The invention relates to a composition for sizing of a surface of paper, board or the like and its use for increasing strength properties of paper, board or the like. The composition has a solids content of 3-30%, and it comprises degraded non-ion is starch, and at least 0.5 weight-% of anionic polyacrylamide, which has a molecular weight, MW, >500 000 g/mol and <2 500 000 g/mol and an anionicity in the range of 4-35 mol-%. The invention further relates also to a method for producing paper, board or the like, which comprises addition of a first strength composition, which comprises a cationic agent, to a fibre stock, formation of a fibrous web from the fibre stock, drying of the fibrous web to dryness of at least 60%, and application of a second strength com position, which comprises an anionic hydrophilic polymer and a starch component, on the surface of the fibrous web.

Methods of producing a multi-ply paper product are provided. The methods comprise applying coagulant and/or hybrid coagulant-flocculant composition to an upper ply substrate disposed adjacent and above a lower ply substrate in an amount such that a portion of the coagulant and/or the hybrid coagulant-flocculant composition passes through the upper ply substrate. Preferably, the lower ply substrate has a greater freeness than the upper ply substrate. The methods of the present disclosure preferably allow for efficient use of RDF chemicals while making use of the innate freeness differences between the upper and lower ply substrates.

Provided is a method for efficiently producing on an industrial scale a high-performance polyvinylamine solution having good handling properties. After producing a polymer containing N-vinylcarboxamide monomer units having a value of the weight average molecular weight (Mw)/number average molecular weight (Mn) of 5 or higher by aqueous solution standing adiabatic polymerization, the polymer is hydrolyzed in an aqueous solvent in the presence of an alkali and an antigelling agent. In a preferred embodiment of the present invention, a polymer powder having a volatile content of 0.1-12% by mass is obtained by drying and pulverizing after producing a (co)polymer, and the powder obtained is stored or transported to the site of use of the polymer solution and hydrolyzed in an aqueous solvent in the presence of an alkali and an antigelling agent when the polymer solution is needed or at the site of use of the polymer solution.

A strength additive system for manufacturing paper, board, tissue or the like includes preferably as separate components, a cationic strength agent, such as a cationic polymer with aldehyde functional groups, and an anionic copolymer obtained by polymerization of a reaction mixture including (meth)acrylamide and anionic monomers, the standard viscosity of the obtained copolymer being in a range of 1.5-5.0 mPas. A method for manufacturing of a paper, board, tissue or the like is further disclosed.

A method of improving dry strength and/or drainage of a paper or paperboard by adding to a paper or paperboard furnish, a graft copolymer composition of a vinyl monomer and a functionalized vinylamine-containing base polymer graft copolymer.

A polymeric structure, which is obtained by polymerisation of (meth) acrylamide and at least one charged monomer in a polymerisation medium comprising at least a first host polymer, which first host polymer comprises polyvinyl alcohol. The polymeric structure may be used in making of paper, board, tissue or the like as a strength agent, or in dewatering of sludge.

The invention relates to powdery, water-soluble, cationic polymer composition comprising at least two different cationic polymers, namely a first cationic polymer and a second cationic polymer, which differ in chemical nature and molecular weight, as well to a method for producing such powdery, water-soluble, cationic polymer composition, and to its use for promoting flocculation in solid-liquid separation, for example as a retention aid in paper manufacture, and in sludge dewatering/wastewater purification.

Embodiments of the present invention relate to a method of making a paper comprising the steps of: a) providing a cationic wet strength resin comprising a polyamidoamine epihalohydrin, a condensation copolymer of epihalohydrin and amine, or combination thereof; b) providing an anionic polymer; c) co-mixing the cationic wet strength resin and the anionic polymer to provide a composition comprising polyelectrolyte complexes; d) providing an aqueous pulp slurry, draining the aqueous pulp slurry on a screen to form a wet fiber web, and drying the wet fiber web to obtain the paper, wherein said co-mixed composition is introduced to the aqueous pulp slurry or on the formed wet fiber web. Embodiments of the present invention further relates to a paper wet strength composition, its use in paper making and a paper obtainable therefrom.

The present invention relates to a silica sol having a pH above about 10, molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, concentration of soluble silica above about 3000 mg SiO2/l, and S-value of from about 18 to about 40%. The invention further relates to a process for producing a silica sol which comprises acidifying an aqueous alkali metal silicate solution to a pH of from 1 to 4 to form an acid sol, alkalizing the acid sol by addition of aqueous alkali metal silicate solution to obtain an intermediate sol and interrupt the addition of aqueous alkali metal silicate solution when the intermediate sol has reached a pH of from about 5 to about 8, stirring the intermediate sol for a time period of from about 10 to about 6000 seconds without addition of aqueous alkali metal silicate solution, alkalizing the intermediate sol by addition of aqueous alkali metal silicate solution to obtain a silica sol having a pH above about 10 and molar ratio of SiO2:M2O, in which M is alkali metal, of from about 6:1 to about 16:1, and optionally adding an aluminum compound to the acid sol, intermediate sol or silica sol. The invention further relates to a silica sol obtainable by the process of the invention. The invention further relates to the use of the silica sol as a flocculating agent, in water purification and in producing paper and board. The invention further relates to a process for producing paper and board which comprises: (i) providing an aqueous suspension comprising cellulosic fibers; (ii) adding to the suspension one or more drainage and retention aids comprising the silica sol; and (iii) dewatering the obtained suspension to provide a sheet or web of paper or board.

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.