digital printing: low migration inkjet inks for indirect...

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

2 R. De Mondt - ILSI Symposium on Food Packaging - November 2012

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


Organisation

53% 8% 39%


Sustainability: what’s your definition ?


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


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


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


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, …


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?


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


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


Dendritic PI

Amount of extracted PI 100 % 36 % 28 %


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


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


Combined technologies

Dendritic meets reactive PI (EP2033949)


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


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


For your kind attention

Dr. Roel De Mondt

Project Manager Inkjet Inks

Email: [email protected]



Dr. Roel De Mondt



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