Modified fiber, methods, and systems

1. A method of forming a crosslinked cellulose product, comprising:

mixing a crosslinking agent with an aqueous mixture of unbonded cellulose fibers having a solids content and containing little to no excess water, the crosslinking agent being added at a solids content of 10-50% and in an amount suitable to achieve a desired level of crosslinking of the unbonded cellulose fibers based on the solids content;

drying the resulting mixture to 85-100% solids; and

curing the dried mixture under conditions effective to crosslink the unbonded cellulose fibers.

2. The method of claim 1 , wherein the aqueous mixture has a solids content of about 25-55%.

3. The method of claim 2 , wherein the aqueous mixture has a solids content of about 35-55%.

4. The method of claim 2 , wherein the aqueous mixture has a solids content of about 40-50%.

5. The method of claim 1 , wherein the crosslinking agent is mixed with the aqueous mixture of unbonded cellulose fibers at ambient conditions.

6. The method of claim 1 , wherein the crosslinking agent is added in an amount no more than that required to achieve a desired level of crosslinking of the unbonded cellulose fibers.

7. The method of claim 1 , further comprising, prior to mixing, processing the aqueous mixture to reduce fiber clumps.

8. The method of claim 1 , wherein mixing is performed in one or more of an extruder, a refiner, and a high-consistency mixer.

9. The method of claim 1 , wherein the amount of crosslinking agent added corresponds to a chemical on pulp range of about 2-14%.

10. The method of claim 1 , further comprising, prior to mixing, forming the aqueous mixture.

11. The method of claim 10 , wherein forming the aqueous mixture includes mixing one or more of wet lap, previously-dried cellulosic fibers, and never-dried cellulosic fibers, with water.

12. The method of claim 11 , wherein forming the aqueous mixture is performed in one or more of an extruder, a hydrapulper, and a high-consistency mixer.

13. The method of claim 11 , wherein forming the aqueous mixture includes adding the cellulose fibers in bale or roll form to a hydrapulper in the presence of water.

14. The method of claim 10 , wherein forming the aqueous mixture includes mixing cellulose fibers with water at a solids content of about 25-55%.

15. The method of claim 10 , wherein forming the aqueous mixture includes mixing cellulose fibers with water at a solids content of lower than about 25%, followed by at least partially dewatering the mixture in order to achieve a solids content of about 25-55%.

16. The method of claim 1 , wherein the crosslinking agent comprises one or more of a polyacrylic acid and a polycarboxylic acid.

17. A method of forming a crosslinked cellulose product, comprising:

forming an aqueous mixture of unbonded cellulose fibers having a solids content of about 40-50%;

mixing a polyacrylic acid crosslinking agent with the aqueous mixture in an amount to achieve a chemical on pulp level of about 2-14%, wherein said crosslinking agent is mixed at ambient conditions;

drying the resulting mixture to 85-100% solids; and

curing the dried mixture under conditions effective to crosslink the unbonded cellulose fibers.

18. The method of claim 1 , performed by a system, the system comprising:

a mixing unit being configured to form, from the aqueous mixture of unbonded cellulose fibers having a solids content of about 25-55% and the crosslinking agent, the substantially homogenous mixture of non-crosslinked, unbonded cellulose fibers and crosslinking agent, at ambient conditions;

a drying unit downstream of the mixing unit and configured to dry the substantially homogenous mixture to a consistency of 85-100% without curing the crosslinking agent; and

a curing unit downstream of the drying unit and configured to cure the crosslinking agent, thereby forming dried and cured crosslinked cellulose fibers.

19. The method of claim 18 , wherein the mixing unit includes a first zone configured to form the aqueous mixture of unbonded cellulose fibers, and a second zone configured to receive both the aqueous mixture and the crosslinking agent and form the substantially homogenous mixture.

20. The method of claim 19 , wherein the first and second zones are two subsequent regions of an extruder.

21. The method of claim 18 , wherein the mixing unit includes a high consistency mixer.

22. Intrafiber crosslinked cellulose pulp fibers produced by the method of claim 1 , wherein the fibers have a chemical on pulp level of about 2-14% and an AFAQ capacity of at least 12.0 g/g.

23. The fibers of claim 22 , wherein the cellulose pulp fibers include hardwood cellulose pulp fibers.

24. The fibers of claim 23 , wherein the cellulose pulp fibers are hardwood cellulose pulp fibers.

25. The fibers of claim 23 , wherein the hardwood cellulose pulp fibers are eucalyptus pulp fibers.

26. The fibers of claim 22 , wherein the cellulose pulp fibers are intrafiber crosslinked with a polyacrylic add and/or polycarboxylic add crosslinking agent.

27. The fibers of claim 22 , having an AFAQ capacity of at least 16.0 g/g.

28. The method of claim 17 , wherein mixing includes adding the crosslinking agent at a solids content of 10-50% to the aqueous mixture.