GB2289895A - Preparation of copolymers of carbon monoxide and an alpha-olefin having more than 10 carbon atoms - Google Patents

Abstract

A process for the preparation of linear alternating copolymers of carbon monoxide with an aliphatic alpha -olefin having more than 10 carbon atoms, which process comprises contacting a mixture of the monomers with a catalyst composition comprising a) a palladium compound, b) an anion, and c) an asymmetric phosphorus bidentate ligand of the general formula R<5>R<6>P-Q-CHR<9>-PR<7>R<8>, wherein Q is a 1,2-ferrocenyl bridging group, R<5>, R<6>, R<7> and R<8> are identical or different optionally polar substituted hydrocarbyl groups and R<9> is hydrogen or an optionally polar substituted hydrocarbyl group; and an isotactic linear alternating copolymer of carbon monoxide with an aliphatic alpha -olefin having more than 10 carbon atoms.

Description

PREPARATION OF COPOLYMERS OF CARBON MONOXIDE AND AN ALPHA-OLEFIN HAVING MORE THAN 10 CARBON ATOMS This invention relates to the preparation of linear alternating copolymers of carbon monoxide and an aliphatic a-olefin having more than 10 carbon atoms. The invention further relates to the resulting copolymers and their use. In these copolymers the units originating in carbon monoxide and the units originating in the olefinically unsaturated compound(s) used in the preparation occur substantially in an alternating order.

The term "regioregular" used hereinafter refers to the way in which the units originating in a monomer CH2-CH-R, R being an aliphatic alkyl group, are bound to units originating in carbon monoxide. Three possibilities are distinguishable, which are termed "head/head", "tail/tail" and "head/tail". They may be represented schematically as follows: head/head: -(CH2)-(CHR)-(CO)-(CHR)-(CH2)- tail/tail: -(CHR)-(CH2)-(CO)-(CH2)-(CHR)head/tail: -(CH2)-(CHR)-(CO)-(CH2)-(CHR) Regioregular copolymer are understood to be copolymers in which the units originating in the monomer CH2=CH-R are bound to the units originating in carbon monoxide predominantly in a head/tail fashion. The degree of regioregularity of such a copolymer is expressed as the average regioregularity, which may be defined as the percentage of the number of units originating in the monomer CH2=CH-R which are bound to the units originating in carbon monoxide in a head/tail fashion.

The term "stereoregular" used hereinafter refers to the configuration of the chiral carbon atoms present in the regioregular copolymer chains relative to the configuration of the chiral carbon atoms together with which they form part of a diad.

A diad in this connection is understood to be a segment of the polymer chain which is made up of two chiral carbon atoms which are interconnected through a -(CH2)-(CO)- bridge. As regards the relation between the configurations of the two chiral carbon atoms of a diad, two possibilities are distinguishable, which are referred to as "isotactic" and "syndiotactic": when the two chiral carbon atoms in a diad have the same configuration this diad is called an isotactic diad, whereas the diad is called syndiotactic when the configurations are opposed. These options can be schematically represented as isotactic: syndiotactic:

The regioregular copolymers can be divided according to the structure of their chains into three classes: 1) Polymer mixtures in which the number of isotactic diads is substantially equal to the number of syndiotactic diads are referred to as atactic.

2) Polymer mixtures in which the number of isotactic diads is larger than the number of syndiotactic diads are referred to as isotactic.

3) Polymer mixtures in which the number of syndiotactic diads is larger than the number of isotactic diads are referred to as syndiotactic.

The atactic polymer mixtures mentioned under 1) are stereoirregular, whereas the other regioregular polymer mixtures mentioned above possess a degree of stereoregularity. The degree of stereoregularity of the isotactic polymer mixtures is expressed as the average stereoregularity or isotacticity, which is understood to be the percentage of isotactic diads, calculated on the total number of diads present in the polymer chains. On the basis of this definition, the isotactic polymer mixtures have an average stereoregularity of more than 50 %.

EP-A-384517 and EP-A-410543 disclose copolymers of carbon monoxide with an aliphatic a-olefin having at least three carbon atoms which are made up of linear chains in which the units originating in carbon monoxide alternate with the units originating in the a-olefin. These copolymers have a certain degree of regioand stereoregularity, more specifically they are isotactic in nature. For the sake of simplicity the polymer mixtures may be described as isotactic linear alternating copolymers. EP-A-385517 discloses that the copolymers in question can be prepared by contacting a mixture of the monomers with a catalyst. composition comprising a) a palladium compound, b) an anion of an acid with a pKa of less than 2, and c) an asymmetric phosphorus bidentate ligand of the general formula R1R2P-R'-PR wherein R' is a bivalent bridging group containing at least two carbon atoms in the bridge, and R1 R2 R3 and R4 are identical or different optionally polar substituted hydrocarbyl groups, such as the (+)-form and the (-)-form of 4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane and (-) -4,5-bis(dibutylphosphinomethyl) -2 ,2-dimethyl-l,3-dioxolane.

EP-A-410543 teaches that when isotactic copolymers are prepared which have a lower degree of isotacticity than required for a certain application, they can be treated to increase their degree of isotacticity, e.g., by extracting the copolymers with a suitable solvent. It is disadvantageous that in this treatment a polymer byproduct is obtained which in many cases has to be discarded because it does not fulfil the requirements as regards tacticity. A further disadvantage is that when the treatment is applied to polymers which are made up of aliphatic a-olefines having, e.g., more than 10 carbon atoms, it becomes increasingly more difficult to carry out the treatment efficiently and with the effect of obtaining a polymer with a high degree of isotacticity.

It would therefore be desirable to modify the polymerisation such that copolymers with a high degree of isotacticity which are based on an aliphatic a-olefin having more than 10 carbon atoms can be prepared efficiently, i.e. such that the treatment can be avoided and also that the rate of polymerisation is improved.

It has now surprisingly been found that this can be accomplished by using in the polymerisation an asymmetric phosphorus bidentate ligand of the general formula R5R6P-Q-CHR9-PR7R8, wherein Q is a 1,2-ferrocenyl bridging group, R5, R6, R7 and R8 are identical or different optionally polar 9 substituted hydrocarbyl groups and R is hydrogen or an optionally polar substituted hydrocarbyl group. A polymerisation rate can be achieved which even exceeds the rate achieved with 1,3-bis(diethylphosphino)propane when used under otherwise comparable conditions.

The latter ligand has been indicated to be excellently suitable for obtaining a high polymerisation rate in the copolymerisation of carbon monoxide and an aliphatic a-olefin, yielding a linear alternating regioregular atactic polymer, cf. EP-A-516238.

It was even more a surprise that the isotacticity of the copolymers obtained can be 95 % or more, substantially without loss of the regioregularity, which typically amounts to more than 95 %, more typically more than 99 %.

Ligands of the general formula R5R6P-Q-CHR9-PR7R8 as defined hereinbefore are known from EP-A-564406.

The present finding thus led to the efficient synthesis of isotactic copolymers of carbon monoxide and aliphatic a-olefins having more than 10 carbon atoms. Unexpectedly it was subsequently found that the latter copolymers have a better performance than comparable regioregular, atactic copolymers when they are used in paraffinic hydrocarbon oils as additive for improving the low temperature properties of the oil, such as the cold filter plugging point. Such use of the atactic copolymers is known from EP-A-468594. The role of the tacticity of a polymeric additive on its effectiveness as paraffinic oil additive1 which has now been found, is unprecedented.

Accordingly, the invention relates to a process for the preparation of copolymers of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymers are made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, which process comprises contacting a mixture of the monomers with a catalyst composition comprising a) a palladium compound, b) an anion, and c) an asymmetric phosphorus bidentate ligand of the general R56 R5R6P 9 78 formula R5R6P-Q-CHR -PR R , wherein Q is a 1,2-ferrocenyl bridging 5 6 7 and 8 group, R , R , R and R are identical or different optionally polar substituted hydrocarbyl groups and R9 is hydrogen or an optionally polar substituted hydrocarbyl group.

The invention further relates to a copolymer of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymer is made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, and which copolymer is isotactic.

The copolymer has preferably an isotacticity of 95 % or more.

A further embodiment of this invention relates to a paraffinic hydrocarbon oil composition containing a paraffinic hydrocarbon oil and as an additive a copolymer of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymer is made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, and which copolymer is isotactic.

The catalyst composition of this invention is based on a palladium compound. The catalyst may be based on a precursor compound containing palladium in its zero-valent state. Preferably the palladium compound is a palladium salt, such as a salt of a carboxylic acid. Particularly suitable is palladium acetate.

The skilled reader will realise that the anion used as component b) of the catalyst composition is weakly or non-coordinating with the palladium. It is preferably an ion of an acid having a pKa of less than 6 (determined in an aqueous solution at 18 "C), suitably less than 4 and in particular less than 2.

Examples of suitable acids having a pKa of less than 2 are mineral acids, such as perchloric acid, sulphonic acids, such as p-toluenesulphonic acid and trifluoromethanesulphonic acid, and halogen carboxylic acids, such as trifluoroacetic acid. The anion may be incorporated in the catalyst composition in the form of an acid or in the form of a salt. Very suitably the anion is incorporated in the form of nickel perchlorate. The quantity of the anion present in the catalyst composition of this invention may vary between wide limits. Suitably the quantity is in the range of from 0.5 - 50 mol, in particular from 1 - 25 mol per mol of palladium.

The phosphorus bidentate ligand of the general formula R56 9 78 R R P-Q-CHR -PR R as defined hereinbefore is asymmetric. Depending of whether R9 is hydrogen or an optionally polar substituted hydrocarbyl group the liganq's structure provides for at least one or at least two elements of chirality. The ligand may be present as an optically inactive mixture of possible stereo isomers or diastereoisomers, or it may be present as an optically active mixture in which there is an excess of a stereoisomer or diastereoisomer, or the ligand consists of one substantially pure stereoisomer or diastereoisomer. The skilled reader will appreciate that it will have no bearing on the isotacticity of the copolymer whether the ligand used consists of one stereoisomer or diastereoisomer or it consists of said stereoisomer or diastereoisomer and its optical antipode.

The group Q of the bidentate ligand is a bivalent 1,2-ferrocenyl group which may contain further substituents attached to the pentadienyl groups, i.e. other than the R5R6P- and R R P-CHR9 - groups in a 1,2-position, but this is not preferred.

The hydrocarbyl groups R5 and R6 are preferably optionally polar substituted aromatic hydrocarbyl groups which typically have 6 to 12 carbon atoms. When they are polar substituted, eligible substituents are for example dialkylamino groups, whereas preferred polar substituents are alkoxy groups, such as methoxy groups.

Polar substituents are typically positioned ortho with respect to the phosphorus atom. The groups R5 and R6 are preferably identical. They are in particular phenyl groups.

The hydrocarbyl groups R7 and R8 are preferably aliphatic groups or more preferably cycloaliphatic groups, such groups typically containing no more than 10 carbon atoms. Optionally they may be connected to one another through a carbon-carbon bond, so that together with the phosphorus atom to which they are attached they form a heterocyclic phosphorus containing group. The groups R7 and R8 are preferably identical. They may in particular be selected for example from ethyl, l-propyl, 2-propyl, l-butyl or 2-butyl groups, more in particular they are cyclohexyl groups.

The group R9 is hydrogen or an optionally polar substituted hydrocarbyl group, typically having no more than 10 carbon atoms.

The group R9 is preferably ether than hydrogen since this may further increase the isotacticity of the polymer obtained. The group R9 is in particular an alkyl group, more in particular a n-alkyl group, such as an ethyl, l-propyl or l-butyl group, most in particular a methyl group.

Very good results can be achieved by using ((R)-l-[(S)-2-(diphenylphosphino)ferrocenyl])ethyldicyclohexylphosphine as the phosphorus bidentate ligand.

The quantity of the phosphorus bidentate ligand present in the catalyst composition of this invention may vary between wide limits. Suitably the quantity is in the range of from 0.5 - 2 mol, in particular from 0.75 - 1.5 mol per mol of palladium.

In order to further increase the rate of polymerisation it is preferred to include in the catalyst composition a quinone, in particular a 1,4-quinone, such as a 1,4-benzoquinone and a 1,4-naphthoquinone. The quantity of quinone suitably lies in the range of from 1- 5000 mol, in particular from 5 - 1000 mol per mol of palladium.

The aliphatic a-olefin used as one of the monomers of the process may be a branched or a straight chain olefin. The aliphatic -olefin may contain hetero atoms1 such as oxygen and nitrogen, which are present when the aliphatic a-olefin is e.g. an olefinically unsaturated ester, alcohol or amide. The aliphatic a-olefin may also contain an aromatic substituent in such a manner that there is no conjugation of the aromatic substituent with the olefinic double bond. The aliphatic a-olefin is typically a hydrocarbon. The aliphatic a-olefin may be a single olefin but also a mixture of a-olefins may be used, or, if desired, a mixture of an a-olefin with ethene. In the latter case the units in the polymer chains originating in ethene do not contribute to the regio- and stereoregularity of the polymer. In such a case the regularity of the polymer is exclusively related to the parts of the polymer chains which contain units originating in the a-olefin.

The aliphatic a-olefin contains more than 10 carbon atoms and typically not more than 40 carbon atoms, in particular not more than 30 carbon atoms. Preferably it is a straight chain olefin.

It is also possible that in addition to aliphatic a-olefins having more than 10 carbon atoms one or more aliphatic a-olefins having not more than 10 carbon atoms are incorporated. Very suitable is a mixture of aliphatic a-olefins of carbon numbers in the range of from 12 to no more than 24. Very good results have been achieved with a polymer based on l-hexadecene.

The preparation of the polymers is preferably carried out by contacting the monomers with a solution of the catalyst composition of this invention in a diluent in which the polymers are insoluble or virtually insoluble. Lower aliphatic alcohols and in particular methanol are suitable as diluents. Very suitable diluents contain for at least 80 %v an aprotic liquid and for at most 20 %v a protic liquid such as a lower aliphatic alcohol. The aprotic liquid may be a polar liquid, such as acetone, methyl acetate, tetrahydrofuran, dioxane, diethyleneglycol dimethyl ether, gamma-butyrolactone, N-methylpyrrolidone or sulpholane, or an apolar liquid, such as n-hexane, cyclohexane or toluene.

Favourable results can be obtained by using a mixture of tetrahydrofuran and methanol. If desired, the polymerisation can also be carried out in the gas phase. The polymer preparation can take place batchwise or continuously.

When the polymerisation is carried out in a diluent which contains a lower aliphatic alcohol the rate of polymerisation may be increased by adding to the polymerisation mixture an ortho ester, such as a trialkyl orthoformate, in particular trimethyl orthoformate. The quantity of the ortho ester may vary between wide limits. Preferably it is used in a quantity of between 100 and 5000 mol, in particular 500 and 3000 mol per mol of palladium.

The quantity of catalyst composition used in the preparation of the polymers may vary within wide limits. Per mol of olefinically unsaturated compound to be polymerised a quantity of catalyst composition is preferably used which contains 10 7 to 10 and in particular 10 to 10 4 mol of palladium.

The preparation of the polymers is preferably carried out at a temperature of 20 - 150 "C and a pressure of 2 - 150 bar and in particular at a temperature of 30 - 130 "C and a pressure of 5 100 bar. Suitably a temperature below 80 "C, in particular below 60 "C is selected as this leads to a higher isotacticity of the copolymer. The molar ratio of the olefinically unsaturated compounds relative to carbon monoxide is preferably 10:1 to 1:10 and in particular 5:1 to 1:5. The polymerisation may be carried out in the additional presence of hydrogen, in which case the quantity of hydrogen amounts suitably to from 0.1 - 0.5 mol per mol of carbon monoxide.

The copolymers according to this invention may be recovered from the polymerisation mixture by any suitable method. Such methods are well known in the art.

According to the present invention the low-temperature properties of paraffinic hydrocarbon oils, such as the cold filter plugging point and the pour point, can be improved by using as an additive an isotactic linear alternating copolymer of carbon monoxide and an aliphatic a-olefin having more than 10 carbon atoms. The copolymer has preferably an isotacticity of 95 % or more. The copolymer may also be used as an aid in extractive dewaxing processes. An example of such a dewaxing process is disclosed in EP-A-482686. Examples of paraffinic hydrocarbon oils include gas oils, diesel oils, lubricating oils and crude oils.

Very favourable results can be achieved with paraffinic gas oils.

The molecular weight of the copolymers which are eligible to be used as additive in the paraffinic hydrocarbon oils may vary between wide limits. By preference, copolymers are used having a weight average molecular weight (Mw) between 10 and 106, in particular between 2x103 and 10 . The preference for a given molecular weight and also for a given number of carbon atoms of the aliphatic a-olefin(s) from which the copolymer is prepared is substantially determined by the nature and the quantity of the paraffins present in the paraffinic hydrocarbon oil. The quantity of copolymer which according to the invention is taken up into the paraffinic hydrocarbon oil may vary between wide limits. It is preferred to employ 1 - 10,900 and in particular 10 - 1000 mg of copolymer per kg of paraffinic hydrocarbon oil.

In addition to the present copolymers further additives may be added to the paraffinic hydrocarbon oil, such as other polymeric additives than copolymers according to this invention, antioxidants, corrosion inhibitors, metal deactivators and so called wax anti settling agents ("WASA"). Other polymeric additives are, for example, commercially available poly (ethene/vinyl carboxylate)s containing 20-35 %w of the vinyl carboxylate, wherein the vinyl carboxylate is vinyl acetate or vinyl propionate. This invention also relates to an additive composition per se comprising a copolymer of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymer is made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, and which copolymer is isotactic, and a poly(ethene/vinyl carboxylate) containing 20 - 35 %w of the vinyl carboxylate, wherein the vinyl carboxylate is vinyl acetate or vinyl propionate. With respect to their ability to improve the low-temperature properties of the paraffinic hydrocarbon oil the copolymers according to this invention may have a synergistic effect with the further additives mentioned, in particular with poly(ethene/vinyl carboxylate).

The polymer constituents of the other polymeric additives have typically a weight average molecular weight between 10 and 106, in particular between 104 and 105. When other polymeric additives are present in the paraffinic hydrocarbon oil, the copolymer according to this invention constitutes preferably 1 - 90 %w of the total of polymeric additives.

The invention will now be illustrated with reference to the following examples. The regio- and stereoregularity of the copolymers prepared according to Examples 1-4 was derived from C-NMR spectra (deutero-hexafluoroisopropanol solvent), by analysing the signals in the carbonyl region.

Example 1 A carbon monoxide/l-hexadecene copolymer was prepared as follows. A stirred autoclave was charged with 300 ml tetrahydrofuran, 300 ml 1-hexadecene and a catalyst solution consisting of 10 ml tetrahydrofuran, 17 ml methanol, 0.09 mmol palladium acetate, 0.45 mmol nickel perchlorate, 0.106 mmol {(R)-l-[(S)-2-(diphenylphosphino)ferrocenyl])ethyldi- cyclohexylphosphine, and 4.7 mmol 1,4-naphthoquinone.

Air present in the autoclave was replaced by carbon monoxide, which was forced in to achieve a pressure of 50 bar. The contents of the autoclave were brought to a temperature of 42 "C. After 20 hours the polymerisation was terminated by cooling to room temperature and releasing the pressure. After the addition of methanol to the reaction mixture the copolymer was filtered off, washed with methanol and dried.

The yield of copolymer was 145 g. The polymerisation rate calculated from the copolymer yield was 760 g copolymer/(g palladium.hour). The isotacticity of the copolymer obtained was more than 95 %.

Example 2 A carbon monoxide/l-hexadecene copolymer was prepared in substantially the same way as in Example 1, but with the following differences: a) 90 ml xylene was used instead of 300 ml tetrahydrofuran, b) 90 ml 1-hexadecene was used instead of 300 ml, and c) the carbon monoxide partial pressure was 35 bar and in addition hydrogen was used at a partial presure of 5 bar.

The yield of copolymer was 14 g. The polymerisation rate calculated from the copolymer yield was 73 g copolymer/(g palladium.hour). The isotacticity of the copolymer obtained was more than 95 %. The weight average molecular weight of the copolymer was 32,500.

Example 3 A carbon monoxide/l-hexadecene copolymer was prepared in substantially the same way as in Example 1, but with the following differences: a) 90 ml xylene was used instead of tetrahydrofuran, b) 90 ml 1-hexadecene was used instead of 300 ml, c) no 1,4-naphthoquinone was present in the catalyst solution, d) the temperature was 60 "C instead of 42 "C, and e) the carbon monoxide partial pressure was 40 bar and in addition hydrogen was used at a partial presure of 1 bar.

The yield of copolymer was 29 g. The polymerisation rate calculated from the copolymer yield was 150 g copolymer/(g palladium.hour). The isotacticity of the copolymer obtained was about 80 %. The weight average molecular weight of the copolymer was 10,200.

Example 4 A carbon monoxide/l-hexadecene copolymer was prepared in substantially the same way as in Example 1, but with the following differences: a) 0.10 mmol of 1,3-bis(diethylphosphino)propane was used instead of t(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]lethyldicyclo- hexylphosphine, and b) the reaction time was 19 hours instead of 21 hours.

The yield of copolymer was 47.4 g. The polymerisation rate calculated from the copolymer yield was 262 g copolymer/(g palladium.hour). The copolymer obtained was atactic.

Example 5 The following polymers, as such or in mixtures, were tested as additives in two gas oils (A and B) in order to lower the cold filter plugging point (CFPP) of the oils, as determined in accordance with Standard Test Method IP 309/83: Additive 1: the isotactic CO/1-hexadecene copolymer of Example 2; Additive 2: the isotactic CO/1-hexadecene copolymer of Example 3; Additive 3: an atactic CO/1-hexadecene copolymer, having Mw 45,700; Additive 4: an atactic CO/l.hexadecene copolymer, having M 24,600; w Additive 5: an atactic CO/1-hexadecene copolymer1 having M 18,400; Additive 6: an atactic CO/1-hexadecene copolymer, having Mw 15,000; Additive 7: a commercially available poly(ethene/vinyl acetate) containing 25 %w vinyl acetate, having M 75,600, melt index w according to ASTM-D1238 350 g/10 min.

Additives 3, 4, 5 and 6 were prepared according to methods disclosed in EP-A-468594; these additives are not according to the invention; they were tested for comparison.

The additives were introduced into the gas oils in the form of 50 %w solution in toluene. The results of the tests are embodied in Table I, where for each of the gas oils the CFPP is reported after addition of the indicated quantity of polymer solution (containing 50 %w of active material), stated as mg of polymer solution per kg gas oil.

Table I Additive M of CO/olefin Added quantity CFPP w copolymer mg/kg gas oil "C Gas oil A -10 1 32,500 300 -16 2 10,200 300 -18 3 ) 45,700 300 -14 4 ) 24,600 300 -16 * 6 ) 15,000 300 -16 1 + 7 32,500 100 + 50 -18 2 + 7 10,200 100 + 50 -20 3 + 7 ) 45,700 100 + 50 -13 * 4 + 7 ) 24,600 100 + 50 -16 * 7 ) - 150 -17 Gas oil B -12 1 + 7 32,500 25 + 25 -27 2 + 7 10,200 25 + 25 -23 * 5 + 7 ) 18,400 25 + 25 -17 7 ) - 50 -14 * ) denotes: for comparison, not according to the invention The 13C-NMR analyses revealed that the copolymers prepared in the Examples 1 - 4 had a linear alternating structure.

The results of Examples 1 and 4 show that by using a ferrocenyl containing bidentate ligand according to this invention a polymerisation rate can be achieved which exceeds the rate achievable with 1,3-bis(diethylphosphino)propane, which is a ligand according to the prior art which has been indicated to be very suitable for obtaining a high polymerisation rate in the copolymerisation of carbon monoxide with an aliphatic a-olefin.

The results in Table I show that when copolymers according to this invention are used as additive for paraffinic hydrocarbon oils the cold filter plugging points of the oils are decreased. The performance of the copolymers according to the invention is better than the performance of comparable atactic copolymers, which can be deduced from the Table by taking the differences in the weight average molecular weights into account: atactic copolymers with weight average molecular weights of 32,500 and 10,200 would give cold filter plugging points of -15 C and -17 "C, respectively, where the isotactic copolymers gave -16 "C and -18 "C. In particular by using the isotactic copolymers in conjunction with a poly(ethene/vinyl acetate) very favourable results can be obtained.

Claims (18)

1. A process for the preparation of copolymers of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymers are made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, which process comprises contacting a mixture of the monomers with a catalyst composition comprising a) a palladium compound, b) an anion, and c) an asymmetric phosphorus bidentate ligand of the general formula R5R6P-Q-CHR9-PR7R8, wherein Q is a 1,2-ferrocenyl bridging group, R5, R61 R7 and R8 are identical or different optionally 9.

polar substituted hydrocarbyl groups and R is hydrogen or an optionally polar substituted hydrocarbyl group.

2. A process as claimed in claim 1, characterised in that in the general formula of the phosphorus bidentate ligand R5 and R6 are identical or different optionally polar substituted aromatic hydrocarbyl groups, R7 and R8 are identical or different 9 cycloaliphatic hydrocarbyl groups, and R is an aliphatic hydrocarbyl group.

3. A process as claimed in claim 2, characterised in that in the general formula of the phosphorus bidentate ligand R5 and R6 are phenyl groups, R7 and R8 are cyclohexyl groups, and R9 is a methyl group.

4. A process as claimed in claim 3, characterised in that the phosphorus bidentate ligand is ((R)-l-[(S)-2-(diphenylphosphino)ferrocenyl]}ethyldicyclohexylphosphine.

5. A process as claimed in any of claims 1 - 4, characterised in that the catalyst composition comprises as the palladium compound a palladium carboxylate, such as palladium acetate.

6. A process as claimed in any of claims 1 - 5, characterised in that the catalyst composition comprises as component b) an anion of an acid having a pKa of less than 2, in particular a mineral acid, such as perchloric acid, a sulphonic acid, such as p-toluenesulphonic acid or trifluoromethanesulphonic acid, or a halogen carboxylic acid, such as trifluoroacetic acid.

7. A process as claimed in any of claims 1 - 6, characterised in that the catalyst composition comprises the phosphorus bidentate ligand in a quantity in the range of from 0.75 - 1.5 mol per mol of palladium and the anion used as component b) in a quantity in the range of from 1 - 25 mol per mol of palladium.

8. A process as claimed in any of claims 1 - 7, characterised in that the catalyst composition comprises as an additional component a quinone, in particular a 1,4-quinone, such as a l,4-benzoquinone or a 1,4-naphthoquinone, in a quantity in the range of from 5 1000 mol per mol of palladium.

9. A process as claimed in any of claims 1 - 8, characterised in that the polymerisation is carried out by contacting the monomers with a solution of the catalyst composition in a diluent containing for at least 80 %v an aprotic liquid and for at most 20 %v a protic liquid such as a lower aliphatic alcohol, and in that it is carried out at a temperature of 30 - 130 "C, a pressure of 5 - 100 bar and a molar ratio of the olefinically unsaturated compounds relative to carbon monoxide of 5:1 to 1:5 and using a quantity of catalyst composition which per mol olefinically unsaturated compound to be polymerised contains 10 - 10 gram atom palladium.

10. A copolymer of carbon monoxide with an aliphatic a-olefin having more than 10 carbon atoms which copolymer is made up of linear chains in which the units originating in the aliphatic a-olefin alternate with units originating in carbon monoxide, and which copolymer is isotactic.

11. A copolymer as claimed in claim 10, charaterised by an isotacticity of 95 % or more.

12. A copolymer as claimed in claim 10 or 11, characterised in that the a-olefin is a straight chain olefin having no more than 30 carbon atoms.

13. A copolymer as claimed in any of claims 10 - 12, characterised in that the copolymers have a weight average molecular weight (Mw) between 10 and 106, in particular between 2x103 and 105.

14. A paraffinic hydrocarbon oil composition containing a paraffinic hydrocarbon oil and as an additive a copolymer as claimed in any of claims 10 - 13.

15. A paraffinic hydrocarbon oil composition as claimed in claim 14, characterised in that it contains the copolymer as claimed in any of claims 10 - 13 in a quantity of 1 - 10,000, in particular in a quantity of 10 - 1,000 mg of copolymer per kg of paraffinic hydrocarbon oil.

16. A paraffinic hydrocarbon oil composition as claimed in claim 14 or 15, characterised in that it contains as a further polymeric additive a poly(ethene/vinyl carboxylate) containing 20 - 35 %w of the vinyl carboxylate, wherein the vinyl carboxylate is vinyl acetate or vinyl propionate.

17. A paraffinic hydrocarbon oil composition as claimed in claim 16, characterised in that the copolymer as claimed in any of claims 10 - 13 constitutes 1 - 90 %w of the total of polymeric additives.

18. An additive composition comprising a copolymer as claimed in any of claims 10 - 13 and a poly(ethene/vinyl carboxylate) containing 20 - 35 %w of the vinyl carboxylate, wherein the vinyl carboxylate is vinyl acetate or vinyl propionate.