Note: Descriptions are shown in the official language in which they were submitted.
CA 02695552 2010-03-04
PROCESS FOR PREPARING LOW MOLECULAR WEIGHT WAX
FIELD OF THE INVENTION
This invention relates to the preparation of polyethylene waxes having a
narrow
molecular weight distribution in a solution polymerization process using a
phosphinimine catalyst.
BACKGROUND OF THE INVENTION
Polyethylene waxes are readily available items of commerce and are used to
prepare such products as paints, inks, cleaning waxes and polishes.
These waxes are prepared by the polymerization of ethylene (and, optionally, a
comonomer such as butene, hexene or octene) in the presence of a catalyst.
Conventional Zeigler Natta catalysts may be used to prepare the waxes, but
extremely
high levels of hydrogen are generally required to produce low molecular
weights.
U.S. patent 5,023,388 teaches the use of a metallocene catalyst to prepare
polyethylene without using disproportionately large amounts of hydrogen.
U.S. patent 6,063,879 (Stephan et al.) teaches the preparation of high
molecular
weight polyethylene in a solution polymerization process using a phosphinimine
catalyst. We have now discovered that the phosphinimine catalyst disclosed in
the
Stephan et al. patent may also be used to prepare low molecular weight
polyethylene
waxes (even in the absence of hydrogen) when used at polymerization
temperatures in
excess of 190 C under polymerization conditions which allow greater than 90%
ethylene conversion.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides:
A process to prepare polyethylene wax having a number average molecular weight
of
from 500 to 10,000 and a molecular weight distribution of from 2 to 4, said
process
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comprising polymerizing ethylene and optionally, at least one C3 to C10 alpha
olefin,
under solution polymerization conditions in a reactor in the presence of:
a) a catalyst defined by the formula:
Cp
[(R1)3-P=NI]n- Me - (I-1)3-n
wherein Me is selected from the group consisting of Ti, Zr, and Hf; n is 1 or
2; Cp is a
monocyclopentadienyl ligand which is unsubstituted or substituted by up to
five
substituents independently selected from the group consisting of a Ci_io
hydrocarbyl
radicals or two hydrocarbyl radicals taken together may form a ring which
hydrocarbyl
substituents or cyclopentadienyl radical are unsubstituted or further
substituted by a
halogen atom, a C1_8 alkyl radical, C1_8 alkoxy radical, a C6-113 aryl or
aryloxy radical; an
amido radical which is unsubstituted or substituted by up to two C1_8 alkyl
radicals; a
phosphido radical which is unsubstituted or substituted by up to two Ci_8
alkyl radicals;
silyl radicals of the formula -Si-(R2)3 wherein each R2 is independently
selected from the
group consisting of hydrogen, a C1_8 alkyl or alkoxy radical, C6_10 aryl or
aryloxy radicals;
germanyl radicals of the formula Ge-(R2)3 wherein R2 is as defined above; each
R1 is
independently selected from the group consisting of a hydrogen atom, a halogen
atom,
C1_10 hydrocarbyl radicals which are unsubstituted by or further substituted
by a halogen
atom, a C1_8 alkyl radical, Ci_g alkoxy radical, a C6..110 aryl or aryloxy
radical, a silyl
radical of the formula -Si-(R2)3 wherein each R2 is independently selected
from the
group consisting of hydrogen, a C1_8 alkyl or alkoxy radical, C6..10 aryl or
aryloxy radicals,
germanyl radical of the formula Ge-(R2)3 wherein R2 is as defined above or two
R1
radicals taken together may form a bidentate C1_10 hydrocarbyl radical, which
is
unsubstituted by or further substituted by a halogen atom, a C1-8 alkyl
radical, C1-8
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alkoxy radical, a C6_10 aryl or aryloxy radical, a silyl radical of the
formula -Si-(R2)3
wherein each R2 is independently selected from the group consisting of
hydrogen, a
C1..8 alkyl or alkoxy radical, C6-10 aryl or aryloxy radicals, germanyl
radicals of the
formula Ge-(R2)3 wherein R2 is as defined above, provided that R1 individually
or two R1
radicals taken together may not form a Cp ligand as defined above; each L1 is
independently selected from the group consisting of a hydrogen atom, of a
halogen
atom, a C1_10 hydrocarbyl radical a C1_10 alkoxy radical, a C5_10 aryl oxide
radical, each
of which said hydrocarbyl, alkoxy, and aryl oxide radicals may be
unsubstituted by or
further substituted by a halogen atom, a C1..8 alkyl radical, C1_5 alkoxy
radical, a C6-10
aryl or aryl oxy radical, an amido radical which is unsubstituted or
substituted by up to
two C1_8 alkyl radicals; a phosphido radical which is unsubstituted or
substituted by up
to two C1_8 alkyl radicals, provided that L1 may not be a Cp radical as
defined above;
and
b) an activator,
with the provisos that:
1) said polymerization conditions are conducted at a temperature of from
190 C to 250 C;
2) at least 85 weight % of said ethylene is converted to polyethylene wax
under said polymerization conditions; and
3) catalyst efficiency, Kp, is less than 300 but greater than 25 [mM x
minutes]l, where mM is the concentration, expressed in millimoles, of said
transition metal Me within said reactor.
As used herein, the term "polyethylene wax" refers to a polymer of ethylene
(and, optionally, an alpha olefin monomer) which has a number average
molecular
weight (Mn) of from about 500 to 10,000. The polyethylene waxes of this
invention are
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further characterized by having a molecular weight distribution, Mw/Mn, of
from 2 to 4
(where Mw is weight average molecular weight).
We have discovered that such waxes may be prepared at high polymerization
temperatures under "forced" solution polymerization conditions. The term
"forced"
means that a very high ethylene conversion is achieved. In particular, the
ethylene
conversion must be greater than 85% (preferably greater than 90%) of the
ethylene fed
to the reactor. This forced condition can be achieved by using a very high
level of
catalyst (such that the catalyst efficiency, as quantified by the kinetic
parameter "Kp" ¨
discussed later) is less than 300. As will be shown in the Examples, wax may
be
produced using these conditions, even in the absence of hydrogen.
All three of these conditions (high temperature, high ethylene conversions and
low catalyst efficiency) are required by the present invention. In other
words, if only two
of these conditions are used, the present catalyst system will generally
provide a higher
molecular weight polyethylene. Moreover, the catalyst efficiency (expressed as
Kp,
described below) is also strongly influenced by impurities. Specifically,
impurities that
are contained in the reactor feedstreams (for example, polar contaminants in
the
solvent or monomers) will typically reduce the catalyst efficiency without
significantly
changing the molecular weight of the polymer. While not wishing to be bound by
theory, it is believed that such impurities interact with the catalyst in a
manner that
reduces or even eliminates the activity of the catalyst molecule that
interacts with the
impurity. The present invention requires comparatively high catalyst
concentrations ¨
even if all reactor feedstreams are highly purified. In other words, a given
catalyst
concentration that provides a high molecular weight thermoplastic polyethylene
for
given reaction conditions and a given ethylene conversion is "too low" for the
process of
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this invention. The molecular weight of the polymer can be reduced (so that
wax is
formed) by then increasing the catalyst concentration and ethylene conversion.
Finally, the Examples show that wax may be produced by the process of this
invention even in the absence of hydrogen. The present invention does
encompass the
use of hydrogen. Hydrogen is a well known chain transfer agent and the use of
hydrogen will generally allow the production of lower molecular weight polymer
under
less forced polymerization conditions.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Part A. Catalyst
The catalyst used in this invention is a Group 4 metal complex of the formula:
Cp
[(R1)3-P=NI]n- Me - (1-1)3-n
wherein Me is selected from the group consisting of Ti, Zr, and Hf; n is 1 or
2; Cp is a
monocyclopentadienyl ligand which is unsubstituted or substituted by up to
five
substituents independently selected from the group consisting of a Ci_io
hydrocarbyl
radicals or two hydrocarbyl radicals taken together may form a ring which
hydrocarbyl
substituents or cyclopentadienyl radical are unsubstituted or further
substituted by a
halogen atom, a C1_8 alkyl radical, C1_8 alkoxy radical, a C6_10 aryl or
aryloxy radical; an
amido radical which is unsubstituted or substituted by up to two Ci_g alkyl
radicals; a
phosphido radical which is unsubstituted or substituted by up to two C1_8
alkyl radicals;
silyl radicals of the formula -Si-(R2)3 wherein each R2 is independently
selected from the
group consisting of hydrogen, a C1_8 alkyl or alkoxy radical, C6_10 aryl or
aryloxy radicals;
germanyl radicals of the formula Ge-(R2)3 wherein R2 is as defined above; each
RI is
independently selected from the group consisting of a hydrogen atom, a halogen
atom,
C1_10 hydrocarbyl radicals which are unsubstituted by or further substituted
by a halogen
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atom, a C1_8 alkyl radical, C1..8 alkoxy radical, a C6_10 aryl or aryloxy
radical, a silyl
radical of the formula -Si-(R2)3 wherein each R2 is independently selected
from the
group consisting of hydrogen, a C1..8 alkyl or alkoxy radical, C6_10 aryl or
aryloxy radicals,
germanyl radical of the formula Ge-(R2)3 wherein R2 is as defined above or two
R1
radicals taken together may form a bidentate C1_10 hydrocarbyl radical, which
is
unsubstituted by or further substituted by a halogen atom, a C1_8 alkyl
radical, C1-8
alkoxy radical, a C6-10 aryl or aryloxy radical, a silyl radical of the
formula -Si-(R2)3
wherein each R2 is independently selected from the group consisting of
hydrogen, a
C1..8 alkyl or alkoxy radical, C6_10 aryl or aryloxy radicals, germanyl
radicals of the
formula Ge-(R2)3 wherein R2 is as defined above, provided that R1 individually
or two R1
radicals taken together may not form a Cp ligand as defined above; each L1 is
independently selected from the group consisting of a hydrogen atom, of a
halogen
atom, a C1_10 hydrocarbyl radical a C1_10 alkoxy radical, a C6_10 aryl oxide
radical, each
of which said hydrocarbyl, alkoxy, and aryl oxide radicals may be
unsubstituted by or
further substituted by a halogen atom, a C1_8 alkyl radical, Ci_8 alkoxy
radical, a C6-10
aryl or aryl oxy radical, an amido radical which is unsubstituted or
substituted by up to
two C1_8 alkyl radicals; a phosphido radical which is unsubstituted or
substituted by up
to two C1_8 alkyl radicals, provided that L1 may not be a Cp radical as
defined above.
As used in this specification the term "cyclopentadienyl" refers to a 5-member
carbon ring having delocalized bonding within the ring and typically being
bound to the
Group 4 metal (M) through covalent i5 -bonds.
In the Group 4 metal complex preferably Cp is unsubstituted. However, if Cp is
substituted preferred substituents include a fluorine atom, a chlorine atom,
C1-6
hydrocarbyl radical, or two hydrocarbyl radicals taken together may form a
bridging
ring, an amido radical which is unsubstituted or substituted by up to two C1_4
alkyl
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radicals, a phosphido radical which is unsubstituted or substituted by up to
two C1-4
alkyl radicals, a silyl radical of the formula -Si-(R2)3 wherein each R2 is
independently
selected from the group consisting of a hydrogen atom and a C1_4 alkyl
radical; a
germanyl radical of the formula -Ge-(R2)3 wherein each R2 is independently
selected
from the group consisting of a hydrogen atom and a C1_4 alkyl radical.
In the Group 4 metal complex preferably each R1 is selected from the group
consisting of a hydrogen atom, a halide, preferably fluorine or chlorine atom,
a C1_4 alkyl
radical, a C1_4 alkoxy radical, a silyl radical of the formula -Si-(R2)3
wherein each R2 is
independently selected from the group consisting of a hydrogen atom and a C1_4
alkyl
radical; and a germanyl radical of the formula -Ge-(R2)3 wherein each R2 is
independently selected from the group consisting of a hydrogen atom and a C1_4
alkyl
radical.
In the Group 4 metal complex preferably each L1 is independently selected from
the group consisting of a hydrogen atom, a halogen, preferably fluorine or
chlorine
atom, a hydrocarbyl such as a C1_6 alkyl radical, a C1_6 alkoxy radical, and a
C6_10 aryl
oxide radical.
Preferred catalysts are those in which M is titanium, each R1 is an alkyl
group
(especially isopropyl or tertiary butyl) and there are 2 L ligands, each of
which is
preferably a halide (especially chlorine).
Part B. Activator
Preferred activators are selected from the groups consisting of aluminoxanes,
ionic activators and mixtures of the two.
The aluminoxane activator may be of the formula (R4)2A10(R4A10)mAl(R4)2
wherein each R4 is independently selected from the group consisting of C1-20
hydrocarbyl radicals and m is from 0 to 50, preferably R4 is a C1_4 alkyl
radical and m is
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from 5 to 30. Commercially available aluminoxanes (as described in the
Examples) are
preferably used for reasons of convenience, but aluminoxanes may be prepared
by
carefully reacting aluminum alkyls with small amounts of water.
Activation of a polymerization catalyst with aluminoxane generally requires a
molar ratio of aluminum in the activator to Group 4 metal in the complex from
10:1 to
1000:1. The process of this invention preferably has an aluminum to Group 4
metal
ratio of at least 50:1 (on a moler basis) most preferably from 50 to 500:1.
High
"absolute" amounts of aluminoxane are generally preferred. Without wishing to
be
bound by theory, it is believed that the high level of aluminum may lead to
lower
molecular weights (which is desired in the production of wax) by a chain
transfer
mechanism to aluminum. (Due to the high levels of transition metal catalyst
that is
preferably used in the process of this invention, the "absolute" levels of Al
are also high
even at relatively low Al/Ti ratios. For example, even at an Al/M ratio of
50/1, an
increase of "X" millimoles of transition metal will increase the Al level by
50 X
millimoles).
The "ionic activator" may be selected from the group consisting of:
(i) compounds of the formula [RI. [B(R7)4] wherein B is a boron atom, R5
is a
cyclic C5_7 aromatic cation or a triphenyl methyl cation and each R7 is
independently selected from the group consisting of phenyl radicals which are
unsubstituted or substituted with from 3 to 5 substituents selected from the
group
consisting of a fluorine atom, a C1_4 alkyl or alkoxy radical which is
unsubstituted
or substituted by a fluorine atom; and a silyl radical of the formula -Si-
(R9)3;
wherein each R9 is independently selected from the group consisting of a
hydrogen atom and a C1_4 alkyl radical; and
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OD compounds of the formula [(R8)t ZH][B(R7)4]- wherein B is a boron
atom, H is a
hydrogen atom, Z is a nitrogen atom or phosphorus atom, t is 2 or 3 and R8 is
selected from the group consisting of C1_8 alkyl radicals, a phenyl radical
which is
unsubstituted or substituted by up to three C1_4 alkyl radicals, or one R8
taken
together with the nitrogen atom may form an anilinium radical and R7 is as
defined above; and
(iii) compounds of the formula B(R7)3 wherein R7 is as defined above.
In the above compounds preferably R7 is a pentafluorophenyl radical, and R5 is
a
triphenylmethyl cation, Z is a nitrogen atom and R8 is a C1_4 alkyl radical or
R8 taken
together with the nitrogen atom forms an anilium radical which is substituted
by two C1-4
alkyl radicals.
The "ionic activator" may abstract one or more L1 ligands so as to ionize the
Group 4 metal center into a cation but not to covalently bond with the Group 4
metal
and to provide sufficient distance between the ionized Group 4 metal and the
ionizing
activator to permit a polymerizable olefin to enter the resulting active site.
Examples of ionic activators include the following compounds:
triethylammonium tetra(phenyl)boron,
tripropylammonium tetra(phenyl)boron,
tri(n-butyl)ammonium tetra(phenyl)boron,
trimethylammonium tetra(p-tolyl)boron,
trimethylammonium tetra(o-tolyl)boron,
tributylammonium tetra(pentafluorophenyl)boron,
tripropylammonium tetra (o,p-dimethylphenyl)boron,
tributylammonium tetra(m,m-dimethylphenyl)boron,
tributylammonium tetra(p-trifluoromethylphenyl)boron,
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tributylammonium tetra(pentafluorophenyl)boron,
tri(n-butyl)ammonium tetra (o-tolyl)boron
N,N-dimethylanilinium tetra(phenyl)boron,
N,N-diethylanilinium tetra(phenyl)boron,
N,N-diethylanilinium tetra(phenyl)n-butylboron,
N,N-2,4,6-pentamethylanilinium tetra(phenyl)boron
di-(isopropyl)ammonium tetra(pentafluorophenyl)boron,
dicyclohexylammonium tetra (phenyl)boron
triphenylphosphonium tetra)phenyl)boron,
tri(methylphenyl)phosphonium tetra(phenyl)boron,
tri(dimethylphenyl)phosphonium tetra(phenyl)boron,
tropillium tetrakispentafluorophenyl borate,
triphenylmethylium tetrakispentafluorophenyl borate,
benzene (diazonium) tetrakispentafluorophenyl borate,
tropillium phenyltris-pentafluorophenyl borate,
triphenylmethylium phenyl-trispentafluorophenyl borate,
benzene (diazonium) phenyltrispentafluorophenyl borate,
tropillium tetrakis (2,3,5,6-tetrafluorophenyl) borate,
triphenylmethylium tetrakis (2,3,5,6-tetrafluorophenyl) borate,
benzene (diazonium) tetrakis (3,4,5-trifluorophenyl) borate,
tropillium tetrakis (3,4,5-trifluorophenyl) borate,
benzene (diazonium) tetrakis (3,4,5-trifluorophenyl) borate,
tropillinum tetrakis (1,2,2-trifluoroethenyl) borate,
triphenylmethylium tetrakis (1,2,2-trifluoroethenyl) borate,
benzene (diazonium) tetrakis (1,2,2-trifluoroethenyl) borate,
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tropillium tetrakis (2,3,4,5-tetrafluorophenyl) borate,
triphenylmethylium tetrakis (2,3,4,5-tetrafluorophenyl) borate, and
benzene (diazonium) tetrakis (2,3,4,5-tetrafluorophenyl) borate.
Readily commercially available ionic activators include:
N,N- dimethylaniliumtetrakispentafluorophenyl borate; triphenylmethylium
tetrakispentafluorophenyl borate ("trityl borate"); and trispentafluorophenyl
boron.
Part C. Monomers and Comonomers
Homopolymer polyethylene waxes are encompassed by this invention.
However, preferred monomers are ethylene and C3-20 alpha olefins. Illustrative
non-
limiting examples of such alpha-olefins are one or more of propylene, 1-
butene, 1-
pentene, 1-hexene, 1-octene and 1-decene.
The polyethylene waxes which may be prepared in accordance with the present
invention preferably comprise not less than 60, preferably not less than 70
weight % of
ethylene and the balance of one or more C4_8 alpha olefins, most preferably
selected
from the group consisting of 1-butene, 1-hexene, 1-octene. The polyethylene
waxes
may contain large amounts of comonomer (and, as a result, have a very low
density of
less than 0.900 g/cc) or be ethylene homopolymers (having a density of greater
than
0.955 g/cc) or copolymer waxes with intermediate levels of comonomer having an
intermediate density.
As previously noted, the waxes of this invention have a number average
molecular weight of from 500 to 10,000 (preferred range is from 500 to 2000).
Comonomer may also be used to reduce the melting point of the wax.
Part D. Solution Polymerization
Solution polymerization processes for the preparation of polyethylene are well
known in the art. These processes are conducted in the presence of a
hydrocarbon
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solvent for the polymer, which solvent is typically a C5-12 hydrocarbon which
may be
unsubstituted or substituted by C1-4 alkyl group, such as pentane, hexane,
heptane,
octane, cyclohexane, methylcyclohexane and hydrogenated naphtha. An additional
solvent is Isopar ETm (C8-12 aliphatic solvent, Exxon Chemical Co.).
Solution polymerizations for polyethylene are generally conducted at
temperatures from about 80 C to about 250 C. The pressure of reaction may be
as
high as about 15,000 psig for the older high pressure processes or may range
from
about 100 to 4,500 psig. However, we have determined that high polymerization
temperatures (especially greater than about 190 C) are preferable for the
preparation
of waxes.
In a solution polymerization the liquid monomers are dissolved/ dispersed in
the
solvent either prior to being fed to the reactor, or for gaseous monomers the
monomer
may be fed to the reactor so that it will dissolve in the reaction mixture.
Prior to mixing,
the solvent and monomers are generally purified to remove polar moieties. The
polar
moieties, or catalyst poisons include water, oxygen, metal impurities, etc.
Preferably
steps are taken before provision of such into the reaction vessel, for example
by
chemical treatment or careful separation techniques after or during the
synthesis or
preparation of the various components. The feedstock purification prior to
introduction
into the reaction solvent follows standard practices in the art, e.g.
molecular sieves,
alumina beds and oxygen removal catalysts are used for the purification of
ethylene,
alpha-olefin, and optional diene. The solvent itself as well (e.g. hexane and
toluene) is
similarly treated. In some instances, out of an abundance of caution excess
scavenging activators may be used in the polymerization process.
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The feedstock may be heated prior to feeding to the reactor. However, in many
instances it is desired to remove heat from the reactor so the feed stock may
be at
ambient temperature to help cool the reactor.
Generally, the catalyst components may be premixed in the solvent for the
reaction or fed as separate streams to the reactor. In some instances
premixing is
desirable to provide a reaction time for the catalyst components prior to
entering the
reaction.
The reactor may comprise a tube or serpentine reactor used in the "high
pressure" polymerizations or it may comprise one or more reactors or
autoclaves. It is
well known that the use in series of two such reactors each of which may be
operated
so as to achieve different polymer molecular weight characteristics. The
residence time
in the reactor system will depend on the design and the capacity of the
reactor.
Generally the reactors should be operated under conditions to achieve a
thorough
mixing of the reactants. On leaving the reactor system the solvent is removed
and the
resulting polymer is finished in a conventional manner.
EXAMPLES
Chemicals and Reagents
Purchased cyclohexane was dried and deoxygenated by passing it through a
bed of deoxygenation catalyst (brand name R311 from BASF), an alumina bed
(brand
name SelexsorbTM COS/CD), and a molesieve (3A/13X) bed.
Purchased o-xylene was further purified by passing through the same
purification beds as described for cyclohexane purification.
Ethylene was purchased from Praxair as polymer grade. The ethylene was
purified and dried by passing the gas through a series of purification beds
including
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alumina (brand: Selexsorb COS), molesieve (type: 13X), and a deoxygenation bed
(brand: Oxiclear6).
Cyclopentadienyltitanium-(tri-tert-butylphosphinimino) dichloride was
synthesized
according the procedure disclosed in the publication (Organometallics, 2003,
22, 1937-
1947) and confirmed with 1H-NMR for 98.9% of purity.
Tritylborate was purchased from Albemarle with minimum 97% of purity.
Methylaluminoxane ("MAO") was purchased from Akzo Nobel under the trade
name MMAO-7, reported to contain 13.0 wt% of Al.
4-ethyl-2,6-di-tert-butyl phenol ("Phenol 1") was purchased from Aldrich with
99 /0 of purity.
Purchased 1-butene was dried by passing a series of columns containing 3A,
COS and 13X.
Butene cyclohexane solution was prepared by passing pure 1-butene gas into
butene absorption vessel containing cyclohexane. The concentration of 1-butene
was
determined by collecting a pressurized sample of 1-buene in cyclohexane using
a
sample loop. The collected sample was then analyzed by gas chromatography (GC-
FID) to obtain a weight % (wt%) of butene in the cyclohexene.
Purchased 1-hexene was dried by in a similar way as 1-butene.
Purchased isopropanol was used without further purification.
Analytical Methods
Polymer molecular weights and molecular weight distributions were measured by
gel permeation chromatography (GPC). The instrument (Waters 150-C) was used at
140 C in 1,2,4-trichlorobenzene and was calibrated using polyethylene
standards.
Polymer branch frequencies were determined by Fourier Transform-Infra Red
(FT-IR). The instrument used was a Nicolet 750 Magna-IRTM spectrophotometer.
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Butene content was determined by GC-FID. Composition was measured by split
injection capillary gas chromatography with flame ionization detection. Sample
injection
was done with a pressurized liquid injection valve system. Component response
factors were assumed to be unity. The GC-FID instrument used was HP 5890
Series 2.
Continuous Polymerization
Continuous polymerizations were conducted on a continuous polymerization unit
(CPU). The CPU contained a 71.5 millilitre (mL) stirred reactor and was
operated
between 160-280 C for the polymerization experiments. An upstream mixing
reactor
having a 20 mL volume was operated at 5 C lower than the polymerization
reactor to a
maximum 220 C. The mixing reactor was used to pre-heat the monomers and some
of the solvent streams. Catalyst feeds and the rest of the solvent were added
directly to
the polymerization reactor as a continuous process. A total continuous flow of
27
mL/minute ("min") into the polymerization reactor was maintained. MAO and
phenol 1
solutions were premixed prior to entering the reactor and the catalyst and the
tritylborate were premixed before entering the reactor. The catalyst was
activated in
situ (in the polymerization reactor) at the reaction temperature in the
presence of the
monomers. Ethylene was supplied to the reactor by a calibrated thermal mass
flow
meter and was dissolved in the reaction solvent prior to the polymerization
reactor. The
comonomers were premixed with the ethylene before entering the polymerization
reactor. Internal reaction temperature is monitored by a thermocouple in the
polymerization medium and can be controlled at the required set point to 0.5
C.
Ethylene and 1-hexene copolymer was made at 1-hexene / ethylene weight ratio
of
0.75. 1 and 1.5. Ethylene and 1-butene copolymers were made at a 1-butene /
ethylene weight ratio of 1. The ethylene was fed at a 2.0 g/min of ethylene to
the
polymerization reactor for the 1-butene runs whereas at a 4.5 g/min of
ethylene for the
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1-hexene runs. The CPU system operated at a pressure of 10.5 Mega Pascals
(MPa).
The solvent, monomer and comonomer streams were all purified by the CPU
systems
before entering the reactor. Q is ethylene conversation (and determined by an
online
gas chromatograph (GC)) and polymerization activity Kp is defined as:
(Kp)(HUT)=(Q (1-Q))(1/catalyst concentration)
wherein Q is the fraction of ethylene monomer converted; HUT is a reciprocal
space
velocity (hold up time) in the polymerization reactor expressed in minutes and
maintained constant throughout the experimental program; and the catalyst
concentration is the concentration in the polymerization reactor expressed in
mmol of
transition metal (Ti) per liter. Thus, the units for Kp are [mM x min]-1 where
mM is the
millimoler concentration of the transition metal in the catalyst (which is
titanium in the
Examples) and min is minutes. The concentration of catalyst used in each
experiment
is shown in Table 1 (expressed as the micromolar concentration of Ti). MAO was
added with an Al/Ti aiming point of 80/1; tritylborate was added with a BiTi
aiming point
of 1.2/1; phenol 1 was added with a phenol 1/AI aiming point of 0.3/1 (where
all of these
ratios are expressed on a moler basis).
Downstream of the reactor the pressure was reduced from the reaction pressure
to atmospheric pressure. The solid polymer was then recovered as a slurry in
the
condensed solvent and was dried by evaporation and vacuum oven before
analysis.
In this set of experiments, polymerization temperature and ethylene conversion
were used to control the polymer molecular weights.
Mn (or number average molecular weight) is reported in Table 1. "PD" (or
"polydispersity", also known as "molecular weight distribution"), which is
calculated by
dividing weight average molecular weight ("Mw") by Mn is also reported in
Table 1.
16
H:\Scott\SCResponse\2Ol0007Canada Amended spec and clatms.docx
TABLE 1
run polymerization Comonomer C2 in
Ti Kp comonomer comonomer
concentration Q %Mn
Pd
# temperature C to C2 ratio feed
(1/mM*min) content type
in reactor
g /min pM wt %
1 230 1 2 37.04
93.6 152.82 14.1 butene 1744 2.82
2 230 1 2 50.00 90.7 75.59
13.7 butene 1582 2.99
3 230 1 2 74.07 92.6
65.54 14.5 butene 1742 2.6
4 240 1 2 74.07 87.5 36.35
10 butene 1457 3.67 0
220 1 1.47 32.03 91.6 130.47
14.4 butene 1998 2.64 0
1.)
6 220 1.01 2 29.11
92.7 168.29 15.6 butene 2232 2.74 0,
ko
0,
7 220 1.01 2 21.49 90.3 167.49
12.8 butene 2600 3.68 0,
0,
1.)
8 210 1.01 2 19.29 92.5 247.72
16 butene 3324 2.47 1.)
0
9 210 1.01 2 13.93 90.1 250.67
13.3 butene 3423 2.94
0
'
224.3 1.5 4.5 22.42 90.7 168.18
18.2 hexene 3185 3.53 0
w
'
11 220 0.7 4.5 14.90 90.9 258.57
9.5 hexene 5228 3.64 0
12 220 1 4.5 16.52 89.4 196.14
10.7 hexene 9288 2.17
C = Centigrade
5 C2 = ethylene
Mn = number average molecular weight
Pd = Mw/Mn
mM = millimoles
pM = micromoles
17
Z:\Scott\SCSpec\2010007can.docx
