REMOVAL OF ODORANTS FROM POST-CONSUMER POLYOLEFIN WASTE

Abstract

A process for treating a recycled polyolefin with an emulsion comprising aqueous and organic phases, as well as the use of said process and/or emulsion for the at least partial removal of volatile organic compounds.

Claims

1. A process for treating a recycled polyolefin, comprising, in the given order: a) providing a recycled polyolefin containing volatile organic compounds; b) contacting the recycled polyolefin with an emulsion (E) comprising: i) an aqueous phase having a pH in the range from 7.0 to 14.0; and ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; c) removing the aqueous phase and the organic phase from the recycled polyolefin; and d) optionally recycling one, or both, of the aqueous phase and the organic phase.

2. The process according to claim 1 wherein the recycled polyolefin of step (a) is in flaked form or pelletized form.

3. The process according to claim 1, wherein step (b) is carried out at a temperature in the range from 10 to 90° C.

4. The process according to claim 1, wherein step (b) is carried out for a time period in the range from 5 minutes to 5 hours.

5. The process according to claim 1, wherein the emulsion (E) is an oil-in-water emulsion, wherein the ratio of water to oil is in the range from 50:50 to 99:1.

6. The process according to claim 1, wherein the emulsion (E) is a water-in-oil emulsion, wherein the ratio of oil to water is in the range from 50:50 to 99:1.

7. The process according to claim 1, wherein the one or more fully saturated organic solvents are selected from the group of linear and branched alkanes and ethers.

8. The process according to claim 1, wherein the combination of recycled polyolefin and emulsion (E) obtained in step (b) is subjected to agitation through mechanical mixing, ultrasonic treatment, mechanical grinding or pump around loop.

9. The process according to claim 1, wherein the process comprises an additional step (c2) of rinsing residue of the emulsion (E) and/or any other foreign material and/or degradation products thereof from the recycled polyolefin, which is carried out after step (c); and/or wherein the process comprises an additional step (c3) of drying the recycled polyolefin, which is carried out after step (c) or step (c2), if present.

10. The process according to claim 1, wherein the aqueous phase removed in step (c) is recycled.

11. The process according to claim 1, wherein the recycled polyolefin originates from post-consumer waste, post industrial waste, or a combination thereof.

12. The process according to claim 1, wherein the process is for the at least partial removal of volatile organic compounds from the recycled polyolefin.

13. The process according to claim 12, wherein the content of at least one hydrophilic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process, and wherein the content of at least one hydrophobic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process.

14.-15. (canceled)

16. The process according to claim 2, wherein the recycled polyolefin in flaked form or pelletized form is shredded prior to step (b).

17. The process according to claim 5, wherein the ratio of water to oil is in the range from 80:20 to 95:5.

18. The process according to claim 6, wherein the ratio of oil to water is in the range from 80:20 to 95:5.

Description

DETAILED DESCRIPTION OF THE INVENTION

Process

[0036] The process for treating a recycled polyolefin according to the present invention, comprises, in the given order, the steps of: [0037] a) providing a recycled polyolefin containing volatile organic compounds; [0038] b) contacting the recycled polyolefin with an emulsion (E) comprising: [0039] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0040] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; [0041] c) removing the aqueous phase and the organic phase from the recycled polyolefin; and [0042] d) optionally, recycling one, or both, of the aqueous phase and the organic phase.

[0043] Step (d) is an optional step, meaning that the process according to the present invention may comprise, in the given order, the steps of: [0044] a) providing a recycled polyolefin containing volatile organic compounds; [0045] b) contacting the recycled polyolefin with an emulsion (E) comprising: [0046] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0047] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; and [0048] c) removing the aqueous phase and the organic phase from the recycled polyolefin.

[0049] Alternatively, the process according to the present invention may comprise, in the given order, the steps of: [0050] a) providing a recycled polyolefin containing volatile organic compounds; [0051] b) contacting the recycled polyolefin with an emulsion (E) comprising: [0052] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0053] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; [0054] c) removing the aqueous phase and the organic phase from the recycled polyolefin; and [0055] d) recycling one, or both, of the aqueous phase and the organic phase.

[0056] The recycled polyolefin preferably contains hydrophilic volatile organic compounds and hydrophobic volatile organic compounds. These compounds typically result from contamination during the first use of the polymer, often when the polymer is used as packaging material, especially for food and/or personal care compositions.

[0057] It is preferred that the recycled polyolefin contains at least one of, preferably all of, the group of hydrophilic volatile compounds consisting of 2,3 butanediol, 2-pentanone and benzaldehyde.

[0058] It is further preferred that the recycled polyolefin contains at least one of, preferably all of, the group of hydrophobic volatile compounds consisting of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane.

[0059] It is particularly preferred that the recycled polyolefin contains at least one of, preferably all of, the group of hydrophilic volatile compounds consisting of 2,3 butanediol, 2-pentanone and benzaldehyde and at least one of, preferably all of, the group of hydrophobic volatile compounds consisting of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane.

[0060] The recycled polyolefin preferably originates from post-consumer waste, post-industrial waste or a combination thereof, most preferably from post-consumer waste.

[0061] Post-consumer waste refers to objects having completed at least a first use cycle (or life cycle), i.e. having already served their first purpose; while industrial waste refers to manufacturing scrap, which does not normally reach a consumer.

[0062] The recycled polyolefin is preferably provided in a flaked form or pelletized form.

[0063] Whilst the process according to the present invention is effective at removing hydrophobic volatile organic compounds and hydrophilic volatile organic compounds from recycled polyolefin in flaked or pelletized form, it is preferred that the recycled polyolefin is shredded prior to the treatment with the emulsion (E) in step (b). This has been found to improve the extraction of the hydrophobic volatile organic compounds and hydrophilic volatile organic compounds both as a result of higher effective surface areas and also improved ease of agitation, should agitation be required.

[0064] It is further preferred that the combination of emulsion (E) and the recycled polyolefin in step (b) is subjected to agitation through mechanical mixing, ultrasonic treatment, mechanical grinding or pump around loop. This agitation helps to expose the surface of the recycled polyolefin to emulsion (E), avoiding that a high concentration of extracted volatile organic compounds at the interface would hinder further extraction.

[0065] As would be understood by the person skilled in the art, all polyolefins typically contain fractions that are soluble in organic solvents, with many polyolefins characterized by their hexane soluble content or xylene soluble content. Although a small amount of polyolefin dissolution may be tolerated, it is better not too dissolve too much of the recycled polyolefin. As such, the person skilled in the art would understand that they would need to avoid using excessive amounts of organic solvent in step b). Minimizing the amount of organic solvent employed would also be advantageous from an economic perspective.

[0066] Preferably, the recycled polyolefin and the emulsion (E) are present in step b) in a weight ratio in the range from 5:95 to 67:33, most preferably in the range from 5:95 to 45:55.

[0067] Step (c) involves the removal of emulsion (E) from the recycled polyolefin. This may be achieved either through a stepwise process, wherein the aqueous phase is first removed, followed by the removal of the organic phase, or wherein the organic phase is first removed, followed by the removal of the aqueous phase, or alternatively through a single step wherein both phases are removed together. Whilst this process is relatively simple to achieve through decanting and/or filtering the mixture, traces of the emulsion (E) and/or either of the aqueous or organic phase can remain on the surface of the recycled polyolefin. These traces of emulsion (E) and/or either of the aqueous or organic phase may contain solubilised volatile organic compounds, and it is therefore advantageous to remove all traces of the emulsion (E).

[0068] This may be achieved through the use of rinsing steps, whereby any foreign material and/or aqueous solutions are rinsed from the surface of the recycled polyolefin.

[0069] As such, it is preferred that the process comprises an additional step (c2) of rinsing residue of the emulsion (E) and/or any other foreign material and/or degradation products thereof from the recycled polyolefin, which is carried out after step (c).

[0070] In addition to, or alternatively to, the rinsing step (c2), it is preferred that the process comprises an additional step (c3) of drying the recycled polyolefin, which is carried out after step (c) or, if step (c2) is present, after step (c2). This drying step removes any residual aqueous phase, organic phase, or rinsing solution that may be present on the surface of the recycled polyolefin.

[0071] The treatment of the recycled polyolefin with the emulsion (E) obtained in step (b) is a washing step, as opposed to a rinsing step as defined herein, and consequently typically lasts 5 minutes or longer, like 5 minutes to 5 hours.

[0072] The treatment of the recycled polyolefin with the emulsion (E) obtained in step (b) preferably lasts 5 minutes to 4 hours, preferably 30 minutes to 3 hours, most preferably 1 to 2 hours.

[0073] It is further preferred that step (b) is carried out at a temperature in the range from 10 to 90° C., more preferably in the range from 20 to 50° C.

[0074] Step (b) is typically carried out without artificially elevating or decreasing the pressure. As such, it is preferred that step (b) is carried out at a pressure in the range from 0.5 to 2.0 atm, more preferably in the range from 0.8 to 1.5 atm, most preferably at 1.0 atm.

[0075] The process as described above and below results in the at least partial removal of volatile organic compounds from the recycled polyolefin.

[0076] It is particularly preferred that the content of at least one hydrophilic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process, and wherein the content of at least one hydrophobic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process

[0077] Whilst there are a large number of hydrophilic volatile organic compounds that may be present in recycled polyolefin, which often differ from batch to batch, there are a number that are particularly useful for determining the effect of the process of the present invention, due to ease of detection and ubiquity in recycled polyolefins. Consequently, it is preferred that the individual contents of hydrophilic volatile compounds are assessed through the detection of 2,3-butanediol, 2-pentanone and benzaldehyde.

[0078] Consequently it is further preferred that at least one of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process.

[0079] It is even further preferred that all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process.

[0080] There are similarly a large number of hydrophobic volatile organic compounds that may be present in recycled polyolefin, which often differ from batch to batch. Analogously to the situation with hydrophilic volatile organic compounds, it is preferred that the individual contents of hydrophobic volatile compounds are assessed through the detection of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane.

[0081] Consequently it is further preferred that at least one of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process.

[0082] It is even further preferred that all of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane have been reduced by at least 90% relative to the content measured before the process.

[0083] In a particularly preferred embodiment, all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone, benzaldehyde, styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane have been reduced by at least 90% relative to the content measured before the process.

Emulsion (E)

[0084] The emulsion (E) of the present invention comprises: [0085] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0086] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0.

[0087] The skilled person would be aware that emulsions may comprise further phases, being immiscible with the aqueous and organic phases as described above, and indeed such complex emulsions are not excluded from the present invention. These complex emulsions may have advantages in the removal of particularly specialised volatile organic compounds; however, in the context of the present invention, it is preferred that the emulsion (E) consists of the aqueous phase and organic phase as described above, since this results in an operationally simple process.

[0088] The emulsion (E) of the present invention may be preformed before contact with the recycled polyolefin in step (b) or alternatively the aqueous phase and the organic phase may be added separately to the recycled polyolefin and the emulsion (E) generated during step (b).

[0089] Dual phase emulsions comprising an aqueous and organic phase are classified as either oil-in-water or water-in-oil emulsions, depending on which component forms the dispersed phase and which forms the continuous phase, which can usually be predicted from the relative amounts (i.e. ratio) of the phases.

[0090] In the following discussion, the terms “oil” and “water” are equivalent to “organic phase” and “aqueous phase” respectively.

[0091] The relative content of the organic and aqueous phases are not particularly limited in the present invention. It is preferred that the ratio of water to oil is in the range from 1:99 to 99:1, more preferably in the range from 5:95 to 99:5.

[0092] In one embodiment, the emulsion (E) of the present invention is an oil-in-water emulsion, wherein the ratio of water to oil is in the range from 50:50 to 99:1, more preferably in the range from 80:20 to 95:5.

[0093] In an alternative embodiment, the emulsion (E) of the present invention is a water-in-oil emulsion, wherein the ratio of oil to water is in the range from 50:50 to 99:1, more preferably in the range from 80:20 to 95:5.

[0094] Whilst the precise ratio between the water and the oil in the emulsion (E) is not critical for achieving effective removal of volatile organic compounds, there are other advantages to certain ratios. In particular, ratios of between 80:20 and 95:5 are useful if the recycling of the major component is to be achieved. Furthermore, the organic phase, whilst relatively inexpensive, is more costly to employ than water, due to waste flow management considerations. Consequently, the embodiment wherein the ratio of water to oil is in the range from 80:20 to 95:5 is particularly preferred from an economic perspective, especially if recycling of the aqueous phase is desired. This embodiment is furthermore advantageous for avoiding excessive polyolefin dissolution in the organic phase.

[0095] The pH of the aqueous phase is in the range from 7.0 to 14.0, preferably in the range from 7.0 to 11.0, most preferably in the range from 7.0 to 9.0.

[0096] The aqueous phase can comprise various additives, such as surfactants, to improve the removal of volatile organic compounds or to improve the stability of the emulsion; however, for reasons of process economy, it is particularly preferred that the aqueous phase essentially consists of water.

[0097] The organic phase of the emulsion (E) needs to be unreactive to the extracted volatile organic compounds, the aqueous phase and the recycled polyolefin, in addition to being highly stable. Furthermore, the polarity must be such that an emulsion is formed with the aqueous phase.

[0098] Consequently, the organic phase must comprise at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0.

[0099] It is preferred that the organic phase comprises at least 95% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0, more preferably at least 98% v/v, most preferably the organic phase consists of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0.

[0100] In a particularly preferred embodiment, the organic phase comprises at least 90% v/v of, more preferably 95% v/v of, yet more preferably at least 98% v/v of, most preferably consists of a single fully saturated organic solvent having a logP value in the range from 1.0 to 10.0.

[0101] The fully saturated organic solvents are preferably selected from the group of linear and branched alkanes and ethers (i.e. containing only carbon, hydrogen and optionally oxygen), more preferably from the group of linear and branched alkanes (i.e. containing only carbon and hydrogen).

[0102] The fully saturated organic solvents must have logP values in the range from 1.0 to 10.0, more preferably in the range from 2.0 to 8.0, most preferably in the range from 3.0 to 6.0.

Use

[0103] The present invention is also directed to a use of the process as described above, as well as the use of the emulsion (E) as described above. All preferable features and preferred embodiments apply equally to the use of the process and the use of the emulsion (E), as to the process itself.

[0104] In one embodiment, the present invention is directed to the use of the process as described above for the at least partial removal of volatile organic compounds from a recycled polyolefin.

[0105] In another embodiment, the present invention is directed to the use of an emulsion (E), comprising: [0106] a) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0107] b) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having log P values in the range from 1.0 to 10.0, for the at least partial removal of volatile organic compounds from recycled polyolefins.

[0108] In both of these uses, it is preferred that the content of at least one hydrophilic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E), and wherein the content of at least one hydrophobic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0109] It is further preferred that at least one of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0110] It is even further preferred that all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0111] It is further preferred that at least one of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0112] It is even further preferred that all of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane have been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0113] In a particularly preferred embodiment, all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone, benzaldehyde, styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane have been reduced by at least 90% relative to the content measured before the process or use of the emulsion (E).

[0114] The present invention may further be characterized by the following items: [0115] 1. A process for treating a recycled polyolefin, comprising, in the given order, the steps of: [0116] a) providing a recycled polyolefin containing volatile organic compounds; [0117] b) contacting the recycled polyolefin with an emulsion (E) comprising: [0118] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0119] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; and [0120] c) removing the aqueous phase and the organic phase from the recycled polyolefin. [0121] 2. A process for treating a recycled polyolefin, comprising, in the given order, the steps of: [0122] a) providing a recycled polyolefin containing volatile organic compounds; [0123] b) contacting the recycled polyolefin with an emulsion (E) comprising: [0124] i) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0125] ii) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having logP values in the range from 1.0 to 10.0; [0126] c) removing the aqueous phase and the organic phase from the recycled polyolefin; and [0127] d) recycling one, or both, of the aqueous phase and the organic phase. [0128] 3. The process according to item 1 or 2 wherein the recycled polyolefin of step (a) is in flaked form or pelletized form. [0129] 4. The process according to item 3 wherein the recycled polyolefin in flaked form or pelletized form is shredded prior to step (b). [0130] 5. The process according to any one of the preceding items, wherein step (b) is carried out at a temperature in the range from 10 to 90° C.

[0131] 6. The process according to any one of the preceding items, wherein step (b) is carried out at a pressure in the range from 0.5 to 2.0 atm. [0132] 7. The process according to any one of the preceding items, wherein step (b) is carried out for a time period in the range from 5 minutes to 5 hours. [0133] 8. The process according to any one of the preceding items, wherein the recycled polyolefin and the emulsion (E) are present in step b) in a weight ratio in the range from 5:95 to 67:33. [0134] 9. The process according to any one of the preceding items, wherein the recycled polyolefin and the emulsion (E) are present in step b) in a weight ratio in the range from 5:95 to 45:55. [0135] 10. The process according to any one of the preceding items, wherein the ratio of water to oil in the emulsion (E) is in the range from 1:99 to 99:1. [0136] 11. The process according to any one of the preceding items, wherein the ratio of water to oil in the emulsion (E) is in the range from 5:95 to 95:5. [0137] 12. The process according to any one of items 1 to 9, wherein the emulsion (E) is an oil-in-water emulsion, wherein the ratio of water to oil is in the range from 50:50 to 99:1. [0138] 13. The process according to any one of items 1 to 9, wherein the emulsion (E) is an oil-in-water emulsion, wherein the ratio of water to oil is in the range from 80:20 to 95:5. [0139] 14. The process according to any one of items 1 to 9, wherein the emulsion (E) is a water-in-oil emulsion, wherein the ratio of oil to water is in the range from 50:50 to 99:1. [0140] 15. The process according to any one of items 1 to 9, wherein the emulsion (E) is a water-in-oil emulsion, wherein the ratio of oil to water is in the range from 80:20 to 95:5. [0141] 16. The process according to any one of the preceding items, wherein the emulsion (E) is preformed before contact with the recycled polyolefin in step (b). [0142] 17. The process according to any one of items 1 to 15, wherein the aqueous phase and the organic phase are added separately to the recycled polyolefin and the emulsion (E) is generated during step (b). [0143] 18. The process according to any one of the preceding items, wherein the one or more fully saturated organic solvents are selected from the group of linear and branched alkanes and ethers. [0144] 19. The process according to any one of items 1 to 17, wherein the one or more fully saturated organic solvents are selected from the group of linear and branched alkanes. [0145] 20. The process according to any one of the preceding items, wherein the combination of recycled polyolefin and emulsion (E) obtained in step (b) is subjected to agitation through mechanical mixing, ultrasonic treatment, mechanical grinding or pump around loop. [0146] 21. The process according to any one of the preceding items, wherein the process comprises an additional step (c2) of rinsing residue of the emulsion (E) and/or any other foreign material and/or degradation products thereof from the recycled polyolefin, which is carried out after step (c); [0147] 22. The process according to any one of the preceding items, wherein the process comprises an additional step (c3) of drying the recycled polyolefin, which is carried out after step (c) or step (c2), if present. [0148] 23. The process according to any one of the preceding items, wherein the aqueous phase removed in step (c) is recycled. [0149] 24. The process according to any one of the preceding items, wherein the recycled polyolefin originates from post-consumer waste, post industrial waste, or a combination thereof [0150] 25. The process according to any one of the preceding items, wherein the recycled polyolefin originates from post-consumer waste. [0151] 26. The process according to any one of the preceding items, wherein the recycled polyolefin contains at least one of, preferably all of, the group of hydrophilic volatile compounds consisting of 2,3 butanediol, 2-pentanone and benzaldehyde. [0152] 27. The process according to any one of the preceding items, wherein the recycled polyolefin contains at least one of, preferably all of, the group of hydrophobic volatile compounds consisting of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane. [0153] 28. The process according to any one of the preceding items, wherein the process is for the at least partial removal of volatile organic compounds from the recycled polyolefin. [0154] 29. The process according to item 28, wherein the content of at least one hydrophilic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process, and wherein the content of at least one hydrophobic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process. [0155] 30. The process according to item 29, wherein at least one of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0156] 31. The process according to item 29, wherein all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process. [0157] 32. The process according to any one of items 29 to 31, wherein at least one of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0158] 33. The process according to any one of items 29 to 31, wherein all of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane have been reduced by at least 90% relative to the content measured before the process. [0159] 34. A use of the process according to any one of items 1 to 27 for the at least partial removal of volatile organic compounds from a recycled polyolefin. [0160] 35. The use according to item 34, wherein the content of at least one hydrophilic volatile organic compound, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process, and wherein the content of at least one hydrophobic volatile organic compound, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process. [0161] 36. The use according to item 35, wherein at least one of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0162] 37. The use according to item 35, wherein all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process. [0163] 38. The use according to any one of items 35 to 37, wherein at least one of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0164] 39. The use according to any one of items 35 to 37, wherein all of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process. [0165] 40. A use of an emulsion (E) comprising: [0166] a) an aqueous phase having a pH in the range from 7.0 to 14.0; and [0167] b) an organic phase comprising at least 90% v/v of one or more fully saturated organic solvents having log P values in the range from 1.0 to 10.0, for the at least partial removal of volatile organic compounds from recycled polyolefins. [0168] 41. The use according to item 40, wherein the content of at least one hydrophilic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process, and wherein the content of at least one hydrophobic volatile organic compound in the recycled polyolefin obtained as a product of the process, as measured by HS-GC/MS, has been reduced by at least 90% relative to the content measured before the process. [0169] 42. The use according to item 41, wherein at least one of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0170] 43. The use according to item 41, wherein all of the individual contents, as measured by HS-GC/MS, of 2,3-butanediol, 2-pentanone and benzaldehyde in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process. [0171] 44. The use according to any one of items 41 to 43, wherein at least one of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process has been reduced by at least 90% relative to the content measured before the process. [0172] 45. The use according to any one of items 41 to 43, wherein all of the individual contents, as measured by HS-GC/MS, of styrene, 2-ethyl-1-hexanol, 2-nonanone, D-limonene, 5-(2-methylpropyl)-nonane and 2,6-dimethyldecane in the recycled polyolefin obtained as a product of the process have been reduced by at least 90% relative to the content measured before the process.

EXAMPLES

1. Definitions/Determination Methods:

[0173] Determination of volatile organic compound content via HS-GC/MS
Static headspace analysis for marker substance determination

[0174] The parameters of the applied headspace gas chromatography mass spectrometry (HS-GC/MS) method are described here.

[0175] For the measurement of a benzene standard 5 μl of a standard solution containing 100 μg/ml benzene in methanol were injected into a 20 ml HS vial and tightly closed with a PTFE cap. Each HS-GC/MS test sequence of sample measurements included the analysis of such a benzene standard. The benzene signal of the corresponding sequence was used for the calculation of the relative normalised area as described further below.

[0176] The samples were also analysed by HS-GC/MS in order to determine potential odorant and hazardous marker substances. Therefore, 2.000±0.100 g samples were weighed in a 20 ml HS vial and tightly sealed with a PTFE cap. For each washing experiment a double determination of the respective sample was performed.

[0177] Applied headspace parameters for the analyses of standards and samples differed in the vial equilibration time and the HS oven temperature. Apart from that, method parameters were kept the same for standard and sample runs. The mass spectrometer was operated in scan mode and a total ion chromatogram (TIC) was recorded for each analysis. The detected substances were tentatively identified by the aid of deconvolution and a minimum match of 800 when the hit was subsequently compared to a mass spectral library. More detailed information on method parameters and data evaluation software is given below: [0178] HS parameter (Shimadzu AOC 5000 Headspace sampler) [0179] Vial equilibration time: 120 min [0180] Oven temperature: 100° C. [0181] Syringe temperature: 110° C. [0182] GC parameter (Shimadzu GC-MS-QP2010) [0183] Column: DB-FATWAX UI UST 446421H [0184] (30 m×250 μm×0.25 μm) [0185] Carrier gas: Helium 5.0 [0186] Flow: 1.3 ml/min [0187] Split: 5:1 [0188] GC oven program: 35° C. for 2 min [0189] 10° C./min until 250° C. [0190] 250° C. for 5 min [0191] MS parameter (Agilent 5975C inert XL MSD) [0192] Acquisition mode: Scan [0193] Scan parameters: [0194] Low mass: 27 [0195] High mass: 200 [0196] Threshold: 10 [0197] Software/Data evaluation [0198] MSD ChemStation E.02.02.1431 [0199] MassHunter GC/MS Acquisition B.07.05.2479 [0200] AMDIS GC/MS Analysis Version 2.71 [0201] NIST Mass Spectral Library (Version 2011) [0202] Microsoft Excel 2016

Data Evaluation

[0203] The benzene standard was evaluated with the same parameters as the sample runs. Therefore, extracted ion chromatograms (EICs) of the measured benzene standards and samples were created. The peak areas required for the further data evaluation were obtained by integrating the corresponding substance peak of the EIC. The applied integration parameters and substance specific ions (m/z ratios) of all marker substances are listed in tables 1 and 2.

TABLE-US-00001 TABLE 1 Retention times and substance specific ions of selected marker substances. Retention Substance specific ion of the Substance time/min corresponding EIC (m/z) Acetaldehyde 1.7 44 Benzene.sup.1 3.9 78 2-Pentanone 4.3 86 2,6-Dimethyl decane 5.1 170 Toluene 5.3 91 Ethylbenzene 6.6 106 1-Butanol 7.2 74 o-Xylene 7.5 106 D-Limonene 7.6 136 5-(2-Methylpropyl)-nonane 8.2 184 Styrene 8.6 104 2-Nonanone 10.5 142 2-Ethyl-1-hexanol 11.9 130 2,3-Butanediol 13.1 90 Benzaldehyde 12.5 106 Acetophenone 14.2 105 .sup.1Relevant for both standards and samples.

[0204] In general it is not possible to exclude the possibility of overlapping peaks in some regions of the HS-GC/MS readout, however this has not been observed to have a significant influence on the values obtained in the data presented in the present application.

TABLE-US-00002 TABLE 2 Integration parameters for the determination of the peak areas. Integration event Value Initial area reject 1000 Initial peak width 0.005 Shoulder detection OFF Initial threshold 10.5

[0205] The substance specific ion peak areas (Area(EIC)x) were normalised by the extracted ion peak area of benzene (Area(EIC).sub.Benzene) and the sample amount in order to obtain the normalised area (norm. Area.sub.x_ see equation 1).

[00002]$\begin{array}{cc}\mathrm{norm}.{\mathrm{Area}}_X=\frac{{\mathrm{Area}\left(\mathrm{EIC}\right)}_X}{\mathrm{Area}{\left(\mathrm{EIC}\right)}_{\mathrm{Benze𝔫e}}*\mathrm{sample}\mathrm{amount}\left[g\right]}& \mathrm{Equation}1\end{array}$

[0206] For each washing experiment the normalised mean area (norm. Area.sub.x) of the two individual analyses (norm. Area.sub.x1, norm. Area.sub.x2) was calculated by using the Excel function AVERAGE (see equation 2).

norm. Area.sub.x=AVERAGE(norm. Area.sub.x1: norm. Area.sub.x2)  Equation 2

[0207] To obtain the relative normalised area (rel. norm. Area.sub.x), the normalised mean area of the respective substance (norm. Area.sub.x) was divided by the normalised mean area of the reference sample (norm. Area.sub.R) as stated in equation 3.

[00003]$\begin{array}{cc}\mathrm{rel}.\mathrm{norm}.{\mathrm{Area}}_X=\frac{\stackrel{\_}{\mathrm{norm}.{\mathrm{Area}}_X}}{\mathrm{norm}.{\mathrm{Area}}_R}& \mathrm{Equation}3\end{array}$

[0208] For the data evaluation three different cases must be distinguished. [0209] 1) The substance specific ion peak was evaluable in both analysis runs of the double determination. The relative normalised area was obtained by applying equations 1, 2 and 3 as described below. [0210] 2) The substance specific ion peak was evaluable in only one analysis run of the double determination. Consequently, the normalised mean area (norm. Area.sub.x) is equal to the normalised area (norm. Area.sub.x). Thus, the so obtained relative normalised area (rel. norm. Area.sub.x) was asterisked (“*”) in the result table. [0211] 3) The substance specific ion peak was not evaluable in neither of the two analysis runs of the double determination. Therefore, the calculation of the relative normalised area (rel. norm. Area.sub.x) was not applicable (“n.a.”) which was indicated in the result table.

[0212] In order to estimate the deviation of the two individual analyses of one corresponding washing experiment the relative standard deviation (RSD.sub.x) was calculated (only applicable to case 1). Therefore, the standard deviation of the two normalised areas (norm. Area.sub.x1, norm. Area.sub.x2) was determined by using the Excel function STDEV.S. To calculate RSD.sub.x the standard deviation (STDEV.S) was divided by the normalised mean area (norm. Area.sub.x, see equation 4).

[00004]$\begin{array}{cc}RS{D}_X=\frac{\mathrm{STDEV}.S\left(\mathrm{norm}.{\mathrm{Area}}_{X1}:\mathrm{norm}.{\mathrm{Area}}_{X2}\right)}{\stackrel{\_}{\mathrm{norm}.{\mathrm{Area}}_X}}& \mathrm{Equation}4\end{array}$

[0213] To refer the standard deviation to the rel. norm. Area.sub.x, the RSD.sub.x was multiplied by the rel. norm. Area.sub.x as described in equation 5.

rel. RSD.sub.x=RSD.sub.x*rel. norm. Area.sub.x  Equation 5

2. Experimental Results:

[0214] In the following experiments, the materials used were as follows:

Recycled Polyolefin:

[0215] The recycled polyolefin employed in the following experiments was obtained from mtm plastics GmbH, Niedergebra, Germany, and is a pre-sorted, unwashed polymer mixture used by mtm plastics GmbH in the preparation of Dipolen S. Consequently the composition of the recycled polyolefin with regard to the content of polyethylene and polypropylene is identical to that of Dipolen S; however the content of small molecule contaminants is likely to be different.

[0216] Dipolen S is a recycled polymer mixture comprising polyethylene and polypropylene obtained from mtm plastics GmbH, Niedergebra, Germany and has a polyethylene content of 40 wt.-% determined by DSC analysis. The melting points determined by DSC were 162° C. (PP) and 128° C. (PE).

[0217] In the following experiments, the recycled polyolefin was obtained in a flaked form; cryo-milling was then undertaken prior to the below experiments in order to enable the experiments to be carried out on a smaller scale than would be the case for the industrial process.

[0218] The calculation of “washing efficiency” was carried out according to the following equation

[00005]$\mathrm{washing}\mathrm{efficiency}=\frac{\left(\mathrm{compound}\mathrm{conc}.\mathrm{before}\mathrm{wash}\right)-\mathrm{compound}\mathrm{conc}.\mathrm{after}\mathrm{wash}}{\left(\mathrm{compound}\mathrm{conc}.\mathrm{before}\mathrm{wash}\right)}$

wherein compound concentrations were measured using HS-GC/MS and expressed in %.

Experimental Procedure:

Inventive Example 1

[0219] 90 ml of water and 10 ml of heptane were added to a 250 ml beaker equipped with a magnetic stir bar and the overhead ultrasound probe (UP400S from Hielscher Ultrasonics GmbH with a 40 mm diameter sonotrode; 400 W, 24 kHz) was inserted into the liquid at approximately 75% of the liquid volume height. The magnetic stirrer and the ultrasound device were switched on and after 2 minutes 10 g of the cryo-milled polymer powder were added to the emulsion, followed by stirring and sonication of the suspension for 1 hour.

[0220] The wash solvent mixture was then removed by filtration and the polymer powder was two times rinsed with water. Each of these rinsing steps was done by contacting the polymer powder for 30 seconds with 100 ml of demineralised water, followed by removal of the water by filtration. The polymer powder was then dried in a vacuum oven at 70° C. for 1 hour.

Inventive Example 2

[0221] As example 1, except that 50 ml of water and 50 ml of heptane were used as the wash solvent mixture instead of 90 ml of water and 10 ml of heptane.

Inventive Example 3

[0222] As example 1, except that 10 ml of water and 90 ml of heptane were used as the wash mixture instead of 90 ml of water and 10 ml of heptane.

Inventive Example 4

[0223] As example 1, except that an Ultraturrax device (IKA T-18 Ultra Turrax Homogenizer) was used instead of the overhead ultrasound probe.

Inventive Example 5

[0224] As example 4, except that a cooling bath was used to keep the temperature during the wash with the water-heptane emulsion at approximately 20° C.

Comparative Example 1

[0225] 100 ml of water as the wash solvent were added to a 250 ml beaker equipped with a magnetic stir bar and an overhead ultrasound probe (UP400S from Hielscher Ultrasonics GmbH with a 40 mm diameter sonotrode; 400 W, 24 kHz) was inserted into the liquid at approximately 75% of the liquid volume height. 10 g of cryo-milled polymer powder were then added and the stirred suspension was sonicated for 1 hour. The liquid phase was then removed by filtration and the polymer powder was two times rinsed with water. Each of these rinsing steps consisted of contacting the polymer powder for 30 seconds with 100 ml of demineralised water, followed by removal of the water by filtration. The polymer powder was then dried in a vacuum oven at 70° C. for 1 hour.

Comparative Example 2

[0226] As comparative example 1, except that 100 ml of heptane were used as the wash solvent instead of 100 ml of water.

TABLE-US-00003 TABLE 3 Lipophilicity and volatility of tested volatile organic compounds Contaminant log P.sub.octanol/water* b.p. 2,3-Butanediol −0.92.sup.1 177° C. 2-Pentanone 0.84.sup.2 102° C. 1-Butanol 0.84.sup.2 118° C. Benzaldehyde 1.48.sup.2 178° C. Styrene 3.05.sup.2 145° C. 2-Ethyl-1-hexanol 2.73.sup.3 185° C. 2-Nonanone 3.16.sup.2 195° C. D-Limonene 4.57.sup.4 176° C. 5-(2-Methylpropyl)-nonane 5.03.sup.5 211° C. 2,6-Dimethyl decane 6.09.sup.6 200° C. *The logP values of the tested volatile organic compounds were not determined experimentally, but are generally accepted literature values, which can be found i.a. at: .sup.1National Center for Biotechnology Information (2020). PubChem Compound Summary for CID 262, 2,3-Butanediol. Retrieved Nov. 13, 2020 from https://pubchem.ncbi.nlm.nih.gov/compound/2_3-Butanediol. .sup.2James Sangster, Octanol-Water Partition Coefficients of simple organic compounds. J. Phys. Chem. Ref. Data, 1989, Vol. 18, No 3, 1111-1226 .sup.3National Center for Biotechnology Information (2020). PubChem Compound Summary for CID 7720, 2-Ethylhexanol. Retrieved Nov. 13, 2020 from https://pubchem.ncbi.nlm.nih.gov/compound/2-Ethylhexanol .sup.4National Center for Biotechnology Information (2020). PubChem Compound Summary for CID 22311, Limonene. Retrieved Nov. 13, 2020 from https://pubchem.ncbi.nlm.nih.gov/compound/Limonene .sup.5https://www.chemsrc.com/en/cas/62185-53-9_216142.html .sup.6https://www.chemsrc.com/en/cas/13150-81-7_122290.html

TABLE-US-00004 TABLE 4 Washing efficiency of water, heptane, and various emulsion washes in terms of the reduction of contaminants (based on contaminants content before the treatment). Water/ Water/ Water/ Water/ Water/ heptane heptane heptane heptane heptane 90:10 90:10 water heptane 90:10 50:50 10:90 (UT)* (UT/ice)** 2,3-Butanediol 100 98 100 100 100 100 100 2-Pentanone 78 92 96 99 99 99 98 Benzaldehyde 100 97 100 100 100 100 97 Styrene 48 96 98 99 98 98 98 2-Ethyl-1-hexanol 49 92 95 98 99 96 94 2-Nonanone 62 100 100 100 100 100 100 D-Limonene 42 100 100 99 100 99 97 5-(2-Methylpropyl)-nonane 8 89 95 98 98 96 100 2,6-Dimethyl decane 30 100 96 100 99 98 98 Hydrophilic average 93 96 99 100 100 100 98 Hydrophobic average 40 96 97 99 99 98 98 *wash undertaken in Ultraturrax machine at 65° C. **wash undertaken in Ultraturrax machine cooled with ice, at approx. 20° C.

[0227] As can be seen from Table 4, the washing efficiency of emulsions, be they water-in-oil or oil-in-water emulsions, are superior to the use of either water or heptane individually. The aqueous washes (i.e. with water alone) typically have lower efficiency for the removal of hydrophilic volatile organic compounds and the heptane washes typically are not fully effective at the removal of hydrophilic volatile organic compounds.

[0228] Of particular importance is the effectiveness of the water/heptane 90:10 emulsion, which allows for the use of low amounts of heptane and the easy recycling of the aqueous phase, both of which add to the economic benefits of the process.

[0229] A further minor improvement can be observed when Ultraturrax has been used, reflecting the importance of emulsion formation and sheer forces. The ice-cooled Ultraturrax results show that it is these features, rather than the temperature that is the source of the improvements.