Recycling of food grade packaging using fluorescent markers

Transcription

1 Final Report Recycling of food grade packaging using fluorescent markers A report on the use of fluorescent marker technology to enable high speed automatic sorting and recycling of used plastic packaging into a range of applications including food grade packaging. Project code: PMP Research date: Date: July 2016

2 WRAP s vision is a world in which resources are used sustainably. Our mission is to accelerate the move to a sustainable resource-efficient economy through re-inventing how we design, produce and sell products; re-thinking how we use and consume products; and re-defining what is possible through reuse and recycling. Find out more at PMP [WRAP, 2016, Banbury, Recycling of food grade packaging using fluorescent marks] Written by: Edward Kosior, Rafi Ahmad, Edwin Billiet, Martin Kay, Jonathan Mitchell, Kelvin Davies. Front cover photography: PET packaging and shrink sleeve label viewed under UV light with and without fluorescent pigment (left). Different pigmented labelled packaging viewed under UV light (right). While we have tried to make sure this report is accurate, we cannot accept responsibility or be held legally responsible for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. This material is copyrighted. You can copy it free of charge as long as the material is accurate and not used in a misleading context. You must identify the source of the material and acknowledge our copyright. You must not use material to endorse or suggest we have endorsed a commercial product or service. For more details please see our terms and conditions on our website at WRAP Recycling of food grade packaging using fluorescent markers Page: 2

3 Executive summary Sorting of used plastic packaging for closed loop recycling back into food packaging requires positive identification and sorting of the recycled materials to a higher standard. The operators of commercial food grade recycling processes are required to demonstrate the recycled materials meet relevant European Food Safety Authority (EFSA) criteria; these require at least 95% (PET) and 99% (HDPE) of the feed material must have been used for food contact in their first life. The initiation of closed loop food grade recycling of PP packaging is awaiting a viable technical solution to differentiate the food grade packaging. The objective of this project was to further develop the fluorescent marker technology investigated in earlier projects that has the potential to meet EFSA requirements and to extend the scope to different applications, enabling and facilitating the sorting of different polymers to a high degree of purity. The scope of the project included the optimisation of fluorescent compounds, evaluation of their stability in the supply chain and the ability of the compounds to be effectively removed during the cleaning and decontamination process. The project investigated the viability of the technology and its capacity to be implemented in the UK and elsewhere. The project demonstrated that the use of commercial labels incorporating fluorescent markers can be used to sort plastic bottles and packaging with high yields and purity. The addition of UV illumination to existing full scale sorting equipment was used to sort packaging with a range of fluorescent pigments. The project was able to demonstrate yields in the range of 88% to 96% and purity levels up to 100% in a single pass. This performance can meet the sorting requirements for food grade plastics especially recycled PET and HDPE (and potentially recycled PP) that require high purity levels. The project showed that commercial labels and markers were removed efficiently without any residues during the simulation of recycling operations ensuring that they would not persist in future applications. In addition, the high temperature extrusion processes encountered in re-melting of plastics created irreversible changes to most of the fluorescent chemical structures and deactivated the markers as shown by oven simulation tests. One of the markers was stable at extrusion temperatures, limiting its application to only those labels that can be removed efficiently during the recycling stages. The markers investigated were shown to withstand the environmental conditions encountered in the packaging supply chain by milk bottles (e.g. refrigeration, moisture and fluorescent lighting) with limited impact on its performance. However, these markers were affected by exposure to outdoor UV light and sorting efficiency after outdoor storage still needs to be validated even though baling of containers would protect the bulk of the labels. The fluorescent markers were used at low addition levels in inks at between 2,000 and 6,000ppm and sorted on high-speed automatic sorting systems running at throughputs of 3m/sec and 1 tonne per hour per metre of belt width as typically found in commercial plants. At a concentration of 2,000ppm, the pigment cost is of the order of per 1,000 labels depending on the pigment selected. The lower limit of detection of WRAP Recycling of food grade packaging using fluorescent markers Page: 3

4 the current label/equipment system was shown to be in the region of 125ppm, providing opportunities for a further ten-fold reduction in pigment cost. Calibration of the sorting equipment to identify the unique signature of a label by using the Near Infrared (NIR) signal combined with fluorescence provided a way of achieving high levels of discrimination and purity in sorting. Therefore, the polymeric composition of the label and the pigment can together become the unique identifier for the packaging. This will provide many combinations based on the opportunity to use materials such as PP, PS, LLDPE and PET as well as others, as sleeves and labels for selective identification and sorting of many applications. Tomra provided a preliminary cost estimate of systems and modification to achieve this unique signature with fluorescent labels at 10-20% of the cost of the existing NIR/Vis sorting unit. A protocol for the use of fluorescent markers in the recycling of packaging has been proposed using two different markers (red and yellow) in conjunction with the label composition and the packaging substrate to designate food-grade and specific non-food grade packaging respectively. Packaging that is food grade and natural in colour would be designated by the food grade marker DR-1 (red), and coloured packaging or any products that need to be removed from a stream (e.g. non-food bottle that contained toxic products) would be designated by DY-1 (yellow). In the case of sorting food grade and coloured plastic, then a combined maker (DR-1 & SC-1) could be used. The signal from this combination would be different from the natural packaging food grade marker (DR-1) and different from the coloured non-food grade marker (DY-1). In order to separate bottles from pots, tubs and trays, a combined maker of DR-1 and DY-1 would be used. This would be useful particularly for PET recycling where there is a desire to separate the two streams due to the differing recycling behaviour. The proposed protocol is summarised in the table below and each combination is unique even though the fluorescent pigment is the same allowing a simple and effective way of discriminating each material and any new materials that need to be added in the future. Table: Protocol for designation of fluorescent markers for Packaging. Bottle type Food grade natural Bottles and full length sleeves Food grade natural Pots, Tubs and Trays Food grade coloured and full length sleeve Non- food grade natural or coloured full length sleeve PET DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 HDPE DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 PP DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 Other Polymers DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 WRAP Recycling of food grade packaging using fluorescent markers Page: 4

5 The widespread use of optical brighteners in labels, plastics colorants and liquid products such as detergents mean that there could be cross over with fluorescent pigments that emit in the blue wavelength region leading to false positives in sorting. For this reason, it is recommended that markers that fluoresce in the blue wavelength spectrum are not used on their own. The final protocols would be based on approved combinations of a range of resins used for labels and sleeves along with the specific pigments used as fluorescent markers. This would involve a registration and profiling the spectrum of each combination of label, fluorescent material and base packaging material. This would generate a database of approved and unique signatures for the packages that would be used to program the sorting equipment of the various manufacturers. The approval process would need to be established on a national and preferably a regional basis to avoid standardisation conflicts when products are marketed in many countries or globally. This project has demonstrated that sorting processes based on fluorescent labels can provide an additional level of information to allow further sub-categorisation of packaging either at the start of sorting or after a primary sorting step. The recycling of food grade PET packaging, food grade HDPE milk bottles and PP rigid packaging are likely starting points for the application of this technology. WRAP Recycling of food grade packaging using fluorescent markers Page: 5

6 Contents 1.0 Introduction Optimisation of fluorescent compounds Sourcing commercially available fluorescent compounds Testing of fluorescent compound profiles Pigment combination evaluation Optimised label structures Limit of detectability on commercial sorting equipment Estimated costs for label and modified sorting equipment Conclusion: Bench scale trials of fluorescent compound stability in supply chain Bench scale environmental stability tests Hand drawn label samples CCL commercial labels Case study - fresh white milk supply chain Assessment of UV and temperature impacts Testing of labels on a commercial dairy filling line Testing of labels from commercial printing process Heat treatment of packaging and labels Conclusion: Bench scale trials of fluorescent compound deactivation during recycling Bench scale testing of deactivation conditions Conclusion Sorting trial demonstrations Selection of compounds for label manufacture Initial static scans Calibration and sorting efficiency trials with hand-made labels Conclusion Sorting trials using commercially prepared labels Commercial label sorting trials Shrink sleeves on PET bottles Wash off labels on PET bottles, Pressure sensitive (PSA) labels and PET bottles WRAP Recycling of food grade packaging using fluorescent markers Page: 6

7 6.1.4 Pressure sensitive labels and HDPE bottles Stretch sleeves Sorting trials with mixture of all bottle and label types Sorting equipment optimisation Sorting of fluorescent label packaging mixed with MRF bottles Conclusion Recycling wash processing trials Conclusion Protocols for the use of fluorescent labels Overall conclusions List of Appendices Reported separately 54 Appendix 1: Evaluation of fluorescent markers Appendix 2: Effect of label backing material and manufacture processes Appendix 3: Effect of lighting exposure in the supply chain Appendix 4: Impact of weathering on fluorescent markers Appendix 5: Bottle wash trials Appendix 6: Cost estimates List of Figures Figure 1: Spectra of pigments showing discrete emissions in the visible spectrum Figure 2: SR-1 pigment on different substrates and spectra of fluorescent backing Figure 3: Emission spectra VM-2 with different backing substrate Figure 4: SG-1 pigment with non-fluorescent backing and on clear film at two concentrations Figure 5: 14-day weathering tests on exposed organic and inorganic pigments Figure 6: Extrapolation of peak intensity over 100 day s exposure for DR-1 pigment Figure 7: 10-day weathering tests on peak emission wavelengths for SC-1 pigment Figure 8: Thermal treatment of label pigments Figure 9: PP pots with 12,500ppm SR-1 on PP self-adhesive labels Figure 10: Granulated labelled and unlabelled PP pots exposed to UV light Figure 11: Fluorescence before and after simulating extrusion conditions Figure 12: Fluorescence before and after heating for 10min Figure 13: Hand drawn self-adhesive labels applied to PET bottles for trials WRAP Recycling of food grade packaging using fluorescent markers Page: 7

8 Figure 14: Bottles being crushed for the sorting trials at TOMRA Figure 15: Labelled bottles at 12,500ppm for calibration trials Figure 16: All types of labels with fluorescent pigments for sorting trials Figure 17: Single and double PSA labels on crushed HDPE bottles ready for sorting Figure 18: Applying Shrink Sleeves and steam tunnel process at CCL labels Figure 19: Mixture of labels with fluorescent pigments with coloured sleeved bottles Figure 20: Coloured PET (left) and Coloured HDPE (right) used in the sorting trials Figure 21: Coloured PET (left) paper labels (right) ejected along with SC Figure 22: Coloured PET (left) and Coloured HDPE (right) used in the sorting trials Figure 23: Mixed coloured HDPE selected in SC-1 sorting trials Figure 24: Persil bottle (left) and liquid detergent bottle (right) Figure 25: PET bottle with shrink sleeve after wash and label separation Figure 26: MRF Sorting Protocol for packaging with fluorescent labels List of Tables Table 1: List of fluorescent marker compounds evaluated Table 2: Emission of pigments (6,250ppm) when excited with UV light at 365nm Table 3: Effect of backing paper on emission intensity Table 4: Estimation of pigment volumes and costs Table 5: Expected label exposure conditions throughout supply chain Table 6: Impact of UV and temperature on fresh milk supply chain Table 7: Impacts of exposure of various pigments to in-situ dairy conditions Table 8: Pigment response after UVC drying Table 9: Positively sorting for single pigments Table 10: Positively sorting for multiple pigments Table 11: Summary of commercial labels prepared by CCL for sorting trials Table 12: Sorting for DR-1 shrink sleeves Table 13: Positively sorting for DY-1 with white backing Table 14: Sorting for PSA labels with DR-1 & SC-1 and SC-1 only pigments Table 15: Sorting PSA labels with fluorescent pigments DR-1 & SC-1 and SC Table 16: Sorting PSA labels on HDPE milk bottles Table 17: Sorting with Stretch Sleeves on PET bottles Table 18: Sorting from mixture of all commercial labelled bottles WRAP Recycling of food grade packaging using fluorescent markers Page: 8

9 Table 19: Sorting fluorescent labels from coloured bottles using the long pass filter Table 20: Sorting fluorescent labels on PET in mixed MRF coloured PET bottles Table 21: Sorting fluorescent labels in mixed MRF coloured HDPE bottles Table 22: Bottles / labels sent for washing trials at Sorema Table 23: Protocol for designation of fluorescent markers for Packaging Glossary Counts Emission Intensity Fluorescent HDPE IR LED LDPE LLDPE MRF ms NIR nm PET PP Unit of measure of Emission Intensity during the integration time. Strength of emitted radiation from fluorescent substance A substance that emits longer wavelength radiation (visible light) while being excited by shorter wavelength radiation (non-visible UV) High Density Polyethylene Infrared Light Emitting Diode Low density polyethylene Linear low-density polyethylene Material Recovery Facility milliseconds Near-Infrared nanometre Polyethylene terephthalate Polypropylene ppm parts per million (10 6 ) PSA ti UV UVC UV-LED Pressure Sensitive Adhesive (label) Integration time (ms) refers to the time the detector is open to the radiation emission from the fluorescent pigment. Ultra Violet Ultra Violet in the C region nm Light emitting diode that emits in the UV region (365nm) WRAP Recycling of food grade packaging using fluorescent markers Page: 9

10 1.0 Introduction Sorting used packaging for closed loop recycling back into food packaging requires positive identification and sorting of the recycled materials, to confirm that at least 99% for HDPE and 95% for PET have been used for food contact in its first life, as required by the European Food Standard Agency (EFSA) 12. Commercial systems for PET and HDPE recycling are under pressure to show that recycled materials meet these criteria and efforts to commence closed loop recycling for PP packaging are pending, finding a viable technical solution. An automated method for sorting post-consumer PET, HDPE and PP packaging to produce a stream consisting of high purity materials that previously have been used for food contact, is not in place. WRAP has been working with industry to develop viable recycling processes to meet demand for recycled plastic packaging for use in food contact packaging. The latest WRAP work 3 conducted by Nextek, identified fluorescent ink and coating applied to labels as a suitable solution for the sorting of packaging, as it can be applied to existing products by conventional means. Required modifications to existing sorting equipment were considered minimal and initial testing indicated the sorted material achieved over 99% purity. It was identified that further trials would be required to optimise the performance, cost effectiveness and demonstrate adequate removal of the label and fluorescent marker at the reprocessing and wash stage. There is wide interest in the use of markers to facilitate rapid sorting of specific categories of plastics as demonstrated by the number of concurrent projects with similar goals, some of which are described here: Polymark 4 is an EU FP7 research project coordinated by Petcore, focussing on the recovery of food grade PET bottles using the concept of adding markers to coatings applied to PET bottles. PETCycle 5 is an EU Life project led by Procter & Gamble (P&G) that also focuses on using non-removable markers to allow sorting and recycling of pigmented PET bottles into non-woven materials using dedicated technology from Polysecure that has been used in PVC window frame recycling. PRISM 6 is an Innovate UK funded project led by Nextek Ltd that is developing novel fluorescent pigments from non-rare earth materials and recycling powders from fluorescent tubes for use on labels, as an extension of the direction established by the initial WRAP project. REFLEX 7 is an Innovate UK funded project led by Axion Consultancy that aims to improve separation in recycling operations for flexible packaging as well as 1 EFSA Journal 2011;9(7):2184 Scientific Opinion on the criteria to be used for safety evaluation of a mechanical recycling process to produce recycled PET intended to be used for manufacture of materials and articles in contact with food 2 COMMISSION REGULATION (EC) No 282/2008 on recycled plastic materials and articles intended to come into contact with foods 3 WRAP, 2014 (IMT ) Optimising the use of machine-readable inks for food packaging WRAP Recycling of food grade packaging using fluorescent markers Page: 10

11 developing a de-inking technology. It is investigating amongst other technologies, digital watermarking that encodes an invisible barcode into the printed surface that allows decoding by optical devices. This extensive level of activity in marker technology and the involvement of a wide range of major brands, resin manufacturers and industry associations suggest that the demand for a viable technology is strong. This could develop into new strategies and standards for recycling of packaging especially where colour and polymer identification are insufficient for the needs of the brand owners in meeting their Corporate Social Responsibility and circular economy goals. A benefit of a workable system would be greater flexibility in product design as difficult-to-recycle items could be subsequently recycled. 2.0 Optimisation of fluorescent compounds The objectives of this work were to identify and source commercially available fluorescent pigments and measure their fluorescence in the visible region that had sufficient intensity to be suitable for detection by existing automated sorting equipment after excitation by suitable UV systems, such as UV-LED s. It was also necessary to assess the durability of the fluorescent pigments when exposed to a range of light (UV) and storage conditions, such as high humidity, heat, cold and freezing. A number of conditions were simulated for a variety of food products. This was done to ensure that the pigments would remain viable until the sorting stage of recycling. Based on the results of this evaluation, candidate fluorescent pigments were selected for use in label manufacture, sorting and washing trials. 2.1 Sourcing commercially available fluorescent compounds Eighteen fluorescent pigments were identified and samples sourced for evaluation. These included three pigments from previous WRAP funded project research 8, and two pigments that are currently the subject of research within an EU funded project (Polymark) 9. The objective was to identify additional pigments that could be strongly excited by suitable UV light sources (at 365nm) and be detected by existing commercial sorting equipment. If pigments with different emission profiles could be identified this may provide a wider range of application in which different packaging articles could be identified by a specific wavelength or a combination of wavelengths. Pigments sourced from a number of suppliers were analysed for their fluorescent capabilities as shown in Table 1. Pigments from Supplier 1 described as inorganic to reflect an inorganic component are in fact organic / inorganic combinations that generally behave like organic pigments. The three pigments later utilised in the commercial label sorting trials and thermal stability testing were all organic pigments. 8 WRAP, 2014 (IMT ) Optimising the use of machine readable inks for food packaging 9 WRAP Recycling of food grade packaging using fluorescent markers Page: 11

12 Table 1: List of fluorescent marker compounds evaluated Supplier 10 ID Pigment code name Emission colour Organic / inorganic Excitation wavelength (nm) Emission wavelength (nm) Supplier 1 1 SR-1 Red Organic 365/ SL-1 Lemon Organic 365/ SC-1 Cyan Organic 365/ ER-1 Red Inorganic 365/ DR-1 Orange Organic No data No data 6 SG-1 Green Organic 365/ SG-2 Green No data CR-1 Red No data 950/ /676/683 9 CB-1 Blue No data 950/ DY-1 Yellow Organic No data No data Supplier 3 11 IR-5 Green Rare earth oxy sulphide 950/ / IR-4 Blue Rare earth oxy sulphide 950 / Supplier VM-3 Blue No data No data No data 14 VM-2 Blue/Green No data No data No data 15 VM-4 Violet No data No data No data Supplier BS-4 Blue Organic BS-2 Blue Organic Supplier PH-1 Blue dye Organic No data No data 10 Continuation of numbering from previous WRAP project (IMT ); suppliers 2, 4-10 were not utilised; suppliers 11, 12, 13 are new. WRAP Recycling of food grade packaging using fluorescent markers Page: 12

13 2.2 Testing of fluorescent compound profiles Self-adhesive PP label materials with pigment concentrations of 3,125ppm, 6,250ppm, 12,500ppm and 25,000ppm were prepared by mixing pigments with a nitrocellulose lacquer and ethyl acetate solvent in a high-speed mixer. Then by using a Myer bar, a consistent layer thickness and pigment weight was applied to A4 sized sheets that were cut to label size of 20cmx10cm as described in the previous WRAP funded project 11. Using a test jig developed in previous work, the samples were mounted in slide carriers and illuminated with various light sources in order to induce emission: 365nm, 640nm, nm and nm. The emitted light from the pigment was collected at 50cm distance with a telescope focussing onto a fibre optic and the emission spectra measured on an Ocean Optics Spectrometer. The relative emission column in Table 2 indicates a comparatively large reduction in brightness of the VM-2 and VM-3 pigments, requiring higher concentrations in order to match the SR-1 dye intensity at lower concentrations. In addition, there was a slight overlap of spectra of the substrate fluorescence with the VM-2 and VM-3 spectra, which may reduce their effectiveness. The spectra for each pigment are shown in the separate Appendix report. Table 2: Emission of pigments (6,250ppm) when excited with UV light at 365nm. Pigment Emission colour Peak wavelength (nm) Peak intensity (counts) Integration time (ms) Relative emission (counts/ms) SR-1 Red , ,000 VM-2 Blue/Green , VM-3 Blue , VM-4 Violet , The VM-2, VM-3 and VM-4 pigments appear to require a laser or other more intense light than an UV-LED to achieve excitation suitable for automated sorting equipment, excitation, which was impractical in the scope of this project Pigment combination evaluation A further element of the project was to demonstrate if different pigments could be used in combinations to provide additional information and sorting options. For example if three pigments with different spectra were suitable for use, up to seven [2 3-1=7] different articles could be identified if they could all be used in various combinations. For practical purposes in commercial applications, all pigment combinations would need to be able to be physically mixed together, applied as a single layer or coating and not have interference from other label components. Most commercial situations for 11 WRAP, 2014 (IMT ) Optimising the use of machine readable inks for food packaging WRAP Recycling of food grade packaging using fluorescent markers Page: 13

14 Emission Intensity (counts) packaging would not be able to apply the pigments as separate discreet layers or to a specific area of print on a label. Three pigments with strong fluorescence in discrete regions of the visible spectrum, which had demonstrated stability in the supply chain and were least likely to have interference from optical brighteners currently used in a range of packaging materials were selected (Figure 1). DR-1 peak wavelength 615nm, sharp emission red region. DY-1 peak wavelength 540nm, broad emission yellow region. SC-1 peak wavelength 455nm, double peak emission blue region. Other pigments listed in Table 1 were found to have excitation wavelengths away from the preferred UV region, a have lower emission intensity at similar concentrations and integration times, or were similar in response to pigments selected, indicating they may be chemically similar. Spectral data was gathered from pigments that were incorporated in nitrocellulose lacquer at 12,500ppm and drawn down onto PP sheet (Figure 1). Figure 1: Spectra of pigments showing discrete emissions in the visible spectrum. 50,000 Individual emission spectra of pigments 40,000 30,000 20,000 10, Wavelength (nm) SC-1 DY-1 DR-1 It was observed that the fluorescence emission from DR-1 was approximately 3 times greater than that recorded for DY-1 and that higher concentrations of DY-1 may be required to ensure labels carrying this pigment are correctly identified during commercial sorting. It was also evident that pigments such as DR-1, which emit within a distinct and narrow wavelength range, are desirable to ensure correct package identification. Obtaining pigments that exhibit this feature also allows for a greater number of pigments that can be clearly identified across the visible spectrum to code a wide range of plastics packaging. WRAP Recycling of food grade packaging using fluorescent markers Page: 14

15 Emission Intensity (counts) 2.3 Optimised label structures A selection of label samples from supplier 11 produced a more intense signal than expected, which was thought to be influenced by the backing paper. Results suggested that the use of a backing sheet where the light can be reflected and pass through the lacquer a second time enhancing the fluorescent intensity. This would allow a reduction of pigment concentration, therefore reducing the cost of the label or the possible use of otherwise lower intensity emitters. Samples were analysed to measure the effect of two types of reflective backing paper, one that had its own background fluorescence, and one that had no inherent fluorescence. The detector integration time (ti) is an important factor for high speed automated sorting, and in the figures attention must be made of the time to develop each spectrum. Fast integration times of a few milliseconds are desirable for high speed automated sorting, and 10ms was the standard integration time, unless otherwise indicated. Intensity levels increased significantly with use of both types of reflective backing as shown in the spectra of SR-1 (Figure 2), which has been scaled to highlight the increased emission intensity. The fluorescent reflective backing however also had a large emission in the blue region (off scale in the spectra of SR-1) and shown in the spectra of the fluorescent backing only in Figure 2. Figure 2: SR-1 pigment on different substrates and spectra of fluorescent backing. 12,000 Spectra of SR-1 pigment with different backing substrates 10,000 8,000 6,000 4,000 2, Wavelength (nm) no backing fluorescent non-fluorescent WRAP Recycling of food grade packaging using fluorescent markers Page: 15

16 Emission Intensity (counts) Emission Intensity (counts) 30,000 Fluorescent backing only 25,000 20,000 15,000 10,000 5, Wavelength (nm) fluorescent The VM-2 has a peak emission at 521nm in the green part of the visible spectrum, approximately 5 times less intense than SR-1. The spectra in Figure 3 show the increased intensity obtained with both fluorescent and non-fluorescent backing, which is emphasised by the reduced integration time compared to the no backing sample. The fluorescent backing influence on the emission wavelength can also be seen. Figure 3: Emission spectra VM-2 with different backing substrate. 60,000 Pigment VM-2 on different substrate backing 50,000 40,000 30,000 20,000 10, Wavelength (nm) no backing (ti=200ms) fluorescent (ti=1ms) non-fluorescent (ti=100ms) SG-1 pigment with the use of a non-fluorescent backing sheet produced a higher intensity shown in Figure 4 and Table 3. Further spectra of the pigments are shown in the separate Appendix report. WRAP Recycling of food grade packaging using fluorescent markers Page: 16

17 Emission Intensity (counts) Emission Intensity (counts) Figure 4: SG-1 pigment with non-fluorescent backing and on clear film at two concentrations. 20,000 SG-1 at 3,125ppm and ti=10ms 15,000 10,000 5, Wavelength (nm) clear backing non-fluorescent 20,000 SG-1 at 6,250ppm and ti=10ms 15,000 10,000 5, Wavelength (nm) clear backing non-fluorescent WRAP Recycling of food grade packaging using fluorescent markers Page: 17

18 Table 3: Effect of backing paper on emission intensity. Pigment concentration (ppm) With backing peak intensity (counts) Without backing peak intensity (counts) Signal increase (with/without backing) Integration time (ti) (ms) 25,000 37,622 19, ,500 16,628 11, ,250 15,973 6, ,125 14,369 2, The results with SG-1 with backing paper show that the peak intensity was approximately double at high pigment concentrations and nearly five times higher at lower pigment concentrations than the peak intensity without backing and using only the clear film. This enhanced benefit for the lower pigment concentration films may improve the cost performance of the pigmented labels by enabling less pigment to be used. 2.4 Limit of detectability on commercial sorting equipment In order to determine the lowest detectable levels of pigments on commercial sorting equipment, hand draw-down sheet samples of DR-1, SC-1 and DY-1 were prepared at concentrations of 12,500; 1,250; 125; 12.5; 1.25 and 0.125ppm and evaluated under static conditions using the UV/detector system at Tomra. The lower limit of detection of the current label / equipment system was shown to be in the region of 125ppm, providing opportunities for further pigment savings and cost reduction. 2.5 Estimated costs for label and modified sorting equipment. The use of fluorescent markers on labels to improve sorting will likely result in additional costs to the supply chain, however by optimising the performance and detection, these costs can be minimised to a small percentage of overall packaging costs. Sorting trials reported successful identification using commercial label samples with pigment concentrations at 2,000ppm. Information from the sorting trial indicates that pigment levels as low as 125ppm would be detectable. The additional material cost for pigments for one thousand 10cm x 10cm labels was estimated at between for the lowest cost pigment at the lowest concentration of 125ppm for the highest cost pigment at the higher concentration of 2,000ppm. These additional pigment costs are estimated at 0.05% to 3.0% for the pigment material only, respective of the 0.75 pence price of an applied label. There may also be some additional material costs for lacquers or coatings and additional operational costs dependent on the final label structure. WRAP Recycling of food grade packaging using fluorescent markers Page: 18

19 To estimate the volume of pigment material required, PP packaging was used as one potential application that utilises 143,000 tonne 12 of PP per year, which equates to 14.3billion 10g packs per year and 0.27 tonne of pigment at 125ppm or 4.3 tonne at 2,000ppm, as shown in Table 4. Table 4: Estimation of pigment volumes and costs. Concentration 2,000ppm 125ppm Pigment cost 190 / kg 750 / kg 190 / kg 750 / kg Pigment / 1,000 labels (mg) Pigment cost / 1,000 labels ( ) Pigment cost (% of label cost) Pigment volume pa (tonne) Table 4 shows that although pigment costs are relatively high on a per kg basis, due to the low applied concentration and label size, the added cost is modest in absolute terms and as a percentage of overall label, cost is less than 1% in all but the highest concentration highest pigment cost scenario. It would be likely that pigment purchase costs would be reduced over time as volumes increased and this would reduce application costs further. Sorting trials used the same UV-LED lamp assembly as was used in the previous WRAP project 13. Existing commercial sorting equipment can be modified with this type of lighting system to enable the detection of the fluorescent marker labels. Costs to retrofit the new lamp and detection requirements are dependent on factors including age, condition and whether the sorting unit was configured for detection and sorting in the visible spectrum, or in the NIR spectrum only. Project partner Tomra provided a preliminary estimate of the cost of the additional UV-LED lighting systems showing modifications at 10-20% of the cost of the existing NIR/Vis sorting unit. These cost estimates may increase if other upgrades are required to older or minimally configured sorting units. 2.6 Conclusion The cost efficiency of fluorescent labels can be significantly improved by the use of a reflective substrate for the label to boost the strength of the emission signal for a given concentration. This can be as simple as using a white or opaque background. This would allow pigments to be used at lower concentrations, while still providing a signal that can be detected under sorting conditions. The estimated pigment cost for label applications is 0.05% to 3.0% of the label cost, and would be smaller as a percentage of overall package cost, which will encourage adoption of the technology, particularly for critical sorting applications such as food grade packaging in the first instance. Based on trial 12 WRAP, 2012 (IMT ) UK market compositional data of polypropylene packaging 13 WRAP, 2014 (IMT ) Optimising the use of machine readable inks for food packaging WRAP Recycling of food grade packaging using fluorescent markers Page: 19

20 results and testing, sorting equipment modification costs have been estimated by Tomra at 10% -20% of the existing equipment cost for many systems. 3.0 Bench scale trials of fluorescent compound stability in supply chain A critical requirement of the project was to demonstrate that labels incorporating fluorescent pigments retain their emission intensity throughout the supply chain, which involves elements of label manufacture, packer/filler, warehouse, retail, consumer, kerbside collection and recycling. Understanding the behaviour of the fluorescent pigment under these various environmental impacts helps to select the most suitable pigments and label design. 3.1 Bench scale environmental stability tests. A range of label samples were mounted in slides and exposed to varying environmental conditions and the change in emission intensity was monitored regularly over a fourteen-day period. The exposure conditions were as follows: Outside: South facing at 30 degree 1.5metres above ground. Fridge: Door shelf in polythene 5 o C. Freezer: Upper shelf in polythene -25 o C. Fluorescent lamp: 30cm front of the tube Hand drawn label samples. The results show that SR-1 (organic pigment) and DR-1 (organic pigment) remained relatively stable in the refrigerator and freeze conditions over a fifteen day period, however the peak intensity dropped significantly after exposure to UV from both the fluorescent lamp and from sunlight after exposure to outside conditions (Figure 5). The DY-1 (organic pigment) remained consistent among all environmental conditions, with some intermediate variations with outside exposure. SC-1 (organic pigment) showed stability after being exposed in the refrigerator and freezer, decreased emission under fluorescent lamp and a greater reduction in emission when exposed to outdoor conditions. It is important to note that although SR-1 and DR-1 had a significant reduction in emissions, their initial peak emission intensity was much higher than for DY-1 and SC-1. Therefore, after fifteen days under fluorescent lamp, peak intensity for SR-1 and DR-1 was reduced to a similar peak intensity as that for DY-1 and SC-1, which was sufficient for detection and sorting. WRAP Recycling of food grade packaging using fluorescent markers Page: 20

21 Emission Intensity (counts) Emission Intensity (counts) Figure 5: 14-day weathering tests on exposed organic and inorganic pigments. 8,000 Pigment SR-1 6,000 4,000 2, Day fridge freezer fluor' tube outside 6,000 Pigment DR-1 4,000 2, Day fridge freezer fluor' tube outside WRAP Recycling of food grade packaging using fluorescent markers Page: 21

22 Emission Intensity (counts) Emission Intensity (counts) Pigment DY-1 1, Day fridge freezer fluor' tube outside Pigment SC-1 3,000 2,500 2,000 1,500 1, Day fridge freezer fluor' tube outside Given the trends in emission reduction over 14 days, it was possible to extrapolate for extended periods for each condition. Using a power law equation, the on-going trends were forecast for fluorescent lamp and outdoor exposure conditions for DR-1 pigment out to 100 days (Figure 6). The results show that outdoor exposure will diminish the signal strength to very low levels in 5-10 days depending on conditions; fluorescent lamp exposure may be tolerated for days for the DR-1 pigment. The DY-1 pigment demonstrated a stable emission intensity after UV exposure from outside and fluorescent tube, as well as refrigerator and freezer conditions, which would prevent a reduction in label performance when recovered packaging is baled and stored outside prior to MRF and recyclers processing. WRAP Recycling of food grade packaging using fluorescent markers Page: 22

23 Emission Intensity (counts) Figure 6: Extrapolation of peak intensity over 100 day s exposure for DR-1 pigment. 7,000 Extrapolated affect of UV exposure for DR-1 6,000 5,000 4,000 3,000 2,000 1, Days exposure Flourescent tube exposure Outside exposure CCL commercial labels. CCL Commercial labels manufactured later in the project were also exposed to the same environmental conditions as the hand drawn labels and changes in emission intensity were monitored over nine days. The full results shown in the separate Appendix report indicated good agreement with the trends found for the hand drawn labels for DR-1 and SC-1 and DY-1 pigments in section For this series of experiments, both peak emission wavelengths for the SC-1 pigment at 472nm and 437nm were monitored, showing no significant difference in the level of performance between the two peak emission wavelengths (Figure 7). WRAP Recycling of food grade packaging using fluorescent markers Page: 23

24 Emission intensity (counts) Emission intensity (counts) Figure 7: 10-day weathering tests on peak emission wavelengths for SC-1 pigment. Pigment SC-1 only, 2,000ppm - PSA 10,000 8,000 6,000 4,000 2, Days fridge freezer fluor' tube outside control Pigment SC-1 only, 2,000ppm - PSA 10,000 8,000 6,000 4,000 2, Days fridge freezer fluor' tube outside control 3.2 Case study - fresh white milk supply chain In-situ tests within a milk-filling line were carried out to understand the impacts of light and temperature on fluorescence response. A survey of the lighting associated with a dairy, storage and local supermarkets revealed a variety of lighting is being used, including older style fluorescent tubes (36 Watts) and newer lower energy LED. The impacts of both lighting types were evaluated. The impacts of temperature from chilled storage and freezing and external UV impacts that are likely to occur when packs are recovered for recycling baled and stored outdoors were also investigated. WRAP Recycling of food grade packaging using fluorescent markers Page: 24

25 3.2.1 Assessment of UV and temperature impacts The manufacturing, supply chain and end of life impacts for fresh white milk production are summarised in Table 5. Table 5: Expected label exposure conditions throughout supply chain. Supply chain Main impacts Ink formulation, label manufacture and application to packaging article Heat, UV curing Packer / filler Refrigeration (chiller), UV from lighting, humidity. Supply chain logistics to retailer, and retail display Refrigeration (chiller), UV from lighting, humidity Consumer Kerbside collection and recycling Refrigeration, UV from lighting and external, humidity External UV, ambient temperatures, humidity The potential UV and temperature impacts that relate to fresh milk from packer and filling lines through the retail, consumption to end of life were considered and shown in Table 6. Table 6: Impact of UV and temperature on fresh milk supply chain. Area Packer Filling / storage Logistics Back of store Retail display Consumer Recovery Recycling Activity Palletised bottles Labels in reels Bottle filling, labelling & palletise Storage, loading, transport Storage, depalletising In store display and retail Refrigeration Comingled collection, sorting & baling Debaling, sorting, washing and extrusion Source of UV High bay (400W) Fluorescent High bay (400W) High bay (400W) Fluorescent (36w), LED Minimal external UV High bay (400W) External UV after baling External UV storage Temperature Ambient Aircondition (10-15 C) Chilled (<5 C) Chilled (<5 C) Chilled (5 C) Refrigerator (<5 C) Ambient Ambient, 85 C wash, +200 C extrusion Duration <6 months 2-3 minutes (15 min w/ stoppage) 24 hours 48 hours 120 hours 72 hours 5-90 days 5-90 days Impact Minimal Minimal Minimal Minimal Moderate Minimal Severe Severe No test In-situ testing with label exposure No test No test Bench scale Fluorescent exposure test at 5 days Test at 5 C and -20 C Test outdoor Test outdoor exposure 15 exposure 15 days days WRAP Recycling of food grade packaging using fluorescent markers Page: 25

26 This assessment indicated that fresh milk packaging had minimal exposure to outdoor sunlight conditions prior to sorting at a recycler. The supermarket retail position on the shelf provided the greatest exposure to fluorescent or other lighting for a maximum of 6 days. After consumption, milk bottles and other packaging are not expected to have significant exposure to sunlight. Kerbside bags, collection trucks and MRFs are all expected to minimise outdoor exposure and any reduction in the emission performance of the label marker. Typically, the MRF would conduct a bottle sort process directly from kerbside collection, and sorted fractions are compressed into bales. These bales are often stored outside in stacks two or three bales high at the MRF or at the plastic recyclers before being sorted again to remove the remaining contamination. The outside exposure of the bale could be for 5-90 days depending on seasonal factors and MRF operations. However, because bottles are baled and stacked before storage, only a small percentage of the bottle labels will have exposure. This may affect yields if storage times are long during summer months but overall the impact on yield is expected to be relatively small Testing of labels on a commercial dairy filling line Milk bottles are filled before labelling and the most common types of labels used are stretch sleeves, wrap around and pressure sensitive labels. All of these commercial labels contain an optical brightener additive, so they can be detected by an on-line sensor to confirm correct labelling. Tests of SC-1 and BS-2 at one dairy showed that they were capable of triggering the on-line sensor. Potentially, the fluorescent marker used in the labels could replace the optical brightener. The impacts on the fluorescence response of eight pigments versus unexposed controls are shown in Table 7 for the exposure to lighting used at a milk filling line (15 minute of exposure) together with the lighting (400W high bay lighting assumed) that are experienced during pre-delivery cold storage. These tests were conducted in situ at a commercial dairy under normal operational conditions. WRAP Recycling of food grade packaging using fluorescent markers Page: 26

27 Table 7: Impacts of exposure of various pigments to in-situ dairy conditions. Pigment code name Peak emission wavelength (nm) Control (counts/10ms) Dairy exposure (counts/ 10ms) Change after exposure (%) SR ,000 83,000-9 SL ,900 9, SC ,000 40, DR ,000 45, SG ,033 5,082 1 DY ,933 9,414 5 BS ,300 1, BS ,000 46, With the exception of pigment BS-2, which showed an anomalous increase attributed to hand prepared sample variation, there is little change in the emission when subjected to exposure to conditions within a typical dairy. Differences can be attributed to variations in the original film deposition and the location of samples taken for testing Testing of labels from commercial printing process Labels were prepared using lacquer containing SR-1 pigment by CCL laboratory to evaluate the impact of Ultra Violet in the range of nm (UVC) for drying of ink after printing, which is a common industrial process. Labels were air-dried or dried using UVC radiation and emission intensity of the two variables for two different concentrations compared in Table 8. WRAP Recycling of food grade packaging using fluorescent markers Page: 27

28 Table 8: Pigment response after UVC drying. Label Pigment (ppm) Detection Time (ms) Peak Intensity 615nm) Marker only 6, ,629 Marker with front treated UV 6, ,105 Marker with back treated UV 6, ,815 Marker only 25, ,830 Marker with front treated UV 25, ,133 Marker with back treated UV 25, ,370 Results showed that the UVC drying process does reduce the emission intensity of the SR-1 pigment; however, intensity was adequate for identification by automatic sorting. The exposure to UVC through the label surface, rather than directly onto the ink surface, reduced the effect of the UVC treatment. Subsequent to this testing, weathering UV exposure identified more UV stable compounds and these could be selected for testing under commercial UVC curing systems to determine the effect of UVC on pigment emission intensity Heat treatment of packaging and labels A number of commercial processes utilise heat and therefore a trial was conducted with commercial labels prepared for sorting trials to determine the conditions that may affect the performance of label pigments. Labels were placed in an air oven at specific temperatures for 10min, then removed and placed under UV light for inspection of residual fluorescence. Results showed that SC-1 was most affected at 100 C. At 150 C, the DR-1 pigment was significantly diminished, and DY-1 remained active. At 200 C, both SC-1 and DR-1 were extinguished, but DY-1 retained some activity. WRAP Recycling of food grade packaging using fluorescent markers Page: 28

29 Figure 8: Thermal treatment of label pigments. Label pigments before thermal treatment After 10min at 100 C After 10min at 150 C After 10min at 200 C The heat treatment also affected the label substrate, initially shrinking the labels and finally melting the polymer materials. However, the activity of the DY-1 pigment was visible in the melted label material. Testing of the SR-1 pigment on labels applied to tubs indicated that fluorescence activity was deactivated after 5min at 220 C (section 4). The persistence of DY-1 at 200 C for 10 min requires further investigation to assess its thermal behaviour. Many thermal processes such as retort and hot filling occur prior to labelling of the packaging and are less likely to be of concern to pigment stability. Where food and beverage hot filling is performed with labelled packaging, the C fill temperatures and the label lacquer being the outer most layer, it is unlikely that these conditions will affect the pigments. The oven test conducted showed that below 100 C the pigments were largely unaffected. In section 6.1 shrink sleeves were applied using a steam tunnel prior to sorting trials. Inspection and the sorting trial itself confirmed that this brief thermal process did not have any significant impact on pigment activity and performance. 3.3 Conclusion Testing indicated that fluorescent markers remained stable during freezer, refrigerator and ambient conditions when not exposed to light. They were also stable to short term exposure to increased temperatures that might be experienced during ink curing or steam tunnels, and hot fill processes during manufacture and application. Consideration of the supply chain and preliminary testing indicated that milk bottles will experience minimal exposure to direct sunlight and moderate exposure to fluorescent or other indoor lighting. This exposure is not expected to have a significant impact on the performance of the fluorescent marker labels. During recycling, there is the WRAP Recycling of food grade packaging using fluorescent markers Page: 29

30 probability that baled bottles that have been sorted by the MRF, will be stored outside for extended periods. However, exposure is limited to a small percentage of labels on the outside of the bale, or bale stack, which should reduce any impact on yield at the recycler when they conduct a further sort to remove the remaining contamination. Some pigments like DY-1, that had demonstrated improved resistance to UV and thermal degradation, may be used to provide a higher level of stability through the entire supply, collection and recycling supply chain. However, this may also limit its application to only those labels that are efficiently removed during the recycling stages. 4.0 Bench scale trials of fluorescent compound deactivation during recycling To progress the technology, it was important to demonstrate that when the packaging was recycled into new applications it did not transfer marker compound functionality from its previous use, which could lead to incorrect identification in any subsequent uses of the recyclate. To demonstrate this, bench scale trials were conducted at the beginning of the project to determine if the fluorescent markers were deactivated by minimal recycling and polymer process conditions. Subsequent testing demonstrated that labels with fluorescent pigments were able to remain active throughout the supply chain. Therefore, packaging articles could be positively identified and separated when they reached the sorting stage of recycling. 4.1 Bench scale testing of deactivation conditions A high emission intensity was obtained from the SR-1 pigment throughout the initial project work with WRAP 14 and was therefore used in this recycling trial. Using the hand drawn label coating, samples were prepared with a 12,500ppm concentration and applied to PP pots, and fluorescent activity tested as shown in Figure 9. Figure 9: PP pots with 12,500ppm SR-1 on PP self-adhesive labels. Labelled and unlabelled pots were then put through a laboratory scale grinder separately, to produce flake as is typical at the start the recycling process. At this stage of the process, some labels became detached, but were retained in the sample. After grinding, the pigment/labels were still present as shown (Figure 10). 14 WRAP, 2014 (IMT ) Optimising the use of machine readable inks for food packaging. WRAP Recycling of food grade packaging using fluorescent markers Page: 30

31 Figure 10: Granulated labelled and unlabelled PP pots exposed to UV light. The flakes were then oven treated for 5min at 220 o C to simulate PP melt extrusion time and temperatures. No fluorescence remained in the flakes after oven treatment. Figure 11: Fluorescence before and after simulating extrusion conditions. Flakes before oven treatment Flakes after oven treatment Emission under UV before oven treatment No emission under UV after oven treatment Figure 11 shows the fluorescence of the flakes before, during and after the oven test, clearly showing that no fluorescence remained after the oven test at PP processing conditions. The black specks that were seen after the oven test were found to be degraded residue of the label adhesive, not the PP or the fluorescent compound. Further analysis at reduced oven temperatures was conducted to determine minimal conditions to eliminate the fluorescent properties of the compound. The fluorescence was significantly diminished after 10 minutes at 100 o C and after 150 o C for 10 minutes the fluorescence was completely destroyed (Figure 12). WRAP Recycling of food grade packaging using fluorescent markers Page: 31

32 Figure 12: Fluorescence before and after heating for 10min. Before heating After heating to 100 C After heating to 150 C 4.2 Conclusion The recycling simulation test results showed that when the fluorescent compounds were heated to temperatures of 150 o C and 220 o C the fluorescent behaviour of the labels was extinguished. Often in the recycling process the label, label lacquer and glue are removed and separated from the bottle, tub or pot by mechanical action or washing conditions, which would also remove the fluorescent marker. This trial demonstrated that if the label were to persist and remain with the packaging, the active fluorescent properties would be extinguished during extrusion to pellets or to new products, preventing any carry over or contamination of the marker into any new products or applications. Additional thermal testing was conducted later in the project using the commercially prepared labels and this is discussed in section Sorting trial demonstrations These trials were conducted on production scale equipment at the Tomra testing facility to evaluate performance under commercial conditions. Although relatively minor modification of the sorting equipment is required in the form of a UV LED light system, it would not be possible to make these modifications and conduct trials at a commercial MRF in the UK due to their production demands. The Tomra facility emulates MRF operating conditions, using a number of processes prior to NIR sorting operating at about 1 tonne per hour. 5.1 Selection of compounds for label manufacture DR-1, DY-1 and SC-1 were selected for the commercial scale demonstrations as they fluoresce strongly under UV light in discrete regions of the visible spectrum (Figure 1). This enabled individual identification of three distinct variables. Additionally, these pigments could be incorporated into inks and lacquers that are used to print a wide range of label formats commonly used for retail packaging. A key objective of the commercial scale investigations was to demonstrate that different pigment emission colours or a combination of pigment emission colours could be used to identify and sort a range of retail packaging and label formats. By demonstrating that fluorescent markers can be used separately or in combination, the number of permutations for identification is significantly increased. 5.2 Initial static scans To establish suitable trial conditions, hand drawn pressure sensitive label samples of DR-1, DY-1, SC-1, and a combined lacquer of DR-1 and DY-1, all at 12,500ppm along with WRAP Recycling of food grade packaging using fluorescent markers Page: 32

33 0ppm control labels were sent for evaluation at the Tomra laboratory using its standard UV and NIR detection system. Static measurements were made of all variables to create a classification for each fluorescent pigment sample that would allow identification of each marker during dynamic trials. 5.3 Calibration and sorting efficiency trials with hand-made labels Hand draw down film samples using each of the three selected pigments at 12,500ppm were prepared on self-adhesive PP film. Labels measuring 17cm x 11.5cm were cut from the film and applied to cylindrical PET bottles given almost complete coverage (Figure 13). PET bottles with un-pigmented labels and unlabelled PET bottles were prepared as controls. Figure 13: Hand drawn self-adhesive labels applied to PET bottles for trials. All bottles were crushed in a press (Figure 14), to reflect the bottle shape from baled recycled packaging, and to stop bottles rolling on the sorting belt, which causes poor sorting. Figure 14: Bottles being crushed for the sorting trials at TOMRA. The following bottle quantity and variables were used in the trial (below and Figure 15): 1) 25 x PET bottles marked with SC-1 (12,500ppm) 2) 25 x PET bottles marked with DR-1 (12,500ppm) 3) 25 x PET bottles marked with DY-1 (12,500ppm) 4) 25 x PET bottles marked with DR-1 (12,500ppm) and SC-1 (12,500ppm) 5) 75 x PET bottles with adhesive label (no pigment) 6) 75 x PET bottles (no label). WRAP Recycling of food grade packaging using fluorescent markers Page: 33

34 Figure 15: Labelled bottles at 12,500ppm for calibration trials. SC-1 DR-1 DY-1 DR-1,Control, SC-1+DR-1 combined,sc-1,dy-1 The sorting calibration trials were undertaken with the conveyor belt operating at commercial speeds of 3m/s. Only target bottles were included at this stage to ensure correct and efficient identification. The number of bottles correctly identified and positively sorted within the eject stream was used to measure efficiency. The results of the calibration trials are shown in Table 9. It was noted that in several instances the bottle was correctly identified, but was not successfully ejected, indicating that further optimisation of the equipment could improve first pass efficiencies further. Unsuccessful ejection can happen if the packaging is not stationary on the conveyor belt, or the sorting equipment is not optimally configured for the type of packaging, and occurs occasionally as part of the automated process. It is not inherent to the fluorescent marker labels or the bottles in the trial, and is minimised only after extended running of the system and fine-tuning of the process. Table 9: Positively sorting for single pigments. Target pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Yield 2 nd pass (%) DR-1 12, NA DY-1 12, SC-1 12, SC-1 & DR-1 12, WRAP Recycling of food grade packaging using fluorescent markers Page: 34

35 After confirming that all pigment types could be successfully identified and ejected in one or two passes, mixtures of bottles with other pigment labels and control bottles were then trialled. These trials also contained non-target bottles to demonstrate that only bottles with the selected pigments was identified and sorted. Non-target bottles included other pigmented label bottles, non-pigment labelled bottles and unlabelled bottles as can be seen in Table 10. High sorting efficiency was achieved in the first pass (92 to 100%) for the individual pigments, 88% for a combination of two pigments) and 100% efficiency obtained for all undetected samples with a second pass. Full experimental details are available in the separate Appendix report. Table 10: Positively sorting for multiple pigments. No. Target Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Purity (%) Yield 2 nd pass (%) 1 DR-1 & DY-1 12, DR-1, DY-1, SC- 1, DR-1 & SC-1 12, SC-1 12, DR-1 12, DY-1 12, DR-1 & SC-1 12, Table 9 and Table 10 show that bottles with different fluorescent pigments could be targeted using automated sorting to eject only selected bottles at high efficiency (92-96% yield and 100% purity) with a first pass and 100% efficiency in two passes. Non-targeted bottles, either without fluorescent labels or with fluorescent labels that were not selected, were not ejected. Two label types were made with a combination of two pigments (DR-1 & SC-1 and DR-1 & DY-1) and they showed a slightly lower sorting efficiency 88%, than the labels with single pigments at 100%. This result may be due to the need to conduct a more detailed calibration of the detectors to exclusively identify the more complex spectrum. For example, when a number of the fluorescent labels were selected to be ejected simultaneously, the yield increased to an average of 98%. This was due to the reduced level of discrimination that was being applied to the sorting process. The purity of the selected bottles with fluorescent labels was consistently high at 100% in all cases. Therefore, the use of fluorescent labels can result in very selective sorting and achieve the purity (>99%) required for food grade plastics like food grade HDPE. WRAP Recycling of food grade packaging using fluorescent markers Page: 35

36 5.4 Conclusion These calibration trials demonstrated that the labels coated with selected fluorescent pigments at 12,500ppm could be readily identified and sorted by UV LED modified automated sorting equipment with very high efficiency and purity comparable to sorting based on NIR. In addition, combinations of pigments may be used to increase the permutations of identifiable labels although the yield was lower on the first pass. The outstanding result was the consistently high purity of the selected fraction at 100% with labels using 12,500ppm fluorescent pigments. This provides a basis for sorting to meet stringent food contact targets for recycled plastics such as food grade rhdpe and rpp which require >99% prior food grade purity. 6.0 Sorting trials using commercially prepared labels CCL Labels prepared pressure sensitive adhesive (PSA), shrink sleeve and stretch sleeve labels for testing on PET and HDPE bottles at reduced concentration levels down to 2,000ppm. A number of fluorescent pigments and pigment combinations were utilised, as well as un-pigmented control labels, which are shown in Figure 16 and summarised in Table 11. Figure 16: All types of labels with fluorescent pigments for sorting trials. WRAP Recycling of food grade packaging using fluorescent markers Page: 36

37 Table 11: Summary of commercial labels prepared by CCL for sorting trials. Label type Pigment Concentration (ppm) Pack type Label size (area) Fluorescent label Shrink sleeve DR-1 2,000 PET bottle 17 x 11.5cm (195.5cm2) Wash off/white backing DY-1 6,000 PET bottle 12.5 x 8.5cm (106.25cm2) Wash off/clear backing DY-1 6,000 PET bottle 12.5 x 8.5cm (106.25cm2) Pressure sensitive SC-1 & DR-1 2,000 (both pigments) PET & HDPE bottle 15 x 5 cm (75.0cm2) Pressure sensitive SC-1 2,000 HDPE bottle 15 x 5 cm (75.0cm2) Stretch sleeve DY-1 & DR-1 6,000 & 2,000 respectively PET bottle 22.0 x 11.7 (257.4cm2) Stretch sleeve DY-1, DR-1 & SC-1 6,000, 2,000 & 2,000 respectively PET bottle 22.0 x 11.7 (257.4cm2) 6.1 Commercial label sorting trials Trials were undertaken to investigate the efficiency of identification and sorting when using a number of different label formats, label areas and pigments on labels made by CCL. As shown in Figure 17, all of the commercially printed labels were applied to the bottles by hand for the sorting trials. WRAP Recycling of food grade packaging using fluorescent markers Page: 37

38 Figure 17: Single and double PSA labels on crushed HDPE bottles ready for sorting. Shrink sleeves were placed on the bottles, then passed through a steam chamber to shrink the label onto the PET bottles as shown in Figure 18 below. Figure 18: Applying Shrink Sleeves and steam tunnel process at CCL labels. Stretch sleeves that were supplied were marginally too tight to apply by hand to the bottles and so were wrapped around the bottles and fixed in place using a PSA label with a fluorescent surface to simulate the effect of a sleeve that is not bonded to the bottle Shrink sleeves on PET bottles PET bottles with DR-1 pigmented shrink sleeve labels were mixed with un-pigmented shrink sleeve bottles, and then sorted using the same process and conditions used in the calibration tests. WRAP Recycling of food grade packaging using fluorescent markers Page: 38

39 Table 12: Sorting for DR-1 shrink sleeves. Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Purity (%) Yield 2 nd pass (%) DR-1 2, Results shown in Table 12 confirmed that the DR-1 pigment applied at 2,000ppm in a lacquer over the surface of the print in the shrink sleeves was readily identified and ejected under commercial sorting conditions Wash off labels on PET bottles, Trials with DY-1 on PSA wash off labels were conducted using two different label background substrates, one clear and one white, placed on PET bottles. Previous work was mostly conducted with a clear substrate, while many commercial labels are printed onto a white background. Earlier tests showed that the white background enhanced the emission of the fluorescent marker. Results in Table 13 show the sorting of the bottles with white backing to determine the sorting yield and a further trial using the clear and the white backing labels mixed together to identify and sort only the white background labels. Table 13: Positively sorting for DY-1 with white backing. Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1st pass (%) Purity (%) Yield 2nd pass (%) Purity (%) DY-1 on white backing 6, DY-1 on white backing 6, Results showed that at 6,000ppm DY-1 labels using a white background were readily identified and sorted with 100% purity and 100% efficiency in two passes. When mixed together, the DY-1 white background bottles were sorted from DY-1 clear background bottles at 96% yield on the first pass and 100% yield in two passes. When the DY-1 clear labels were tested separately, the results were inconsistent with nearly all bottles being selected. This was interpreted by Tomra as being due to the dominance of the PET signal in the region of the clear label due to its transparency. This could be addressed by finetuning the response of the detector to the label. This issue is further addressed in section Pressure sensitive (PSA) labels and PET bottles PSA labels with a coloured logo and two types of fluorescent coatings were printed and applied to PET bottles. One had a combination of SC-1 and DR-1 pigments each at 2,000 ppm and the other had only DR-1 at 2,000 ppm. Each label type was tested separately to establish that they could be identified and sorted effectively. Results confirmed both WRAP Recycling of food grade packaging using fluorescent markers Page: 39

40 label types were sorted with 94-95% efficiency on the first pass and 100% efficiency after two passes (Table 14). Table 14: Sorting for PSA labels with DR-1 & SC-1 and SC-1 only pigments. Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Yield 2 nd pass (%) DR-1 & SC-1 2, SC-1 2, Bottles with both label types were then mixed together with additional non-pigmented labelled PET bottles to determine if the two label types could be separated and to measure sorting efficiency. Results in Table 15 show when targeting SC-1 only bottles, the yields were higher than expected due to other bottles with the combined pigment system also being selected, resulting in a lower purity of final SC-1 bottles. This reinforced the findings from the calibration study that showed the discrimination was more difficult when the target pigment was present in both labels. When the two labels (both SC-1 and DR-1+SC-1) were selected for sorting, the yield was still above 100% due to the presence of non-pigmented bottles. This could be attributed to the inherent blue emission of the optical brightener used in the PET bottles being selected in error as SC-1, which also emits in the blue region. Tomra advised that this limitation in the trial could be reduced by further fine-tuning of the sorting criteria, which is also addressed in section 6.3. Table 15: Sorting PSA labels with fluorescent pigments DR-1 & SC-1 and SC-1. Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Total eject Yield 1 st pass (%) Purity (%) DR-1 & SC-1, SC- 1 (SC-1 selected) DR-1 & SC-1, SC- 1 (both selected) 2, , While these results may be improved with further optimisation of the sorting system, it indicates that there may be some fluorescent pigment combinations that are more difficult to reliably identify and sort with high efficiency when the same pigment is contained in both labels at low concentrations and high sorting speeds. Further investigation of pigment combinations and sorting equipment programming and optimisation is required to understand these limitations and preferred combinations Pressure sensitive labels and HDPE bottles PSA labels with the Nextek logo, DR-1 pigment and SC-1 +DR-1 pigment were placed onto 4-pint (2.2-litre) HDPE milk bottles. Some bottles had one (5cmx15cm) label placed on each side, other bottles had two labels (5cmx15cm) positioned on each side of the bottle to simulate a larger label, before being crushed. The single label trial was devised to provide information performance with a minimal label size that was approximately WRAP Recycling of food grade packaging using fluorescent markers Page: 40

41 half the size of a typical PSA milk bottle label. The double label format provides a total label area of 150cm 2 on each side, which was close to the commercial single label size for a 4-pint milk bottle of approximately 8cmx21cm, equal to an area of 160cm 2, with the difference that labels were applied to two sides of the bottle for sorting efficiency measurements. It would be expected that bottles with a single label on each side would be sorted less efficiently, due to the small size of the label on a large bottle activating the ejectors that correspond to the size of the label and this may not be sufficient to successfully eject a bottle over the sorting partition. In comparison, PET bottles tested earlier in this trial all had labels around the entire circumference of the bottle, with a large exposure area relative to the size of the bottle. The PSA labels used on the HDPE bottles were 5cm x 15cm, covering only a small part of the 2.2-litre bottle facing. Both single and double label formats were tested with the pigment combinations in a series of trials as shown in Table 16. Table 16: Sorting PSA labels on HDPE milk bottles. Trial Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Labels per side Yield 1 st pass (%) 9.0 DR-1 & SC-1 2, DR-1 & SC-1 2, DR-1 & SC-1 2, & SC-1 2, & SC-1 2, Despite the relatively small label-to-bottle size, results showed a sorting yield of 79%, for bottles with only single labels per side based on DR-1 & SC-1. When bottles with two labels per side were tested in trial 9.1, the yield increased to 100%. In trials 9.2 and 10, 100% of the two label bottles were successfully ejected on the first pass for both pigment combinations, as well as a large number of the single label bottles. Of particular note in trial 10, 92% of the SC-1 single (half sized) labelled bottles and 100% of the full-size label bottles were correctly sorted, indicating an increased level of performance for this pigment with HDPE bottles. This higher performance is reflected in trial 11 where a re-test of the single label provided a yield of 98% Stretch sleeves The printed stretch sleeve labels supplied by CCL were too small to be fitted by hand, and so were tightly wrapped around the PET bottles and fixed in place with a pressure sensitive label with a fluorescent surface. Labels using different pigment combinations were evaluated and the results shown in Table 17. WRAP Recycling of food grade packaging using fluorescent markers Page: 41

42 For trials 12 and 13, it was observed that bottles were being detected but not successfully ejected. The sorting equipment was optimised with software, ejection air and the location of the splitter bar adjustment, to improve the success of the ejection and results are shown in Table 17. Table 17: Sorting with Stretch Sleeves on PET bottles. Trial Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Yield 2 nd pass (%) 12 DR-1 & SC-1 2, DY-1 6, DR-1 & SC-1, DY-1 2, , Bottles with a mixture of fluorescent label types were evaluated in trial 14 with high first pass efficiency of 96% and 100% successfully sorted in the second pass. It is useful to note that the labels do not contain the same pigment, which improved the yield and sorting efficiency, compared to having to discriminate between labels that used the same pigment in a multi-pigment label configuration, as in section 6.1.3, Table Sorting trials with mixture of all bottle and label types Two large trials were conducted in which all of the commercial labelled bottles were mixed together and sorting targeted just one of the fluorescent pigment label types. Results are shown in Table 18. Table 18: Sorting from mixture of all commercial labelled bottles. Trial Bottle type Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Total eject Yield 1 st pass (%) Purity (%) 15 HDPE SC-1 2, PET DR-1 2, In trial 15, the impact of printed labels with ink colours similar to the florescent ink emission colour was tested. Labels with a printed image of blue mountains were selected on some of the non-targeted PET bottles. When targeting HDPE bottles with only the SC-1 pigment label, also emitting in the blue region, the blue mountain image was being falsely identified and ejected with the target HDPE SC-1 labelled bottles. This resulted high overall yields of 122%, but a low purity. In addition, a number of the SC-1 PSA labels had begun to detach, due to re-running the same bottles through the process several times, and this caused a number of target bottles to be missed. Together, these factors resulted in a low yield of 65% of the target HDPE bottles and a low purity of 53%. WRAP Recycling of food grade packaging using fluorescent markers Page: 42

43 In trial 16 where shrink sleeves with DR-1 were targeted, the overall yield was 154%, and purity at 53% was again affected by misidentification primarily from the DY-1 labels that also contained a red coloured stripe. A yield of 94% and purity of 61% was achieved for just the PET bottles with DR-1 labels in the first pass. TOMRA advised the system could be further optimised to improve discrimination of the overlap in the spectra from the red ink stripe on the DY-1 labels and the targeted DR-1 labels. The important observation from this trial was the confirmation that the presence of label ink colours with emission wavelengths close to the target wavelength from the fluorescent pigments could result in false positive identification. Moreover, that the selection of fluorescent pigment and the design of the label on the bottle needs to be performed carefully to avoid false positives from background ink label colours. However, Tomra is confident that further optimisation of the software and equipment adjustments would enable better discrimination of the fluorescent markers and the elimination of the influence of other colours. This is discussed in section Sorting equipment optimisation In order to improve discrimination when coloured items were present during sorting, Tomra applied a visible light filter to the sorting system that excluded visible light from the halogen lamps normally used in the system. This would still allow the detection of visible light that was initiated by the UV light source and the NIR signals to pass through to the detector. This arrangement would allow simultaneous signatures of fluorescence and NIR to be used to identify the labels being sorted and at the same time supressing the effect of the presence of coloured bottles. To test this arrangement, bottles with three fluorescent labels (DR-1, SC-1, and DY-1) were mixed with sleeved bottles that had a wide range of colours that overlapped the colour of the fluorescence of these labels as shown in Figure 19 and the results of the sorting are shown in Table 19. Figure 19: Mixture of labels with fluorescent pigments with coloured sleeved bottles. WRAP Recycling of food grade packaging using fluorescent markers Page: 43

44 Table 19: Sorting fluorescent labels from coloured bottles using the long pass filter. Trial Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Purity (%) 17 DR-1 2, SC-1 2, DY-1 2, The results were particularly notable for the high level of purity of the selected label in the range of %. This showed that sorting with the long pass filter was particularly effective in excluding the presence of the many colours from the sleeved bottles. The yields achieved for SC-1 and DY-1 (73% and 85%) could potentially be improved with further sorter setting optimisation as demonstrated by the high yields for DR Sorting of fluorescent label packaging mixed with MRF bottles The real challenge for sorting bottles with fluorescent labels would be to examine the sorting efficiency when they were mixed with many bottles obtained from Evolve Polymers, a UK MRF. This was done in two stages, firstly with mixed, coloured PET and then with mixed coloured HDPE bottles to simulate the worst-case scenarios encountered in the sorting operations as shown in Figure 20. Figure 20: Coloured PET (left) and Coloured HDPE (right) used in the sorting trials. WRAP Recycling of food grade packaging using fluorescent markers Page: 44

45 In each case, 50 bottles with fluorescent labels were mixed with 990 other bottles and then sorted using the visible light filter, with results shown in Table 20. Table 20: Sorting fluorescent labels on PET in mixed MRF coloured PET bottles. Trial Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Purity (%) 20 DR-1 2,000 1, SC-1 2,000 1, SC-1 optimised 2,000 1, DY-1 2,000 1, The results for pigment DR-1 showed very high purity (99%) and high yield of 94% in one pass, demonstrating that this pigment could be readily selected from the other coloured bottles at levels suited for food grade applications. The results for SC-1 showed lower purity and yield when initially tested due to the selection of other types of bottles with paper labels that included optical brightener that also produced fluorescence in the same wavelength range as SC-1. The bottles selected in trial 21 and the fluorescence of the other bottles are shown in Figure 21 before optimisation of the sorter settings. Figure 21: Coloured PET (left) paper labels (right) ejected along with SC-1. This result showed that the presence of optical brightener is relatively common and can lead to false positives if these bottles are not eliminated from selection. In order to prevent selection of the labels with optical brightener, the sorting equipment was calibrated with the specific NIR and fluorescence spectrum of the label. This resulted in the specification of a new material with a very specific signature and consequently achieved a sorting yield of 90% and a purity of 100% as shown in trial 22. In trial 23 the sorting of DY-1 showed high selectivity for the DY-1 labelled bottle and also for Mountain Dew bottles and Aldi yellow detergent bottles that also had strong fluorescence in the yellow wavelength. This reduced selectivity could be rectified in the same manner as for the SC-1 pigment. WRAP Recycling of food grade packaging using fluorescent markers Page: 45

46 Figure 22: Coloured PET (left) and Coloured HDPE (right) used in the sorting trials. The sorting trials of MRF mixed coloured HDPE mixed with fluorescent labelled bottles was conducted with three fluorescent pigments and the results are shown in Table 21. The results for DY-1 and the pigment combination of DR-1 & SC-1 were identical and showed a yield of 80% and purity of 100%. When the sorting trial for pigment SC-1 was conducted, a large number of Persil bottles were selected along with a smaller number of other bottles that showed fluorescence consistent with the presence of optical brightener as shown in Figure 23 and 24. This is parallel to the situation with the PET bottles that use optical brightener within labels and bottles as shown in Figures 21 and 22. Table 21: Sorting fluorescent labels in mixed MRF coloured HDPE bottles. Trial Pigment Concentration (ppm) Total number of bottles Number of bottles targeted Yield 1 st pass (%) Purity (%) 24 DR-1 & SC-1 2,000 1, DY-1 2,000 1, SC-1 2,000 1, In addition, some of the MRF bottles were contaminated with a detergent product residue as shown in Figure 24 that contained optical brightener pigments, leading to false positives and reductions in the purity and selectivity of the sorting process. Figure 23: Mixed coloured HDPE selected in SC-1 sorting trials WRAP Recycling of food grade packaging using fluorescent markers Page: 46

47 Figure 24: Persil bottle (left) and liquid detergent bottle (right). The sorting of labels based on pigment SC-1 was made difficult due to the widespread use of the optical brightener and the crossover of the spectrum with the fluorescence of SC Conclusion Sorting trials have been able to confirm that a number of commercially available fluorescent pigments can be incorporated into the structure of a wide range of label types at concentrations in the range of 2,000 to 6,000ppm. When applied to packaging, these labels were successfully identified and sorted with high efficiency and purity using automated sorting equipment that was modified with a UV LED light source. Combinations of fluorescent pigments on a single label were shown to be possible, thus increasing the number of potential applications, and enabling a high level of selectivity for the positive identification of specific types of packaging. However, careful selection of fluorescent pigments and regular ink colours is still required to prevent both yield losses and false positives that would reduce the purity of the target fraction. The calibration of the sorting equipment to identify the unique signature of a label by using the NIR signal combined with fluorescence provided a way of achieving high levels of discrimination and purity in sorting. This means that the polymeric composition of the label and the pigment can together become the unique identifier for the package. This will provide many combinations based on the opportunity to use materials such as PP, PS, LLDPE and PET as well as others, as sleeves and labels for many applications Optimisation of the sorting software programmes, would further improve the discrimination between different fluorescent pigments and standard colours used in printing, to improve yields and purity. 7.0 Recycling wash processing trials The following bottle / label combinations (Table 22) were processed at Sorema to assess whether labels could be removed during standard washing procedures that are used by WRAP Recycling of food grade packaging using fluorescent markers Page: 47

48 plastic repressors. The bottles were cut to 10mm flakes and subjected to a hot alkaline wash at 85 C, followed by sink float separation, drying and air classification. Table 22: Bottles / labels sent for washing trials at Sorema. Bottle type Label type Pigment Concentration (ppm) Weight (kg) PET Shrink sleeves DR-1 2, PET Stretch sleeves DR-1 & SC-1, DY-1 2, , HDPE PSA labels DR-1 & SC-1, SC-1 2, PET PSA labels DR-1 & SC-1, SC-1 2, The flakes all showed freedom from labels and any fluorescent ink residue. Shrink sleeves and pressure sensitive labels were based on PET films and were recovered in the sink fraction and separated by air classification. Stretch sleeves were separated in the float fraction from the PET bottles. Figure 25 shows the absence of any fluorescence from DR-1 in the washed and separated PET flake material. Figure 25: PET bottle with shrink sleeve after wash and label separation. 7.1 Conclusion Results showed fluorescent PSA, peel-off PSA, shrink and stretch sleeve labels were readily removed by the washing technologies used for food grade recycling processes. The labels that use no adhesive such as shrink and stretch sleeves are particularly suited for fluorescent sorting due to their ease of separation and wrap around characteristics ensuring that a fluorescent surface is visible after crushing during baling. 8.0 Protocols for the use of fluorescent labels In the sorting of mixed plastic packaging (with or without fluorescent labels) it is typical to initially sort the materials into single polymer streams such as HDPE, PET and PP. In terms of priority for marking containers, the materials of key interest would be where higher valued materials would be separated or where regulations must be met. This WRAP Recycling of food grade packaging using fluorescent markers Page: 48

49 situation is directly applicable to the opportunity to identify food grade HDPE, PP and PET. In the future, new materials like polyethylene furanoate (PEF) or new bio-based plastics may emerge as high value targets for recycling. It has been shown that a unique signature of the label material and the fluorescent pigment on a specific polymer package (PET, HDPE, PP etc.) can be generated using the combined NIR and fluorescent signals. It is possible to use one fluorescent marker to designate food grade status across all the main packaging polymers as well as new materials to be introduced in the future. The unique signal is not constrained by the colour of the packaging, provided the visible light filter is used in front of the lamps. This avoids a visible light signal coming from the packaging, except for the fluorescent signal generated by UV excitation. The NIR excitation and detection works as normal, allowing the polymer to be identified by the reflected NIR signal. The signal used for food grade status should be readily identifiable by the sorting equipment and not confused with other materials that might inadvertently create false signals such as optical brighteners that are in commercial use. A pigment such as DR-1 (red light emission) with a high emission efficiency and narrow bandwidth would perform this function. It has been shown that ranges of packaging products already use optical brighteners in the plastic (PET and HDPE), in the paper label and in the contents (as found in detergent). This means that SC-1 (blue light emission) should not be used on its own as it fluoresces in the same wavelength region as optical brighteners even though it is a particularly bright and readily discriminated pigment. For packaging that uses full body sleeves that cover the base polymer, the key issue is whether the base polymer is clear or opaque and whether it is food grade or not. In the case of PET, where sleeves are extensively used, the food grade marker (DR-1) would be used for bottles that are clear and food grade. This would mean that these bottles would be directed into the clear food grade bottle stream. In order to separate bottles from pots tubs and trays (all un-pigmented), a combined maker of DR-1 & DY-1 would be used. This would be particularly useful for PET recycling where there is a desire to separate the two streams due to the differing recycling behaviour. Since coloured PET bottles (except light blue and light green) are usually directed away from bottle applications and directed into textile and non-food markets, it is expedient to use a combination marker to differentiate them from the clear food grade stream. The marker designated for this category is DR-1 & SC1. The use of a marker or marker combination for each category allows the sorters to be used in either positive sorting mode or negative sorting mode depending on the needs of the sorting operation allowing savings in utilities, energy and cost. The same principles can be used for HDPE and PP and any other plastic. Packaging that is food grade and natural in colour would be designated by the food grade marker DR-1 and coloured packaging or any products that need to be especially WRAP Recycling of food grade packaging using fluorescent markers Page: 49

50 removed from a stream (non-food bottle that contained toxic products) would be designated by DY-1. In the case of sorting packaging that was food grade and also coloured, then a combined maker (DR-1 & SC-1) could be used. For natural un-pigmented pots, tubs and trays the combined marker DR-1& DY-1 could be used provided there was a requirement to differentiate them from bottles. The signal from these combinations would be different from the natural food grade marker and the coloured non-food grade marker (DY-1). The protocol is summarised in Table 23 and Figure 26 and each combination is unique even though the fluorescent pigment is the same, allowing a simple and effective way of discriminating each material and any new materials that need to be added in the future. Table 23: Protocol for designation of fluorescent markers for packaging. Bottle type Food grade natural Bottles and full length sleeves Food grade natural Pots, Tubs and Trays Food grade coloured and full length sleeve Non- food grade natural or coloured full length sleeve PET DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 HDPE DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 PP DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 Other polymers DR-1 DR-1 & DY-1 DR-1 & SC-1 DY-1 WRAP Recycling of food grade packaging using fluorescent markers Page: 50

51 Figure 26: MRF Sorting Protocol for packaging with fluorescent labels. The final protocols would be based on approved combinations of a range of resins used for labels and sleeves along with specific pigments used as fluorescent markers. This would involve a registration and profiling of the spectrum of each combination of label, fluorescent material and base packaging material. This would generate a database of approved and unique signatures for the packages that would be used to program the sorting equipment made by the various manufacturers. The approval process would need to be established on a national and preferably a regional basis to avoid standardisation conflicts when products are marketed in many countries or globally. Ideally, the fluorescent markers could be applied to the outside of clear plastics using a white substrate to improve the emission strength, however the use of white substrate should allow the label to be widely used with coloured packaging, even black packaging. The use of clear substrates is possible; however, the labels will require higher levels (12,500ppm or 6,000ppm instead of 2,000ppm) of fluorescent pigment to ensure high yield rates. WRAP Recycling of food grade packaging using fluorescent markers Page: 51

52 Wrap around labels or pressure sensitive adhesive labels on the major faces of packaging are preferred to give the package maximum chance of being detected after crushing during the baling process. The coverage of the labels on the packaging is important and the current results show that at least 25% of the package should be covered to ensure accurate ejection. Larger labels provide greater sorting yields and allow lower levels of pigment to be used. 9.0 Overall conclusions This project demonstrated that the use of commercial labels incorporating fluorescent markers can be used to sort plastic bottles and packaging with high levels of yield and purity achieved. The addition of UV-LED illumination to existing full-scale commercial sorting equipment enabled sorting of packaging with a range of fluorescent pigments. Trials were able to demonstrate yields in the range of 88% to 96%, with purity levels up to 100% in a single pass. This performance will meet the sorting requirements for food grade plastics, especially recycled HDPE and PP that require purity levels greater than 99% and 95% respectively. The recycling processes in food grade recycling operations remove the labels and markers, ensuring that they would not persist in future applications. In addition, any high temperature extrusion process creates irreversible changes to their chemical structures and deactivates the markers. The markers investigated withstood the conditions in the packaging supply chain encountered by milk bottles with limited impact on its performance. These markers were, however, affected by exposure to outdoor UV light and the durability after outdoor storage still needs to be validated, even though baling of containers will protect the bulk of the labels. The labels can be used effectively at low addition levels in inks at between 2,000 and 6,000ppm and be effectively sorted on high-speed automatic sorting systems running at 3 m/sec and 1 tonne per hour per metre of belt width. The performance of the fluorescent sorting system was also dependent on the design of the labels. Factors such as label/package area ratio, the use of non-transparent reflective substrates, the concentration of pigments and selection of the specific pigments all had a major impact on the performance of the total sorting system. At a concentration of 2,000ppm, the pigment cost is in the order of per 1,000 labels dependant on pigment type. The lower limit of detection of the current label / equipment system was shown to be in the region of 125ppm providing opportunities for further pigment cost reduction. Tomra has made a preliminary estimate of the cost of the additional UV-LED lighting systems and modifications at 10-20% of the cost of the existing NIR/Vis sorting unit. These estimates may increase if other upgrades are required to older or minimally configured sorting units. A protocol for the use of fluorescent markers in the recycling of food grade packaging has been proposed using two different markers (red and yellow) to respectively designate food grade (natural colour) and non-food grade status of packaging. WRAP Recycling of food grade packaging using fluorescent markers Page: 52

53 Packaging that is coloured and food grade can use a combined red and blue marker to differentiate it from food grade natural packaging and non-food packaging. Especially for PET, pots tubs and trays (natural and food grade) can be differentiated from bottles by the use of a combined red and yellow marker. The use of fluorescent pigments singly or in combinations can be used to identify plastics with full body sleeves to ensure that they are directed to the correct sorting category prior to recycling. The investigations in the sorting software optimisation showed that it is possible to create new material signatures for polymeric sleeves and labels and fluorescent pigments that provide the opportunity for a system of coordinating and approving a larger number of unique codes to allow positive sorting of packaging into subcategories. The big potential of this sorting process is as an extension to the methods of sorting packaging that requires an additional level of information to allow further subcategorisation. The food grade recycling of PET packaging, HDPE milk bottles and PP rigid packaging are likely starting points for the application of this technology. WRAP Recycling of food grade packaging using fluorescent markers Page: 53

54 List of Appendices Reported separately Appendix 1: Evaluation of fluorescent markers Appendix 2: Effect of label backing material and manufacture processes Appendix 3: Effect of lighting exposure in the supply chain Appendix 4: Impact of weathering on fluorescent markers Appendix 5: Bottle wash trials Appendix 6: Cost estimates WRAP Recycling of food grade packaging using fluorescent markers Page: 54

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