Method for recovering polyolefin from waste materials and polyolefin products recovered in such a manner

Abstract

A method for selectively extracting and recovering pure polyolefin polymers from waste containing multiple polymers by using one or more solvents at different temperatures to selectively dissolve one or more polymers from the mixture. Generally, a vegetable oil-based recycling method is presented that basically includes three main steps: extraction of waste polyolefins from mixed waste by dissolving in vegetable oil, highly purifying the polyolefins using sequential filters with gradually decreasing pore sizes for each filter, and precipitation of the selected and / or purified polyolefins in a liquid miscible with vegetable oil. Further provided is a polyolefin product with a purity exceeding 99% recovered by this method.

Description

Technical Field

[0001] The present invention relates to a method for recycling polyolefins from waste products including polypropylene, polyethylene, copolymers and mixtures thereof. The present invention generally relates to dissolution, dissolution via melting, the use of vegetable oils and mixtures thereof for the selective dissolution of polyolefins, and their extraction and recovery from multi-component plastic waste or plastic waste mixtures.

Background Art

[0002] The need for plastic recycling is increasing with the growing environmental concern and the increasing importance of the circular economy. In this regard, compared to other methods, plastic recycling by solvent-based extraction has been successful in extracting selected polymers from mixed plastic waste and provides recycled polymers with higher purity compared to conventional mechanical recycling methods, so its importance is increasing. This solvent-based extraction method generally includes dissolution of the collected material in a solvent, filtration to remove impurities, precipitation of the polymer, separation of the recovered polymer, thorough washing, and drying.

[0003] However, many problems occur in the solvent-based extraction process. Many of the chemicals used to dissolve plastics are harmful to the environment and organisms, which is a very important obstacle to the widespread use of this recycling method. Most of the solvents used are petroleum-based with a high carbon footprint and cost. Another drawback of this process is that the presence of residual solvents in the recycled polymers, although slight, limits their reuse in many applications of these obtained polymers and results in a decrease in their value and price.

[0004] The prior art JP2002003860A discloses an apparatus and method for converting waste plastics into oil / fuel by melting the waste plastics in vegetable oil. According to the patent application, plastics from mixed household waste are dissolved in solvent oils such as edible oil, vegetable oil and mineral oil in order to dehydrate, dechlorinate and increase the calorific value of the plastics.

[0005] Another prior art, WO9909092A1, discloses a method for reprocessing polymer products such as tires and PVC-coated metal products. This process includes treating the polymer products with at least one vegetable oil and exposing the vegetable oil in contact with the polymer products to a high temperature for a sufficient time to liquefy the polymer. Then, the liquefied polymer is separated from the metal and canvas / belt products in the polymer products in order to recover the polymer, metal, and canvas / belt products.

[0006] As described above, there is research in the literature regarding the use of vegetable oil in plastic recycling. However, until now, there has been no method that provides virgin-like quality and purified polymers and provides a solution for removing residual solvents in the recycled polymer structure.

[0007] It is essential to develop a more environmentally friendly, non-toxic, more economical, and more environmentally friendly solvent and a plastic recycling method using these solvents.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The main object of the present invention is to overcome the above-mentioned drawbacks of the prior art.

[0009] A further object of the present invention is to develop an effective recycling method that can extract polyolefins in pure form from mixed waste and enables the use of vegetable oil as a solvent.

[0010] A further object of the present invention is to provide a method that enables the use of vegetable oil as a polyolefin solvent that is more economical, renewable, and environmentally friendly compared to solvents currently used in the chemical and / or solvent-based recycling and purification of plastics.

[0011] Another object of the present invention is to provide a method for extracting polyolefins from multi-component plastic waste or plastic waste mixtures using vegetable oil as a solvent and alkanes as non-solvents.

[0012] Another object of the present invention is to provide a method with optimal precipitation conditions to minimize the amount of residual oil in the extracted polyolefins.

[0013] Another object of the present invention is to provide a method with an optimal temperature for the processability and separability of each polyolefin type.

[0014] Another object of the present invention is to provide a method for recycling coated polyolefin packaging films (coated with metals, poly(vinyl alcohol), poly(vinylidene chloride), etc.) using vegetable oil as a solvent and alkanes as non-solvents.

[0015] Another object of the present invention is to replace currently used solvents, petroleum-based decalin, tetrachloroethylene, xylene, toluene / petroleum ether, or any other solvent with environmentally friendly vegetable oil.

[0016] Other objects of the present invention will become apparent from the accompanying drawings, the following brief description, and the appended claims.

Means for Solving the Problems

[0017] The present invention provides a method for selectively extracting and recovering pure polyolefin polymers from waste containing multiple polymers by using one or more solvents at different temperatures to selectively dissolve one or more polymers from the mixture. The present invention generally involves the extraction of waste polyolefins from mixed waste by dissolving in vegetable oil, the high purification of polyolefins using sequential filters by gradually reducing the pore size of each filter, and a vegetable oil-based recycling method that basically includes three main steps: the precipitation of the selected and / or purified polyolefins in a liquid miscible with vegetable oil.

[0018] A method for extracting and recovering polyolefins from a waste mixture, comprising: (i) selectively extracting polyolefins from the mixed waste by mixing the waste material with vegetable oil and heating at a specific temperature according to the type of polyolefin; (ii) separating undissolved materials from the solution by filtration through a coarse filter; (iii) purifying the filtered mixture containing the dissolved polyolefin with a fine filter while maintaining its initial temperature; (iv) precipitating the purified mixture in a liquid that is miscible with the vegetable oil and does not dissolve the polyolefin under the precipitation conditions; (v) separating the precipitated polyolefin from the vegetable oil / non-solvent mixture; (vi) thoroughly washing the precipitated polyolefin to purify and remove the remaining oil; (vii) drying the separated polyolefin; and (viii) separating the vegetable oil / non-solvent mixture through distillation, essentially including that the recovered non-solvent is recovered from the top of the distillation column and the recovered vegetable oil is recovered from the bottom of the distillation vessel.

[0019] Another aspect of the recycling method provides high-purity polyolefins from a mixed material using vegetable oil as a solvent. This method includes the following steps: selectively dissolving polyolefins in a plastic waste mixture using vegetable oil as a solvent; highly purifying the polyolefins by sequentially using filters with gradually decreasing pore sizes for each filter; separating the vegetable oil from the filtered and purified polyolefins through filtration in the presence of a non-solvent that dissolves the vegetable oil and precipitation of the filtered and purified solution, separating and thoroughly washing the precipitate, and drying the recycled polymer.

[0020] In a possible embodiment, the vegetable oil / non-solvent ratio used in the precipitation step is greater than 1:1 (v / v), preferably greater than 1:3 (v / v).

[0021] In a possible embodiment, the concentration of the waste mixture in the vegetable oil ranges from 5 to 30% by weight.

[0022] In a possible embodiment, the waste mixture contains polyethylene and polypropylene together, and the waste mixture is mixed with vegetable oil by heating in the range of 140 to 155 °C to selectively dissolve and recover polyethylene from the mixture according to the above steps, then the unfiltered portion is remixed with vegetable oil and heated to 185 °C to dissolve and recover polypropylene according to the above steps.

[0023] In a possible embodiment, one or more polyolefin products having a purity exceeding 99% are recovered according to the method.

[0024] In a possible embodiment, one or more polyolefin products having a residual solvent content of less than 1% are recovered according to the method.

[0025] In a possible embodiment, one or more polyolefin products having a non-solvent content of less than 1% are recovered according to the method.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0027] A method for recovering polyolefin from waste materials, comprising the steps of mixing the waste materials with vegetable oil and heating at a temperature in the range of 120°C to 200°C to obtain a mixture containing dissolved polyolefin; filtering the mixture through a coarse filter; purifying the filtered mixture containing dissolved polyolefin by further filtration through a second filter; precipitating the purified polyolefin by adding the filtered mixture at its initial temperature into a liquid that is a non-solvent miscible with vegetable oil and below the boiling point of the non-solvent; separating the precipitated solid polyolefin from the vegetable oil / non-solvent mixture; and washing the separated polyolefin with the non-solvent and drying it under an inert atmosphere.

[0028] According to one embodiment of the present invention, the method further comprises the step of fractionating the vegetable oil / non-solvent mixture via distillation, wherein the recovered non-solvent is recovered from a distillation column and the recovered vegetable oil is recovered from the bottom of the distillation apparatus.

[0029] According to one embodiment of the present invention, the first coarse filter has a pore size in the range of 5 to 40 μm. According to one embodiment of the present invention, the second filter has a pore size in the range of 100 nm to 450 nm.

[0030] According to one embodiment of the present invention, the method further comprises the step of passing the filtered mixture through an adsorption column such as an activated carbon column.

[0031] According to one embodiment of the present invention, two-stage filtration is used to remove impurities in the obtained mixture. First, if there are non-polyolefin and substances insoluble in vegetable oil in the mixture, these insoluble substances are removed by coarse filtration. An average pore size of 5 microns or more is sufficient for coarse filtration, preferably 37 microns (400 mesh). A second filtration is necessary using a filter having an average pore size of 1 micron or less, preferably 0.1 micron, to remove the remaining fillers, pigments and various additives in the solution containing the dissolved portion of the input material.

[0032] According to one embodiment of the present invention, when the polyolefin obtained is precipitated in heptane at a temperature in the range of 20°C to 30°C between step (iv) and step (vi), the method further includes a step of reflux washing the obtained polyolefin in a boiling non-solvent.

[0033] According to another embodiment of the present invention, when the polyolefin obtained is precipitated in heptane at a temperature in the range of 22°C to 37°C between step (iv) and step (vi), the method further includes a step of reflux washing the obtained polyolefin in boiling heptane.

[0034] According to one embodiment of the present invention, the input waste material may be any organic and inorganic mixture containing polyolefin, preferably at least 30% polyolefin. According to one embodiment of the present invention, the polyolefin is polypropylene or polyethylene, a copolymer, or a combination thereof.

[0035] According to one embodiment of the present invention, the vegetable oil is in the form of a triglyceride which is an ester formed by the addition of three fatty acids to glycerol. Soybean oil, grape seed oil, and cocoa butter are examples of fats derived from seeds. Olive oil, palm oil, and rice bran oil are examples of fats from other parts of fruits. In another aspect of the present invention, the vegetable oil can be selected from the list including canola oil, sunflower oil, cottonseed oil, corn, olive, peanut, and coconut oil, or a combination of two or more thereof.

[0036] According to the present invention, the dissolution and polyolefin extraction temperature is 140°C or higher, preferably 155°C for waste containing only polyethylene-type polyolefin, and 170°C or higher, preferably 185°C for waste containing only polypropylene-type polyolefin. In the case of a combination of polyethylene and polypropylene-type polyolefins in the same waste mixture, polyethylene is first extracted at 155°C, followed by extraction of the remaining polypropylene at 185°C.

[0037] In a possible embodiment, the non-solvent is an alkane, preferably an aliphatic or cyclic saturated hydrocarbon having 6 to 9 carbon atoms. Alternatively, the non-solvent is an aliphatic or cyclic saturated hydrocarbon having more than 6 carbon atoms. In another exemplary embodiment, the aliphatic or cyclic saturated hydrocarbon contains 7 carbon atoms having 1 chiral carbon atom. In a preferred embodiment, the non-solvent is heptane, hexane or cyclohexane.

[0038] According to the invention, the vegetable oil / non-solvent ratio used in the precipitation step is greater than 1:1 (v / v), preferably greater than 1:3 (v / v). According to this embodiment, the waste mixture containing polyolefin was in a concentration range of 5 to 30% by weight in the recycling solvent.

[0039] According to the invention, the precipitation of the recovered polyolefin is carried out by dropping a hot solution into the non-solvent at its boiling temperature or a temperature slightly lower than that. For example, when heptane is used as the non-solvent, the precipitation temperature is 98 °C or lower. Performing the precipitation at a lower temperature increases the amount of residual solvent trapped in the recovered polyolefin.

[0040] According to an embodiment of the invention, when the polyolefin is separated from the mixture formed after precipitation, some solvent may remain in and on the surface of the polyolefin particles, and they can be washed and rinsed thoroughly with the non-solvent for removal.

[0041] According to the invention, the drying process is carried out under an inert atmosphere, optionally with heat and / or under vacuum, to reduce the risk of oxidation by removing oxygen from the environment and to ensure better removal of the non-solvent.

[0042] Example 1: Extraction and recovery of high-purity polypropylene from waste carpet. Waste carpets containing cotton, wool, jute, PAN, PET, PU and SBR were shredded into small pieces. The recycling process of polypropylene in the waste carpet includes a dissolution step, hot filtration, subsequent hot fine filtration, a precipitation step, separation of the precipitated polypropylene, thorough washing, and drying.

[0043] In the dissolution step, the required amount of pretreated raw material was put into canola oil. The mixture was stirred at 185 °C for 2 hours with a magnetic stirrer under reflux. In the filtration step, a two-stage filtration was applied to remove impurities (coarse undissolved materials and pigments respectively). A stainless steel mesh with a pore size of 37 μm was used as the coarse filter to remove the coarse undissolved materials. For hot fine filtration, a filtration cell with an active filtration area of 14.6 cm 2 was used. The filtration cell was wrapped with a flexible heating tape and heated to 190 °C before filtration. A PTFE membrane with a pore size of 0.2 μm was used to remove pigments in the filtration cell. The solution was directly filtered into heptane for precipitation. The pigments were captured by the PTFE membrane during hot filtration, and the pigment-free polypropylene polymer precipitated in heptane. For precipitation, the canola oil to non-solvent ratio was selected as 1:3 v / v. The waste carpet / canola oil solution was filtered through a membrane into heptane at 98 °C. Then, the recovered polypropylene was separated from the solvent / non-solvent mixture. The precipitated polypropylene granules were isolated from the canola and heptane mixture. Next, the obtained recycled polypropylene polymer was thoroughly washed and then dried in an oven at 50 °C under vacuum (50 mbar) for 5 hours. For the separation of the solvent / non-solvent mixture, the solvent / non-solvent mixture was separated by a rotary evaporator at the end of the process for reuse, and the efficiency of the process was evaluated regarding solvent recovery. The amount of canola oil used in the dissolution step was 88.76 ml, the amount of recovered canola oil was 87.04 ml, and the recovery efficiency was 98.06%. The amount of heptane used in the precipitation step was 577.49 ml, the amount of recovered heptane was 421.13 ml, and the recovery efficiency was 78.12%. The amount of polypropylene in the waste was 80.75%, the amount of recovered polypropylene was 76.37%, and the recovery efficiency was 95%.

[0044] Using a spectrometer for the FTIR analysis of canola oil, waste carpet material, coarse filter waste, pure polypropylene, and recycled polypropylene polymer, it was confirmed that the recycled polypropylene obtained through solvent-based recycling using canola oil as a solvent exhibited a structure and composition similar to that of pure polypropylene newly synthesized from petroleum-based products. In the range of 4000~650 cm -1 a spectrum was obtained by averaging at least 32 scans with a signal resolution of 4 cm -1 . The obtained FTIR spectra are shown in Figures 1 and 2.

[0045] In the FTIR spectrum of pure polypropylene pellets, the peaks at 2950 cm -1 , 2917 cm -1 , 2866 cm -1 and 2838 cm -1 indicated C-H stretching. The strong peak at 1376 cm -1 indicated in-plane bending of CH3, while the single rounded peak at 1452 cm -1 corresponded to the C-H asymmetric deformation vibration of isolated -CH2 in the homopolymer polypropylene. The peaks at 1167 cm -1 , 998 cm -1 , 842 cm -1 could be assigned to the characteristic vibrations of the isotactic polypropylene polymer.

[0046] The chemical compositions of the carpet waste and coarse filter waste could not be accurately identified due to the mixed nature of these materials, but for the waste carpet, assigned to pigments, additives, and impurities, in the range of 600~1750 cm -1The peaks observed between disappeared in the spectrum of the recycled polypropylene polymer, indicating that the pigments and additives were successfully removed by sequential filtration to which they were applied. In the FTIR spectrum of the recycled polypropylene, mainly characteristic peaks of pure polypropylene were observed. Furthermore, the signal of canola oil, mainly the peak at 1742 cm -1 corresponding to the carbonyl peak, was not observed in the spectrum of the recycled polypropylene polymer. Thus, it was confirmed from the FTIR spectrum of the recycled polypropylene polymer that the recycled polypropylene did not contain the solvent (canola oil).

[0047] Example 2: Selective dissolution and recovery of polymers from a mixture of polypropylene and polyethylene using canola oil as the solvent and heptane as the non-solvent. The present invention provides a method for recovering both polyethylene and polypropylene from a mixture of plastics. Since the waste contains both polyethylene and polypropylene, first, polyethylene is dissolved in vegetable oil at 155 °C, and the insoluble polypropylene is filtered off. The above process is used to recover the dissolved polypropylene, and the process includes high purification of polyethylene using sequential filtration by gradually reducing the pore size of each filter, filtration of the vegetable oil into heptane in which it is dissolved, separation of the vegetable oil from the filtered and purified polyethylene through precipitation of the purified solution, separation and thorough washing of the precipitate, and drying of the recycled polyethylene. Thereafter, the residual waste containing no polyethylene is dissolved in canola oil by heating at 185 °C for the recovery of polypropylene. After the dissolution of polypropylene, the procedures of filtration, precipitation, separation, washing, and drying are carried out throughout the polypropylene recovery process.

[0048] Polyethylene and polypropylene have a rather simple chemical nature consisting only of carbon and hydrogen atoms linked by covalent bonds, resulting in a few signals in the FTIR spectrum as seen in Figures 3 and 4. In the FTIR spectrum of pure polyethylene, characteristic peaks are observed at 2919 cm -1 , 2850 cm -1 , 1470 cm -1 , and 718 cm -1 . On the other hand, the peaks at 2919 and 2850 cm -1 are assigned to -CH2 asymmetric and symmetric stretching respectively; the peak at 1464 corresponds to the bending vibration of -CH2, and 730 cm -1 corresponds to -CH2 rocking. The peaks observed in the spectrum of recycled polyethylene were identical to the characteristic peaks of pure polyethylene, indicating that the recycled polyethylene obtained by the applied recycling process was the same as pure polyethylene and was in a pure state (free of the polypropylene and vegetable oil used). Referring to Figures 3 and 4, in the FTIR spectrum of pure polypropylene pellets, the peaks at 2950 cm -1 , 2917 cm -1 , 2866 cm -1 and 2838 cm -1 showed C-H stretching. The strong peak at 1376 cm -1 indicated the in-plane bending of CH3, while the single rounded peak at 1452 cm -1 corresponded to the C-H asymmetric deformation vibration of isolated -CH2 in the homopolymer polypropylene. The peaks at 1167 cm -1 , 998 cm -1 , 842 cm -1 were assigned to the characteristic vibrations of isotactic polypropylene. The peaks observed in the spectrum of recycled polypropylene were identical to the characteristic peaks of pure polypropylene, indicating that the recycled polypropylene obtained by the applied recycling process was the same as pure polypropylene and was in a pure state (free of the polyethylene and vegetable oil used).

[0049] Example 3: Precipitation of extracted polypropylene at different non-solvent temperatures. Pure polypropylene pellets were dissolved in canola oil at 185 °C at a ratio of 5% (w / v). The resulting solution was dropped into heptane at 7 °C, 24 °C, and 98 °C to precipitate polypropylene. The canola oil / heptane ratio was 1:3 (v / v) in this experiment. When the hot mixture was poured into heptane at its boiling point, the mixture was initially clear and transparent. However, as it cooled slowly and the temperature approached 80 °C, the solution began to turbid as the polypropylene began to solidify slowly. As the temperature of the mixture dropped below approximately 80 °C, this turbid state became more apparent. However, when the same hot solution was poured into heptane at 24 °C, the final temperature of the mixture did not exceed 65 °C, and precipitation was observed immediately upon pouring the solution. Similarly, immediate precipitation was observed when the hot solution was poured into heptane at 7 °C. In another precipitation test, when the initial temperature of heptane was below room temperature, the resulting polypropylene product had a yellowish color, indicating a higher content of trapped canola oil. This was also confirmed by FTIR analysis as shown in Figures 5, 6, and 7. The spectrum of the recycled polypropylene polymer precipitated at 7 °C showed a peak at 1743 cm -1 indicating that canola oil was trapped in the polymer, but it decreased in the polypropylene sample obtained at the precipitation temperature of 24 °C and completely disappeared in the polypropylene sample obtained at the precipitation temperature of 98 °C. It can be concluded that the residual solvent (canola oil) remaining in the recovered polypropylene product decreased due to the slow solidification and crystallization that occurred when precipitation was carried out using preheated heptane (up to 98 °C). This is an important step for reducing the residual solvent in the final polypropylene product.

[0050] Example 4: Precipitation of dissolved polypropylene at various solvent-non-solvent ratios. Pure polypropylene pellets were dissolved in canola oil at a ratio of 5% (w / v) at 185 °C. The resulting solution was dropped into heptane at 98 °C, and three separate experiments were conducted with the solvent-to-nonsolvent ratio varied as 1:3, 1:5, and 1:10 (v / v). As seen in Figure 8, the FTIR spectra of the recycled polypropylene polymers obtained by varying the solvent-to-nonsolvent ratio showed no signs of residual canola oil (the peak at 1743 cm -1 was not visible).

[0051] Example 5: Reflux wash the final polypropylene in boiling heptane. Pure polypropylene pellets were dissolved in canola oil at a ratio of 5% (w / v) at 185 °C. The resulting solution was dropped into heptane at 24 °C to precipitate the polypropylene. The obtained polypropylene was reflux washed in boiling heptane for 2 hours. It was observed that the initial state of the polypropylene was yellower than the polypropylene washed under these conditions. Reflux washing in boiling heptane extracted and removed the remaining canola oil from the polypropylene polymer.

[0052] The invention described in the claims including the method and / or the solvent-nonsolvent combination provides the following advantages: - Preserve rapidly decreasing landfill space - Reduce the demand for fossil fuels - Treat heterogeneous plastic-based waste - Provide recovery performance while considering the environment - Provide an economical and environmental method for the recovery of carpet materials - Separate multiple incompatible polymers from a polymer mixture

Claims

1. A method for recovering polyolefin from waste materials, i. Mixing the waste materials with vegetable oil and heating at a temperature in the range of 120 °C to 200 °C to obtain a mixture containing dissolved polyolefin; ii. Filtering the mixture through a coarse filter; iii. Purifying the filtered mixture containing dissolved polyolefin by further filtration through a second filter; iv. Precipitating the purified polyolefin by adding the filtered mixture at its initial temperature into a liquid that is a non-solvent miscible with the vegetable oil and at a temperature below the boiling point of the non-solvent; v. Separating the precipitated solid polyolefin from the vegetable oil / non-solvent mixture; vi. Washing the separated polyolefin with the non-solvent and drying it under an inert atmosphere. A method comprising the above steps.

2. The method according to claim 1, further comprising fractionating the vegetable oil / non-solvent mixture through distillation, wherein the recovered non-solvent is recovered from the distillation column and the recovered vegetable oil is recovered from the bottom of the distillation column.

3. The method according to claim 1 or 2, further comprising, between step (iv) and step (vi), (iv') when the purified polyolefin solution precipitates in the non-solvent in a temperature range of 20 °C to 30 °C, reflux washing the obtained polyolefin in the boiling non-solvent.

4. The method according to claim 1 or 2, further comprising, between step (iv) and step (vi), (iv') when the purified polyolefin solution precipitates in heptane in a temperature range of 22 °C to 27 °C, reflux washing the obtained polyolefin in the boiling heptane.

5. The method according to claim 1, further comprising, between the step (iii) and the step (iv), (iii') passing the filtered mixture through an adsorption column.

6. The method according to claim 5, wherein the adsorption column is an activated carbon column.

7. The method according to any one of claims 1 to 6, wherein the coarse filter has a pore size in the range of 5 to 40 μm.

8. The method according to any one of claims 1 to 7, wherein the second filter has a pore size in the range of 100 nm to 450 nm.

9. The method according to any one of claims 1 to 8, wherein the polyolefin separated from the non-solvent is dried at a temperature in the range of 30°C to 60°C.

10. The method according to any one of claims 1 to 9, wherein the vegetable oil is selected from canola oil, sunflower oil, olive oil, coconut oil, cottonseed oil, or a combination of two or more thereof.

11. The method according to any one of claims 1 to 10, wherein the polyolefin is polypropylene, polyethylene, a copolymer, or a combination thereof.

12. The method according to any one of claims 1 to 11, wherein the non-solvent is an aliphatic or cyclic saturated hydrocarbon having 5 carbon atoms.

13. The method according to any one of claims 1 to 11, wherein the non-solvent is an aliphatic or cyclic saturated hydrocarbon having more than 6 carbon atoms.

14. The method according to any one of claims 1 to 11, wherein the aliphatic or cyclic saturated hydrocarbon contains 7 carbon atoms having 1 chiral carbon atom.

15. The method according to any one of claims 1 to 11, wherein the non-solvent is heptane, hexane, or cyclohexane.

16. The method according to any one of claims 1 to 15, wherein the vegetable oil / non-solvent ratio used in the precipitation process is greater than 1:1 (v / v), preferably greater than 1:3 (v / v).

17. The method according to any one of claims 1 to 16, wherein the concentration of the waste material in the vegetable oil is in the range of 5 to 30% by weight.

18. The method according to any one of claims 1 to 17, wherein the waste material contains polyethylene and polypropylene together, and the waste mixture is heated at a temperature in the range of 140 to 155 °C to selectively dissolve and recover polyethylene from the mixture first, and then the temperature is raised to 185 °C to dissolve and recover polypropylene, and then mixed with vegetable oil.

19. One or more polyolefin products having a purity exceeding 99% and recovered according to any one of claims 1 to 18.

20. One or more polyolefin products having a non-solvent content of less than 1% and recovered according to any one of claims 1 to 18.

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