Application and Outlook of Environment-Friendly Reactive Dyes in Wood Dyeing Industry

Abstract

The increasing shortage of supply of large-diameter-class and high-quality natural forest resources is caused by the intensification of the crisis of forest resources and changes in the structure of forest resources. As a result, excellent and valuable tree species are expensive and then they are gradually replaced by a large number of low-quality fast-growing plantation wood. Wood dyeing technology can improve the decorative of fast-growing wood and add value to their products, and can achieve efficient use of resources of fast-growing plantations. In current wood dyeing industry, acid dyes have all long been used, however, dye uptake of acid dyes in wood dyeing is very low (generally less than 30%), about 70% to 80% of acid dyes cannot be used and then left in dyeing wastewater resulting in high chroma and difficult treatment of dyeing wastewater. At the same time, because acid dyes for wood staining depend on the intermolecular forces of smaller bond energy, when the external environment changes dyes easily lose not only affecting the application of dyed wood but also bringing about environmental pollution. So dyeing wood with acid dyestuffs can not meet environmental protection requirements. M-type reactive dyes containing 2 reactive groups with advantages of high fixation, low hydrolysis and environmental requirements were selected to dye fast-growing plantation wood. Dye uptakes of reactive dyes were all above 55%, which were significantly higher than the dye uptakes of acid dyes, thus the emission of dye in the dyeing wastewater could be reduced, and the objective of energy-saving and emission reduction could be achieved. Furthermore reactive dyes react with the chemical compositions of wood through reactive groups to form covalent bonds of larger bond energy and then to fix on the wood. And thus problems of dyeing depth and color fastness restricting current wood staining techniques with acid dyestuffs can be removed, moreover, the loss of dyes bringing about environmental pollution can be avoided in the process of late application (finishing and gluing) of dyed wood. Application of environmental-friendly M-type reactive dyes in wood dyeing technology can reduce a significant burden on the treatment of dyeing wastewater, not only bringing huge economic benefits to the enterprises, but also bringing enormous environmental benefits to society. In today's dyeing and printing industry of serious pollution, environmental-friendly M-type reactive dyes applied in wood dyeing industry will have great practical significance and social meaning.