Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
C: 21582~0
TS 0377
PROCESS FOR THE COPOLYMERIZATION OF CARBON MONOXIDE
WITH AN OLEFINICALLY UNSATURATED COMPOUND
This invention relates to a process for the
copolymerization of carbon monoxide with an olefinically
unsaturated compound and to a catalyst composition.
EP-A-619335 discloses a process for the
copolymerization of carbon monoxide with an olefinically
unsaturated compound which comprises contacting the
monomers with a catalyst composition based on a Group
VIII metal, a ligand and a boron hydrocarbyl compound.
This process is suitable for preparing linear copolymers
of carbon monoxide with an olefinically unsaturated
compound. The copolymers are in particular alternating
copolymers or, in other words, copolymers in which the
monomer units originating in carbon monoxide alternate
with the monomer units originating in the olefinically
unsaturated compound.
Applicant has experienced that the copolymerization
process of EP-A-619335 has a major disadvantage in that
it suffers from a rapid decay of the polymerization rate
and deactivation of the catalyst. Within an hour the
rate of polymerization has been seen to become
unattractively low, such that residence times in excess
of one hour do not contribute in a meaningful way to the
economy of the process.
Applicant has attempted to reverse this situation,
for example, by supplying additional Group VIII metal
compound during the copolymerization. The results were,
however, not satisfactory.
It has now surprisingly been found that a substantial
improvement with respect to the stability of the
polymerization rate can be achieved by selecting a
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specific class of ligands in combination with applying a
stirring power above a certain m;nimllm value.
Thus, the present invention relates to a process for
the copolymerization of carbon monoxide with an
olefinically unsaturated compound comprising contacting
the monomers in the presence of a liquid diluent with a
catalyst composition which is based on
(a) a source of a Group VIII metal,
(b) a bidentate ligand of the general formula
R1R2M1-R-M2R3R4 wherein M1 and M2 independently represent
a phosphorus, arsenic or antimony atom, R1, R2, R3 and R4
independently represent unsubstituted or substituted
hydrocarbyl groups on the understanding that at least one
of R1, R2, R3 and R4 represents a polar substituted aryl
lS group and R represents a bivalent bridging group
containing at least two carbon atoms in the bridge, and
(c) a boron hydrocarbyl compound,
with application of a stirring power transmitted to the
polymerization mixture of at least 0.25 kW/m3.
Because of the improved stability of the
polymerization rate residence times exceeding 1 hour, in
particular exceeding 1.5 hours, more in particular
exceeding 3 hours, can be applied in a meaningful way.
The invented process also allows for the preparation of a
larger quantity of copolymer relative to the quantity of
Group VIII metal employed. Further, EP-A-619355
recommends to apply a large excess of the boron
hydrocarbyl compound over the Group VIII metal, for
example such that the molar ratio of boron/Group VIII
metal is about 50:1. The present process may
advantageously be carried out using a molar ratio of
boron/Group VIII metal which is lower than the value
recommended in EP-A-619335, for example less than 25:1.
Thus, besides being attractive from an economic point of
view, the invented process is also attractive in that the
C 21~8240
quantity of catalyst remnants in the prepared polymer can
be lower, which is generally beneficial to polymer
properties such as the melt stability.
In the present specification and claims the term
"Group VIII metal" encompasses the noble metals
ruthenium, rhodium, palladium, osmium, iridium and
platinum, and the iron group metals iron, cobalt and
nickel.
The catalyst composition suitable for use in the
process of the invention is based on a source of cations
of the said metal(s). Suitable sources of cations of
metals of Group VIII include salts of mineral acids, such
as salts of sulphuric acid, nitric acid and phosphoric
acid, and salts of sulphonic acids, such as
methanesulphonic acid and para-toluenesulphonic acid.
Preferred sources are salts of carboxylic acids, in
particular those having up to 6 carbon atoms, such as
acetic acid, propionic acid and trifluoroacetic acid. If
desired, as cation source use may be made of the metals
in their elemental form, or in a zero-valent state
thereof, e.g. in complex form, such as complexes wherein
the Group VIII metal is covalently bonded to one or two
hydrocarbyl groups. These covalently bonded hydrocarbyl
groups may be aliphatic or aromatic and contain typically
up to 12 carbon atoms. Preferred covalently bonded
hydrocarbyl groups are aliphatic groups, in particular n-
alkyl groups, such as methyl and n-butyl groups.
Catalyst compositions based on a noble Group VIII
metal are preferred, those based on palladium being most
preferred. A preferred source of palladium is palladium
(II) acetate.
In addition to a Group VIII metal the catalyst
composition contains a boron hydrocarbyl compound. The
boron hydrocarbyl compound is typically a hydrocarbyl-
borane of the general formula BXYZ wherein X, Y and Z
~153240
-
denote independently a substituted or unsubstituted
hydrocarbyl group, a hydroxy group, a substituted or
unsubstituted hydrocarbyloxy group or a halogen atom, on
the understanding that at least one of X, Y and Z denotes
a substituted or unsubstituted hydrocarbyl group. The
said hydrocarbyl groups and the hydrocarbyl groups of the
hydrocarbyloxy groups may be aliphatic or aromatic
groups, such groups typically having up to 12 carbon
atoms. Preferred hydrocarbyl groups are aryl groups
which may or may not be substituted. Preferred
substituents of the hydrocarbyl groups are electron
withdrawing groups or atoms, such as trihalomethyl
groups, nitro groups and halogen atoms. Hydrocarbyl
groups of which all hydrogen atoms are replaced by
substituents are included in the term "hydrocarbyl
group". The hydrocarbyl groups are in particular phenyl
groups, more particularly perfluorophenyl or 3,5-bis(tri-
fluoromethyl)phenyl groups. Examples of suitable
aliphatic groups are ethyl, n-butyl and n-hexyl groups.
Halogen atoms X, Y or Z are preferably fluorine.
Examples of hydrocarbylboranes are phenyldifluoroborane,
phenylboronic acid and hexylboronic acid. It is
preferred that all three groups X, Y and Z are
hydrocarbyl groups. Preferred hydrocarbylboranes are
triphenylborane, tris(perfluorophenyl)borane and
tris[3,5-bis(trifluoromethyl)phenyl]borane.
Other suitable boron hydrocarbyl compounds are salts
containing one or more hydrocarbylborate anions per
molecule, such as salts of the general formula
MeBZlZ2Z3Z4 wherein Me is an alkali metal, for example
lithium or sodium, and zl, z2, z3 and Z4 denote
independently a substituted or unsubstituted hydrocarbyl
group. The hydrocarbyl groups zl, z2, z3 and Z4 may be
of the same types and may be selected according to the
same preferences as indicated above for the groups X, Y
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and Z. Examples are lithium tetraphenylborate and sodium
tetrakis(perfluorophenyl)borate.
The quantity of boron hydrocarbyl compound may be
varied between wide limits. However, as indicated
hereinbefore, it is a particular feature of this
invention that the boron hydrocarbyl compound may be used
in a quantity such that the molar ratio of boron to the
Group VIII metal is less than 25. More in particular
this ratio is in the range of 0.1-20, preferably in the
range of 0. 5-15, more preferably in the range of l-lO.
It is advantageous to supply a part of the boron
hydrocarbyl compound during the polymerization in order
to gain a further improvement in maintaining the
polymerization rate at the initial level. For example,
40~ or less, preferably 5-30~, of the boron hydrocarbyl
compound is supplied at the start of the polymerization
and the remainder is supplied in a later stage, prior to
work-up, in a continuous fashion or stepwise.
The catalyst composition of the invented process is
further based on a bidentate ligand of the general
formula
RlR2Ml-R-M2R3R4 (I)
with Ml, M2, Rl, R2, R3J R4 and R as defined
hereinbefore.
In the ligands of formula (I) Ml and M2 preferably
represent phosphorus atoms. Rl, R2, R3 and R4 may
independently represent optionally polar substituted
alkyl, aryl, alkaryl, aralkyl or cycloalkyl groups, on
the understanding that at least one of Rl, R2, R3 and R4
represents an aryl group which is polar substituted.
Suitable polar groups include halogen atoms, such as
fluorine and chlorine, alkoxy groups such as methoxy and
ethoxy groups and alkylamino groups such as methylamino-,
dimethylamino- and diethylamino groups. Alkoxy groups
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and alkylamino groups contain in particular up to
5 carbon atoms in each of their alkyl groups.
It is preferred that each of Rl, R2, R3 and R4
represents an aryl group, typically a phenyl group,
substituted at an ortho position with respect to Ml or
M2, with a polar group, in particular an alkoxy group,
especially a methoxy group.
In the ligands of formula (I), R preferably
represents a bivalent organic bridging group containing
from 2 to 4 bridging atoms, at least two of which are
carbon atoms. Examples of such groups R are -CH2-CH2-,
-CH2-CH2-CH2-, and -CH2-CH2-CH2-CH2-. Preferably R is a
trimethylene group. Preferred ligands are l,3-bis-
[bis(2,4-dimethoxyphenyl)phosphino]propane, l,3-bis[bis-
(2,4,6-trimethoxyphenyl)phosphino]propane and, more
preferred, l,3-bis[bis(2-methoxyphenyl)phosphino]propane.
It is preferred to have in the ligand incorporated a
bridging group which consists of three atoms in the
bridge of which the middle atom is a carbon or silicon
atom which carries one or two substituents containing
carbon, hydrogen and optionally oxygen, and the two outer
bridging atoms are carbon atoms, typically the carbon
atoms of methylene groups (-CH2-). The use of such
ligands, which thus have a branched bridging group, is
advantageous because it provides a further improvement in
maintaining the polymerization rate at the initial level.
Accordingly, the present invention also relates to a
catalyst composition which is based on
(a) a source of a Group VIII metal,
(b) a bidentate ligand of the general formula
RlR2Ml-R-M2R3R4 wherein Ml and M2 independently represent
a phosphorus, arsenic or antimony atom, Rl, R2, R3 and R4
independently represent unsubstituted or substituted
hydrocarbyl groups on the understanding that at least one
of Rl, R2, R3 and R4 represents a polar substituted aryl
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-- 7
group and R repres-ents a bivalent bridging group which
consists of three atoms in the bridge of which the middle
atom is a carbon or silicon atom which carries one or two
substituents containing carbon, hydrogen and optionally
oxygen, and the two outer bridging atoms are carbon
atoms, and
(c) a boron hydrocarbyl compound.
The substituents which may be attached to the middle
atom of the branched bridging group may be, for example,
aliphatic or aromatic hydrocarbyl groups and they may
contain ether linkages, such as in alkoxyalkyl groups.
They have-typically up to 15 carbon atoms, more typically
up to 10 carbon atoms. If the middle atom carries two
substituents these substituents may suitably be connected
-to one another by an additional link, i.e. other than by
the middle atom of the bridge, so that they form together
with that middle atom a ring structure. For exampIe,
such a situation rèpresents itself when the substituents
together form a -CH2-CH2-CH2-CH2- group or a
-CH2-O-C(CH3)2-O-CH2- group.
If the middle atom of the branched bridging group is
a carbon atom this carbon atom is typically substituted
with the following group(s):
- a hydroxy group and an alkyl group such as a methyl
group, or
- two alkyl groups, preferably identical alkyl groups,
such as methyl groups, or
- a single group selected from aryl groups, such as the
phenyl group, aralkyl groups such as the benzyl group,
alkyl groups such as the propyl group, aralkyloxy groups
such as the benzyl group or the 2,4,6-trimethylbenzyloxy
group, alkoxyalkoxy groups such as the methoxyethoxy
group, and hydroxyalkyl groups such as the 6-hydroxyhexyl
group.
2158240
If the middle atom of the branched bridging group is
a silicon atom it is typically substituted with two alkyl
groups, preferably identical alkyl groups, such as methyl
groups.
Particularly preferred ligands are 2-hydroxy-2-
methyl-1,3-bis[bis(2-methoxyphenyl)phosphino]propane,
2,2-dimethyl-1,3-bis(2-methoxyphenyl,phenylphosphino)-
propane, 2,2-dimethyl-1,3-bis[bis(2-methoxyphenyl)-
phosphino]propane, 2-phenyl-1,3-bis[bis(2-methoxyphenyl)-
phosphino]propane, 2-benzyl-1,3-bis[bis(2-methoxyphenyl)-
phosphino]propane, 2-propyl-1,3-bis[bis(2-methoxyphenyl)-
phosphino]propane, 2-benzyloxy-1,3-bis[bis(2-methoxy-
phenyl)phosphino]propane, 2-(2,4,6-trimethylbenzyloxy)-
1,3-bis[bis(2-methoxyphenyl)phosphino]propane, 2-
ethoxymethoxy-1,3-bis[bis(2-methoxyphenyl)phosphino]-
propane. The ligands mentioned here are known from EP-A-
300583, EP-A-296687, EP-A-454270 and EP-A-585493.
The amount of bidentate ligand supplied may vary
considerably, but is usually dependent on the amount of
metal of Group VIII, present in the catalyst composition.
Preferred amounts of bidentate ligands are in the range
of 0.5 to 8, preferably in the range of 0.5 to 2 moles
per gram atom of metal of Group VIII.
The performance of the catalyst composition may be
improved by incorporating therein an organic oxidant
promoter, such as a quinone. Preferred promoters are
selected from the group consisting of benzoquinone,
naphthoquinone and anthraquinone. The amount of promoter
is advantageously in the range of 1-50, preferably in the
range of 1 to 10 mole per gram atom of metal of
Group VIII.
The amount of catalyst used in the process of the
invention may vary between wide limits. As indicated
hereinbefore it is advantageous to employ the least
quantity of catalyst composition as possible in relation
21~824~
to the quantity of copolymer to be prepared. Recommended
quantities of catalyst composition are in the range of
10-8 to lO-2, calculated as gram atoms of metal of Group
VIII per mole of olefinically unsaturated compound to be
copolymerized with carbon monoxide. Preferred quantities
are in the range of 10-7 to 10-3 on the same basis.
It is advantageous to carry out the copolymerization
process in the presence of a protic compound. An
advantage of using a protic compound resides in further
maintaining the polymerization rate at the initial level.
Examples of protic compounds are acids (such as sulphonic
acids, carboxylic acids and adducts of boric acid and
glycols or salicylic acids), alcohols and water. They
have typically 15 or fewer carbon atoms, if any.
Preferred acids are those having a pKa of less than 6,
more preferably less than 4 and in particular less than
2, when measured in aqueous solution at 18 C. Preferred
protic compounds are alcohols, such as primary, secondary
and tertiary aliphatic alcohols and phenols. They may be
mono-alcohols or polyols, such as glycols. Preferred
alcohols are the lower alcohols, normally understood to
be the mono-alcohols which are completely miscible with
water, in particular methanol and ethanol. The quantity
of the protic compound employed may vary between wide
ranges. Eligible quantities of the acids are in the
range of 0.5-200, in particular in the range of l.0 to
50, more in particular in the range of l.0-lO equivalents
per gram atom of Group VIII metal. When the protic
compound is an alcohol, in particular a lower alcohol, it
may function in the copolymerization as the liquid
diluent or it may be incorporated therein, for example in
a quantity up to 50~ by volume, in particular 5-30~ by
volume, relative to the total volume of the diluent.
Olefinically unsaturated compounds which can be used
as monomers in the copolymerization process of the
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-- 10 --
invention, include compounds consisting exclusively of
carbon and hydrogen and compounds which in addition
comprise hetero atoms, such as unsaturated esters.
Unsaturated hydrocarbons are preferred. Examples of
suitable monomers are lower a-olefins, i.e. olefins
containing from 2 to 6 carbon atoms, such as ethene,
propene and butene-1, cyclic olefins such as
cyclopentene, aromatic compounds, such as styrene and
alpha-methylstyrene and vinyl esters, such as vinyl
acetate and vinyl propionate. Preference is given to
ethene and mixtures of ethene with another a-olefin, such
as propene or butene-1.
Generally, the molar ratio of on the one hand carbon
monoxide and on the other hand the olefinically
unsaturated compound(s) is selected in the range of 1:10
to 5:1. Preferably the molar ratio is in the range of
1:5 to 2:1, substantially equimolar ratios being
preferred most.
The copolymerization process of this invention is
carried out in the presence of a liquid diluent.
Preferably a diluent is used in which the copolymer to be
prepared forms a suspension, in which case a diluent may
be selected in which the copolymer is insoluble or
virtually insoluble. Examples of liquid diluents are
ketones (e.g. acetone), chlorinated hydrocarbons (e.g.
chloroform or dichloromethane), aromatics (e.g. toluene,
benzene, chlorobenzene) and protic diluents, such as the
lower alcohols (e.g. methanol and ethanol). Mixtures of
liquid diluents may be used as well, for example protic
diluents may comprise aprotic compounds. Particularly
preferred are aromatic diluents and protic diluents
because these provide a further improvement in
maintaining the polymerization rate at the initial level.
When the process of this invention is carried out
such that the prepared copolymer is formed as a
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-- 11 --
suspension in the liquid diluent it is advantageous to
have a solid particulate material suspended in the
diluent before the monomers are contacted with the
catalyst composition. This embodiment of the process is
S advantageous in that it provides a further improvement in
maintaining the polymerization rate at the initial level.
In this embodiment the catalyst is preferably used as a
solution in the diluent. Alternatively it may be
advantageous that a catalyst is used which is deposited
on the solid particulate material or, otherwise, which is
chemically bound to the solid particulate material.
Catalysts of the latter type are known in the art, for
example from EP-A-511713, EP-A-404228 and EP-A-619334.
Typically a copolymer of carbon monoxide and an
lS olefinically unsaturated compound is used as the solid
particulate material, in particular a copolymer which is
based on the same monomers as the copolymer to be
prepared. The latter means that, for example, when a
linear alternating copolymer of carbon monoxide and
ethene will be prepared a linear alternating copolymer of
carbon monoxide and ethene from an earlier polymer
preparation will be suspended in the diluent. Other
suitable solid particulate materials may be inorganic or
organic materials, such as silica, alumina, talc, soot
and polymers, for example polyethene, polypropene and
polystyrene.
The solid particulate material is suitably used in a
quantity of 0.1-20 %w, relative to the weight of the
diluent, more suitably in a quantity of 0.5-10 %w. The
bulk density of the solid particulate material is
typically in the range of 50-1000 kg/m3, in particular in
the range of 100-500 kg/m3. The solid particulate
material has typically an average particle size of
10-6-10-3 m, in particular 10-6-5x10-4 m. The average
particle size is determined as follows. With the aid of
21~8210
a commercially available particle size analyser, a
cumulative weight distribution of a representative sample
of the solid particulate material is determined as a
function of the particle size. The cumulative weight
S distribution function is converted into a cumulative
surface area distribution function, as described by
Terence Allen in Particle Size Measurement (Chapman and
Hall, London, 1981), p. 122 ff. The average particle
size is found as the median of the cumulative surface
area distribution function.
The copolymerization process of this invention is
carried out with the application of a stirring power
transmitted to the polymerization mixture of at least
0.25 kW/m3, in particular at least 0.5 kW/m3. When the
lS stirring power applied is less than 0.25 kW/m3 there is a
depletion of monomer, in particular of carbon monoxide,
in the liquid phase which causes a decay of the rate of
copolymerization. A stirring power of at least
0.25 kW/m3 improves this situation. When a diluent is
used in which the copolymer to be prepared forms a
suspension it is advantageous to apply a stirring power
of at least 0.5 kW/m3, in particular at least 1.0 kW/m3.
A practicable maximum of the power density is 20 kW/m3.
A preferred range of the power density is from 1.5 to
15 kW/m3. The stirring power may be transmitted to the
polymerization mixture by any suitable means, for
example, a stirring device, a jet mixer or a gas stream.
The copolymerization process is usually carried out
at a temperature in the range of 20 to 200 C, preferably
at a temperature in the range of 30 to 150 C. The
reaction is conveniently performed at a pressure in the
range of 2 to 200 bar, pressures in the range of 20 to
100 bar being preferred. The process is typically
carried out at a scale at which the quantity of liquid
diluent exceeds 10 kg. The process may be carried out as
21~8~U
a batch process or as a continuous process. In the
latter case it is advantageous to apply two or more
reactors connected in series, because this increases the
quantity of polymer which can be prepared within a given
period of time using a certain reaction volume and a
certain quantity of catalyst.
The copolymers obtained according to the invention
are suitable as thermoplastics for fibres, films or
sheets, or for injection moulding, compression moulding
and blowing applications. They may be used for
applications in the car industry, for the manufacture of
packaging materials for food and drinks and for various
uses in the domestic sphere.
The invention will be illustrated by the following
examples. The diluents were analytical grade chemicals,
which were used as purchased.
EXAMPLE 1 (for comparison)
A copolymer of carbon monoxide with ethene and
propene was prepared as follows.
Tris(perfluorophenyl)borane (0.247 g, 0.48 mmoles)
was weighed in air into a dried Schlenk tube and
dissolved in lO0 ml dichloromethane. The solution was
transferred to a 300 ml autoclave equipped with baffles
and an inclined blade stirrer. Subsequently 25 g propene
was added. The autoclave was pressurised to 30 bar with
premixed carbon monoxide and ethene (l:l molar ratio).
The stirring power applied was about 3 kW/m3. The
autoclave was heated to 70 C. L2Pd(CH3CO2)2 (0.0154 g,
0.025 mmoles), wherein L2 denotes l,3-bis(diphenyl-
phosphino)propane, taken up in lO ml dichloromethane was
injected into the autoclave. The autoclave was
pressurised with the carbon monoxide/ethene mixture to
50 bar and maintained at that pressure for l hour by
supplying additional carbon monoxide/ethene mixture. The
2158240
- 14 -
pressure was released and the autoclave was allowed to
cool to room temperature.
The polymer product was recovered by filtration,
washed with dichloromethane and dried.
Polymerization rates were calculated from the rate of
addition of the carbon monoxide/ethene mixture. The
initial polymerization rate was 10.7 kg
copolymer/(g palladium.hour); the rate after 1 hour, i.e.
prior to the release of pressure, was 1.0 kg
copolymer/(g palladium.hour). Thus, the rate decay was
90% .
EXAMPLE 2
A copolymer of carbon monoxide with ethene and
propene was prepared following the procedures outlined in
Example 1, but with 0.025 mmoles L2Pd(CH3C02)2, L2
denoting 1,3-bis[bis(2-methoxyphenyl)phosphino]propane
instead of 1,3-bis(diphenylphosphino)propane.
The initial polymerization rate was 6.5 kg
copolymer/(g palladium.hour). After 1 hour, i.e. prior
to the release of pressure, the polymerization rate was
5.0 kg copolymer/(g palladium.hour). The decay of the
rate was 25%.
EXAMPLE 3
A copolymer of carbon monoxide with ethene and
propene was prepared following the procedures outlined in
Example 1, but with 0.025 mmoles L2Pd(CH3C02)2, L2
denoting 2-sila-2,2-dimethyl-1,3-bis[bis(2-methoxy-
phenyl)phosphino]propane instead of 1,3-bis(diphenyl-
phosphino)propane.
The initial polymerization rate was 11.0 kg
copolymer/(g palladium.hour). After 1 hour, i.e. prior
to the release of pressure, the polymerization rate was
11.0 kg copolymer/(g palladium.hour). There was no decay
in the rate of polymerization.
2158240
EXAMPLE 4 (for comparison)
A copolymer of carbon monoxide with ethene and
propene was prepared following the procedures outlined in
Example 1, with the differences that the copolymerization
was not terminated after 1 hour, and that after one hour
additional L2Pd(CH3CO2)2 (0.028 g, 0.047 mmoles), wherein
L2 denotes 1,3-bis(diphenylphosphino)propane, dissolved
in 20 ml dichloromethane was injected into the autoclave.
At the moment of the injection of additional
L2Pd(CH3CO2)2 the polymerization rate was 0.1 kg
copolymer/(g palladium.hour).
During the hour subsequent to the injection of
additional L2Pd(CH3CO2)2 no increase, but only a further
decrease of the polymerization rate was detected.
