Board with improved compression strength

1. A corrugated fiberboard, comprising cellulosic fibers, wherein said corrugated fiberboard has at least one of a geometrical tensile index in the range of from 32 to 65 Nm/g, a fracture toughness index in the range of from 14 to 24 Jm/kg, and a ring crush index in the range of from 5 to 10 Nm/g measured at relative humidity of 85% RH;

wherein

the cellulosic fibers comprise a mixture of fibers having a Schopper-Riegler (SR) value in the range of 15 to 28 and microfibrillated cellulose fibers, wherein the mixture comprises said microfibrillated cellulose in a range of from 1% to 5% by weight of the dry content of the cellulosic fibers, wherein the corrugated fiberboard comprises a hydrophobic sizing additive, and wherein the corrugated fiberboard comprises a fluting and a liner.

2. The corrugated fiberboard as claimed in claim 1 , wherein the hydrophobic sizing additive is alkylketene dimer (AKD), succinic anhydrides (ASA), rosin sizes, or styrene maleic anhydride (SMA), or emulsions or modifications or mixtures thereof.

3. The corrugated fiberboard of claim 1 , wherein the corrugated fiberboard has a basis weight in the range of 250 to 450 g/m 2 , and a thickness in the range of 400 to 500 μm.

4. A method of manufacturing a corrugated fiberboard comprising cellulosic fibers, wherein the corrugated fiberboard comprises a fluting and a liner, wherein the corrugated fiberboard has at least one of a geometrical tensile index in the range of from 32 to 65 Nm/g, a fracture toughness index in the range of from 14 to 24 Jm/kg, and a ring crush index in the range of from 5 to 10 Nm/g measured at relative humidity of 85% RH, and wherein the corrugated fiberboard is produced from a base pulp

wherein

the base pulp comprises cellulosic fibers having a Schopper-Riegler value in the range of 15 to 28,

and wherein said method comprises the steps of

providing a furnish comprising said base pulp;

adding a microfibrillated cellulose solution to said furnish, wherein the content of the microfibrillated cellulose is in the range of 1% to 5% by weight of the dry content of the cellulosic fibers; and

adding a hydrophobic sizing additive in a wet end process.

5. The method as claimed in claim 4 , wherein the hydrophobic sizing additive is alkylketene dimer (AKD), succinic anhydrides (ASA), rosin sizes, or styrene maleic anhydride (SMA), or emulsions or modifications or mixtures thereof.

6. The method as claimed in claim 4 , wherein either one of the fluting and the liner, or both the fluting and the liner of the corrugated fiberboard are manufactured from said furnish.

7. The method as claimed in claim 6 , wherein said base pulp is a virgin pulp or a recycled pulp.

8. The method as claimed in claim 7 , wherein the base pulp is a chemical pulp, mechanical pulp, thermomechanical pulp, or chemi-thermomechanical pulp.

9. A corrugated fiberboard, comprising cellulosic fibers obtained by the method of claim 4 , having at least one of a geometrical tensile index in the range of from 32 to 65 Nm/g, a fracture toughness index in the range of from 14 to 24 Jm/kg, and a ring crush index in the range of from 5 to 10 Nm/g measured at relative humidity of 85% RH, wherein said cellulosic fibers comprise a mixture of fibers and microfibrillated cellulose wherein said fibers have a SR value of 15 to 28, wherein the corrugated fiberboard comprises a hydrophobic sizing additive, and wherein the corrugated fiberboard comprises a fluting and a liner.