Holz als Roh- und Werkstoff

, Volume 50, Issue 5, pp 212–220 | Cite as

Increased pine tannins extraction and wood adhesives development by phlobaphenes minimization

  • V. J. Sealy-Fisher
  • A. Pizzi


The phlobaphenes formation and precipation during sulphite/water extraction of pine tannins from pine bark was minimized by blocking tannin self-condensation by the addition of small amounts of a strong nucleophile such as phloroglucinol, m-phenylenediamine and urea, the latter due to its low cost for industrial application. These inhibitors reacted preferentially with the reaction intermediates formed in the tannins self-condensation mechanism, stopping the reaction reaching the molecular rearranged precipates known as phlobaphenes. The principle of inhibition appears to be effective at both the laboratory and industrial level. The results of laboratory and industrial extractions and the results of the adhesives from the modified pine tannin extract/urea adducts obtained are presented. The pine tannin/urea extracts proved to yield good thermosetting wood adhesives for panel products. The minimization of phlobaphenes precipitation increased the yield from 19% to 25% industrial scale.


Tannin Bark Condensed Tannin Sulphite Phloroglucinol 
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Verbesserte Tanninextraktion und Kleberentwicklung durch Minimierung der Phlobaphen-Reaktion


Die Bildung und Ausfällung von Phlobaphenen während der Extraktion von Kiefernrinde wurde verringert durch Blockieren der Tanninkondensation durch geringe Zusätze stark nukleophiler Reagentien wie Phloroglucin, m-Phenylendiamin und Harnstoff (letzterer wegen der geringen Kosten für die industrielle Herstellung). Diese Inhibitoren reagierten vor allem mit Zwischenprodukten der Tanninkondensation. Dabei wird die Bildung der durch molekulare Umlagerungen entstehenden Phlobaphene gestoppt. Die Unterdrückung der Phlobaphenbildung gelingt sowohl im Labor- als auch im technischen Maßstab. Die Ergebnisse der Extraktion und der Leimherstellung aus diesen modifizierten Tanninen mit Harnstoffzusatz werden beschrieben. Diese Kleber eignen sich gut zur Heißverleimung von Platten. Aufgrund der Unterdrükkung der Phlobaphenbildung erhöhte sich die Ausbeute der technischen Extraktion von 19 auf 25%.


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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • V. J. Sealy-Fisher
    • 1
  • A. Pizzi
    • 1
  1. 1.Department of ChemistryUniversity of the WitwatersrandJohannesburgSouth Africa

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