Study On The Prepressing Problem Of Plywood And Environmental Urea-Formaldehyde Resin Adhesive

At present, no caul plate technology in the course of loader and unloader are used mostly in plywood factories. Because the veneers which are not flat and warp hinder the press loader regular running, the veneer must be glued to form one integral. Besides, plywood manufacture generally use polar veneer as core veneer, but because the following problem existed that polar veneer that moisture content was high distorted obviously after drying, thickness expansion rate of water absorbing was great and pH value of polar veneer was basicity, prepressing technology of veneer in plywood need higher tack of UF resin adhesive. At present, most of panels are used in furniture manufacture and indoor renovation and they are glued by UF resin adhesive, so formaldehyde emission problem exist generally. Nowadays, the' state promulgated the standard, in order to adapt the development of new situation our plywood enterprises have to find a way in the aspect of production technology and manufacture of UF resin adhesive.This paper researched veneer (especially polar veneer) prepressing problem of plywood mainly. Through single factor experiments, we find finally the main factor thatinfluenced prepressing effect of plywood--moisture content of veneer. So aiming atmoisture of veneer, we added two modifying agents to UF resin adhesive, then this problem was resolved. At the same time prepressing property meet our needs, wet strength have to achieve the state standard. Because UF resin adhesive were used in plywood, storage life, formaldehyde emission and tack of it must be considered.Wet strength of plywood which were made with UF resin adhesive reached the state standard (more than 0.7MPa); formaldehyde emission meet the need of Fc0 level of JAS standard in Japan, namely average value is less than 0.5mg/L and maximum 0.7mg/L. Storage life of UF resin adhesive we made is longer than 30 days (20 ).