Polymerization catalyst systems, their preparation, and use

Details Polymerization catalyst systems, their preparation, and use Polymerization catalyst systems, their preparation, and use

1999-10-18

2001-07-31

Wu, David W. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S129000, C526S151000, C526S097000, C502S152000, C502S159000, C502S151000, C502S111000, C502S109000

Reexamination Certificate

active

06268453

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the polymerization of olefins. In another aspect this invention relates to transition metal based catalyst systems for the polymerization of olefins. The invention is particularly related to a method for preparing a solid cocatalyst suitable for producing solid transition metal catalyst systems.
BACKGROUND OF THE INVENTION
The discovery that metallocenes of transition metals can be used as catalysts for the polymerization of olefins has led to significant amounts of research since it was found that different metallocenes could produce different types of polymers. One of the earliest references to the use of metallocenes in the polymerization of olefins is U.S. Pat. No. 2,827,446 which discloses a homogeneous, i.e. liquid, catalyst system of bis(cyclopentadienyl) titanium dichloride and an alkyl aluminum compound. The activity of such systems was not, however, as high as would be desired. It was latter discovered that more active catalyst systems would result if the metallocene was employed with an alkylaluminoxane cocatalyst, such as that disclosed in U.S. Pat. No. 3,242,099. One drawback of such metallocene-based catalyst system is that they generally must be used with large amounts of alkylaluminoxane cocatalysts, which are significantly more expensive than the alkyl aluminum cocatalysts. There is therefore a need for cocatalysts that would be effective in smaller amounts.
Various techniques are known for producing alkylaluminoxane, the simplest being to add water in a controlled fashion to an alkylaluminum compound such as disclosed in the aforementioned U.S. Pat. No. 3,242,099. Other techniques for producing such aluminoxanes involve reacting alkylaluminum compounds with solids containing water. See, for example, EPC 208,561; USSR Inventor Certificate 566,844: JP 60/289223; and U.S. Pat. Nos. 4,544,762; and 4,665,208.
For many commercial processes it is necessary to develop solid catalysts that are suitable for the particular type of commercial scale equipment employed. U.S. Pat. No. 4,431,788 teaches that a catalyst system can be prepared by reacting a solid having labile hydrogen atoms, such as starch, with an aluminum alkyl and then combining that product with a metallocene. Similarly German patent 3,240,382 teaches reacting alkyl aluminum compounds with solids containing water to produce solids coated with alkylaluminoxanes. Examples of other supported cocatalysts prepared by reacting organoaluminum compounds with solids containing water are disclosed in EPC 386,644; and U.S. Pat. Nos. 4,904,631; 4,912,075; 4,925,821; 5,006,500; 5,008,228; and 5,529,965.
The presence of soluble aluminoxane or polymerization catalyst, even on solid catalyst systems, has also been found to often be detrimental in commercial slurry type polymerization processes, the thought being that when the aluminoxane and/or polymerization catalyst is present in a dissolved form it contributes to the formation of fouling in the polymerization reactors. Accordingly, merely depositing aluminoxane on a solid support has not been found to be a particularly beneficial technique for preparing a catalyst system for slurry type polymerization processes, as some remaining soluble species usually result in reactor fouling.
One object of the present invention is to provide a simplified method of preparing a solid cocatalyst that can readily be used to form a solid catalyst system that can be used in the polymerization of olefins. Another object is to provide a cocatalyst that is more cost effective than alkylaluminoxanes. Another object is to provide a new type of solid cocatalyst system particularly suitable for use with metallocenes. Another object is to provide solid transition metal containing catalyst systems suitable for polymerizing olefins. Still another object is to provide a process for polymerizing olefins, especially in slurry type polymerization.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a method for polymerizing an olefin using a solid catalyst system. The catalyst system is prepared by combining an olefin polymerization catalyst with a solid cocatalyst. The solid cocatalyst is prepared by reacting a suitable support base with an organoaluminum compound and then reacting that product with an activity promoting amount of water.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention an organoaluminum compound is reacted with a suitable support base or carrier in a liquid diluent and then with water to produce a new type of solid which can be used as a cocatalyst for transition metal olefin polymerization catalysts.
The terms “support base”, “support”, and “carrier” as used herein refer to the material that produces a solid when reacted with the organoaluminum compound and water. The support base thus does not have to actually be a solid. The term “base” in the phrase “support base” does not refer to the pH but just to the material which is the center upon which the solid cocatalyst is formed. It is contemplated that the support base can be any organic, organometallic, or inorganic compound capable of affixing the organoaluminum compound either through absorption, adsorption, Lewis Acid/Lewis Base interactions, or by reaction with hydroxyl groups of the support base.
A wide range of materials can be used as the support base. Generally, any material that will result in a solid cocatalyst that remains insoluble in the polymerization diluent during the polymerization process can be employed as the support base. Thus the support base includes materials that form solids when reacted with an organoaluminum compound and water as well as solids that are insoluble in the particular liquid diluent that is present during the polymerization. It is generally preferred that the support base be capable of yielding a particulate solid cocatalyst. The support base can be a material having surface groups which are known to react with organoaluminum compounds or a material which is free of surface groups which react with organoaluminum compounds. Some examples of materials envisioned for use as a support base include starch, lignin, cellulose, sugar, silica, alumina, silica-alumina, titania, zirconia, zeolites of silica and/or alumina, magnesia, calcium carbonate, aluminum trifluoride, boron oxide, magnesium dichloride, boric acid, activated carbon, carbon black, organoboranes, organoboroxines, Si(OMe)
3
Me, hydrocarbyl polyalcohols, boric acid, alumina, polyethylene, polyethylene glycol, and the like. One embodiment comprises dissolving polyethylene in a suitable organic solvent then adding the organoaluminum compound and then adding the water to produce a solid cocatalyst. It is generally preferred that the support base that is reacted with the organoaluminum compound be relatively free of water, i.e. that it contain less than about 5 weight percent water, more preferably less than 1 weight percent water.
The term organoaluminum compound as used herein refers to compounds of the formula R
n
AlX
3−
wherein n is a number in the range of 1 to 3, each R is the same or different organo radical, preferably a hydrocarbyl radical, and each X is a halide. Typically the organo radicals would have 1 to 12 carbon atoms, more preferably 1 to 5 carbon atoms. Some examples of organoaluminum compounds include trialkylaluminum compounds, triarylaluminum compounds, dialkylaluminum hydrides, diarylaluminum hydrides, aryl alkyl aluminum hydrides, dialkylaluminum halides, alkyl aluminum dihalides, alkyl aluminum sesquihalides, and the like. Some specific examples of such organoaluminum compounds include trimethylaluminum, triethylaluminum, dimethylaluminum chloride, triisopropylaluminum, triisobutylaluminum, trihexylaluminum, diethylaluminum chloride, ethyl aluminum dichloride, ethyl aluminum sesquichloride, dimethyl aluminum chloride, and the like. The currently preferred organoaluminum compounds are the alkyl aluminum compounds, especially the trialkyl aluminum compounds. It is also within the scope of the present

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