The present disclosure provides methods and compositions for strengthening paper. The methods may include a step of spraying an anionic polymer onto a paper sheet to increase the strength of the paper sheet. The anionic polymer may have amino groups, amide groups, or a combination of amino groups and amide groups. These groups may be functionalized with an aldehyde. Methods may also include a step of adding a wet end composition to a wet end of the papermaking process.

The present disclosure provides methods and compositions for strengthening paper. The methods may include a step of spraying an anionic polymer onto a paper sheet to increase the strength of the paper sheet. The anionic polymer may have amino groups, amide groups, or a combination of amino groups and amide groups. These groups may be functionalized with an aldehyde. Methods may also include a step of adding a wet end composition to a wet end of the papermaking process.

Provided are a method for manufacturing paper with which it is possible to easily manufacture paper wherein water-filterability and yield are excellent and hydrophilia is suppressed without using a cationic polymer or silica, a device for manufacturing an additive for manufacturing paper, and a device for manufacturing paper. The method for manufacturing paper is a method having a reactant generating step for generating a reactant by subjecting an acrylamide polymer to a Hoffman elimination reaction, and a supply step for supplying the reactant to a paper machine within 24 hours of the start of the Hoffman elimination reaction. The acrylamide polymer preferably includes an acrylamide polymer having a intrinsic viscosity of 12.5-28 dl/g and anionization of 0.3 meq/g or less.

Provided are a method for manufacturing paper with which it is possible to easily manufacture paper wherein water-filterability and yield are excellent and hydrophilia is suppressed without using a cationic polymer or silica, a device for manufacturing an additive for manufacturing paper, and a device for manufacturing paper. The method for manufacturing paper is a method having a reactant generating step for generating a reactant by subjecting an acrylamide polymer to a Hoffman elimination reaction, and a supply step for supplying the reactant to a paper machine within 24 hours of the start of the Hoffman elimination reaction. The acrylamide polymer preferably includes an acrylamide polymer having a intrinsic viscosity of 12.5-28 dl/g and anionization of 0.3 meq/g or less.

A method to produce dried single-layer or multi-layer paper is disclosed. The method comprises, for a single-layer paper, preparing and spraying a partially dehydrated first fibrous web with a spray solution or suspension to give a sprayed partially dehydrated first fibrous web, and dehydrating the sprayed partially dehydrated first fibrous web by applying heat to form a dried single-layer paper; or, for a multi-layer paper, preparing and spraying a partially dehydrated layer compound with a spray solution or suspension to form a sprayed layer compound, and dehydrating the sprayed layer compound by applying heat to form a dried multi-layer paper. The spray solution or suspension comprises water and at least one water-soluble polymer P, which is obtained by polymerizing: (i) a monomer of formula H.sub.2CCHNHC(0)R.sup.1, where R.sup.1 is H or C.sub.1-C.sub.6- alkyl; and (ii) one or more ethylenically unsaturated monomers different from monomer (i).

The invention relates to a lightweight linerboard for corrugated board with good strength properties and which reduces problems with washboarding in the thereof produced corrugated board. The linerboard of the invention comprises at least one ply comprising 20-80 wt % CTMP from wood fibers and 20-80 wt % chemical pulp, all percentages calculated on the total fiber weight of said first ply, wherein the CTMP exhibits a bulk of at least 2.5 cm.sup.3/g.

The invention relates to a lightweight linerboard for corrugated board with good strength properties and which reduces problems with washboarding in the thereof produced corrugated board. The linerboard of the invention comprises at least one ply comprising 20-80 wt % CTMP from wood fibers and 20-80 wt % chemical pulp, all percentages calculated on the total fiber weight of said first ply, wherein the CTMP exhibits a bulk of at least 2.5 cm.sup.3/g.

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 starchor 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 invention relates to a method for producing dried single-layer or multi-layer paper containing the steps for a single-layer paper

(A) Dewatering a first aqueous fibrous suspension, thereby creating a first fibrous web having a dry content between 14% wt. and 25% wt.,
(D-1) Dehydrating the first fibrous web by pressing, thereby creating a partially dehydrated first fibrous web,
(E-1) Spraying the partially dehydrated first fibrous web on at least one surface side with a spray solution or spray suspension, which results in a sprayed partially dehydrated first fibrous web,
(F-1) Dehydrating the sprayed partially dehydrated first fibrous web by applying heat to form the dried single-layer paper,
or containing the above step (A) and steps for a multi-layer paper
(B) Dewatering a second aqueous fibrous suspension, thereby creating a second fibrous web having a dry content between 14% wt. and 25% wt.,
(C) assembling the first fibrous web to the second fibrous web such that the two fibrous webs touch each other on an entire surface side, thereby resulting in a layer compound,
(D-2) Dehydrating the layer compound by pressing, whereby a partially dehydrated layer compound is formed,
(E-2) Spraying the partially dehydrated layer compound on at least one surface side with a spray solution or spray suspension, whereby a sprayed layer compound is formed,
(F-2) Dehydrating the sprayed layer compound by applying heat means to form the dried multi-layer paper,
wherein the spray solution or spray suspension contains (e-a) Water and (e-b) at least one water-soluble polymer P, which can be obtained by polymerizing of (i) 40 to 85 mol % of a monomer of Formula I

##STR00001##

in the R.sup.1=H or C.sub.1-C.sub.6-Alkyl, (ii) 15 to 60 mol % of one or more ethylenically unsaturated monomers which are different from a monomer of the Formula I,
wherein the total amount of all monomers (i) and (ii) is 100 mol %, and optionally by subsequent partial or complete hydrolysis of the units of the monomers of the formula (I) polymerized into the polymer P to form primary amino or amidine groups, wherein the proportion of water is at least 75% wt., based on the spray solution or the spray suspension.

A method of making an absorbent structure including forming a stock mixture of fibers, a cationic wet strength resin, an anionic polyacrylamide and a cellulase enzyme, and at least partially drying the stock mixture to form a web.