Process for producing sized paper and cardboard with polyelectrolytes and epoxide-amine-polyamide reaction products

A process for producing paper or cardboard, sized in the pulp, on a paper machine, with an epoxide-amine-polyamide reaction product, comprising the steps of adding to the pulp fiber suspension, which has a pH value of 5 to 8,

• (A) a water-soluble high molecular weight polyelectrolyte, which is cationic if the pH value of the fiber suspension is 6.5 to 8 and anionic if the pH value of the fiber suspension is 5 to 7, followed by
• (B) A water-soluble or water-dispersible salt of an epoxide-amine-polyamide reaction product;
• wherein the cationic polyelectrolyte is selected from the group consisting of a cationically modified starch;
• cationically modified carbohydrates from guar flour or locust bean flour having molecular weights of 250,000 to 350,000;
• a cationally modified alginic acid having a degree of polymerization of 800 to 1200;
• a condensation product from dicyandiamide or cyanamide, formaldehyde and an ammonium halide;
• a cationic polyacrylic amide;
• an epichlorohydrin adduct of a reaction product from a polyalkylenepolyamine and an aliphatic dicarboxylic acid;
• an epichlorohydrin adduct of a reaction product from a polyalkylenepolyamine and dicyandiamide or cyanamide;
• and an epichlorohydrin adduct of a reaction product from a polyalkylenepolyamine, dicyandiamide or cyanamide, and an aliphatic dicarboxylic acid which is unesterified or esterified with alkanols;
• wherein the anionic polyelectrolyte is selected from the group consisting of a dimerized condensation product from a naphthalenesulphonic acid and formaldehyde;
• a copolymer from acrylic acid and acrylic amide;
• or an alkali metal salt or ammonium salt of alginic acid, having a degree of polymerization of 800 to 1200;
• wherein component (B) is a salt of the reaction product from
• (a) 1.0 epoxide group equivalent of a polyglycidyl ether of 2,2-bis(4'-hydroxyphenyl)-propane,
• (b) 0.4 to 0.6 amino group equivalent of a mono-fatty amine having 16 to 18 carbon atoms, and
• (c) 0.3 to 0.5 amino group equivalent of a polyalkeneaminopolyamide from
• (c') polymerised linoleic or linolenic acid, and
• (c") diethylenetriamine, triethylenetetramine or tetraethylenepentamine,
• in the form of an aqueous preparation having a solids content of 25 to 35 percent by weight and a pH value of 4 to 5;
• wherein component (A) is added in an amount which is 0.01 to 1 percent by weight, relative to the dry-fiber content of the fiber suspension;
• wherein component (B) is added in an amount which is 0.1 to 3 percent by weight, relative to the dry-fiber content of the fiber suspension;
• and wherein component (A) is added 8 to 80 seconds before the fiber suspension reaches the breastbox of the paper machine, and component (B) 3 to 50 seconds before the fiber suspension reaches the breastbox, however at least 5 seconds after the addition of component (A).