Low-Energy Curing of Coatings Using Ultraviolet Light
"In UV-curing applications, a thin liquid coating is applied to a surface and, under the influence of a bright light, it dries instantaneously," said Neckers. "In a typical commercial line, for example, surfaces can be dried on conveyor belts that move at 1,000 or more feet per minute."
Neckers and his team of researchers have developed a new series of catalysts that allows curing of epoxy soybean oil as a coating. Previous catalysts always produced colored products, but the new developments alleviate this problem and provide a thin, colorless film.
Polymerization of common olefins, such as ethylene and propolyene, can be accomplished through the use of Ziegler Natta catalysts. A Ziegler Natta catalyst is a mixture of metal alkyl from group I-III and a transition metal salt from group IV-VIII. These catalysts are used to prepare highly crystalline, high-density, highly useful polymers. The catalysts are not generally used in photopolymerization.
Neckers began research in March to see if Ziegler Natta catalysts could be synthesized photochemically. The basis of this research stems from taking a commercially valuable polymer that can be made from monomers and trying to make them photochemically. If this works, Neckers should be able to take a common monomer, such as soybean oil, with the catalyst and expose it to light to activate the polymerization. This should produce hard polymers from soybean oil that can be used as coatings instead of soft polymers that are clear and colorless.
In the experiment, a Ziegler Natta catalyst was combined with a photoprecursor. The precursor in the presence of a polymerizable olefin was irradiated to achieve polymerization.
To date, photopolymerization has been accomplished on styrene and isoprene using both visible and ultraviolet light. This demonstrates that a new type of catalyst was formed with the use of a photoinitiator. Future work will try to discover the mechanism that causes the reaction and transfer the knowledge to work on internal olefins such as soybean oil products.
Neckers is a McMaster distinguished research professor at Bowling Green. His research team consists of Ph.D. students and postdoctoral fellows. These students are at various levels in their training; however, when they complete their studies, most will become industrial chemists at companies that use or develop UV-cured products.
The United Soybean Board is composed of 62 U.S. soybean farmers appointed by the Secretary of Agriculture to invest soybean checkoff funds. The soybean checkoff is a farmer-supported marketing and research fund collected on each bushel of U.S. soybeans sold. The USB invests these funds on behalf of the 600,000 U.S. soybean farmers in activities designed to increase the global use of U.S. soybeans and to reduce production costs. Checkoff-funded investment areas include human and animal health and nutrition, research and development of new uses, and research to improve soybean composition and production efficiencies.
For more information on soy coatings, contact Cindy Hackmann, Osborn & Barr Communications, 888/235.4332, e-mail firstname.lastname@example.org; or Circle Number 62.