Process for the manufacture of paper and paperboard

Abstract

Process for the Manufacture of Paper and Paperboard The present invention relates to a process of making paper or paperboard in which a cellulosic thin stock is provided and subjected to one or more shear stages and then drained and a moving screen to form a sheet which is dried, wherein the process employs a retention system which is applied to the thin stock, said retention system comprising as components i) a blend of different cationic polymers and ii) a microparticulate material, in which the blend of cationic polymers comprises, a) a cationic polymer having a charge density of from 0.5 and below 3 mEq per gram and a molar mass of greater than 700,000 Da, which cationic polymer is selected from polymers containing vinyl amine units and polyethylenimine, b) a cationic polymer having a charge density of below 3 mEq per gram and an intrinsic viscosity of at least 3 dl/g, wherein one of the components of the retention system is dosed into the thin stock after the final shearing stage and the other is dosed into the thin stock before the final shearing stage.

Dependencies are inferred from the claim text.