• Journal of the Korean Wood Science and Technology
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• v.24 no.4
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• pp.1-6
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• 1996

Extracts from bark have been studied with a view to producing water-proof wood adhesives. Lately many softwoods, such as radiata pine from New Zealand and larch from Siberia, Russia, have been imported and utilized, and their residual barks would be expecting as potential raw materials for something useful chemicals. The great effort toward utilization of bark extractives as a chemical feedstock has been made on a worldwide level. However few report has been done for the utilization of tree bark extractives in Korea. Hot-water extracts were prepared from barks of Japanese larch(Larix leptolepis). Siberian larch(Larix gmelinii) and Radiata pine(Pinus radiata). The effect of various factors, such as particle size, liquor ratio, extraction temperature, and reaction time, on the extractive yields was discussed. Particle sizes affected the hot-water extractives: the finer the particle size, the higher extractives and extract efficiency. Higher temperature and higher liquor ratio were more effective. Extractives from Japanese larch were relatively less than those from Siberian larch and Radiata pine barks. Formaldehyde precipitates was the highest in extractives of Radiata pine barks. It could be concluded that Siberian larch bark was the best raw material for tannin adhesives, because its extractive yield was higher than those of the other barks.

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.23-27
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• 1997

Alkali-soluble extracts were prepared from barks of Japanese larch(Larix leptolepis). Siberian larch(Larix gmelineii) and Radiata pine(Pinus radiata) The effect of various factors, such as particle size, liquor ratio, extraction temperature, and reaction time, on the extracts yield was investigated. Particle sizes affected the alkali-soluble extracts; the finer the particle size, the higher extracts and extract efficiency. High temperature and high liquor ratio were more effective. In the range of 0.25% to 1% NaOH concentration, alkali extracts were increased with the increasing alkali concentration. However, extract yields were leveled off above 0.5% alkali concentration. Extractions with NaHCO3 were almost equivalent to those of NaOH extraction. 1% NaOH and 1% NaHCO3 resulted in the highest yields of alkaline extracts. Extracts from Japanese larch were lower than those from Siberian larch and Radiata pine barks. Siberian larch bark was the best raw material for tannin adhesives, because its extractive yield was higher than those of the other barks. Concerning pH of alkaline media during extraction, small increases of the extract yields were resulted at range of pH 7 to pH 9, while a large increases from pH 9.0 to pH 12. This phenomenon is attributed to higher alkalinity.

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.37-41
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• 1997

Hot-water soluble extracts were prepared from medium-sized barks of Siberian larch (Larix gmelineii). The extracts were fractionated by ultrafiltration method for producing uniform quality of adhesives. Molecular weight distribution of the extracts was ranged of 100 to 300.000. pH of the extracts affected amounts of flux, and the range of pH 6~pH 8 was proper for wood adhesives, because of easy concentration and fast gelation time. Removal of particles greater than $0.45{\mu}m$ from the extracts increased both filtration speed (flux) and yields of solids in the filtrates. In ultrafiltration process. operating pressure, filtrate temperature, and flow rate significantly increased with the increase of individual condition. Ultrafiltration using PM10 membrane was very effective to fractionate and concentrate the extracts. Removal of large particles greater than 0.45 m from the extracts increased filtration speed(flux) and yields of solids in the filtrates. A gelation time was accelerated with the increasing pH of the extracts and its concentration. The Stiasny precipitate(26%) from the filtrate obtained by PM 10 membrane was very lower than that(78%) of the retentates. This ultrafiltration method was efficient for obtaining high yield purified phenolic compounds.