Edwin TafelmeierLaboratory Manager

LOW MIGRATION ANDUV INKS -THE FUTURE OF PRINTINGON FOOD PACKAGING

UV-Inks -

Problematic Substances:

Photoinitiators and Monomers

Usually polymeric and oligomericsubstances of UV inks are no problem.Monomers and photoinitiators havea much higher migration potential.However these substances are essentialingredients of UV-inks. It is not possibleto formulate UV-inks without photo-initiators.

Small molecules diffuse throughmaterials much easier than big ones.Many of the traditional photoinitiatorsand their by-products have quite a lowmolecular weight thus presenting a highmigration potential. Especially since theso-called “ITX-scandal” of 2005/2006photoinitiators contained in UV printinginks have become a real issue of foodpackaging manufacturers.

In that case however, contamination offoodstuff was not caused by migrationthrough the packaging material but byset-off of chemicals from the printedside to the inside of the packagingmaterial. This started a process still notcompletely finished today. Three yearsafter ITX photoinitiators have beendetected the photoinitiator substancesbenzophenone and 4-methylbenzo-phenone were detected in foodstuffalso.

This was a good reason for the EuropeanPrinting Ink Association EuPIA to defineguidelines for Good ManufacturingPractices in respect to the use of photo-initiators in low-migration printing inks.

Food safety regulations set high standards for packaging materials. Con-sequently this also applies to inks used for printing on food packaging.Any foodstuff which may possibly be harmful is deemed to be unsafe.Generally UV curing inks contain potentially harmful substances. Thismainly applies to the uncured printing ink. However the cured ink film stillpresents a potential risk. Therefore according to the EuPIA Guideline curedUV-inks are not suitable for direct food contact.

According to Regulation (EC) No. 1935/2004 materials and articles in contactwith food must not transfer their constituents to food in quantities whichcould:

● endanger human health,

● bring about an unacceptable change in the composition of the food, or

● bring about a deterioration in the organoleptic characteristics of thefood (scent, taste).

In accordance with “Good Manufacturing Practice” UV-curing inks maybe used for printing onto the non-food contact surface of food packaging.Thus printing inks must be formulated and processed in a way thatsubstances from the printed outer side of the packaging do not transferto the food-contact side, neither by set-off (roll printing) or by migrationthrough the packaging material.

Commercial photoinitiators have beensplit up into two main groups. Firstgroup contains photoinitiators which donot tend to migrate due to their highmolecular weight so that values below10 ppb in food material can be expected.This group also comprises substanceswhich may migrate, but have beenevaluated in respect to migrationpotential. Those substances have aspecific migration limit.

The second group lists photoinitiatorswith a migration potential which hasnot been sufficiently evaluated. Thesephotoinitiators may only be used withadditional use of a barrier inside thepackaging (such as aluminum foil) toexclude any potential migration.

Guidelines and Legislation

Following the above mentioned “ITX-crisis” Nestlé has issued their own“Guidance Note for Packaging Inks” asat that time there were no legalrequirements. In 2010 the SwissOrdinance on Materials and Articles inContact with Food became effective.This was the first binding legislation forpackage printing inks in Europe. Howeverthe “Swiss Ordinance” is legally bindingin Switzerland only. In Germany the 5thdraft issued by the Federal Ministry forFood and Agriculture (BMEL) currentlyexists. This draft contains regulationssimilar to the “Swiss Ordinance” like apositive list of substances for manu-facturing food packaging inks.

However to date that draft has not beenratified. As soon as this regulationbecomes effective there will be a two-year transition period before fullimplementation becomes a legal re-quirement.

In addition EuPIA has set guidelines forall members to implement.

The potential problem is that differentguidelines and regulations are quitesimilar but not absolutely congruent.

The Definition of “Nothing”

Substances used for packagingmaterials without sufficient evaluationdata must not be found in foodstuffs atall. As “nothing” a limit value of 10 ppb(parts per billion) has been determined.Compared to the number of inhabitantsof Germany this would be less than oneperson.

The EuPIA Guideline on Printing Inksspecifies that toxic or so-called CMRsubstances of categories 1A and 1B(carcinogenic, mutagenic or toxic forreproduction) must not be used inprinting inks. Use of these substancesis forbidden for packaging printing inks,regardless of their migration potential.As a member of EuPIA we do not usesuch raw materials at all. The limit valueof 10 ppb for non-evaluated substancesis so low, that according to currentknowledge any harm to humans can beexcluded.

FRES

H M

ILK

1,5%

Future Perspectives

At present UV ink manufacturers arefacing many and quite demandingchallenges. There is only a small choiceof accredited monomers, whichdrast ical ly reduces formulat ionpossibilities.

We quote the summary of the dossier“Will food packaging run out of printinginks”* of one of the leading experts forprinting inks for food packaging inGermany, Dr. Jürgen Baro of BASF:

“Raw material manufacturers will puta lot of efforts in supplying thenecessary documents for admissionof their raw materials to the positivelist before the regulation becomeseffective”.

Surely first the focus will be on rawmaterials preferred for flexographic,gravure or offset printing. We will seeif the results will present anythingsuitable for screen ink formulations.

In theory low migration UV screen inksfor package printing are possible.However in our experience they do notshow the excellent properties andperformance printers are used to.

There are possible reductions inadhesion and/or resistance properties.We, Coates Screen Inks GmbH, areconfident that we will meet thisdemanding challenge in close co-operation with our customers. We areon the right course...*)ISSN-No. 0949-9717Published by: G&K TechMedia GmbH

Are UV-Low Migration Inks

suitable for printing on food

packaging without restriction?

The term “Low Migration” only refersto the fact that the manufacturer avoidedor reduced the use of substances witha high migration potential in the inkformulation. As a first step many inkmanufacturers started to follow thecorresponding EuPIA guidelines whenchoosing photoinitiators. Thus thereshould have been a significant reductionof exceeding of limit values due tomigrating photoinitiators. In addition tophotoinitiators with a low molecularweight, however commercial acrylicmonomers also show a significantmigration potential. The barrier functionof polyethylene or polypropylenepackaging materials is quite low;therefore most of the commonUV-curing inks used so far can no longerbe applied. PET or compound materialsmay be better in that respect. In additionto ink formulation and packaging materialthere are many more factors influencingconformity to food regulations. Mig-ration tests are essential. Theoreticalcalculations (modelling) may be helpful,however in that case you have to knowall conditions. Experimental migrationtests are much more reliable as theyalso detect substances one did notexpect based on the formulation. Theseare the so-called NIAS components (Not

Intentionally Added Substances), whichcould have been introduced with rawmaterials used or during the manu-facturing process. They could also bedecomposition products of the sub-stances contained in the formulation.

Finally the content of the packaging isanother factor influencing the migrationpotential of substances into food.Presently there is no general answer tothe question whether a certain UV inkis suitable for printing on food packaging.In our industry currently some ask theslightly provocative, however not veryserious question, if UV-curing and foodpackaging are not a contradiction inthemselves.