Abstract
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.
Zusammenfassung
Bedingungen für die Extraktion von Tanninen aus der Rinde vonPinus radiata wurden untersucht mit dem Ziel, hohe Ausbeuten und hohe Extrakt-Qualitäten zu erreichen für die Produktion von Holzleimen. Eine vierstufige Extraktion (2xHeißwasser/NaOH/Heißwasser) führte bei Anwendung eines Preßdrucks von 2 MPa bereits nach 2 Stufen zu einer Verdoppelung der bisherigen Ausbeuten. Die Endausbeute aus handelsüblichen Kiefernrinden betrug 30%. Die Extraktion führte zu einer hohen Reinheit der Polyflavanoide. Die Viskosität konnte durch Sulfonieren der in Wasser unlöslichen Anteile erreicht werden. Aus den Extrakten wurden anschließend Sperrholzkleber hergestellt, die den Anforderungen einer „Typ A-Bindung” (volle Wetter- und Koch beständigkeit) genügten.
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The authors thank Mr M. Spicer at CSIRO, Division of Building, Construction and Engineering, for his help in preparing the extracts and CSR Wood Panels at Mt Gambier for supplying the samples of radiata pine bark.
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Yazaki, Y., Collins, P.J. Wood adhesives fromPinus radiata bark. Holz als Roh-und Werkstoff 52, 185–190 (1994). https://doi.org/10.1007/BF02615220
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DOI: https://doi.org/10.1007/BF02615220