A Chemical Process for Converting Soy Flour into a PF-Like Adhesive

摘要

Adhesives based on soybean protein were important in the early development of the Douglas fir plywood industry. However, the development of highly durable, exterior-grade synthetic adhesives from petrochemicals resulted in a long -term decline in the production of soybean adhesives. Cold-press soybean adhesives fell from about 28% of the market in 1954 to almost zero in 1970; while hot-press soybean adhesives (containing dried blood) rose to a peak of 45% in 1956, then fell to near zero in 1973 (Conner, 1989). Nevertheless, intermittent declines in | petroleum supplies and increases in petroleum prices, together with the worldwide interest in development of environmentally friendly adhesives from renewable resources, have stimulated a renewed interest in soybean adhesives. Efforts have been made to find new ways to overcome limitations inherent in use of soy flour in gluing wood. A recent study (Kreibich, 1997) has shown that a concentrated soy protein-based resin was capable of finger-jointing green lumber at room temperature when used with phenol-resorcinol-formaldehyde (PRF) resin in a modified finger-jointing operation. Altering the structure of the soy protein to reduce costs, Vajayendran (1998 and 1999) and Clay (1999) have shown that a mixed hydrolyzed soy flour/PRF resin system can be applied to the two sides of lumber at room temperature in a finger-joint operation. More recently, soybean -based adhesive resins were formulated by crosslinking hydrolyzed soy flour with 30 percent (w/w) of phenol formaldehyde prepolymer for bonding MDF and flakeboard that met the product performance requirements (Kuo, 2000).