Polymer separation

Abstract: Process for the separation of polymers, wherein linear alternating polymers of carbon monoxide with ethene and/or propene and optionally in addition with one or more other α-olefins, which polymers have an M n of less than 2500, are separated by treatment with a liquid having at 20°C a dielectric constant of between 2 and 10 into a soluble fraction with a lower M n and an insoluble fraction with a higher M n .

Description: The invention relates to a process for the separation of polymers of carbon monoxide with one or more α-olefins. Linear polymers of carbon monoxide with ethene and/or propene and optionally in addition with one or more other α-olefins in which polymers the units from carbon monoxide on the one hand and the units from the olefins on the other hand are present in a substantially alternating arrangement can be prepared by contacting the monomers with a catalyst composition containing a Group VIII metal and a phosphorus bidentate ligand of the general formula R 1 R 2 P-R-PR 3 R 4 in which R 1 to R 4 represent identical or different alkyl groups in which alkyl groups the carbon atom that occurs linked to phosphorus carries at least two hydrogen atoms and R is a divalent organic bridging group containing at least two carbon atoms in the bridge connecting the two phosphorus atoms to each other. Using these catalyst compositions, linear alternating polymers are obtained with an average molecular weight, calculated as number average ( M n ), of more than 10,000. For some applications there is a need for such polymers with a considerably lower M n . These polymers can be used as such or can serve as starting material for the preparation of other valuable polymers by conversion of at least a part of the carbonyl groups present in the polymers as functional groups into other functional groups. The applicant recently carried out an investigation into the preparation of the present polymers with a low M n . In the course of this investigation is was found that when using the above-mentioned catalyst compositions, polymers with a M n of less than 2500 can be prepared in a high yield by carrying out the polymerization in the presence of hydrogen. It was further found that by using catalyst compositions containing a Group VIII metal and a tetraalkyldiphosphine, the desired polymers with an M n of less than 2500 can also be prepared in the absence of hydrogen, provided that a diphosphine of the general formula R 5 R 6 P-R-PR 7 R 8 is used in which R 5 to R 8 represent identical or different alkyl groups in which alkyl groups the carbon atom that occurs linked to phosphorus carries only one hydrogen atom and R has the previously indicated meaning. Use of these catalyst compositions also enables polymers with an M n of less than 2500 to be prepared in a high yield. The polymers with an M n of less than 2500 prepared as described above have a relatively wide molecular weight distribution. For some applications there is a need for such polymers with a narrower molecular weight distribution. In the course of continued research by the applicant into the present polymers with an M n of less than 2500 it has now surprisingly been found that these polymers can be separated by treatment with certain liquids into a soluble fraction with an M n which is lower than that of the polymers which were subjected to the treatment and an insoluble fraction with an M n which is higher than that of the polymers which were subjected to the treatment. The polymer fractions thus obtained each have a molecular weight distribution which is narrower that that of the polymers which were subjected to the treatment. To achieve the desired separation, the liquid used should have a dielectric constant with a value of between 2 and 10 at 20°C. The patent application therefore relates to a process for the separation of polymers wherein linear polymers of carbon monoxide with ethene and/or propene and optionally in addition with one or more other α-olefins, in which polymers the units from carbon monoxide on the one hand and the units from the olefins on the other hand are present in a substantially alternating arrangement and which polymers have an M n of less than 2500, are separated by treatment with a liquid having at 20°C a dielectric constant of between 2 and 10 into a soluble fraction with an M n which is lower than that of the polymers which were subjected to the treatment and an insoluble fraction with an M n which is higher than that of the polymers which were subjected to the treatment. The patent application further relates to the polymer fractions obtained from this separation and to shaped objects consisting at least partly of these polymer fractions. In the process according to the invention the polymers are treated with a liquid having at 20°C a dielectric constant of between 2 and 10. There is preference for liquids which at 20°C have a dielectric constant of between 2.5 and 8. Examples of suitable liquids are dialkylethers such as dimethylether, diethylether and diisopropylether with a dielectric constant at 20° of 5,0, 4.3 and 3.9 respectively. The higher the dielectric constant of the liquids at 20°C, the more of the polymers to be treated will dissolve in them. Lower aliphatic alcohols such as methanol and ethanol with a dielectric constant at 20°C of 33 and 24 respectively are unsuitable for the present purpose, since the polymers dissolve therein almost completely. Lower aliphatic hydrocarbons such as n-pentane with a dielectric constant at 20°C of 1.8 are also unsuitable for the present purpose, since the polymers are almost completely insoluble therein. Very favourable results were obtained by using diethylether and diisopropylether as treatment liquids. Depending on the chosen treatment conditions, more or less of the polymers will dissolve in a given liquid. For example, in general more of the polymers will enter into solution the longer the treatment time, the higher the treatment temperature and the greater the quantity of liquid used per unit weight of polymer. The treatment according to the invention can be carried out at room temperature as well as at higher temperatures. If desired, the treatment can be carried out at the boiling point of the liquid or at an even higher temperature by carrying out the treatment under pressure. In the process according to the invention, short treatment times of a few minutes as well as longer treatment times of some hours are eligible. In the process a small quantity of liquid such as 1 ml per g polymer as well as a larger quantity of liquid such as 1 1 per g polymer can be used. Favourable results can be obtained according to the invention by treating the polymers for about 1 hour at room temperature under stirring with about 10 ml liquid per g polymer. As was mentioned above, polymers which are eligible for use as starting material for the process according to the invention can be prepared by contacting the monomers in the presence of hydrogen with a catalyst composition containing a Group VIII metal and a phosphorus bidentate ligand of the general formula R 1 R 2 P-R-PR 3 R 4 . This polymerization is preferably carried out at a hydrogen partial pressure of between 1 and 50 bar and in particular between 2 and 40 bar. An additional reduction of the average molecular weight can be achieved in this polymerization by carrying out the polymerization additionally in the presence of a compound of the general formula CH 2 =C(R 9 )-C(=0)X where R 9 represents hydrogen or an alkyl group and X is a hydroxyl group, an alkoxy group or an optionally alkyl substituted amino group. A very suitable compound for this purpose is methylacrylate. As was also mentioned above, polymers which are eligible for use as starting material for the process according to the invention can also be prepared in the absence of hydrogen by contacting the monomers with a catalyst composition containing a Group VIII metal and a phosphorus bidentate ligand of the general formula R 5 R 6 P-R-PR 7 R 8 . In this patent application, Group VIII metals are understood to be the noble metals ruthenium, rhodium, palladium, osmium, iridium and platinum, as well as the iron group metals iron, cobalt and nickel. In the catalyst compositions the Group VIII metal is preferably selected from palladium, nickel and cobalt. Palladium is particularly preferred as Group VIII metal. The incorporation of the Group VIII metal in the catalyst compositions preferably takes place in the form of a salt of a carboxylic acid, in particular in the form of an acetate. In the phosphorus bidentate ligands which are eligible for use in the catalyst compositions, the alkyl groups R 1 to R 8 preferably each contain not more than 6 carbon atoms. There is also preference for phosphorus bidentate ligands in which the groups R 1 to R 4 are the same as one another and the groups R 5 to R 8 are the same as one another. Examples of suitable groups R 1 to R 4 are the methyl, the ethyl, the n-propyl and the n-butyl groups. Examples of suitable groups R 5 to R 8 are the 2-propyl, the 2-butyl and the 2-pentyl groups. As regards the bridging group R present in the phosphorus bidentate ligands, there is preference for bridging groups containing three atoms in the bridge, of which at least two are carbon atoms. Examples of suitable bridging groups R are the -CH 2 -CH 2 -CH 2 - group, the -CH 2 -C(CH 3 ) 2 -CH 2 - group and the -CH 2 -Si(CH 3 ) 2 -CH 2 - group. As a very suitable phosphorus bidentate ligand of the general formula R 1 R 2 P-R-PR 3 R 4 can be mentioned 1,3-bis(di n-butylphosphino)propane. As very suitable phosphorus bidentate ligands of the general formula R 5 R 6 P-R-PR 7 R 8 can be mentioned 1,3-bis(di 2-propylphosphino)propane and 1,3-bis(di 2-butylphosphino)propane. The phosphorus bidentate ligands in the catalyst compositions are preferably used in a quantity of 0.5-2 and in particular 0.75-1.5 mol per g.atom Group VIII metal. In addition to a Group VIII metal and a phosphorus bidentate ligand, the catalyst compositions used in the polymer preparation preferably also contain an anion of an acid with a pKa of less than 4 and in particular an anion of an acid with a pKa of less than 2. Examples of acids with a pKa of less than 2 are mineral acids such as perchloric acid, sulphonic acids such as para-toluenesulphonic acid and trifluoromethanesulphonic acid, and halocarboxylic acids such as trifluoroacetic acid. The incorporation of the anion of an acid with a pKa of less than 4 in the catalyst composition can take place in the form of an acid and/or in the form of a salt. A nickel salt such as nickel perchlorate is very suitable as a salt. The anion is preferably present in the catalyst compositions in a quantity of 1-100 and in particular 2-50 mol per g.atom Group VIII metal. In addition to a Group VIII metal, a phosphorus bidentate ligand and optionally an anion of an acid with a pKa of less than 4, the catalyst compositions which are eligible for use in the polymer preparation preferably also contain an organic oxidizing agent. Examples of suitable organic oxidizing agents are 1,2- and 1,4-quinones, aliphatic nitrites such as butyl nitrite and aromatic nitro compounds such as nitrobenzene and 2,4-dinitrotoluene. 1,4-quinones are preferred, and in particular 1,4-benzoquinone and 1,4-naphthoquinone. The organic oxidizing agent is preferably present in the catalyst compositions in a quantity of 5-5000 and in particular 10-1000 mol per g.atom Group VIII metal. If the process according to the invention is employed for the separation of polymers of carbon monoxide with ethene and/or propene and also with one or more other α-olefins, said α-olefins preferably contain fewer than 10 carbon atoms per molecule. The process according to the invention is particularly important for the separation of polymers of carbon monoxide with ethene and/or propene. The preparation of the polymers according to the invention is preferably carried out in the presence of a liquid diluent. Polar liquids are preferably used as diluents. These liquids can be protic or aprotic. An example of a suitable protic liquid is methanol. Examples of suitable aprotic liquids are acetone and tetrahydrofuran. If desired, the polymerization can also be carried out in the gas phase. The polymer preparation can be carried out either batchwise or continuously. In the preparation of linear alternating polymers of carbon monoxide with propene and optionally also with one or more other α-olefins using catalyst compositions containing a Group VIII metal and a tetraalkyldiphosphine, polymers are obtained in which some of the units from carbon monoxide are present in optionally 3-alkyl-substituted 2,5-furandiyl groups. This furan formation can be effectively supressed by carrying out the polymerization in the presence of a liquid diluent consisting substantially of one or more of the α-olefins used as monomers with three or more carbon atoms per molecule. It was, incidentally, found in the course of the applicant's investigation that led to the present invention that polymer molecules in which the above-mentioned furan structures occur dissolve, in the process according to the invention, preferentially in the applied treatment liquid. Consequently, if these structures are present in the starting material, of the two polymer fractions obtained, the fraction with the higher average molecular weight will exhibit a sharply reduced degree of furanization. The quantity of catalyst composition used in the preparation of the polymers can vary within wide limits. Per mol olefinically unsaturated compound to be polymerized a quantity of catalyst composition is preferably used which contains 10 -7 -10 -3 and in particular 10 -6 -10 -4 g.atom Group VIII metal. 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. The molar ratio of the olefinically unsaturated compounds relative to carbon monoxide is preferably 10:1-1:10 and in particular 5:1-1:5. The invention will now be illustrated with reference to the following examples: Example 1 A carbon monoxide/propene copolymer was prepared as follows. 200 ml propene was introduced into a stirred autoclave with a volume of 300 ml. After the autoclave contents had been brought to 80°C, carbon monoxide was forced in until a pressure of 55 bar was reached and then hydrogen until a pressure of 58 bar was reached. A catalyst solution was then introduced into the autoclave consisting of: 4 ml acetone, 0.02 mmol palladium acetate, 0.1 mmol nickel perchlorate, and 0.024 mmol 1,3-bis(di n-butylphosphino)propane. During the polymerization the pressure was kept constant by forcing in carbon monoxide. After 16 hours the polymerization was terminated by cooling the reaction mixture to room temperature and releasing the pressure. The polymer was isolated by evaporating down the reaction mixture. 5.7 g copolymer was obtained with an M n of 1140. The degree of furanization was less than 5%. Example 2 1 g of the carbon monoxide/propene copolymer prepared according to example 1 was mixed with 10 ml diethylether and the mixture was stirred for 1 hour at room temperature. The mixture was separated by filtration into a residue that, after drying, produced 0.25 g copolymer with an M n of 1525 and a filtrate that, after evaporating down, produced 0.75 g copolymer with an M n of 1010. Example 3 1 g of the carbon monoxide/propene copolymer prepared according to example 1 was mixed with 10 ml diisopropylether and the mixture was stirred for 1 hour at room temperature. The mixture was separated by filtration into a residue that, after drying, produced 0.50 g copolymer with an M n of 1500 and a filtrate that, after evaporating down, produced 0.50 g copolymer with an M n of 840. Of the examples 1-3, examples 2 and 3 are according to the invention. In these examples a carbon monoxide/propene copolymer with an M n of less than 2500 was separated by treatment with a liquid, which at 20°C had a dielectric constant of between 2 and 10, into a polymer fraction with a higher M n and a polymer fraction with a lower M n . Example 1 falls outside the scope of the invention and has been included in the patent application for comparison. Example 1 relates to the preparation of the copolymer used as starting material for the treatment. The degree of furanization is understood in this patent application as being the number of units from carbon monoxide present in optionally 3-alkyl-substituted 2,5-furandiyl groups as a percentage of the total number of units from carbon monoxide that are present in the polymers. The degree of furanization was determined with the aid of NMR analysis. It was also established by NMR analysis that the polymers prepared according to example 1 were built up from linear chains in which the units from carbon monoxide on the one hand and the units from propene on the other hand occurred in an alternating arrangement.

Claims: Process for the separation of polymers, characterized in that linear polymers of carbon monoxide with ethene and/or propene and optionally in addition with one or more other α-olefins, in which polymers the units from carbon monoxide on the one hand and the units from the olefins on the other hand are present in a substantially alternating arrangement and which polymers have an M n of less than 2500, are separated by treatment with a liquid which at 20°C has a dielectric constant of between 2 and 10 into a soluble fraction with an M n which is lower than that of the polymers which were subjected to the treatment and an insoluble fraction with an M n which is higher than that of the polymers which were subjected to the treatment. Process according to claim 1, characterized in that at 20°C the treatment liquid has a dielectric constant of between 2.5 and 8. Process according to claim 1 or 2, characterized in that as treatment liquid a dialkylether such as diethylether or diisopropylether is used. Process according to one or more of claims 1-3, characterized in that the treatment is carried out by stirring the polymers for about 1 hour at room temperature with about 10 ml of the treatment liquid per g polymer. Process according to one or more of claims 1-4, characterized in that the polymers have been prepared by contacting the monomers in the presence of hydrogen with a catalyst composition containing a Group VIII metal and a phosphorus bidentate ligand of the general formula R 1 R 2 P-R-PR 3 R 4 in which R 1 to R 4 represent identical or different alkyl groups in which alkyl groups the carbon atom that occurs linked to phosphorus carries at least two hydrogen atoms and R is a divalent organic bridging group containing at least two carbon atoms in the bridge connecting the two phosphorus atoms to each other. Process according to claims 5, characterized in that the polymerization is carried out in the presence of a compound of the general formula CH 2 =C(R 9 )-C(=0)X where R 9 represents hydrogen or an alkyl group and X is a hydroxyl group, an alkoxy group or an optionally alkyl substituted amino group preferably methylacrylate. Process according to one or more of claims 1-4, characterized in that the polymers are prepared by contacting the monomers in the absence of hydrogen with a catalyst composition containing a Group VIII metal and a phosphorus bidentate ligand of the general formula R 5 R 6 P-R-PR 7 R 8 in which R 5 to R 8 represent identical or different alkyl groups in which alkyl groups the carbon atom that occurs linked to phosphorus carries only one hydrogen atom and R has the meaning indicated in claim 5. Process according to claim 5 or 7, characterized in that as phosphorus bidentate ligand the catalyst composition contains 1,3-bis(di n-butylphosphino)propane, 1,3-bis(di 2-propylphosphino) propane or 1,3-bis(di 2-butylphosphino)propane. Process according to one or more of claims 5-8, characterized in that the polymerization is carried out at a temperature of 20-150°C, a pressure of 2-150 bar and a molar ratio of the olefinically unsaturated compounds relative to carbon monoxide of 10:1-1:10 and using a quantity of catalyst composition which contains 10 -7 -10 -3 g.atom Group VIII metal per mol olefinically unsaturated compound to be polymerized. Process according to one or more of claims 1-9, characterized in that it is applied for the separation of polymers of carbon monoxide with ethene and/or propene.

Inventors: KEIJSPER JOHANNES JACOBUS, KEIJSPER, JOHANNES JACOBUS
Applicants: SHELL INT RESEARCH, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1992
Main classification: C08G67
IPC codes: C08G67