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
2000-06-09
2002-07-02
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...
C502S133000, C502S134000, C502S108000, C502S109000
Reexamination Certificate
active
06413901
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new transition metal-based supported olefin polymerization catalyst systems, novel methods of producing such catalysts and methods of polymerizing alpha-olefins to provide polyolefins, and preferably high density polyethylene and linear low density polyethylene. More particularly, this invention relates to the preparation of ultra high active catalyst compositions comprising at least a transition metal compound, a magnesium-containing compound and a polymeric material.
2. Description of the Prior Art
Several publications are referenced in this application. These references describe the state of the art to which this invention pertains, and are incorporated herein by reference.
The field of olefin polymerization catalysis has witnessed many remarkable discoveries during the last 50 years. In particular, two broad areas of invention stand out. Firstly, the discovery of Ziegler-Natta catalysts in the 1950's, which are still being used extensively in the polyolefins industry. Secondly, and more recently, the discovery of the highly active metallocene-based catalysts. Since the discoveries of these systems, extensive research work was conducted in order to improve their performance.
However, despite the progress in these areas, there are still certain limitations as recognized by those of ordinary skill in the art. For example, conventional Ziegler-Natta catalysts often display limited activity, which reflects on the high catalyst residues. On the other hand, the metallocene-based catalysts intrinsically possess high activity, though the catalyst precursors and, in particular, the cocatalysts required for polymerization, such as aluminoxanes or borane compounds, are very expensive. Further, another limitation that both catalyst systems share is the lengthy method of preparation.
Traditionally, the active components of both Ziegler-Natta and metallocene catalysts are supported on the inert carriers to enhance the catalyst productivity and improve and control the product morphology. Magnesium chloride and silica have predominantly been used for the preparation of supported olefin polymerization catalysts. U.S. Pat. No. 4,173,547 to Graff describes a supported catalyst prepared by treating a support, for example silica, with both an organoaluminum and an organomagnesium compound. The treated support was then contacted with a tetravalent titanium compound. In a simpler method, U.S. Pat. No. 3,787,384 to Stevens et al. discloses a catalyst prepared by first reacting a silica support with a Grignard reagent and then combining the mixture with a tetravalent titanium compound.
However, procedures typically used for the preparation of suitable magnesium chloride and silica supports such as spray drying or re-crystallization processes are complicated and expensive.
Hence, all methods described in the aforementioned patents of catalyst preparation present the inconvenience of being complicated, expensive and do not allow consistency of particle size and particle size distribution. Also, despite the extensive and increasing use of the described supports for Ziegler-Natta catalysts, the support materials themselves have several deficiencies. For example, in the case of silica, high calcination temperatures are required to remove water, which is a common catalyst poison. This represents a significant proportion of the preparation of the catalyst. The use of silica as a support results in the support remaining largely in the product, which can affect the product properties, such as optical properties, or processing.
Certain polymeric materials have also been used for supporting titanium and magnesium compounds. However, most of the polymeric supports used so far have been based on polystyrene or styrene-divinylbenzene copolymers. U.S. Pat. No. 5,118,648 to Furtek and Gunesin describe a catalyst prepared using styrene-divinylbenzene as a polymeric support. The preparation of the catalyst was carried out by suspending the polymeric support in a solution of a magnesium dihalide or a magnesium compound capable of being transformed into a magnesium dihalide, for example, by titanium tetrachloride treatment, and subsequently evaporating the solvent. Hence, the active catalyst components were deposited on the polymeric support by physical impregnation. Other physical impregnation methods include that described by U.S. Pat. No. 4,568,730 to Graves whereby polymer resins of styrene-divinylbenzene are partially softened and the active catalyst components homogeneously mixed in the resin to form a mass, which was subsequently pelletized or extruded into catalyst particles. However, the activity of the above-described polymer supported catalysts is not significantly higher than that of silica-based Ziegler-Natta catalysts.
Polypropylene and polyethylene have also found use as polymeric supports where the polymeric material is typically ground with the catalyst components, which represents a difficult and complicated catalyst preparation procedure. In addition, there remains a significant concern as to the ability of the support material to retain the active species, deposited by physical impregnation, during polymerization conditions and thus generate, for example, fines. Hsu et al., Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 32, 2135 (1994), has used poly(ethylene-co-acrylic acid) as a support for Ziegler-Natta catalysts. Though, the catalyst activity was found to be similar to that of the magnesium chloride supported catalyst.
SUMMARY OF THE INVENTION
The present invention provides ultra highly active supported olefin polymerization catalysts comprising at least one transition metal compound, at least one magnesium compound and defined polymer particles. The polymer particles used in catalyst preparation have a mean particle diameter of 5 to 1000 &mgr;m and a pore volume of at least 0.1 cm
3
/g and a pore diameter of at least from 20 to 10,000 angstroms, preferably from 500 Å to 10,000 Å and a surface area of from 0.1 m
2
/gm to 100 m
2
/gm, preferably from 0.2 m
2
/gm to 15 m
2
/gm.
DETAILED DESCRIPTION OF THE INVENTION
One aspect of the invention relates to improved catalyst systems. The solid catalyst component (catalyst precursor) used in the present invention contains at least a transition metal compound, at least a magnesium compound, and a polymeric material having a mean particle diameter of 5 to 1000 &mgr;m, a pore volume of 0.1 cm
3
/g or above and a pore diameter of 20 to 10,000 angstroms, preferably from 500 Å to 10,000A and a surface area of from 0.1 m
2
/gm to 100 m
2
/gm, preferably from 0.2 m2/gm to 15 m
2
/gm.
The transition metal compound used for the synthesis of the solid catalyst component in the invention is represented by the general formula M(OR
1
)
n
X
4−n
, wherein M represents a transition metal of Group 4, 5, 6, 7 or 8-10 of the Periodic Table of the elements, R
1
represents a hydrocarbon having 1 to 20 carbon atoms, X represents a halogen atom and n represents a number satisfying 0≦n≦4. Nonlimiting examples of the transition metal are titanium, vanadium, or zirconium. Examples of R
1
include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl and the like.
Preferred examples of the above mentioned compounds include the following: titanium tetrachloride, methoxy titanium trichloride, dimethoxy titanium dichloride, ethoxy titanium trichloride, diethoxy titanium dichloride, propoxy titanium trichloride, dipropoxy titanium dichloride, butoxy titanium trichloride, butoxy titanium dichloride, vanadium trichloride, vanadium tetrachloride, vanadium oxytrichloride, and zirconium tetrachloride.
The magnesium compounds used for the catalyst synthesis in the invention include Grignard compounds represented by the general formula R
2
MgX, wherein R
2
is a hydrocarbon group of 1 to 20 carbon atoms and X is a halogen atom. Other preferred magnesium compounds are represented by the general formula R
3
R
4
Mg, wherein R
3
and R
4
are each a hydro
Abu-Raqabah Atieh
Moman Akhlaq
Nallaveerapan Navin
Bell Mark L.
Kramer Levin Naftalis & Frankel
Pasterczyk J.
Saudi Basic Industries Corporation
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