Solvent-based recycling with a roll-to-roll processing step

Abstract

Subject-matter of the present invention is a method for removing at least one polymer component from plastic waste film material, wherein the plastic waste film material comprises at least a first polymer to be solved and a second polymer component, wherein the method comprises the steps of moving said plastic film material across at least one solvent bath which is filled with a solvent, wherein said solvent is a solvent for the first polymer component to be solved, and wherein at least the second polymer component is non-soluble in said solvent.

Claims

1. Method for removing at least one polymer component from plastic waste film material, wherein the plastic waste film material comprises at least a first polymer component to be solved and a second polymer component, wherein the method comprises the steps of (i) moving the plastic film material across at least one solvent bath, which is filled with a solvent, wherein the solvent is a solvent for at least the first polymer component to be solved, and wherein at least the second polymer component is non-soluble in the solvent, wherein said plastic film material is rolled material, and wherein said plastic film material is being passed by at least a rolling drum across at least one bath which is filled with the solvent.

2. Method according to claim 1, wherein the plastic film material is subject to mechanical pretreatment including a washing step.

3. Method according to claim 1, comprising a step of decolorization of the solved first polymer component.

4. Method according to claim 1, wherein the bath and the space above said bath are arranged in a gas-tight system.

5. Method according to claim 1, wherein the solvent bath has an average temperature of at least 30° C., preferably of at least 40° C., more preferably of at least 60° C., even more preferably of at least 80° C. even more preferably of at least 100° C., even more preferably of at least 120° C., even more preferably of at least 140° C.

6. Method according to claim 1, wherein the solvent is selected from the group comprising ketones such as acetone, butanone, esters such as ethyl acetate, benzyl acetate, organic acids such as formic acid or acetic acid, alkanes such as n-heptane or n-octane, cyclic alkanes such as cyclohexane and methylcyclohexane, water and/or mixtures thereof.

7. Method according to claim 1, wherein the solvent of the least one bath is an aqueous solution, wherein said aqueous solution is selected from the group comprising acids and bases, preferably NaOH, NH3, HCl, HNO3, acetic acid and/or mixtures thereof.

8. Method according to claim 1, wherein said first polymer component to be solved is selected from the group comprising polymeric components, additives, impurities, metal components, printing inks, adhesives and/or mixtures thereof.

9. Method according to claim 8, wherein the first polymer is selected from the group comprising low-density polyethylene (LDPE), polypropylene (PP), high density polyethylene (HDPE), polyamide (PA) and/or combinations thereof.

10. Method according to claim 1, wherein said second polymer component is selected from the group comprising secondary components, auxiliary components, polymeric components, additives, impurities, metal components, printing inks, adhesives and/or combinations thereof.

11. Method according to claim 1, a wherein the solvent is separated from the solved first polymer component by thermal solvent separation, mechanical solid-liquid separation, cross-flow filtration and/or Flash evaporation.

12. Method according to claim 11, wherein said plastic film material is delivered from the rolling drum(s) to an extruder.

13. Method according to claim 1, wherein said plastic film material is selected from the group comprising plastic waste, post-industrial use polymers and combinations thereof, complex plastics comprising numerous polymeric and non-polymeric components, plastic films, polymeric film, multilayer films, polymer multilayer films, foils, plastic foils, multilayer foils, trays, plastic trays, multilayer trays, plastic composites, metal-plastic composites, paper-metal plastic composites, paper-plastic composites.

14. Method according to claim 13, wherein said plastic film material is selected from the group comprising PE/Al/PET, PE/PET, PE/PA, PE/PP, and/or a combination of polymer/polymer, polymer/metal, polymer/metal/polymer etc.

15. Method according to claim 14, wherein said film comprises at least two layers, polymer/polymer or polymer/metal.

16. Method according to claim 14, wherein said layers of the multilayer film are selected from the group comprising a layer of polymeric components, metal layers, paper layers and/or combinations thereof.

Description

FIGURE DESCRIPTION

[0222] FIG. 1: Presentation of the claimed method, wherein the plastic film material (6) is being passed by at least 4 rolling drums (1, 2, 3, 4) across at least one rinsing bath (7) which is filled with a solvent (5) and/or mixture thereof. The rolling drums are designed towards each other to move said plastic film material in a continuous flow (8) across said at least one bath. The arrows (9) indicate the direction of rotation of the rolling drum.

[0223] FIG. 2: IR spectrum of the upper and bottom layers of the PE/PA film before being dissolved

[0224] FIG. 3: DSC of the PE/PA film before being dissolved

[0225] FIG. 4: DSC of the extracted material of the PE/PA film

[0226] FIG. 5: DSC of the undissolved material of the PE/PA film

[0227] FIG. 6: IR spectrum of the upper and bottom layers of the PE/PA/PE film before being dissolved

[0228] FIG. 7: DSC of the PE/PA/PE film before being dissolved

[0229] FIG. 8: DSC of the extracted material of the PE/PA/PE film

[0230] FIG. 9: DSC of the undissolved material of the PE/PA/PE film

[0231] FIG. 10: IR spectrum of the upper and bottom layers of the PE/PET film before being dissolved

[0232] FIG. 11: DSC of the PE/PET film before being dissolved

[0233] FIG. 12: DSC of the material extracted by methyl cyclohexane from the PE/PET film

[0234] FIG. 13: DSC of the undissolved material of the PE/PET film after the extraction with methyl cyclohexane

[0235] FIG. 14: DSC of the material extracted by a 50:50 v/v mixture of n-heptane and methyl cyclohexane from the PE/PET film

[0236] FIG. 15: DSC of the undissolved material of the PE/PET film after the extraction with a 50:50 v/v mixture of n-heptane and methyl cyclohexane

EXAMPLES

Example 1

[0237] Process for extraction of PE from plastic film waste comprising PE [0238] 1. Preparation of PE film waste by mechanical pretreatment including a washing step with water at room temperature. [0239] 2. Moving said PE film material across a rinsing bath which is filled with n-heptane at 90° C., wherein n-heptane is a solvent for the first polymer component to be solved, wherein said second polymer component is non-soluble in n-heptane in order to enrich the plastic film material with the second polymer component. [0240] 3. Dissolution of PE at 90° C. in n-heptane in 60 min. For this step, the plastic film waste is treated in a stirred rinsing bath with the solvent n-heptane for 60 min. [0241] 4. The undissolved phase represents the film drawn from the rolls, no complex solid-liquid separation needs to be provided. The film is purged by air or nitrogen and dried and can then be extruded or resold as a rewound film.

Example 2

[0242] According to this example plastic waste is provided that comprises 98 wt % transparent foil, 2 wt % colored foil, 4 wt % HDPE-Foil, and less than 0.2 wt % of metal and wood (based on total weight of solid content). The transparent foil and colored foil largely comprises LDPE. It is perforated and optionally washed and then inserted into a solvent of heptane at an average temperature of 85 to 95° C. for 60 min resulting in a suspension or solution comprising dissolved LDPE. Afterwards undissolved components of said suspension are removed by mechanical solid-liquid separation in a centrifuge. Cross-flow filtration using a membrane with a pore size of 180 kDa made out of polysulfone forms a feedstock comprising LDPE. Said feedstock may have a gel-like consistency. It is degassed and extruded resulting in LDPE polymer pellets.

Example 3

[0243] Example for a method for recycling plastic material comprising a solvent-based extraction of a thermoplastic target polymer from a suspension or a solution, wherein a cross-flow filtration unit having a membrane is used. The following steps are performed: [0244] 1. Washing of a PE/PA-multilayer (20-90 wt % PE, mean value 70%) material from post-industrial source [0245] 2. Moving said PE/PA-multilayer s into a n-heptane solvent bath to achieve a 5 wt % solution knowing rate of PE in input, where the solvent bath is under temperature at 90° C. [0246] 3. Separating dissolved polymer and plastic film comprising non-dissolved PA- [0247] 4. Adding Ethyl Acetate as polar extractant, that isn't solvent for PE with 50 wt % to achieve a 10 wt % polymer solution counting solvent/non-solvent system together [0248] 5. To reduce solvent content increase pressure of the solution up to 10 bar and press it through a membrane unit, applying a Polyethersulfone-membrane with a pore size >0.1 μm to enable micro filtration [0249] 6. Solution with reduced solvent content (50 wt %) extrudes in a twin-screw de-gassing extruder with a melt filtration unit. At the end of the extruder there is a underwater pelletizing system to achieve polymer pellets as a final product [0250] 7. Polyamide-flakes are directly extrudes in a twin-screw degassing extruder with melt filtration and underwater pelletizing system,

Example 4

[0251] Analysis of the PE/PA Film

[0252] Infrared Spectroscopy

[0253] The upper and the bottom layers of the film were analyzed by attenuated total reflectance IR (FIG. 2). The IR-spectrum of the upper layer corresponds to PA and the IR-spectrum of the bottom layer corresponds to PE (characteristic peaks are defined in Table 9).

TABLE-US-00003 TABLE 9 Characteristic IR peaks of PE and PA. LDPE/HDPE CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3 CH.sub.3 (CH.sub.2).sub.n (CH.sub.2).sub.n Area 2975- 2940- 2870- 1480- 1465- 1390- 732-728 722-712 [cm-1] 2950 2915 2840 1440 1440 1370 PA6 NH CH.sub.2 CH.sub.2 C═O NH—C═O CH.sub.2 (CH.sub.2).sub.n (CH.sub.2).sub.n Area 3300- 2940- 2870- 1641 1542 1480- 732-728 722-712 [cm-1] 3000 2915 2840 1440

[0254] Differential Scanning Calorimetry

[0255] The material was analyzed by differential scanning calorimetry (FIG. 3)

[0256] According to the DSC analysis, the material has the following composition:

TABLE-US-00004 TABLE 10 Composition of the PA/PE material Peak of the Melting Identified Calculated Mass Sample area Component fraction PA/PE 111.6 ° C. LDPE 65 % 122.1 ° C. LLDPE 10 % 219.8 ° C. PA 6 25 %

[0257] Based on the IR and DSC data, the analyzed film contains at least two layers: the upper layer of PA and the bottom layer of PE.

[0258] Process for extraction of PE from PE/PA film

[0259] 640 g of methylcyclohexane was poured into a beaker. The solvent was heated to 95° C. A sample of a PE/PA film with the dimensions 7×26 cm was fixed on a cylindrical base and placed into a solvent bath for 30 minutes under stirring. The cylindrical base was freely transmissible for the solvent. After that the undissolved material was removed and the solvent was evaporated under reduced pressure to obtain the extracted material. The extracted material and the undissolved material were analyzed by DSC (FIGS. 4 and 5).

[0260] Fixing the film on a cylindrical base provides the fixed and directed path of the film through a solvent bath, prevents rolling the material up and ensures that the largest possible surface area of the film is in contact with the solvent. An unfixed material tends to roll up due to the different expansion of the film polymeric components and bends in the direction of the material that has the lower coefficient of linear expansion. Fixing the film on the cylindrical base prevents this process and serves for perfect modelling the conditions of a process, in which a plastic film material is being passed at least a rolling drum across at least one solvent bath. As a result, tensions in the material arise, which promote the penetration of the solvent into the material and hence increase the yield of the dissolution and decrease the dissolution time, thus improving the efficiency of the dissolution process.

[0261] The results of the experiments are summarized in Table 11.

TABLE-US-00005 TABLE 11 Overview of the experiments with the fixed PE/PA film and an edge length of 7 × 26 cm Experiment 1 Experiment 2 Experiment 3 Mass of solvent 640.52 g 640 g 640.53 g Temperature of solvent 95 ° C. 95 ° C. 95 ° C. Stirring time 30 min 30 min 30 min Initial mass of foil 4.72 g 5.02 g 4.61 g Mass of dissolved fraction 3.01 g 3.2 g 3.1 g Mass of undissolved 1.53 g 1.66 g 1.52 g fraction Theoretical yield (PE) 3.53 g 3.75 g 3.44 g Yield 85.4% 85.3% 90.0%

[0262] The results of the DSC analyses of the dissolved and undissolved materials are summarized in Table 12.

TABLE-US-00006 TABLE 12 Overview of the DSC analyses of the dissolved and undissolved components. LDPE LLDPE PA Experiment 1 dissolved 68 % 32 % 0 % Experiment 1 undissolved % 3 % 97 % Experiment 2 dissolved 70 % 30 % 0 % Experiment 2 undissolved % 9 % 91 % Experiment 3 dissolved 70 % 30 % 0 % Experiment 3 undissolved % 1 % 99 %

Example 5

[0263] Analysis of the PE/PA/PE Film

[0264] Infrared Spectroscopy

[0265] The upper and the bottom layers of the film were analyzed by attenuated total reflectance IR (FIG. 6). The IR-spectra of the upper layer and the bottom layer correspond to PE (characteristic IR peaks are defined in Table 9).

[0266] Differential Scanning Calorimetry

[0267] The material was analyzed by differential scanning calorimetry (FIG. 7).

[0268] According to the DSC analysis, the material has the following composition:

TABLE-US-00007 TABLE 13 Composition of PE/PA/PE material. Sample Melting point Component Mass fraction PE/PA/PE 109.4 ° C. LDPE 46 % 117.1 ° C. LLDPE 33 % 206.2 ° C. PA 6.66 22 %

[0269] Presence of PA was confirmed. Based on the IR and DSC data, the analyzed film contains at least three layers: the upper and the bottom layers of PE and the middle layer of PA.

[0270] Process for extraction of PE from PE/PA/PE film

[0271] The extraction of PE from a PE/PA/PE film was performed analogously to Example 4. The extracted material and the undissolved material were analyzed by DSC (FIGS. 8 and 9).

[0272] The results of the experiments are summarized in Table 14.

TABLE-US-00008 TABLE 14 Overview of the experiments with the fixed PE/PA/PE film and an edge length of 7 × 26 cm Experiment 1 Experiment 2 Experiment 3 Mass of solvent 640.06 g 640.14 g 640.48 g Temperature of solvent 95 ° C. 95 ° C. 95 ° C. Stirring time 30 min 30 min 30 min Initial mass of foil 3.42 g 3.07 g 2.72 g Mass of dissolved 1.13 g 1 g 0.9 g fraction Mass of undissolved 2.16 g 1.96 g 1.8 g fraction Theoretical yield (PE) 2.68 g 2.40 g 2.13 g Yield 42.2 % 41.6 % 42.3 %

[0273] The results of the DSC analyses of the dissolved and undissolved materials are summarized in Table 15.

TABLE-US-00009 TABLE 15 Overview of the DSC analyses of the dissolved and undissolved components. LDPE LLDPE PA Experiment 1 dissolved 67 % 33 % 0 % Experiment 1 undissolved 34 % 6 % 60 % Experiment 2 dissolved 68 % 32 % 0 % Experiment 2 undissolved 29 % 7 % 64 % Experiment 3 dissolved 65 % 35 % 0 % Experiment 3 undissolved 27 % 6 % 67 %

Example 6

[0274] Analysis of PE/PET Film

[0275] Infrared Spectroscopy

[0276] The upper and the bottom layers of the film were analyzed by attenuated total reflectance IR (FIG. 10). The IR-spectrum of the upper layer corresponds to PET and the IR-spectrum of the bottom layer corresponds to PE (characteristic peaks are defined in Table 16).

TABLE-US-00010 TABLE 16 Characteristic IR peaks of PE and PET. LDPE/ HDPE CH.sub.3 CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3 CH.sub.3 (CH.sub.2).sub.n (CH.sub.2).sub.n Area 2975- 2940- 2870- 1480- 1465- 1390- 732- 722- [cm-1] 2950 2915 2840 1440 1440 1370 728 712 PET ρ-disubst. CH.sub.2 CH.sub.2 C═O p-disubst CH.sub.2 p-disubst CH.sub.2 Area 3909- 2970- 2900- 1730- 1615- 1470- 1465- 1370- [cm-1] 3015 2940 2850 1710 1485 1440 1400 1330 CO CO CH.sub.2 p-disubst p-disubst Area 1270- 1150- 900- 880- 750- [cm-1] 1240 1100 840 850 700

[0277] Differential Scanning Calorimetry

[0278] The material was analyzed by differential scanning calorimetry (FIG. 11).

[0279] According to the DSC analysis, the material has the following composition:

TABLE-US-00011 Sample Melting point Component Mass fraction PE/PET 108.9 ° C. LDPE 64 % 121.2 ° C. LLDPE 27 % 250.0 ° C. PET 9 %

[0280] Based on the IR and DSC data, the analyzed film contains at least two layers: the upper layer of PET and the bottom layer of PE.

[0281] Process for Extraction of PE from PE/PET Film

[0282] The extraction of PE from a PE/PET film was performed analogously to Example 4 with two different extraction media:methyl cyclohexane and a 50:50 v/v mixture of n-heptane and methyl cyclohexane. The extracted material and the undissolved material were analyzed by DSC (FIGS. 12-15).

[0283] The results of the experiments are summarized in Tables 17 and 18.

TABLE-US-00012 TABLE 17 Overview of the experiments with the fixed PE/PET film and an edge length of 7*26 cm and (extraction with methyl cyclohexane). Solvent: methyl cyclohexane Experiment 1 Experiment 2 Experiment 3 Mass of solvent 640.3 g 640.63 g 640.35 g Temperature of solvent 95 ° C. 95 ° C. 95 ° C. Stirring time 30 min 30 min 30 min Initial mass of foil 3.61 g 2.27 g 2 g Mass of dissolved 2.29 g 1.7 g 1.46 g fraction Mass of undissolved 0.48 g 0.38 g 0.32 g fraction Theoretical yield (PE) 3.30 g 2.07 g 1.83 g Yield 69.48 % 82.03 % 79.96 %

TABLE-US-00013 TABLE 18 Overview of the experiments with the fixed PE/PET film and an edge length of 7*26 cm and (extraction with a 50:50 v/v mixture of n-heptane and methyl cyclohexane). Solvent: n-heptane/ methyl cyclohexane Experiment 1 Experiment 2 Experiment 3 Mass of solvent 643.15 g 640.06 g 641.34 g Temperature of solvent 95 ° C. 95 ° C. 95 ° C. Stirring time 30 min 30 min 30 min Initial mass of foil 2.07 g 2.11 g 2.02 g Mass of dissolved 1.49 g 1.57 g 1.46 g fraction Mass of undissolved 0.35 g 0.38 g 0.4 g fraction Theoretical yield (PE) 1.89 g 1.93 g 1.84 g Yield 78.84 % 81.50 % 79.16 %

[0284] The results of the DSC analyses of the dissolved and undissolved materials are summarized in Tables 19 and 20.

TABLE-US-00014 TABLE 19 Overview of the DSC analyses of the dissolved and undissolved components (extraction with methyl cyclohexane). LDPE LLDPE PET Experiment 1 dissolved 64 % 36 % 0 % Experiment 1 undissolved 0 % 1 % 99 % Experiment 2 dissolved 72 % 23 % 0 % Experiment 2 undissolved 0 % 0 % 100 % Experiment 3 dissolved 56 % 44 % 0 % Experiment 3 undissolved 0 % 0 % 100 %

TABLE-US-00015 TABLE 20 Overview of the DSC analyses of the dissolved and undissolved components (extraction with a 50:50 v/v mixture of n-heptane and methyl cyclohexane). LDPE LLDPE PET Experiment 1 dissolved 66 % 33 % 0 % Experiment 1 undissolved 12 % 23 % 66 % Experiment 2 dissolved 71 % 29 % 0 % Experiment 2 undissolved 0 % 2 % 98 % Experiment 3 dissolved 53 % 47 % 0 % Experiment 3 undissolved 26 % 25 % 49 %