March 3 - 5,1999, Karlsruhe, Germany - FZK

antisolvent, as expected, especially at low
temperature. However, at higher temperatures the
antisolvent effect decreases. We also tested whether
10 wt% polymer could be dissolved in pure CQ2, but
this proved to be impossible within a range of 1000
to 3000 bar and 40 to 170 °C.
Polymerisations of a-olefins in scC0 2 are
therefore expected to be precipitation
polymerisations.
Pressure (bar)
4000
3500
3000
2500
2000
1500
* 0 wt% C02 ' 20.0 wt% C02
- \
. \ .
-1
\
i 1 1— 1 J 1
40 50 60 70
Temperature (°C)
Figure 4: Cloud point pressures of 10 wt% EPM
(Mn=46 kg/mole, Mw/Mn=2.5, 46 wt% ethylene), x
wt% C0 2 and 90-x wt% ethylene as a function of
temperature.
Polymerisations at low pressure
Preliminairy polymerizations of 1-hexene have
been conducted to test whether the catalyst would be
affected by C0 2. The results using the same catalyst
stock solution are shown in table 1. The 1-hexene
could not properly be dried over molsieves and
proved to contain water. It is believed that the water
reduces the activity of the catalyst significantly by
complexation. Further differences in yield can be
ascribed to slow deactivation of the catalyst over
time as the experiments 1 to 4 were performed in
that sequence. From these experiments, it was
concluded that C0 2 does not inhibit or deactivate the
catalyst to a large extent, although the results are not
conclusive in this respect.
Table 1: Polymerization of 1-Hexene under Argon
and low C0 2 pressure.
Experiment Reaction condition Yield (g)
1 Argon, 1 bar 1.34
2 Argon, 1 bar 1.26
3 C02,4.8bar 1.23
4 C02,4.8bar 1.15
"Reaction conditions: 0.03 mmol catalyst, 50 mL
1-hexene, 50 mL CC12H2, 25°C, 3 hours reaction
time
25
Polymerisations at high pressure
Following the described method, a glass ampulla
containing 0.045 g catalyst has been put in the
reactor and 10.67 g 1-hexene is added subsequently.
The mixture appears to be homogeneous above
approximately 100 bar and 34.5 °C. After raising the
pressure to approx. 150 bar, the homogeneous
solution turned slightly yellow, indicating that the
catalyst has at least partially been dissolved. The
mixture turned opaque at the same time indicating
the formation of an insoluble polymer phase. The
pressure was further raised to 239 bar by adding
C0 2. The reaction mixture turned more opaque
during a reaction time of 2 hours and the pressure
decreased to 227 bar. A rubberlike polymer has been
obtained at a yield of 2.40 g.
As the palladium complex is able to polymerise a
range of a-olefins and functionalized monomers in
organic solvents, it is expected to do so in scC0 2 as
well. In our view this opens the way to a whole
range of new polymerisation processes.
Conclusions
The results of the investigated ternairy phase
behaviour of EPM, ethene and C0 2 show that C0 2 is
an antisolvent for the polymer. The antisolvent
effect decreases as the temperature increases.
The preliminairy results regarding the catalyst
indicate that the catalyst is not affected by C0 2 and
that production of elastomers based on olefins can
be performed using the catalyst investigated.
Acknowledgement
The advise and help of R. Duchateau with the
synthesis of the palladium catalyst and E. Goetheer
with the polymerisation experiments is greatly
acknowledged. The high pressure phase behaviour
measurements have been performed in the group of
Th. De Loos at the Delft Technical University.
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