U.S. patent application number 14/951731 was filed with the patent office on 2017-05-25 for composite paper pulp composition and method of making.
The applicant listed for this patent is Verso Corporation. Invention is credited to James Edward Bradbury, Mikhail Vladimirovich Levit.
Application Number | 20170145634 14/951731 |
Document ID | / |
Family ID | 58720686 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170145634 |
Kind Code |
A1 |
Bradbury; James Edward ; et
al. |
May 25, 2017 |
COMPOSITE PAPER PULP COMPOSITION AND METHOD OF MAKING
Abstract
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.
Inventors: |
Bradbury; James Edward;
(Wiscoinsin Rapids, WI) ; Levit; Mikhail
Vladimirovich; (Atlanta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Verso Corporation |
Memphis |
TN |
US |
|
|
Family ID: |
58720686 |
Appl. No.: |
14/951731 |
Filed: |
November 25, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21D 1/20 20130101; D21B
1/04 20130101; D21H 11/12 20130101; D21H 11/08 20130101; D21H 11/10
20130101; D21H 17/01 20130101 |
International
Class: |
D21D 1/20 20060101
D21D001/20; D21B 1/04 20060101 D21B001/04; D21H 11/12 20060101
D21H011/12; D21H 11/08 20060101 D21H011/08; D21H 11/10 20060101
D21H011/10 |
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.
Description
TECHNICAL FIELD
[0001] 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
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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
[0018] 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.
[0019] FIG. 1 is a flow diagram of one example of a co-pulping
process for making a composite pulp composition disclosed
herein.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] FIG. 14 is a graph illustrating the tensile strength index
of bleached samples of the SW control and blended composite pulp
compositions disclosed herein.
[0033] 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
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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-US-00001 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
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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 N.sup.2/g to about 6.7 m N.sup.2/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.
[0052] 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 (H.sub.2O.sub.2) 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.
[0053] Paper sheets made from samples of the composite pulp
compositions disclosed herein bleached with 3% H.sub.2O.sub.2 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
m.sup.2/kg to about 55 m.sup.2/kg, a coefficient of absorption (572
nm) in a range from about 4.0 m.sup.2/kg to about 4.8 m.sup.2/kg, a
tear strength index in a range from about 5.5 mN*m.sup.2/g to about
6.5 mN*m.sup.2/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% H.sub.2O.sub.2 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
m.sup.2/kg to about 56 m.sup.2/kg, a coefficient of absorption (572
nm) in a range from about 2.9 m.sup.2/kg to about 3.9 m.sup.2/kg, a
tear strength index in a range from about 5.5 mN*m.sup.2/g to about
6.5 mN*m.sup.2/g, and a tensile strength index in a range from
about 27 N*m/g to about 32 N*m/g.
[0054] 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.
[0055] 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.
[0056] 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)
[0057] 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.
[0058] 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)
[0059] 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.
[0060] Each of the SW samples was bleached by adding a solution of
3.0% H.sub.2O.sub.2 per OD weight of SW pulp, 0.05% MgSO.sub.4 per
OD weight of SW pulp, 3.0% Na.sub.2SiO.sub.2 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.degree. C. for a
retention time of 1 hour. Additional SW bleaching samples were made
with 5.0% H.sub.2O.sub.2 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% H.sub.2O.sub.2, and SW
bleached with 5% H.sub.2O.sub.2, which are provide in FIGS. 10-13
relative to test data from composite pulp compositions further
disclosed below.
EXAMPLE 3
[0061] 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-US-00002 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
N.sup.2/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
[0062] 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.
[0063] 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.
[0064] CS10 samples were bleached by adding a solution of 3.0% of
H.sub.2O.sub.2 per OD weight of CS10, 0.05% MgSO.sub.4 per OD
weight CS10, 3.0% Na.sub.2SiO.sub.2 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.degree. C. for a retention time of 1 hour.
Additional bleaching samples were made with 5.0% H.sub.2O.sub.2.
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% H.sub.2O.sub.2, and CS10 bleached with 5%
H.sub.2O.sub.2, 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
[0065] 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
[0066] FIGS. 3-4, respectively. FIG. 5 provides test data on metals
present in the ash for CS20 and the other examples.
[0067] 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-US-00003 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
N.sup.2/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
[0068] 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% H.sub.2O.sub.2, and
CS20 bleached with 5% H.sub.2O.sub.2, 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
[0069] 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.
[0070] 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-US-00004 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
N.sup.2/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
[0071] 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
[0072] 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.
[0073] 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-US-00005 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
N.sup.2/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
[0074] 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% H.sub.2O.sub.2, and
OS10 bleached with 5% H.sub.2O.sub.2, 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
[0075] 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.
[0076] 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-US-00006 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
N.sup.2/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
[0077] 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% H.sub.2O.sub.2, and
OS20 bleached with 5% H.sub.2O.sub.2, 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
[0078] 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.
[0079] 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-US-00007 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
N.sup.2/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
[0080] 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
[0081] 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
[0082] 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.
[0083] 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.
[0084] 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.
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