SUSTAINABLE METHODS TO SEPARATE AND RECOVER POLYETHYLENE AND POLYPROPYLENE FROM MIXED PLASTIC WASTE STREAMS

Abstract

Sustainable methods to separate and recover polypropylene (PP) and polyethylene (PE) from mixed plastic wastes are described. The method utilize a class of green solvents, namely, oils, which can selectively dissolve PP, but not PE or other polymers. When re-precipitated, the recovered PP has properties similar to virgin PP.

Claims

1. A method of separating polypropylene (PP) from mixed plastic waste, the method comprising: adding mixed plastic waste to an oil maintained at a temperature ranging from about 180? C. to about 230? C. for a time sufficient to dissolve PP from the mixed plastic waste in the oil, thereby forming an oil-PP solution; separating the oil-PP solution from the mixed plastic waste using a solid-liquid separation technique; and allowing the oil-PP solution to cool, thereby forming an oil-PP mixture, to recover the PP.

2. The method of claim 1, wherein a concentration of PP in the oil-PP solution is less than about 2 wt %, and the cooling results in formation of a distinct solid phase of oil-infused PP.

3. The method of claim 1, wherein a concentration of PP in the oil-PP solution is greater than about 2 wt %, and the cooling results in formation of a homogeneous gel-like or wax-like solid phase containing oil and PP.

4. The method of claim 1, wherein the temperature is about 200? C.

5. The method of claim 1, wherein the mixed plastic waste comprises polyethylene terephthalate (PET), PE, PP, polyvinyl chloride (PVC), polystyrene, and nylon.

6. The method of claim 1, wherein the oil comprises soybean oil, rapeseed oil, canola oil, sunflower oil, safflower oil, peanut oil, cottonseed oil, coconut oil, palm oil, olive oil, avocado oil, flaxseed oil, sesame oil, hemp seed oil, corn oil, yellow grease, waste cooking oil, brown grease, algae oil, or a combination thereof.

7. The method of claim 1, comprising adding an anti-solvent to the oil-PP mixture to aid re-precipitation of the PP and facilitate removal of oil.

8. The method of claim 7, further comprising separating the re-precipitated PP from the oil and the anti-solvent.

9. The method of claim 8, further comprising separating the oil from the anti-solvent.

10. The method of claim 7, wherein the anti-solvent is hexane, ethanol, propanol, butanol, isopropyl alcohol, other linear or branched alcohol, er other organic solvent with a high affinity for oil, or a mixture thereof.

11. The method of claim 7, wherein the anti-solvent is incubated with the oil-PP mixture at a second temperature ranging from room temperature to about 70? C. for a time of from 2 min to 2 h.

12. (canceled)

13. The method of claim 1, wherein the mixed plastic waste is a polyolefin mixture containing PE and PP, the mixed plastic waste being obtained by separating polyolefins from mixed plastics using a sink-floatation method to recover the polyolefin mixture.

14. (canceled)

15. The method of claim 1, wherein the time ranges from about 2 minutes to about 60 minutes.

16. A method for removing hydrophilic pigments, adhesives, and food residues from plastic waste, the method comprising incubating a plastics mixture in an acid solution at an elevated temperature for a first time sufficient to dissolve pigments or adhesives and to dislodge or hydrolyze food residues adhered to plastic surfaces in the plastics mixture while keeping polymer structures in the plastics mixture intact.

17. The method of claim 16, wherein the elevated temperature is about 90? C.

18. The method of claim 16, wherein the first time is about 90 minutes.

19. The method of claim 16, wherein the plastics mixture comprises PET, PE, PP, PVC, polystyrene, and nylon.

20. The method of claim 16, wherein the acid is a mineral acid, an organic acid, or a combination thereof.

21. (canceled)

22. A recycled material comprising: one of polypropylene (PP) or polyethylene (PE); and an oil in an amount of less than 2% by weight; wherein the oil is attached to surfaces or void spaces of the PP or PE.

23. The recycled material of claim 22, wherein the oil comprises soybean oil, rapeseed oil, canola oil, sunflower oil, safflower oil, peanut oil, cottonseed oil, coconut oil, palm oil, olive oil, avocado oil, flaxseed oil, sesame oil, hemp seed oil, corn oil, yellow grease, waste cooking oil, brown grease, algae oil, or a combination thereof.

24. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The patent or application file may contain one or more drawings executed in color and/or one or more photographs. Copies of this patent or patent application publication with color drawing(s) and/or photograph(s) will be provided by the U.S. Patent and Trademark Office upon request and payment of the necessary fees.

[0047] FIG. 1A: Photographs showing solubility test of plastics in waste cooking oil. Only PP was soluble.

[0048] FIG. 1B: Photographs showing solubility test of plastics in coconut oil. Only PP was soluble.

[0049] FIG. 1C: Generic flow diagram illustrating a non-limiting example system for a process to recover PP and PE from mixed plastic waste.

[0050] FIG. 2A: Total and component-mass balance data obtained from lab-scale experiments to separate and recover PP from mixed plastic waste using triglycerides (here waste cooking oil) through a dissolution/re-precipitation method.

[0051] FIG. 2B: Thermal degradation profiles of pristine PP and recovered PP (rPP) produced from the dissolution/re-precipitation method described herein.

[0052] FIG. 2C: DSC profiles of pristine PP and recovered PP (rPP) produced from the dissolution/re-precipitation method described herein.

[0053] FIG. 2D: FTIR profiles of pristine PP and recovered PP (rPP) produced from the dissolution/re-precipitation method described herein.

[0054] FIG. 3A: Total and component-mass balance data obtained from integrating the widely used sink-floatation method with the dissolution/re-precipitation method described herein to separate and recover PP and PE from mixed plastic waste.

[0055] FIG. 3B: Thermal degradation profiles of pristine high-density polyethylene (HDPE) and recovered HDPE (rHDPE) produced from the method described herein.

[0056] FIG. 3C: DSC profiles of pristine HDPE and recovered HDPE (rHDPE) produced from the dissolution/re-precipitation method described herein.

[0057] FIG. 3D: FTIR profiles of pristine HDPE and recovered HDPE (rHDPE) produced from the dissolution/re-precipitation method described herein.

[0058] FIG. 4: Method for decontaminating pigments, adhesives, inorganics, and food wastes from post-consumer plastics. The illustrated method is an effective strategy to decontaminate pigments, adhesives, food waste, and inorganics from post-consumer plastics.

[0059] FIG. 5A: Method for recovery of PP and PE from a polyolefin mixture containing post-consumer PE milk bottles and post-consumer PP food containers.

[0060] FIG. 5B: Thermal degradation profiles pristine PP, post-consumer PP, and recovered post-consumer PP produced from the dissolution/re-precipitation method described herein.

[0061] FIG. 5C: DSC profiles of pristine PP, post-consumer PP, and recovered post-consumer PP produced from the dissolution/re-precipitation method described herein.

[0062] FIG. 5D: Thermal degradation profiles pristine PE, post-consumer PE and recovered post-consumer PE produced from the dissolution/re-precipitation method described herein.

[0063] FIG. 5E: DSC profiles of pristine PE, post-consumer PE, and recovered post-consumer PE produced from the dissolution/re-precipitation method described herein.

[0064] FIG. 5F: FTIR profiles of pristine PP, post-consumer PP, and recovered post-consumer PP produced from the dissolution/re-precipitation method described herein.

[0065] FIG. 5G: FTIR profiles of pristine PE, post-consumer PE, and recovered post-consumer PE produced from the dissolution/re-precipitation method described herein.

[0066] FIG. 6A: Mass balance from method for recovery of PP and PE from mixed polyolefin floats obtained from a commercial PET recycling process.

[0067] FIG. 6B: Thermal degradation profiles pristine PP, and recovered PP produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0068] FIG. 6C: DSC profiles of pristine PP, and recovered PP produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0069] FIG. 6D: Thermal degradation profiles pristine PE, and recovered PE produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0070] FIG. 6E: DSC profiles of pristine PE, and recovered PE produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0071] FIG. 6F: FTIR profiles of pristine PP, and recovered PP produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0072] FIG. 6G: FTIR profiles of pristine PE, and recovered PE produced from mixed polyolefin floats obtained from a commercial PET recycling process.

[0073] FIG. 7A: Mass balance from method for recovery of PP from surgical masksa PP rich material.

[0074] FIG. 7B: Thermal degradation profiles pristine PP, waste PP in the form of masks, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0075] FIG. 7C: DSC profiles of pristine PP, waste PP in the form of masks, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0076] FIG. 7D: FTIR profiles of pristine PP, waste PP in the form of masks, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0077] FIG. 8A: Mass balance from non-limiting example method for recovery of PP from MLP.

[0078] FIG. 8B: Thermal degradation profiles pristine PP, waste PP present within feedstock MLP, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0079] FIG. 8C: DSC profiles pristine PP, waste PP present within feedstock MLP, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0080] FIG. 8D: FTIR profiles pristine PP, waste PP present within feedstock MLP, and recovered PP produced from the dissolution/re-precipitation method described herein.

[0081] FIG. 9A: Photograph of MLP before incubation (no delamination)

[0082] FIG. 9B: Photograph of MLP after incubation (delamination)

[0083] FIG. 10A: Schematic of recycling and reusing of oil and anti-solvent in the dissolution/re-precipitation method described herein.

[0084] FIG. 10B: FTIR profile of waste cooking oil, waste cooking oil after 1st recycle, hexane, and hexane after 1st recycle in the dissolution/re-precipitation method described herein.

[0085] FIG. 11: Schematic illustration of the experimental setup used in the examples herein.

[0086] FIG. 12: Images of recovered PP powder and subsequently formed PP pellets from the dissolution/re-precipitation process.

DETAILED DESCRIPTION

[0087] Throughout this disclosure, various publications, patents, and published patent specifications are referenced by an identifying citation. The disclosures of these publications, patents, and published patent specifications are hereby incorporated by reference into the present disclosure in their entirety to more fully describe the state of the art to which this invention pertains.

[0088] Provided herein are dissolution and re-precipitation processes which utilize waste resources and green solvents to separately recover and upcycle PP and PE from mixed plastic waste streams. The methods may produce virgin-like high quality recycled PP and PE from zero-value feedstocks, and may produce recycled PET without PP contamination. The methods may also be used to produce oil-infused PP and PE that may be used as high value low slip plastic material.

[0089] In accordance with the present disclosure, highly selective dissolution of PP in certain green solvents has been discovered. The solvents are widely available, inexpensive, non-toxic, and biodegradable. Further, the solvents have high boiling points so that fugitive losses during processing can be prevented. The solvents are also compatible with several generally regarded as safe (GRAS) anti-solvents, of which several have low boiling points that would allow favorable energy use during recovery of solvent and anti-solvent from their mixtures. It is demonstrated in the examples herein that the solvent selectively dissolves PP from mixed plastics waste as well as from MLP. In addition, it is demonstrated herein that fillers and pigments can be largely removed (and in some cases, recovered) from PP. The recovered PP is shown to have high purity and virgin-like properties even when challenging mixed plastic, multilayer, and pigmented/filled materials were used as feed.

[0090] An additional use of the methods herein is in the recovery of PE. Of the plastics that are currently in use, PP and PE (together referred to as polyolefins) have lower densities than water (except for plastic foams). All other major plastics PET, polystyrene, polyamides, and PVChave a higher density than water. This property difference allows easy separation of mixtures of PP and PE from other plastics via flotation in water a prevalent plastics recycling industry practice called sink and float separation. However, conventionally, there has been a problem separating PP and PE from polyolefin mixtures because the densities of PP and PE are very similar (0.94-0.96 g/cm.sup.3). Since conventional processes do not separate PE and PP, the recycling potential of these plastics is severely restricted. When widely available floats, primarily containing PE and PP, are used as feed in the methods described herein, the selective dissolution of PP also generates a purified PE residue from the binary mixtures.

[0091] In accordance with the present disclosure, vegetable/plant oils and waste oils/fats (especially yellow grease, brown grease, animal fats, and the like), either individually or in a mixture as solvent, can be used to selectively recover, recycle, and/or upcycle PP and/or PE from mixed plastic wastes. Vegetable/plant oils and waste oils/fats are considered green solvents because of low toxicity, low volatility, availability from renewable sources, biodegradability, non-corrosiveness, and low carbon footprint. The methods herein may be described as including dissolution/re-precipitation of PP in vegetable/plant oils and waste oil/fats.

[0092] The methods herein are sustainable methods to exclusively recover PP from mixed plastic wastes, MLP wastes, and post-consumer wastes. In accordance with the present disclosure, it has been observed that PP dissolves in oils in the temperature range of 180-230? C. while other polymers (such as PE, PET. PVC, polystyrene, and nylon) do not dissolve in oils at these temperatures. This observed phenomenon allows for the design of methods to separately recover PP from mixed plastic wastes and MLP wastes.

[0093] In general, the method involves adding an oil, such as a cooking oil (e.g., a vegetable oil) to a mixture of plastics, and incubating the mixture at a temperature ranging from about 180? C. to about 230? C. for a time ranging from about 5 minutes to about 1 hour, so as to cause dissolution of the PP in the oil. In some non-limiting examples, the temperature is about 200? C. and the time is about 15 minutes. However, many other temperatures within the range of from about 180? C. to about 230? C., and other incubation times, are possible and encompassed within the scope of the present application. Any triglyceride-containing oil, such as, but not limited to, yellow grease, cooking oil, brown grease, non-edible oil, and vegetable oils can be used in the methods described herein. Non-limiting examples of suitable oils include soybean oil, rapeseed oil, canola oil, sunflower oil, safflower oil, peanut oil, cottonseed oil, coconut oil, palm oil, olive oil, avocado oil, flaxseed oil, sesame oil, hemp seed oil, corn oil, algae oil, and combinations thereof. Advantageously, the oil is a green solvent.

[0094] The oil-PP solution can be separated from the remaining plastic wastes through any conventional solid-liquids separation technique, such as, but not limited to, filtration, evaporation, or distillation. The oil-PP solution can then be allowed to cool to room temperature. The cooled oil-PP solution is referred to herein as an oil-PP mixture. When the PP concentrations in oil are less than about 2 wt %, the cooling results in formation of a distinct solid phase of oil infused PP, different from the liquid oil phase. When the PP concentrations in the oil are more than about 2 wt %, a distinct oil-PP phase separation does not occur after cooling. Instead, the cooling produces a homogeneous gel-like or wax-like solid phase containing oil and PP. In either case (low or high solids concentrations), addition of an anti-solvent causes removal of the infused oil and results in the recovery of PP. Suitable anti-solvents include, but are not limited to, hexane, ethanol, propanol, butanol, isopropyl alcohol, other linear or branched alcohols, or other organics with a high affinity for oil, or a mixture thereof. The re-precipitated PP, a solid, is easily separated from the oil (and optional anti-solvent) through any conventional solid-liquid separation technique, thereby separating PP from the mixture of plastics. When an anti-solvent is used, the anti-solvent and oil can then be separated from each other, and can be re-used in the process if desired.

[0095] Referring now to FIG. 1C, depicted is a block diagram of a non-limiting example system for employing a method for separating and purifying PP and PE from mixed plastics waste. The following Table 1 displays the function of the equipment depicted and numbered B1-B6 in the system in FIG. 1C.

TABLE-US-00001 TABLE 1 Equipment summary for the example system depicted in FIG. 1C for the recovery of PP and PE from mixed plastic waste Equipment Function B1 Separator B2 Re-precipitator and Centrifuge B3 PE Purification B4 Solvent-Anti-solvent Separator B5 PP Purification B6 Additives Remover

[0096] Referring to FIG. 1C, plastic waste streams 1, which is a polyolefin mixture obtained from a sink & float method, and 2, which is a green solvent (oil) stream, may be added to a separator B1, in which the plastic waste streams 1, 2 are incubated in an oil maintained at a temperature ranging from about 180? C. to about 230? C. so as to selectively dissolve PP. The PP dissolves in oil and is separated, such as through gravity filtration, and delivered to the re-precipitator and centrifuge B2 where an anti-solvent stream 5 is added to aid the precipitation of PP. The non-dissolved plastic waste stream 3 from the separator B1 is delivered to a PE purification apparatus B3. In B3, undissolved PE from B1 is treated with an anti-solvent stream 8 to remove any infused oil from PE so as to produce purified PE (stream 18) and a stream 10 of leftover mixture of oil and anti-solvent. In the re-precipitator and centrifuge B2, the oil-PP mixture in stream 4 is re-precipitated out of the oil with the use of an anti-solvent (stream 5) to produce re-precipitated PP (stream 6) and a mixture of oil and anti-solvent in stream 7. The re-precipitated PP in stream 6 is delivered to a PP purification apparatus B5 for purification to produce a further purified PP stream 15, for example by contacting the re-precipitated PP stream 6 with a second anti-solvent stream 9 at an elevated temperature and pressure. The streams 7, 10, 11 of leftover mixture of oil and anti-solvent are combined in stream 12 and delivered to the solvent-anti-solvent separator B4 which separates the anti-solvent 13 from the oil 14. The anti-solvent 13 and oil 14 can then be re-used in the process if desired. The purified PP 15 is subjected to one or more processes to remove additives (for example, a water wash to remove additives released from the PP matrix during dissolution) in the additives remover B6, which produces pure PP 16 and removed additives 17.

[0097] The methods herein are sustainable, energy-efficient, and capable of recovering virgin-like quality PP and PE from mixed plastic wastes and MLP waste. These methods also have the capability to remove PP contamination in PET recycled streams from existing plastic recycling facility. Furthermore, advantageously, oil-infused PP and PE may be used for high-value applications (upcycling), such as ultrahigh strength fibers and films, and no-slip plastics (low-coefficient of friction). The recovered PP may have residual oil (less than 2% by weight) attached to surfaces or void spaces of the polymer.

EXAMPLES

[0098] In these examples, by integrating with the conventional sink-floatation method (which involves separation based on density) or without, the separation of PP or PE from mixed plastic wastes is demonstrated. When integrated with the sink-float method, greater than 98% of PP and PE present in the mixed wastes was separately recovered. This is significant because the conventional sink-floatation method, widely used in industry, produces a polyolefin mixture of PP and PE that cannot be further separated by known conventional methods.

Example 1

[0099] Individual plastics PE, PP, PET, polystyrene (PS), nylon, and polyurethane (PU) were incubated in hot waste cooking oil (FIG. 1A) and hot coconut oil (FIG. 1B) (200? C. for 15 min). Only PP dissolved under both conditions while the other plastics remained insoluble. In a follow up experiment, mixed plastic waste containing PET, PE, PP, PVC, and nylon was added to waste cooking oil (WCO) maintained at 200? C. Only PP dissolved in the waste cooking oil at this temperature, which facilitates easy separation of PP from plastic mixtures using conventional solid-liquid operation. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated, which was then separated from the oil. The mass balance of this process is shown in FIG. 2A, which demonstrates separate recovery of >87% of PP present in the mixed plastic waste. Filaments made from recycled PP have similar Young's Modulus (891?51 MPa) when compared to pristine PP material (785?54 MPa). Also, the thermal properties (degradation temperature and melting point) of recycled PP from the dissolution/re-precipitation method were similar to virgin PP (see FIGS. 2B, 2C). Melt flow index of recycled PP (9.27 g/10 min) measured as per ASTM D1238 standard procedures, were comparable to that of pristine PP (11.48 g/10 min). Also, the molecular fingerprint (FTIR spectrum) of recycled PP from the dissolution/re-precipitation method were similar to virgin PP (see FIG. 2D). Therefore, the dissolution/re-precipitation technique using green solvents produces virgin-like quality of recycled PP from mixed plastic wastes.

Example 2

[0100] The dissolution/re-precipitation method also has the ability to recover both PP and PE separately from mixed plastic wastes by integrating with the sink-floatation method. The sink-floatation method separates polyolefins from mixed plastic wastes and is widely used by plastic recycling companies. A polyolefin mixture containing PE and PP recovered from the sink-floatation method was incubated in waste cooking oil at 200? C. for 15 min to dissolve PP. Hot oil containing soluble PP was separated from the insoluble PE. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated and was separated. The mass balance of this experiment is shown in FIG. 3A, which demonstrates recovery of >99% of PP and PE separately that were present in the mixed plastic waste. Thermal properties and mechanical properties of recovered PP (FIGS. 2B, 2C) and PE (FIGS. 3B, 3C) from this dissolution/re-precipitation in waste oils/fats method were similar to pristine PP and HDPE material. Also, the molecular fingerprint (FTIR spectrum) of recycled HDPE from the dissolution/re-precipitation method were similar to virgin HDPE (see FIG. 3D). Therefore, the dissolution/re-precipitation technique using green solvents produces virgin-like quality of recycled PP and HDPE from mixed plastic wastes.

Example 3

[0101] Post-consumer plastics are contaminated with pigments, adhesives, food residues and inorganic material (i.e., fillers) that may pose challenges to recycling as well as upcycling processes. A two-step process may be used to decontaminate post-consumer plastics, as shown in FIG. 4. During the first step, pigments, adhesives and food residuesprimarily consists of starch, glucose, proteins, and lipidsare easily separated by incubating post-consumer plastic mixture in 5% acidified water or methanol or polar solvents at 90? C. for 90 min. During this process, pigments, adhesives and food residues completely dissolve in acid solutions while the plastics remain intact. (Plastics do not degrade in acidified aqueous and methanol solutions around the temperature of 90? C.). Therefore, post-consumer plastic without pigments, adhesives and food residues can be collected from the first-step of the process.

[0102] Post-consumer plastic has fillers or inorganic materials such as glass fibers, calcium carbonate, talc, mica muscovite, glass beads, carbon black, dolomite, zinc oxide, and titanium oxide to improve thermal/mechanical properties, and minimize permeability of oxygen and moisture. These fillers can be separated from plastic wastes by incubating in oil maintained in the temperature interval of 120-270? C. for 15-30 min. In this example, post-consumer PE was incubated in oil at 200? C. for 30 min. The recovered PE from thermal treatment in waste oils did not contain inorganic fillers. TG analysis of post-consumer PE with 2.7 wt % fillers before and after thermal treatment in waste cooking oil at 200? C. demonstrates the feasibility of fillers separation from post-consumer plastics.

[0103] As mentioned in Example 2 above, the dissolution/re-precipitation method also has the ability to recover both PP and PE separately from mixed plastic wastes by integrating with the sink-floatation method. The following examples (example 4, 5, 6, and 7) utilized real world plastic wastes which were subjected to this dissolution/re-precipitation method to recover PP and PE (where applicable).

Example 4

[0104] PE milk bottles and PP food containers are widely used as household single use plastic objects. TG analysis of post-consumer PE indicates ? 0.2 wt % TiO.sub.2 filler and TG analysis of post-consumer PP indicates ? 22 wt % talc filler. The dissolution/re-precipitation method also has the ability to recover both PP and PE separately from mixed plastic wastes. A polyolefin mixture containing post-consumer PE milk bottles and post-consumer PP food containers was caustic washed and cut into 4?4 mm flakes. This post-consumer polyolefins waste was then incubated in waste cooking oil at 200? C. for 20 min to dissolve PP. Oil containing PP was separated from the PE by gravity separation. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated, which was easily separated from the oil using solid-liquid operations. The mass balance of this experiment is shown in FIG. 5A, which demonstrates recovery of >92% of PP and >94% PE separately that were present in post-consumer polyolefins waste. Thermal properties of recovered PP (FIGS. 5B, 5C) and PE (FIGS. 5D, 5E) from this dissolution/re-precipitation in waste oils/fats method were similar to pristine PP and PE material and also similar to actual post-consumer PP and PE which was subjected to separation using green solvents. Also, the molecular fingerprint (FTIR spectrum) of recovered PP (FIG. 5F) and PE (FIG. 5G) from this dissolution/re-precipitation in waste oils/fats method was similar to pristine PP and PE material and also similar to actual post-consumer PP and PE. Therefore, the dissolution/re-precipitation technique using green solvents produces virgin-like quality of recycled PP and PE from post-consumer polyolefins waste.

Example 5

[0105] Polyolefins waste from PET recycler is floats obtained from a commercial PET recycling plant. This feedstock was provided by a Toledo based PET recycling company. These floats usually contain bottle caps and liner material. However, the exact composition of PP and PE in this feedstock was unknown. Along with PP and PE, this feedstock also contained various fillers, pigments, and other additives. This feedstock was used as received. This polyolefin waste was then incubated in waste cooking oil at 220? C. for 15 min to dissolve PP. Oil containing PP was separated from PE by gravity separation. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated, which was separated from the oil using solid-liquid operations. The mass balance of this experiment is shown in FIG. 6A, which demonstrates recovery of >72% of PP based on initial feed mass. Thermal properties of recovered PP (FIGS. 6B, 6C) and PE (FIGS. 6D, 6E) from this dissolution/re-precipitation in waste oils/fats method were similar to pristine PP and PE. Also, the molecular fingerprint (FTIR spectrum) of recovered PP (FIG. 6F) and PE (FIG. 6G) from this dissolution/re-precipitation in waste oils/fats method was similar to pristine PP and PE material. Therefore, the dissolution/re-precipitation technique using oil produces virgin-like quality of recycled PP and PE from polyolefin waste from PET recycler.

Example 6

[0106] Nonwoven PP is used in surgical masks because it is nontoxic, breathable, hydrophobic (water-resistant), lightweight, and provides filtration. These masks have been used and discarded by people at an accelerated rate especially due to the Covid-19 pandemic. TG analysis of surgical masks also confirm the PP content present in masks. The dissolution/re-precipitation method also has the ability to recover PP from mixed plastic wastes or PP rich waste streams. Waste PP masks were cut into 4?4 mm flakes and then incubated in waste cooking oil at 200? C. for 15 min to dissolve PP. Oil containing PP was separated from the rest of the materials by gravity separation. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated, which was easily separated from the oil using solid-liquid operations. The mass balance of this experiment is shown in FIG. 7A, which demonstrates recovery of >98% of PP that were present in mixed plastic wastes or PP rich waste streams. Thermal properties of recovered PP (FIGS. 7B, 7C) from this dissolution/re-precipitation in waste oils/fats method were similar to pristine PP also similar to waste PP used as feedstock. Also, the molecular fingerprint (FTIR spectrum) of recovered PP (FIG. 7D) from this dissolution/re-precipitation in waste oils/fats method was similar to pristine PP also similar to waste PP used as feedstock. Therefore, the dissolution/re-precipitation technique using green solvents produces virgin-like quality of recycled PP from mixed plastic wastes or PP rich waste streams.

Example 7

[0107] MLP material is composed of multiple layers of different polymers that are combined using innovative technologies in order to achieve optimal functional properties for various applications including food and medical. These MLPs are typically composed of PE, PP, PET, EVOH, paper, metal, others, and a combination thereof. The dissolution/re-precipitation method herein also has the ability to recover PP from MLP. Waste MLPs obtained from particular commercial food packaging were cut into 4?4 mm flakes and then incubated in waste cooking oil at 200? C. for 15 min to selectively dissolve PP. Oil containing PP was separated from the rest of the materials by gravity separation. Upon cooling the oil-PP solution to room temperature and addition of anti-solvent, PP re-precipitated, which was easily separated from the oil using solid-liquid operations. The mass balance of this experiment is shown in FIG. 8A, which demonstrates recovery of PP that were present in the MLP. Thermal properties of recovered PP (FIGS. 8B, 8C) from this dissolution/re-precipitation in waste oils/fats method were similar to pristine PP and also similar to waste PP present within feedstock MLP. Also, the molecular fingerprint (FTIR spectrum) of recovered PP (FIG. 8D) from this dissolution/re-precipitation in waste oils/fats method was similar to pristine PP and also similar to waste PP present within feedstock MLP. Therefore, the dissolution/re-precipitation technique using green solvents produces virgin-like quality of recycled PP from MLP.

Example 8

[0108] MLP material is composed of multiple layers of different polymers that are combined using innovative technologies in order to achieve optimal functional properties for various applications including food and medical. These MLP's are typically composed of PE, PP, PET, EVOH, paper, metal, others, and a combination thereof. The dissolution/re-precipitation method herein also has the ability to delaminate these layers. Waste MLP's obtained from some commercial food packaging were cut into 4?4 mm flakes and then incubated in waste cooking oil at 200? C. for 15 min. After incubation, the MLP material, which looked like a single layer of material, started delaminating. FIG. 9A and FIG. 9B show photographs of the MLP before (FIG. 9A) and after (FIG. 9B) incubation confirming the process of delamination.

Example 9

[0109] The dissolution and re-precipitation method herein uses oil for selective dissolution of PP, and an anti-solvent is added to oil containing the dissolved PP to cause re-precipitation of the PP. In this case, hexane was added to the re-precipitated, oil-infused PP and incubated at 50? C. for 1 h. This allowed removal of residual oil from the PP. Additional washes with anti-solvent can also be implemented to further remove trace quantities of oil, if desired. The separation and recycling of oil and anti-solvent was undertaken. The mixture of waste cooking oil and hexane used as anti-solvent was subjected to separation based on boiling point difference in a rotovap equipment. The rotovap was operated at 50? C. temperature and 335 mBar pressure. The separated oil and anti-solvent can be used for further dissolving PP and causing PP re-precipitation, respectively, in subsequent separation experiments. In each experiment, a simulated mixture of PP and PE was used. A total of 4 times recycling for both oil and anti-solvent was successfully demonstrated. A schematic of these recycle and reuse experiments is shown in FIG. 10A. The FTIR profile of waste cooking oil, waste cooking oil after 1st recycle, hexane, and hexane after the 1st recycle is shown in FIG. 10B, which shows that neither solvent nor anti-solvent was degraded upon use in the PP recovery process. The TGs also confirm that the oil and anti-solvent did not contain any measurable carryover PP.

Example 10

[0110] Solubility of PP in oil was measured at increasing concentrations of PP. Low concentrations of 1-2% (g PP/g oil) as well as higher concentrations of 10% to 50% (g PP/g oil) were tested. PP was completely soluble in hot oil even when concentrations were as high as 50%. However, at very high concentrations (>30%), the hot oil-PP solution became visibly more viscous. Up to a concentration of 20%, the solution viscosity was not visibly increased relative to hot oil. At all concentrations (up to 50%), PP could be re-precipitated via addition of anti-solvent.

Experimental Set-Up

[0111] A schematic of the experimental set-up used in Examples 1-10 is shown in FIG. 11. The setup involved a hot plate, a Pyrex glass bowl, a stainless-steel screen/filter, and a magnetic stirrer. The hot plate was the heat source to maintain oil-plastic mixtures in the temperature range of 180-230? C. The pyrex glass bowl was placed on the hot plate while the stainless-steel screen was placed inside the glass bowl. A magnetic stirrer was placed below the sieve to create a vortex and ensure adequate mixing. 100-140 g of oil was used in these experiments so that the stainless-steel screen was submerged in oil. Used cooking oil was first preheated to 180-230? C. and then the polyolefin mixture was added to a stainless-steel screen that was lowered into the hot oil. Within 15 min, complete dissolution of PP in used cooking oil was observed while PE settled on the stainless-steel screen. PE was recovered by simply removing the stainless-steel screen from the submerged used cooking oil. PP was precipitated by cooling the oil-PP mix to room temperature and addition of anti-solvent. Recovered PE as well as PP was stored for further TG/DSC analysis, compositional analysis, and product development.

[0112] Certain embodiments of the compositions and methods disclosed herein are defined in the above examples. It should be understood that these examples, while indicating particular embodiments of the invention, are given by way of illustration only. From the above discussion and these examples, one skilled in the art can ascertain the essential characteristics of this disclosure, and without departing from the spirit and scope thereof, can make various changes and modifications to adapt the compositions and methods described herein to various usages and conditions. Various changes may be made and equivalents may be substituted for elements thereof without departing from the essential scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof.