U.S. patent application number 11/151097 was filed with the patent office on 2006-12-14 for catalyst compositions comprising small silica support materials and methods of use in polymerization reactions.
This patent application is currently assigned to UNIVATION TECHNOLOGIES, LLC. Invention is credited to Maria Angelica Apecetche, Michael David Awe, Phuong Anh Cao, Ryan Winston Impelman, Ann Marie Schoeb-Wolters.
Application Number | 20060281879 11/151097 |
Document ID | / |
Family ID | 36982668 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060281879 |
Kind Code |
A1 |
Apecetche; Maria Angelica ;
et al. |
December 14, 2006 |
Catalyst compositions comprising small silica support materials and
methods of use in polymerization reactions
Abstract
Improved catalyst compositions, and polymerization processes
using such improved catalyst compositions, are provided. An example
of an improved catalyst composition is a supported catalyst system
that includes at least one titanium compound, at least one
magnesium compound, at least one electron donor compound, at least
one activator compound, and at least one silica support material,
the at least one silica support material having a median particle
size in the range of from 20 to 50 microns with no more than 10% of
the particles having a size less than 10 microns and no more than
10% of the particles having a size greater than 50 microns.
Inventors: |
Apecetche; Maria Angelica;
(Bridgewater, NJ) ; Cao; Phuong Anh; (Old Bridge,
NJ) ; Awe; Michael David; (Langhorne, PA) ;
Schoeb-Wolters; Ann Marie; (Lebanon, NJ) ; Impelman;
Ryan Winston; (Houston, TX) |
Correspondence
Address: |
Kevin M. Faulkner;Univation Technologies, LLC
Suite 1950
5555 San Felipe
Houston
TX
77056-2746
US
|
Assignee: |
UNIVATION TECHNOLOGIES, LLC
HOUSTON
TX
|
Family ID: |
36982668 |
Appl. No.: |
11/151097 |
Filed: |
June 13, 2005 |
Current U.S.
Class: |
526/123.1 ;
502/103; 502/115; 502/118; 526/124.3 |
Current CPC
Class: |
C08F 210/16 20130101;
C08F 4/6543 20130101; C08F 4/025 20130101; C08F 10/00 20130101;
C08F 210/16 20130101; C08F 210/16 20130101; C08F 2/34 20130101;
C08F 2500/18 20130101; C08F 4/651 20130101; C08F 210/14 20130101;
C08F 2500/12 20130101; C08F 10/00 20130101; C08F 2/34 20130101;
C08F 210/16 20130101; C08F 210/16 20130101; C08F 210/16
20130101 |
Class at
Publication: |
526/123.1 ;
526/124.3; 502/103; 502/115; 502/118 |
International
Class: |
C08F 4/44 20060101
C08F004/44; B01J 31/00 20060101 B01J031/00 |
Claims
1. A process for making polyolefins, comprising contacting, in a
reactor, ethylene and at least one comonomer selected from the
group consisting of C3 to C8 alpha olefin in the presence of a
supported catalyst system comprising at least one titanium
compound, at least one magnesium compound, at least one electron
donor compound, at least one activator compound, and at least one
silica support material, the at least one silica support material
having a median particle size in the range of from 20 to 50 microns
with no more than 10% of the particles having a size less than 10
microns and no more than 10% of the particles having a size greater
than 50 microns.
2. The process of claim 1, wherein the at least one magnesium
compound has the formula MgX.sub.2, wherein X is selected from the
group consisting of Cl, Br, I or mixtures thereof
3. The process of claim 2, wherein the at least one magnesium
compound is selected from the group consisting of: MgCl.sub.2,
MgBr.sub.2 and MgI.sub.2.
4. The process of claim 1, wherein the at least one titanium
compound has the formula Ti(OR).sub.aX.sub.b, wherein R is selected
from the group consisting of: a C.sub.1 to C.sub.14 aliphatic
hydrocarbon radical, a C.sub.1 to C.sub.14 aromatic hydrocarbon
radical, and COR' where R' is a C.sub.1 to C.sub.14 aliphatic or
aromatic hydrocarbon radical; X is selected from the group
consisting of Cl, Br, I and mixtures thereof; a is selected from
the group consisting of 0, 1 and 2; b is 1 to 4 inclusive; and
a+b=3 or 4.
5. The process of claim 1, wherein the at least one titanium
compound is selected from the group consisting of: TiCl.sub.3,
TiCl.sub.4, Ti(OCH.sub.3)Cl.sub.3, Ti(OC.sub.6H.sub.5)Cl.sub.3,
Ti(OCOCH.sub.3)Cl.sub.3 and Ti(OCOC.sub.6H.sub.5)Cl.sub.3.
6. The process of claim 1, wherein the at least one silica support
material has a median particle size in the range of from 20 to 35
microns.
7. The process of claim 1, wherein the at least one silica support
material has a median particle size in the range of from 20 to 30
microns.
8. The process of claim 1, wherein the at least one silica support
material has a particle size distribution in which no more than 10%
of the particles have a size below 12 microns, and no more than 8%
of the particles have a size above 50 microns.
9. The process of claim 1, wherein the at least one silica support
material has a surface area of at least 200 square meters per
gram.
10. The process of claim 1, wherein the at least one silica support
material has an average pore volume of at least 1.4 ml/gram.
11. A supported catalyst system comprising at least one titanium
compound, at least one magnesium compound, at least one electron
donor compound, at least one activator compound, and at least one
silica support material, the at least one silica support material
having a median particle size in the range of from 20 to 50 microns
with no more than 10% of the particles having a size less than 10
microns and no more than 10% of the particles having a size greater
than 50 microns.
12. The supported catalyst system of claim 11, wherein the at least
one magnesium compound has the formula MgX.sub.2, wherein X is
selected from the group consisting of Cl, Br, I or mixtures
thereof
13. The supported catalyst system of claim 11, wherein the at least
one magnesium compound is present in the catalyst system in an
amount in the range of from 1.5 to 7 moles of magnesium compound
per mole of titanium compound.
14. The supported catalyst system of claim 11, wherein the at least
one titanium compound has the formula Ti(OR).sub.aX.sub.b, wherein
R is selected from the group consisting of: a C.sub.1 to C.sub.14
aliphatic hydrocarbon radical, a C.sub.1 to C.sub.14 aromatic
hydrocarbon radical, and COR' where R' is a C.sub.1 to C.sub.14
aliphatic or aromatic hydrocarbon radical; X is selected from the
group consisting of Cl, Br, I and mixtures thereof; a is selected
from the group consisting of 0, 1 and 2; b is 1 to 4 inclusive; and
a+b=3 or 4.
15. The supported catalyst system of claim 14, wherein the at least
one titanium compound is selected from the group consisting of:
TiCl.sub.3, TiCl.sub.4, Ti(OCH.sub.3)Cl.sub.3,
Ti(OC.sub.6H.sub.5)Cl.sub.3, Ti(OCOCH.sub.3)Cl.sub.3 and
Ti(OCOC.sub.6H.sub.5)Cl.sub.3.
16. The supported catalyst system of claim 11, wherein the at least
one silica support material has a median particle size in the range
of from 20 to 35 microns.
17. The supported catalyst system of claim 11, wherein the at least
one silica support material has a median particle size in the range
of from 20 to 30 microns.
18. The supported catalyst system of claim 11, wherein the at least
one silica support material has a particle size distribution in
which no more than 10% of the particles have a size below 12
microns, and no more than 8% of the particles have a size above 50
microns.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polymerization process
using improved catalyst compositions. Specifically, the catalyst
compositions of the present invention relate to a Ziegler-Natta
type catalyst compound that includes a small silica support
material, and demonstrate improved productivity.
BACKGROUND OF THE INVENTION
[0002] Advances in polymerization and catalysis have resulted in
the ability to produce many new polymers having improved physical
and chemical properties useful in a wide variety of superior
products and applications. With the development of new catalysts,
the choice of polymerization (solution, slurry, high pressure or
gas phase) for producing a particular polymer have been greatly
expanded. Also, advances in polymerization technology have provided
more efficient, highly productive and economically enhanced
processes.
[0003] As with any new technology field, particularly in the
polyolefins industry, a small savings in cost often determines
whether a commercial endeavor is even feasible. The industry has
been extremely focused on developing new and improved catalyst
systems. Some have focused on designing the catalyst systems to
produce new polymers, others on improved operability, and many more
on improving catalyst productivity. The productivity of a catalyst,
that is, the amount of polymer produced per gram of the catalyst,
usually is the key economic factor that can make or break a new
commercial development in the polyolefin industry.
[0004] Ziegler-Natta catalyst systems are utilized extensively in
commercial processes that produce high density and low-density
polyethylenes in a variety of molecular weights. Production rates
in certain gas phase reactors may be limited in their ability to
discharge from the reactor the polymer particles that are produced
during the reaction. In certain of such cases, an increase in the
bulk density of the polymer particles may increase the production
rate of the reactor. Generally, Ziegler-Natta catalysts that have
increasing activity and productivity, and that are used in gas
phase operations. may tend to produce polymer products that have
decreasing bulk density. If a reactor is limited in its ability to
discharge the polymer product, the use of a high activity catalyst
may result in a decrease in the bulk density of the polymer
product.
[0005] Considering the discussion above, a need exists for higher
productivity catalyst systems capable of providing the efficiencies
necessary for implementing commercial polyolefin processes. Thus,
it would be highly advantageous to have a polymerization process
and catalyst system capable of producing polyolefins with improved
catalyst productivities and reactor performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] A more complete understanding of the present disclosure and
advantages thereof may be acquired by referring to the following
description taken in conjunction with the accompanying drawings,
wherein:
[0007] FIG. 1 is an exemplary process flow diagram for an exemplary
reaction system with which an exemplary catalyst system of the
present invention may be employed.
[0008] FIG. 2 is an exemplary silica dehydration profile used in
certain exemplary embodiments of the present invention.
[0009] FIG. 3 illustrates particle size distributions for a sample
of Davison 955 silica and a sample of Ineos ES757 silica.
[0010] FIG. 4 illustrates particle size distributions for a sample
of Davison 955 silica that was screened through 325 mesh.
[0011] FIG. 5 is a graphical illustration of ethylene flow versus
reaction time for certain exemplary polymerization processes
employing exemplary catalyst systems that used a variety of
exemplary support materials.
[0012] FIG. 6 is a graphical illustration of the results of a
statistical analysis of the activity demonstrated by exemplary
laboratory-prepared catalyst precursors.
[0013] FIG. 7 is a graphical illustration of the relationship
between catalyst system productivity and polymer product bulk
density for certain exemplary catalyst systems.
[0014] FIG. 8 is a graphical illustration of the relationship
between catalyst system productivity and polymer product bulk
density for certain exemplary catalyst systems.
[0015] While the present invention is susceptible to various
modifications and alternative forms, specific exemplary embodiments
thereof have been shown by way of example in the drawings and are
herein described in detail. It should be understood, however, that
the description herein of specific embodiments is not intended to
limit the invention to the particular forms disclosed, but on the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the
invention as defined by the appended claims.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0016] It now has been found that polymers (e.g., ethylene
homopolymers and copolymers) readily can be produced with desirable
physical properties and catalyst system productivities in a low
pressure gas phase fluid bed reaction process in the presence of a
specific high productivity catalyst that is impregnated on a porous
particulate silica having a particle size in a particular range, as
is also detailed below.
High Activity Catalyst
[0017] The compounds used to form the catalysts of the present
invention include at least one titanium compound, at least one
magnesium compound, at least one electron donor compound, at least
one activator compound and at least one silica material, exemplary
embodiments of which are illustrated below.
[0018] Generally, the titanium compound has the formula
Ti(OR).sub.aX.sub.b wherein [0019] R is a C.sub.1 to C.sub.14
aliphatic or aromatic hydrocarbon radical, or COR' where R' is a
C.sub.1 to C.sub.14 aliphatic or aromatic hydrocarbon radical;
[0020] X is selected from the group consisting of Cl, Br, I or a
mixture thereof; [0021] a is 0, 1 or 2; [0022] b is 1 to 4
inclusive; and [0023] a+b=3 or 4.
[0024] The titanium compounds individually may be present in the
catalysts of the present invention, or the titanium compounds may
be present in combinations thereof. A nonlimiting list of suitable
titanium compounds includes TiCl.sub.3, TiCl.sub.4,
Ti(OCH.sub.3)Cl.sub.3, Ti(OC.sub.6H.sub.5)Cl.sub.3,
Ti(OCOCH.sub.3)Cl.sub.3 and Ti(OCOC.sub.6H.sub.5)Cl.sub.3.
[0025] Generally, the magnesium compound has the formula MgX.sub.2
wherein [0026] X is selected from the group consisting of Cl, Br, I
or mixtures thereof.
[0027] Such magnesium compounds may be present individually in the
catalysts of the present invention, or the magnesium compounds may
be present in combinations thereof. A nonlimiting list of suitable
magnesium compounds includes MgCl.sub.2, MgBr.sub.2 and MgI.sub.2.
In certain exemplary embodiments of the present invention, the
magnesium compound may be anhydrous MgCl.sub.2. Generally, the
magnesium compound may be present in the catalysts of the present
invention in an amount in the range of from 0.5 to 56 moles of
magnesium compound per mole of titanium compound. In certain
exemplary embodiments of the present invention, the magnesium
compound may be present in the catalysts of the present invention
in an amount in the range of from 1.5 to 11 moles of magnesium
compound per mole of titanium compound. In certain exemplary
embodiments of the present invention, the magnesium compound may be
present in the catalysts of the present invention in an amount in
the range of from 1.5 to 7 moles of magnesium compound per mole of
titanium compound. Generally, the titanium compound and the
magnesium compound may be used in a form that will facilitate their
dissolution in the electron donor compound, as described herein
below.
[0028] The electron donor compound generally may be any organic
compound that is liquid at 25.degree. C., and that may be capable
of dissolving both the titanium compound and the magnesium
compound. In certain embodiments of the present invention, the
electron donor compound may be a Lewis base. A nonlimiting list of
suitable electron donor compounds includes such compounds as alkyl
esters of aliphatic and aromatic carboxylic acids, aliphatic
ethers, cyclic ethers and aliphatic ketones. In certain
embodiments, suitable electron donor compounds may be alkyl esters
of C.sub.1 to C.sub.4 saturated aliphatic carboxylic acids; alkyl
esters Of C.sub.7 to C.sub.8 aromatic carboxylic acids; C.sub.2 to
C.sub.8, and preferably C.sub.3 to C.sub.4, aliphatic ethers;
C.sub.3 to C.sub.4 cyclic ethers, and, in certain embodiments,
C.sub.4 cyclic mono- or di-ethers; C.sub.3 to C.sub.6, and, in
certain embodiments, C.sub.3 to C.sub.4, aliphatic ketones. In
certain exemplary embodiments, the electron donor compound may be
methyl formate, ethyl acetate, butyl acetate, ethyl ether, hexyl
ether, tetrahydrofuran, dioxane, acetone or methyl isobutyl ketone,
among others.
[0029] The electron donor compounds may be present individually in
the catalysts of the present invention, or they may be present in
combinations thereof. Generally, the electron donor compound may be
present in the range of from 2 to 85 moles of the electron donor
compound per mole of the titanium compound. In certain embodiments,
the electron donor compound may be present in the catalysts of the
present invention in an amount in the range of from 3 to 10 moles
of the electron donor compound per mole of the titanium
compound.
[0030] The activator compound generally has the formula
Al(R'').sub.cX'.sub.dH.sub.e wherein [0031] X' is Cl, or OR''';
[0032] R'' and R''' are the same or different, and are C.sub.1 to
C.sub.14 saturated hydrocarbon radicals; [0033] d is 0 to 1.5;
[0034] e is 1 or 0; [0035] and c+d+e=3.
[0036] Such activator compounds may be present individually in the
catalysts of the present invention, or they may be present in
combinations thereof. A nonlimiting list of suitable activator
compounds includes Al(C.sub.2H.sub.5).sub.3,
Al(C.sub.2H.sub.5).sub.2Cl, Al(i-C.sub.4H.sub.9).sub.3,
Al.sub.2(C.sub.2H.sub.5).sub.3Cl.sub.3,
Al(i-C.sub.4H.sub.9).sub.2H, Al(C.sub.6H.sub.13).sub.3,
Al(C.sub.8H.sub.17).sub.3, Al(C.sub.2H.sub.5).sub.2H and
Al(C.sub.2H.sub.5).sub.2(OC.sub.2H.sub.5).
[0037] Generally, the activator compound may be present in the
catalysts of the present invention in an amount in the range of
from 10 to 400 moles of activator compound per mole of the titanium
compound, and in certain embodiments may be present in the range of
from 15 to 60 moles of the activator compound per mole of the
titanium compound, and in certain embodiments may be present in the
range of from 2 to 7 moles of the activator compound per mole of
the titanium compound.
[0038] The silica support that may be employed in the catalysts of
the present invention generally has a particle size distribution
within the range of from 2 microns to 100 microns, and a median
particle size in the range of from 20 microns to 50 microns. In
certain exemplary embodiments, the silica support has a particle
size distribution within the range of from 2 microns to 80 microns.
In certain exemplary embodiments, the silica support has a median
particle size in the range of from 20 microns to 35 microns, and in
the range of from 20 to 30 microns in certain exemplary
embodiments. In certain exemplary embodiments, the silica support
has a particle size distribution in which no more than 10% of the
particles have a size below 10 microns, and no more than 10% of the
particles have a size greater than 50 microns. In certain exemplary
embodiments, the silica support has a particle size distribution in
which no more than 10% of the particles have a size below 12
microns, and no more than 8% of the particles have a size greater
than 50 microns. As the size of the silica support decreases, the
productivity of the supported catalyst generally increases, as does
the FAR value of film formed from resin produced by the supported
catalyst. In certain exemplary embodiments, this may be accompanied
by an increase in the bulk density and a decrease in the average
particle size of such resin. Accordingly, the silica supports used
in the improved catalysts of the present invention may facilitate,
inter alia, greater productivity from the improved catalysts as
well as the production of polymers having greater bulk density. In
certain exemplary embodiments, the improved catalysts of the
present invention comprising these silica supports may have a
productivity (as based on a mass balance) that is at least 3,000
pounds polymer per pound of catalyst per hour; and that is at least
4,500 pounds polymer per pound of catalyst per hour in certain
exemplary embodiments, and that is at least 6,000 pounds polymer
per pound of catalyst per hour in certain exemplary embodiments,
and that is at least 7,000 pounds polymer per pound of catalyst per
hour in certain exemplary embodiments; and that is at least 9,000
pounds polymer per pound of catalyst per hour in certain exemplary
embodiments. Certain exemplary embodiments of the catalysts of the
present invention may have even greater productivities. In certain
exemplary embodiments, the polymers produced from the processes of
the present invention that employ improved catalysts that include
these silica supports may have a settled bulk density of at least
21.5 pound per cubic foot in certain exemplary embodiments; and at
least 22.5 pound per cubic foot in certain exemplary embodiments,
and at least 23.5 pound per cubic foot in certain exemplary
embodiments; and at least 24.0 pound per cubic foot in certain
exemplary embodiments. Certain exemplary embodiments of the
polymers produced from the processes of the present invention that
employ improved catalysts that include these silica supports may
have even greater settled bulk densities.
[0039] In certain exemplary embodiments, the silica support
employed in the present invention has an average pore diameter of
greater than 100 Angstrom units, and in certain exemplary
embodiments, greater than 150 Angstrom units. It also may be
desirable for such silica support to have a surface area of
.gtoreq.200 square meters per gram, and in certain exemplary
embodiments, .gtoreq.250 square meters per gram. In certain
exemplary embodiments, the average pore volume of such silica
support ranges from 1.4 ml/gram to 1.8 ml/gram.
[0040] The silica support generally should be dry, that is, free of
absorbed water. Drying of the silica support generally is performed
by heating it at a temperature of .gtoreq.600.degree. C.
Catalyst Preparation: Formation of Precursor
[0041] The improved catalysts of the present invention may be
prepared by first preparing a precursor composition from the
titanium compound, the magnesium compound, and the electron donor
compound, as described below, then impregnating the silica support
with the precursor composition, and then treating the impregnated
precursor composition with an activator compound as described
below.
[0042] Generally, the precursor composition may be formed by
dissolving the titanium compound and the magnesium compound in the
electron donor compound at a temperature in the range of from
20.degree. C. up to the boiling point of the electron donor
compound. The titanium compound can be added to the electron donor
compound before, or after, the addition of the magnesium compound,
or concurrent therewith. The dissolution of the titanium compound
and the magnesium compound may be facilitated by stirring, and in
some instances by refluxing, these two compounds in the electron
donor compound. After the titanium compound and the magnesium
compound are dissolved, the precursor composition may be isolated
by crystallization or by precipitation with a C.sub.5 to C.sub.8
aliphatic or aromatic hydrocarbon such as hexane, isopentane or
benzene. The crystallized or precipitated precursor composition may
be isolated, generally in the form of fine, free-flowing particles
having an average particle size in the range of from 10 to 100
microns.
[0043] When prepared according to the procedure above, the
precursor composition has the formula:
Mg.sub.mTi.sub.1(OR).sub.nX.sub.p[ED].sub.q wherein: [0044] ED is
the electron donor compound; [0045] m is .gtoreq.0.5 to .ltoreq.56,
and, in certain exemplary embodiments, .gtoreq.1.5 to .ltoreq.11;
[0046] n is 0, 1 or 2; [0047] p is .gtoreq.2 to .ltoreq.116, and,
in certain exemplary embodiments, .gtoreq.6 to .ltoreq.14; [0048] q
is .gtoreq.2 to .ltoreq.85, and, in certain exemplary embodiments,
.gtoreq.3 to .ltoreq.10; [0049] R is a C.sub.1 to C.sub.14
aliphatic or aromatic hydrocarbon radical, or COR' wherein R' is a
C.sub.1 to C.sub.14 aliphatic or aromatic hydrocarbon radical;
[0050] X is selected from the group consisting of Cl, Br, I or
mixtures thereof; and [0051] the subscript for the element titanium
(Ti) is the arabic numeral one. Catalyst Preparation: Impregnation
of Precursor in Support
[0052] The precursor composition then may be impregnated, in a
weight ratio of about 0.003 to 1, and, in certain exemplary
embodiments, about 0.1 to 0.33, parts of the precursor composition
into one part by weight of the carrier material.
[0053] Before being impregnated, the silica support is dehydrated
at 600 .degree. C., and also is treated with an aluminum alkyl
compound (e.g., "TEAL"). Dehydrated silica supports that have been
treated with TEAL may be referred to herein as TEAL-on-silica, or
"TOS." The impregnation of the dehydrated, activated silica support
(e.g., the TOS) with the precursor composition may be accomplished
by dissolving the precursor composition in the electron donor
compound, and by then admixing the dehydrated, activated silica
support with the precursor composition to impregnate the
dehydrated, activated silica support. The electron donor compound
then may be removed by drying at temperatures of .ltoreq.60.degree.
C.
[0054] The silica support also may be impregnated with the
precursor composition by adding the silica support to a solution of
the chemical raw materials used to form the precursor composition
in the electron donor compound, without isolating the precursor
composition from such solution. The excess electron donor compound
then may be removed by drying, or by washing and drying at
temperatures of .ltoreq.60.degree. C.
Activation of Precursor Composition
[0055] Generally, the precursor composition will be fully or
completely activated, e.g., it will be treated with sufficient
activator compound to transform the Ti atoms in the precursor
composition to an active state. Suitable activators include, but
are not limited to, tri-n-hexyl aluminum, triethyl aluminum,
diethyl aluminum chloride, trimethyl aluminum, dimethyl aluminum
chloride, methyl aluminum dichloride triisobutyl aluminum,
tri-n-butyl aluminum, diisobutyl aluminum chloride, isobutyl
aluminum dichloride, (C.sub.2H.sub.5)AlCl.sub.2,
(C.sub.2H.sub.5O)AlCl.sub.2, (C.sub.6H.sub.5)AlCl.sub.2,
(C.sub.6H.sub.5O)AlCl.sub.2, (C.sub.6H.sub.12O)AlCl.sub.2 and the
corresponding bromine and iodine compounds).
[0056] The precursor composition first may be partially activated
outside the polymerization reactor with enough activator compound
so as to provide a partially activated precursor composition having
an activator compound/Ti molar ratio of >0 to <10:1, and, in
certain exemplary embodiments, from 4 to 8:1. This partial
activation reaction may be carried out in a hydrocarbon solvent
slurry followed by drying of the resulting mixture (to remove the
solvent), at temperatures between 20 to 80.degree. C., and, in
certain exemplary embodiments, between 50 to 70.degree. C. The
solvent for the activator(s) should be non-polar and capable of
dissolving the activator(s), but not the precursor composition.
Among the solvents which can be employed to dissolve the
activator(s) are hydrocarbon solvents, such as isopentane, hexane,
heptane, toluene, xylene, naptha and aliphatic mineral oils such as
but not limited to Kaydol.TM., Hydrobrite.TM. 550 and the like.
[0057] The resulting product is a free-flowing solid particulate
material that readily may be fed to the polymerization reactor. The
partially activated and impregnated precursor composition may be
fed to the polymerization reactor where the activation may be
completed with additional activator compound, which may be the same
or a different compound.
[0058] In certain exemplary embodiments, the additional activator
compound and the partially activated impregnated precursor
composition optionally may be fed to the reactor through separate
feed lines. In certain of such embodiments, the additional
activator compound may be sprayed into the reactor in either
undiluted form (e.g., "neat"), or in the form of a solution of the
additional activator compound in a hydrocarbon solvent (e.g.,
isopentane, hexane, or mineral oil). Such solution may contain
about 2 to 30 weight percent of the activator compound. In certain
of such embodiments, the additional activator compound may be added
to the reactor in such amounts as to provide, along with the
amounts of activator compound and titanium compound fed with the
partially activated and impregnated precursor composition, a total
Al/Ti molar ratio in the reactor of .gtoreq.10 to 400, and, in
certain exemplary embodiments, from 15 to 60. The additional
amounts of activator compound added to the reactor may react with,
and complete the activation of, the titanium compound in the
reactor.
[0059] In a continuous gas phase process, such as the fluid bed
process disclosed below, discrete portions of the partially
activated precursor composition impregnated on the silica support
are continuously fed to the reactor, along with discrete portions
of additional activator compound, during the continuing
polymerization process, and may replace active catalyst sites that
are expended during the course of the reaction.
The Polymerization Reaction
[0060] The polymerization reaction may be conducted by contacting a
stream of monomer(s), in a gas phase process (such as in the fluid
bed process described below), and substantially in the absence of
catalyst poisons (e.g., moisture, oxygen, CO, CO.sub.2, and
acetylene) with a catalytically effective amount of the completely
activated precursor composition at a temperature and at a pressure
sufficient to initiate the polymerization reaction.
[0061] In order to achieve the desired density ranges in certain
exemplary copolymers produced by the present invention, it may be
well to copolymerize enough of the .gtoreq.C.sub.3 comonomers with
ethylene to achieve a level of >0 to 10 mol percent of the
C.sub.3 to C.sub.8 comonomer in the copolymer. The amount of
comonomer that may be used to achieve this result will depend on
the particular comonomer(s) employed.
[0062] Table 1 below provides a listing of the amounts, in moles,
of various comonomers that may be copolymerized with ethylene in
order to provide polymers having a desired density range (e.g.,
within the range of from 0.91 to 0.97) at any given melt index.
Table 1 also indicates the relative molar concentration, of such
comonomers to ethylene, which may be present in the recycled gas
stream of monomers under reaction equilibrium conditions in the
reactor. TABLE-US-00001 TABLE 1 Gas Stream Comonomer/Ethylene molar
Comonomer Mole % in copolymer ratio propylene >0 to 10 >0 to
0.9 butene-1 >0 to 7.0 >0 to 0.7 pentene-1 >0 to 6.0 >0
to 0.45 hexene-1 >0 to 5.0 >0 to 0.4 octene-1 >0 to 4.5
>0 to 0.35
[0063] Referring now to FIG. 1, illustrated therein is an exemplary
fluidized bed reaction system that may be used in the practice of
the processes of the present invention. With reference thereto, the
reactor 1 generally includes a reaction zone 2 and a
velocity-reduction zone 3.
[0064] The reaction zone 2 includes a bed of growing polymer
particles, formed polymer particles and a minor amount of catalyst
particles fluidized by the continuous flow of gaseous components in
the form of make-up feed and recycle gas through the reaction zone
2. To maintain a viable fluidized bed, the mass gas flow rate
through the bed generally will be above the minimum flow required
for fluidization, and, in certain exemplary embodiments, may be in
the range of from 1.5 to 10 times G.sub.mf and, in certain
exemplary embodiments, in the range of from 3 to 6 times G.sub.mf.
G.sub.mf is used in the accepted form as the abbreviation for the
minimum mass gas flow required to achieve fluidization, as may be
set forth further in, for example, C. Y. Wen and Y. H. Yu,
"Mechanics of Fluidization," Chemical Engineering Progress
Symposium Series, Vol. 62, p. 100-111 (1966).
[0065] Generally, the bed will contain particles that may prevent
the formation of localized "hot spots" and that may entrap and
distribute the particulate catalyst throughout the reaction zone 2.
On start up, the reactor 1 usually may be charged with a base of
particulate polymer particles before gas flow is initiated. Such
particles may be identical in nature to the polymer to be formed,
or may be different therefrom. When different, the particulate
polymer particles provided as a base may be withdrawn with the
desired formed polymer particles as the first product. Eventually,
a fluidized bed of the desired polymer particles supplants the
start-up bed.
[0066] In certain exemplary embodiments, the partially activated
precursor composition (impregnated on the SiO.sub.2 support) used
in the fluidized bed may be stored for service in a reservoir 4
under a blanket of a gas that is inert to the stored material, such
as nitrogen or argon.
[0067] Fluidization is achieved by a high rate of gas recycle to
and through the bed, typically in the order of about 50 times the
rate of feed of make-up gas. The fluidized bed has the general
appearance of a dense mass of viable particles in possible
free-vortex flow as created by the percolation of gas through the
bed. The pressure drop through the bed may be equal to, or slightly
greater than, the mass of the bed divided by the cross-sectional
area, and thus may depend on the geometry of the reactor 1.
[0068] Make-up gas may be fed to the bed at a rate equal to the
rate at which particulate polymer product is withdrawn. The
composition of the make-up gas may be determined by a gas analyzer
5 positioned above the bed. The gas analyzer 5 may determine the
composition of the gas being recycled, and the composition of the
make-up gas may be adjusted accordingly to maintain an essentially
steady state gaseous composition within the reaction zone 2.
[0069] To facilitate complete fluidization, the recycle gas and,
where desired, part of the make-up gas, may be returned over gas
recycle line 6 to the reactor 1 at point 7 below the bed. A gas
distribution plate 8 may be located at this point above the point
of return to aid in fluidizing the bed.
[0070] The portion of the gas stream that does not react in the bed
constitutes the recycle gas which is removed from the reaction zone
2, preferably by passing it into a velocity reduction zone 3 above
the bed where entrained particles may be given an opportunity to
drop back into the bed.
[0071] The recycle gas then may be compressed in a compressor 9 and
then passed through a heat exchanger 10 wherein the heat of
reaction may be removed from it before it is returned to the bed.
The temperature of the bed is controlled at an essentially constant
temperature under steady state conditions by constantly removing
heat of reaction. No noticeable temperature gradient exists within
the upper portion of the bed. A temperature gradient will exist in
the bottom of the bed in a layer of about 6 to 12 inches, between
the temperature of the inlet gas and the temperature of the
remainder of the bed. The recycle gas is then returned to the
reactor 1 at its base 7 and to the fluidized bed through
distribution plate 8. The compressor 9 also can be placed
downstream of the heat exchanger 10.
[0072] The distribution plate 8 may play an important role in the
operation of the reactor 1. The fluidized bed contains growing and
formed particulate polymer particles as well as catalyst particles.
As the polymer particles are hot and possibly active, it may be
well to prevent them from settling, for if a quiescent mass is
allowed to exist, any active catalyst contained therein may
continue to react and cause fusion. Diffusing recycle gas through
the bed at a rate sufficient to maintain fluidization throughout
the bed is, therefore, beneficial. The distribution plate 8 serves
this purpose, and may be a screen, slotted plate, perforated plate,
a plate of the bubble cap type and the like. The elements of the
distribution plate 8 all may be stationary, or the distribution
plate 8 may be of the mobile type disclosed in U.S. Pat. No.
3,298,792. Whatever its design, it generally will diffuse the
recycle gas through the particles at the base of the bed to keep
the bed in a fluidized condition, and also serve to support a
quiescent bed of resin particles when the reactor 1 is not in
operation. The mobile elements of the distribution plate 8 may be
used to dislodge any polymer particles entrapped in or on the
distribution plate 8.
[0073] Hydrogen may be used as a chain transfer agent in the
polymerization reaction of the present invention. The ratio of
hydrogen/ethylene monomer employed generally will vary between 0 to
2.0 moles of hydrogen per mole of the ethylene monomer in the gas
stream.
[0074] Any gas inert to the catalyst and reactants can also be
present in the gas stream. In certain exemplary embodiments, the
activator compound may be added to the reaction system downstream
from heat exchanger 10. Thus, the activator compound may be fed
into the gas recycle system from dispenser 11 through line 12.
[0075] Compounds of the formula Zn(R.sub.a)(R.sub.b), wherein
R.sub.a and R.sub.b are the same or different C.sub.1 to C.sub.14
aliphatic or aromatic hydrocarbon radicals, may be used (in
conjunction with hydrogen), with the catalysts of the present
invention, as molecular weight control or chain transfer agents,
e.g., to increase the melt index values of the copolymers that are
produced. From 0 to 100, and, in certain embodiments, from 20 to 30
moles of the Zn compound (as Zn) would be used in the gas stream in
the reactor 1 per mol of titanium compound (as Ti) in the reactor
1. The zinc compound would be introduced into the reactor 1,
preferably in the form of a dilute solution (2 to 30 weight
percent) in a hydrocarbon solvent or absorbed on a solid diluent
material, such as silica, in amounts of 10 to 50 weight percent.
These compositions tend to be pyrophoric. The zinc compound may be
added alone, or with any additional portions of the activator
compound that are to be added to the reactor 1, from a feeder (not
shown) which could be positioned adjacent dispenser 11.
[0076] Generally, the fluid bed reactor 1 will be operated at a
temperature below the sintering temperature of the polymer
particles to ensure that sintering will not occur. For the
production of the polymers in the process of the present invention,
an operating temperature of 30 to 150.degree. C. generally may be
employed. In certain exemplary embodiments, temperatures of 70 to
95.degree. C. may be used to prepare products having a density in
the range of from 0.91 to 0.92, and temperatures in the range of
from 80 to 100.degree. C. may be used to prepare products having a
density in the range of >0.92 to 0.94.
[0077] The fluid bed reactor 1 is operated at pressures of up to
1000 psi, and in certain exemplary embodiments may be operated at a
pressure of from 150 to 400 psi, with operation at the higher
pressures in such ranges favoring heat transfer, because, inter
alia, an increase in pressure increases the unit volume heat
capacity of the gas.
[0078] The partially activated and SiO.sub.2 supported precursor
composition is injected into the bed at a rate equal to its
consumption at a point 13 that is above the distribution plate 8.
In certain exemplary embodiments, the catalyst may be injected at a
point in the bed where good mixing of polymer particles occurs. The
injection of the catalyst at a point above the distribution plate 8
may be beneficial because, inter alia, the catalysts used in the
practice of the invention are highly active, such that injection of
the catalyst into the area below the distribution plate 8 may cause
polymerization to begin there and eventually cause plugging of the
distribution plate 8. Injection into the viable bed, instead, aids
in distributing the catalyst throughout the bed and tends to
preclude the formation of localized spots of high catalyst
concentration which may result in the formation of "hot spots."
Injection of the catalyst into the reactor 1 above the bed may
result in excessive catalyst carryover into the recycle line where
polymerization may begin and plugging of the line and heat
exchanger 10 eventually may occur.
[0079] A gas that is inert to the catalyst, such as nitrogen or
argon, may be used to carry the partially reduced precursor
composition, and any additional activator compound or non-gaseous
chain transfer agent that is used, into the bed.
[0080] The production rate of the bed is controlled by the rate of
catalyst injection. The production rate may be increased by simply
increasing the rate of catalyst injection, and may be decreased by
reducing the rate of catalyst injection.
[0081] Because any change in the rate of catalyst injection will
change the rate of generation of the heat of reaction, the
temperature of the recycle gas entering the reactor 1 may be
adjusted upwards and downwards to accommodate the change in rate of
heat generation. This facilitates the maintenance of an essentially
constant temperature in the bed. Complete instrumentation of both
the fluidized bed and the recycle gas cooling system may be useful
to facilitate, inter alia, the detection of any temperature change
in the bed so as to enable the operator to make a suitable
adjustment in the temperature of the recycle gas.
[0082] Under a given set of operating conditions, the fluidized bed
is maintained at essentially a constant height by withdrawing a
portion of the bed as product at a rate equal to the rate of
formation of the particulate polymer product. Because the rate of
heat generation is directly related to product formation, a
measurement of the temperature rise of the gas across the reactor 1
(the difference between inlet gas temperature and exit gas
temperature) may be determinative of the rate of particulate
polymer formation at a constant gas velocity.
[0083] In certain exemplary embodiments, the particulate polymer
product may be continuously withdrawn at a point 14 at or close to
the distribution plate 8 and in suspension with a portion of the
gas stream that may be vented as the particles settle to minimize
further polymerization and sintering when the particles reach their
ultimate collection zone. The suspending gas may also be used to
drive the product of one reactor to another reactor.
[0084] The particulate polymer product conveniently may be
withdrawn through the sequential operation of a pair of timed
valves 15 and 16 defining a segregation zone 17. While valve 16 is
closed, valve 15 may be opened to emit a plug of gas and product to
the zone 17 between it and valve 15, which then may be closed.
Valve 16 then may be opened to deliver the product to an external
recovery zone. Valve 16 then may be closed to await the next
product recovery operation. The vented gas containing unreacted
monomers may be recovered from zone 17 through line 18 and
recompressed in compressor 19 and returned directly, or through a
purifier 20, over line 21 to gas recycle line 6 at a point upstream
of the recycle compressor 9.
[0085] Finally, the fluidized bed reactor 1 is equipped with an
adequate venting system to allow venting of the bed during start up
and shut down. The reactor 1 does not require the use of stirring
means and/or wall scraping means. The recycle gas line 6 and the
elements therein (e.g., compressor 9, heat exchanger 10) generally
should have smooth surfaces, and should be devoid of unnecessary
obstructions so as not to impede the flow of recycle gas.
[0086] The highly active catalyst system of this invention may
yield a fluid bed product having an average particle size of from
0.01 to 0.04 inches, and, in certain exemplary embodiments, from
0.02 to 0.03 inches, in diameter wherein the catalyst residue may
be very low. The polymer particles are relatively easy to fluidize
in a fluid bed.
[0087] The feed stream of gaseous monomer, with or without inert
gaseous diluents, may be fed into the reactor at a space time yield
of about 2 to 10 pounds/hour/cubic foot of bed volume.
[0088] The term virgin resin or polymer as used herein means
polymer, in granular form, as it is recovered from the
polymerization reactor.
[0089] The catalysts of the present invention also may be used in
the gas phase reaction process and apparatus disclosed in U.S. Pat.
No. 4,255,542, which corresponds to European Patent Application No.
79101169.5, which was filed Apr. 17, 1979 and which was published
on Oct. 31, 1979 as Publication No. 4966. These references disclose
the use of an entirely straight sided fluid bed reactor that
employs heat exchange means within the reactor.
The Polymer Products
[0090] A variety of polymers may be produced as products of the
methods of the present invention. The polymers that may be prepared
with the catalysts of the present invention include, inter alia,
copolymers that include a major mol percent (e.g., .gtoreq.90%) of
ethylene, and a minor mol percent (e.g., .ltoreq.10%) of one or
more C.sub.3 to C.sub.8 alpha olefins. Generally, the C.sub.3 to C8
alpha olefins will not contain any branching on any of their carbon
atoms that may be closer than the fourth carbon atom from the
double bond. Examples of suitable C.sub.3 to C.sub.8 alpha olefins
include, but are not limited to, propylene, butene-1, pentene-1,
hexene-1, 4-methyl pentene-1, heptene-1 and octene-1. In certain
exemplary embodiments of the present invention, the C.sub.3 to
C.sub.8 alpha olefins may include propylene, butene-1, hexene-1,
4-methyl pentene-1 and octene-1.
[0091] The polymers that may be prepared with the catalysts of the
present invention generally have a molecular weight distribution
(Mw/Mn) in the range of from 2.5 to 6.0. In certain exemplary
embodiments of the present invention, the polymers may have a
molecular weight distribution in the range of from 2.7 to 4.1.
Another means of indicating the molecular weight distribution value
(Mw/Mn) of a polymer involves a parameter referred to as the melt
flow ratio (MFR). For the polymers of the present invention, an MFR
range of .gtoreq.20 to .ltoreq.40 corresponds to a Mw/Mn value
range of 2.5 to 6.0, and an MFR value range of .gtoreq.22 to
.ltoreq.32 corresponds to an Mw/Mn value range of 2.7 to 4.1.
[0092] The polymers that may be prepared with the catalysts of the
present invention generally have a density in the range of from
.gtoreq.0.91 to .ltoreq.0.97. In certain exemplary embodiments, the
polymers may have a density in the range of from .gtoreq.0.916 to
.ltoreq.0.935. In certain exemplary embodiments, the density of
certain exemplary copolymers that may be prepared with the
catalysts of the present invention, at a given copolymer melt index
level, may be regulated by, inter alia, the amount of the one or
more C.sub.3 to C.sub.8 comonomers that may be copolymerized with
the ethylene. In certain embodiments of the present invention in
which C.sub.3 to C.sub.8 comonomers are not reacted with ethylene
in the presence of a catalyst of the present invention, the
ethylene generally will homopolymerize with the catalysts of the
present invention, thereby providing homopolymers. In certain
exemplary embodiments, the homopolymers produced in accordance with
the present invention may have a density of .gtoreq.0.96. Thus, the
density of the polymers that may be prepared with the catalysts of
the present invention progressively may be lowered through the
addition of progressively larger amounts of one or more C.sub.3 to
C8 comonomers. The amount of each of the various C.sub.3 to C.sub.8
comonomers that may be used to provide a copolymer having a desired
density generally will vary from comonomer to comonomer, under the
same reaction conditions. Thus, for an operator to provide a
copolymer having the same given density at a given melt index
level, the operator generally may add larger molar amounts of the
different C.sub.3 to C.sub.8 comonomers, in the following order:
C.sub.3>C.sub.4>C.sub.5>C.sub.6>C.sub.7>C.sub.8.
[0093] The polymers that may be prepared with the catalysts of the
present invention generally have a standard or normal load melt
index in the range of from .gtoreq.0.01 to about 100. In certain
exemplary embodiments, the polymers may have a standard or normal
load melt index in the range of from 0.5 to 80. The polymers may
have a high load melt index (HLMI) in the range of from 11 to 2000.
The melt index of the polymers that may be prepared with the
catalysts of the present invention may be a function of a variety
of factors including, inter alia, the temperature of the
polymerization reaction, the density of the copolymer, the ratio of
hydrogen to ethylene monomer present during the reaction, and the
ratio of C.sub.3 to C.sub.8 comonomer to ethylene monomer present
during the reaction. Thus, an operator may increase the melt index
of the polymers by, inter alia, increasing the polymerization
temperature, and/or by decreasing the density of the copolymer,
and/or by increasing the hydrogen/ethylene monomer ratio, and/or by
increasing the ratio of C.sub.3 to C.sub.8 comonomer to ethylene
monomer. In addition to hydrogen, an operator optionally may
include other chain transfer agents (e.g., dialkyl zinc compounds)
to further increase the melt index of the polymers.
[0094] The polymers of the present invention generally have an
unsaturated group content of .ltoreq.1. In certain exemplary
embodiments, the polymers of the present invention may have an
unsaturated group content in the range of from .gtoreq.0.1 to
.ltoreq.0.3 carbon-carbon double bond per 1000 carbon atoms.
[0095] The polymers of the present invention generally have a
residual catalyst content, which may vary depending on the
productivity of the catalyst system. For a catalyst system having a
productivity level of .gtoreq.100,000 pounds of polymer per pound
of residual metal in the polymer, the polymers of the present
invention produced through a process using such catalyst system may
have a residual catalyst content, expressed in terms of parts per
million (ppm) of titanium metal, in the range of from >0 to
.ltoreq.10 ppm. For catalyst systems having a productivity level of
.gtoreq.200,000 pounds of polymer per pound of residual metal in
the polymer, the residual catalyst content may be in the range of
from >0 to .ltoreq.5 ppm. For catalyst systems having a
productivity level of .gtoreq.500,000 pounds of polymer per pound
of residual metal in the polymer, the residual catalyst content in
the polymers produced therefrom may be in the range of from >0
to .ltoreq.2 ppm. The homopolymers and copolymers of the present
invention are readily produced by the processes of the present
invention at productivities of up to 500,000 pounds of polymer per
pound of residual metal in the polymer.
[0096] The polymers of the present invention generally are granular
materials that have an average particle size in the range of from
0.01 to 0.06 inches in diameter. In certain embodiments, the
polymers have an average particle size in the range of from 0.02 to
0.03 inches, in diameter. The particle size may be an important
factor for the purposes of readily fluidizing the polymer particles
in a fluid bed reactor. The granular copolymers and homopolymers of
the present invention have a bulk density in the range of from 19
pounds per cubic foot to 35 pounds per cubic foot. Expressed in
different units, the granular copolymers and homopolymers of the
present invention have a bulk density in the range of from 0.304
gram per cubic centimeter to 0.561 gram per cubic centimeter.
[0097] The polymers of the present invention may be useful in a
variety of manners, including, but not limited to, the production
of film therefrom, as well as in other molding applications. When
the polymers of the present invention are to be used for
film-making purposes, an operator may elect to use embodiments of
the polymers of the present invention that have a density in the
range of from .gtoreq.0.916 to .ltoreq.0.935, and in certain
embodiments, a density in the range of from .gtoreq.0.917 to
.ltoreq.0.928, a molecular weight distribution (Mw/Mn) in the range
of from .gtoreq.2.7 to .ltoreq.4.1, and in certain embodiments, a
molecular weight distribution (Mw/Mn) in the range of from
.gtoreq.2.8 to .ltoreq.3.1; and a standard melt index in the range
of from >0.5 to .ltoreq.5.0, and in certain embodiments, a
standard melt index in the range of from .gtoreq.0.7 to
.ltoreq.4.0. Generally, the films that may be produced from the
polymers of the present invention may have a thickness in the range
of from >0 to .ltoreq.10 mils, and in certain embodiments, a
thickness in the range of from >0 to .ltoreq.5 mils, and in
certain embodiments, a thickness in the range of from >0 to
.ltoreq.1 mil.
[0098] When the polymers of the present invention are to be used in
injection molding of flexible articles (e.g., houseware materials),
an operator may elect to use embodiments of the polymers of the
present invention that have a density in the range of from
.gtoreq.0.920 to .ltoreq.0.940, and in certain exemplary
embodiments, a density in the range of from .gtoreq.0.925 to
.ltoreq.0.930; a molecular weight distribution Mw/Mn in the range
of from .gtoreq.2.7 to .ltoreq.3.6, and in certain embodiments a
molecular weight distribution Mw/Mn in the range of from
.gtoreq.2.8 to .ltoreq.3.1; and a standard melt index in the range
of from .gtoreq.2 to .ltoreq.100, and in certain embodiments a
standard melt index in the range of from .gtoreq.8 to
.ltoreq.80.
[0099] To facilitate a better understanding of the present
invention, the following examples of some of the exemplary
embodiments are given. In no way should such examples be read to
limit, or to define, the scope of the invention.
EXAMPLE 1
[0100] For laboratory-prepared precursors, silicas first were
dehydrated under nitrogen flow in a laboratory Carbolite Vertical
Furnace, Model No. VST 12/32/400/2408 CP-FM supplied by Carbolite,
Inc., provided with a quartz glass tube of 3.0 cm outer diameter
and 70 cm in total length, and two thermocouples. One thermocouple
was placed in a thermowell within the quartz glass tube, while the
other was affixed to the skin of the quartz glass tube by placing
it between the two folding halves of the furnace, then clamping the
folding halves shut. The thermocouples were hooked up to a Nomad
OM-SP1700 data logger supplied by Omega Engineering. A collection
flask for excess blowout silica was attached at the top of the
tube, which in turn was attached to a bubbler via a glass
elbow.
[0101] About 25-30 grams of silica was poured via a funnel into the
quartz glass tube to fill the tube about 2/3 full within the
heating zone. A preset program was started to begin the
dehydration, using a Eurotherm 2408 Programmable Temperature
Controller. A typical ramp and soak profile is shown in FIG. 2. The
gas flow (in this case nitrogen) was preset to about 50-100 cubic
centimeters per minute.
[0102] At the end of the dehydration cycle (typically overnight),
the silica was discharged into a clean, dry, N.sub.2-purged bottle
and maintained in an inert atmosphere. The data logger information
was downloaded to a computer file.
[0103] Three different silicas (Davison-955, Screened Davison-955
and Ineos ES757) were used to prepare laboratory-scale supported
catalyst precursor compositions. Certain properties of these
silicas are presented in the table below. The screened Davison-955
silica consisted of the fraction of Davison 955 silica that passed
through a 325 mesh (44 .mu.m) screen. TABLE-US-00002 TABLE 2
Average Pore Average Pore Volume Surface Area Diameter Particle
Size Silica Type (cm.sup.3/g) (m.sup.2/g) ({acute over ( )})
(.mu.m) Davison-955 1.62 310 209 45 Screened 1.62 310 209 18
Davison-955 Ineos ES757 1.62 315 200 25
[0104] The hydroxyl content of the three silicas then was
characterized by titration with TiCl.sub.4 in a hexane solution.
After washing and drying of the treated silica, the titanium
content of the treated silica (a measure of the presence of
hydroxyl groups in the silica) was determined by a
spectrophotometric method. The hydroxyl content of the three
silicas is reported in the table below. The hydroxyl content was
determined by TiCl.sub.4 titration that binds to the surface
OH-groups. The final titanium content, measured by a
spectrophotometric method, is an indication of the OH-group content
at a given dehydration temperature of the silica. TABLE-US-00003
TABLE 3 Hydroxyl Content at 600.degree. C. as determined by
TiCl.sub.4 Silica Type titration (mmol OH/g) Davison 955 0.59
Screened Davison-955 0.55 Ineos ES757 0.59
[0105] The silicas used as support material in the three
laboratory-scale catalyst precursors have a particle size
distribution shown in Tables 4 and 5 below, and in FIGS. 3 and 4.
TABLE-US-00004 TABLE 4 Particle Size Distribution of Davison 955
and Ineos ES757 Silicas by Malvern Analyzer Davison 955 Ineos ES757
Particle Size (.mu.m) silica (weight %) Silica (weight %) 4.338
0.22 0.37 4.639 0.25 0.4 4.962 0.32 0.49 5.307 0.4 0.59 5.675 0.46
0.66 6.07 0.51 0.72 6.492 0.56 0.77 6.943 0.61 0.82 7.425 0.66 0.87
7.942 0.71 0.92 8.494 0.76 0.97 9.084 0.82 1.03 9.715 0.88 1.1
10.391 0.95 1.18 11.113 1.04 1.28 11.885 1.13 1.4 12.711 1.23 1.54
13.595 1.36 1.71 14.54 1.5 1.91 15.55 1.66 2.17 16.631 1.85 2.49
17.787 2.05 2.87 19.024 2.28 3.34 20.346 2.51 3.85 21.76 2.72 4.34
23.273 2.93 4.84 24.89 3.1 5.29 26.62 3.23 5.68 28.47 3.33 5.88
30.449 3.41 5.8 32.566 3.47 5.51 34.829 3.5 5.13 37.25 3.52 4.69
39.839 3.5 4.15 42.608 3.45 3.56 45.57 3.41 3 48.737 3.38 2.45
52.125 3.3 1.96 55.748 3.16 1.5 59.623 2.96 1.09 63.767 2.78 0.79
68.199 2.59 0.55 72.939 2.4 0.26 78.009 2.2 0.02 83.431 2 0 89.23
1.8 0 95.432 1.61 0 102.065 1.42 0 109.159 1.24 0 116.747 1.09 0
124.861 0.9 0 133.54 0.75 0 142.822 0.62 0 152.749 0.48 0 163.366
0.37 0 174.721 0.27 0 186.865 0.19 0 199.854 0.13 0 213.745 0.05
0
[0106] TABLE-US-00005 TABLE 5 Particle Size Distribution of
Screened Davison 955 Silica by Microtrac Analyzer Particle Size
(.mu.m) Weight % 150.5 0 106.5 0 75 2 53 3 36.5 11 26.5 22 19 18
13.5 18 9.5 13 6.5 6 5 7
[0107] For the screened Davison 955 silica, the median particle
size was determined to be 18 micrometers.
[0108] About 9.5 grams of each of the three types of silica was
placed in an oven-dried, air-free 100 mL Schlenk flask having a
stir bar and rubber septum, to which about 50 ml of dry, degassed
hexane and 3 mL of triethylaluminum (TEAL) heptane solution (1.54
M) were added. Each of the three mixtures was stirred for about 30
minutes in an oil bath at 40.degree. C., after which point the oil
bath temperatures raised to 70.degree. C. and vacuum dried to
complete dryness. The resulting mixtures may be referred to as
laboratory TEAL-on-silica (laboratory TOS).
[0109] For each type silica, laboratory catalyst precursor
compositions at mole ratios Mg/Ti=3 and Mg/Ti=5 were prepared
according to the following procedure. In an oven dried, air-free
100 mL Schlenk flask provided with stir bar and rubber septum,
about 0.35 grams of [TiCl.sub.3, 0.33AlCl.sub.3], and 0.50 g of
MgCl.sub.2 were mixed in 18.5 mL of dry, degassed tetrahydrofuran
(THF) supplied by Aldrich. The compound referred to as [TiCl.sub.3,
0.33 AlCl.sub.3] is a mixed compound that is obtained by the
reduction of TiCl.sub.3 with metallic aluminum; the mixed compound
thus contains 1 molecule of AlCl.sub.3 per 3 molecules of
TiCl.sub.3. The operation was carried out in a "dry box." The flask
was then placed in an oil bath over a stir/heating plate inside a
hood. The septum was replaced by a condenser with a glass joint and
provided with circulating cold water and a small N.sub.2 flow
through it. The oil bath was heated at 80.degree. C., resulting in
an internal temperature between 70 and 72.degree. C. The system was
maintained under stirring for about 2 hours until all solids
dissolved in the refluxing THF. The solution was allowed to cool
down, and was transferred to another oven-dried, air-free 100 ml
Schlenk flask provided with stir bar and rubber septum containing
5.0 grams of laboratory TOS slurried in 20 ml of THF. (The transfer
of solution was performed inside the dry box.) The flask was placed
in the oil bath and the mixture was stirred for about 30 minutes at
80.degree. C., then flushed with a N.sub.2 vent for about 4-5 hours
until most of the THF evaporated. The resulting catalyst precursors
further were dried for 4 hours under vacuum (mechanical pump,
10.sup.-5 mmHg) in a water bath at 45.degree. C. The elemental
composition of the laboratory prepared precursors was determined by
Induced Coupled Plasma (ICP) analysis and is reported in the table
below. TABLE-US-00006 TABLE 6 Ti Mg Al THF Precursor (mmole/gram)
(mmole/gram) (mmole/gram) (weight %) Mg/Ti Precursor 1 0.268 0.841
0.466 13.4 3.1 Precursor 2 0.247 0.751 0.45 14.1 3.0 Precursor 3
0.303 0.814 0.498 13.0 2.7
[0110] Precursor 1 comprised Davison 955 silica, had a
magnesium/titanium ratio of 3, and is taken as a control.
[0111] Precursor 2 comprised Ineos ES-757 silica, and had a
magnesium/titanium ratio of 3.
[0112] Precursor 3 comprised screened Davison 955 silica, and had a
magnesium/titanium ratio of 3.
[0113] When precursors having mole ratios Mg/Ti=5 were prepared,
the MgCl.sub.2 loading was increased to meet this ratio (e.g., the
ratio of Mg/Ti=5). To facilitate the solubility of MgCl.sub.2 in
THF, an amount of ethanol (ranging within EtOH/Mg mole ratios of
from about 0.5 to about 2) was added to the THF solvent.
[0114] The light pink free-flowing powder precursors were then
ready to be tested in polyethylene polymerization reactions.
[0115] A one liter stirred stainless steel jacketed
reactor-autoclave equipped with a stirrer and a thermocouple was
used for the polymerization reactions with Precursors 1-3. The
reactor was thoroughly dried under a nitrogen purge at elevated
temperatures (>100.degree. C.) before each run. About 40 mL of
dry, degassed 1-hexene (a co-monomer) was added via syringe to the
empty reactor that was cooled at 60.degree. C. after purging, or,
in certain experiments, 40 mL of condensed 1-butene was loaded to
reactor by an automated injection pump. About 500 mL of dry
degassed isobutane was converted into liquid in a pressure tower
and fed to the reactor. At this point tri-ethyl aluminum alkyl
(TEAL) was injected to reactor with a syringe as a dilute (1.54 M)
heptane solution. The TEAL acts as cocatalyst and also scavenges
impurities (e.g., oxygen or moisture) that could deactivate the
catalyst. Unless otherwise noted, 0.4 mmole TEAL was used in each
experiment. The liquids were stirred at 650 rpm while the reactor
was heated until the working temperature of 85.degree. C. was
reached. Next, a computer-controlled flow meter introduced about
1000 or 1500 mL of hydrogen, after which (and by the same
mechanism) ethylene was fed until the reactor reached a total
pressure of 125 psi. The polymerization reaction then was initiated
by introducing 0.04 grams of laboratory catalyst precursor by means
of a pressure injection device, which further will be described.
The final pressure of the reactor was 380 psi. Ethylene was allowed
to flow to maintain its partial pressure of 125 psi. The reactor
operative variables (e.g., temperature, pressure and ethylene flow)
were recorded along the reaction time, and stored in a computer
through a data acquisition system. After a reaction period of 30
minutes, the ethylene flow was stopped, and the reactor was
depressurized to ambient pressure while the temperature of the
reactor was reduced to about 45.degree. C., at which point the
reactor was opened. The mass of polymer produced by the reaction
was determined after allowing all of the remaining comonomer to
evaporate, until the polymer weight stabilized for a desired period
of time, which generally was in the range of from 1 to 4 hours.
[0116] The catalyst injection system used to conduct these
experiments consists of a 5 mL stainless steel cylinder provided
with valves and connectors in its extremes, coupled to a 50 mL
cylinder that is attached via a flexible metal tubing to a 500 mL
stainless steel bomb. The stainless steel bomb is capable of
holding up to 400 psi of N.sub.2. The catalyst precursor first was
weighed and placed inside the 5 mL cylinder. About 5 mL of
isopentane was placed in the 50 mL cylinder. The cylinders then
were coupled through the connectors, but valves (resembling globe
valves) isolated the content of each from the other. All these
operations were carried out inside a dry box. After loading the
catalyst, the device was removed from the dry box and connected to
a reactor port through the small cylinder. In a nearly vertical
position, the 5 mL-50 mL cylinders tandem was connected through the
extreme of the large cylinder to the bomb pressurized with N.sub.2
at 400 psi by a flexible metal tubing. The bomb was isolated from
the cylinders by another valve, such that the bomb could be
pressurized either before or after being connected to the
cylinders. Through a fast, and coordinated, opening/closing of
valves, the nitrogen confined in the bomb pushed the isopentane
contained in the large cylinder through the small cylinder, thus
impelling the catalyst to the reactor. It was proved that the
catalyst was quantitatively transferred into the pressurized
reactor.
[0117] The results of the polymerization tests using laboratory
catalyst precursors are set forth in the table below.
TABLE-US-00007 TABLE 7 Precursor Titanium Loaded to Loaded to
Activity Productivity Run Reactor Reactor Yield (grams PE)/ (grams
PE)/ No. Precursor (grams) (mmol) (grams) [(mmol Ti)(h)] [(grams
Precursor)(h)] 1 Precursor 1 0.0768 0.02058 178 17,296 4,635 2
Precursor 1 0.0402 0.01077 99 18,378 4,925 3 Precursor 1 0.0411
0.01101 99 17,976 4,818 4 Precursor 1 0.0403 0.01080 101 18,703
5,012 Average: 18,088 Average: 4,847 5 Precursor 2 0.0409 0.0101
152 30,092 7,433 6 Precursor 2 0.0404 0.0100 123 24,652 6,089 7
Precursor 2 0.0409 0.0101 191 37,813 9,340 8 Precursor 2 0.0412
0.0102 135 26,532 6,553 9 Precursor 2 0.0408 0.0101 136 26,691
6,667 Average: 29,098 Average: 7,186 10 Precursor 3 0.0408 0.01024
134 21,679 6,569 11 Precursor 3 0.0404 0.0122 122 19,933 6,040 12
Precursor 3 0.0416 0.0126 131 20,786 6,298 Average: 21,024 Average:
6,370
[0118] The laboratory-prepared catalyst precursors having a
magnesium-to-titanium mole ratio of 3, with small particle size
ES757 silica ("Precursor 2") demonstrated superior performance to
that displayed by other laboratory-prepared catalyst precursors
having similar compositions but different silica supports. These
findings are additionally supported, and may be better visualized,
by FIG. 5, which depicts a plot of ethylene flow versus reaction
time that was obtained during laboratory isobutane slurry
polymerizations. FIG. 5 displays the ethylene flow (as recorded by
a computer-controlled Hastings mass flow meter Model HFC 202)
versus reaction time. The ethylene flow is expressed as standard
liters per minute (SLPM), which is the volume occupied by a given
mass of gas at standard temperature and pressure (e.g., 0 degrees
C. and 1 atmosphere of pressure). The representation of the
ethylene flow during the reaction time may be referred to as the
"kinetic profile."
[0119] The greater ethylene uptake corresponding to laboratory
prepared precursors employing ES757 silica (as compared to
precursors employing different silica support materials) is
consistent with the comparatively greater yield of polymer product
that was shown in Table 7.
[0120] A statistical analysis of the laboratory polymerization
results (performed using software supplied by JMP Software)
established the standard deviation and confidence interval by
analyzing the variance (anova). The analysis of the variance checks
whether differences among the means exist.
[0121] The statistical results are presented in Tables 8 and 9
below, and in FIG. 6. In FIG. 6, a diamond appears around each
group of data points. The line across the diamond represents the
group mean. The vertical span of each diamond represents the 95%
confidence interval for each group. TABLE-US-00008 TABLE 8 Std.
Std. Err. Lower Upper Level Number Mean Dev. Mean 95% 95% Davison 4
18,088.3 606.12 303.1 17,124 19,053 955 Ineos 5 29,098.4 5,259.61
2,352.2 22,568 35,629 ES-757 Screened 3 21,024.3 826.22 477.0
18,972 23,077 Davison 955
[0122] The results in Table 8 are derived from a mathematical
operation that fits means for each group using standard deviations
computed within each group. TABLE-US-00009 TABLE 9 Level Mean Ineos
ES-757 A 29,098.400 Screened Davison 955 B 21,024.333 Davison 955 B
18,088.250
[0123] The results in Table 9 are from a comparison of means made
by using the Tukey-Kramer HSD ("Honestly Significant Difference").
The Tukey-Kramer HSD is a test that is sized for all differences
among the means. The means comparison made by using the
Tukey-Kramer HSD criteria determines that levels not connected by
the same letter are significantly different.
[0124] Thus, Example 1 demonstrates, inter alia, that laboratory
catalyst precursors prepared with silica support materials that
have a smaller particle size and a narrower particle size
distribution may demonstrate desirable productivity and may be
useful in polymerization processes to generate polymer products
having desirable physical properties.
EXAMPLE 2
[0125] Scaled-up catalyst compositions were prepared in a pilot
plant laboratory using a jacketed vessel (that may be referred to
as a mix tank) according to the procedure set forth below. The
capacity of the mix tank is on the order of about 2 pounds of
catalyst material.
[0126] Silica dehydrated at 600.degree. C. has a hydroxyl nominal
concentration of 0.7 mmole OH/gram. The TEAL-on-Silica ("TOS")
prepared for these scaled-up batches has a target aluminum loading
of 0.5 mmole/gram. As TEAL reacts with hydroxyl according to a
1-to-1 molar ratio, then about 0.2 mmole OH/gram will remain
unreacted on the TOS.
[0127] First, about 850 grams of silica were charged to the mix
tank, for ES 757 silica and Davison 955-600 silica. About 3.5
liters of isopentane then were added, after which about 0.59 grams
of 10% TEAL in isopentane (0.93 ml) were added for every gram of
silica charged. The TEAL reacts exothermically with the silica to
form ethane. Accordingly, the TEAL charge was metered so as to keep
the reactor temperature under a target setting of 35.degree. C. The
foregoing mixture was mixed for 30 minutes at a pressure of 10
psig. Drying was initiated by heating the jacket to 60.degree. C.
and reducing the internal reactor pressure to 5 psig. A nitrogen
sweep was initiated. When the internal reactor temperature had
stabilized between 55.degree. C. and 60.degree. C. for 2 hours, the
mix tank contents were discharged. As noted above, the target
aluminum loading for the scaled-up TEAL-on-Silica (scaled-up TOS)
was 0.5 mmole/gram silica.
[0128] Scaled-up catalyst precursors were prepared according to the
following procedure. About 3,500 grams of tetrahydrofuran (THF) was
charged to the mix tank. The water content of the THF was less than
40 ppm of water. Magnesium chloride (MgCl.sub.2) was added to the
dry THF. The mix tank was pressurized to 5 psig and heated until
the contents reached a temperature of 60.degree. C. Stirring at 150
rpm was initiated. About 38.6 grams of ethanol were added, which
dissolves the MgCl.sub.2 almost instantly. Mixing continued for
about 30 minutes, after which about 66.8 grams of TiCl.sub.3, 0.33
AlCl.sub.3 were charged. The mixture was mixed for an hour. The mix
tank then was cooled so that the temperature of the contents fell
below 50.degree. C. About 800 grams of scaled-up TOS was charged
and mixed for about 30 minutes.
[0129] The contents of the mix tank then were dried by heating the
jacket of the mix tank to about 85.degree. C., and reducing the
internal pressure within the jacket by an incremental inch of
pressure at a time until the pressure reached -5 inches of mercury.
The internal pressure then was reduced to full vacuum, and a
nitrogen sweep was initiated. When the temperature of the contents
stabilized between 80 and 83.degree. C. for three hours, the mix
tank was pressurized to 5 psig, and cooled to below 40.degree. C.,
at which point the scaled-up catalyst was discharged.
[0130] The catalyst precursors prepared as described above then
were converted into catalyst compositions by treatment with at
least one, and no more than two, activators. The relative amounts
of the activator(s) were varied with respect to Ti content, to
provide an Al:Ti molar ratio of about 1 to 5 of each one of the
activators. First, about 800 grams of catalyst precursor was
charged to a clean and inert mix tank. About 1,600 grams of solvent
was slurried into the mix tank. The mixture was stirred at about
150 rpm, and the mix tank was pressurized to 5 psig. The mixture
was mixed for 30 minutes, before drying was initiated through
heating the jacket of the mix tank to 60.degree. C. A nitrogen
sweep also was begun, once the material became free-flowing. The
material was dried until the reactor temperature stabilized at
about 57.degree. C. for one hour. The mix tank then was cooled to
below about 40.degree. C., and the catalyst composition contained
therein was discharged therefrom.
[0131] Different catalyst formulations were prepared by varying the
relative amounts of the selected activators, one of them containing
an halogen atom, in such a way that their respective Al/Ti molar
ratios were within the range of from 1 to 5. A total of 9 different
catalyst formulations were prepared, comprising precursors prepared
with both Davison 955 and ES757 silicas. The catalyst formulations
comprising precursors prepared with Davison 955 silicas were
labeled as A, C, D and E. The catalyst formulations comprising
precursors prepared with Ineos ES757 silicas were labeled as A1,
C1, D1, and E1. As each catalyst series progresses from A to E
there is a consistent increase of the Al/Ti mole ratio for the
halogen-containing activator, which is accompanied by an increase,
although to a lower magnitude, of the non-halogen containing
activator. The sample catalyst compositions prepared as described
above then were used in polymerization reactions.
[0132] A one liter stirred stainless steel jacketed
reactor-autoclave equipped with a stirrer and a thermocouple was
used for the polymerization reactions. The reactor was thoroughly
dried under a purge of nitrogen at 100.degree. C. for 1 hour and
cooled down to 45.degree. C. before each run. About 0.8 mL of
heptane dilute solution (1.54 M) of TEAL then was added to the
reactor to act as cocatalyst and passivate any impurities. After
stirring for 15 minutes, 0.15 gram catalyst was charged. The
reactor then was sealed, and 1500 or 3000 cubic centimeters of
hydrogen was charged as indicated in the tables that follow, after
which the reactor was heated to 65.degree. C. At this point,
ethylene flow was initiated, and continued until the reactor
reached polymerization conditions of 200 psi at 85.degree. C.
[0133] Ethylene was allowed to flow to maintain the reactor
pressure at 200 psi during the 30 minute reaction period. Ethylene
uptake is measured through a computer-controlled flow meter. The
temperature of the reactor was reduced to 45.degree. C. while the
reactor was depressured to ambient pressure, after which the
reactor was opened. After allowing the solvent to evaporate, the
mass of polymer produced from the reaction was determined. The
polymer produced from the reaction then was characterized to
determine a number of parameters, including Melt Flow Index (MI),
High Load Melt Flow (HLM), and bulk density (BD).
[0134] Tables 10 and 11 below set forth certain parameters
determined from laboratory ethylene homo-polymerizations conducted
as set forth above with experimental scaled-up improved
precursors.
[0135] Table 12 sets forth certain parameters determined from
laboratory ethylene homo-polymerizations conducted as set forth
above with scaled-up catalyst formulations at activation Al/Ti
ratios located in the low end and in the medium end of the 1 to 5
range are compared to parameters of conventional Control Catalysts
1 and 4 (medium Al/Ti ratio range, e.g., containing an Al/Ti ratio
that is about 2.5) and Control Catalysts 2 and 3 (at the lower end
of the Al/Ti ratio range, e.g., containing an Al/Ti ratio that is
close to 1) at comparable Al/Ti ratios. TABLE-US-00010 TABLE 10
Catalyst Titanium H2 Loaded Loaded to Loaded to Activity to Reactor
Reactor Reactor Yield (grams PE)/ Sample Catalyst (mL) (grams)
(mmol) (grams) [(mmol Ti)(h)] 13 Scaled-Up 1,500 0.0490 0.0127 82
12,913 Davison 955 Silica Precursor 14 Scaled-Up 1,500 0.0408
0.0102 111 21,764 Ineos ES-757 Silica Precursor
[0136] TABLE-US-00011 TABLE 11 Flow Melt Productivity Melt Index
Index Settled Bulk (grams PE)/ (MI) (HLMI) MFR Density Sample
Catalyst [(grams cat)(hr)] (dg/minute) (dg/minute) (HLMI/MI)
(grams/cm3) 13 Scaled-Up 3,347 Not Not Not 0.330 Davison Determined
Determined Determined 955 Silica Precursor 14 Scaled-Up 5,441 0.21
5.50 26.2 0.352 Ineos ES- 757 Silica Precursor
[0137] TABLE-US-00012 TABLE 12 H2 Loaded Productivity to (grams
PE)/ Melt Index Flow Melt Settled Bulk Reactor [(grams (MI) Index
(HLMI) MFR Density Sample Catalyst (mL) cat)(hr)] (dg/minute)
(dg/minute) (HLMI/MI) (grams/cm.sup.3) 15 Control Catalyst 1 3,000
1,369 1.59 47.60 29.9 0.366 [Davison 955 silica, Mg/Ti = 3] 16
Control Catalyst 4 3,000 760 1.00 29.60 29.8 0.390 [Davison 955
silica, Mg/Ti = 3] 17 ScaleUp Catalyst C1 3,000 1,846 2.38 75.20
31.6 0.342 [Davison 955 silica, Mg/Ti = 5, with ethanol] 18 ScaleUp
Catalyst E1 3,000 1,976 1.32 40.20 30.0 0.415 [Ineos ES-757 silica,
Mg/Ti = 5, with ethanol] 19 Control Catalyst 2 3,000 4,547 1.40
41.20 29.4 0.272 [Davison 955 silica, Mg/Ti = 3] 20 Control
Catalyst 3 3,000 2,655 1.50 45.90 30.5 0.323 [Davison 955 silica,
Mg/Ti = 3] 21 ScaleUp Catalyst A 3,000 3,698 1.20 35.80 29.8 0.285
[Davison 955 silica, Mg/Ti = 3] 22 ScaleUp Catalyst A 3,000 5,141
1.40 42.50 30.4 0.336 [Ineos ES-757 silica, Mg/Ti = 5, with
ethanol]
[0138] The relationship between productivity and bulk density of
the experimental scaled-up catalysts is illustrated in FIG. 7.
[0139] Example 2 demonstrates, inter alia, that the improved
experimental catalysts prepared using supports that use ES757
silica having a smaller particle size and narrower particle size
distribution appear to demonstrate a desirable
productivity-vs.-bulk-density relationship, which may correlate
across a variety of magnesium-to-titanium ratios.
EXAMPLE 3
[0140] Sample catalyst compositions prepared in the manner
described above were reacted in a polymerization process in a pilot
plant reactor.
[0141] Polymerization was conducted in a 24 inch diameter gas-phase
fluidized bed reactor operating at approximately 300 psig total
pressure. The reactor bed weight was approximately 500-600 pounds.
Fluidizing gas was passed through the bed at a velocity of
approximately 2.0 feet per second. The fluidizing gas exiting the
bed entered a resin-disengaging zone located at the upper portion
of the reactor. The fluidizing gas then entered a recycle loop and
passed through a water-cooled heat exchanger and cycle gas
compressor. The shell side water temperature was adjusted to
maintain the reaction temperature to the specified value. Ethylene,
hydrogen, 1-hexene and nitrogen were fed to the cycle gas loop just
upstream of the compressor at quantities sufficient to maintain the
desired gas concentrations. Triethylaluminum cocatalyst was fed to
the reactor in quantities sufficient to support reaction. Gas
concentrations were measured by an on-line vapor fraction analyzer.
The catalyst was fed to the reactor bed through a stainless steel
injection tube at a rate sufficient to maintain the desired polymer
production rate. Nitrogen gas was used to disperse the catalyst
into the reactor. Product was withdrawn from the reactor in batch
mode into a purging vessel before it was transferred into a product
drum. Residual catalyst and cocatalyst in the resin were
deactivated in the product drum with a wet nitrogen purge.
[0142] The properties of the sample catalyst compositions, and the
results of the polymerization reactions are set forth in the tables
below. TABLE-US-00013 TABLE 13 Partial Productivity Residence
Ethylene (lbs PE)/ Productivity Time Pressure (lbs (Ti ICP-
H.sub.2/C.sub.2 C.sub.6/C.sub.2 Sample Catalyst (hours) (psi)
Catalyst) based) (mol/mol) (mol/mol) 23 Control Catalyst B 3.7 110
5,257 3,709 0.155 0.142 [Davison 955 silica, Mg/Ti = 3] 24 ScaleUp
Catalyst C 4.8 110 6,160 6,552 0.142 0.113 [Davison 955 silica,
Mg/Ti = 3] 25 ScaleUp Catalyst C 4.0 79 6,114 4,383 0.147 0.137
[Davison 955 silica, Mg/Ti = 5, with ethanol] 26 ScaleUp Catalyst E
3.6 110 9,421 7,149 0.123 0.110 [Davison 955 silica, Mg/Ti = 5,
with ethanol] 27 ScaleUp Catalyst D1 4.7 110 4,758 4,545 0.185
0.134 [Ineos ES-757 silica, Mg/Ti = 5, with ethanol] 28 ScaleUp
Catalyst D1 4.3 79 3,195 3,344 0.190 0.159 [Ineos ES-757 silica,
Mg/Ti = 5, with ethanol] 29 ScaleUp Catalyst C1 5.0 110 7,066 Not
0.166 Not [Ineos ES-757 silica, Determined Determined Mg/Ti = 5,
with ethanol] 30 ScaleUp Catalyst C1 5.5 79 5,085 4,985 0.138 0.149
[Ineos ES-757 silica, Mg/Ti = 5, with ethanol] 31 ScaleUp Catalyst
E1 3.7 110 9,005 4,202 0.146 0.126 [Ineos ES-757 silica, Mg/Ti = 5,
with ethanol] 32 ScaleUp Catalyst E1 5.0 79 4,780 8,419 0.136 0.146
[Ineos ES-757 silica, Mg/Ti = 5, with ethanol]
[0143] TABLE-US-00014 TABLE 14 Settled Bulk C6/C2 Melt Index
I.sub.2 MFR Density Density Sample Catalyst (mol/mol)
(g)/[(dg)(min)] (I.sub.21/I.sub.12) (grams/cm.sup.3) (lbs/ft.sup.3)
23 Control Catalyst B 0.142 0.945 32.54 0.9187 20.9 [Davison 955
silica, Mg/Ti = 3] 24 ScaleUp Catalyst C 0.113 0.707 31.26 0.9228
20.3 [Davison 955 silica, Mg/Ti = 3] 25 ScaleUp Catalyst C 0.137
0.641 33.00 0.9176 20.5 [Davison 955 silica, Mg/Ti = 5, with
ethanol] 26 ScaleUp Catalyst E 0.110 0.627 34.04 0.9226 17.9
[Davison 955 silica, Mg/Ti = 5, with ethanol] 27 ScaleUp Catalyst
D1 0.134 0.759 30.38 0.9228 24.1 [Ineos ES-757 silica, Mg/Ti = 5,
with ethanol] 28 ScaleUp Catalyst D1 0.159 0.885 29.67 0.9178 23.7
[Ineos ES-757 silica, Mg/Ti = 5, with ethanol] 29 ScaleUp Catalyst
C1 Not 0.748 31.55 0.9180 21.9 [Ineos ES-757 silica, Determined
Mg/Ti = 5, with ethanol] 30 ScaleUp Catalyst C1 0.149 0.90 Not
0.9195 22.3 [Ineos ES-757 silica, Determined Mg/Ti = 5, with
ethanol] 31 ScaleUp Catalyst E1 0.126 0.727 31.42 0.9212 22.6
[Ineos ES-757 silica, Mg/Ti = 5, with ethanol] 32 ScaleUp Catalyst
E1 0.146 0.714 32.27 0.9176 22.1 [Ineos ES-757 silica, Mg/Ti = 5,
with ethanol]
[0144] The above example demonstrates, inter alia, the experimental
improved catalysts prepared with the small particle size ES757
silica led to both enhanced productivity and polymer products that
demonstrated improved settled bulk density. The unexpected increase
of the resin bulk density with increased productivity is generally
opposite to that demonstrated by polymerizations conducted with
conventional catalysts, and is highly beneficial for the fluid bed
operation. These findings are further illustrated in FIG. 8.
[0145] Therefore, the present invention is well adapted to carry
out the objects and attain the ends and advantages mentioned as
well as those that are inherent therein. While the invention has
been depicted, described, and is defined by reference to exemplary
embodiments of the invention, such a reference does not imply a
limitation on the invention, and no such limitation is to be
inferred. The invention is capable of considerable modification,
alternation, and equivalents in form and function, as will occur to
those ordinarily skilled in the pertinent arts and having the
benefit of this disclosure. The depicted and described embodiments
of the invention are exemplary only, and are not exhaustive of the
scope of the invention. Consequently, the invention is intended to
be limited only by the spirit and scope of the appended claims,
giving full cognizance to equivalents in all respects.
* * * * *