Supported olefin polymerization catalyst, its preparation...

Details Supported olefin polymerization catalyst, its preparation... Supported olefin polymerization catalyst, its preparation...

1995-08-02

2001-09-18

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...

C526S160000, C526S943000, C526S114000, C502S104000, C502S113000, C502S117000, C502S120000

Reexamination Certificate

active

06291611

ABSTRACT:

The invention relates to a new process for the preparation of a supported olefin polymerization catalyst. The invention also relates to a supported olefin polymerization catalyst prepared by such a process and its use for the homo- and copolymerization of olefins as well as a novel process for the preparation of polyethylene having a high bulk density.
Alpha-olefins, including ethylene, have so far been polymerized (homo- or copolymerized) by using heterogenous catalyst systems made up of a procatalyst based on a transition metal and a cocatalyst based on aluminum alkyl. It has been observed that the homogenous or supported catalyst systems, the pro-catalyst component of which is based on metallocene compounds such as bis (cyclopentadienyl) titanium dialkyl or bis (cyclopentadienyl) zirconium alkoxy, or chlorides of these, alumoxane or an ionic activator having been used as their activator, are also useful in the polymerization of ethylene.
A generally known problem in the use of metallocene catalysts is the poor morphology of the forming polymer material; this is seen in particular in a low bulk density and in the polymer being non-homogenous. Since the so-called replica phenomenon applies to polymerization, i.e. the forming polymer particles obtain a morphology similar to that of the catalyst particles used for their preparation, the problem can be solved only by improving the morphology of the catalyst used for the polymerization.
DE patent publication 2 608 863 discloses the use, for ethylene polymerization, of a catalyst system made up of bis-(cyclopentadienyl)titanium dialkyl, aluminum trlalkyl, and water. DE patent publication 2 608 933 describes an ethylene polymerization catalyst system made up of zirconcenes having the general formula (Cp)
n
ZrY
4−n
, where Cp is a cyclopentadienyl, n is a numeral 1-4, Y is group R, CH
2
AlR
2
, CH
2
CH
2
AlR
2
or CH
2
CH(AlR
2
)
2
, R being an alkyl group or a metal alkyl group; of an aluminum trialkyl cocatalyst; and of water.
European patent application 35242 discloses a method for the preparation of ethylene polymers and atactic propylene polymers in the presence of a halogen-free Ziegler-Natta catalyst system made up of (1) a cyclopentadienyl compound having the formula (Cp)
n
MY
4−n
, where Cp and n are the same as above, M is a transition metal, preferably zirconium, and Y is a hydrogen atom, a C
1
-C
5
alkyl group or metal alkyl group or a radical having the general formula CH
2
AlR
2
, CH
2
CH
2
AlR
2
or CH
2
CH(AlR
2
)
2
, where R is a C
1
-C
5
alkyl group or metal alkyl group; and of (2) alumoxane serving as an activator.
Homogenous catalyst systems in which a metallocene or alumo-xane is used have been disclosed, for example, in EP patent application 69951 and U.S. Pat. No. 4,404,344. It has been known in the art to support the metallocene catalyst on a carrier. DE 3240382C2 teaches a catalyst, which comprises alumoxane and a cyclopentadienyl titanium or zirconium compound supported on a dried inorganic filler, which can be any inorganic compound, also silicate, quartz and aluminium-oxid. However, excess amounts of solvents are used and the inventors strive to get filler into the polymer. Use of supports for metallocene catalysts is also disclosed in EP 0037894B1.
Application publication 862625 discloses a method for the preparation of a supported catalyst intended for olelefin polymerization, wherein alumoxane in an inert hydrocarbon solvent and a metallocene of a 4A, 5A or 6A metal of the Periodic Table are added to a slurry of the support in an inert hydro-carbon solution.
EP patent publication 279863 describes the preparation, by a slurry process, of a catalyst intended for the polymerization of alpha-olefins. The catalyst thereby obtained is further given a finishing treatment by polymerizing olefin onto its surface; this suggests a poor morphology of the original catalyst, an attempt being made to improve it by this so-called prepolymerization.
Publication U.S. Pat. No. 5,017,665 discloses a catalyst suitable for the copolymerization of ethylene and 1,4-hexadiene, the catalyst being prepared by adding 330 ml of a 10% alumoxane solution in toluene to 800 g of silica powder (Davison 948). Thereafter, 250 ml of toluene is further added to the silica treated with alumoxane, whereafter 2.5 g of bis(indenyl) zirconium dichloride slurried in 40 ml of toluene is added to the obtained slurry. Finally the treated support is dried. Table I of the said patent publication shows that the activity of the obtained catalyst is not very good; with a catalyst feed rate of 1 g of catalyst per hour, only approx. 100 g of polyethylene per hour is obtained, which is a very low activity for practical purposes.
Publications EP-347129 and U.S. Pat. No. 5,001,205 disclose a process for the preparation of a bis (cyclopentadienyl) zirconium alumoxane catalyst on a silica support, wherein 30 ml of a methyl alumoxane solution in toluene was poured onto 15 g of silica gel and was dried. Thereafter a solution of bis (cyclopentadienyl) zirconium dichloride derivative in toluene was added in drops to 2 g of the said alumoxane-treated silica gel, and a small amount of toluene was further added to form a slurry. Finally the slurry was dried, and a supported catalyst havina a zir-conium concentration of approx. 0.5% by weight was obtained. Before the actual polymerization, the catalyst was coated by prepolymerization. Thus, the catalysts of these publications are also prepolymerized, which suggests a poor morphology of the original catalyst, an attempt being made to improve it by prepolymerization.
Patent CA-1268753 describes the bonding of a metallocene to a support, but in this publication a reaction product of a metallocene and alumoxane on the support is not formed; the alumoxane serves as a conventional cocatalyst,
Publication U.S. Pat. No. 5,240,894 discloses a process for the preparation of a supported metallocent/alumoxane catalyst system, wherein first a metallocene/alumoxane reaction solution is formed, a porous support is added to the solution, the solvent is removed by evaporation, and the formed catalyst precursor is possibly subjected to prepolymerization, Although this publication proposes the mixing of the support with a completed metallocene/alumoxane reaction product, the need for prepolymerization suggests deficient morphology of the catalyst. The process described in this U.S. publication is characterized in that the solvent is used in excess relative to the pore volume of the support. In this case the adsorption of the catalyst components requires an affective evaporation step, in which case the above-mentioned components, when precipitating, tend to be accumulate on the surface of the support rather than to be adsorbed evenly inside the pores. this slurry method is typical of the prior art.
The methods generally used in the prior-art patent literature for the preparation of supported metallocene-alumoxane catalysts are most commonly so-called slurry processes, in which an inert support is slurried in an inert hydrocarbon such as pentane, heptane or toluene. The catalyst components metallocene and alumoxane are then added to this slurry. In some cases the support is treated separately with a solution of the metallocene and separately with a solution of the alumoxane. Thereafter the inert hydrocarbon is evaporated by using a high temperature and/or vacuum. The product obtained is a catalyst in which the active components are attached to a sopport. Judging from the above, there have always been the problems of poor morphology of the catalyst, an uneven distribution of the substances on the support, and thus also a poor quality of the polymer particles and a low catalyst activity.
The object of the present invention is to provide a supported olefin polymerization catalyst having as good an activity as possible. The invention also aims at as good a catalyst morphology as possible, in turn giving aood morphology to the forming olefin polymer. The aim is additionally to provide a supported olefin polymerization catalyst i

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