PREPARATION OF CARBON MONOXIDE POLYMERS

Abstract: A process for the preparation of co-polymers of carbon monoxide and one or more ethylenically unsaturated compounds by contacting the monomers, under polymerization conditions, with a catalyst system comprising a) a source of cations of one or more metals of Group VIII of the Periodic Table and b) a bidentate ligand, in the additional presence of a minor amount of a compound containing a hydride moiety.

Description: PREPARATION OFCARBONMONOXIDEPOLYMERS The invention relates to a process for the preparation of co-polymers of carbonmonoxide with one or more compounds containing an ethylenically unsaturated bond. Linear co-polymers in which units originating from carbon monoxide substantially alternate with units originating from ethylenically unsaturated compounds, have been extensively described in the patent literature. Convenient methods for the preparation of these co-polymers are disclosed in, inter alia, EP 181014 and EP 248483. In these, and similar, preparation methods the monomers, viz. carbonmonoxide and one or more ethylenically unsaturated compounds, are contacted with a suitable catalyst, usually a catalyst system based on a metal of Group VIII of the Periodic Table. The co-polymers obtained, typically having an average molecular weight, calculated as number average (M ) , of more than 10.000, have established utility as thermo plastics. They may be processed by means of conventional techniques into films, sheets, plates, fibres, shaped articles such as containers for foods and drinks and parts for the car industry. For obtaining co-polymers with optimal properties for the intended use, it is advantageous to minimize variations in the average molecular weight of the co-polymers produced. Therefore it would be desirable to perform the co-polymerization process under such conditions that the average molecular weight of the product can be controlled and substantially remains at the desired value. For other uses than the above-mentioned outlets for thermoplastic products, it is preferred to apply products having considerably lower average molecular weights, e.g. of 2500 or lower. These products, viz. oligomers and low molecular weight co-polymers, may be used as such, or may be applied as starting materials for the preparation of other valuable products, e.g. as intermediates for the production of plastics, as blending components or as plasticizers for other polymers. It would therefore also be of advantage if the polymerization process could be carried out under such conditions that these co-polymers with lower molecular weight are predominantly formed. It has already been proposed to subject the co-polymers with an average molecular weight of more than 10,000 to a fractionation treatment and to separate the low molecular fraction therefrom. This method has the disadvantage of being time-consuming and moreover the yield of the desired low molecular fraction is generally very low. It has further been proposed to increase the temperature at which the co-polymerization is carried out. Although the formation of products with lower molecular weight is thus enhanced, the stability of the catalyst system often becomes a problem. The molecular weight of the co-polymers produced can also be reduced by addition of molecular hydrogen during the reaction. It has appeared, however, that with most catalyst systems a significant reduction in molecular weight only occurs by applying large amounts of hydrogen, say of 60 mol % or more, based on carbon monoxide. Apart from the unattractiveness of a high hydrogen consumption, the use of large quantities of hydrogen moreover often results in a reduction of the metal of Group VIII, accompanied by inactivation of the catalyst system. Only in exceptional cases, by selection of specific ligands in the catalyst system, the desired reduction in molecular weight of the co-polymers can be achieved, without impairing the activity of the catalyst system. Surprisingly, it has now been found that an adequate control of the average molecular weight of the formed co-polymers is achieved and that also, if desired, products having a relatively low molecular weight may be prepared, when the co-polymerization reaction is carried out in the presence of a minor amount of a compound containing a hydride moiety. The invention may be defined as relating to a process for the preparation of co-polymers of carbon monoxide and one or more ethylenically unsaturated compounds by contacting the monomers, under polymerization conditions, with a catalyst system comprising a) a source of cations of one or more metals of Group VIII of the Periodic Table and b) a bidentate ligand, in the additional presence of a minor amount of a compound containing a hydride moiety. Suitable compounds containing a hydride moiety include compounds comprising one or more hydrogen atoms, typically linked to a central metal or non-metal atom. Usually compounds are applied in which a single hydride group is present, but compounds comprising more than one hydride moiety per molecule are likewise suitable. The hydride nature of the hydrogen atoms in the compounds applied may be promoted by the prevailing reaction conditions and depends, inter alia, on the polarizability of the selected compounds. Examples of suitable compounds containing a hydride moiety are hydrides of metals such as tin, germanium and lead and of non-metals such as silicon. It is considered that in view of the polarizability of the hydrogen-hydrogen bond in molecular hydrogen, application of this compound in principle is feasible as well. Preferred compounds are silanes, such as SiH, , aryl silanes such as diphenyl silane and triphenylsilane, alkylsilanes, such as tri- methylsilane, triethylsilane, tripropylsilane, 1,1,1-trimethyldi- silane, 1,1,2-trimethyldisilane, tris- (trimethylsilyl)silane and alkylarylsilanes such as dimethylphenylsilane and diphenylethyl- silane. Most preferred are triarylsilanes, in particular tri¬ phenylsilane. Further examples of suitable compounds containing a hydride moiety are stannanes such as SnH, , tributylstannane and triphenylstannane and germananes. According to the invention a minor amount of a compound containing a hydride moiety is provided. Although not wishing to be bound by any theory, it is believed that the said compound acts as a chain transfer agent and that, accordingly, the amounts applied are advantageously those generally applicable for other chain transfer agents. The presence of relatively large amounts of compounds containing a hydride moiety can be disadvantageous, as this may result in the reduction of the Group VIII metal and, consequently, in the inactivation of the catalyst. The preferred amount in which the compound containing a hydrogen moiety is applied, depends to a large extent on the desired molecular weight of the co-polymer produced. For controlling the molecular weight of the co-polymers and minimizing any occurring variations of the molecular weight, small amounts of the compound containing a hydride moiety usually suffice, whereas for preparing co-polymers with a substantially reduced molecular weight applying otherwise the same reaction conditions, a somewhat higher amount may be required. In practice, the amount is preferably in the range of 10 to 10 mol per gramatom of Group VIII metal of the catalyst system. ■ 2 5 Most preferably the amount is selected in the range of 10 to 10 on the same basis. The compound containing a hydride moiety may be supplied separately to the reactor. Conveniently it is supplied together with one or more of the other reactor components. If desired, part of the compound containing a hydride moiety may be initially supplied to the reactor, whilst the remaining part is added continuously, or in increments during the reaction. The catalyst system used in the process of the invention comprises a source of cations of one or more metals of Group VIII, i.e. the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinium and the iron group metals, iron, cobalt and nickel. Preferably the Group VIII metal is selected from the group consisting of palladium, cobalt and nickel. In particular, good results are obtained with catalyst systems comprising a source of palladium cations. As source of Group VIII metal cations, preferably salts are used. Suitable salts include mineral salts such as sulphates, nitrates and phosphates. Other suitable salts are salts of sulphonic acids such as methylsulphonic acid, trifluoromethanesulphonic acid and p-toluenesulphonic acid. Preferably a salt of a carboxylic acid is used, such as acetic acid, propionic acid, trifluoracetic acid, oxalic acid and citric acid. In particular preferred sources of cations of Group VIII metals are the acetates of these metals. As source of Group VIII metal-cations use may also be made of the metals in their elemental form, or in a zero-valent state thereof, e.g. in complex form, for example tetrakis(triphenylphos- phine)palladium (0) These sources are generally applied in combination with a protic acid, thus yielding the metal cations in situ. The catalyst system of the invention additionally comprises a bidentate ligand, i.e. a compound containing two sites which can form a complexing bond with the metal(s) of Group VIII. The two complexing sites are believed to contribute significantly to the formation of stable catalyst systems. Preferred bidentate ligands can be indicated by the general formula R 1 R 2 -M 1 -R-M 2 -R 3 R 4 (I) 1 2 wherein M and M independently represent phosphorus, arsenic, 1 2 3 4 antimony or nitrogen atoms, R ,R ,R and R independently represent substituted or non-substituted hydrocarbylgroups and R represents a bivalent bridging group containing at least two atoms in the bridge. 1 2 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 aryl, alkyl, alkaryl, aralkyl or 1 2 3 4 cycloalkylgroups. Preferably at least one of R , R , R and R represents an arylgroup, in particular an arylgroup, substituted by one or more polar groups. Suitable polar groups include halogen atoms, such as fluorine or chlorine atoms, alkoxy groups such as methoxy- or ethoxygroups and (di)alkylaminogroups such as methylamino- , dimethylamino- , ethylamino- and diethylaminogroups. 1 2 3 4 If one or more of R , R , R and R represents an arylgroup, preference is given to a phenylgroup. Preferably a substituted phenylgroup is present, whereby one 1 2 or both orthopositions with respect to M and/or M are substituted with an alkoxygroup, preferably a methoxygroup. Such alkoxy group substituted ligands may lead to increased polymerization rates as shown in the examples disclosed herein. In the ligands of formula (I) R preferably represents a bivalent bridging group containing two to four bridging atoms, at least two of which are carbon atoms. Examples of suitable groups R are : -CH 2 -CH 2 - ; -CH 2 -CH 2 -CH 2 - ; -CH 2 -Si(CH 3 ) 2 -CH 2 - ; -CH 2 -CH 2 -CH 2 -CH 2 - and -CH 2 -C(CH 3 ) 2 -CH 2 -. In addition to a source of cations of one or more metals of Group VIII and a bidentate ligand, the catalyst systems of the invention preferably comprise a source of anions. As suitable sources of anions, acids or salts thereof may be mentioned, in particular acids having a pKa of 4 or less, preferably of less than 2. Examples of suitable acids are mineral acids such as perchloric acid, sulphonic acids such as para-toluenesulphonic acid and methanesulphonic acid and halogen-carboxylic acids such as trifluoroacetic acid. If desired, the source of anions can be combined with the source of cations of Group VIII metals and be provided as a single compound, such as a palladium-fluoroacetate, or nickel perchlorate. The amount of catalyst used in the process of the invention may vary considerably. Advantageously an amount is applied in the range of 10 to 10 gramatom of Group VIII metal(s) per mole of ethylenically unsaturated compound to be co-polymerized. Preferably -6 -2 the amount is in the range of 10 to 10 on the same basis. Ethylenically unsaturated compounds, suitable to be used as starting material, include unsaturated compounds consisting exclusively of carbon and hydrogen and compounds comprising in addition one or more hetero-atoms, such as oxygen or nitrogen atoms. Examples are unsaturated esters, such as methylacrylate and vinylacetate. Unsaturated hydrocarbons are, however, preferred. Suitable examples are the lower olefins, such as ethene, propene and 1-butene, cyclic olefins such as cyclopentene and aryl- substituted olefins such as styrene. Ethene and mixtures of ethene and propene are in particular preferred starting materials. The molar ratio between the monomer reactants, viz. on the one hand carbon monoxide and on the other hand the ethylenically unsaturated compound(s) is advantageously selected in the range of 5:1 to 1:5, preferably in the range of 1.5:1 to 1:1.5, substantially equimolar amounts being most preferred. The co-polymerization reaction is preferably carried out in the presence of a liquid diluent. Apolar as well as polar diluents are suitable, such as pentane or acetone. Preference is given to organic protic diluents, in particular to alcohols such as propanol-1 and me hanol. The reaction is generally performed at temperatures in the range of 20-150°C and at pressures in the range of 2-150 bar. Preferred reaction temperatures are in the range of 30-130°C and preferred pressures are selected in the range of 5 to 100 bar. The invention will be illustrated by the following, non-limiting examples. Example 1 A co-polymer of carbon monoxide and ethene was prepared as follows: As reactor, a 250 mL mechanically stirred autoclave was used which was charged with 133 mL of methanol. In order to remove air from the reactor, the autoclave was pressurized with an equimolar ethene/carbon monoxide mixture to 40 bar, whereupon the pressure was released. This procedure was repeated twice. Subsequently, the temperature was raised to 85°C and an equimolar mixture of ethene and carbon monoxide was introduced until the pressure was 55 bar. Finally, a catalyst solution was supplied consisting of 0.020 mmol of palladium (II) acetate (1.8 mg Pd) , 0.022 mmol of l,3-bis(di- phenylphosphino)propane (7.4 mg) and 0.045 mmol of p-toluene- sulphonic acid (6.8 mg) in 7 mL of acetone. After a reaction period of 1.5 hour the polymerization was terminated by cooling the reaction mixture to ambient temperature and by releasing the pressure. Solid product was filtered off and dried. 10.53 g Polymer was obtained, the average polymerization rate being 4.0 kg product per g palladium and per hour. The limiting viscosity number (LVN) , measured in m-cresol at 60°C, was 0.88 dL/g, corresponding to an average molecular weight (M ) of 11,000. Example 2 A co-polymer of carbon monoxide and ethene was prepared, substantially as described in Example 1, with the following differences: i) as reactor a 160 mL autoclave was used; ii) the autoclave was charged with- 78 mL of methanol, containing 2.2 g triphenylsilane; iϋ) the reaction temperature was 87°C. 19.20 g Polymer was obtained, the average polymerization rate being 4.1 kg product per g palladium and per hour. The LVN, measured in m-cresol at 60°C was 0.34 dL/g, corresponding with an average molecular weight (M ) of 4000. Example 3 A co-polymer of carbon monoxide and ethene was prepared, substantially as described in Example 1 with the following differences: i) the reaction temperature was 95°C; ii) the reactor was charged with 171 ml of methanol; iii) the catalyst solution comprised 2.0 mg of Pd, 8.2 mg of 1,3-bis(diphenylphosphino)propane and 8.2 mg of p-toluenesulphonic acid in 4 mL of acetone; iv) The reaction period was 1.22 hour. 25.84 g Polymer was obtained, the average polymerization rate being 10.8 kg of product per g palladium and per hour. The average molecular weight, determined by end-group analysis with the aid of 13 C NMR spectrometry, was 5900. The analysis showed that ethyl and ester end-groups had been formed. Example 4 A co-polymer of carbon monoxide and ethene was prepared, substantially as described in Example 3 with the following dif erences: i) as reactor a 160 mL autoclave was used; ii) the autoclave was charged with 88 mL of methanol, containing 0.29 g of triethylsilane; iii) the catalyst solution comprised 2.0 mg of Pd, 8.1 mg of 1,3-bis(diphenylphosphino)propane and 8.6 mg of p-toluenesulphonic acid in 4 mL of acetone; iv) The reaction period was 1.55 hour. 25.2 g Polymer was obtained, the average polymerization rate being 8.3 kg product per g palladium and per hour. The average molecular weight, determined by end-group analysis (13C NMR) was 5000. The analysis moreover showed, that ethyl, ester and acetal end-groups had been formed. Example 5 A co-polymer of carbon monoxide and ethene was prepared, substantially as described in Example 4 with the following differences: i) the autoclave was charged with 84 ml of methanol, containing 2.9 g of triethylsilane; ii) the reaction period was 1.93 hour. 3.42 g Polymer was obtained, the average polymerization rate being 0.9 kg product per g palladium and per hour. The average molecular weight, determined by end group analysis ( 13C NMR) was 1900. The analysis showed the presence of ethyl, ester and acetal end-groups. Example 6 A co-polymer of carbon monoxide and ethene was prepared, substantially as described in Example 3, with the following differences: i) the catalyst solution contained 8.4 mg of p-toluene sulphonic acid instead of 8.2 mg; ii) the autoclave was charged with 171 mL of methanol containing 4.2 g of triphenylsilane; iii) the reaction period was 0.91 hour. 19.9 g Polymer was obtained, the average polymerization rate being 11.0 kg of product per g palladium and per hour. The average - molecular weight (M , determined by end-group analysis ( C NMR) was 1800. The analysis moreover showed that ethyl, ester and acetal end-groups had been formed. When repeating this experiment with half, respectively double the amount of triphenylsilane, the polymer yields and 0 polymerization rates were 16.2 g and 10.5 kg/g/hr, respectively 17.7 g and 9.7 kg/g/hr, whereas the average molecular weights (M ) were 2070, respectively 950. When again repeating this experiment now using 10.9 mmol triphenylstannane instead of triphenylsilane and polymerizing 5 during 1.45 hrs but otherwise under identical conditions the yield was 11.0 g, the polymerization rate was 5.8 kg/g/hr and the average mol. wt (M ) was 3860. Of the above Examples, Examples 2, 4, 5 and 6 are according to the invention. Examples 1 and 3 have been included for comparison 0 only. As can be seen from the experiments described in Examples 1 and 2, addition of a compound containing a hydride moiety significantly reduces the molecular weight of the co-polymer produced. 5 From the experiments described in Examples 3, 4 and 5 it can be seen that adding a larger amount of the hydride containing compound results in a further decrease in molecular weight of the co-polymer obtained. Example 7 0 A copolymer of carbon monoxide and ethene was prepared as described in Example 3 with the following differences: i) reaction temp.: 99 °C; ii) reaction period: 0.70 hr; iii) catalyst: 7 mg Pd, 0.010 mmol 1,3-bis(o-methoxydiphenyl- 5 phosphino)propane, 0.022 mmol p-toluenesulphonic acid in 3 ml acetone ; iv) 15.7 mmol triphenylsilane in 150 ml methanol. 14.2 g Polymer was obtained, the polymerization rate was 21.1 kg/g/hr and the average mol. wt, (M ) was 5820. When repeating this experiment under the same conditions apart from a) omission of added triphenylsilane and b) reaction period 1.5 hr, the polymer yield was 11.3 g, the pol. rate was 7.5 kg/g/hr and M was 47480. It thus appears that with this catalyst system the presence of triphenylsilane markedly increases the polymerization rate. A similar effect is also found when substituting trifluoroacetic acid for p-toluenesulphonic acid as shown in following Example 8. Example 8 Example 7 is repeated under the same conditions apart from now adopting: i) reaction temp.: 90 °C; ii) reaction period 1.5 hr; iii) catalyst 1 mg Pd, 0.010 mmol 1,3-bis(o-methoxydiphenyl- phosphino)propane, 0.029 mmol trifluoroacetic acid in 3 ml acetone. Polymer yield was 14.2 g, polymerization rate was 19.1 kg/g/hr, M was 8690. When repeating this experiment under the same conditions apart from now omitting triphenylsilane and polymerizing for 1 hr, the results were as follows: polymer yield 4.5 g, polymerization rate 8.7 kg/g/hr, M 20430.

Claims: C L A I M S 1. A process for the preparation of co-polymers of carbon monoxide and one or more ethylenically unsaturated compounds by contacting the monomers, under polymerization conditions, with a catalyst system comprising a) a source of cations of one or more metals of Group VIII of the Periodic Table and b) a bidentate ligand, in the additional presence of a minor amount of a compound containing a hydride moiety. 2. A process as claimed in claim 1, characterized in that a silane is used as compound containing a hydride moiety. 3. A process as claimed in claim 1 or 2, characterized in that an arylsilane, in particular triphenylsilane is used. 4. A process as claimed in any of claims 1-3, characterized in that the amount in which the compound containing a hydride moiety is applied is in the range of 10 to 10 mol per gramatom of Group 2 5 VIII metal, in particular in the range of 10 to 10 on the same basis. 5. A process as claimed in any of claims 1-4, characterized in that a catalyst system is used comprising a source of palladium cations. 6. A process as claimed in any of claims 1-5, characterized in that a catalyst system is used comprising a bidentate ligand of the formula 1 2 1 2 3 4 R R -M -R-M -R R (I) wherein M 1 and M2 independently represent phosphorus, arsenic, 1 2 3 4 antimony, or nitrogen atoms, R ,R ,R and R independently represent substituted or non-substituted hydrocarbyl groups and R represents a bivalent bridging group containing at least two atoms in the bridge. 7. A process as claimed in claim 6, characterized in that in the bidentate ligand of formula (I) at least one of R ,R , R and R represents a phenylgroup substituted by a polar group, in particular an alkoxygroup, at one or both ortho positions with 1 2 respect to M or M . 8. A process as claimed in any of claims 1-7, characterized in that the catalyst system additionally comprises a source of anions being an acid having a pKa of less than 4 or a salt thereof. 9. A process as claimed in any one of claims 1 to 8, characterized in that as ethylenically unsaturated compound ethene, or a mixture of ethene and propene is used. 10. A process as claimed in any one of claims 1-9, characterized in that the co-polymerization is carried out at a temperature in the range of 30-130°C and at a pressure in the range of from 5 to 100 bar.

Inventors: KLUSENER PETER ANTON AUGUST, STIL HANS ARIE, VAN LEEUWEN PETRUS WILHELMUS N, KLUSENER, PETER, ANTON, AUGUST, STIL, HANS, ARIE, VAN LEEUWEN, PETRUS, WILHELMUS, NICOLAAS, MARIA
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1993
Main classification: C08G67
IPC codes: C08G67