Study on Environmental-Friendly Dyeing Processes of Fast-Growing Plantation Veneers

Wood is light, has high strength and beautiful appearance, and needs a small amount of power to process it. Of four major materials (steel, cement, wood and plastics) in the world, wood is the only green material and biological resource that is renewable, recyclable, and can be naturally degraded. With natural high-quality forest resources increasingly reducing, they are gradually replaced by a large number of low-quality fast-growing plantation wood. Paulownia and Poplar are important fast-growing plantation tree species in China. By dyeing, we can improve their decorative and added values to efficiently use the resources of fast-growing wood. At present wood dyeing industry, acid dyes have all long been used on wood dyeing, however, due to low dye uptake of acid dyes in wood dyeing (generally less than 30%), about 70% to 80% of dyes cannot be used and then left in dyeing wastewater resulting in high chroma and difficult treatment of dyeing wastewater. In response to this situation, 3 primary colors of M-type reactive dyes were selected to dye Paulownia and Poplar veneer in the paper. Different from acid dyes, M-type reactive dyes contain 2 reactive groups in the structure which can react with the cellulose and hemicellulose of the wood to form stable chemical bonds, and then have advantages of high fixation, low hydrolysis and environmental requirements. Through orthogonal test and range analysis, the optimal dyeing process was obtained. In the condition of this optimal dyeing process, dye uptakes of reactive dyes on Paulownia are as follows: red of M-3BE 59.2%, yellow of M-3RE 65.3% and blue of M-2GE 50.3%, dye uptakes of reactive dyes on Poplar veneer are as follows: red of M-3BE 67.8%, yellow of M-3RE 68.6% and blue of M-2GE 58.9%, which are all significantly higher than dye uptakes of acid dyes. Through the use of reactive dyes on the fast-growing wood staining, the emission of dyes in the dyeing wastewater is reduced. So a new dyeing way of fast-growing plantation wood which is energy saving, environmental protection and friendly to human health is provided.