| abstract |
The present invention is: a polyacrylamide-based dry paper-strengthening agent containing amphoteric polyacrylamide, the polyacrylamide-based dry paper-strengthening agent being characterized in that the amphoteric polyacrylamide is obtained by polymerizing (a) 70-99.8 mol% of (meth)acrylamide, (b) 0.1-15 mol% of a cationic vinyl polymer, and (c) 0.1-15 mol% of an anionic vinyl polymer, the weight-average molecular mass (A) of the polyacrylamide-based dry paper-strengthening agent is 2,000,000-10,000,000, the ratio [(A)/(B)] between the weight-average molecular mass (A) and the B-type viscosity (B)(mPa∙s) of a 20 mass% aqueous solution obtained by adjusting the polyacrylamide-based dry paper-strengthening agent so that the solids concentration in the polyacrylamide-based dry paper-strengthening agent is 20 mass% at 25°C is equal to or greater than 500, and the thread length in a 20-mass% aqueous solution at 25°C is 5-60 mm; and a method for manufacturing paper-in which the polyacrylamide-based dry paper-strengthening agent is used. |