We offer large quantities of dimethyl-5-sulfoisophthalate(as sipm, dmsip, dms, sip)/synonyms: Dimethyl-5-sulfoisophthalate sodium salt; 1,3 benzene-dicarboxylic acid; 5 sulfo-1,3-dimethyl ester sodium salt/cas no.3965-55-7. It is used as a dyeing modifier of cation dyeable polyester(cdpet) in filament/nylon yarn produce. The dyed yarn treated with the modified cdpet is bright and lustrous, having a complete range of color and dying deeply.