木材保護着色塗料で塗装した木製サッシの耐候性評価 Estimation of Weather Resistance of Wooden Sashes Finished with Exterior Stains
エクステリア木材用に開発された5種類の木材保護着色塗料により木製サッシを塗装し, その耐候性評価および屋外暴露における塗装木材の挙動を, 重量・寸法変化, 色差変化などにより検討した. 保護塗料には, 木材中に浸透し塗膜を造らない含浸型塗料と, 薄い塗膜を造る半造膜型塗料を用いた. 含浸型塗料は, 無塗装材に比べて重量変化で約20%, 寸法変化で約35%, また半造膜型塗料では重量変化で50から60%, 寸法変化で約55%の抑制効果が認められた. 木製サッシの寸法変化では, 縦使いした部材の木口面付近の寸法変化が大きく, 塗装により1/2程度に低下し他の部位との差が縮小した. サッシの部位別の色差変化では, 水平面の変色が著しいことが観察された. また, 縦桟よりも横桟の方が変色が大きく, これも塗装により部位間の差が縮小した. 以上の結果から次の結論を得た. 1) 木製サッシでは縦使いした木材の木口面処理と横使いした木材の水平面の処理が重要である. 2) 含浸型塗料の性能は半造膜型塗料より劣るが, 劣化の進行が遅いため表面の美観の急激な低下はない. 3) 半造膜型は塗膜の劣化と共に急激な性能および美観の低下が認められる. 4) 保護塗料の塗り替え時期は, 含浸型, 半造膜型共に2年程度と考えられる.
Commercial wooden sashes and smaller wood specimens were finished with 5 kinds of exterior stains (pigmented stains) which were either of the penetrating or semi-film forming type. Finished wood was exposed outdoors and its weather resistance and the performance of the finishes were periodically evaluated by mainly their weight and dimensional changes, and color difference. Weight and dimensional changes in wood samples finishes with penetrating type stains were improved by approximately 20% and 35%, respectively. Finishing with semi-film forming type stains also improved weight changes by about 50 to 60% and dimensional changes by 55%. Exterior exposure of full-sized sashes resulted in large dimensional changes in the cross section of the longitudinal components of the frame. In finished sashes, dimensional changes in the cross section of the longitudinal components were approximately 50% smaller and dimensional changes between the various parts of the sashes were also reduced. Large color changes were observed at the upper surface of horizontal sash frames during exterior exposure and a noticeable difference in color between the horizontal and vertical frames developed over time. However, color differences between sash components was reduced as a result of finishing with exterior stains. From these results, it can be concluded that finishing is a highly effective means of improving the weather resistance of wooden sashes and that water proofing of the cross sections of longitudinal frames and careful finishing of the horizontal surfaces should be undertaken before sashes are exposed outdoors. Property enhancement produced by penetrating type stains was inferior to that of semi-film forming type stains. However, the mode of failure of penetrating type stains was superior to that of film forming type, since wood surfaces treated with the former showed gradual deterioration over time whereas the deterioration of those finished with semi-film forming type stains occurred quite suddenly. Furthermore once films degraded, property enhancement provided by the finish decreased markedly. The first maintenance interval for penetrating and semi-film forming type finishes was similar, approximately two years.
マテリアルライフ 9(4), 188-195, 1997-10-01
MATERIALS LIFE SOCIETY, JAPAN