Interview: “Sustainable solutions for all inks ingredients”
In general, what are the trends in raw materials for food packaging inks?
Janet Preston and Anabelle Elton-Legrix: Some of the main trends are concerning the safety and stewardship of all ink ingredients. The key is to have a final ink in which the components are clearly identified and qualified. This is especially important for any ink which will be printed onto food contact materials. Ink companies are striving for increased compliance with regulatory laws and industry guidelines to give greater transparency and accountability to their customers. The raw materials and production of inks are regulated by EuPIA (the European printing ink association) guidelines and Good Manufacturing Practice (GMP) for inks and varnishes which are designed to be printed onto food contact materials. This includes the safety of the raw materials into formulations, their potential to migrate, the composition of the inks as well as quality control and hygiene management. In terms of mineral supply (clays, calcium carbonates and talcs) the quality of the raw materials and consistency is a key requirement. We strive to have the highest levels of product stewardship and have ISO 9001 for quality management, ISO 14001 environmental accreditation. The UK analytical labs are accredited with ISO 17025 to ensure the highest level of analytical competence. Recycling and reuse of materials is growing in importance, moving through cradle to grave to cradle to cradle mentality thereby reusing our earth’s raw materials in a sustainable way.
What can be done to make printing inks more sustainable?
Preston and Legrix: One trend is a move away from solvent based inks to water-based system, although the technical challenges mean it is often necessary to incorporate some co-solvents. Another trend is towards the inclusion of renewable sourced vegetable oil rather than mineral oil as an ink solvent. Advantages include possible faster degradation during recycling, lower rates of VOCs emissions, and lower levels of contaminants such as heavy metals.
Optimisation of CO2 footprint is a key trend which may mean logistics optimisation; producing inks in one site but then having regional blending centres strategically located. The CO2 of the separate components in the ink is also a valid consideration. Imerys for example have cut the CO2 emissions by 7 % between 2012 and 2017 (average for all minerals). The choice of mineral will also impact the carbon footprint. For example, in white inks, extension of the TiO2 pigment will not only improve the cost efficiency of the ink but will also improve the carbon foot print of the formulation.
The carbon footprint of TiO2 is 5.3 kgCO2e/kgTiO2 product whereas the carbon foot print of clays and calcium carbonates is significantly lower (0.1-0.85 kg CO2 e/kg kaolin slurry – dry PCC). Sustainability also includes ethics, corporate responsibility, reduction in use of resources such as energy and water, reducing air emissions and maximising recycling and most companies are developing policies to address these important issues as described on their company websites. Imerys for example, has a dedicated corporate social responsibility (CSR) group dedicated to promoting positive and innovative improvements.
In how far can mineral additives improve the behaviour of printing inks?
Preston and Legrix: In the cost conscious and very competitive ink and printing industry there is an ever-present drive for decreasing costs. Mineral extenders such as kaolin and calcium carbonate are often the lowest cost component of an ink, a common and useful strategy is therefore to add as much mineral without compromise in the final ink properties. However, minerals also bring technical benefits to the inks, e.g. they add bulk to the ink and help with the physical coverage over the surface of the substrate. In some cases, extenders are added to help hold the ink on the surface of the paper where the colour is actually required and prevent penetration / strike through into the bulk of the paper. Variations in the extent and type of mineral use exist even within the same type of ink.
Some of these differences are due to local mineral availability and logistics issues, but others are due to the ink technical performance. In offset printing the choice of calcium carbonate or kaolin is important to help control the viscosity as well as pick up and release of the fountain solution. Different extenders or fillers can bring different properties to the ink. Kaolin has a platey structure and can therefore allow higher gloss if the platelets are aligned in the final dried ink. Calcium carbonates impart a white shade and give a lower low shear viscosity (allowing more to be added to a flexo ink for example).