IN Brief:
- European patent EP4107326 protects a primer placed between plastic substrates and printing layers.
- The protected approach includes solvent-based and water-based primer technology, including complex flexible packaging constructions.
- The patent was granted in August; the fresh company announcement was published on 20 October.
Siegwerk has described how its European patent EP4107326 protects a primer intended to remove printing ink from plastic packaging during recycling. Announced on 20 October, the development concerns technology already granted patent protection on 5 August 2026, rather than a patent newly issued in October. The primer forms an intermediate layer beneath the print that can be released under suitable alkaline washing conditions, with potential applications in selected flexible food packaging structures.
The method places a functional primer between the plastic substrate and the printed layer. During a suitable alkaline washing operation, the primer is intended to allow the overlying printing layer to detach so that it can be removed before the cleaned polymer is reprocessed. The concept covers solvent-based and water-based primer formulations and extends beyond simple surface printing to certain more complex flexible constructions in which the ink is located between additional layers.
Printing inks are important to food packaging because they carry product information, traceability markings and branding while helping differentiate products on crowded shelves. Their colours, binders and associated coatings can become contaminants when packaging is ground and washed for mechanical recycling. Residual pigments may discolour the polymer; unwanted material can affect the consistency of the output or narrow its available end uses. The process therefore has to consider print performance during the pack’s original life and removal performance after collection.
The pack structure determines whether released printing can actually be separated. A surface-printed mono-material film may enter a comparatively straightforward washing process, while a laminated pouch can trap inks between barrier, adhesive and polymer layers. Those layers may need to be separated or processed differently before washing can remove the ink cleanly. Sorting, material identification and contamination control therefore remain necessary even when the primer performs as intended, particularly where food packaging combines several functional materials.
Siegwerk has tested deinking systems on different ink, substrate and packaging combinations and points to work with partners on a deinkable mono-material flexible pouch recognised by a German Packaging Award. These examples demonstrate practical development, not universal recycling performance. The 20 October announcement does not establish a single ink-removal percentage across products, operating yields at industrial recycling plants or clearance for recycled polymer to be used in food contact applications.
Primer chemistry has to satisfy competing requirements. Printing must remain firmly attached during converting, heat sealing, packing, transport and normal handling, yet be releasable in a controlled end-of-life process. Premature loss of adhesion would impair print quality and potentially create rejects during manufacture. A system engineered solely to release ink quickly might therefore be unsuitable unless it also meets the physical and chemical demands of the packaging line. The relevant balance depends on the substrate, press process, subsequent coatings and anticipated processing conditions.
In an alkaline wash, the primer must release the print under the equipment’s specific chemical concentration, temperature, residence time and agitation conditions. Detached ink then has to be removed from the process liquor so that pigment and binder residues do not redeposit on the plastic. The patent describes how release can occur, but recovery performance also depends on plant configuration and water treatment. Siegwerk has not specified a universally applicable washing recipe or confirmed that existing recycling lines can adopt the system without modifications.
Removing ink from recycled polymer does not, by itself, establish that the material may safely be used in food-contact packaging. The suitability of any recycled polymer for a particular application depends on applicable rules, feedstock control, decontamination capability and the end use. Converters must also maintain the original pack’s protective functions, particularly where oxygen, moisture or grease barriers are needed to protect product quality. A deinkable decoration layer does not eliminate those requirements.
The European patent follows a US patent granted in May 2025, forming part of Siegwerk’s wider work on printing and recycling compatibility. The company has separately worked on ink formulations compatible with established polyethylene and polypropylene recycling streams. Compatibility within those streams and intentional ink removal are related but different approaches: one seeks to tolerate certain printed components, while the other seeks to remove them before reprocessing.
Siegwerk’s broader ink and recycling portfolio now includes this patented primer, but it does not make every printed flexible pack recyclable. Commercial relevance will rest on the complete pack: the substrate, barriers, adhesives, printed construction and available collection and washing route. Quantified plant-scale evidence on polymer yield, contamination and water use will be needed to assess how widely the system can be deployed in food packaging supply chains.
