Method of manufacture of low-formaldehyde wood fibre or chip board bonded with tannin formaldehyde resin

摘要

Low-formaldehyde wood fibre or chip boards bonded with tannin formaldehyde resin are manufactured by a method in which the tannin is applied to the fibre or chips partly as powder and partly as liquid. The boards so manufactured are then treated with formaldehyde-active substances. Preferably the proportion of binder added as powder is at least 10 wt.% and is 40 wt.% maximum. Liquid binder preferably has a controlled Ph, which may be 4, 8 or 10. The binder preferably contains at least 0.5% urea with respect to the tannin.