METHOD OF PREPARING MOLDING MATERIAL FOR MANUFACTURING FACING LAYER OF CHIPBOARDS Russian patent published in 1999 - IPC

FIELD: manufacture of building materials. SUBSTANCE: hydrolysis lignin and wood filler, prior to be mixed with urea- formaldehyde resin, are subjected to joint treatment with 25% ammonium hydroxide aqueous solution. Weight ratio of ammonium hydroxide solution to mixture of hydrolysis lignin and wood filler (on conversion to absolutely dry substances) ranges from 1:20 to 1: 5. Treatment is carried out at 70-100 C for 15-25 min and followed by drying to moisture content 9-12% at 100-130 C. Amounts of starting components of molding material are the following, wt %: urea- formaldehyde resin 8-13, hydrolysis lignin 20-39, and wood filler 53- 67. EFFECT: increased water resistance and strength of chipboards, simplified technology. 3 cl, 3 tbl