Waste Minimization in the Manufacture of Flexible Polyurethane Foams: Quantification of Auxiliary Blowing Agent Volatilization

Experimental investigations were conducted to quantify the volatilization dynamics of blowing agent loss and to examine innovative means to maintain safe worker conditions while simultaneously recovering the auxiliary blowing agent. Methylene chloride-blown polyurethane foams with representative formulations were prepared to determine overall weight loss, auxiliary blowing agent weight loss and foam temperature profiles versus time. Approximately 60 percent of the methylene chloride is lost within the first ten minutes of the process; the residual 40 percent is lost slowly by diffusion over 24 hours. Based on the collected data, a model was developed which predicts tunnel concentrations of methylene chloride as a function of formulation, tunnel length, conveyor speed and air flow. Retrofit of a foam line to isolate the tunnel and drastically reduce exhaust flows will eliminate worker exposure to isocyanates and significantly increase tunnel concentrations of the auxiliary blowing agent. This increase in ambient blowing agent concentration should allow for recovery by conventional means. A project to demonstrate this isolation/concentration/ recovery/recycle strategy is currently underway at a North Carolina foamer.