Mg, Ca and Zn, R.sup.4 and R.sup.

Abstract: A vanadium catalyst composition comprising:(i) the reaction product of a vanadium trihalide wherein the halogen is chlorine, bromine, or iodine, or mixtures thereof, and an electron donor, which is a liquid, organic Lewis base in which the vanadium trihalide is soluble;(ii) a silica support onto which component (i) is impregnated;(iii) a salt admixed with the silica support, the cation of said salt being selected from the group consisting of Groups I and II of the Periodic Chart of the Atoms;(iv) a halocarbon promoter; and(v) a hydrocarbyl aluminum cocatalyst.

Abstract: Crystalline magnesium olefin polymerization catalyst components capable of producing polymer with improved activity and morphological properties are disclosed and claimed. In particular, the components are prepared by reacting a crystalline alkoxy magnesium compound with a halide of tetravalent titanium.

Abstract: The present invention relates to an improvement of the known Ziegler catalyst which comprises a combination of a titanium-containing component and an organoaluminum component, and the present invention is characterized by a specific titanium-containing component. Namely, this titanium-containing component is obtained by contacting a known titanium-containing component of the Ziegler type catalyst which comprises Ti, Mg and a halogen, with an alkoxyalkylsilane compound which is characterized in that at least one of the alkyl groups has a branched structure. This catalyst does not require a so-called external electron donor, and no reduction of the polymerization velocity caused by the use of the electron donor is entailed. When this catalyst is used, a propylene/ethylene block copolymer in which the molecular weight of the propylene/ethylene copolymer portion and/or the polyethylene portion is increased, that is, the rigidity and impact strength are increased, can be prepared.

Abstract: A catalyst component for alpha olefine-polymerizing catalysts which comprise an organoaluminum compound, an external electron donor, and a solid catalyst component obtained when a solid carrier component containing magnesium has reacted with a titanium halide compound, in addition to a procedure for manufacturing the same. The catalyst component is produced by reacting a solid carrier component with a titanium halide compound with or without the presence of an internal electron donor. The solid carrier component is prepared by(a) dissolving or suspending a magnesium compound in ethanol or water,(b) adding to the solution or suspension, hydrochloric acid in a substantially stoichiometric quantity to the magnesium, to completely dissolve the same,(c) drying the magnesium solution with the aid of periodic azeotropic distillation, and(d) precipitating the solid carrier component from the thus-dried solution.

Abstract: A catalyst component for alpha olefine-polymerizing catalysts which comprise an organoaluminum compound, an external electron donor, and a solid catalyst compound obtained when a solid carrier component containing magnesium has reacted with a titanium halide compound, in addition to a procedure for manufacturing the same. The catalyst component is produced by reacting a solid carrier component with a titanium halide compound with or without the presence of an internal electron donor. The solid carrier component is prepared by(a) precipitating a water-soluble magnesium compound from an aqueous solution thereof by adding an alkali thereto,(b) separating the thus-precipitated magnesium component and dissolving the same in hydrochloric acid,(c) evaporating the solution until dry,(d) heating the obtained salt mixture at 130.degree. to 150.degree. C.

Abstract: A catalyst component for alpha olefine-polymerizing catalysts which comprise an organoaluminum compound, an external electron donor, and a solid catalyst compound obtained when a solid carrier component containing magnesium has reacted with a titanium halide compound, in addition to a procedure for manufacturing the same. The catalyst component is produced by reacting a solid carrier component with a titanium halide compound with or without the presence of an internal electron donor. The solid carrier component is prepared by(a) dissolving, in hydrochloric acid, a magnesium compound selected from the group consisting of magnesium hydroxide, magnesium carbonate, magnesium oxide, and natural and/or synthetic minerals containing the same,(b) evaporating the solution until dry,(c) heating the obtained salt mixture at 130.degree. to 150.degree. C.

Abstract: A catalyst component for alpha olefine-polymerizing catalysts which comprise an organo-aluminum compound, an external electron donor, and a solid catalyst component obtained when a solid carrier component containing magnesium has reacted with a titanium halide compound, in addition to a procedure for manufacturing the same. The catalyst component is produced by reacting a solid carrier component with a titanium halide compound with or without the presence of an internal electron donor. The solid carrier component is prepared by(a) dissolving a natural or synthetic mineral containing magnesium and aluminum in hydrochloric acid,(b) evaporating the solution until dry,(c) calcinating the obtained salt mixture from the evaporated solution by heating the same at a temperature of about 130.degree.-150.degree. C.

Abstract: Monocarboxylic anhydrides of the general formula (RCO).sub.2 O are made by reacting a carboxylic acid ester or dialkylether of the general formulae RCOOR and ROR, respectively, in which R stands for one and the same alkyl radical having from 1-4 carbon atoms, with carbon monoxide in gas phase, in the presence of iodine or bromine or their compounds as a reaction promoter and also in the presence of a carrier-supported catalyst containing noble metal compounds of group VIII of the Periodic System, at temperatures of 130.degree.-400.degree. C. and under pressures of 1-150 bars. To this end, a novel carrier-supported catalyst is used in which the carrier material has a noble metal/chelate-compound formed of the noble metal compound and a chelator containing organonitrogen, organophosphorus, organoarsenic or organosulfur groups applied to it.

Abstract: Ethylene and alpha-olefins are homopolymerized or copolymerized with another olefin monomer in the presence of a catalyst system comprising an organo metal cocatalyst and a titanium-containing catalyst component, said titanium-containing catalyst component being obtained by reacting together a porous particulate material, an organic magnesium compound, an oxygen-containing compound, an acyl halide, titanium tetrachloride and Cl.sub.2, Br.sub.2 or an interhalogen compound and treating the solids with an organometallic compound of a Group IIa, IIb or IIIa metal.

Abstract: A process for activating a titanium or vanadium compound and producing polyethylene comprising (i) dissolving a divalent magnesium halide and a Lewis acid having the formula R.sub.m A1X.sub.n or R.sub.m BX.sub.

Abstract: In a process for producing olefin polymer or copolymer by using a catalyst composed of (A) a solid titanium catalyst component containing magnesium, titanium, halogen and an electron donor and derived from a magnesium-containing solid carrier obtained by contacting a magnesium compound in the liquid state with a precipitant, and (B) an organometallic compound of a metal selected from the group consisting of metals of Groups I to III of the periodic table; the improvement wherein(I) said catalyst component (A) is a reaction product of (iv) a titanium compound in the liquid state and a magnesium-containing solid carrier formed by contacting(i) a magnesium compound in the liquid state having no reducing ability and not containing a tetraalkoxy-, tetracycloalkoxy- or tetraaryloxy-titanium compound, said magnesium compound being selected from the specified group, with(ii) a precipitant other than a titanium compound, in the presence or absence of (iii) an electron donor having no active hydrogen, and(II) said reac

Abstract: A process for polymerizing or copolymerizing ethylene, characterized in that ethylene or a mixture of ethylene with other .alpha.-olefin is polymerized in the presence of a catalyst comprising:[I] a solid catalyst component (B) obtained by reacting the following three components:(a) a reaction product (A) of an organomagnesium compound with a hydropolysiloxane or a silicon compound in which organic groups and hydroxyl groups are bonded to silicon atoms,(b) a silicon compound of the formula R.sub.l.sup.1 Si(OR.sup.2).sub.m X.sub.4-(l+m), wherein R.sup.1 is a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms, R.sup.2 is a hydrocarbon group having from 1 to 12 carbon atoms, X is a halogen atom, l is 0, 1 or 2, and m is a number of from 0 to 4, and(c) a titanium compound of the formula Ti(OR.sup.3).sub.n X.sub.4-n, wherein R.sup.

Abstract: A catalyst composition for polymerizing alpha-olefins is prepared by treating a carrier with a mixture of at least one organomagnesium composition of the formula(OR').sub.n Mg(OR).sub.m (I)where R and R' are the same or different C.sub.1 -C.sub.12 hydrocarbyl groups, m and n are each 0, 1 or 2, m+n=valence of Mg, and a compound of the formulaMX.sub.p (II)where M is Si, C, Ge or Sn, X is Cl or Br, and p is the valence of M, in a solvent capable of dissolving the mixture. The product of this step may or may not be dried. Subsequently, it is contacted with a transition metal compound.The polymer resins produced with the resulting catalyst have relatively narrow molecular weight distribution and high melt index values.

Abstract: A process for producing catalyst ingredient for use in olefin polymerization which comprises contacting (A) a magnesium hydrocarbyloxide and (B) a silicon compound having hydrogen-silicon bonds in the presence of a hydrocarbon medium, contacting the thus obtained solid product (C) a halogenated titanium compound in the presence or absence of a hydrocarbon medium and then adding to contact (D) an electron donating compound.

Abstract: A solid catalyst component which can produce .alpha.-olefin polymers having a high stereoregularity and a good powder fluidity, stably and with a good efficiency in gas phase polymerization, particularly in gas phase copolymerization, a catalyst for .alpha.-olefin polymerization using the above solid catalyst component and a process for producing the above catalyst component, are provided,which solid catalyst component is charcterized in that it contains titanium as an active ingredient and is in the form of hollow fine particles, andwhich process is characterized by adding a reaction product (I) of an organoaluminum compound (A) with an electron dnor (B.sub.1) to TiCl.sub.4 and reacting these under agitation in a baffle ratio of 0.35 or less with a power required for agitation of 2.50 KW/m.sup.3 or less at a temperature of 0.degree. to 70.degree. C. for a period of 1 to 10 hours and further reacting an electron donor (B.sub.

Abstract: A catalyst for the polymerization of olefins, said catalyst comprising a transition metal containing support catalyst component and an aluminum alkyl cocatalyst, said transition metal containing catalyst component obtained by contacting an inorganic metal oxide with an organomagnesium compound and an alcohol, drying the contact product, treating the dried contact product with an acyl halide, a halogen such as chlorine, a transition metal halide such as titanium tetrachloride, and in the last step treating the titanium-containing component with an organoaluminum compound such as tri-n-hexylaluminum.

Abstract: Disclosed is a catalyst component for polymerization of an olefin, which consists essentially of a contact reaction product of (A) a solid composition obtained by mixing and contacting a precipitating agent with a contact reaction product between a magnesium dihalide and a titanium tetraalkoxide and/or a polymer thereof, the addition of the precipitating agent being carried out with stirring at a stirring intensity lower than a level (2nf) two times the floatation limit stirring intensity (nf) of the reaction system, with (B) a liquid titanium compound and/or a halogen compound of silicon.This catalyst component has a high activity and provides a polymer in which the particle size is relatively large and the particle size distribution is sharply controlled.

Abstract: A process for producing a catalyst component for polymerization of olefins which comprises contacting (a) a metal oxide with (b) a magnesium alkoxide, contacting the resulting contact product with (c) a halogen-containing compound, and finally contacting the resulting contact product with (d) a titanium compound.

Abstract: A catalyst component for polymerization of olefins which is prepared by contacting a product obtained by contacting (A) a magnesium alkoxide, (B) a silicon compound having the hydrogen-silicon bond, and (C) a titanium compound with one another, with (D) (a) a hydrocarbon, (b) a halogenated hydrocarbon, and/or (c) a halide of an element selected from the elements of Groups IIIa, IVa, and Va of the Periodic Table.

Abstract: A process for producing a catalyst component for polymerization of olefins which comprises contacting (a) a metal oxide with (b) an organomagnesium compound represented by the formula RMgR' wherein R denotes a hydrocarbyl group and R' denotes a hydrocarbyl group or a halogen atom, contacting the resulting contacting product with (c) carbon dioxide, and further contacting the resulting contact product with (d) a titanium compound. Optionally, the carbon dioxide contacted product can be treated with the halogen-containing compound prior to contact with the titanium compound.

Abstract: Catalysts for polymerization and copolymerization of olefins to form polymers having a high degree of isotacticity and fast rate of crystal transformation. The catalysts embody a component made by chlorinating a magnesium alkyl with chlorine or a mixture of chlorine and alkyl chloride to form a carrier, contacting the carrier first with liquid TiCl.sub.4, then with a Lewis base, and after that at least once with TiCl.sub.4 in the absence of Lewis base.

Abstract: The invention relates to a catalytic titanium component useful for the polymerization of alkenes-1 and for the copolymerization of alkenes-1 with each other or with ethylene, containing a halogenated titanium compound, an electron donor, and a metal halide obtained by conversion of an organic metal compound with a halogenating agent of the formula RX.sub.m, wherein R is a hydrocarbon group, a hydrogen atom or a halogen atom, X is a halogen atom, and m is a whole number from 1-10. The catalytic titanium component according to the invention is characterized in that the metal halide has been obtained by conversion of a combination of an organic aluminium compound and an organic magnesium compound with the halogenating agent into the corresponding metal halide, for instance by means of a reaction with hydrogen chloride or an alkyl chloride.

Abstract: A process for preparing spherical particles of a compound with the general formula Mg(OR).sub.2-a (OR').sub.a is disclosed. In the process R is an alkyl group with from 2 to 8 carbon atoms, R' is an alkyl group with from 1 to 7 carbon atoms and a is a number of from 0 to 0.5. The process comprises preparing a homogeneous solution of a compound Mg(OR).sub.2 in an aliphatic alcohol with the general formula R'OH, spray-drying the solution at a temperature of from 15.degree. to 85.degree. C., suspending the spray-dried solid particles in an aliphatic alcohol with the formula ROH in which R is the same alkyl group as present in the said compound Mg(OR).sub.2, heating the suspension in order to remove an alcohol with the formula R'OH from the liquid phase by distillation and separating the solid particles from the liquid phase.

Abstract: A solid hydrocarbon-insoluble, alpha-olefin polymerization catalyst component with superior activity, stereospecificity and morphology characteristics, comprises the product formed by (a) complexing a magnesium alkyl composition with an organophosphoryl compound; (b) reacting the resulting stable complex with a compatible precipitation agent to form a solid component; and (c) reacting the resulting solid with a titanium (IV) compound and an electron donor compound in a suitable diluent.

Abstract: An intermetallic compound is disclosed formed by(a) mixing a compound having the structural formula R(R')Mg where R and R' are the same or different and are hydrocarbyl of 1 to 10 carbon atoms with a compound having the structural formula R.sup.1.sub.m Si(OR.sup.2).sub.n X.sub.4-(m+n) where R.sup.1 and R.sup.

Abstract: A process for preparing a catalyst component for the polymerization of olefins which comprises the steps of contacting (a) a magnesium dialkoxide soluble in an inert solvent, (b) a silicon compound having the hydrogen-silicon bond, and (c) an electron donor compound with one another in the presence of an inert solvent, and contacting the resulting reaction product with (d) a titanium compound.

Abstract: A catalyst component for polymerization of olefins which is prepared by reacting a magnesium alkoxide with a silicon compound having at least one hydrogen-silicon bond, contacting the reaction product with a carboxylic acid halide and/or carboxylic acid anhydride, and contacting the resulting contact product with a titanium compound.

Abstract: A catalyst component for the polymerization of olefins which is prepared by contacting a contact reaction product of (a) a metal oxide, (b) an organic magnesium compound, and (c) an alkoxy group-containing compound held in contact with (d) a titanium compound.

Abstract: A catalyst support consisting essentially of a mixture of silica and magnesium chloride, said support having a porous structure and containing less than 100 micromoles of hydroxyl groups per gram of support; the process of making such support by heating such mixture at a temperature below about 720.degree. C. in the presence of a dehydrating agent, and catalysts consisting essentially of such support and at least one active component.

Abstract: Ethylene and alpha-olefins are homopolymerized or copolymerized with another olefin monomer in the presence of a catalyst system comprising an organo metal cocatalyst and a titanium-containing catalyst component, said titanium-containing catalyst component being obtained by reacting together a porous particulate material, an organic magnesium compound, an oxygen containing compound, an acyl halide and titanium tetrachloride, a Group IIIa hydrocarbyl metal dihalide and Cl.sub.2, Br.sub.2, an interhalogen or mixtures thereof.

Abstract: An intermetallic compound is disclosed. The compound is formed by reacting a first reaction product, the first reaction product being the product of reaction of a polymeric transition metal oxide alkoxide with a reducing metal having a higher oxidation potential than the transition metal, the polymeric transition metal oxide alkoxide being the product of the controlled partial hydrolysis of a transition metal alkoxide, with a first halide activator to produce a second reaction product. The second reaction product, in turn, is reacted with a second halide activator to form the intermetallic compound. The intermetallic compound is useful as a catalyst component in a catalyst system for the polymerization of alpha-olefins. The catalyst system includes, in addition to the intermetallic compound, a cocatalyst, an organic compound which includes an element selected from the group consisting of aluminum and boron.

Abstract: Ethylene and alpha-olefins are homopolymerized or copolymerized with another olefin monomer in the presence of a catalyst system comprising an organo metal cocatalyst and a titanium-containing catalyst component, said titanium-containing catalyst component being obtained by reacting together a porous particulate material, an organic magnesium compound, a halogen agent other than Cl.sub.2, Br.sub.2 and an interhalogen compound, titanium tetrachloride and Cl.sub.2, Br.sub.2, an interhalogen or mixtures thereof.

Abstract: Novel titanium compounds or complexes are prepared by reacting a titanium compound such as titanium tetraisopropoxide with a compound containing at least one aliphatic hydroxyl group. These compounds and/or complexes are useful as the transition metal component in supported Ziegler-Natta catalysts.

Abstract: Ethylene and alpha-olefins are homopolymerized or copolymerized with another olefin monomer in the presence of a catalyst system comprising an organo metal cocatalyst and a titanium-containing catalyst component, said titanium-containing catalyst component being obtained by reacting in the presence of a porous particulate material, a halogen, an organic magnesium compound, an oxygen-containing compound, titanium tetrachloride and treating the solids with an organometallic compound of a Group IIa, IIb or IIIa metal.

Abstract: A catalyst, a process of forming the catalyst, and polymerizing at least one alpha-olefin with the catalyst, said catalyst produced by precipitating a composition from a solution of a metal halide, for example, magnesium dihalide, and a transition metal compound, for example, titanium tetraalkoxide, in the presence of a particulate diluent, for example, polymeric fibrils, with an agent selected from among specified organometallic compounds, metal halides and oxygen-containing metal halides, hydrogen halides and organic acid halides. The composition is preferably further treated with a halide ion exchanging source, for example, titanium tetrahalide to form a particularly active catalyst. The catalyst is preferably used in combination with a cocatalyst comprising a metal hydride or organometallic compound selected from an element of Periodic Groups IA, IIA and IIIA.

Abstract: A catalyst component for the polymerization of olefins which is prepared by contacting a reaction product of dihydrocarbyl magnesium and a halogen-containing alcohol held in contact with a titanium compound.

Abstract: Lewis base-bridged intermetallic compounds comprising the reaction product of a transition metal alkoxide with a reducing metal having a higher oxidation potential than the transition metal in the presence of a Lewis base and said reaction product being associated by coordinate covalent bridges formed from the Lewis base and composed of donor atoms selected from the group consisting of oxygen, nitrogen, sulfur and phosphorous; and catalyst components and systems for the polymerization of alpha olefins.

Abstract: A vanadium containing catalyst component useful for polymerizing olefins to polyolefins having a high molecular weight and broad molecular weight distribution comprising polymerizing the olefins in the presence of a catalyst comprising (a) a vanadium containing catalyst component obtained by contacting an inert support material with an organoaluminum compound, a halogenating agent and a vanadium compound, and (b) an aluminum alkyl cocatalyst.

Abstract: A catalyst for polymerizing olefins is the product resulting from heating in an inert hydrocarbon diluent a mixture of (A) an organomagnesium material, (B) an epihalohydrin, (C) a reducing halide source and (D) a transition metal compound.

Abstract: A solid catalyst component for .alpha.-olefin polymerization which, when produced, causes any troubles due to its small particle size and when used, yields a spherical polymer of a suitably less particle size and a high bulk density with a slightest quantity of atactic polymer and affording a very good dispersibility of powdery additives therein in spite of its narrow particle size distribution, and a process for producing the same, are provided, which solid catalyst component comprises Ti and Cl as active ingredients, having an average particle diameter of 2 to 10.mu., a specific surface area of 100 m.sup.2 /g or more and a diffraction line corresponding to a distance between lattices of 4.80 to 5.10 .ANG. by way of X-ray diffraction; and which process is characterized in that when TiCl.sub.4 is reduced with a reducing agent comprising an organoaluminum compound to produce a solid intermediate, there is employed an agitation intensity defined by definite values of agitation power and baffle ratio.

Abstract: An olefin polymerization catalyst prepared by reacting a metal dihalide and a transition metal, then reacting that component with a precipitating agent, and then reacting the resulting solid with an activating component, wherein multiple activation steps are used so that it is possible to obtain a given level of activity with less activating component.

Abstract: An olefin polymerization catalyst prepared by reacting an admixture of anhydrous magnesium dihalide and hydrous magnesium dihalide with reactants including benzoic acid ester, an alkoxytitanium compound, an organoaluminum halide, and a titanium halide.

Abstract: A solid-hydrocarbon insoluble, alpha-olefin polymerization catalyst component with superior activity, stereospecificity and morphology characteristics, comprises the product formed by (a) complexing a magnesium alkyl composition with an ortho disubstituted hindered aromatic acid ester; (b) reacting the resulting complex with a compatible precipitation agent to form a solid component; and (c) reacting the resulting solid with a titanium(IV) compound and an electron donor compound in a suitable diluent.