The use of organosolv lignin to reduce press vent formaldehyde emissions in the manufacture of wood composites

Abstract

Two organosolv lignin fractions obtained from the ALCELL® process were evaluated for their effect on formaldehyde emissions when used as a partial replacement for phenol-formaldehyde (PF) resins during the manufacture of waferboard and particleboard. The use of a lignin dispersion to replace 20 percent of the solids in a liquid PF resin reduced press vent formaldehyde emissions by 3 8 percent in waferboard manufacture and resulted in panels with strength equal to or better than the control. Replacing 20 percent of a powder PF face resin with dry lignin powder in waferboard resulted in a 17 percent reduction of press vent emissions. For either type of panel, only trace amounts of formaldehyde were measured from control and experimental panels. In particleboard manufacture, replacing 20 percent PF resin solids of a liquid resin with a low molecular weight lignin fraction (unmodified and also after methylolation) resulted in a 38 to 45 percent reduction of press vent formaldehyde emissions. Panel emissions were reduced 29 to 37 percent. At this substitution level, there was little effect on physical properties. It is concluded that regular, as well as low molecular weight organosolv lignin is an effective means of scavenging free formaldehyde from PF binder systems during pressing, thus reducing the total amount of formaldehyde that is being liberated into the environment during manufacturing. These scavenging effects were attained without any significant detrimental effects on the physical properties of waferboard and particleboard.