Our expertise for your development projects: MOWITAL^® the alternative for printed interlayers for packaging

Films with NC-based inks are not easy to recycle

Recycling packaging films can be challenging if they are printed with coloured inks based on binders such as nitrocellulose (NC). The limited temperature resistance of the binders makes it more difficult to recycle films made of e.g. polyethylene (PE) or polypropylene (PP). Challenges identified in tests are the release of significant amounts of gases that irritate the respiratory system, an unpleasant odour and discoloration of the recyclate. However, technology for de-inking packaging films is still at the test stage. Moreover, it is often impossible to separate the ink from the film because it is not possible to access the inks in the printed interlayer.

Stricter regulations on the horizon

On September 1, 2023, Germany’s Central Packaging Register Agency (ZSVR) published a revised version of its minimum standard for measuring recyclability. This lists PE interlayer films printed with NC-based inks as non-recyclable if their dimensions exceed DIN A4. While classification as non-recyclable is not a marketing ban, it makes films printed with NC-based inks less attractive all round, for example, for distributors, converters, food producers, etc., – if only because of the related recycling debate.

PVB resins are an alternative

One attractive alternative is polyvinyl butyral (PVB), which has been used as a binder in the printing of packaging for decades. Kuraray produces a wide range of PVB resin grades, which it markets as MOWITAL^®. PVB has better heat stability than NC. Moreover, in comparable conditions it does not release aggressive or toxic gases. That is a benefit in both thermal recovery and recycling processes. A complex de-inking process is unnecessary when recycling films printed with PVB-based inks. What is more, dry nitrocellulose is classified as an explosive – so PVB is easier to handle.

Selecting the optimum MOWITAL^® grade

Dr. Florian Mummy, Senior Manager R&D for the MOWITAL® brand and a member of Kuraray’s Technology Scouting team: "When it comes to recycling, MOWITAL^®-based inks have key benefits because of the chemical properties of PVB. It’s easier to separate the packaging film and there are no toxic emissions that affect people or the environment. The result is a high-quality film recyclate that can be used to produce packaging of comparable quality.” Even so, it is important to select the right PVB grade. “Two of our binders, MOWITAL^® B 16 H and B 20 H, are especially suitable for use as binders for printing inks. B 16 H has a low molecular weight and low solution viscosity. MOWITAL^® B 14 S has even lower viscosity. In fact, Kuraray is the only producer worldwide that offers such a low-viscosity product.”