Process for recovering polyolefin from waste and polyolefin product recovered thereby

Abstract

The present invention provides a method for selectively extracting and recovering pure polyolefin polymers from waste containing a plurality of polymers by selectively dissolving one or more polymers from a mixture using one or more solvents at different temperatures. The present invention generally proposes a vegetable oil-based recovery process comprising essentially three main steps, i.e. Extraction of spent polyolefin from mixed waste by dissolution in vegetable oil, advanced purification of the polyolefin by gradual reduction of the pore size of each filter using sequential filters; and precipitating the selected and / or purified polyolefin in a liquid miscible with the vegetable oil. The invention also provides a polyolefin product having a purity greater than 99% recovered from the process.

Description

Technical Field

[0001] The present invention relates to a method for recovering polyolefins from waste products, including polypropylene, polyethylene, their copolymers and mixtures. The present invention generally relates to the use of vegetable oils and mixtures thereof for dissolving, selectively dissolving polyolefins by melt dissolving, and extracting and recovering them from multi-component plastic waste or plastic waste mixtures. Background Art

[0002] With the increasing environmental concerns and the growing importance of circular economy, the demand for plastic recycling is increasing. In this regard, plastic recycling through solvent-based extraction is becoming increasingly important as it has been successful in extracting selected polymers from mixed plastic waste and provides recycled polymers with higher purity compared to traditional mechanical recycling methods. This solvent-based extraction method generally involves dissolving the collected material in a solvent, filtering to remove impurities, precipitating the polymer, separating the recovered polymer, washing thoroughly and drying.

[0003] However, many problems arise in solvent-based extraction processes. Many of the chemicals used to dissolve plastics are harmful to the environment and organisms, which is a very important obstacle to the widespread application of this recycling method. Most of the solvents used are petroleum-based, with a high carbon footprint and cost. Another disadvantage of this process is that the recovered polymers contain residual solvents, which, although in small amounts, limits the reuse of these resulting polymers in many applications, leading to a decrease in their value and price.

[0004] Prior art JP2002003860A discloses a device and method for converting waste plastics into oil / fuel by melting the waste plastics in vegetable oil. According to the patent application, plastics in mixed domestic waste are dissolved in solvent oil such as edible oil, vegetable oil, and mineral oil, and dehydrated and dechlorinated to 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), wherein the method comprises the steps of treating the polymer product with at least one vegetable oil, and contacting the vegetable oil in contact with the polymer product at a high temperature for a sufficient period of time to liquefy the polymer. The liquefied polymer is then separated from the metal and canvas / belt products in the polymer product to recover the polymer, metal and canvas / belt products.

[0006] As mentioned above, there are studies in the literature on the use of vegetable oils in plastic recycling, but so far, no method has provided both a purified polymer of the same virgin quality and a solution to remove residual solvents in the recycled polymer structure.

[0007] It is imperative to adopt more environmentally friendly, non-toxic, more economical and greener solvents and develop plastic recycling methods that utilize these solvents.

[0008] Purpose of the Invention

[0009] The main purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art.

[0010] Another object of the present invention is to develop an efficient recycling process which can extract polyolefins in pure form from mixed waste and can use vegetable oils as solvent.

[0011] Yet another object of the present invention is to provide a process that allows vegetable oils to be used as polyolefin solvents that is more economical, renewable, and environmentally friendly than the solvents currently used in chemical and / or solvent-based recycling and purification of plastics.

[0012] Another object of the present invention is to provide a method for extracting polyolefins from multi-component plastic waste or a mixture of plastic wastes using vegetable oil as solvent and alkane as non-solvent.

[0013] Another object of the present invention is to provide a process with optimal precipitation conditions to minimize the amount of residual oil in the extracted polyolefin.

[0014] Another object of the present invention is to provide a process having an optimum temperature for processability and separation for each polyolefin type.

[0015] Another object of the present invention is to provide a method for recycling coated polyolefin packaging films (metal-coated, polyvinyl alcohol-coated, polyvinylidene chloride-coated, etc.) using vegetable oil as a solvent and alkanes as a non-solvent.

[0016] Another object of the present invention is to replace the currently used solvents, petroleum based decalin, tetrachloroethylene, xylene, toluene / petroleum ether or any other solvents with environmentally friendly vegetable oils.

[0017] Other objects of the present invention will become apparent from the drawings, brief description in the following sections, and the appended claims. Summary of the invention

[0018] The present invention provides a method for selectively extracting and recovering pure polyolefin polymers from waste materials containing multiple polymers by selectively dissolving one or more polymers from the mixture using one or more solvents at different temperatures. The present invention generally proposes a vegetable oil-based recovery method, which basically includes three main steps: extracting waste polyolefins from mixed waste materials by dissolving in vegetable oil; using sequential filters to perform high-level purification of polyolefins by gradually reducing the pore size of each filter; and precipitating the selected and / or purified polyolefins in a liquid miscible with the vegetable oil.

[0019] A method for extracting and recovering polyolefins from a waste mixture essentially comprises the following steps: (i) mixing the wastes into vegetable oil, selectively extracting polyolefins from the mixed waste by heating at a specific temperature depending on the type of polyolefin, (ii) separating the insoluble matter from the solution by filtering through a coarse filter, (iii) purifying the filtered mixture containing dissolved polyolefins by passing through a fine filter while maintaining its initial temperature, (iv) precipitating the purified mixture in a liquid which is miscible with said vegetable oil and does not dissolve said polyolefin under said 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, (viii) separating the vegetable oil / non-solvent mixture by distillation, recovering the recovered non-solvent from the top of the distillation column and recovering the recovered vegetable oil from the bottom of said distillation column.

[0020] Another aspect of the recovery method is to use vegetable oil as a solvent to provide high-purity polyolefins from mixed materials. The method includes the following steps: using vegetable oil as a solvent to selectively dissolve polyolefins in the plastic waste mixture; using sequential filters to perform high-grade purification of the polyolefins by gradually reducing the pore size of each filter; separating the vegetable oil from the filtered and purified polyolefins by precipitation of the filtered and purified solution in the presence of a non-solvent that dissolves the vegetable oil; separating and thoroughly washing the precipitate; and drying the recovered polymer.

[0021] In one possible embodiment, the ratio of vegetable oil / non-solvent used in the precipitation step is greater than 1:1 (v / v), preferably greater than 1:3 (v / v).

[0022] In one possible embodiment, the concentration of the waste mixture in the vegetable oil ranges from 5% to 30% by weight.

[0023] In one possible embodiment, the waste mixture includes both polyethylene and polypropylene. According to the above steps, the waste mixture is mixed into vegetable oil by heating at a temperature ranging from 140°C to 155°C to first selectively dissolve and recover polyethylene from the mixture, and then the unfiltered portion is re-mixed into the vegetable oil and heated to 185°C according to the above steps to dissolve and recover polypropylene.

[0024] In one possible embodiment, a polyolefin product having a purity greater than 99% is recovered according to the method.

[0025] In one possible embodiment, the method recovers a polyolefin product having a residual solvent content of less than 1%.

[0026] In one possible embodiment, a polyolefin product having a non-solvent content of less than 1% is recovered according to the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 and Figure 2 FTIR spectra of rapeseed oil, waste carpet material, coarse filter waste, pure polypropylene and recycled polypropylene polymer according to Example 1 are shown.

[0028] Figure 3 and Figure 4 The FTIR spectra of recycled polyethylene compared to pure polyethylene and the FTIR spectra of recycled polypropylene compared to pure polypropylene according to Example 2 are shown.

[0029] Figure 5 , Figure 6 and Figure 7 Shown are FTIR spectra of recovered polypropylene precipitated in heptane according to Example 3 at 7°C, 24°C and 98°C.

[0030] Figure 8 Shown are FTIR spectra of recovered polypropylene precipitated in heptane at 98°C with varying solvent to non-solvent ratios according to Example 4. DETAILED DESCRIPTION

[0031] A method for recovering polyolefins from waste materials comprises the following steps: mixing the waste materials into vegetable oil and heating at a temperature ranging from 120°C to 200°C to obtain a mixture containing dissolved polyolefins; filtering the mixture through a coarse filter; purifying the filtered mixture containing dissolved polyolefins by further filtering with a second filter; precipitating the purified polyolefin by adding the filtered mixture at its initial temperature to a non-solvent liquid miscible with the vegetable oil at or below the boiling point of the non-solvent; separating the precipitated solid polyolefin from the vegetable oil / non-solvent mixture; washing the separated polyolefin with a non-solvent; and drying under an inert atmosphere.

[0032] According to one embodiment of the present invention, the method further comprises the step of fractionating the vegetable oil / non-solvent mixture by 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.

[0033] According to one embodiment of the present invention, the pore size of the first coarse filter ranges from 5 μm to 40 μm. According to one embodiment of the present invention, the pore size of the second filter ranges from 100 nm to 450 nm.

[0034] According to one embodiment of the present invention, the method further comprises the step of passing the filtered mixture through an adsorption column (eg, an activated carbon column).

[0035] According to one embodiment of the present invention, two-stage filtration is used to remove impurities from the resulting mixture. First, if there are non-polyolefin and vegetable oil-insoluble substances in the mixture, these insoluble substances are removed by coarse filtration. An average pore size of 5 microns and above is sufficient for coarse filtration, preferably 37 microns (400 mesh). In order to remove the remaining fillers, pigments and various additives in the solution containing the dissolved portion of the input material, a second filtration is required using a filter with an average pore size of 1 micron or less, preferably 0.1 micron.

[0036] According to one embodiment of the present invention, between step (iv) and step (vi), the method further comprises the step of washing the obtained polyolefin in a boiling non-solvent under reflux when the polyolefin is precipitated in the heptane at a temperature ranging from 20°C to 30°C.

[0037] According to another embodiment of the present invention, between step (iv) and step (vi), the process further comprises the step of washing the obtained polyolefin in boiling heptane under reflux when the polyolefin is precipitated in heptane at a temperature ranging from 22°C to 37°C.

[0038] According to one embodiment of the present invention, the input waste material can be any organic and inorganic mixture containing polyolefins, preferably containing at least 30% polyolefins. According to one embodiment of the present invention, the polyolefin is polypropylene or polyethylene, their copolymers or combinations thereof.

[0039] According to one embodiment of the present invention, the vegetable oil is a form of triglyceride, and triglyceride is an ester formed by the addition of three fatty acids and glycerol. Soybean oil, grape seed oil and cocoa butter are all examples of fats from seeds. Olive oil, palm oil and rice bran oil are examples of fats from other parts of fruits. The vegetable oil described in another aspect of the present invention can be selected from the following list: rapeseed oil, sunflower seed oil, cottonseed oil, corn oil, olive oil, peanut oil and coconut oil, or a combination of two or more thereof.

[0040] According to the invention, for waste containing only polyethylene type polyolefin, the dissolution and polyolefin extraction temperature is 140° C. and above, preferably 155° C.; for waste containing only polypropylene type polyolefin, the dissolution and polyolefin extraction temperature is 170° C. and above, preferably 185° C. If a combination of polyethylene and polypropylene type polyolefin is mixed in the same waste mixture, polyethylene is first extracted at 155° C., and then the remaining polypropylene is extracted at 185° C.

[0041] In one 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, of which there is 1 chiral carbon atom. In a preferred embodiment, the non-solvent is heptane, hexane or cyclohexane.

[0042] 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 the embodiment, the concentration of the waste mixture containing polyolefins in the recovery solvent ranges from 5 wt% to 30 wt%.

[0043] According to the invention, the polyolefin to be recovered is precipitated by dropping a hot solution into a non-solvent at or slightly below its boiling point. For example, if heptane is used as the non-solvent, the precipitation temperature will be 98° C. or below. When precipitation is performed at a lower temperature, the amount of residual solvent trapped in the recovered polyolefin increases.

[0044] According to one embodiment of the present 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, which can be removed by sufficient washing and rinsing with a non-solvent.

[0045] According to said invention, the drying process is carried out under an inert atmosphere, optionally under heating and / or vacuum, in order to reduce the risk of oxidation and ensure better removal of the non-solvent by removing oxygen from the environment.

[0046] Example 1: Extraction and recovery of high purity polypropylene from waste carpet.

[0047] Waste carpets including cotton, wool, jute, PAN, PET, PU and SBR are shredded into small pieces. The recovery process of polypropylene in the waste carpets includes a dissolution step, hot coarse filtration followed by hot fine filtration, a precipitation step, separation of the precipitated polypropylene, thorough washing and drying.

[0048] In the dissolution step, the required amount of pretreated raw material was placed in rapeseed oil. The mixture was stirred at 185°C under reflux with a magnetic stirrer for 2 hours. In the filtration step, two-stage filtration was used to remove impurities (coarse insoluble matter and pigments, respectively). A stainless steel mesh with a mesh size of 37 μm was used as a coarse filter to remove coarse insoluble matter. A hot fine filtration with an effective filtration area of ​​14.6 cm 2 The filter unit 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 the pigment in the filter unit. The solution was filtered directly into heptane for precipitation. During the hot filtration, the pigment was captured by the PTFE membrane, while the polypropylene polymer without pigment was precipitated in heptane. For precipitation, a 1:3 v / v ratio of rapeseed oil to non-solvent was selected. The waste carpet / rapeseed oil solution was filtered through the membrane into heptane at 98 °C. Afterwards, the recovered polypropylene was separated from the solvent / non-solvent mixture. The precipitated polypropylene particles were separated from the rapeseed oil and heptane mixture. The recovered polypropylene polymer obtained was then washed thoroughly and then dried in an oven at 50 °C under vacuum (50 mbar) for 5 h. For the separation of the solvent / non-solvent mixture, the solvent / non-solvent mixture was separated for reuse by a rotary evaporator at the end of the process, and the efficiency of the process in terms of solvent recovery was evaluated. The amount of rapeseed oil used in the dissolution process was 88.76 ml, the amount of rapeseed oil recovered was 87.04 ml, and the recovery rate was 98.06%. The amount of heptane used in the precipitation process was 577.49 ml, the amount of heptane recovered was 421.13 ml, and the recovery rate was 78.12%. The amount of polypropylene in the waste was 80.75%, the amount of polypropylene recovered was 76.37%, and the recovery rate was 95%.

[0049] FTIR analysis of rapeseed oil, waste carpet material, coarse filter waste, pure polypropylene and recycled polypropylene polymers was performed using a spectrometer to confirm that the recycled polypropylene obtained by solvent-based recycling using rapeseed oil as a solvent shows a similar structure and composition to pure polypropylene newly synthesized from petroleum-based products. -1 Up to 650cm -1 The signal resolution is 4cm within the range -1 , and average at least 32 scans to obtain the spectrum. The FTIR spectrum obtained is as follows Figure 1 and Figure 2 shown.

[0050] In the FTIR spectrum of pure polypropylene particles, 2950cm -1 、2917cm -1 、2866cm -1 and 2838cm -1 The peak at 1376 cm -1 The strong peak at 1452 cm -1 The single round peak at 1167 cm corresponds to the CH asymmetric deformation vibration of isolated -CH2 in homopolymer polypropylene. -1 、998cm -1 、842cm -1 The peak at can be attributed to the characteristic vibration of isotactic polypropylene polymer.

[0051] Although the exact chemical composition of the carpet waste and coarse filter waste could not be identified due to the mixed nature of these materials, the 600 cm -1 Up to 1750cm -1 The peaks between (attributed to pigments, additives and impurities) disappeared in the spectrum of the recovered polypropylene polymer, indicating that the pigments and additives were successfully removed by the applied sequential filtration. The characteristic peaks of pure polypropylene were mainly observed in the FTIR spectrum of the recovered polypropylene. In addition, the FTIR spectrum of the recovered polypropylene polymer confirmed that the recovered polypropylene did not contain solvent (rapeseed oil) because no signal of rapeseed oil (mainly 1742cm -1 The peak corresponding to the carbonyl peak).

[0052] Example 2: Selective dissolution and recovery of polymer from a mixture of polypropylene and polyethylene using rapeseed oil as solvent and heptane as non-solvent.

[0053] The present invention provides a method for recovering polyethylene and polypropylene from a plastic mixture. Since the waste contains both polyethylene and polypropylene, the polyethylene is first dissolved in vegetable oil at 155°C, and then the insoluble polypropylene is filtered out. The aforementioned method is used to recover the dissolved polypropylene, wherein the method includes using sequential filters to perform high-level purification of the polyethylene by gradually reducing the pore size of each filter, separating the vegetable oil from the filtered and purified polyethylene by precipitating the filtered and purified solution into heptane in which the vegetable oil is dissolved, separating and thoroughly washing the precipitate, and then drying the recovered polyethylene. Subsequently, the residual waste that does not contain polyethylene is dissolved in rapeseed oil by heating at 185°C to recover the polypropylene. After the polypropylene is dissolved, the processes of filtering, precipitation, separation, washing, and drying are performed in the entire polypropylene recovery process.

[0054] The chemical nature of polyethylene and polypropylene is quite simple, consisting only of carbon atoms and hydrogen atoms connected by covalent bonds, resulting in a small number of signals in their FTIR spectra, such as Figure 3 and Figure 4 In the FTIR spectrum of pure polyethylene, a -1 、2850cm -1 、1470cm -1 and 718cm -1 The characteristic peak at 2919cm -1 and 2850cm -1 The peaks at 1464 cm-1 are attributed to the asymmetric and symmetric stretching of –CH2, respectively; -1 The peak at 730 cm corresponds to the bending vibration of -CH2, while the peak at 730 cm -1 The peak at corresponds to the rocking vibration of -CH2. The peaks observed in the spectrum of the recycled polyethylene are the same as the characteristic peaks of pure polyethylene, indicating that the recycled polyethylene obtained by this recycling process is the same as pure polyethylene and is in a pure state (without polypropylene and the used vegetable oil). Figure 3 and Figure 4 , in the FTIR spectrum of pure polypropylene pellets, at 2950 cm -1 、2917cm -1 、2866cm -1 and 2838cm -1 The peak at 1376 cm -1 The strong peak at 1452cm -1 The single round peak at 1167cm corresponds to the CH asymmetric deformation vibration of the isolated –CH2 in the homopolymer polypropylene. -1 、998cm -1 、842cm -1The peaks at are attributed to the characteristic vibrations of isotactic polypropylene. The peaks observed in the spectrum of the recycled polypropylene are consistent with the characteristic peaks of pure polypropylene, indicating that the recycled polypropylene obtained by this recycling process is the same as pure polypropylene and is in a pure state (without polypropylene and the used vegetable oil).

[0055] Example 3: Precipitation of polypropylene extracted at different non-solvent temperatures.

[0056] Pure polypropylene particles were dissolved in rapeseed oil at a ratio of 5% (w / v) at 185°C. The resulting solution was dripped into heptane at 7°C, 24°C and 98°C to precipitate polypropylene. In the experiment, the ratio of rapeseed oil / heptane was 1:3 (v / v). When the hot mixture was poured into heptane at its boiling point, the mixture was clear and transparent at first. But when it was slowly cooled and the temperature approached 80°C, the solution began to become turbid as the polypropylene began to slowly solidify. This turbid state became more obvious when the temperature of the mixture dropped below about 80°C. 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 after the solution was poured. Similarly, when the hot solution was poured into heptane at 7°C, precipitation was observed immediately. In a separate precipitation test, when the initial temperature of the heptane was room temperature or lower, the resulting polypropylene product was light yellow, indicating that the rapeseed oil content captured was higher. Figure 5 , Figure 6 and Figure 7 This is also confirmed by the FTIR analysis seen in Figure 1. Although the spectrum of the recovered polypropylene polymer precipitated at 7°C shows a peak at 1743 cm -1 The peak at , indicating the presence of rapeseed oil trapped in the polymer, is reduced in the spectrum of the polypropylene sample obtained at a precipitation temperature of 24 ° C, and completely disappears in the spectrum of the polypropylene sample obtained at a precipitation temperature of 98 ° C. It can be concluded that when the precipitation is carried out using preheated heptane (up to 98 ° C), slow solidification and crystallization occur, so the residual solvent (rapeseed oil) remaining in the recovered polypropylene product is reduced. This is an important step to reduce the residual solvent in the final polypropylene product.

[0057] Example 4: Precipitation of dissolved polypropylene at various solvent-nonsolvent ratios.

[0058] Pure polypropylene particles were dissolved in rapeseed oil at 185°C at a ratio of 5% (w / v). The resulting solution was dropped into heptane at 98°C in three independent experiments with solvent to non-solvent ratios of 1:3, 1:5, and 1:10 (v / v), respectively. Figure 8As shown, the FTIR spectra of the recovered polypropylene polymer obtained by varying the ratio of solvent to non-solvent showed no signs of residual rapeseed oil (at 1743 cm -1 The peak at is not visible).

[0059] Example 5: Washing of the final polypropylene in boiling heptane under reflux.

[0060] Pure polypropylene particles were dissolved in rapeseed oil at a ratio of 5% (w / v) at 185°C. The resulting solution was dropped into heptane at 24°C to precipitate polypropylene. The resulting polypropylene was washed in boiling heptane under reflux for 2 hours. It was observed that the initial state of the polypropylene was more yellow than the polypropylene washed under these conditions. The residual rapeseed oil remaining in the polypropylene polymer was extracted and removed by washing in boiling heptane under reflux.

[0061] The claimed invention comprises a process and / or solvent-non-solvent combination having the following advantages:

[0062] - Saves rapidly shrinking landfill space

[0063] - Reduce the demand for fossil fuels

[0064] -Processing of heterogeneous plastic waste

[0065] -Provides recycling performance while being environmentally conscious

[0066] - Provide an economical and environmentally friendly method for recycling carpet materials

[0067] -Separation of multiple incompatible polymers from polymer mixtures.

Claims

1. A method for recovering polyolefin from waste materials, comprising the following steps: i. mixing the waste into vegetable oil and heating at a temperature ranging from 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 the dissolved polyolefin by further filtering through a second filter, iv. precipitating the purified polyolefin by adding the filtered mixture at its initial temperature to a non-solvent liquid miscible with the vegetable oil at or 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 under an inert atmosphere.

2. The method of claim 1 further comprising the step of fractionating the vegetable oil / non-solvent mixture by 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 column.

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

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

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

7. The method according to any one of the preceding claims 1 to 6, wherein the pore size of the coarse filter ranges from 5 μm to 40 μm.

8. The method according to any one of the preceding claims 1 to 7, wherein the pore size of the second filter ranges from 100 nm to 450 nm.

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

10. The method according to any one of the preceding claims 1 to 9, wherein the vegetable oil is selected from rapeseed 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 the preceding claims 1 to 10, wherein the polyolefin is polypropylene, polyethylene, copolymers thereof or combinations thereof.

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

14. The process according to any one of the preceding claims 1 to 11, wherein the aliphatic or cyclic saturated hydrocarbon comprises 7 carbon atoms, of which there is 1 chiral carbon atom.

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

16. The method according to any one of the preceding claims 1 to 15, wherein 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).

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

18. A method according to any one of the preceding claims 1 to 17, wherein the waste comprises both polyethylene and polypropylene, the waste mixture is mixed into a vegetable oil by heating at a temperature in the range of 140°C to 155°C to first selectively dissolve and recover polyethylene from the mixture, and then the temperature is increased to 185°C to dissolve and recover polypropylene.

19. Polyolefin product recovered according to the preceding claims with a purity greater than 99%.

20. Polyolefin product recovered according to the preceding claim having a non-solvent content of less than 1%.

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