Alkyl Chain Cross-Linked Sulfobutylated Lignosulfonate: A Highly Efficient Dispersant for Carbendazim Suspension Concentrate

A new family of highly water-soluble alkyl chain cross-linked sulfobutylated lignosulfonates (AASLSs) with a three-dimensional network structure and naked alkyl sulfonic acid groups were readily prepared by using 1,4-butane sultone (BS) and C6H12Br2 by a one step reaction in water, which simultaneously improved the sulfonation degree and molecular weight. GPC, 1H NMR, FTIR and functional group content tests confirmed their cross-linked chemical structure and efficient nucleophilic substitution reaction mechanism. Furthermore, the dispersion properties of AASLSs in a carbendazim suspension concentrate (SC) system were investigated. AASLS4 with high molecular weights (Mw) and moderate sulfonation degrees showed suspensibility of 99% in 45% carbendazim SC after hot storage at 50 °C for 14 days. Meanwhile, AASLS4 also showed smaller SC particle size and better rheological performance than commercial lignosulfonate. The adsorption isotherms and ζ-potential of AASLSs on carbendazim SC particles were studied to reveal the dispersion mechanism. The alkyl chain cross-linked structure and long alkyl chain-containing sulfonic acid groups contribute to the excellent dispersion properties on carbendazim SC. Our modification approach for lignin might provide a novel concept and prospective avenue for the design of efficient dispersants.