WOOD ADHESIVES FROM PINUS-RADIATA BARK

Conditions for extracting bark of radiata pine (Pinus radiata D. Don) were examined with the purpose of obtaining high yield and high qualit y extractives for wood adhesives. A four-stage squeeze extraction comp rising a two-stage extraction with hot water and one-stage extraction with NaOH aqueous (pH 8.3) solution followed by a one-stage washing wi th hot water doubled the extractives yield obtained by the first two-s tage hot water extraction alone and resulted in a total extractives yi eld Of 30% from commercially available samples of the radiata pine bar k. Furthermore, high purity of polyflavanoids in the extractives was o btained by the four-stage squeeze extraction and viscosity reduction w as achieved by sulphitation of the insoluble fraction of the extractiv es. Subsequently, unfortified plywood adhesives of sufficiently high q uality to satisfy the requirements for Type A bond (fully weather and boil proof) were readily formulated from the high yield extractives.