METHOD FOR INCREASING THE DRY STRENGTH OF PAPER, PAPERBOARD, AND CARDBOARD

摘要

Process for the production of paper, board and cardboard having high dry strength by addition of (a) at least one trivalent cation in the form of a salt, (b) at least one water-soluble cationic polymer and (c) at least one water-soluble amphoteric polymer to the paper stock, draining of the paper stock with sheet formation and subsequent drying of the paper products, the water-soluble cationic polymer (b) being selected from the group consisting of the (i) polymers comprising vinylamine units and (ii) polymers comprising ethylenimine units.