Final Report: Conversion of Natural Adhesive to Marketable FormEPA Contract Number: EPD04043
Title: Conversion of Natural Adhesive to Marketable Form
Investigators: Combie, Joan
Small Business: Montana Biotech SE Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2004 through August 31, 2004
Project Amount: $69,588
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text | Recipients Lists
Research Category: Nanotechnology , SBIR - Nanotechnology , Small Business Innovation Research (SBIR)
Levan, a polysaccharide not previously available in more than gram quantities, has been found to have adhesive properties. Unlike petrochemical-based adhesives, levan is derived from a renewable resource, sugar. Also, unlike the carcinogenic formaldehyde found in most manufactured woods, levan is safe for both users and the environment. A scaled-up production method for levan has been developed.
One hurdle remains before levan can become a marketable adhesive. An adhesive bond of levan is vulnerable to the deleterious effects of water. Although there are numerous methods for decreasing the water solubility of a material, the moieties responsible for the adhesive properties of levan also are responsible for the interaction with water. Therefore, some innovative approaches were proposed to solve the dilemma and make this safe, environmentally friendly adhesive into an all-around adhesive suitable for use in everything from contact with food to making fiberboard. Both cross-linking procedures and protective materials were proposed as methods for increasing the water resistance of the levan adhesive while maintaining adhesive strength. The goal of this research project was to maintain at least 80 percent of the parent levan adhesive strength, while making a product that is sufficiently water resistant and looses no more than 5 percent of its zero-time adhesive strength after soaking in water for 24 hours.
A levan-based adhesive was developed for wood that was stronger than the wood coupons being tested and that has maintained adhesive strength after soaking in water for 3 weeks(up to the time of this report). Numerous cross-linking and protective agents were tested. For most formulations, bonds broke within minutes of exposure to water. Some were less resistant to water than the parent levan. Montana Biotech SE, Inc., found that levan had a low hydroxyl number. This apparently resulted in insufficient cross-linking to provide water resistance.
One formulation, however, far exceeded the metrics, with a water-resistant bond that was stronger than the test coupons. This successful formulation for a wood adhesive has remained impervious to water for 3 weeks (at the time of this report) and is stronger than the wood coupons. The cross-linking agent is a food grade polymeric HDI (Bayhydur 303). Limited qualitative testing also indicated potentially successful use on plastics. Interestingly, this formulation was unsuitable for aluminum, the other substrate listed in the proposal for testing. A second formulation that did not meet the metrics but did show improved resistance to water was developed for aluminum. This method involved a protective wax and cross-linking with hexamethoxymethylmelamine.
A water-resistant wood adhesive was developed using a food-grade cross-linking agent at a cost that will allow competitive pricing. Although some optimization and alterations of the catalysts will be required prior to marketing, the Phase I research demonstrated the feasibility of converting levan into a safe, affordable wood adhesive.
The wood, board, and paper industries use 4 billion pounds of adhesive in the United States each year, with another 1 billion pounds of formaldehyde-based materials going into the production of manufactured woods such as particleboard, oriented strand board, and plywood. The cross-linked levan-based wood adhesive developed during Phase I has the potential for use in some of these areas. The opportunity to move away from petrochemicals and the toxic formaldehyde- based wood bonding materials for some nonstructural applications will be attractive for customers. Additional potential applications for the water-resistant, levan adhesive have been identified and samples have been submitted to representative companies for testing. These uses include carpeting, home repair, and the packaging industries.