LED UV and Migration - a topic for 2019
By Tom Kerchiss, RK Print Coat Instruments
Almost every day now it seems that some topic associated with an environmental issue surfaces on social media or is highlighted on the television news and on current affairs programs and in the national newspapers. Arguably and as far as the print, pack and consumable sectors are concerned the need to minimise the use of solvent based materials, eliminate VOC emissions as far as possible and seek ‘green’ recyclable or renewable alternatives became apparent to all concerned as a raft of legislation came into affect and industry on an international basis realised that sustainability and cleaner processing was to become the way forward
The late 1980s and early 90s for many was a particularly exciting period for
product developers, converters, packaging professionals and others engaged in producing and supplying consumables and components. The introduction of water-based inks/coatings, adhesives and energy curable technologies grabbed headline attention in trade journals and elsewhere.
As far as solvent-based materials concerned the future has become brighter and at least alternatives are on offer that do not compromise on quality and performance and which do not impact on the environment and on health and safety.
Solvent-less materials, UV curable inks and coatings, most of which are comprised of 100 per cent solids with no volatiles or flammable together with industry acceptable systems such as solvent-less laminators and other equipment often provide good reason not to use solvents.
Nevertheless and despite significant drawbacks such as the need for expensive solvent reclaim systems it must be said that there are still situations where solvents remain the only viable option for difficult substrates. In this regard and with respect to many other aspects of processing and production much still needs to be done; environmental compliance, meeting health and safety, protecting current and future generations is still a work in progress.
Low migratory UV inks, coatings/adhesives etc., are being formulated to tackle the potential risk of the aforementioned contaminating or migrating into the product contained within, affecting texture, odour, taste, appearance and health of consumers. Inks and additives together with resin and other component parts theoretically migrate by at least two recognisable routes, diffusion and set off. Migration as a result of diffusion can occur as a result of minute molecules travelling too and across packaging layers. The extent to which migration can occur can be complex. For instance: a paper-based material with a large pore size may theoretically allow for the diffusion of a material substance with a smaller molecular structure. Other factors that may play a role in diffusion in some instances include temperature, storage time, the size of a pack and materials or surface volume ratio of food product, etc.
Instances of set off migration can occur when a surface printed layer is bought into contact with a non-printed contact surface and the conditions allow for the migration in with a food product, a baby care item, and tobacco goods. Set off problems can be influenced by the pressure exerted on the processed material web through winding and stacking etc.
Inks and other components must be dried/cured sufficiently prior to a product being wound up, stored and distributed, prompting interest and development in system/components that enhance productivity and quality such as LED UV lamps and pre-press colour communication devices such as the FlexiProof LED UV for users and producers of flexographic inks and for inks that are being designed with low migratory properties.
The successful implementation of low migratory LED UV cured inks, coatings and adhesives is a team effort, its far from being the case whereby the ink supplier hands over a can of ready formulated ink.
An ink can work properly when cured at a certain speed but might fail when cured at another speed as a result of dwell time, etc. Good housekeeping and a degree of trial and experimentation are needed throughout the supply chain. Pilot, coating, printing and laminating systems such as the Rotary Koater and VCM designed and developed by RK Print Coat Instruments as well as other trialling and product development equipment and systems also help in bringing products to market and for resolving production/quality issues.
Breakthrough developments seldom occur in isolation or take place overnight. A better understanding of chemical partitioning or migration and light manipulation technology has resulted in much attention being focussed on inks that can be cured using LED.
Prototyping and pre-press monitoring are important in every area of product development. A FlexiProof for example in pre-press picks up on performance issues tied in with the ink such as gloss, printability, scuff resistance, chemical resistance, durability and flexibility. The FlexiProof family of devices, which includes the original and award winning FlexiProof 100, the FlexiProof UV and the new FlexiProof LED UV, can also be used to determine how the ink/substrate interact over time and for colour matching and other colour communication purposes such as proofing and the preparation of colour samples for customer evaluation and approval.
The LED UV system integrated in with the FlexiProof LED UV incorporates the Phoseon Firejet UV system with the energy output from the light emitting diodes (LEDs) specifically tailored for output at 385 or 395 nanometre wavelengths.
LED UV lamps are engineered with a much narrower spectral output than the wavelengths outputted by traditional mercury vapour lamps. LEDs such as those integrated in with the FlexiProof LED UV are solid-state devices requiring only a small power unit. The energy/heat output is significantly lower than with mercury arc lamps and there is no warm up requirement, lams start up and are ready for operation straight away.
RK Print Coat Instruments Ltd
Litlington, Royston, Hertfordshire SG8 0QZ
www.rkprint.com sales@rkprint.com
Source: RK Print Coat Instruments Ltd
