The effects of pulping variables on the molecular weight and molecular weight distribution of dissolved lignin have been studied. Kraft lignins were prepared by cooking Slash pine (Pinus caribaea) wood chips in a pilot-scale batch circulation digester. Four pulping variables, effective alkali, sulfidity, cooking temperature, and time-at-temperature. were arranged in a very broad input space under a central composite experimental design, and their effects on the molecular weight of dissolved lignin were examined by means of fifteen-parameter quadratic models.
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