DEVELOPMENT OF CHEMICAL MARKERS

Transcription

1 DEVELOPMENT OF CHEMICAL MARKERS Peter Reinig Fraunhofer IPMS Polymark Training & Webinar 15 March 2017 Petcore Europe Premises, Brussels

2 Note: Development of chemical markers and marker characterization has been performed by (Dr. Laura Pilon & Dr. Angela Stewart) 2

3 What is on the agenda? Marking concept & marker criteria Marker development & evaluation process Marker addition Marker removal Summary 3

4 How to sort food contact PET? MARK it! 4

5 Target closed-loop process 5

6 Food contact marking Positive identification Negative identification Fewer incidences of nonfood PET in food PET recycling stream Fewer marker options (must be food contact approved) Food contact recycling stream higher value Better take-up of marker use More marker options (non-food contact) What is the benefit for manufacturers to include the marker? Greater potential for mistakes 6

7 Coding Methods 1. Single marker for each characteristic of interest a) Minimum of 2 markers needed, more markers gives more options for identification i. Food/non-food ii. Simple/Complex (e.g. barrier, additives, blends) b) Not efficient in terms of number of markers vs number of codes 2. Binary code Choice of coding method depends on the number of a) More efficient in marker numbers i. 2 markers allows coding of 3 characteristics (plus blank) ii. 3 markers allows coding of 7 characteristics (plus blank) suitable markers available 3. Ratio code binary extended by use of different relative intensity of marker signals a) 2 markers in different ratios allows coding of 6 or more characteristics b) Very efficient in number of markers required c) Challenging in terms of marker stability and instrumentation 7

8 Chemical Marker Selection Criteria Food contact approved Suitable spectral features in UV/NIR (or fluorescence) High thermal stability (compounding) Removal of marker must be possible Commercial availability in suitable quantities No change of product appearance (e.g. colour) 8

9 Develop & characterize suitable marker(s) Apply the marker : coating (of preform / after blow mold) immersion in bulk (additive for preform) on label physical imprint Optically detect the marker : UV (absorption) How to mark PET? 9 VIS (fluorescence) NIR (absorption)

10 Marker blended with polymer Pros No major changes to bottle production process No additional tooling Analysis can occur at any point during sorting process Cons May get interference from polymer and other additives Direct contact with bottle content Difficult to detect low concentrations Expensive to add high concentrations More difficult to remove 10

11 Coating on bottle Pros Physical removal easier Thermal stability not so critical Less interference from polymer and other additives Easier to detect Smaller amount of marker required, lower cost Limited contact of coating material with bottle contents Cons Another production step Coating may not be sufficiently durable Need to carry out chemistry to incorporate marker into coating more permanently (affects food contact approval) 11

12 Label on bottle Pros Physical removal easier Thermal stability not so critical Cons Article needs to be oriented correctly to enable accurate sorting Labels typically come off too easily 12

13 Marker Evaluation Methods & Criteria Optical properties UV/Visible absorbance Ideally no/limited absorbance in visible (i.e. no strong colouration) and UV absorbance in range nm Visible fluorescence Maximum in range nm NIR reflectance Ideally in range nm Chemical, thermal, mechanical properties Solubility/dispersibility/miscibility Water insoluble markers ideal for beverage bottle coatings due to low migration Thermal stability Degradation temperature >280 o C required for PET compounding 13

14 Chemical marker evaluation process Food contact approval Optical response Stability Capability 14

15 Food contact approval Desk-based literature & database study reference frame COMMISSION REGULATION (EC) No 282/2008 on recycled plastic materials and articles intended to come into contact with foods and amending Regulation (EC) No 2023/2006 COMMISSION REGULATION (EU) No 10/2011 on plastic materials and articles intended to come into contact with food (lists more than 800 food contact materials) approximately 130 potential markers/families evaluated 15

16 Chemical marker evaluation process Food contact approval (130) Optical response (16) Stability Capability 16

17 Optical spectral properties of PET Transmission Reflection UV VIS NIR 17

18 Optics: UV ( nm) Pros High sensitivity Potentially low cost Degradable under high dose UV exposure Cons Interference from PET limits useful wavelength range Interference from other UV absorbers (e.g. stabilisers) 18

19 Optics: NIR ( nm) Pros Good penetration into material Broad wavelength range available Wide range of possible compounds as for mid- IR Detection technology already in place Cons Interference from polymer and any other additives Low marker signal Expensive detector technology (compared to UV/VIS) 19

20 Spectral Properties of Markers visual in daylight under UV light (365 nm) 20

21 Chemical marker evaluation process Food contact approval (130) Optical response (16) Stability (6) Capability 21

22 Marker Addition & Stability Compounding High thermal stability needed Easy to add to polymer using a masterbatch approach Difficult to remove Limited investment at manufacturing stage High investment at recycling stage Coating Lower thermal stability requirement Easy to apply (e.g. spray, dip, curtain) Easy to remove Higher investment at manufacturing stage Limited investment at recycling stage 22

23 Thermal Stability of Markers 4 markers showed sufficient thermal stability to be used directly in extrusion compounding with PET Sample Number Thermal decomposition temperature Td (onset C) Degradation temperature >280 o C required for PET compounding 23

24 Marker addition compounding into PET Test miscibility of markers with PET and thermal stability to process conditions Masterbatch approach 1%, 0.1%, 0.01% Markers 4, 5, 7 & 12 Standard PET processing conditions Measured melt temperature 285 o C 24

25 Marker addition compounding into PET Marker + PET (0.1%, 0.01%) in daylight Marker + PET (0.1%, 0.01%) and virgin PET under UV light 365 nm

26 Solubility of Markers Sample Solubility Solubility Solubility Solubility Number Water Ethanol Acetone Dichloromethane 4 sl sl i i 5 s s i i 6 i i sl s 7 i i i i 8 i i sl s 9 sl s s 10 sl s s i 11 i i sl s 12 i i sl s 13 i s s 14 s s sl 15 i s s s 16 i i sl s 17 i s 18 i s Solubility : s = soluble, sl = slightly soluble, i = insoluble 26

27 Marker addition coating onto PET Requirements Water-based formulation; Water resistant in use; Removable in caustic wash mixtures; Suitable for food contact Solution Acrylic copolymer with ionised acid groups (volatile alkali) 27

28 Marker addition - coating onto PET Due to high hydrophobicity, additives needed to disperse marker pigment in water Stable dispersion (dilution and coating formulation) achieved using a combination of the following ingredients with centrifugal mixing: ID Marker [Marker] wt% [Solsperse 46000] wt% [BYK012] wt% [Tween 80] wt% D D Solsperse hyperdispersant BYK 012 defoamer Tween 80 stabiliser 28

29 Marker addition : coated PET bottles for lab tests clear PET 0.1 wt% on clear PET 1.0 wt% on clear PET 29 marker #7

30 Testing of coated PET bottles for lab tests Colour (Petcore rpet protocol) 0.1wt% marker 1.0 wt% marker Water resistance (ASTM) Ambient 38 o C clouding (temporary) Detergent resistance (ASTM) Ambient 74 o C clouding (permanent) Adhesion (ASTM) Cross-hatch tape test 30

31 Marker Removal Compounded Coated Thermal degradation - Degradation products remain Photochemical reaction - Degradation products remain in material - Dimerisation/isomerisation/ rearrangement Products of unknown toxicity Chemical degradation - e.g. addition of catalyst during re-extrusion Degradation products remain Extraction - PET resistant to extraction 31 processes Washing - Solvent process - Water-based (alkaline process)

32 Marker Removal Evaluation by visual inspection under UV lamp (365 nm) Coated PET flakes (1.0wt%) marker #7 after 10 min. washing in 2%NaOH (60 C) + hot water rinse after 10 min. washing in 2%NaOH (60 C) + caustic rinse 32

33 Where are we now? 4. Suitable for compounding with PET or coating, strongly coloured, water soluble 5. Suitable for compounding with PET or coating, some visible fluorescence, water soluble 6. Envirotoxin, potential allergen 7. Suitable for compounding with PET or coating, strong fluorescence, strong colour, water insoluble 8. Envirotoxin 9. Already used in PET as a scavenger for acetaldehyde, potential allergen 10. No suitable spectral signature, only EFSA approved as monomer, envirotoxin 11. UV absorber, no fluorescence 12. Suitable for compounding with PET or coating, strong fluorescence, practically colourless, water insoluble 13. Visible fluorescence, suitable for coating 14. Visible fluorescence, suitable for coating, water soluble 15. Visible fluorescence, suitable for coating 16. UV absorbance/no fluorescence 17. Too volatile, fragrance (migration?) 18. Too volatile, fragrance (migration?) 19. No commercial supplier could be found markers reduced to 6

34 Chemical marker evaluation process Food contact approval (130) Optical response (16) Stability (6) Capability 34

35 Markers : Further Downselection PET λ max (7) 490 nm (see above) as dispersed pigment (no coating matrix) λ max (7) 400, 430, 450 nm as dissolved dye in solvent [Plastics Additives & Compounding, 2003, 5, 42-46] 7 4 PET and #9 fluorescence are coincident as expected, #9 also overlaps #7 and #12 are well separated at peak maxima and high intensity Other shortlisted markers had insufficient fluorescence intensity (#4, #5, #13, #15) PET/#9 fluorescence and presence of other optical brighteners interferes with marker #14 35

36 Markers : Further Downselection λ max (7) 490 nm (see above) as dispersed pigment (no coating matrix) λ max (7) 400, 430, 450 nm as dissolved dye in solvent [Plastics Additives & Compounding, 2003, 5, 42-46] 36 PET PET and #9 fluorescence are coincident as expected, #9 also overlaps #7 and #12 are well separated at peak maxima and high intensity Other shortlisted markers had insufficient fluorescence intensity 6 (#5, markers #13, #15) PET/#9 reduced fluorescence to 2 and presence of other optical brighteners interferes with marker #14

37 Prioritised Marker Candidates marker #12 marker #7 Suitable for a 2-marker approach 37

38 Marker of choice : 4,4 -bis(2-benzoxazolyl)stilbene marker #7 Food contact approval: COMMISSION REGULATION (EU) No 10/2011 on plastic materials and articles intended to come into contact with food 38

39 Summary Within POLYMARK we identified proper candidates for chemical food-contact approved markers : Markers can be used both for compounding and coating Flexible, temporary marker addition with coating approach Removal of coated marker by existing recycling plant washing (NaOH) Marker detection using inexpensive UV-excitation/VIS-fluorescence More details: 39 Removable Identification Technology to Differentiate Food Contact PET in Mixed Waste Streams