Presidential Green Chemistry Challenge: 1996 Greener Reaction Conditions Award
The Dow Chemical Company
100 Percent Carbon Dioxide as a Blowing Agent for the Polystyrene Foam Sheet Packaging Market
Innovation and Benefits: Dow developed a process for manufacturing polystyrene foam sheets that uses carbon dioxide (CO2) as a blowing agent, eliminating 3.5 million pounds per year of traditional blowing agents. Traditional blowing agents deplete the ozone layer or contribute to ground-level smog. In addition, Dow will obtain CO2 only from existing commercial and natural sources that generate it as a byproduct, so this process will not contribute to global CO2 levels.
Summary of Technology: In recent years the chlorofluorocarbon (CFC) blowing agents used to manufacture polystyrene foam sheet have been associated with environmental concerns such as ozone depletion, global warming, and ground-level smog. Due to these environmental concerns, The Dow Chemical Company has developed a novel process for the use of 100 percent carbon dioxide (CO2). Polystyrene foam sheet is a useful packaging material offering a high stiffness-to-weight ratio, good thermal insulation value, moisture resistance, and recyclability. This combination of desirable properties has resulted in the growth of the polystyrene foam sheet market in the United States to over 700 million pounds in 1995. Current applications for polystyrene foam include thermoformed meat, poultry, and produce trays; fast food containers; egg cartons; and serviceware.
The use of 100 percent CO2 offers optimal environmental performance because CO2 does not deplete the ozone layer, does not contribute to ground-level smog, and will not contribute to global warming because CO2 will be used from existing byproduct commercial and natural sources. The use of CO2 byproduct from existing commercial and natural sources, such as ammonia plants and natural gas wells, will ensure that no net increase in global CO2 results from the use of this technology. CO2 is also nonflammable, providing increased worker safety. It is cost-effective and readily available in food-grade quality. CO2 also is used in such common applications as soft drink carbonation and food chilling and freezing.
The Dow 100 percent CO2 technology eliminates the use of 3.5 million pounds per year of hard CFC-12 and soft HCFC-22. This technology has been scaled from pilot-line to full-scale commercial facilities. Dow has made the technology available through a commercial license covering both patented and know-how technology. The U.S. Patent Office granted Dow two patents for this technology (5,250,577 and 5,266,605).
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