Patent ID: 8501972

Claim:
A solid fatty acid alkyl ester sulfonate metal sail, having an endothermic peak area between 50° C. and 130° C. which is at least 50% more than an endothermic peak area between 0° C. and 130° C. when determined using a differential scanning calorimeter, wherein the solid fatty acid alkyl ester sulfonate metal salt has a water content of 10 mass % or less, and the fatty acid alkyl ester sulfonate metal salt is represented by formula (1): wherein R 1 is a straight-chain or branched alkyl or alkenyl group having 14 or 16 carbon atoms; R 2 is a straight-chain or branched alkyl group having 1 to 4 carbon atoms; M is an alkali metal ion or alkaline earth metal ion; and X is 1 when M is an alkali metal ion, and ½ when M is an alkaline earth metal ion.