The release liner is a paper, filmic or hybrid paper-plastic film carrier material. The liner is coated on one or both sides with a very thin layer of silicone, and its function is to act as a carrier to protect the adhesive/label until it is applied.
“Release liners are indispensable to carry and protect pressure sensitive adhesive (PSA) products,” explains Andrea Lackner, director of R&D and innovations, Mondi Release Liner. “They are used in a wide variety of industries such as labels, tapes and graphic arts, as well as the hygiene and medical industry.”
As Angel Harvey, senior product manager – variable information and prime paper, Avery Dennison Label and Packaging Materials, notes, the liner serves as a label’s backing before conversion and application, protecting the adhesive during shipment, storage and converting. During the application of the label, the liner is peeled away, and a silicone-based coating on the liner’s side facing the adhesive allows for the liner’s fast and easy removal.
Functionally, the liner serves as an adhesive carrier, release surface, dieutting base and label transporter, all while preventing oxidation
AWA Alexander Watson Associates, host of the AWA Global Release Liner Industry Conference & Exhibition, has studied this segment extensively. Based on AWA’s data, the global release liner market accounted for 56,748 million square meters in 2020. Asia represents 40% of the market, while North America and Europe comprised 27% apiece.
According to Corey Reardon, president and CEO of AWA, and his team, the global release liner market experienced growth in 2020 despite the COVID-19 pandemic. Asia was a significant driver of the segment’s growth, as it contained the spread of the outbreak much earlier. These steps enabled quicker recovery.
“Overall, worldwide annual market growth in 2020 was estimated to be 2.7%,” AWA states in its Global Release Liner Annual Review. “Going into 2021, AWA forecasts a growth of 4.0% globally as some market segments recover and others stabilize.
“Worldwide, compound annual volume growth expectations are forecast to be approximately 3.8% for the period 2020-2023, which is expected to generate an additional estimated 6,790 million square meters of release liner by 2023,” the report continues.
Multiple materials make up the release liner landscape. Glassine/SCK paper is the predominant material, as it comprises 36% of the global market with 20,377 million square meters. Polyolefin coated paper and clay coated paper account for 16% and 13% of the market, respectively. Meanwhile, PET films are the driver in the filmic space, representing 7,629 million square meters and growing at a rate of 4.5% – the biggest growth rate of all materials. PE films and PP films garnered 6% and 2% of the global market, respectively.
“There are regional differences regarding release liner base, but glassine/SCK papers dominate, representing 36% of worldwide demand,” states AWA. “This is largely driven by their use in the high-volume pressure sensitive label market. Film release base now accounts for 22% of the worldwide total.”
AWA’s research shows that the largest segment for release liners is pressure sensitive labelstock, which accounts for an estimated 48% of the total global market. The tapes segment follows, with 14%, and the total industrial segment (building and construction, composites, electronics, and other industrial) with 12%.
Most every product in the label and package printing industry is designed with sustainability in mind, and release liners are no exception. Suppliers are increasingly developing alternative carriers and coatings, as well as products that are designed for recycling like downgauging material.
“The release liner industry is further developing ways to become more sustainable, exploring every aspect of the value chain to see where sustainability improvements of all kinds can be made,” comments Mondi’s Lackner. “We’re creating end-of-life-scenarios and closing the loop for release liners. Looking at the entire value chain is essential. We at Mondi work together with customers and suppliers in order to create a sustainable product and process from the bottom up.”
Avery Dennison has established a pilot program with RoadRunner Recycling for matrix waste recycling to divert waste from landfills in North America. The company also works closely with converters looking to recycle their film and paper liner recycling, helping connect them with recyclers in their area that can support these initiatives.
“Label liners make up a relatively small part of a packaging solution, but they can have a big impact on sustainability,” says Avery Dennison’s Harvey. “As part of our efforts to reduce the environmental impact of labeling and help establish a circular economy, an increasing percentage of our liners and other label materials are responsibly sourced, made with recycled content, use less material and are recyclable.”
Avery Dennison identifies liner selection as a critical part of this process, as well. The company’s thinner liners are produced with fewer fossil fuels, water and energy, resulting in fewer greenhouse gas emissions and less waste. Thinner liners also allow for more labels per roll, reducing transportation and waste along with changeovers, downtime and the space needed for storage. Plus, Harvey adds, rPET liners are made with 30% post-consumer recycled content from PET bottles.
Lackner concedes that the industry still needs to make strides in the liner recycling process. Mondi leans on a special infrastructure to provide collection and sorting streams to address various aspects of matrix and release liner recycling, including analyzing technical issues and promoting the use and creation of recycling networks.
“Currently, release liners are often discarded once the PSA products are used, but technically release liners can be recycled,” adds Lackner. “This requires a recycling infrastructure, which is still being researched and developed. There are technologies in place, but it is all about making sure that they can cover the needs of the industry.”
As Calvin Frost, founder of Channeled Resources Group and longtime L&NW columnist, explains, silicone release liners – both paper and film – are recyclable, with one exception. “The anomaly is polycoated liners,” says Frost. “These liners are used in a variety of applications where stay-flat characteristics are required. Interestingly, because our industry has become more interested in sustainability and reducing non-recyclables from the landfill, we are seeing heavier clay coated liners, which are recyclable, replace polycoated product. They provide the same stay-flat characteristics and are competitive in price.”
However, this begs the question: If liners are recyclable, why aren’t we as an industry recycling more than 7-10% of available liners? “The answer is logistics and packaging,” continues Frost. “These two issues can be solved if the supply chain is willing to commit to following simple practices. There is a third problem, which is more complex, namely education. We need to teach the paper industry that there is value in the fiber, and that silicone is not deleterious to the recycling process. If we focus on solving these three problems – packaging, logistics and education – we have an opportunity to redirect upwards of 400,000 tons per year of spent liner from the landfill into useful applications.”
To further promote recycling in this key area, Mondi joined CELAB (Circular Economy for Labels) in 2020. CELAB is an industry-led initiative founded by companies in the self-adhesive label industry to create greater circularity for its products. By joining this consortium, Mondi will collaborate with partners to facilitate the recycling of release liners.
While sustainable endeavors are critical on the manufacturing level, Mondi has also partnered with its customers to help streamline this process. The company performs research and in-house calculations in order to support customers’ targets, which often include conducting CO2 calculations to fully understand what impact these products have at a comparable level.
“Many customers do appreciate guidance when it comes to understanding how release liners can support the sustainability of their products,” says Lackner. “For example, we can optimize transport costs through the lighter weights of certain papers, improve energy use in production, focus on sustainable procurement or use recycled fiber offerings to reduce the CO2 footprint.”
In 2018, Mondi unveiled a customer-centric EcoSolutions approach, where it works together with customers and partners in the value chain in order to meet their sustainability goals. Mondi developed an agenda specific to its release liner plants to work toward a holistic approach in creating not only sustainable products, but a more sustainable value chain.
“Mondi starts at the beginning, such as getting more sustainable raw materials for products, optimizing logistics, and focusing on local supply chains in order to reduce the carbon footprint of our own production, considering the circularity of the product by looking at recycling options and collection streams, so that products can stay in a circular economy,” Lackner adds.
Suppliers have engineered a wide range of solutions to optimize the performance and recyclability of release liners.
These products have come a long way to reach their current functionality. According to Channeled Resources, early silicone polymers were silicone gums dispersed in solvent, and this technology was developed in the 1940s. These dispersions were needed to get silicone diluted or thin enough to be applied with coating technology at that time.
“Silicones were emulsified and diluted in water in an attempt to move away from solvent dispersion,” explains Tom Ray, technical director, Channeled Resources Group. “In the 1970s ‘solventless’ silicone technology was developed using platinum and rhodium catalyst systems, and multi-roll coating technology was developed to apply thin films of silicone. This was the standard for many years. Recently, polymers have moved to lower viscosity, with the addition of anti-misting additives as coating speeds have increased. Anchorage additives have improved the silicone adhesion to film substrates. And most recently, next generation anchorage additives, coupled with faster crosslink technology, are pushing platinum catalyst levels down for improved cost while retaining good anchorage and cure.”
Avery Dennison’s popular paper liners include 40# SCK, 40#CK, 44#PK and 40# BG. Super calendared liners have proven to be excellent in diecutting, says Harvey, and they’re ypically used for roll-to-roll applications. The 40# SCK and 40#CK liners are optimal for paper facestocks, with 40# BG the ideal choice for film facestocks. Meanwhile, 44#PK has been engineered for both paper and film facestocks.
Avery Dennison’s filmic liners provide a no-label appearance and strength. However, they are not suitable for perfing, punching or fanfolding, and are strictly intended for roll-to-roll. Machine-finished or lay-flat liners are often used on prime and industrial label applications when the labels are sheeted. “PET is the second most common liner material with a growing market share,” says Avery Dennison’s Harvey. “Paper and PET liners can both be paired with paper or filmic facestocks.
“Technology in coatings continues to evolve in a variety of segments, whether that is specialty into high performance applications or into broad coatings utilized in the PSL industry,” adds Harvey. “Avery Dennison continues to look at coating technology, as well as materials used in the release liners, for ways to continually innovate in this space.”
According to Mondi’s Lackner, release liner technology has improved in terms of speed. High-speed coating is one aspect, and other technological developments include double coating heads. These allow for the coating of two sides of a base material in just one machine run, enabling higher operational efficiency.
“High-speed printing further allows the production of customized release liners to meet customers’ requirements,” explains Lackner.
Mondi, which boasts a wide breadth of release liner products, recently launched its EverLiner labelite and EverLiner M R products. EverLiner labelite is a lighter option to standard glassine liners for label applications, with the same thickness of 58 gsm glassine but engineered to a reduced weight of 47 gsm. This results in 20% material savings, the company notes, and its lighter weight allows for optimized transportation.
Meanwhile, EverLiner M R is the first release liner on the market using a recycled base paper, adds Lackner. The machine glazed paper (MG) with 70% FSC-recycled certified content reduces the number of fresh fibers used, and the FSC certification ensures responsible sourcing.
Mondi has also debuted its NextLiner, which utilizes a recycled base paper with a coating made from renewable resources. “This is the world’s first sustainable polycoated kraft (PCK) paper release liner,” adds Lackner. “Using recycled fibers and renewable materials can have a positive impact on the environmental footprint of NextLiner, used in graphic arts, tapes and other industrial applications.
As release liners continue to improve in terms of performance and recyclability, there is a growing trend toward linerless labels – which undoubtedly influences the liner market. There are benefits and challenges associated with this space, and UPM Raflatac has been quite active in promoting the segment.
For example, UPM Raflatac recently partnered with Toshiba to provide linerless label products to the European market. Through this collaboration, customers of both Toshiba and UPM Raflatac can take advantage of the tested and approved combination of Toshiba’s BV420D-GL linerless printer and UPM Raflatac’s OptiCut linerless label material.
“E-commerce business is requesting flexible, efficient and sustainable solutions,” says Angel de Juan, general manager, Toshiba, Auto ID Europe. “By partnering with UPM Raflatac we are able to offer our European customers a global linerless portfolio, which is a perfect match with our newly launched linerless printer.”
UPM Raflatac has announced the launch of its newly developed Linerless OptiCut product. UPM Raflatac’s in-house-developed adhesive technology used in OptiCut is available for each of the primary direct thermal linerless end-use environments – from retail and logistics to quick service and takeout restaurants. OptiCut minimizes service time and offers customers a linerless product with maximum uptime of printer applicators, fewer reel changes and a crisp barcode on the package, the company says. “We have developed OptiCut in collaboration with our partners across the value chain. Our innovative and sustainable solution is the optimal choice when you are looking for clean cutting performance on the printer combined with excellent adhesion on the package,” says Mauri Suomela, senior vice president, paper laminates, UPM Raflatac.
Linerless innovation is growing at a rapid pace, too. NAStar Inc. has patented TwoFer Shelf Tags, which are back-to-back shelf tags without a liner that use an alternating adhesive and release coated pattern designed for the retail sector. Users can easily pull apart TwoFer Shelf Tags from one another, doubling the label quantity per sheet of material while eliminating liner waste. Plus, TwoFer Twin Signage, with two facestocks and no liner, is the newest member of NAStar’s sustainable TwoFer Linerless Label Solutions product line. This fully recyclable product supports the sustainability goals of its users by having zero liner waste.
“The TwoFer family of products eliminates silicone-coated liners and has two pattern-coated face sheets married together,” explains John Short, marketing director at NAStar, Inc. “The TwoFer Shelf Tags themselves are two paper-based labels constructed together, and they have film-like performance and excel in a variety of retail environments, even in the refrigerator and freezer sections of the store, without curl. When separated, you’re left with two useable, unique shelf tags that are ready to be affixed on the shelf.”
Linerless products can be advantageous, and the adoption of thermal linerless labels offers several advantages. These include more labels per reel, variable label length, less storage space, less weight and bulk for lower transportation costs, and no release liner waste. There are challenges, though.
“Any challenges are mainly related to the limited possible label shapes and the need for specific dispensing devices, which include cutters that can handle exposed adhesives,” notes Mondi’s Lackner. “Linerless solutions can therefore be a valid option for certain defined applications such as retail and weigh-scaling labels, transportation and warehousing, fast food package sealing and more.”