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While soy-protein-based wood adhesives have been around for centuries, they have largely been replaced by petroleum-based adhesives since the World War II era. However, soy adhesives are making a comeback as a result of current research funded by the United Soybean Board and the soybean checkoff program. This research focuses on developing and commercializing two new soy products:
- A soy/phenol-resorcinol-formaldehyde (PRF) system for use in oriented strand board (OSB) and plywood.
- A soy meal/flour formaldehyde-free adhesive to replace urea formaldehyde (UF) adhesives.
Hydrolyzed soy proteins added to phenol formaldehyde (PF) resins provide reduced costs without degrading performance. Ongoing research from the soybean checkoff involves the optimization of hybrid PF-soy adhesives in phenol products, as well as the replacement of UF with soy-based alternatives in order to completely eliminate formaldehyde emissions from adhesives in interior applications. Soy-based products represent one alternative to urea-based products for interior applications where legislation now restricts emissions of formaldehyde.
While soy offers many environmental advantages over other wood adhesives, the benefits don’t stop there. New soy adhesives promise both improved performance and economics to the wood products industry.
Formaldehyde pricing depends on the price of methanol, which has fluctuated greatly in the past few years due to worldwide shortages. Urea pricing rose as a result of increased ammonia costs before dropping significantly last year. The costs of phenol are attributed to the cost of the base stock petroleum, which has followed the same trends as urea. Soy meal/flour costs remained consistent for many years before increasing recently in response to a greater demand. In spite of recent price increases, however, soy meal/flour remains an inexpensive raw material for wood adhesives.
Soy has a history of success in the adhesives industry. A soy-based, formaldehyde-free adhesive has been commercialized recently for use in the manufacture of hardwood plywood. Under a licensing agreement from Oregon State University, Hercules (now Ashland) granted a license to Columbia Forest Products to practice the OSU soy adhesive patents. Columbia has converted all seven of its manufacturing operations from urea formaldehyde to soy-based technology; the company now produces and sells its decorative plywood panels under the PureBond® name.
The future looks bright for soy-based adhesives as well. New markets are emerging for soy in heat-resistant adhesives, biobased composites and enzymatic processing for new soy hydrolysates. New applications have also been found in the construction adhesives and sealants market. For example, Bondaflex has introduced products that are developed by replacing petrochemical polyols with soy-based alternatives in urethane adhesives. According to Bondaflex, the soy component offers improved adhesion on a wide variety of substrates.
For more information about soy-based adhesives, visit the USB’s website.