Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02218638 1997-10-16
...
POLYMERIZATION OF a-OLEFINS WITH TRANSITION
METAL CATALYSTS BASED ON BIDENTATE LIGANDS
CONTATNING PYRIDINE OR OUINOLINE MOIETY
Background of the Invention
This iYivention relates to catalysts useful in
polymerizing a-olefins. In particular, it relates to the
polymerization c_~ ethylene using transition metal catalysts
with bidentatF ligands containing pyridine or quinoline
moieties. Unlike the reaction products disclosed in U.S. Patent
No. 3,900,452 wherein titanium in the TiC13 - pyridinate forms a
non-sigma bond to the nitrogen on the heterocyclic ring, the
compounds of the invention contain a titanium which forms a non-
sigma bond to the-nitrogen as well as a sigma bond to an oxygen
atom which in turn is bond to the heterocyclic ring.--
Until recently, polyolefins have been made primarily
using conventional Ziegler catalyst systems. A Ziegler
catalyst typically consists of a transition metal-containing
compound and one or more organometallic compounds. For
example, polyethylene has been made using Ziegler catalysts
such as titanium trichloride and diethylaluminum chloride, or
a mixture of t;--anium tetrachloride, vanadium oxytrichloride,
and triethylaluminum. These catalysts are inexpensive but
they have low activity and therefore musts be used at high
concentrations. The catalyst residue in the polymers produces
a yellow or grey color and poor ultraviolet and long term
stability, and chloride-containing residues can cause
corrosion in polymer processing equipment. It is therefore
sometimes necessary to either remove catalyst residues from
the polymer or add neutralizing agents and stabilizers to the
','ZSDC-0 SHEET
CA 02218638 1997-10-16
' '.. ..' ,
polymer to overcome the deleterious effects of the residues
anc: this adds to production costs. Furthermore, Ziegler
cat lysts produce polymers having a broad molecular weight
distribution, which is undesirable for some applications, such
as injection,molding. They are also poor at incorporating a-
olefin co-monomers, making it difficult to control polymer
density. Large quantities of excess co-monomer may be
required to achieve a certain density and many higher a-
olefins, such as 1-octene, can be incorporated at only very
low levels, if at all.
Although substantial improvements in Ziegler catalyst
systems have occurred since their discovery, these catalysts
are now being replaced with recently discovered metallocene
catalyst systems. A metallocene catalyst typically consists
of a transition metal compound that has one or more
cyclopentadienyl ring ligands. Metallocenes have low
activities when used with organometallic compounds, such as
aluminum alkyls, which are used with traditional Ziegler
catalysts, but very high activities when used with
aluminoxanes as cocatalysts. The activities are generally so
high that catalyst residues need not be removed from the
polymer. Furthermore, they produce polymers with high
mol=::ular weights and narrow molecular weight distributions.
They also incorporate a-olefin co-monomers well.
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SNEET
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.. . .. ~
However, at higher temperatures metallocene catalysts
tend to 1._oduce lower molecular weight polymers. Thus, they
are usefu_ for gas phase and slurry polymerizations of
ethylene, which are conducted at about 80 C to about 95 C, but
in general,they do not work well as temperatures are
increased. The polymerization of ethylene in solution at higher
temperatures is desirable because it allows great flexibility for
producing polymers over a wide range of molecular weights and
densities as well as the use of a large variety of different co-
monomers. Solution polymerization permits the production of
polymers that are useful in many different applications. For
example, both high molecular weight, high density polyethylene
(PE) film useful as a barrier film for food packaging and low
density ethylene co-polymers with good toughness and high
impact str-zgth can be made.
Summary of the Invention
We have discovered novel bidentate pyridine transition
metal compounds which have excellent activity as a-olefin
polymerization catalysts. We have also discovered that
bidentate quinoline transition metal compounds, which were
heretofore unsuspected of possessing any catalytic properties,
are also excellent polymerization catalysts for a-olefins.
These catalysts produce polymers having properties very close
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SNEL T
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~ . , . : .
..,
to the properties of polymers produced using metallocene
catalysts. That is, the polymers have a narrow molecular
weight distribution and a uniform co-monomer incorporation.
nescri.ntion of the PreferredEmbodiments
The transition metal catalysts of this invention
containing the bidentate pyridine based ligand have the
general formula
R' R.
R' O R'
N
M
L (X)2
where Y is 0, S, NR, ~ R
I
i TJNR- or fo
R
n n
each R is independently selected from hydrogen or C1 to C6
alkyl, each R' is independently selected from R, Cl to C. alkoxy,
C6 to Q aryl, halogen, or gF , M is titanium, zirconium, or
hafnium, each X is independently selected from halogen, C1 to C.
alkyl, Cl to C6 alkoxy, or
R
- N
R
L is X, cyclopentadienyl, C1 to6 C alkyl substituted
cyclopentadienyl, indenyl, fluorenyl, or
R' R'
R! O R!
N
Y-
"m" is 0 to 4, and "n" is 1 to 4.
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.. , .. .
In the formula, the Y group is preferably oxygen as those
compounds are easier to make. For the same reason the R group
is preferably methyl and "R'" is preferably hydrogen. The L
group is preferably halogen, most preferably chlorine, as those
cata! sts give superior properties and are easier to prepare.
For the same reasons, the X group is preferably halogen,
especially chlorine, and the M group is preferably titanium.
Preparation of the bidentate pyridine complexes is
illustrated in the examples, but generally they can be
0 prepared by reacting a substituted pyridine precursor having
an acidic proton with a compound having the formula MX3L in
the presence of an HX scavenger. The reaction is
stoichiometric and stoichiometric amounts of scavenger are
preferred. Examples of suitable scavengers include compounds
that are more basic than the substituted pyridine, such as
triethylamine, pyridine, sodium hydride, and butyl lithium.
if t:e scavenger is a stronger base than the substituted
pyridine one can make a salt of the substituted pyridine and
begin with that. While the reaction is preferably performed
in a solvent, only partial solubility of the reactants is
required. An aprotic solvent, such as tetrahydrofuran (THF),
ether, toluene, or xylene, can be used at about 0.2 to about
20 wt%~ solids, and preferably at about 5 5o about 10 wtlr
solids. The reaction can occur at about -78 C to about room
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. . .,~ -
temperature. As the reaction proceeds a precipitate is formed
and the product can be extracted with toluene, methylene
chloride, diethyl ether, or a similar extractant.
The bidentate quinoline transition metal catalysts of
this invention have the general formula
R' R'
R'
R'
PN R' R' Y - i -tX)2
L
where R, R', L, M, X, and "n" where previously defined.
The quinoline transition metal catalysts are made in a
similar manner to the pyridine trar_sition metal catalysts
except that one begins with a substituted quinoline such as 8-
hydroxy quinoline (also known as 8-quinolinol) instead of the
substituted pyridine. Also, butyl lithium can be used in a
solvent to make the lithium salt of 8-hydroxy quinoline, which
can also be used as the starting material.
Since the catalyst is normally used in conjunction with
an organometallic co-catalyst, it is preferable to dissolve
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t1i4~11
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= , = ... .
.. .. .
the catalyst in a solvent in which the co-catalyst is also
soluble. For example, if methylaluminoxane (MAO) or
,)olymethylaluminoxane (PMAO) is the co-catalyst, then toluene,
cylene, benzene, or ethylbenzene could be used as the solvent.
The preferred co-catalyst is MAO as it results in high
activity and, a polymer having a narrower molecular weight
distribution. The mole ratio of the organometallic co-
catalyst to catalyst when used in a polymerization is
generally in the range 0.01:1 to 100,000:1, and preferably
ranges from 1:1 to 10,000:1.
An alternative co-catalyst is an acid salt that contains
a non-coordinating inert anion (see U.S. Patent No.
5,064,802). The acid salt is generally a non-nucleophilic
compound that consists of bulky ligands attached to a boron or
aluminum atom, such as lithium tetrakis(pentafluorophenyl)
borate, lithium tetrakis(pentafluorophenyl)aluminate,
anilinium tetrakis(pentafluorophenyl)borate, and mixtures
thereof. The anion which results when these compounds react
with the catalyst is believed to be weakly coordinated to the
metal-containing cation. The mole ratio of acid salt to
catalyst can range from about 0.01:1 to about 1000:1, but is
preferably about 1:1 to 10:1. While there is no limitation on
the method of preparing an active catalyst
system from the catalyst and the acid salt, preferably they
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. . . .~ = -õ ,
, = . ,
are mixed in an inert solvent at temperatures in the range of
about -78 C to about 150 C. They can also be mixed in the
presence of monomer if desired. The acid salt can be used in
combination with the organometallic cocatalysts described
earlier.
The catalyst and co-catalyst can be used in a support
such as silica gel, alumina, silica, magnesia, or titania, but
supports are not preferred as they may leave contaminants in
the polymer. However, a support may be required, depending
0 upon the process being utilized. For example, a support is
generally needed in gas phase polymerization processes and
slurry polymerization processes in order to control the
particle size of the polymer being produced and in order to
prevent fouling of the reactor walls. To use a support, the
catalyst and co-catalyst are dissolved in the solvent and are
precipitated onto the support material by, for example,
evaporating the solvent. The co-catalyst can also be
deposited on the support or it can be introduced into the
reactor separately from the supported catalyst.
The catalyst is used in a conventional manner in the
polymerization of olefinic hydrocarbon monomers. While
unsaturated monomers, such as styrene, can be polymerized using
the catalyst of this invention, it is particularly useful for
polymerizing a-olefins such as propylene, 1-butene, 1-hexene,
1-octene, and especially ethylene.
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The catalyst is also useful in a conventional manner for
copolymerizing mixtures of unsaturated monomers such as
ethylene, propylene, 1-butene, 'i-hexene, 1-octene, and the
like; mixtures of ethylene and di-olefins such as 1,3-
butadiene, 1,4-hexadiene, 1,5-hexadiene, and the like; and
mixtures of ethylene and unsaturated comonomers such as
norbornene, ethylidene norbornene, vinyl norbornene,
norbornadiene, and the like.
The catalysts of this invention can be utilized in a
variety of different polymerization processes. They can be
utilized in a liquid phase polymerization process (slurry,
solution, suspension, bulk phase, or a combination of these),
in a high pressure fluid phase, or in a gas phase
polymerization process. The processes can be used in series
or as individual single processes. The pressure in the
polymerization reaction zones can range from about 15'psia to
about 50,000 psia and the temperature can range from about
-78 C to about 300 C.
EXAMPLE 1
Synthesis of Bis(2-Ayridinoxv)titanium Dichloride
To a solution of 0.02 moles of 2-hydroxy pyridine and
0.02 moles of triethylamine in 50 mL of THF, a solution of
0.01 moles of titanium tetrachloride was added dropwise at 0 C
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and stirred overnight at room temperature. After filtration,
the THF solution was evaporated and the product was extracted
from the residue. The product has the formula:
O
I. Cl Ti-CI
O N
EXAMPLE 2
Preparation of (Cyclopentadienyl)
(2-Pyridinoxy) Titanium Dichloride
To a solution of 0.002 moles of cyclopentadienyl titanium
trichloride in 50 mL of ether a solution of 2-hydroxy pyridine
(0.002 moles) and triethylamine (0.002 moles) in 50 mL of
ether was added at 0 C and stirred overnight. The product was
recovered from the ether filtrate. The product has the
formula:
Qo
II , CI--Ti---Cl
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EXAMPLE 3
General Procedure For Preparation
of Ouinolinoxv Transition Metal Catalysts
Toluene slurries of lithium salts of various 8-quinolinol
derivatives (prepared using butyl lithium) were combined with
the corresponding titanium or zirconium compound (titanium
tetrachioride, zirconium tetrachloride, cyclopentadienyl
titanium trichloride, or cyclopentadienyl zirconium
trichloride) at -78 C and stirred overnight at room
temperature. The complexes were recovered from the reaction
mixture by extraction with toluene or methylene chloride. To
prepare 8-quinolinoxy titanium trichloride (III),
C19
O
CI ~Ti 'CI
Ci
a slurry of 0.01 moles of the lithium salt of 8-
hydroxyquinoline in 30 ml of toluene (prepared from 1.45 g
(0.01 moles) of quinolinol and MeLi) was added at -78 C to a
solution of 1.9 g (0.01 moles) of TiC14 in 20 ml of toluene
and stirred overnight at room temperature. The precipitate
was separated, washed with toluene, and extracted with 100 ml
of CH2C12. After the methylene chloride had been removed, a
brown microcrystalline solid (0.7 g) was isolated.
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Similarly, 8-(2-methyl-5,7-dichloroquinolin)oxytitanium
trichloride (IV) (2.3 g)
ci
00
CH3 N ci
ci ~.I 1 IC1
Ci
IV
was prepared starting with a lithium salt made from 2.28 g
(0.01 moles) of 5,7-dichloro-2-methyl-8-quinolinol.
A similar procedure was used to prepare 1.0 g of the
comparative complex bis[8-(2-methyl-5,7-
dichloroquinolin)oxy]zirconiumdichloride (V)
ci
00
CHs N ci
Cl Zr~O
0,00 C1
Ci ri CHs
00
ci
(V)
from 2.28 g (0.01 moles) of 5,7-dichloro-2-methyl-8-quinolinol
and 1.165 g (0.005 moles) of zirconium tetrachloride.
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To prepare (cyclopentadienyl)-(8-quinolinoxy)zirconium
dichioride (VI)
ON
C1--Zr~o
Cl." 6
(VI)
and (cyclopentadienyl)-[8-(2-methyl-5,7-
dichloroquinolin)oxy]zirconium dichloride (VII)
C!
~ ~
CH3 N CI
CI ~Zr/O
CI
(VII)
lithium salts made from 1.45 g (0.01 moles) of 8-quinolinol or
1.15 g (0.005 moles) of 5,7-dichloro-2-methyl-8-quinolinol,
respectively, were reacted with equimolar amounts of
cyclopentadienyl zirconium trichloride in toluene at -78 C.
After stirring overnight and filtering, the products (0.62 g
= of VI and 1.7 g of VII) were isolated from the toluene
solution.
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. . . . ' ,'
=. ,. ;
EXAMPLE 4
Polymerizations
All polymerizations in this study were conducted in a
1.7 L reactor. Prior to conducting a polymerization, the
reactor was "baked-out" by heating to 130 C and holding at
that temperature for 30 minutes under a nitrogen purge.
Ethylene, hydrogen, hexene, butene, and nitrogen were treated
by passage through columns containing 13X molecular sieves.
For a typical polymerization, the reactor was charged with
0 0.850 L of hexane or toluene and, using a syringe, the
required volume of diluted PMAO (AKZO). The desired amount of
hydrogen was added to the reactor by monitoring the pressure
drop (AP) from a 1 L stainless vessel pressurized with
hydrogen. A toluene solution of catalyst was added to the
reactor by nitrogen over pressure. The reactor was maintained
at isothermal conditions throughout the run. Ethylene was
admitted to the reactor and controlled at 150 psi with feed on
demand via a pressure regulator. After the reactor
temperature and pressure stabilized, the catalyst slurry was
charged into the reactor and polymerization initiated.
Ethylene flow was monitored via a Brooks mass flow meter.
Polymerization was terminated by venting the reactor and
the polymer was recovered by filtration. The polymer was
stabilized by the addition of about 1000 ppm of butylated
hydroxytoluene/hexane (BHT) and further devolatilized 2 hours
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- ~~.1 lt .',}i1' :
.+~+,
CA 02218638 1997-10-16
WO 96/33202 PCT/US96/03656
at 80 C in a vacuum oven. Melt flow properties of the polymer
were determined in accordance with ASTM D-1238. Polymer
densities were measured on compression molded samples in a
density gradient column in accordance with ASTM D-1505 85.
The following table gives the reaction conditions.
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Co-Monomer Catalyst Molar Ratio FReaction
Run Catalyst Temp. C) Co-Monomer (grams (mmoles) Al/M H2, AP Time Min
1 I 80 None 0 9.5E-3 1897 0 15
N
2 I 80 None 0 4.7E-3 3795 0 15
3 I 80 None 0 4.7E-3 1897 20 15
4 I 80 None 0 4.7E-3 1897 50 10
5 I 80 Butene 20 4.7E-3 1897 20 15
6 II 80 None 0 9.OE-3 1001 0 60 r)
7 III 80 Butene 10 8.4E-3 1074 10 30 >
8 III 80 None 10 8.4E-3 1074 10 30
9 IV 80 Butene 0 6.6E-3 1324 0 30
10 IV 80 Butene 10 6.6E-3 1324 10 30
CA 11* V 80 Butene 10 1.14E-2 1175 0 10
12* V 80 Butene 10 4.06E-3 1645 0 10
13* V 80 Butene 10 8.12E-3 1645 0 10
14 VI 80 Butene 10 6.74E-3 991 0 15
15 VI 80 Butene 10 1.35E-2 991 0 15
16 VI 80 Butene 10 1.35E-2 1288 5 15
17 VI 80 Butene 10 1.89E-2 1132 15 15
18 VI 110 Butene 10 1.89E-2 1132 0 15
19 VII 80 Butene 10 1.10E-2 1212 0 15
20 VII 80 Butene 10 1.10E-2 1212 5 15
21 VII 110 Butene 10 1.54E-2 1126 15 15
o22 VII 80 Butene 10 1.54E-2 1126 0 15
23 VII 80 Butene 10 1.54E-2 2078 0 15
n the table, A " is ratio of moles of aluminum in PMAD to mo es of metal
(titanium or
zirconium) in the catalyst. *Comparative Example
, ' ~ .
.
The following table gives the result of the polymerizations.
Catalyst M12 M120 MFR Density Mw/Mn
Run Productivity
(kg/gM/h) 1 179.0 <0.01 <0.01 -
2 153.2 <0.01 <0.01 -
3 165.5 <0.01 1.8 -
4 133.1 <0.01 2.47 -
5 272.9 <0.01 0.964 - y
6 62.9 <0.01 <0.01 -
7 99.2 0.90 16.9 18.9 0.9513 2.51
8 167.9 0.41 4.2 10.2 3.67
~.. '
9 103.2 <0.01 - -
10 24.8 <0.01 - -
~:.
11* low - - -
12* none - - - *Camparative Example 15 13* none - - -
14 none - - -
98.1 <0.01 1.15 -
16 177.7 0.93 21.4 23.1
17 137.6 1.31 34.5 26.3
18 159.0 0.81 16.1 19.8
19 119.8 <0.01 .83 -
20 198.7 0.46 11.4 24.7
21 157.8 0.63 17.8 28.2
22 160.1 0.06 12.8 -
2112.1 0.06 1.84 29.7
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In the table, kg/gm/h is kilograms polymer produced per
gram of catalyst per hour. The melt index of the polymer was
measured according to ASTM D-1238, Condition E and Condition
F. M12 is the melt index measured with a 2.16 kg weight
(Condition E). M120 is the melt index measured with a 21.6 kg
weight (Condition F). MFR is the ratio of M120 to M12. The
polymer density was measured according to ASTM D-1505. The
molecular weight distribution of the polymer was measured
using a Waters 150C gel permeation chromatograph at 135 C with
1,2,4-dichlorobenzene as the solvent. Both weight average
molecular weight (Mw) and the ratio of Mw to Mn (number
average molecular weight) are used to characterize the
molecular weight distribution.
The catalysts of this invention gave good productivities
and high molecular weight polymers, as evidenced by very low
MI values, and Catalysts VI and VII did so even at higher
temperatures (110 C).
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