Supported phosphinimine polymerization catalyst

Details Supported phosphinimine polymerization catalyst Supported phosphinimine polymerization catalyst

2002-09-16

2004-03-23

Lu, Caixia (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C502S119000, C502S120000, C502S155000, C526S160000, C526S165000, C526S129000, C526S943000

Reexamination Certificate

active

06710143

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to catalyst systems for olefin polymerizations.
BACKGROUND OF THE INVENTION
The use of fluorided alumina as a support material for Phillips-type chromium polymerization catalysts has been widely disclosed in the patent literature. The following U.S. Pat. Nos. (USP) relate to this technology: 5,221,720; 5,221,655; 5,221,654; 5,219,962; and 5,219,817 (all McDaniel et al, and all assigned to Phillips Petroleum Company). Similarly U.S. Pat. No. 4,100,337 (Noshay et al, assigned to Union Carbide Corporation) teaches the use of fluorided silica supports for chromium polymerization catalysts.
Halogenated catalyst supports are also known for use with other types of ethylene polymerization catalysts. For example, U.S. Pat. No. 4,536,484 (Lacombe et al, assigned to Atochem) teaches the preparation of a functionalized support (by the reaction of an organoaluminum compound with a functionalized magnesium compound) followed by the chlorination of the functionalized support. The resulting support is used with a Ziegler-Natta type catalyst and an aluminoxane cocatalyst.
Similarly, European patent application EP 906,920 (Saudemont et al, assigned to Elf Atochem) teaches the preparation of a functionalized support, followed by the fluorination of the functionalized support. The resulting support material allows the use of aluminum alkyls as active cocatalysts for metallocene catalysts. This is a desirable result as aluminum alkyls are less expensive than aluminoxanes. However, EP 906,920 also shows that directly fluorided supports (where “directly fluorided” refers to supports which were not functionalized before being treated with a source of fluorine) do not provide catalytic activity when used with aluminum alkyls (see comparative example 25 of the '920 application).
In contrast, we have now discovered that of a directly fluorided metal oxide provides an excellent support for a phosphinimine/aluminum olefin polymerization catalyst.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides a supported catalyst system for olefin polymerization comprising:
a) a directly fluorided metal oxide;
b) an aluminoxane; and
c) a catalyst which is a complex of a group 4 metal having at least one phosphinimine ligand.
The present invention also provides a process to prepare polyolefins using the catalyst technology of this invention.
DETAILED DESCRIPTION
The use of metal oxide supports in the preparation of olefin polymerization catalysts is known to those skilled in the art. An exemplary list of suitable metal oxides includes oxides of aluminum, silicon, zirconium, zinc and titanium. Alumina, silica and silica-alumina are metal oxides which are well known for use in olefin polymerization catalysts and are preferred for reasons of cost and convenience. Silica is particularly preferred.
It is preferred that the metal oxide have a particle size of from about 1 to about 200 microns. It is especially preferred that the particle size be between about 30 and 100 microns if the catalyst is to be used in a gas phase or slurry polymerization process and that a smaller particle size (less than 10 microns) be used if the catalyst is used in a solution polymerization.
Conventional porous metal oxides which have comparatively high surface areas (greater than 1 m
2
/g, particularly greater than 100 m
2
/g, more particularly greater than 200 m
2
/g) are preferred to non-porous metal oxides.
The “directly fluorided” metal oxides used in this invention are prepared by directly treating the metal oxide with a source of fluoride. [By way of clarification, the present invention does not encompass the use of “functionalized supports” which are taught in the aforementioned U.S. Pat. No. 4,536,484 and/or EP 906,920. In other words, the present invention eliminates the need for the pretreatment/functionalization which is required by the cited prior art.]
The term “directly fluorided” is meant to broadly refer to the treatment of the metal oxide with a source of fluoride. Any inorganic or organic fluorine containing material which provides fluoride may be used. A review of these materials is given in the aforementioned U.S. Pat. No. 4,100,337 and the references cited therein. Exemplary sources of fluoride include HF, ammonium fluorides (such as NH
4
HF
2
NH
4
BF
4
, (NH
4
)
2
SiF
6
) and alkali metal fluorides such as LiF, KF and NaF. The use of inorganic fluorides is preferred. The use of NaF is especially preferred. Conventional techniques to prepare the fluorided metal oxide may be used (as disclosed in the previously mentioned references). However, in a particular preferred embodiment of this invention, silica is simply contacted with an aqueous solution of fluoride at an acidic pH (as described further in the Examples). This is an inexpensive and convenient process with the further advantage that it does not produce waste byproducts which are expensive to handle or dispose of.
The amount of fluoridation agent present in the liquid is preferably from 0.1 to 20 weight % based on the weight of the silica. Alcohols or an aqueous alcohol solution may also be used in place of the water as the contacting liquid. Preferred contacting conditions include times from about 1 minute to about 3 days (especially from about 10 minutes to about 3 hours) at a temperature of from about 10° C. to 200° C. (under pressure) with particularly preferred temperatures being from about 20° C. to 80° C. After contacting the silica and sodium fluoride, the fluorided silica is removed from the liquid and preferably calcined prior to treatment with the aluminoxane.
Conventional calcining conditions may be employed—i.e. calcining temperatures of from about 150° C. to about 900° C. for periods of time ranging from about 10 minutes to about 48 hours. Preferred calcining conditions include temperatures of from 200° C. to 700° C. for times of from 1 to 8 hours.
The directly fluorided metal oxide used in this invention preferably has a fluorine content of from 0.01 to 15 weight % based upon the weight of the fluorine and metal oxide.
The fluorided metal oxide is preferably first contacted with an aluminoxane.
Aluminoxanes are readily available items of commerce which are known to be cocatalysts for olefin polymerization catalysts (especially group 4 metal metallocene catalysts). A generally accepted formula to represent aluminoxanes is:
(R)
2
AlO(RAlO)
m
Al(R)
2
wherein each R is independently an alkyl group having from 1 to 6 carbon atoms and m is between 0 and about 50. The preferred aluminoxane is methylaluminoxane wherein R is predominantly methyl. Commercially available methylaluminoxane (“MAO”) and “modified MAO” are preferred for use in this invention. [Note: In modified MAO, the R groups of the above formula are predominantly methyl but a small fraction of the R groups are higher hydrocarbyls—such as ethyl or butyl—so as to improve the solubility of the “modified MAO” in aliphatic solvents.]
The directly fluorided metal oxide and aluminoxane are preferably contacted together using conventional techniques to prepare supported catalysts such as mixing the aluminoxane and fluorided metal oxide together in a linear or aromatic hydrocarbon (such as hexane or toluene) at a temperature of from 10 to 200° C. for a time of from 1 minute to several hours. The amount of aluminoxane is preferably sufficient to provide from 1 to 40 weight % aluminoxane (based on the combined weight of the aluminoxane and the fluorided metal oxide). The intermediate product which is produced by these steps is a “supported aluminoxane” catalyst component. A catalyst molecule is then deposited on the supported aluminoxane. The catalyst molecule is a complex of a group 4 metal which is characterized by having at lease one phosphinimine ligand. Preferred catalyst are defined by the formula:
wherein M is selected from titanium, hafnium and zirconium, L
1
is a phosphinimine ligand; L
2
is a ligand selected from the group consisting of a phosphinimine ligand, a cyclopentadienyl ligand which may op

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