Absorbent sheet having regenerated cellulose microfiber network
View Patent ↗An absorbent paper sheet for tissue or towel includes from about 99 percent to about 70 percent by weight of cellulosic papermaking fiber and from about 1 percent to about 30 percent by weight fibrillated regenerated cellulose microfiber which was regenerated form a cellulosic dope utilizing a tertiary amine N-oxide solvent or an ionic liquid. Fibrillation of the microfiber is controlled such that it has a reduced coarseness and a reduced freeness as compared with unfibrillated regenerated cellulose microfiber from which it is made and provides at least one of the following attributes to the absorbent sheet: (a) the absorbent sheet exhibits an elevated SAT value and an elevated wet tensile value as compared with a like sheet prepared without fibrillated regenerated cellulose microfiber; (b) the absorbent sheet exhibits an elevated wet/dry CD tensile ratio as compared with a like sheet prepared without fibrillated regenerated cellulose microfiber; (c) the absorbent sheet exhibits a lower GM Break Modulus than a like sheet having like tensile values prepared without fibrillated regenerated cellulose microfiber; or (d) the absorbent sheet exhibits an elevated bulk as compared with a like sheet having like tensile values prepared without fibrillated regenerated cellulose microfiber. In some embodiments, the pulp is pre-treated with debonder to enhance the wet/dry CD tensile ratio of the sheet.
1. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers disintegrated into shorter fibrils having a CSF value of less than 175 mL and a number average diameter of up to about 4 microns, wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet.
2. The method of making absorbent sheet according to claim 1 , wherein the aqueous furnish has a consistency of 2 percent or less.
3. The method of making absorbent sheet according to claim 1 , wherein the aqueous furnish has a consistency of 1 percent or less.
4. The method of making absorbent sheet according to claim 1 , wherein the nascent web is compactively dewatered with a papermaking felt.
5. The method of making absorbent sheet according to claim 1 , wherein the compactively dewatered web is applied to a Yankee dryer and creped therefrom.
6. The method of making absorbent sheet according to claim 1 , wherein the compactively dewatered web is applied to a rotating cylinder and fabric-creped therefrom.
7. The method of making absorbent sheet according to claim 1 , wherein the nascent web is at least partially dewatered by throughdrying.
8. The method of making absorbent sheet according to claim 1 , wherein the nascent web is at least partially dewatered by impingement air drying.
9. The method of making absorbent sheet according to claim 1 , wherein said fiber mixture includes southern softwood Kraft and southern hardwood Kraft.
10. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers have a CSF value of less than 50 mL.
11. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers have a CSF value of less than 25 mL.
12. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers have a CSF value of 0 mL.
13. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers have a CSF value of less than 100 mL, a weight average diameter of less than 1 micron, a weight average length of less than 400 microns and a fiber count of greater than 2 billion fibers/gram.
14. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers have a weight average diameter of less than 0.5 microns, a weight average length of less than 300 microns and a fiber count of greater than 10 billion fibers/gram.
15. The method of making absorbent sheet according to claim 1 , wherein the fibrillated regenerated cellulose microfibers has a weight average diameter of less than 0.25 microns, a weight average length of less than 200 microns and a fiber count of greater than 50 billion fibers/gram.
16. The method of making absorbent sheet according to claim 1 , wherein said fibrillated regenerated cellulose microfibers have a number average fibril width of less than about 4 micrometers, and wherein the number average fiber length of the fibrillated regenerated cellulose fibers is less than about 250 micrometers.
17. The method of making absorbent sheet according to claim 1 , wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 150 micrometers.
18. The method of making absorbent sheet according to claim 1 , wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 100 micrometers.
19. The method of making absorbent sheet according to claim 1 , wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 75 micrometers.
20. A method of making base sheet for tissue comprising:
(a) preparing an aqueous furnish comprising southern hardwood fiber and fibrillated regenerated cellulose microfiber disintegrated into shorter fibrils having a CSF value of less than 100 mL; a number average diameter of up to about 4 microns and a fibril count of more than 400 million fibrils per gram wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet.
21. The method of making base sheet for tissue according to claim 20 , wherein the fibrillated regenerated cellulose fiber has a fibril count of more than 1 billion fibrils per gram.
22. The method of making base sheet for tissue according to claim 20 , wherein the fibrillated regenerated cellulose fiber has a fibril count of more than 100 billion fibrils per gram.
23. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the fibrillated regenerated cellulose microfibers have a CSF value of less than 100 mL, a weight average diameter of less than 1 micron, a weight average length of less than 400 microns and a fiber count of greater than 2 billion fibers/gram.
24. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the fibrillated regenerated cellulose micro fibers have a weight average diameter of less than 0.5 microns, a weight average length of less than 300 microns and a fiber count of greater than 10 billion fibers/gram.
25. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the fibrillated regenerated cellulose microfibers has a weight average diameter of less than 0.25 microns, a weight average length of less than 200 microns and a fiber count of greater than 50 billion fibers/gram.
26. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein said fibrillated regenerated cellulose microfibers have a number average fibril width of less than about 4 μm, and wherein the number average fiber length of the fibrillated regenerated cellulose fibers is less than about 250 micrometers.
27. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 150 micrometers.
28. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 100 micrometers.
29. A method of making absorbent cellulosic sheet comprising:
(a) preparing an aqueous furnish with a fiber mixture including from about 99 percent to about 70 percent of a pulp-derived papermaking fiber, the fiber mixture also including from about 1 to 30 percent by weight of fibrillated regenerated cellulose microfibers having a CSF value of less than 175 mL wherein the regenerated cellulose is prepared from a cellulosic dope of dissolved cellulose comprising a solvent selected from ionic liquids and tertiary amine N-oxides,
(b) depositing the aqueous furnish on a foraminous support to form a nascent web and at least partially dewatering the nascent web; and
(c) drying the web to provide absorbent sheet, wherein the number average fiber length of the fibrillated regenerated cellulose microfibers is less than about 75 micrometers.