Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1993-12-29
2001-04-10
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...
C526S113000, C526S118000, C526S119000, C526S128000, C526S160000
Reexamination Certificate
active
06214949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a catalyst system which is a combination of at least one unbridged metallocene catalyst and at least one heterogeneous catalyst. Combining at least one unbridged metallocene catalyst with the heterogeneous catalyst affects the molecular weight (M
w
), the molecular weight distribution (MWD or M
w
/M
n
) and the melt flow index of the resulting polymer. Combining at least one unbridged metallocene catalyst and at least one bridged metallocene catalyst with the heterogeneous catalyst affects the xylene solubles in addition to the molecular weight, the molecular weight distribution and melt flow index of the resulting polymer.
2. Description of the Prior Art
It is known that two or more homogeneous catalysts, such as those based on metallocene compounds, may be combined to effect properties, such as molecular weight distribution. U.S. Pat. No. 4,530,914 discloses use of a catalyst system comprising two or more metallocenes in the polymerization of a-olefins, primarily ethylene, to obtain a broad molecular weight distribution. The metallocenes each have different propagation and termination rate constants. The metallocenes are mixed with an alumoxane to form the catalyst system.
It is also known that metallocenes may be affixed to a support to simulate a heterogeneous catalyst. U.S. Pat. No. 4,808,561 discloses reacting a metallocene with an alumoxane and forming a reaction product in the presence of a support. The support is a porous material like talc, inorganic oxides such as Group IIA, IIIA IVA or IVB metal oxides like silica, alumina, silica-alumina, magnesia, titania, zirconia and mixtures thereof, and resinous material such as polyolefins, e.g., finely divided polyethylene. The metallocenes and alumoxanes are deposited on the dehydrated support material.
In U.S. Pat. No. 4,701,432 a support is treated with at least one metallocene and at least one non-metallocene transition metal compound. To form a catalyst system a cocatalyst comprising an alumoxane and an organometallic compound of Group IA, IIA, IIB and IIIA is added to the supported metallocene
on-metallocene. The support is a porous solid such as talc or inorganic oxides or resinous materials, preferably an inorganic oxide, such as silica, alumina, silica-alumina, magnesia, titania or zirconia, in finely divided form. By depositing the soluble metallocene on the support material it is converted to a heterogeneous supported catalyst. The transition metal compound, such as TiCl
4
, is contacted with the support material prior to, after, simultaneously with or separately from contacting the metallocene with the support.
It is known that Cp
2
TiCl
2
in the presence of alkylaluminum compounds polymerizes ethylene but not propylene whereas in the presence of methylalumoxane (MAO) Cp
2
TiCl
2
polymerizes propylene also to produce atactic polypropylene. Combination of dimethyl titanocene and its Cp-substituted analogues and TiCl
3
for propylene polymerizations has been reported in U.S. Pat. No. 2,992,212 and in “Thermoplastic Elastomers Based on Block Copolymers of Ethylene and Propylene”, G. A. Lock,
Advances in Polyolefins
, p. 59-74, Raymond B. Seymour, Ed. MAO was not used in this polymerization.
It would be advantageous to change polymer properties in a polymerization processes using a conventional supported Ziegler-Natta catalyst by the combination with at least one metallocene catalyst which may interact or modify the Ziegler-Natta catalyst in addition to producing polymer.
SUMMARY OF THE INVENTION
Accordingly, an object of this invention is to change polymer properties in polymerization processes using a conventional supported Ziegler-Natta catalyst and at least one unbridged metallocene catalyst.
And, an object of this invention is to change polymer properties in polymerization processes using a conventional supported Ziegler-Natta catalyst, one unbridged metallocene catalyst and one bridged metallocene catalyst.
Also, an object of this invention is to produce a polyolefin having high molecular weight and broad molecular weight distribution.
Further, an object of this invention is to produce a polyolefin having high molecular weight, broad molecular weight distribution and fractional melt flow index.
Moreover, an object of this invention is to produce a polyolefin having high molecular weight, broad molecular weight distribution, fractional melt flow index and low xylene solubles.
These and other objects are accomplished by a catalyst system comprising at least one metallocene catalyst and at least one heterogeneous catalyst, i.e, cyclopentadienide compound and conventional Ziegler-Natta catalyst, respectively, with an alkylaluminum co-catalyst, an alumoxane co-catalyst (for some purposes) and an organosilicon selectivity control agent.
The catalyst system may be used in a process for the polymerization of propylene comprising:
a) selecting a conventional Ziegler-Natta catalyst component;
b) contacting the catalyst with a metallocene compound of
(CpR
4
)
a
(CpR′
4
)
b
M′R*
v−(a+b)
where Cp is a cyclopentadienyl ring, a and b are 0 or 1, indicating whether the particular Cp ring is present, but at least one of a or b must be 1; M′ is titanium or zirconium and if M′ is zirconium a is 1 and b is 0, R* is a hydride, a halogen or a hydrocarbyl from 1-20 carbon atoms, v is the valence of M′;
c) contacting an electron donor containing silicon with an organoaluminum co-catalyst compound; wherein said external electron donor having the general formula SiR
m
(OR′)
4−m
where R is selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group and a vinyl group; R′ is an alkyl group; and m is 0-3, wherein when R is an alkyl group, R may be identical with R′; when m is 0, 1 or 2, the R′ groups may be identical or different; and when m is 1, 2 or 3, the R groups may be identical or different and wherein said aluminum trialkyl co-catalyst is described by the formula AlR′
3
where R′ is an alkyl of from 1-8 carbon atoms and R′ may be the same or different;
d) adding the catalyst to the electron donor/co-catalyst mixture to form a catalyst system;
e) introducing the catalyst system into a polymerization reaction zone containing a monomer under polymerization reaction conditions; and
f) extracting polypropylene from the reactor having a molecular weight of at least 300,000 and a melt flow index of less than or equal to 1.
The catalyst system may also be used in a process for the polymerization of propylene comprising:
a) selecting a conventional Ziegler-Natta catalyst component;
b) contacting the catalyst with a metallocene compound of
(CpR
4
)
a
(CpR′
4
)
b
M′R*
v−(a+b)
where Cp is a cyclopentadienyl ring, a and b are 0 or 1, indicating whether the particular Cp ring is present, but at least one of a or b must be 1; M′ is titanium, R* is a hydride, a halogen or a hydrocarbyl from 1-20 carbon atoms, v is the valence of M′;
c) contacting an electron donor containing silicon with an organoaluminum co-catalyst compound; wherein said external electron donor having the general formula SiR
m
(OR′)
4−m
where R is selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group and a vinyl group; R′ is an alkyl group; and m is 0-3, wherein when R is an alkyl group, R may be identical with R′; when m is 0, 1 or 2, the R′ groups may be identical or different; and when m is 1, 2 or 3, the R groups may be identical or different and wherein said aluminum trialkyl co-catalyst is described by the formula AlR′
3
where R′ is an alkyl of from 1-8 carbon atoms and R′ may be the same or different;
d) adding an alumoxane of the general formula (R—Al—O—)
n
in the cyclic form and R(R—Al—O)—
n
—AlR
2
in the linear form wherein R is an alkyl group with one to five carbon atoms and n is an integer from 1 to about 20;
e) adding the catalyst to the electron
Reddy B. Raghava
Shamshoum Edwar S.
Fina Technology, Inc.
Wheelington Jim D.
Wu David W.
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