A composition for increasing paper strength includes a dialdehyde-modified polyacrylamide strengthening agent, a water soluble compound that is soluble at about 5 wt % or greater in water at about 25° C., and water. The water soluble compound is typically present in a weight amount that is greater than a weight amount of the strengthening agent. The composition is formed by combining the strengthening agent and the water soluble compound in aqueous media to form the composition, wherein on a dry basis the water soluble compound is typically present in a greater amount than the strengthening agent, drying the composition to form a powder or paste that has a water content of less than about 10 weight percent and is stable after storage at about room temperature for about six months, and reconstituting the powder or paste by adding water thereto. The reconstituted composition may then be used to make paper.

Finely divided, cationic, aqueous polymer dispersion which is obtainable by emulsion polymerisation of ethylenically unsaturated monomers in an aqueous liquid containing a cationic prepolymer as a dispersant, wherein the cationic prepolymer is prepared in the presence of at least one polymerisation initiator by polymerisation of (a) from 15 to 45% by weight of at least one ethylenically unsaturated monomer comprising at least one quaternary ammonium group; (b) from 5 to 80% by weight of at least one optionally substituted styrene; (c) from 0 to 50% by weight of at least one C 1-12 alkyl (meth) acrylate; (d) from 0 to 10% by weight of at least one ethylenically unsaturated monomer comprising an acid group; (e) from 0 to 10% by weight of at least one ethylenically unsaturated monomer comprising an amine group; and (f) from 0 to 20% by weight of at least one non-ionic ethylenically unsaturated monomer differing from (b), (c) and (e), the sum of (a)+(b)+(c)+(d)+(e)+(f) being 100% by weight, in a first emulsion polymerisation in the presence of at least one non-ionic emulsifier, and thereafter, in the aqueous liquid containing the cationic prepolymer a second emulsion polymerisation is carried out, in the presence of at least one polymerisation initiator, of a monomer mixture comprising (i) from 10 to 70% by weight of at least one of an optionally substituted styrene or (meth) acrylonitrile; (ii) from 30 to 90% by weight of at least one CMS alkyl (meth) acrylate; (iii) from 0 to 30% by weight of at least one vinyl ester of linear or branched C.sub.1-30 carboxylic acids; and (iv) from 0 to 30% by weight of at least one non-ionic ethylenically unsaturated monomer differing from (i), (ii) and (iii), the sum of (i)+(ii)+(iii)+(iv) being 100% by weight, and the first emulsion polymerisation and/or the second emulsion polymerisation is optionally carried out in the presence of from 0 to 10% by weight of at least one polymerisation regulator. The polymer dispersions according to the present invention are suitable for use as sizing agents for paper, board and card board.

The present invention relates to a complex of polymers and to the use thereof in a method of making paper, cardboard or the like. This complex of polymers is obtained by polymerizing water-soluble monomers: in the presence of a host polymer that comprises vinylamine functions and of a non-polymeric transfer agent, and in the absence of a branching or crosslinking agent of the ethylenic polyfunctional type. It is obtained as from a mass ratio of anionic monomer to water that is greater than 0.035.

A method of enhancing paper strength properties is provided. The method comprises treating a paper sheet precursor with a polyaluminum salt, and a strengthening agent, wherein the strengthening agent comprises a dialdehyde-modified polyacrylamide copolymer and a polyacrylamide copolymer. The polyaluminum salt may be polyaluminum chloride. The methods have been demonstrated to provide, among other things, improvements in retention, strength, and dewatering.

A method of increasing chemical efficiency of chemical additives in a papermaking system includes the steps of providing thick stock pulp comprising soluble lignin, process water, and at least about 2% by weight of cellulosic fiber based on total weight of thick stock pulp, and adding at least one organic polymer to the thick stock pulp to reduce the amount of soluble lignin therein. The organic polymer is chosen from cationic polymers, non-ionic polymers and combinations thereof.

Strengthening resins and processes for making and using same. In some embodiments, a resin mixture can include a solvent and a strengthening resin. The strengthening resin can include one or more hydrophobic monomers incorporated therein. The strengthening resin can have a chemical formula of (I). The chemical formula (I) can include:

##STR00001##

where each R.sup.2 can be derived from a hydrophobic monomer.

Provided herein is an aqueous polymer dispersion (A) obtainable by free radical emulsion copolymerizing a first ethylenically unsaturated monomer blend having 15 to 100% by weight of at least one C1-C4-alkyl (meth)acrylate, in the presence of a water-soluble redox system having a first free radical initiator for free radical emulsion copolymerization and an aqueous prepolymer composition (B) obtainable by free radical emulsion copolymerizing in a polymerization solvent having C1-6-carboxylic acid and C1-6-carboxylic acid anhydride a second ethylenically unsaturated monomer blend with 5 to 50% by weight of at least one ethylenically unsaturated quaternary amine, and 10 to 95% by weight of at least one optionally substituted styrene, in the presence of a second free radical initiator.

A method is disclosed for dewatering of sludge from a pulp, paper or board making process, such as deinking sludge, including obtaining of an aqueous sludge including an aqueous phase and a fibre material suspended in the aqueous phase. The sludge is subjected to a pre-thickening step, where a first part of the aqueous phase is removed from the sludge and to a pressing step, where a second part of the aqueous phase is removed from the sludge, thereby obtaining a dry pressed sludge. Before or at the pre-thickening step a polymer composition having a charge density of at the most 1.7 meq/g, preferably at most 1.5 meq/g, more preferably at most 1.1 meq/g, is added to the sludge.

A polymer composition includes a first host polymer, which is a copolymer of (meth)acrylamide and at least one cationic first monomer, and a second polymer, which is a copolymer of (meth)acrylamide and at least one cationic second monomer. The second polymer is polymerised in presence of the first host polymer, and the first host polymer has a higher cationicity than the second polymer, the difference in cationicity of the first host polymer and the second polymer being at least 3 mol-%, at least 5 mol-%, more preferably at least 7 mol-%. The polymer composition has a standard viscosity of >2.0 mPas, measured at 0.1 weight-% solids content in an aqueous NaCl solution (1 M), at 25 C., using Brookfield VII T viscometer with UL adapter. The invention relates also to uses of said polymer composition.

A method for manufacture of paper, board or the like, comprising the step of dissolving a composition into aqueous solution, whereby an aqueous treatment solution is obtained for adding the obtained treatment solution to the pulp. The composition comprising a copolymer of acrylamide and at least one cationic monomer, the copolymer comprising cationic monomers at least 15 mol-%, calculated from total amount of monomers, and an ionic crosslinker agent comprising at least two carboxyl groups, wherein the equivalent ratio of carboxyl groups:cationic monomer is between 1:20 and 1:0.5.