Method for making paper and cardboard with high dry strength and resulting papers and cardboards

Abstract From the Canadian patent

The invention concerns a method for making a sheet of paper and/or cardboard and the like, which consists, prior to forming said sheet in adding to the , fibrous suspension, separately or mixed in any sequence of introduction, into one or more injection points, at least three dry strength agents respectively: a first agent corresponding to a (co)polymer having a cationic filler density higher than 1 meq/g and exhibiting primary amine functions; a second agent corresponding to a synthetic organic (co)polymer having a cationic filler density higher than 0.1 meq/g; and a third agent corresponding to a (co)polymer having an anionic filler density higher than 0.1 meq/g.