A method for providing a treated cellulose-comprising mixed starting material (110), in particular a mixed starting material (110) for forming a, in particular regenerated, cellulosic molded body (102) is described. The method comprises: i) providing (10) a first starting material (101a) which comprises a lignocellulosic raw material, ii) providing (1) a second starting material (101b) which comprises a cellulose-containing lignin-free product, iii) mixing (15) the first starting material (101a) and the second starting material (101b) to a mixed starting material (101), and iv) at least partially commonly treating (20) the first starting material (101a) and the second starting material (101b) for obtaining the treated mixed starting material (101), in particular a mixed pulp.

The invention discloses a corrugated packaging material with a low weight and high strength properties, which material can be recycled with the office paper recycling stream. The corrugated packaging material of the invention exhibits good strength and stiffness properties, a low wash board tendency and provides a good printing surface.

A method of producing a paper or paperboard product having at least one ply comprising high yield pulp (HYP), comprising the steps of: —providing a furnish comprising at least 50% of high yield pulp (HYP) of a total pulp content in said furnish, said high yield pulp being produced with a wood yield above 85%; —dewatering the furnish to form a moist web and pressing said moist web to a dry solids content of at least 40-70%; and —densifying the moist web to a density above 600 kg/m3 in a press nip of a paper machine at a temperature above a softening temperature of water-saturated lignin comprised in said high yield pulp to provide a paper or paperboard product, containing at least 30% high yield pulp (HYP) of a total pulp content of said product.

A method of producing a paper or paperboard product having at least one ply comprising high yield pulp (HYP), comprising the steps of: —providing a furnish comprising at least 50% of high yield pulp (HYP) of a total pulp content in said furnish, said high yield pulp being produced with a wood yield above 85%; —dewatering the furnish to form a moist web and pressing said moist web to a dry solids content of at least 40-70%; and —densifying the moist web to a density above 600 kg/m3 in a press nip of a paper machine at a temperature above a softening temperature of water-saturated lignin comprised in said high yield pulp to provide a paper or paperboard product, containing at least 30% high yield pulp (HYP) of a total pulp content of said product.

According to an example aspect of the present invention, there is provided a multilayered fibrous sheet, such as paperboard, having a first layer comprising a first fibrous material, a second layer, spaced apart from the first layer, comprising a second fibrous material, and a third layer between the first and the second layers, comprising a third fibrous material, wherein at least one of the first and the second fibrous materials comprises or consists of a mixture of chemical pulp and mechanical pulp; and the third fibrous material comprises or consists of mechanical pulp.

According to an example aspect of the present invention, there is provided a multilayered fibrous sheet, such as paperboard, having a first layer comprising a first fibrous material, a second layer, spaced apart from the first layer, comprising a second fibrous material, and a third layer between the first and the second layers, comprising a third fibrous material, wherein at least one of the first and the second fibrous materials comprises or consists of a mixture of chemical pulp and mechanical pulp; and the third fibrous material comprises or consists of mechanical pulp.

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.

Various embodiments of the present invention relate to surface enhanced pulp fibers, various products incorporating surface enhanced pulp fibers, and methods and systems for producing surface enhanced pulp fibers. Various embodiments of surface enhanced pulp fibers have significantly increased surface areas compared to conventional refined fibers while advantageously minimizing reductions in length following refinement. The surface enhanced pulp fibers can be incorporated into a number of products that might benefit from such properties including, for example, paper products, paperboard products, fiber cement boards, fiber reinforced plastics, fluff pulps, hydrogels, cellulose acetate products, and carboxymethyl cellulose products. In some embodiments, a plurality of surface enhanced pulp fibers have a length weighted average fiber length of at least about 0.3 millimeters and an average hydrodynamic specific surface area of at least about 10 square meters per gram, wherein the number of surface enhanced pulp fibers is at least 12,000 fibers/milligram on an oven-dry basis.

Various embodiments of the present invention relate to surface enhanced pulp fibers, various products incorporating surface enhanced pulp fibers, and methods and systems for producing surface enhanced pulp fibers. Various embodiments of surface enhanced pulp fibers have significantly increased surface areas compared to conventional refined fibers while advantageously minimizing reductions in length following refinement. The surface enhanced pulp fibers can be incorporated into a number of products that might benefit from such properties including, for example, paper products, paperboard products, fiber cement boards, fiber reinforced plastics, fluff pulps, hydrogels, cellulose acetate products, and carboxymethyl cellulose products. In some embodiments, a plurality of surface enhanced pulp fibers have a length weighted average fiber length of at least about 0.3 millimeters and an average hydrodynamic specific surface area of at least about 10 square meters per gram, wherein the number of surface enhanced pulp fibers is at least 12,000 fibers/milligram on an oven-dry basis.