Surface enhanced pulp fibers at a substrate surface
A paper product having improved printing characteristics and a method of making the paper product. This paper product has a fibrous substrate and top layer of surface enhanced pulp fibers that is integrally coupled to the top surface of the fibrous substrate. The paper product is produced by providing an aqueous slurry formed from a blend of cellulosic fibers and water and at least partially dewatering the aqueous slurry of cellulosic fibers and water to form the fibrous substrate. Subsequently, a surface treatment formed from an aqueous composition of water and surface enhanced pulp fibers is applied to the top surface of the fibrous substrate and thereafter the treated fibrous substrate is dried to form a paper product having enhanced printing characteristics.
1. A method of making a paper product having improved printed characteristics, comprising the steps of:
depositing an aqueous slurry comprising a blend of cellulosic fibers and water onto a wire moving in a machine direction;
at least partially dewatering the aqueous slurry of cellulosic fibers and water to form a fibrous substrate;
applying a surface treatment to a top surface of the fibrous substrate to form a treated fibrous substrate, wherein:
the surface treatment comprises an aqueous composition that comprises hardwood pulp fibers and water;
the hardwood pulp fibers have a length weighted average fiber length of at least 0.19 millimeters (mm) and an average hydrodynamic specific surface area of at least 10 square meters per gram (m 2 /g); and
the hardwood pulp fibers have a concentration of 0.5 to 7.5 percent in the aqueous composition; and
drying the treated fibrous substrate to form a paper product, wherein a basis weight of the hardwood pulp fibers in the formed paper product is between 1 and 20 gsm.
2. The method of claim 1 , wherein the hardwood pulp fibers are applied to the top surface of the fibrous substrate in the aqueous composition at a consistency of between 0.5 to 1.5 percent.
3. The method of claim 1 , wherein the basis weight of the hardwood pulp fibers in the formed paper product is between 3 to 5 gsm.
4. The method of claim 1 , wherein a weight of the hardwood pulp fibers in the formed paper product is between 2 to 15 percent of a weight of the fibrous substrate in the formed paper product.
5. The method of claim 1 , wherein a weight of the hardwood pulp fibers in the formed paper product is between 2 to 20 percent of a weight of the fibrous substrate in the formed paper product.
6. The method of claim 1 , wherein the surface treatment comprises at least one of: a starch composition; a pigmentation composition; and a surface coating formulation.
7. The method of claim 1 , wherein: the depositing step is performed by the use of a first head box; and the applying step comprises dispersing a substantially uniform layer of the aqueous composition onto the top surface of the fibrous substrate by the use a second head box positioned downstream of the first head box.
8. The method of claim 1 , wherein the applying step comprises dispersing a substantially uniform layer of the aqueous composition onto the top surface of the fibrous substrate by the use of at least one of: a two-roll size press; a rod-metering size press; a blade coater; a fountain coater; a cascade coater; and a spray applicator.
9. The method of claim 1 , wherein: the hardwood pulp fibers are a first plurality of hardwood pulp fibers; and the blend of cellulosic fibers comprises a second plurality of hardwood pulp fibers forming between 2% to 20%, by weight, of the fibrous substrate, the second plurality of hardwood pulp fibers having a length weighted average fiber length of at least 0.20 mm and an average hydrodynamic specific surface area of at least 10 m 2 /g.
10. The method of claim 1 , wherein the aqueous composition comprises starch and between 0.2% to 5.0%, by weight, of the aqueous composition is the hardwood pulp fibers.
11. The method of claim 10 , wherein the aqueous composition has a viscosity of 10 to 220 centipoise.
12. The method of claim 1 , wherein, prior to the applying step, the hardwood pulp fibers are chemically reacted with a composition configured to enhance ink jet printing characteristics of the paper product.
13. The method of claim 1 , wherein the hardwood pulp fibers are made by refining hardwood pulp with an energy input of between 400 to 1,800 kilowatt-hours/ton.
14. The method of claim 1 , wherein the hardwood pulp fibers are made by refining hardwood pulp at a specific edge load of less than 0.2 Ws/m until an energy consumption of at least 450 kWh/ton is reached.
15. The method of claim 1 , wherein the hardwood pulp fibers have a fiber count of at least 12,000 fibers per milligram on an oven-dry basis.
16. The method of claim 14 , wherein the length weighted average length of the hardwood pulp fibers is at least 60% of the original length weighted average length of the hardwood pulp fibers prior to the refining.
17. The method of claim 1 , wherein the length weighted average fiber length of the hardwood pulp fibers is at least 0.4 mm and the average hydrodynamic specific surface area of the hardwood pulp fibers is at least about 12 m 2 /g.
18. The method of claim 14 , wherein the average hydrodynamic specific surface area of the hardwood pulp fibers is at least 4 times greater than the average specific surface area of the hardwood pulp fibers prior to refining.
19. The method of claim 14 , wherein the hardwood pulp is refined using a pair of ultrafine refiner plates that have a bar width of 1.0 millimeters or less and a groove width of 1.6 millimeters or less.
20. The method of claim 1 , wherein a basis weight of the fibrous substrate in the formed paper product is between 30 and 75 gsm.