Organic compounds -- part of the class 532-570 series – Organic compounds – Aluminum containing
Reexamination Certificate
2000-12-15
2003-02-11
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Aluminum containing
C556S179000, C556S181000, C526S160000, C526S943000, C502S103000, C502S117000
Reexamination Certificate
active
06518445
ABSTRACT:
TECHNICAL FIELD
This invention relates to the provision of novel methylaluminoxane compositions, to especially useful solutions of such methylaluminoxanes in hydrocarbon solvents other than aromatic hydrocarbon solvents, and to the preparation of such compositions and solutions.
In the ensuing description and in the claims hereof, reference is sometimes made to solubility in n-heptane because this is a typical, representative saturated hydrocarbon which serves as a very convenient point of reference for comparisons of solubility. However, such references to n-heptane does not constitute a limitation or restriction on the scope of this invention as regards hydrocarbons used, as the invention produces methylaluminoxane compositions that have improved solubility in a variety of liquid aliphatic and cycloaliphatic hydrocarbons as compared to the solubility of previously reported methylaluminoxane in the same respective hydrocarbons.
BACKGROUND
Hydrocarbylaluminoxanes complexed with transition metal compounds are known to be effective olefin polymerization catalysts. See for example, U.S. Pat. No. 3,242,099 to Manyik et al. Methylaluminoxanes prepared by partial hydrolysis of trimethylaluminum under various conditions are commonly-used effective co-catalyst components. However as is well known, methylaluininoxanes have been found to have poor solubility in non-aromatic hydrocarbon solvents. See in this regard, U.S. Pat. Nos. 4,960,878 to Crapo et al.; 5,041,584 to Crapo et al.; 5,066,631 to Sangokoya et al.; 5,308,815 to Sangokoya; 5,847,177 to Sangokoya et al.; 6,001,766 to Kissin et al., and Japan Kokai 01/258,686 to Kioka et al.
Disclosures from which it is possible to calculate or at least estimate total aluminum concentrations in non-aromatic solvents include U.S. Pat Nos. 4,530,914 to Ewen et al.;
U.S. Pat. No. 4,544,762 to Kaminsky et al.; U.S. Pat. No. 4,701,432 to Welborn; U.S. Pat. No. 4,752,597 to Turner; U.S. Pat. No. 4,791,180 to Turner; and U.S. Pat. No. 5,066,631 to Sangokoya et al.; and Ott, University of Hamburg Thesis, 1999. It appears that the highest reported total aluminum concentration in these documents is 3.85 wt % in heptane—see Example 3 of U.S. Pat. No. 5,066,631 to Sangokoya et al. It appears from an abstract of a paper by Matthias Ott, entitled
Optimization of Methylaluminoxane Preparation
, Fortschr.-Ber. VDI Reihe 3 (1999),627, I-III, V-XVI, 1-137 (Accession number 2000:106460 CAPLUS) that it is speculated that it will be possible to prepare methylaluminoxane solutions of up to 10% in heptane with the use of the “Eisbandreaktor” referred to therein.
The poor solubility of methylaluminoxanes in non-aromatic solvents is most unfortunate because polyolefin manufacturers of products that come into contact with foodstuffs desire to minimize as much as possible, if not eliminate, aromatic hydrocarbons from the raw materials and processing operations used. The manufacturers would much prefer raw materials and operations in which less toxic non-aromatic hydrocarbons are employed.
Considerable past efforts have been devoted to various ways of modifying methylaluminoxanes in order to increase their solubility in non-aromatic hydrocarbons. These efforts generally involve either the addition or inclusion of other components to improve such solubility, or the treatment of the methylaluminoxane in such a way that a substantial portion of methylaluminoxane, e.g., at least 25 percent by weight of the total methylaluminoxane on a dry basis, exists or remains as a precipitate and is not included in the solution. Such precipitates are believed -to be composed of higher molecular weight oligomers and are isolated by filtration, decantation, or other liquid-solids physical separation procedure.
Whatever their makeup, such precipitates are usually discarded as waste, thereby leaving in solution a lower molecular weight methylaluminoxane fraction which generally contains more than about 30 mole percent trimethylaluminum and is more soluble in non-aromatic solvents. A number of examples of such approaches are described in the patent literature.
It would be of considerable advantage if a way could be found of providing new methylaluminoxane compositions having superior solubility characteristics in various non-aromatic hydrocarbons, especially paraffinic and cycloparaffinic hydrocarbons, without need for (a) addition or inclusion of other components to improve such solubility, or (b) treatment of the methylaluminoxane in such manner that results in loss of a substantial portion of its original content.
THE INVENTION
This invention involves, inter alia, the discovery that it is indeed possible to form and provide such new methylaluminoxane compositions having significantly higher solubility in non-aromatic hydrocarbons without addition of any third component to increase solubility, and without recourse to processing that removes substantial portions of higher molecular weight components from the methylaluminoxane.
Accordingly, in one of its embodiments this invention provides a methylaluminoxane composition wherein:
A) the composition is a solid at 25° C.;
B) the composition has a total aluminum content in the range of about 39 to about 47 wt % based on the total weight of the composition in the solid state;
C) the composition is either free of aluminum in the form of trimethylaluminum or if trimethylaluminum is present in the composition, not more than about 30 mole %, preferably no more than about 20 mole %, and most preferably no more than about 10 mole % of the total aluminum present in the composition is in the form of trimethylaluminum;
D) the composition in the solid state contains no more than about 2000 ppm (wt/wt) of aromatic hydrocarbon;
E) the cryoscopic number average molecular weight of the composition as determined in benzene is at least-about 1000, preferably at least about 1100, and more preferably at least about 1200 atomic mass units; and
F) the composition has sufficient solubility in n-heptane at 25° C. to provide a solution containing at least 4 wt %, preferably at least 5 wt %, and most preferably at least 7.5 wt % of dissolved aluminum.
Another embodiment of this invention is a method of preparing the above 5 methylaluminoxane compositions. The method comprises subjecting a solution of methylaluminoxane in an aromatic hydrocarbon solvent to distillation at a temperature no higher than about 25° C. under reduced pressure of below 1×10
−5
millimeters of mercury to form a solid methylaluminoxane composition that complies with each of the criteria set forth above as A) through F), inclusive.
Pursuant to another embodiment of this invention there is provided a composition which comprises a solution of methylaluminoxane in a non-aromatic hydrocarbon solvent, wherein:
a) if any trimethylaluminum is present in the solution, no more than about 30 mole %, preferably no more than about 20 mole %, and more preferably no more than about 10 mole % of the total dissolved aluminum in the solution is trimethylaluminum;
b) the solution has a total dissolved aluminum content above 4 wt %, preferably 5 wt % or more, and more preferably at least about 7.5 wt %, based on the total weight of all dissolved aluminum components of the methylaluminoxane plus the weight of the non-aromatic hydrocarbon solvent;
c) the solution contains, if any, no more than 2000 ppm (wt/wt) of aromatic hydrocarbon, based on the total weight of all dissolved aluminum components of the methylaluminoxane plus the total weight of the hydrocarbon solvent (i.e., including the weight of the aromatic hydrocarbon, if any, in the solution); and
d) the methylaluminoxane in the solution has a cryoscopic number average molecular weight as determined in benzene of at least 1000, more preferably at least 1100, and most preferably at least 1200 atomic mass units.
Still another embodiment of this invention is a method of preparing the compositions of the immediately preceding paragraph. The method comprises subjecting a solution of methylaluminoxane in an aromatic hydrocarbon solvent to distillation
Beard William R.
Brantley Noel H.
Albemarle Corporation
Nazario-Gonzalez Porfirio
Pippenger Philip M.
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