U.S. patent application number 09/841743 was filed with the patent office on 2001-12-27 for ethylene polymerization process.
Invention is credited to Lee, Clifford C., Liu, Jia-Chu, Mack, Mark P., Wang, Shaotian.
Application Number | 20010056161 09/841743 |
Document ID | / |
Family ID | 24052975 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010056161 |
Kind Code |
A1 |
Wang, Shaotian ; et
al. |
December 27, 2001 |
Ethylene polymerization process
Abstract
A gas phase polymerization of ethylene is disclosed. The process
uses a single-site catalyst containing at least one heteroatomic
ligand selected from boraaryl, azaborolinyl, pyridinyl, pyrrolyl,
indolyl, indenoindolyl, carbazolyl, and quinolinyl. The catalysts
are immobilized onto a support. The process comprises polymerizing
an ethylene that contains from about 5 to about 15 mole % of a
C.sub.3-C.sub.10 .alpha.-olefin and gives polyethylene having a
reduced viscosity.
Inventors: |
Wang, Shaotian; (Mason,
OH) ; Liu, Jia-Chu; (Mason, OH) ; Mack, Mark
P.; (West Chester, OH) ; Lee, Clifford C.;
(Cincinnati, OH) |
Correspondence
Address: |
Dr. Shao Guo
Lyondell Chemical Company
3801 West Chester Pike
Newtown Square
PA
19073
US
|
Family ID: |
24052975 |
Appl. No.: |
09/841743 |
Filed: |
April 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09841743 |
Apr 25, 2001 |
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09515839 |
Feb 29, 2000 |
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6255415 |
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Current U.S.
Class: |
526/160 ;
526/161; 526/348.2; 526/348.4; 526/348.5; 526/348.6; 526/901;
526/943 |
Current CPC
Class: |
C08F 2/34 20130101; C08F
4/65916 20130101; C08F 210/14 20130101; C08F 4/65912 20130101; C08F
10/00 20130101; C08F 10/02 20130101; C08F 210/16 20130101; C08F
10/02 20130101; C08F 210/16 20130101; C08F 4/6592 20130101; C08F
4/65908 20130101; C08F 4/659 20130101; C08F 10/00 20130101; Y10S
526/943 20130101 |
Class at
Publication: |
526/160 ;
526/901; 526/348.2; 526/348.4; 526/348.5; 526/348.6; 526/161;
526/943 |
International
Class: |
C08F 004/44 |
Claims
We claim:
1. A process that comprises polymerizing ethylene containing about
5 to about 15 mole % of a C.sub.3-C.sub.10 .alpha.-olefin in gas
phase in the presence of a supported catalyst comprising: (a) an
organometallic compound that contains at least one indenoindolyl
ligand; (b) an optional activator; and (c) a support; wherein the
polymer produced has a density within the range of about 0.890 to
about 0.930 g/mL.
2. The process of claim 1 wherein the polymerization is performed
at a temperature within the range of about 50.degree. C. to about
250.degree. C.
3. The process of claim 1 wherein the C.sub.3-C.sub.10
.alpha.-olefin is selected from the group consisting of propylene,
1-butene, 1-pentene, 1-hexene, 1-octene, and mixtures thereof.
4. The process of claim 1 wherein the support is selected from the
group consisting of inorganic oxides and chlorides, and organic
polymer resins.
5. The process of claim 1 wherein the activator is selected from
the group consisting of alumoxanes, alkyl aluminums, alkyl aluminum
halides, anionic compounds of boron or aluminum, trialkylboron
compounds, and triarylboron compounds.
6. The process of claim 1 wherein the process is performed at a
pressure within the range of about 300 psi to about 5,000 psi.
7. The process of claim 1 wherein the polymer produced has a
density within the range of about 0.900 to about 0.920 g/mL.
Description
[0001] This is a continuation-in-part of Appl. Ser. No. 09/515,839,
filed Feb. 29, 2000.
FIELD OF THE INVENTION
[0002] The invention relates to an ethylene polymerization process.
More particularly, the invention relates to a gas phase
polymerization of ethylene with a single-site catalyst. The process
produces polyethylene having a reduced density.
BACKGROUND OF THE INVENTION
[0003] Linear low density polyethylene (LLDPE), which has a density
from 0.916 to 0.940 g/mL, has penetrated all traditional markets
for polyethylene, including film, molding, pipe, and wire and
cable. Due to its strength and toughness, LLDPE has been largely
used in the film market, such as produce bags, shopping bags,
garbage bags, diaper liners, and stretch wrap. LLDPE has been
primarily made with conventional Ziegler catalysts. It is typically
produced by copolymerization of ethylene with a long chain
.alpha.-olefin such as 1-butene, 1-hexene, or 1-octene.
[0004] In the early 1980's, Kaminsky discovered a new class of
olefin polymerization catalysts known as metallocenes (see U.S.
Pat. Nos. 4,404,344 and 4,431,788). A metallocene catalyst consists
of a transition metal compound that has one or more
cyclopentadienyl (Cp) ligands. Unlike Ziegler catalysts,
metallocene catalysts are usually soluble in olefins or
polymerization solvents and give homogeneous polymerization
systems. Since these catalysts have a single reactive site
(compared with multiple reactive sites of Ziegler catalysts), they
are also called "single-site" catalysts. Metallocene catalysts are
more reactive than conventional Ziegler catalysts, and they produce
polymers with narrower molecular weight distributions. Because
single-site catalysts enhance incorporation of long chain
.alpha.-olefin comonomers into polyethylene, they are of particular
interest in the production of LLDPE.
[0005] Over the last decade, non-metallocene single-site catalysts
have also been developed rapidly. Non-metallocene single-site
catalysts contain non-Cp ligands, which are usually heteroatomic
ligands, e.g., boraaryl, azaborolinyl, pyridinyl, pyrrolyl,
indolyl, indenoindolyl, carbazolyl, or quinolinyl groups. The
development of non-metallocene single-site catalysts has provided
the polyolefin industry with more choices of catalysts and
opportunities for optimizing the products or production
processes.
[0006] Non-metallocene single-site catalysts have most of the
characteristics of metallocene catalysts, including high activity.
However, they produce polyethylenes that have relatively high
density. For example, boraaryl-based single-site catalysts produce
polyethylenes that have densities from about 0.93 to about 0.97
g/mL (see U.S. Pat. No. 5,554,775). It is of significant interest
to further lower the density of the polyethylenes produced with
non-metallocene single-site catalysts.
SUMMARY OF THE INVENTION
[0007] The invention is a gas phase polymerization process for
making ethylene polymers, particularly polymers that have reduced
densities. The process uses a single-site catalyst containing at
least one heteroatomic ligand selected from boraaryl, azaborolinyl,
pyridinyl, pyrrolyl, indolyl, indenoindolyl, carbazolyl, and
quinolinyl. The catalysts are immobilized onto a support. The
process comprises polymerizing in gas phase an ethylene that
contains from about 5 to about 15 mole % of a C.sub.3-C.sub.10
.alpha.-olefin in the presence of the supported catalyst.
[0008] We have surprisingly found that the gas phase process of the
invention significantly increases the incorporation of
.alpha.-olefin into polyethylene and lowers the polyethylene
density compared to slurry phase process. Using the gas phase
process of the invention, we have successfully prepared ethylene
polymers that have densities similar to those prepared with
metallocene single-site catalysts.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The invention is a gas phase polymerization process for
preparing a linear low density polyethylene that has a density
within the range from about 0.890 to 0.930 g/mL. The process
includes supporting a single-site catalyst. The single-site
catalysts suitable for use in the invention are organometallic
compounds having a heteroatomic ligand. Suitable metals are Group
3-10 transition or lanthanide metals. Preferably, the metal is
titanium, zirconium, or hafnium. Zirconium is particularly
preferred. Suitable heteroatomic ligands include substituted or
non-substituted boraaryl, azaborolinyl, pyridinyl, pyrrolyl,
indolyl, indenoindolyl, carbazolyl, and quinolinyl, and the
like.
[0010] In addition to a heteroatomic ligand, other ligands are
used. The total number of ligands satisfies the valence of the
transition metal. The ligands can be bridged or non-bridged. Other
suitable ligands include substituted or non-substituted
cyclopentadienyls, indenyls, fluorenyls, halides, C.sub.1-C.sub.10
alkyls, C.sub.6-C.sub.15 aryls, C.sub.7-C.sub.20 aralkyls,
dialkylamino, siloxy, alkoxy, and the like, and mixtures thereof.
Cyclopentadienyls and indenyls are preferred.
[0011] Methods for preparing heteroatomic ligand-containing
single-site catalysts are available in the literature. For example,
U.S. Pat. Nos. 5,554,775, 5,539,124, 5,756,611, and 5,637,660, the
teachings of which are herein incorporated by reference, teach how
to make single-site catalysts that contain boraaryl, pyrrolyl,
azaborolinyl, or quinolinyl ligands. Co-pending Appl. Ser. Nos.
09/417,510 and 09/826,545, the teachings of which are herein
incorporated by reference, teaches how to prepare indenoindolyl
ligand-containing single-site catalysts.
[0012] The single-site catalyst is immobilized on a support. The
support is preferably a porous material such as inorganic oxides
and chlorides, and organic polymer resins. Preferred inorganic
oxides include oxides of Group 2, 3, 4, 5, 13, or 14 elements.
Preferred supports include silica, alumina, silica-aluminas,
magnesias, titania, zirconia, magnesium chloride, and crosslinked
polystyrene. Preferably, the support has a surface area in the
range of about 10 to about 700 m.sup.2/g, a pore volume in the
range of about 0.1 to about 4.0 mL/g, an average particle size in
the range of about 10 to about 500 .mu.pm, and an average pore
diameter in the range of about 10 to about 1000 .ANG.. They are
preferably modified by heat treatment, chemical modification, or
both. For heat treatment, the support is preferably heated at a
temperature from about 100.degree. C. to about 800.degree. C.
Suitable chemical modifiers include organoaluminum, organosilicon,
organomagnesium, and organoboron compounds.
[0013] The single-site catalysts are supported using any known
techniques. For example, U.S. Pat. Nos. 5,747,404 and 5,744,417,
the teachings of which are incorporated herein by reference, teach
how to support single-site catalysts onto a polysiloxane or a
silylamine polymer. In one suitable method, the single-site
catalyst is dissolved in a solvent and combined with the support.
Evaporation of the solvent gives a supported catalyst.
[0014] The catalyst is used with an activator. Activators can be
either mixed with single-site catalysts and supported together on a
support or added separately to the polymerization. Suitable
activators include alumoxane compounds, alkyl aluminums, alkyl
aluminum halides, anionic compounds of boron or aluminum,
trialkylboron and triarylboron compounds, and the like. Examples
are methyl alumoxane, ethyl alumoxane, triethylaluminum,
trimethylaluminum, diethylaluminum chloride, lithium
tetrakis(pentafluorophenyl) borate, triphenylcarbenium
tetrakis(pentafluorophenyl) borate, lithium
tetrakis(pentafluorophenyl) aluminate, tris(pentafluorophenyl)
boron, tris(pentabromophenyl) boron, and the like. Other suitable
activators are known, for example, in U.S. Pat. Nos. 5,756,611,
5,064,802, and 5,599,761, and their teachings are incorporated
herein by reference.
[0015] Activators are generally used in an amount within the range
of about 0.01 to about 100,000, preferably from about 0.1 to about
1,000, and most preferably from about 0.5 to about 300, moles per
mole of the single-site catalyst.
[0016] The process of the invention includes polymerizing ethylene
in the gas phase over the supported catalyst. Methods and apparatus
for gas phase polymerization of ethylene with Ziegler catalysts are
well known, and they are suitable for use in the process of the
invention. For example, U.S. Pat. No. 5,859,157, the teachings of
which are herein incorporated by reference, teaches in detail a gas
phase polymerization of ethylene with a Ziegler catalyst.
[0017] In one suitable method, the polymerization is conducted
batchwise where ethylene is gradually fed into a reactor in which a
supported single-site catalyst is dispersed in-situ. In another
method, the polymerization is conducted continuously where both
ethylene and a dispersed catalyst are continuously fed into a
reactor, and polymer product is continuously withdrawn from the
reactor.
[0018] The supported catalyst is preferably dispersed into a
preformed polyethylene prior to polymerization. The dispersion
process is preferably performed in-situ, i.e., a preformed
polyethylene and the supported catalyst are added into the reactor
in which polymerization takes place. The preformed polyethylene and
the supported catalyst can be mixed by melting or by dissolving in
a hydrocarbon solvent. When a solvent is used, it is removed from
the catalyst before polymerization takes place. Preformed
polyethylene can be prepared by Ziegler or single-site catalysts.
The ratio of preformed polyethylene/supported single-site catalyst
is preferably from about 100/1 to about 1,000,000/1.
[0019] The polymerization is preferably conducted under high
pressure. The pressure is preferably in the range of about 150 to
about 15,000 psi, more preferably from about 500 to about 5,000
psi, and most preferably from about 1,000 to about 2,000 psi.
Generally, the higher the pressure, the more productive the
process. Polymerization temperature is preferably within the range
from 50.degree. C. to 250.degree. C., more preferably from
75.degree. C. to 150.degree. C.
[0020] Chain transfer agents such as hydrogen can be used to
control the molecular weight of the product. The proportion of
hydrogen used can be varied. For example, if less hydrogen is used,
a higher molecular weight polymer will be produced.
[0021] Ethylene polymers made by the process include polyethylene
and copolymers of ethylene with a C.sub.3-C.sub.10 .alpha.-olefin.
Suitable .alpha.-olefins include propylene, 1-butene, 1-hexene, and
1-octene, and the like, and mixture thereof. The molar ratio of
ethylene/.alpha.-olefin is within the range of about 85/15 to 95/5.
The invention produces ethylene polymers having a density within
the range from about 0.890 to about 0.930 g/mL, preferably 0.900 to
0.920 g/mL. The polymers are widely used in the industry for making
polyethylene films, sheets, molded parts, and other products.
[0022] The following examples merely illustrate the invention.
Those skilled in the art will recognize many variations that are
within the spirit of the invention and scope of the claims.
EXAMPLE 1
Gas Phase Polymerization With Quinolinoxy-Based Single-Site
Catalyst
[0023] Preparation Of (8-Quinolinoxy)TiCl.sub.3
[0024] 8-Quinolinol powder (1.45 g, 10 mmol) is added into a flask,
stirred, and purged with nitrogen at 25.degree. C. for 10 minutes.
Heptane (100 mL) is then added into the flask. The reactor contents
are stirred at 40.degree. C. with nitrogen flow for 20 minutes.
Titanium tetrachloride (TiCl4) solution in heptane (10 mL, 1.0
mole/L) is added dropwise into the flask over 30 minutes.
Additional heptane (100 mL) is then added to the reaction mixture
and stirred at 25.degree. C. with nitrogen flow for 4 hours.
Stirring is discontinued and the reaction mixture is settled
overnight. A light-red solid is formed and precipitated from the
solution. The solid is isolated by decanting the solvents.
[0025] Preparation Of (8-Quinolinoxy)Ti(CH.sub.2-Ph).sub.3
[0026] Ethylene dichloride (100 mL) is added into the solid
prepared above in a flask. The reactor contents are stirred, and
purged with nitrogen at 25.degree. C. for 30 minutes.
Benzylmagnesium chloride (Cl-Mg-CH.sub.2-Ph) solution in diethyl
ether (1.0 mole/L, 30 mL) is added dropwise into the flask over 7
hours with stirring at 25.degree. C. The solvent is removed by
distillation, yielding the catalyst complex
(8-Quinolinoxyl)Ti(CH.sub.2-Ph).sub.3.
[0027] Supporting The Catalyst Onto Silica
[0028] Silica (1.0 g, Silica 948, product of Davison Chemical
Company) is modified with hexamethyl disilazane (HMDS), aged for
three weeks, and calcined at 600.degree. C. for 4 hours. Heptane (5
mL), dibutyl magnisium (0.6 mmol) and the catalyst
(8-quinolinoxyl)Ti(CH.sub.2-Ph).sub.3 (0.2 mmol) are mixed and
added into the treated silica with stirring in a flask at
25.degree. C. for 30 minutes, resulting in a purple slurry. The
solvent is then removed at 43.degree. C. by nitrogen purge and the
solid then dried under vacuum for 15 minutes, yielding
silica-supported (8-quinolinoxyl)Ti(CH.sub.2-Ph).sub.3 catalyst
(1.1 g).
[0029] Gas Phase Polymerization of Ethylene
[0030] The polymerization is conducted in a batch reactor. The
supported catalyst prepared above (0.6 g), triethylaluminum (TEAL,
co-catalyst, 2.7 mL, 1.0 mole/L in heptane), and LLDPE (200 g) are
charged into a two-liter stainless steel reactor. The reactor
contents are heated to 75.degree. C. with agitation for 30 minutes
to disperse the catalyst. The reactor is pressured with ethylene
(100 psi), hydrogen (20 psi), and nitrogen (180 psi). 1-Hexene (6
mL) is gradually added into the reactor during the course of
polymerization. The polymerization is carried out at 75.degree. C.
for 4 hours, and then terminated by cooling the reactor contents to
25.degree. C. About 800 grams of polymer is produced, and 200 grams
of it is used for the next batch. The polyethylene of the fourth
batch has a density of 0.918 g/mL.
COMPARATIVE EXAMPLE 2
Slurry Phase Polymerization With Quinolinoxyl Based Singe-Site
Catalyst
[0031] The procedure of example 1 is repeated but the
polymerization is conducted in a slurry phase. The supported
catalyst prepared in Example 1 (0.6 g), TEAL (2.7 mL,1.0 mole/L in
heptane), and isobutane (200 mL) are charged into the reactor. The
reactor is pressured with ethylene (100 psi), hydrogen (20 psi),
and nitrogen (180 psi). 1-Hexene (6 mL) is gradually added into the
reactor during the course of polymerization. The polymerization is
carried out at 75.degree. C. for 4 hours. The polyethylene has a
density of 0.941 g/mL.
EXAMPLE 3
Gas Phase Polymerization With Borabenzene Based Single-Site
Catalyst
[0032] Preparation of Supported Catalyst
[0033] (1-Methylboratabenzene) (cyclopentadienyl) zirconium
dichloride (10.4 g) and trityl tetrakis (pentafluorophenyl) borate
(40.2 g) are dissolved in dry toluene (314 g). The solution is
added dropwise to the silica (363 g, treated as in Example 1) under
nitrogen protection with stirring at 25 C. for one hour. The
solvent is removed by nitrogen purge and then dried under vacuum at
40.degree. C., yielding the supported catalyst (385 g). The
supported catalyst is a free-flowing orange-yellow powder with 2.5%
by weight of the borabenzene catalyst complex and 9.7% by weight of
borate activator.
[0034] Gas Phase Polymerization
[0035] Polymerization is performed in a 2L stainless steel batch
reactor. The supported catalyst prepared above (0.535 g), TEAL (1.5
mL, 1.0 mole/L in heptane), and polyethylene (157 g, prepared by
slurry phase polymerization, having a density of 0.948 g/mL and
recurring unit of 1-hexene 4.3% by weight) are charged into the
reactor. The reactor contents are heated at 82 C. for 30 minutes to
disperse the catalyst. The reactor is then pressured with ethylene
(194 psi), hydrogen (17 psi) and nitrogen (165 psi). 1-Hexene (45
mL) is gradually added into the reactor during the course of
polymerization. The polymerization is carried out at 82.degree. C.
for 4 hours and then terminated by cooling the reaction mixture to
25.degree. C. About 440 grams of polymer is collected which has a
density of 0.932 g/mL and contains 7.9% by weight of recurring unit
of 1-hexene.
COMPARATIVE EXAMPLE 4
Slurry Phase Polymerization With Borabenzene Based Single-Site
Catalyst
[0036] The procedure of Example 3 is repeated but the
polymerization is conducted in a slurry phase in a 1 L stainless
steel reactor. The supported catalyst prepared in Example 3 (0.268
g), TEAL (0.5 mL,1.0 mole/L in heptane), and isobutane (350 mL) are
charged into the reactor. The reactor is pressured with ethylene
(194 psi), hydrogen (17 psi) and nitrogen (165 psi). 1-Hexene (21
mL) is gradually added into the reactor during the course of
polymerization. The polymerization is carried out at 82.degree. C.
for 4 hours. The polyethylene has a density of 0.941 g/mL.
EXAMPLE 5
Gas Phase Polymerization With Indenoindolyl Based Single-Site
Catalyst
[0037] The general procedure of Example 3 is followed.
Bis(5,8-dimethyl-5,10-dihydroideno[1,2-b]indolyl)zirconium
dichloride (see structure I) is prepared by reacting 0.5 equivalent
of zirconium tetrachloride with 1.0 equivalent of an indenoindolyl
monoanion. The monoanion is generated from
5,8-dimethyl-5,10-dihydroindeno[1,2-b]indole and 1.1 equivalent of
n-butyllithium. The indole compound is prepared by the method of
BUU-Hoi and Xuong (J. Chem. Soc. (1952) 2225) by reacting
p-tolylhydrazine with 1-indanone in the presence of sodium
acetate/ethanol, followed by reaction of the secondary amine
product with iodomethane in the presence of a basic catalyst (NaOH
or Na2CO3) to give the desired N-methylated product (I).
[0038] Bis(5,8-dimethyl-5,10-dihydroideno[1,2-b]indolyl)zirconium
dichloride is immobilized onto a silica. An ethylene that contains
up to about 15 mole % of 1-butene is polymerized in gas phase in
the presence of the supported catalyst and methalumoxane (MAO)
activator. The polyethylene produced is expected to have a density
within the range of about 0.890 to about 0.930 g/mL. 1
COMPARATIVE EXAMPLE 6
Bulk Polymerization With Indenoindolyl Based Single-Site
Catalyst
[0039] The general procedure of Example 5 is repeated but the
polymerization is performed in bulk with the non-supported
bis(5,8-dimethyl-5,10-dihydroideno[1,2-b]indolyl)zirconium
dichloride. The polyethylene is expected to have a density greater
than 0.930 g/mL.
* * * * *