Abstract: Properties of N-dodecyl-N,N-dimethyl-N-benzyl sulfobetaine (DBSB) as a phosphate-free detergent builder to replace 4A zeolite were investigated.Results showed that lime soap dispersion power (LSDP) of DBSB achieves 3%.When LAS is blended with DBSB,its calcium tolerance is enhanced.In case the mass fraction of DBSB in the blend system of LAS and DBSB achieves 15%,its calcium tolerance can be elevated from 5 mmol·L^-1 to 30 mmol·L^-1.Formulating DBSB into standard phosphate-free laundry powder to replace 4A zeolite will retain its good detergency with significant improvement of resistance to hard water.Via orthogonal designed experiments,an optimized formulation 5 was recommended that shows better detergency in water with hardness of 250 and 400 mg·L^-1 as comparing with 4A zeolite formulated phosphate-free laundry powder formulation 6.In addition,residual ash content caused from the laundry powder formulation 5 is lower than that from formulation 6;the DBSB formulated product displays lower foam with all other specifications,such as pH,total active matter content and free alkalinity in conformity with that specified in the China national standard.

Key words: dodecyl benzyl sulfobetaine, phosphate-free detergent builder, hard water resistance, phosphate-free laundry powder