Ether Extractives of Red Pine and Possible Means of Reducing Resin Exudation

When red pine is used for exterior siding, considerable resin may exude from knots. Most of the resin is composed of solid resin acids and fatty acids with terpenes serving as a solvent. Any alteration or removal of the terpene fraction may alleviate the exudation problem. Likewise, a change in the fatty acids may also accomplish this. Solvent seasoning of air-dried knotty red pine boards with acetone removed about 90 percent of terpenes in two 1-hour cycles. Six 1-hour acetone cycles removed 99 percent of the terpenes. Weatherometer tests showed that resin exudation was eliminated using this procedure. Kiln-drying and steam treatments also removed some terpenes. A 26-percent solution of boron trifluoride converted about 85 percent of the terpenes in the outer 1/4- inch section of knots into viscous, very high boiling, or nonvolatile products. Preliminary tests indicate that unchanged terpenes in the interior of the knot can break through this layer exuding onto the surface. Preliminary weatherometer tests indicate that brushing ethylenediane or methoxyethylamine onto knotty surfaces yielded a definite reduction in resin exudation. Since the resin acid fraction of the exudate is dissolved in the fatty acid fraction, conversion of the latter into salts which are insoluble in terpenes reduces exudation.

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