Process for the manufacture of paper and paperboard

A process of making paper or paperboard, comprising subjecting a cellulosic thin stock to one or more shear stages and then draining through a moving screen to form a sheet which is dried,

• wherein the process employs a retention system which is applied to the thin stock, the retention system comprising as components
• i) a blend of different cationic polymers, and
• ii) a microparticulate material, which microparticulate material is selected from colloidal silica and bentonite,
• in which the blend of cationic polymers comprises:
• a) from 50 ppm to 3000 ppm dose rate of a cationic polymer having a charge density of from 1 to 2 mEq per gram and a molar mass of from greater than 700,000 Da to 3 million Da, which cationic polymer is selected from polymers comprising vinyl amine units, and
• b) from 50 ppm to 1000 ppm dose rate of a cationic polymer haying a charge density of below 3 mEq per grain and an intrinsic viscosity of at least 10 dl/g, which cationic polymer is a cationic polyacrylamide comprising acrylamide and from 5 to 10 mole % of at least one water-soluble cationic ethylenically unsaturated monomer,
• wherein i) the blend of cationic polymers is dosed into the thin stock prior to the final shearing stage and ii) the microparticulate material is dosed into the thin stock after the final shearing stage, and
• wherein the ppm dose rate is based on the active weight of the cationic polymer relative to a dry weight of the cellulosic thin stock suspension,
• 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.