A composition is provided 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.multidot.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.sub.1/An.sub.1.gtoreq.1 (1)
Ca.sub.2/An.sub.2<1 (2)
Ca.sub.3/An.sub.3.gtoreq.1 (3)
.vertline.(Ca.sub.1-An.sub.1)-(Ca.sub.3-An.sub.3).vertline..gtoreq.1.5
(4)
wherein Ca.sub.1 and An.sub.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.sub.2 and An.sub.2, and Ca.sub.3 and An.sub.3, respectively
represent the total mole number of the cationic monomer units and the
total mole number of the anionic monomer units in the second and third
amphoteric polymers. The composition is excellent in various flocculation
and dewatering performances for various types of sludge, in particular,
for sludge high in ratio of excess sludge, and can be used for process
yield improvement in papermaking process.
Una composizione è fornita che contiene i polimeri anfoteri che contengono, come unità costituenti del monomero, un'unità cationica del monomero, un'unità anionica del monomero e facoltativamente un'unità non ionica del monomero ed aventi lle 0.5% viscosità salate di 10 - 120 mPa.multidot.s, in cui i polimeri anfoteri detti contengono un primo polimero anfotero che soddisfano la seguente espressione (1) e un secondo polimero anfotero che soddisfa la seguente espressione (2) o un terzo polimero anfotero che soddisfa le seguenti espressioni (3) e (4): Ca.sub.1/An.sub.1.gtoreq.1 (1) Ca.sub.2/An.sub.2
