COMPOSITE PAPER PULP COMPOSITION AND METHOD OF MAKING

Composite pulp compositions for making paper are disclosed that include agricultural residue fibers, softwood fibers, and water. The composite pulp compositions are made by blending an agricultural residue with softwood chips and simultaneously and mechanically pulping the mixture of agricultural residue and softwood in one or more TMP and/or RMP operations. The agricultural residue is present in an amount in a range from about 1% to about 30% of the oven dry weight of the composite pulp composition. Co-pulping the agricultural residue with the softwood improves the tear strength properties of the composite pulp composition. Blended pulp compositions are also disclosed that include a chemical pulp or chemi-mechanical pulp blended with the composite pulp compositions having agricultural residue fibers and softwood fibers. Paper products made from the composite pulp compositions and blended pulp compositions are also disclosed herein.

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Description
TECHNICAL FIELD

Disclosed herein are pulp compositions for making paper, specifically composite pulp compositions that include agricultural residue fibers, and methods of making the composite pulp compositions.

SUMMARY

Disclosed herein are composite pulp compositions for making paper, the composite pulp compositions having agricultural residue fibers and softwood fibers that have been simultaneously co-pulped, the co-pulping process providing enhanced strength characteristics to the composite pulp composition having an agricultural residue component.

In one aspect of the disclosure, a process for making a composite pulp composition is disclosed that includes providing an agricultural residue, providing a softwood, combining the agricultural residue with the softwood to form a composite mixture, and subjecting the composite mixture to one or more Thermo-Mechanical Pulping (TMP) operations or one or more Refiner Mechanical Pulping (RMP) operations. In another aspect, the process for making the composite pulp composition includes subjecting the composite mixture to one or more TMP operations and one or more RMP operations.

In another aspect, the process for making a composite pulp composition includes subjecting the composite mixture to a TMP operation to produce a first intermediate pulp, subjecting the first intermediate pulp to a first RMP operation to produce a second intermediate pulp, and subjecting the second intermediate pulp to a second RMP operation to produce the composite pulp composition. In another aspect, the process for making a composite pulp composition includes recovering the composite pulp composition. In another aspect, co-pulping of the agricultural residue with the softwood causes hemicelluloses in the agricultural residue to deposit on surfaces of a plurality of softwood fibers of the softwood.

In another aspect of the disclosed process, the softwood is softwood chips and the agricultural residue is one or more of a corn stover, wheat straw, oat straw, canola straw, barley residue, flax straw, rice straw, or combinations thereof. In another aspect, the process includes size-reducing the agricultural residue, which may include one or more of grinding, chopping, or milling the agricultural residue into a plurality of discrete pieces. In another aspect, the process includes screening the agricultural residue to provide a consistently-sized agricultural residue to the TMP operation. The softwood chips may range in size from about 3.0 mm to about 34.0 mm, and the agricultural residue may range in size from about 1.0 inches to about 3.0 inches.

In another aspect of the disclosure, an amount of the agricultural residue in the composite mixture is in a range of about 1% to about 30% per oven dry weight of the composite mixture. In another aspect, the agricultural residue includes a first residue and a second residue different than the first residue, and an amount of the first residue is in a range of about 1% to about 50% of the oven dry weight of the agricultural residue with the balance of the agricultural residue being the second residue.

In another aspect of the disclosed process, one or more of the TMP operations or RMP operations utilizes a disc refiner having a first plate and a second plate rotating relative to the first plate. In another aspect, a distance between the first plate and the second plate is in a range of about 0.005 to about 0.012 inches. In another aspect of the disclosed process, the first RMP operation utilizes a disc refiner having plates spaced apart by a first distance, and the second RMP operation utilizes a disc refiner having plates spaced apart a second distance. The second distance is the same as or less than the first distance.

In another aspect, the disclosed process includes bleaching the composite pulp composition. Pulp bleaching processes are known and widely used in the pulp and paper industry. In one aspect, the bleaching includes contacting the composite pulp composition with hydrogen peroxide and, more particularly about 3% to 5% hydrogen peroxide. In another aspect, the disclosed process includes providing a chemical pulp or chemi-mechanical pulp and blending the chemical pulp or chemi-mechanical pulp with the composite pulp composition to make a blended composite pulp composition.

In another aspect, paper products, such as writing papers, gift wrap paper, wrapping tissue paper, napkins, greeting card stock, for example, are disclosed that are made from composite pulp compositions disclosed herein and made by the process disclosed herein.

In another aspect of the disclosure, a process for making a composite pulp composition includes providing an agricultural residue, providing a softwood, combining the agricultural residue with the softwood to form a composite mixture, subjecting the composite mixture to one or more TMP or RMP operations, and recovering the composite pulp composition. In one manifestation, the materials of the composite mixture are first subjected to a TMP process followed by one or more RMP processes. TMP and RMP processes are known in the art. However, the process is open to the use of TMP alone, RMP alone, TMP followed by RMP, TMP followed by RMP followed by a second RMP (FIG. 1), RMP processes in sequence, TMP processes in sequence, etc.

In another aspect of the disclosure, a composite pulp composition for making a paper includes agricultural residue fibers, softwood fibers, and water. The agricultural residue and softwood are mixed together and simultaneously and mechanically pulped in one or more of a TMP or RMP operation such that hemicelluloses from the agricultural residue is deposited on the softwood fibers to impart additional strength to the composite pulp composition.

In another aspect of the disclosure, a composite pulp composition for making a paper product is manufactured by a process that includes the steps of providing an agricultural residue, providing a softwood, and co-pulping the agricultural residue and the softwood in one or more TMP or RMP operations. In another aspect, an amount of agricultural residue fibers from the agricultural residue is in a range of about 1% to about 30% of the oven dry weight of the composite pulp composition. In another aspect, the agricultural residue comprises a mixture of a first agricultural residue and a second agricultural residue, and an amount of the first agricultural residue is in a range of about 1% to about 50% of the oven dry weight of the agricultural residue in the composite pulp composition.

In another aspect of the disclosure, a paper composition includes chemical-processed pulp fibers or chemi-mechanical-processed pulp fibers in an amount in a range of about 1% to about 25% of the oven dry weight of fibers in the paper composition, the fibers including the agricultural residue fibers, softwood fibers, and chemical or chemi-mechanical fibers. The agricultural residue fibers and the softwood fibers are co-pulped in one or more TMP or RMP operations, wherein an amount of the agricultural residue fibers is in a range of about 0.1% to about 30% per oven dry weight of the agricultural residue fibers and the softwood fibers, and wherein hemicellulose from the agricultural residue fibers is deposited on one or more of the softwood fibers.

Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 2 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, and so forth.

All references to singular characteristics or limitations of the present process shall include the corresponding plural characteristic or limitation, and vice-versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. The indefinite articles “a” and “an” mean “one or more,” unless explicitly limited to the singular.

All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.

The method disclosed herein can comprise, consist of, or consist essentially of the essential elements and limitations of the method described herein, as well as any additional or optional ingredients, components, or limitations described herein or otherwise useful in the pulping or paper-making arts.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a flow diagram of one example of a co-pulping process for making a composite pulp composition disclosed herein.

FIG. 2 is a graph illustrating the weighted average fiber length of composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 3 is a graph illustrating the ash content of the composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 4 is a chart providing data on the percentage of selected metals in the ash content of the composite pulp compositions made by the process in FIG. 1.

FIG. 5 is a graph illustrating the tear strength index of a softwood (SW) control and composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 6 is a graph illustrating the tensile strength index of the SW control and the composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 7 is a graph illustrating the ISO brightness of the composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 8 is a graph illustrating the bulk (cc/g) of the composite pulp compositions made by the process in FIG. 1 per agricultural residue substitution level.

FIG. 9 is a graph illustrating the ISO brightness of bleached samples of the SW control and the composite pulp compositions made by the process in FIG. 1.

FIG. 10 is a graph illustrating the TAPPI opacity of bleached samples of the SW control and the composite pulp compositions made by the process in FIG. 1.

FIG. 11 is a graph illustrating the coefficient of light scattering and the coefficient of light absorption of bleached samples of the SW control and the composite pulp compositions made by the process in FIG. 1.

FIG. 12 is a graph illustrating the tensile strength index and the tear strength index of bleached samples of the SW control and the composite pulp compositions made by the process in FIG. 1.

FIG. 13 is a chart providing data on the ISO brightness, TAPPI opacity, coefficient of light scattering, coefficient of absorption, tear strength index, and tensile strength index for bleached and unbleached samples of the SW control and the composite pulp compositions made by the process in FIG. 1.

FIG. 14 is a graph illustrating the tensile strength index of bleached samples of the SW control and blended composite pulp compositions disclosed herein.

FIG. 15 is a graph illustrating the tear strength index of bleached samples of the SW control and blended composite pulp compositions disclosed herein.

 DETAILED DESCRIPTION

Reference is now made in detail to the description of the embodiments as illustrated in the drawings and figures. While several embodiments are described in connection with these drawings, there is no intent to limit the disclosure to the embodiment or embodiments disclosed herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents.

Composite pulp compositions for making paper are disclosed herein that generally include softwood fibers and agricultural residue fibers in the form of an aqueous slurry for use in a paper-making process. As used herein, the term “paper” includes paperboard, and the term “paper-making” includes manufacturing paperboard. The composite pulp compositions may also include one or more additives to modify the properties of the pulp and the paper made therefrom. In one example, the composite pulp compositions are made by mixing the agricultural residue with softwood chips to form a composite mixture and co-processing or co-pulping the composite mixture to form the composite pulp composition. Co-pulping the agricultural residue with the softwood chips produces a composite pulp composition with improved physical properties, higher yields, and lower cost than other pulp compositions produced by other methods, particularly softwood pulps or pulps made by chemical or chemi-mechanical processes.

Unless otherwise indicated herein, when used as the basis for a composition by weight, the term “composite mixture” refers to the mixture consisting of the softwood and the agricultural residue exclusive of any other additives. After pulping, when used as the basis for a composition by weight, the term “composite pulp composition” refers to the mixture of softwood and agricultural residue fibers exclusive of any other additives. Unless otherwise indicated herein, the term oven dry weight (OD weight) refers to the oven dry weight of fibers—softwood and/or agricultural residue fibers—and generally does not include the weight of other additives, such as pigments.

Agricultural residues are derived from plant materials remaining after a crop is harvested and can include the leaves, stalks, and roots of the harvested plants. Agricultural residue, also referred to as field residue, can be generally defined as the parts of the plant crops that are not consumed as food or harvested for other commercial uses and can include stems, stalks, leaves, grain leaves, chaff (seed coating), corn husks, corn cobs, and other parts of the plant. Apart from the roots, generally all other portions of the field residue of a crop may be useful as agricultural residue materials for making pulp for paper. The quantity of these agricultural residues can be significant relative to the crop harvested from the plants. A residue ratio, or residue to product ratio (RPR), of the agricultural residue is defined as the oven-dry weight of the field residue divided by the oven-dry weight of the harvested crop. For example, corn has a residue ratio of about 1:1, and oat straw has a residue ratio about 1.3:1. Agricultural residues can include, but are not limited to, wheat straw, oat straw, corn or maize stover, flax straw, rice straw, canola straw, barley straw, sugar cane bagasse, abaca, hemp, kenaf, switchgrass, other crop residues from plant based materials grown as crops, or combinations thereof. Agricultural residues may also be obtained from other commercial crops, such as olives, rapeseed, rye, soybeans, sunflowers, triticale, sugar beets, millet, sorghum, cassava, jute, or cotton, for example. The preceding lists are not intended to be all-encompassing but to include the most common plant-based materials for which the residual material is often left in the field following harvest. The composite pulp compositions may include fibers from only a single type of agricultural residue, such as wheat straw or corn stover, or may include two or more types of agricultural residue, such as a mixture of corn stover and oat straw, for example.

Agricultural residues include various amounts of cellulose, hemicellulose, and lignin, among other compounds and substances. Cellulose may be present in the agricultural residue in an quantities ranging from about 20% to about 50% of the OD weight of the agricultural residue. Hemicellulose may be present in the agricultural residue in quantities ranging from about 15% to about 55% of the OD weight of the agricultural residue. Lignin may be present in the agricultural residue in a quantity ranging from about 10% to about 25% of the OD weight of the agricultural residue. The agricultural residues may have an ash content ranging from about 1% to about 10% of the OD weight of the agricultural residue. The following table provides data on the approximate amounts of cellulose, hemicellulose, and lignin in various suitable agricultural residues. The values in Table 1 given as a wight percentage of dry matter (%).

TABLE 1 Cellulose Hemicellulose Lignin Wheat Straw 34.2 23.7 13.9 Oat Straw 37.6 23.3 12.9 Corn Stover 36.1 21.4 17.2 Barley 33.3 20.4 17.1 Flax Straw 23.3 53.8 23.3 Rice Straw 44.0 20.1 19.0 Canola Straw 42.4 16.4 14.2

Softwood materials containing softwood fibers may be obtained from conifer trees, which may generally include needle-bearing or cone-bearing trees, but may not be limited thereto. Softwood trees are generally characterized as non-porous woods that do not have large verticals pores called vessels that are present in hardwood trees to transport water up the tree. Examples of softwoods include, but are not limited to, various species of pine, fir, spruce, redwood, cedar, cypress, and hemlock trees, among others. Softwoods generally cost less than hardwoods due to the ability to farm softwood trees, such as the Southern pine, for example. Softwoods have longer fibers than hardwoods, and this longer length imparts additional strength to papers made from softwood fibers.

The composite pulp compositions may be characterized as having a substitution level, which is the approximate amounts of softwood replaced by the agricultural residue. The substitution level may also be thought of as a weight percent of agricultural residue relative to the total weight of fibers—softwood and agricultural residue—in the composite pulp composition on an oven dry weight (OD weight) basis. The composite pulp compositions may have a substitution level of agricultural residue fibers in a range from about 1% to about 30% of the OD weight of the composite pulp in one aspect, or from about 5% to about 25% of the OD weight of the composite pulp in another aspect, or from about 10% to about 20% of the OD weight of composite pulp in yet another aspect, or from about 10% to about 15% of the OD weight of the composite pulp in a fourth aspect.

The agricultural residue may be a mixture of two or more agricultural residues, e.g., a first agricultural residue and a second agricultural residue. In one aspect, the second agricultural residue is a different type of agricultural residue than the first agricultural residue. A quantity of the first agricultural residue may be in a range from about 1% to about 50% of the total OD weight of agricultural residue mixture in one aspect, or from about 10% to about 40% of the total OD weight of agricultural residue mixture in another aspect, or from about 10% to about 20% of the total OD weight of agricultural residue mixture in yet another aspect. A quantity of the second agricultural residue makes up the balance of the total OD weight of agricultural residue mixture. Although composite pulp compositions containing two different agricultural residues are described above, it can be appreciated that the agricultural residue can be a mixture of more than two different types of agricultural residues, such as three, four, five, six, or seven different types of agricultural residues, for example.

One or more additives may be added to the composite pulp compositions for modifying the characteristics of the composite pulp compositions and/or the paper made therefrom. Typical additives may include: binders, fillers, internal sizing, dyes, and other additives. Binders, such as starch, for example, may be added to improve the strength—bursting strength, tensile strength, and folding strength—of paper made from the pulp by increasing inter-fiber bonding. Fillers, such as clay, calcium carbonate, or titanium dioxide, for example, can be used to improve optical characteristics or physical qualities, such as smoothness and finish, of papers made from the composite pulp. Internal sizing, such as rosin or an alkaline internal sizing additive, works to inhibit the penetration of liquids, which can cause a substantial decrease in the strength of the paper. Wet strength additives, such as urea formaldehyde resins can be added to provide wet strength to papers made from the composite pulp. Rather than resisting penetration of liquids into the paper, wet strength additives impart strength to the paper after the paper has already been wetted. Dyes, pigments, and optical brighteners (fluorescent brighteners) can be added to influence the appearance of the paper. Other additives may include defoaming agents, mineral additives to absorb pitch, biocides to prevent bacterial growth in the paper making system, lubricating additives to control surface friction, coating binders to facilitate adhesion of a coating onto a coated paper product, and retention agents to retain ingredients during water removal from the paper during the paper-making process. Additives may be added before or after the co-pulping operations.

The composite pulp compositions disclosed herein may also be blended with hardwood pulps or pulps made from chemical or chemi-mechanical processes to make a blended composite pulp composition. Blended composite pulp compositions may have an amount of composite pulp composition in a range from about 5% to about 95% of the OD weight of the blended composite pulp, or from about 20% to about 80% of the OD weight of the blended composite pulp in another aspect, or from about 25% to about 75% of the OD weight of the blended composite pulp in yet another aspect.

Referring now to FIG. 1, the composite pulp compositions of the present disclosure are produced using a co-pulping process 10 generally including providing agricultural residue 12 as disclosed herein, providing softwood 14, forming a composite mixture by blending or mixing the agricultural residue and the softwood in a blending operation 16, and subjecting the composite mixture to one or more pulping operations 18, e.g. TMP and/or RMP processes.

The one or more agricultural residues 12 provided to the process may be size-reduced 20 into smaller pieces so that the agricultural residue material 12 can be effectively mixed with the softwood material and processed in the pulping operation 18. The agricultural residue may be size-reduced to a size in a range of about 0.5 inches to about 6 inches in the longest dimension, or preferably in a range of about 1.0 inches to about 3.0 inches in the longest dimension. The agricultural residue may be size-reduced 20 using an industrial chopper-shredder, a grinder, a mill such as a Wiley mill, or other size-reducing apparatus or process. In one aspect, the agricultural residue is size-reduced 20 using a Wiley mill with a vacuum line. After the size-reducing operation 20, the agricultural residue may be screened 22 to provide a more consistent agricultural residue feed stream and a more homogeneous composite mixture for feeding to the pulping operations 18. Screening 22 may be accomplished with an appropriately sized screen, slot, sieve, or other device for separating larger pieces of agricultural residue from the feed. The agricultural residue can also be washed to remove unwanted substances, such as dirt or pesticides, from the agricultural residue.

The softwoods are generally provided as chips, which may be further size-reduced 24 so that the softwood chips can be effectively mixed with the agricultural residue in the blending operation 16 and processed in the pulping operation 18. Softwood chips may have a size in a range of about 3.0 mm to about 34.0 mm in one aspect, or in a range of 8.1 mm to 29.0 mm in another aspect. The softwood chips may be screened 26 to provide a consistent feed of softwood and a consistent composite mixture for feeding to the pulping operations 18.

The agricultural residue and the softwood chips are blended together in a blending operation 16 to form a composite mixture. Water 15 may also be added to the composite mixture during or after the blending operation, prior to feeding the composite mixture to the pulping process 18. The consistency of the composite mixture prior to primary refining can be in a range of about 30.0% to about 45.0% on an OD weight basis, or in a range of about 38.0% to about 42.0% on an OD weight basis.

The composite mixture of softwood chips and agricultural residue is then fed to a pulping operation 18, which may include one or more mechanical pulping operations, such as Thermo-Mechanical Pulping (TMP) or Refiner-Mechanical Pulping (RMP) operations, for example. The mechanical pulping operations mechanically separate the fibers of the softwood and agricultural residue, ultimately reducing the softwood and agricultural residue to individual fibers or smaller agglomerates of fibers. A typical RMP process generally includes mechanically grinding the composite material between two rough or irregular surfaces called refiner plates that are separated by a gap and move relative to one another. A typical TMP process can be characterized as an RMP process in which the composite mixture is externally heated before or during the mechanical pulping operation, the external heating supplementing the heat generated internally by the mechanical grinding process. In one aspect, steam may be used in a TMP process to provide the external heat to the composite mixture in a heating step prior to feeding the composite mixture to the mechanical refiner operation. TMP and RMP processes and operating conditions are well known in the art.

The quality of the pulp resulting from the pulping operation may be influenced by the consistency and/or moisture content of the composite material fed to the pulping operation, the type of agricultural residue material present in the composite mixture, the feed rate of composite material, the pressure in the mechanical refiner 34, the refiner plate 36 pattern/design, and the gap between the refiner plates 36. The mechanical energy imparted to the composite mixture is inversely proportional to the distance (gap) between the refiner plates 36, such that the smaller the gap between the plates 36, the more energy is imparted to the composite material. The RMP operations can be characterized as low-energy, medium-energy, and high-energy depending on the distance between the plates 36 relative to the average size of the discrete pieces of the composite mixture. As the composite mixture is reduced to smaller and smaller discrete pieces of material and single fibers in successive pulping operations, the distance between the plates 36 in successive pulping operations may be reduced to maintain a high-energy condition.

Referring back to FIG. 1, an exemplary pulping operation 18 for making the composite pulp compositions may include a TMP operation 28, a first RMP operation 30, and a second RMP operation 32, operated in series. The composite mixture is fed to the TMP operation 28, which produces a first intermediate pulp. The first intermediate pulp is then fed to the first RMP operation 30, in which the first intermediate pulp is further refined into a second intermediate pulp. The second intermediate pulp is then fed to a second RMP operation 32, in which the second intermediate pulp is further refined into the composite pulp composition presently disclosed. The first and second RMP operations 30, 32 may be operated in low-energy, medium-energy, or high-energy conditions. In one manifestation, the materials of the composite mixture are first subjected to a TMP process followed by one or more RMP processes. TMP and RMP processes are known in the art. However, the process is open to the use of TMP alone, RMP alone, TMP followed by RMP, TMP followed by RMP followed by a second RMP (FIG. 1), RMP processes in sequence, TMP processes in sequence, etc. In one aspect, the pulping operation 18 does not include any ancillary chemical or chemi-mechanical pulping operations, such as kraft or sulfite pulping processes, for example.

The composite pulp compositions disclosed herein exhibit an average fiber length in a range from about 0.8 mm to about 1.7 mm. Co-pulping of the agricultural residue with the softwood produces a composite pulp composition having increased fiber length over pure softwood pulp in a range from about 1% to about 18% in one aspect, or from about 2% to about 15% in another aspect, or from about 7% to about 15% in yet another aspect. Paper produced from the composite pulp compositions may have a tear index in a range from about 4.75 m N2/g to about 6.7 m N2/g. Tear index indicates the resistance of a paper sheet to tearing and is measured as the force required to tear a piece of paper at standard conditions. Paper made with the composite pulp compositions exhibited an increase in tear index over paper made from 100% softwood, the increase in tear strength being in a range from about 1% to about 10%, or from about 2% to about 9% in another aspect, or from about 5% to about 9% in yet another aspect. Paper made with the composite pulp compositions showed an increase in bulk over softwood fiber papers, the increase in bulk being in a range from about 1% to about 28%, or from about 4% to about 19% in another aspect, or from about 4% to about 12% in yet another aspect. Papers made with the composite pulp compositions (unbleached) exhibited an ISO brightness in a range from about 39% to about 46% and a tensile strength index in a range from about 17 N m/g to about 35 N m/g. Not to be bound by the theory, it is believed that the co-pulping of the agricultural residue and the softwood causes hemicelluloses—in particular xylans—from the agricultural residue to deposit onto the softwood fibers, thereby imparting improved properties to papers made from the composite pulp compositions.

Following co-pulping operations, the composite pulp compositions may undergo one or more bleaching operations. Mechanical pulps can be bleached to an acceptable brightness level using hydrogen peroxide (H2O2) in a single-step process. The hydrogen peroxide may be completely consumed at the end of the bleaching process, eliminating the need for further processing. Chelating agents, such as EDTA, may be used to remove transition metal ions, which catalyze the decomposition of hydrogen peroxide, from the composite pulp composition to maximize the effectiveness of the bleaching process. Other additives, such as manganese salts or sodium silicates, may also be added to improve the bleaching process. A hydrogen peroxide bleaching process oxidizes the color-producing bodies (chromophores) in the lignin present in mechanical pulps. Bleaching makes the composite pulp composition brighter and more stable to light exposure. Bleaching with a one-stage hydrogen peroxide process can preserve the strength properties of the composite pulp composition by removing only the color-producing bodies and leaving the lignin present in the pulp.

Paper sheets made from samples of the composite pulp compositions disclosed herein bleached with 3% H2O2 may have an ISO brightness in a range from about 50% to about 61%, a TAPPI opacity (572 nm) in a range from about 91% to about 95%, a coefficient of light scattering (572 nm) in a range from about 50 m2/kg to about 55 m2/kg, a coefficient of absorption (572 nm) in a range from about 4.0 m2/kg to about 4.8 m2/kg, a tear strength index in a range from about 5.5 mN*m2/g to about 6.5 mN*m2/g, and a tensile strength index in a range from about 27 N*m/g to about 32 N*m/g. Paper sheets made from composite pulp samples disclosed herein bleached with 5% H2O2 may have an ISO brightness in a range from about 64% to about 67%, a TAPPI opacity (572 nm) in a range from about 90% to about 95%, a coefficient of light scattering (572 nm) in a range from about 53 m2/kg to about 56 m2/kg, a coefficient of absorption (572 nm) in a range from about 2.9 m2/kg to about 3.9 m2/kg, a tear strength index in a range from about 5.5 mN*m2/g to about 6.5 mN*m2/g, and a tensile strength index in a range from about 27 N*m/g to about 32 N*m/g.

Bleaching may also include multi-stage processes, and/or may be accomplished using other chemicals, such as sodium dithionate, chlorine, sodium hypochlorite, chlorine dioxide, and oxygen. Certain bleaching processes, such as those involving chlorine or sodium hypochlorite for example, work by removing the lignin from the mechanical pulp rather than just the color-producing bodies, which may reduce the yield and strength of the mechanically produced composite pulp compositions.

The composite pulp compositions, bleached or unbleached, may be used to make paper using any known and conventional paper making process or machine, such as a Fourdrinier paper machine or twin-wire paper machine, for example. Prior to making paper, the composite pulp composition may be further screened and/or cleaned to remove any contaminants or debris, including any unground or partially ground softwood chips or agricultural residue. Following the paper making processes, the finished paper may be slit into sheets and wound onto rolls for transportation to downstream converting operations. In some cases, the web may be slit and cut into sheets and packaged. As previously discussed, the composite pulp compositions may be blended with one or more other pulps, such as kraft pulps or sulfite pulps, to make a blended pulp with enhanced properties.

The composite pulp compositions disclosed herein may be used for niche grades of paper products that may be suitable for niche or seasonal markets. Papers made from the composite pulp composition may be suitable for gift wrap, food labels, beer and/or water bottle labels, paper products for crafts and decorations, wrapping tissue, napkins, greeting cards, writing papers, stationery, diaries, and other papers, although the uses for the composite pulp composition is not intended to be limited thereto.

EXAMPLE 1 (Comparison)

A pulp comprising 100% OD weight corn stover was first attempted. Corn stover was harvested “green” and the cobs removed. The corn stover was size-reduced using an industrial chopper-shredder to pass through a 2-3 inch slot. An appropriate amount of water was added to 5 kg (OD weight) of the size-reduced corn stover, and the corn stover/water mixture was fed to a TMP refining process at 0.5 kg/min. The TMP process included a 12 inch diameter disc refiner with an aggressive plate pattern (D2B505—see FIG. 2) and a distance between the plates of about 0.0055 inches. TMP refining of 100% corn stover did not produce a usable pulp.

A second feed mixture of 5 kg (OD weight) of 100% corn stover in water was subjected to an RMP process that included two passes through a 12 inch disc refiner with no external heat added. The disc refiner used the same aggressive plate pattern (plate pattern D2B505). The distance between the plates was 0.012 inches (low energy) for the first pass and 0.005 inches (high energy) for the second pass. Two-pass RMP processing of the corn stover produced a pulp capable of being formed into a paper, but the pulp exhibited poor formation. Hand sheets made from the pulp exhibited very low values for tensile strength index and tear index. EXAMPLE 2

(Control)

For a control against which to evaluate the composite pulp compositions disclosed herein, a pulp was made using 100% softwood chips (SW). The SW material was subjected a refining process that included a TMP refining process, a first RMP process, and a second RMP process. Each refining process utilized a 12 inch diameter disc refiner with an aggressive plate pattern (D2B505). The SW material was fed at a rate of about 0.5 kg/min. For the TMP process, the distance between the plates was set at 0.0055 inches. Mulitple samples were run at different energy levels in the RMP processes. Pulps from these samples were tested for Pulmac shives, average fiber length, and ash content. Weighted averages of fiber length and ash content for the SW pulp are included in FIGS. 3-4. Hand sheets were produced using the SW pulp samples, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. The test data was used to calculate weighted average values of the tear strength index, tensile strength index, bulk, and ISO brightness for SW pulp, which are included in FIGS. 6-9 in comparison to properties of the composite pulp compositions described below.

Each of the SW samples was bleached by adding a solution of 3.0% H2O2 per OD weight of SW pulp, 0.05% MgSO4 per OD weight of SW pulp, 3.0% Na2SiO2 per OD weight of SW pulp, and 0.2% EDTA per OD weight of SW pulp to 80.0 grams (OD weight) of SW pulp. The SW bleaching samples were placed in sealed bags, which were placed in a water bath at 70° C. for a retention time of 1 hour. Additional SW bleaching samples were made with 5.0% H2O2 with all other constituent quantities remaining constant. Following bleaching, hand sheet samples were made from each of the SW bleaching samples and tested to measure the brightness, opacity, coefficient of light scattering, coefficient of light absorption, tensile strength index, and tear strength index. Sample data was used to calculate average values for non-bleached SW, SW bleached with 3% H2O2, and SW bleached with 5% H2O2, which are provide in FIGS. 10-13 relative to test data from composite pulp compositions further disclosed below.

EXAMPLE 3

A composite pulp composition having 10% OD weight corn stover as the agricultural residue material (CS10) was produced. Corn stover was harvested “green” and the cobs removed. The corn stover was size-reduced using an industrial chopper-shredder to pass through a 2-3 inch slot. Softwood chips and water were added to the corn stover to make a composite mixture having a corn stover amount of about 10% of the OD weight of the composite mixture. The composite mixture was subjected to a refining process that included a TMP refining process, a first RMP process, and a second RMP process, as shown in FIG. 1. Each refining process utilized a 12 inch diameter disc refiner with an aggressive plate pattern (D2B505). The composite mixture was fed at a rate of about 0.5 kg/min. For the TMP process, the distance between the plates was set at 0.0055 inches. Multiple samples were run at different energy levels in the RMP processes. The following table (Table 3) provides the distances between the disc refiner plates for each step in the refining process for each of the samples.

TABLE 3 CS10 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 6.04 5.04 6.67 6.03 Tensile Strength Index (Nm/g) 34.6 32.3 30.4 32.1 Bulk (cc/g) 2.53 2.54 2.69 2.58 ISO Brightness (%) 44.96 44.92 44.23 45.12

The resulting CS10 pulp compositions were tested for average fiber length and ash content. The four samples of CS10 had a weighted average fiber length of 1.085 mm, and an average ash weight percent of 0.52%. Comparisons of the average fiber length and ash content of CS10 to SW pulp of Example 2 and the other examples of composite pulp compositions is provided FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for CS10 and the other examples.

The four samples of CS10 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness according to industry standard test methods. Results of these tests are provided in the Table 3 above. Average values for tear strength index, tensile strength index, bulk, and ISO brightness compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

CS10 samples were bleached by adding a solution of 3.0% of H2O2 per OD weight of CS10, 0.05% MgSO4 per OD weight CS10, 3.0% Na2SiO2 per OD weight CS10, and 0.2% EDTA per OD weight of CS10 to 80.0 grams (OD weight) of CS10. The bleaching samples were placed in sealed bags, which were placed in a water bath at 70° C. for a retention time of 1 hour. Additional bleaching samples were made with 5.0% H2O2. Following bleaching, hand sheet samples were made from the bleached CS10 samples and tested to measure the brightness, opacity, coefficient of light scattering, coefficient of light absorption, tensile strength index, and tear strength index. Sample data was used to calculate average values for non-bleached CS10, CS10 bleached with 3% H2O2, and CS10 bleached with 5% H2O2, which are provided in FIGS. 10-13. FIG. 14 provides numeric testing data from the bleaching study. CS10 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 4

A composite pulp composition having 20% corn stover as the agricultural residue material (CS20) was produced according to the process described in Example 3. The resulting CS20 pulp compositions were tested for average fiber length and ash content and the data combined to calculate a weighted average fiber length of 1.099 mm and an average ash weight percent of 0.57%. Comparisons of the average fiber length and ash content of CS20 to that of the SW pulp of Example 2 and the other examples of composite pulp compositions is provided

FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for CS20 and the other examples.

The four samples of CS20 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. Results of these tests are provided in the Table 4 below. Average values for tear strength index, tensile strength index, bulk, and ISO brightness of CS20 compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

TABLE 4 CS20 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 6.23 5.30 5.96 6.28 Tensile Strength Index (Nm/g) 28.4 32.3 24.4 31.5 Bulk (cc/g) 2.95 2.62 3.04 2.76 ISO Brightness (%) 42.90 42.71 42.38 43.1

CS20 samples were bleached according to the procedures previously described for Example 3. Following bleaching, hand sheet samples were made from the bleached CS20 samples and tested to measure the brightness, opacity, coefficient of light scattering, coefficient of light absorption, tensile strength index, and tear strength index. Sample data was used to calculate average values for non-bleached CS20, CS20 bleached with 3% H2O2, and CS20 bleached with 5% H2O2, which are reported in FIGS. 10-13. FIG. 14 provides numeric testing data from the bleaching study. CS20 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 5

A composite pulp composition having 30% corn stover as the agricultural residue material (CS30) was produced according to the process described in Example 3. The resulting CS30 pulp compositions were tested for average fiber length and ash content and the data combined to calculate a weighted average fiber length of 1.162 mm and an average ash weight percent of 0.64%. Comparisons of the average fiber length and ash content of CS30 to that of the SW pulp of Example 2 and the other examples of composite pulp compositions is provided FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for CS30 and the other examples.

The four samples of CS30 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. Results of these tests are provided in the Table 5 below. Average values for tear strength index, tensile strength index, bulk, and ISO brightness of CS30 compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

TABLE 5 CS30 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 6.32 4.75 5.38 5.60 Tensile Strength Index (Nm/g) 23.4 26.5 19.3 25.3 Bulk (cc/g) 3.07 2.86 3.22 2.92 ISO Brightness (%) 40.23 40.61 39.72 40.37

No bleaching samples of CS30 were made. CS30 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 6

A composite pulp composition having 10% oat straw as the agricultural residue material (OS10) was produced. Oat straw, without the grain, was ground using a Wiley mill with a vacuum line so that the oat straw pieces passed through a 1 inch screen. The oat straw was further washed with tap water. The resulting size-reduced oat straw was mixed with softwood chips and subjected to the mechanical pulping process described in conjunction with Example 3. The resulting OS10 pulp compositions were tested for average fiber length and ash content and the data combined to calculate a weighted average fiber length of 1.244 mm and an average ash weight percent of 0.52%. Comparisons of the average fiber length and ash content of OS10 to that of the SW pulp of Example 2 and the other examples of composite pulp compositions is provided FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for OS10 and the other examples.

The four samples of OS10 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. Results of these tests are provided in the Table 6 below. Average values for tear strength index, tensile strength index, bulk, and ISO brightness of OS10 compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

TABLE 6 OS10 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 5.50 5.42 5.98 5.89 Tensile Strength Index (Nm/g) 17.0 25.6 21.9 26.9 Bulk (cc/g) 3.77 2.96 3.33 2.83 ISO Brightness (%) 44.11 44.95 44.81 45.27

The OS10 samples were bleached according to the procedures previously described for Example 3. Following bleaching, hand sheet samples were made from the bleached OS10 samples and tested to measure the brightness, opacity, coefficient of light scattering, coefficient of light absorption, tensile strength index, and tear strength index. Sample data was used to calculate average values for non-bleached OS10, OS10 bleached with 3% H2O2, and OS10 bleached with 5% H2O2, which are provided in FIGS. 10-13. FIG. 14 provides numeric testing data from the bleaching study. OS10 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 7

A composite pulp composition having 20% oat straw as the agricultural residue material (OS20) was produced. Oat straw, without the grain, was ground using a Wiley mill with a vacuum line so that the oat straw pieces passed through a 1 inch screen. The oat straw was further washed with tap water. The resulting size-reduced oat straw was mixed with softwood chips and subjected to the mechanical pulping process described in conjunction with Example 3. The resulting OS20 pulp compositions were tested for average fiber length and ash content and the data combined to calculate a weighted average fiber length of 1.265 mm and an average ash weight percent of 0.63%. Comparisons of the average fiber length and ash content of OS20 to that of the SW pulp of Example 2 and the other examples of composite pulp compositions is provided FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for OS20 and the other examples.

The four samples of OS20 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. Results of these tests are provided in the Table 7 below. Average values for tear strength index, tensile strength index, bulk, and ISO brightness of OS20 compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

TABLE 7 OS20 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 6.07 5.20 6.49 6.27 Tensile Strength Index (Nm/g) 27.6 28.2 23.6 29.8 Bulk (cc/g) 3.05 2.70 2.95 2.72 ISO Brightness (%) 43.81 43.14 42.59 43.17

The OS20 samples were bleached according to the procedures previously described for Example 3. Following bleaching, hand sheet samples were made from the bleached OS20 samples and tested to measure the brightness, opacity, coefficient of light scattering, coefficient of light absorption, tensile strength index, and tear strength index. Sample data was used to calculate average values for non-bleached OS20, OS20 bleached with 3% H2O2, and OS20 bleached with 5% H2O2, which are provided in FIGS. 10-13. FIG. 14 provides numeric testing data from the bleaching study. OS20 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 8

A composite pulp composition having 30% oat straw as the agricultural residue material (OS30) was produced. Oat straw, without the grain, was ground using a Wiley mill with a vacuum line so that the oat straw pieces passed through a 1 inch screen. The oat straw was further washed with tap water. The resulting size-reduced oat straw was mixed with softwood chips and subjected to the mechanical pulping process described in conjunction with Example 3. The resulting OS30 pulp compositions were tested for average fiber length and ash content and the data combined to calculate a weighted average fiber length of 1.265 mm and an average ash weight percent of 0.63%. Comparisons of the average fiber length and ash content of OS30 to that of the SW pulp of Example 2 and the other examples of composite pulp compositions is provided FIGS. 3-4, respectively. FIG. 5 provides test data on metals present in the ash for OS30.

The four samples of OS30 were used to make hand sheets, which were then tested for tear strength index, tensile strength index, bulk, and ISO brightness. Results of these tests are provided in the Table 8 below. Average values for tear strength index, tensile strength index, bulk, and ISO brightness of OS30 compared to sheets made with SW pulp and other examples of composite pulp compositions are provided in FIGS. 6-9.

TABLE 8 OS30 - Process Conditions and Results Sample 1 2 3 4 TMP Gap (inches) 0.0055″ 0.0055″ 0.0055″ 0.0055″ First RMP Gap (inches) 0.012″ 0.012″ 0.007″ 0.007″ Second RMP Gap (inches) 0.007″ 0.005″ 0.012″ 0.007″ Tear Strength Index (m N2/g) 5.83 5.32 6.07 5.41 Tensile Strength Index (Nm/g) 30.9 30.1 25.5 27.8 Bulk (cc/g) 2.79 2.69 3.09 2.82 ISO Brightness (%) 41.52 40.93 41.27 40.72

No bleaching samples of OS30 were made. OS30 composite pulp produced paper with acceptable characteristics and having greater average fiber length and improved tear strength relative to papers made with SW fibers.

EXAMPLE 9

A composite pulp composition was made with about 15% OD weight of corn stover, about 15% OD weight of oat straw, and the balance OD weight softwood chips. The corn stover and oat straw agricultural residue materials were prepared according to the above procedures described in conjunction with Examples 3 and 6, respectively. The resulting size-reduced oat straw and corn stover agricultural residue materials were mixed together with softwood chips and subjected to the mechanical pulping process described in conjunction with Example 3. Handsheets made from the resulting composite pulp composition having 15% OD weight corn stover and 15% OD weight oat straw exhibited properties comparable to the previous Examples.

EXAMPLE 10

Blended pulp compositions were made by blending bleached samples of CS10, CS20, and CS30 with 25% OD weight of purchased kraft pulp. Prior to blending, the purchased kraft pulp was refined by 5000 revolutions of a PFI mill. The blended pulp compositions were made into hand sheets and tested against hand sheets made from samples of CS10, CS20, and CS30 from Examples 3-5. Test results are provided in FIGS. 15-16. The addition of 25% OD weight of purchased and refined kraft pulp to the composite pulp compositions reinforced the sheets and slightly increased brightness.

Composite pulp compositions having up to 30% agricultural residue as disclosed herein may provide improved tear strength index to paper made therefrom. The composite pulp compositions disclosed herein and subjected to bleaching with hydrogen peroxide may provide acceptable brightness and optical properties while maintaining the physical strength (tear and tensile) of the paper made therefrom. The composite pulp compositions disclosed herein may result in increased strength of papers made therefrom. Not to be limited to the theory, it is believed that this increase in strength may be due to combination of the hemicellulose-rich agricultural residue fibers with the softwood fibers. Composite pulp compositions disclosed herein may also have lower raw material costs due to the substitution of low cost agricultural residue material for a portion of the softwood material, among other benefits. The disclosed process for making a composite pulp composition having an agricultural residue fiber component reduces the use of chemicals in pulp processing, which reduces the need for expensive chemical recovery systems or wastewater discharge treatment systems, thus, thus further reducing raw material costs and reducing the cost of environmental compliance.

Although the process is shown and described with respect to certain embodiments, it is obvious that modifications will occur to those skilled in the art upon reading and understanding the specification, and the present process and resulting product includes all such modifications.

Claims

1. A process for making a composite pulp composition comprising:

providing an agricultural residue;
providing a softwood;
combining the agricultural residue with the softwood to form a composite mixture; and
subjecting the composite mixture to one or more TMP operations and/or one or more RMP operations.

2. The process of claim 1, wherein the composite mixture is subjected to one or more TMP operations and one or more RMP operations.

3. The process of claim 1, further comprising:

subjecting the composite mixture to a TMP operation to produce a first intermediate pulp;
subjecting the first intermediate pulp to a first RMP operation to produce a second intermediate pulp; and
subjecting the second intermediate pulp to a second RMP operation to produce the composite pulp composition.

4. The process of claim 3, wherein the first RMP operation utilizes a disc refiner having plates spaced apart by a first distance, and the second RMP operation utilizes a disc refiner having plates spaced apart a second distance, wherein the second distance is the same as or less than the first distance.

5. The process of claim 1, further comprising collecting the composite pulp composition for use in a paper-making process.

6. The process of claim 1, wherein co-pulping of the agricultural residue with the softwood causes hemicelluloses in the agricultural residue to deposit on surfaces of one or more softwood fibers.

7. The process of claim 1, wherein the agricultural residue is one or more of a corn stover, wheat straw, oat straw, canola straw, barley residue, flax straw, rice straw, sugar cane bagasse, abaca, hemp, kenaf, switchgrass, or combinations thereof.

8. The process of claim 1, further comprising size-reducing the agricultural residue.

9. The process of claim 8, wherein size-reducing the agricultural residue includes one or more of grinding, chopping, or milling the agricultural residue into a plurality of discrete pieces.

10. The process of claim 1, further comprising screening the agricultural residue to provide a consistently-sized agricultural residue to the TMP operation.

11. The process of claim 1, wherein an amount of the agricultural residue in the composite mixture is in a range of about 1% to about 30% per oven dry weight of the composite mixture.

12. The process of claim 1, wherein the agricultural residue comprises a mixture of a first agricultural residue and a second agricultural residue different than the first agricultural residue, wherein an amount of the first agricultural residue is in a range of about 1% to about 50% of the oven dry weight of the mixture, the balance of the mixture being the second agricultural residue.

13. The process of claim 1, wherein one or more of the TMP operation or RMP operation utilizes a disc refiner having a first plate and a second plate rotating relative to the first plate.

14. The process of claim 13, wherein a distance between the first plate and the second plate is in a range of about 0.005 to about 0.012 inches.

15. The process of claim 1, further comprising bleaching the composite pulp composition.

16. The process of claim 15, wherein the bleaching includes contacting the composite pulp composition with hydrogen peroxide.

17. The process of claim 1, further comprising adding a chemical pulp or chemi-mechanical pulp to the composite pulp composition to make a blended composite pulp composition.

18. A composite pulp composition manufactured by the process of claim 1.

19. A paper product made from the composite pulp composition of claim 18.

20. The paper product of claim 19, further comprising a secondary pulp composition, wherein the secondary pulp composition is made from one or more of a chemical or chemi-mechanical process.

21. A process for making a composite pulp composition for making paper products, the process comprising:

providing an agricultural residue;
providing a softwood;
combining the agricultural residue with the softwood to form a composite mixture;
subjecting the composite mixture to a TMP operation to produce a first intermediate pulp;
subjecting the first intermediate pulp to a first RMP operation to produce a second intermediate pulp; and
subjecting the second intermediate pulp to a second RMP operation to produce the composite pulp composition.

22. A composite pulp composition for making a paper product, the pulp composition comprising:

agricultural residue fibers;
softwood fibers; and
water;
wherein an agricultural residue and softwood chips are mixed together and simultaneously and mechanically pulped in one or more of a TMP or RMP operation such that hemicellulose from the agricultural residue fibers is deposited on the softwood fibers to impart additional strength to the composite pulp composition.

23. A composite pulp composition for making a paper product, the composite pulp composition manufactured by a process comprising the steps of:

providing an agricultural residue;
providing a softwood;
co-pulping the agricultural residue and the softwood in one or more of a TMP or RMP operation.

24. The composite pulp composition of claim 23, wherein an amount of agricultural residue fibers from the agricultural residue is in a range of about 1% to about 30% of the oven dry weight of the composite pulp composition.

25. The composite pulp composition of claim 24, wherein the agricultural residue comprises a first agricultural residue and a second agricultural residue, wherein an amount of the first agricultural residue is in a range of about 1% to about 50% of the oven dry weight of the agricultural residue in the composite pulp composition.

26. A composite pulp composition for making paper, the composite pulp composition comprising:

agricultural residue fibers, wherein a portion of the agricultural residue fibers comprises hemicellulose;
softwood fibers; and
water;
wherein at least a portion of the hemicellulose is partially or fully deposited on the softwood fibers and a content of the agricultural residue fibers is in a range of about 1% to about 30% of the oven dry weight of the composite pulp composition.

27. A paper composition comprising:

chemical-processed pulp fibers or chemi-mechanical-processed pulp fibers in an amount in a range of about 1% to about 25% of the oven dry weight of the paper composition; and
agricultural residue fibers; and
softwood fibers;
wherein the agricultural residue fibers and the softwood fibers have been co-pulped in one or more TMP or RMP operations, wherein an amount of the agricultural residue fibers is in a range of about 0.1% to about 30% per oven dry weight of the agricultural residue fibers and the softwood fibers, and wherein hemicellulose from the agricultural residue fibers is deposited on the softwood fibers.
Patent History
Publication number: 20170145634
Type: Application
Filed: Nov 25, 2015
Publication Date: May 25, 2017
Inventors: James Edward Bradbury (Wiscoinsin Rapids, WI), Mikhail Vladimirovich Levit (Atlanta, GA)
Application Number: 14/951,731
Classifications
International Classification: D21D 1/20 (20060101); D21B 1/04 (20060101); D21H 11/12 (20060101); D21H 11/08 (20060101); D21H 11/10 (20060101);