A PROCESS FOR THE PREPARATION OF CO-POLYMERS OF CARBON MONOXIDE AND ETHYLENICALLY UNSATURATED COMPOUNDS
The invention relates to a process for the preparation of co-polymers of carbon monoxide with one or more compounds comprising an ethylenically unsaturated bond.
It is known that co-polymers of carbon monoxide and one or more ethylenically unsaturated compounds, in which co-polymers the units originating from carbon monoxide substantially alternate with the units originating from the ethylenically unsaturated compounds, may be prepared by reacting the monomers under polymerization conditions in the presence of a suitable catalyst. According to EP-181014 the preparation of these co-polymers can be carried out in the liquid phase, i.e. such that the continuous phase is formed by a liquid diluent, usually a non-polymerizable liquid, such as methanol, in which the catalyst dissolves, but the formed co-polymers are substantially insoluble. The preparation of the co-polymers may also proceed in the gas phase, whereby the continuous phase is formed by gaseous carbon monoxide and possibly one or more of the other monomers, if they are present in the gas phase under the prevailing polymerization conditions. A process for the gas phase manufacture of linear alternating co-polymers is described in EP-248483.
It is considered that, in comparison with the liquid phase preparation of co-polymers of carbon monoxide and one or more ethylenically unsaturated compounds, there is merit in the preparation of such co-polymers in the gas phase, because the isolation and purification of the product which - in liquid phase operation of the process - normally requires a filtration or centrifugation step, is facilitated. Since these steps involve considerable costs when the process is .arried out on a technical scale, it is regarded as a major advantage when such isolation and purification steps can be omitted.
In the known embodiments of the co-polymerization process i.e. both in embodiments carried out in the liquid phase and in those carried out in the gas phase, usually a catalyst system is applied which is based on a compound of a metal from Group VIII of the Periodic Table, an anion of an acid with a pKa of less than 2, with the exception of hydrohalogenic acids, and a bidentate ligand. It is believed that when using such a catalyst system in a liquid phase operation of the process, polymerization will only occur when an anion originating from the liquid diluent (usually a lower alcohol such as methanol) has been incorporated in the catalyst system. It is further believed that with these catalyst systems also in gas phase operation of the process, incorporation of a small amount of such anions in the catalyst system is required for obtaining good polymerization results. It has accordingly been proposed to supply small amounts of a compound generating such anions during the gas phase process, in order to achieve a prolonged polymerization activity of the catalyst system. However, it will be clear that it would simplify the process if the use of such anion generating compounds can be omitted without impairing the polymerization results.
It has now been found that by selecting a particular catalyst system, the presence of the said anion generating compounds is no longer necessary. Moreover it has been observed that the co-polymers thus prepared are characterized by a high crystallinity.
The invention can be defined as relating to a process for the preparation of co-polymers which comprises reacting carbon monoxide and one or more ethylenically unsaturated compounds under polymerization conditions in the presence of an added catalyst system based on
(a) at least one metal selected from the Groups VI, VII and/or VIII of the Periodic Table; and
(b) a stabilizing organic compound attached by a covalent bond via a carbon atom to (one of) the said metal(s), and containing at
least one group capable of forming an additional, non-covalent, bond with (one of) the said metal(s).
If desired, the process may be carried out in the presence of a non-polymerizable liquid diluent. The process of the invention is particularly advantageous when a diluent is selected which may not be able to generate anions, such as an aprotic diluent. As has been explained above, it is preferred to operate the polymerization process in the substantial absence of a non-polymerizable liquid diluent. According to the invention, the catalyst is, inter alia, based on one or more metals selected from the Groups VI, VII and/or VIII of the Periodic Table.
These metals include chromium, molybdenum and tungsten (Group VI), manganese and rhenium (Group VII) and iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum (Group VIII). They will further be indicated herein as metal(s) (a). Among these metals, those of Group VIII are preferred, in particular palladium, rhodium and nickel.
Catalysts based on palladium as metal (a) are most preferred. In the catalyst system the metal (a) may be present as a zero valent metal, or as a cation. Very suitable are catalyst systems comprising a metal (a), in particular palladium, as a monovalent cation, linked to one or more other components of the catalyst system. According to the invention the catalyst system is further based on a stabilizing organic compound containing at least one group, capable of forming a non-covalent bond with a metal (a). In the present description the stabilizing organic compound will be referred to as compound (b) . i is considered likely that the stabilizing effect of the compound (b) is related to the absence of any hydrogen atom which is in a beta position with respect to the metal (a) and readily accessible to that metal. Furthermore electronic factors and steric properties may be involved in the stabilizing function of the compounds (b) .
Typically such a stabilizing organic compound is selected that upon formation of the additional, non-covalent bond a 5- or 6-membered ring is formed comprising the metal (a) , the carbon atom of the stabilizing organic compound covalently bound to the metal (a) and one or more atoms of the group forming the non-covalent bond. Any other atom of said 5- or 6-membered ring is an atom of the stabilizing organic compound and is preferably a carbon atom, but may also be, for example, nitrogen, silicon or germanium. Preferred compounds (b) may be found among the compounds comprising a cyclic moiety in their molecules and having up to 15 carbon atoms. Accordingly preference is given to compounds (b) containing a mono-, bi- or polycyclic moiety, in particular to compounds containing a mono-, or bicyclic structure. Suitable examples of such moieties are those derived from cyclopentadiene, bornene, norbornene, norbornadiene, camphene, naphthalene, styrene, indene and bicyclooctene. Also suitable are cyclic structures comprising one or more hetero atoms, such as structures derived from indole, benzopyran and pyrrole.
Examples of greatly preferred catalyst systems are systems wherein the metal (a) is linked to a norborn-1-yl or a norborn-3-en-l-yl group of the compound (b) , or, alternatively, to an ethyl group of the compound (b) .
Suitable groups present in the stabilizing organic compound (b) and capable of forming non-covalent bonds (NCB) with a metal (a) include atoms or groups of atoms with electron withdrawing properties.
Usually the said groups comprise an oxygen atom, for example an oxygen atom forming part of an acyl, acyloxy, alkoxy carbonyl or a sulphonyl group.
Preferred NCB forming groups include acyl and alkoxycarbonyl groups, typically having up to 10 carbon atoms, in particular acyl groups such as acetyl, propionyl or acyloxy groups such as acetoxy and propionyloxy groups. Acetyl groups are in particular preferred NCB forming groups.
Accordingly, as regards compound (b) preferred catalyst systems are based on 2-acetylnorbornene or 2-acetylnorbornadiene which are linked to a metal (a) via the carbon atom at position 1 and which form a non-covalent bond with that metal via the oxygen ^ atom of the acetylgroup.
In the process according to the invention preferably a catalyst system is used which, in addition of metal (a) and compound (b) , comprises one or more ligands capable of complexing with metal (a) . -•-' Suitable ligands include monodentate, bidentate and polydentate ligands, as well as ligands which, in addition to one or more complexing sites, comprise at least one site which can form a non-complexing bond with the metal (a) .
Bidentate ligands are preferred, as it would appear that the 1-* presence of two complexing sites in one molecule significantly contributes to the formation of stable catalysts.
A preferred group of bidentate ligands can be indicated by the general formula
1 2 1 2 3 4 R R M -R-M R R (I)
1 2 0 In this formula each of M and M independently represents a
1 2 3 phosphorus, arsenic, antimony or nitrogen atom, each of R , R , R
4 and R independently represents a substituted or non-substituted hydrocarbyl group and R represents a divalent organic bridging group containing at least one carbon atom in the bridge.
1 2 5 in the ligands of formula (I) M and M preferably represent
1 2 3 4 phosphorus atoms. R , R , R and R may independently represent optionally substituted alkyl, aryl, alkaryl, aralkyl or cycloalkyl groups typically having up to 15 carbon atoms. Preferably at least
1 2 3 4 one of R , R , R and R represents an aromatic group, in 0 particular an aromatic group substituted by one or more polar groups.
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 5 diethylamino groups.
If one or more of R1, R2, R3 and R4 represents a substituted aryl group, preference is given to a phenyl group substituted at
1 2 one or both ortho positions with respect to M or M , with an alkoxy group, preferably a methoxy group. In the ligands of formula (I) , R preferably represents a divalent organic bridging group containing from 2 to 4 bridging atoms, at least two of which are carbon atoms.
Examples of suitable groups R are: -CH.--CH,--; -CH„-CH„-CH-- ;
-CH2-Si(CH3)2-CH2-; -CH2-C(CH3)2-CH2 and -CH2-CH2-CH2-CH2- . Another preferred group of bidentate ligands can be indicated by the general formula
wherein X and Y independently represent organic bridging groups, each containing 3 or 4 atoms in the bridge at least 2 of which are carbon atoms. The bridging groups X and Y are preferably identical. Particularly suitable bidentate ligands of this type are 2,2' -bipyridine and 1,10-phenanthroline.
Other suitable bidentate ligands are for example bis thio- compounds such as l,2-bis(ethylthio)ethane and 1,2-bis(propylthio)- ethene and mixed ligands such as l-diphenylphosphino-3-ethylthio- propane.
Preferred monodentate ligands may be indicated by the general formula
R5R6R7M3 (II),
3 wherein M represents a phosphorus, arsenic or antimony atom and each of R , R and R independently represents a substituted or unsubstituted hydrocarbyl group, typically having up to 15 carbon atoms.
3 5 6 7
Preferably M represents a phosphorus atom. R , R and R are preferably phenyl groups. Other preferred monodentate ligands may be indicated by the
8 9 10 - 8 9 general formula R R P-R -S0_ wherein R and R independently
represent substituted or non-substituted hydrocarbyl groups, typically having up to 15 carbon atoms, and R represents an organic bridging group having 1 - 4 carbon atoms in the bridge.
These monodentate ligands carry a negative charge which may compensate a positive charge of a metal (a), if there is any. It g is preferred to use an aromatic sulphonate of which the groups R
9 8 9 and R are identical. If the groups R and R are substituted aryl groups they are preferably alkoxy substituted, the substitution typically being ortho with respect to the phosphorus atom. Very suitable ligands of this kind are 2-(dicyclohexylphosphino)benzene- sulphonate or 2-(diphenylphosphino)benzenesulphonate.
The catalyst system according to the invention may contain one or more weakly or non-coordinating anions in order to compensate for any positive charge which the total of the metal(s) (a), compound (b) and, optionally, the ligand(s) may have. Preferred weakly or non-coordinating anions are selected from the anions of acids with a pKa of less than 6, more in particular less than 2. Examples of such anions are the anions of trifluoroacetic acid, p-toluenesulphonic acid and HBF, . Anions of HBF, are particularly preferred.
For the preparation of the catalyst systems according to the invention use may be made of a method known per se. Reference is made in particular to the preparation methods described in Organometallics, Vol 9, No.6 (1990) pages 1736-1739 and in Journal of Organometallic Chemistry, 424 (1992) C12-C16. Details of specific catalyst systems are furthermore mentioned in the examples described hereinafter.
The catalyst systems of the invention include compositions which are novel. As novel compositions are claimed complexes of the general formula
[LPdQ][A]n (III) wherein Q stands for 2-acylnorborn-l-yl, 2-acylnorborn-3-en-l-yl or a 2-acylethyl group, n is 0 or 1, A stands for a weakly or non-coordinating anion and, if n is 1, L stands for a bidentate
1 2 1 2 3 4 1 2 3 ligand of the general formula R R M -R-M R R , wherein R , R , R
4 and R independently represent substituted or non-substituted
1 2 hydrocarbyl groups, M and M independently represent phosphorus, arsenic, antimony or nitrogen and R represents a divalent organic bridging group containing at least one carbon atom in the bridge, or, if n - 0, L stands for a sulphonate anion of the general
8 9 10 - 8 9 formula R R P-R -SO, wherein R and R independently represent
10 substituted or non-substituted hydrocarbyl groups and R represents an organic bridging group having 1 - 4 carbon atoms in the bridge. Preferred complexes are those of which the acyl group of Q is an acetyl group. Preferred ligands L are l,3-bis(diphenyl- phosphino)propane and 1,3-bis[bis(2-methoxyphenyl)phosphino]propane
(n is 1) or 2-(dicyclohexylphosphino)benzenesulphonate and
2-(diphenylphosphino)benzenesulphonate (n is 0). Preferred weakly or non-coordinating anions are as defined hereinbefore.
The amount of catalyst added in the copolymerization process of the invention may vary between wide limits. Generally the amount
-8 -2 of catalyst is such that 10 to 10 gram atom of metal (a) per molecule of ethylenically unsaturated compound to be copolymerized is present. Preferably, the catalyst is used in an amount of 10 .3 to 10 gram atom of metal (a) per molecule of ethylenically unsaturated compound.
If desired a catalyst system may be used which is supported on a carrier, usually in order to facilitate the introduction of the catalyst system in the reactor. Suitable carrier materials may be inorganic, such as silica, alumina or charcoal, or organic, such as cellulose or dextrose. Furthermore as carrier material a polymer may be used, for example polyethylene, polypropylene, polystyrene or a copolymer of carbon monoxide with an ethylenically unsaturated compound such as the co-polymers of the process of the invention.
Ethylenically unsaturated compounds suitable to be used as starting material in the co-polymerization process of the invention include compounds consisting exclusively of carbon and hydrogen and compounds which in addition comprise one or more hetero-atoms, such as unsaturated esters. Unsaturated hydrocarbons are preferred, in
particular those having 2-10 carbon atoms. Suitable examples are lower olefins such as ethene, propene and 1-butene, cyclic compounds such as cyclopentene and aromatic compounds such as styrene and alpha-methyl styrene. Preference is given to the use of
5 ethene, propene or a mixture of ethene and propene.
The molar ratio between the monomers, viz. carbon monoxide and the ethylenically unsaturated compound(s) , is generally selected in the range of 5:1 to 1:5. Preferably the said molar ratio is selected in the range of 1.5:1 to 1:1.5 and most preferably the
10 monomers are used in substantially equimolar amounts.
The process of the invention is advantageously carried out in the further presence of a chain-transfer agent. Preferably a gaseous chain-transfer agent is used, in particular hydrogen. The chain-transfer agent may be applied in admixture with the monomers
15 used as starting material, or can be supplied separately, for example shortly after the co-polymerization reaction has started.
The preparation of the co-polymers is preferably carried out at a temperature in the range of 20-200 βC, although the use of a reaction temperature outside that range is not precluded.
20 Preferably the reaction temperature is selected in the range of
25-120 βC.
Suitable pressures generally are within the range of 1-200 bar, but preferably the pressure is in the range of 10-100 bar.
The higher the molecular weight of the co-polymers according
25 to the invention, the higher will be in general the intrinsic viscosity they exhibit. For the determination of the intrinsic viscosity of a co-polymer according to the invention, four solutions are prepared by dissolving the co-polymer in four different concentrations at 100 °C in m-cresol. For each of these
•*υ solutions, the viscosity is measured in a viscometer at 100 βC relative to m-cresol at 100 βC.
If T represents the outflow time of m-cresol and T the outflow time of the polymer solution, the relative viscosity (η .) is obtained from η ,-T /T . From η - the inherent viscosity 'rel p' o 'rel J
35 (17. , ) can be calculated according to the formula:
In η rel
'irih c where c represents the concentration of the co-polymer in grams per 100 ml solution. By plotting graphically the η . , found for each of the four solutions against the corresponding concentration c and then by extrapolating to c-0, the intrinsic viscosity [ η ] in dl/g is found. Instead of "instrinsic viscosity", this patent application will henceforth use the term recommended by the International Union of Pure and Applied Chemistry, viz. "Limiting Viscosity Number" (LVN) . The co-polymers according to the invention generally have an LVN of between 0.2 and 4.0 dl/g. Preferred co-polymers have an LVN of between 0.3 and 3 dl/g.
The co-polymers obtained according to the invention have a high crystallinity and exhibit good mechanical properties. They may be processed by means of the usual techniques into films, sheets, plates, fibres, shaped articles and the like. The copolymers with a relatively low molecular weight are suitable for use as intermediates for the production of plastics, as blending components and as plasticizers for other polymers.
The co-polymers with high molecular weight are suitable as premium thermoplastics for fibers or films, or for injection moulding, compression moulding or blowing applications. These high molecular weight co-polymers may be used for many applications, such as in the car industry, for the manufacturing of packaging materials for foods and drinks, as constructional and building material, as insulating material in the production of cables and for various applications in the domestic sphere.
The invention will further be illustrated by the following examples. Example 1
A carbon monoxide/ethene copolymer was prepared as follows.
A complex of the formula [Pd(C H1QC0Me) (PPh- - (BF, ) wherein C-.H--.C0Me stands for 2-acetyl-norborn-l-yl and PPh_ for triphenylphosphine, was placed in an autoclave as a dry solid (2.8 mg Pd).
The autoclave had been previously heated to 110 °C for 2 hours and then cooled under a stream of nitrogen to ensure minimal residual water.
The autoclave was then flushed three times with CO before being pressurized to 20 bar with CO and an additional 20 bar with ethene (total pressure 40 bar) .
Subsequently the autoclave was heated such that the internal temperature was 43 °C.
After 18 hours the autoclave was cooled to room temperature and depressurized. It contained 135 mg of polymer powder. Example 2
A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 13.8 mg was used of a complex of the formula
[LPd(C H 0COCH_)] (BF, ) (containing 1.7 mg palladium), wherein
L stands for l,3-bis[bis(2-methoxyphenyl)phosphino]propane and
C7H1f,C0CH_ for 2-acetylnorborn-l-yl, instead of the complex of the formula [Pd(C7H1()C0CH3) (PPh^] (BF4) , b. the polymerisation temperature was 100 "C instead of 43 °C, and c. the reaction time was 1 hour instead of 18 hours. The yield of polymer was 0.34 g. Example 3 A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 8.2 mg was used of a complex of the formula [LPd(C-.H10COCH_)] (BF, ) (containing 1.7 mg palladium), wherein stands for 1,10-phenanthroline and C...H..-C0CH.- for
2-acetylnorborn-l-yl, instead of the complex of the formula [Pd(C7H10COCH3) (PPh3)2] (BF4) , and b. the polymerisation temperature was 100 °C instead of 43 °C. The yield of polymer was 0.9 g.
Example 4
The procedures of Example 1 were substantially repeated, except for the following differences: a. 35.7 mg was used of a complex of the formula (LPd)(CH»COO)„ (containing 5 mg palladium), wherein L stands for l,3-bis[bis- (2-methoxyphenyl)phosphino]propane, instead of the complex of the formula [Pd(C-.H10COCH3)(PPh3)2] (BF4) , b. the polymerisation temperature was 100 °C instead of 43 βC, and c. the reaction time was 3 hour instead of 18 hours.
The polymer yield was negligible.
Examples 5 - 9
In Examples 5 - 9 a complex was used which was impregnated onto 5.0 g of a carrier prior to the introduction into the autoclave. The carrier was a carbon monoxide/ethene/propene terpolymer obtained by polymerisation of carbon monoxide with ethene and propene in methanol in the presence of a catalyst obtained by combining palladium acetate, 1,3-bis[bis-
(2-methoxyphenyl)phosphino]propane and trifluoroacetic acid. The impregnation was effected by evenly distributing a solution of the complex to be used in 3 ml dichloromethane over 5 g of the carrier and drying the mixture obtained in nitrogen at 50 °C over
30 minutes.
Example 5 A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 15.0 mg was used of a complex of the formula [LPd(C7H10COCH3)](BF.) (containing 5.0 mg palladium), wherein stands for l,3-bis(diphenylphosphino)propane and C-H--.C0CH., for 2-acetylnorborn-l-yl, instead of the complex of the formula [Pd(C7H1()COCH3) (PPl -).,] (BF4) , b. prior to introduction into the autoclave the complex was impregnated onto a carrier, c. the polymerisation temperature was 100 °C instead of 43 βC, and
d. the reaction time was 1 hour instead of 18 hours. The quantity of polymer prepared was 2.5 g. Example 6
A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 17.2 mg was used of a complex of the formula LPd(C7H. _COCH,) (containing 3.0 mg palladium), wherein L stands for
2-(diphenylphosphino)benzenesulphonate and C-.H.nC0CH, for 2-acetylnorborn-l-yl, instead of the complex of the formula [Pd(C7H1()C0CH3)(PPh3)2. (BF4) , b. prior to introduction into the autoclave the complex was impregnated onto a carrier, c. the polymerisation temperature was 100 βC instead of 43 βC, and d. the reaction time was 1 hour instead of 18 hours. The quantity of polymer prepared was 1.0 g.
Example 7
A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 19.0 mg was used of a complex of the formula LPd(CH-.CH„C0CH-) (containing 4.0 mg palladium), wherein L stands for 2-(diphenylphosphino)benzenesulphonate, instead of the complex of the formula [Pd(C7H10COCH3)(PPh^] (BF4) , b. prior to introduction into the autoclave the complex was impregnated onto a carrier, c. the polymerisation temperature was 100 "C instead of 43 "C, and d. the reaction time was 1 hour instead of 18 hours.
The quantity of polymer prepared was 0.53 g.
Example 8
A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences:
a. 20.65 mg was used of a complex of the formula LPd(C7H1f)C0CH,) (containing 4.0 mg palladium), wherein L stands for
2-(dicyclohexylphosphino)benzenesulphonate and C-H--C0CH, for 2-acetylnorborn-l-yl, instead of the complex of the formula [Pd(C7H10COCH3)(PPh3)2](BF4), b. prior to introduction into the autoclave the complex was impregnated onto a carrier, c. the polymerisation temperature was 100 °C instead of 43 °C, and d. the reaction time was 1 hour instead of 18 hours.
The quantity of polymer prepared was 0.11 g.
Example 9
A carbon monoxide/ethylene copolymer was prepared substantially following the procedures of Example 1, except for the following differences: a. 27.0 mg was used of a complex of the formula [LPd C7H.0COCH3)] (BF4) (containing 4.0 mg palladium), wherein L stands for 1,3-bis(diphenylphosphino)propane and C.-H-_C0CH, for 2-acetylnorborn-l-yl, instead of the complex of the formula [Pd C.-H10COCH3)(PPhj),,] (BF4> , b. prior to introduction into the autoclave the complex was impregnated onto a carrier, c. 5 bar hydrogen was present in addition to carbon monoxide and ethene, . the polymerisation temperature was 80 °C instead of 43 βC, and e. the reaction time was 1 hour instead of 18 hours. The quantity of polymer prepared was 1.2 g. Example 10
The procedures of Example 1 were substantially repeated, except for the following differences: a. 5.0 g of the carrier as used in Examples 5 - 9, but without being impregnated, was introduced into the autoclave, instead of the complex of the formula [Pd(C-,H10COCH3) (PPh.-)2] (BF4) , b. the polymerisation temperature was 80 °C instead of 43 βC, and c. the reaction time was 1 hour instead of 18 hours.
No measurable quantity of polymer was formed.
13 With the aid of C NMR analysis it was established that the products obtained in Examples 1-3 are polymers substantially consisting of linear chains in which units derived from carbon monoxide are alternating with units derived from ethene. It was further established that the products obtained in Examples 5-9 contained the same polymers in addition to the terpolymer which was used as the carrier.