Note: Descriptions are shown in the official language in which they were submitted.
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CATALYST POSITION AND PI~~SS FOR POLYMERIZING
POLYN~iS HAVING MULTIhfODAL MOLEICIJLAR WEIGHT DTSrRIH~TI'ION
ion relates to catalyst precursor
~positians; to catalyst compositions; and to processes for
~l~izit~g alpi~a-olefins to form polymers having multimodal
molecular weight distributions. More particularly, this
invention relates to a catalyst, and a method for preparati~
f, ~~ proc~oes high density polyethylene (FmPE) having a
multimodal molecular weight distribution: The ir~ntion is also
directed to an olefin polymerization p~ooess carried out with the
~~~ of the invention which produces polymers of mu.7.timodal
~lweight distributiari in a single polymerizatiar~ reactor
ur~er steady state polymerization conditions.
Various processes have been proposed for the production
of polymers having multimodal molecular weight distribution. The
term "multimodal molecular weight distribution" means that two or
a pegs are readily disG~ernible in a plat of molecular weight
as a function of fraction of the polymer having the given
molecular r~aeight, such as that obtained by gel permeation
chraaat.~raphy (GPC) analysis of the polymex. One such process
own to us utilizes tandem reactors operated in series, wherein
in the first reactor the olefin is polymerized in the presence of
a catalyst arid substantially in the absence of hydrogen as a
chain'trar~sfer a~tt~ ~ ~ ~ ~ferred to the second,
~~ ~~, wherein polymerization is cnr~ducted in the
prese~ooe of relatively large amounts of hydrogen. The first
the high molecaxlar weight component, and the
second reaG~tOr the low molecular weight c~onent of the final
polymer p1~oduct. Such a method of producing aaxltinadal molecular
CA 02042961 1997-09-22
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weight distribution polymers is expensive, c~nnberscene, and time
consumixyg.
She present invention seeks to provide an olefin
polymerization catalyst capable of producing polymers of
multimodal molecular weight distribution in a side
polymerization reactor un3er steady state polymerization
conditions.
In the drawings:
Figure 1 represents a Gel Permeation Qzroanatography (GPC)
chrcanatogram of molecular weight distribution of a
commercially produced bimodal polymer ("Cain L5005"*, obtained from
Cain Chemicals, Inc.).
Figure 2 represents a GPC graph of molecular weight
distrilxztion of a polymer produced with the catalyst and the
process of this invention discussed in ale 2.
Figure 3 represents a GPC graph of a molecular weight
distribution of a polymer produced with the catalyst and the
process of this invention discussed in ale 4.
According to the present invention, there is providecT an
olefin polymerization catalyst precursor com~sition supported on
a porous carrier prising:
i) a magnesium odd;
ii) a zirconium ~o~.u~d; arr3
~ ) a titaniimm candor a vanadimn oc~oond.
wherein, during the preparation of the catalyst
precursor composition, the titanium oc~ound and/or
vanadilnn d is added prior to the zirconium
~e catalyst precursor is supported on a carrier. 'Ihe
carrier materials used herein are usually inorganic, solid,
* Trademark
CA 02042961 1997-09-22
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particulate porous materials. Zhe_se carrier materials include
such inorganic materials as oxides of silicon and/or alumirnmm.
~e carrier materials are used as dry powders having an average
particle size from 1 micron to 250 microns, preferably frcan 10
microns to 150 microns. Zhe carrier materials are also porous
and have a surface area of at least 3 square meters per gram, and
preferably at least 50 square meters per gram. 'I3~e carrier
material should be dry, that is, free of absorbed water. Drying
of the carrier material can be effected by heating at a
temperature frcan 100° to 1000°C, and preferably at about
600°C.
i~en the carrier is silica, it is heated at a temperature of at
least 200°C, preferably frcan 200° to 850°C, and most
preferably
at about 600°C. the carrier material nnlst contain at least scene
active hydroxyl (OH) groups to produce the catalyst ition
of this invention. 'Ihe term "active OH groups" means hydroxyl
groups that react chemically with metal-alkyl cc~paunds, such as
magnesium and/or almnirnnn alkyls.
In the most preferred embodiment, the carrier is silica
which, prior to the use thereof in the first catalyst synthesis
step, has been dehydrated by fluidizing with nitrogen and heating
at about 600°C for about 16 hours to achieve a surface hydroxyl
concentration of about 0.7 mmols/c~n. 'Ihe silica of the most
preferred embodiment is a hick surface area, amorphous silica
(surface area = 300m2/gm; pane volume of 1.65 csn3/gm), and it is
a material marketed under the trademarks of "Davison 952" or
"Davison 95S" bY ~ ~~.~ .cal Division of W.R. c~aoe and
~~ s~~ ~s ~ of spherical particles, e.g.,
as obtained by a sp~raY-drying process.
'Ihe carrier material is suitably slurried in an organic
solvent for, and the resulting slurry is contacted with, at least
ors mag~~sium o~.md. ~e slurry of the carrier material in
the solvent is prepared by introducing the carrier material into
the solvent, preferably while stirring, and heating the mi~tbzre
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to a t~exature from 50° to 90°C, preferably froan 50° to
85°C.
The slurry is then contacted with the magnesiwn cue, while
the heating is continued at the aforementioned te~rature.
The magnesium oc~o~urri preferably has the form0.zla
~J(~)2. R m~2n. ~' R3(2 k) ~
R, RZ, R2 and R3,
which may be the same or different, each represent an
alkyl group, such as a C2 to C~ alkyl, preferably a C4
to C8 alkyl, more preferably a C4 alkyl;
k, m and n each represent 0, 1, or 2, providing that m +
n is equal to the valency of Mg; and X represents a
halogen, preferably a chlorine, atom.
Mixtures of such oar~cx~nds may be utilised. The magnesium
ootapotmd nest be soluble in the organic solvent and capable of
being deposited onto the carrier containing the active OH groups.
Stx3.table limn con~wrxls are Grignard reagents, e.g.,
methyium l~aaide, cfiloride or iodide, ethy7magnesium
snide, chloride or iodide, propylmagnesium chloride, xrcanide or
iodide, isopropylmagnesium chloride, brcanide or iodide,
n-butylmag~sivn chloride, broanide or iodide, isobutylmagnesium
chloride, bromide or iodide; magnesium alkoxides, such as
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magnesium methoxide, magnesium ethoxide, magnesium propoxide,
magnesium butoxide, magnesium pentoxi.de, magnesium hexoxide,
magnesium heptoxide, magnesium octoxide; dialkylmlgnesium
co~npour~ds, wherein the alkyl groups may be the same or different,
such as dimethyium, diethylmagnesium, dip~y7magnesium,
dibutyhaagnesium, dipenty7magnesium, dihexylmagnesium,
dihepty7.magnesium, dioctylmagnevsium, dinonylmagnesium,
methyl-ethylmagnesium, methyl-propy7magnesium,
methyl-butylmagnesium, or propyl-butylmagnesiamn; and magnesium
dihalides, such as magnesium dichloride. Di.buty7magnesium was
found to be particularly preferred in one embodiment of the
invention.
Subsequently, at least one organic e~ound may be
optionally added to the slurry. Suitable organic oc~ocnds
include an alcohol of the formula, R-OH; a ketone of the forrm~la,
Ra0--R'; an ester of the fla, ROOOR'; an acid of the formula,
l~Ii; or an organic silicate of the formula, Si (fit) 4, where R
and R1, which may be the same or different, each represents a .
linear, bandied or cyclic alkyl grcxzp of 1 to 12 carbon atcans,
such as methyl, ethyl, propyl, butyl, isobutyl, cyclopropyl,
decyl or dodecyl. In each of the organic aompOUnds R may also be
a mixture of any of the aforementioned alkyl groups. Aleohols,
such as 1-butaryol, are preferred.
Subsequently, a titanium and/or a vanadium c~o~nd is
suitably added to the slurry and heating the mixture is continued
at the afararnemiomed t.~exature, i.e., frcen 50 to 90°C,
preferably from 50 to 85°C. Suitable titanium or vanadium
c~npau~ds used herein are such compouryds which are soluble in the
organic solvents used in the synthesis. R~les of such
onds include a titanium halide, titanium oxyhalide or a
mixtt~e thereof, for example titanium tetrachloride or titanium
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oxytrichloride; a vanadium halide, a vanadiwn oxyhalide or a
mixture thereof, for example vanadium tetrachloride or vanadium
oxytrichloride; and a titanium or vanadium alkoxide, wherein the
alkoxic'~ moiety o~ises a branched or unbrarached alkyl group
frcan 1 to 20 carbon atoms, preferably from 1 to 6 carbon atoms.
Titani~n ocar~ounds, and particularly tetravalent titanitun
oca~ounds, are preferred. The most preferred titanium ~
is titaniinn tetrachloride. Haa~evex, if vanadimn alkoxides alone,
without any other titaniwn or vanadimn founds containing
chlorine (C1) or b~nine (Hr) ataens are used in this step of the
catalyst synthesis, such vanadiwn alkoxides mast be chlorinated
or b~roaninated in the manner known to those skilled in the art to
produce an active catalyst.
The aforementioned titanium or vanadium compout~s may be
used individually or mixtures of such titaniwn or vanaditun
Cnmpaands may also be used and generally no restrictions are
in~osed on the titanium or vanadium ors which may be
included. Ar~y titanium or vanadium ~ that may be used
alone may also be used in conjunction with other titanium or
vanadium compounds.
Subsequently, at least one zirconium oampawnd is
suitably irrtroduoed into the slurry desirably together with a
prcmater. The zirconium o~ound has the fornwl.a
CpmZrYnX(2-n)
wherein
Cp repra cycldienyl group,
m represents 1, 2 or 3; Y and X, which may be the
same or different, each represent a halogen atoan,
particularly a chlorine at~n, a C1 to C6 alkyl group
or a hydrogen atcan; and
n represents 0 ar 1.
F-5629-L 20~2~~~
5liitable zirconium ends are dicyclopentadienyl zirconium
dihalide ar~ dicyclopentadierryl zirconium monoalkyl nanohalide,
wherein the halide atc~ns are dzlorine, b~aine or iodide
preferably chlorine, and the alkyl groups are C1 to C6 alkyl
Mixtures of the zirconium c~au~ds may also be used.
Dicyclapentadienyl zirconium dichloride is particularly preferred
in one embodiment of the invention.
Zhe is at least ~e aluminoacane oonq~au~d of the
formula
R
R2A1-O-(Al-O)ri A1R2
(~ (R) 0) m
wherein
m represents an integer fran 3 to 50;
n represents zero or an integer from 1 to 50; and
R represents a linear, branched or cyclic C1 to C~
alkyl group, such as methyl, ethyl, propyl, butyl,
isobutyl, cyclohexyl, decyl or dodeLyl.
Each of the alwninrnrar~e canpounds may oomtain different R
and mixtures of the aluminoacane compounds may also be
used. M~ethylaluminohcar~e is a particularly preferred prosmoter in
one embodiment of the irnrention. 'Ihe prodnatex is used to
impregnate the zirconium compound onto the carrier. Without
wishing to be bound by any theory of operability, it is believed
F-5629-L
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that the prcanater enables the zirconium cnd to be deposited
onto the carrier. The amount of the pxna~ater is stx"h that it
will prcmate the deposition of the entire amount of the zirconium
compound onto the carrier. In a preferred embodiment, the amount
of the p~oter is such that all of it will be deposited onto the
carrier, arid substantially none will remain in the solvent. The
slurry is stirred for about 1 to about 5 hours at the
aforem~eotioned temperature and the solvent is removed by
filtration or distillation under vacuum, so that the te~~erature
does not exceed 90°C. All of the catalyst synthesis steps must
be conducted at the aforementioned temperature of about 50 to
about 90°C, preferably about 50 to about 85°C, because, it is
believed, higher temppxatures may destroy titanium as the active
polymerization site. For example, maintaixiing the mixture of all
of the aforementioned ooanpaunds in the solvent at 115°C for
several hours is believed to destroy titanium as the active
polymerization site.
Suitable organic solvents are materials in which all of
the reactants used herein, i.e., the magnesium cx~pound, the
titanium and/or vanadium ecanpo~u~ds, the zirconium cxm~ound, the
promoter and the optional organic ooanpwnds are at least
partially soluble and which are liquid at reaction terrpexatures.
Preferred organic solvents are benzene, toluene, ethylbenzene, or
xylene. The most preferred solvent far one embodiment of the
invention is toluene. Prior to use, the solvent should be
purified, such as by percolation silica gel arul/or
molecular sieves, to remove traces of water, oxygen, polar
eats, and other materials capable of adversely affecting
catalyst activity.
F-5629-L
20~2~0~
_ g _
In the most preferred embodiment of the synthesis of this
catalyst it is important to add only such amounts of all of the
catalyst synthe'Sis reactants, i.e., the magnesium, zirconium,
titanium and/or vanadium ends, the p~:~anoter and the optional
organic compounds, that will be deposited - physically or
chemically - onto the support since any excess of the reactants
in the solution may react with other synthesis d~emicals and
precipitate outside of the support. the carrier drying
te~perature affects the rnm~ber of sites on the carrier available
for the reactants -- the higher the drying t~rrperature the lower
the rnnnber of sites. Thus, the exact molar ratios of the
~~agnesium, zirconium, titanium and/or vanadium c~OUnds, the
p~rx~c~ter and the optional organic oo~qaoiuxls to the hydroxyl
grrx~ps will vary and must be determined on a case-by-case basis
to assure that only so much of each of the reactants is added to
the solution as will be deposited onto the support from the
solvent without leaving any excess thereof in the solution.
Thus, the molar ratios given below are intended to serve only as
an approximate guideline and the exact of the catalyst
synthesis reactants in this embodiment must be controlled by the
functional limitation discussed above, i.e., it xm~st not be
greater than that which can be deposited onto the support. If
greater than that amount is added to the solvent, the excess may
react with other reactants, thereby forming a precipitate outside
of the support which is detrimental in the synthesis of our
catalyst and moust be avoided. The amount of the various
reactants which is mat greater than that deposited onto the
support can be detxrmined in any oorxvventional manner, e.g., by
F-5629-L
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adding the reactant, such as the magnesium C~o~d, to the
slurry of the carrier in the solvent, while stirring the slurry,
until the magnesitun c~owxl is detected as a solution in the
solvent.
Four example, for the silica carrier heated at about 200
to about 850°C, the amt of the magnesi~n ooh added to the
slurry is such that the molar ratio of Mg to the hydroxyl
(OH) o~ the solid carrier is about 0.1 to about 3, preferably
about 0.5 to about 2, more preferably about 0.7 to about 1.5,
most preferably about 0.8 to about 1.2, depexydixig upon the
trature at which the carrier material was dried. The
magnesium voa~u~d dissolves in the solvent to farm a solution.
For the same silica carrier, subjected to the aforementioned heat
treatment, if a titanium odd is used in the synthesis, the
molar ratio of fine Ti to OH on the car~°ier is about 0.1:1
to about 10:1, preferably about 1:1; if a vanadiwn o~ow~d is
used in the synthesis, the molar ratio of V to the OH groups i.a
about 0.1:1 to about 10:1, preferably about 1:1, and if a mixture
of titanium and vanadium coa~uryds is used, the molar ratio of
the sum of V and Ti to the OH groups on the solid carrier is
about 0.1:1 to about 10:1, preferably about 1:1. The amount of
the ~ added to the slurry is such that the molar ratio of
A1, derived fraan the praanater, to the OH groups on the solid
carrier is about 0.1 to about 3, preferably about 0.5 to about 2,
more preferably about 0.7 to about 1.5, and most preferably about
0.8 to about 1.2, deperyding upon the temperature at which the
carrier material was dried. The Ti:Zr or V:Zr molar ratios in
the final catalyst c~OSition are about 1:1 to about 50:1,
F-5629-L
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preferably about 10:1 to about 20:1. If optional organic
grids are used in the synthesis, the amount thereof will be
such that they will react with substantially all of the magnesium
~s deposited up to that point in the catalyst synthesis
onto the carrier.
It is also possible to add the amounts of the various
reactants which are in excess of those which will be kited
aaito the support and then re~mve, e.g., by filtration and
washing, any e~aoess of the reactants. However, this alternative
is less desirable than the most preferred embodiment described
above. Thus, in the preferred embodiment, the amamt of the
magnesium, ziro~ium, titanium aixl/o~r vanadium oompau~ds; the
pratadter and the optional oceanic ocxnpouryds, used in the
synthesis i.s not greater than that which can be deposited onto
the c~rriex. The exact molar ratios of Mg to Zr, Ti and/or V and
of Mg, Zr, Ti and/or V to the hydroxyl groups of the carrier will
therefore vary (depending, e.g., on the carrier drying
Mature) and trust be determined on a case-by-case basis.
The resulting solid, referred to herein as a catalyst
p~eca~z~sar, is combined with a catalyst activator. The activator
is a mixture of a conventional olefin polymerization catalyst
ao-catalyst used to activate the titanium or vanadium sites, and
an activator suitable to activate the zirconium sites.
~ ~,~.~i~l ~talyst used herein is any one or a
combi,rsation of any of tip materials commonly employed to activate .
Ziegler-Natta olefin polymerization catalyst ocmponents
i n; ng at least one oa~c~.u~d of the elements of Gds 7B,
IIA, IIB, IIIB, ar IVB of the Periodic cW art of the Elements,
publi.ahed by Fisher Scientific Oon~ax~y, Catalog Number 5-702-10,
CA 02042961 1997-09-22
F-5629 L
1978. E~les of such co-catalysts are metal alkyls, hydrides,
alkyl.hydr-ides, and alkylhalides, such as alkyllithium c~ounds,
dialkylzinc ~otu~ds, trialkylboron compounds, trialkylaluminum
cc~po~ux3s, alkylaluminum halides and hydrides, arr3
tetraalkylgermanium onds. Mixtures of the oo-catalysts may
also be employed. Specific examples of useful co-catalysts
include n-Lxxtyllithium, diethylzinc, di n prapylzinc,
triethylbomn, triethylaluzai.num, triisokutylalumi.rnun,
tri-n-hexylahmtiin~n, ethylahm~i~n dichloride, dib~nide, and
dihydride, isobutyl alimtirnun dichloride, dibrornide, arid
dihydride, diethylaluminum chloride, bromide, and hydride,
di-n-propylaluminum chloride, hromide, arid hydride,
diisobutylaluminum chloride, bromide and hydride,
tetramethylgPrman i tan, and tetraethylgPr~n i tun. Organcenetallic
co-catalysts which are preferred in this invention are C~a~zp IIIB
metal alkyls and dialky7halides having 1 to about 20 carbon atoms
per alkyl radical. Mare preferably, the oo-catalyst is a
trialkylaluminum d having 1 to 6, preferably 1 to 4 carbon
at~ans per alkyl radical. The most preferred co-catalyst is
trimethylaluminum. Other co-catalysts which can be used herein
are disclosed in Stevens et al, U.S. Patent No. 3,787,384, column
4, line 45 to column 5, line 12 and in Strobel et al, U.S. Patent
4,148,754, column 4, line 56 to column 5, line 59,
The oo-catalyst is employed in an apt which is at least
effective to pate the polymerization activity of the titanium
and/or vanadium sites of the catalyst of this invention.
Preferably, at least about 10 parts by weight of the oo-catalyst
are employed per part, by weight, of the V ar Ti in the catalyst
F-5629-L
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precursor, although higher weight ratios of the co-catalyst to
the V or Ti in the catalyst precursor, such as 15:1, 30:1, 50:1
or higher, are also suitable and often give satisfactory results.
The activatar suitable for activating the ziraonimn sites
is distinLrt fray the co~m~entional activators described above.
The ziiroo~iwn sites activator is a linear and/or cyclic
alumihoocane species pr~ared frcria the interaction of R3A1 and
water, where R is a C1 - C~ alkyl, with the amount of water
controlling the average molecular weight of the aluminoxane
molecule. As is Jmaan to those skilled in the art, the rate of
ackliti~ of tt~e water to R3Al, the concentration of the R3A1 and
water, and the temperature of the reaction may control catalyst
pzroperties, sudr'as catalyst activity, molecular,weight and
nalecular weight distribution of the polymers made with the
~talyst having its zirc~iiaa sites activated with the zirconimn
sites activator.
The zirconiwn sites activator is preferably an
aha~nrn~ne of the formula
R
~'°_ ~1~7.~°) ri ~1R2
four a linear alwninoxar~e, where n is 0, 1, 2 or 3, and/or
(Al (R) -0~
far a,cyclic aluminoxane, wherein m is an integer frcam 3 to 50,
a~ R for both the linear and fine cyclic aluminoxane is the same
or different linear, branched or cyclic alkyl group of 1 - 12
carboys, swch as methyl, ettryl, prc~yl, butyl, isobutyl,
ill, decyl ar dodecyl~ Each of the aluminoxane com~u~ds
may voa~t2~in different R groups and mixtures of the alumihoxane
ca~po~u~ds may also be used.
a
F-5629 L
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The most preferred activator for the zirconium sites is
methylalumirnm~o~car~e. Sinve the ocrmnercially-available
methylahani~oocane is believed to contain trimethylaluminum, in
the most preferred embodiment tl~ addition of such a oo~nnercial
~Y~.umi~no~cane to the catalyst precursor is sufficient to
activate both the zirconium sites and the titanium and/or
vanadiW n sites.
~talyst precursors of the present irnrention are
in the substantial abser~oe of water; oxygen, and other
~talyst poisons: Such catalyst poisons can be excluded during
the catalyst preparation steps by ar~y well lam methods, e:g.,
bY ~'Y~! ~ ~ ati.o~n under an atmosphere of nitrogen,
argon or attier inert 9~. ~ inert ,gas put~ge can serve the dual
p~pose of excludiryg external coiataininants during the Preparation
and r~maving undesirable reacti~ by-products resulting from the
preparation of catalyst precursor. Purification of the solvent
e~loyed in the catalyst synthesis is also helpful in this
regard.
The far' may be activated in situ by adding the
~~ and the mixture of the activators separately to the
polymerization mediwn. It is also possible to carbine the
~ar and the activators before the introduction thez°eDf into
~ pal~~,zation medium, e.g., for up to about 2 hours prior to
the introductioa~ thereof irito the polymerization medium at a
tune of fran about _40 to about 100°C.
Olefins, especially alpha--olefins, are polymerized with
the catalysts pr~ared aooomdi.ng to the present invention by any
~~le process: S~h processes include polymerizations carried
out in suspension; in solution; or in the gas phase. Gas phase
polymerization reactions are preferred, e.g., those taking place
~ a ~ and, especially, fluidized bed reactars.
F-5629 L
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Because of the uniqe~e nature of the catalyst of this
invention, relatively low amo~~nts of hydrogen are added
intentionally to the reaction medium during the polymerization
reaction to ooaztrol moleGVlar weic~t of the polymer product.
Typical hydrogen (H2): ethylene (C2 ) molar gas phase ratios in
the reactor are between about 0.01 and abort 0.2, preferably
chart 0.02 to about 0.05. The reactiari te~erature is about 70
~, 100°C, residence time is about l to about 5 hours, and
the a~ma~u~.s of olefins used in the reactor are such that the
ethylene partial a in the reactar~ is about 50 to about 250
hsi. ~Ylene aloe or in oonjunctiari with higher
alpha-olefins is polymerized. At these polymerization process
condithons polymers having multimodal molecular weight
thstribution are obtained. The polymerizatioa~ carried out in a
sirygle polymerizathon reactor in the p~esenoe of the catalyst of
this invetnthon ~ polymers having bimodal molecular weight
distribution, having polymer chains whose molecular weight ranges
from about 1,000 to about 1,000,000. Without whshing to be bound '
by any theory of operability, it is believed that the bimodal
molecular w~ehght distribution is obtained because the zirconium
(Zr) catalytic sites under certain polymerization conditions,
h.e:, the amo~mts of hydrogen specified herein, pmduae
relatively short polymer dzains, having relatively low molecular
weight: In c~txast the titaniwn (Ti) and/or vanadium (V)
catalytic sites, undex the same polymerization conditions,
pzroduoe relatively lomg polymer drains, of relatively high
molecular weight. The polymer product, therefore, contains bath
types of polymer drains, resulting in the mu7.timodal molecular
The mu7.timodal molecular weight
distribution is important because the resins having such
F-5629 L
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2~4~961
molecular weight distritutio~n are relatively easily processed,
e.g., in an extruder, and because such resins produce films
having good strength proppxties.
The molecular weight distribution of the polymers
p~aZ~ed in the p~esenoe of the catalysts of the p~sent
inccrentiaa~, ~ ~~ ~ melt flaw ratio (1~'R) values,
varies fraa about 50 to about 300, preferably about 100 to about
200 for medium density polyethylene (1~PE) products having a
~i~ of about 0:930 to abaft 0.940 g/oc, arid an I2 (melt
) of 0.01 to about 1 g/10 min: Cbn~xsely, I~PE
~. ~ with the catalysts of this in~ntiari, have a
density of about 0.940 to about 0:960 g/oc, flow index (I21)' of
about 1 to about 100, preferably about 4 to about 40, 1~'R values
of about 50 to about 300, preferably about 100 to abaft 200. As
is la~aan to those skilled in the art, at the aforementioned flora
'values, these 1~'R values~are indicative of a relatively
b~oa~d molecular weight distribution of the polymer. As is elso
lo~aan to those skilled in the Wit, such 1~R values are indicative
of the polymers specially suitable for high density polyethylene
(I~PE) film arid blaa molding applications. The gel permeation
~y (~) trays of polymers produced with the mixed
metal catalyst of this inventi~ show bn~oad and bimodal molecular
w~aight distributiah (1~1D) : The de~tai.ls of ttie 1~1D are controlled
by catalyst vompositiari arid reaction vo~ditions. The bimodal 1~1D
be'exploited to pmodcoe the proper balance of merhanic~7.
pip; ~ p~ooes.,gabirity:
The catalysts pared aoooxdi~ to the present invention
are highly active arid may ~~ the activity of at least about l.o
too about 10.0 kilograms of polymer per gram of catalyst per 100
psi of: e~thyler~e in about 1 hour.
CA 02042961 1997-09-22
F-5629-L
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Zhe linear polyethylene polymers prepared in accordance
with the present invention are homapolymers of ethylene ar-
oopolymers of ethylene with one or more C3-C10 alpha-°lefins'
'mss. ~lY~ having two moncmPxic units are possible as well
as terpolymers having three moncaneric units. Particular examples
of such polymers include ethylene/propylene copolymers,
ethylene/1-butane copolymers, ethylene/1-hexane copolymers,
ethylene/1-octane copolymers, ethylene/4~nethyl-1 pentane
copolymers, ethylene/1-but~ne/l~exene texpolymers,
ethylene/propylene/1-hexane terpolymers and
ethylene/pmpylene/1-k~ztene terpolymers. Ethylene/1-hexane is
the most preferred copolymer polymerized in the process of and
with the catalyst of this invention.
'Ihe polyethylene polymers produced in accordance with the
present invention preferably contain at least about 80 percent by
weic~t of ethylene units.
A particularly desirable method for producing
polyethylene polymers according to the present invention is in a
fluid bed reactor. Such a reactor and means for operating it are
de'saibed by Levine et al, U.S. Patent No. 4,011,382, Karol_et
al, U.S. Patent 4,302,566 and by Nowlin et al, U.S. Patent
4,481,301. The polymer produced in such a reactor
cor~tains the catalyst particles because the catalyst i.s not
separated frcan the polymer.
'Ihe following ales illustrate the invention.
~e properties of the polymers produced in the ales
arid any calculated process parameters were determined by the
following test methods:
F-5629-L
-1~ - 2~~2~~6~.
Density: AS~I D 1505 A plaque is made and conditioned
for one hour at 100°C to approach equilibrium crystallinity.
Measur~aeat far density is then made in a density gradient
cohutai; reported as gue;/oc.
Melt Irydex (1~) ~ I2: AS'~i D-1238--Oondition E--Measured
at 190°C-reported as ~an~ per 10 minutes.
High Load Melt Irydex (HIl~) . I21. ASIM D-1238--Condition
F--Measured at 10 times tl~ weight used in tl~ melt index test
above.
Melt Flow Ratio (MFR)=I21/I2
Productivity: A sample of the resin p~duct is asked,
and the meight percent of ash is determined; since the ash is
substantially coal of the catalyst, 'the prod~tivity is thus
the pads of polymer psroduoed per pow~d of total catalyst
ooa~sumed: The amount of Ti, Mg. V an Al in the ash is determined
by elemental analysis.
F~(~LE 1
~(CatalVSt Precursor Syr~esisJ~
All procedures were performed under a dry nitrogen
atmosphere.
9pIl~ION (A) : 0.317 groans of zirconium
dicyclopentadienyl dichloride (Cp2ZrC12) was transferred to a 100
~, f~ ~ then 50 mls of dry toluene were added.
flask was placed into a 50°C oil bath until a clear solution
was formed:
gp~pN (B): 50 mls of dry toluene and 12 mls of
methylalum3rnm~oocane (MAID) (4.6 wt% A1 in toluene) were added to a
200 cc pear flask. The pear flask was placed into an oil bath
F-5629-L
- 19 -
set to 50°C. Next, 20 mls of solution (A) was added to the pear
flask to yield a clear light yellow solution.
CYST fREPARATIC~1 90IlJFION: 10.095 grams of Davison
Cynical ~a~apany's grade 955 silica which had been heated at
600°C for about 16 hours under a dry nitrogen purge was weighed
into a 500 oc pear flask cantainirg a etic stirring bar., the
flask was placed into a 80°C oil bath and 50 mls of dry toluene
was added to the flask. Next, 7.2 mls of dibutylmagnesium (0.973
1/~~ ~ ~ ~e silica/toluene slurry. The contents of
the- flask w~exe stirred for 50 minutes. den, p,80 mls of neat
~taniwin tetrachloride was added to the flask. The slurry turned
a dark blown color and stirring was- oo~xtirn~ed far 60 mirn~tes.
Finally, the eWire oo~ntems of solution (B) ~ siphohed into
the catalyst preparation flas)c, arid the slurry was stirred for 60
.~~ all solvents were removed by
evaporation under a nitrogen purge. Catalyst yield was 12.805
of a dark-b~ac~m free-flaaing powder.
F.~~AI~'i~ 2
.(~3~'iza~ion Process)
An athylene~l-hexane copolymer, was prepares with the
catalyst fox of Ele 1 in the following representative
A 1.6 liter stainless steel autoclave, maintained at
about :50°C, was filled with 0.750 literss of dry he~car~e, 0.030
liters of dry 1-he~cene, and 5.1 mmols of methylalwnirnunoxane
(1~D) while under a slag nitrogen purge. The reactor was closed,
the stirring rate was set at about 900 rpm, the internal
attire was increased to 70°C, and the internal pressure was
raised fran 8 psi to ll psi with hydrogen. Ethylene was
int~roduoed to maintain the pressure at about 114 psi. Next,
0:0349 gr~ of the Fle 1 catalyst precursor was introduced
into the reactor with ethylene over pressure and the te~erature
Was increased and held at 85°C. The polymerization was cantirn~ed
F-5629-L
- 20 -
for 60 minutes, arid then the ethylene supply was s~t~ed and the
rector allowed to cool to rocen temperature. 110 grams of
polyethylene wexe collected.
The Nd~ID of the polymer was examined by GPC, and the
results clearly showed that the polymer had a bimodal 1~5~1D (Figure
2) .
F~~LE 3
~Catal~st Pr~ursor Synthesis)
191.4 grams of Davison grade 955 silica which was
previously dried at 600°C for 16 hours was added to a nitrogen
pied, 4-neck, 3-liter round-bottcen flask fitted with an
overhead stirrer. Toluene (800 mls) was added to the flask and
the flask was placed into an ail bath maintained at 60°C. Next,
129 mls of dibutyiwn (1.04 Molar solution in heptane) was
added to the silica/toluene slurry. The solution was stirred for
35 minutes. Then, 15.0 mls of neat TiCl4 was diluted with 50 mls
of dry toluene and added to the flask. The solution was stirred
for 60 mirmtes. Finally, 93 mls of methyl aluminoxane (4.6 wt%
A1) and 2.41 g of Cp2ZrCl2 were added to a 125 ml addition funnel
to yield a clear yellow solution. This solution was added to the
silica/toluene slurry and the oil bath t.~erature was i.nGreased
'to 80-85°C.
The slurry was heated far 3 hours. After this time, the
oil bath te~erature was lowexed to 50°C and stirrixig was stopped
to allay the silica to settle. The supernatant liquid was
decanted and the silica was washed three times with 1500 mls of
dry hexane. The silica was dried under a nitrogen purge to yield
about 233 of dry, free-flowing powder.
E~A,T~~'LE 4
SPol~m~rization Pmoess)
The catalyst precursor v~sition of ale 3 was used
to prepare an ethylene/1 hexane co-polymer in a fluid bed, pilot
plant reactor operated substantially in the manner dislosed by
F-5629 L 20~~9~~
- 21 -
Nowlin et al, U.S. Patent 4,481,301. A steadystate operation
was obtained by contirnmusly feeding the catalyst precursor, 1~0
activator, and reactant gases (ethylene, 1-l~xene and hydrogen)
to the reactor while also continuously withdrawing polymer
product from the reactor. The reactor operating conditions were
as follows:
Ethylene 210 psi
(C6:/C2 ) vapor mole ratio 0.039
(Ii2/C2 ) vapor mole ratio 0.050
Production Rate 24.9 lbs/hr
Catalyst Productivity 3000 grams
polym x/cpn catalyst
Resic~enoe Time 2.5 twhrs
~ 90C
1~0 feed 270 mls/hr (1.0
wt%
Al in toluene)
The polymer had the following properties:
Density 0. 942 c, fms/cc
Flaw Index (I21) 16.3 c~ns/lo min
The molecular weight distribution of the polymer was
exaomined by GPC and the results clearly showed that the polymer
had a bimodal I~7D (Figure 3).
