Patent ID: 7704939

Claim:
A surfactant which comprises a neutralized salt (AB1) and/or a neutralized salt (AB2), the neutralized salt (AB1) comprising: an acidic compound (A1) containing at least each one of an acid group (X1) of an acid having the difference of heat of formation in an acid dissociation reaction (Q1) of 3 to 200 kcal/mol and a hydrophobic group (Y) containing 1 to 36 carbon atoms; and a nitrogen-containing basic compound (B) having the difference of heat of formation in a proton addition reaction (Q2) of 10 to 152 kcal/mol, wherein (X1) is at least one species selected from the group consisting of a sulfonic acid group, sulfuric acid group, phosphoric acid group, phosphonic acid group, carboxymethyloxy group, carboxyethyloxy group, (di)carboxymethylamino group, (di)carboxyethylamino group, a group represented by the formula (1), and a group represented by the formula (2): —C(H) a (W) b —COOH (1) —Ar(W) c —COOH (2) where W represents a nitro group, cyano group, trihalomethyl group, formyl group, acetyl group, alkyloxycarbonyl group, alkylsulfonyl group, ammonio group, or a halogen atom; Ar represents an aryl group containing 5 to 14 carbon atoms; a is an integer of 0 or 1, b is an integer of 1 or 2, and c is an integer of 1 to 8; and the carbon number of an alkyl in the alkyloxycarbonyl group and alkylsulfonyl group is 1 to 3, and the neutralized salt (AB2) comprising: a polymer (A2) having at least one acid group (X2) within a molecule thereof; and the nitrogen-containing basic compound (B) having a difference of heat of formation in a proton addition reaction (Q2) of 10 to 152 kcal/mol, wherein the nitrogen-containing basic compound (B) is a compound containing at least one of: N═P—N skeleton within a molecule (B-3) thereof, and a proton sponge derivative (B-4).