Note: Descriptions are shown in the official language in which they were submitted.
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Serial No. Patent Application
FTaspeslagh, Folie ~ LAB 158
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BACKGROUND INVENTION
SYNDIOTACTIC COPOLYMERS OF PROPYLENE AND OLEFINS
FIELD OF' INVENTION: The present invention relates to copolymers
of propylene and olefins having from 2 to 1a. carbon atoms having
a novel stereoregular microstructure and more particularly random
copolymers of propylene and olefins having from 2 to 1o carbon
atoms ire which the microstructure of the side chains is highly
syndiotactic except for polyethylene units. More particularly 'the
present invention relates to syndiotactic random copolymers of
propylene and olefins having from 4 to 8 carbon atoms, wherein the
polypropylene units and the polyolefin units have each syndiatactic
microstructure in the random copolymer.
DESCRIPTION OF PRTOR ART: As is well know, olefins polymers or
copolymers such as polypropylene, polybutene, polypentene... etc.
are generally produced by techniques such as radical
polymerization, anionic polymerization, cationic polymerization arid
polymerization using a Ziegler-type catalyst, as well as copolymers
of propylene with other olefins. These polymers axe dividect into
three groups, isotactic, syndiotactic and atactic polymers,
depending on the steric configuration of side chains thereof. It
.has heretofore been known that usual radical, anionic and cationic
polymerization methods provide olefin polymers having mainly an
1
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Serial No. . Patent Application
Haspeslagh, Folie LAB 15S
atactic structure, and that the polymerization methads using a
Ziegler-type catalyst provide olefin polymers having mainly an
isotactic or atactic structure.
The isotactic structure is typically desca-ibed as having the
alkyl groups attached to the tertiary carbon atoms of successive
monomeric units on 'the same side of a hypothetical plane through
the main chain of the polymer, e.g., the alkyl groups are all above
or below the plane. Another way of describing the structure is
through the use of NMR. Bovey's NMR nomenclature for an isotactic
pentad is ...mmmm... with each "m°' representing a "meso" dyad or
successive alkyl groups on the same side in the plane. As know in
the art, any deviation or inversion in the structure of the chain
lowers the degree of isotac~ticity of the polymer.
In contrast to the isotactic structure, syndiotactic polymers
are those in which the alkyl groups attached to the tertiary carbon
atoms of successive monomeric units in the chain lie on alternate
sides of the plane of the polymer. In NMR nomenclature, this
pentad is described as ...rrr... in which the °°r°'
represents a
"racemic" dyad, i.e., alkyl groups on alternate sides of the plane.
The percentage of r dyads in the chain determines the degree of
syndiotacticity of the polymer. A number of methods of preparing
olefin homopolymers or copolymers and their structures have been
'reported. Preparation of syndiotactic polypropylene is disclosed
and its particular microstructure is claimed in U.S. Patent
2
CA 02029077 2001-11-09
Serial No. Patent Application
Haspeslagh, Folie LAB 158
4,892,851. However, preparation of random copolymers of propylene
and olefins having from 2 to 10 carbon atoms of very high
syndiotactic structure has not yet been disclosed.
SUMMARY OF THE INVENTION
The present invention provides random copolymers of propylene
and olefins having from 2 to 10 carbon atoms having a very high
syndiotactic index and with a novel syndiotactic microstructure.
The novel microstructure for the syndiotactic copolymers included
within the present invention has blocks of repeating racemic (r)
dyads connected by units predominantly consisting of a pair of meso
(m) dyads, i.e., a meso triad "mm". The predominant structure of
each polymer in the copolymer chain is described in NMR
nomenclature as ...rrrmmrrr...
Preferably, the degree of syndiotacticity in the polypropylene
units in the copolymer chain consists of greater than 80~ racemic
dyads, most preferably, greater than 90~ racemic dyads, and the
deviations from the repeating racemic pattern are predominantly
meso triads, while the degree of syndiotacticity for the
polyolefins units, except polyethylene units, in the copolymer
consist of greater than 70~ racemic dyads. ;
The present invention relates to random copolymers of
_~propylene and olefins having from 2 to 10 carbon atoms having a
degree of polymerization of not less than 5 and having a
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CA 02029077 2001-09-26
Serial No. Patent Application
Haspeslagh, Folie LAB 158
stereoregular structure which is mainly syndiotactic.
The novel microstructure is obtained through use of a
stereorigid metallocene catalyst described by the formula:
Ra ( CPRn) ( CPR l m) MeQk
wherein each Cp is a cyclopentadienyl or substituted
cyclopentadienyl ring; each R and each R' is the same or different
and is a hydrocarbyl radical having 1-20 carbon moms; R" is a
structural bridge between the two Cp rings imparting stereorigidity
to the catalyst; Me is a transition metal; and each Q is a
hydrocarbyl radical or.is a halogen. Further, R'm may be selected
so that (CpR'm) is a substantially different substituted
cyclopentadienyl ring than (CpRn) . This catalyst was disclosed and
claimed in U.S. Patent No. 4,892,851. It was discovered that the
use of a metallocene catalyst as described above with
,15 cyclopentadienyl ligands that are substantially different in terms
of their substituents, and thus their electrical and steric
effects, produces not only a predominantly syndiotactic polymer
rather than an isotactic polymer but also syndiotactic copolymers
having the novel microstructure described above.
The novel microstructure of syndiotactic copolymers is
obtained by utilizing at least one of the catalysts described by
the above formula and introducing the catalyst into a
polymerization reaction zone containing both olefin monomers. In
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CA 02029077 2001-09-26
Serial No. Patent Application
Haspeslagh, Folie LAB 158
addition, an electron donor compound and/or a cocatalyst such as
alumoxane may be introduced into the reaction zone. Further, the
catalyst may also be pre-polymerized prior to introducing it into
the reaction zone and/or prior to the stabilization of reaction
conditions in the reactor. A prepolymerization process is
disclosed in U.S. Patent No. 4,767,735.
The present invention also includes a process for producing
syndiotactic homopolymers of olefin having from 4 to 8 carbon atoms
in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
The copolymers of propylene and olefins of the present
invention have a syndiotactic structure and include syndiotactic
propylene-ethylene,propylene-butene,propylene-pentene,propylene-
4-methylpentene, propylene-hexene, propylene-octene and analogs.
This novel syndiotactic structure of the copolymers of the
invention consists predominantly of the structure described in NMR
nomenclature as ...rrrmmrrrr... and consists of a very high
percentage of racemic dyads. The copolymers can be produced to
varying specifications for melting points, molecular weights, and
molecular weight distributions. The tacticity of the copolymers
of the invention is determined by the nuclear magnetic resonance
,(NMR) method. In more detail, the tacticity of the homopolymers
of olefins is determined by analyzing the signal of C, carbon of
. 5
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Serial No. Patent Application
Haspeslagh, folie ~ LAB 158
an aromatic ring and the signal of methine-methylene carbon in NMR
(nuclear magnetic resonance spectrum as measured using an isometric
carbon), or the proton signal o H-NMR. The tacticity can be
determined by NMR for each given number of constituting units
connected continuously, such as a dyad in which the number of
constituting units is two, a triad in which the number of
constituting units is three, and a pentad in which the number of
constituting units is five. The term °'copolymer having mainly a
syndiotactic structure" as used herein means that each polymer
units present in the random copolymer has such a syndiotactic
structure that the syndiotacticity expressed in terms of the dyad
([r] value) is not less than 80% for the propylene units anc~ 70%
for the olefins units, except those formed from ethylene in which
the [r] value for the propylene units and the ethylene units is riot
less than 80%. The metallocene catalysts of the present invention
may be described by the formula R"(CpR~)(CpR'm)MeQk wherein each Cp
is a cyclopentadienyl or substituted cyclopentadienyl ring; R and
R' are hydrocarbyl radicals having 1-20 carbon atoms and each may
be the same or different; R" is a structural bridge between the two
Cp rings imparting stereorigidity to the catalyst, and R" is
preferably selected from the group consisting of an alkyl radical
having 1-4 carbon atoms or a hydrocarbyl radical containing
silicon, germanium, phosphorus, nitrogen, boron, or aluminum; Me
is a group 4b, 5b or 6b metal from 'the Periodic Table of Elements;
6
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Berial No._Patent Application
Haspeslagh, Folie ' I,d~B 1~8 ,
each Q is a hydrocarbyl radical having 1-20 carbon atoms or is a
halogen; 0 < k < 3 ; 0 < n < 4 ; and ~. < m < 4 . Tn order to be
syndio--specific, it was discovered that the catalyst must have
substantially different Cp ring substi'tuents. Therefore, R'm is
selected such that (CpR'm) is a substantially different substituted
ring than (CpR~). In order 'to produce a syndiotactic polymer, the
characteristics of the groups substituted directly on the
cyclopentadienyl rings seem to be important. Where there is a
substantial difference in the characteristics of the ring
substituents, either electrical, steric or other difference
resulting in a substantially different effect on the metal complex
as compared with symmetrical rings, then the catalyst can be
eacpected to produced predominantly syndiotactic polymers.
In a preferred catalyst useful in producing polymers of the
present invention, Me is titanium, zirconium, hafnium or vanadium;
Q is preferably a halogen, and it is most preferably chlorine; and
k is preferably 2, but it may vary with the valence of the metal
atom. E:cemplary hydrocarbyl radicals include methyl, ethyl,
propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl,
octyl, nonyl, decyl, cetyl, phenyl, and the like. Other
hydrocarbyl radicals include other alkyl, aryl, alkenyl, alkylaryl
or arylalkyl radicals. Further, Rn and R'm may include hydrocarbyl
radicals attached to a single carbon atom in the Cp~ring. A
preferred catalyst is isoprapyl(fluorenyl) (cyclopentadienyl) Zr
7
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Serial No. _ Patent Application
Haspeslagh, Folie LAB 158
dichloride.
The catalyst may be prepared by any method known in the art.
The Examples below disclose two methods of preparing the catalyst
with the second method being preferred as it produces a more stable
and active catalyst. It is important that the catalyst complex be
°'clean" as usually low molecular weight, amorphous polymer is
produced by impure catalyst. Generally, the preparation of the
catalyst complex consists. of forming and isolating the Cp or
substituted Cp ligands which are then reacted with a halogenated
metal to form the complex.
The metallocene catalyst of 'the present invention are useful
in many of the polymerization processes known in the art including
many of those disclosed especially far the use of isotactic
copolymers of propylene and other .olefins. When the catalyst of
t5 the presewt invention are used in these types of processes,
syndiotactic copolymers are produced rather than isotactic
copolymers. A preferred polymerization procedure includes the step
of prepolymerizing the catalyst and/or precontacting the catalyst
with a cocatalyst and the olefin monomers prior to introducing the
catalyst into a reaction zone.
Consistent with the prior disclosures of metallocene catalysts
for the production of isotactic polymers, the catalysts of the
.present invention are particularly useful in combination with an
aluminum cocatalyst, preferably an alumoxane, an alkyl aluminum,
8
CA 02029077 2001-09-26
Serial No. Patent Application
Haspeslagh, Folie ~$ 158
or a mixture thereof. In addition, a complex may be isolated
between a metallocene catalyst as described herein and an aluminum
cocatalyst in accordance with the teachings of European Patent
Publication no. 226,463 published on,June 24, 1987 and assigned to
Exxon Chemical Patents Inc. with Howard Turner listed as the
inventor. The alumoxanes useful in combination with the catalysts
of the present invention may be represented by the general formula
(R-Al-O-) in the cyclic form and R (R-Al-0) n-ALR2 in the linear form
wherein R is an alkyl group with one to five carbon atoms and n is
an integer from 1 to about 20. Most preferably, R is a methyl
group. The alumoxanes can be prepared by various methods known in
the art. Preferably, they are prepared by contacting water with a
solution of trialkyl aluminum, such as trimethyl aluminum, in a
suitable solvent such as benzene. Another preferred method includes
the preparation of alumoxane in the present of a hydrated copper
sulfate as described in U.S. Patent no. 4,404,344. This method
comprises treating a dilute soluction of trimethyl aluminum in
toluene with copper sulfate. The preparation of other aluminum
cocatalysts useful in the present invention may be prepared by
2o methods known to those skilled in the art.
The invention having been generally described; the following
examples are given as particular embodiments of the invention and
9
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Serial No. Patent Application
Haspeslagh, Folie LAH 158
to demonstrate the practice and advantages thereof. It is
understood that the examples are given by way of illustration and
are not intended to limit 'the specification or the claims to follow
in any manner. The examples given below illustrate the, present
invention and its various advantages and benefits in more detail.
Synthesis procedures are described for zirconium metallocene
catalysts. The general catalyst formula for the catalyst produced
by these methods is iso-propyl(fluorenyl)(cyclopentadienyl) ZrCl2.
PREPARATION OF THE CATALYST - METHOD A
The synthesis procedures for. the catalyst were performed under
an inert gas atmosphere using a vacuum Atmospheres glove box or
Schlenk techniques. The synthesis process generally comprises the
steps of 1) preparing the halogenated or alkylated metal compound,
2) preparing the ligand, 3) synthesizing the complex, and ~)
purifying the complex.
In Method A, a halogenated metal compound was prepared using
tetrahydrofuran ( "THF°' ) as a solvent resulting in THF bound in with
the final catalyst complex. Specifically, bIeCI4THF was prepared as
described in Manner, L., Inora. Synth. 21, 135-36 (1982). In the
Examples below, Me is zirconium and hafnium, but it may also
include titanium or other transition metals.
The ,substituted dic clo entadien 1 1i and ma be '
Y p y g y prepared
.using various processes known in the art depending upon the
selection of the specific bridge or ring substituents. ~In the
. ~n Irn <'Y, i'p /1 ~..~ '~~
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Serial No. _ Patent Application
Haspeslagh, Folie LAB 158
preferred embodiments shown in the Examples below, the ligand is
2,2-isopropyl-(fluorene)cyclopentadiene. To prepare this ligand,
44 gms (0.25 mol) of fluorene were dissolved in 350 ml THF in a
round bottom flask equipped with a side arm and dropping funnel.
Contained within the funnel were 0.25 mol of tri-methyl lithium
(CH3Li} in ether (1.4M). The CH3Li was added dropwise to the
fluorene solution and the deep orange-red solutian was stirred for
several haurs. After gas evolution had ceased, the solution was
cooled to -78°C and 100 m1 of THF containing 26.5 mgs (0.25 mol}
of 6,6-dimethylfulvene was added dropwise to the solution. .The red
salution was gradually warmed to room temperature and stirred
overnight. The solution was treated with 200 ml of water and
stirred for ten minutes. The organic fraction of the solution was
extracted several times with 100 ml portions of diethylether, and
the combined organic phases were dried aver magnesium sulfate.
Removal of the ether fram the organic phases left a yellow solid
which was dissolved in 500 ml of chloroform and recrystallized by
addition of excess methanol at 2°C to yield a white powder.
The elemental analysis of the ligand showed carbon to be 91. 8 %
by weight of the.compound and hydrogen to be 7.4% by weight. This
corresponds to the weight percentages for CzjH2o, of 92. 6 % for carbon
and 7.4% for hydrogen. The NMR spectrum for the ligand establishes
the structure to include one cyclopentadienyl ring attached by an
isopropyl bridge to a second cyclopentadienyl ring that is
11
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Serial No. Patent Application
Haspeslagh, Folie ~ LAB 1.58
substituted to form a fluorenyl radical.
A syndiospecific catalyst complex was synthesized using the
ligand and the metal tetrachloride-THF complex. The catalyst was
formed by adding 0.05 mol of N-butyl lithium and heacane (1.6M) was
added dropwise to a 100 ml THF solution containing 6.8 mgs (0.025
mal) of the Cp ligand described above. The solution was stirred
at 35°C for twelve hours after which 9.4 gms (0.025 mol) of ZrCl4-
2THF contained in 200 ml of THF were rapidly cannulated together
with the ligand solution into a 500 ml round bottom flask with
vigorous stirring. The deep orange-red solution was stirred for
twelve hours under reflux. A mixture of LiC1 and a red solid were
isolated by removing the solvents under vacuum.
Catalyst complexes produced in accordance with Method A are
noted to be somewhat impure and extremely air and moisture
!5 sensitive. Tn the Examples below, Method A catalysts were purified
using one or more of the following purification procedureso
1. Extraction with pentane. Trace quantities of a yellow
impurity contained in the solid red catalyst complex were
repeatedly extracted with pentane until 'the pentane became
?0 colorless.
2. Fractional recrystallization. The red complex was
separated from the white LiC1 by dissolving it in 1_00 ml of
'toluene, filtering it through a fine porosity sintered glass frit,
and forming a saturated Solution by adding pentane. The red
12
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Serial No. Patent Application
Haspeslagh, Folie ' LAB 158
zirconium complex was isolated using crystallization at -20°C.
3. Chromotography on bio-beads. 50 gms of bio-beads SM-2
(20-50 mesh spherical, macroreticular styrene-divinylbenzene
copolymer from Bio-Rad laboratories) were dried under vacuum at
70°C for ~8 hours in a 30 x 1.5 centimeter column. The beads were
then equilibriated with toluene for several hours. ~1 concentrated
solution of the red catalyst complex in toluene was eluded down the
column with 150~200 ml of toluene. The complex was recovered by
evaporating the toluene under vacuum.
PREPARATION OF THE CATALYST ~ METHOD B
As an alternative synthesis procedure, Method B provides
catalyst that are more air stable, more active, and produce a
higher percentage of syndiotactic polypropylene. In this process,
methylene chloride is used as a non-coordinating solvent. The
process described below uses hafnium as the transition metal, but
the procedure is adaptable for use with zirconium, titanium or
other transition metals. The substituted dicyclopentadienyl ligand
was synthesized in THF in the same manner as described in Method
A above. The red dilithio salt of the ligand (0.025 mol) was
isolated as disclosed in Method A by removing the solvents under
vacuum and by washing with pentane. The isolated red dilithio salt
was dissolved in 125 m1 of cold methylene chloz~ide at -78°C. The
';
_~HfCl4 slurry was rapidly cannulated into the flask containing the
ligand solution. The mixture was stirred for two haurs~at -78°c
;'
;.
13
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Serial No. Patent Application
Haspeslagh, Folie ' LAB 158
allowed to warm slowly to 25°C and stirred for an additional 12
hours. An insoluble white sale (LiC1) was filtered off. A
moderately air sensitive, yellow powder was obtained by cooling the
brown/yellow methylene chloride solution to -20°C for l2 hours and
cannulating away the supernatant. The bright yellow product was
washed on the sintered glass filter by repeatedly filtering off
cold supernatant that had been cannulated back aver it. The
catalyst complex was isolated by pumping off the solvents using a
vacuum, and it was stored under dry, deoxygenated argon. The
process yielded 5.5 mgs of catalyst complex.
The elemental analysis of 'the hafnium catalyst complex
prepared using Method B showed that the catalyst consisted of
48.79% by weight of carbon, 3.4% hydrogen, 15.14% chlorine and
33.2% hafnium. These percentages compare with the theoretical
analysis for CZ~FIi8HfC12 which is 48.39% carbon, 3.45% hydrogen,
13.59% chlorine and 34.11% hafnium. Similarly, zirconium catalysts
produced using Method B show elemental analysis close,to the
expected or theoretical values. Further, some of the hafnium
complexes illustrated in the Examples below were made using 96%
pure HfCl~ which also contains about 4% ZrCl~. Still other catalyst
samples were made using 99.99% pure HfCI~. Differences cari be seen
in the molecular weight distributions of the polymers produced with
the pure Hf catalyst compared with the polymers produced using the
catalysts which contain a small percentage of zirconium. The mixed
14
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Serial No. Patent Application
Haspeslagh, Folie ° LAB 158 .
catalyst produces a polymer with a broader molecular. weight
distribution than that produced by a pure catalyst system.
The examples below illustrate the present invention in more
details. The results of the polymerization process and the
analysis of the polymer are shown in Table 1 for Examples 1-4 and
in Table 2 for Examples 5-9.
EXAMPLES 1-4 '
1 liter of liquid propylene was added into a dried 1.5 liter
glass reactor equipped with inclined stirrer.
To this, were injected a solution of 3 mg isopropyl fluorenyl
cyclopentadienyl titanium dichloride in 5 ml of a 10 wto solutions
of MAO in toluene previously precontacted in a glove box under
nitrogen. The reactor was thermostated at 60°C (and was left
polymerizing for 1 hour under four different ethylene pressures).
The polymers were recovered by venting off the monomer gas.
Approximately 120 g of polymeric material were respectively
collected. Their characteristics are shown on table 2.
13~ ~~ analysis of the different propylene-ethylene sequences
indicate that the ethylene incorporation is predominantly random
and that even for the copolymer with the highest ethylene content
(Example 4) the number of sequences having a length longer than 2
monomer units is only about 20% of the total amount of sequences
'(see SDE 2j.
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Serial No. _ Patent Application
Haspeslagh, Folie ~g 158
EXAbiPbES 5-9
A dried 1.5 liter glass reactor equipped with inclined stirrer
was filled under nitrogen flow with 1 liter of five different
liquid monomer mixtures of propylene and hexane. To this, were
injected a solution of 8 mg isopropyl fluorenyl eyclopentadienyl
titanium dichloride in 40 ml of a 1o wt% solutions of MAO in
toluene previously precontacted in a glove box.under nitrogen. The
reactor was thermostated at 60°C and was left polymerizing for 1
hour. All copolymers proved to be soluble in the monomer mixture
and were recovered by, distilling of the monomer under reduced
pressure. Approximately Zoo g of polymeric material were
respectively collected. Their characteristics are shown an Table
2.
The ratio of the 13C NMR peak at 41.0 to 41.9 ppm (CHz for
hexane-hexane blocks) with the peak at 23.5 ppm (CHZ(2) in the
hexane branch) is an indication for the randomness or block type
incorporation of the 1-hexane. For example 2 this ratio is only
13.7 indicating that the majority of the 1-hexane is incorporated
as isolated comonomer between two propylene monomers. This~ratio
increase to 71.8% for example 3 and to 81.1% for example 4
indicating 'the block formation of polyhexene at increased hexane
concentration.
obviously, numerous modifications and variations ~~f the
present invention are possible in light of the above teachings.
16
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Serial Noa . Patent Application
Haspeslagh, Folie LAB 158
It is therefore to be understood that within the scope of the
appended claims, the invention may be practiced otherwise than as
specifically described herein
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Serial No. Patent Application
Haspeslagh, Folie ~ LAB 158
TABLE 1
Ex CZ(mole-'k) Cz(mole~) Mn MWD Tm(°C) Hm(cal/gr) Tg(°C) SDE2
Starting in Mw/Mn
Reactants Polymers
1 0 0 42549 2.396 136.2 10.05 0 0
2 4 19.75 18797. 2.466 - - -25.32 10.24
3 8 27.93 16731 2.257 - -29.62 13.22
4 25 57.7.9 1.26.562.51 125.3 1.16 -51.02 21.24
MWD - Molecular Weight Distributian
Tm - Melting Paint
Hm - Melt Enthalpy
Tg - Glass Transition Temperature
18
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Serial No. . Patent Application
Haspeslagh, Folie LAB 158 '
TABLE
2
Ex.Cd(mole~) C6(mole%) Mn MWD Tg (C) Ratio of
in monomer in polymer Mw/Mn ~~C NMR
mixture peaks (%)
0 0 42549 2.396 0 -
6 16.7 17.8 22136 2.754 --24.27 13.7
7 83.3 86.7 16786 2.996 --34.49 71.8
8 90.9 95.5 14480 2.981 --40.42 81.1
9 100 100 8569 1.905 --32.19 --
MWD - Molecular Weight,Distribution
Tg - Glass Transition Temperature
19
