For the recycling of paper and fresh fiber board, it is important that ink and varnish films are fragmented into small hydrophobic (water repellent) particles during the recycling process in order to become detached and more easily separated from the substrate fiber. But present standard UV inks still often show poor deinkability as they form a solid, chemically, and mechanically resistant layer that is strongly attached to the cellulose fiber like an adhesive plastic layer. Therefore, they are difficult to remove during the recycling process, resulting in big color spots in the recycled paper.
Studies have also shown that prints coated with water-based dispersion varnishes and UV-curing flexo varnishes, similar to UV standard inks, very often produce problems during the paper and board deinking recycling process. During the recycling process, the printed varnish layers are fragmenting either into too small (water-based varnishes) or too big particles (UV varnishes) and cannot successfully be separated from the cellulose fibers. Packaging printing UV offset inks and conventional oil-based inks are often covered with standard UV flexo varnishes. In particular, this problem hampers the recyclability of valuable virgin fiber-based carton board.
Based on Siegwerk’s Sicura Low NRGY UV/ LED UV ink series, launched in 2019 as the first UV/LED offset ink system with deinking properties for coated and uncoated types of paper, the gained knowledge has been transferred to other new Siegwerk UV curable ink products. Siegwerk’s experts have developed another UV offset ink series, especially designed for offset and packaging printing of non-food solutions: Sicura Plast SP. The ink series has excellent deinking properties when compared to the deinkability of conventional oil-based sheetfed offset inks, the company says.
The deinkability of Sicura Plast SP alone, and in combination with the new deinkable UV flexo varnishes, has been proven by using the INGEDE method 11, the officially approved industry standard for deinking testing. Today, the full range of process, base and special colors of the new ink system is available and already in use at various Siegwerk customers. Moreover, Siegwerk’s developers have also launched the first deinkable UV flexo varnishes, the company adds.
“Our new UV flexo varnishes are recyclable by the standard flotation deinking process also used for the recycling of printed ink films on paper and virgin fiber board without any adaption. This enables us to offer commercial and packaging printers the complete package of recyclable UV offset inks plus varnishes. A very good example of Siegwerk’s Circular Economy strategy, which enables our customers to become more sustainable – in this case by increasing the recyclability of paper,” explains Thomas Glaser, head of Technology Sheetfed at Siegwerk.
The company’s new deinkable UV flexo varnishes offer the same performance properties as standard UV flexo varnishes and can be applied inline and off-line using standard flexo coating units. With its deinkable solutions Siegwerk has improved the recyclability of UV-cured prints while supporting the EU’s defined recycling target for paper and cardboard packaging. The stipulated recycling rate increased from 60% today up to 85% by 2030.
“Siegwerk works continuously on enhancing the deinkability of our inks and varnishes, contributing to the improved recyclability of packaging, further driving the development of innovative circular solutions in line with a Circular Economy approach,” adds Glaser.