Recycling Compatible Adhesives

By Steve Katz | July 7, 2009

Commercially available, RCAs allow converters to become greener while helping the paper recycling industry.

Sustainable practices can range from the general to the very specific, and converters can examine each application and portion of the workflow to find places where they can become more environmentally friendly. There are certain jobs that afford converters the opportunity to use consumables that make them greener that might not exist in other applications. An example is Recycling Compatible Adhesives (RCAs), designed for use on paper-to-paper applications. Think about a piece of direct mail with a label on it, or simply a postage stamp affixed to an envelope, and you get the idea.

Before going further, in order to eliminate confusion, it's important to point out that adhesives themselves are not recyclable. Paper is, of course. But when self-adhesive labels are affixed to paper, and the paper then enters the recycling stream, problems arise in the paper recycling process. Paper labels attached to paper products can interfere with the recycling process if the adhesive cannot be removed. RCAs were developed to address these issues and help the paper recycling industry.

The players

There are several key players that have been and continue to be involved in the development and subsequent push toward increased RCA usage. Among these entities are the United States Postal Service (USPS), the Forest Products Laboratory of the USDA Forest Service, and the Tag & Label Manufacturers Institute (TLMI). There's also a story to how it all got started.

"It's become something of an urban legend as far as what pushed it over the edge," says Carl Houtman of the Forest Products Laboratory (FPL), Madison, WI, USA. "As the legend goes, in the early 1990s, some students were learning about recycling, and in their research they came across recycling problems caused by postage stamps. So the kids wrote letters to the US Postal Service, thus bringing the issue to the attention of the USPS, which in turn took the issue very seriously – so the story goes," Houtman says.

What happened next is not legend, but a well documented process that defined the terms and processes involved in the creation of RCAs. Houtman explains: "In 1995, the USPS sponsored a conference during which the adhesive industry was invited to participate in its Environmentally Benign Pressure Sensitive Adhesives for Postage Stamp Applications program. Thirteen companies participated by submitting adhesive samples. To determine whether an adhesive was recycling compatible, a protocol needed to be developed. The results of this work led to a three-tier evaluation process with the development of laboratory, pilot-scale and mill-scale recycling protocols."

The Forests Products Laboratory was commissioned by the USPS to develop the testing protocols for qualifying what would become known as Environmentally Benign Adhesives (EBAs), which were the precursor to RCAs. EBAs were tested and qualified by the USPS for their specific usage on postage stamps. RCAs are distinguished from EBAs in that they are adhesives or adhesive coatings for the broader-based product applications.

Along with Houtman, Richard Oldack, the founder of Dyna-Tech, an adhesive manufacturer based in Grafton, WV, USA, also played a major role in the R&D, testing, and promotion of RCAs. As the first chairman of TLMI's Sub-committee on Recycling Compatible Adhesives, Oldack worked with Houtman and Fred Gustafson of 3M, Office Supplies Division, to educate the label industry and develop and simplify the testing and qualifying process.

Oldack wrote the testing protocols for RCAs ­with the label converter in mind. "Label construction differs from PS stamps in that stamps have a water-soluble barrier between the paper and the adhesive. We took the USPS EBA specification and tests from the Postal Services Specification USPS P-1238F and rewrote them to make them apply to labelstock. We wanted to make it simple for label converters to qualify their products," Oldack says, adding that there are obstacles to overcome. "Usually when you introduce a new product to the market, there are two main objections – cost and technical. The reason why I wrote several papers, published in TLMI's Illuminator and in Progress in Paper Recycling, was to overcome the technical objections," he says.

TLMI has since adopted the USPS EBA/RCA standards as its guideline for converters that wish to qualify their adhesives as being recycling compatible.

Fred Gustafson is the current chair of the TLMI Sub-committee on Recycling Compatible Adhesives. He talks about increasing a converter's awareness. "The TLMI sub-committee on RCAs has been working to encourage the use of RCAs in paper-to-paper labels. We are happy to report that RCAs and RCA label products are commercially available. Customers are now buying these labels and using them on catalogs, envelopes, and other applications. Help the paper industry and help your business. Ask your adhesive supplier for recycling compatible adhesives for your paper-to-paper labels. If all PSA labels were converted into RCAs, it would have a huge, positive impact on the paper recycling industry. Remember, paper is now more likely to be recycled than landfilled. That means more paper labels are being recycled than ever before," Gustafson says.

The process

Recycling compatible adhesives have everything to do with the paper recycling process. Current recycling statistics reveal that it continues to be on the rise. Gustafson says that in the US the recycling rate is now 57 percent – the highest it's ever been. With that said, more labels are being recycled than ever before as well.

With the paper recycling rate in the US at an all-time high, Gustafson notes that the importance of the recyclability of waste paper has never been greater. "Paper labels with pressure sensitive adhesives are a component of waste paper, being used on folders, envelopes, magazines, boxes and other paper products. This means that many labels will end up in the recycled paper waste stream. Converters now have the opportunity to improve the recyclability of waste paper by converting to RCAs on their paper-to-paper labels," he says.

A closer look at the paper recycling process reveals the burden caused by conventional pressure sensitive adhesives. Paper that goes to the recycling stream contains a host of substances that are considered contaminants, including inks, plastics, metals and adhesives. While the recycling process takes measures that remove these contaminants, conventional PSAs are a problem.

Paper recycling involves reducing the paper to a pulp, followed by screening the pulp. "During the pulping of waste paper, paper labels are broken down into paper fibers and adhesive particles. The shear forces in the pulper tend to shred the adhesive into small particles that pass through the screens that follow the pulper," Gustafson explains.

The problem arises in the production and use of the recycled paper pulp. According to the standards developed by the USPS, here's what happens: "PSAs present in recycled paper can become small particles during processing and result in 'stickies' that can build up on process equipment and cause defects in the final paper product. Paper recycling mills pay a price for stickies problems including lower product selling prices, down time, and equipment clean up costs." Today, the cost of stickies to paper companies is estimated to be more than $850 million per year.

"The most problematic adhesives are those that are attached to a paper backing such as paper labels. During pulping, as the paper is reduced to individual paper fibers, the adhesive tends to shred into particles that are too small to be easily removed," according to the USPS.

RCAs have been created to alleviate the problems caused by stickies, thus ensuring that the paper the adhesive is adhering to remains recyclable. "RCAs are designed to resist these shear forces and remain large enough to be removed by screens. The remaining adhesive passing through the screens is substantially removed by flotation," Gustafson explains.

In other words, RCAs resolve the stickies problem by keeping the adhesive large enough so that it won't pass through the screen, continue through the recycling stream and gum up the equipment and machinery. And it's an effective process, adds Gustafson. "In laboratory and pilot scale recycling trials, more than 99 percent of the adhesive was removed by a combination of screening and flotation, two common cleaning operations in the recycled paper industry. Screening removes materials that are larger than the screen opening, typically 0.004" to 0.006". Flotation removes small particles by passing air through a pulp slurry containing a surfactant. The small particles attach themselves to air bubbles that come to the surface in the foam," he says.

The RCA specification and test methods adopted by TLMI are derived from the US Postal Service Specification P-1238F for postage stamps with EBAs. By meeting the RCA specification, an adhesive supplier or converter can qualify either an adhesive or an adhesive coated paper product as recycling compatible. Qualified PSAs also conform to the requirements of Federal Executive Order EO 13148, Section 702, "Greening the Government Through Leadership in Environmental Management – Environmentally Benign Adhesives." This executive order required the use of RCAs in all US governmental paper to paper label applications.

Oldack outlines the hypothetical chain of events in an article published in Progress in Paper Recycling (February 2005) that could one day lead to RCAs becoming the industry standard. "First was the adoption by the USPS for its pressure sensitive stamps. Second is the implementation of EO 13148 throughout the Federal government, which requires usage of RCAs for all PS paper to paper labeling applications. Next, individual states would start insisting on them, followed by the retail markets," he states.

Recently, the state of Wisconsin mandated that all of its adhesives be RCAs, a landmark for the RCA movement. So, the ball is rolling, but educating the label industry continues.

The push, performance and price

While adhesive and labelstock suppliers have taken the issue of sustainability head on, there is now a concerted effort to offer consumers RCAs. The USPS converted all of the adhesive on self adhesive postage stamps to RCAs in 2001. Since then, their commercial availability continues to grow and converters can purchase RCAs from several adhesive suppliers. The consensus among labelstock and adhesive suppliers is this: Generally, they should not cost more than conventional adhesives and they perform just as well.

Mike Witte, manager, Pressure Sensitive Adhesives Business, Franklin Adhesives & Polymers, Columbus, OH, USA, discusses his RCA observations. "We are seeing more and more inquiries for adhesive products that have any kind of 'green' attributes, and that certainly includes recycling compatibility. Historically, end users have not been willing to pay a premium for such attributes, which slowed entry of these products into the marketplace. I think this is changing as awareness grows and the ability to differentiate products by virtue of environmental friendliness gives label producers competitive advantages. I think the next steps will be to develop and promote sustainable materials for both face and adhesive materials; and that biodegradability will become the next target for both facestock and adhesive," he says.

Franklin Adhesives and Polymers has gained RCA certification in part as a result of the division's joint research project with the University of Minnesota, which was funded by the US Department of Energy, to reduce or eliminate residual adhesive from waste paper during recycling. "Residual adhesive adheres to papermaking equipment during the manufacture of paper from recycled paper, leading to machine down time and specks or tears in the final paper products. We focus on developing green adhesives and the university research team wanted to test our pressure sensitive adhesives for recycling compatibility. They found that three of the formulas we provided them are easily removed from paper during re-pulping," Witte says.

Franklin offers two FPL-certified recycling compatible adhesives: Covinax 324-39 and Covinax 379-05. "Covinax 324-39 is a vinyl acrylic co-polymer for general-purpose permanent pressure sensitive adhesives on tapes and labels. It is used for corrugated substrates, polyolefin films, glass and metals and is easily converted into rolls or sheets without sticky edge problems. This formula can be transfer-coated on most rod, gravure or roll coaters.

"FPL-certified Covinax 379-05 is an acrylic adhesive for permanent pressure sensitive applications, including pharmaceutical label applications requiring adhesion to curved or irregularly shaped surfaces. The balance between peel and shear strength also renders this formula easily convertible to rolls or sheets. It is specifically designed to be transfer-coated on slot die coaters and can be used on most rod or roll coaters," Witte says, adding, "In our case, the products that are recycling compatible are very cost effective; no development costs were incurred to achieve recycling compatibility."

MACtac, Stow, OH, USA, is another adhesive manufacturer that is heavily involved in increased RCA usage and has USPS qualified products. MACtac met the specifications set forth by the United States Postal Service that cover pressure sensitive adhesive stamp papers with liner, used for producing postage stamps that are recyclable.

Allison Hazel, marketing manager, MACtac Printing Products, discusses the qualification process. "Qualified suppliers have demonstrated their ability to produce stamp paper (facestock), release liner backing and pressure-sensitive adhesive in compliance with the requirements of the Specification USPS P-1238F. Once MACtac demonstrated our ability to do this, we were listed on the Qualified Products List (QPL). It is a mandatory requirement that all stamp products procured for US postage stamp production are obtained from one of the qualified suppliers," she says.

Hazel notices the recent attention RCAs have been getting. "The last several years have seen a boom of both desire and need for environmentally friendly products, including labelstocks. We receive requests weekly and sometimes daily for information on RCAs. MACtac's ST95 and MP910 adhesives are two of our best selling acrylic emulsion permanent adhesives and function well in many areas," she says.

"Ultimately RCA adhesives are better for our environment because they allow paper to be recycled without the adhesive clogging the screens during the recycling process. But the question always comes back to price, and will the printer and the end user pay for what is good for the environment. I do believe that the green movement is here to stay, and we will begin to see more government regulations in the future that will require improvements for recycling products. At MACtac, they do not cost more, but depending on where they are sourced, they could, potentially."

Dyna-Tech is another adhesive manufacturer working toward to the promotion of RCAs with the goal of making them a mainstream option for label converters. The company manufactures a variety of RCA qualified products as well as those that are USPS EBA certified. Dan Ratka, technical director for Dyna-Tech, says, "RCAs perform the same as other adhesives. Most are for general purpose permanent adhesives applications, but one of the things we're trying to do is build an emphasis on applying RCA technology to all adhesive applications. It's possible to make all different grades and varieties. I am confident the technology can be expanded to anything."

Like Richard Oldack, Ratka emphasizes education and says that when people start asking for it, RCAs have the potential to become the mainstream option. "People don't want to use it unless it's going to be required by government or the end users ask for it specifically. We're trying to educate people. There is no drop in performance at all. The limitation is more in the chemistry to make it. In general, because you have a limited selection of materials to make them, it's more difficult to reduce costs. You're using the same materials, but the blend is different. So it's in our hands, the adhesive makers. It's not harder to make, but it limits the raw materials that can be used. The chemistry isn't more difficult, it just has to be developed. For now, demand is lacking because people are simply not aware of it," he says.

Kevin Rinehart, market segment leader, sustainability, for Avery Dennison Fasson Roll, Mentor, OH, USA, says that while he hasn't found there to be an increased push for RCAs, education has been a priority due to how specific RCA applications are in the labeling industry. "EBA and RCA acronyms can be misleading and drive assumptions that these are good for things in general, when they are actually somewhat specific in the environmental benefit they deliver," he says.

The company markets two adhesives as EBA/RCAs. "When used as designed, these adhesives do not distinguish themselves from a performance standpoint in coating or converting processes. We consider these general purpose emulsion adhesives that work across a variety of applications. We do not position RCAs at a premium. This is, of course, dependent on the total PS construction. For example a custom spec with an RCA might be positioned at a premium to a stock product. Performance of these adhesives is, in many cases, equivalent to non-RCA counterparts. There is not a significant trade-off or highly improved performance in converting, unless you consider the end of life scenario where the adhesive delivers its unique functionality.

"I know TLMI is putting a concerted effort behind this technology and I support the effort. However, the opportunities to spread this technology are limited by the application needs. It does not make sense for us to market RCA technology in the beer and beverage marketplace where the substrate is glass or plastic and the adhesive does not 'pay off' in the end of life."

Laura Cummings, environmental and sustainability manager, UPM Raflatac, Mills River, NC, USA, talks about the importance of gathering all the facts regarding an application when it comes to achieving sustainability. "Many label applications are sufficiently different from postage stamps that simply specifying a paper label with an RCA adhesive on any wood fiber based substrate is probably not sufficient to guarantee the end product is recyclable. The important thing is that the entire supply chain works together to design end products that are readily recyclable," she says.

Cummings says that specifying use of an RCA is helpful for customers who want to promote the recyclability of a product that is already commonly recycled (like a cardboard box). "RCAs are also helpful to customers wanting to maximize the potential for a labeled product that is not widely recycled to be successfully recycled (like some retail packaging). However, it is essential to consider the composition of the material to be recycled in its entirety to make credible recycling claims. A paper label with an RCA on a plastic package is a recycling challenge, to say the least. RCA products provide additional value to our customers and their customers regarding the versatility of the product and applications / specifications that are met. RCA may be laminated to materials that are either certified or contain post consumer waste, which would have an additional charge versus our standard products.

"We believe in the long term. As manufacturers continue to redesign packaging to be right-sized and recyclable to meet customers' demands for green products, more packaging material bearing pressure sensitive labels will be collected for recycling. We also expect over the long term as demand decreases the availability and increases the cost of commodities (including paper fiber), the more cost-effective it will become to recycle these materials. And as recycling increases, the demand for RCAs will increase."

Information on how to qualify adhesives and adhesive coated products is available on the TLMI website at http://www.tlmi.com/recycling-standards.php.

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