1. Field of the Invention
This invention relates to a catalyst component or catalyst that is useful for the stereoregular polymerization or copolymerization of alpha-olefins and more particularly concerns a magnesium-containing supported titanium-containing catalyst component or catalyst that is useful for producing a homopolymer or copolymer of an alpha-olefin.
2. Discussion of the Prior Art
Although many polymerization and copolymerization processes and catalyst systems have been described for polymerizing or copolymerizing alpha-olefins, it is highly desirable to develop a catalyst component or a catalyst that has improved activity for catalyzing such reactions. It is also advantageous to tailor a process and catalyst system to obtain a specific set of properties of a resulting polymer or copolymer product. For example, in certain applications a product with a broader molecular weight distribution is desirable. Such a product has a lower melt viscosity at high shear rates than a product with a narrower molecular weight distribution. Many polymer or copolymer fabrication processes which operate with high shear rates, such as injection molding, oriented film, and thermobonded fibers, would benefit with a lower viscosity product by improving throughput rates and reducing energy costs. Thus, it is highly desirable to develop a catalyst or catalyst component that is useful for producing a homopolymer or copolymer of an alpha-olefin having a broadened molecular weight distribution. Also important is maintaining high activity and low atactic levels such as measured by hexane soluble and extractable materials formed during polymerization or copolymerization.
Magnesium-containing supported titanium halide-based alpha-olefin polymerization or copolymerization catalyst components or catalyst systems containing such components are now well known in the art. Typically, these catalyst components and catalyst systems are recognized for their performance based on activity and stereospecificity. Numerous individual processes or process steps have been disclosed which have as their purpose the provision of improved supported, magnesium-containing, titanium-containing, electron donor-containing olefin polymerization or copolymerization catalysts. More particularly, Arzoumanidis et al., U.S. Pat. Nos. 4,866,022; 4,988,656; and 5,013,702 disclose a method for forming a particularly advantageous alpha-olefin polymerization or copolymerization catalyst or catalyst component that involves a specific sequence of specific individual process steps such that the resulting catalyst or catalyst component has exceptionally high activity and stereospecificity combined with very good morphology. A solid hydrocarbon-insoluble, alpha-olefin polymerization or copolymerization catalyst or catalyst component with superior activity, stereospecificity and morphology characteristics is disclosed as comprising the product formed by 1) forming a solution of a magnesium-containing species from a magnesium hydrocarbyl carbonate or magnesium carboxylate; 2) precipitating solid particles from such magnesium-containing solution by treatment with a transition metal halide and an organosilane as a morphology controlling agent; 3) reprecipitating such solid particles from a mixture containing a cyclic ether; and 4) treating the reprecipitated particles with a transition metal compound and an electron donor.
Arzoumanidis et al., U.S. Pat. No. 4,540,679 discloses a process for the preparation of a magnesium hydrocarbyl carbonate by reacting a suspension of a magnesium alcoholate in an alcohol with carbon dioxide and reacting the magnesium hydrocarbyl carbonate with a transition metal component. Arzoumanidis et al., U.S. Pat. No. 4,612,299 discloses a process for the preparation of a magnesium carboxylate by reacting a solution of a hydrocarbyl magnesium compound with carbon dioxide to precipitate a magnesium carboxylate and reacting the magnesium carboxylate with a transition metal component.
While each of the processes of the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702 affords alpha-olefin polymerization or copolymerization catalysts or catalyst components which have high activity for polymerizing or copolymerizing alpha-olefins to produce homopolymer or copolymer products which have desirable characteristics, it is highly desirable to develop additional alpha-olefin polymerization or copolymerization catalysts or catalyst components--and methods for the manufacture thereof--that have even further improved catalytic activity and that afford polymers or copolymers which also have broadened molecular weight distribution.
For example, Karayannis, Cohen and Ledermann, pending U.S. patent application Ser. No. 07/862,960, filed Apr. 3, 1992, now U.S. Pat. No. 5,227,354, disclose a solid, hydrocarbon-insoluble catalyst or catalyst component and a method of production thereof, which are based on the catalyst or catalyst components and methods of production thereof, respectively, of the aforesaid U.S. Pat. Nos. 4,540,679; 4,612,299; 4,866,022; 4,988,656; and 5,013,702, wherein the resulting catalyst or catalyst component is a product formed by: A. forming a solution of a magnesium-containing species in a liquid, wherein the magnesium-containing species is formed by reacting a magnesium-containing compound with carbon dioxide or sulfur dioxide; B. precipitating solid particles from the solution of the magnesium-containing species by treatment with a titanium halide; and D. treating the precipitated particles with a titanium compound and an electron donor; wherein the treated precipitated particles from Step D comprise magnesium and vanadium components, and wherein vanadium is introduced into at least one of (i) the aforesaid magnesium-containing species in Step A by reacting the magnesium-containing compound or species with a vanadium-containing compound or complex, or (ii) the aforesaid solid particles precipitated in Step B by treatment of the magnesium-containing species with a titanium halide and a vanadium-containing compound or complex; or (iii) the aforesaid precipitated particles treated in Step D by treatment of the precipitated particles with a titanium compound, an electron donor and a vanadium-containing compound or complex that is free of a halide component. Use of the catalyst or catalyst component disclosed in the aforesaid Karayannis, Cohen and Ledermann pending patent application for the polymerization or copolymerization of an alpha-olefin affords polymers or copolymers which have a broadened molecular weight distribution, but such pending patent application does not disclose a substantial increase in catalytic activity for such polymerization or copolymerization.
Similarly Tachibana et al., U.S. Pat. No. 5,084,429 discloses a catalyst for use in polymerization of olefins which comprises a carrier mainly composed of a magnesium compound precipitated from a solution and a catalytic component supported on the carrier and selected from titanium halides, vanadyl halides and vanadium halides is described. The catalyst is obtained by a process which comprises: (A) mixing (a) at least one magnesium compound with (c) a saturated or unsaturated monohydric or polyhydric alcohol for reaction in dissolved state in the presence of (b) carbon dioxide in an inert hydrocarbon solvent to obtain component (A); (B) subjecting the component (A) to mixing and reaction with (d) a titanium and/or a vanadyl halide and/or a vanadium halide of the general formula, VX.sub.r (OR.sup.8).sub.4-n and also with (e) at least one boron compound, silicon compound and/or siloxane compound thereby obtaining solid product (I): (C) reacting the solid product (I) with (f) a cyclic ether with or with R.sup.12 OH thereby causing dissolution and re-precipitation to obtain solid product (II): and (D) subjecting the solid product (II) to further reaction with (g) component (B) consisting of a titanium halide and/or a vanadyl halide and/or a vanadium halide and/or a SiX.sub.S (OR.sup.9).sub.4-s, thereby obtaining solid product (III), followed either by further reaction with a mixture of the component (B) and (h) an electron donor or by reaction of (g) with the solid product (III) obtained by the reaction between the solid product (II) and (h) or (h) with (j) electron donor, thereby obtaining solid product (IV) for use as the catalytic component.
Catalysts for the polymerization of olefins containing other relevant combinations of metal components have also been disclosed. For example, Albizzati et al., U.S. Pat. No. 5,082,817 discloses a catalyst for the polymerization of olefins, obtained by means of the reaction of: (a) a compound of a transition metal, typically titanium, containing at least one metal-halogen linkage, supported on a magnesium halide in the active form, with (b) a compound of titanium, zirconium or hafnium containing at least one metal-carbon linkage. Similarly, Howard et al., U.S. Pat. No. 4,228,263 discloses a catalyst for the polymerization of propylene, which is the reaction product of (a) a metal oxide such as aluminum oxide, titanium oxide, silica and magnesia or physical mixtures thereof, and (b) an organometallic compound of zirconlure, titanium or hafnium.
In addition, polymer or copolymer morphology is often critical and typically depends upon catalyst morphology. Good polymer morphology generally involves uniformity of particle size and shape, a narrow particle size distribution, resistance to attrition and an acceptably high bulk density. Minimization of very small particles (fines) typically is very important especially in gas-phase polymerizations or copolymerizations in order to avoid transfer or recycle line pluggage. Therefore, it is highly desirable to develop alpha-olefin polymerization and copolymerization catalysts and catalyst components that have good morphology, and in particular, a narrow particle size distribution. Another property which is important commercially is the maintenance of an acceptably high bulk density.