Patent ID: 6919111

Claim:
A cellulosic multi-ply paperboard comprising: (a) predominately cellulosic fibers; (b) bulk and porosity enhancing additive interspersed with said cellulosic fibers in a controlled distribution throughout the thickness of said paperboard; and (c) size press applied binder coating, optionally including a pigment adjacent both surfaces of the paperboard and penetrating into the board to a controlled extent; the overall fiber weight “w” of the paperboard being at least about 40 lbs. per 3000 square foot ream (i) the distribution of the bulk and porosity enhancing additive throughout the thickness of the paperboard, and (ii) the penetration of the size press applied pigment into the board, both being controlled to simultaneously produce at a fiber mat density of 3, 4.5. 6.5, 7, 8.3, and 9 pounds per 3000 square foot ream at a fiberboard thickness of 0.001 inches; and (A) a GM Taber stiffness of at least about 0.00246 w 2.63 grams-centimeter/fiber mat density 1.63 ; and (B) at a fiber mat density of about 3 to about 9 pounds per 3000 square foot ream and fiberboard thickness of 0.001 inches, a GM tensile strength of at least about 615+13.18 w pounds per inch.