DEVELOPMENT OF CHEMICAL MARKERS - …. Peter Reinig... · Development of chemical markers and...

www.polymark.org

DEVELOPMENT OF CHEMICAL MARKERS

Peter Reinig – Fraunhofer IPMS ([email protected])

Polymark Training & Webinar 15 March 2017

Petcore Europe Premises, Brussels

POLYMARK (311777) is funded by the European Community’s Seventh Framework Programme

Note:

Development of chemical markers and marker characterization has been performed by

(Dr. Laura Pilon & Dr. Angela Stewart)

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• Marking concept & marker criteria

• Marker development & evaluation process

• Marker addition

• Marker removal

• Summary

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What is on the agenda ?


4

How to sort food contact PET ?

MARK it !


5

Target closed-loop process

Food contact marking

• Positive identification • Fewer incidences of non-

food 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

• Negative identification • More marker options

(non-food contact) • What is the benefit for

manufacturers to include the marker?

• Greater potential for mistakes

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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

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)

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


Choice of coding method depends on the number of suitable markers available

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• 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)

Chemical Marker Selection Criteria

POLYMARK (311777) is funded by the European Community’s Seventh Framework Programme 8


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• 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)

VIS (fluorescence)

NIR (absorption)

How to mark PET ?

Marker blended with polymer

No major changes to bottle production process

No additional tooling Analysis can occur at any

point during sorting process

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

Pros Cons


Coating on bottle

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

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)

Pros Cons


Label on bottle

Physical removal easier Thermal stability not so

critical

Article needs to be oriented correctly to enable accurate sorting

Labels typically come off too easily

Pros Cons


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 300-400 nm

– Visible fluorescence • Maximum in range 450-700 nm

– NIR reflectance • Ideally in range 800-2500 nm

• Chemical, thermal, mechanical properties

– Solubility/dispersibility/miscibility • Water insoluble markers ideal for beverage bottle coatings due to low

migration – Thermal stability

• Degradation temperature >280oC required for PET compounding


Chemical marker evaluation process


Food contact approval

Optical response

Stability

Capability

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Food contact approval


approximately 130 potential markers/families evaluated

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)

http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32008R0282&from=de







http://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:OJ.L_.2011.012.01.0001.01.ENG&toc=OJ:L:2011:012:FULL




Food contact approval (130)

Optical response (16)

Stability

Capability

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Optical spectral properties of PET


Transmission

Reflection

UV VIS NIR

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Optics: UV (200-400 nm)

High sensitivity Potentially low cost Degradable under high

dose UV exposure

Interference from PET limits useful wavelength range

Interference from other UV absorbers (e.g. stabilisers)

Pros Cons

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Optics: NIR (800-2500 nm)

Good penetration into material

Broad wavelength range available

Wide range of possible compounds as for mid-IR

Detection technology already in place

Interference from polymer and any other additives

Low marker signal Expensive detector

technology (compared to UV/VIS)

Pros Cons

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visual in daylight under UV light (365 nm)


Spectral Properties of Markers

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Stability (6)

Capability

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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


Thermal Stability of Markers

• 4 markers showed sufficient thermal stability to be used directly in extrusion compounding with PET


Degradation temperature >280oC required for PET compounding

Sample Number

Thermal decomposition temperature Td (onset °C)

4 326 5 292 7 305

12 293

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 285oC



Marker + PET (0.1%, 0.01%) in daylight

Marker + PET (0.1%, 0.01%) and virgin PET under UV light 365 nm 25

4 5 12 7

Marker addition – compounding into PET

Solubility of Markers


Sample Number

Solubility Water

Solubility Ethanol

Solubility Acetone

Solubility 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

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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)


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:

– Solsperse 46000

hyperdispersant – BYK 012 defoamer – Tween 80 stabiliser

ID

Mar

ker

[Mar

ker]

w

t%

[Sol

sper

se

4600

0] w

t%

[BYK

012]

w

t%

[Tw

een

80]

wt%

D7 7 35.1 7.3 0.7 0.7

D12 12 47.2 9.4 0.5 0.5



Marker addition : coated PET bottles for lab tests

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clear PET 0.1 wt% on clear PET

1.0 wt% on clear PET

marker #7

Testing of coated PET bottles for lab tests

• Colour (Petcore rPET protocol) – 0.1wt% marker – 1.0 wt% marker

• Water resistance (ASTM) – Ambient – 38oC – clouding (temporary)

• Detergent resistance (ASTM) – Ambient – 74oC – clouding (permanent)

• Adhesion (ASTM) – Cross-hatch tape test


Compounded

• 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

processes

Coated

• Washing - Solvent process - Water-based (alkaline process)


Marker Removal

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

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


16 markers reduced to 6

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Stability (6)

Capability

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Markers : Further Downselection


• λmax(7) ≈ 490 nm (see above) as dispersed pigment (no coating matrix)

• λmax(7) ≈ 400, 430, 450 nm as dissolved dye in solvent [Plastics Additives & Compounding, 2003, 5, 42-46]

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• 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

4 7

12 14 9 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 (#5, #13, #15)

• PET/#9 fluorescence and presence of other optical brighteners interferes with marker #14

Markers : Further Downselection


• λmax(7) ≈ 490 nm (see above) as dispersed pigment (no coating matrix)

• λmax(7) ≈ 400, 430, 450 nm as dissolved dye in solvent [Plastics Additives & Compounding, 2003, 5, 42-46]

6 markers reduced to 2

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4 7

12 14 9 PET

Prioritised Marker Candidates

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marker #7

marker #12

Suitable for a 2-marker approach


Marker of choice : 4,4’-bis(2-benzoxazolyl)stilbene

marker #7

COMMISSION REGULATION (EU) No 10/2011 on plastic materials and articles intended to come into contact with food

Food contact approval:

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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: Removable Identification Technology to Differentiate Food Contact PET in Mixed Waste Streams

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http://polymark.org/system/files/generated/files/Polymark report_preliminary technical results.pdf

DEVELOPMENT OF CHEMICAL MARKERS - …. Peter Reinig... · Development of chemical markers and...

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