Abstract: A papermaking agent exhibiting an excellent freeness and paper strength effect with little increase in viscosity after long-term storage. A papermaking agent including a (meth)acrylamide polymer containing two or more starches (a1) selected from the group consisting of unmodified starch, oxidized starch, esterified starch, etherified starch, amidated starch, cationic starch, amphoteric starch and crosslinked starch, a (meth)acrylamide (a2), a polymerizable monomer having an amino group (a3), a polymerizable monomer having a carboxy group (a4) and a polymerizable monomer having a sulfonate group (a5) as essential constituent components.

Abstract: A relatively inexpensive papermaking agent having a high concentration and a high molecular weight that exhibits an excellent freeness and paper strength effect obtained using starches which are biomass materials. A papermaking agent which is a (meth)acrylamide polymer containing starches (a1), a (meth)acrylamide (a2), a polymerizable monomer having an amino group (a3), a polymerizable monomer having a carboxy group (a4) and a polymerizable monomer having a sulfonate group (a5) as essential constituent components, wherein the ratio between the amount of the component (a1) used in terms of non-volatile content weight and a total amount of the components (a2) to (a5) used is [(a1)/{(a2)+(a3)+(a4)+(a5)}]=5/95 to 45/55, and wherein the (meth)acrylamide polymer has a non-volatile content concentration of 22 to 35 weight %, and a weight average molecular weight of 1,500,000 to 7,000,000.

Abstract: Provided is a powdery paper-strengthening agent comprising an amphoteric (meth)acrylamide-based polymer (A) having a weight-average molecular weight of 1,000,000 to 7,000,000, wherein the amphoteric (meth)acrylamide-based polymer (A) comprises, as constituent monomers, (meth)acrylamide which is an (a1) component, a cationic unsaturated monomer which is an (a2) component, an anionic unsaturated monomer which is an (a3) component, and a crosslinkable unsaturated monomer which is an (a4) component, and wherein an aqueous solution, in which the amphoteric (meth)acrylamide-based polymer (A) is dissolved in a calcium chloride aqueous solution having an electrical conductivity of 4 mS/cm at 25° C. so as to be 1% by weight, has a maximum turbidity of 10 to 2500 NTU at pH 3 to 9.