Methods of forming crosslinked cellulose include mixing a crosslinking agent with cellulose mat fiber fragments composed of hydrogen-bonded cellulose fibers and having a solids content of about 45-95% to form a substantially homogenous mixture of non-crosslinked, individualized cellulose fibers, drying the resulting mixture to 85-100% solids, then curing the dried mixture under conditions effective to crosslink the cellulose fibers. Some of such methods may include fragmenting a cellulose fiber mat to form the mat fragments. Systems include a mixing unit (such as a high-consistency mixer) configured to form, from the mat fragments and a crosslinking agent, a substantially homogenous mixture of non-crosslinked, individualized cellulose fibers and crosslinking agent, at ambient conditions, a drying unit to dry the substantially homogenous mixture to a consistency of 85-100%, and a curing unit and to cure the crosslinking agent to form dried and cured crosslinked cellulose fibers.

A paper-making aid composition, as well as processes for increasing tensile strength in paper and paper-making processes are provided. The paper-making composition comprises an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin present in the paper-making aid composition at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6. The processes utilize an anionic dialdehyde-modified polyacrylamide and PAE resin at certain ratios. The anionic dialdehyde-modified polyacrylamide and PAE resin may be added to the pulp slurry as a composition or separately.

A paper-making aid composition, as well as processes for increasing tensile strength in paper and paper-making processes are provided. The paper-making composition comprises an anionic dialdehyde-modified polyacrylamide and a polyamide polyamine-epichlorohydrin (PAE) resin present in the paper-making aid composition at a weight ratio of PAE resin to anionic dialdehyde-modified polyacrylamide of from about 5:1 to about 1:1.6. The processes utilize an anionic dialdehyde-modified polyacrylamide and PAE resin at certain ratios. The anionic dialdehyde-modified polyacrylamide and PAE resin may be added to the pulp slurry as a composition or separately.

A method of producing paper and board by using at least one water-soluble amphoteric polymer is provided. The water-soluble amphoteric polymer is obtained by copolymerizing a monomer mixture containing a) at least one N-vinylcarboxamide, b) at least one monoethylenically unsaturated monomer having at least one free acid group or at least one acid group in salt form, c) optionally at least one monoethylenically unsaturated monomer other than components (a) and (b), and d) optionally at least one compound having two or more ethylenically unsaturated double bonds, and then partly or wholly hydrolyzing the COR.sup.1 groups of the polymer. The cationic monomer units and the anionic monomer units differ in their respective molar fractions, each based on the total number of moles of all monomer units, by not more than 10 mol % in absolute terms.

Disclosed is a method for producing an aldehyde crosslinked polyacrylamide composition useful for strengthening paper. The method includes steps, wherein a) an aldehyde crosslinker and polyacrylamide are mixed in water to form an aqueous solution of aldehyde crosslinked polyacrylamide prepolymer; b) acid is added to the aqueous prepolymer solution to adjust the pH of the solution to a value from 1 to 5; c) storing and transporting the prepolymer solution to the location where the final glyoxalated polyacrylamide composition will be used; and d) adding a base to the stabilized prepolymer solution to adjust the pH of the solution to a value from 5.5 to 12, and e) allowing the aldehyde crosslinker and polyacrylamide contained in the aldehyde crosslinked polyacrylamide prepolymer solution to react further and form aldehyde crosslinked polyacrylamide composition useful for strengthening paper.

Disclosed is a method for producing an aldehyde crosslinked polyacrylamide composition useful for strengthening paper. The method includes steps, wherein a) an aldehyde crosslinker and polyacrylamide are mixed in water to form an aqueous solution of aldehyde crosslinked polyacrylamide prepolymer; b) acid is added to the aqueous prepolymer solution to adjust the pH of the solution to a value from 1 to 5; c) storing and transporting the prepolymer solution to the location where the final glyoxalated polyacrylamide composition will be used; and d) adding a base to the stabilized prepolymer solution to adjust the pH of the solution to a value from 5.5 to 12, and e) allowing the aldehyde crosslinker and polyacrylamide contained in the aldehyde crosslinked polyacrylamide prepolymer solution to react further and form aldehyde crosslinked polyacrylamide composition useful for strengthening paper.

Bleached polyacrylic acid crosslinked cellulose fibers with reduced furfural content are disclosed. The reduced furfural content is accompanied by a strong reduction of malodor associated with crosslinked fibers. Methods of furfural reduction include treatment with hydrogen peroxide in the absence of alkaline or other bleaching agents subsequent to curing polyacrylic acid crosslinked cellulose fibers. Some embodiments of treated polyacrylic acid crosslinked cellulose fibers have a furfural content lower than 1.3 ppm. In some embodiments, the reduction of furfural content of the treated crosslinked fibers compared to untreated crosslinked fibers is at least 55%. In some embodiments, furfural content decreases with aging of the treated crosslinked fibers.

The invention provides methods and compositions for increasing the strength of a paper sheet. The method involves adding to the paper sheet an amine containing polymer. The amine containing polymer interacts with materials such as GPAM or starch to make the paper stronger in terms including tensile strength, surface strength and bulk strength.

The invention provides methods and compositions for increasing the strength of a paper sheet. The method involves adding to the paper sheet an amine containing polymer. The amine containing polymer interacts with materials such as GPAM or starch to make the paper stronger in terms including tensile strength, surface strength and bulk strength.

A method of increasing the drainage performance of a pulp slurry during the manufacture of paper products by adding (a) at least one microfibrillated cellulose and (b) at least one associative polymer or at least one branched or crosslinked copolymer to the pulp slurry. This addition occurs before the dewatering step where the pulp slurry is formed into a fibrous mat.