Digital printing: Low Migration inkjet inks for indirect food packaging
Roel De Mondt, Phd – Agfa Gevaert N.V. – Belgium
ILSI Europe Packaging Symposium – Berlin – November 2012
Session II: Sustainable food contact materials
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Outline
Organisation
Sustainability in digital printing for food packaging
Background on UV curable and Low Migration inkjet inks
Innovations in Low Migration inks
Summary and conclusions
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Sustainability: what’s your definition ?
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Sustainable development
Development that meets the needs of the present without compromising the ability of future generations to meet their own needs
“The process which fulfils social, economical and environmental needs successfully for the
longer term and for future generations is called a sustainable process.”
! UNDERWRITERS LABORATORIES INC.: Standard for Sustainability for Printing Inks
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Drivers to go to Digital UV IJ printing for Packaging
Cost and time savings
Converters become ‘print service providers’
Flexibility and speed: faster turnarounds: no more time-consuming and costly plate- or roll-making and processing. UV inks with long open time and fast curing
The ability to print on a wide range of substrates gives digital presses important versatility over other printing methods, especially in UV.
Digital printing’s ability to do variable data printing (VDP), enabling the production of unique products
Safety, track and trace, and brand protection.
Reducing the environmental footprint by reducing substrate waste and working without VOC and without pre-coats using UV inks.
Regulation (EU) 1169/2011 provide info on the energy value and 6 nutrients in a nutrition table in a language easily understood by consumers easily visible, clearly legible and, where appropriate, indelible defined minimum font sizes drive to more variable printing and shorter runs digital
printing
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Sustainable digital printing for food packaging?
Communication
Accessible health
information
QR
Food safe print
VOC
Substrate scrap
Transportation
Warehousing
See Environment
Short run
Lead times
Sustainable
Digital printing
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What is a UV-curable (inkjet) ink made of and what should it (not) do?
UV curable monomer
Photoinitiator(s) and synergists
Colorant: pigment with dispersant
Surfactant
Stabilizer/Inhibitor
Any UV inkjet ink has to fulfill:
• Shelf life: at least 12 months, transporting all over the world, all
climates and seasons
• Jetting performance and reliability: ink behaviour inside the
printhead and during printing process
• Image quality and ink spreading
• Curing: solidification of the ink at the right speed
• Optical properties: gloss, colour, sharpness, …
• Physical properties: adhesion, flexibility, scratch resistance, …
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Low Migration digital printing inks
Myth : Low Migration inks don’t exist, especially not for UV Inkjet
LM inks can fulfill the requirements set out in legislations and requirements, if proper care is taken in designing and maintaining the whole print system (substrate-ink-printhead-curing)
What can go wrong?
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How to create LM inks ?
The ink carrier in UV inkjet
Preferred for LM: Highly reactive, bulky, multifunctional monomers
In contrast with viscosity and high cure speed…
The photoinitiators
Tackled by our team by using: •low viscous, highly reactive monomers, in-house invented, produced under license
externally.
•specific combinations of polymeric, reactive (acrylate functionalised: focus on Norrish Type
II and amine synergists), multifunctional and proven low toxicity photoinitiators.
Norrish Type I
Norrish Type II
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Dendritic PI’s
Polymeric initiators have been known for some time and are commercially available, but polymers are typically not at inkjet viscosity
Solution A special design of the polymer architecture
Dendritic structures have high molecular weight…
… but a compact size low viscosity
BUT: they are obtained in multistep synthesis: so
Even better solution Specifically designed technology (e.g. EP 1616920 B, EP 1674499 B)
Hyperbranched polymeric initiators = “imperfect” dendritic structures
They are obtained in a two step synthesis: so
Value of this technology acknowledged by third parties
PI manufacturers interested in this technology: EPO opposition
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Dendritic PI
Amount of extracted PI 100 % 36 % 28 %
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Polymerisable PI’s O
O
O
N
O
O
S
ON
OO
O
O
OO
N
O
O
O
O
S
O
OO
O
O
O
O
O
N
O
O
w/w/% Ink 1 Ink 2 Ink 3 Ink 4
DPGDA 42.5 41.5 45 43.5
TMPTA 40 40 40 40
Cpd I 10
Cpd II 10
Ref PI 1 7
Ref PI 2 7.5
Cpd III 5.5 6.5
EHA 6 7
DBP 2 2 2 2
Ref 1 Cpd II
Cpd I
Ref 2
Cpd III
EHA
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Polymerisable PI’s EP2189477
The polymerisable compounds create an ink formulation that: yields lower amounts of extractables than their “regular”
counterparts
maintains comparable cure speeds with an ink viscosity in the range of inkjet applications.
Viscosity
25 ºC (mPa.s)
Curing speed
(rating: 0-5)
Extractable
initiator
(mg/m²)
Extractable
co-initiator
(mg/m²)
Ink 1 37 2 0 0
Ink 2 35 2 0 0
Ink 3 31 1 19 2
Ink 4 30 1 39 13
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Combined technologies
Dendritic meets reactive PI (EP2033949)
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Sample Viscosity
@ 25 ºC (mPa.s)
Curing speed
(rating 0-5)
Extractable
initiator (mg/m2)
Extractable
co-initiator
(mg/m2)
INV-1 85 0 0 0
INV-2 92 0 0 0
INV-3 68 0 0 0
INV-4 37 2 0 0
INV-5 35 2 0 0
C-1 31 1 19 2
C-2 30 1 39 13
Setup Results
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Summary and conclusions
Sustainable packaging and digital printing
Digital printing can be an answer to the need for sustainable packaging
e.g., digital printing lowers waste (substrates and inks, printing too much of the same), renders lower cost, brings quality information to the public in a safe way
Printing inks and food packaging
Food packaging (primary) needs the use of Low Migration inks
UV inkjet allows to print on many different types of packaging at high printing speed
LM UV inks need careful design, especially in the case of IJ inks, because of the low viscosity
Printing process and food packaging
UV-curable printing process requires control of all parameters (e.g. curing, ink load, …)
The legal boundaries can be used as a source of information: e.g. the Swiss Ordinance
UV-curable inkjet inks
It is possible to formulate LM inks based on commercial compounds, but standard LM ink compounds (high MW, multifunctional) easily result in a viscosity too high for inkjet printing
Proprietary UV-curable Low Migration inkjet ink technology
the right choice of monomers: low viscous and highly reactive
innovations on the photoinitiator and co-initiator side: dendritic or polymerisable photoinitiators yield highly reactive low viscosity ink formulations with low extractables
this also results into formulation flexibility for adding compounds to tune the ink’s functionality: adhesion, flexibility, withstand post-treatments such as sterilisation
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For your kind attention
Dr. Roel De Mondt
Project Manager Inkjet Inks
Email: [email protected]
19 R. De Mondt - ILSI Symposium on Food Packaging - November 2012
For your kind attention
Dr. Roel De Mondt
Project Manager Inkjet Inks
Email: [email protected]
20 R. De Mondt - ILSI Symposium on Food Packaging - November 2012
For your kind attention
Dr. Roel De Mondt
Project Manager Inkjet Inks
Email: [email protected]
21 R. De Mondt - ILSI Symposium on Food Packaging - November 2012
For your kind attention
Dr. Roel De Mondt
Project Manager Inkjet Inks
Email: [email protected]