Patent ID: 6132558
Filing Date: 2000-10-17
Classification: D21H

Abstract:
A process for the production of paper or cardboard or both, which comprises:a) adding first and second water-soluble, cationic polymers in succession to pulp, wherein after the addition of the second water-soluble cationic polymer, the pulp is subjected to at least one shearing stage, and flocculating the mixture by adding a flocculating agent selected from the group consisting of bentonite, colloidal silica, and clay;b) forming a sheet from the mixture of step a); andc) drying the sheet formed in step b);wherein:said first water-soluble cationic polymer is a polyethyleneimine having a molar mass, M.sub.w, of more than 500,000, or a polymer containing vinylamine units and having a molar mass M.sub.w, of from 5,000 to 3,000,000 added in an amount of 0.001 to 0.8% by weight based on the weight of dry pulp.said second water-soluble cationic polymer is a cationic polyacrylamide, cationic starch, or polymer containing vinylamine units, the molar mass, M.sub.w of said polymer being at least 4,000,000 added in an amount of 0.001 to 0.8% weight based on the weight of dry pulp.