US Patent 11077648 Board with improved compression strength

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 4 to 24 Jm/kg, and a ring crush index in the range of from 5 to 10 Nm/g5 measured at relative humidity of 85% RH; wherein the cellulosic fibers comprises a mixture of less refined fibers having a Schopper-Riegler (SR) value in the range of 15 to 28 and microfibrillated cellulose fibers, wherein mixture comprises said microfibrillated cellulose in a range of from 1% to 5% by weight of the dry content of the cellulosic fibers.