A Landmark case: Using more scrap need not mean adding more contaminants

Incorporating more recyclate and scrap into products can help you reach your sustainability goals and trim your resin purchasing costs. But no matter how controlled the source of the scrap is, it also will introduce more contaminants into your process. Landmark Plastic Corp. shares its solution.

Landmark (Akron, OH) is a processor of thermoformed and injection molded plant packaging systems, supplying its customers (mainly distributors and greenhouses in North America) with more than 500 SKUs from its 200,000-ft² processing facility. According to the U.S. Dept. of Agriculture (USDA), the “nursery and greenhouse” crops industry in the United States is worth more than $17 billion/yr, with more than 7000 operations throughout the country. Supporting this industry from the U.S. plastics processing industry are more than a billion plastic pots and flat trays.

Landmark incorporates an increasing percentage of postconsumer scrap into its molded and thermoformed plant packaging.

For Landmark, this demand, coupled with the push toward greener practices, means the processor takes in more and more plastic scrap to be used to process new pots from recycled material. No matter how secure the source, introducing more scrap to a compound’s recipe will also introduce more contaminants.

“We take in millions of pounds of someone else’s scrap every month,” says Brian Maloney, production manager for injection molding at Landmark. “All of it is heavily contaminated with both ferrous and nonferrous metal, and it’s all dumped into our material hoppers daily.

“We’re increasing our use of scrap plastic every day. It’s what our customers want and, because of the lower cost over virgin plastic, we’re seeing the effect on our bottom line.”

To bring this scrap up to the quality evels required, Landmark officials chose a trio of equipment supplied by Eriez (Erie, PA) for detecting and separating this contamination. Upon delivery to its facility, Landmark runs the scrap it sources through an Eriez SC-481 Syncro-Sieve screen separator to separate fine plastic dust from the scrap. A rotary motor with an adjustable weight system powers the units, allowing for application-specific separation control. Depending on how the weights are positioned, the flow pattern on the screen decks is affected, increasing or decreasing the product retention time and in turn improving or reducing the separation efficiency, enabling users to adjust the system based on test sampling of the scrap (if more impurities, then increase the retention time).

Thanks to metal removal and other safeguards, Landmark’s increased use of PCR has not resulted in shorter life of screw tips and other delicate components of the injection machine.

The scrap then passes through a second system, a TGH2 magnetic grate that houses the supplier’s Xtreme-brand rare earth magnets, to remove any ferrous contamination. According to Eriez, removal of the magnets is easy, allowing them to be cleaned as iron collects on them. Finally, a pass through an E-Z Tec DSP low-profile vertical reject metal detector helps Landmark remove the nonferrous contamination; this third unit actually also can detect and remove ferrous, nonferrous, and stainless metal contaminants. The low profile makes the equipment easy to fit in tight spaces.

Maloney says prior to installing the three Eriez units, Landmark was using simple magnets to pull out all the ferrous contamination, “but the nonferrous metal was killing us. It ruined the screw tips and other delicate parts of our injection molding machines,” leading to excessive downtime. Landmark also uses Eriez’s magnets and separating equipment in its thermoforming operation where, as in its injection molding operation, 50% of the raw material base is now recycled. The magnets screen contamination to protect the raw material grinders in this part of the Landmark system. —Matt Defosse