Studies On The Biotechnological Bleaching Of Hemp Fiber

The bleaching of hemp fiber is different from that of cotton fiber due to the different components of these two fibers. The content of lignin in hemp fiber is as high as more than 20%. Even after retting and pretreatment of hemp fiber, the lignin is still more than 7%. The higher capability of removing lignin is necessary during the bleaching of hemp fiber. Nowadays, peroxide is often used as the bleaching agent in the total chlorine-free bleaching system for cotton. The disadvantage of peroxide bleaching is that it has much influence on cellulose but shows lower capability for degrading lignin. So this system is not suitable for bleaching hemp fiber.This research is concerned with a new approach to degrading the lignin by biochemical technology in place of chloride bleaching or other chemical methods. The biodegradation capability of eight epiphytes for lignin was investigated. It was found that white rot fungi and woody shelf fungi had the best ability to degrade both the lignin and the cellulose. White rot fungi could degrade lignin in hemp fabric in the experiment, so it was thought that this technology could replace the existing chloride bleaching technology. During the biodegradation of lignin in hemp fabric, the white rot fungi had good adaptability and better degradation effect than woody shelf fungi. Therefore white rot fungi was considered as a bleaching agent. The best technology condition of biodegradation lignin of hemp fabric was as follows: bio-reaction time 72 hours, first culture time 24 hours, biodegrading lignin time 9 hours, stacking time 12 hours. After the biodegradation of lignin, the best bleaching technology of hemp fabric was as follows: the boiling in caustic soda solution for an hour, the dipping in vitriol for 4-5 minutes at 40-50℃, the stacking for an hour, the hydroxide peroxide bleaching for an hour at 70℃. After the treatment as described above, the white degree of hemp fabric reached to 86.50% and the strength reached to 880 N. In this research, a new approach to chloride-free bleaching during the bleaching of hemp fabric was carried out using the pretreatment white rot fungi and the degradation of lignin, followed by hydroxide peroxide bleaching...