スギ間伐材へのレゾール型フェノール樹脂初期縮合物の吸着性と吸着処理の材質に及ぼす効果

Abstract

レゾール型フェノール樹脂の比較的希薄な水溶液からの吸着処理によるスギ間伐材の材質改良の可能性を探ることを目的として, 市販レゾール型フェノール樹脂 (PH) 及びレゾールの最も初期の生成物の1つであるサリゲニン (SA) の木材への吸着性と, 吸着処理の寸法安定性及び機械的性質に及ぼす効果を検討した。吸着性の検討には主に40 - 80meshの木粉を, 寸法安定性及び木口面硬さの検討には木口試験片 (40mm×20mm×4mm : R×T×L) を, 静的曲げ試験により得られる機械的性質の検討にはまさ目試験片 (60mm×10mm×2mm : L×R×T) を用いた。得られた主な知見は, (1) SAの吸着速度はまさ目試験片では木粉及び木口試験片に比して遅いが, 平衡吸着量には木材の形状による差は認められない。(2) SAは心・辺材の別, 成熟度の違いによってその吸着性にほとんど差を示さない。また, それらの吸着等温線は低濃度域での立ち上りが鈍く, 高濃度域まで濃度とともに吸着量が増加する。一方, PHの吸着量は低濃度域ではSAよりも鋭い立ち上りを示すが, 高濃度域ではSAよりもはるかに低い。(3) 処理により得られたパルキング効果をSA処理とPH処理で比較すると, SA処理の方がはるかに高い。両吸着質の吸着量の差を反影しているものと考えられる。(4) SA処理は35 - 40％の膨潤抑制効果を与える。しかしPHの場合, 処理により吸湿性が高くなり, 負の効果を示す。(5) SA処理により, 木口面硬さ, 曲げヤング係数及び曲げ破壊係数のいずれも, PH処理以上に向上する。しかし, 曲げ破壊仕事量は処理により低下する。ただし, その低下量はSA処理による方が小さい。

This study aims to get some information as to the possibility of improvement in dimensional stability and mechanical properties of thinned wood of Sugi by means of the adsorption of resols from their relatively dilute aqueous solutions. Adsorbates used were one of commercially available resol type phenol-formaldehyde resin (PH: Ohshika resin D-19) and saligenin (SA: o-methylol phenol) which has the simplest structure in the resols. Four sorts of wood meal (40-80 mesh) from mature sap, immature sap, mature heart and immature heart wood were mainly used for examination of adsorptivities of both resins. For examination of the dimensional stability and the hardness on end grain, and for examinations of some static bending properties of the treated wood, cross sections (40 mm×20 mm×4 mm: R×T×L), and radial sections (60 mm×10 mm×2 mm: L×R×T) were used, respectively. The results obtained were as follows: (1) The adsorption of SA on radial sections takes longer time than on wood meal and cross sections attributing to the difficulty of SA diffusion into the specimens. However, the adsorbed amounts at equilibrium are not different for the shapes of the adsorbents. (cf. Fig. 1) (2) The adsorption isotherms of SA on four sorts of wood meal are similar. Their adsorbed amounts are gradually increase with increasing concentration even in the low concentration range, the increases continue in the relatively high concentration range around 5%. On the other hand, isotherm of PH shows steep rise in the low concentration range, however its adsorbed amount in the high concentration range is lower by far than that of SA. (cf. Fig. 2 and 3) (3) The bulking effect obtained by means of the SA treatment is far higher than that of PH treatment. This should be attributed to the difference of adsorbed amounts of both resins. (cf. Tables 1 and 2) (4) SA treatment gives significant antiswelling efficiency as high as 35-40%. However, PH treatment results in negative effect because of increasing hygroscopicity of cell wall by the treatment. (cf. Table 3) (5) SA treatment improves hardness on end grain, modulus of elasticity and modulus of rupture more than PH treatment. Work to maximum load decreases by both treatment, though the decrease is less for SA treatment. (cf. Tables 4 and 5)