Synthesis and Properties of Rosin-Modified Lignosulfonates

Rosin-modified lignosulfonates were prepared according to the following procedure: firstly, sulfomethylation of kraft lignin; secondly, preparation of 2,3-epoxypropyl ester of rosin; thirdly, preparation of modified-rosin lignosulfonates via etherification of sulfomethylated lignin with 2,3-epoxy propyl ester of rosin. Experimental results show that the optimum conditions for synthesis of 2,3-epoxy propyl ester of rosin are as follows: molar ratio for n(rosin): n (epichlorohydrin): n (NaOH) is1:6:1, reaction temperature is 100 °C(for rosin ester) and 75 °C(for 2,3-epoxypropyl ester of rosin, the same below), reaction time is 5.5 h and 3 h respectively. When molar ratio of lignosulfonate to 2,3-epoxypropylester of rosin is 1/5, rosin-modified lignosulfonates were prepared at 55 °Cfor 4.5 h with pH 11.5. Hydrophilic sulfonic group and the lipophilic adbietic group were incorporated into the molecular structure of kraft lignin via corresponding reactions. The surface tension of 10 g/L aqueous solution of rosin-modified lignosulfonate is 49.3 mN/m.