Process Makes Commingled Scrap Suitable For Molding

By: 
February 27, 2003

A company in Brigham City, Utah, ReSyk Inc., has developed a technique to make parts from mixed recyclate without the need to remove contaminants or separate polymers. Two companies now are using the technology.

ReSyk was formed in 1999 to commercialize recycling technology that creates bonds similar to crosslinking between different polymers, notes Chris Brough, chief operating officer. It supplies equipment in the U.S. and may license the technology elsewhere.

Brough says he has not found any combination of polymers that the process cannot handle. Bonds are formed directly between almost all polymers, including thermosets. Phenolics, however, don’t bond but act like fillers.

The technique can deal with non-ferrous metals, labels, paint, adhesives, solvents and other contaminants, Brough says. It can work with up to 40% oil-impregnated filter media, 10% copper, and 20% aluminum. ReSyk has made parts from feeds with 50% wood. Steel and glass, however, should be avoided because they cause significant equipment wear. Glass-filled polymers can be processed with some increase in maintenance costs, though.

In the process, a grinder reduces the feed to 3/8-in chips that then go to a special compounder. Batches of 1 to 10 lb remain in that unit for 4 to 13 s, depending upon their makeup.

The compounder uses high-speed blending at 200 to 400°F to create the bonds, says Brough. “We have found a way to slightly alter the different polymers to make them unstable… They will bond to form a stable molecular unit. This bond is permanent.”

Viscous blobs exit the compounder and immediately go for processing, generally via compression molding although extrusion also is an option.

Part properties typically resemble those of the most prevalent polymer in the mix, Brough says. So, end-product requirements may restrict potential feed streams. If desired, uv stabilizers and colorants can be used.

Because parts usually have a mottled look, the process is best suited for applications where esthetics is not crucial, Brough admits. Relatively large parts usually make most sense, as they maximize the cost advantage of using recyclate. ReSyk has prototyped products ranging from tire chocks to roof shingles to wire spools.

A system with a 3000-lb/h compounder and up to six presses for compression molding would run $350,000 to $450,000, says Brough, depending upon part size, while one with an extrusion line would cost around $350,000. ReSyk makes the compounder and buys the other equipment.

The first commercial system was installed at Bermco in Perry, ut, in mid-2000 to make garbage-can wheels. Since then, ReSyk has supplied two other units, to Universal Industrial Sales, Lindon, ut, for guardrail spacer blocks, and Recycled Plastic Products (RPP), Bluffdale, ut, for garbage-can wheels.

RPP has bought the Bermco unit and moved it to Bluffdale, says Todd Bogh, vp.

The company now produces about 2000 10-in- and 12-in-dia garbage-can wheels per day via 11 compression molding presses. These wheels are competitively priced but are solid, unlike rivals, and weigh 3 to 3.5 lb versus 1 lb, Bogh says. They are more stable and offer better performance, he claims.

RPP has just started molding other products including garden stepping stones and road barricades.

ReSyk’s Brough is hoping that several other units will be in place by year-end. An Indiana recycling firm is considering molding pallets from industrial waste, while a Wisconsin outfit that handles computer scrap may mold paving stones. A California company may turn agricultural plastics waste like sheeting into stakes by ram extrusion.

Even closer is a project for a Texas maker of pipe for drilling rigs. Hunting Composite, in Houston, intends to install a ReSyk unit by mid-year to mold thread protectors for pipe, primarily from used thread protectors.

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