Abstract: A catalyst for production of 1,4-polybutadiene which comprisesas the catalyst component (A) a transition metal compound represented by the formula M(R).sub.l (OR').sub.m X.sub.n-(l+m), wherein M denotes a transition metal atom, R and R' each denote a hydrocarbon group of 1-20 carbon atoms, X denotes a halogen atom, and l, m and n denote numerals satisfying the equations l.gtoreq.0, m.gtoreq.0 and n-(l+m).gtoreq.0, n corresponding to the valence of the transition metal,as the catalyst component (B) an organoaluminum compound represented by the formula AlR.sup.1.sub.a X'.sub.3-a, wherein R.sup.1 denotes a hydrocarbon group of 1-20 carbon atoms, X denotes a halogen atom, and a denotes a numeral satisfying the equation 1.gtoreq.a.gtoreq.3, or an aluminoxane obtained by the reaction of said organoaluminum compound with water, andas the catalyst component (C) an organic compound having at least two hydroxyl groups.

Abstract: An olefin metathesis catalyst system and process for the metathesis polymerization of cyclic olefins, such as dicyclopentadiene, are disclosed. The catalyst system comprises the reaction product of:(a) an imido transition metal halide complex of formula: ##STR1## wherein Ar is C.sub.6-20 aryl, preferably phenyl; M is a transition metal selected from the second and third rows of Groups 5, 6, 7 and 8 of the Periodic Table (IUPAC 1989 convention) and including for example niobium, tantalum, molybdenum, tungsten, rhenium, ruthenium or osmium, preferably tungsten or molybdenum; R is independently halide, C.sub.1-20 alkyl, C.sub.1-12 alkoxy, C.sub.1-12 haloalkyl, C.sub.6-20 aryl, C.sub.6-20 aryloxy, cyano or combinations thereof; L is independently a complexing ligand selected from carbonyl, C.sub.1-12 alkoxy, C.sub.1-12 haloalkoxy, C.sub.1-12 alkyl ethers, including mono-, di- and higher ethers, C.sub.12 alkylnitriles, C.sub.5-20 pyridines, C.sub.

Abstract: A catalyst for production of 1,4-polybutadiene which comprisesas the catalyst component (A) a transition metal compound represented by the formula M(R)l(OR')m X.sub.n-(l+m), wherein M denotes a transition metal atom, R and R' each denote a hydrocarbon group of 1-20 carbon atoms, X denotes a halogen atom, and l, m and n denote numerals satisfying the equations l.gtoreq.0, m.gtoreq.0 and n-(l+m).gtoreq.0, n corresponding to the valence of the transition metal,as the catalyst component (B) an organoaluminum compound represented by the formula AlR.sup.1.sub.a X'.sub.3-a, wherein R.sup.1 denotes a hydrocarbon group of 1-20 carbon atoms, X denotes a halogen atom, and a denotes a numeral satisfying the equation 1.ltoreq.a.ltoreq.3, or an aluminoxane obtained by the reaction of said organoaluminum compound with water, andas the catalyst component (C) an organic compound having at least two hydroxyl groups.

Abstract: A catalyst and process for the polymerization of cyclic olefins, such as dicyclopentadiene, are disclosed. The catalyst comprises the reaction product of a transition metal halide and a 1,4-hydroquinone of the general formula: ##STR1## wherein R is independently selected from the group of hydrogen, C.sub.1-12 alkyl, C.sub.6-20 aryl, halide, and C.sub.1-6 haloalkyl. Optional co-catalysts include borohydrides, organo tin hydrides and organo aluminum compounds. Polymerization can be carried out in a reaction injection molding process to prepare a molded article.

Abstract: A catalyst and process for the metathesis polymerization of cyclic olefins, such as dicyclopentadiene, are disclosed. The catalyst comprises the reaction product of a transition metal halide preferably tungsten, molybdenum, or tantalum halides and a diaryl carbinol of the formula ##STR1## wherein G is independently C.sub.1-12 alkyl, C.sub.1-12 alkoxy, C.sub.1-12 alkylamino, C.sub.6-20 aryl, halide, or C.sub.1-6 haloalkyl; g is independently 0 to 4; R is independently hydrogen or G or the R's are combined as a single bond or as a bridging group X, where X is CH.sub.2, CH.sub.2 CH.sub.2, O, S, SO, SO.sub.2 or NR.sup.1, and R.sup.1 is H or C.sub.1-6 alkyl. Optional co-catalysts include borohydrides, organo tin hydrides and organo aluminum compounds. Polymerization can be carried out in a reaction injection molding process to prepare a molded article.

Abstract: A catalyst for producing higher flow index linear low density polyethylene with relatively narrower molecular weight distributions is described. The catalyst is formed by treating silica having reactive OH groups with a dialkylmagnesium in a solvent for said dialkylmagnesium; then adding to said solvent a carbonyl containing compound to form an intermediate which is subsequently treated with a transition metal to form a catalyst precursor. The catalyst precursor is activated with triethylaluminum.

Abstract: A process for the production of thermoset copolymers having tailored product properties such as high glass transition temperature and/or increased cross-linking, the process comprising contacting a comonomer mixture with a methathesis catalyst system obtainable by combining at least a catalyst component and an activator component, wherein the comonomer is selected from compounds according to the formulae: ##STR1##

Abstract: A process for preparing a polymerization catalyst useful for the polymerization of olefins is provided comprising contacting a metal dihalide compound wherein the metal is selected from Group 2 and Group 12 of the Periodic Table and a transition metal compound which is a hydrocarbyloxide of a transition metal selected from Group 4 and Group 5 to form a first catalyst component; contacting the first catalyst component with at least one organoaluminum precipitating agent, wherein at least at the commencement of this step, the temperature at which such contacting is carried out is greater than about 70.degree. C. to about 150.degree. C. to form a solid product, and contacting the solid product with an activating agent to form a catalyst. Other aspects of the invention provide a catalyst prepared by the above described method and a polymerization process employing the thus prepared catalyst.

Abstract: A catalyst and process for the polymerization of cyclic olefins, such as dicyclopentadiene, are disclosed. The catalyst includes a transition metal compound and a borohydride co-catalyst, with optional boron halide promoter. Polymerization can be carried out in a reaction injection molding process to prepare a thermoset molded article.

Abstract: Improved lower .alpha.-olefin polymerization catalysts are produced from an organoaluminum cocatalyst, a selectivity control agent and a specified magnesium-containing, titanium-containing, halide-containing procatalyst. The procatalyst is produced from an electron donor, tetravalent titanium halide and a complex alkoxide compound formed from magnesium alkoxide, titanium alkoxide and a phenolic compound. The catalyst is utilized to produce poly-.alpha.-olefin in good yield, which polymer is characterized by a relatively low xylene solubles content and a relatively high bulk density.

Abstract: Herein is disclosed a vulcanizable rubber composition comprising a copolymer rubber constituted of ethylene, propylene and nonconjugated polyene, wherein ethylene/propylene molar ratio is 78/22 to 97/3 and the total content of propylene and nonconjugated polyene is 6 to 30% by mole in said copolymer rubber. By the use of the rubber composition of the present invention, a vulcanized product excellent in tensile strength, heat resistance, oil resistance, compression set resistance and flex behavior can be obtained. The vulcanized product can be used as automobile parts and other innumerable articles such as socket cover, heat resistant hose, electric wire, condenser cap, heat resistant belt, vibration-proof rubber, hoses weather strip, seal sponge, black side wall of tire, etc.

Abstract: High cis-1,4-polybutadiene can be synthesized by polymerizing 1,3-butadiene monomer with a three component nickel catalyst system containing (a) an organonickel compound, (b) an organoaluminum compound, and (c) a fluorine containing compound. However, the molecular weight of the high cis-1,4-polybutadiene prepared is typically too high to be utilized as a non-oil extended rubber. This invention is based upon the discovery that halogenated phenols act to reduce the molecular weight and to increase the molecular weight distribution of high cis-1,4-polybutadiene prepared with such nickel based catalyst systems. The use of halogenated phenols as modifiers in such polymerizations does not change the microstructure of the high cis-1,4-polybutadiene produced.

Abstract: A supported alpha-olefin polymerization catalyst composition is synthesized by reacting (1) a slurry of a solid catalyst carrier in a non-polar solvent, e.g., hexane, with a dialkyl organomagnesium composition; (2) contacting the slurry of step (1) with a chlorinated alcohol; (3) contacting the slurry of step (2) with at least one transition metal compound; (4) removing the non-polar solvent to obtain a dry-flowing powder; and, (5) activating the powder with an activator. The resulting catalyst composition has high polymerization activity in the polymirazation of C.sub.2 -C.sub.10 alpha-olefins and exhibits very good higher (C.sub.3 -C.sub.10) alpha-olefin incorporation properties in the copolymerization of ethylene with the higher alpha-olefins.

Abstract: An ethylene-.alpha.-olefin copolymer is disclosed, which comprises ethylene and an .alpha.-olefin having from 3 to 10 carbon atoms, has an ethylene/.alpha.-olefin molar ratio of from 88/12 to 98/2, and which has a number average molecular weight of from 35,000 to 80,000 and a weight average molecular weight/number average molecular weight ratio of from 1.8/1 to 3.0/1 as determined by gel permeation chromatography. A process for producing the ethylene-.alpha.-olefin copolymer is also disclosed. The ethylene-.alpha.-olefin copolymer exhibits excellent transparency and excellent low-temperature heat-sealing properties. The process is advantageous from the standpoint of equipment, energy and cost.

Abstract: An ethylene-.alpha.-olefin copolymer comprising ethylene and an .alpha.-olefin having from 3 to 10 carbon atoms, the copolymer having an .alpha.-olefin content of from 1.0 to 8.0 mol %, a density of from 0.900 to 0.930 g/cm.sup.3, and a melt flow rate of from 0.1 to 100 g/10 min., the programed-temperature thermogram of said copolymer as determined with a differential scanning calorimeter after being completely melted and then gradually cooled showing an endothermic peak (a) in a range of from 75.degree. to 100.degree. C. and an endothermic peak (b) in a range of from 120.degree. to 140.degree. C., with the ratio of an endotherm at the endothermic peak (b), .DELTA.Hb, to an endotherm at the endothermic peak (a), .DELTA.Ha, i.e., .DELTA.Hb/.DELTA.Ha, being from 0.03 to 2.0. The copolymer provides a film exhibiting excellent physical properties required for packaging film.

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: A supported alpha-olefin polymerization catalyst composition is synthesized by reacting (1) a slurry of a solid catalyst carrier in a non-polar solvent, e.g., hexane, with a dialkyl organomagnesium composition; (2) contacting the slurry of step (1) with a chlorinated alcohol; (3) contacting the slurry of step (2) with at least one transition metal compound; (4) removing the non-polar solvent to obtain a dry-flowing powder; and, (5) activating the powder with an activator. The resulting catalyst composition has high polymerization activity in the polymerization of C.sub.2 -C.sub.10 alpha-olefins and exhibits very good higher (C.sub.3 -C.sub.10) alpha-olefin incorporation properties in the copolymerization of ethylene with the higher alpha-olefins.

Abstract: Allyloxy activated surface coatings of free radical-polymerizable compounds having fugitive acid stabilized metal drier and peroxide free radical initiator form durable films over urethane substrates.

Abstract: A metathesis polymerization catalyst composition comprising a binuclear catalyst, wherein said binuclear catalyst is a mixture of at least two transition metal components, wherein a first transition metal component is a halide complex of tungsten, an oxyhalide complex of tungsten or a mixture thereof and a second transition metal component is a halide complex of a transition metal selected from the group consisting of high valent transition metals belonging to Groups IV or V of the Periodic Table, from about 1 to about 3 moles of phenolic compound per mole of tungsten component, activated by a metathesis catalyst activator and containing a rate moderator.

Abstract: Solutions of VCl.sub.4 in inert organic solvent are stabilized by incorporation of decomposition retardants being halogenated organic compounds having at least two halogen atoms attached to the same carbon atom and activated by adjacent electron donor groups or carbon-carbon double bonds. One of the especially preferred stabilizers is butyl perchlorocrotonate. The solutions are useful in polymerization processes.

Abstract: Allyolxy activated surface coatings of free radical-polymerizable compounds having fugitive acid stabilized metal drier and peroxide free radical initiator form durable films over urethane substrates.

Abstract: Disclosed is the incorporation into a two-part metathesis-catalyst system of a halogen containing hydrocarbyl additive, where the hydrocarbyl additive contains at least one trihalogen substituted atom or at least one activated halogen atom. The use of this catalyst system to polymerize dicyclopentadiene results in a thermoset polymer containing low levels of residual monomer. Also disclosed is a preferred embodiment of dicyclopentadiene polymerization where the two parts of the metathesis-catalyst system, plus dicyclopentadiene are combined in the mixing head of a reaction injection molding machine and then injected into a mold where the dicyclopentadiene rapidly sets up into a thermoset polymer.

Abstract: Coating compositions comprising (a) free-radical polymerizable compound, (b) metal drier reversibly inhibited to catalyzing free-radical polymerization by a fugitive acid and (c) an allyloxy compound exhibiting long pot life and rapid cure, e.g. at elevated temperature, to hard, tough coatings.

Abstract: This invention concerns the production of 1,4-cis polybutadiene, or copolymers of butadiene with other related diolefins, through the catalytic polymerization or copolymerization of butadiene monomer by a continuous or discontinuous process carried out in the absence or substantial absence of solvents or diluents and operating in the presence of solid bodies.

Abstract: This invention concerns the production of 1,4-cis polybutadiene or copolymers of butadiene with other related diolefins through the catalytic polymerization or copolymerization of butadiene monomer by a continuous or discontinuous process carried out in the absence or substantial absence of solvents or diluents, operating in two successive phases (the first at a T<30.degree. C. and the second at a T=or>30.degree. C.) by control of the molecular weights.

Abstract: Disclosed is a method of making a cross-linked poly(dicyclopentadiene) with a metathesis-catalyst system, where the metathesis-catalyst system contains an organoaluminum or organoaluminum halide activator and a pentavalent tantalum catalyst. In a preferred embodiment, the cross-linked polymer is formed by combining, in a first place, a plurality of reactant streams, one reactant stream which contains the activator, a second reactant stream which contains the catalyst and at least one reactant stream which contains dicyclopentadiene; then injecting the combined reactant streams into a second place, such as a mold, where polymerization occurs. Use of the pentavalent tantalum catalyst results in the formation of a cross-linked polymer having less color and greater transparency than cross-linked poly(dicyclopentadiene) made without a pentavalent tantalum catalyst.

Abstract: Isoprene polymers and copolymers are prepared by a polymerization process carried out in the absence of solvents and in the presence of a catalytic system comprising (a) at least one element or compound of an element pertaining to Group IIIB of the Periodic Table, (b) at least one aluminium alkyl derivative, (c) at least one organic halogen derivative or at least one halide of an element able to exist in at least two valency states with the halide corresponding to a higher state than the minimum, or at least one halogen or at least one hydrogen halide acid, (d) at least one compound containing one or more hydroxyl groups of which the hydrogen can be substituted, the ratio of component (b) to component (a) being equal to or less than 20.

Abstract: A process for producing an olefin copolymer rubber by slurry-polymerizing ethylene, at least one .alpha.-olefin and at least one non-conjugated diene in a poor solvent for the copolymer in the presence of a catalyst consisting of an organometallic compound (the first component) and a transition metal compound (the second component), characterized by using, an organoaluminum compound as the first component of the catalyst, and using, as the second component, a modified vanadium compound obtained by contacting a vanadium compound with at least one compound selected from the group consisting of the compounds represented by the following formulas: ##STR1## wherein R is a hydrocarbon group of 1 to 20 carbon atoms and X.sub.1, X.sub.2 and X.sub.3 are independently halogen atoms or alkoxyl groups. This process can prevent a gel from being formed during polymerization.

Abstract: A titamium containing catalyst component for olefin polymerizations which comprises contacting (a) a metal oxide, (b) a dihydrocarbyl magnesium, and (c) a hydrocarbyloxy group-containing compound with one another, contacting the thus obtained contact product with (d) a halogen-containing alcohol, and finally contacting the thus obtained contact product with (e) an electron donor compound and (f) 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: 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 and a Group IIIa hydrocarbyl metal dihalide and prepolymerizing the solid with a minor amount of ethylene.

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: 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, an acyl halide and a vanadium compound, and (b) an aluminum alkyl cocatalyst.

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 and a Group IIIa hydrocarbyl metal dihalide.

Abstract: Ziegler-Natta catalysts which are polymer supported compounds or complexes of elements of the d-block transition metals, lanthanide or actinide series are disclosed. An example of the polymer support is chloromethylated polystyrene-divinyl benzene copolymer covalently bonded to catechol. An example of the compound or complex of an element of the transition metal, lanthanide or actinide series is that which results when catechol which is covalently bonded to the polymer is contacted with titanium tetraisopropoxide. These catalysts are useful in preparing polymers with reduced halide content which reduces corrosion in polymer processing equipment.

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: Olefins are polymerized in the presence of, as a catalyst therefor, the catalytic reaction product resulting from heating a mixture of(A) at least one hydrocarbon soluble organomagnesium material;(B) at least one epihalohydrin;(C) at least one reducing halide source; and(D) at least one transition metal (Tm) compound.

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: 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, an acyl halide and a vanadium compound, and (b) an aluminum alkyl cocatalyst.

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 and Cl.sub.2, Br.sub.2 or an interhalogen.

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 and a Group IIIa hydrocarbyl metal dihalide.

Abstract: A highly active and stereoselective olefin polymerization catalyst component is obtained by halogenating a magnesium compound of the formula MgR'R" wherein R' is an alkoxide or aryloxide group and R" is an alkoxide or aryloxide group or halogen, with a halide of tetravalent titanium in the presence of a halohydrocarbon, and contacting the halogenated product with an acid halide and a tetravalent titanium compound.

Abstract: A method for preparing synthetic oils characterized by a high viscosity index and prepared from 1-olefin is described. The method comprises polymerizing a 1-olefin or a mixture of 1-olefins in the presence of(a) at least one transition metal halide catalyst,(b) at least one alkyl aluminum compound containing up to about 15 carbon atoms in each alkyl group and up to about 40 carbon atoms per molecule as a co-catalyst, and(c) a saturated alkyl fluoride.The homopolymers and copolymers prepared in accordance with the method of the invention generally are characterized by a high viscosity index such as between about 100 to 300. The homopolymers and copolymers are useful as synthetic lubricants and as additives to synthetic or mineral oil lubricants for modifying the viscosity index characteristics of the lubricants.

Abstract: Disclosed is the incorporation into a two-part metathesis-catalyst system of a halogen containing hydrocarbyl additive, where the hydrocarbyl additive contains at least one trihalogen substituted atom or at least one activated halogen atom. The use of this catalyst system to polymerize dicyclopentadiene results in a thermoset polymer containing low levels of residual monomer. Also disclosed is a preferred embodiment of dicyclopentadiene polymerization where the two parts of the metathesis-catalyst system, plus dicyclopentadiene are combined in the mixing head of a reaction injection molding machine and then injected into a mold where the dicyclopentadiene rapidly sets up into a thermoset polymer.

Abstract: An improved process is described for preparing conjugate diolefin polymers or copolymers having a high content of 1,4-cis units and high chain linearity, the process using a particular catalytic system prepared from a compound of a metal chosen from those of Group III B of the Periodic System which have an atomic number of between 21 and 103, preferably neodymium, an organic halogen derivative, and an aluminium alkylhydride or trialkyl.

Abstract: Process for the preparation of copolymers consisting of 25-85% by wt. of ethylene, 15-75% by wt. of at least one other 1-alkene and optionally up to 20% by wt.

Abstract: Process for the preparation of copolymers consisting of 25-85% by wt. of ethylene, 15-75% by wt. of at least one other 1-alkene and optionally up to 20% by wt. of a polyunsaturated compound with application of a catalyst system containing a compound of a metal from sub-groups IV-VI of the periodic system and a compound of a metal from groups I-III of the periodic system, in which at least one hydrocarbon group is bound directly to the metal atom via a carbon atom, the polymerization being carried out in the presence of certain halogen containing activators.

Abstract: An .alpha.-olefin polymerizing catalytic component which has a support capable of supporting a large amount of titanium and has the titanium work efficiently for polymerizing the .alpha.-olefin; and a method for carrying out homo- or co-polymerization of an .alpha.-olefin by using a catalyst system which consists of the catalytic component and an organo-aluminium compound. The catalytic component is obtained basically by allowing an organo-magnesium compound and a carbon tetrahalide to react with each other in the presence of an organic acid ester; by treating a solid product formed through this reaction with an organic compound of phenol; and then by further treating the product with a halogen-containing titanium compound.

Abstract: According to this invention, there is provided a magnesium-containing solid, obtained by contacting the reaction product of (1):a magnesium-containing solid, obtained by contacting the reaction product of:(a) metallic magnesium;(b) a halogenated hydrocarbon of the general formula RX in which R stands for an alkyl, aryl or cycloalkyl group having 1 to 20 carbon atoms, and X stands for a halogen atom; and(c) an alkoxy compound of the general formula X'.sub.m C(OR').sub.4-m in which X' stands for a hydrogenor halogen atoms, or an alkyl, aryl or a cycloalkyl group having 1 to 10 carbon atoms, R' stands for an alkyl, aryl or cycloalkyl group having 1 to 20 carbon atoms and m is 0, 1 or 2, with (2) an organic aluminum compound.The magnesium-containing solid is employed as a carrier for a transition metal halide. The supported transition metal halide in combination with an aluminum alkyl cocatalyst such as aluminum triethyl is usefully employed for the polymerization of olefins.

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 silicon tetrachloride or boron trichloride and a specified transition metal compound such as VOCl.sub.3, bis(n-butoxy) titanium dichloride or zirconium tetrabenzyl. 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.