Polymers from kraft pulping spent liquor

Forest industry side streams form a poorly utilized source of raw materials that could be refined to value-added chemicals as will be shown in this article. Most of the side streams are used today for energy production and earth construction. During kraft pulping half of wood is dissolved into black liquor. This black liquor is combusted to recover the cooking chemicals and energy. Black liquor contains various organic compounds such as lignin and aliphatic acids. Exploitation of these acids has gained scattered interest, although some, such as glycolic and lactic acids, have currently well-established uses. Isolation of individual acids is one, although not the only, way of converting such a side stream into more value-added products. Polymers of glycolic and lactic acids were polymerized from model compounds. These polymers can be used for packaging applications ranging from hot melts to aqueous coatings and films. Polyglycolic acid copolymers have interesting barrier and mechanical properties. It is also possible to polymerize a model mixture of three smallest black liquor hydroxy acids, which could decrease the need to isolate individual acids. The polymerization was not sensitive to the ratio of these three acids