LIGNIN DERIVATIVES .1. ALKANOATES

The synthesis, isolation, chemical and molecular structure determination, and the thermal properties are described for several esters of aliphatic monocarboxylic acids with non-sulfonated lignins. Chemical modification of lignin by acylation with carboxylic anhydrides can be performed in the conventional pyridine/anhydride mixture; or it may employ mixtures of acid. anhydride. and sodium alkanoate. On the average 0.7 to 1.4 OAcyl groups were introduced per phenylpropane unit according to aminolysis and H-NMR spectroscopy. The addition of hydrogen peroxide to the esterification mixture during the final stage of acylation represents a convenient and effective peroxyalkanoic acid bleaching step. This simultaneously reduces the derivatives' molecular weight distributions by 50 to 60%. Lignin alkanoates are derivatives with improved solubility as compared to the starting materials; with distinctly discernable glass transition temperatures; with the ability to undergo melt-flow with low density polyethylene; and with superior polymer decomposition characteristics. The acylation by increasingly bulky monocarboxylic acids results in declining thermal softening temperatures.