Phenolated lignin, reaction with

FIGURE 11.6 Initial reaction on treatment of a phenolic lignin unit with oxygen and alkali. 

FIGURE 11.19 Reaction mechanism for oxidation of a phenolic lignin nnit with chlorine dioxide. 

The reaction of the Scheme 8.23 results in the formation of a substitnted phenolate ion and a radical. The radical is further reduced by the next AQ (Dimmel et al. 1985). The keto groups in lignin can be involved in the analogous reaction with AQ. This leads to formation of the ketyl fnnctions which originate analogous fragmentation processes. 

Thus, almost all the reactions of lignin substructure model dimers by the enzyme are explained on the basis of cation radical intermediates and their subsequent reactions with nucleophiles such as H2O and intramolecular hydroxyl groups, and with radicals such as di oxygen (for non-phenolic substrates), or on the basis of phenoxy radical intermediates (for phenolic substrates). 

Cure Rate of the Phenolated SEL Resins. 13C NMR spectra of the phenolated SEL formaldehyde-treated resins revealed the formation of methylol groups. A similar cure reaction to resole type phenolic resins is expected to occur with the phenolated lignin-based resins. Since cure rate normally determines production capacity of a board mill, it is important that new types of adhesives have at least the same cure rate as the conventional phenolic adhesives. Cure analysis of resins has usually been examined by... 

Examples where the phenolic hydroxy groups were utilized include the preparation of lignin epoxies by reaction with epichlorohydrin (2), esterifications with bis-acid chlorides (3) and cyanuric chloride (4), and polymerization with aziridines (5). 

The major functional groups in lignin are methoxy, phenolic hydroxy, aliphatic hydroxy, and carboxy groups. During reaction with alkylene oxide, most of the functional groups of lignin, besides methoxy groups, become... 

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