U.S. patent application number 10/969387 was filed with the patent office on 2005-03-10 for olefin polymerization catalyst compositions and method of preparation.
Invention is credited to Cuthbert, Thomas R., Kilty, Peter A..
Application Number | 20050054792 10/969387 |
Document ID | / |
Family ID | 23132254 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050054792 |
Kind Code |
A1 |
Kilty, Peter A. ; et
al. |
March 10, 2005 |
Olefin polymerization catalyst compositions and method of
preparation
Abstract
A method of making a solid procatalyst composition for use in a
Ziegler-Natta olefin polymerization catalyst composition, said
method comprising: contacting a solid precursor composition
comprising magnesium, titanium, and alkoxide moieties with a
titanium halide compound and an internal electron donor in any
order, in a suitable reaction medium to prepare a solid procatalyst
composition, separating the solid procatalyst from the reaction
medium, further exchanging residual alkoxide functionality of the
solid procatalyst composition for chloride functionality by
contacting the same two or more times with benzoyl chloride
halogenating agent under metathesis conditions for a period of time
sufficient to prepare a solid procatalyst composition having a
decreased alkoxide content compared to the alkoxide content of the
solid procatalyst composition before said exchange, and recovering
the solid procatalyst composition.
Inventors: |
Kilty, Peter A.; (Sugar
Land, TX) ; Cuthbert, Thomas R.; (Houston,
TX) |
Correspondence
Address: |
UNION CARBIDE CHEMICALS AND PLASTICDS TECHNOLOGY
CORPORATION
P.O. BOX 1967
MIDLAND
MI
48674
US
|
Family ID: |
23132254 |
Appl. No.: |
10/969387 |
Filed: |
October 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10969387 |
Oct 20, 2004 |
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10138141 |
May 1, 2002 |
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6825146 |
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60294183 |
May 29, 2001 |
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Current U.S.
Class: |
526/124.3 ;
502/104; 502/107; 502/115; 502/116; 502/126; 502/127; 502/128;
526/125.2; 526/125.3; 526/125.7 |
Current CPC
Class: |
C08F 210/06 20130101;
C08F 10/06 20130101; C08F 210/06 20130101; C08F 10/06 20130101;
C08F 110/06 20130101; C08F 2/001 20130101; C08F 110/06 20130101;
C08F 10/06 20130101; C08F 10/06 20130101; C08F 2500/18 20130101;
C08F 4/651 20130101; C08F 4/6548 20130101; C08F 2500/12 20130101;
C08F 2500/18 20130101; C08F 210/16 20130101 |
Class at
Publication: |
526/124.3 ;
526/125.2; 526/125.3; 526/125.7; 502/107; 502/115; 502/104;
502/116; 502/126; 502/127; 502/128 |
International
Class: |
C08F 004/02 |
Claims
1. A process for polymerizing an olefin monomer comprising
contacting the olefin monomer under polymerization conditions with
a Ziegler-Natta olefin polymerization catalyst composition
comprising a solid procatalyst composition, a cocatalyst; and a
selectivity control agent, wherein the solid procatalyst
composition is prepared by contacting a solid precursor composition
comprising magnesium, titanium, and alkoxide moieties with a
titanium halide compound and an internal electron donor in any
order, in a suitable reaction medium to prepare a solid procatalyst
composition, separating the solid procatalyst composition from the
reaction medium, further exchanging residual alkoxide functionality
of the solid procatalyst composition for chloride functionality by
contacting the same two or more times with benzoyl chloride under
metathesis conditions for a period of time sufficient to prepare a
solid procatalyst composition having a decreased alkoxide content
compared to the alkoxide content of the solid procatalyst
composition before said exchange and without cooling of the
procatalyst composition by greater than 25.degree. C., and
recovering the solid procatalyst composition.
2. A process according to claim 1 wherein propylene or a mixture of
propylene and ethylene is polymerized.
3 A process according to claim 1 conducted in two or more gas-phase
polymerization reactors operating in series wherein the polymer in
an ethylene/propylene rubber modified polypropylene containing at
least 40 weight percent rubber.
Description
CROSS REFERENCE STATEMENT
[0001] This application is a Divisional of U.S. Ser. No.
10/138,141, filed May 1, 2002, which in turn claims benefit of
priority from U.S. Provisional Application No. 60/294,183, filed
May 29, 2001, the teachings of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to improved polymerization
catalyst compositions of the Ziegler-Natta type, procatalysts for
use in forming such catalyst compositions, methods of making such
catalyst compositions and procatalysts, and to methods of using the
catalyst compositions to make an olefin polymer.
[0003] Ziegler-Natta olefin polymerization catalyst compositions
typically comprise a solid component containing magnesium, titanium
and halide moieties in combination with an internal electron donor
(which combination is referred to as the "procatalyst"), a
substance that is capable of converting the procatalyst to an
active polymerization catalyst (referred to as a "cocatalyst"), and
a selectivity control agent (SCA) or external donor. Suitable
internal electron donors especially include aromatic mono- or
di-alkylesters or ether derivatives thereof, such as
alkylbenzoates, dialkylphthalates, and C.sub.1-4 alkyl ether
derivatives thereof. Conventional cocatalysts include aluminum
trialkyls, such as triethylaluminum or triisobutylaluminum. The
cocatalyst may be combined or complexed with some or all of the
internal electron donor, selectivity control agent, or both, if
desired. Although variations in any of these catalyst components
will influence the performance of the resultant catalyst, the
component that appears to offer the greatest opportunity for
modification to produce greater catalyst activity is the
procatalyst.
[0004] Various methods of preparing procatalysts are previously
disclosed in the patent art. Examples include: U.S. Pat. Nos.
5,247,032, 5,247,031, 5,229,342, 5,153,158, 5,151,399, 5,146,028,
5,124,298, 5,106,806, 5,082,907, 5,077,357, 5,066,738, 5,066,737,
5,034,361, 5,028,671, 4,990,479, 4,927,797, 4,829,037, 4,816,433,
4,728,705, 4,548,915, 4,547,476, 4,540,679, 4,535,068, 4,472,521,
4,460,701, 4,442,276, and 4,330,649. One preferred method from
among the foregoing disclosures is a method of forming a
"procatalyst precursor" from a mixture of magnesium dialkoxides and
titanium alkoxides and reacting the mixture with titanium
tetrachloride in the presence of an alcohol, an aromatic hydroxide
compound, and an aromatic solvent, especially chlorobenzene. In
this manner, a solid material is recovered by selective
precipitation upon removal of alcohol from the solution. This
precursor may thereafter by contacted with an internal electron
donor and washed with TiCl.sub.4 in a halohydrocarbon solvent to
form the desired procatalyst. Among the foregoing disclosures, U.S.
Pat. No. 5,124,298 and U.S. Pat. No. 5,082,907, disclose that an
acid chloride, such as benzoyl chloride or phthaloyl chloride, may
be used in combination with the TiCl.sub.4 and a halohydrocarbon in
at least one such wash step to further facilitate the replacement
of at least a portion of the alkoxide moieties. In U.S. Pat. No.
4,535,068 benzoyl chloride was contacted with a magnesium alkoxide
precursor compound both during preparation of a procatalyst and in
a subsequent step. The reference stated that the benzoyl chloride
contacting step may occur either before or simultaneously with
halogenation by means of a tetravalent titanium halide.
SUMMARY OF THE INVENTION
[0005] According to the present invention, there is provided a
method of making a solid procatalyst composition for use in a
Ziegler-Natta olefin polymerization catalyst composition, said
method comprising:
[0006] contacting a solid precursor composition comprising
magnesium, titanium, and alkoxide moieties with a titanium halide
compound and an internal electron donor in any order, in a suitable
reaction medium to prepare a solid procatalyst composition,
[0007] separating the solid procatalyst composition from the
reaction medium,
[0008] further exchanging residual alkoxide functionality of the
solid procatalyst composition for chloride functionality by
contacting the same two or more times with benzoyl chloride under
metathesis conditions for a period of time sufficient to prepare a
solid procatalyst composition having a decreased alkoxide content
compared to the alkoxide content of the solid procatalyst
composition before said exchange, and
[0009] recovering the solid procatalyst composition.
[0010] Also included in the present invention are the solid
procatalysts resulting from the foregoing methods of preparation;
olefin polymerization catalysts comprising one or more of the
foregoing procatalyst compositions, a cocatalyst, and optionally a
selectivity control agent; an improved olefin polymerization
process comprising contacting an olefin monomer under olefin
polymerization conditions in the presence of the foregoing catalyst
composition; as well as polyolefin polymers formed thereby.
[0011] The catalyst compositions of the present invention are
useful in preparing .alpha.-olefin polymers having relatively high
bulk density. Moreover, they enable the preparation of
polypropylene impact copolymers, especially polypropylene that is
impact modified by ethylene/propylene copolymers prepared in situ,
having increased rubber contents, at elevated polymerization
temperatures, without disadvantageous formation of polymer particle
agglomerates.
DETAILED DESCRIPTION
[0012] All reference to the Periodic Table of the Elements herein
shall refer to the Periodic Table of the Elements, published and
copyrighted by CRC Press, Inc., 1999. Also, any reference to a
Group or Groups shall be to the Group or Groups as reflected in
this Periodic Table of the Elements using the IUPAC system for
numbering groups. For purposes of United States patent practice,
the contents of any patent, patent application or publication
referenced herein are hereby incorporated by reference in their
entirety herein, especially with respect to the disclosure of
structures, synthetic techniques and general knowledge in the art.
The term "comprising" when used herein with respect to a
composition or mixture is not intended to exclude the additional
presence of any other compound or component. The term "aromatic" or
"aryl" refers to a polyatomic, cyclic, ring system containing
(4.delta.+2) .pi.-electrons, wherein .delta. is an integer greater
than or equal to 1.
[0013] As mentioned above, the olefin polymerization procatalyst
precursors employed in the invention comprise magnesium moieties.
Sources for such magnesium moieties include anhydrous magnesium
chloride, magnesium dialkoxides or aryloxides, or carboxylated
magnesium dialkoxides or aryloxides. Preferred sources of magnesium
moieties are magnesium di-(C.sub.1-4)alkoxides, especially
diethoxymagnesium. Additionally the precursors comprise titanium
moieties. Suitable sources of titanium moieties include titanium
alkoxides, titanium aryloxides, and titanium halides. Preferred
precursors comprise one or more magnesium di-(C.sub.1-4)-alkoxides
and one or more titanium tetra-(C.sub.1-4)-alkox- ides.
[0014] Various methods of making procatalyst precursor compounds
are known in the art. These methods are described, inter alia, 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; 5,077,357; 4,442,276; 4,540,679;
4,547,476; 4,460,701; 4,816,433; 4,829,037; 4,927,797; 4,990,479;
5,066,738; 5,028,671; 5,153,158; 5,247,031; 5,247,032, and
elsewhere. In a preferred method, the preparation involves
chlorination of the foregoing mixed magnesium and titanium
alkoxides, and may involve the use of one or more compounds,
referred to as "clipping agents", that aid in forming specific
compositions. Examples of suitable clipping agents include
trialkylborates, especially triethylborate, phenolic compounds,
especially cresol, and silanes.
[0015] A preferred procatalyst precursor for use herein is a mixed
magnesium/titanium compound of the formula
Mg.sub.dTi(OR.sup.e).sub.eX.su- b.f wherein R.sup.e is an aliphatic
or aromatic hydrocarbon radical having 1 to 14 carbon atoms or COR'
wherein R' is an aliphatic or aromatic hydrocarbon radical having 1
to 14 carbon atoms; each OR.sup.e group is the same or different; X
is independently chlorine, bromine or iodine; d is 0.5 to 5,
preferably 2-4, most preferably 3; e is 2-12, preferably 6-10, most
preferably 8; and f is 1-10, preferably 1-3, most preferably 2. The
precursors are ideally prepared by controlled precipitation through
removal of an alcohol from the reaction mixture used in their
preparation. An especially desirable reaction medium comprises a
mixture of an aromatic liquid, especially a chlorinated aromatic
compound, most especially chlorobenzene, with an alkanol,
especially ethanol, and an inorganic chlorinating agent. Suitable
inorganic chlorinating agents include chlorine derivatives of
silicon, aluminum and titanium, especially titanium tetrachloride
or titanium trichloride, most especially titanium tetrachloride.
Removal of the alkanol from the solution used in the chlorination,
results in precipitation of the solid precursor, having especially
desirable morphology and surface area. Moreover, the resulting
precursors are particularly uniform particle sized and resistant to
particle crumbling as well as degradation of the resulting
procatalyst.
[0016] The precursor is converted to a solid procatalyst by further
reaction (halogenation) with an inorganic halide compound,
preferably a titanium halide compound, and incorporation of an
internal electron donor. If not already incorporated into the
precursor in sufficient quantity, the electron donor may be added
separately before, during or after halogenation. Any method of
making, recovering and storing the solid precursor is suitable for
use in the present invention.
[0017] One suitable method for converting the solid procatalyst
precursor into a polymerization procatalyst is by reacting the
precursor with a tetravalent titanium halide, an optional
hydrocarbon or halohydrocarbon, and an electron donor (if not
already present). The preferred tetravalent titanium halide is
titanium tetrachloride.
[0018] The optional hydrocarbon or halohydrocarbon employed in the
production of olefin polymerization procatalyst preferably contains
up to 12 carbon atoms inclusive, more preferably up to 9 carbon
atoms inclusive. Exemplary hydrocarbons include pentane, octane,
benzene, toluene, xylene, alkylbenzenes, and the like. Exemplary
aliphatic halohydrocarbons include methylene chloride, methylene
bromide, chloroform, carbon tetrachloride, 1,2-dibromoethane,
1,1,2-trichloroethane, trichlorocyclohexane, dichlorofluoromethane
and tetrachlorooctane. Exemplary aromatic halohydrocarbons include
chlorobenzene, bromobenzene, dichlorobenzenes and chlorotoluenes.
Of the aliphatic halohydrocarbons, compounds containing at least
two chloride substituents are preferred, with carbon tetrachloride
and 1,1,2-trichloroethane being most preferred. Of the aromatic
halohydrocarbons, chlorobenzene is particularly preferred.
[0019] Any electron donor can be used in the present invention so
long as it is capable of converting the precursor into a
procatalyst. Suitable electron donors are those electron donors
free from active hydrogens that are conventionally employed in the
formation of titanium-based procatalysts. Particularly preferred
electron donors include ethers, esters, amines, imines, nitriles,
phosphines, stibines, and arsines. The more preferred electron
donors, however are carboxylic acid esters or ether derivatives
thereof, particularly C.sub.1-4 alkyl esters of aromatic
monocarboxylic or dicarboxylic acids and C.sub.1-4 alkyl ether
derivatives thereof. Examples of such electron donors are
methylbenzoate, ethylbenzoate, isopropylbenzoate, isobutylbenzoate,
ethyl p-ethoxybenzoate, ethyl-p-methoxybenzoate,
isopropyl-p-ethoxybenzoate, isobutyl-p-ethoxybenzoate,
diethylphthalate, dimethylnaphthalenedicarboxy- late,
diisopropylphthalate, diisobutylphthalate,
diisopropylterephthalate, and diisobutylterephthalate. The electron
donor can be a single compound or a mixture of compounds, but
preferably the electron donor is a single compound. Particularly
preferred internal electron donors are: ethylbenzoate, ethyl
p-ethoxybenzoate, di(n-butyl)phthalate, and
di(isobutyl)phthalate.
[0020] In one embodiment of the invention, the electron donor may
be formed in situ, by contacting the procatalyst precursor with an
organic halogenating agent, especially benzoyl chloride or phthalyl
dichloride, simultaneously with the foregoing precursor forming
step or halogenation step using an inorganic halide compound
(procatalyst forming step). Sufficient electron donor usually is
provided or prepared in situ, so that the molar ratio of electron
donor to the magnesium present in the solid procatalyst at this
stage of the preparation is from about 0.01:1 to about 3:1,
preferably from about 0.05:1 to about 2:1.
[0021] The manner in which the procatalyst precursor, the optional
hydrocarbon or halohydrocarbon, the electron donor, and the
chlorinating agent are contacted may be varied within wide limits.
In one embodiment, the tetravalent titanium halide is added to a
mixture of the electron donor and procatalyst precursor. More
preferably however, the procatalyst precursor first is mixed with
the tetravalent titanium halide and optional halohydrocarbon, and
the electron donor is added last, after a period lasting from 10 to
30 minutes of precontact between the precursor and halogenating
agent. Ideally, the contact time and temperature are controlled in
order to obtain a solid product having a desired particle
morphology. Preferred contacting times of the precursor with the
remaining ingredients in the procatalyst composition forming
process are at least 10, preferably at least 15 and more preferably
at least 20 minutes, up to 1 hour, preferably up to 45 minutes,
most preferably up to 35 minutes, at a temperature from at least
25, preferably at least 50, most preferably at least 60.degree. C.,
to a temperature up to 100, preferably up to 90, most preferably up
to 80.degree. C. At combinations of higher temperatures or longer
contacting times, particle morphology, especially particle size,
size distribution and porosity of the resulting solid, procatalyst
composition and the catalysts formed therefrom is adversely
affected.
[0022] A preferred procatalyst for use herein is a mixed
magnesium/titanium compound of the formula:
Mg.sub.d'Ti(OR.sup.e).sub.e'X- .sub.f'(ED).sub.g' wherein R.sup.e
is an aliphatic or aromatic hydrocarbon radical having 1 to 14
carbon atoms or COR' wherein R' is an aliphatic or aromatic
hydrocarbon radical having 1 to 14 carbon atoms; each OR.sup.e
group is the same or different; X is independently chlorine,
bromine or iodine; ED is an electron donor, especially
ethylbenzoate; d' is 1 to 36, preferably 6-18, most preferably
10-14; e' is 0-3, preferably 0.01-2, most preferably 0.01-1; f' is
20-40, preferably 25-35, most preferably 27-29; and g' is 0.1-3,
preferably 0.5-2.5, most preferably 1-2.
[0023] The next step according to the invention involves a
multi-step, metathesis or exchange reaction with benzoyl chloride
as an organic chlorinating agent in order to convert residual
alkoxide moieties in the solid procatalyst to chloride moieties.
Benzoyl chloride is the preferred metathesis reagent due to the
fact that the alkyl benzoate which is formed as a by-product of the
chlorination appears to be a more effective internal donor than are
the alkyl phthalates, resulting in a more efficient polymerization
catalyst. Desirably, the residual alkoxide content of the resulting
solid, exchanged, procatalyst composition is 5 weight percent or
less, more preferably 3 weight percent or less, most preferably 1
weight percent or less. The foregoing metathesis procedure is
repeated at least one time (2 contactings total), preferably two
times (3 contactings total), as desired until a suitable
procatalyst composition is attained. Contacting with benzoyl
chloride in at least two steps is preferred in order to achieve
maximum catalyst efficiency. One or more of the previously
mentioned halogenating agents, preferably TiCl.sub.4, can be
present in combination with the benzoyl chloride metathesis
reagent, and preferably is present during at least the first and
second contactings for best results.
[0024] The exchange process is desirably conducted at an elevated
temperature from 45 to 120.degree. C., preferably from 70 to
115.degree. C., most preferably from 85 to 110.degree. C., over a
time period of from 10 minutes to 3 hours, preferably from 30
minutes to 90 minutes, most preferably from 40 to 80 minutes. After
each of the foregoing exchanges, the solid, exchanged procatalyst
composition is separated from the exchange mixture, desirably by
filtration, and may be rinsed with a hydrocarbon, halohydrocarbon
or halocarbon solvent, if desired. Such filtration step may occur
over a time period from 10 minutes to 2 hours, preferably from 30
minutes to 100 minutes. It is generally preferred that all of the
foregoing chlorination and exchange steps, including intervening
filtrations or other form of recovery, and optional washings, occur
without substantial cooling of the procatalyst composition. By
substantial cooling is meant cooling by more than 25.degree. C.
[0025] After the foregoing exchange procedure, the resulting solid,
exchanged, procatalyst composition is separated from the reaction
medium employed in the final process, preferably by filtering to
produce a moist filter cake. The resulting filter cake may again be
halogenated one or more times according to the previously disclosed
procedure, if desired. The moist filter cake desirably is then
rinsed or washed with a liquid diluent, preferably an aliphatic
hydrocarbon to remove unreacted TiCl.sub.4 and may be dried to
remove residual liquid, if desired. Typically the solid, exchanged
procatalyst composition is washed one or more times with an
aliphatic hydrocarbon such as isopentane, isooctane, isohexane,
hexane, pentane, or octane. The solid, exchanged, and optionally
washed, procatalyst composition then can be separated and dried or
slurried in a hydrocarbon, especially a relatively viscous,
aliphatic hydrocarbon such as mineral oil for further storage or
use.
[0026] The resulting solid, exchanged procatalyst composition is
desirably in the form of porous particles. The resulting
composition desirably corresponds to the formula:
Mg.sub.d"Ti(OR.sup.e).sub.e"X.sub.f"(ED).sub.- g" wherein R.sup.e
is an aliphatic or aromatic hydrocarbon radical having 1 to 14
carbon atoms or COR' wherein R' is an aliphatic or aromatic
hydrocarbon radical having 1 to 14 carbon atoms; each OR.sup.e
group is the same or different; X is independently chlorine; ED is
an electron donor, especially ethylbenzoate; d" is 1 to 36,
preferably 6-18, most preferably 10-14; e" is 0-2, preferably 0-1,
most preferably 0-0.5; f" is 20-40, preferably 25-35, most
preferably 27-29; and g" is 0.1-3, preferably 0.5-2.5, most
preferably 1-2.
[0027] Desirably, the resulting solid, exchanged, procatalyst
composition has the following particle physical properties as
measured by BET, nitrogen porosimetry, and laser particle analyzer:
an average surface area of at least 100 m.sup.2/g, preferably at
least 250 m.sup.2/g, an average pore volume of at least 0.18
cm.sup.3/g, preferably at least 0.20 cm.sup.3/g, mean particle size
from 20 to 40 .mu.m, preferably from 24 to 30 .mu.m, and particle
size distribution having D10 from 3 to 15 .mu.m, D50 from 18 to 30
.mu.m and D90 from 35 to 75 .mu.m. This mean particle size is
somewhat less than the mean particle size of a composition that has
not been exchanged, and the distribution is somewhat narrower than
a composition that is not subjected to the multi-step exchange
process as disclosed herein.
[0028] Before, in combination with, or after being exchanged
according to the present invention, the procatalyst composition may
be further treated according to one or more of the following
procedures. The solid procatalyst composition may be contacted
(halogenated) with a further quantity of titanium halide compound,
if desired; it may be substituted with a different halide salt
compound or a complex thereof; it may be contacted (extracted) with
a solvent, especially a halohydrocarbon; it may be rinsed or
washed, heat treated; or aged. The foregoing techniques are
previously known in the art with respect to different procatalyst
compositions. The foregoing additional procedures may be combined
in any order or employed separately, or not at all.
[0029] It is believed, without wishing to be bound by such belief,
that further halogenating by contacting the previously formed
procatalyst composition with a titanium halide compound, especially
a dilute solution thereof in a halohydrocarbon diluent, results in
desirable modification of the procatalyst composition, possibly by
removal of certain inactive metal compounds that are soluble in the
foregoing diluent. Accordingly, in a highly preferred embodiment of
the present invention the exchange process is conducted in the
presence of a titanium halide and a halohydrocarbon diluent,
especially TiCl.sub.4 and chlorobenzene. Highly desirably, the
exchange utilizes a mixture of inorganic halogenating
agent/diluent/exchange agent on a molar basis from
1/20-10,000/0.0001-0.1. Most preferably a mixture of
TiCl.sub.4/monochlorobenzene/benzoylchloride is used in a molar
ratio range from 1/100-2000/0.001-0.01. The quantity of the
foregoing exchange reagent (organic chlorinating agent) used with
respect to the solid procatalyst (based on moles of Ti species in
the procatalyst/moles exchange reagent) is from 1/1 to 1/100,
preferably from 1/2 to 1/10.
[0030] Substitution refers to a process by which the procatalyst
may be further modified by incorporation of a halide salt compound
therein. Suitable halide compounds include those compounds that are
capable of removing titanium species from the solid procatalyst
material or adjusting the type or quantity of titanium species in
the procatalyst composition without detrimentally affecting the
resulting catalyst properties. It is preferred that the halide salt
compound be soluble in the medium that contains the procatalyst or
the precursor components. The halide salt compound (if different
from the titanium compound used to prepare the present solid,
procatalyst composition) may be employed by itself, or it may be
complexed with another compound, such as an internal electron
donor.
[0031] More than one halide salt compound may be used in the
substitution process if desired. Suitable halide salt compounds for
the foregoing substitution procedure include: TiCl.sub.4,
ZrCl.sub.4, VCl.sub.4, WCl.sub.6, VOCl.sub.3, SnCl.sub.4,
SiCl.sub.4 and mixtures thereof. Soluble complexes of such metal
halides complexed with the appropriate ligands, such as diisobutyl
phthalate (DIBP), also may be used as well. Examples include
ZrCl.sub.4(DIBP) and VCl.sub.4(DIBP). A preferred reagent is
TiCl.sub.4. If a complex of a metal salt is employed, it is
desirable that some quantity of TiCl.sub.4 be included in the
substitution mixture. The presence of a small quantity of
TiCl.sub.4 in the substitution medium has desirably been found to
reduce adverse affects caused by release of electron donor from the
procatalyst composition during the substitution. The substitution
step may be combined with the present exchange procedure, if
desired.
[0032] In a further preferred embodiment, the solid procatalyst
composition is extracted to remove non-active titanium halide
species by exposure to a suitable diluent optionally at elevated
temperature. One such process involves contacting the solid
procatalyst, optionally additional electron donor, and an
halohydrocarbon at an elevated temperature, for example, a
temperature of up to about 150.degree. C., for a period of time
following the foregoing exchange. It is particularly preferred to
conduct the extraction at a temperature greater than 45.degree. C.,
preferably greater than 85.degree. C., more preferably greater than
115.degree. C., and most preferably greater than 120.degree. C., to
a temperature up to about 300.degree. C., more preferably up to
about 200.degree. C., and most preferably up to about 150.degree.
C.
[0033] Best results are obtained if the materials are contacted
initially at or about ambient temperature and then heated.
Sufficient tetravalent titanium halide may be provided to further
convert any residual alkoxide moieties of the procatalyst to halide
groups at the same time as the extraction. The extraction process
is conducted in one or more contacting operations, each of which is
conducted over a period of time ranging from a few minutes to a few
hours and it is preferred to have a halohydrocarbon present during
each contacting.
[0034] Suitable extractants include aliphatic, cycloaliphatic, or
aromatic hydrocarbons, halogenated derivatives thereof, and
mixtures thereof. Exemplary aliphatic hydrocarbons include pentane,
octane and the like. Exemplary cycloaliphatic hydrocarbons include
cyclopentane, cyclohexane, cyclooctane, and the like. Exemplary
aromatic hydrocarbons include benzene, alkylbenzenes,
dialkylbenzenes, and the like. Exemplary halogenated derivatives of
the foregoing include methylenechloride, methylenebromide,
chloroform, carbon tetrachloride, 1,2-dibromoethane,
1,1,2-trichloroethane, trichlorocyclohexane, dichlorofluoromethane,
tetrachlorooctane, chlorinated benzenes, bromobenzene,
dichlorobenzene, chlorinated toluenes, and the like. Particularly
preferred aliphatic hydrocarbons include pentane, isopentane,
octane, and isooctane. Particularly preferred aromatic hydrocarbons
include benzene, toluene, and xylene. Particularly preferred
halohydrocarbons include carbon tetrachloride,
1,1,2-trichloroethane, chlorinated benzenes and chlorinated
toluenes. Most highly preferred extractants are aromatic
hydrocarbons and halohydrocarbons, especially toluene, xylene,
ethylbenzene, chlorobenzene and dichlorobenzene. Desirably the
extractant selected has a boiling point above the temperature used
in the extraction so as to avoid the use of high pressure
equipment.
[0035] The amount of extractant employed can be any effective
amount capable of removing titanium species from the solid
procatalyst. It is preferred that the extractant be used in an
amount ranging from 0.1 to about 1000 milliliters per gram of solid
procatalyst material. More preferably, the amount of extractant
used ranges from about 1 to about 500 mL/g of solid procatalyst,
and most preferably from about 5 to about 50 mL/g of solid
procatalyst.
[0036] The amount of time the solid procatalyst material and the
extractant are contacted is not critical so long as it is
sufficient to remove undesired, soluble titanium species from the
solid procatalyst material. There is no upper limit on the duration
of contact from an efficacy standpoint, but economics typically
play a role on the length of time the components will be contacted
with one another. Preferably, the components are contacted from
about 2 minutes to about 12 hours, more preferably from about 5
minutes to about 4 hours, and most preferably, from about 15
minutes to about 2 hours. Longer contact times and/or repeated
extractions may be required if lower extraction temperatures or
less efficient extractants are employed. The extraction may be
conducted at any suitable pressure, but preferably atmospheric
pressure or elevated pressures are employed.
[0037] Typically unextracted, solid, procatalysts have a titanium
content anywhere from about 2.5 wt percent to about 6 wt percent,
as determined by plasma emission spectroscopy. In contrast, an
extracted, solid procatalyst of the present invention has from 5 up
to 80 weight percent less titanium content, more preferably from 7
up to 75 weight percent less titanium, and most preferably,
anywhere from 10 to about 70 weight percent less titanium content
than a similarly prepared but unextracted composition. The
extraction may be repeated any number of times with the same or
varied reagents, concentrations of reagents, temperatures of
reaction and time of reaction in order to achieve the desired
titanium content of the solid procatalyst.
[0038] The solid, exchanged procatalyst composition serves as one
component of a Ziegler-Natta catalyst composition, in combination
with a cocatalyst and a selectivity control agent. The cocatalyst
component 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, especially
organoaluminum compounds. Examples include trialkylaluminum
compounds and alkylaluminum halide compounds in which each alkyl
group independently has from 1 to 6 carbon atoms. The preferred
organoaluminum cocatalysts are triethylaluminum,
triisopropylaluminum, and triisobutylaluminum. The cocatalyst is
preferably employed in a molar ratio of aluminum to titanium of the
procatalyst of from about 1:1 to about 150:1, but more preferably
in a molar ratio of from about 10:1 to about 100:1.
[0039] The final component of the Ziegler-Natta catalyst
composition (when used to polymerize C.sub.3 and higher
.alpha.-olefins) is the selectivity control agent (SCA), or
external electron donor. Typical SCAs are those conventionally
employed in conjunction with titanium-based Ziegler-Natta
catalysts. Illustrative of suitable selectivity control agents are
those classes of electron donors employed in procatalyst production
as described above, as well as organosilane or polyorganosilane
compounds containing at least one silicon-oxygen-carbon linkage.
Suitable silicon compounds include those of the formula,
R.sup.1.sub.mSiY.sub.nX.sub.p, or oligomeric or polymeric
derivatives thereof, 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. Highly preferably, R.sup.1 in at
least one occurrence is not a primary alkyl group, and the
non-primary carbon thereof 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. Each
R.sup.1 and R.sup.2 may be the same or different, and, if a
polyatomic radical, 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 a sterically hindered aliphatic- or a
cycloaliphatic- group. When R.sup.2 is aromatic it may have from 6
to 10 carbon atoms. Silicon compounds in which two or more silicon
atoms are linked to each other by an oxygen atom, such as,
siloxanes or polysiloxanes, may also be employed, provided the
requisite silicon-oxygen-carbon linkage is also present.
[0040] The preferred selectivity control agents are alkyl esters of
ring alkoxy-substituted aromatic carboxylic acids or dicarboxylic
acids, especially ethyl p-methoxybenzoate or ethyl p-ethoxybenzoate
(PEEB), or siloxane compounds, such as n-propyltrimethoxysilane,
cyclohexylmethyldimethoxysilane, or dicyclopentyldimethoxysilane.
In one embodiment of the invention the foregoing selectivity
control agent may form at least a portion of the electron donor
added during procatalyst production. In an alternate modification,
the selectivity control agent is added only after formation of the
procatalyst and may be added to a catalyst forming mixture or to an
olefin polymerization mixture simultaneously or non-simultaneously
with addition of the cocatalyst.
[0041] The selectivity control agent preferably is provided in a
quantity of from 0.01 mole to about 100 moles per mole of titanium
in the procatalyst. Preferred quantities of selectivity control
agent are from about 0.5 mole to about 50 mole per mole of titanium
in the procatalyst.
[0042] The olefin polymerization catalyst is produced by any
suitable procedure of contacting the exchanged, solid procatalyst,
the cocatalyst and the selectivity control agent. The method of
contacting is not critical. The catalyst components or combinations
thereof can be precontacted prior to polymerization to form a
preactivated catalyst, or the components can be contacted
simultaneously with contact with an olefin monomer. In one
modification, the catalyst components simply are mixed in a
suitable vessel and the preformed catalyst thereby produced is
introduced into the polymerization reactor when initiation of
polymerization is desired. In an alternate modification, the
catalyst components are separately introduced into the
polymerization reactor and the catalyst is formed in situ. In a
final embodiment, the catalyst components may be introduced into
one polymerization reactor and prepolymerized with one or more
olefin monomers and subsequently contacted with additional olefin
monomers, which may be the same or different from the olefin
monomers used in the prepolymerization. The subsequent
polymerization may take place in the same or in a different
polymerization reactor and may include separate addition of one or
more of the catalyst components during said subsequent
polymerization.
[0043] The olefin polymerization catalyst may be used in slurry,
liquid phase, gas phase or bulk, liquid monomer-type polymerization
processes as are known in the art for polymerizing olefins, or in a
combination of such processes. 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 three components of the catalyst system, that is, the
solid procatalyst component, cocatalyst and SCAs. In accordance
with the process, discrete portions of the catalyst components are
continuously or semi-continuously fed to the reactor in
catalytically effective amounts together with the alpha-olefin and
any additional components, while the polymer product is
continuously or semi-continuously removed therefrom. Fluidized bed
reactors suitable for continuously polymerizing alpha-olefins have
been previously described and are well known in the art. Suitable
fluidized bed reactors useful for this purpose are described in
U.S. Pat. Nos. 4,302,565, 4,302,566 and 4,303,771 and
elsewhere.
[0044] 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. Additionally, a liquid
condensing agent may be included in the reaction mixture as well.
The foregoing procedures are referred to as "condensing mode."
Operating a fluidized bed reactor in condensing mode generally is
known in the art and described in, U.S. Pat. Nos. 4,543,399 and
4,588,790, and elsewhere. The use of condensing mode has been found
to be especially useful to increase catalyst activity, lower the
amount of xylene solubles in isotactic polypropylene, and to
improve overall catalyst performance when using catalysts prepared
according to the present invention.
[0045] The precise procedures and conditions of the polymerization
are broadly conventional but the olefin polymerization process, by
virtue of the use therein of the polymerization catalyst formed
from exchanged, solid procatalysts of the invention, provides a
polyolefin product and particularly a polypropylene product having
a relatively high bulk density in quantities that reflect the
relatively high productivity of the olefin polymerization catalyst.
Desirably, the bulk density of the resulting polymer (.rho..sub.bd)
as determined by gravimetric analysis is at least 0.33 g/cm.sup.3,
more preferably at least 0.35 g/cm.sup.3. Increase in bulk density
allows higher reactor capacity utilization or efficiency of
operation, and accordingly is desired.
[0046] Moreover, the polyolefin product of the invention desirably
allows for incorporation of enhanced rubber content when compared
to rubber modified polyolefins, (especially ethylene/propylene
rubber (EPR) modified isotactic polypropylene) made by a catalyst
made from an unexchanged, but otherwise similar procatalyst, due,
it is believed, to better dispersion of the rubber within the
polyolefin matrix. Preferably, the rubber content of such polymers
is capable of being increased 30 percent by weight, preferably at
least 40 percent by weight over a similarly prepared catalyst
composition that has not been exchanged as disclosed herein, at the
same polymerization temperature, without significant increase in
polymer agglomerate formation. Surprisingly, rubber modified
polymers according to the invention containing high rubber contents
of at least 40, preferably at least 45, and most preferably at
least 50 weight percent may retain acceptable flow properties in
the reactor under gas phase polymerization conditions resulting in
less plugging of reactor components, thereby resulting in reduced
levels of production or even shutting down of the reactor.
[0047] The xylene solubles content of the polyolefin products of
the invention preferably are less than 5 weight percent, more
preferably 2.5-4.5 weight percent. In addition, the polyolefin
product preferably will contain reduced amounts of the catalyst
residue. Preferably, the polymer will have a titanium content of
less than about 1.times.10.sup.-3 weight percent, more preferably
less than 1.times.10.sup.-4 weight percent, most preferably less
than 5.times.10.sup.-5 weight percent.
[0048] The polymerization product of the present invention can be
any product, including homopolymers, copolymers, terpolymers, and
the like. Usually, the polymerization product is a homopolymer such
as polyethylene or polypropylene, particularly polypropylene.
Alternatively and preferably for the reasons previously stated, the
catalyst and process of the invention are useful in the production
of copolymers including copolymers of ethylene and propylene such
as EPR and polypropylene impact copolymers, such as EPR modified
polypropylene, when two or more olefin monomers are supplied to the
polymerization process. Those skilled in the art are capable of
carrying out suitable polymerization of homopolymers, copolymers,
terpolymers, or other product using liquid, slurry or gas phase
reaction conditions, using the guidelines provided herein.
[0049] The invention is further illustrated by the following
examples that should not be regarded as limiting of the present
invention.
EXAMPLES
[0050] In the following examples, the following testing methods
were used to determine the values reported in the tables. In the
tables, a blank cell indicates that no data were taken for that
particular portion of the experiment. The measurements of the mean
diameters of the particles and the particle distribution were
performed with a Malvern 1600.TM. laser granulometer, available
from Malvern Corporation. The specific surface area (BET) was
determined by the isothermal physical adsorption of nitrogen at the
temperature of liquid nitrogen (S. Brunauer, P. H. Emmett, and E.
Teller, Adsorption of gases in multimolecular layers, J. Am. Chem.
Soc., 60, 309 (1938)). The pore volume was determined by nitrogen
absorption porosimetry. The measurements were performed after
treatment of the samples under vacuum for 2 hours at room
temperature.
[0051] Ti percent--percent titanium was determined by analyzing the
catalysts using plasma emission spectroscopy.
[0052] Melt Flow was determined according to ASTM 1238, Condition
L;
[0053] Bulk Density is apparent bulk density determined according
to ASTM D1895-96;
[0054] Productivity--(kg of polymer per gram of procatalyst).
Calculated by weighing the total amount of polymer produced and
dividing by the total amount of procatalyst injected into the
reactor.
[0055] XS--xylene solubles, unless indicated otherwise was measured
by the .sup.13C NMR method as described in U.S. Pat. No.
5,539,309,or the gravimetric XS method of 21 CFR 177.1520.
(Optionally the quantity of extracted polymer may be determined by
measuring the refractive index of the extract, rather than weighing
the residue after drying).
Example 1
[0056] A series of nine olefin polymerization procatalysts were
prepared using a procatalyst precursor comprising magnesium,
titanium, alkoxide and halide moieties. The precursor composition
is prepared by reacting magnesium diethoxide, titanium
tetraethoxide, and titanium tetrachloride, in a mixture of
orthocresol, ethanol and chlorobenzene at a temperature of about
75.degree. C. for about 2 hours. The solid reaction product is
precipitated by removing ethanol from the solution (by heating to
about 90.degree. C.), washing with isopentane or isooctane and
drying. The resulting dried, solid composition comprises primarily
a compound of the empirical formula:
Mg.sub.3Ti(OC.sub.2H.sub.5).sub.8Cl.sub.2.
[0057] This precursor composition was next converted to procatalyst
compositions by contacting with TiCl.sub.4 and ethylbenzoate
electron donor. In each preparation, approximately 3.6 grams of the
precursor was added to a 150 ml flask. A 50/50 volume mixture of
TiCl.sub.4 and chlorobenzene (65 ml) was added to the flask,
followed by 0.4 ml of ethylbenzoate. The flask was heated in
approximately 5 to 7 minutes to 70.degree. C., and maintained at
that temperature under constant agitation for 30 minutes. The
resulting slurry was filtered through a fritted disc at the bottom
of the flask, while maintaining the temperature at 70.degree.
C.
[0058] The resulting solid, procatalyst composition was next
subjected to exchange and further halogenation by contacting with a
mixture of TiCl.sub.4, chlorobenzene, and benzoylchloride at
95.degree. C. Specifically, 65 ml of an equal volume mixture of
TiCl.sub.4 and chlorobenzene was added to the flask containing the
recovered procatalyst followed by 0.5 ml of benzoylchloride, and
the mixture was rapidly heated to 95.degree. C. The contents were
maintained at that temperature for 60 minutes, and then filtered as
before while retaining the recovered solids at 95.degree. C. This
exchange procedure was repeated once more under substantially
identical conditions (specifically the benzoylchloride content was
reduced to 0.4 ml). After filtering, the solids were cooled to
about 25.degree. C., washed three times with three 70 ml aliquots
of isooctane, and dried in a stream of dry nitrogen for several
hours. The resulting catalyst compositions have average BET surface
area of 270 m.sup.2/g, average pore diameter of 3.1 nm, and average
pore volume 0.209 cm.sup.3/g.
[0059] The resulting exchanged procatalyst compositions were tested
for olefin polymerization activity by charging 0.70 mmoles of
triethylaluminum cocatalyst, 0.35 mmoles ethyl p-ethoxybenzoate
SCA, and 16.2 mg of the procatalyst composition into an autoclave
reactor containing 1375 grams of liquid propylene and 13 mmole
H.sub.2 for one hour at 67.degree. C. After venting and cooling of
the polymerization reactor, the product was collected, dried in
air, and weighed. Properties of the isotactic polypropylene product
including loose bulk density and percent xylene solubles, along
with activity of the catalyst, were measured and are displayed in
Table 1.
1 TABLE 1 Polymer bulk density Productivity XS Run (g/cm.sup.3)
(kg/g) (percent) 1 0.375 17.1 -- 2 0.376 15.1 4.3 3 0.377 16.5 3.9
4 0.370 14.0 4.2 5 0.373 18.3 4.3 6 0.376 16.4 4.2 7 0.374 18.1 4.3
8 0.384 14.7 3.7 9 0.373 15.2 4.5 Avg. 0.375 16.2 4.2
Example 2
[0060] In a large scale preparation of procatalyst composition
according to the invention, 6.9 m.sup.3 of an equal volume of mixed
TiCl.sub.4 and chlorobenzene at 13.degree. C. were pumped into a
stainless steel heated pressure vessel equipped with a stirrer.
Approximately 483 kg of a precursor composition prepared
substantially according to the procedure of Example 1 was added,
followed by about 8.6 liters of ethylbenzoate electron donor. The
reactor was heated to 70.degree. C. with stirring and held at that
temperature for 40 minutes. The reactor contents were filtered over
a period of 1 hour while maintaining a temperature of approximately
70.degree. C.
[0061] The solid product was recovered and returned to the empty
reaction vessel. A preheated (70.degree. C.) mixture (50/50 by
volume) of TiCl.sub.4 and chlorobenzene (9 m.sup.3) was added
followed by 10.7 liters of benzoylchloride. The mixture was stirred
and allowed to heat to a final temperature of 93.degree. C. over a
period of 20 minutes, then filtered as before over a one hour
period. The foregoing exchange with benzoylchloride was repeated a
second time using slightly less benzoyl chloride (8.5 L).
[0062] The resulting solid, procatalyst composition (still at
93.degree. C.) was rinsed with isopentane 10 m.sup.3) for about 2
hours while gradually reducing the temperature to ambient
conditions (20.degree. C.). Dry nitrogen at a temperature of about
45.degree. C. was used to dry the catalyst cake over a period of 2
hours. After drying, the solid procatalyst composition was blended
with mineral oil and used in preparation of olefin polymers. The
resulting solid catalyst composition had similar average BET
surface area, average pore diameter and average pore volume
properties to those prepared in runs 1-9. Average particle size
distribution data were as follows:
D.sub.10=13.7 .mu.m, D.sub.50=25.0 .mu.m, D.sub.90=55.4 .mu.m.
[0063] Polymerization Conditions:
[0064] Ethylene/propylene rubber modified polypropylene impact
copolymers were prepared in twin, gas-phase olefin polymerization
reactors operating in series. The reactors were each equipped with
a distributor plate under which the fluidization gas was
introduced. The gas exited the top of the fluidized bed and was
conveyed through piping to a compressor and a cooler, which was
used to control the temperature of the cycle gas, thereby
controlling the temperature in the fluidized bed. After cooling,
the cycle gas was then reintroduced below the distributor plate at
a rate to maintain fluidization of the reactor contents. The first
reactor contained propylene as the only olefin, hydrogen in a
H.sub.2/C.sub.3H.sub.6 molar ratio of about 0.03 (run 10) or 0.027
(run 11), and operating temperature of 66.degree. C. The
fluidized-bed reactor was operated under 430 psi, (3.08 MPa) total
pressure with a propylene partial pressure of 340 psi (2.3 MPa). A
superficial gas velocity of 1.2 ft/sec (0.36 m/sec) was used to
fluidize the polymer bed weighing about 75 lbs (34 Kg) of
polymer.
[0065] The catalyst slurry was metered with a syringe pump into a
stream of 5 lbs/hr (2.3 kg/hr) of propylene, which conveyed the
catalyst to the reactor. Solutions of triethylaluminum (TEAL) and
ethyl p-ethoxybenzoate (SCA) were introduced separately into the
reactor at locations on the recycle line to provide a molar ratio
Al/Ti of 50:1 and Al/SCA of 2.1:1. Total SCA concentration in the
reactor was maintained below about 250 ppm by weight.
[0066] After polymerization in the first reactor the polymeric
product was passed to a second reactor operating under similar
gas-phase polymerization conditions, excepting that additional
catalyst and SCA were not added, the temperature was raised to
70.degree. C., ethylene was added to the reactor to provide
ethylene/propylene ratios of 0.79 (run 10) or 0.825 (run 11), an
H.sub.2/C.sub.3H.sub.6 ratio of 0.18 (run 10) or 0.09 (run 11), and
a reactor pressure of 346 psi (2.4 MPa) with a propylene partial
pressure of 140 psi (965 kPa) and an ethylene partial pressure of
111 psi (765 kPa) (run 10) or 115 psi (793 kPa) (run 11). Ethylene
and propylene were added continuously during the polymerization.
Results and polymer properties are contained in Table 2.
2TABLE 2 Produc- Polymer bulk tivity Melt flow density Flow Quality
Run (kg/g) (g/10 min) Fc.sup.1 Ec.sup.2 (g/cm.sup.3).sup.3
Index.sup.4 10 9.3 3.7 16.5 62 0.341 0.87 11 10.0 1.75 28 62 0.328
0.78 .sup.1Weight percent rubber in the copolymer. .sup.2Weight
percent ethylene in the copolymer. .sup.3Apparent bulk density,
ASTM D1895-96. .sup.4A measure of particle flowability determined
by use of a Sotax .TM. flow measuring instrument at 23.degree. C.,
available from Sotax A.G., Basel, Switzerland. Qualitative flow
ratings based on such values are: 0.9-1 = very good, 0.8-0.9 =
good, 0.7-0.8 = satisfactory, 0.6-0.7 = marginal, 0.5-0.6 =
unsatisfactory, 0.4-0.5 = poor, 0.3-0.4 = very poor.
Example 3
[0067] The reaction conditions of Example 2 were substantially
repeated employing reduced residence time in the first reactor in
order to produce polymers containing higher rubber contents.
Products having 40, 45 and 53 weight percent rubber and Flow
Quality Index values of 0.68, 0.62 and 0.58, respectively, were
prepared.
* * * * *