Tissues and paper towels incorporating surface enhanced pulp fibers and methods of making the same

1. A tissue comprising:

a first plurality of first fibers that are hardwood fibers;

a second plurality of second fibers including softwood fibers and surface enhanced pulp fibers (SEPF) having a length weighted average fiber length that is at least 0.20 millimeters (mm), wherein the SEPF are made by refining a pulp feed, the refining including for each of one or more mechanical refiners:

introducing the pulp feed between two refining elements of the refiner, each of the refining elements comprising:

a plurality of bars, each protruding from a surface of the refining element and having a width that is less than or equal to 1.3 mm; and

a plurality of grooves defined by the bars, each having a width that is less than or equal to 2.5 mm; and

rotating at least one of the refining elements;

wherein refining the pulp feed is performed such that the refiner(s) consume at least 300 kilowatt-hours (kWh) per ton of fiber in the pulp feed; and

two or more fiber layers that include:

one or more first fiber layers that comprise the first fibers, at least one of the first fiber layer(s) defining one of opposing upper and lower surfaces of the tissue; and

one or more second fiber layers that comprise the second fibers;

wherein by weight:

at least 90% of the second fibers are the softwood fibers; and

between 1% and 10% of the second fibers are the SEPF.

2. The tissue of claim 1 , wherein by weight:

between 50% and 80% of the fibers of the tissue are the first fibers; and

at least 20% of the fibers of the tissue are the second fibers.

3. The tissue of claim 1 , wherein:

the one or more first fiber layers comprise two first fiber layers, each defining a respective one of the upper and lower surfaces of the tissue; and

each of the one or more second fiber layers is disposed between the two first fiber layers.

4. The tissue of claim 1 , wherein a total basis weight of the second fiber layer(s) is between 25% and 35% of the total basis weight of the first fiber layer(s).

5. The tissue of claim 1 , wherein by weight:

at least 90% of the fibers of the first fiber layer(s) are the first fibers; and

at least 90% of the fibers of the second fiber layer(s) are the second fibers.

6. The tissue of claim 1 , wherein:

a maximum cup crush load of the tissue is less than or equal to 1.0 Newton (N); and

a tensile strength of the tissue is greater than or equal to 200 N/m.

7. The tissue of claim 1 , wherein:

the tissue comprises one or more plies; and

the basis weight of the tissue is less than or equal to 21 grams per square meter (gsm) per ply.

8. The tissue of claim 1 , wherein the SEPF are softwood fibers.

9. The tissue of claim 1 , wherein by weight:

between 65% and 75% of the fibers of the tissue are the first fibers; and

at least 25% of the fibers of the tissue are the second fibers.

10. The tissue of claim 1 , wherein the length weighted average fiber length of the SEPF is at least 0.20 mm and the average hydrodynamic specific surface area of the SEPF is at least 10 m 2 /g.

11. The tissue of claim 1 , wherein the hardwood fibers of the first fibers comprise bleached eucalyptus fibers.

12. The tissue of claim 1 , wherein the softwood fibers of the second fibers comprise northern bleached softwood kraft fibers.

13. A tissue comprising:

a first plurality of first fibers that are hardwood fibers;

a second plurality of second fibers including softwood fibers and surface enhanced pulp fibers (SEPF) having a length weighted average fiber length that is at least 0.20 millimeters (mm), wherein the SEPF are made by refining a pulp feed, the refining including for each of one or more mechanical refiners:

introducing the pulp feed between two refining elements of the refiner, each of the refining elements comprising:

a plurality of bars, each protruding from a surface of the refining element and having a width that is less than or equal to 1.3 mm; and

a plurality of grooves defined by the bars, each having a width that is less than or equal to 2.5 mm; and

rotating at least one of the refining elements;

wherein refining the pulp feed is performed such that the refiner(s) consume at least 300 kilowatt-hours (kWh) per ton of fiber in the pulp feed; and

two or more plies;

wherein:

by weight:

between 50% and 80% of the fibers of the tissue are the first fibers and at least 20% of the fibers of the tissue are the second fibers;

at least 90% of the second fibers in a first ply of the two of more plies are the softwood fibers; and

between 1% and 10% of the second fibers in the first ply are the SEPF; and

the basis weight of the tissue is less than or equal to 21 grams per square meter (gsm) per ply.

14. The tissue of claim 13 , wherein:

a maximum cup crush load of the tissue is less than or equal to 1.06 Newtons (N); and

a tensile strength of the tissue is greater than or equal to 220 N/m.

15. A method of making a tissue, the method comprising:

refining a pulp feed to generate surface enhanced pulp fibers (SEPF) by:

for each of one or more mechanical refiners:

introducing the pulp feed between two refining elements of the mechanical refiner, each refining element comprising:

a plurality of bars, each bar protruding from a surface of the refining element and having a width that is less than or equal to 1.3 mm; and

a plurality of grooves defined by the bars, each groove having a width that is less than or equal to 2.5 mm; and

rotating at least one of the refining elements,

wherein refining the pulp feed is performed such that the one or more mechanical refiners consume at least 300 kilowatt-hours (kWh) per ton of fiber in the pulp feed;

providing a first plurality of first fibers that are hardwood fibers;

generating a second plurality of second fibers by mixing together softwood fibers and the SEPF;

forming one or more first fiber layers comprising the first fibers, at least one of the one or more first fiber layers defining one of opposing upper and lower surfaces of the tissue;

forming one or more second fiber layers comprising the second fibers; and

disposing each of the one or more second fiber layers between the one or more first fiber layers,

wherein by weight:

at least 90% of the second fibers are the softwood fibers, and

between 1% and 10% of the second fibers are the SEPF.