Catalyst for olefin polymerization

Details Catalyst for olefin polymerization Catalyst for olefin polymerization

2002-02-13

2004-05-11

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...

C526S161000, C526S165000, C502S120000, C502S152000, C502S154000, C502S155000

Reexamination Certificate

active

06734266

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to catalyst used for olefin polymerizations, especially ethylene polymerization.
BACKGROUND OF THE INVENTION
The use of an aluminoxane as a cocatalyst for ethylene polymerization catalyst was reported by Manyik et al in U.S. Pat. No. 3,231,550.
Subsequently, Kamisky and Sinn discovered that aluminoxanes are excellent cocatalysts for metallocene catalysts, as disclosed in U.S. Pat. No. 4,404,344.
The use of a supported aluminoxane/metallocene catalyst is further described in, for example, U.S. Pat. No. 4,808,561.
However, aluminoxanes are expensive materials so it is desirable to optimize the use thereof.
The use of phosphated and/or sulfated metal oxides has been proposed to improve the performance of chromium oxide polymerization catalysts. See, for example, U.S. Pat. Nos. 4,364,839; 4,444,966; and 4,619,980.
We have now discovered that the use of a sulfated metal oxide support substantially improves the activity of ethylene polymerization catalysts when used with an aluminoxane cocatalyst.
SUMMARY OF THE INVENTION
The present invention provides a catalyst system for olefin polymerization comprising:
a) a catalyst support component comprising aluminoxane which is deposited on a sulfated metal oxide; and
b) an organometallic complex of a group 4 metal.
In another embodiment, the present invention provides a process to prepare a catalyst system for olefin polymerization comprising:
a) preparing a sulfated metal oxide by contacting a metal oxide with sulfuric acid;
b) preparing a catalyst support component by depositing aluminoxane upon said sulfated metal oxide; and
c) depositing an organometallic complex of a group 4 metal upon said catalyst support component.
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 sulfated metal oxides used in this invention are prepared by directly treating the metal oxide with a material having an SO
4
group (such as sulfuric acid). Other exemplary (non-limiting) sulfating agents include simple salts of sulfate (such as sodium or calcium sulfate) and ammonium sulfate.
The sulfated metal oxide may be calcined using conventional calcining techniques (for example, heating the sulfated metal oxide at a temperature of from 20 to 800° C. for from 1 to 24 hours).
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
AIO(RAIO)
m
Al(R)
2
wherein each R is independently an alkyl group having from 1 to 8 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, butyl or octyl—so as to improve the solubility of the “modified MAO” in aliphatic solvents.]
The sulfated metal oxide and aluminoxane are contacted together so as to form the catalyst component of this invention. This is preferably done using conventional techniques such as mixing the aluminoxane and sulfated metal oxide together in an aliphatic 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 sulfated metal oxide).
The resulting catalyst component is suitable for use in olefin polymerization reactions when combined with a polymerization catalyst. These catalysts contain a group 4 metal. It is especially preferred to provide an Al:M mole ratio of from 10:1 to 200:1, especially 50:1 to 150:1 in the finished catalyst complex (where Al is the aluminum provided by the aluminoxane and M is the group 4 metal). The catalyst component (i.e. the sulfated metal oxide/aluminoxane) may be combined with the polymerization catalyst using techniques which are conventionally used to prepare supported aluminoxane/metallocene catalysts. Such techniques are well known to those skilled in the art. In general, a hydrocarbon slurry of the catalyst component may be contacted with the catalyst complex. It is preferred to use a hydrocarbon in which the catalyst complex is soluble. The examples illustrate suitable techniques to prepare the “catalyst systems” of this invention. Particularly preferred catalysts are organometallic complexes of a group 4 metal, as defined by the formula:
wherein M is selected from titanium, hafnium and zirconium; L
1
and L
2
are independently selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl (including indenyl and fluorenyl) and heteroatom ligands, with the proviso that L
1
and L
2
may optionally be bridged together so as to form a bidentate ligand. It is further preferred that n=2 (i.e. that there are 2 monoanionic activatable ligands).
As previously noted, each of L
1
and L
2
may independently be a cyclopentadienyl ligand or a heteroatom ligand. Preferred catalysts include metallocenes (where both L
1
and L
2
are cyclopentadienyl ligands which may be substituted and/or bridged) and monocyclopentadienyl-heteroatom catalysts (especially a catalyst having a cyclopentadienyl ligand and a phosphinimine ligand), as illustrated in the Examples.
Brief descriptions of exemplary ligands are provided below.
Cyclopentadienyl Ligands
L
1
and L
2
may each independently be a cyclopentadienyl ligand. As used herein, the term cyclopentadienyl ligand is meant to convey its broad meaning, namely a substituted or unsubstituted ligand having a five carbon ring which is bonded to the metal via eta-5 bonding. Thus, the term cyclopentadienyl includes unsubstituted cyclopentadienyl, substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl and substituted fluorenyl. An exemplary list of substituents for a cyclopentadienyl ligand includes the group consisting of 1) C
1-10
hydrocarbyl radical (which hydrocarbyl radicals are unsubstituted or further substituted); 2) a halogen atom; 3) C
1-8
alkoxy radical; 4) a C
6-10
aryl or aryloxy radical; 5) an amido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals; 6) a phosphido radical which is unsubstituted or substituted by up to two C
1-8
alkyl radicals; 7) silyl radicals of the formula —Si—(R
1
)
3
wherein each R
1
is independently selected from the group consisting of hydrogen, a C
1-8
alkyl or alkoxy radical C
6-10
aryl or aryloxy radicals; and 8) germanyl radicals of the formula Ge—(R
1
)
3
wherein R
1
is as defined directly above.
Activatable Ligands
L
3
is an activatable ligand. The term “activatable ligand” refers to

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