Wood Laminating Adhesive System for Ribbon Spreading

Equipment and techniques are described for “ribbon” or “extruded” adhesives. From a laboratory equipment standpoint, two extrusion systems are discussed–air pressurized glue tank reservoir, and positive displacement pump. Conventional phenolresorcinol-formaldehyde adhesives used in lumber laminating were evaluated and found to be too thin to perform satisfactorily in ribbon spreading. The ribbons of the adhesive “sagged” when vertically positioned. The use of organic fillers and thixotropic agents reduced the sag tendency. Fillers gave viscous adhesive mixes that did not “clean-up” satisfactorily. A thixotropic adhesive system did not “sag” and “clean-up” was good. Douglas-fir and southern, pine lumber laminates were found to give acceptable bond performance. They met requirements for AITC tests for water-proofness, compressive shear strength, and percent wood failure. Advantages for ribbon spreading are: 1) The cleanliness of a gluing operation is improved. 2) The control of adhesive spread rates is quite accurate. Thus, adhesive spreads can be changed easily to control the effect of changes in lumber and ambient temperatures and moisture content differences. 3) As a result of increased control of adhesive spread rates and improved housekeeping, minimum adhesive waste is realized. Thus, the overall cost of the gluing operation will be reduced. 4) Because the adhesive is applied in ribbons, a smaller adhesive surface area results, with reduction of solvent evaporation and absorption. 5) A significant contribution of ribbon spreading will be “streamlining” the production in a laminating plant. Because the lumber is spread on only one surface, a continuous conveyorized laminating operation is feasible.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member