Preparation and Evaluation of Mordants for Neutral Rosin Size Emulsion from Lignin

摘要

Mordants for neutral rosin size emulsion from lignin were prepared and their abilities evaluated. To convert lignin into the mordant, an amino group was introduced to lignin by the Mannich reaction and the reaction with glycidyltrimethylammonium chloride (GTA). In this study, kraft lignin and phe-nolated sulfuric acid lignin (P-SAL) were used. In an experimental system composed of the handsheets made with LBKP, sizing agent and lignin derivatives, a Mannich reaction product prepared from kraft lignin failed to exhibit any mordant characteristic, whereas Mannich reaction products (MP-SAL) prepared from P~SAL were highly effective as mordants. MP-SAL with ethylamino group especially showed higher performance. The MP-SAL with the higher pK, value of the introduced amino group also had higher performance. In the rosin emulsion-alum system, MP-SAL and GP-SAL, the latter of which is the reaction product of P-SAL with GTA, enhanced the sizing effectiveness under acidic to neutral pH range. The handsheets prepared with MP-SAL or GP-SAL in addition to alum still showed the sizing effectiveness after chloroform extraction, although the sizing effectiveness of the handsheets prepared only with alum disappeared after chloroform extraction. Thus, these results suggest that the enhancement of sizing effectiveness contributed to greater association between the size and the fiber surfaces with the addition of MP-SAL or GP-SAL. A decrease in brightness was observed when MP-SAL or GP-SAL was used as a mordant. According to the Kubelka-Munk theory, the brightness of original pulp with85% brightness was calculated to decrease 16. 9% and 4.3% by adding 0. 2% MP-SAL and 0.2% GP-SAL, respectively, but the brightness decrease of a pulp with 50% brightness by adding 0.2% MP-SAL and 0. 2% GP-SAL was only 1.9% and 0. 6%, respectively. This suggested that the lignin derivatives are as capable as a mordant in newspaper and mechanical papers, which do not require a high level of brightness