High yield fiber sheets

Claim 1

A process for preparing sheets of high yield wood pulp fibers comprising the steps of: (A) providing substantially non-delignified and relatively undamaged softwood high yield fibers having a Canadian standard freeness value greater than about 700 ml; (B) providing hardwood high yield fibers wherein said hardwood fibers: (i) have a Canadian standard freeness value of from about 50 ml to about 400 ml; (ii) have been prepared separately from said softwood fibers; and (iii) have been prepared by a process comprising the steps of: (a) treating hardwood with an aqueous solution comprising from about 2% to about 40% by weight of a treating agent selected from the group consisting of alkali metal sulfite, alkali metal bisulfite, sulphur dioxide with alkali metal hydroxide, and mixtures thereof at a temperaure of from about 130° C. to about 190° C. for from about 1 minute to about 60 minutes; and (b) defibrating said treated hardwood; (C) mixing said softwood and hardwood fibers to form a papermaking furnish comprising at least about 75% by weight said softwood and hardwood fibers and wherein the weight ratio of said softwood fibers to said hardwood fibers is from about 2.33:1 to about 19:1; and (D) wet forming said sheets from said papermaking furnish.