Process for the manufacture of a paper or a cardboard having improved retention

An improved process for manufacturing paper or cardboard having improved retention, consisting of adding a polyacrylamide as the sole flocculent and a bentonite to a fibrous suspension of pulp, the steps comprising:

• dissolving in water a branched cationic polyacrylamide powder having a cationcity from about 10 to 45 mol percent;
• wherein said branched polyacrylamide is a cationic copolymer of acrylamide and of an unsaturated cationic ethylenic monomer, chosen from the group consisting of quaternised dimethylaminoethyl acrylate (DMAEA), salified dimethylaminoethyl acrylate (DMAEA), quaternised dimethylaminoethyl methacrylate (DMAEMA), salified dimethylaminoethyl methacrylate (DMAEMA), dimethyldiallyl-ammonium chloride (DADMAC), acrylamidopropyltrimethyl-ammonium chloride (APTAC), and methacrylamido-propyltrimethylammonium (MAPTAC);
• and wherein said polyacrylamide is branched by a branching agent consisting of a polyfunctional compound having at least two reactive groups chosen from the group consisting of double bonds, aldehyde bonds, and epoxy bonds,
• introducing said dissolved branched cationic polyacrylamide into the fibrous suspension at a concentration of 0.03 to 1.0 per thousand (0.03 to 1.0%) by weight of dry weight of the fibrous suspension;
• shearing the suspension containing said dissolved branched cationic polyacrylamide;
• and
• adding bentonite thereto at a concentration of 0.1 to 0.5 percent (0.1 to 0.5%) of dry weight of the fibrous suspension while stirring to form a resulting suspension.