The present invention relates to a process for manufacturing a sheet of paper and/or board from a fibrous suspension, according to which, before the formation of said sheet, added to the fibrous suspension, at one or more injection points, are at least two retention aids respectively: (a) at least one water-soluble organic cationic polymer P1 having a cationicity greater than 2 meq.Math.g.sup.1, and (b) at least one water-soluble amphoteric polymer P2 of at least one anionic monomer and of at least one cationic monomer.

The polymer P2 is added to the fibrous suspension after dissolving, in aqueous solution, the polymer P2 previously obtained by one of the following polymerization techniques: gel polymerization, suspension polymerization, inverse emulsion polymerization, dispersion polymerization.

The polymer P2 has a factor F>2, said factor F being defined by the formula: F=UL.sup.2[(100A)/(100C)] with UL: Brookfield viscosity of the polymer P2 at 0.1% by weight in a 1M aqueous solution of NaCl, at 23 C., with a UL module and at 60 rev.Math.min.sup.1, A and C corresponding respectively to the molar percentages of the anionic and cationic monomers of the polymer P2.

The present invention relates to a process for manufacturing a sheet of paper and/or board from a fibrous suspension, according to which, before the formation of said sheet, added to the fibrous suspension, at one or more injection points, are at least two retention aids respectively: (a) at least one water-soluble organic cationic polymer P1 having a cationicity greater than 2 meq.Math.g.sup.1, and (b) at least one water-soluble amphoteric polymer P2 of at least one anionic monomer and of at least one cationic monomer.

The polymer P2 is added to the fibrous suspension after dissolving, in aqueous solution, the polymer P2 previously obtained by one of the following polymerization techniques: gel polymerization, suspension polymerization, inverse emulsion polymerization, dispersion polymerization.

The polymer P2 has a factor F>2, said factor F being defined by the formula: F=UL.sup.2[(100A)/(100C)] with UL: Brookfield viscosity of the polymer P2 at 0.1% by weight in a 1M aqueous solution of NaCl, at 23 C., with a UL module and at 60 rev.Math.min.sup.1, A and C corresponding respectively to the molar percentages of the anionic and cationic monomers of the polymer P2.

Drainage and press dewatering system for manufacture of paper, board or the like, comprising (a) amphoteric polyacrylamide, which is a copolymer obtained by polymerizing (meth)acrylamide and 1-80 mol-% of cationic monomers and/or 0.1-70 mol-% of anionic monomers, the polyacrylamide having an intrinsic viscosity in the range of 6-38 dl/g, (b) inorganic microparticles of siliceous material, such as colloidal silica or bentonite, and (c) a high-charged cationic coagulant having a charge density over 5 meq/g and preferably over 6 meq/g determined at pH 6 and selected from aluminium based coagulants, organic polymers and mixtures thereof.

Drainage and press dewatering system for manufacture of paper, board or the like, comprising (a) amphoteric polyacrylamide, which is a copolymer obtained by polymerizing (meth)acrylamide and 1-80 mol-% of cationic monomers and/or 0.1-70 mol-% of anionic monomers, the polyacrylamide having an intrinsic viscosity in the range of 6-38 dl/g, (b) inorganic microparticles of siliceous material, such as colloidal silica or bentonite, and (c) a high-charged cationic coagulant having a charge density over 5 meq/g and preferably over 6 meq/g determined at pH 6 and selected from aluminium based coagulants, organic polymers and mixtures thereof.

The present invention relates to a new process for improving dewatering when manufacturing a film comprising high amounts of microfibrillated cellulose (MFC) without negatively impacting the film properties. According to the present invention a high amount of nanoparticles is used as an additive, optionally together with a polymer.

The invention relates to a ply of a linerboard for corrugated board, which ply exhibits high strength properties and which enables the production of lightweight linerboards. The ply of the invention comprises 20-80 wt % CTMP from wood fibers and 80-20 wt % chemical pulp, calculated on the total fiber weight of said ply and strength additives chosen from the group of microfibrillated cellulose (MFC), anionic or cationic polymers and starch or combinations thereof. The ply exhibits a geometric SCT index of above 22 Nm/g and a density of below 680 kg/m.sup.3, preferably of below 650 kg/m.sup.3.

The present disclosure provides an improved process for making paper or paper board. The process comprises providing a cellulosic fibre suspension comprising recycled fibre material, and having a conductivity of at least 1.5 ms/cm; and adding a glyoxalated copolymer of acrylamide and cationic monomers and inorganic siliceous microparticles to the fibre suspension, sequentially or simultaneously. Advantages comprise improved productivity of the process, and paper strength.

The present disclosure relates to a dry strength agent composition, use of an amine-containing cationic polymer for enhancing the dry strength of paper, and a method for enhancing the dry strength of paper. The dry strength agent composition includes at least two components. The first component is an amine-containing cationic polymer and the second component may be one or more anionic or amphoteric polymers.

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.

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.