Study On Dyeing Technology Of The Birch Veneer And Color Fastness Of The Dyed Veneer

The wood resource, esp. rare wood species, is short in China, but the demand of excellentwood products is even increasing. Lots of artificial veneers were produced to solve thecontradiction of demand and supply of wood. Poplar and Birch are two common wood specieswith abundant resource and good osmosis, which are therefore adapted to produce artificialveneer. Based on the studies on the veneer blenching, dyeing and dye-fixing of Poplar andBirch, the best techniques were optimized, which established the foundation for production.The hydrogen peroxide (H₂O₂) was used as blenching agent in this study. When bath ratiowas 1:15 and pH at 10, the optimum technology for blenching 1.5-mm poplar veneer was asfollows, the concentrations of H₂O₂, Na₂SiO₃ and Pergal O were 2%, 0.15% and 0.25%,respectively, and the time for 3h, the temperature at 60℃. For 1.5ram thick Birch veneer, theoptimum technology was that the concentrations of H₂O₂, Na₂SiO₃ and Pergal O were 3%,0.15% and 0.3%, respectively, and the time for 2h, the temperature at 60℃. The study alsoblenched Mongolian Oak wood that is a species of poor osmosis and has colored. It indicatedthat the treatments, such as extraction by ethanol, pretreatment with NaOH, applying surfactant,heating and pressing, would increase the permeation of blenching liquid into wood, andtherefore improve the even blenching.The Birch veneer was dyed with C.I.Acide orange 7. The study optimized the dyeingtechnology as follows. When light orange were dyed, the concentrations of dye, NaCl andPergal O were 0.5%, 0.5% and 0.5%, respectively, pH at 4, temperature at 85℃and time for4h. When dark orange were dyed, the concentrations of dye, NaCl and Pergal O were 1%, 0.1%and 0.05%, respectively, pH at 4, temperature at 85℃and time for 4h. It also discovered thatcolor in center veneer dyed with dye concentration 1% was better than that with 0.5%; duringdyeing the NaCl accelerate the dyeing while the Pergal O made dye distributed even butdecrease the dyeing rate. The dyeing would be well improved when the NaCl mixed withPergal O.The veneer water resistance would be improved metal salt. It found that the effects ofsome salts on color change were as follows, K₂Cr₂O₄＞CuSO₄＞Na₂CO₃=NaHCO₃＞ KAI(SO₄)₂=Na₂SO₄=NaCl and the color fastness effect was as follows, K₂Cr₂O₄＞KAI(SO₄)₂＞NaCl＞Na₂SO₄＞CuSO₄＞Na₂CO₃=NaHCO₃. The KAI(SO₄)₂ was the best saltto fasten color and made dyed wood little color change. The salt K₂Cr₂O₄ had excellent colorfastness but it led dyed wood to great color change. The rest 5 salts had poor color fastness.The pretreatment of veneers with chitosan before dyed could improve the water resistance lightresistance, but the color changed seriously and the center veneer was poorly dyed. Post-treatment with chitosan after dyeing could not only improve the water resistance and lightresistance but also ensure even dyeing in center veneer. The best chitosan concentration forpost-treatment was 1%. And the birch veneer after dyeing post-treated with 1mL 1% chitosancould give best color fastness, for the lightness and color difference respective were only -0.22and 0.25NBS after water resistance test and only -0.73 and 3.19NBS after light resistance test,respectively.