木質材料の改良に関する研究(第21報) : タンニン酸およびアルギン酸塩による木材の寸法安定化

In order to prepared the dimensional stabilized wood having hygroscopicity similar to wood itself, the sapwood of Hinoki (Chamaecyparis obtusa Sieb. et Zucc.) was treated with hygroscopic tannic acid and sodium alginate aqueous solutions of varying concentrations. Further, vapor-phase acetylation of the tannic acid and sodium alginate impregnated wood was carried out with acetic anhydride-pyridine system at 70℃ for 20 hours. The hygroscopicity and dimensional stability were evaluated by the moisture absorption and amounts of swelling in tangential direction of treated wood to control at 20℃ and 93 percent relative humidity.
The results obtained are as follows :
(1) The hygroscopicities of woods treated with tannic acid and sodium alginate are the same as or more than that of control, and depend on the amount of impregnant in wood. Swelling is reduced by 20 percent.
(2) The acetylation of tannic acid and sodium alginate impregnated wood results in remarkable bulking effect. The anti-swelling efficiency and moisture-excluding efficiency are 30 to 60 percent and 20 to 60 percent, respectively. In particular, the reduction of hygroscopicity accompanying the acetylation of sodium alginate impregnated wood is 40 percent, while the anti-swelling efficiency is 60 percent. This suggests that the preparation of an improved wood having both properties of hygroscopicity and dimensional stability is possible.
(3) Increased dimensional stability is attributed to the bulking effect than to a reduced hygroscopicity of wood substrates.