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
2001-06-08
2003-01-28
Lu, Caixia (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Plural component system comprising a - group i to iv metal...
C502S115000, C502S118000, C502S119000, C526S124300, C526S124700
Reexamination Certificate
active
06511935
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of making olefin polymerization catalysts from magnesium, transition metal and halogen-containing olefin polymerization procatalysts, and their use as a catalyst component for the polymerization of olefin monomers. The procatalysts are prepared by halogenating a magnesium and transition metal-containing alkoxide complex, and optionally contacting the halogenated product with an electron donor. The procatalyst then can be converted to an olefin polymerization catalyst by contacting it with a cocatalyst and optionally a selectivity control agent.
2. Description of Related Art
Polymers and copolymers of lower &agr;-olefins, particularly, ethylene, propylene and butylene are widely used throughout the world. These polymeric products are relatively inexpensive to manufacture, and they exhibit a number of commercially useful properties. These polymers are most commonly utilized in the form of highly crystalline solids. During the polymerization process, whether it be by liquid pool, gas phase, slurry phase or any other commonly utilized process, it is beneficial for the polymer particles (and consequently the catalyst particles) to be of a satisfactory shape and size. As examples: denser particles allow for higher hourly production rates; spheroidal particles allow for higher polymer bulk density; narrow particle size distribution allows for better gas phase fluidization. Overly small catalyst and polymer particles (commonly called fines) are also undesirable.
When ethylene is polymerized, the process is less complicated than with higher olefins in that the product type is not greatly influenced by the manner in which the ethylene molecules add to the growing polymeric chain during polymerization. The polymeric product of ethylene does not generally exist in stereoisomeric forms. The simpler catalysts required to effect this polymerization can normally be obtained by straightforward chlorination of a catalyst precursor. If the shape of the catalyst particle and thus the shape of the resulting polymer particle is of importance, the catalyst precursor must be sufficiently robust so that it can withstand the rigors of this chlorination step.
When propylene is polymerized, however, the presence of pendant methyl groups on the polymeric chain provides a possibility of several product types, depending on the steric regularity with which propylene molecules add to the growing chain. Much if not most of the commercial polypropylene results from the stereoregular addition of propylene molecules in a regular head-to-tail manner. The form of polymer having a substantial proportion of random addition of propylene units is termed atactic and this amorphous form is less desirable. If present in a significant proportion, the atactic polymer must be removed through an extraction process to provide a more desirable crystalline material.
These polymers typically are formed by using a polymerization catalyst. The activity of the catalyst is significant in that the more polymer produced per unit weight of catalyst the better. The early titanium, chromium or vanadium catalysts were of low activity and the product contained a significant proportion of catalyst residues. These residues had to be removed in an effort to obtain commercially satisfactory properties.
More recent titanium-based olefin polymerization catalysts are stereoregulating and have sufficient activity to avoid extraction and deashing. These high activity catalysts typically are prepared via chlorination of a magnesium containing precursor, in the presence of an electron donor compound, to form a solid procatalyst that usually contains magnesium, titanium and halide moieties, and comprises additionally a cocatalyst (usually an organoaluminum compound) and an optional selectivity control agent (SCA) for propylene polymerization. The magnesium containing complex is typically referred to as a “precursor”, the solid titanium-containing compound typically is referred to as a “procatalyst”, the organoaluminum compound, whether complexed or not, usually is referred to as the “cocatalyst” and the third component external electron donor, whether used separately or partially or totally complexed with the organoaluminum compound, is referred to as the “selectivity control agent.” Throughout this disclosure, these terms will be used in accordance with the aforementioned designations. As before, if the shape of the catalyst particle and thus the shape of the resulting polymer particle is of importance, the catalyst precursor must be sufficiently robust so that it can withstand the rigors of the chlorination process.
Many chemical combinations of procatalysts, cocatalysts and selectivity control agents are known in the art to produce active catalysts. Through considerable experience, however, certain materials are of greater interest than others. For example, there is significant research in the area of procatalysts, which typically contain some chemical combination of magnesium, titanium tetrachloride and an internal electron donor. These internal electron donors usually are oxygen containing compounds such as tetrahydrofuran and aromatic esters such as ethyl benzoate or ethyl p-toluate. Conventional cocatalysts include an aluminum trialkyl such as triethylaluminum or triisobutylaluminum that is often complexed with a portion of the selectivity control agent (or external electron donor), which also is typically an aromatic ester or an organosilane. Although variations in any of these catalyst components will influence the performance of the resultant catalyst, the component that appears to offer the greatest opportunity for modification to produce greater catalyst activity is the procatalyst.
The literature is rife with disclosures relating to the various known methods of preparing procatalysts. For example, Kioka, et al., U.S. Pat. No. 4,330,649, the disclosure of which is incorporated by reference herein in its entirety, describes a solid catalyst component (procatalyst) that is prepared by heating a soluble magnesium compound such as magnesium chloride with a higher alcohol in the presence of an ester to produce a solution. This solution contains a “precursor” of the procatalyst, which then is added to titanium tetrachloride and an electron donor (internal) to form the procatalyst. A number of United States patents issued to Robert C. Job (and Robert C. Job, et al.,) describe various mechanisms for preparing magnesium-containing, titanium-containing compounds that are useful as precursors for the production of procatalysts that are ultimately useful in preparing catalysts for the polymerization of &agr;-olefins. For example, U.S. Pat. Nos. 5,034,361; 5,082,907; 5,151,399; 5,229,342; 5,106,806; 5,146,028; 5,066,737; 5,122,494, 5,124,298, and 5,077,357, the disclosures of which are incorporated by reference herein in their entirety, disclose various procatalyst precursors. U.S. Pat. No. 5,034,361 discloses solubilizing a magnesium alkoxide in an alkanol solvent by interaction of the magnesium alkoxide compound and certain acidic materials. This magnesium alkoxide then can be used either directly as a magnesium-containing catalyst precursor, or can be reacted with various titanium compounds to produce a magnesium and titanium-containing catalysts precursor.
U.S. Pat. Nos. 5,082,907; 5,151,399; 5,229,342; 5,106,806; 5,146,028; 5,066,737; 5,122,494, 5,124,298, and 5,077,357 disclose various magnesium and titanium-containing catalyst precursors, some of which are prepared by using the aforementioned magnesium alkoxide as a starting material. These precursors are not active polymerization catalysts, and they do not contain any effective amounts of electron donor. Rather, the precursors are used as starting materials in a subsequent conversion to an active procatalyst. Magnesium and titanium-containing procatalysts are formed by chlorinating the magnesium and titanium-containing precursor with a tetravalent titanium halide, an optional hydrocarbon and an option
Lu Caixia
Union Carbide Chemicals & Plastics Technology Corporation
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