Ozonization of lignin

Ozonization of lignin forms derivatives of muconic acid that have the unique chemical structure of conjugated double bonds with two carboxyl groups. These derivatives have great potential for chemical modification. The ozonized lignin of white birch was soluble in epoxy resin at 120°C, and the free carboxyl groups were found to react with epoxide. This paper discusses developmental work on the preparation of pre-reacted ozonized lignin/epoxy resins the dynamic mechanical properties of cured resins and preliminary results of the application of these resins as wood adhesives. 

Isolation and Ozonization of Lignin. The wood meal of white birch (Be-tula papyrifera Marsh.) was steamed for 15 min at 180°C, and extracted with water at 60°C, followed by extraction with methanol as shown in Figure 2. The methanol-soluble part was dried under vacuum after removal of methanol. The yield of methanol extract was 75% based on the amount of lignin present in the original wood. 

In an early study on the ozonation of lignin, Freudenberg et al (1935) found that both lignin and methylated lignin were more quickly oxidized in glacial acetic acid than in water Nakano and his coworkers (Matsumoto et al 1984a,b, 1986, Habu et al 1990) used acetic acid/water/methanol (16 3 1, v/v/v) as the reaction medium This mixture was also used by Sarkanen and his coworkers (Tsutsumi et al 1990 and unpubl work)... 

Temperature can evidently influence the course of ozonation per se, but the literature does not indicate the nature or yield of the final ozone-cleavage products are temperature-dependent. Therefore, the fact that most ozonations of lignin have been carried out within the convenient temperature range of 0-25 °C would seem justified. 

In this section, examples of information available from ozonation of lignin model compounds, related compounds, and lignins will be presented. Table 6.7.2 lists the monomeric and dimeric lignin model compounds that have been ozonated. 

T Eriksson, J Gierer. Relative rates of ozonation of lignin model compounds. 3rd International Symposium on Wood and Pulping Chemistry, Vancouver, Canada. Proceedings, Vol. 2, pp. 29-30, 1985. 

Hatakeyama H, Tonooka T, Nakano J, Migita N (1967) Ozonization of lignin model compounds. Kogyo Kagaku Zasshi. 70 2348-2352... 

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