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Making performance paper greener

Mead joins list of papermakers to develop processes permitting recovery of troublesome paper packaging. Repulpable wet-strength board could be a major boost to paper recovery.
FILED IN:  Sustainability  > Strategy
One by one modified paper packaging materials that were prohibited from joining conventional paper recycling and recovery programs are being altered to make them acceptable to repulping operations that recover paper fibers. Early last year Weyerhaeuser Co. (Tacoma WA) announced that its RecyclaWax coated corrugated liner was proven repulpable in most paper recovery processes. Now Mead Coated Board System (Atlanta GA) has revealed that a new formulation for its wet-strength Carrier Kote® paperboard will permit that paper to be repulped with systems in place for old corrugated containers (OCC). Mead has been awarded a "composition and method" patent PW is told. At last October's InterBev show in Atlanta Bob Dover Mead Packaging's director of environmental technology told Packaging World that the company's two paper machines at its Mahrta AL paper mill will be converted to dedicated production of the Carrier Kote with the new formula by mid-1995.
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The development stems from the use of a new wet-strength resin at Mead's Chillicothe OH laboratory. It dissipates in a pulp slurry at temperatures as low as 110°F. Historically paperboard used for beverage multipacks like 12- and 24-count wraps for bottles and cans employed a resin additive that resisted the effects of moisture and humidity on the strength of the paper. This wet-strength additive would separate from the paper fibers in a pulp slurry but only at temperatures above 170°F. And Dover admits not many repulping operations were designed for temperatures that high. Consequently most paper and paperboard recycling programs specifically prohibited the inclusion of beverage overwraps just as they refuse to accept frozen food and dairy cartons. These packages are typically paper that is coated with polyethylene film or resin that delivers the same moisture resistance to the package. How important will Mead's development be to paper recovery? In terms of percentage of waste paper all wet-strength beverage overwraps account for only 1 to 2% of total discards. So even if Mead licenses all other beverage wrap producers to adopt the new formula the total volume affected won't be huge. But it's volume that simply could not be recovered at all in the past. Improving board quality In fact the most important effect of adding beverage overwrap material to the OCC recycling stream will be in improving the quality of the recycled paper produced by the mills that operate the repulping facilities. That's because the paperboard overwrap is still primarily made of virgin paper (80% virgin for Mead) that includes long paper fibers. The OCC stream in contrast is increasingly made up of corrugated that has already been recycled once or twice or more. Each time through the process the paper fibers are shortened. As the paper fibers are shortened the strength of the paper is reduced so you need more paper to achieve the same strength of virgin paper. In analyzing properties of paper grades Mead reports that its coated natural kraft Carrier Kote is some 40% stronger than OCC and 65% stronger than a coated recycled board. These measurements were based on a comparison of tensile burst and tear tests. By adding even a small percentage of virgin fiber from the beverage wraps it's believed that the performance of the resulting recycled corrugated liner will be enhanced. It's still far too early to tell whether that performance impovement will be measurable. Mead has only conducted repulping trials at its own mills. "Independent repulping trials are planned for the near future" says Dover. Thus far Mead has tested its new formula Carrier Kote board at levels up to as high as 25% in the OCC stream without any process problems he reports. Gaining acceptance As good as all this sounds Mead recognizes that it won't be easy to convince collectors and recyclers to accept and process its repulpable board-especially if the paperboard from another beverage company cannot be processed similarly. This is why Mead knows it will have to work with its customers and with state and recycling officials to promote the recyclability of its customers' carriers. Unlike Weyerhaeuser however Mead has no plans to offer its patented technology to competitors unless it's on a licensing arrangement. "Only our customers will have this material in 1995" Dover says. "After all we spent considerable time and money to develop this formula and process. Since we won't be pricing this material at a premium volume increases are the way we can recover our investment." Naturally Mead plans to persuade soft drink and brewery purchasing executives of the benefits of the new material and the need to have other paperboard vendors offer the same repulpable wet-strength board. By that time it's possible that other resin companies may offer additives to other paper companies that will offer the same performance as Mead's new paper does. Because all of Mead's wet-strength Carrier Kote will incorporate the new material some time this year it will have to be priced competitively with other carrier board. Whether end users will find a way to identify its recyclability is not yet known. Working with bioplastics If you thought degradability was dead welcome to 1995. Biodegradable plastic materials may in fact play a role in enhancing the environmental properties of paper packaging. EcoPLA(TM) from Cargill's Corn Milling Division (Minneapolis MN) is a bioplastic that may be used as a coating or film laminate that will allow both the paper and plastic to decompose naturally. What makes EcoPLA different from earlier biodegradable plastics is that this resin may be used in creating packages through converting technologies of coating thermoforming and by injection molding. The material however is still available only in small quantities from Cargill's 4-ton/yr pilot plant in Savage MN. Next year a full-scale production plant in Blair NE is expected to produce 50 tons/yr or more-assuming that product trials are successful. Because the material is most similar to polystyrene Cargill sees applications in thermoformed trays and deli containers as well as injection-molded cutlery. However the company also expects that EcoPLA will be extruded into film that can be used with papers. Because of inherent properties like high surface tension and a high coefficient of friction it may permit downgauging compared to coating with polyethylene. The resulting EcoPLA/paperboard can make drink cups and packaging that needs to be resistant to moisture and water. Still at a projected cost of $1/lb it's unlikely that the material would be used to convert coated corrugated into a repulpable material for recycling purposes. But it could be used with sanitary papers for more sophisticated applications. Overseas Novamont Milan Italy has developed Mater-Bi a corn-based plastic that is now being used to make bags for collection of compostable waste. The resin is being produced at Terni from a plant with a capacity of 24 tons/yr. All of these developments both here and overseas show the promise for converting paper packaging that can't be recycled today into high performance materials that will be reused in the future.

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