Laccase-Mediator Catalyzed Modification of Wood Fibers: Studieson the Reaction Mechanism and Making of Medium-Density Fiberboard

摘要

Owing to the constant increase of prices of the process for petrochemical resin and the possibility of harmful formaldehyde emissions from industrial produced medium-density fiberboards (MDF), enzymatic binder systems are discussed as an environmentally friendly alternative for gluing lignocelluloses such as wood fibers. In this work laccase-mediator systems (LMSs) were used to activate the lignin on wood fiber surfaces. Two different mediators were tested, vanillic acid (VAN) and 4-hydroxybenzoic acid (HBA), of which HBA performed best. Carbon-13 nuclear magnetic resonances (l3C-NMR) and electron spin resonances (ESR) of LMS-treated thermomechanical pulp (TMP) fibers were determined for qualitative and quantitative analysis of lignin activation. Analysis outputs were transferred to produce MDF using a dry process. 1 C-NMR revealed more structural changes in the wood fibers using LMS with HBA than LMS with VAN. ESR spectroscopy indicated a higher amount of phenoxy radicals after treatment with LMScontaining HBA as a mediator. The data correlated well with the quality of MDF. The best mechanical technological properties were achieved by using HBA within the LMS, so that the European Norms could be fulfilled. But VAN also performed well, which showed a high potential to produce ecofriendly MDF by using LMSs in the future.