RECYCLING : No Longer Glossing Over Magazine Pages
Glossy magazines have now joined the paper trail into the recycling revolution.
Until recently, glossy paper magazines and catalogues tripped up recycling mills. The clay-based coating that creates sheen was hard to remove, and inks tended to cling to the clay.
“Glossy magazine paper has bright, strong fiber that’s valuable for recycling efforts, whether you’re making recycled newsprint, copier paper or paper towels,” said Sandra Foley, manager of International Paper’s Lock Haven, Pa., mill.
The key is new flotation de-inking systems that American paper mills are adopting and refining--technology that European and Japanese mills have exploited for nearly 30 years.
The paper trail begins when collection trucks deliver magazines and catalogues to a materials-processing facility. Besides de-inking, magazine paper must undergo a series of steps to remove other contaminants--everything from wax to staples to lost TV remote controls.
At the processing plant, a conveyor belt carries the magazines across an elevated sorting area. There, workers pluck off obvious contaminants, such as plastic grocery bags.
The conveyor moves the magazines to a baler or into sturdy boxes called gaylords. Bales or gaylords travel by truck or rail car to de-inking facilities.
When the magazines first arrive at the de-inking plant, they move through a wire cutter, where a blade slips under the baling wire, cuts it and releases loose magazines onto a conveyor. Workers seize any remaining visible contaminants.
The pulper acts like a giant kitchen blender, stirring the paper with water into a thin, porridge-like pulp. Caustic chemicals may also be mixed in. As the fibers expand, ink bursts free, ready for later removal.
From the pulper, the liquid--pulp is roughly 95% water--will run through a series of purifying steps. The order and number of these steps depend on how clean the pulp must become for the final product. The inside of a cereal box, for example, needn’t be pristine white. Newsprint requires clean pulp. Most mills consider the sequence of these cleansing processes a proprietary secret.
Ink removal was the big problem until the recent introduction of flotation de-inking. The process floats the ink away on bubbles. Inside a flotation de-inking vat, nozzles inject air into the pulp, touching off bubbles that rise to the top. As they ascend, the bubbles pick up ink from the fibers, forming a gray foam on the surface.
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“The flotation process is very similar to the bubbles that are formed when you wash dishes, do laundry or give your child a bubble bath,” Foley said.
Different processes remove other contaminants, such as glues, non-paper inserts and staple wire. Plastics, adhesives and hot melts are particularly characteristic of magazines and catalogues. Collectively known as “stickies,” they are difficult to capture and remove.
To purge the pulp of these and other contaminants, plants use centrifugal cleaners to separate fiber from materials that are either lighter or heavier.
In addition, mills pass pulp through pressure screens, surfaces punctured with holes or slots. Round holes tend to capture flat, flaky materials and thin debris such as wires and hair. Slots are more effective in eliminating chunkier waste.
After magazine pulp has been thoroughly cleaned, it heads for the final step--the paper machine.
As mills compete for old magazines, communities benefit because trash-disposal problems dwindle. The amount of recycled content in newsprint is expected to reach an average of 40% by the end of the decade.
