MALDI-TOF study of oligomers distribution in spray-dried glyoxalated lignin for wood adhesives

Spray drying of glyoxalated lignin used in tannin/lignin adhesives for exterior- and interior-grade wood particleboard and other types of panels has been shown to be capable of maintaining its reactivity after spray drying with no decrease in performance of the adhesive once the spray-dried material is re-dissolved in water. This indicates that spray drying is a very suitable method for long-term storage of the adhesive without loss of performance. A clear variation in the distribution of oligomers in the material after spray drying has been observed by Matrix-Assisted Laser Desorption/Ionization Time of Flight analysis. One effect of the reaction that has been noticed with aging is the assembly of the monomers and lower molecular mass oligomers such as dimers into structures of higher molecular weight as a consequence of their condensation with glyoxal and the formation of glyoxylene bridges between them.