| The purpose of optimizing the bleaching process of birch is to improve its color disfigurement and colorstability in application.Hydrogen peroxide,sodium hydroxide,sodium silicate were chosen as main bleaching components and polyethylene glycol,ascorbic acid,benzotriazole,polyvinyl pyrrolidone were photostability agent.The effect of the bleaching components,photostability agent, time and temperature on 3 measurements,which included whiteness,color uniformity and stability of bleached birch veneer,was analyzed through orthogonal experiment design.Besides,supplement of Hydrogen peroxide during bleaching liquor recycling and methods of color regulation for discolored birch were also researched.The result showed that:(1)Dosage of Hydrogen peroxide has the most significant effect The optimization process for bleaching birch veneer should take 4%hydrogen peroxide,0.4%sodium silicate,1%sodium hydroxide in 60min at 60℃.Birch veneer bleached has high whiteness and uniformity in the process.The colorstability represents fine after drying.(2)Treatment with photostability agents shows a obvious improvement on photostability of birch. The treatment methods of photostability agent have the most significant effect on improving photostability of bleached veneer.The 0.4%B enzotriazole us ed in washing process represents best photostability.(3)Discolored part of specimens pretreated in sodium hydroxide solution,then bleaching the whole,which represents better result.The optimized prescription for discolored birch to dyed after bleaching in order to attain reproduction the color of normal birch.(4)Bleaching liquor can be used circularly with supply of Hydrogen peroxide,and the supplement should be 52.23%of initial concentration.(5)The chromophore groups of wood are broken,and the auxochrome group as hydroxyl changes. Some extraction in the wood is also removed during bleaching.In the conditions of this research, photostability agents combine with birch wood without chemical union according to FTIR.
|
PDF Full Text Request