METHOD AND SYSTEM FOR TREATING POLYMER WASTE COMPRISING HETEROATOMIC POLYMERS

Abstract

The present invention relates to a method for producing a hydrocarbon product from mixed polymer waste, preferably plastic waste and/or post consumer plastic waste, wherein said mixed polymer waste comprises 50-99.5 wt % polyolefins and 0.5-50 wt % polymer comprising heteroatoms, based on the total weight of the mixed polymer waste, comprising: (i) feeding said mixed polymer waste into an extruder, preferably a single screw extruder; (ii) adding chemicals, preferably alkali metal salt and/or alkali earth metal salt, to said mixed polymer waste to degrade said polymer comprising heteroatoms; (iii) removing degradation products derived from said polymer comprising heteroatoms from said hydrocarbon product; and (iv) collecting the hydrocarbon product. The method and system of the present invention may be used as a pre-treatment in recycling mixed polymer waste to produce a hydrocarbon product ideally suited for pyrolysis.

Claims

1. A method for producing a hydrocarbon product from mixed polymer waste, wherein said mixed polymer waste comprises 50-99.5 wt % polyolefins and 0.5-50 wt % polymer comprising heteroatoms, based on the total weight of the mixed polymer waste, comprising: (i) feeding said mixed polymer waste into an extruder; (ii) adding chemicals, to said mixed polymer waste to degrade said polymer comprising heteroatoms; (iii) removing degradation products derived from said polymer comprising heteroatoms from said hydrocarbon product; and (iv) collecting the hydrocarbon product.

2. A method as claimed in claim 1, wherein said mixed polymer waste comprises 50-99 wt % polyolefins, based on the total weight of the mixed polymer waste composition.

3. A method as claimed in claim 1, wherein said polyolefins are selected from polyethylene, polypropylene, polystyrene and mixtures thereof.

4. A method as claimed in claim 1, wherein said mixed polymer waste comprises 1-50 wt % polymer comprising heteroatoms, based on the total weight of the mixed polymer waste composition.

5. A method as claimed in any claim 1, wherein said polymer comprising heteroatoms is selected from polyethylene terephthalate (PET), polyamide (PA), polyurethane (PU), biopolymers (e.g. polylactic acid, polyhydroxyalkanoates), cellulose, poly(ethylene-co-vinyl acetate) (EVA), poly(vinyl alcohol-co-ethylene) (EVOH), polycarbonate, poly(acrylonitrile-co-butadiene-co-styrene) (ABS), poly(styrene-co-acrylonitrile) (SAN), polymethylmethacrylate (PMMA) and mixtures thereof.

6. A method as claimed in claim 1, wherein said mixed polymer waste further comprises non-polymeric compounds comprising heteroatoms.

7. A method as claimed in claim 1, wherein said mixed polymer waste is mixed with alkali metal salt, and/oralkali earth metal salt prior to feeding said mixed polymer waste to the extruder.

8. A method as claimed in claim 7, wherein the mixture of alkali metal salt and/or alkali earth metal salt and mixed polymer waste is all fed into the extruder

9. A method as claimed in claim 1, wherein said extruder is at a temperature of at least 300 C.

10. A method as claimed in claim 1, wherein the residence time of said mixed polymer waste in said extruder is 0.1-20 minutes.

11. A method as claimed in claim 1, wherein said polymers comprising heteroatoms and optionally non-polymeric compounds comprising heteroatoms, are simultaneously degraded in said extruder.

12. A method as claimed in claim 1, wherein the degradation products derived from the polymer comprising heteroatoms, and optionally from non-polymeric compounds comprising heteroatoms, are removed in the form of volatiles and via a devolatization outlet of the extruder, the extruder die or a devolatization unit connected to the extruder exit.

13. A method as claimed in claim 1, wherein the degradation products derived from the polymer comprising heteroatoms, and optionally from non-polymeric compounds comprising heteroatoms, are removed in the form of solids and via a melt filter.

14. A method as claimed in claim 1, wherein said hydrocarbon product comprises 0-5 wt % polyethylene terephthalate (PET), based on the total weight of the hydrocarbon product, and/or said hydrocarbon product comprises 0-5 wt % polyamide (PA), based on the total weight of the hydrocarbon product.

15. A method as claimed in claim 1, wherein said polyolefins present in said mixed polymer waste undergo cracking in said extruder, and preferably wherein said hydrocarbon product has: a lower weight average molecular weight than said mixed polymer waste; a lower complex viscosity, Eta (0.5) than said mixed polymer waste; a lower complex viscosity, Eta (200) than said mixed polymer waste; and/or a higher MFR2 than said mixed polymer waste.

16. A method as claimed in claim 1, further comprising pyrolysis of said hydrocarbon product.

17. A system for producing a hydrocarbon product from mixed polymer waste, comprising: an extruder for conversion of mixed polymer waste comprising 50-99.5 wt % polyolefins and 0.5-50 wt % polymer comprising heteroatoms into a mixture of hydrocarbon product and degradation products derived from the polymer comprising heteroatoms; a melt filter for receiving the mixture of hydrocarbon product and degradation products from the extruder and removing solid degradation products from said hydrocarbon product; and a degassing unit for receiving the hydrocarbon product from the melt filter and removing volatile degradation products from said hydrocarbon product.

18. A method for recycling mixed polymer waste comprising a pre-treatment to remove polymer comprising heteroatoms, wherein said pre-treatment comprises a method as defined in claim 1.

19. A system for recycling mixed polymer waste, comprising: an extruder for conversion of mixed polymer waste comprising 50-99.5 wt % polyolefins and 0.5-50 wt % polymer comprising heteroatoms, and chemicals into a mixture of hydrocarbon product and degradation products derived from the polymer comprising heteroatoms; a melt filter for receiving the mixture of hydrocarbon product and degradation products from the extruder and removing solid degradation products from said hydrocarbon product; a degassing unit for receiving the hydrocarbon product from the melt filter and removing volatile degradation products from said hydrocarbon product; and a pyrolysis unit for receiving the hydrocarbon product from the degassing unit and pyrolysing said the hydrocarbon product.

Description

[0119] The invention will now be described using the following non-limiting examples and Figures, wherein:

[0120] FIG. 1 is a block diagram of a preferred system of the present invention, wherein an extruder, a melt filter, and a degassing unit are each connected in series. The mixed polymer waste and chemicals, preferably alkali metal salt and/or alkaline earth metal salt, are fed into the extruder, and solid degradation products from heteroatom-containing polymer and optionally non-polymeric heteroatom-containing compounds are removed from the hydrocarbon product in the melt filter and volatile degradation products are removed in the degassing unit. The resulting hydrocarbon product, which is cracked polyolefin, has a lower molecular weight, lower viscosity and higher MFR2 than the mixed polymer waste starting material. It is much more suitable as a feedstock for a pyrolysis unit. The hydrocarbon product is pumped to a delivery device from which it is sprayed into a pyrolysis unit.

[0121] FIG. 2 shows the MFR2 of virgin LLDPE, LDPE and PP after extrusion. Virgin grade non-extruded references are close to MFR2 1 for PE, and MFR2-3 for PP;

[0122] FIG. 3 shows the average MW (GPC) of virgin LLDPE, LDPE and PP after extrusion as well as virgin grade non-extruded references;

[0123] FIG. 4 shows the complex viscosity (Pas) at 0.5 and 200 rad/sec for LLDPE and PP after extrusion in the range 300-380 C. and 20-60 RPM, as well as non-extruded virgin references;

[0124] FIG. 5 shows the remaining PET and PA-6 (wt %) in samples deriving from feedstock containing 10-30 wt % PET and PA, extruded at 370 C. and 20 RPM, in alkaline conditions;

[0125] FIG. 6 shows the MFR2 of PET and PA-6 in 10-30 wt % PA/PET/PE samples extruded at 370 C. and 20 RPM in alkaline conditions;

[0126] FIG. 7 shows the remaining PET and PA-6 (wt %) in samples deriving from feedstock containing 5 wt % PET and PA, extruded at 350 and 370 C. and 20-200 RPM, in alkaline conditions;

[0127] FIG. 8 shows the MFR2 in 5 wt % PET/PE or PA-6/PE extruded in the temperature range 350-380 C. and 20-200 RPM in alkaline conditions;

[0128] FIG. 9 shows the remaining PET and PA-6 (wt %) in samples deriving from feedstock containing 10 wt % PET and PA, extruded at temperatures in the range 350-380 C. and at 20-60 RPM, in alkaline conditions;

[0129] FIG. 10 shows the MFR2 in 5 wt % PA/5 wt % PET in LLDPE blends extruded in the range 350-380 C. and 20-60 RPM, in alkaline conditions;

[0130] FIG. 11 shows the remaining PA-6 left (wt %) in samples deriving from PA-6/PE feedstock extruded in the temperature range 350-380 C. and 20-60 RPM in alkaline conditions;

[0131] FIG. 12 shows the MFR2 of PA-6/PE extruded in the temperature range 350-380 C. and 20-60 RPM in alkaline conditions;

[0132] FIG. 13 shows the PA-6 left (wt %) in PE/PA-6 samples deriving from multilayer films extruded in the temperature range 350-370 C. and 20-100 RPM in alkaline conditions;

[0133] FIG. 14 shows MFR2 of PE/PA-6 deriving from multilayer films extruded in the temperature range 350-370 C. and 20-100 RPM in alkaline conditions;

[0134] FIG. 15 shows complex viscosity (Pa*s) for extruded PET/PE, PA/PE and PA/PET/PE in alkaline conditions against a baseline 5 wt % PET/PE extruded and virgin LLDPE included as a reference; and

[0135] FIG. 16 shows the remaining PET (wt %) in samples deriving from 5 wt % PET/PE model waste after extrusion in a twin screw extruder under different conditions.

EXAMPLES

Materials

[0136] The following materials listed in Table 1 were prepared and mixed to simulate post-consumer waste (PCW) comprising PET and PA from multilayer film packaging.

[0137] As a reference, a PE/PA-6 multilayer film with 34 wt % PA was included in some experiments, marked MF. The film was shredded and diluted with LLDPE to reach 5% PA in the feed.

TABLE-US-00001 TABLE 1 Material Grade Supplier Virgin PE pellets C4-LLDPE (Q1018N) for film extrusion Total Virgin PE pellets LDPE FT5430 for film extrusion Borealis Virgin PP pellets Homopolymer HC110BF for film Borealis extrusion Virgin PA-6 pellets Ultramid B40LN for film extrusion BASF Virgin PET pellets RAMA-PET N180, a general-purpose Indorama grade for bottles, film and Ventures thermoforming Additive: Sodium NaOH Sigma-Aldrich hydroxide Additive: Calcium Ca(OH).sub.2 Sigma-Aldrich hydroxide

Sample Preparation

[0138] Virgin LLDPE (Q1018N, Total) was mixed with pure extrusion grade PA-6 (B40LN, BASF, 5-15 wt %) and/or PET (RAMA-PET N180, 5-15 wt %) to simulate typical and extreme PCW compositions. Sodium hydroxide (NaOH, Sigma-Aldrich) and/or calcium hydroxide (Ca(OH).sub.2, Sigma-Aldrich) was dissolved in distilled water (5-12 wt %) and stirred into the polymer blends in various concentrations (0.5-2 wt %). The homogeneous blends were extruded immediately after preparation.

[0139] Samples comprising LDPE and/or PP were prepared in an analogous manner.

Extrusion

[0140] Unless otherwise stated, the materials were extruded in a GA25-25D single screw extruder in the temperature range 350 to 380 C. The RPM range was 20 to 200 revolutions per minute (RPM), corresponding to a residence time of 4.0-4.7 minutes to 0.5-0.8 minutes, respectively (see Table 2 below). The conversion of RPM to residence time was measured by determining the amount of time it takes for a sample to pass through the extruder at different RPM levels. The extrudate samples were collected at stable operating conditions and were cooled to room temperature for analysis.

TABLE-US-00002 TABLE 2 Conversion of RPM to minutes RPM Residence Time, min 200 0.5-0.8 100 1-1.2 60 1.4-1.8 20 4.0-4.7

[0141] A number of experiments were also conducted to compare the performance of the above-mentioned GA25-25D extruder, with a screw designed for optimal venting out of the extruder die, to screw designed for optimal mixing. Both arrangements employed the same extruder, but with different screws. The second arrangement, herein referred to as screw 2 is the GA-25D extruder with a mixing screw in place. It has a D of 25 mm and several mixing elements.

[0142] During extrusion, the degradation products that are volatiles (e.g. CO.sub.2, H.sub.2O, ethylene glycol, low MW hydrocarbons) are removed through the extruder (there is a slight vacuum at the end of the extruder). The salts formed (e.g. sodium/calcium benzoate, sodium/calcium terephthalate, sodium/calcium carbonate) were extruded with the homogeneous blend and subsequently removed from the blend in a melt filter.

FTIR Analysis

Sample Preparation for FTIR Analysis:

The samples were prepared for analysis by cutting and milling the samples to granulates approximately 5-10 mm size. The sample granulates were hot pressed to films of 0.1 mm thickness with a hot press (M-4411 Collin 200P hydraulic press) using a copper mould with Teflon sheets. At least 2 parallels were pressed of each sample.

Hot Press Program:

[0143] 30 sec. at 15 bar [0144] 10 sec. at 30 bar [0145] 10 sec. at 70 bar [0146] 40 sec. at 250 bar [0147] 300 sec. at 250 bar (cooling)

Data Acquisition:

[0148] FTIR spectra were recorded in transmission mode with film holder using a Perkin-Elmer Spectrum TWO equipped with a LiTaO.sub.3 detector and Spectrum10 software. [0149] The spectral range was 450-4700 cm-1 and 12-16 scans were recorded per spectrum with a scan resolution 4 cm-1

Data Analysis:

[0150] For quantification of PA-6 or PET in the PE samples, the software Perkin-Elmer SpectrumQuant, version 10.6.0.893 was used. [0151] PLS method with Principal Component Analysis (PCA) was used for quantification. Standard error of estimate (SEE) for each component; 0.4 wt % for PE, 0.2 wt % for PA and 0.3 wt % for PET. [0152] Parallels with more than 0.5% deviation were investigated further using up to 5 parallels. [0153] The calibration model was established using relevant compounded PE/PA. PE/PET and PE/PA/PET reference blends. The calibration samples were milled and compounded using the same polymer grades as in the model waste feedstock to ensure homogeneity.

Melt Flow Rate (MFR)

[0154] The MFR2 of the extruded granulated melt was measured according to NS-EN ISO1133-1:2011 using a Davenport Melt Flow Indexer, Model 3. The conditions used were: 2.16 kg load; die diameter 0.5 mm; die length 8 mm. The MFR unit is g/10 min at 2.16 kg. The measurement is conducted at 190 C. (PE) and 230 C. (PP) and the pre-heating was 5 minutes. Two parallels were used. [0155] Maximum measurable value is 600-700 g/10 min at 2.16 kg load (ca. 20 in standard deviation).

GPC

Gel Permeation Chromatography was carried out according to ISO16014-1, -2, -4, 2012 using a GPC-IR5 MCT from Polymer Char equipped with an IR5 MCT Infrared detector. The polymer samples were dissolved in trichlorobenzene (TCB) at 160 C. for 1-4 hours (0.25-1.8 mg/mL). The columns 1 PL gel Guard and 4 PL gel 20 m MIXED-A were heated to 150 C. Two parallels were used.
GPC was used for determination of: [0156] MwMass average molecular mass [0157] MnNumber average molecular mass [0158] Mw/MnPolydispersity of the sample

Complex Viscosity Measurements

Complex viscosity, *, is a measure of the total resistance to flow as a function of angular frequency. * was measured according to ISO6721-10:2015 using an RDA II W-4408 instrument. The samples were compression moulded into plates with dimensions 1.5 mm thickness and 30 mm diameter. The preheat time was 200 s to reach 300 C. The test conditions were 300 C.; frequency range 0.1-300 rad/sec; scraping off gap 1.25 mm; measuring gap 1.20 mm; plate geometry Plate-Plate; plate diameter 25 mm.
The method is used to determine values of the following dynamic rheological properties: [0159] W: Angular velocity, rad/sec [0160] G: Storage modulus [0161] G: Loss modulus

[00001]$\mathrm{Complex}\mathrm{modulus}{G}^{}={\left(G^2+G^2\right)}^{1/2}$$\mathrm{Complex}\mathrm{Viscosity}\mathrm{Eta}=G^{*}/w$

Where eta (0.5): Complex viscosity at frequency 0.5 rad/sec and eta (200): Complex viscosity at frequency 200 rad/sec are reported herein.

Liquid Chromatography, HPLC-UV

TABLE-US-00003 Method Liquid chromatography according to M730533 Definitions HPLC is a chromatographic technique that separates components in a mixture by use of liquid. The technique is used for both qualitative and quantitative analyses. Instrument Agilent 1200 Specimen type Polymer sample milled to powder before extraction Test conditions 1. Sample preparation: Extraction 2. Chromatographic conditions: Column: C-18 Mobile phase: Water/AcN/IPA-gradient Detector: UV, 276 nm
Gas Chromatography with Mass Spectrometric Detector, GC-MS

TABLE-US-00004 Method Gas Chromatography with MS detector according to M730544 Definitions The GC separates the chemical mixture, and the MS identifies and quantifies the chemicals based on their structure Instrument Agilent 6890 Specimen type Polymer sample milled to powder before extraction Test conditions Sample preparation: Extraction Chromatographic conditions: Column: HP-5 Carrier gas: Helium Detector: Mass Spectrometric, MS

Results

Example 1a: Degradation of Virgin PE and PP

[0162] Selected pure virgin grades, LLDPE, LDPE and PP, were extruded in a GA25-25D single screw extruder at 300, 350, 370 and 380 C. using 20 or 60 revolutions per minute (RPM), corresponding to a residence time of approximately 1.4-1.8 and 4.0-4.7 minutes. The extrudate samples were collected after obtaining steady state conditions and cooled in room temperature. (800 g/10 min at 2.16 kg is set as value whenever the melt flow rate is too high for correct measurement (normally over 700). MFR2 was used to measure the viscosity of the melt after extrusion. Each of LLDPE and PP was investigated more closely with dynamic rheology to measure complex viscosity at different shear rates at 300 C. The polymer molecular weight and distribution were analysed by GPC. The results are shown in Table 3 and in FIGS. 2-4.

TABLE-US-00005 TABLE 3 Complex viscosity * at 0.5 Complex T, rad/s, viscosity * at Feedstock RPM C. MW MN Mw/Mn MFR2 Pa*s 200 rad/s, Pa*s Virgin 50 350 116900 28200 4.2 1 2134 549 LLDPE ref Virgin 50 300 111400 25700 4.3 0.7 2533 445 LLDPE Virgin 20 300 1.2 LLDPE Virgin 50 350 98600 26500 3.7 1.4 1562 306 LLDPE Virgin 20 350 47300 13850 3.4 19 124 95 LLDPE Virgin 60 370 42000 10900 3.9 63 169 107 LLDPE Virgin 20 370 31900 10700 2.9 111 23 22.5 LLDPE Virgin 60 380 17500 6400 3 95 LLDPE Virgin 20 380 8950 2750 3.3 280 7.50 5 LLDPE Virgin 20 380 9200 2800 3.3 800* 4.5 3.9 LLDPE (screw 2) Virgin 72000 13550 5.6 0.8 LDPE ref Virgin 60 350 63000 10800 5.7 1.4 LDPE Virgin 20 350 58000 9500 5.8 10 LDPE Virgin 60 370 65200 9700 6.7 6.4 LDPE Virgin 20 370 32300 7000 4.6 174 2.66 2.5 LDPE Virgin 60 380 58000 9500 6.4 13 LDPE Virgin 20 380 22500 5700 3.9 800* LDPE Virgin 20 370 27800 5400 5.1 222 9.1 7.9 HDPE (screw 2) Virgin 20 380 21500 5400 4.6 614 3.56 2.7 HDPE (screw 2) Virgin PP 347300 43900 8 2.9 695 131 ref Virgin PP 50 300 232400 22950 10 17 Virgin PP 60 350 128650 28100 5 800* 62.5 40 Virgin PP 20 350 93800 21250 4.4 184 11.5 9 Virgin PP 60 370 111400 14250 7.96 85 24 17 Virgin PP 20 370 59800 12300 4.85 800* 4 0.5 Virgin PP 60 380 81550 11150 7.54 226 4 6.5 Virgin PP 20 380 36300 9900 3.67 800* 1.5 1.1 *800 is given as the value for MFR2 when the MFR is too high for accurate measurement under standard conditions.

[0163] FIG. 2 shows the MFR2 for LDPE, LLDPE and PP before and after extrusion. The melt flow rate increases abruptly between 37 and 380 C. and from 60 RPM to 20 RPM. PP is more easily degraded compared to PE.

[0164] FIG. 3 shows the average molecular weight from GPC for PP, LDPE and LLDPE. The degree of cracking is significant at 350, 370 and 380 C. 20 RPM results in more pre-cracking.

[0165] FIG. 4 shows the complex viscosity measured for LLDPE and PP before and after extrusion. Corresponding to MFR2 and MW, the PP and LLDPE grades exhibit significantly lower viscosity at higher temperatures and lower RPM.

[0166] Comparison of the results for LLDPE with the standard screw and screw 2 show that employing a screw designed for mixing reduces the molecular weight and viscosity to higher levels. The MFR2 was, in fact, too high to measure.

[0167] HDPE was also degraded similarly to LLDPE and LDPE.

[0168] This experiment demonstrates the baseline degradation, referred to as pre-cracking, of virgin LDPE, LLDPE and PP upon extrusion in the range 300-380 C. and 20-60 RPM.

Example 1b: Analysis of Additives in Extruded PP, LLDPE, and HDPE

[0169] Table 4 below lists common additives present in PE and PP typically used for packaging. These additives, and their degradation products, are well known and can be identified by HPLC, GC-MS and GC-FID.

TABLE-US-00006 TABLE 4 Typical Degradation conc, Products in Additive Code CAS Grades ppm Chemical structure literature Tris(2,4-di-tert- butylphenyl) phosphite AO- 168 31570- 04-4 LLDPE, PP, HDPE <1000 ppm [00001] Arvin 4 2,4-di-tert butylphenol Arvin 2 p-tert- butylphenol Oxidised AO-168 Tris(2,4-di-tert- butylphenyl)- phosphate Octadecyl 3- (3,5- di-tert-butyl-4- hydroxyphenyl) propionate AO- 1076 2082- 79-3 LLDPE PE and PP <1000 ppm [00002] Arvin substances 3, 5, 6, 7, 8, 9, 10 Pentaerythritol Tetrakis(3-(3,5- di-tert-butyl-4- hydroxyphenyl) propionate) AO- 1010 6683- 19-8 PP <500 ppm [00003] Arvin substances 1, 3, 5, 6, 7, 8, 9, 10 Ca stearate AS- 100 1592- 23-0 LLDPE, HDPE, PP film 400- 1500 [00004] CaCO.sub.3, H.sub.2O, hydrocarbons

[0170] Table 5 below lists the additives that were identified in the PP, LLDPE and HDPE grades employed before and after extrusion (LDPE was not included because it did not contain any additives). Extrusion was carried out at 380 C. and 20 RPM, with or without alkaline solution. The effect of pre-mixing the polymer with an alkaline solution (1 wt % NaOH, 1 wt % Ca(OH).sub.2, 5 wt % H.sub.2O) was studied. The additives and their degradation products were detected by HPLC and GC-MS as described above. ND means not detected.

TABLE-US-00007 TABLE 5 Total AO-168 is AO-168 + oxidised AO-168 AO- AO- AO-168 AO-168 Arvin 2 1010 1076 Polymer (wt consumed Total AO-168 Arvin 4 (wt (wt (wt grade Treatment ppm) (%) (wt ppm) (wt ppm) ppm) ppm) ppm) PP Virgin ref 730 6 780 320 PP Extruded 160 76 670 10 80 PP Extruded/w ND ND ND 180 Detected ND alkaline solution LLDPE Virgin ref 700 13.5 810 390 LLDPE Extruded 210 72 760 7 130 LLDPE Extruded/w ND ND ND 150 ND ND alkaline solution HDPE Virgin ref HDPE Extruded 340 60 840 10 40 HDPE Extruded/w ND ND ND 170 Detected ND alkaline solution

[0171] The results show that the process of the invention effectively degrades the heteroatom containing additives commonly present in PP, LLDPE and HDPE. Specifically, in PP and HDPE Arvin 2 and Arvin 4, which are the hydrolysis products of AO-168 were detected. Residual AO-168, A-1010 and A-1076 were not detected in polymers, which underwent extrusion in the presence of alkaline solution.

Example 2: Removal of 10-30% PET/PA from PE Blends

[0172] Virgin LLDPE (Q1018N, Total) was mixed with pure extrusion grade PA-6 (B40LN, BASF, 5-15 wt %) and PET (RAMA-PET N180, 5-15 wt %) to simulate PCW compositions. Three sample compositions were prepared: 1) 5% PA-6 and 5% PET in PE; 2) 10% of PET and 10% PA in PE, and; 3) 15% PA and 15% PET in PE. Sodium hydroxide (NaOH, Sigma-Aldrich) and calcium hydroxide (Ca(OH).sub.2, Sigma-Aldrich) was added to the 3 samples: 1) 1.5% NaOH and 1% Ca(OH).sub.2; 2) 3 wt % NaOH+2% Ca(OH).sub.2, and 3) 4.5% NaOH+3% Ca(OH).sub.2. Distilled water was added to the mixture and kept constant at 12 wt %. The homogeneous blends were extruded immediately after preparation in a GA25-25D single screw extruder at 370 C. and 20 revolutions per minute (RPM), corresponding to a residence time of approximately 4.0-4.7 minutes. The extrudate samples were collected after obtaining steady state conditions and cooled in room temperature. The volatised side products exiting the extruder with the polymer melt were vented out, and hence separated from the polymer.

[0173] The samples were prepared for analysis as described above. FTIR spectra were recorded using the acquisition method, and then analysed, as described above. MFR2 was measured at standard conditions (190 C.) using 0.5 mm die as described above. Selected samples were investigated more closely with dynamic rheology to measure complex viscosity at different shear rates at 300 C. The results are shown in Table 6 below and in FIGS. 5 and 6.

TABLE-US-00008 TABLE 6 Ca(OH).sub.2 H.sub.2O Removal Removal # Feedstock NaOH % % % PET % PA-6% PET % PA % MFR2 PAPET-1 5% PA + 5% 1.5 1 12 1.6 0.2 1.5 0.2 68 70 40 PET PA/PET-2 10% PA + 10% 3 2 12 1.7 0.2 2.9 0.2 83 81 40 PET PA/PET-3 15% PA + 15% 4.5 3 12 1.9 0.3 2.4 0.2 87 84 100 PET

[0174] The results demonstrate the efficient, concurrent, removal of PA-6 and PET from feedstock comprising 5%, 10% and 15 wt % of both PET and PA-6 in LLDPE (i.e. up to 30% wt compounds containing heteroatoms). Specifically, the results show 68-87% concurrent removal of PA and PET from feed containing up to 30 wt % heteroatom-containing polymer after extrusion at 370 C. and 20 RPM in aqueous alkaline conditions. This test feedstock contains significantly more heteroatom-containing polymers that conventional PCW feedstock. It is surprising that the process is able to remove so much PET and PA, even from feedstock containing a total of 30 wt % PET and PA. The result for the feedstock comprising 15 wt % PET and PA-6 shows that the hydrocarbon product emerging from the extruder contains 1.9 wt % PET and 2.4 wt % PA, which is less than the amount of PET and PA typically present in PCW that can be recycled. Thus the process provides a highly efficient method to remove heteroatom-containing polymers from highly contaminated PCW prior to further processing to achieve recycling.

[0175] The MFR2 results indicate that the viscosities of the hydrocarbon product produced in the process is higher than, or comparable to baseline degradation of LLDPE (111 vs. 100) at these conditions.

Example 3: Effect of RPM

[0176] The sample preparation and analysis procedure were as described above and in Experiment 1. The experiments were carried out at temperatures in the range 350-370 C., and at 20-200 RPM, using the recipes and conditions set out in Table 6. The results are shown in Table 7, and FIGS. 7 and 8.

TABLE-US-00009 TABLE 7 NaOH Ca(OH).sub.2 H.sub.2O T, PET PA Removal Removal Sample # Feedstock % % % RPM C. % % PET % PA % MFR2 PET-1 5% PET/ 2 8 200 350 3.5 0.2 30 1.8 PE PET-2 5% PET/ 2 8 100 350 2.9 0.2 42 PE PET-3 5% PET/ 2 8 60 350 1.3 0.1 74 PE PET-4 5% PET/ 2 8 20 350 0.4 0.1 92 PE PET-5 5% PET/ 2 2 8 200 350 3.1 0.2 38 2.5 PE PET-6 5% PET/ 2 2 8 100 350 2.1 0.2 58 PE PET-7 5% PET/ 2 2 8 60 350 1.3 0.2 74 PE PET-8 5% PET/ 2 2 8 20 350 0.9 0.1 82 PE PET-9 5% PET/ 0.5 0.5 5 100 370 1.9 0.2 62 15 PE PET-10 5% PET/ 0.5 0.5 5 60 370 1.4 0.2 72 120 PE PET-11 5% PET/ 0.5 0.5 5 20 370 0.7 0.1 86 35 PE PET-12 5% PET/ 0.5 0.5 12 20 370 1.2 0.1 76 32 PE PET-13 5% PET/ 0.5 0.5 12 60 380 1.6 0.1 68 17 PE PET-14 5% PET/ 0.5 0.5 12 20 380 1.1 0.1 78 100 PE PET-15 5% PET/ 1 0.5 12 20 370 0.75 0.1 85 500* PE PA-1 5% PA/PE 1 0.5 12 200 370 2.5 0.1 50 2.1 PA-2 5% PA/PE 1 0.5 12 60 380 1.3 0.1 5.2 PA-3 5% PA/PE 1 0.5 12 20 380 0.9 0.1 22 PA-4 5% PA/PE 1 0.5 12 100 370 2.1 0.1 56 2.5 PA-5 5% PA/PE 1 0.5 12 60 370 1.8 0.1 64 4.1 PA-6 5% PA/PE 1 0.5 12 20 370 1.2 0.1 76 20 PA-7 5% PA/PE 1 0.5 12 100 350 1.9 0.2 62 MF PA-8 5% PA/PE 1 0.5 12 20 350 0.7 0.1 86 MF PA-9 5% PA/PE 2 12 100 350 2.3 0.3 58 1.4 MF PA-10 5% PA/PE 2 12 20 350 1.2 0.2 76 5.9 MF

[0177] The results show that the PET and PA are degraded and removed during extrusion wherein the mixed polymer waste has a residence time in the extruder between 0.5-4.7 min. The removal of PET and PA in PE is significantly more efficient at 20 RPM (residence time 4.0-4.7 min) than at 200 RPM (residence time 0.5-0.8 min) and 100 RPM (residence time 1.0-1.2 min). This is consistently the case regardless of the PET/PA content, the alkaline mix and the water content. Whilst alkaline hydrolysis of PA appears to be slower than for PET, both PA and PET can be concurrently removed from PCW. MFR2 increases with decreasing RPM, but is affected by the wt % PET and PA present when compared to baseline LLDPE degradation.

[0178] This experiment also included some multilayer film (MF) to compare the results for a real film versus the feedstock specifically prepared for development purposes. The results appear to be comparable.

Example 4: Process Window for Efficient Concurrent Removal of PET and PA

[0179] The sample preparation and analysis procedure were as described above and in Experiment 1. The experiments were carried out at temperatures of 350, 370 and 380 C. using 60 and 20 revolutions per minute (RPM), corresponding to a residence time of 1.4-1.8 minutes and 4.0-4.7 minutes respectively, using the recipes and conditions set out in Table 8. The results are shown in Table 8 and in FIGS. 9 and 10.

TABLE-US-00010 TABLE 8 Removal Removal Sample # Feedstock RPM T, C. PET % PA-6% PET % PA % MFR2 PAPET-4 5% PA-6, 5% PET 20 350 0.9 0.1 1.7 0.2 82 66 22 PAPET-5 5% PA-6, 5% PET 60 350 1.5 0.1 1.4 0.2 70 72 3.6 PAPET-1 5% PA-6, 5% PET 20 370 1.6 0.2 1.5 0.2 68 70 40 PAPET-6 5% PA-6, 5% PET 60 370 2.3 0.3 2.1 0.3 54 58 10 PAPET-7 5% PA-6, 5% PET 20 380 1.4 0.1 1.3 0.2 72 74 32 PAPET-8 5% PA-6, 5% PET 60 380 1.2 0.1 1.7 0.1 76 66 4.9

[0180] The results show that concurrent removal of mixed PA and PET is efficient at 20 RPM in the temperature 350-380 C. range. MFR2 is significantly lower at 60 RPM vs. 20 RPM.

Example 5: Process Window for PA Removal

[0181] The sample preparation and analysis procedure were as described above and in Experiment 1. The experiments were carried out using the recipes and conditions set out in Table 9. In this experiment model waste is represented both as blended PA-6 and LLDPE pellets and multilayer film (MF) flakes for comparison with a more realistic feed. The results are shown in Table 9 and in FIGS. 11 and 12 for the PA-6/PE blends and in Table 10 and FIGS. 13 and 14 for the multilayer film.

TABLE-US-00011 TABLE 9 Sample NaOH Ca(OH).sub.2 H.sub.2O Removal # Feedstock % % % RPM T, C. PA % PA % MFR2 PA-11 5% PA/PE 1 0.5 12 60 350 1.6 0.1 68 3 PA-12 5% PA/PE 1 0.5 12 20 350 1.2 0.1 76 2.7 PA-5 5% PA/PE 1 0.5 12 60 370 1.8 0.1 64 4.1 PA-6 5% PA/PE 1 0.5 12 20 370 1.2 0.1 76 20 PA-2 5% PA/PE 1 0.5 12 60 380 1.3 0.1 74 5.2 PA-3 5% PA/PE 1 0.5 12 20 380 0.9 0.1 82 22 PA-8 5% PA/PE 1 0.5 12 20 350 0.7 0.2 86 22 MF PA-13 5% PA/PE 1 0.5 12 20 370 0.9 0.2 82 51 MF PA-14 5% PA/PE 0.5 0.5 12 60 370 1.5 0.1 70 12 PA-15 5% PA/PE 0.5 0.5 12 20 370 1.2 0.1 76 24 PA-16 5% PA/PE 0.5 0.5 12 20 370 1.4 0.2 72 37 MF PA-17 5% PA/PE 1 1 12 60 350 2.5 0.2 50 1.2 PA-18 5% PA/PE 1 1 12 20 350 2.3 0.3 54 4.5 PA-19 5% PA/PE 0.5 12 60 370 1.6 0.2 68 5.6 PA-20 5% PA/PE 0.5 12 20 370 1.5 0.2 70 23 PA-10 5% PA/PE 2 12 20 350 1.2 0.2 76 5.9 MF PA-21 5% PA/PE 2 12 20 370 1.4 0.2 72 36 MF

TABLE-US-00012 TABLE 10 Sample Ca(OH).sub.2 H.sub.2O Removal # Feedstock NaOH % % % RPM T, C. PA % PA % MFR2* PA-13 5% PA/PE 1 0.5 12 20 370 0.9 0.2 82 51 MF PA-7 5% PA/PE 1 0.5 12 100 350 1.9 0.2 62 1.4 MF PA-8 5% PA/PE 1 0.5 12 20 350 0.7 0.2 86 5.9 MF PA-16 5% PA/PE 0.5 0.5 12 20 370 1.4 0.1 72 37 MF PA-22 5% PA/PE 2 12 100 370 2.3 0.2 54 1.4 MF PA-21 5% PA/PE 2 12 20 370 1.4 0.2 72 36 MF PA-9 5% PA/PE 2 12 100 350 2.3 0.2 54 2 MF PA-10 5% PA/PE 2 12 20 350 1.2 0.2 76 5 MF

[0182] Corresponding to examples 2 and 3, the results indicate that PA-6 is removed more efficiently at 20 RPM vs. 60 RPM in the range 350-380 C. Small variations are observed across the chemical recipes and temperature range. The results suggest that residence time (RPM) is the most significant factor in determining the efficiency of PA-6 removal.

Example 6: Effect of Water

[0183] The sample preparation and analysis procedure were as described above and in Experiment 1. The experiments were carried out using the recipes and conditions set out in Tables 11.1 and 11.2. Tables 11.1 and 11.2 also show the results achieved.

TABLE-US-00013 TABLE 11.1 Sample Ca(OH).sub.2 T, H.sub.2O PET PA- PET PA # Feedstock NaOH % % C. (%) % 6% removal % removal % MFR2 PET-11 5% PET/PE 0.5 0.5 370 5 0.7 0.1 86 35 PET-12 5% PET/PE 0.5 0.5 370 12 1.2 0.2 74 32 PA-23 5% PA/PE 0.5 0.5 370 5 1.6 0.2 68 20 PA-15 5% PA/PE 0.5 0.5 370 12 1.2 0.1 76 17

TABLE-US-00014 TABLE 11.2 Sample Ca(OH).sub.2 H.sub.2O T, PET # Feedstock NaOH % % % RPM C. PET % removal % MFR2 PET-16 5% 0 0 0 100 350 4.9 0.2 98 7.6 PET/PE PET-17 5% 0 0 0 50 350 4.8 0.2 96 3 PET/PE PET-6 5% 2 2 8 100 350 2.1 0.2 58 PET/PE PET-7 5% 2 2 8 50 350 1.3 0.2 74 PET/PE PET-18 5% 2 2 5 100 350 3.6 0.2 28 9 PET/PE PET-19 5% 2 2 5 50 350 3.1 0.2 38 22 PET/PE PET-2 5% 2 8 100 350 2.9 0.2 42 PET/PE PET-3 5% 2 8 50 350 1.3 0.1 74 PET/PE PET-20 5% 2 5 100 350 3.6 0.3 28 2.2 PET/PE PET-21 5% 2 5 50 350 2.8 0.2 44 4.5 PET/PE PET-22 5% 4 4 5 100 350 3.5 0.2 30 8.2 PET/PE PET-23 5% 4 4 5 50 350 2.1 0.2 58 30 PET/PE PET-24 5% 4 5 100 350 3.7 0.2 26 2.5 PET/PE PET-25 5% 4 5 50 350 3 0.2 40 6.3 PET/PE

[0184] The results in these tables show that PET is more efficiently removed using a higher amount of (e.g. 8%) water as opposed to a lower amount (e.g. 5%) water. This suggests that aqueous hydrolysis is generally preferable. Without wishing to be bound by theory, it is thought that using higher % wts of water promotes hydrolytic degradation over thermal degradation. This is desirable as hydrolytic degradation gives rise to degradation products that can be removed from the extrudate. Moreover, at least some of the degradation products are in the form of monomers that can be recovered and recycled.

Example 7: Complex Viscosity for Purified PET/PE, PA/PE and PA/PET/PE Blends

[0185] Some purified extrudates were selected for complex viscosity measurements. The following data provide further insight in viscosity of a relevant product stream vs. the baseline degradation.

[0186] Table 12 lists complex viscosities measured at 0.5 and 200 rad/s of selected samples from experiment 1-5; PET/PE, PA/PE and one PET/PA/PE. FIG. 15 shows a complex viscosity crossplot at 0.5 and 200 rad/s, compared to virgin LLDPE and baseline extruded PET/PE.

TABLE-US-00015 TABLE 12 Complex Complex viscosity viscosity Sample Feeds NaOH Ca(OH).sub.2 H.sub.2O PET PA- 0.5 rad/s, 200 rad/s, # tock % % % T C. RPM % 6% MFR2 Pa*s Pa*s PAPET-7 5% 1.5 1 12 380 20 1.4 0.1 1.3 0.2 32 45 27 PA-6, 5% PET PET-17 5% PET/ 0 0 0 350 50 4.8 0.2 7.6 295 145 PE PET-8 5% PET/ 2 2 8 350 20 0.9 0.1 78 7 PE PET-14 5% PET/ 0.5 0.5 12 380 20 1.1 0.1 600 17 11 PE PET-4 5% PET/ 2 0 8 350 20 0.4 0.1 313 18 PE PA-24 5% PA/ 0.5 0.5 0 370 20 1.7 0.1 29 64 23 PE PA-6 5% PA/ 1 0.5 12 370 20 1.2 0.1 20 435 190 PE

[0187] The results demonstrate that the complex viscosity of the extruded hydrocarbon product is in the range of the baseline degradation of LLDPE in the process window 350-380 C. and 20-60 RPM.

Example 8Analysis of Volatile Degradation Products

[0188] The sample preparation was conducted as described in Experiment 1 and is summarised in Table 13 below. The homogeneous blends were extruded immediately after preparation in a GA25-25D single screw extruder at 380 C. and 20 revolutions per minute (RPM), corresponding to a residence time of approximately 3.5-4 minutes. The polymer melt samples was collected after obtaining steady state conditions and cooled in room temperature.

[0189] Two extrusion trials with a duration of 4-5-hours were conducted with 2 different water compositions to collect enough of the condensable side product for analyses. The degradation product was separated from the polymer stream in a buffer tank (hopper tank) as a volatile product in, immediately after being collected from the extruder using a slight vacuum. The volatile product exiting the extruder die and polymer melt was condensed and collected during extrusion. Some of the product was condensed in the condenser, rather than in the round flask further downstream, indicating higher boiling point. This was also collected and analysed separately (sample PA-26). The condensable products were analysed by HPLC, which was calibrated for specific substances expected from PA-6, PA-6.6 and PET. The results are summarised in Table 13 below.

TABLE-US-00016 TABLE 13 Ca(OH).sub.2, Process Residual Substance Sample NaOH, % % H.sub.2O, % Collection conditions PA wt % identified by HPLC PA- 1 1 12 Round flask 380 C., 20 0.9 0.1 - Caprolactam 25.5% RPM PA/PE PA- 1 1 12 In condenser 380 C., 20 0.9 0.1 - Caprolactam 262.5% (deposited) RPM PA/PE PA- 1 1 5 Round flask 380 C., 20 1.4 0.1 - Caprolactam 27.5% RPM PA/PE

Example 9Analysis of Salts Produced by Degradation

[0190] The sample preparation was conducted as described in Experiment 1 as summarised below in Table 14 below. Two extrusion trials were conducted with different compositions of the chemical package. The homogeneous blends were extruded immediately after preparation in a GA25-25D single screw extruder at 350 C. and 20 and 60 revolutions per minute (RPM). The extrudate samples were collected after obtaining steady state conditions and cooled at room temperature. HPLC measurements were carried out to identify compounds in the polymer melt after extrusion of 5% PET in LLDPE model waste with NaOH and NaOH/Ca(OH).sub.2/H.sub.2O. The method identifies sodium or calcium benzoate or terephthalate. (The method cannot distinguish between terephthalate and benzoate, or whether the associated cation is sodium or calcium).

TABLE-US-00017 TABLE 14 Na or Ca terephthalate/ NaOH, Ca(OH).sub.2, Residual PET benzoate, mol Sample % % H.sub.2O, % wt % (FTIR) Process conditions ppm PET-4 2 8 0.4 0.1 350 C., 20 RPM 60 PET-7 2 2 8 1.3 0.1 350 C., 60 RPM 40

[0191] Sodium and/or calcium benzoate/terephthalate side products were identified by HPLC analysis in the extruded PE/PET material. These are the expected products from alkaline hydrolysis of PET. PET-4 contained 60 ppm sodium benzoate/terephthalate. PET-7 contained 40 ppm of sodium and/or calcium benzoate/terephthalate. (Due to overlapping peaks in the chromatogram, the contribution from the individual substances could not be determined).

Example 10: Use of a Twin Screw Extruder

[0192] This example demonstrates that the method can be carried out in a twin screw extruder. It is beneficial due to its mixing abilities for incompatible elements in the feed.

[0193] The sample preparation of 5% PET/PE and chemicals was carried out by the method explained for example 1. The feed rate of the model waste to the extruder was 1 kg/h using a hopper with a screw feeder. The twin screw extruder was set to its minimum 120 RPM which corresponds to 50 sec residence time. This is the lowest RPM possible. The feedstock was extruded at 370 C. and 380 C.

[0194] The twin screw extruder has screw diameter of 18 mm and l/d=60 and operates in co-rotating configuration.

[0195] Table 15 and FIG. 16 show the PET remaining in the polymer melt after extrusion with pre-mixed dry alkali hydroxides or NaOH and Ca(OH).sub.2 or as an aqueous solution, using various amounts of water. One reference trial with extrusion of the 5% PET/PE feedstock without the chemicals show that thermal degradation is significant under these conditions. The optimal point according to this data set is when NaOH, Ca(OH).sub.2 and water was added in stoichiometric amounts (0.5% water).

TABLE-US-00018 TABLE 15 NaOH, Ca(OH).sub.2 H.sub.2O Residual PET wt % Process Sample # Feedstock % % % (FTIR) conditions PET-26 5% PET/PE 0 0 0 1.3 0.1 380 C., 120 RPM PET-27 5% PET/PE 1 2 0 1.5 0.1 370 C., 120 RPM PET-28 5% PET/PE 1 2 0 0,6 0.3 380 C., 120 RPM PET-29 5% PET/PE 1 2 0.5 0.7 0.2 370 C., 120 RPM PET-30 5% PET/PE 1 2 0.5 0.4 0.1 380 C., 120 RPM PET-31 5% PET/PE 1 2 5 2.3 0.2 370 C., 120 RPM PET-32 5% PET/PE 1 2 5 1.5 0.2 380 C., 120 RPM