Cross-linked fluff pulp fibers for use in, for example, acquisition layers in absorption products can be found in the patent literature. Cross-linking improves properties such as the wet resilience of fluff pulp fiber networks. Among the more commonly seen cross-linkers are polycarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid (BTCA). These acids form ester bonds with the hydroxyl groups in the fiber wall. In this study, softwood kraft pulp fibers were cross-linked with BTCA. The swelling behavior of the fibers and properties related to acquisition in absorption products were studied. It was found that the water retention value (WRV) decreased as a consequence of the introduced cross-linker. After deprotonization of a large part of the introduced carboxylic acids, the WRV increased, but the cross-linker was still able to limit significant swelling of the fiber wall. The wet bulk under load of fiber networks, composed of cross-linked fibers, generally increased with a decrease in WRV. Furthermore, it was found that the property development obtained after a cross-linking reaction with BTCA may be predicted by introducing a relative reaction intensity, RIrel, that takes into account both time and temperature in the curing step. This shows that the time and temperature in the curing step are interchangeable.
Locating the Reaction Site of 1,2,3,4-Butanetetracarboxylic Acid Carboxyl and Cellulose Hydroxyl in the Esterification Cross-Linking
