PROCESS FOR PREPARING POLYALKENAMERS FOR PACKAGING APPLICATIONS

Abstract

The present invention relates to a process for producing cycloalkenamer-containing compositions, comprising the steps of: a) converting at least one cycloalkene by ring-opening metathetic polymerization to obtain a polyalkenamer-containing product mixture, and b) working up the product mixture to remove monomers and oligomers of the cycloalkenes to obtain the polyalkenamer-containing composition by extraction with CO.sub.2, whereby the polyalkenamers are polymers of cycloalkenes which comprise at least five cycloalkane monomer units, wherein the extraction comprises at least two stages: b0) an extraction with liquid CO.sub.2, then b1) an extraction with supercritical CO.sub.2, then b2) an extraction with gaseous CO.sub.2, then b0) an extraction with liquid CO.sub.2, then and then b3) an extraction with supercritical CO.sub.2.

Claims

1. A process for producing a polyalkenamer-containing composition, comprising the steps of: a) converting at least one cycloalkene by ring-opening metathetic polymerization to obtain a polyalkenamer-containing product mixture, and b) working up the product mixture to remove monomers and oligomers of the cycloalkenes to obtain the polyalkenamer-containing composition by extraction with CO.sub.2, wherein the polyalkenamers are polymers of cycloalkenes which comprise at least five cycloalkane monomer units, wherein the extraction comprises at least the consecutive stages: b0) an extraction with liquid CO.sub.2, b1) an extraction with supercritical CO.sub.2, b2) an extraction with gaseous CO.sub.2, b0) an extraction with liquid CO.sub.2, and b3) an extraction with supercritical CO.sub.2.

2. The process according to claim 1, wherein extraction in stage b2 is conducted at a temperature in the range from 0 C. to 99 C. and a pressure in the range from 0 bar to 73 bar, with adjustment of pressure and temperature with respect to one another such that the CO.sub.2 remains in gaseous form.

3. The process according to claim 2, wherein the pressure is below and the temperature is above the critical value for CO.sub.2.

4. The process according to claim 1, wherein the extraction in stages b1 and b3 is conducted at a temperature in the range from 31 C. to 99 C. and a pressure in the range from 74 bar to 1000 bar.

5. The process according to claim 1, wherein the relative mass throughput is between 10 kg and 500 kg of CO.sub.2 per polyalkenamer-containing product mixture.

6. The process according to claim 1, wherein a separation of the CO.sub.2 extractant from monomers and oligomers is effected after step b3.

7. The process according to claim 6, wherein the CO.sub.2 for separation is gaseous.

8. The process according to claim 6, wherein the CO.sub.2 for separation is supercritical and an adsorbent takes up the monomers and oligomers.

9. The process according to claim 8, wherein the adsorbent is selected from activated carbon, alumina, silica and mixtures.

10. The process according to claim 1, wherein the cycloalkene is selected from the group consisting of cyclobutene, cyclopentene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cyclododecene, cycloocta-1,5-diene, 1,5-dimethylcycloocta-1,5-diene, cyclodecadiene, norbornadiene, cyclododeca-1,5,9-triene, trimethylcyclododeca-1,5,9-triene, norbornene (bicyclo[2.2.1]hept-2-ene), 5-(3-cyclohexenyl)-2-norbornene, 5-ethyl-2-norbornene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, dicyclopentadiene and mixtures thereof.

11. The process according to claim 1, wherein the polyalkenamer-containing product mixture obtained in a) is in solid form and is granulated or pulverized to particles prior to step b).

12. The process according to claim 1, wherein the conversion of cycloalkenes is conducted in the presence of a catalyst, preferably comprising at least one transition metal halide and an organometallic compound or comprising at least one transition metal-carbene complex.

Description

[0047] FIG. 1 shows a schematic construction of a plant in which the process I is conducted. The CO.sub.2 is retained in a reservoir vessel (1). Arranged downstream is a high-pressure pump or a compressor (2). Upstream of the autoclave (extraction vessel) (4) is a heat exchanger (3). Downstream of the autoclave, the CO.sub.2 is guided into a separation vessel (5) where the mono- and oligomers Z are collected. The gas removed from the separation vessel (5) is liquefied in a condenser (6) and fed back to the reservoir vessel (1).

[0048] FIG. 2 demonstrates a plant construction for a process II. In a departure from the apparatus of process I, the separation vessel is replaced by a pressure vessel (7) into which the CO2 is guided; this apparatus contains the adsorbent. The gas is subsequently conducted to the autoclave (4) via pump (2) and heat exchanger (3). The reservoir vessel (1) is not shown in FIG. 2; it is outside the circuit in order to assure an isobaric mode of operation.

[0049] The processes can be performed continuously. While the polyalkenamer-containing product mixture has been extracted in a first autoclave, a second autoclave may be equipped with further product mixture. After processing the first autoclave, supercritical or gaseous CO.sub.2, respectively, is directed to the second autoclave. The pressure in the first autoclave is relieved. This process has the advantage to use supercritical or compressed CO.sub.2 without any additional energy input.

[0050] The CO.sub.2 flows through the polyalkenamer-containing product mixture, for example, in a radial or axial manner. In the case of radial inflow, it has been found to be favourable when the flow direction leads from the outside inward. This gives rise to a backup, with the consequence that the CO.sub.2 is more homogeneously distributed in the bed.

[0051] The amount of supercritical CO.sub.2 is unrestricted. The ratio of the total weight of supercritical CO.sub.2 based on the total weight of the polyalkenamer-containing product mixture is preferably in the range of 1:1 to 500:1, preferably in the range of 10:1 to 200:1 and more preferably in the range of 20:1 to 50:1.

[0052] The CO.sub.2 may contain a cosolvent. Suitable cosolvents are selected from the group of the aromatic hydrocarbons such as toluene, alkanes, chlorinated alkanes, alcohols, alkanecarboxylic esters, aliphatic ketones, aliphatic ethers, water and mixtures thereof. A preferred cosolvent is hexane. It is preferred that the CO2 contains less than 10 wt.-% cosolvent, based on the mass of CO2 and cosolvent, more preferably 0.5-7.5 wt.-%, most preferably 1-6 wt.-%.

[0053] Oligomers in the context of this invention especially include the dimer, trimer and tetramer of the cycloalkene used. Polyalkenamers in the context of this invention are polymers of cycloalkenes comprising at least five cycloalkene monomer units.

[0054] It is preferable that the sum total of monomer, dimer, trimer and tetramer (impurities) in the polyalkenamer-containing composition is less than 20 000 ppm, based on the total weight of the composition. More preferably less than 10 000 ppm, even more preferably less than 3500 ppm and especially less than 1000 ppm of impurities are present.

[0055] The di-, tri- and tetramers are determined quantitatively as follows:

[0056] Sample preparation: 400 mg of sample in each case are weighed accurately into a 10 ml standard flask and about 8 ml of dichloromethane are added. With the aid of an agitator, the sample is dissolved (ideally overnight); subsequently, the standard flask is made up to the mark with dichloromethane and mixed again. 50 l of the sample solution thus obtained are injected with a microlitre syringe into a pad of silanized glass wool within a TDS tube. The tube is left to stand in a fume hood for about 30 minutes, so that the solvent can evaporate.

[0057] External standard solution: 50 mg of hexadecane are weighed accurately into a 100 ml standard flask, made up to the mark with methanol and homogenized by shaking. 5 l of this solution (corresponding to about 2.5 g) are applied to a Tenax tube. This external standard is analysed once at the start and once at the end of the sequence.

[0058] The determination was effected by means of an Agilent 6890 gas chromatograph with ChemStation software; parameters: Rtx-5 separation column; length: 60 m; internal diameter: 250 m; film thickness: 0.25 m; carrier gas: helium; column supply pressure: 203.1 kPa; oven temperature: 50 C.-10 C./min-320 C. (33 min); split: 50:1; detector temperature: 280 C. (Thermal Aux)). The thermal desorption unit has been set up as follows: Gerstel TDSA; TDS oven (initial temperature: 20 C.; equilibration time: 1 min; initial time: 0.5 min; heating rate: 60 C./min; end temperature: 280 C.; hold time: 10 min); cold application system (initial temperature: 150 C. (with liquid N.sub.2 cooling); equilibration time: 1 min; initial time: 0.5 min; heating rate: 10 C./s; end temperature: 300 C.; hold time: 5 min). In addition, the following settings were used: transfer temperature: 300 C.; desorption mode: Solvent VentingDry Purge; venting time: 0.5 min; sample mode: Remove Tube.

[0059] The semiquantitative evaluation was effected against the external standard hexadecane. The response factor is assumed to be 1. Only the peak groups corresponding to the oligomers are integrated. The dimers elute around 20 min, the trimers at about 28 min and the tetramers around 37 min. Whether the peaks belong to the integrated region is determined using the mass spectra, the oligomers being easily characterizable by the ion masses (e.g. m/z=220, m/z=330 and m/z=440: di-, tri- and tetramer of polyoctenamer, respectively).

[0060] The monomer was determined as follows: Sample preparation: 300 mg of sample are weighed accurately into each of 6 headspace vials, 5 ml of dodecane are added and the mixture is homogenized by agitation. Two mixtures are analysed as samples. To each of two further mixtures are added 5 l of the spiking solution. To each of the two other mixtures are added 10 l of the spiking solution. Spiking solution: 300 mg of cyclooctane and 40 mg of cyclooctene are weighed accurately into a 25 ml standard flask and made up to the mark with dodecane and homogenized by shaking. 5 ml of this solution are pipetted into a 25 ml standard flask and made up to the mark with dodecane and homogenized by shaking.

[0061] The determination was effected by means of an Agilent 7890 gas chromatograph with ChemStation software; parameters: separation column 1: fused silica CP-SIL 8CB; length: 50 m; internal diameter: 530 m; film thickness: 1 m; separation column 2: fused silica DB-WAX; length: 60 m; internal diameter: 530 m; film thickness: 1 m; carrier gas: nitrogen; column supply pressure: 10.15 psi; oven temperature: 50 C. (4 min)-5 C./min-130 C.-30 C./min-180 C. (10 min); injector temperature: 160 C.; detector temperature: 230 C.; detector H.sub.2 flow: 40 ml/min; detector air flow: 400 ml/min; make-up flow (N.sub.2): 25 ml/min.; headspace sampler: TurboMatrix 40 Perkin Elmer: oven temperature: 100 C.; needle temperature: 120 C.; transfer temperature: 150 C.; headspace pressure: 130 kPa; thermostating time: 60 min; pressure buildup time: 0.5 min; injection time: 0.16 min: needle residence time: 0.2 min; vial vent: yes. The quantitative evaluation was effected by the standard addition method on the two separation columns and over both spiking operations with a validated Excel sheet.

[0062] The conversion of the cycloalkene(s) can be conducted without solvent. Alternatively, the reaction can be conducted in at least one solvent. Suitable solvents are, for example, saturated aliphatic hydrocarbons such as hexane, heptane, octane, nonane, decane, dodecane, cyclohexane, cycloheptane or cyclooctane; aromatic hydrocarbons such as benzene, toluene, xylene or mesitylene; halogenated hydrocarbons such as chloromethane, dichloromethane, chloroform or carbon tetrachloride; ethers such as diethyl ether, tetrahydrofuran or 1,4-dioxane; ketones such as acetone or methyl ethyl ketone; esters such as ethyl acetate; and mixtures of the aforementioned solvents. More preferably, the solvent for the reaction is selected from the group consisting of aliphatic and aromatic hydrocarbons, here especially preferably hexane and toluene and especially hexane. Additionally selected with preference are tetrahydrofuran, methyl ethyl ketone, chloromethane, dichloromethane, chloroform or mixtures thereof, very particular preference being given to hexane or toluene. The content of solvents may be set, for example, to a value of 20% to 60% by weight, preferably of 40% to 60% by weight, based on the total weight of cycloalkene and solvent.

[0063] In the choice of solvents for the ring-opening metathesis reaction, it should be noted that the solvent should not deactivate the catalyst or the catalytically active species. This can be recognized by the person skilled in the art by simple experiments or by studying the literature. In the case of catalyst systems containing aluminium organyls, aromatic or aliphatic hydrocarbons bearing no heteroatoms are especially suitable.

[0064] In a further embodiment of the invention, the solvent mixture may contain a stabilizer. This can diffuse into the polyalkenamer and increase its storage stability and/or processing stability. Suitable stabilizers may be selected from the group of the sterically hindered phenols, for example 2,5-di-tert-butylhydroquinone, 2,6-di-tert-butyl-p-cresol, 4,4-thiobis(6-tert-butylphenol), 2,2-methylenebis(4-methyl-6-tertbutylphenol), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 4,4-thiobis-(6-tert-butylphenol), 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2,6-di(tert-butyl)-4-methylphenol (BHT), 2,2-methylenebis(6-tert-butyl-p-cresol), from the group of the organic phosphites, for example triphenyl phosphite, tris(nonylphenyl) phosphite, the group of the organic thio compounds, for example dilauryl thiodipropionate, pentaerythritol tetrakis(3-laurylthiopropionate) and ascorbic acid and mixtures thereof.

[0065] The stabilizer may be present within a range from 5 to 7500 ppm, preferably 25 to 750 ppm, based in each case on the weight-average molecular weight of the polyalkenamer, preferably polyoctenamer. It is possible to add the stabilizer according to one of the following steps:

[0066] The stabilizer can be incorporated into the melt of the polymer, for example via compounding in an extruder. The stabilizer can either be metered in directly or added via a masterbatch. This can also occur only in the course of further processing to give a blend with a polymer and/or the production of shaped bodies, for example films. Another option is to dissolve the stabilizer in a suitable solvent and to apply it to the particles of the polyalkenamer. Subsequently, the solvent is removed, for example by a drying step, in which elevated temperature and/or reduced pressure are used. The stabilizer then remains on the surface of the particles and/or is absorbed into the particles during the drying. Another option is to apply the stabilizer to the particles as a powder coating.

[0067] It is also possible to produce a mixture in which polyalkenamer particles including a stabilizer in a relatively high concentration are present alongside polyalkenamer particles containing no stabilizer or a lower concentration of stabilizer.

[0068] In addition, the polyalkenamer composition, preferably polyoctenamer composition, may contain dyes (soluble colourants).

[0069] In a preferred embodiment of the process according to the invention, the cycloalkene is selected from the group consisting of cyclobutene, cyclopentene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cyclododecene, cycloocta-1,5-diene, 1,5-dimethylcycloocta-1,5-diene, cyclodecadiene, norbornadiene, cyclododeca-1,5,9-triene, trimethylcyclododeca-1,5,9-triene, norbornene (bicyclo[2.2.1]hept-2-ene), 5-(3-cyclohexenyl)-2-norbornene, 5-ethyl-2-norbornene, 5-vinyl-2-norbornene, 5-ethylidene-2-norbornene, dicyclopentadiene and mixtures thereof. Particular preference is given to cyclopentene, cycloheptene, cyclooctene and cyclododecene. Cyclooctene is a very particularly preferred cycloalkene because of its availability and ease of handling. It is possible to use two or more cycloalkenes, so as to form copolymers of the polyalkenamer. The cycloalkenes may be substituted by alkyl groups, aryl groups, alkoxy groups, carbonyl groups, alkoxycarbonyl groups and/or halogen atoms.

[0070] In one embodiment of the process according to the invention, a standard solvent extraction can be conducted prior to the CO.sub.2 extraction or after the CO.sub.2 extraction. This can further reduce the proportion of monomers and oligomers. The solvent extraction can be undertaken within a temperature range from 20 C. up to the boiling range of the solvent mixture (reflux), preferably to 60 C., more preferably in the range from 30 C. to 50 C. and even more preferably in the range from 35 C. to 45 C. However, the temperature within the ranges of values mentioned is limited by the boiling point of the solvent and the properties of the polyalkenamers. For example, the temperature should not be above the melting point of a semicrystalline polymer or the glass transition temperature of an amorphous polymer, preferably at least 5 C. below the boiling range. It is possible in principle to extract the polyalkenamer in the molten state. However, this is less preferred since the discrete particles originally present can form lumps or coalesce. This reduces the surface area of the extraction material, and the extraction rate falls. As a result, the product obtained has to be converted back to a homogeneous particulate form after the extraction, for example by granulation or grinding.

[0071] Illustrative solvents for the solvent extraction may be selected from hexane, heptane, diamyl ether, diethyl ether, butyl butyrate, ethyl amyl ketone, butyl acetate, methyl isobutyl ketone, methyl amyl ketone, amyl acetate, ethyl n-butyrate, carbon tetrachloride, diethyl carbonate, propyl acetate, diethyl ketone, dimethyl ether, toluene, ethyl acetate, tetrahydrofuran, benzene, tetrachloroethylene, chloroform, methyl ethyl ketone, chlorobenzene, dichloromethane, chloromethane, 1,1,2,2-tetrachloroethane, ethylene dichloride, acetone, 1,2-dichlorobenzene, carbon disulphide, 1,4-dioxane, cresol, aniline, pyridine, N,N-dimethylacetamide, cyclohexanol, cyclohexanone, butyl alcohol, 2-butyl alcohol, acetonitrile, dimethyl sulphoxide, N,N-dimethylformamide, furfuryl alcohol, propylene glycol, 1,2-propylene carbonate, ethanol, methanol, propanol, isopropanol, butanols, ethylene glycol, ethylene carbonate, glycerol, water or mixtures thereof. The person skilled in the art will be able to find suitable solvents or mixtures by simple preliminary experiments.

[0072] The solvent extraction can be conducted in various forms; for example, it is possible to employ the principle of Soxhlet extraction, such that the material to be extracted is contacted semi-continuously with fresh solvent. The solvent extraction can also be conducted in such a way that, for example, in a stirred tank, the volume of solvent at a particular time is exchanged completely or partially for a new volume of solvent, in which case this can be repeated several times. In addition, it is possible to conduct the solvent extraction in such a way that a solvent recycling operation is integrated, in which case the recycling may relate to one or more components of the mixture. As the case may be, it may then be necessary to meter more of one or more of the components into the recyclate in order to re-establish the original mixing ratio. In addition, the solvent extraction can also be conducted in such a way that the ratio of the components changes in the course of the solvent extraction, in which case the change may be constant or occur in jumps.

[0073] The solvent extraction is preferably conducted under inert gas.

[0074] The temperature and/or the pressure can be kept constant during the solvent extraction. It is also conceivable that temperature or pressure are varied in the course of the extraction operation.

[0075] After the solvent extraction, the polyalkenamer-containing composition can be separated from the remaining solvent, for example, by decanting it off or filtering. Alternatively or additionally, a drying operation can be conducted, for example under reduced pressure and/or at elevated temperature, in order to remove the solvent.

[0076] The polyalkenamer-containing product mixture obtained in a) may be in solid form or dissolved in solvent. Preferably, the solvent is removed. This can be undertaken by heating or reducing the pressure, for example by means of vacuum degassing. Prior to the performance of step b) (CO.sub.2 extraction) or prior to the performance of an optional solvent extraction, the product mixture is preferably pelletized to particles, for example by strand pelletization or underwater pelletization, or pulverized, for example by spray-drying or grinding. In a preferred embodiment, the polyalkenamer-containing product mixture obtained in a) is in solid form and is pelletized or pulverized to particles prior to step b). Preferably, the mean mass of the particles is less than 100 g/1000, more preferably less than 10 g/1000 and especially preferably less than 1 g/1000. This includes mean masses up to a maximum size of 1000 g/1000. The particles preferably have a diameter of at least 0.3 mm, more preferably of at least 0.5 mm and most preferably of at least 0.8 mm.

[0077] To determine the mean mass, about 2-3 g of the particles are applied to a clean underlayer, for example a sheet of paper. Subsequently, all grains in this sample are counted and transferred to a petri dish; spikes of length >1.0 cm or chains of pellets >1.0 cm are excluded (discarded) and are not assessed here. The number of pellet grains is noted; it has to be min. 150. Subsequently, the pellet grains are weighed accurately to 0.1 g and expressed on the basis of 1000 pellets. If there are less than 150 pellet grains, a new, correspondingly larger particle volume has to be taken as sample.

[0078] The process according to the invention can be conducted continuously or batchwise.

[0079] The polyalkenamer, preferably polyoctenamer, preferably has a weight-average molecular weight (Mw) of 5000 g/mol to 500 000 g/mol, preferably of 10 000 g/mol to 250 000 g/mol and more preferably of 20 000 to 200 000 g/mol. The molecular weight is determined by means of Gel Permeation Chromatography (GPC) against a styrene standard. The measurement is based on DIN 55672-1.

[0080] Sample preparation: The samples are dissolved with a content of 5 g/l in tetrahydrofuran at room temperature. They are filtered prior to injection into the GPC system (0.45 m syringe filter). The measurement is effected at room temperature.

[0081] Column Combination

[0082] 15 cm, 5 m, 100 , (styrene-divinylbenzene copolymer)

[0083] 130 cm, 5 m, 50 , (styrene-divinylbenzene copolymer)

[0084] 130 cm, 5 m, 1000 , (styrene-divinylbenzene copolymer)

[0085] 130 cm, 5 m, 100 000 , (styrene-divinylbenzene copolymer)

[0086] Mobile phase: ultrapure tetrahydrofuran, stabilized

[0087] Flow rate: 1 ml/min

[0088] Detection: refractive index detector

[0089] Calibration: polystyrene

[0090] The desired molar mass can be established, for example, in the presence of at least one chain transfer agent, which allows the chain buildup to be stopped. Suitable chain transfer agents are, for example, acyclic alkenes having one or more non-conjugated double bonds which may be in terminal or internal positions and which preferably do not bear any substituents. Such compounds are, for example, pent-1-ene, hex-1-ene, hept-1-ene, oct-1-ene or pent-2-ene. In addition, it is possible to use cyclic compounds having a double bond in the side chain thereof, for example vinylcyclohexene.

[0091] The cis/trans ratio of the cycloalkenamers can be adjusted by methods familiar to the person skilled in the art. For example, the ratio is dependent on catalysts, solvents, stirring intensity or temperature or reaction time. Preferably, the trans content is at least 55%. The cis/trans ratio is determined by means of .sup.1H NMR in deuterochloroform.

[0092] The conversion of the cycloalkene can be effected in the presence of at least one catalyst. Suitable catalysts are, for example, transition metal halides which, together with an organometallic compound as cocatalyst, form the species which is catalytically active for the polymerization. The metal in the organometallic compound differs here from the transition metal in the halide. Alternatively, it is possible to use transition metal-carbene complexes. Useful transition metals include metals of groups 4 to 8, for example molybdenum, tungsten, vanadium, titanium or ruthenium. Metals in the organometallic compound are, for example, aluminium, lithium, tin, sodium, magnesium or zinc. Suitable catalysts and the amounts thereof to be used are detailed, for example, in EP-A-2017308.

[0093] Preference is given to using a catalyst system containing at least one alkylaluminium chloride, tungsten hexachloride or mixtures. Suitable alkylaluminium chlorides are ethylaluminium dichloride (EtAlCl.sub.2) and ethylaluminium sesquichloride, which may also be used in mixtures. A preferred catalyst system contains tungsten hexachloride and ethylaluminium dichloride or, in a particularly preferred embodiment, consists of these two compounds. The mass ratio of the aluminium chlorides to tungsten hexachloride is preferably one to six. Particular preference is given to a ratio of two to five. To activate the catalyst, acidic compounds such as alcohols can be used.

[0094] The tungsten hexachloride can be used within a range from 0.1 to 0.04 mol %, more preferably from 0.1 to 0.01 mol %, based on the cycloalkene used. The alkylaluminium chlorides are preferably within a range from 0.2 to 0.08 mol %, more preferably 0.2 to 0.02 mol %, based on cycloalkene.

[0095] The conversion of the cycloalkenes can be conducted either isothermally or adiabatically. The temperature is preferably within a range between 20 and 120 C. This is dependent particularly on the monomers used and any solvent present. A particularly preferred temperature is in the range from 10 to 60 C. The reaction preferably takes place in a protective gas atmosphere. In the case of an adiabatic process regime, the temperature can be determined via parameters such as amount of catalyst, rate of catalyst addition, time of termination of the reaction, etc. The preferred temperature range here is 20 to 50 C.

[0096] On attainment of the desired reaction time, the polymerization can be ended by inactivation of the catalyst system. For this purpose, for example, it is possible to add a suitable amount of CH-acidic compound. Suitable examples for this purpose are alcohols such as methanol, ethanol, propanol, etc., or else carboxylic acids such as acetic acid.

[0097] The polyalkenamer-containing composition obtained by the process according to the invention can be used in packaging materials, wherein the packaging materials are preferably used for food and drink.

EXAMPLES

[0098] A. Polymer

[0099] Vestenamer 8012 (Polyoctenamer) of Evonik, Germany was used as the polyalkenamer-containing product mixture (average dimension of the granules is about 3 mm3 mm4 mm). Before extraction, it was refined by a re-granulation process. Vestenamer 8012 was fed into a twin screw extruder Werner&Pfleiderer ZSK30 via the main hopper. The barrel temperature was 125 C. A screw speed of 250 rpm was applied and the throughput of the polymer was chosen to be 6 kg/h. The effective melt temperature at the die was measured with a thermometer to be 186 C. After leaving the front plate of the extruder at the die the melt strand was cooled in a water bath and after that in air. Then the polymer strand was pelletized with a pelletizer (cutter). The cutter was operated at a strand speed of 57 m/min. The re-granulation process was conducted until an amount of 100 kg of polymer (average dimension of the granules is about 1 mm1 mm1 mm) was obtained.

[0100] Determination of Molecular Weight

[0101] The molecular weights of the polymers were determined by gel permeation chromatography (method: cf. description).

TABLE-US-00001 Mn in g/mol Mw in g/mol Mp in g/mol Polydispersity Polymer 8600 130700 92900 15.0

[0102] Mn=number average molecular weight

[0103] Mw=weight average molecular weight

[0104] Mp=peak molecular weight

[0105] Trans content of double bonds

[0106] The trans-content of double bonds of both polymers was determined by .sup.1H NMR in deuterochloroform (CDCl.sub.3). The trans-content was 80% for the polymer.

[0107] Average Particle Weight

[0108] The average weight of the particles is 2.1 g/1000.

[0109] (method: cf. description)

[0110] Oligomers Before Extraction

TABLE-US-00002 Dimer/mg/kg Trimer/mg/kg Tetramer/mg/kg Polymer 4805 9110 6653

[0111] B. Extraction

[0112] The autoclave of an extraction system according to FIG. 1 (process I) was charged with the polyoctenamer-containing composition to be worked up (extraction material; polymer). Stages b0, b1, b2 and b3 were conducted in the same plant.

[0113] In a non-inventive example #1 the polymer was extracted by steps b0 and b1 without stages b2 and b3. An inventive example #2 comprised steps b0, b1, b2 and b3. In both cases the sum of CO.sub.2 (solvent/feed ratio) were identical.

[0114] Stages b0 and b1

[0115] Carbon dioxide was set above the critical pressure by means of a high-pressure pump. The heat exchanger was closed manually and the extraction valve was partially open on manual mode for dissipating compression heat. The temperature was 20 C. (below the critical conditions). The carbon dioxide was in the liquid state of matter and flew into the composition in the autoclave until extraction pressure (260 bar) was matched (duration: 10 minutes). From now on step b1 started and the heat exchanger was on extraction temperature (40 C.), the extraction valve was working on automatically mode (set point 260 bar) and the carbon dioxide flew through the composition in the autoclave.

[0116] The process was conducted with a separator (process I). The autoclave was charged with the polyoctenamer. The CO.sub.2 was withdrawn from a reservoir vessel and brought to the supercritical extraction pressure with a high-pressure pump. The temperature (increased by the heat exchanger) was above the critical temperature of CO.sub.2. Subsequently, the supercritical CO.sub.2 flew continuously through the autoclave with the extraction material in an axial manner by means of the same high-pressure pump, and the CO.sub.2-soluble mono- or oligomers dissolved accordingly. The supercritical carbon dioxide was guided continuously through the extraction material.

[0117] The laden CO.sub.2 was then expanded into a separator under non-supercritical conditions (pressure <73.8 bar, temperature <31 C.). This cooled the gas down to give a wet vapour. An extract-rich liquid gas phase and a virtually extract-free gas phase were formed. For the separation, the liquid carbon dioxide was evaporated continuously at 45 bar and then brought to the separation temperature of 27 C. in an isobaric manner. The substances dissolved in the liquid CO.sub.2 separate out continuously in the vessel bottoms.

[0118] The gaseous CO.sub.2 was drawn off continuously in unladen form from the top space of the separator, liquefied in a condenser at 12 C. and 45 bar and fed back to the reservoir vessel of the high-pressure pump.

[0119] If the CO.sub.2-soluble substances had been extracted completely (the amount of CO.sub.2 needed for this purpose was determined empirically), the extraction was complete. The empirical determination was effected by conducting the extraction in several steps and determining the amount of oligomers obtained. The determination had ended when virtually no oligomers were obtained any longer in the separator.

[0120] Stage b2

[0121] The autoclave containing the partial cleaned polyoctenamer was then decompressed to atmospheric pressure. The CO.sub.2 changed its physical condition to gaseous. The gaseous state was kept for 75 minutes.

[0122] Stages b0 and b3

[0123] Steps b0 and b3 were running equal to former step b0 and step b1. 2075 kg of CO.sub.2 were used in each case (b1 or b3, respectively). The autoclave containing the cleaned polyoctenamer was then decompressed.

[0124] Results of the Extraction

TABLE-US-00003 Starting Stage Extraction Extraction weight/ b2 pressure/ temperature/ # kg and b3 S/F bar C. 1* 83 no 50 260 40 2 83 yes 50 (25 b1 and 25 b3) 260 40 *non-inventive

[0125] Evaluation

[0126] The oligomers were determined in a double determination according to the instructions in the description.

TABLE-US-00004 Tetramer/ # Dimer/mg/kg Trimer/mg/kg mg/kg Polymer** 4805 9110 6653 1* <100 <100 1321 2 <100 <100 1087 *= non inventive **before extraction

[0127] By performing the inventive extraction method, it was possible to significantly reduce oligomers compared to the product mixture that had not been worked up with steps b2 and b3.