Method for preparing a silica gel supported metallocene-alumoxane catalyst

This invention relates to a process for preparing a supported metallocene alumoxane catalyst for use in the slurry or liquid phase polymerization of olefins. The invention particularly relates to the use of silica gel containing from about 10 to about 50 percent by weight adsorbed water as the catalyst support material. It has been found that such silica gel may be safely added to an aluminum trialkyl solution to form by direct reaction with the adsorbed water content of the silica gel catalyst support material the alumoxane component of the catalyst system. An alumoxane coated silica gel is formed to which a metallocene may be added. The resulting material can either be used in this slurry state for slurry polymerization or can be used for liquid phase polymerization of olefins.

FIELD OF THE INVENTION 
This invention relates to a process for preparing a supported metallocene 
alumoxane catalyst for use in the liquid or slurry phase polymerization of 
olefins. The invention particularly relates to the use of silica gel 
containing from about 10 to about 40 percent by weight adsorbed water as 
the catalyst support material. It has been found that such silica gel may 
be safely added to an aluminum trialkyl solution to form, by direct 
reaction with the adsorbed water content of the silica gel catalyst 
support material, the alumoxane component of the catalyst system. 
BACKGROUND TO THE INVENTION 
Olefin polymerization catalysts comprising a metallocene and an aluminum 
alkyl component were first proposed in about 1956. Australian patent 
220436 proposed for use as a polymerization catalyst a 
bis-(cyclopentadienyl) titanium, zirconium, or vanadium salt as reacted 
with a variety of halogenated or unhalogenated aluminum alkyl compounds. 
Although such complexes were capable of catalyzing the polymerization of 
ethylene, such catalytic complexes, especially those made by reaction with 
an aluminum trialkyl, had an insufficient level of catalytic activity to 
be employed commercially for production of polyethylene or copolymers of 
ethylene. 
Later it was found that certain metallocenes such as bis-(cyclopentadienyl) 
titanium, or zirconium dialkyls in combination with aluminum alkyl/water 
cocatalyst form catalyst systems for the polymerization of ethylene. Such 
catalysts are discussed in German Patent Application 2,608,863 which 
discloses a polymerization catalyst for ethylene consisting of 
bis-(cyclopentadienyl) titanium dialkyl, aluminum trialkyl and water. 
German Patent Application 2,608,933 discloses an ethylene polymerization 
catalyst consisting of a cyclopentadienyl zirconium salt, an aluminum 
trialkyl cocatalyst and water. European Patent Application No. 0035242 
discloses a process for preparing ethylene and atactic propylene polymers 
in the presence of a halogen free cyclopentadienyl transition metal salt 
and an alumoxane. Such catalysts have sufficient activity to be 
commercially useful and enable the control of polyolefin molecular weight 
by means other than hydrogen addition ---- such as by controlling the 
reaction temperature or by controlling the amount of cocatalyst alumoxane 
as such or as produced by the reaction of water with an aluminum alkyl. 
To realize the benefits of such catalyst systems, one must use or produce 
the required alumoxane cocatalyst component. An alumoxane is produced by 
the reaction of an aluminum alkyl with water. The reaction of an aluminum 
alkyl with water is very rapid and highly exothermic. Because of the 
extreme violence of the reaction, the alumoxane cocatalyst component has, 
heretofore, been separately prepared by one of two general methods. 
Alumoxanes may be prepared by adding an extremely finely divided water, 
such as in the form of a humid solvent, to a solution of aluminum alkyl in 
benzene or other aliphatic hydrocarbons. The production of an alumoxane by 
such procedures requires use of explosion-proof equipment and very close 
control of the reaction conditions in order to reduce potential fire and 
explosion hazards. For this reason, it has been preferred to produce 
alumoxane by reacting an aluminum alkyl with a hydrated salt, such as 
hydrated copper sulfate. In such procedure a slurry of finely divided 
copper sulfate pentahydrate and toluene is formed and mantled under an 
inert gas. Aluminum alkyl is then slowly added to the slurry with stirring 
and the reaction mixture is maintained at room temperature for 24 to 48 
hours during which a slow hydrolysis occurs by which alumoxane is 
produced. Although the production of alumoxane by a hydrated salt method 
significantly reduces the explosion and fire hazard inherent in the wet 
solvent production method, production of an alumoxane by reaction with a 
hydrated salt must be carried out as a process separate from that of 
producing the metallocene alumoxane catalyst itself. This process is also 
slow and produces hazardous wastes that create disposal problems. Further, 
before the alumoxane can be used for the production of the active catalyst 
complex, the hydrated salt reagent must be separated from the alumoxane to 
prevent it from becoming entrained in the catalyst complex and thus 
contaminating any polymer produced therewith. 
Only in those situations wherein a hydrated material is of a chemical 
composition acceptable as a filler material for a filled polyolefin 
composition may it be used to produce a metallocene/alumoxane catalyst 
complex by direct reaction with an aluminum alkyl solution. Hence U.S. 
Pat. No. 4,431,788 discloses a process for producing a starch filled 
polyolefin composition wherein an aluminum trialkyl is first reacted with 
starch particles of a moisture content below 7 weight percent. The starch 
particles are then treated with a (cyclopentadienyl)-chromium, titanium, 
vanadium or zirconium alkyl to form a metallocene alumoxane catalyst 
complex on the surface of the starch particles. An olefin is then 
polymerized about the starch particles by solution or suspension 
polymerization procedures to form a free-flowing composition of 
polyolefin-coated starch particles. German Patent 3,240,382 likewise 
discloses a method for producing a filled polyolefin composition which 
utilizes the water content of an inorganic filler material to directly 
react with an aluminum trialkyl and produce thereon an active metallocene 
alumoxane catalyst complex. Polymer is produced by solution or gas phase 
procedures at the filler surface to uniformly coat the filler particles 
and provide a filled polymer composition. 
German Patent 3,240,382 notes that the activity of a metallocene alumoxane 
catalyst is greatly impaired or lost when prepared as a surface coating on 
an inorganic material. Although German Patent 3,240,382 suggests that an 
inorganic material containing absorbed or adsorbed water may be used as a 
filler material from which the alumoxane cocatalyst component may be 
prepared by direct reaction with an aluminum trialkyl, the only water 
containing inorganic filler materials which are identified as capable of 
producing the alumoxane without adversely affecting the activity of the 
metallocene alumoxane catalyst complex are certain inorganic materials 
containing water of crystallization or bound water, such as gypsum or 
mica. German Patent 3,240,382 does not illustrate the production of a 
catalyst coated inorganic filler material wherein the inorganic material 
is one having absorbed or adsorbed water. Nor does German Patent 3,240,382 
describe an inorganic filler material having absorbed or adsorbed water 
which has surface area or pore volume properties suitable for service as a 
catalyst support for a liquid or slurry phase polymerization procedure. 
European Patent 0,170,059 discloses a process for forming alumoxanes for 
catalysts in polymerization of olefins. Specifically, it discloses adding 
a finely divided porous solid, e.g., silica dioxide or aluminum oxide, to 
a non-aqueous medium, adding water to that medium and then mixing in 
aluminum trialkyl to form alumoxane. After the alumoxane is formed, a 
transition metal compound (metallocene) is added, followed by the monomer. 
Since water and porous solid are added separately into the reactor, this 
technique basically involves adding aluminum trialkyl to water which 
yields a catalyst not being attached to any solid support. The catalyst 
produced in this process can cause severe reactor fouling during the 
polymerization due to the nature of the unsupported catalyst. 
It would be desirable to devise an economical, reproducible, and clean 
process whereby an active supported metallocene/alumoxane catalyst could 
be produced for use in liquid or slurry phase polymerization. To be 
economical the process should dispense with the requirement of producing 
the alumoxane component as a separate component apart from the procedure 
by which the catalyst itself is prepared. To be reproducible, the 
procedure should specify the exact procedure of producing the porous solid 
material which contains the right amount of water absorbed or adsorbed on 
its surface so that it could generate alumoxane with a high degree of 
catalytic activity. To be clean, the catalyst produced in the 
polymerization system should not cause the fouling of the reactor during 
the polymerization so that it could be applied to commercial production. 
SUMMARY OF THE INVENTION 
The process of this invention utilizes as the catalyst support material 
silica particles having a surface area in the range of about 10 m.sup.2 /g 
to about 700 m.sup.2 /g, preferably about 100-500 m.sup.2 /g and desirably 
about 200-400 m.sup.2 g, a pore volume of about 3 to about 0.5 cc/g and 
preferably 2-1 cc/g and an adsorbed water content of from about 10 to 
about 50 weight per cent, preferably from about 20 to about 40 weight per 
cent, and most preferably about 35 weight percent. Such silica particles 
are referred to hereafter as a "water-impregnated" silica gel. The silica 
gel supported metallocene alumoxane catalyst is prepared by adding the 
water-impregnated silica gel to a stirred solution of aluminum trialkyl in 
an amount sufficient to provide a mole ratio of aluminum trialkyl to water 
of from about 10:1 to about 1:1, preferably 5:1 to about 1:1; thereafter 
adding to this stirred solution a metallocene in an amount sufficient to 
provide an aluminum to transitional metal ratio of from about 1000:1 to 
1:1, preferably from about 300:1 to 10:1, most preferably from about 150:1 
to about 30:1. The contact of the water-impregnated material with aluminum 
trialkyl forms an alumoxane compound attached to the surface of the 
support. The reaction between the supported alumoxane with metallocene 
compound produces a supported catalyst with high catalytic activity in a 
liquid medium. Of course, the silica gel can be contacted with the 
metallocene and alumoxane in any order or simultaneously, but the 
above-described order of addition is preferred. The supported catalyst 
greatly reduces the reactor fouling during the polymerization due to the 
formation of granular polymer particle. 
The catalyst complex formed by this process can be used for polymerization 
of olefins by conventional liquid or slurry phase polymerization 
procedures. In both cases, aluminum trialkyl, water-impregnated silica, 
metallocene, comonomer, as well as ethylene feed can be added continuously 
into the reactor while polymer product is continuously removed from the 
reactor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is directed toward a method for preparing a supported 
catalyst system for use in the liquid or slurry phase polymerization of 
olefins, particularly lower alpha-olefins, such as ethylene, propylene, 
and butene-1, hexene-1 and octene-1. The catalyst is especially useful for 
the production of linear low density polyethylene (LLDPE). The polymers 
are intended for fabrication into articles by extrusion, injection 
molding, thermoforming, rotational molding, and the like. In particular, 
the polymers prepared with the catalyst complex and by the method of this 
invention are homopolymers or copolymers of ethylene with higher 
alpha-olefins having up to about 10 carbon atoms. Illustrative of the 
higher alpha-olefins are hexene-1 and octene-1. 
In the process of the present invention, ethylene, either alone or together 
with alpha-olefins having up to about 10 carbon atoms, is polymerized in 
the presence of a silica gel supported catalyst system comprising at least 
one metallocene and an alumoxane. In accordance with this invention, 
olefin copolymers, particularly copolymers of ethylene and higher 
alpha-olefins having from 3-10 carbon atoms, can also be produced. 
The active catalyst complex prepared by the process of this invention 
comprises a metallocene and an alumoxane adsorbed onto the surface of a 
silica gel support material. Alumoxanes are oligomeric aluminum compounds 
represented by the general formula (R-Al-O).sub.y which is believed to be 
a cyclic compound and R(R-Al-O-).sub.y AlR.sub.2, which is a linear 
compound. In the general formula, "R" is a C.sub.1 -C.sub.10 alkyl group 
such as, for example, methyl, ethyl, propyl, butyl, and pentyl and "y" is 
an integer from 2 to about 30 and represents the degree of oligomerization 
of the alumoxane. Preferably, "R" is methyl and "y" is about 4 to about 25 
and most preferably 6-25. Generally, in the preparation of alumoxanes 
from, for example, the reaction of aluminum trimethyl and water, a mixture 
of linear and cyclic compounds is obtained. Generally, an alumoxane having 
a higher degree of oligomerization will, for a given metallocene, produce 
a catalyst complex of higher activity than will an alumoxane having a 
lower degree of oligomerization. Hence, the procedure by which alumoxane 
is produced by direct reaction of an aluminum trialkyl with a 
water-impregnated silica gel should ensure the conversion of the bulk 
quantity of the aluminum trialkyl to an alumoxane having a high degree of 
oligomerization. In accordance with this invention the desired degree of 
oligomerization is obtained by the order of addition of reactants as 
described hereinafter. 
The metallocene may be any of the organometallic coordination compounds 
obtained as a cyclopentadienyl derivative of a transition metal. 
Metallocenes which are useful for preparing an active catalytic complex 
according to the process of this invention are the mono, bi and tri 
cyclopentadienyl or substituted cyclopentadienyl metal compounds and most 
preferably, bi-cyclopentadienyl compounds. The metallocenes particularly 
useful in this invention are represented by the general formulas: 
EQU (Cp).sub.m MR.sub.n X.sub.q (I.) 
wherein Cp is a cyclopentadienyl ring, M is a Group 4b or 5b transition 
metal and preferably a Group 4b transition metal, R is a hydrocarbyl group 
or hydrocarboxy group having from 1 to 20 carbon atoms, X is a halogen, 
and m is a whole number from 1 to 3, n is a whole number form 0 to 3, and 
q is a whole number from 0 to 3, 
EQU (C.sub.5 R'.sub.k).sub.g R".sub.s (C.sub.5 R'.sub.k)MQ.sub.3-g, II. and 
EQU R".sub.s (C.sub.5 R'.sub.k).sub.2 MQ' III. 
wherein (C.sub.5 R'.sub.k) is a cyclopentadienyl or substituted 
cyclopentadienyl, each R' is the same or different and is hydrogen or a 
hydrocarbyl radical such as alkyl, alkenyl, aryl, alkylaryl, or arylalkyl 
radicals containing from 1 to 20 carbon atoms, a silicon-containing 
hydrocarbyl radical, or a hydrocarbyl radical wherein two carbon atoms are 
joined together to form a C.sub.4 -C.sub.6 ring, R" is C.sub.1 -C.sub.4 
alkylene radical, a dialkyl germanium or silicone, or an alkyl phosphine 
or amine radical bridging two (C.sub.5 R'.sub.k) rings, Q is a hydrocarbyl 
radical such as aryl, alkyl, alkenyl, alkylaryl, or arylalkyl having 1-20 
carbon atoms, hydrocarboxy radical having 1-20 carbon atoms or halogen and 
can be the same or different, Q' is an alkylidene radical having from 1 to 
about 20 carbon atoms, s is 0 or 1, g is 0, 1 or 2; when g is 0, s is 0; k 
is 4 when s is 1 and k is 5 when s is 0 and M is as defined above. 
Exemplary hydrocarbyl radicals are methyl, ethyl, propyl, butyl, amyl, 
isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 
2-ethylhexyl, phenyl, and the like. Exemplary alkylene radicals are 
methylene, ethylene, propylene, and the like. Exemplary halogen atoms 
include chlorine, bromine and iodine and of these halogen atoms, chlorine 
is preferred. Exemplary of the alkylidene radicals is methylidene, 
ethylidene and propylidene. 
Of the metallocenes, zirconocenes and titanocenes are most preferred. 
Illustrative but non-limiting examples of these metallocenes which can be 
usefully employed in accordance with this invention are 
monocyclopentadienyl titanocenes such as, cyclopentadienyl titanium 
trichloride, pentamethylcyclopentadienyl titanium trichloride; 
bis(cyclopentadienyl) titanium diphenyl; the carbene represented by the 
formula Cp.sub.2 Ti.dbd.CH.sub.2 . Al(CH.sub.3).sub.2 Cl and derivatives 
of this reagent such as Cp.sub.2 Ti.dbd.CH.sub.2 . Al(CH.sub.3).sub.3, 
(Cp.sub.2 TiCH.sub.2).sub.2, 
##STR1## 
Cp.sub.2 Ti.dbd.CHCH.sub.2 CH.sub.2, Cp.sub.2 Ti.dbd.CH.sub.2 . 
AlR'''.sub.2 Cl, wherein Cp is a cyclopentadienyl or substituted 
cylopentadienyl radical, and R''' is an alkyl, aryl, or alkylaryl radical 
having from 1-18 carbon atoms; substituted bis(Cp)Ti(IV) compounds such as 
bis(indenyl)Ti diphenyl or dichloride, bis(methylcyclopentadienyl)Ti 
diphenyl or dihalides and other dihalide complexes; dialkyl, trialkyl, 
tetra-alkyl and penta-alkyl cyclopentadienyl titanium compounds such as 
bis(1,2-dimethylcyclopentadienyl)Ti diphenyl or dichloride, 
bis(1,2-diethylcyclopentadienyl)Ti diphenyl or dichloride and other 
dihalide complexes; silicone, phosphine, amine or carbon bridged 
cyclopentadiene complexes, such as dimethyl silyldicyclopentadienyl 
titanium diphenyl or dichloride, methylenedicyclopentadienyl titanium 
diphenyl or dichloride and other dihalide complexes and the like. 
Illustrative but non-limiting examples of the zirconocenes which can be 
usefully employed in accordance with this invention are, cyclopentadienyl 
zirconium trichloride, pentamethylcyclopentadienyl zirconium trichloride, 
bis(cyclopentadienyl)zirconium diphenyl, bis(cyclopentadienyl)zirconium 
dichloride, the alkyl substituted cyclopentadienes, such as bis(ethyl 
cyclopentadienyl)zirconium dimethyl, 
bis(.beta.-phenylpropylcyclopentadienyl)zirconium dimethyl, 
bis(methylcyclopentadienyl)zirconium dimethyl, and dihalide complexes of 
the above; di-alkyl, tri-alkyl, tetra-alkyl, and penta-alkyl 
cyclopentadienes, such as bis(pentamethylcyclopentadienyl)zirconium 
dimethyl, bis(1,2-dimethylcyclopentadienyl)zirconium dimethyl, 
bis(1,3-diethylcyclopentadienyl)zirconium dimethyl and dihalide complexes 
of the above; silicone, phosphorus, and carbon bridged cyclopentadiene 
complexes such as dimethylsilyldicyclopentadienyl zirconium dimethyl or 
dihalide, methylphosphine dicyclopentadienyl zirconium dimethyl or 
dihalide, and methylene dicyclopentadienyl zirconium dimethyl or dihalide, 
carbenes represented by the formulae Cp.sub.2 Zr.dbd.CH.sub.2 P(C.sub.6 
H.sub.5).sub.2 CH.sub.3, and derivatives of these compounds such as 
Cp.sub.2 ZrCH.sub.2 CH(CH.sub.3)CH.sub.2. 
Bis(cyclopentadienyl)hafnium dichloride, bis(cyclopentadienyl)hafnium 
dimethyl, bis(cyclopentadienyl)vanadium dichloride and the like are 
illustrative of other metallocenes. 
Generally the use of a metallocene which comprises a bis(substituted 
cyclopentadienyl) zirconium will provide a catalyst complex of higher 
activity than a corresponding titanocene or a mono cyclopentadienyl metal 
compound. Hence bis(substituted cyclopentadienyl) zirconium compounds are 
preferred for use as the metallocene. 
Heretofore the alumoxane component of the active catalyst complex has been 
separately prepared then added as such to a catalyst support material 
which is then treated with a metallocene to form the active catalyst 
complex. One procedure heretofore employed for preparing the alumoxane 
separately is that of contacting water in the form of a moist solvent with 
a solution of aluminum trialkyl in a suitable organic solvent such as 
benzene or aliphatic hydrocarbon. As before noted this procedure is 
attendant with fire and explosion hazards which requires the use of 
explosion-proof equipment and carefully controlled reaction conditions. In 
an alternative method heretofore employed for the separate production of 
alumoxane, an aluminum alkyl is contacted with a hydrated salt, such as 
hydrated copper sulfate. The method comprised treating a dilute solution 
of aluminum alkyl in, for example, toluene, with a copper sulfate 
pentahydrate. A slow, controlled hydrolysis of the aluminum alkyl to 
alumoxane results which substantially eliminates the fire and explosion 
hazard but with the disadvantage of the creation of hazardous waste 
products that must be disposed of and from which the alumoxane must be 
separated before it is suitable for use in the production of an active 
catalyst complex. Separate production of the alumoxane component by either 
procedure is time consuming and costly. Correspondingly, the use of a 
separately produced alumoxane greatly increases the cost of producing a 
metallocene alumoxane catalyst. 
In accordance with the present invention the alumoxane component of the 
catalyst complex is prepared by direct reaction of an aluminum trialkyl 
with the material utilized as the catalyst support, namely a 
water-impregnated silica gel. Silica useful as the catalyst support is 
that which has a surface area in the range of about 10 to about 700 
m.sup.2 g, preferably about 100-500 and desirably about 200-400 m.sup.2 g, 
a pore volume of about 3 to about 0.5 cc/g and preferably 2-1 cc/g, and an 
adsorbed water content of from about 10 to about 50 weight percent, 
preferably from about 20 to about 40 weight percent, and most preferably 
about 35 weight percent. The particle size of the silica should be from 
about 10.mu. to about 100.mu., and preferably from about 30.mu. to about 
60.mu. (1.mu.=10.sup.-6 m). Hereafter, silica having the above identified 
properties is referred to as water-impregnated silica gel. 
Water-impregnated silica gel may be formed by adding sufficient water to 
commercially available silica gel (Davidson 948) to create an aqueous 
slurry. Because silica gel possesses many fine pores, it is extremely 
adsorbent and will rapidly become saturated. Once the aqueous slurry is 
formed, excess water can be removed by filtration, followed by air drying, 
or only air drying, to a free flowing powder state. Drying at elevated 
temperatures is not recommended because it could substantially decrease 
the amount of adsorbed water. 
Water-impregnated silica gel, as defined above, is added over time, about a 
few minutes, to a stirred solution of aluminum trialkyl, preferably 
trimethyl aluminum or triethyl aluminum, in an amount sufficient to 
provide a mole ratio of aluminum trialkyl to water of from about 10:1 to 
1:1, preferably about 5:1 to 1:1. The solvents used in the preparation of 
the catalyst system are inert hydrocarbons, in particular a hydrocarbon 
that is inert with respect to the catalyst system. Such solvents are well 
known and include, for example, isobutane, butane, pentane, hexane, 
heptane, octane, cyclohexane, methylcyclohexane, toluene, xylene and the 
like. Also suitable for use as the aluminum trialkyl are tripropyl 
aluminum, tri-n-butyl aluminum tri-isobutyl aluminum, tri(2-methylpentyl) 
aluminum, trihexyl aluminum, tri-n-octyl aluminum, and tri-n-decyl 
aluminum. 
Upon addition of the water-impregnated silica gel to the solution of 
aluminum trialkyl, the water content of the silica gel controllably reacts 
with the aluminum trialkyl to produce an alumoxane which is deposited onto 
the surface of the silica gel particles. Although the reaction of the 
aluminum trialkyl with the water content of the silica gel proceeds 
relatively quickly, that is, it is generally completed within the time of 
about 5 minutes, it does not occur with the explosive quickness of that 
which occurs with free water. The reaction may be safely conducted in 
conventional mixing equipment under a mantle of inert gas. 
Thereafter a metallocene is added to the stirred suspension of alumoxane 
silica gel product in an amount sufficient to provide a mole ratio of 
aluminum to transition metal of from about 1000:1 to about 1:1, preferably 
from about 300:1 to about 10:1 and most preferably from about 150:1 to 
about 30:1. The mixture is stirred for about 1 minute to about 10 minutes 
at ambient or an elevated temperature of about 85.degree. C. to permit the 
metallocene to undergo complete complexing reaction with the adsorbed 
alumoxane. 
For a continuous polymerization process in liquid medium, it is important 
to minimize the reactor fouling in order to minimize the interruption of 
the operation. The major source of reactor fouling is the formation of 
polymer on the surface of process equipment such as reactor vessel, 
agitator, and transfer lines. The cause of polymer formation on equipment 
surface is mainly due to the very fine catalyst particles. These fine 
particles are attracted on the equipment surfaces due to the static 
charge. The attracted catalyst particles catalyze the formation of polymer 
on the equipment surface. In order to minimize the reactor fouling, it is 
important to minimize the formation of very fine catalyst particles in the 
reactor. One effective approach of minimizing the formation of very fine 
catalyst particles in a liquid medium is to attach the catalyst on a 
support material. It was observed that the catalyst formed by reacting 
aluminum trialkyl with water in liquid hydrocarbon followed by metallocene 
can cause severe reactor fouling. This reactor fouling can be minimized by 
using the supported catalyst developed in this invention. 
The order of addition between the water-impregnated silica gel and the 
aluminum trialkyl is important wit regards to the activity of the 
supported catalyst which results upon addition of the metallocene. A 
supported catalyst composition of little or no activity results when an 
aluminum trialkyl is added to a stirred solvent suspension of 
water-impregnated silica gel. It has been found that to prepare a 
supported catalyst composition of acceptable or high activity the order of 
mixing must be one wherein the water-impregnated silica gel is added to a 
stirred solution of the aluminum trialkyl. It is believed that this order 
of mixing forces the aluminum trialkyl to undergo reaction in the context 
of a transient localized excess of aluminum trialkyl compared to a 
transient localized deficiency of water. Under a mixing condition which 
slowly adds water-impregnated silica gel to a stirred solution of aluminum 
trialkyl, the bulk content of the aluminum trialkyl converts to an 
alumoxane with a degree of oligomerization of about 6-25 (y=6-25). 
Production of an alumoxane with this degree of oligomerization results in 
a final metallocene alumoxane catalyst complex of useful or high activity. 
A reverse order of mixing, that is, addition of an aluminum trialkyl to a 
stirred solvent suspension of water-impregnated silica gel yields a 
catalyst which has a poor degree of catalytic activity. 
In addition to the importance of proper mixing order in achieving a 
supported catalyst of useful activity, it has also been observed that the 
water content of the water-impregnated silica gel influences final 
catalyst activity. Hence the water-impregnated silica gel should have an 
adsorbed water content of from about 10 to about 50 weight percent. 
Preferably the adsorbed water content should be from about 20 to about 40 
weight percent. Maximum catalyst activity for a given metallocene 
component is generally observed wherein the adsorbed water content of the 
water-impregnated silica gel used as a support is about 35 weight percent. 
Further influencing the degree of activity attained in the final supported 
catalyst complex is the mole ratio of aluminum trialkyl to the adsorbed 
water content of the water-impregnated silica gel. The quantities of 
aluminum trialkyl employed should, in comparison to the quantity of 
water-impregnated silica gel of specified adsorbed water content, be 
selected to provide a mole ratio of aluminum trialkyl to water of from 
about 10:1 to about 1:1, preferably from about 5:1 to about 1:1, more 
preferably from about 3:1 to about 1:1. It has been observed that for a 
given metallocene, a maximum catalyst activity is generally observed in 
the aluminum trialkyl to water mole ratio range of about 5:1 to about 1:1. 
Depending upon the particular aluminum trialkyl selected for use, 
commercially acceptable catalyst activities are exhibited in the aluminum 
trialkyl to water mole ratio range of about 3:1 to about 1:1. 
Also influencing the cost of production and the level of catalytic activity 
obtained in the final supported catalyst complex is the mole ratio of 
aluminum to transition metal of the metallocene component. The quantity of 
metallocene added to the alumoxane adsorbed silica gel solids should be 
selected to provide an aluminum to transition metal mole ratio of from 
about 1000:1 to about 1:1, preferably from about 300:1 to about 10:1, and 
most preferably from about 150:1 to about 30:1. From the standpoint of 
economic considerations it is desirable to operate in the lower ranges of 
the aluminum to transition metal mole ratio in order to minimize the cost 
of catalyst production. The procedure of this invention is one which 
provides the maximum conversion of the aluminum trialkyl component to the 
most efficacious form of alumoxane, hence permits the safe production of a 
supported metallocene alumoxane catalyst of useful activity with low 
quantities of the costly aluminum trialkyl component. 
By appropriate selection of the type and relative amounts of the 
metallocene and the aluminum trialkyl cocatalyst precursor, one can attain 
by the present method the particular active catalyst complex desired for 
any particular application. For example, higher concentrations of 
alumoxane in the catalyst system generally result in higher molecular 
weight polymer product. Therefore, when it is desired to produce a high 
molecular weight polymer a higher concentration of aluminum trialkyl is 
used, relative to the metallocene, than when it is desired to produce a 
lower molecular weight material. For most applications the ratio of 
aluminum in the aluminum trialkyl to total metal in the metallocene can be 
in the range of from about 300:1 to about 20,:1, and preferably about 
200:1 to about 50:1. 
The molecular weight of the polymer product can be controlled by the 
judicious selection of substituents on the cyclopentadienyl ring and use 
of ligands for the metallocene. Further, the comonomer content can be 
controlled by the judicious selection of the metallocene. Hence, by the 
selection of catalyst components it is possible to tailor the polymer 
product with respect to molecular weight and density. Further, one may 
tailor the polymerization reaction conditions over a wide range of 
conditions for the production of polymers having particular properties. 
In the examples following, the melt index (MI) and melt index ratio (MIR) 
were determined in accordance with ASTM test D1238. 
EXAMPLE 1 
Water-impregnated silica gel was employed in accordance with the procedure 
of this invention to prepare a silica gel supported (nBuCp).sub.2 
ZrCl.sub.2 methyl alumoxane catalyst complex which was used in a slurry 
phase polymerization process as follows: 
One hundred (100) grams of silica gel (Davison 948) was treated with enough 
water to form a slurry mixture. This slurry was air dried at room 
temperature to a free flowing state to form water-impregnated silica gel. 
The water content of this material measured by weight loss on ignition at 
1000.degree. C. was 37 wt.%. 
A freshly cleaned 2.2 liter autoclave was heated to 60.degree. C. and 
flushed with purified N.sub.2 for 30 minutes. It was cooled to room 
temperature, and eight hundred (800) milliliters of dried, oxygen free 
hexane was charged into the autoclave followed by the addition of five (5) 
milliliters of trimethylaluminum/heptane solution (1.62 M). The autoclave 
was heated to 85.degree. C., and one hundred thirty (130) milligrams of 
water-impregnated Davison 948 silica gel was injected into the autoclave 
using a dry injection tube. The resulting mixture was allowed to react for 
five (5) minutes. One (1) milligram of (n-C.sub.4 H.sub.9 C.sub.5 
H.sub.4).sub.2 ZrCl.sub.2 dissolved in one (1) milliliter toluene was 
injected into the autoclave to form the catalyst in situ. One hundred 
(100) milliliters of butene-1 was pushed into the reactor by ethylene 
pressure, and the reactor was pressurized to 150 psi with ethylene. The 
reaction was allowed to proceed for 20 minutes, and it yielded 39 grams of 
resin with 2.8 MI and 20.1 MIR and a density of 0.936. 
EXAMPLE 2 
The catalyst was prepared in the same manner as the catalyst in Example 1 
except that ten (10) milliliters of trimethylaluminum/heptane solution 
were used during the co-catalyst preparation. Polymerization of ethylene 
and 1-butene was performed as in Example 1. After the reaction, 49 grams 
of resin was recovered with 1.7 MI and 20.8 MIR and a density of 0.937. 
EXAMPLE 3 
The catalyst was prepared in the same manner as the catalyst in Example 1 
except that fifteen (15) milliliters of trimethylaluminum/heptane solution 
were used during the co-catalyst preparation. Polymerization of ethylene 
and 1-butene was performed as Example 1. The reaction lasted 40 minutes 
yielding 46 grams of resin with 5.4 MI and 24.8 MIR and a density of 
0.945. 
EXAMPLE 4 
The catalyst was prepared using the same quantities of ingredients as in 
Example 1. However, the wet silica was first contacted with the 
metallocene, dried to a free flowing solid (silica contained 37 wt.% 
water) and thereafter contacted with TMA. On polymerizing in the manner of 
Example 1, one (1) gram of resin was recovered. 
EXAMPLE 5 
Example 4 was repeated identically with the exception that fifteen (15) 
milliliters of TMA/heptane solution were used during the co-catalyst 
preparation. Upon polymerization in the manner of Example 1, two grams of 
resin were recovered. 
EXAMPLE 6 
Example 2 was repeated with the exception that one (1) milligram of 
(C.sub.2 H.sub.5).sub.2 ZrCl.sub.2 dissolved in one (1) milliliter of 
toluene was used during the catalyst preparation. After 40 minutes of 
polymerization, forty-five (45) grams of resin were recovered. The resin 
manifested an MI of 9.1 and an MIR of 28.5. 
EXAMPLE 7 
Example 2 was repeated with the exception that 
bis(cyclopentadienyl)titanium dichloride was substituted for the 
zirconocene. After 20 minutes of polymerization, two grams of resin were 
recovered. 
EXAMPLE 8 
The catalyst was prepared in the same manner as Example 2 with the 
exception that one-hundred thirty (130) milligrams of Al(OH).sub.3 with a 
water content of 39 wt.% were substituted for the silica. The 
polymerization resulted in forty-one (41) grams of resin being recovered 
with an MI of 1.0 and an MIR of 18.4. 
EXAMPLE 9 
Example 8 was repeated with the exception that five (5) milliliters of 
trimethyl aluminum/heptane solution were employed in the catalyst 
preparation. The polymerization resulted in forty-one (41) grams being 
recovered with an MI of 0.9 and an MIR of 22.7. 
EXAMPLE 10 
A catalyst was prepared in the same manner as in Example 2 with the 
exception that one-hundred thirty (130) milligrams of Mg(OH).sub.2 with a 
water content of 31 wt.% were substituted for the silica. After 40 minutes 
of polymerization, six (6) grams of resin were recovered. 
EXAMPLE 11 
A catalyst was prepared in the same manner as Example 10 with the exception 
that five (5) milliliters of trimethyl aluminum/heptane solution were used 
during the catalyst preparation. After polymerization, one (1) gram of 
resin was recovered. 
EXAMPLE 12 
A catalyst was prepared in the same manner as in Example 12 with the 
exception that ten (10) milliliters of triethyl aluminum/heptane solution 
were used during the catalyst preparation. After polymerization in the 
manner of Example 12, one (1) gram of resin was recovered. 
EXAMPLE 13 
A catalyst was prepared in the same manner as in Example 12 with the 
exception that five (5) milliliters of triethyl aluminum/heptane solution 
were employed for the catalyst preparation. Upon polymerization in the 
same manner as Example 12, one (1) gram of resin was recovered. 
Table I summarizes the result obtained in the preceding examples: 
TABLE I 
______________________________________ 
Polymerization Data 
Metallocene/ Yield MI 
Example AlR.sub.3 (ml) 
Support gm/hr (dg/min) 
MIR 
______________________________________ 
1 Zr/TMA (5) SiO.sub.2 
117 2.8 20.1 
2 Zr/TMA (10) SiO.sub.2 
147 1.7 20.8 
3 Zr/TMA (15) SiO.sub.2 
69 5.4 24.8 
4 TMA (5) Zr/SiO.sub.2 
3 -- -- 
5 TMA (15) Zr/SiO.sub.2 
6 -- -- 
6 Zr*/TMA (10) 
SiO.sub.2 
67 9.1 28.5 
7 Ti/TMA (10) SiO.sub.2 
6 -- -- 
8 Zr/TMA (10) Al(OH).sub.3 
123 1.0 18.4 
9 Zr/TMA (5) Al(OH).sub.3 
123 0.9 22.7 
10 Zr/TMA (10) Mg(OH).sub.2 
9 -- -- 
11 Zr/TMA (5) Mg(OH).sub.2 
1.5 -- -- 
12 Zr/TEAL (10) 
SiO.sub.2 
3 -- -- 
13 Zr/TEAL (5) SiO.sub.2 
3 2.8 20.1 
______________________________________ 
Zr = (nBuCp).sub.2 ZrCl.sub.2, Zr* = Cp.sub.2 ZrCl.sub.2, T = Cp.sub.2 
TiCl.sub.2. 
Conditions: 
800 ml hexane, 100 ml butene1, 85.degree. C., 150 psig total pressure, 13 
mg support. 
The invention has been described with reference to its preferred 
embodiments. From this description, a person of ordinary skill in the art 
may appreciate changes that could be made in the invention which do not 
depart from the scope and spirit of the invention as described above and 
claimed hereafter.