A method for producing dried multilayer paper is provided comprising dewatering a first aqueous fibrous suspension, thereby creating a first fibrous web; dewatering a second aqueous fibrous suspension, thereby creating a second fibrous web; spraying one or more of a first fibrous web and a second fibrous web with a spray solution or spray suspension, thereby producing at least one sprayed fibrous web; assembling the first fibrous web with the second fibrous web; dehydrating the resulting layer compound by pressing; then dehydrating by supplying heat, which creates the dried multilayer paper. The spray solution or spray suspension contains water and at least one water-soluble polymer P. The polymer P is obtained by polymerizing: 40 to 85 mol % of a monomer of Formula I ##STR00001##
in which R.sup.1=H or C.sub.1-C.sub.6-Alkyl; and 15 to 60 mol % of one or more ethylenically unsaturated monomers.

A sheet manufacturing apparatus includes a defibrating unit configured to defibrate in an atmosphere a raw material that contains a fiber, a mixing unit configured to mix in the atmosphere a defibrated material that the defibrating unit has defibrated and a resin, an accumulating unit configured to accumulate a mixture of the defibrated material and the resin that the mixing unit has mixed, a liquid application unit configured to apply a liquid to a portion of an accumulation of the mixture that the accumulating unit has accumulated, and a heating unit configured to form a sheet by heating the accumulation to which the liquid application unit has applied the liquid.

A sheet manufacturing apparatus includes a defibrating unit configured to defibrate in an atmosphere a raw material that contains a fiber, a mixing unit configured to mix in the atmosphere a defibrated material that the defibrating unit has defibrated and a resin, an accumulating unit configured to accumulate a mixture of the defibrated material and the resin that the mixing unit has mixed, a liquid application unit configured to apply a liquid to a portion of an accumulation of the mixture that the accumulating unit has accumulated, and a heating unit configured to form a sheet by heating the accumulation to which the liquid application unit has applied the liquid.

A method for manufacturing a multi-layered paperboard is disclosed, which includes at least two fibrous layers, in which method at least one layer of the multi-layered paperboard is treated by applying an aqueous solution of a first strength component in dissolved form including anionic strength polymer and/or amphoteric strength polymer composition on a surface of layer, and an aqueous solution of a cationic second strength component in dissolved form is added to a fibre stock from which at least one of the fibrous layers joined together is formed.

A method for manufacturing a multi-layered paperboard is disclosed, which includes at least two fibrous layers, in which method at least one layer of the multi-layered paperboard is treated by applying an aqueous solution of a first strength component in dissolved form including anionic strength polymer and/or amphoteric strength polymer composition on a surface of layer, and an aqueous solution of a cationic second strength component in dissolved form is added to a fibre stock from which at least one of the fibrous layers joined together is formed.

The present invention provides a book paper suitable for both inkjet and offset printing. The inventive printing paper comprises a base substrate with a grammage of below 100 gsm comprising at least 50 wt % mechanical cellulosic pulp fibers and having a total filler content of below 15 wt %. The substrate is surface treated with a composition comprising pigments in a range of 15-30 wt %, starch in a range of 20-40 wt %, latex in a range of 10-20 wt % and a multivalent metal salt in a range of 10-30 wt %.

Fibrous products having an improved softness are provided, which have beneficial effects on the skin upon use. The fibrous product includes a fibrous material in which this material has at least one of lactic acid or a salt thereof in an amount of, per ply provided, in the range of from about 0.1 to about 15 g/m.sup.2, and in some embodiments, in the range of from about 1.0 to about 1.5 g/m.sup.2. A water activity of the fibrous product is from about 0.03 to 0.85. The salt of lactic acid may, for example, be sodium lactate, potassium lactate, and/or calcium lactate.

Fibrous products having an improved softness are provided, which have beneficial effects on the skin upon use. The fibrous product includes a fibrous material in which this material has at least one of lactic acid or a salt thereof in an amount of, per ply provided, in the range of from about 0.1 to about 15 g/m.sup.2, and in some embodiments, in the range of from about 1.0 to about 1.5 g/m.sup.2. A water activity of the fibrous product is from about 0.03 to 0.85. The salt of lactic acid may, for example, be sodium lactate, potassium lactate, and/or calcium lactate.

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.