Patent ID: 7141181

Claim:
A composition which comprises amphoteric polymers comprising, as constituent monomer units, a cationic monomer unit, an anionic monomer unit, and optionally a nonionic monomer unit and having a 0.5% salted viscosity of 10 to 120 mPa·s, wherein said amphoteric polymers comprise a first amphoteric polymer satisfying the following expression (1), and a second amphoteric polymer satisfying the following expression (2) or a third amphoteric polymer satisfying the following expressions (3) and (4): Ca 1 /An 1 ≧1 (1) Ca 2 /An 2 <1 (2) Ca 3 /An 3 ≧1 (3) |(Ca 1 −An 1 )−(Ca 3 −An 3 )|≧1.5 (4) wherein Ca 1 and An 1 respectively represent the total mole number of the cationic monomer units and the total mole number of the anionic monomer units in the first amphoteric polymer on a condition that the total mole number of all the constituent monomer units in the first amphoteric polymer is converted to be 100 mol; on a condition similar to the above, Ca 2 and An 2 respectively represent the total mole number of the cationic monomer units and the total mole number of the anionic monomer units in the second amphoteric polymer; and on a condition similar to the above, Ca 3 and An 3 respectively represent the total mole number of the cationic monomer units and the total mole number of the anionic monomer units in the third amphoteric polymer, wherein said cationic monomer unit is selected from the group consisting of tertiary salts of dialkylaminoalkyl (meth)acrylates, quaternary salts of dialkylaminoalkyl (meth)acrylates, tertiary salts of dialkyl (meth)acrylamides, and quaternary salts of dialkyl (meth)acrylamides.