When it comes to sustainable flexible packaging, there are a variety of challenges for the industry to overcome, such as plastics ending up in landfills or oceans.
However, brands and CPCs want to overcome these challenges and take flexible packaging to new sustainability heights. To help contribute to sustainability initiatives, brands and their converter partners are introducing these three themes: recyclability, compostability and biorenewability.
To accommodate consumer demand and lower environmental impact, many brands have started to adopt the United Nations’ 2030 Agenda for Sustainable Development by setting aggressive sustainability goals to achieve, by or before 2030. Converters and their partners are also working to achieve their own sustainability goals and are toiling hard to ensure packaging is as eco-friendly as possible.
Inks and coatings play a critical role in helping brands, CPCs and converters meet these goals.
In order to meet these environmental objectives, two key flexible packaging markets—roll-fed labels and shrink sleeves—are focused on improving current labeling processes to increase the recyclability of polyethylene terephthalate (PET) bottles.
The roll-fed industry, for example, has utilized lamination technology to help protect labels from scratches, scuffs or other environmental challenges that could possibly affect the brand’s reputation caused by damaged labels. However, this technique uses two pieces of film—typically polyethylene and polypropylene—which are glued together with an adhesive over the ink to form the protective layer.
Laminated labels are not considered ideal in the recycling process of a labeled PET bottle, as the added films create a barrier for the ink, adding a further obstacle in the recycling process of the entire bottle. Additionally, with the lamination technique, there is nowhere for the waste stream to go. Inks and adhesives do not belong with either of the films. This means the label ends up in landfill without the chance of recycling.
Meanwhile, a mono-web technique allows for only one single film to be printed, meaning one less barrier to reach the ink and therefore more options for label recycling. With this method, printers can surface print a film and utilize an overprint varnish (OPV) for increased protection. For example, by using quality inks and OPVs to impart gloss, scratch, coefficient of friction (CoF) and adhesive properties, printers can eliminate a film layer without jeopardizing performance.
By making this transition to mono-web, there is only one supply stream, which can then be included into one recycling raw material stream, making the label easier to be recycled. Heavily driven by CPCs and brand sustainability goals, the mono-web strategy already has widespread adoption for water bottles. Soft drink bottles are expected to follow.
The shrink sleeve market has also turned its focus to the recyclability of labels. There are two popular methods for recycling a PET bottle with a shrink sleeve label. When the bottle is recycled, it is sent to a recycler to be ground up and placed in a caustic recycling bath where, depending on the film used, two processes could occur:
- If the label used a floatable film, then the ink remains on the film while it is removed from the label. In this scenario, the PET bottle is recycled while the film and the ink are landfilled
- A relatively recent trend is to utilize a crystallizable PET film, whereby the label is ground up with the PET bottle and the ink is removed by a caustic water solution and disposed of, resulting in a clean film for recycling. Both the film and the polyester from the bottle are now mixed, causing the film to become the next generation of the bottle during the recycling process. This can increase the yield, and thus the profitability, for the recycler
By using crystallizable film, the bottle becomes a truly recyclable package with greatly reduced need for landfill. Crystallizable films are starting to become a popular solution in shrink sleeve, with an expectation of a large percent of North America transitioning to this method.
Inks that support compostable packaging are another route to which many markets are looking for improved sustainability. More specifically, the snack food industry is looking to compostable solutions for its packaging. Snack foods typically come in high SKUs, or high-volume packages, which greatly hinder recycling. However, with compostable packages, these brands can still achieve their sustainability goals without sacrificing flexibility or the number of product iterations.
A key factor in creating a compostable package is ensuring that the inks and coatings used do not interfere with the substrate compostability. If any of the components fail to achieve compostability standards, there is a direct impact on the overall compostability of the package. Therefore, inks that support industry compostability standards are typically paired with compostable films, which today are predominantly polylactic acid (PLA) or cellophane.
While the ink itself would be considered an “additive,” meaning it does not exceed a certain percentage in weight, and is not expected to play an active part in the composting process, it still must undergo strict eco-toxicity and chemical analysis tests, carried out by independent accredited laboratories. The tests ensure ink does not adversely impact the process by introducing contaminants that inhibit the microbial degradation process critical to composting.
To ensure the inks are truly compostable, companies rely on certifications provided by independent entities, such as TÜV Austria, that carry out laboratory tests on the finished packaging product or on its separate components (including the inks) to prove they fully meet European EN 13432 or North American ASTM D6400 and D6868 compostable standards. If certified, the material used is considered compostable, as it refrains from leaving excessive levels of toxins, heavy metals or plastic residues in the soil.
To receive the certification, three tests are conducted:
- The first is performed to understand if the material can be converted to carbon dioxide by organisms already at a compost pile in a reasonable timeframe
- The second tests the ability to fragment, meaning the products do not clog screening equipment
- The third evaluates the material and its ability to support plant growth
Converters who use inks and coatings that are certified can reassure their customers that they are achieving their sustainability goals by ensuring the materials used will biodegrade completely when composted.
Brands are also prioritizing sustainability through the use of biorenewable inks. Utilizing inks that are made with renewable and eco-friendly materials, such as plants, rather than materials such as petroleum, contributes to the sustainability of a package.
As its platform for sustainability, the fast food market has taken a strong interest in biorenewable inks. By incorporating biorenewable inks for paper packaging such as paper bags, wraps, clamshells and paperboards, fast food companies are reaching their sustainability goals in an alternative way.
Unlike compostability and recyclability initiatives, which typically use solvent-based inks, many fast food companies work with water-based printers and are turning to water-based inks that have a higher bio-renewable content (BRC) to contribute to their packaging needs.
However, it’s important that claims of biorenewable materials are verified by a separate third-party lab to avoid misconceptions and false assertions. The National Association of Printing Ink Manufacturers (NAPIM) has a comprehensive program to verify bio-renewable claims and help ink manufacturers with their verification needs.
According to NAPIM, biorenewable inks are derived from tree, plant, insect and/or animal materials. These include gums, resins, waxes, solvents, oils and other polymer building blocks. Independent verification that an ink contains a certain percentage of bio-renewable content can be achieved through NAPIM’s biorenewable content program, which assigns inks with an index number. This is a universal program for the printing ink industry for calculating and reporting the BRC of an ink as delivered to the printer. An index number of 60, for example, means an ink contains 60 percent renewable content.
Greenhouse Gases & Waste Cuts
One of the simplest things the packaging industry can do to help achieve a circular economy is to utilize materials, such as inks and coatings, that align with valid sustainability initiatives.
By incorporating recyclable, compostable and biorenewable inks and coatings into packaging processes, this industry can reduce greenhouse gas (GHG) emissions, minimize waste production and help to achieve objectives which align with the United Nations’ 2030 Agenda for Sustainable Development.