Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Plural component system comprising a - group i to iv metal...
Reexamination Certificate
2000-07-27
2002-05-28
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S119000, C502S113000, C502S114000, C502S132000, C502S133000, C502S134000, C502S110000, C502S129000
Reexamination Certificate
active
06395669
ABSTRACT:
FIELD OF THE INVENTION
The instant invention relates to a mixed metallocene/Ziegler polymerization catalyst component and catalyst system for the polymerization or copolymerization of one or more alpha-olefins.
The mixed metallocene/Ziegler polymerization catalyst component of the present invention when used with one or more aluminum-containing cocatalysts, produces a catalyst system which produces olefin polymer films having improved clarity and strength properties compared with olefin polymer films produced using catalyst systems of the prior art.
BACKGROUND OF THE INVENTION
Traditionally, ethylene and alpha-olefins have been polymerized or copolymerized in the presence of hydrocarbon insoluble catalyst systems comprising a transition metal component, such as titanium, and an aluminum alkyl. An example of such a system is set. forth in U.S. Pat. No. 4,374,753. That system includes a transition metal component formed by reacting certain organic silicon compounds with an oxide, such as a silica or alumina, having surface hydroxyl groups. The reaction product is thereupon reacted with an organomagnesium compound. This product, in turn, is reacted with an alcohol. The final catalyst component is formed by reaction of the previous product with a halide or an alkoxide of titanium, vanadium, zirconium or mixtures thereof.
More recently, active homogeneous catalyst systems comprising a bis(cyclopentadienyl)-transition metal dialkyl, an aluminum trialkyl, and water have been found to be useful for the polymerization of ethylene. Such catalyst systems are referred to in the art as homogeneous metallocene catalyst-systems and are generally recognized as being unsupported. U.S. Pat. Nos. 4,404,344, 4,522,982, 4,590,914 and 4,937,299 describe various homogeneous metallocene catalyst systems of this type used in alpha-olefin polymerizations.
An advantage of a metallocene/aluminoxane homogeneous catalyst system is the very high activity obtained-in ethylene polymerization. Another significant advantage is, unlike olefin polymers produced in the presence of conventional heterogeneous Ziegler-type catalysts, terminal unsaturation is present in polymers produced in polymerization reactions conducted in the presence of homogeneous metallocene catalysts. Nevertheless, these metallocene-catalysts suffer from a disadvantage; that is, the ratio of aluminoxane to metallocene is high, for example, on the order of 1,000 to 1 or greater. Such voluminous amounts of aluminoxane require extensive posttreatment of the polymer product obtained in order to remove the undesirable aluminum.
A second disadvantage of homogeneous metallocene catalysts, which disadvantage is also associated with traditional heterogeneous Ziegler-type catalysts, is the multiplicity of delivery systems required for introducing the individual catalyst components into the polymerization reactor.
In an attempt to overcome the problems mentioned hereinabove, supported, also known in the art as heterogeneous, metallocene catalyst systems have been developed. One such supported metallocene catalyst system is described in U.S. Pat. No. 5,086,025 to Chang. Chang discloses a process for preparing a supported metallocene-aluminoxane catalyst system for use in liquid or slurry phase polymerization of olefins wherein the preparation of the supported heterogeneous metallocene catalyst involves initially reacting silica gel with an aluminum trialkyl solution to form a support material for the metallocene component and thereafter contacting the treated support material with a metallocene.
In addition to the use of heterogeneous metallocene catalyst systems, the art has recognized that benefits may be obtained by joining metallocene with Ziegler-Natta catalyst technology in low pressure polyolefin synthesis in conventional reactors; these preparations, generally known as mixed catalyst systems, thus comprise a catalyst component which includes Ziegler-Natta and metallocene catalytic agents. Some pertinent examples of such art follow.
U.S. Pat. No. 4,701,432 to Wellborn, Jr. is directed to an olefin polymerization catalyst component which comprises a support treated with a metallocene of a Group IVB or VB metal and at least one non-metallocene compound of a Group IVB, VB or VI transition metal. A catalyst system is also set forth which includes the aforementioned catalyst component and a cocatalyst comprising an aluminoxane and an organometallic compound of a metal of Groups IA, IIA, IIB or IIIA.
U.S. Pat. No. 5,032,562 to Lo et al. discloses a supported olefin polymerization catalyst composition comprising a precursor and a catalyst activator. The catalytic precursor comprises a magnesium compound, e.g., dibutylmagnesium, a cyclopentadienyl group-containing zirconium compound, a titanium and/or a vanadium compound and an organic compound. The catalyst activator is a mixture of a conventional Ziegler-Natta cocatalyst and a zirconium site activator, e.g., methylaluminumoxane. The catalyst is used in the presence of small amounts of hydrogen to produce polymers having a multimodal molecular weight distribution in a single reactor.
U.S. Pat. Nos. 5,077,255 and 5,183,867 to Welborn, Jr. disclose an olefin polymerization supported catalyst comprising the supported reaction product of at least one metallocene of a metal of Group IVB, VB or VIB of the Periodic Table, a non-metallocene transition metal-containing compound of a Group IVB, VB or VIB metal and an aluminoxane. The supported product is reportedly useful for the polymerization of olefins especially ethylene and especially for the copolymerization of ethylene and other mono- and diolefins.
U.S. Pat. No. 5,120,696 to Tsutsui et al. provides olefin polymerization catalysts and a method of preparing the same. Specifically, in one embodiment, this references discloses an olefin polymerization catalyst that comprises: (A) a solid titanium catalyst component containing titanium, magnesium and a halogen as its essential ingredients, said catalyst component having supported thereon (B) a transition metal compound containing a ligand having a cycloalkadienyl skeleton and, if necessary, (C) an organoaluminum oxy-compound. In another embodiment, there is disclosed an olefin polymerization catalyst composition that comprises (A) a solid containing a transition metal compound having a cycloalkadienyl skeleton and supporting thereon; (B) a titanium catalyst component containing titanium, magnesium and a halogen as its essential ingredients, and, if necessary (C) an organoaluminum oxy-compound.
Japanese Patent Publication No. 7-2922 published Jan. 6, 1995 includes an example which discloses the synthesis of an olefin polymerization catalyst in which biscyclopentadienyl zirconium dichloride is added to hexamethyldisilazane modified silica in the solvent, dichloromethane. After evaporation of the solvent, a lavender colored solid is formed. A solution of triethylaluminum-diethylmagnesium complex in heptane is then added to the solid followed by the addition of first n-butanol and then titanium tetrachloride, each in the form of heptane solutions. The catalyst is employed in the polymerization of ethylene. The polymerization occurs in the presence of modified methyl aluminoxane, i.e. methyl aluminoxane containing isobutyl groups.
Notwithstanding these efforts, the art continues to seek olefin polymerization catalysts that have improved properties associated with the many uses to which olefin polymers are put.
SUMMARY OF THE INVENTION
The present invention is directed to a mixed metallocene/Ziegler polymerization catalyst component which is useful in the polymerization or copolymerization of one or more alpha-olefins. More specifically, the mixed metallocene/Ziegler catalyst component of the instant invention comprises a metallocene compounds commonly utilized in the formation of a Ziegler-type polymerization catalyst component.
In accordance with the instant-invention, and representative thereof, a catalyst component is prepared by contacting an organic or silica support material with at least one transition meta
Ellis Stella L.
Fries Richard W.
Hooks Patricia A.
Klendworth Douglas D.
Lindstrom Keta M.
Bell Mark L.
Carroll Kevin M.
Equistar Chemicals LP
Pasterczyk J.
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