Patent ID: 8187421

Claim:
An absorbent paper sheet comprising pulp-derived papermaking fiber and up to 75% by weight fibrillated regenerated cellulose microfiber having a CSF value of less than 175 mL, and wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from: tertiary amine N-oxides; cellulose dissolving imidazolium salts; cellulose dissolving pyridinium salts; cellulose dissolving pyridazinium salts; cellulose dissolving pyrimidinium salts; cellulose dissolving pyrazinium salts; cellulose dissolving pyrazolium salts; cellulose dissolving oxazolium salts; cellulose dissolving 1,2,3-triazolium salts; cellulose dissolving 1,2,4-triazolium salts; cellulose dissolving thiazolium salts; cellulose dissolving piperidinium salts; cellulose dissolving pyrrolidinium salts; cellulose dissolving quinolinium salts; and cellulose dissolving isoquinolinium salts, the pulp-derived papermaking fiber being arranged in a fibrous matrix and the regenerated cellulose microfiber being sized and distributed in the fiber matrix to form a microfiber network therein, and wherein fibrillation of the microfiber is controlled such that it has a reduced coarseness and a reduced freeness as compared with unfibrillated microfiber from which it is made, such that the microfiber network provides at least one of the following attributes to the absorbent sheet: (a) the absorbent sheet exhibits an SAT value at least 15% higher and an elevated wet tensile value at least 40% higher as compared with a like sheet prepared without fibrillated regenerated cellulose microfiber; (b) the absorbent sheet exhibits a wet/dry CD tensile ratio at least 25% higher than a like sheet prepared without fibrillated regenerated cellulose microfiber; (c) the absorbent sheet exhibits a GM Break Modulus at least 20% lower than a like sheet having like tensile values prepared without fibrillated regenerated cellulose microfiber; or (d) the absorbent sheet exhibits a specific bulk at least 5% higher than a like sheet having like tensile values prepared without fibrillated regenerated cellulose microfiber, with the proviso that the sheet includes more than 25% by weight fibrillated regenerated cellulose microfiber disintegrated into shorter fibrils having a CSF value of less than 175 mL and a number average diameter of up to about 4 microns.