Process for preparing polyalkenamers for packaging applications

Abstract

A process for producing cycloalkenamer-containing compositions involves converting at least one cycloalkene by ring-opening metathetic polymerization to obtain a polyalkenamer-containing product mixture. The product mixture is worked up to remove monomers and oligomers of the cycloalkenes to obtain the polyalkenamer-containing composition by extraction with CO.sub.2. The extraction involves at least two stages: an extraction with liquid CO.sub.2 under the supercritical conditions, and then an extraction with supercritical CO.sub.2. Such cycloalkenamer-containing compositions can be used, for example, in the field of packaging materials, especially for food and drink.

Claims

1. A process of preparing a packaging material, the process comprising producing a polyalkenamer-containing composition by a process comprising: a) converting at least one cycloalkene by ring-opening metathetic polymerization to obtain a polyalkenamer-containing product mixture, and b) working up the polyalkenamer-containing product mixture by an extraction with CO.sub.2, thereby removing at least one monomer and/or at least one oligomer of the at least one cycloalkene to obtain the polyalkenamer-containing composition, wherein the extraction comprises at least two stages: b1) an extraction with liquid CO.sub.2 and then b2) an extraction with supercritical CO.sub.2 wherein the polyalkenamer-containing composition is suitable for a packaging material.

2. The process according to claim 1, wherein the extraction in stage b1 is conducted at a temperature in the range from 0 C. to 99 C. and a pressure in the range from 10 bar to 1000 bar, and wherein the extraction in stage b1 comprises keeping CO.sub.2 in liquid form by adjusting pressure and temperature with respect to one another.

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

4. The process according to claim 1, wherein the extraction in stage b2 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 a 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, further comprising separating CO.sub.2 extractant from the at least one monomer and/or at least one oligomer.

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

8. The process according to claim 6, wherein the CO.sub.2 extractant is supercritical and an adsorbent takes up the at least one monomer and/or at least one oligomer.

9. The process according to claim 8, wherein a pressure is maintained with respect to step b2 and a temperature is reduced, providing isobaric conditions.

10. The process according to claim 8, wherein the adsorbent is selected from the group consisting of activated carbon, alumina, silica and mixtures thereof.

11. 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.

12. The process according to claim 1, wherein converting at least one cycloalkenes is conducted in the presence of a catalyst.

13. The process according to claim 12, wherein the catalyst comprises at least one transition metal halide and an organometallic compound or wherein the catalyst comprises at least one transition metal-carbene complex.

14. The process according to claim 1 wherein the packaging material is suitable as a food packaging and/or a drink packaging.

15. The process according to claim 1, wherein no supercritical CO.sub.2 is present in b1) the extraction with liquid CO.sub.2, and wherein a polyalkenamer in the polyalkenamer-containing composition is not sintered or compressed in b) working up the product mixture.

16. The process according to claim 1, wherein the polyalkenamer-containing composition has a total content of monomer, dimer, trimer, and tetramer impurities of less than 20,000 ppm.

17. The process according to claim 1, wherein a polyalkenamer component of the polyalkenamer-containing composition has a weight-average molecular weight (Mw) of 5000 g/mol to 500 000 g/mol.

18. A process for producing a polyalkenamer-containing composition, the process comprising: a) converting at least one cycloalkene by ring-opening metathetic polymerization to obtain a polyalkenamer-containing product mixture, and b) working up the polyalkenamer-containing product mixture by an extraction with CO.sub.2, thereby removing at least one monomer and/or at least one oligomer of the at least one cycloalkene to obtain the polyalkenamer-containing composition, wherein the extraction comprises at least two stages: b1) an extraction with liquid CO.sub.2 and then b2) an extraction with supercritical CO.sub.2, wherein the polyalkenamer-containing product mixture obtained in a) is in solid form and is granulated or pulverized to particles prior to b) working up the product mixture.

Description

(1) 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).

(2) 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 CO.sub.2 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.

(3) 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 CO.sub.2 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.

(4) 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.

(5) 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.

(6) 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 CO.sub.2 contains less than 10 wt.-% cosolvent, based on the mass of CO.sub.2 and cosolvent, more preferably 0.5-7.5 wt.-%, most preferably 1-6 wt.-%.

(7) 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.

(8) 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.

(9) The di-, tri- and tetramers are determined quantitatively as follows:

(10) 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.

(11) 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.

(12) 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.

(13) 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).

(14) The monomer was determined as follows:

(15) 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.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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:

(21) 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.

(22) 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.

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

(24) 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.

(25) 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.

(26) 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.

(27) 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.

(28) The solvent extraction is preferably conducted under inert gas.

(29) 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.

(30) 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.

(31) 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.

(32) 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.

(33) The process according to the invention can be conducted continuously or batchwise.

(34) The polyalkenamer, preferably polyoctenamer, preferably has a weight-average molecular weight (M.sub.w) 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.

(35) 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.

(36) Column Combination

(37) 15 cm, 5 m, 100 , (styrene-divinylbenzene copolymer)

(38) 130 cm, 5 m, 50 , (styrene-divinylbenzene copolymer)

(39) 130 cm, 5 m, 1000 , (styrene-divinylbenzene copolymer)

(40) 130 cm, 5 m, 100 000 , (styrene-divinylbenzene copolymer)

(41) Mobile phase: ultrapure tetrahydrofuran, stabilized

(42) Flow rate: 1 ml/min

(43) Detection: refractive index detector

(44) Calibration: polystyrene

(45) 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.

(46) 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.

(47) 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.

(48) 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.

(49) 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.

(50) 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.

(51) 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.

(52) The invention likewise provides for the use of at least one polyalkenamer-containing composition according to the invention or of at least one composition obtained by the process according to the invention in packaging materials, wherein the packaging materials are preferably used for food and drink.

EXAMPLES

(53) A. Polymer

(54) Polymer 1: Vestenamer 8020 (Polyoctenamer) of Evonik, Germany was used as the polyalkenamer-containing product mixture (average dimension of the granules is about 3 mm3 mm4 mm).

(55) Polymer 2: Polymer 2 was produced from polymer 1 by a re-granulation process. Polymer 1 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 2 (average dimension of the granules is about 1 mm1 mm1 mm) was obtained.

(56) Determination of Molecular Weight

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

(58) TABLE-US-00001 Mn in g/mol Mw in g/mol Mp in g/mol Polydispersity Polymer 1 8700 156100 114000 18.0 Polymer 2 9100 164300 116900 18.1 Mn = number average molecular weight Mw = weight average molecular weight Mp = peak molecular weight
Trans Content of Double Bonds

(59) 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 polymer 1 and polymer 2.

(60) Average Particle Weight

(61) Polymer 1: The average weight of the particles is 54.0 g/1000.

(62) Polymer 2: The average weight of the particles is 2.1 g/1000.

(63) (method: cf. description)

(64) Oligomers Before Extraction

(65) TABLE-US-00002 Tetramer/ Monomer/mg/kg Dimer/mg/kg Trimer/mg/kg mg/kg Polymer 1 42 3520 9576 6487 Polymer 2 18 1629 9969 6604
B. Extraction

(66) The autoclave of an extraction system according to FIG. 1 (process I) or FIG. 2 (process II) is charged with the polyoctenamer-containing composition to be worked up (extraction material; polymer 1 or polymer 2). Stages b1 and b2 are conducted in the same plant.

(67) Stage b1

(68) Carbon dioxide is set above the critical pressure by means of a high-pressure pump. The heat exchanger is closed manually. The temperature is 20 C. (below the critical conditions). The carbon dioxide is in the liquid state of matter and flows through the composition in the autoclave. 20 kg of CO.sub.2 were used in each case.

(69) Stage b2Process I

(70) The process is conducted with a separator (process I). The autoclave is charged with the polyoctenamer. The CO2 is withdrawn from a reservoir vessel and brought to the supercritical extraction pressure with a high-pressure pump. The temperature (increased by the heat exchanger) is above the critical temperature of CO2. Subsequently, the supercritical CO2 flows continuously through the autoclave with the extraction material in an axial manner by means of the same high-pressure pump, and in so doing dissolves the CO.sub.2-soluble mono- or oligomers. The supercritical carbon dioxide is guided continuously through the extraction material.

(71) The laden CO2 is then expanded into a separator under non-supercritical conditions (pressure<73.8 bar, temperature<31 C.). This cools the gas down to give a wet vapour. An extract-rich liquid gas phase and a virtually extract-free gas phase are formed. For the separation, the liquid carbon dioxide is 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 CO2 separate out continuously in the vessel bottoms.

(72) The gaseous CO2 is 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.

(73) If the CO2-soluble substances have been extracted completely (the amount of CO2 needed for this purpose is determined empirically), the extraction is complete. The empirical determination is effected by conducting the extraction in several steps and determining the amount of mono- and oligomers obtained. The determination has ended when virtually no mono- or oligomers are obtained any longer in the separator.

(74) The autoclave containing the cleaned polyoctenamer is then decompressed. The polyoctenamer can be removed from the autoclave for oligomer determination.

(75) Addition of Cosolvent

(76) First of all, 750 g or 1500 g of acetone (5% by weight or 10% by weight) or 750 g of hexane (5% by weight) are mixed into the CO2 until S/F=15. Subsequently, the vessel volume of the autoclave is exchanged twice with CO2. Thereafter, CO2 is added without cosolvent with S/F=35. The cosolvent is removed by initially charging 1000 g of water in the separator, in order to wash the cosolvent out of the gas phase.

(77) Stage b2Process II

(78) In a departure from process I, no separator is used. However, a vessel arranged downstream of the autoclave containing 300 g of activated carbon as adsorbent. The process is conducted in an isobaric and isothermal manner. The S/F values are correspondingly higher.

(79) Results of the Extraction after Performance of Stage b2

(80) TABLE-US-00003 Extraction Extraction Starting Stage pressure/ temperature/ # weight/g b1 Process S/F bar C. Cosolvent Adsorbent Comments 1* 1500 no I 60 260 35 no no polymer 1; granules sintered 2* 2000 no I 50 260 35 no no granules sintered 3 1000 yes I 50 420 40 no no no sintering 4 1000 yes I 50 260 40 5% no no sintering acetone 5 1000 yes I 50 260 40 10% no no sintering acetone 6 1000 yes I 50 260 40 no no no sintering 7 2200 yes I 50 260 43 no no no sintering 8 1000 yes I 50 260 40 5% no no sintering hexane 9 800 yes II 400 260 40 no activated no sintering carbon 10 1000 yes II 200 250-270 40 no activated no sintering carbon *noninventive

(81) Unless stated otherwise, polymer 2 was used.

(82) The experiments without the first extraction stage b1 lead to sintering of the polyoctenamer granules used, both in the case of size 3 mm3 mm4 mm (polymer 1) and in the case of size 1 mm1 mm1 mm (polymer 2) (examples 1 and 2). If, in contrast, liquid CO.sub.2 is used at first, no sintering of the granules is observed.

(83) Evaluation

(84) The mono- and oligomers were determined in a double determination according to the instructions in the description.

(85) TABLE-US-00004 Tetramer/ # Monomer/mg/kg Dimer/mg/kg Trimer/mg/kg mg/kg Polymer 2 18 1629 9969 6604 3 1 <100 156 1797 4 n.d. <100 223 1389 5 n.d. 199 1010 2883 6 2 <100 525 2472 7 n.d. <100 810 2199 8 n.d. <100 <150 1913 9 3 <100 <150 1276 10 3 <100 <150 1763 n.d. = not determined

(86) By the extraction method, it was possible to significantly reduce oligomers compared to the product mixture that had not been worked up. If the extraction pressure is increased (420 bar in Example 3 compared to 260 bar in Example 6), the oligomer content can be lowered further. The use of a cosolvent (Examples 4, 5 with acetone and 8 with hexane) has an entirely positive effect on the result, but the proportion of the cosolvent must not become too high: Example 4 with 5% acetone shows better extraction results than Example 5 with 10% acetone. An increase in the extraction temperature from 35 C. or 40 C. to 43 C. does not show any significant effect.

(87) Process II (Examples 9, 10), just like process I (Examples 3 to 8), is suitable for the oligomer removal. Compared to process I, lower oligomer contents are determined.