Collect Rubber From Multiple Waste Streams
Of the 50 million pounds of waste rubber that Ecore uses each year, the majority comes from scrap tires; other sources include tire buffings, roofing membranes, and industrial plants. The York, Pa., company prefers commercial tires, which make up about 90 percent of the shredded and whole tires delivered to its plant, due to the rubber’s quality and consistency. Besides rubber, tires also contain steel cord, nylon, and a slew of debris picked up over time—rocks, stones, glass, chewing gum—none of which can appear in the finished products.
Liberate the Rubber
The shredded tires are sent through an attrition mill—dubbed the “Liberator”—that vigorously knifes apart and cuts down the shreds. Air is used to separate the materials by weight. This initial pass at separating debris and metal from rubber extracts about 90 percent from the roughly 2 tons of scrap steel that Ecore recovers from scrap tires each day. A series of vibratory beds and air further separates the debris from the rubber.
Distill the Rubber Again and Again … and Again
The rubber, which still has some contaminants such as stones and small bits of metal, is transported inside the plant through negatively pressured ductwork. Ecore uses a triple-distillation process that sends the particles through a series of vibrating screens, magnetized beds, and de-stoners to extract the rubber from other materials. The rubber is milled into smaller particles and screened by size into designated stockpiles. Ecore uses about 10 different particle sizes. Very little is wasted: Even the dust captured by the plant’s air filters is collected for reuse in applications such as asphalt and paint.
The rubber particles now enter the manufacturing stream to become floor tile, carpet backing, or acoustical insulation. A machine resembling an oversized cake mixer blends the rubber with a binder, color admixture, and binding catalysts for about 8 minutes. The mixture is transferred to a pressurized, 76-inch-tall cylinder where it gestates for a day. The halves of the cylinder—or cake pan—are then unclamped, revealing the congealed mold or log, which can be cut and peeled like a Swiss roll into a rubber mat at the desired thickness. At 2 millimeters thick, the mat can span 1 mile in length.