A dispersing agent for coal-water slurry

Claim 1

A dispersing agent for a coal-water slurry, comprising a polyelectrolyte made by reacting an alkali metal compound, an alkali earth metal compound, ammonia or an amine with a modified α-olefin-maleic anhydride copolymer comprising a structural unit [I] based on the α-olefin, a structural unit [II] based on maleic anhydride and a modified structural unit selected from the group consisting of [A] a terminal group [III] of the general formula wherein R 1 represents a hydrocarbon residue having 4 to 30 carbon atoms, and [B] a structural unit [IV] of the general formula wherein R 2 represents a hydrocarbon residue having 4 to 30 carbon atoms and n is zero or 1, the structural unit [IV] being contained in the main chain , the molar ratio of the unit [IV] to the unit [II] ranging from 0.005 to 0.2, said copolymer containing units [I] and [II] in such an amount that the molar ratio unit [I] to unit [II] is in the range of from 0.8 to 3.0 and having a weight average molecular weight of 1 ,000 to 20,000.