Process for preparing polyalkenamers for packaging applications
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 2 . The extraction involves at least two stages: an extraction with liquid CO 2 under the supercritical conditions, and then an extraction with supercritical CO 2 . Such cycloalkenamer-containing compositions can be used, for example, in the field of packaging materials, especially for food and drink.
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 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 2 and then
b2) an extraction with supercritical CO 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 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 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 2 per polyalkenamer-containing product mixture.
6. The process according to claim 1 , further comprising separating CO 2 extractant from the at least one monomer and/or at least one oligomer.
7. The process according to claim 6 , wherein the CO 2 extractant is gaseous.
8. The process according to claim 6 , wherein the CO 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 2 is present in b1) the extraction with liquid CO 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 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 2 and then
b2) an extraction with supercritical CO 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.