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United States Patent |
5,625,016
|
Schiffino
,   et al.
|
April 29, 1997
|
High temperature solution polymerization process
Abstract
This invention is a solution process for the preparation of high molecular
weight ethylene-.alpha.-olefin-diolefin copolymers comprising contacting
ethylene, one or more .alpha.-olefin monomer, and optionally one or more
diene monomer, with a catalyst system at a polymerization temperature at
or above about 80.degree. C., ethylene, one or more .alpha.-olefin
monomer, and optionally one or more diene monomer, with a catalyst system
comprising an unbridged Group 4 metal compound having a bulky
monocyclopentadienyl ligand, a uninegative bulky Group 15 ligand and two
uninegative, activation reactive ligands and a catalyst activator
compound. The process can be advantageously practiced a reaction
temperature of at least 80.degree. C., most preferably above 100.degree.
C., to achieve high number average molecular weight polymer having high
.alpha.-olefin monomer and diene monomer contents with high diene
conversion rates. The process is particularly suitable for the preparation
of elastomeric ethylene-propylene or ethylene-propylene-diene monomer
elastomers.
Inventors:
|
Schiffino; Rinaldo S. (Kingwood, TX);
Crowther; Donna J. (Baytown, TX)
|
Assignee:
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Exxon Chemical Patents, Inc. (Wilmington, DE)
|
Appl. No.:
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545973 |
Filed:
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October 20, 1995 |
Intern'l Class: |
C08F 004/643; C08F 002/04; C08F 210/18 |
Field of Search: |
526/126,127,134,160,170,132,133,282,336,912,943
|
References Cited
U.S. Patent Documents
5264405 | Nov., 1993 | Canich | 502/103.
|
5321106 | Jun., 1994 | LaPointe | 526/126.
|
5408017 | Apr., 1995 | Turner et al. | 526/134.
|
5502017 | Mar., 1996 | Marks et al. | 502/103.
|
Foreign Patent Documents |
94-80683 | Mar., 1994 | JP.
| |
WO92/14766 | Sep., 1992 | WO.
| |
WO95/07941 | Mar., 1995 | WO.
| |
Other References
"Dialkylamido derivative of [(.eta..sup.5 -C.sub.5 Me.sub.5)TiCl.sub.3 ],
[{(.eta..sup.5 -C.sub.5 Me.sub.5 TiCl.sub.2 }.sub.2 (.mu.-O)] and
[{(.eta..sup.5 -C.sub.5 Me.sub.5 TiCl}.sub.3 (.mu.-O)]: X-ray crystal
structure of [(.eta..sup.5 -C.sub.5 Me.sub.5)Ti(NMe.sub.2).sub.3 ]",
Mart'n et al, Journal of Organometallic Chemistry, 467 (1994), 79-84.
|
Primary Examiner: Teskin; Fred
Attorney, Agent or Firm: Muller; W. G., Malpass, Jr.; G. D.
Claims
We claim:
1. A process for the preparation of high molecular weight
ethylene-.alpha.-olefin copolymers, or ethylene-.alpha.-olefin-diolefin
copolymers, comprising contacting in solution at a polymerization
temperature at or above about 80.degree. C., ethylene and one or more
.alpha.-olefin monomer, or, contacting in solution at a polymerization
temperature at or above about 80.degree. C., ethylene, one or more
.alpha.-olefin monomer, and one or more diene monomer, with a catalyst
system prepared from at least one unbridged Group 4 metal compound having
a bulky monocyclopentadienyl ligand, a uninegative bulky Group 15 ligand
and two uninegative, activation reactive ligands and at least one catalyst
activator compound.
2. The process of claim 1 wherein said unbridged Group 4 metal compound has
the formula:
CpJQ.sup.1 Q.sup.2 M
wherein:
M is Zr, Hf or Ti;
Cp is a bulky cyclopentadienyl ring which is substituted with from two to
five substituent groups R, and each substituent group R is, independently,
a radical selected from hydrocarbyl, silyl or germyl radicals having from
I to 20 carbon, silicon or germanium atoms, substituted hydrocarbyl, silyl
or germyl radicals as defined wherein one or more hydrogen atoms is
replaced by a halogen radical, an amido radical, a phosphido radical, an
alkoxy radical, an aryloxy radical or any other radical containing a Lewis
acidic or basic functionality; C.sub.1 to C.sub.20 hydrocarbyl-substituted
metalloid radicals wherein the metalloid is selected from the Group IV A
of the Periodic Table of Elements; halogen radicals; amido radicals;
phosphido radicals; alkoxy radicals; or alkylborido radicals; or, Cp is a
cyclopentadienyl ring in which at least two adjacent R-groups are joined
together and along with the carbon atoms to which they are attached form a
C.sub.4 to C.sub.20 ring system which may be saturated, partially
unsaturated or aromatic, and substituted or unsubstituted the substitution
being of one or more R group as defined above;
J is the substituted, bulky Group 15 heteroatom ligand which is substituted
with two substituent groups R.sup.1, and each substituent group R.sup.1
is, independently, a radical selected from hydrocarbyl, silyl or germyl
radicals having 1 to 20 carbon, silicon or germanium atoms, substituted
hydrocarbyl, silyl or germyl radicals as defined wherein one or more
hydrogen atoms is replaced by a halogen radical, an amido radical, a
phosphido radical, an alkoxy radical, or an aryloxy radical; C.sub.3 to
C.sub.20 hydrocarbyl-substituted metalloid radicals wherein the metalloid
is selected from the Group IV A of the Periodic Table of Elements; halogen
radicals; amido radicals; phosphido radicals; alkoxy radicals; or
alkylborido radicals; and,
each Q is independently a radical selected from halide; hydride;
substituted or unsubstituted C.sub.1 to C.sub.20 hydrocarbyl; alkoxide;
aryloxide; amide; halide or phosphide; or both Q together may be an
alkylidene or a cyclometallated hydrocarbyl or any other divalent anionic
chelating ligand, with the proviso that where any Q is a hydrocarbyl
radical, such Q is not a substituted or unsubstituted cyclopentadienyl
radical.
3. The process according to claim 2 wherein the R.sup.1 groups are the same
and are characterized by having electron-withdrawing characteristics
equivalent to or greater than --SiMe.sub.3.
4. The process according to claim 1 wherein said polymerization temperature
is 100.degree. to 150.degree. C.
5. The process according to claim 1 wherein said catalyst activator is an
alumoxane compound.
6. The process according to claim 1 wherein said catalyst activator is an
alkylaluminum compound.
7. The process according to claim 1 wherein said catalyst activator is an
ionizing anion pre-cursor.
8. The process of claim 1 wherein ethylene, one or more .alpha.-olefin
monomer, and one or more diene monomer are contacted with said catalyst
system.
9. The process of claim 1 wherein the catalyst is
pentamethylcyclopentadienylbis-trimethylsilylamidotitanium dichloride and
the activator is methyalumoxane.
10. The process of claim 1 wherein the catalyst is
pentamethylcyclopentadienylbis-trimethylsilylamidotitanium dimethyl and
the activator is dimethylanilinium tetra (perfluorophenyl) borate.
Description
TECHNICAL FIELD
This invention relates to the preparation of high molecular weight
ethylene-containing copolymers under high temperature solution
coordination polymerization conditions using catalyst systems based on
monocyclopentadienyl derivatives of Group 4 metals.
BACKGROUND OF THE INVENTION
Polymers comprising ethylene and at least one or more .alpha.-olefin and
optionally one or more diolefin make up a large segment of polyolefin
polymers and will be addressed for convenience as
"ethylene-.alpha.-olefin-diolefin copolymers" herein. Such polymers range
from crystalline polyethylene copolymers to largely amorphous elastomers,
with a new area of semi-crystalline "plastomers" in between. In
particular, ethylene-.alpha.-olefin-diolefin elastomers are a well
established class of industrial polymers having a variety of uses
associated with their elastomeric properties, their thermo-oxidative
stability, their solubility in hydrocarbon oleaginous fluids, and their
capability for modifying the properties of polyolefin blends. Included in
this terminology are the commercially available EPM (ethylene-propylene
monomer) and EPDM (ethylene-propylene-diene monomer) rubbery polymers,
both being vulcanizable by cross-linking, the addition of the diolefin,
also known as diene monomer, providing increased ease of both
cross-linking and functionalization.
Commercially prepared ethylene-.alpha.-olefin-diolefin elastomers have been
traditionally been made via Ziegler-Natta polymerization with homogenous
catalyst systems largely based on vanadium or titanium. Newer metallocene
catalyst compounds have received attention due to their ease of larger
monomer incorporation and potential increases in polymerization
activities. Although broadly described as suitable for polyolefin solution
polymerization processes, metallocene catalysts have shown limitations in
their molecular weight capabilities. Due to relatively fast termination
(or chain transfer) reactions, such as the .beta.-hydride elimination
reaction, metallocene catalysts tend to produce polymers and copolymers of
low molecular weights at high temperatures (M.sub.n not more than about
50,000). This problem becomes more pronounced when the .alpha.-olefin
comonomer content is relatively high (above 10 mol. %), which further
depresses the molecular weight. In addition, the incorporation of
diolefins at high conversions are important, for example in the efficient
production of effectively curable EPDM rubbers.
Japanese Unexamined patent application publication 94-80683 describes
unbridged monocyclopentadienyl Group 4-6 metal compounds said to provide
benefits for polypropylene polymerization and exemplifies the production
of atactic polypropylene with (cyclopentadienyl) (bistrimethylsilylamide)
titanium dichloride activated with methylalumoxane at 40.degree. C. The
catalyst is said to be an active catalyst for polyolefin polymerization at
temperatures of from -100.degree. C. to 200.degree. C., desirably at
-50.degree. C. to 100.degree. C. Synthesis of this catalyst is described
here and in "Dialkylamido derivative of [(.eta..sup.5 --C.sub.5
Me.sub.5)TiCl.sub.3 ], [{(.eta..sup.5 --C.sub.5 Me.sub.5 TiCl.sub.2
}.sub.3 (.mu.--O) and [{(.eta..sup.5 --C.sub.5 Me.sub.5 TiCl}.sub.3
(.mu.--O)]: X-ray crystal structure of [(.eta..sup.5 --C.sub.5
Me.sub.5)Ti(NMe.sub.2).sub.3 ", Mart'n et al, Journal of Organometallic
Chemistry, 467 (1994), 79-84.
Catalyst systems based on monocyclopentadienyl titanium compounds activated
with alumoxane suitable for the preparation of ethylene-.delta.-olefin
copolymers of high molecular weight and high .alpha.-olefin content are
described in U.S. Pat. No. 5,264,405. This patent teaches that the
cyclopentadienyl group should be fully substituted with methyl groups and
bridged to an amido group having having an aliphatic or alicyclic
hydrocarbyl ligand bonded through a 1.degree. or 2.degree. carbon.
Copolymerization of ethylene with propylene in Example 45 with a bridged
monocyclopentadienyl Group 4 metal catalyst compound at 80.degree. C.
produced a copolymer with 20 wt.% ethylene having an M.sub.n of about
20,080. In Example 55 with the same catalyst as with Example 45, at a
reaction temperature of 140.degree. C., an ethylene-propylene copolymer
having a density of 0.863, indicative of an amorphous ethylene copolymer,
exhibited an M.sub.n of about 46,500.
U.S. Pat. No. 5,321,106 describes a broad class of Group 4 or Lanthanide
series metal compounds useful as addition polymerization catalysts for
ethylenically unsaturated monomers where activated by a cationic oxidizer,
the compounds comprising an anionic or non-anionic ligand system ("L"),
one of several being --NR.sub.2 where R is a hydrocarbyl, silyl, germyl,
or a substituted hydrocarbyl, silyl, germyl group of from 1 to 24 carbon,
silicon, or germanium atoms. The preferred catalysts are
monocyclopentadienyl compounds having a divalent substituted
cyclopentadienyl group linked through a Y heteroatom ligand, inclusive of
nitrogen hetroatoms, to the Group 4 or Lanthanide series metal.
Polymerization example 2 illustrates a preferred catalyst used for
copolymerization of ethylene and 1-octene at a temperature of 150.degree.
C.
The most commercially interesting molecular weight for elastomeric
ethylene-a-olefin-diolefin copolymers exceeds about 50,000 M.sub.n.
Further, the incorporation of high levels of diolefins, beyond those
commercially provided by traditional Ziegler catalysts, is highly desired
for improved capabilities for crosslinking in vulcanizates and in graft
functionalization with non-hydrocarbyl moieties for improved
compatibilities and applications requiring greater affinity to
non-hydrocarbyl chemical compounds. Additionally, the use of high
temperature solution processes provide the potential for industrial
benefits in ease of handling the amorphous elastomers since their
solubility in the polymerization solvent increases and solution viscosity
is accordingly decreased. A traditional bottleneck in the manufacture of
elastomeric polymers at high temperatures is their resulting low molecular
weight. Thus an ability to capitalize on inherent solution viscosity
improvements at operating temperatures higher than about 80.degree. C.
while retaining high molecular weight polymers with high comonomer content
is important.
INVENTION DISCLOSURE
The invention is a solution process for the preparation of high molecular
weight ethylene-.alpha.-olefin-diolefin copolymers comprising contacting
ethylene, one or more .alpha.-olefin monomer, and optionally one or more
diene monomer, with a catalyst system prepared from at least one a
catalyst activator and at least one unbridged Group 4 metal compound
having a bulky monocyclopentadienyl ligand, a uninegative bulky amido
ligand and two uninegative, activation reactive ligands at a
polymerization temperature between about 80.degree. C. and 160.degree. C.
By use of the invention process copolymer having high number average
molecular weight (M.sub.n), high .alpha.-olefin incorporation and high
diolefin conversion to incorporated monomer can be prepared under
economically advantageous reaction temperatures. In particular,
ethylene-.alpha.-olefin-diolefin elastomers and plastomers of molecular
weights greater than 55,000 M.sub.n can be prepared under the high
temperature reaction conditions.
BEST MODE AND EXAMPLES OF THE INVENTION
The ethylene-.alpha.-olefin-diolefin copolymer elastomer or plastomer, of
this invention (hereinafter referred to as "EPC") is meant to include
copolymers, terpolymers, tetrapolymers, etc. It typically comprises
ethylene, one or more alpha-olefins, and optionally, one or more diene
monomers; it is typically substantially amorphous; and it will typically
have a substantially random arrangement of at least the ethylene and the
alpha-olefin monomers. Though focused on EPC, the process will have
utility for polyethylene copolymers (having ethylene and one or more
.alpha.-olefin comonomer such as described herein) having lower
incorporation of the comonomers such that it is not elastomeric or
plastomeric as defined below but useful otherwise in the manner known in
the art for such crystalline and semi-crystalline polymers. Typically the
polyethylene copolymers will have a polymer density of 0.86 to 0.93, while
the elastomers generally will include those copolymers with even lower
densities.
The EPC capable of preparation in accordance with the invention process
generally can have a molecular weight range typically between about 55,000
and up to about 500,000 or higher, more typically between about 60,000 and
300,000 where the molecular weight is number-average ("M.sub.n ").
Typically elastomeric EPC is "substantially amorphous", and when that term
is used to define the EPC elastomers of this invention it is to be taken
to mean having a degree of crystallinity less than about 25% as measured
by means known in the art, preferably less than about 15%, and more
preferably less than about 10%. The three major known methods of
determining crystallinity are based on specific volume, x-ray diffraction,
and infrared spectroscopy. Another well-established method, based on
measurement of heat content as a function of temperature through the
fusion range, is carried out using differential scanning calorimetric
measurements. It is known that these independent techniques lead to
reasonably good experimental agreement. The degree of randomness of the
arrangement of monomers in the EPC elastomeric polymers also affects the
crystallinity and is appropriately characterized by the degree of
crystallinity.
Additionally, it is known in the art that the tendency of a particular
combination of catalyst system and monomers to produce blocky, random, or
alternating polymers can be characterized by the product of the reactivity
ratios defined for the given monomers under the specific reaction
conditions encountered. If this product is equal to 1.0, the sequence
distribution will be perfectly random; the more the product is less than
1.0, the more the monomers will tend to have a "blocky" sequence
distribution. Generally speaking, the segments of a polymer which
crystallize are linear segments of a polymer which have a number of
identical (both by chemical make-up and stereo-specific orientation) units
in a row. Such segments are said to be "blocky". If there is little or no
such sequential order within the segments making up a polymer chain, that
chain will be very unlikely to conform itself into the correct shape to
fit into the spatial order of a crystal and will accordingly exhibit a low
degree of crystallinity. See, "Ethylene-Propylene Copolymers. Reactivity
Ratios, Evaluation and Significance", C. Cozewith and G. Ver Strate,
Macromolecules, Vol. 4, No. 4, 482-489 (1971). The EPC elastomers of this
invention accordingly can be characterized in one embodiment by the
limitation that its method for preparation has a reactivity ratio product
less than 2.0, preferably less than about 1.5, and more preferably less
than about 1.25.
The EPC of the invention will contain about 10 to about 90 weight percent
ethylene, preferably about 20 to 85 weight percent ethylene. The EPC
elastomers of the invention preferably contain from 35 to 75 weight
percent ethylene.
The .alpha.-olefins suitable for use in the preparation of the EPC, or for
the polyethylene copolymers, are preferably C.sub.3 to C.sub.20
.alpha.-olefins, but will include higher carbon number olefins such as
polymerizable macromers having up to one hundred carbon atoms, or more.
Illustrative non-limiting examples of such .alpha.-olefins are one or more
of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 1-decene.
Included in the term .alpha.-olefins for the purposes of describing
effectively copolymerized monomers are the constrained-ring cyclic olefins
such as cyclobutene, cyclopentene, norbornene, alkyl-substituted
norbornes, alkenyl-substituted norbornes, and the higher carbon number
cyclic olefins known in the art. The .alpha.-olefin content of the EPC
ranges depending upon selection of the specific .alpha.-olefin or
.alpha.-olefins, being more for lower carbon number monomers, for example,
about 10 to about 90 wt. %, preferably about 30 to about 80 wt. % for
propylene; and, 5 to 35 mol. %, preferably 7.5 to 25 mol. % and most
preferably 10 to 20 mol. % for 1-octene. The EPC plastomers typically have
comonomer incorporation of from about 10 mol. % to about 25 mol. %, and
the EPC elastomers typically have above about 25 mol. % .alpha.-olefin
incorporation. For the more crystalline polyethylene copolymers the range
of comonomer incorporation will typically be below 10 mol. % and more
typically below about 8 mol. %.
The diene monomers, or diolefins, useful in this invention include those
typically used in known EPDM polymers. The typically used diene monomers
are generally selected from the easily polymerizable non-conjugated dienes
and can be straight chain, hydrocarbon diolefins or
cycloalkenyl-substituted alkenes, having about 6 to about 15 carbon atoms,
for example:
A. straight chain acyclic dienes such as 1,4-hexadiene and 1,6 octadiene.
B. branched chain acyclic dienes such as 5-methyl-1,4-hexadiene;
3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene and the mixed
isomers of dihydro-myricene and dihydro-ocinene;
C. single ring alicyclic dienes such as 1,3-cyclopentadiene;
1,4-cyclohexadiene; 1,5-cyclo-octadiene and 1,5-cyclododecadiene;
D. multi-ring alicyclic fused and bridged ring dienes such as
tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene;
bicyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alklindene, cycloalkenyl and
cycloalkylidene norbornenes such as 5-methylene-2-norbornene (MNB),
5-ethylidene-2-norbornene, 5-isopropylidene-2-norbornene,
5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,
5-vinyl-2-norbornene; and
E. cycloalkenyl-substituted alkenes, such as allyl cyclohexene, vinyl
cyclooctene, allyl cyclohexene, vinyl cyclooctene, allyl cyclodecene,
vinyl cyclododecene.
Of these, the preferred dienes are dicyclopentadiene, 1,4-hexadiene,
5-methylene-2-norbornene, 5-ethylidene-2-norbornene and
5-vinyl-2-norbornene. Particularly preferred dienes are
5-ethylidene-2-norbornene and 1,4-hexadiene. It will be apparent that a
mix of such dienes can also be utilized. The content of the optional diene
monomer in the EPC elastomer can be 0 to about 20 weight percent, and if
used, preferably 0.5 to about 15 weight percent, and most preferably about
2.0 to about 12.0 weight percent. Surprisingly, diene incorporation
greater than 5.0 wt. %, even greater than either 8.0 wt. % or 10.0 wt. %
is made possible using the process of this invention. The content of the
optional diene monomer in the plastomer or ethylene copolymer of the
invention can range similarly as that for the EPC elastomer, but will be
preferably in the lower ranges, for example 0.1 to 8 mol. %.
The unbridged Group 4 metal compounds of this invention typically comprise
Group 4 transition metals having ancillary ligands including a
substituted, bulky cyclopentadienyl ligand, a substituted, bulky Group 15
heteroatom ligand, the cyclopentadienyl ligand and heteroatom ligands not
covalently bound, and two uninegative, activation reactive ligands at
least one of which that can be abstracted for activation of the remaining
metal compound to a catalytically active state and one of which is either
similarly abstractable or has a sigma bond to the transition metal into
which an olefin or diolefin can insert for coordination polymerization.
Thus the unbridged monocyclopentadienyl metallocene compounds of the
present invention can be represented by the formula:
CpJQ.sup.1 Q.sup.2 M
wherein:
M is Zr, Hf or Ti;
Cp is a bulky cyclopentadienyl ring which is substituted with from two to
five substituent groups R, and each substituent group R is, independently,
a radical selected from hydrocarbyl, silyl or germyl radicals having from
1 to 20 carbon, silicon or germanium atoms, substituted hydrocarbyl, silyl
or germyl radicals as defined wherein one or more hydrogen atoms is
replaced by a halogen radical, an amido radical, a phosphido radical, an
alkoxy radical, an aryloxy radical or any other radical containing a Lewis
acidic or basic functionality; C.sub.1 to C.sub.20 hydrocarbyl-substituted
metalloid radicals wherein the metalloid is selected from the Group IV A
of the Periodic Table of Elements; halogen radicals; amido radicals;
phosphido radicals; alkoxy radicals; or alkylborido radicals; or, Cp is a
cyclopentadienyl ring in which at least two adjacent R-groups are joined
together and along with the carbon atoms to which they are attached form a
C.sub.4 to C.sub.20 ring system which may be saturated, partially
unsaturated or aromatic, and substituted or unsubstituted the substitution
being of one or more R group as defined above;
J is the substituted, bulky Group 15 heteroatom ligand which is substituted
with two substituent groups R.sup.1, and each substituent group R.sup.1
is, independently, a radical selected from hydrocarbyl, silyl or germyl
radicals having 1 to 20 carbon, silicon or germanium atoms, substituted
hydrocarbyl, silyl or germyl radicals as defined wherein one or more
hydrogen atoms replaced by a halogen radical, an amido radical, a
phosphido radical, an alkoxy radical, or an aryloxy radical; C.sub.3 to
C.sub.20 hydrocarbyl-substituted metalloid radicals wherein the metalloid
is selected from the Group IV A of the Periodic Table of Elements; halogen
radicals; amido radicals; phosphido radicals; alkoxy radicals; or
alkylborido radicals; and,
each Q is independently a radical selected from halide; hydride;
substituted or unsubstituted C.sub.1 to C.sub.20 hydrocarbyl; alkoxide;
aryloxide; amide; halide or phosphide; or both Q together may be an
alkylidene or a cyclometallated hydrocarbyl or any other divalent anionic
chelating ligand, with the proviso that where any Q is a hydrocarbyl
radical, such Q is not a substituted or unsubstituted cyclopentadienyl
radical.
Such compounds can also include an L.sub.w complexed thereto wherein L is a
neutral Lewis base such as diethylether, tetrahydrofuran, dimethylaniline,
aniline, trimethylphosphine, n-butylamine, and the like; and "w" is a
number from 0 to 3.
The term "cyclopentadienyl" refers to a 5-member ring having delocalized
bonding within the ting and typically being bound to M through .eta..sup.5
-bonds, carbon typically making up the majority of the 5-member positions.
Examples of the unbridged monocyclopentadienyl metallocene compounds of the
invention include:
pentamethylcyclopentadienyltitaniumbistrimethylsilylamido dichloride,
tetramethylcyclopentadienyltitaniumbistrimethylsilyl-amidodichloride,
pentaphenylcyclopentadienyltitanium bistrimethylsilylamidodichloride,
pentabenzylcyclopentadienyl titaniumbistrimethylsilylamidodichloride,
tetraphenyl- cyclopentadienyltitaniumbistrimethylsilylamidodichloride,
tetraphenylcyclopentadienyltitaniumbistrimethylsilylamido dichloride,
bistrimethylsilylcyclopentadienyltitanium
bistrimethylsilylamidodichloride, tristrimethylsilylcyclopentadienyl
titaniumbistrimethylsilylamidodichloride, trimethylsilyl,
t-butylcyclopentadienyltitaniumbistrimethylsilylamidodichloride,
bist-butylcyclopentadienyltitaniumbistrimethylsilylamidodichloride,
indenyltitaniumbistrimethylsilylamidodichloride,
2-phenylindenyltitaniumbistrimethylsilylamidodichloride,
2,4-diphenylindenyltitaniumbistrimethylsilylamidodichloride,
2-methylindenyltitaniumbistrimethylsilylamidodichloride,
2-methyl,4-phenylindenyltitaniumbistrimethylsilylamidodichloride,
fluorenyltitaniumbistrimethylsilylamidodichloride, pentamethyl
cyclopentadienyltitaniumtrimethylsilyltriphenylsilylamidodichloride,
tetramethylcyclopentadienyltitaniumtrimethylsilyltriphenylsilylamidodichlo
ride,
pentaphenylcyclopentadienyltitaniumtrimethyl-silyltriphenylsilylamidodichl
oride,
pentabenzylcyclopentadienyl-titaniumtrimethylsilyltriphenylsilylamidodichl
oride,
tetraphenylcyclopentadienyltitaniumtrimethylsilyltriphenylsilyl-amidodichl
oride,
tetraphenylcyclopentadienyltitaniumtrimethylsilyltriphenylsilylamidodichlo
ride,
bistrimethylsilylcyclopentadienyl-titaniumtrimethylsilyltriphenylsilylamid
odichloride,
tristrimethylsilylcyclopentadienyltitaniumtrimethylsilyl-triphenylsilylami
dodichloride, trimethylsilyl, t-butylcyclopentadienyl
titaniumtrimethylsilyltriphenylsilylamidodichloride,
bistbutylcyclopentadienyltitaniumtrimethylsilyltriphenylsilyl-amidodichlor
ide, indenyltitaniumtrimethylsilyltriphenylsilyl-amidodichloride,
2-phenylindenyltitaniumtrimethylsilyltriphenyl-silylamidodichloride,
2,4-diphenylindenyltitaniumtrimethylsilyl-triphenylsilylamidodichloride,
2-methylindenyltitanium trimethylsilyltriphenylsilylamidodichloride,
2-methyl,4-phenyl-indenyltitaniumtrimethylsilyltriphenylsilylamidodichlori
de, fluorenyltitaniumtrimethylsilyltriphenylsilylamidodichloride,
pentamethylcyclopentadienyltitaniumbistiphenylsilylamido-dichloride,
tetramethylcyclopentadienyltitaniumbistriphenylsilyl-amidodichloride,
pentaphenylcyclopentadienyltitaniumbistriphenyl-silylamidodichloride,
pentabenzylcyclopentadienyltitaniumbis-triphenylsilylamidodichloride,
tetraphenylcyclopentadienyltitanium-bistriphenylsilylamidodichloride,
tetraphenylcyclopentadienyl-titaniumbistriphenylsilylamidodichloride,
bistrimethylsilylcyclopen-tadienyltitaniumbistriphenylsilylamidodichloride
, tristrimethylsilylcyclopentadienyltitaniumbistriphenylsilyl-amidodichlori
de, trimethylsilyl,
t-butylcyclopentadienyl-titaniumbistriphenylsilylamidodichloride,
bist-butyl cyclopentadienyltitaniumbistriphenylsilylamidodichloride,
indenyltitaniumbistrimethylsilylamidodichloride,
2-phenylindenyltitaniumbistriphenylsilylamidodichloride,
2,4-diphenylindenyltitaniumbistriphenylsilylamidodichloride,
2-methylindenyltitaniumbistriphenylsilylamidodichloride, 2- methyl,
4-phenylindenyltitaniumbistriphenylsilylamidodichloride,
fluorenyltitaniumbistriphenylsilylamidodichloride,
pentamethylcyclopentadienyltitaniumbistriisopropylsilyl-amidodichloride,
tetramethylcyclopentadienyltitaniumbis-triisopropylsilylamidodichloride,
pentaphenylcyclopentadienyl-titaniumbistriisopropylsilylamidodichloride,
pentabenzyl-cyclopentadienyltitaniumbistriisopropylsilylamidodichloride,
tetraphenylcyclopentadienyltitaniumbistriisopropylsilylamido-dichloride,
tetraphenylcyclopentadienyltitaniumbistriisopropylsilyl-amidodichloride,
bistrimethylsilylcyclopentadienyltitaniumbistriiso-propylsilylamidodichlor
ide,
tristrimethylsilylcyclopentadienyl-titaniumbistriisopropylsilylamidodichlo
ride, trimethylsilyl,
t-butylcyclopentadienyltitaniumbistriisopropylsilylamidodichloride,
bist-butylcyclopentadienyltitaniumbistriisopropylsilylamido-dichloride,
indenyltitaniumbistriisopropylsilylamidodichloride,
2-phenylindenyltitaniumbistriisopropylsilylamidodichloride,
2,4-diphenylindenyltitaniumbistriisopropylsilylamidodichloride,
2-methylindenyltitaniumbistriisopropylsilylamidodichloride,
2-methyl,4-phenylindenyltitaniumbistriisopropylsilylamidodichloride,
fluorenyltitaniumbistriisopropylsilylamidodichloride,
pentamethylcyclopentadienyltitaniumtriisopropyltrimethylsilylo
amidodichloride,
tetramethylcyclopentadienyltitaniumtriisopropyl-trimethylsilylamidodichlor
ide,
pentaphenylcyclopentadienyl-titaniumtriisopropyltrimethylsilylamidodichlor
ide, pentabenzylcyclopentadienyltitaniumtriisopropyltrimethylsilyl
amidodichloride,
tetraphenylcyclopentadienyltitaniumtriisopropyl-trimethylsilylamidodichlor
ide,
tetraphenylcyclopentadienyltitanium-triisopropyltrimethylsilylamidodichlor
ide,
bistrimethylsilylcyclopentadienyltitaniumtriisopropyltrimethylsilylamidodi
chloride,
tristrimethylsilylcyclopentadienyltitaniumtriisopropyltrimethylsilylamidod
ichloride, trimethylsilyl,
t-butylcyclopentadienyl-titaniumtriisopropyltrimethylsilylamidodichoride,
bist-butyl-cyclopentadienyltitaniumtriisopropyltrimethylsilylamidodichlori
de, indenyltitaniumtriisopropyltrimethylsilylamidodichloride,
2-phenylindenyltitaniumtriisopropyltrimethylsilylamidodichloride,
2,4-diphenylindenyltitaniumtriisopropyltrimethylsilyl amidodichloride,
2-methylindenyltitaniumtriisopropyltrimethylsilyl-amidodichloride,
2-methyl,4-phenylindenyltitaniumtriisopropyl-trimethylsilylamidodichloride
, fluorenyltitaniumtriisopropyltrimethylsilylamidodichloride,
pentamethylcyclopentadienyltitaniumbistributylsilylamidodichloride,
tetramethylcyclopentadienyltitaniumbistributylsilylamidodichloride,
pentaphenylcyclopentadienyltitaniumbistributylsilylamidodichloride,
pentabenzylcyclopentadienyltitaniumbistributylsilylamidodichloride,
tetraphenylcyclopentadienyltitaniumbistributylsilylamidodichloride,
tetraphenylcyclopentadienyltitaniumbistributylsilylamidodichloride,
bistrimethylsilylcyclopentadienyltitaniumbistributylsilylamido-dichloride,
tristrimethylsilylcyclopentadienyltitaniumbistributylsilyl-amidodichloride
, trimethylsilylt-butylcyclopentadienyltitaniumbisttibutylsilylamidodichlor
ide, bist-butylcyclopentadienyltitaniumbistributylsilylamidodichloride,
indenyltitaniumbistributylsilylamidodichloride,
2-phenylindenyltitaniumbistributylsfiylamidodichloride,
2,4-diphenylindenyltitaniumbistributylsilylamidodichloride,
2-methylindenyltitaniumbistributylsfiylamidodichloride, 2-methyl,
4-phenylindenyltitaniumbistributylsilylamidodichloride,
fluorenyltitaniumbistributylsilylamidodichloride.
Substituted versions where a hydride, hydrocarbyl, germyl or silyl group
replaces one or both chlorides are suitable in accordance with invention
particularly where ionizing anion precursors are activators. Separate or
in situ alkylation is typical, e.g., dimethyl replacing dichloride.
A genetic characterizing feature of these invention compounds is the
inclusion of the bulky substitution on both of the cyclopentadienyl and
amido ligands. It is believed that the inclusion of these bulky
substituents provides kinetic stability so that the active metal center is
stabilized to the high temperature reaction conditions preferably
employed. Thus the inclusion of five methyl groups on the Cp ring with two
trimethylsilyl groups on the amido group sufficiently stabilizes an
unbridged monocyclopentadienyl titanium compound such that it approaches
the temperature stability of the bridged monocyclopentadienyl titanium
compounds typically said to be the preferred, highly preferred and most
highly preferred compounds in prior art discussions, see for example, U.S.
Pat. Nos. 5,064,802 and 5,321,106.
The unbridged monocyclopentadienyl metallocene compounds according to the
invention may be activated for olefin polymerization catalysis in any
manner sufficient both to remove or complex one Q group such that the
metal center becomes sufficiently electron deficient to attract
olefinically unsaturated monomers and such that the other Q bond is either
itself, or is abstracted and substituted with another Q bond, sufficiently
weak so as to permit insertion of it into the olefinically unsaturated
monomer to yield a growing polymer, in the manner of traditional
coordination/insertion polymerization. The traditional activators of
metallocene polymerization art are suitable, those typically include Lewis
acids such as aluminum alkyls or alumoxane compounds, and ionizing anion
pre-cursors that abstract one Q so as ionize the metal center into a
cation and provide a counter-balancing noncoordinating anion.
The term "noncoordinating anion" means an anion which either does not
coordinate to said transition metal cation or which is only weakly
coordinated to said cation thereby remaining sufficiently labile to be
displaced by a neutral Lewis base. "Compatible" noncoordinating anions are
those which are not degraded to neutrality when the initially formed
complex decomposes. Further, the anion will not transfer an anionic
substituent or fragment to the cation so as to cause it to form a neutral
four coordinate metallocene compound and a neutral by-product from the
anion. Noncoordinating anions useful in accordance with this invention are
those which are compatible, stabilize the metallocene cation in the sense
of balancing its ionic charge in a +1 state, yet retain sufficient
lability to permit displacement by an ethylenically or acetylenically
unsaturated monomer during polymerization. Additionally, the anions useful
in this invention will be large or bulky in the sense of sufficient
molecular size to largely inhibit or prevent neutralization of the
metallocene cation by Lewis bases other than the polymerizable monomers
that may be present in the polymerization process. Typically the anion
will have a molecular size of greater than or equal to about 4 angstroms.
Descriptions of ionic catalysts for coordination polymerization comprised
of metallocene cations activated by ionizing anion pre-cursors appear in
the early work in EP-A-0 277 003, EP-A-0 277 004, U.S. Pat. Nos. 5,198,401
and 5,278,119, and WO92/00333. These teach a preferred method of
preparation wherein metallocene (bis Cp and mono Cp) are protonated by an
anionic precursors such that an alkyl/hydride group is abstracted from a
transition metal to make it both cationic and charge-balanced by the
non-coordinating anion. The use of ionizing ionic compounds not containing
an active proton but capable of producing the both the active metallocene
cation and an noncoordinating anion is also known. See, EP-A-0 426 637,
EP-A- 0 573 403 and U.S. Pat. No. 5,387,568. Reactive cations other than
Bronsted acids capable of ionizing the metallocene compounds include
ferrocenium triphenylcarbonium and triethylsilylinium cations. Any metal
or metalloid capable of forming a coordination complex which is resistant
to degradation by water (or other Bronsted or Lewis Acids) may be used or
contained in the anion of the second activator compound. Suitable metals
include, but are not limited to, aluminum, gold, platinum and the like.
Suitable metalloids include, but are not limited to, boron, phosphorus,
silicon and the like. The description of non-coordinating anions and
precursors thereto of these documents are incorporated by reference for
purposes of U.S. patent practice.
An additional method of making the ionic catalysts uses ionizing anion
precursors which are initially neutral Lewis acids but form the cation and
anion upon ionizing reaction with the metallocene compounds, for example
tris(pentafluorophenyl) boron acts to abstract an alkyl, hydride or silyl
ligand to yield a metallocene cation and stabilizing non-coordinating
anion, see EP-A-0 427 697 and EP-A-0 520 732. Ionic catalysts for addition
polymerization can also be prepared by oxidation of the metal centers of
transition metal compounds by anionic precursors containing metallic
oxidizing groups along with the anion groups, see EP-A-0 495 375. The
description of non-coordinating anions and precursors thereto of these
documents are similarly incorporated by reference for purposes of U.S.
patent practice.
Examples of suitable anion precursors capable of ionic cationization of the
metallocene compounds of the invention, and consequent stabilization with
a resulting noncoordinating anion include trialkyl-substituted ammonium
salts such as:
triethylammonium tetra(phenyl)boron,
tripropylammonium tetra(phenyl)boron,
tri(n-butyl)ammonium tetra(phenyl)boron,
trimethylammonium tetra(p-tolyl)boron,
trimethylammonium tetra(o-tolyl)boron,
tributylammonium tetra(pentafluorophenyl)boron,
tripropylammonium tetra (o,p-dimethylphenyl)boron,
tributylammonium tetra(m,m-dimethylphenyl)boron,
tributylammonium tetra(p-trifluoromethylphenyl)boron,
tributylammonium tetra(pentafluorophenyl)boron,
tri(n-butyl)ammonium tetra (o-tolyl)boron and the like;
N,N-dialkyl anilinium salts such as:
N,N-dimethylanilinium tetra(phenyl)boron,
N,N-diethylanilinium tetra(phenyl)boron,
N,N-diethylanilinium tetra(phenyl)n-butylboron,
N,N-2,4,6-pentamethylanilinium tetra(phenyl)boron and the like;
dialkyl ammonium salts such as:
di-(isopropyl)ammonium tetra(pentafluorophenyl)boron,
dicyclohexylammonium tetra (phenyl)boron and the like;
and triaryl phosphonium salts such as:
triphenylphosphonium tetra)phenyl)boron,
tri(methylphenyl)phosphonium tetra(phenyl)boron,
tri(dimethylphenyl)phosphonium tetra(phenyl)boron and the like.
Further examples of suitable anion precursors include those comprising a
stable carbonium ion, and a compatible non-coordinating anion. These
include:
tropillium tetrakispentafluorophenyl borate,
triphenylmethylium tetrakispentafluorophenyl borate,
benzene (diazonium) tetrakispentafluorophenyl borate,
tropillium phenyltris-pentafluorophenyl borate,
triphenylmethylium phenyl-trispentafluorophenyl borate,
benzene (diazonium) phenyltrispentafluorophenyl borate,
tropillium tetrakis (2,3,5,6-tetrafluorophenyl) borate,
triphenylmethylium tetrakis (2,3,5,6-tetrafluorophenyl) borate,
benzene (diazonium) tetrakis (3,4,5-trifluorophenyl) borate,
tropillium tetrakis (3,4,5-trifluorophenyl) borate,
benzene (diazonium) tetrakis (3,4,5-trifluorophenyl) borate,
tropillium tetrakis (3,4,5-trifluorophenyl) aluminate,
triphenylmethylium tetrakis (3,4,5-trifluorophenyl)aluminate,
benzene (diazonium) tetrakis (3,4,5-trifluorophenyl) aluminate,
tropillinum tetrakis (1,2,2-trifluoroethenyl) borate,
triphenylmethylium tetrakis (1,2,2-trifluoroethenyl) borate,
benzene (diazonium) tetrakis (1,2,2-trifluoroethenyl)borate, tropillium
tetrakis
(2,3,4,5-tetrafluorophenyl)borate,
triphenylmethylium tetrakis (2,3,4,5-tetrafluorophenyl)borate,
benzene (diazonium) tetrakis (2,3,4,5-tetrafluorophenyl) borate, etc.
Where the metal ligands include Q halide moieties, such as in (pentamethyl
cyclopentadienyl) (ditrimethylsilyl amido) titanium dichloride, which are
not capable of discrete ionizing abstraction under standard conditions,
these moieties can be converted via known alkylation reactions with
organometallic compounds such as lithium or aluminum hydrides or alkyls,
alkylalumoxanes, Grignard reagents, etc. See EP-A-0 500 944, EP-A1-0 570
982 and EP-A1-0 612 768 for processes describing the reaction of alkyl
aluminum compounds with dihalide substituted metallocene compounds prior
to or with the addition of activating anion precursor compounds.
Known alkylalumoxanes are additionally suitable as catalyst activators,
particularly for the invention metal compounds comprising the halide
ligands. The alumoxane component useful as catalyst activator typically is
an oligomeric aluminum compound represented by the general formula
(R--Al--O).sub.n, which is a cyclic compound, or R(R--Al--O).sub.n
AlR.sub.2, which is a linear compound. In the general alumoxane formula R
is a C.sub.1 to C.sub.5 alkyl radical, for example, methyl, ethyl, propyl,
butyl or pentyl and "n" is an integer from 1 to about 50. Most preferably,
R is methyl and "n" is at least 4. Alumoxanes can be prepared by various
procedures known in the art. For example, an aluminum alkyl may be treated
with water dissolved in an inert organic solvent, or it may be contacted
with a hydrated salt, such as hydrated copper sulfate suspended in an
inert organic solvent, to yield an alumoxane. Generally, however prepared,
the reaction of an aluminum alkyl with a limited amount of water yields a
mixture of the linear and cyclic species of the alumoxane.
When using ionic catalysts comprising unbridged Group 4 metal cations and
non-coordinating anions, the total catalyst system will generally
additionally comprise one or more scavenging compounds. The term
"scavenging compounds" as used in this application and its claims is meant
to include those compounds effective for removing polar impurities from
the reaction solvent. Such impurities can be inadvertently introduced with
any of the polymerization reaction components, particularly with solvent,
monomer and catalyst feed, and adversely affect catalyst activity and
stability. It can result in decreasing or even elimination of catalytic
activity, particularly when a metallocene cation-noncoordinating anion
pair is the catalyst system. The polar impurities, or catalyst poisons
include water, oxygen, metal impurities, etc. Preferably steps are taken
before provision of such into the reaction vessel, for example by chemical
treatment or careful separation techniques after or during the synthesis
or preparation of the various components, but some minor amounts of
scavenging compound will still normally be required in the polymerization
process itself Typically the scavenging compound will be an organometallic
compound such as the Group-13 organometallic compounds of U.S. Pat. Nos.
5,153,157, 5,241,025, EP-A- 638 and WO-A-91/09882 and WO-A-94/03506, noted
above, and that of WO-A-93/14132. Exemplary compounds include triethyl
aluminum, triethyl borane, tri-isobutyl aluminum, isobutyl aluminumoxane,
and n-octyl aluminum, those having bulky substituents covalently bound to
the metal or metalloid center being preferred to minimize adverse
interaction with the active catalyst. When an alkyl aluminum or alumoxane
is used as activator, any excess over the amount of metallocene present
will act as scavenger compounds and additional scavenging compounds may
not be necessary. The amount of scavenging agent to be used with
metallocene cation-noncoordinating anion pairs is minimized during
polymerization reactions to that amount effective to enhance activity. In
the process described in this invention, it was found that there is an
optimum contact time between the scavenger compound and the reaction
mixture to maximize catalyst activity. If the contact time is too long,
detrimental catalyst deactivation might occur.
The high temperature solution process for the production of the EPC
elastomers or plastomers, or ethylene copolymers, in accordance with this
invention improves process economics and increases product capabilities.
For process economics, the combination of high reactor temperature and
solvent recovery systems brings significant cost improvements. The
improved economics of the high temperature solution process compared with
the conventional process is related to the operation of polymerization
reactor at higher polymer concentration than in conventional solution
process. The higher polymer concentrations are possible due to improvement
in the solution viscosity at higher temperatures. A high reactor exit
temperature improves the efficiency of the solvent recovery systems
resulting in improved recycling economics. High efficiency recycling
systems are crucial in considering the future of solution based processes
in comparison with the competitive options, such as gas phase. In
addition, efficient solvent recycling also reduces the environmental
impact of the process with respect to volatile organic compound emissions
to meet increasingly more restrictive regulatory levels. Additionally, the
use of the invention process allows for high diolefin conversion from
monomer to incorporated mer unit in the polymer, thus reducing cost of
separation and recycle. Typical conversion ratios of diolefin monomer can
range from 20%, 30% or up to as high as 40%, and higher.
The polymerization process of the invention involves contacting the
polymerizable monomers (ethylene, .alpha.-olefin and, optionally diene
monomer) in solution with the described ionic catalyst system, preferably
at high reaction temperatures, from about 80.degree. C. to 160.degree. C.
or above, and is suitably conducted in the following manner. The solvent
is heated to reaction temperature prior to introduction into the reaction
vessel. The solvent is then provided to the reaction vessel after
polymerizable monomer is introduced in either liquid, gas or solution form
into that reaction solvent. A reaction medium is formed comprising the
solvent within which the catalyst system and monomers are contacted for
the polymerization reaction. Typically, the scavenging compound is
introduced into the reaction solvent to reduce or eliminate catalyst
poisons present in any of the reaction medium components prior to
introduction into the reactor. If the scavenging compound and activator
are different, and contacted with each other for sufficient time, adverse
effects on the effectiveness of that activator might occur. In this
process, the activator and metallocene compound are contacted in the
polymerization reaction vessel in the presence of the polymerizable
monomers, comprising the in-situ activation.
Typically the reaction is conducted at pressures from atmospheric to 500
psig (1-35 bar), preferably from 100 to 300 psig (8 to 21 bar). Preferred
reaction temperatures are above 80.degree. C., more preferably at or above
100.degree. C., for instance 110.degree. C. and above. Preferably the
upper limit to the reaction temperature in this solution process is not
greater than 160.degree. C., preferably 150.degree. C. Typically the
polymerization reaction will be exothermic and the reactor will be chilled
or cooled in accordance with known methods to assure that temperatures do
not exceed those reasonably suitable for the polymer being produced.
The feedstock purification prior to introduction into the reaction solvent
follows standard practices in the art, e.g. molecular sieves, alumina beds
and oxygen removal catalysts are used for the purification of ethylene,
.alpha.-olefin, and optional diene. The solvent itself as well, e.g.,
hexane and toluene, are similarly treated. Purification of the dienes was
observed to increase diene conversion, best results were obtained when the
diene was fractionally distilled with CaH.sub.2 as the purification
method.
The .alpha.-olefin monomer(s) and diene monomer(s), if included, are
introduced in an amount proportional to the levels of incorporation
desired for the polymer to be produced and the effective reactive ratios
for the polymerizable monomers in the presence of the specific catalyst
chosen. In the preferred embodiment the combination of the .alpha.-olefin
monomer(s) in reaction solvent as introduced into the reactor and
effective vapor pressure of the .alpha.-olefin monomer(s) is maintained
according to the rate of incorporation into the copolymer product. In an
alternative embodiment, the partial pressure in the reactor will be
provided by ethylene alone in which situation the .alpha.-olefin
monomer(s) are added solely with reaction solvent. The amounts and vapor
pressure will vary according to catalyst selection and polymer to be
produced, but can be empirically determined well within the skill in the
art, particularly in view of the description provided in the following
examples.
The catalyst activator, e.g., non-coordinating anion precursor, ionizing
anionic precursor, or alumoxane, can be introduced along with or
separately from introduction of the optional diolefin monomer(s), if used.
The diolefin can be provided in an amount effective for its rate of
reaction and rate of conversion. The catalyst activator can be provided in
an amount that is equal to 0.2 to 10 molar equivalents of the Group 4
metallocene compound, preferably 0.25 to 5, and even more preferably 0.33
to 3.0, when a noncoordinating anion precursor. Typically the provision of
the noncoordinating anion precursor activator will be in an effective
solvent, typically an aromatic solvent such as toluene. When the activator
is alumoxane, it can be used in an amount that is equal to 0.5 to 10,000
molar equivalents of the metallocene compound, preferably 0.75 to 5000,
and even more preferably 1.0 to 500. Preferably the alumoxane will be used
in an amount empirically determined to suffice for concurrent removal of
impurities and activation, but only in such amounts as necessary to
accomplish those functions. Monitoring of polymerization activity by known
methods will permit on-line adjustment of alumoxane to assure neither
excess nor deficit amounts are maintained for unwanted periods.
The scavenging compounds are provided separately afterwards or with one of
the foregoing feedstreams, in an amount suitable to increase the activity
of the catalyst but in an amount lower than that at which depression of
reactivity is observed. Typically an effective amount of the scavenging
compound is about 0 (e.g., with an alumoxane activator) to 100 mol. ratio
based upon the ratio of scavenging compound to activator, preferably the
ratio is 0.3 to 30, and most preferably it is 0.5 to 10.
Promptly thereafter, preferably within not more than about 1 minute, more
preferably within 30 seconds, the metallocene compound is contacted with
the activator in the presence of the polymerizable monomers so as to limit
the residence time of the scavenging compound with the activator. The
metallocene is typically provided in an aliphatic or aromatic solvent,
which can be any of those suitable as polymerization medium. For ease of
reference the examples below refer to the metallocene in solvent as
"catalyst solution". Though any order of activation will have at least
some suitability, the order of addition described herein is particularly
suitable for use with ionizing activators that provide the stabilized
metallocene cation-noncoordinating anion pair. Since alumoxane can act as
a suitable scavenger compound, its addition as activator in accordance
with the described process eliminates the need to introduce a scavenger
and the preference for limited time of contact between scavenger and
activator is largely eliminated so long as the addition of the metallocene
to activator containing solution is in the presence of polymerizable
monomers. In this manner premature activation can be avoided.
Ethylene gas is then provided into the reaction vessel in an amount
proportional to the level of incorporation desired and the effective
reactive ratios for the polymerizable monomers in the presence of the
specific catalyst chosen, as with the .alpha.-olefin monomer(s). The
polymerization starts upon contact of the monomers with the activated
catalyst and the rates of supply of each of the components of the system
are adjusted for stable operations at the level of production, molecular
weight, monomer incorporation and equipment limitations. The reaction
temperature may be permitted to exceed the initial temperature but will
preferably be at all times greater than the lower limit of the ranges
described above for the invention process.
The solvents for the polymerization reaction will comprise those known for
solution polymerization, typically the aliphatic solvents represented by
hexane, or the aromatic solvents, represented by toluene. Additional
examples include heptane, cyclohexane, and Isopar E (C.sub.8 to C.sub.12
aliphatic solvent, Exxon Chemical Co., U.S.). Preferably the solvent is
aliphatic, most preferably it is hexane.
Though not strictly necessary for the solution polymerization process as
described, the catalyst according to the invention may be supported for
use in alternative gas phase, bulk, or slurry polymerization processes
where the high temperature benefits of the catalysts are sought to be
applied. Numerous methods of support are known in the art for
copolymerization processes for olefins, particularly for catalysts
activated by alumoxanes, any is suitable for the invention process in its
broadest scope. See, for example, U.S. Pat. No. 5,227,440. An example of
supported ionic catalysts appears in WO 94/03056. When using a Lewis acid
ionizing catalyst activator a particularly effective method is that
described in co-pending application U.S. Ser. No. 08/474,948 filed Jun. 7,
1995. The support method of this co-pending application describes the use
of a Lewis acid noncoordinating anion precursor (e.g., trisperfluorophenyl
boron) which is covalently bound to silica-containing supports through
retained hydroxy groups which as an initially formed activator complex
donates the hydroxyl hydrogens as protons for protonation of the Group 4
transition metal compound to catalytically active cations. A bulk, or
slurry, process utilizing supported, biscyclopentadienyl Group 4
metallocenes activated with alumoxane co-catalysts is described as
suitable for EPM and EPDM in U.S. Pat. Nos. 5,001,205 and 5,229,478, these
processes will additionally be suitable with the catalyst systems of this
application. Each of the foregoing documents is incorporated by reference
for purposes of U.S. patent practice. In these examples ENB represents
5-ethylidene-2-norbornene, IPA is isopropyl alcohol, GPC is gel permeation
chromatography, TIBAL is triisobutyl aluminum.
Though the Examples and the discussion are directed to a single reactor
configuration and narrow polydispersity polymers, it is well-known that
the use in series of two such reactors each operated so as to achieve
different polymer molecular weight characteristics, or by blending
polymers from different reactor conditions or utilizing two or more
different transition metal catalysts in one or more reactors, can yield
improved processing polymers. The disclosures of U.S. Pat. No. 4,722,971
and WO 93/21270 are instructive and are incorporated for purposes of U.S.
patent practice. Though directed to the use of vanadium catalysts, the
substitution of the catalyst systems of this invention into one such
reactor, or two different invention catalysts into two such reactors, or
similar use in two separate polymerizations with subsequent physical
blending of the polymer products, will permit tailoring of characteristics
(e.g., molecular weights and diene contents) suitable for balancing
vulcanization properties with processability. Similarly, the use of mixed
catalyst systems, the invention catalysts with themselves or with others,
in one or more such reactors will permit preparation of bimodal or
multimodal EPC polymers having improved processing properties.
The following examples are presented to illustrate the foregoing
discussion. All parts, proportions and percentages are by weight unless
otherwise indicated. Although the examples may be directed to certain
embodiments of the present invention, they are not to be viewed as
limiting the invention in any specific respect. Methods of determining
M.sub.n and monomer contents by NMR and GPC for the illustrative EPDM
examples of the invention are described in U.S. Pat. No. 5,229,478 which
is incorporated by reference for purposes of U.S. patent practice. For
measurement of comonomer contents in the EPC elastomers, the method of
ASTM D3900 for ethylene-propylene copolymers between 35 and 85 wt. %
ethylene was used. Outside that range the NMR method was used. See also,
U.S. Pat. No. 4,786,697 which is incorporated by reference for purposes of
U.S. patent practice.
EXAMPLES
EXAMPLE 1
Synthesis of EPDM
The polymerizations were conducted in a 500 cc autoclave reactor operated
at the temperature of 115.degree. C. in the batch mode for the polymer and
semi-batch for the ethylene monomer. The following procedure was used for
the polymerizations:
The reactor was charged with 250 cc of purified hexane, 5 cc of 10 wt. %
toluene solution of MAO (activator) and 3 cc of purified ENB (fractional
distillation with CaH.sub.2).
The reactor was heated to 115.degree. C., resulting in a hexane vapor
pressure of approximately 37 psig (2.5 bar).
Propylene was added to the reactor to reach 110 psig (7.48 bar) pressure
(liquid phase molar conc.=0.856M).
Ethylene was added to the reactor to reach 235 psig (16 bar) pressure
(liquid phase conc.=0.871M ). These conditions determined the intial
ethylene/propylene molar ratio equal to 1.018. The ethylene/ENB molar
ratio was 10.43.
The catalyst solution was pumped to the reactor to maintain the
polymerization rate constant as indicated by the make-up flow rate of
ethylene to the reactor. The pumping was adjusted to keep this rate at
about 0.1 SLPM (standard L/min, standard conditions 1 bar, 21.1.degree.
C.), to target approximately 10 g yield of polymer.
Irganox.RTM. 1076 was added to the hexane solution to the final
concentration of 0.1 mg/cc to prevent sample degradation. The polymers
were worked-up from the solution by precipitation with IPA. After
filtering and removing free solvents, the polymer samples were dried under
vacuum at 90.degree. C. for about 1 hour.
The analysis of the polymers were done by .sup.1 H-NMR for ENB content and
GPC for EPDM molecular weight.
TABLE 1
______________________________________
Results for Example 1
Catalyst: pentamethylcyclopentadienylbis-
trimethylsilylamidotitanium dichloride
Activator: methylalumoxane
Temperature:
115.degree. C.
Pressure: 235 psig
Polymer
Catalyst Ethyl- Propyl-
ENB
Yield Usage ene ene % PD
(g) (mg) % wt % wt wt M.sub.n
(MWD)
______________________________________
11.7 19.2 73.5 21.22 5.28 100589
2.1
9 19.2 71.6 21.86 6.5 118358
1.85
______________________________________
EXAMPLE 2
Synthesis of EPDM
The same procedure as described in Example 1 was carried out with the
noncoordinating anion activator and with the following differences:
At room temperature, after the reactor was charged with 200 cc of hexane,
50 cc of the 1.5.times.10.sup.-3 M of the activator solution in toluene
was added. The reactor was then heated up to 115.degree. C., as in Example
1.
To the pressurized reactor after the addition of ethylene, 10 microliters
of 2M TIBAL solution in pentane was added as the scavenger at least one
minute before the start of the catalyst pumping.
TABLE 2
______________________________________
Results for Example 2
Catalyst:
pentamethylcyclopentadienylbis-
trimethylsilylamidotitanium dimethyl
Activator:
dimethylanilinium tetra (perfluorophenyl) borate
Temperature:
115.degree. C.
Pressure:
235 psig
Polymer
Catalyst Ethyl- Propyl-
ENB
Yield Usage ene ene % PD
(g) (mg) % wt % wt wt M.sub.n
(MWD)
______________________________________
6.4 3 62.89 31.71 5.4 86303 2.13
11.8 2.4 64.33 30.83 4.84 77145 2.27
4.16 5.64 63.43 31.20 5.37 104497
2.05
______________________________________
COMPARATIVE EXAMPLE 2
Synthesis of EPDM
The same procedure as described in Example 2 was carried out the following
catalyst:
TABLE 3
______________________________________
Results for Comparative Example 2
Catalyst:
cyclopentadienylbis-trimethylsilylamidotitanium
dimethyl
Activator:
dimethylanilinium tetra(perfluorophenyl)borate
Temperature:
115.degree. C.
Pressure:
235 psig
Polymer
Catalyst Ethyl- Propyl-
ENB
Yield Usage ene ene %
(g) (mg) % wt % wt wt M.sub.n
PD
______________________________________
1.3 15 61.64 25.01 13.35
9367 2.58
1.77 30 70.79 20.58 8.63 7293 2.84
2.51 45 68.53 22.48 8.99 8177 3.99
______________________________________
Comparative Example 2 illustrated the requirement of bulky Cp ligands to
the titanium catalyst for improvement of molecular weights. The M.sub.n
for the pentamethylcyclopentadienyl substituted catalyst was at least 10
times higher than for the cyclopentadienyl substituted catalyst of JA
94-80683.
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