Tracing Migration -Zeller+Gmelin operates a special analytical centre for the development of low-migration ink systems
Zeller+Gmelin operates a special analytical centre for the development of low-migration ink systems
Andreas Rascher (Product Manager Printing Inks at Zeller+Gmelin GmbH & Co. KG in Eislingen/Germany)
Zeller+Gmelin consider it a shared responsibility of both the ink industry and the printer to reduce or avoid undesirable migration in label and packaging printing. The ink manufacturer based in Eislingen has introduced various new initiatives. For example they have looked at different methods of avoiding migration through the selection of inks and by using the facilities available in their in-house analysis laboratory, a facility which is also at the customers' disposal. However, the author points out that the ink industry is dependent on the help of the printers in solving this problem and emphasises the necessity of observing certain basic requirements during the printing process in order to eliminate migration.
After the adoption of the 1935/2004 directive for packaging in contact with food, Zeller+Gmelin GmbH & Co.KG, Eislingen/Germany has expanded their analytical department especially in the field of the analysis of printing ink systems. Their analytical centre is specially used for the development of low-migration inks, for raw material control and raw material selection as well as for the internal verification of test samples.
Currently, packaging and raw materials are tested via gas chromatography with mass spectrometry (GC-MS, see picture 1) and fluid chromatography with mass spectrometry (LC-MS, see picture 2).
Analysis techniques
The examination method of chromatography involves a mixture of substances is being separated allowing the contained substances to be detected individually. An analytical separating column works on the same principle. The substances to be separated each remaining in the separating column for different periods of time.
By means of mass spectrometry (MS or MS/MS) the individual substances can be clearly defined by their mass. If two substances have the same mass, their fragmentation pattern is examined (the way a substance breaks down). By this, substances can be clearly identified.
Low-migration UV-printing ink systems
The findings gained in the analytical centre were incorporated by Zeller+Gmelin into the development and production of all their low-migration UV-ink systems used for the printing of primary food packaging and labels. Whether printed on paper or foil, these low-migration ink series meet the specification of printing labels and flexible packaging for which low migration is required.
External and internal analyses demonstrate that with migration tests a value of 10 ppb with 95 % of ethanol can be improved on with an appropriate application of the inks.
The following low-migration ink series for a variety of applications are currently available from Zeller+Gmelin:
UV-flexo printing: Uvaflex Y71, low-migration UV-flexo ink for the printing of flexible packaging and labels.
UV-offset printing: Uvalux U41, low migration UV-offset ink for universal application on paper and foil. The ink has been particularly developed for high press speeds and in addition the ink features very low odour.
Uvalux U71, optimised with regard to adhesion, low-migration UV-offset ink especially for the printing of critical foil materials.
UV-printing moulded containers: Uvacurid C71, low-migration UV-printing ink for the direct printing of plastic moulded food containers for like cups, lids and buckets, for indirect letterpress.
Zeller+Gmelin are also able to confirm that all their low-migration ink series are Nestlé compliant and possess the official approval of that food company.
In addition to their own internal examination Zeller+Gmelin always have their low-migration ink series examined and assessed by independent analysis institutes. This double checking enables the ink manufacturer to state that their inks offer maximum product safety to printers, packaging customers and consumers.
Special customer service
Furthermore, as a special service, Zeller+Gmelin will also offer the resources in their analysis centre to their customers.
Printers and manufacturers of primary food packaging and labels for food packaging can have their print products examined and analysed in order to obtain findings on the migration potential of the inks and printing process before sending the packaging to a neutral, external analysis institute.
This way the printer is able to discover early in the process whether packaging complies with the legal limit value of 10 ppb. This can prevent unpleasant surprises and ultimately save both time and money. An internal migration analysis at Zeller+Gmelin takes approximately three weeks. Suitable printed samples are necessary for providing a meaningful analysis.
Handling of printed samples
The preparation of suitable printed samples and the way these are handled are crucial for a meaningful migration analysis. Not every printed sample is suitable for an analysis. Certain conditions have to be adhered to. The following printed samples are required:
•- sample of original substrates,
•- sample of original substrates irradiated with UV,
•- printed samples without varnish,
•- printed samples with varnish.
The printed samples should have a minimum size of 10 x 10 cm and provide sufficient area coverage. Immediately after preparation, the analysis samples must be packed in aluminium foil:
Packaging printing (roll-roll): With the production of roll to roll each sample has to be separately wound on a sleeve. The analysis samples must be packed in aluminium foil immediately after preparation.
Label printing: The printed samples should have a minimum size of 10 x 10 cm and provide sufficient area coverage. In addition original empty containers to which the labels are applied are required. The analysis samples must be packed in aluminium foil immediately after preparation without stamping and without lattice printing.
Printing of moulded containers: With the printing of moulded containers (for example yoghurt container) a stack of 20 pieces/cups minimum is required per sample. The analysis samples must be stacked and packed in aluminium foil immediately after preparation (no single cups).
Metal decoration: The metal sheets should be taken from a pile of 5 to 10 sheets. The sheets are then cut into parts of approximately DIN A4 size (10 x 10 cm minimum). The analysis samples must be stacked and packed in aluminium foil immediately after preparation (no single sheets).
Cleaning of all components
The first prerequisite for low-migration printing is the cleaning of the printing press. With regard to the printing ink special importance is to be placed on the cleaning of the following components:
•- ink duct,
•- press cylinders,
•- ink feeding hoses,
•- printing blankets,
•- printing plates.
In addition, the following specifics need to be observed here:
Ink feeding hoses: For printing with low-migration ink systems, the hoses need to be replaced.
Press cylinders/printing blankets/printing plates: Rubber rollers, printing blankets and printing plates coming into contact with wet printing ink will absorb the components of the printing ink. One single cleaning process is never sufficient to remove this residue. Therefore, before starting a low-migration printing job the printing press should be run with low-migration systems for several hours in order to draw out the existing residual substances on the rubber rollers. For the same reason printing samples for migration analysis should always be taken out at the end of a printing job.
In order to exclude the risk of contamination due to non-low-migration systems ideally a printing press should be used with low-migration systems only.
Finally at this point it has to be emphasized once more that the use of a low-migration printing ink or of a low-migration varnish alone does not necessarily guarantee that the print will meet low migration limits. The entire process must be considered including all the components and factors that have an influence on the migration result. This includes:
•- the substrate,
•- the cleanliness of the machine,
•- the UV-radiators,
•- the press cylinders and rubber blankets,
•- the ink formulation,
•- the colour strength and ink laydown as well as
•- the design of the packaging or the label.
Conclusion
Part of the process of producing a conforming packaging is a close exchange of information between the individual links of the packaging chain. Zeller+Gmelin are of the opinion that the printing ink manufacturer cannot shoulder the responsibility alone. All participants of the supply chain need to actively assume part of that responsibility. According to Zeller+Gmelin this understanding is being accepted more and more in the industry and this must be seen as a good thing as only by working together can the industry meet the given legal requirements.
((captions))
Picture 1: Gas chromatography with mass spectrometry (GC-MS).
Picture 2: Fluid chromatography with mass spectrometry (LC-MS).
Picture 3: Analytical separating column (HP-LC).
Picture 4: Chromatogram of a mass spectrometry.
Picture 5: Such a crumpled printed sample is useless for the analysis.
Picture 6a and 6b: Printed samples can also be useless due to contamination.
Picture 7: This printed samples has a too small diameter for the analysis.
Picture 8: As the ink coverage is insufficient, a migration analysis cannot be carried out here.
Photos: Zeller+Gmelin
To the editor:
Should you have any questions on the present text please either contact
Zeller+Gmelin GmbH & Co. KG
Schlossstrasse 20
D-73054 Eislingen/Fils
phone +49 (0) 71 61 - 8 02 - 0
telefax +49 (0) 71 61 - 8 02 - 3 55
e-mail: druckfarben@zeller-gmelin.de
or press agencyflexible kommunikation
Luzer Straße 6
D-97204 Höchberg
Telefon +49 (0)9 31 - 40 51 66
Telefax +49 (0)9 31 - 40 51 67
e-mail: flexible.kommunikation@t-online.de
After publishing please send one specimen copy each to both addresses - a pdf-file is also acceptable as evidence. Thank you very much!