Southwest Research Institute® (SwRI®) News
Printer Friendly VersionBiocidal polymers
Timed release of biocidal polymer coatings shows potential for improving the safety and longevity of numerous household, medical, and food products over a wide range of applications.
San Antonio — November 20, 1995 — A new technology that uses a series of polymer films and coatings impregnated with a precursor to the biocide chlorine dioxide (ClO2), which can be released at precisely targeted times, was described to trustees today at Southwest Research Institute® (SwRI®) 48th annual meeting.
“The adaptable release chemistry of biocidal polymers,” says Dr. Stephen Wellinghoff, Institute scientist in the Chemistry and Chemical Engineering Division and project director, “provides a wide variety of potential applications in the manufacture and packaging of household, health care, agricultural, and food products.”
“The technology is safe, versatile, and inexpensive,” Wellinghoff added. “This makes it particularly appropriate at a time when international regulations increasingly limit forms of packaging, encourage improved standards of food safety, and give preference to environmentally safe products and procedures. We can work with clients on developing a variety of release kinetics.”
The program is sponsored by Bernard Technologies, a privately held health and food safety technology company based in Chicago, Illinois. Development of the technology has resulted in patents granted or pending to SwRI. The technology is licensed exclusively to Bernard Technologies and the Institute will receive royalties. Bernard Technologies plans to introduce the biocidal polymers under the trade name Microgardetm to certain markets.
ClO2 has been recognized since the 1960s as a potentially useful chemical for neutralizing odors and for controlling bacteria, fungi, and viruses. It is widely used in a variety of applications such as skin disinfection, contact lens care, swimming pool maintenance, and the treatment of drinking water, and is often preferred to chlorine. In March, 1995, the U.S. Food and Drug Administration approved the use of ClO2 as a rinse for fresh poultry.
“The key discovery of this new application,” said Dr. Peter Gray, spokesman for Bernard, “is the sustained generation of ClO2 from a solid form over a long period. In current applications ClO2 is generated as a gas in water, which limits its use. We now have a commercial method to deliver the biocide in a dry matrix form. Microgardetm represents a unique combination of polymer science and solid state chemistry.”
Chlorine dioxide is a broad spectrum biocide that attacks membranes and fundamental cellular processes. This preempts the tendency of many life forms to build up resistance and develop mutant strains. ClO2 is also effective at extremely low levels — on the order of several parts per million — and well below the point at which odor can be detected. The release system developed to date is both optically clear and aesthetically pleasing, an important characteristic in the health care and food industries.
The biocide can be incorporated into a wide variety of polymer films and coatings, from paraffin and microcrystalline waxes to polyethylenes. The polymer coatings are responsive to temperature and moisture. There are two components in the controlled release design. One is an acid-releasing component that can be released quickly, in a matter of days or hours, or more slowly over a period of months. The second is a chlorite-containing component.
“Institute scientists are exploring different methods of film application,” said Wellinghoff. The polymer can be sprayed, melt-coated, or infused into a stamp-sized coupon punched onto a storage box. The technology appears to be easy to incorporate into many manufacturing systems.
For more information about biocidal polymers, contact Deborah Deffenbaugh, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-2046, Fax (210) 522-3547.
