Packaging ink supplier Siegwerk and APK AG, a producer of plastic recyclate, have completed de-inking trials of twofold printed LDPE films.
The strategic co-operation of the two companies, which started in October, contributes its first ground breaking insights to facilitating the efficient recycling of flexible packaging applications.
Alina Marm, head of circular economy hub at Siegwerk, said, “Design for recycling – ideally enabling product to product recycling – is crucial to closing the loop for flexible packaging. For Siegwerk this means providing innovative printing inks and lacquers, which facilitate high-quality recycling – for example, by allowing easy de-inking while keeping full performance during the use phase.”
Printing inks represent a major challenge when it comes to manufacturing a plastic recyclate of sound quality from post-consumer packaging waste.
Klaus Wohnig, CEO of APK AG, said “The goal of a quality-driven recycling process is to create a recyclate, which is as transparent as feasible, and which can once more be reused in packaging applications. Successful de-inking is essential.”
The research and development unit of APK AG recently tested several LDPE-film samples, which had been printed twofold with Siegwerk’s yellow, red, black, and blue inks. The test series aimed to establish, whether APK AG’s solvent-based recycling technology Newcycling could fully remove Siegwerk’s inks from the polymer matrix.
The film samples were treated with the solvent and dissolved. But, the polymer solution still contained printing ink-components. The dispersed inks were then removed with a filter unit designed for the process de-inking.
The de-inking tests of the red, black and blue samples produced a near-virgin transparency. In case of the film printed with yellow ink, a marginal yellowness remained after the treatment.
Ralf Leineweber, head of global technology development at Siegwerk said, “We consider the entire life cycle of the packaging – from design, to use phase, and finally recycling. We are very pleased that printing inks from Siegwerk have proven to be suitable for solvent-based recycling processes. We have mastered a much-discussed challenge for efficient recycling of flexible packaging.”
Newcycling comprises a step of physical pre-treatment of plastic waste, which is also done in conventional mechanical recycling processes.
After this, APK AG adds a solvent-based process step, which purifies the polymer from additives – such as printing inks.
In contrast to chemical recycling, the polymer’s molecular structure stays intact the entire process. Consequently, the energy that has been invested into polymerisation is preserved.
