where R is an alkyl group having 1 to 12 carbons, structure of which may be a straight chain or branched structure; X is --H or SO3M (where M is a counter ion that is a hydrogen ion, alkaline metal ion, ammonium ion, or organic ammonium ion); EO is an ethylene oxy group; PO is a propylene oxy group; n and m are repeating units, representing mean values in one of substances expressed in formula (I)