Kinetics of Cross-Linking Softwood Kraft Pulp with 1,2,3,4-Butanetetracarboxylic Acid

Cross-linking of polysaccharides has been well studied in both the pulp and textile industries. One of the more investigated cross-linking agents is 1,2,3,4-butanetetracarboxylic acid (BTCA). The intrafiber cross-linking of cotton cellulose with BTCA has attracted great interest. In the case of wood pulp, reaction kinetics has been studied relatively little; instead, investigations have focused on fiber and paper properties. In this study, softwood kraft pulp fibers were cross-linked with BTCA, and the kinetics of the reaction was investigated and modeled. It was found that the reaction follows second-order kinetics, dependent on both the concentration of BTCA and the concentration of accessible hydroxyl groups in the fiber wall. It was further found that the initial concentration of accessible hydroxyl groups was proportional to the initial concentration of BTCA, thus simplifying the model into a second-order rate equation dependent only on the concentration of BTCA. A cross-linking reaction was confirmed by performing conductometric titration