KRAFT LIGNIN RECOVERY AND ITS USE IN THE PREPARATION OFLIGNIN-BASED PHENOL FORMALDEHYDE RESINSFOR PLYWOOD

摘要

Lignin was precipitated from kraft black liquor using carbon dioxide. To remove the residual black liquor and to purify the lignin, a pilot press filter or a pilot belt filter was used, and their performance was compared. The purity, molecular weight distribution, morphology, chemical and thermal properties of the final lignin product were characterized. The results showed that the lignin recovered from both the filter press and the belt filter was sufficiently pure to be used as a fuel in the lime kiln (or in most other combustion processes), or in any of the several possible high-value applications. No major difference was observed in the physico-chemical properties of lignins produced using a belt filter vs. a filter press. However, the solids content of the lignin filtered through the press filter was about 2 times higher than the one obtained using the belt filter, and the filtration rate obtained with the filter press was 5 to 6 times higher than that obtained with the belt filter. The purified lignin product recovered from the filter press was used to substitute 30, 40 and 50% of the phenol present in the formulation of the lignin-phenol-formaldehyde (LPF) resins used as an adhesive for the preparation of plywood samples. The results showed that up to 30% of phenol could be replaced by kraft lignin, without any major change in plywood shear strength.