2003 Designing Greener Chemicals Award
Shaw Industries, Inc.
EcoWorx™ Carpet Tile: A Cradle-to-Cradle Product
Innovation and Benefits: Conventional backings for carpet tiles contain bitumen, polyvinyl chloride (PVC), or polyurethane. EcoWorx™ carpet tiles have a novel backing that uses less toxic materials and has superior adhesion and dimensional stability. Because EcoWorx™ carpet tiles can be readily separated into carpet fiber and backing, each component can be easily recycled.
Historically, carpet tile backings have been manufactured using bitumen, polyvinyl chloride (PVC), or polyurethane (PU). While these backing systems have performed satisfactorily, there are several inherently negative attributes due to their feedstocks or their ability to be recycled. Although PVC has, to date, held the largest market share of carpet tile backing systems, it was Shaw’s intent to design around PVC due to the health and environmental concerns around vinyl chloride monomer, chlorine-based products, plasticized PVC-containing phthalate esters, and toxic byproducts of combustion of PVC, such as dioxin and hydrochloric acid. While some claims are accepted by the Agency for Toxic Substances and Disease Registry (ATSDR) and the U.S. EPA, those resulting from publicly debated consumer perceptions provide ample justification for finding a PVC alternative.
Due to the thermoset cross-linking of polyurethanes, they are extremely difficult to recycle and are typically downcycled or landfilled at the end of their useful life. Bitumen provides some advantages in recycling, but the modified bitumen backings offered in Europe have failed to gain market acceptance in the United States and are unlikely to do so.
Shaw selected a combination of polyolefin resins from Dow Chemical as the base polymer of choice for EcoWorx™ due to the low toxicity of its feedstocks, superior adhesion properties, dimensional stability, and its ability to be recycled. The EcoWorx™ compound also had to be designed to be compatible with nylon carpet fiber. Although EcoWorx™ may be recovered from any fiber type, nylon-6 provides a significant advantage. Polyolefins are compatible with known nylon-6 depolymerization methods. PVC interferes with those processes. Nylon-6 chemistry is well-known and not addressed in first-generation production.
From its inception, EcoWorx™ met all of the design criteria necessary to satisfy the needs of the marketplace from a performance, health, and environmental standpoint. Research indicated that separation of the fiber and backing through elutriation, grinding, and air separation proved to be the best way to recover the face and backing components, but an infrastructure for returning postconsumer EcoWorx™ to the elutriation process was necessary. Research also indicated that the postconsumer carpet tile had a positive economic value at the end of its useful life. The cost of collection, transportation, elutriation, and return to the respective nylon and EcoWorx™ manufacturing processes is less than the cost of using virgin raw materials.
With introduction in 1999 and an anticipated lifetime of ten to fifteen years on the floor, significant quantities of EcoWorx™ will not flow back to Shaw until 2006 to 2007. An expandable elutriation unit is now operating at Shaw, typically dealing with industrial EcoWorx™ waste. Recovered EcoWorx™ is flowing back to the backing extrusion unit. Caprolactam recovered from the elutriated nylon-6 is flowing back into nylon compounding. EcoWorx™ will soon displace all PVC at Shaw.
Read on about the 2003 Academic Award.
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