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
1999-10-06
2002-08-20
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...
C502S124000, C502S167000, C502S121000, C502S122000, C502S125000, C502S126000, C502S162000, C502S168000, C502S172000
Reexamination Certificate
active
06436864
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the field of catalysis, and more particularly relates to electron donor compounds for use with Ziegler-Natta polymerization catalysts. The invention additionally relates to novel Ziegler-Natta catalyst systems that employ an unsaturated nitrogenous compound as an electron donor, to methods for manufacturing Ziegler-Natta catalyst systems containing such compounds, and to methods for polymerizing addition polymerizable monomers, e.g., olefins, using a Ziegler-Natta catalyst system that employs an unsaturated nitrogenous compound as an internal and/or external electron donor.
BACKGROUND
The extensive use of polymers in daily life is largely attributable to improvements in polymer manufacturing processes as well as improvements in polymer properties. For polyolefin production, the work of Karl Ziegler and Giulio Natta, in the early 1950s, has served as a starting point for numerous advances in the technology.
The basis of the Ziegler catalysts was a complex of a transition metal compound with an organometallic compound (see Ziegler et al., U.S. Pat. Nos. 3,903,017, 4,063,009 and 4,125,698). One of the most preferred examples was titanium tetrachloride combined with triethylaluminum in a hydrocarbon solution. Using the new catalyst, Ziegler produced long chain polyethylene molecules from ethylene at atmospheric pressure. The polymerization of other olefins was also possible using the Ziegler catalysts.
Polymers produced using the early Ziegler catalysts were typically amorphous. Amorphous polymers, such as amorphous polyethylene, have inadequate material properties for a number of applications. Although the Ziegler catalyst systems made it easier to produce linear polyolefins, the resulting polymers had many properties like those of the polymers produced using competing processes involving either thermal-high pressure processes or chromium oxide catalysts. See F. Albert Cotton and Geoffrey Wilkinson, “Advanced Inorganic Chemistry: A Comprehensive Text,” 3rd ed., Wiley & Sons, Inc., 1972, pp. 794-795.
Giulio Natta et al., U.S. Pat. Nos. 3,197,452 and 3,957,743, developed improved Ziegler type catalysts that permitted the production of higher quality polyolefins with stereochemical control properties, i.e. stereospecificity. The Natta catalysts allowed production of long chain polyolefins that were crystalline rather than amorphous. Control of the polymer stereochemistry required a crystalline catalyst surface. See Brian L. Goodall, “Polypropylene: Catalyst and Polymerization Aspects,” in
Polypropylene and Other Polyolefins,
ed. Ser van der Ven (Amsterdam: Elsevier Science Publishers B.V., 1990), at pp. 1-25. The stereospecificity depended on the particular crystalline phase. Titanium halides were found to produce the highest catalytic activity. Favored compounds were titanium trichloride and titanium tetrachloride with titanium trichloride preferred; both compounds gave similar results when used to produce crystalline polypropylene. Crystalline polypropylene was also obtained using vanadium, chromium, zirconium, and molybdenum compounds. Aluminum alkyls other than triethylaluminum produced crystalline polymers as well.
Further efforts to improve the performance of Ziegler-Natta catalysts included the use of a catalyst support for the active components of the catalyst. For example, Mayr et al., U.S. Pat. No. 4,495,338, describe the use of magnesium or zinc halide support materials with Ziegler-Natta catalyst components. Treatment of the catalyst with an electron donor (and/or polymerization in the presence of an electron donor) has also been found to increase the activity and selectivity of Ziegler-Natta catalysts. Several varieties of compounds have been found to have suitable properties as electron donors. Electron donating compounds used to process the transition metal component of Ziegler-Natta catalysts are called “internal” electron donors, while those added during or immediately prior to polymerization are termed “external” electron donors.
Bailly et al., EP 336,545, described a method for preparing high activity Ziegler-Natta catalysts supported on magnesium dichloride substrates. As part of the catalyst preparation process, the magnesium dichloride support was contacted with electron donor compounds (i.e., as “internal” electron donors) prior to incorporating the titanium component. The specified electron donors had labile hydrogen; suitable donor compounds included water, alcohols, phenols, thiols, and hydrogen sulfide. An optional step was also suggested that included treatment with an ester of an aromatic acid. The esters were chosen from ethyl benzoate, methyl paratoluate, and dibutyl or diisobutyl phthalate.
Although internal electron donors improved the selectivity and activity of Ziegler-Natta catalysts to some extent, a significant amount of amorphous polymer was still produced. It was later found that including an additional catalyst preparation step could increase the crystalline yield. The solution was to use a first electron donor treatment for the titanium component as well as a second electron donor treatment for the aluminum compound processing step (see Goodall supra).
Giannini et al., U.S. Pat. No. 4,107,414, processed Ziegler-Natta catalyst components supported on magnesium dichloride substrates with both internal and external electron donor compounds. The resulting catalysts had high activity and increased stereospecificity. Some of the recommended internal electron donor compounds were veratrol, ethyl benzoate, acetone, dimethylmalonate, and tetrahydrofuryl methyl ether. Giannini et al. also found that the diamines and esters of oxygenated organic and inorganic acids were particularly suitable for improving the activity and stereospecificity of the catalysts. Suitable external electron donor compounds included esters of oxygenated organic and inorganic acids.
Albizzati et al., U.S. Pat. No. 4,522,930, also describe use of both internal and external electron donors in Ziegler-Natta catalyst systems. The proposed internal electron donor compounds were ethers, ketones, lactones, esters, and compounds containing nitrogen, phosphorous and/or sulfur atoms. The external electron donors were compounds that contained Si—OR, Si—OCOR, or Si—NR
2
groups.
Further development work on Ziegler-Natta catalysts led to the discovery of diethers as electron donors; see, e.g., EP 728,741 (Morini et al.), EP 361,949 (Scordamaglia et al.), and EP 362,705 (Barbe et al.).
To improve the performance of diether electron donors for Ziegler-Natta catalysts, mixtures of diethers plus other electron donors have been used in preparation of the catalysts. For example, Iiskola et al., U.S. Pat. No. 5,869,418, describe an external electron donor containing a diether compound and an alkoxysilane. The two-component external donor mixtures were found to result in an increase in isotacticity and a broader molecular weight distribution for the polymeric product.
To further improve the performance of diether electron donors, Albizzati et al., U.S. Pat. No. 5,068,213, produced catalysts using modified diethers or polyethers as internal electron donors. The modification included adding at least one heteroatom (nitrogen, sulfur, phosphorus, silicon, non-ether oxygen, halogen) and/or double bond to the diether or polyether. The result of using the modified diethers was a Ziegler-Natta catalyst with high activity and stereospecificity without the need for external electron donors.
Although the diether-prepared Ziegler-Natta catalysts are being adopted extensively for commercialization, there is still a significant need to further improve the performance of Ziegler-Natta catalysts. Another reason for continued development of Ziegler-Natta catalysts is the continuing need to further increase polymer processability and decrease the cost of producing both catalysts and polymers.
Thus, the art provides Ziegler-Natta catalysts prepared using selected compounds or selected classes of compounds having electron donor properties that improve catalyst per
Bell Mark L.
Hartrum J. Elin
Pasterczyk J.
Reed Dianne E.
Reed & Associates
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