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 quality extractives for wood adhesives. A four-stage squeeze extraction comprising a two-stage extraction with hot water and one-stage extraction with NaOH aqueous (pH 8.3) solution followed by a one-stage washing with hot water doubled the extractives yield obtained by the first two-stage hot water extraction alone and resulted in a total extractives yield Of 30% from commercially available samples of the radiata pine bark. Furthermore, high purity of polyflavanoids in the extractives was obtained by the four-stage squeeze extraction and viscosity reduction was achieved by sulphitation of the insoluble fraction of the extractives. Subsequently, unfortified plywood adhesives of sufficiently high quality to satisfy the requirements for Type A bond (fully weather and boil proof) were readily formulated from the high yield extractives.