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
2000-03-02
2001-02-27
Wu, David W. (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...
C502S232000, C502S152000, C556S173000, C556S179000
Reexamination Certificate
active
06194340
ABSTRACT:
This relates generally to soluble aluminoxane derivatives and more particularly to siloxy-aluminoxane compositions obtained by the reaction of hydrocarbylsiloxanes and aluminoxanes which, in the presence of metallocenes, form catalytically active compositions for olefin polymerization.
U.S. Pat. No. 3,740,384 discloses that the addition of dihydroxysiloxane to non-metallocene organo-zirconium catalyst systems in the absence of aluminoxanes gave improved catalyst activity in olefin polymerization. Likewise, U.S. Pat. No. 4,945,076 describes the improved activity in olefin polymerization which is obtained by the addition of dihydroxysiloxane to a catalyst system consisting of a metallocene and an aluminoxane. The resulting ethylene polymer is said to have acquired a lower melt flow rate (MFR) than those produced without the silicon compound. U.S. Pat. No. 5,034,549 discloses that a preformed catalyst component is obtained by the reaction of dihydroxysiloxane or silicon diol with a zirconocene. The patent further alleges that this catalyst component, when used in conjunction with methyl-aluminoxane, formed a good catalyst system for olefin polymerization.
All the above mentioned disclosures describe the use of alkoxy-silanes having Si—O—C bonds, silicon diols having Si—OH bonds and dihydroxysiloxanes having both the Si—O—Si and Si—OH bonds. The reagents used in the present invention, namely hydrocarbylsiloxanes, have only the Si—O—Si bonds. The chemical reactivity of the hydrocarbyl-siloxanes is significantly different from those of the silanols, silyl ethers, silyl esters and hydroxy disiloxanes (1.
Comprehensive Organometallic Chemistry,
Vol. 2, Chap. 9; Pergamon Press, 1982: 2.
Comprehensive Organic Chemistry,
Vol. 3, Chap. 13 Pergamon Press N.Y. 1979). Those skilled in the art would appreciate the fact that silicon compounds having Si—OH bonds generally undergo dehydration and condensation reactions. These reactions are rarely observed in the case of hydrocarbylsiloxanes. Thus, one could not anticipate any obvious similarity between the reactions of silanols, silyl ethers and silyl esters compared to hydrocarbylsiloxanes. In fact one would not expect to isolate under similar conditions, the same product described in U.S. Pat. No. 5,034,549 by substituting an hydrocarbylsiloxane for the dihydroxysiloxane or silicon diol, as this would require the breaking of Si—O bond which is more difficult than breaking the SiO—H bond.
Methylaluminoxane is the most important aluminoxane used as co-catalyst in polymerization reactions. It is usually obtained in aromatic solvents, in which it is only temporarily soluble. Methylaluminoxane solutions are usually plagued with instability with respect to gel formation or solid precipitation within a short period. Dilute toluene solutions of methylaluminoxane (10 weight percent or less) are reasonably stable to gel formation or solid precipitation for a couple of weeks at room temperature. However, the stability of methylaluminoxane solution drastically decreases as the concentration increases to about 20 weight percent or more.
My U.S. Pat. No. 5,391,529, whose disclosure is incorporated herein by reference, relates to aluminoxanes reacted with alkyldisiloxanes to form novel, soluble siloxy-aluminum compounds which, in combination with metallocenes, provide olefin polymerization catalysts having very high activity.
It has now been found that the reaction products of aluminoxanes with other hydrocarbylsiloxanes, such as aryl, alkyl-aryl and cycloalkyl disiloxanes and polysiloxanes, including cyclic polysiloxanes, provide aluminoxanes containing hydrocarbylsiloxane moieties which impart stability to the aluminoxanes such that the aluminoxanes are not only more soluble in organic solvents but do not easily form gels during storage. For example, a concentrated MAO solution (20 weight percent or above) can be treated with cyclic or linear siloxane compounds to give solution stable, concentrated siloxy-methylaluminoxane compositions, which, after further solvent removal, produce 25-60 weight percent siloxy-methylaluminoxane solutions having enhanced solution stability. Alternatively, one can treat a dilute solution of the MAO solution with siloxanes to form stable siloxy-methylaluminoxane compositions which can optionally be further concentrated to give 25-60 weight percent siloxy-methylaluminoxane solutions.
In accordance with this invention there is provided a siloxy-aluminoxane composition which comprises an aluminoxane which contains hydrocarbylsiloxane moieties which are substantially free of Si—OH bonds, wherein the molar portion of aluminum to hydrocarbylsiloxane is from about 1:1 to 1000:1.
Also provided is an olefin polymerization catalyst comprising a metallocene of a transition, lanthanide or actinide metal and a siloxy-aluminoxane composition which comprises an aluminoxane which contains hydrocarbylsiloxane moieties which are substantially free of Si—OH bonds, wherein the molar portion of aluminum to hydrocarbylsiloxane is from about 1:1 to 1000:1.
The siloxy-aluminoxane compositions are obtainable by the reaction of an aluminoxane and a hydrocarbyldi- or polysiloxane such that the aluminoxane contains hydrocarbyl-siloxane moieties which are chemically bonded thereto.
Preferred aluminoxanes for use in making the siloxy-aluminoxane compounds are hydrocarbylaluminoxanes.
Hydrocarbylaluminoxanes may exist in the form of linear or cyclic polymers with the simplest compounds being a tetraalkylaluminoxane such as tetramethylaluminoxane, (CH
3
)
2
AlOAl(CH
3
)
2
, or tetraethylaluminoxane, (C
2
H
5
)
2
AlOAl(C
2
H
5
)
2
. The compounds preferred for use in olefin polymerization catalysts usually contain about 4 to 20 of the repeating units:
where R is C
1
-C
10
alkyl and especially preferred are methyl-aluminoxanes (MAO). The methylaluminoxanes can contain some higher alkyl groups to improve their solubility. Such modified methylaluminoxanes are described, for example, in U.S. Pat. No. 5,157,008.
The aluminoxanes can be prepared as known in the art by the partial hydrolysis of trialkylaluminum compounds. The trialkylaluminum compounds can be hydrolyzed by adding either free water or water containing solids, which can be either hydrates or porous materials which have absorbed water. Because it is difficult to control the reaction by adding water per se, even with vigorous agitation of the mixture, the free water is preferably added in the form of a solution or a dispersion in an organic solvent. Suitable hydrates include salt hydrates such as, for example, CuSO
4
•5H
2
O, Al
2
(SO
4
)
3
•18H
2
O, FeSO
4
•7H
2
O, AlCl
3
•6H
2
O, Al(NO
3
)
3
•9H
2
O, MgSO
4
•7H
2
O, ZnSO
4
•7H
2
O, Na
2
SO
4
•10H
2
O, MgCl
2
•6H
2
O, Na
3
PO
4
•12H
2
O, LiBr•2H
2
O, LiCl•1H
2
O, LiI•2H
2
O, LiI•3H
2
O, KF•2H
2
O, NaBr•2H
2
O and the like and alkali or alkaline earth metal hydroxides such as, for example, NaOH•H
2
O, NaOH•2H
2
O, Ba(OH)
2
•8H
2
O, KOH•2H
2
O, CsOH•1H
2
O, LiOH•1H
2
O and the like. Mixtures of any of the above hydrates can be used. The mole ratios of free water or water in the hydrate to total alkyl aluminum compounds in the mixture can vary widely, such as for example from about 2:1 to 1:4 with ratios of from about 4:3 to 1:3.5 being preferred.
Such processes for preparing hydrocarbyl-aluminoxanes are described, for example, in U.S. Pat. No. 4,908,463. The methylaluminoxanes contain varying amounts, of from about 5 to 35 mole percent, of the aluminum value as unreacted trimethylaluminum.
The hydrocarbylsiloxanes for use in the invention have hydrocarbyl groups which preferably contain from about 1 to 30 carbon atoms and include linear and/or branched alkyl groups which contain from about 1 to 24 carbon atoms, cycloalkyl groups which contain from about 3 to 24 carbon atoms and alkylaryl or aryl groups which contain from about 6 to 30 carbon atoms. The hydrocarbylsiloxanes are chosen from di-siloxanes and linear or cyclic polysiloxanes. Th
Albemarle Corporation
Lu Caixia
Pippenger Philip M.
Wu David W.
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