The invention relates to a strength agent for paper, board or the like. The strength agent comprises a first component, which is refined cellulosic fibres having a refining level of >70° SR, and a second component, which is a synthetic cationic polymer having a charge density of 0.1-2.5 meq/g, determined at pH 2.7, and an average molecular weight of >300 000 g/mol. The invention relates also to a use of the strength agent and to a method for increasing strength properties of paper, board or the like.

The invention relates to a strength agent for paper, board or the like. The strength agent comprises a first component, which is refined cellulosic fibres having a refining level of >70° SR, and a second component, which is a synthetic cationic polymer having a charge density of 0.1-2.5 meq/g, determined at pH 2.7, and an average molecular weight of >300 000 g/mol. The invention relates also to a use of the strength agent and to a method for increasing strength properties of paper, board or the like.

The invention relates to a method for modifying nanofibrillar cellulose composition, comprising—preparing fibrous dispersion of ionically charged nanofibrillar cellulose (NFC), and—applying heat treatment at a temperature of at least 90° C. to the fibrous dispersion until the viscosity of NFC starts to decrease. The viscosity of the heat-treated NFC is reversible by applying shear forces to the NFC.

The invention relates to a method for modifying nanofibrillar cellulose composition, comprising—preparing fibrous dispersion of ionically charged nanofibrillar cellulose (NFC), and—applying heat treatment at a temperature of at least 90° C. to the fibrous dispersion until the viscosity of NFC starts to decrease. The viscosity of the heat-treated NFC is reversible by applying shear forces to the NFC.

The present invention relates to a process for producing paper, card and board. The present invention is based on the discovery that controlling solids content during the process in a specified manner provide enhanced initial web strength of the paper prior to drying and allows for higher machine speeds in the paper production process as compared to known processes.

The present invention relates to a process for producing paper, card and board. The present invention is based on the discovery that controlling solids content during the process in a specified manner provide enhanced initial web strength of the paper prior to drying and allows for higher machine speeds in the paper production process as compared to known processes.

Treated substrates and methods of forming the same are provided. In an exemplary embodiment, a treated substrate includes lignocellulose and a polymer fixed to the lignocellulose to form the treated substrate. The polymer includes a succinic moiety that can reversibly change between a succinic anhydride and a succinic acid moiety. The treated substrate has a wet tensile index of about 3 newton meters per gram or less.

Treated substrates and methods of forming the same are provided. In an exemplary embodiment, a treated substrate includes lignocellulose and a polymer fixed to the lignocellulose to form the treated substrate. The polymer includes a succinic moiety that can reversibly change between a succinic anhydride and a succinic acid moiety. The treated substrate has a wet tensile index of about 3 newton meters per gram or less.

A method for the production of paper or cardboard is provide comprising the following steps: (A) Adding a water soluble polymer P to a first aqueous pulp suspension, wherein polymer P is obtainable by Polymerizing to a polymer V of (i) 33 to 83 mol % of a monomer of formula I ##STR00001## in which R.sup.1═H or C.sub.1-C.sub.6 alkyl, (ii) 6 to 56 mol % of diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride or a salt form of a monoethylenically unsaturated monomer, (iii) 11 to 61 mol % of a monoethylenically unsaturated carboxylic acid, sulfonic acid or phosphonic acid, or salt forms thereof, (iv) 0 to 50 mol % of one or more ethylenically unsaturated monomers, and hydrolyzing the N—C(═O)R.sup.1 groups to form primary amino or amidine groups, (B) dehydrating the second aqueous pulp suspension to a wet paper structure, (C) dehydrating the wet paper structure.

A method for the production of paper or cardboard is provide comprising the following steps: (A) Adding a water soluble polymer P to a first aqueous pulp suspension, wherein polymer P is obtainable by Polymerizing to a polymer V of (i) 33 to 83 mol % of a monomer of formula I ##STR00001## in which R.sup.1═H or C.sub.1-C.sub.6 alkyl, (ii) 6 to 56 mol % of diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride or a salt form of a monoethylenically unsaturated monomer, (iii) 11 to 61 mol % of a monoethylenically unsaturated carboxylic acid, sulfonic acid or phosphonic acid, or salt forms thereof, (iv) 0 to 50 mol % of one or more ethylenically unsaturated monomers, and hydrolyzing the N—C(═O)R.sup.1 groups to form primary amino or amidine groups, (B) dehydrating the second aqueous pulp suspension to a wet paper structure, (C) dehydrating the wet paper structure.