PrintCYC finds PU-based inks enable recyclate film production through mechanical recycling

18 Jan 2022 --- Huber Group-backed PrintCYC project has discovered that standard pigments for flexo- and rotogravure printing show “excellent” compatibility with recycling and enable recyclates comparable to virgin film.

This finding opens a “wide range” of reuse possibilities in different film and packaging applications, the consortium indicates.

Both pigment types (yellow and red) showed optimal recyclability, leading to odor- and defect-free, color-stable polypropylene (PP) recyclates. The colored recyclates’ material properties were analyzed technically and analytically.

Early last year, PrintCYC began this project phase, investigating the impact of pigments on the recyclability of printed packaging films. Inorganic pigments are mostly temperature stable and supposed to be recyclable without degradation.

However, organic azo-pigments like most standard red and yellow pigments are more temperature-sensitive and might re-split into critical components. The pigments yellow (Pigment Yellow 17) and red (Pigment Red 57:1) selected for the recycling trials are commercially available standard pigments for flexo- and rotogravure printing.

Thermoforming films with recyclate
PrintCYC found the PU-based printing inks enabled the production of color-stable, odorless and defect-free recyclates from fully printed PP-based packaging films by mechanical material recycling.

Increased amounts of rPP reduce energy consumption in cup production (Image credit: PrintCYC).The recyclates were incorporated into flat films without any issues and deep-drawn on Kiefel thermoforming machines with lower energy consumption.

In addition, with the increasing proportion of recycled material, savings of up to 20% in heating energy could be observed in the production of deep-drawn PP cups compared to virgin material. This effect can be further enhanced by using dark recyclates due to the better heat absorption.

Non-food packaging alternative
Kiefel successfully thermoformed both colored trays and cups from the recycled PP flat films on its KMD and KTR series machines. “The machine settings practically did not have to be changed from processing of new material,” notes Olaf Tanner, head of project and product management in Kiefel’s Packaging Division.

“The shape, appearance and functionality of the deep-drawn, recycled packaging is so good that it represents a real alternative to non-food packaging made from virgin material.”

PrintCYC found standard pigments for flexo- and rotogravure printing show “excellent” compatibility with recycling.PrintCYC consortium
The PrintCYC consortium was established in 2019 to support the transformation of printed polyolefin-based packaging films toward a circular economy by evidence-based industrial trials.

Key stakeholders include leading machine manufacturers Brückner Maschinenbau, Erema, Kiefel and PackSYS Global, the printing ink manufacturer hubergroup Print Solutions, and Profol, one of the market leaders for PP cast films.

The initiative is coordinated by Dr. Annett Kaeding-Koppers, an independent packaging expert and environmental sustainability consultant.

PrintCYC is connected to converters and in continuous dialogue with brandowners, recyclers, and platforms such as Ceflex and Forum Rezyklat to discuss and share results.

Recycled packaging
In the project’s starting phase between 2019-2020, PrintCYC successfully produced PP and polyethylene film and packaging samples containing more than 50% recyclate from post-industrial sources.

Focusing on the recyclability of the binders NC (nitrocellulose), PU (polyurethane) and PVB (polyvinyl butyral), the initiative identified the binder PU as the most temperature resistant and, therefore, as the best recycling-ready solution for mechanical recycling without de-inking.

For the next project phases, PrintCYC is looking for partners to test and evaluate closed-loop printed PP packaging scenarios and to further improve relevant design for recycling guidelines.

Edited

By Natalie Schwertheim

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