Copolymers of carbon monoxide

Abstract: Novel copolymers of carbon monoxide with an alpha-olefin having at least three carbon atoms in the molecule, made up of linear and alternating chains, having a stereo-regular structure, can be prepared by copolymerizing the monomers in the presence of a catalyst composition based upon a palladium compound, an anion of an acid with a pKa of less than 2, and an asymmetric bisphosphine.

Description: The invention relates to novel copolymers of carbon monoxide with an alpha-olefin having at least three carbon atoms in the molecule, and to a process for their preparation. Linear copolymers of carbon monoxide with ethene, in which polymers the units originating in carbon monoxide on the one hand and the units originating in ethene on the other hand, occur in alternating order, can be prepared by contacting the monomers with a catalyst composition based upon: a) a palladium compound, b) an anion of an acid with a pKa of less than 2, and c) a symmetric bisphosphine of the general formula (R¹)₂P-R-P(R¹)2, wherein R¹ is an optionally polar-substituted hydrocarbyl group and R is a bivalent organic bridging group containing at least two carbon atoms in the bridge that connects the two phosphorus atoms. For the structure of the copolymers obtained, it makes no difference whether they are prepared using a catalyst composition which includes a bisphosphine in which R¹ is aromatic, or a bisphosphine in which R¹ is aliphatic. In both cases, the same linear alternating carbon monoxide/ethene copolymers are obtained. The Applicant has recently carried out an investigation into whether the afore-mentioned catalyst compositions can be employed to prepare linear alternating copolymers of carbon monoxide with an alpha-olefin having at least three carbon atoms in the molecule (for the sake of brevity referred to as C₃+alpha-olefins). In the investigation it was found that such copolymers can indeed be prepared in this way. Contrary to what was first observed during the preparation of the carbon monoxide/ethene copolymers, it was also found that for the structure of the carbon monoxide/C₃+alpha-olefin copolymers obtained, it is very important which bisphosphine is present in the catalyst composition used. When a catalyst composition is employed which includes a bisphosphine in which R¹ is aromatic, such as 1,3-bis[bis(2-methoxyphenyl)phosphino]propane, the copolymer obtained is regio-irregular, whereas when a catalyst composition is employed which includes a bisphosphine in which R¹ is aliphatic, such as 1,3-bis(di-n-butylphosphino)propane, the copolymer obtained is regio-regular but stereo-irregular. The descriptions regio-regular and regio-irregular refer to the way in which the monomers have been incorporated in the polymer chains. If this incorporation has come about in a regular way, then in the resulting copolymers, the units originating in the C₃+alpha-olefin are attached substantially in a head/tail fashion to the units originating in carbon monoxide. Such copolymers are referred to as regio-regular. If the incorporation has occurred in a random way, then in the resulting copolymers, the units originating in the C₃+alpha-olefin are attached in a head/tail fashion to no more than about 50% of the units originating in carbon monoxide. Such copolymers are referred to as regio-irregular. On the basis of the configurations of the asymmetric carbon atoms present in the polymer chains, the regio-regular copolymers can be divided into stereo-regular and stereo-irregular copolymers. If the configuration of the asymmetric carbon atoms present in the polymer chain is substantially regular, the copolymers are referred to as stereo-regular. If it is a random configuration, the copolymers are referred to as stereo-irregular. The latter copolymers are obtained when during the copolymerization of carbon monoxide with a C₃+alpha-olefin, use is made of a symmetric bisphosphine (R¹)₂P-R-P(R¹)₂, wherein R¹ is aliphatic. Further research done by the Applicant into the preparation of linear alternating copolymers of carbon monoxide with a C₃+alpha-olefin has now shown that stereo-regular copolymers can be prepared by contacting the monomers with a catalyst composition on the basis of the afore-mentioned components a) and b) and as component c) an asymmetric bisphosphine of the general formula R³R⁴P-R⁵-PR³R⁴, wherein R³ and R⁴ are identical or different optionally polar-substituted hydrocarbyl groups and R⁵ is a bivalent organic bridging group containing at least two carbon atoms in the bridge that connects the two phosphorus atoms. In the present patent application, asymmetric bisphosphines should be taken to be bisphosphines whose molecules have such a structure that a plane of symmetry is missing, so that they are not superposable on their mirror images. Depending on the number of asymmetric centres in the bisphosphines, the latter can occur in various optically active forms. Optically inactive mixtures of optically active bisphosphines may also be used. When optically inactive mixtures of optically active bisphosphines are used in the catalyst compositions as components c), then the copolymers obtained are stereo-regular linear alternating carbon monoxide/C₃+alpha-olefin copolymers which are optically inactive. When an optically active bisphosphine is used in the catalyst composition as component c), then the copolymers obtained are stereo-regular linear alternating carbon monoxide/C₃+alpha-olefin copolymers which also show optical activity. Stereo-regular linear alternating copolymers of carbon monoxide with a C₃+alpha-olefin are novel. Naturally, this holds both for the optically inactive and for the optically active copolymers. The present patent application therefore relates to novel copolymers of carbon monoxide with a C₃+alpha-olefin, which copolymers are made up of linear chains in which the units originating in carbon monoxide on the one hand and the units originating in the applied alpha-olefins on the other hand, occur in alternating order, and which copolymers are stereo-regular. The present patent application further relates to a process for the preparation of such copolymers. As regards the monomers used in the preparation of the copolymers of the invention, it is preferred to employ C₃+alpha-olefins with at most 10 carbon atoms in the molecule, and in particular propene. The copolymers of the invention may be prepared by contacting the monomers with a solution of a catalyst composition in a diluent, which catalyst composition is based upon: a) a palladium compound, b) an anion of an acid with a pKa of less than 2, and c) an asymmetric bisphosphine of the general formula R³R⁴P-R⁵-PR³R⁴, wherein R³ and R⁴ are identical or different optionally polar-substituted hydrocarbyl groups and R⁵ is a bivalent organic bridging group containing in the bridge that connects the two phosphorus atoms, at least two carbon atoms. The preparation of the copolymers of the invention is preferably carried out at a temperature of from 20 to 100°C, an overall pressure of from 5 to 150 bar and by employing such a quantity of catalyst composition as to contains 10⁻⁷ to 10⁻³ mol of palladium per mol of olefin to be polymerized. Special preference is given to a preparation carried out at a temperature in the range of from 30 to 85°C, an overall pressure in the range of from 20 to 100 bar and by employing such a quantity of catalyst composition as to contain 10⁻⁶ to 10⁻⁴ mol of palladium per mol of olefin to be polymerized. The molar ratio of the C₃+alpha-olefin relative to carbon monoxide in the mixture to be polymerized is preferably from 10:1 to 1:10 and in particular from 5:1 to 1:5. Very suitable diluents are lower aliphatic alcohols, such as methanol, and mixtures thereof with cyclic ethers, such as tetrahydrofuran. The palladium compound employed in the catalyst composition as component a) is preferably a palladium salt of a carboxylic acid, and palladium acetate in particular. Examples of suitable acids with a pKa of less than 2 (determined in aqueous solution at 18°C) are mineral acids, such as perchloric acid, sulphonic acids, such as para-toluenesulphonic acid, and halogen carboxylic acids, such as trifluoroacetic acid. In the catalyst compositions, component b) may be incorporated in the form of an acid and/or in the form of a salt. A very suitable acid is trifluoroacetic acid and a very suitable salt is nickel perchlorate. Preferably, the quantity of component b) present in the catalyst compositions is from 0.5 to 50 and in particular from 1 to 25 mol per mol of palladium. In the asymmetric bisphosphines of the general formula R³R⁴P-R⁵-PR³R⁴ that are eligible to be used as component c) in the catalyst compositions, preferably the groups R³ and R⁴ each contain not more than 10 carbon atoms. Preferably, groups R³ and R⁴ are identical with one another. In the general formula of the asymmetric bisphosphines the groups R³ and R⁴ are bound to each other through a phosphorus atom. If desired, yet another bond may exist between the groups R³ and R⁴, which thus together with the phosphorus atom form part of a cyclic structure. Examples of such asymmetric bisphosphines are alpha,omega-bis(3,4-dialkoxyphospholano)nC₂+-alkanes such as 1,2-bis(3,4-dimethoxyphospholano)ethane. Preference is given to asymmetric bisphosphines which in the bridge linking the two phosphorus atoms contain at least two carbon atoms which individually or together are part of a cyclic structure. Examples of asymmetric bisphosphines in which the bridge that connects the two phosphorus atoms with one another contains four carbon atoms, two of which together form part of a cyclic structure, are trans-4,5-bis-(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane and trans-1,2-bis-(diphenylphosphinomethyl)-cyclohexane. Examples of asymmetric bisphosphines in which the bridge that connects the two phosphorus atoms with one another contains four carbon atoms, three of which together form part of a cyclic structure, are 2-diphenylphosphinomethyl-4-diphenylphosphinopyrrolidine and N-tert.butoxycarbonyl-2-diphenylphosphinomethyl-4-diphenylphosphinopyrrolidine. An example of an asymmetric bisphosphine in which the bridge that connects the two phosphorus atoms with one another contains two carbon atoms which together form part of a cyclic structure, is trans-2,3-bis(diphenylphosphino)bicyclo[2.2.1]heptene-5. An example of an asymmetric bisphosphine in which the bridge that connects the two phosphorus atoms with one another contains four carbon atoms which in pairs form part of two separate cyclic structures, is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl. The preparation of copolymers of the invention gave very favourable results when use was made of catalyst compositions containing as component c) either (+) or (-)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane, or (-)-4,5-bis(dibutylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane. The asymmetric bisphosphines are preferably employed in the catalyst compositions in a quantity of from 0.5 to 2 and in particular of from 0.75 to 1.5 mol per mol of palladium. It is preferred that in addition a 1,4-quinone be incorporated as component d) in the present catalyst compositions that are used in the preparation of the polymers of the invention. For this purpose, 1,4-benzoquinones and 1,4-naphthoquinones are very suitable. The quantity of 1,4-quinone used preferably lies in a range of from 1 to 5000 mol and in particular in a range of from 5 to 1000 mol per mol of palladium. The invention will now be illustrated with the aid of the following examples. Example 1 A carbon monoxide/propene copolymer was prepared as follows. A mechanically stirred autoclave with a capacity of 300 ml was charged with 130 ml of tetrahydrofuran and 75 ml of propene. After the contents of the autoclave were brought to 42°C, carbon monoxide was blown in until a pressure of 40 bar was reached. Subsequently, a catalyst solution was introduced into the autoclave, which comprised 27 ml methanol, 9 ml toluene, 0.06 mmol palladium acetate, 0.426 mmol nickel perchlorate, 0.72 mmol 1,3-bis[bis(2-methoxyphenyl)phosphino]propane, and 3.0 mmol 1,4-naphthoquinone. Polymerization was terminated after 67.28 hours by cooling the reaction mixture to room temperature and releasing the pressure. The reaction mixture was stirred into methanol and the copolymer was filtered off, washed with methanol and dried at 50°C. 9.9 g of copolymer was obtained. The polymerization rate was 23 g copolymer/(g palladium.hour). Example 2 A carbon monoxide/propene copolymer was prepared substantially in the same way as in Example 1, except for the following differences a) 110 ml instead of 130 ml of tetrahydrofuran and 80 ml instead of 75 ml of propene were introduced into the autoclave, b) the catalyst solution used comprised 8.5 ml methanol, 21.5 ml tetrahydrofuran, 0.043 mmol palladium acetate, 0.21 mmol nickel perchlorate, and 0.052 mmol 1,3-bis(di-n-butylphosphino) propane and 3.0 mmol 1,4-naphthoquinone, and c) the reaction time was 64.5 instead of 67.28 hours. 63 g of copolymer was obtained. The polymerization rate was 214 g copolymer/(g palladium.hour). Example 3 A carbon monoxide/propene copolymer was prepared substantially in the same way as in Example 1, except for the following differences a) 110 ml instead of 130 ml of tetrahydrofuran was introduced into the autoclave, b) carbon monoxide was blown in until a pressure of 45 bar instead of 40 bar was reached, c) the catalyst solution used comprised 21.5 ml tetrahydrofuran, 8.5 ml methanol, 0.044 mmol palladium acetate, 0.21 mmol nickel perchlorate, 0.047 mmol (+)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane, and 3.0 mmol 1,4-naphthoquinone, d) the reaction time was 66.2 instead of 67.28 hours, and e) the reaction mixture was stirred into water instead of methanol. 0.8 g of copolymer was obtained. The polymerization rate was 2.6 g copolymer/(g palladium.hour). Example 4 A carbon monoxide/propene copolymer was prepared substantially in the same way as in Example 3, except for the following differences a) 130 ml instead of 110 ml of tetrahydrofuran was introduced into the autoclave, b) the catalyst solution comprised 0.053 mmol of (-)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane instead of 0.047 mmol of the (+)-form of this compound, and c) the reaction time was 42.3 instead of 66.2 hours 0.44 g of copolymer was obtained. The polymerization rate was 2.2 g copolymer/(g palladium.hour). Example 5 A carbon monoxide/propene copolymer was prepared substantially in the same way as in Example 1, except for the following differences a) 110 ml instead of 130 ml of tetrahydrofuran and 87 ml instead of 75 ml of propene were introduced into the autoclave, b) carbon monoxide was blown in until a pressure of 45 bar instead of 40 bar was reached, c) the catalyst solution used comprised 1.4 ml methanol, 3.9 ml tetrahydrofuran, 0.091 mmol palladium acetate, 0.65 mmol nickel perchlorate, 0.105 mmol (-)-4,5-bis(dibutylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane, and 6.3 mmol 1,4-naphthoquinone, d) the reaction time was 65.1 instead of 67.28 hours, and e) the reaction mixture was stirred into water instead of methanol. 6.83 g of polymer was obtained. The polymerisation rate was 10.8 g copolymer/(g Pd.hour). Of Examples 1-5, Examples 3-5 are examples in accordance with the invention. Examples 1 and 2 fall outside the scope of the invention and have been included herein for comparison. With the aid of ¹³C-NMR analysis it was established in the first place that the copolymers prepared according to Examples 1-5 had a linear structure and that in these copolymers, the units originating in carbon monoxide on the one hand and the units originating in propene on the other hand, occurred in alternating order. Further, it was established that the copolymers prepared according to Examples 2-5 had a regio-regular structure in which the units originating in propene were attached to more than 80% of the units originating in carbon monoxide in a head/tail fashion, and that the copolymers prepared according to Example 1 had a regio-irregular structure in which the units originating in propene were attached to only about 50% of the units originating in carbon monoxide in a head/tail fashion. Finally, it was established that of the copolymers with a regio-regular structure prepared according to Examples 2-5, the copolymers prepared according to Example 2 had a stereo-irregular structure, while the copolymers prepared according to Examples 3-5 had a stereo-regular structure. When dissolved in hexafluoro-isopropanol, the copolymers prepared according to Examples 3-5 showed a specific rotation [alpha] 25 / D of -6.7°, +6.6°, and +10.4°, respectively. The copolymers prepared according to Example 3 had a melting point of about 165°C.

Claims: Copolymers of carbon monoxide with an alpha-olefin having at least three carbon atoms in the molecule, characterized in that they are made up of linear chains in which the units originating in carbon monoxide on the one hand and the units originating in the applied alpha-olefin on the other hand, occur in alternating order, and in that they have a stereo-regular structure. Copolymers as claimed in claim 1, characterized in that they are optically active. Copolymers as claimed in claim 1 or 2, characterized in that the alpha-olefin has at most ten carbon atoms in the molecule. Process for the preparation of copolymers as claimed in one or more of claims 1-3, characterized in that the monomers are contacted with a solution of a catalyst composition in a diluent, which catalyst composition is based upon a) a palladium compound, b) an anion of an acid with a pKa of less than 2, and c) an asymmetric bisphosphine of the general formula R³R⁴P-R⁵-PR³R⁴, wherein R³ and R⁴ are identical or different optionally polar-substituted hydrocarbon groups and R⁵ is a bivalent organic bridging group containing at least two carbon atoms in the bridge that connects the two phosphorus atoms. Process as claimed in claim 4, characterized in that it is carried out at a temperature in the range of from 20 to 100°C, an overall pressure in the range of from 5 to 150 bar, a molar ratio of the olefin relative to carbon monoxide in the mixture to be polymerized, in the range of from 10:1 to 1:10, and by using such a quantity of catalyst composition as to contain 10⁻⁷ to 10⁻³ mol of palladium per mol of olefin to be polymerized. Process as claimed in claim 4 or 5, characterized in that a catalyst composition is employed which includes 0.5 to 50 mol of component b) and 0.5 to 2 mol of component c) per mol of palladium. Process as claimed in one or more of claims 4-6, characterized in that a catalyst composition is employed which includes as component c) a bisphosphine in which the groups R³ and R⁴ each contain not more than 10 carbon atoms. Process as claimed in claim 7, characterized in that a catalyst composition is employed which includes as component c) a bisphosphine in which the groups R³ and R⁴ are identical groups. Process as claimed in one or more of claims 4-8, characterized in that a catalyst composition is employed which includes as component c) a bisphosphine in which the two or more carbon atoms in the bridge that connects the two phosphorus atoms individually or together are part of a cyclic structure. Process as claimed in one or more of claims 4-9, characterized in that a catalyst composition is employed which includes as component c) a bisphosphine which is optically active, such as (+) or (-)-4,5-bis(diphenylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane, or (-)-4,5-bis(dibutylphosphinomethyl)-2,2-dimethyl-1,3-dioxolane.

Inventors: WONG PUI KWAN, WONG, PUI KWAN
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1990
Main classification: C08G67
IPC codes: C08G67