Manufacturing paper employing a polymer of acrylic or methacrylic acid

In the manufacture of paper wherein the paper-forming material is contacted with an aqueous slurry containing a retention agent and a pigment or filler, and then the slurry is de-watered to form paper, the improvement wherein the aqueous slurry comprises a highly concentrated aqueous suspension of a pigment or filler produced by grinding such pigment or filler in the presence of water and an additive comprising an amphoteric water soluble polymer which incorporates

• a) 90 to 30%-wt acrylic acid and/or methacrylic acid
• b) 10 to 60%-wt of a compound of the formula ##STR3## wherein R.sub.1 stands for hydrogen or the methyl radical, R.sub.2 and R.sub.3, which are either the same or different, stand for the methyl or ethyl radical, and an alkylene radical having 1 to 5 C atoms stands for X
• c) 0 to 50%-wt of acrylamidomethylpropane sulfonic acid
• d) 0 to 10%-wt of another ethylenically unsaturated compound selected from the group consisting of acrylamide, acrylic acid methylester, hydroxypropyl acrylate, and acrylonitrile and the molecular weight, measured at a pH value of 8.0, is smaller than 100,000.