Chemical Recycling of Polyurethanes and Applications for the Recyclates

Abstract

The recycling of thermoset materials, including polyurethane, has always posed unique challenges. Traditional approaches to recycling such materials include mechanical regrinding and the use of the regrind as filler. Chemical recycling of polyurethanes by such means as hydrolysis, aminolysis, and glycolysis, is for the most part considered economically uncompetitive compared to formulating with virgin raw materials. To protect our environment and avoid land filling with polyurethanes, BASF has invested resources and technology to develop what are believed to be practical approaches to the chemical recycling of polyurethane process and end-of-life waste. Initially, we employed the well-established glycolysis technology developed at BASF Schwarzheide, Germany. BASF Corporation's Wyandotte, MI, Laboratory has continued research and development in this area, concentrating on modifying the chemistry and process to suit our polyurethane customers in North America. Our second generation chemistry results in homogeneous recycled polyols with residual amine content of less than 0.1% in a "one-pot" process operating at ambient pressure and moderate temperatures. Further, it eliminates the need for installing sophisticated control mechanisms and minimizes the separation and disposal of any hazardous materials. Recyclate products made from RIM waste streams were to be available commercially in the fall, 1997.

The properties of the recyclate are generally dependent on the properties of the polyurethane waste stream. A glycolysate from a high density non-cellular rigid polyurethane, made using the second generation technology, can be reformulated into a variety of rigid and semi-rigid foams at up to 100% polyol loading while providing excellent mechanical and physical properties in the finished product. Examples include polyisocyanurate foam, insulation non-critical foam, structural foam, friable energy absorbing foam, low density void filling foam, elastomeric coatings, rigid non-cellular polyurethane, and molded semi-flexible foam. This paper describes our efforts in chemical recycling of polyurethane waste streams and our success in incorporating the resultant glycolysates into a wide variety of polyurethane products.