U.S. patent application number 09/895939 was filed with the patent office on 2001-12-13 for off-line preactivated catalysts and prepolymerized catalysts.
Invention is credited to Morse, David Bell.
Application Number | 20010051697 09/895939 |
Document ID | / |
Family ID | 26796902 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051697 |
Kind Code |
A1 |
Morse, David Bell |
December 13, 2001 |
Off-line preactivated catalysts and prepolymerized catalysts
Abstract
Catalysts that have been preactivated and/or prepolymerized are
disclosed whereby a magnesium and titanium-containing procatalyst
component is contacted with a co-catalyst and an external electron
donor (and optionally with an olefin monomer to prepare a
prepolymerized catalyst) prior to polymerization to form a
preactivated and/or prepolymerized catalyst. The preactivated
and/or prepolymerized catalyst then is separated from the mixture,
and dried to form a solid preactivated and/or prepolymerized
catalyst. This dried catalyst then can be stored and subsequently
shipped to a polymerization site where it can be used in gas phase
polymerization. The preactivated and/or prepolymerized catalyst can
be used in gas phase polymerization as extremely high activity
catalysts, and do not cause a rapid rise in reaction temperature
causing overheating, undesirable formation of agglomerates,
coagulation of polymer, and ultimately, reactor failure.
Inventors: |
Morse, David Bell; (Houston,
TX) |
Correspondence
Address: |
THE DOW CHEMICAL COMPANY
INTELLECTUAL PROPERTY SECTION
P. O. BOX 1967
MIDLAND
MI
48641-1967
US
|
Family ID: |
26796902 |
Appl. No.: |
09/895939 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09895939 |
Jun 29, 2001 |
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09395239 |
Sep 13, 1999 |
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60100204 |
Sep 14, 1998 |
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Current U.S.
Class: |
526/119 ;
502/113; 502/125; 526/118; 526/125.3; 526/128; 526/904 |
Current CPC
Class: |
C08F 10/00 20130101;
C08F 10/00 20130101; C08F 10/00 20130101; C08F 10/00 20130101; C08F
4/6492 20130101; C08F 4/654 20130101; C08F 4/6465 20130101; C08F
10/00 20130101; C08F 4/6567 20130101 |
Class at
Publication: |
526/119 ;
526/118; 526/125.3; 526/128; 526/904; 502/113; 502/125 |
International
Class: |
C08F 004/44 |
Claims
What is claimed is:
1. A process for preparing a solid olefin polymerization catalyst
composition comprising: a) contacting a magnesium compound selected
from the group consisting of magnesium dialkoxides,
magnesium-titanium alkoxides and carbonated magnesium alkoxides
with a tetravalent titanium halide, a polycarboxylic acid ester,
optionally an alcohol and further optionally, a phenol or
substituted phenol compound, in a halohydrocarbon liquid, and
recovering the resulting solid reaction product; b) recontacting
the solid reaction product one or more times with the tetravalent
titanium halide and optionally the polycarboxylic acid ester, in a
halohydrocarbon liquid, and further optionally, at the same time or
separately, contacting the solid reaction product with an acid
halide compound corresponding to the acid moiety of the
polycarboxylic acid ester, to form a second solid reaction product,
and recovering the resulting second solid reaction product; c)
contacting the second solid reaction product with an organoaluminum
co-catalyst compound and at least one silicon-containing external
electron donor compound containing at least one
silicon-oxygen-carbon bridge in an inert diluent in the substantial
absence of an olefin to form a solid, olefin polymerization
catalyst composition; and d) recovering the resulting solid, olefin
polymerization catalyst composition.
2. The process of claim 1 wherein the silicon-containing external
electron donor compound is of the formula
R.sup.1.sub.mSiY.sub.nX.sub.p wherein, R.sup.1 is a hydrocarbyl
group having from 4 to 20 carbon atoms, and having a non-primary
carbon atom attached directly to the silicon atom, Y is --OR.sup.2
or --OCOR.sup.2 wherein R.sup.2 is a hydrocarbyl group containing 1
to 20 carbon atoms, X is hydrogen or halogen, m is a number from 0
to 3, n is a number from 1 to 4, p is a number from 0 to 1, and
m+m+p=4.
3. The process of claim 1 wherein two silicon-containing external
electron donor compounds are used.
4. The process of claim 3 wherein the two silicon-containing
external electron donor compounds are dicyclopentyldimethoxysilane
and either n-propyltrimethoxysilane or tetraethoxysilane.
5. The process of claim 1 additionally comprising the step of e)
drying the resulting solid, olefin polymerization catalyst
composition.
6. The process of claim 1 wherein in step b) the solid reaction
product is contacted with an acid halide compound corresponding to
the acid moiety of the polycarboxylic acid ester.
7. The process of claim 6 wherein the tetravalent titanium halide
is titanium tetrachloride, the polycarboxylic acid ester is
diisobutylphthalate, and the acid halide is phthaloyl
dichloride.
8. The process of claim 1 wherein step c) is conducted at a
temperature less than 40.degree. C.
9. A process for preparing a mixture of two or more solid olefin
polymerization catalyst compositions comprising: preparing a first
solid, olefin polymerization catalyst composition according to the
process of claim 1; preparing a second solid, olefin polymerization
catalyst composition according to the process of claim 1, said
second solid, olefin polymerization catalyst composition differing
from said first solid, olefin polymerization catalyst composition;
and combining the first and second solid, olefine polymerization
catalyst compositions, and recovering the resulting product.
10. The process of any one of claims 1-9 additionally comprising
the step of contacting from 1 to 10 grams of propylene per gram of
solid, olefin polymerization catalyst composition under
prepolymerization conditions and recovering the resulting
product.
11. The process of claim 10 wherein the prepolymerization is
conducted at a temperature less than 40.degree. C.
12. A solid olefin polymerization catalyst composition prepared
according to the process of any one of claims 1-9.
13. A solid olefin polymerization catalyst composition prepared
according to the process of claim 10.
14. A solid olefin polymerization catalyst composition prepared
according to the process of claim 11.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to solid catalyst materials
that have been preactivated using co-catalyst components that may
be subjected to prepolymerization, and the use thereof in the
production of polyolefins. The invention also relates to preparing
the preactivated and/or prepolymerized catalysts separate from the
principle polymerization system, separating the catalysts from
their reaction mixture and then using the catalysts in a method of
making a polyolefin. The preactivated and/or prepolymerized
catalysts preferably are carried into the polymerization reactor in
a carrier containing at least an inert gas and a liquid
solvent.
[0003] 2. Description of Related Art
[0004] Ziegler-Natta catalysts are well known for catalyzing the
polymerization of olefins. Conventional Ziegler-Natta catalysts are
those that contain a procatalyst made from contacting an internal
electron donor, a titanium source, a magnesium source and a
halogenating agent (which may be combined with one of the other
components). This procatalyst then typically is combined with an
external selectivity control agent ("SCA") and an aluminum alkyl to
produce the Ziegler-Natta catalyst system. See, e.g., U.S. Pat. No.
4,393,182 to Job. Generally, the selectivity control agents may be
any of several classes of electron donative compounds, but one
class that has been studied extensively is the class of
organosilicon compounds having at least one Si--O (i.e., siloxy)
bond. These compounds include tetra, tri, bi and mono alkoxy
silanes. While these SCAs are good selectivity control agents, they
usually provide for only a limited range of polymer product
properties, such as a narrow range of available polymer molecular
weight distribution (MWD) within the range that is available
through the use of various internal electron donors.
[0005] It is known that any two of the three final components of
the catalyst system may be brought together shortly before
introduction into the primary polymerization reactor. Also, it is
known that all three components may be brought together (the
procatalyst, co-catalyst, and SCA) prior to introduction to the
polymerization reactor in a method known as preactivation. Finally,
it is also known that the preactivated material, either separately
or simultaneously, may be exposed to an olefin (procatalyst,
co-catalyst, SCA(s) and monomer(s)) to form a prepolymer, and then
subjecting the prepolymer to primary polymerization in a primary
polymerization reactor. The preactivation and prepolymerization
methods especially serve to form highly active catalysts.
[0006] When such highly active catalysts are used, the
polymerization in the polymerization reactor begins very rapidly,
immediately upon introduction of the preactivated catalyst and/or
prepolymerized catalyst to the reactor. The rapid reaction results
in an attendant rapid rise in reaction temperature causing
overheating, undesirable formation of agglomerates, coagulation of
polymer, and ultimately, reactor failure. This is particularly true
in gas phase polymerization systems. To avoid this rapid rise in
temperature, preactivated and prepolymerized catalysts may be fed
directly to the polymerization reactor in the slurry or suspension
in which the catalysts were formed (i.e., on-line or in-line). It
previously was thought that feeding a preactivated and/or
prepolymerized catalyst to a gas phase reactor in solid form
(together with additional co-catalyst, SCA(s), monomer(s), recycle
and condensed gas, etc., as needed; i.e., off-line prepared
catalyst material) would cause immediate and intense reaction
inside the gas phase reactor resulting in the aforementioned
disadvantages.
[0007] U.S. Pat. No. 4,721,763 discloses a process for polymerizing
olefins whereby a prepolymerization stage is conducted in a liquid
phase prior to gas phase polymerization. In this process,
prepolymerization is effected by contacting the olefin with a
Ziegler catalyst system in the liquid phase (suspension or slurry)
and then subjecting the prepolymerized catalyst to a second
prepolymerization in the gas phase and then subjecting that
prepolymer to polymerization in the gas phase. Thus, the activity
of the catalyst is reduced significantly before being fed to the
full-scale polymerization reactor by conducting two
prepolymerization steps. The two-stage prepolymerization approach
is very costly and an inefficient mechanism to prepolymerize a
catalyst.
[0008] U.S. Pat. No. 5,610,244 discloses a process for polymerizing
ethylene in a fluidized bed whereby a titanium or
vanadium-containing catalyst component is preactivated or
prepolymerized prior to being fed to a gas phase polymerizer. The
precontacting and prepolymerization are conducted in-line whereby
the solid catalyst component and co-catalyst
(triethylaluminum-TEAL) are contacted briefly, and then they are
fed to a prepolymerizer loop reactor and then fed directly to the
reactor.
[0009] International Pat. Publication No. WO 88/02376 discloses a
process for polymerizing olefins whereby a solid magnesium and
titanium-containing catalyst procatalyst component is
prepolymerized prior to being fed to a gas phase reactor. In
accordance with the process, the catalyst components are contacted
with monomer in a liquid phase loop reactor to form a prepolymer,
whereby the weight ratio of monomer to solid catalyst procatalyst
component is at least about 6000:1, and the residence time is less
than 400 seconds. The prepolymer then is directly fed in-line
together with the other unreacted components to a gas phase
reactor. On-site in-line preactivation and prepolymerization may
help to solve the problem of excess heat generation by feeding the
components in a liquid stream to the reactor, but it requires
additional processing and additional equipment at the gas phase
polymerization plant. In addition, these in-line preactivation and
prepolymerization methods typically do not result in any
significant savings in terms of raw material usage, or in capital
cost savings at the polymerization plant.
SUMMARY OF THE INVENTION
[0010] There exists a need to develop preactivated or
prepolymerized catalysts that can be prepared off-line and sold to
polymer manufacturers. There also exists a need to provide polymer
manufacturers with extremely high activity catalysts, such as
preactivated and/or prepolymerized catalysts, that do not result in
rapid rise in reaction temperature causing overheating, undesirable
formation of agglomerates, coagulation of polymer, and ultimately,
reactor failure. In addition, there exists a need to provide a
preactivated and/or prepolymerized catalyst that can be used to
polymerize olefins in high yield using less solid catalyst and
external selectivity control agent (SCA).
[0011] It is therefore a feature of the invention to provide
preactivated and/or prepolymerized catalysts that can be used to
make polyolefin polymers in high yield at high production rates and
at reduced costs. It is an additional object of the present
invention to provide an economically efficient method of making
polyolefin polymers using preactivated and prepolymerized catalysts
resulting in polymers with improved physical properties, including,
for example, increased bulk density, decreased average particle
size and varied molecular weight distribution (MWD).
[0012] In accordance with these and other features of the present
invention, there is provided a solid preactivated catalyst
component that includes (a) a solid procatalyst component which is
the reaction product of a magnesium compound, a tetravalent
titanium halide and an internal electron donor, with (b) a
cocatalyst, and (c) at least one silicon compound. The solid
preactivated catalyst component is prepared by a process comprising
contacting a procatalyst (A) comprising the reaction product of (i)
a magnesium compound, (ii) a tetravalent titanium halide and (iii)
an internal electron donor, with (B) a co-catalyst, and (C) at
least one silicon-containing external electron donor, which may be
the same or different than the internal electron donor (iii) to
form a solid preactivated catalyst. The solid preactivated catalyst
then is separated from the remaining components of the mixture
resulting from contacting the aforementioned components, and then
dried to form a dry, solid preactivated catalyst component. The
catalyst components preferably are contacted for a period of time
sufficient to form a preactivated catalyst which can be fed
immediately or later to a polymerization reactor, or which can be
prepolymerized prior to feeding to a polymerization reactor.
[0013] In accordance with another feature of the invention, there
is provided a method of polymerizing an olefin in the gas phase
comprising polymerizing an olefin monomer in a gas phase reactor in
the presence of the aforementioned solid preactivated catalyst, a
co-catalyst and an external electron donor, wherein the amount of
the external electron donor used is from 10 to 90% of the amount of
external donor that would be used with the same catalyst components
that were not preactivated. In the method, the preactivated
catalyst preferably is fed to the reactor in an inert carrier.
[0014] In accordance with another feature of the invention, there
is provided a prepolymerized olefin polymerization catalyst
prepared by a process comprising contacting a procatalyst (A)
comprising the reaction product of (i) a magnesium compound, (ii) a
tetravalent titanium halide and (iii) an internal electron donor,
with (B) a co-catalyst, and (C) at least one silicon-containing
external electron donor, which may be the same or different than
the internal electron donor (iii) to form a solid preactivated
catalyst. The solid preactivated catalyst then is contacted with an
olefin monomer to form a solid prepolymerized catalyst. The solid
prepolymerized catalyst then is separated from the remaining
components of the mixture resulting from contacting the
preactivated catalyst with the monomer. Finally, the solid
prepolymerized catalyst is dried to form a dry, solid
prepolymerized catalyst.
[0015] In accordance with yet another feature of the invention,
there is provided a method of polymerizing an olefin in the gas
phase comprising polymerizing an olefin monomer in a reactor in the
presence of the aforementioned prepolymerized catalyst, a
co-catalyst and an external electron donor, wherein the amount of
the external electron donor used is from 10 to 90% of the amount of
external donor that would be used with the same catalyst components
that were not prepolymerized. In the method, the prepolymerized
catalyst preferably is fed to the reactor in an inert carrier.
[0016] In accordance with another feature of the invention, there
is provided a method of making a preactivated catalyst comprising
contacting a procatalyst (A) comprising the reaction product of (i)
a magnesium compound, (ii) a tetravalent titanium halide and (iii)
an internal electron donor, with (B) a co-catalyst, and (C) at
least one silicon-containing external electron donor, which may be
the same or different than the internal electron donor (iii) to
form a solid preactivated catalyst. The solid preactivated catalyst
then is separated from the remaining components of the mixture
resulting from the above-mentioned contacting. The separated
preactivated catalyst then is dried to form a dry, solid
preactivated catalyst.
[0017] These and other objects of the invention will be readily
apparent to those skilled in the art upon reading the detailed
description of preferred embodiments that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 depicts an exemplary gas phase polymerization reactor
system.
[0019] FIG. 2 depicts two bar graphs illustrating how the addition
of isopentane to a nitrogen catalyst carrier stream can reduce the
particle size distribution of the resulting polymer particles.
[0020] FIG. 3 is a graph illustrating an increase in bulk density
with the addition of isopentane to a nitrogen catalyst carrier
stream.
[0021] FIG. 4 is a graph illustrating a decrease in average
particle size with the addition of isopentane to a nitrogen
catalyst carrier stream.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Throughout this description, the term "preactivated" denotes
a catalyst system whereby some or all of the catalyst components,
preferably Ziegler-Natta catalyst components (solid magnesium and
titanium-containing component, cocatalyst and SCA) are contacted
with one another prior to polymerization for a period of time
sufficient to preactivate the catalyst system, and then dried.
Throughout this description, the term "prepolymerized" and the
expression "prepolymerized catalyst" denotes contacting some or all
of the catalyst components, preferably Ziegler-Natta catalyst
components, with an olefin (either the same or different olefin
from that ultimately polymerized) to form a prepolymer. This
prepolymerized catalyst then is added to the polymerization reactor
with additional cocatalyst and optionally additional similar or
different SCA and polymerized together with an olefin monomer or
monomers to produce the olefin polymer, copolymer, terpolymer, and
the like, and mixtures thereof.
[0023] The magnesium and titanium-containing catalyst component
employed in the preparation of the solid procatalyst component can
be any component containing magnesium, titanium and halogen that is
capable of polymerizing an .alpha.-olefin. This magnesium and
titanium-containing component can be prepared by any manner known
in the art. Ostensibly, the magnesium compound can be any magnesium
compound capable of reacting with a titanium component and an
internal electron donor to form an effective polymerization
procatalyst. Preferably, the magnesium compound is a magnesium
halide, alkyl, aryl alkoxide, aryloxide, dialkoxide, a carbonated
magnesium dialkoxide, a carbonated magnesium diaryloxide, or a
magnesium titanium alkoxide complex. Most preferably, the magnesium
compound is a carbonated magnesium diaryloxide, or a magnesium
titanium akoxide complex. Magnesium compounds containing one
alkoxide and one aryloxide group can also be employed, as well as
magnesium compounds containing a halogen in addition to one
alkoxide or aryloxide group, or containing additional electron
donating compounds. The alkoxide groups, when present, most
suitably contain from 1 to 8 carbon atoms, preferably from 2 to 6
carbon atoms. The aryloxide groups when present, most suitably
contain from 6 to 10 carbon atoms. When halogen is present, it is
preferably chlorine.
[0024] Among the magnesium dialkoxides and diaryloxides which can
be employed are those of the formula
Mg(O(C(O)OR').sub.x(OR").sub.2-x, wherein R' and R" are alkoxide or
aryloxide groups or halogen, and x is about 0.1 to about 2. The
most preferred magnesium compounds are carbonated magnesium
ethoxides (CMEO), 1
[0025] and magnesium diethoxide or Mg.sub.3Ti(OEt).sub.8X.sub.2
where Et represents ethyl and X is preferably chloride.
[0026] Optionally, the magnesium may be halogenated with an
additional halogenating agent, e.g., thionyl chloride or
alkylchlorosilanes, prior to its contact with the tetravalent
titanium halide.
[0027] The magnesium compound also can be prepared as a solid
precursor component whereby a magnesium compound first is reacted
with at least one titanium compound and at least one alcohol in the
presence of a solvent, and the precursor component is crystallized
from the solution, separated and dried. Preferably, magnesium
ethoxide (Mg(OEt).sub.2 is reacted with titanium tetraalkoxide,
preferably titanium tetraethoxide (Ti(OEt).sub.4 and a titanium
tetrahalide, preferably TiCl.sub.4, in the presence of o-cresol,
ethyl alcohol and monochlorobenzene. Most preferably, the magnesium
and titanium-containing precursor component has the formula
Mg.sub.3Ti(OEt).sub.8Cl.sub.2. Any of the magnesium-containing
precursor compounds described in U.S. Pat. Nos. 5,034,361;
5,082,907; 5,151,399; 5,229,342; 5,106,806; 5,146,028; 5,066,737;
and 5,077,357, the disclosures of which are incorporated by
reference herein in their entirety, can be used in the present
invention.
[0028] The titanium compound employed in the preparation of the
solid magnesium and titanium-containing procatalyst component (a),
which typically entails reacting the magnesium and
titanium-containing precursor described above with a titanium
compound, can be any titanium compound capable of reacting with the
magnesium component and an internal electron donor to form an
effective polymerization procatalyst. Preferably, the titanium
compound is a tetravalent titanium halide that contains at least
two halogen atoms, and preferably contains four halogen atoms. Most
preferably these halogen atoms are chlorine atoms. However,
titanium compounds containing up to two alkoxy and/or aryloxy
groups can also be employed. The alkoxy groups, when present, most
suitably contain from 1 to 8 carbon atoms, preferably from 2 to 6
carbon atoms. The aryloxy groups, when present, most suitably
contain from 6 to 12 carbon atoms, preferably from 6 to 10 carbon
atoms. Examples of suitable alkoxy- and aryloxy-titanium halides
include diethoxy titanium dibromide, isopropoxy titanium triiodide,
dihexoxy titanium dichloride, and phenoxy titanium trichloride.
[0029] The magnesium compound can be reacted (i.e., halogenated)
with a tetravalent halide, preferably a tetravalent titanium
halide, in the presence of an internal electron donor and
preferably a halohydrocarbon. If desired, an inert hydrocarbon
diluent or solvent may also be present, although this is not
necessary. The halohydrocarbon employed may be aromatic, aliphatic,
or alicyclic. Most preferably, the halogen of the halohydrocarbon
is chlorine. Aromatic halohydrocarbons are preferred, particularly
those containing from 6 to 12 carbon atoms, preferably 6 to 10
carbon atoms. Preferably such halohydrocarbons contain 1 or 2
halogen atoms, although more may be present if desired. Suitable
aromatic halohydrocarbons include, but are not limited to,
chlorobenzene, bromobenzene, dichlorobenzene,
dichlorodibromobenzene, chlorotoluene, dichlorotoluene and
chloronaphthalene.
[0030] The aliphatic halohydrocarbons which can be employed
suitably contain from 1 to 12 carbon atoms, preferably from 1 to 9
carbon atoms and at least 2 halogen atoms. Suitable aliphatic
halohydrocarbons include dibromomethane, trichloromethane,
1,2-dichloroethane, trichloroethane, dichlorofluoroethane,
hexachloroethane, trichloropropane, chlorobutane, dichlorobutane,
chloropentane, trichlorofluorooctane, tetrachloroisooctane,
dibromodifluorodecane, carbon tetrachloride and
trichloroethane.
[0031] The alicyclic halohydrocarbons which can be employed contain
from 3 to 12 carbon atoms, and preferably from 3 to 9 carbon atoms,
and at least 2 halogen atoms. Suitable alicyclic halohydrocarbons
include dibromocyclobutane and trichlorocyclohexane.
[0032] The preferable internal electron donor is a polycarboxylic
acid ester, though other internal electron donors as are known in
the art that are suitable for use with the magnesium titanium
olefin polymerization catalysts may be employed. See, e.g., U.S.
Pat. No. 4,393,182 to Job, which is incorporated herein by
reference. Suitable esters have two ester groups attached to
adjacent carbon atoms of the molecule and lie in a single plane.
Such esters include: (a) polycarboxylic acid esters containing two
ester groups which are attached to ortho carbon atoms of a
monocyclic or polycyclic aromatic ring, each of said ester groups
being further linked to a branched or unbranched chain hydrocarbon
radical, (b) polycarboxylic acid esters containing two ester groups
which are attached to vicinal carbon atoms of a non-aromatic
monocyclic or polycyclic ring and which lie in a cis configuration
with respect to each other, each of said ester groups being further
linked to a branched or unbranched chain hydrocarbon radical, and
(c) polycarboxylic acid esters containing two ester groups which
are attached to vicinal double bonded carbon atoms of an
unsaturated aliphatic compound and which lie in a syn configuration
with respect to each other, each of said ester groups being further
linked to a branched or unbranched chain hydrocarbon radical.
[0033] Examples of the polycarboxylic acid esters include, but are
not limited to, dimethyl phthalate, diethyl phthalate, di-n-propyl
phthalate, diisopropyl phthalate, di-n-butyl phthalate, diisobutyl
phthalate, di-tert-butyl phthalate, diisoamyl phthalate,
di-tert-amyl phthalate, dineopentyl phthalate, di-2-ethylhexyl
phthalate, di-2-ethyldecyl phthalate,
diethyl-1,2-fluorenedicarboxylate, diisopropyl-1,2-ferrocene
dicarboxylate, cis-diisobutyl-cyclobutane-1,2-dicarboxylate,
endo-diisobutyl-5-norbornene-2,3-dicarboxylate and
endo-diisobutyl-bicyclo[2.2.2]oct-5-ene-2,3-dicarboxylate,
diisobutyl maleate, and diisoamyl citraconate. Dibutyl phthalate is
most preferred. Esters of the following acids also may be used:
ciscyclobutane-1,2-dicarb- oxylic acid,
endo-5-norbornene-2,3-dicarboxylic acid, endo
dicyclopentadiene-2,3-dicarboxylic acid, and endo
bicyclo[3.2.1]oct-2-ene- -6,7-dicarboxylic acid.
[0034] If desired, the esters may be substituted with one or more
substituents which are inert under the reaction conditions employed
during esterification, as well as during preparation of the solid
catalyst component and polymerization with said catalyst component.
Suitable compounds include maleic acid, citraconic acid, and the
like.
[0035] Halogenation of the magnesium compound with the preferred
halogenated tetravalent titanium halide can be effected by
employing an excess of the titanium halide. At least 2 moles of the
titanium halide should ordinarily be employed per mole of the
magnesium compound. Preferably from 4 moles to 100 moles of the
titanium halide are employed per mole of the magnesium compound,
and most preferably from 4 moles to 20 moles of the titanium halide
are employed per mole of the magnesium compound.
[0036] The halohydrocarbon can be employed in an amount sufficient
to dissolve the titanium halide and the internal electron donor,
and to adequately disperse the magnesium compound. Usually, the
dispersion contains from 0.005 to 2.0 moles of the solid magnesium
compound per mole of halohydrocarbon, preferably from 0.01 to 1.0
mole of the solid magnesium compound per mole of the
halohydrocarbon. The internal electron donor typically is employed
in an amount sufficient to provide a molar ratio of said compound
to the titanium halide of from 0.0005:1 to 2.0:1, preferably from
0.001:1 to 0.1:1.
[0037] Halogenation can be effected at a temperature of from about
60.degree. C. to about 150.degree. C., preferably from about
70.degree. C. to about 120.degree. C. Usually the reaction is
allowed to proceed over a period of 0.1 to 6 hours, preferably
between about 0.5 to about 3.5 hours. For convenience, halogenation
is usually effected at atmospheric pressure, although higher and
lower pressures can be employed if desired. The halogenated
product, like the starting magnesium compound, is a solid material
which can be isolated from the liquid reaction medium by
filtration, decantation or any suitable method.
[0038] After the solid halogenated product has been separated from
the liquid reaction medium, it may be treated one or more times
with additional tetravalent titanium halide to remove residual
alkoxy and/or aryloxy groups and maximize catalyst activity and
other desired properties. Preferably, the halogenated product is
treated at least twice with separate portions of the tetravalent
titanium halide. Generally, the reaction conditions employed to
treat the halogenated product with the titanium halide are the same
as those employed during the initial halogenation of the magnesium
compound, although it is not necessary that the internal electron
donor be present during this treatment though it may be. A
halohydrocarbon usually is employed, however, to dissolve the
titanium halide and disperse the solid, halogenated product.
[0039] To assist in the removal of residual alkoxy and/or aryloxy
moiety from the halogenated product, the latter such treatment may
be effected in the presence of an acid halide. While it is possible
to employ the acid halide separately, for convenience it is
preferable to employ it together with the titanium halide dissolved
in the halohydrocarbon. If desired, the halogenated product may be
treated with the acid halide before or after it is treated with the
titanium compound for the second time. From 5 mmol to 200 mmol of
the acid halide are generally employed per gram atom of magnesium
of the halogenated product. Preferably, the halide moiety of the
acid halides is chloride and the acid moiety corresponds to the
polycarboxylic acid moiety of the inside electron donor employed in
the preparation of the solid catalyst component. Suitable acid
halides include phthaloyl dichloride, 2,3-naphthalenedicarboxylic
acid dichloride, endo-5-norbornene-2,3-dicarb- oxylic acid
dichloride, maleic acid dichloride, citraconic acid dichloride, and
the like.
[0040] After the solid halogenated product has been treated one or
more times with additional tetravalent titanium halide, it is
separated from the liquid reaction medium by filtration, siphoning,
and the like, washed with an inert hydrocarbon to remove unreacted
titanium compounds, and dried. The solid halogenated product also
can be suspended in mineral oil with addition of aliphatic
hydrocarbon solvent, and then separated by filtration, drying, and
the like to form a procatalyst.
[0041] The final washed procatalyst product suitably has a titanium
content of from about 0.5 percent by weight to about 6.0 percent by
weight, preferably from about 1.5 percent by weight to about 4.0
percent by weight. The atomic ratio of titanium to magnesium in the
final procatalyst product usually is between about 0.01:1 and about
0.2:1, preferably between about 0.02:1 and about 0.1:1. The
internal electron donor typically is present in the procatalyst in
a ratio of internal electron donor to magnesium of from about
0.005:1 to about 10.0:1, preferably from about 0.02:1 to about
2.0:1.
[0042] The magnesium and titanium-containing procatalyst serves as
component (a) in the Ziegler-Natta catalyst system. The cocatalyst
component (b) employed in the Ziegler-Natta catalyst system may be
chosen from any of the known activators of olefin polymerization
catalyst systems employing a titanium halide, but organoaluminum
compounds are preferred. Trialkylaluminum compounds are
particularly preferred, particularly those wherein each of the
alkyl groups contain from 1 to 6 carbon atoms. Suitable
organoaluminum cocatalysts include compounds having the formula
Al(R'").sub.dX.sub.eH.sub.f wherein: X is F, Cl, Br, I or OR"", R'"
and R"" are saturated hydrocarbon radicals containing from 1 to 14
carbon atoms, which radicals may be the same or different, and, if
desired, substituted with any substituent which is inert under the
reaction conditions employed during polymerization, d is 1 to 3, e
is 0 to 2, f is 0 or 1, and d+e+f=3.
[0043] Such cocatalysts can be employed individually or in
combination thereof and include compounds such as
Al(C.sub.2H.sub.5).sub.3, Al(C.sub.2H.sub.5).sub.2Cl,
Al.sub.2(C.sub.2H.sub.5).sub.3Cl.sub.3, Al(C.sub.2H.sub.5).sub.2H,
Al(C.sub.2H.sub.5).sub.2(OC.sub.2H.sub.5),
Al(i-C.sub.4H.sub.9).sub.3, Al(i-C.sub.4H.sub.9).sub.2H,
Al(C.sub.6H.sub.13).sub.3 and Al(C.sub.8H.sub.17).sub.3.
[0044] The final component of the Ziegler-Natta catalyst system is
the selectivity control agent (SCA), or external electron donor. It
is preferred in the present invention to use at least one silicon
compound as the SCA. Useful silicon compounds of the invention
contain at least one silicon-oxygen-carbon linkage. Suitable
silicon compounds include those having the formula
R.sup.1.sub.mSiY.sub.nX.sub.p wherein: R.sup.1 is a hydrocarbon
radical containing from 4 to 20 carbon atoms, Y is --OR.sup.2 or
--OCOR.sup.2 wherein R.sup.2 is a hydrocarbon radical containing
from 1 to 20 carbon atoms, X is hydrogen or halogen, m is an
integer having a value of from 0 to 3, n is an integer having a
value of from 1 to 4, p is an integer having a value of from 0 to
1, and preferably 0, and m+n+p=4. R.sup.1 should be such that there
is at least one non-primary carbon in the alkyl and preferably,
that such non-primary carbon is attached directly to the silicon
atom. Examples of R.sup.1 include cyclopentyl, t-butyl, isopropyl
or cyclohexyl. Examples of R.sup.2 include ethyl, butyl, isopropyl,
phenyl, benzyl and t-butyl. Examples of X are Cl and H.
[0045] Each R.sup.1 and R.sup.2 may be the same or different, and,
if desired, substituted with any substituent which is inert under
the reaction conditions employed during polymerization. Preferably,
R.sup.2 contains from 1 to 10 carbon atoms when it is aliphatic and
may be sterically hindered or cycloaliphatic, and from 6 to 10
carbon atoms when it is aromatic.
[0046] Silicon compounds in which two or more silicon atoms are
linked to each other by an oxygen atom, i.e., siloxanes or
polysiloxanes, may also be employed, provided the requisite
silicon-oxygen-carbon linkage is also present.
[0047] If more than one silicon compound is utilized in the present
invention, the two or more compounds must be separate and distinct
from each other and have different reactivities. This reactivity
difference may be measured in terms of hydrogen response which can
be determined in two ways: (1) by maintaining a constant hydrogen
concentration for given polymerization reaction conditions and
determining the difference in melt flow of two polymers made with
two catalysts of the present invention, except each of the two
catalysts has only one of the two silicon compounds as the sole
external electron donor; or (2) by determining the hydrogen
concentration necessary to achieve a given melt flow polymer at
specified polymerization reaction conditions made with two
catalysts of the present invention except each of the two catalysts
has one of the two different silicon compounds as the sole external
electron donor. For example, if the resulting melt flows of the
polymers made with these two catalysts vary by at least about an
order of magnitude (i.e., a factor of ten), then the two silicon
compounds can be said to have commercially relevant different
reactivities. This definition of differing reactivities is not
intended to be limiting because, as is apparent to one of ordinary
skill in the art, other ways of determining silicon compound
reactivity may be used.
[0048] To achieve this difference in reactivities of the silicon
compounds, it is likely that each of the silicon compounds will
have a different number of alkoxy and/or halide functionalities
thereon, with one silicon compound having a greater number of such
alkoxy and halide groups than the other. This may be expressed such
that n+p (per the formula above) of one silicon compound is greater
than the n+p of the other silicon compound used herein and more
preferably, p=0 and the "n" values of the two silicon compounds are
different from each other. It is preferred that one silicon
compound be a dialkoxy silane, e.g., methyl cyclohexyl
dimethoxysilane, diphenyl dimethoxy silane or dicyclopentyl
dimethoxysilane, and the other be a tri or tetra-alkoxy silane,
e.g., n-propyltrimethoxy silane, ethyltriethoxysilane or
tetraethoxysilane. Skilled artisans understand that the first
silicon and second silicon "compounds" may each be groups of
different silicon molecules, so long as each of these two groups as
a whole has different reactivity from the other.
[0049] Each of the silicon compounds can be present at molar ratios
of the silicon compound to titanium of from about 1:1 to about
50:1. Preferably the silicon compounds are present from about 3:1
to about 40:1. Most preferably they are present from about 5:1 to
about 30:1. The ratio between the silicon compounds varies
depending upon the relative reactivities of the compounds, the
polymerization reactor performance, and the desired polymer
properties.
[0050] The procatalyst can be preactivated or used to
"prepolymerize" a monomer or monomers before use in the primary
polymerization. One of the potential advantages of preactivated and
prepolymerized catalysts is that they can be more productive
because they enter the reactor as active catalysts. There is little
to no inherent induction time so no residence time in the reactor
is wasted by using a preactivated or prepolymerized catalyst. This
is particularly important for polypropylene impact copolymers
because it is believed that catalyst particles that do not make
enough homopolymer in the first reactor and hence remain active,
are then carried into the second reactor together with the
homopolymer. The presence of these still active catalyst particles
in the second reactor is believed to cause the formation of large
rubber particles in the second reactor that become gels and
decrease impact resistance. This is known as catalyst "bypassing"
and a common problem of linked continuously stirred tank reactors
(CSTRs) While not intending to be bound to any theory, the present
inventors believe that preactivation and prepolymerization should
reduce, and perhaps eliminate, the adverse effects of catalyst
bypassing on impact copolymer properties.
[0051] Preactivation may be accomplished in several ways. First the
procatalyst, cocatalyst and silicon compound(s) may be suspended in
an inert diluent, such as one or more hydrocarbons, including, but
not limited to, toluene, isooctane, isopentane, and
halohydrocarbons, such as o-chlorotoluene or monochlorobenzene.
This mixture then is agitated. During agitation it is preferred
that the suspension remain at ambient or below temperature. The
catalyst may then be separated from the reaction mixture, washed
with an inert hydrocarbon or halohydrocarbon to remove excess
reactant and dried. Filtering is preferred over heating for such
drying, although either or both could be used. If a second silicon
compound is to be used and was not optionally added before this
combination, it may then be physically blended with this catalyst,
but at least one silicon compound preferably was chemically blended
with the catalyst.
[0052] The procatalyst, cocatalyst and silicon compound(s) can be
contacted with one another for a period of time sufficient to
preactivate the procatalyst. That is, the components are contacted
for a period of time sufficient to prepare a catalyst component
that is more capable of polymerizing an olefin monomer than the
individual catalyst components alone. Preferably, the activity of
the preactivated component is increased by greater than 50%, more
preferably greater than 100% and most preferably greater than 200%,
when compared to the individual catalyst components alone, which
typically are incapable of polymerizing an olefin monomer.
[0053] The components preferably are contacted for a period of from
10 seconds to 5 hours, more preferably from about 30 seconds to 4
hours, and even more preferably, from about 1 minute to about 1
hour. Those skilled in the art are capable of determining the
appropriate contact time sufficient to form a preactivated
catalyst. Typically, the preactivated catalyst is one which will
polymerize an olefin without addition of cocatalyst, when compared
to a procatalyst, which polymerizes no olefin without addition of
cocatalyst. Preactivation usually is carried out in the substantial
absence of olefin monomer, preferably less than 1 wt. %, more
preferably less than 0.1 wt. %, and most preferably less than 0.05
wt. % olefin monomer.
[0054] Alternatively or in conjunction with preactivation,
prepolymerization may be used to preactivate the catalyst. A small
amount of olefin may be added to the mixture of procatalyst,
cocatalyst and at least one silicon compound thereby initiating
polymerization. The catalyst may optionally be isolated from the
reaction solvent before contact with the prepolymerization olefin
monomer. The amount of olefin monomer for use in such
prepolymerization should be at least 0.03 grams of olefin per gram
of catalyst. The greater the amount of olefin used, the greater the
amount of polymer initially produced. The olefin need not be the
same as the olefin to be polymerized, and propylene is preferred.
Again, if a second silicon compound is used, and was not previously
added, then it can be physically mixed with the rest of the
catalyst. Optionally, additional co-catalyst may be used during the
prepolymerization reaction.
[0055] It is possible also to form two prepolymerized or
preactivated catalysts per either of the above-described methods,
each with at least one silicon compound and either physically blend
the two catalysts together or add the two prepolymerized catalysts
together into the polymerization reactor.
[0056] Preactivation or prepolymerization of the catalyst typically
results in the partial or complete removal of the internal electron
donor. Therefore, when the catalyst is used, there may be no
internal electron donor left, and the cocatalyst and the SCA act as
the electron donor. When such a preactivated or prepolymerized
catalyst is ultimately fed to a polymerization reactor,
substantially less SCA is needed in the primary polymerization
reactor. No additional SCA is required however typically, anywhere
from 10 to 99% less SCA can be used to advantageously vary
polyolefin product properties in the primary polymerization if
preactivated or prepolymerized catalysts are used, when compared to
using conventional Ziegler-Natta catalyst components that have not
been preactivated and/or prepolymerized. Preferably, anywhere from
about 50 to about 98% less SCA can be used, and even more
preferably, from about 80 to about 95% less SCA can be used in the
primary polymerization when preactivated and/or prepolymerized
catalysts are employed, thereby resulting in significant raw
material cost savings.
[0057] The cocatalyst and the selectivity control agent preferably
are employed in preactivation and/or prepolymerization in such
amounts as to provide an atomic ratio of metal (e.g., Al) in the
cocatalyst to titanium in the procatalyst of from 0.5:1 to 100:1,
more preferably from 2:1 to 50:1. After contacting the components
to form a preactivated and/or prepolymerized catalyst, the solid
preactivated and/or prepolymerized component is separated from the
reaction mixture. Any means known in the art may be employed to
effect separation of the solid component. The solid component then
preferably is washed and dried again using techniques known in the
art. Skilled artisans are capable of separating, optionally
washing, and drying the solid preactivated and/or prepolymerized
catalyst using the guidelines provided herein.
[0058] The preactivated and/or prepolymerized catalyst may be
suspended by placing it in an inert diluent, such as mineral oil or
light hydrocarbon, such as isopentane, hexane, or propane, or it
may be left dry and fed as a dry solid to the reactor. For ease of
delivery to the reactor and for storage, it is preferred to slurry
the catalyst.
[0059] The catalysts may be used in slurry, liquid phase, gas phase
and liquid monomer-type reaction systems as are known in the art
for polymerizing olefins. Commercial polymerization preferably is
conducted in a fluidized bed polymerization reactor, however, by
continuously contacting an .alpha.-olefin having 3 to 8 carbon
atoms with the preactivated and/or prepolymerized catalyst, and
optionally, additional cocatalyst and SCA. In accordance with the
process, discrete portions of the catalyst components are
continually fed to the reactor in catalytically effective amounts
together with the alpha-olefin while the polymer product is
continually removed during the continuous process. Fluidized bed
reactors suitable for continuously polymerizing alpha-olefins have
been previously described and are well known in the art. Fluidized
bed reactors useful for this purpose are described, e.g., in U.S.
Pat. Nos. 4,302,565, 4,302,566 and 4,303,771, the disclosures of
which are incorporated herein by reference. Those skilled in the
art are capable of carrying out a fluidized bed polymerization
reaction using the guidelines provided herein.
[0060] It is preferred sometimes that such fluidized beds are
operated using a recycle stream of unreacted monomer from the
fluidized bed reactor. In this context, it is preferred to condense
at least a portion of the recycle stream. Alternatively,
condensation may be induced with a liquid solvent. This is known in
the art as operating in "condensing mode." Operating a fluidized
bed reactor in condensing mode generally is known in the art and
described in, for example, U.S. Pat. Nos. 4,543,399 and 4,588,790,
the disclosures of which are incorporated by reference herein in
their entirety.
[0061] Advantageously, the use of condensing mode has been found to
lower the amount of xylene solubles in isotactic polypropylene and
improve catalyst performance when using the preactivated and/or
prepolymerized catalyst of the present invention.
[0062] This invention also pertains to a novel way of injecting
slurried catalyst into a fluidized bed by using a combination of
inert liquid solvent and inert gaseous species. Because the
catalysts of the present invention are preactivated, some standard
types of transportation may not be suitable because polymerization
may occur during conveying to the reactor, causing the piping to
plug. For example, preactivated and/or prepolymerized catalysts, if
fed to the reactor together with monomer feed, can cause premature
polymerization in the feed line, which can lead to plugging. Thus,
if the preactivated and/or prepolymerized catalyst is conveyed to
the primary polymerization reactor together with some or all of the
monomer to be polymerized, polymerization in the feed line can be
avoided by using high flow rates preferably with Reynolds numbers
above about 20,000, to ensure turbulent flow and mixing of the
reactants. Optionally, it is known in the art to use stringent
temperature control to limit the rate of reaction during
prepolymerization although these methods impact significant
operational restrictions and costs to the polymerization system. It
is preferred, however, to feed the preactivated and/or
prepolymerized catalyst to the primary polymerization reactor using
a carrier other than the olefin to be polymerized.
[0063] The use of an inert gaseous species as the sole carrier can
be effective because it does not plug the feed tube. However, large
particles and chips may form in the fluidized bed, eventually
resulting in discharge system failure due to plugging. In addition,
a liquid solvent carrier by itself can cause high levels of
hydrocarbon to build in the reactor resulting in high dew points
and problems with polymerization reactor operation. The present
inventors have surprisingly found, however, that the use of a
liquid solvent and an inert gas carrier together as a carrier is a
successful way of injecting the preactivated and/or prepolymerized
catalysts into the reactor, and it achieves good operability. In
addition, conveying the preactivated and/or prepolymerized catalyst
to the primary polymerization reactor with a liquid solvent and an
inert gas enables the production of polymer having a narrower
particle size distribution, greater bulk density and smaller
particle size. The mass flow ratio between the inert gas and the
liquid solvent should be between 0.01:1.0 and 100:1, and preferably
0.01:1 to 10:1.
[0064] Hydrocarbons such as alkanes (e.g., propane, isopentane
(iC.sub.5), hexane, heptane, and isooctane) and aromatics,
substituted and unsubstituted, (e.g., toluene, xylene, naphtha) are
preferred as the liquid solvent. The inert gas may be any inert gas
compound that does not react with the catalyst. Preferably, the
inert gas is selected from nitrogen, ethane, methane, H.sub.2,
helium, argon, neon, krypton, and xenon.
[0065] Generally, catalyst feed lines to polymerization reactors
contain from 1 weight percent to 75 weight percent of the catalyst
(inclusive of slurry solvents). The amount of total solvent
introduced into the reactor should be carefully controlled to avoid
the use of excessive quantities of various liquids which could
interfere with the operation of the fluidized bed.
[0066] The inert gas should be substantially free of catalyst
poisons, such as H.sub.2O, O.sub.2, CO, CO.sub.2, C.sub.2H.sub.2,
and the like. Gas impurity problems may be solved by installing a
small purification column in the gas carrier stream. A molecular
sieve bed may be installed on the gas carrier line before the
junction with the catalyst stream. Gas stream purification methods
are well known in the art.
[0067] An exemplary method for feeding the catalyst to the system
is set forth in FIG. 1. FIG. 1 shows a reactor system 4, including
an inert gas feed line 1, a catalyst feed line 2, a solvent feed
line 3, reactor system 4, recycle line 5 for the reactor,
compressor 6, optional heat exchanger or condenser 7, polymer
withdrawal stream 8, and olefin feed line 10. An optional solvent
feed line for inducing condensing mode is depicted as feed line 9
although solvent line 3 may also be used for this purpose. It is
noted that the solvent may be mixed with the gas or catalyst prior
to the gas being combined with the catalyst and that FIG. 1 is only
a preferred embodiment of such a feed mechanism.
[0068] The olefins for use herein include, inter alia, ethylene,
propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1,
heptene-1, 1, 4-butadiene, and octene-1 with propylene being
preferred. Mixed olefin streams may also be used.
[0069] The olefins useful in the process of the present invention
may, if desired, also be employed to produce copolymers by
copolymerizing them with another olefin in one or more reaction or
reactor stages. Such copolymerizations are particularly useful in
processes which employ sequential polymerization cycles to produce
polymers having improved impact properties, e.g., by
homopolymerizing an alpha-olefin in one reactor and subsequently
copolymerizing the alpha-olefin with another olefin in a second
reactor in the presence of the product of the first reactor. This
technique produces polypropylene-polyethylene impact copolymers by
a multi-stage process wherein propylene is homopolymerized in one
reaction zone and then copolymerized with ethylene in a separate
reaction zone, arranged in sequence with the first reaction zone,
in the presence of the homopolymer produced in the first reaction
zone. When multiple reactors are employed in this manner, it is
sometimes necessary to add additional amounts of cocatalyst to the
second reactor to maintain an active catalyst although not usually
required in the present invention. Additional amounts of the
procatalyst and selectivity control agents are generally not
required. If desired, most preferably, one SCA is used in the first
reactor (e.g., an akyl, cycloalkyl dialkoxysilane or a dicycloalkyl
dialkoxysilane) and a second SCA is used in the second reactor
(e.g., an alkyl trialkoxysilane).
[0070] Hydrogen may also be added to the reaction mixture as a
chain transfer agent to regulate molecular weight. Generally,
hydrogen is added to the reaction mixture in an amount sufficient
to produce a mole ratio of hydrogen to olefin of from about
0.00001:1 to about 0.5:1. In addition to hydrogen, other chain
transfer agents may be employed to regulate the molecular weight of
the polymers.
[0071] To maintain a viable fluidized bed, the superficial gas
velocity of the gaseous reactor mixture through the bed must exceed
the minimum flow required for fluidization and preferably is at
least 0.06 meter per second above minimum flow. Ordinarily, for
manufacturing polypropylene the superficial gas velocity does not
exceed 0.75 m/s, and most usually no more than 0.4 m/s is
sufficient.
[0072] Pressures of up to about 7000 kPa can be employed in the
process, although pressures of from about 70 kPa to about 3500 kPa
are preferred. The partial pressure of the olefin employed is
usually maintained between about 56 kPa to about 2800 kPa. To
produce polypropylene in a commercially viable manner, it is
customary to employ polymerization temperatures of about 50.degree.
C., while temperatures of about 65.degree. C. are preferred, as
such temperatures result in polymers having desirable polymer
properties. However, temperatures in excess of about 120.degree. C.
should be avoided to prevent agglomeration of the polymer product.
Higher temperatures can be employed depending on the pressure
maintained in the reactor.
[0073] Polypropylene polymers produced in accordance with the
process of the present invention usually have a melt flow rate of
from about 0.1 g/10 minutes to about 3000 g/10 minutes, preferably
of from about 1 g/10 minutes to about 1000 g/10 minutes. The melt
flow of a polymer varies inversely with its molecular weight and is
defined by the desired polymer product properties.
[0074] Polypropylene-containing polymers produced in accordance
with the process of the present invention typically are granular
materials having an average particle size of from about 0.01 to
about 0.20 centimeters, usually of from about 0.02 to about 0.13
centimeters, in diameter. The particle size is important for the
purpose of readily fluidizing the polymer particles in the
fluidized bed reactor and may be different for different reactor
operations.
[0075] Polypropylene-containing polymers produced in accordance
with the process of the present invention usually have a bulk
density of from about 200 kilograms per cubic meter to about 500
kilograms per cubic meter.
[0076] The molecular weight distribution of polymers produced with
the present preactivated and/or prepolymerized catalysts can be
broadened or narrowed while not adversely affecting the other
properties of the polymer, including xylene solubles, productivity,
hydrogen response and modulus.
[0077] The invention now will be described in more detail with
reference to the following non-limiting examples.
EXAMPLES
[0078] The following Examples are designed to illustrate the
process of the present invention and are not intended as a
limitation upon the scope thereof.
Examples 1-11
Procatalyst Preparation
[0079] The following catalysts were made with a precursor of
carbonated magnesium ethoxide (CMEO), of approximately 15 .mu.m in
diameter, TiCl.sub.4 and di-isobutyl phthalate which were dissolved
in monochlorobenzene (MCB) and heated at 90-115.degree. C. for one
to two hours and filtered. The procatalyst was contacted twice more
with TiCl.sub.4 and MCB and heated and filtered. The procatalysts
had Ti weight percents of 1.5-3.5, ethoxide weight percents of 0.05
to 0.6, and di-isobutyl phthalate weight percents of 4.0 to 15.0.
This procatalyst is denoted simply by the letter "C."
[0080] In the preparation of an additional procatalyst material, a
magnesium and titanium-containing precursor of approximately 25
.mu.m in diameter first was prepared and then this precursor was
reacted with TiCl.sub.4 and di-isobutyl phthalate as described
above. The precursor was prepared by reacting magnesium ethoxide
(Mg(OEt).sub.2) with titanium tetraethoxide (Ti(OEt).sub.4),
TiCl.sub.4, o-cresol, and ethyl alcohol in the presence of
monochlorobenzene (MCB). The solid product was crystallized,
filtered, washed and subsequently washed twice more. The filter
cake then was de-watered and dried with circulating heated nitrogen
to produce a solid precursor component. This solid precursor
component then was reacted with TiCl.sub.4 and di-isobutyl
phthalate as described above to generate a procatalyst component
designated as "M."
Preactivated Catalyst Preparation
[0081] The procatalysts C and M were preactivated by contacting the
procatalyst according to Table 1 in an inert hydrocarbon first with
triethyl aluminum (TEAL) and then the SCAs. The amount and type of
inert hydrocarbon was sufficient to maintain good mixing in the
desired manufacturing equipment The reaction mixture was optionally
temperature regulated at or slightly below ambient temperature
depending upon the heat transfer characteristics of the
manufacturing system but critically maintained below 40 degrees
Celsius. The mixture then was mildly agitated for between 15 and 60
minutes. The solid component was then separated from the reaction
mixture by filtration and re-suspended in fresh inert hydrocarbon
of appropriate volume followed by mild agitation. The solid was
again separated from the hydrocarbon with optional repetitions
depending upon the manufacturing efficiency. The remaining
hydrocarbon was then extracted from the solid by an efficient
manipulation of temperature, pressure, and flow with an inert gas
but maintained below about 150 degrees Fahrenheit. The final solid
was then slurried in a common mineral oil of appropriate viscosity
to protect the active catalyst from exposure to air and water and
also to provide an efficient means of handling the preactivated
catalyst material. The resulting material is stable to
auto-decomposition for a period of more than one year. These
preactivated catalysts were denoted R1, R2, R55, R82, and S.
Prepolymerized Catalyst Preparation
[0082] The procatalysts C and M were prepolymerized by contacting
according to Table 1 in an inert hydrocarbon first with triethyl
aluminum (TEAL) and then the SCAs. The amount and type of inert
hydrocarbon was sufficient to maintain good mixing in the desired
manufacturing equipment The reaction mixture was optionally
temperature regulated at or slightly below ambient temperature
depending upon the heat transfer characteristics of the
manufacturing system but critically maintained below 40 degrees
Celsius. The mixture then was mildly agitated for between 15 and 60
minutes. Optionally at this point, the mixture was exposed to
propylene at a rate and pressure adequate to maintain the
temperature limitations set forth above. The amount of propylene
was varied for different preparations between about 1 gram
propylene per gram procatalyst to about 10 gram per gram. After
consumption of the propylene, the solid component was separated
from the reaction mixture by filtration and re-suspended in fresh
inert hydrocarbon of appropriate volume followed by mild agitation.
If propylene had not been added during the initial reaction as
stated above, the propylene could now be added to the mixture of
prepared preactivated catalyst in inert hydrocarbon. Optionally at
this point additional TEAL was added if the manufacturing
capability was sufficient to meet the temperature requirements
stated above. Finally, the solid was again separated from the
hydrocarbon with optional repetitions depending upon the
manufacturing efficiency. The remaining inert hydrocarbon was then
extracted from the solid by an efficient manipulation of
temperature, pressure, and flow with an inert gas but maintained
below about 150 degrees Fahrenheit. The final solid was then
slurried in a common mineral oil of appropriate viscosity to
protect the active catalyst from exposure to air and water and also
to provide an efficient means of handling the preactivated catalyst
material. The resulting material is stable to auto-decomposition
for a period of more than one year. These prepolymerized catalysts
were denoted as N1, N2, N3, and M.
1TABLE 1 DESCRIPTION OF PREACTIVATED AND PREPOLYMERIZED CATALYSTS
SCA/Ti Al/Ti Catalyst (mole) (mole) Description R1 7.0 25.0
DCPDMS/TEAL preactivated C R2 10.0 20.0 ETES/TEAL preactivated C
R55 -- -- 50% R1/50% R2 physical mixture R82 -- -- 80% R1/20% R2
physical mixture S 10 and 5 40.1 ETES and DCPDMS/TEAL preactivated
C N1 7.0 25.0 DCPDMS/TEAL and C prepolymerized with 1 gm
propylene/gm catalyst N2 7.0 25.0 DCPDMS/TEAL and C prepolymerized
with 10 gm propylene/gm catalyst N3 7.0 25.0 DCPDMS/TEAL and C
prepolymerized with 3 gm propylene/gm catalyst T 5 15.0 NPTMS/TEAL
preactivated C T-C 11 25 NPTMS/TEAL preactivated C M 7 25
DCPDMS/TEAL and M prepolymerized with 1 gm propylene/gm catalyst
DCPDMS = dicyclopentyl dimethoxy silane ETES = ethyl
triethoxysilane NPTMS = n-propyl trimethoxysilane
[0083] Polymerizations
[0084] The aforementioned catalysts (including preactivated and
prepolymerized catalysts) were utilized in various polymerization
reactions with propylene. Examples 1-7 were liquid phase
polypropylene polymerizations (LIPP) in a 1 gallon autoclave, using
a ratio of titanium to TEAL of 1:60, and a hydrogen content to
maintain a vapor pressure of about 400 psig. Examples 8-11 also
were standard LIPP reactions using a Ti:Al ratio of 1:60, and a
hydrogen equivalent to maintain a melt flow (MF) of about 2-5. In
examples 9 and 11, the hydrogen partial pressure was increased to
600 psig to measure the effect on MF. The results of the LIPP
reactions are shown in Tables 2 and 3 below.
2TABLE 2 POLYMERIZATION REACTIONS YD (Kg pp/ YD (g gm polymer
.times. BD (bulk Cata- % cata- 10.sup.6/ density) Ex. lyst Ti lyst)
gm Ti) (g/cc) XS (% W) MF (dg/min) 1 R1 1.5 21.6 1.5 0.41 3.0 3.3 2
R1 1.5 18.3 1.2 0.41 3.3 0.8 3 R1 1.3 23.5 1.8 0.40 2.9 3.3 4 R2
1.5 21.2 1.4 0.35 6.0 41 5 R2 1.2 19.5 1.7 0.33 6.6 26 6 M 0.9 10.8
1.2 0.44 2.6 3.3 7 S 1.4 21.5 1.5 0.40 4.2 11
[0085]
3TABLE 3 POLYMER PREPARATIONS H2 BD XS MF Ex. Catalyst (psig)
(g/cc) (% w) (dg/min) 8 R-55 200 0.32 3.4 2.3 9 600 0.39 4.2 18 10
R-82 200 0.38 3.6 2.2 11 600 0.40 4.0 6.2
[0086] As shown in Table 2, preactivated catalysts can be used in
liquid phase polymerizations to produce polypropylene in high
yield, without adversely affecting the selectivity, bulk density
and melt flow. It was generally thought, however, that if these
preactivated catalysts were fed to a gas phase reactor, rapid
polymerization would occur causing undesirable generation of heat,
increase of agglomeration, tube plugging, reactor sheeting and
ultimately reactor shut down.
[0087] Table 3 shows that the physically-mixed catalysts R-55 &
R-82 demonstrated a surprisingly strong melt flow response (i.e.,
non-linear) and decidedly better high melt flow performance than
expected. These particular catalysts are suited for higher melt
flow products, a regime where both the melt flow difference between
the constituent catalysts is the highest and where
hydrogen-efficient silanes such as ETES exhibit the best
performance.
Examples 12-17
[0088] Some of the catalysts listed in Table 1 above were subjected
to a high TEAL LIPP polymerization and/or a high temperature
polymerization. The high TEAL polymerizations shown in Table 4
below were conducted in the same manner as the liquid phase
polymerizations of Examples 1-11, but with a TEAL:Ti molar ratio of
250:1. The high temperature polymerizations were conducted in the
same manner as the liquid phase polymerizations of Examples 1-11,
but at a temperature of 80.degree. C. The high temperature and high
TEAL polymerizations ran at both the elevated TEAL and temperature,
but otherwise conditions were the same as the standard liquid phase
polymerizations of examples 1-11.
[0089] The high TEAL and high temperature polymerizations were
conducted in an attempt to investigate extreme reaction conditions
such as may be present in a poorly mixed polymerization reactor.
The data for laboratory gas phase polymerization shown in Table 4
was gathered by carrying out polymerization using the indicated
catalyst in a specialized small scale reactor at a temperature of
67.degree. C., a TEAL:Ti ratio of 60:1 and hydrogen in an amount
used to generate a 2-5 MF polymer using a conventional catalyst.
The results shown in Table 4 below are all in terms of xylene
solubles (XS) expressed as percentages of the weight of polymer
produced, which is an indicator of selectivity of the catalyst and
critical catalyst performance.
4TABLE 4 POLYMERIZATION REACTIONS Xs(%) catalyst gas std high high
high TEAL & Ex. system phase LIPP TEAL temp high temp 12 T-C
2.2 2.0 5.0 13 T 3.9 2.2 14 R1 3.7 3.1 2.9 4.0 15 N1 2.6 3.2 3.1
3.0 16 R2 6.6 6.5 11.8 17 S 4.6 4.2 5.4 4.8
[0090] The data in Table 4 shows a relatively good correlation
between high TEAL and high temperature LIPP polymerizations and gas
phase polymerizations. Table 4 also reveals that while operating a
higher TEAL did not significantly affect selectivity, extended LIPP
with higher TEAL and high temperature did decrease selectivity. As
indicated, reaction conditions might still exist in a gas phase or
poorly mixed other polymerization reactor which would result in
undesirable catalyst and reactor performance. Importantly, the
polymerization performance is a function of the desired polymer
product and hence, particular catalyst used. There is a need for
polymerization control when using preactivated and/or
prepolymerized catalysts.
Examples 18-21
[0091] Examples 18-21 were carried out in the same manner as
examples 1-11, except the LIPP polymerizations were conducted using
prepolymerized procatalysts N1, N2 and N3. The amount of hydrogen
used in these examples was that required to yield a MF within the
range of 2 to 5. The data are tabulated in Table 5 below.
5TABLE 5 POLYPROPYLENE PREPARATIONS YD (g polymer .times. BD XS
H.sub.2 Example Catalyst % Ti 10.sup.6/gm Ti) (g/cc) (%) (psig) 18
N1 0.8 1.4 0.39 3.3 500 19 N1 0.8 1.2 0.39 2.9 (frac. MF) 20 N3
0.38 21 N2 0.2 0.8 0.36 2.9 600
[0092] The results of LIPP polymerization using prepolymerized
procatalysts are similar to the results shown in Table 2 using
preactivated procatalysts. For example, these data reveal that
prepolymerized procatalysts can be used in liquid phase
polymerizations to produce polypropylene in high yield, without
significantly adversely affecting the selectivity, bulk density and
melt flow. It was generally thought, however, that if these
prepolymerized catalysts were fed to a gas phase reactor, rapid
polymerization would occur causing undesirable generation of heat,
increase of agglomeration, tube plugging, reactor sheeting and
ultimately reactor shut down.
Examples 22-40
Gas Phase Experiments
[0093] Preactivated and prepolymerized catalysts were used to
produce polypropylene homopolymer in a fluid bed gas phase reactor.
The reaction conditions were P.apprxeq.3.times.10.sup.6 Pa,
P.sub.pp.apprxeq.2.3.times- .10.sup.6 Pa, T=65.degree. C. in a gas
phase reactor with a reactor superficial gas velocity of about 0.3
m/sec. A recycle stream, at about 15 m/s was used as well. The
reactor system was set up essentially as shown in FIG. 1. TEAL was
used as the cocatalyst. A small sieve bed was installed near the
reactor to remove contaminants in the nitrogen feed. The mass flow
ratio for mixed isopentane/nitrogen carriers (N.sub.2/iC.sub.5) was
about 1.35. The results of the gas phase polymerizations are set
forth in Table 6 below.
6TABLE 6 Example 22 23 24 25 Catalyst: R R1 N1 N2 Carrier N2 N2 N2
N2 Carrier Flow Rate Reaction Conditions: H2/C3 Molar Ratio 0.02956
0.02378 0.02193 0.01787 Average Residence Time (hr.) 1.46666
1.95620 2.77471 6.90204 Bed Weight (kg) 25.5 26.6 26.4 26.1
Fluidized Bulk Density (kg/m{circumflex over ( )}3) 190.3 190.2
131.6 132.2 TEAL Concentration (wgt. %) 5.00 5.00 5.00 5.00 TEAL
Flow Rate (cc/hr.) 188.92 247.6 301.19 298.8 SCA DCPDMS SCA
Concentration (wgt. %) 5.00 SCA Flow Rate (cc/hr.) 251.9 TEAL/SCA
Molar Ratio 1.5 Al/Ti Molar Ratio 213 58 54 114 SCA/Ti Molar Ratio
131.0 Resin Properties: Melt Flow (dg/min.) 5.93 4.324 4.19 7.192
Xylene Solubles (%) 1.13 1.38 1.76 3.22 Productivity (kg/g-Ti)
1369.9 1111.1 735.3 980.4 Settled Bulk Density (kg/m{circumflex
over ( )}3) 367.8 372.6 424.0 438.1 Average Particle Size (cm)
0.0620 0.0719 0.0310 % on #10 Mesh Screen 0 0 0 0 % Fines (<120
Mesh) 1.5 3.52 11.56 9.6899 Example # 26 27 28 29 30 Catalyst: 205
205 R1 R1 R1 Carrier nitrogen nitrogen nitrogen nitrogen
N.sub.2/iC.sub.5 Carrier Flow 2.27 1.91 2.27 2.27 2.27 (kg/hr)
Reaction Conditions: H2/C3 Molar 0.0318 0.1027 0.0170 0.0220 0.0220
Ratio Average 2.3 3.8 3.3 3.3 2.7 Residence Time (hr.) Bed Weight
25.71 37.51 25.26 29.29 26.89 (kg) Fluid Bulk 170.10 238.30 145.88
163.65 136.51 Density (kg/m{circumflex over ( )}3) TEAL 5 5 5 5 5
Concentration (wgt. %) TEAL Flow 59.88 90.717 100.9 122.15 135.03
Rate (cc/hr.) SCA DCPDMS DCPDMS DCPDMS DCPDMS SCA 5 5 0.5 2
Concentration (wt. %) SCA Flow Rate 108.11 159.49 101.69 49.238
(cc/hr.) TEAL/SCA 1.11 1.14 24.03 13.72 Molar Ratio Al/Ti Molar 106
107 84 122 167 Ratio SCA/Ti Molar 67.13 112.74 5.57 13.92 Ratio
Resin Properties: Melt Flow 5.48 31.9 4.52 4.35 4.8 (dg/min.)
Xylene 1.27 1.56 1.99 2.3 1.3 Solubles (%) Productivity 1053 1053
654 741 1053 (kg/g-Ti) Settled Bulk 318.59 306.09 424.04 447.60
459.29 density (kg/m{circumflex over ( )}3) Average 0.06 0.07 0.10
0.12 0.00 Particle Size (cm) % Fines 1.31 1.80 3.31 3.37 10.33
(<120 Mesh) Example 31 32 33 34 35 Catalyst: R1 R1 R82 R82 R55
Carrier nitrogen/ nitrogen/ nitro- nitrogen/ nitrogen/ iC5 iC5
gen/iC5 iC5 iC5 Carrier Flow 2.27 2.27 2.27 2.27 2.27 (kg/hr)
Reaction Conditions: H2/C3 Molar 0.0219 0.1701 0.0175 0.0236 0.0117
Ratio Avg Residence 2.1 2.4 2.6 2.6 2.3 Time (hr.) Bed Weight 26.04
30.72 27.14 27.56 26.22 (kg) Fluid Bulk 139.21 164.55 137.54 134.33
142.28 Density (kg/m{circumflex over ( )}3) TEAL 5 5 5 5 5
Concentration (wgt. %) TEAL Flow 80.837 79.041 80.538 79.939 78.741
Rate (cc/hr.) SCA NPTMS DCPDMS SCA Conc. 0.15 2 (wt. %) SCA Flow
148.78 200.88 Rate (cc/hr.) TEAL/SCA 26.06 1.99 Molar Ratio Al/Ti
Molar 103 83 87 73 53 Ratio SCA/Ti Molar 3.33 35.80 Ratio Resin
Properties: Melt Flow 4.25 121.06 5.36 3.67 4.95 (dg/min.) Xylene
1.56 2.76 2.62 1.17 3.7 Solubles (%) Productivity 1020 1111 885 725
621 (kg/g-Ti) Settled Bulk 468.59 478.04 459.29 456.89 452.24
density (kg/m{circumflex over ( )}3) Average 0.03 0.03 0.03 0.03
0.03 Particle Size (cm) % Fines 10.92 9.84 12 16.33 11.9 (<120
Mesh) Example 36 37 38 39 40 Catalyst: R55 S S M M Carrier
nitrogen/ nitrogen/ nitrogen nitrogen/ nitrogen/ iC5 iC5 iC5 iC5
Carrier Flow 2.27 2.27 1.91 2.27 1.68 (kg/hr) Reaction Conditions:
H2/C3 Molar 0.0219 0.0130 0.0381 0.0190 0.0225 Ratio Avg Residence
2.2 2.2 3.0 2.2 3.5 Time (hr.) Bed Weight 27.04 27.01 33.10 27.84
26.67 (kg) Fluid Bulk 133.44 136.98 234.44 133.83 98.00 Density
(kg/m{circumflex over ( )}3) TEAL 5 5 5 5 5 Concentration (wgt. %)
TEAL Flow 86.226 107.78 56.588 109.28 109.88 Rate (cc/hr.) SCA
DCPDMS DCPDMS SCA 2 2 Concentration (wt. %) SCA Flow 207.3 198.74
Rate (cc/hr.) TEAL/SCA 2.08 2.77 Molar Ratio Al/Ti Molar 48 136 77
46 65 Ratio SCA/Ti Molar 23.99 32.28 Ratio Resin Properties: Melt
Flow 3.79 6.49 33.43 3.75 3.58 (dg/min.) Xylene 1.19 2.95 4.17 3.37
0.94 Solubles (%) Productivity 543 592 1000 403 465 (kg/g-Ti)
Settled Bulk 459.29 449.84 421.47 461.54 475.64 density
(kg/m{circumflex over ( )}3) Average 0.03 0.03 0.05 0.05 0.04
Particle Size (cm) % Fines 14.71 13.2 6.90 8.0999 8.71 (<120
Mesh) 205 denotes SHAC .RTM. 205 catalyst, which is commercially
available from Union Carbide corporation, Danbury, Ct.
[0094] The comparative examples are the gas phase polymerization
experiments carried out using conventional catalysts that were not
preactivated or prepolymerized (examples 22, 26 and 27). As can be
seen from the examples above, a catalyst that has been preactivated
or prepolymerized off-line can be used in gas phase polymerization
to produce polypropylene in high yield, without significantly
adversely affecting the selectivity, bulk density and melt flow. In
addition, despite what was generally thought in the art,
preactivated and prepolymerized catalysts can be used in a gas
phase polymerization reactor without causing undesirable generation
of heat, increase of agglomeration, tube plugging, reactor sheeting
and ultimately reactor shut down Based on examples 23-25, 28, 29
and 38, when the preactivated and/or prepolymerized catalysts were
fed to the gas phase reactor using nitrogen only as the carrier,
there were some minor problems controlling the particle size, and
some agglomerates (about 0.5 cm -1.25 cm) formed. The number of
large particles was reduced by raising the reactor temperature, but
they were not completely eliminated. However, the addition of about
1.0 to 0.6 kg/hr of iC5 to the N.sub.2 carrier flow in examples
30-37, 39 and 40 completely eliminated the agglomerates or
chunks.
[0095] FIG. 2 shows the average particle size distribution for the
36 hours before and after adding iC5 to the catalyst carrier for
R1. Before iC5 was added, over 20% of the polymer had a particle
size so high it would not go through the largest screen. Within 12
hours, these polymer particles had disappeared. The number of
particles on the 18 mesh screen also substantially decreased to
about 20% of what it was without iC5 and the number of particles
passing through the 120 mesh screen more than doubled. In addition,
it is clear to see that the molecular weight distribution narrowed
upon addition of isopentane.
[0096] Indeed, this decrease in average particle size, and hence,
increase in bulk density, was further demonstrated in examples 33
and 34 when homopolymer polypropylene was made using R-82 catalyst.
The N.sub.2 carried the catalyst for approximately 4.6 meters and
iC5 (0.2-0.4 kg/hr) was injected 2-5 cm prior to the reactor. FIG.
4 clearly shows a significant decrease in average particle size,
starting at about 0.08 cm and reducing it to 0.025 cm. FIG. 3 shows
that the bulk density increased from 0.396 g/cc to 0.465 g/cc with
the use of isopentane in accordance with a preferred embodiment of
the present invention.
[0097] Comparing the comparative examples (22, 26 and 27), with the
inventive samples, it is clear to see that the use of preactivated
and prepolymerized can significantly reduce the amount of SCA added
to the reactor, without adversely affecting the productivity,
selectivity or melt flow. Given the knowledge in the art extant at
the time of this invention, it is unexpected that off-line
preactivated and/or prepolymerized catalysts could be used at all
in gas phase polymerization, much less used advantageously to
reduce the amount of SCA, increase the bulk density and reduce the
particle size.
[0098] Product Properties
[0099] Molecular Weight Distribution (MWD)
[0100] Table 7 below shows the molecular weight distribution
results for polypropylene homopolymers by gel permeation
chromatography (GPC). R82 produced the broadest molecular weight
distribution (MWD). The narrowest MWD's were made with R1. The
addition of NPTMS did broaden the MWD of polypropylene made with
R1, but did not make the MWD as broad as the catalysts that used
ETES. Adding DCPDMS to R55 reduced the xylene solubles and narrowed
the MWD.
7TABLE 7 MWD FOR EACH CATALYST Melt Flow Mn Catalyst (dg/min)
(g/mol) Mw/Mn Mz/Mn R 5.48 48,000 5.58 18.9 R1 4.52 59,800 4.52
15.2 R1 4.80 58,100 4.53 13.2 R1 4.25 55,700 4.99 16.0 R82 5.36
45,600 6.00 20.9 R55 4.95 52,700 5.20 17.5 R55 3.79 58,400 4.89
15.5 S 6.49 49,300 5.14 17.6 M 3.75 64,000 4.32 12.5
[0101] While the invention has been described in detail with
reference to particularly preferred embodiments and examples, those
skilled in the art recognize that various modifications may be made
to the invention without significantly departing from the spirit
and scope thereof All documents mentioned above are incorporated by
reference herein in their entirety.
* * * * *