Dispersing agents and novel lignin derivative using kraft lignin

A kraft lignin discharged during pulping using lignin derivative obtained as a raw material, to provide a dispersant which exhibits high dispersing performance and, to provide a novel lignin derivative from kraft lignin. A dispersing agent of the present invention, the lignin derivative having at least one constituent unit derived from kraft lignin and / or at least one water-soluble monomer, at least one constitutional unit derived from a salt thereof contains. The novel lignin derivative of the present invention has kraft lignin and / or at least one constituent unit derived from a salt thereof and at least one polyalkylene oxide chain and at least one anionic functional group. .BACKGROUND