EPA to fund 'green engineering' initiative

In an attempt to curtail the annual use of 36 billion pounds of toxic solvents in the production of acrylic polymers, the US Environmental Protection Agency (EPA) is funding 'green engineering' research by Virginia Tech chemical engineering professor Don Baird.

About six billion tons of acrylic polymers are produced each year, primarily for use by the textile industry in the manufacture of fibres. Baird is developing a process to replace the toxic solvents used in production of acrylic polymers with carbon dioxide (CO2).

Solvents reduce the viscosity of acrylic polymers during fibre spinning and other shaping operations, Baird explained. After these operations, solvents are removed in a process that includes a water bath. The toxic solvents then must be separated from the water to prevent environmental contamination.

Although US regulations require that manufacturers take pains to collect the solvents and keep them out of the environment, small amounts do escape into ground water and rivers, Baird noted. Even small amounts of the 36 billion pounds of solvents used annually pose a problem that the EPA would like to eliminate.

Super-critical - or high-pressure - CO2 can be used in place of solvents in acrylic polymer production, Baird said, and would offer distinct advantages.

Because the gas occurs naturally, it can be taken from the air and then dispelled back into the air after the fibre-spinning process is completed. Replacing solvents with CO2 would reduce the costs of manufacturing acrylic polymers as well as the expense of recovering and disposing of solvents.

In addition, CO2 does not pose a threat to the environment. 'The gas is non-toxic, non-flammable, chemically inert, completely recoverable and inexpensive,' Baird said.

The project does pose challenges. In order to make the super-critical CO2 suitable for acrylic polymer processing, Baird will have to design a chamber that can bring the gas down from the high-pressure state to normal atmospheric pressure in order to prevent polymer foaming.

The Virginia Tech researcher must also develop a method that will enable the CO2 to rapidly interact with the acrylic polymers during production.