Note: Descriptions are shown in the official language in which they were submitted.
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ARTICLES OF MANUFACTURE MADE FROM PULP COMPOSITION
FIELD OF THE INVENTION
[0001] The disclosure relates to articles of manufacture made from
pulp compositions.
BACKGROUND
[0002] Pulp is a lignocellulosic'fibrous material prepared by
chemically or mechanically separating cellulose fibers from wood, or non-
wood fiber sources.
[0003] "Pulping" generally refers to the reduction of a bulk fiber
source material into its component fibers. Wood and other plant
materials used to make pulp generally contain three main components
(apart from water): cellulose fibers (desired for papermaking), lignin (a
three-dimensional polymer that binds the cellulose fibers together) and
hemicelluloses (shorter branched carbohydrate polymers). The aim of
pulping is to break down the bulk structure of the fiber source, be it chips,
stems or other plant parts, into the constituent fibers.
[0004] Chemical pulping achieves this by degrading the lignin into
small, water-soluble molecules which can be washed away from the
cellulose and hemicellulose fibers without depolyrnerizing them.
Depolymerizing the cellulose weakens the fibers and lowers the strength
of the pulp obtained. Although lignin in pulp may enhance strength, a
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pulp having a high degree of delignification may ease the bleaching
process.
[0005] Generally, existing pulping processes do not provide pulps
having a sufficient reduction in Kappa without the use of multiple
delignification processes and/or unacceptable destruction or weakening
of the cellulose in the pulp. Thus, there is a need for an improved pulping
process that can achieve a pulp with desired characteristics and at the
same time eliminate many of the steps necessary in the current art.
[0006] In addition, agricultural renewable fiber (ARE) is an
environmentally-friendly alternative to the use of wood as a fiber source.
ARE represents an economically-promising source of nonwood fibers.
But, given the fragile nature of agricultural residues, ARF pulps currently
available on the market do not have sufficient strength for many industrial
uses, e.g., making printing and writing grade paper. Thus, there is a
need for high quality, consistent ARF pulps that can substitute the pulps
made from wood fibers for production of articles of manufacture.
SUMMARY OF THE INVENTION
[0007] One aspect of the disclosure relates to an article of
manufacture made from a pulp composition comprising an ARE pulp.
[0008] In one embodiment, the ARF pulp has an unbleached Kappa
number of about 15 or less, and strength parameters sufficient for
paperma king.
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[0009] In another embodiment, the ARF pulp made from a pulping
method comprising cooking a first mixture comprising fibers, water, an
alkali, and a delignification selectivity enhancing chemical for a cooking
time and at a cooking condition sufficient to form a first pulp having a
desired Kappa number of about 15 or less and strength parameters
sufficient for papermaking.
DESCRIPTION OF THE DRAWINGS
[0010] Figure 1: Effect of anthraquinone (AQ) concentration applied
in the cooking process on the Kappa number of obtained pulps for high
H-factor and low H-factor processes.
[0011] Figure 2: Flowchart of a pulping process according to an
embodiment of the present disclosure.
DETAILED DESCRIPTION
[0012] One aspect of the disclosure relates to articles of manufacture
made from a pulp composition comprising an ARF pulp.
[0013] Examples of articles of manufacture produced from a pulp
composition comprising an ARF pulp include, without limitation, tissue,
printing and writing papers, communication papers, bleached board, food
contact packaging papers such as OGR, bleached packaging grades,
liquid packaging, the more exotic papers such as wet strength papers
and release liner, recycled linerboard and molded packaging products.
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[0014] The ARF pulp may be a bleached or an unbleached pulp.
Examples of articles of manufacture produced from a pulp composition
comprising a bleached ARF pulp include, without limitation, tissue,
printing and writing papers, communication papers, bleached board, food
contact packaging papers such as oil and grease resistant ("OGR"),
bleached packaging grades, liquid packaging and the more exotic papers
such as wet strength papers and release liner. Examples of articles of
manufacture produced from a pulp composition comprising an
unbleached ARF pulp include, without limitation, recycled linerboard and
molded packaging products. In certain embodiments, the use of the
bleached or unbleached ARF pulp may improve the performance of the
article of manufacture.
[00151 ARF includes fibers obtained from agricultural productions.
Examples of ARF include, without limitation, bagasse, wheat straw, rice
straw, corn stover (stalks, leaves and husks), soy residuals, coconut
tissues, cotton stalks, palm baskets, kenaf, industrial hemp, seed flax
straw, textile flax straw, sisal, hesperaloe, rye grass, and mixtures thereof.
In one embodiment, the ARFs are bagasse or corn stover.
[0016] The ARF pulp as disclosed herein exhibits exceptional
bonding characteristics. Although the fibers in ARF pulp are generally
short fibers, due to the superior bonding characteristics, the fibers
unexpectedly perform more like long fibers, show physical dimensions
similar to a hardwood fiber, and have a strength that allows them to
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substitute in portion, if not entirely, for Northern bleached softwood kraft
(NBSK) or similar. These bonding characteristics result in outstanding
final paper sheet strength to meet today's demanding customer
specifications. This sheet strength is achieved with a fraction of the usual
refining energy required by wood fibers, a significant cost savings to
tissue applications and others requiring refining wood pulps to develop
strength. In certain embodiments, the fiber count per milligram is 19,000.
[0017] Premium grade bath tissue meeting North American Premium
Specifications has been manufactured using minimal amounts of NBSK
by directly substituting the ARF pulp without any further refining.
[0018] In one embodiment, the ARF pulp has an unbleached Kappa
number of about 15 or less, and strength parameters sufficient for
papermaking.
[0019] Kappa number reflects the hardness, bleachability, or degree
of delignification of pulp. Generally, a pulp having a Kappa number of
about 5 or lower can be bleached by chlorine dioxide (elemental chlorine
free (ECF) techniques) or without chlorine compounds (totally chlorine
free (TCF) techniques) to provide a bleached pulp having a desired
brightness (e.g., ISO brightness of less than 50%, ISO brightness of
about 60% or higher, about 70% or higher, about 80% or higher, about
84% or higher, about 88% or higher, about 80 to about 90%, or about
90% or higher). Generally, it takes more than one pulping step
(sometimes referred to as cooking or delignification) to lower the Kappa
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number while retaining the strength parameters of the pulp. A pulp
having a higher Kappa number will make ECF or TCF bleaching difficult,
requiring oxygen delignification and/or ozone, and/or far more peroxide.
Alternatively, a pulp having a higher Kappa number can be bleached by
chlorine. Therefore, an ARF pulp having a sufficiently low Kappa number
and sufficiently high strength parameters will be appreciated in the art.
[0020] Many
methods of measuring the degree of delignification have
been developed in the art, but most are variations of the permanganate
test. The normal permanganate test provides a permanganate or "Kappa
number," which is the number of cubic centimeters of tenth normal (0.1 N)
potassium permanganate solution consumed by one gram of oven dried
pulp under specified conditions. For example, it may be determined by
TAPP1 Standard Test T-236. The acceptable Kappa number range will
vary depending upon the intended use of the pulp (e.g., the Kappa
number requirements for brown paperboard may vary from about 50 to
about 90, while the requirements for white paper stock may be less than
5).
[0021] Tensile, tear index, and burst index are examples of strength
parameters of a pulp to be used to make articles, e.g., paper or paper
products. Generally higher strength parameters of a pulp are desired to
provide higher strength for the articles made therefrom. A pulp obtained
from wood fibers usually shows better strength parameters compared to
a pulp obtained from non-wood fibers (e.g., ARFs such as bagasse).
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However, some of the strength parameters (e.g., tensile) of the pulp
compositions disclosed herein are unexpectedly similar to or better than
those of the pulp made from wood (see, e.g., Example 9, Table 2).
[0022] Examples of the strength parameters of a pulp that are
sufficient for papermaking include, without limitation, a tensile of at least
about 5.50 km, a tear index of at least about 6.00 mN.m2/g, a burst index
of at least about 3.00 kPa.m2/g, and combinations thereof.
[0023] In certain embodiments, the pulp compositions have a Kappa
number of about 15 or less, about 10 or less, or about 5 or less.
[0024] In certain embodiments, the pulp compositions also have a
high freeness.
100251 The term "freeness," as used herein refers to "pulp freeness,"
refers to the drainage rate of pulp, or how "freely" the pulp will give up its
water. Freeness is important in papermaking in that, if the freeness is too
low, it is not possible to remove enough water on the paper machine to
achieve good sheet structure and strength. Often, mechanical pulps
have low freeness due to harsh action imparted to the raw material,
which produces fines and particles which plug up the draining paper mat.
Many chemical pulping processes using whole-stalk (both bast and core)
nonwood fiber source materials have problems with poor freeness, due to
characteristics of the core fraction.
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[0026] Some embodiments do not suffer from the freeness problems
of prior art processes. Indeed, some ARF pulps disclosed herein have
high freeness. The freeness is much higher than traditional nonwood
pulps eliminating the concern about table capacity on the paper machine
when substituting for wood based pulps. As used herein, the term "high
freeness" is meant to refer to freeness of at least about 400 mL CSF and
above.
[0027] In certain embodiments, the ARF pulp disclosed herein has
freeness of at least about 400, 425, 450, 475, 500, 525, or 550 mL CSF.
[0028] In certain embodiments, the ARE pulp has an ISO brightness
of about 60% or higher, and strength parameters sufficient for
papermaking.
[0029] There are a number of methods of measuring pulp brightness.
This parameter is usually a measure of reflectivity and its value is
typically expressed as a percent of some scale. The International
Standards Organization (ISO) brightness test is used herein. In certain
embodiments, the ARE pulp of the disclosure has an ISO brightness of
less than 50%. In certain embodiments, the ARF pulp of the disclosure
should have an ISO brightness of about 60% or higher (suitable for use in
the manufacture of printing and writing grade paper).
[0030] In certain embodiments, the ARE pulp has an ISO brightness
of about 60% or higher, about 70% or higher, about 80% or higher, about
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84% or higher, about 88% or higher, about 80 to about 90%, or about
90% or higher.
[0031] In another embodiment, the ARF pulp is made from a pulping
method comprising cooking a first mixture comprising ARF fibers, water,
an alkali, and a delignification selectivity enhancing chemical for a
cooking time and at a cooking condition sufficient to form a first pulp
having a desired Kappa number of about 15 or less, and strength
parameters sufficient for papermaking. The cooking step can comprise a
single cooking step to achieve the desired pulp.
[0032] in one embodiment, the fibers used in the pulping method are
ARFs. In another embodiment, the ARFs are bagasse or corn stover. In
another embodiment, the fibers used in the pulping method are wood
fibers, e.g., hard or soft wood fibers.
[0033] Examples of the strength parameters sufficient for
papermaking include, without limitation, a tensile of at least about 5.50
km, a tear index of at least about 6.00 mN.m2/g, a burst index of at least
about 3.00 kPa.m2/g, where the starting material prior to cooking has a
Kappa number of about 60 or greater, and combination thereof.
[0034] The concentration of the alkali in the first mixture may be
from
about 10% to 30% by weight, about 15% by weight to about 25% by
weight, about 20% by weight to about 22% by weight, about 20% by
weight to about 22.5% by weight, about 20% by weight, about 21% by
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weight, about 22% by weight, about 22.5% by weight, about 24%, or
about 27% by weight of the fiber feed (oven dried). An example of the
alkali is, without limitation, sodium or potassium hydroxide, which may
also contain sulfur chemistries. As used herein, "OD," and "O.D." are
oven-dried. Other examples of suitable alkali additive include ammonia
and ethanolamine or derivatives thereof.
[0035] Examples of a delignification selectivity enhancing chemical
include, without limitation, anthraquinone (AQ) or derivatives thereof.
The concentration of AQ or a derivative thereof in the first mixture may be
about 0.2% to about 1.0% by weight, at least about 0.1% by weight, at
least about 0.17% by weight, at least about 0.2% by weight, at least
about 0.25% by weight, at least about 0.27% by weight, at least about
0.3% by weight, at least about 0.35% by weight, at least about 0.4% by
weight, at least about 0.45% by weight, at least about 0.5% by weight, at
least about 0.55% by weight, at least about 0.6% by weight, at least
about 0.65% by weight, at least about 0.7% by weight, at least about
0.75% by weight, at least about 0.8% by weight, or at least about 0.85%
by weight of the OD fiber feed.
[0036] The liquid to dry fiber ratio (LNV) of the first mixture is the
total
liquid amount compared to completely dry fiber, e.g., the weight of liquor
applied to a unit weight of oven dried digester feed. It includes all liquids
involved in cooking, and can be from about 4, 5, 6, 7, 8, or 9 to about 10,
about 7, or about 8.
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[0037] The term "consistency", as used herein in referring to
"reaction
consistency," "mixture consistency" and to "pulp consistency," denotes
percent (%) solids of the reaction mixture, the mixture, or the pulp slurry,
e.g., the weight% of a fiber (usually pulp rather than raw fiber) in a
pulp/water slurry.
[0038] The cooking conditions may be at a cooking temperature and
a cooking pressure. The cooking temperature may be from about 120 C
to about 200 C, about 150 C to about 190 C, or about 165 C to about
185 C, about 175 C, lower than about 175 C, no higher than 175 C,
about 165 C, lower than about 165 C, or no higher than 165 C. The
cooking pressure may be from about 60 psi/g to about 150 psi/g, 120
psi/g to about 150 psi/g, or about 130 psig to about 140 psig.
[0039] The cooking time sufficient to form the first pulp at a cooking
condition depends on the condition, and may be from about 15 minutes
to about 180 minutes, from about 15 minutes to about 120 minutes, from
about 15 minutes to about 90 minutes, from about 30 to about 90 minutes,
from about 30 to about 60 minutes, about 53 minutes, about 50 minutes,
about 40 minutes, about 35 minutes, or about 34 minutes at the
maximum cooking temperature.
[0040] In certain embodiments, the first mixture is heated from a
lower temperature to a desired temperature during a first cooking time,
and is maintained at the desired temperature for a second cooking time.
For example, a desired temperature may be about 90 C to about 200 C,
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about 120 C to about 200 C, about 150 C to about 190 C, or about
165 C to about 185 C, about 185 C, about 175 C, or about 165 C.
The lower temperature may be about room temperature, about 90 C,
about 120 C, about 150 C, or about 165 C. The first cooking time may
be about 1 minute to about 120 minutes, about 1 minute to about 90
minutes, about 1 minute to about 60 minutes, about 5 minute to about
120 minutes, about 5 minute to about 90 minutes, about 5 minute to
about 60 minutes, or about 60 minutes. The second cooking time may
be about 15 minutes to about 180 minutes, about 15 minutes to about
120 minutes, about 15 minutes to about 90 minutes, from about 30 to
about 90 minutes, from about 30 to about 60 minutes, about 53 minutes,
about 50 minutes, about 40 minutes, about 35 minutes, or about 34
minutes. In certain embodiments, the cooking condition is at a cooking
pressure of about 130 psi/g to about 140 psi/g and the desired
temperature is about 175 C. The lower temperature is about 90 C, the
first cooking time is 60 minutes, and the second cooking time is about 40
minutes.
[0041] In certain embodiments, the cooking temperature is from
about 120 C to about 200 C, and the cooking time is from about 15, 20,
or 30 to about 45, 50, 60, 70, 80, or 90 minutes. In certain embodiments,
the cooking temperature is from about 150 C to about 190 C, and the
cooking time is from about 30 to 60 minutes. In certain embodiments, the
cooking temperature is from about 165 C to about 185 C, and the
cooking time is from about 35 to about 45 minutes.
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[0042] In certain embodiments, the temperature of the first mixture is
dropped in to a digester simulation at the desired temperature. For
example, a second mixture having every ingredient of the first mixture
except ARFs may be prepared at the desired temperature, then ARFs
are added into the second mixture to form the first mixture. The cooking
time at the desired temperature may be about 15 minutes to about 180
minutes, about 15 minutes to about 120 minutes, about 15 minutes to
about 90 minutes, from about 30 to about 90 minutes, from about 30 to
about 60 minutes, about 53 minutes, about 50 minutes, about 40 minutes,
about 35 minutes, or about 34 minutes.
[0043] In the prior art, a pulp made from a first cooking step usually
has a higher Kappa number or has damaged or destroyed the desired
properties of the cellulose. For example, pulp made from bagasse known
in the art generally has a Kappa number of about 20 or higher. Such
pulp must be further delignified to reduce the Kappa number (e.g.,
oxygen delignification and/or ozone treatment), and/or bleached by
chlorine. Such delignification and/or chlorine treatment are likely to
damage the strength and other parameters of the obtained pulp and
increase process costs.
[0044] The Kappa number of the first pulp is about 5 or lower, about
7 or lower, about 10 or lower, or about 15 or lower. The first pulp having
a Kappa number of 5 or lower can be bleached by TCF or ECF to obtain
pulp that is suitable for making paper with desired brightness (e.g. ISO
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brightness of less than 50%, about 60% or higher, about 70% or higher,
about 80% or higher, about 84% or higher, about 88% or higher, about
80 to about 90%, or about 90% or higher).
[0045] In certain embodiments, the Kappa number of the first pulp
decreases as the amount of AQ applied to the cooking process increases
(Figure 1).
[0046] H-factor indicates relative speed of lignin dissolution. It
depends on cooking time and temperature. H-factor's dependency on
temperature is very strong due to delignification temperature dependency.
Even a difference of couple of degrees in cooking temperature can make
a significant difference in pulp quality. H-factor has been defined so that 1
hour in 100 C is equivalent with H-factor 1. Generally a higher H-factor
in the cooking process is more likely to provide a lower Kappa number of
the first pulp.
[0047] H-factor can be calculated by
16115 ,
H = f(43,2-
e T dt
0 , wherein t is time and T is
temperature (Kelvin degree).
[0048] In certain embodiments, the pulping process is performed at a
H-factor of about 20 or higher, about 50 or higher, about 100 or higher,
about 200 or higher, about 300 or higher, about 400 or higher, about
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1000 or higher, about 200, about 300, about 400, about 1000, about
1100 or higher, about 1400 or higher, about 1700 or higher, about 2000
or higher, about 2500 or higher, about 3000 or higher, about 2000 to
about 3000.
[0049] In another embodiment, the cooking condition is a pressurized
cooking condition. The pulping method further comprises cooling the first
pulp to lower than its boiling point before the first pulp is released from
the pressurized cooking condition. Cellulose fibers in an alkaline matrix
released to atmospheric pressure while still above the boiling point of
weak black liquor will suffer damage. The damage may be severe. To
avoid such damage, the first pulp may be cooled to within the
temperature range of about 70 to about 95 C before being released from
the pressurized cooking condition. In certain embodiments, the blowline
is cooled to lower than its boiling point before the first pulp is released
from the pressurized cooking condition. In certain embodiments, the first
' pulp is diluted with cooled wash water to lower its temperature to lower
than its boiling point before the first pulp is released from the pressurized
cooking condition.
[0050] In another embodiment, the pulping method further comprises
a cleaning step. In the cleaning step, unwanted materials (e.g. unwanted
mineral material, unwanted cellulosic material, and burned or partially
burned fibers) are removed from the fibers before addition of the fibers
into the first mixture, from the first mixture, or from a pulp obtained after
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one or more steps of the pulping process (e.g. the first pulp, a bleached
pulp, and/or a pulp obtained from each stage of bleaching (e.g. chelation,
oxygen enriched alkaline peroxide bleaching)).
[0051] Examples of the unwanted mineral material include, without
limitation, rocks, sand, rust, soil, tramp metal, trash, and very fine
(silicate)
particles. These particles may wear out equipment, reduce brightness,
affect freeness, and contribute to high ash content. The unwanted
mineral material may be removed from the fibers before added into the
first mixture, from the first mixture and/or from the pulp.
[0052] Examples of the unwanted cellulosic material include, without
limitation, pith (parenchyma cells, and other nonfibrous cells). The
unwanted cellulosic materials have little structural paper-making value,
but they may use up chemicals and plug the sheet. The unwanted
cellulosic materials may be difficult to remove from the pulp. Therefore,
removal of the unwanted cellulosic materials as much as is practical from
the fibers and/or from the first mixture is desired.
[0053] Examples of the burned or partially burned bagasse particles
include, without limitation, carbon and char. Carbon, char, and partially
burned bagasse particles may reduce finished pulp brightness if they are
microscopic in size. If these particles are large, they will show up as dirt.
Removal of these particles from the fibers before added into the first
mixture, from the first mixture and/or from the pulp is desired.
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[0054] The cleaning steps for raw fibers may comprise a single or
multiple cleaning stages. For example, in a first cleaning stage gentle
agitation is applied to the raw fibers to provide shear and release some of
the pith attached to the fibers.
[0055] In a second cleaning stage, rocks and coarse sands are
removed from the raw fibers by centrifugal cleaner.
[0056] In a third cleaning stage, the raw fibers are mixed at a first
cleaning consistency in water for a first cleaning time to form a first
cleaning mixture, then filtered with a first cleaning screen. A gentle
agitation is optionally applied to the mixing step. The first cleaning
consistency may be low to moderate, for example, from about 0.5% to
about 10%, about 1%, or about 2% by weight. The water can be at a
temperature of about 20 C to about 100 C, about 80 C to about 100 C,
or about 60 C. The first cleaning time can be from 1 minute to about 1
hour, or about 10 minutes. Optionally, a small quantity of detergent may
be used to accelerate wetting. The first cleaning screen may be a coarse
screen (about 0.5 cm or larger). The first cleaning mixture may be
poured through the screen. The fibers which are retained on top of the
screen are removed often to prevent forming a thick layer (about 1 cm or
less in thickness). Much higher consistencies and much thicker layers
prevent separation.
[0057] The fiber purification steps for the first pulp involve the
separation of the spent chemicals and dissolved non-pulp materials in a
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process known as washing. Washing is also used to denote using a
surfactant then rinsing with water removing small unwanted particles both
visible to the naked eye and those particles that are microscopic in size.
Cleaning involves the separation of the desired fibers from the undesired
fibers and other material such as sand, char or material that was not
processed completely in the pulping step with systems known as screens
and cleaners. Examples of process equipment of the first type would be
rotary drum vacuum washers, wash presses and diffusion washing units.
Examples of process equipment of the second type would be pressure
pulp screens and centrifugal cleaners.
[0058] Additionally, for example, unwanted cellulosic and/or mineral
materials may be removed from the pulp by actively rinsing the pulp with
clean water. The pulp may be optionally diluted to form a lower
consistency (e.g., about 1.0%) before the rinsing. The rinsing step may
be carried out in a box with a screen mesh floor, wherein the pulp mat
which forms on the mesh is not allowed to accumulate. As soon as a
layer of washed pulp begins to form on the mash, it is removed and
saved.
[0059] A diffusion washer is a multi stage diffusion unit operating at
the cooking conditions to improve the washing efficiency. In certain
embodiments, a diffusion unit has 5 or more stages of washing.
Optionally, a pressure diffuser is used after each step of washing to allow
energy reductions by never cooling the process.
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[0060] To achieve good separation during cleaning, it is preferred to
maintain a thinner pulp mat formed on the screen. In certain
embodiments, the pulp mat has a thickness of less than 1 inch, or less
than 0.5 inch before it is removed from the screen. The size of the holes
on a screen may be about 1/8 inch, or about 3/8 inch.
[0061] Optionally, the screen may be vibrated during the separation.
For example, without limitation, the vibration can be from about 0.1 to
about 2 inch, about 0.1 to about 1 inch, about 0.1 to about 0.5 inch, about
0.25 to about 0.5 inch.
[0062] In certain embodiments, prior to digesting, the raw fibers, the
first mixture, or the pulp is cleaned by dropping to a screen for separation
of unwanted materials. The raw fibers, the first mixture, or the pulp is
dropped at an angle other than 90 to prevent plugging. The angle may
be about 45 or larger. It is desired to have a consistent pouring speed to
feed the screen to keep the material distribution more level and
consistent across the screen surface.
[0063] In certain embodiments, unwanted materials are separated
from the raw fibers, the first mixture, or the pulp by a vertical hammermill
or by a trammel screen. This is the first processing step of preparing the
raw bagasse for shipment to the pulp mill and is called moist depithing.
[0064] In another embodiment, the pulping method further comprises
bleaching the first pulp to provide a bleached pulp. In certain
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embodiment, the pulp composition has an ISO brightness of about 60%
or higher, about 70% or higher, about 80% or higher, about 84% or
higher, about 88% or higher, about 80 to about 90%, or about 90% or
higher.
[0065] The bleaching step may involve chlorine, chlorine dioxide
(ECF techniques) or no chlorine compounds (ICE techniques). A
bleaching step comprises one or multiple stages. Each stage may or
may not include a bleaching agent. Each stage may be performed
separately or be performed in combination with another stage at the
same time. Optionally, a cleaning step is performed after each stage
(e.g., via wash press, diffusion washer, or a diffuser washer). For
example, in a C stage, chlorine is applied. In a PO, Ep, P, P1 or P2
stage, hydrogen peroxide is applied. In an E stage, an extraction with
sodium hydroxide is applied. In a D, D1, or D100 stage, chloride dioxide
is applied. In an Eop stage, sodium hydroxide is applied, and hydrogen
peroxide and a small amount of oxygen gas is added. In an 0 stage,
oxygen gas is applied. In a Q stage, a chelating agent is applied to
remove metals. In a PO stage, alkaline peroxide and oxygen are applied
at the same time to improve peroxide efficacy.
[0066] Optionally a wash is performed after each stage of reaction is
completed.
[0067] Chelation is a step to protect peroxide used as a bleaching
chemical in the next stage. Examples of chelating agent include, without
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limitation, ethylenediaminetetraacetic acid (EDTA), diethylene triamine
pentaacetic acid (DTPA), and diethylenetriamine penta(methylene
phosphonic acid (DTPMPA). In certain embodiments, the pH of a pulp to
be treated is adjusted to 4.0 to remove calcium and other metals. The
pulp is treated with a chelating agent (e.g. EDTA, DTPA) and an acid (e.g.
H2SO4) at a chelation temperature of 80 C or higher, and for a chelation
time of 10 minutes to 30 minutes or longer. When DTPMPA is used no
pH adjustment is necessary. The target for all the chelants is primarily
Mn, which causes catalytic loss of hydrogen peroxide. The chemicals
may be added via a high shear chemical mixer or any other suitable
equipment/method known in the art. In certain embodiments, the pulp is
adjusted to a consistency of about 5 to about 30%, about 10 to about
30%, about 15 to about 20%, about 10%, about 15%, or about 20%
before the chelation treatment. In certain embodiments, the pulp
obtained from the chelation stage is washed before proceeding to the
next stage. A wash may be performed in a wash press which presses
then dilutes and represses the pulp for wash. The wash may be
performed by other methods or equipments known in the art.
[0068] In certain embodiments, e.g., where the first pulp has a Kappa
number of higher than about 5-15, a chlorine bleaching approach may
be first applied to the first pulp to reduce the Kappa value to lower than
about 5-15 (C stage), and then the less harmful hydrogen peroxide may
substitute for hypochlorite if desired. For example, a C/Eop/PO or a
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C/Ep/PO bleach sequence may be applied for the bleaching step
replacing prior art sequence C/E/H or C/EOP/H or C/EP/H.
[0069] In certain embodiments, the first pulp has a Kappa number of
about 5-15 or less, an ECF or TCF approach is applicable.
[0070] An ECF approach comprises one or more stages selected
from the group consisting of D, D100, DI, Ep, D, PO, and Fop. ECF
means that at least some chlorine dioxide is used. The "E" in ECF
stands for "Elemental" meaning that no chlorine gas per se is applied.
These replaced older sequences which were commonly C/E/H or its
variants.
[0071] A TCF approach commonly comprises one or more stages
selected from the group consisting of Q, P, PO, and 0. The "T" in TCF
stands for Totally. TCF sequences might also include a variety of other
chemistries such as ozone "Z", peracetic acid, Caro's acid, sodium
hydrosulfite, among others.
[0072] In certain embodiments, a TCF approach comprises a Q stage
followed by multiple atmospheric peroxides stages or by a single
atmospheric P stage followed by a PO stage. In the Q stage, chelation is
performed as described supra, with 0.5% chelating agent and 0.4%
H2SO4 at 80 C for 30 minutes, and no H2SO4 but applying the same
conditions if DTPMPA is used. In a PO stage, bleaching is accomplished
in a single extreme alkaline peroxide bleaching stage that is enriched
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with oxygen to improve peroxide efficacy. Most or even all the brightness
gain may be accomplished in the P/PO stage. In certain embodiments,
the pulp (e.g., about 5 to about 30%, about 10 to about 30%, about 15 to
about 20%, about 10%, about 15%, or about 20%) is mixed with steam,
caustic (NaOH, about 2.6% by weight of the dry pulp), oxygen (pressure
of 60 psi/g), hydrogen peroxide (about 6.0% to about 9.0 percent, about
6.0% or about 7.0% by weight of the dry pulp), sodium silicate (about
4.0% by weight of the dry pulp), magsulfate (about 0.3% by weight of the
dry pulp) at a temperature of about 120 C for about 120 minutes. This
stage may be performed in a high shear pulp/steam/chemical mixture, or
any other suitable equipment/method known in the art. The ISO
brightness of the bleached pulp is about 60% or higher, about 70% or
higher, about 80% or higher, about 84% or higher, about 88% or higher,
about 80 to about 90%, or about 90% or higher. The yield may be about
90% of feed fiber or higher, about 94% of feed fiber or higher, about 95%
of feed fiber or higher.
[0073] In certain embodiments, a TCF approach has a sequence of
Q/P1/Q/P2 and Q/P1/P0 and Q/P1/Q/P0, and Q/PO wherein the Q
stage and the P and PO stages are the same as described supra. In the
P and PO stages, the pulp obtained from a first Q stage (optionally
washed, consistency being about 5 to about 30%, about 10 to about 30%,
about 15 to about 20%, about 10%, about 15%, or about 20%) is treated
with caustic (NaOH, about 0.7% by weight of the dry pulp), hydrogen
peroxide (about 1.0% by weight of the dry pulp), sodium silicate (about
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4.0% by weight of the dry pulp), magnesium sulfate (about 0.3% by
weight of the dry pulp) at a temperature of about 80 C for about 30
minutes, and the final pH is about 10.6. The ISO brightness of the
bleached pulp is about 60% or higher. The obtained pulp is then treated
with another Q stage and a P2/P0 stage as described supra.
[0074] In another embodiment, a pulping method is carried out as
shown in the flow chart of Figure 2. In the bagasse washing step, the
bagasse starting materials are washed with white water, i.e., the process
water obtained from a paper making system such as process water
obtained from different washes as shown in the figure, to provide washed
bagasse (which is used for cooking in the digester step) and bagasse
wash water effluent (which is lead to the drain), as described supra. After
digestion, the resulted pulping mixture is sent for washes by different
wash methods as described supra. The obtained wash water effluent is
sent for further treatments. The washed bagasse is chelated as
described supra, washed as described supra, and then bleached in the
bleaching step. Although only one bleaching box is shown in the figure, a
single or multiple stage of bleaching may be incorporated, as described
supra. In certain embodiments, the washing between the steps may be
optional. After the pulp is bleached, it is washed, cleaned, and dried &
bailed.
[0075] EXAMPLES
[0076] Example 1. Cleaning of raw fibers
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[0077] Bagasse was used as an example of raw fibers. Bagasse was
first hydrated for 10 minutes with hot clean water (temperature of water
was above room temperature, about 40 C, or 60 C), under moderate
agitation, at a consistency of 0.5% to 2.0%. Pith and sand were
separated from the fibers in a Trammel Screen, which was a rotating
drum that lifted and dropped the material and accepted water and pith
through 118th inch holes up to W holes. The rejected material was
collected and removed from the screen to prevent accumulation, and
disposed, and was dried before added into the pulping process. The
washing yield was about 80% or higher, or about 85.9%, depending on
quality of the bagasse starting material.
[0078] Example 2. Soda AQ pulping of bagasse
[0079] OD bagasse (cleaned as described in Example 1, Kappa
number was 89) was treated with sodium hydroxide (20% by weight of
the OD bagasse) and AQ (0.3% by weight to the dry weight of OD
bagasse) at a liquid to dry fiber ratio of 7 (consistency of about 12.5%), at
maximum temperature of about 175 C for 35 or 40 minutes. Time to the
maximum temperature was 60 minutes.
[0080] The target H-factor was 1060, as low as 20, and as high as
3000, and the temperature of the pulping reaction was 120 C to 185 C.
The Kappa number of the obtained pulp was 4.5.
[0081] Example 3. Washing of pulp
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[0082] A pulp obtained from Example 2 was washed in a pressure
diffuser washer designed specifically to accomplish all washing with a
single unit without introducing undesired modifications to the pulp. The
temperature of the wash water was chosen to cool the pulp temperature
to about 100 C, 95 C, 90 C, 85 C, 80 C or lower. The output went to
a bleaching step and was cooled to 100 C or less to prevent flashing.
[0083] Example 4. Chelation stage of pulp (Q stage)
[0084] A pulp obtained from Example 3 was adjusted to a
consistency of 15% and pH 4 by H2SO4 (about 0.4% by weight of the dry
weight of pulp), then treated with DTPA (0.5% by weight of the dry weight
of pulp) at 80 C for 10 minutes. The pulp obtained was washed in a
wash press before proceeding to the next stage.
[0085] Example 5. Alkaline peroxide bleaching of pulp (P2/P0 stage)
[0086] The washed pulp obtained from Example 4 was adjusted to a
consistency of 15% and proceeding to the P2/P0 stage. The pulp (15%
consistency) was mixed with steam, caustic (Na0H, 2.6% by weight of
the dry pulp), oxygen (pressure of 60 psig), hydrogen peroxide (7.0% by
weight of the dry pulp), sodium silicate (about 4.0% by weight of the dry
pulp), magnesium sulfate (about 0.3% by weight of the dry pulp) at a
temperature of about 120 C for about 120 minutes in a high shear
pulp/steam/chemical mixture. The ISO brightness of the bleached pulp
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was 86% or higher, and was up to 89.2. The yield was about 94% of
feed fiber or higher. The terminal pH was 10.2.
[0087] Example 6. Cleaning and drying of bleached pulp
[0088] The bleached pulp obtained from Example 5 was diluted to
<2% consistency, and processed through centrifical cleaners to remove
sand, soil particles and other dirt and unwanted materials. These
cleaners had a 20 psig differential at the cleaner. A 1% yield loss
occurred at this stage.
[0089] After the bleached pulp was cleaned, it was formed into a
sheet and pressed to 50% dry solid before drying in an air impingement
dryer. The minimum dryness was 92%. The sheets were cut to desired
size and stacked into bales of desired dimensions and weight. These
bales were wrapped and tied and stored for shipment.
[0090] Example 7. ECF bleaching of a pulp obtained from Example 3
[0091] An ECF bleaching having a sequence of D100/E/D was
performed on a pulp having Kappa number of 5 or lower.
[0092] D100 stage (low pH, about 2,4, ECF stage to delignify pulp): A
pulp having consistency of 10% was treated at 50 C for 60 minutes at a
Kappa factor of 0.25. The final pH was 2.5, and residual chlorine was
small to non-detectable.
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[0093] Ep stage: The pulp obtained from the D100 stage was treated
with hydrogen peroxide (0.50% to 0.8% by weight of the weight of the dry
pulp) at 80 C for 60 minutes. The final pH was 10.5-11.0, and the final
ISO brightness of the obtained pulp was about 80-82%. The viscosity of
the bleached pulp was high.
[0094] D stage: The pulp obtained from Ep stage was treated with
chlorine dioxide (1.2% by weight of the weight of the dry pulp) at 80 C
for 150 minutes. The final pH was 3.5-4.0, the residual chloride dioxide
was 0.05%, and the final ISO brightness of the bleached pulp was about
89%. The viscosity of the bleached pulp was high.
[0095] Example 8. TCF bleaching of a pulp obtained from Example 3
[0096] A TCF bleaching having a sequence of Q/P/PO having the
following reaction condition was performed on a pulp having Kappa
number of 5 or lower.
[0097] Q stage: A pulp having a consistency of 10% was treated with
DTPMPA (0.5-0.7% by weight of the weight of the dry pulp) at 80 C for
30 minutes. The final pH was 7.
[0098] P stage: The pulp obtained from the Q stage was treated with
hydrogen peroxide (2.0% by weight of the weight of the dry pulp), sodium
hydroxide (1.0-1.1% by weight of the weight of the dry pulp), DTPMPA
(0.25% by weight of the weight of the dry pulp), MgSO4 (0.60% by weight
of the weight of the dry pulp), NaSiO3 (0.50% by weight of the weight of
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the dry pulp) at 85 C for 60 minutes. The final pH was 10.5-11.0, and
the final ISO brightness of the obtained pulp was about 80%. The
residual was about 0.05%. The viscosity of the bleached pulp was high.
[0099] PO stage: The pulp obtained from the P stage can be treated
with hydrogen peroxide (5% by weight of the weight of the dry pulp),
DTPMPA (0.25% by weight of the weight of the dry pulp), MgSO4 (0.60%
by weight of the weight of the dry pulp), NaSiO3 (0.50% by weight of the
weight of the dry pulp) at 120 C for 120 minutes. A final ISO brightness
of the bleached pulp can be 88.00%. A viscosity of the bleached pulp
can be high.
[00100] Example 9. Benchmark strength of a pulp product made from
bagasse
[00101] I) Cleaning of the bagasse starting materials.
[00102] Bagasse # 11 was cleaned by the same procedure as
described in Example 1 except that a 3/8" sieve was used instead of the
1/8" sieve.
[00103] II) Cooking
[00104] The cleaned bagasse was treated with sodium hydroxide
(22% by weight of the OD bagasse) and AQ (0.2% by weight to the dry
weight of OD bagasse) at a liquid to dry fiber ratio of 8.0 (consistency of
about 12%), at a maximum temperature of about 165 C for 35 minutes.
Time to the maximum temperature from 90 C was 60 minutes.
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[00105] The target H-factor was 452. The Kappa number of the
screened and quick dried pulp was 5.0, the cooking yield was 56.8%, the .
yield of the screened pulp was 55.8%, total rejects was 1.0% (4- 0.010"),
and the viscosity of the pulp was 44.0 mPa.s.
[00106] The pulp obtained was box-washed pulp by first diluting the
pulp to a consistency of 1.0%, and then rinsing the pulp in a box with a
screen mesh floor, wherein the pulp mat which forms on the mesh was
not allowed to accumulate of more than 1 inch. As soon as a layer Of
washed pulp began to form on the mash, it was removed and saved for
the next step of process.
[00107] III) Bleaching
[00108] The washed pulp was bleached by an ECF sequence of
D100/Ep/D1 to provide pulp A4420-1-D1 box washed. A duplicate
washed pulp sample was bleached by a TCF sequence of Q/P1/P0 to
provide pulp A4420-2-P0 box washed.
[00109] The ECF sequence of D100/Ep/D1 was carried out using the
following conditions:
[00110] D100 stage: A pulp having consistency of 10% was treated
with C102 (1.15% as C12) at 50 C for 60 minutes using a Kappa factor of
0.25. The final pH was 2.0, and the residual chlorine was 0.02 g/L (as
avail Ci2).
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[00111] Ep stage: The pulp obtained fro the D100 stage was treated
with hydrogen peroxide (0.5% by weight of the weight of the dry pulp),
NaOH (0.7% by weight of the weight of the dry pulp), and MgSO4 (0.1%
by weight of the weight of the dry pulp), at 80 C for 60 minutes. The
final pH was 11.2, and the final ISO brightness of the obtained pulp was
about 75.6%. The viscosity of the bleached pulp was very 21.4 mPa.s
[00112] D stage: The pulp obtained from Ep stage was treated with
chlorine dioxide (1.5 to 1.7% by weight of the weight of the dry pulp) and
NaOH (0.70% by weight of the weight of the dry pulp), at 80 C for 150
minutes. The final pH was 4, the residual chloride dioxide was 0.09%,
and the final ISO brightness of the bleached pulp was about 88.4%.
[00113] The TCF sequence of Q/PO was carried out using the
following conditions.
[00114] Q stage: A pulp having a consistency of 10% was treated with
DTPMPA (0.5% by weight of the weight of the dry pulp) at 80 C for 30
minutes. The final pH was 6.6.
[00115] P1 stage. The pulp obtained from the Q stage was treated
with hydrogen peroxide (2.0% by weight of the dry pulp), sodium
hydroxide (1.1% by weight of the dry pulp), DTPMPA (0.5% by weight of
the dry pulp), Magsulfate (0.6% by weight of the dry pulp), Sodium
Silicate (1.0% by weight of the dry pulp) at 85C for sixty minutes. The
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final pH was 11.2 and the ISO brightness of the pulp was about 67.7%.
The residual peroxide was 1.25%.
[00116] PO stage: The pulp obtained from the P1 stage was treated
with hydrogen peroxide (6.0% by weight of the weight of the dry pulp),
sodium hydroxide (2.8% by weight of the weight of the dry pulp),
DTPMPA (0.5% by weight of the weight of the dry pulp), MgSO4 (0.60%
by weight of the weight of the dry pulp), NaSiO3 (3.0% by weight of the
weight of the dry pulp) at 120 C for 120 minutes. The final pH was 11.2,
and the final ISO brightness of the obtained pulp was about 86%. The
residual hydrogen peroxide was about 0.39%.
[00117] Table 1 shows the Kappa number and ISO brightness of pulp
A4420-1-D1 box washed (pulp 9-1) and pulp A4420-2-Po box washed
(pulp 9-2).
Table 1. Kappa number and ISO brightness of pulp 9-1 and pulp 9-2.
Analysis Unit Pulp 9-1 Pulp 9-2
Kappa Number of the pulp before bleaching 4.57 4.57
ISO brightness 89 86.5
Overall yield >50 >50
[00118] Table 2 shows benchmark strength of pulp A4420-1-D1 box
washed (pulp 9-1) and pulp A4420-2-Po box washed (pulp 9-1)
compared with bagasse pulp obtained from a Thailand mill (pulp 9-3),
and standard pulps from bagasse (pulp 9-4, bleached bagasse pulp, pulp
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atlas pulp #60) at 0 revolution in a TAPPI standard PFI analysis, and
standard pulps from wood (pulp 9-5, eucalyptus bleached Kraft cenrtl.
coastl. Brazil pulp, pulp atlas pulp #35) at revolutions of 0, 1000, and
2000 in a TAPP! standard PFI analysis,.
Table 2. Benchmark strength of pulps obtained from the
embodiment, pulp from bagasse from another mill, standard pulp
from bagasse, and standard pulp from wood
Analysis Unit Pulp Pulp Pulp Pulp Pulp
9-1 9-2 9-3 9-4 9-6
24 grams, 0.2 mm gap Feed/mill gap
PFI, TAPP] Revolutions 0 0 0 0 0
1000 200(
C.S. Freeness nnL 538 571 488 484 500 399
362
Basis weight, g/m2 67.30 67.50 66.16 66.79
67.00 66.19 66.9
conditioned
Bulk cc/g 1.31 1.32 1.48 1.51 1.74
1.53 1.50
Burst factor 39 35 16
Burst index kPa.m2/g 3.85 3.40 1.57 2.13 0.88
2.40 3.09
Tear factor 66 62 63
Tear index mN.m2/g 6.49 6.09 6.17 6.15 4.40
9.39 9.84
Tensile strength kN/m 4.37 4.10
Tensile km 6.61 6.20 3.26 4.018 2.161 4.568 5.69
Tensile index N.m/g 64.9 60.8 32.0 39.4 21.2
44.8 55.9
Stretch 2.71 2.56 1.87 2.22 1.03 2.63 3.12
Tensile Energy J/m2 84.0 74.2 28.1 41.9 9.3
54.7 80.8
Absorption
Porosity, Gurley sec/100m I 32 27 , 12
Fold, MIT count 182 97
Zero Span, km 11.0 10.8 8.18 8.94
13.87 15.13 15.5
Pulmac (dry)
_ Optical Properties
Opacity 66.7 66.7 73.14 78.16
Fiber Quality Analyzer:
Population fibers/mg 17,731 17,267 16,263 10,702* 21,943
AFL, arithmetic mm 0.51 0.51 0.42 0.522 0.580
LWAFL mm 1.04 1.05 0.87 1.14 0.76
WWAFL mm 1.77 1.81 1.53 1.90 0.94
Coarseness mg/m 0.111 0.113 0.146 0.179 0.079
Curl, 0.099 0.109 0.078 0.076 0.102
length weighted
Kink index 1/mm 1.15 1.25 0.96 1.03 1.68
Percent fines 32.16 30.93 42.39 37.01 17.77
< 0.2 mm,
arithmetic
Percent fines 8.78 8.40 12.62 9.43 3.59
< 0.2 mm,
length weighted
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Bauer McNett Fiber Classification
retained on 18.6 19.0 11.0
+ 28 mesh
retained on 37.3 36.5 41.2
+ 65 mesh
retained on 19.9 19.8 16.5
+ 100 mesh
retained on 10.3 10.3 12.9
+ 200 mesh
total retained 86.1 85.6 81.6
fines through 13.9 14.4 18.4
-200 mesh
*most likely, an anomaly.
[00119] A standard PFI mill method (TAPP! Test Method T-248) was
used to evaluate pulp quality for papermaking. A pulp was "beaten" or
"refined" in a laboratory setting for certain revolutions to reflect further
processing of the pulp in a mill. A zero revolution number meant no
further process was done to the pulp. The data of a standard wood pulp
(pulp 9-5) showed that further processing of the pulp lowers the freeness,
but improves strength parameters such as burst, tear and tensile
parameters. The bagasse pulps obtained from this embodiment (pulps 9-
1 and pulp 9-2) with no revolutions had higher freeness, tensile and burst
parameters than those of the standard hardwood pulp (pulp 9-5) with or
without revolutions. The bagasse pulps obtained from this embodiment
(pulps 9-1 and pulp 9-2) with no revolutions had higher tear and stretch
parameters than those of the standard wood pulp (pulp 9-5) without
revolutions. This showed that the bagasse pulps obtained from this
= embodiment had very good papermaking quality without further
processing necessary for wood pulps.
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[00120] Characters of the bagasse pulps obtained from this
embodiment (pulps 9-1 and pulp 9-2) were also compared with those of
known bagasse pulps (pulp 9-3 obtained from a Thailand mill and pulp 9-
4, a standard bagasse pulp from the Pulp Atlas) at different revolutions
(Table 3).
Table 3. Selected parameters of bagasse pulps obtained from Soda
AQ pulping process
Analysis PFI, TAPPI C.S. Burst Tear Tensile Tensile StrE
Freeness index index index
Unit Revolutions mL kPa.m2/g mN.m2/9 km N.m/g %
Pulp 9-1 0 538 3.85 6.49 6.61 64.9
2.71
200 389 4.49 6.21 7.55 74.0
2.7E
800 230 4.77 5.89 8.14 79.8
2.9E
Pulp 9-2 0 571 3.40 6.09 6.20 60.8
2.5E
200 436 4.16 5.78 6.86 67.3
2.74
800 294 4.49 5.37 7.65 75.3
2.84
Pulp 9-3 0 488 1.57 6.17 3.26 32.0
1.87
250 362 2.37 6.36 4.38 42.9
2.71
1000 244 2.90 6.33 5.00 49.0
2.9E
Pulp 9-4 0 484 2.13 6.15 4.018 39.4
2.22
250 344 3.05 5.84 4.819 47.3 2.98
750 258 3.44 5.84 5.416 53.1 3.1
[00121] Table 3 shows selected parameters of bagasse pulps
produced from different sources with different resolutions.
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[00122] The freenesses of the pulps obtained from the embodiment
(pulp 9-1 and pulp 9-2) were about 10% to about 18% higher than those
of the bagasse pulps obtained from other sources (pulp 9-3 and pulp 9-4)
when revolutions were 0.
[00123] The burst indexes of pulp 9-1 and pulp 9-2 were about 60% to
150% higher than those of pulp 9-3 and pulp 9-4 when revolutions were 0.
Although the burst indexes of pulp 9-3 and pulp 9-4 increased at higher
revolutions, the burst index of pulp 9-3 at 1000 revolutions and the burst
index of pulp 9-4 at 750 revolutions were still lower than that of pulp 9-1
or pulp 9-2 at zero revolutions.
[00124] The tensile parameters of pulp 9-1 and pulp 9-2 were about
54% to about 100% higher than those of pulp 9-3 and pulp 9-4 when
revolutions were 0. Although the tensile parameters of pulp 9-3 and pulp
9-4 increased at higher revolutions, the tensile parameters of pulp 9-3 at
1000 revolutions and the tensile parameters of pulp 9-4 at 750
revolutions were still lower than those of pulp 9-1 or pulp 9-2 at zero
revolution.
[00125] The tear and stretch parameters of pulp 9-1 and pulp 9-2 were
also higher than those of the pulp 9-3 and pulp 9-4.
[00126] The pulp obtained from the embodiment had significantly
higher burst index than that of the reference bagasse pulps, about 60%
to about 150% higher.
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[00127] The improved strength parameters of pulp 9-1 and pulp 9-2
compared to the reference bagasse pulps were significant and
unexpected, and were also found in other pulp produced by the pulping
method disclosed in this disclosure from bagasse or other fiber sources
(e.g., corn stover, Example 11 disclosed below).
[00128] Example 10. Effect of cleaning in the pulp process on
benchmark strength of the final pulp products obtained from soda AQ
process
[00129] 1) Cleaning of bagasse
[00130] Bagasse # 6 was cleaned according to the procedure as
described in Example 1.
[00131] II) Cooking
[00132] The cleaned bagasse was treated with sodium hydroxide
(20% by weight of the OD bagasse) and AQ (0.3% by weight to the dry
weight of OD bagasse) at a liquid to dry fiber ratio of 7.0 (consistency of
about 12.5%), at a maximum temperature of about 175 C for 34 minutes.
Time to the maximum temperature was 60 minutes.
[00133] The target H-factor was 1056, temperature pulping reaction
was 175 C. The Kappa number of the screened pulp was 4.1, the
cooking yield was 57.9%, the yield of the screened pulp was 56.6%, total
rejects was 1.3% (+ 0.010"), and the viscosity of the pulp was 38.3
rnPa.s.
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[00134] III) Bleaching
[00135] Pulp A4354-1-P was obtained by bleaching the pulp obtained
from the cooking step by a TCF bleaching having a sequence of Q/P
having the following reaction condition.
[00136] Q stage: A pulp having a consistency of 10% was treated with
DPTA (0.5-0.7% by weight of the weight of the dry pulp) at 80 C for 30
minutes. The pH was 4.
[00137] P stage: The pulp obtained from the Q stage was treated with
hydrogen peroxide (2.0% by weight of the weight of the dry pulp), sodium
hydroxide (1.0-1.1% by weight of the weight of the dry pulp), DTPMPA
(0.25% by weight of the weight of the dry pulp), MgSO4 (0.60% by weight
of the weight of the dry pulp), NaSiO3 (0.50% by weight of the weight of
the dry pulp) at 85 C for 60 minutes. The final pH was 10.5-11.0, and
the final ISO brightness of the obtained pulp was about 84.75%. The
residual was about 0.05%.
[00138] Pulp A4354-2-P was obtained from the same process as the
pulp A4354-1-P, further including cleaning the pulp obtained from the
cooking step by box-washing before the TCF bleaching.
[00139] Box-washed pulp was obtained by first diluting the pulp to a
consistency of 1.0%, and then rinsing the pulp in a box with a screen
mesh floor, wherein the pulp mat which forms on the mesh was not
allowed to accumulate of more than 1 inch. As soon as a layer of
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washed pulp began to form on the mash, it was removed and saved for
the next step of process.
[00140] Benchmark strength of pulp A4354-1-P (pulp 10-1) and pulp
A4354-2-P (pulp 10-2) are shown in Table 4 below.
Table 4. Benchmark strength of pulp A4354-1-P (pulp 10-1) and pulp
A4354-2-P (pulp 10-2)
Analysis Unit pulp 10-1 pulp 10-2
24 grams, 0.2 mm gap
PFI, TAPPI Revolutions 0 0
C.S.Freeness mL 465 506
Basis weight, conditioned girn2 66.50 66.43
Bulk cc/g 1.45 1.41
Burst factor 33 33
Burst index kPa.m2/g 3.22 3.23
Tear factor 59 59
Tear index mN.m2/g 5.74 5.76
Tensile km 5.88 6.00
Tensile index N.m/g 57.7 58.8
Stretch 2.31 2.40
Tensile Energy Absorption J/m2 63.0 66.3
Porosity, Gurley sec/100m1 27 24
Zero Span, Pulmac (dry) km 10.3 10.0
Optical Properties:
Brightness, ISO 84.75 85.6
Opacity 68.4 68.1
CIE Color
L* 95.29 95.53
a* -0.67 -0.67
b* 2.77 2.53
Hunter Color
93.98 94.27
a -0.69 -0.69
2.81 2.57
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[00141] The results show that at 0 revolutions, both pulp A4354-1-P
and pulp A4354-2-P have desired strength (e.g., tear, tensile, and burst),
and desired C.S. freeness suitable for paperrnaking. The box-washing
step increased C.S. Freeness of the final bleached pulp and provided a
more desired product.
[00142] Example 11. Soda AQ pulping of corn stover
[00143] Pulp 11 (pulp L1503-2-Po) was made from corn stover by the
following procedures:
[00144] I) Cleaning of corn stover
[00145] Aged damp corn stover was soaked in cold water for 1 hour,
refined at 0.080" gap with standard plates, washed on a 4.75 mm sieve,
and then washed on a 1.4 m screen.
[00146] II) Cooking
[00147] The cleaned corn stover was treated with sodium hydroxide
(20% by weight of the OD corn stover) and AQ (0.2% by weight to the dry
weight of OD corn stover) at a liquid to dry fiber ratio of 7.0 (consistency
of about 12.5%), at a maximum temperature of about 165 C for 8
minutes. Time to the maximum temperature was 48 minutes.
[00148] The target H-factor was 200, temperature pulping reaction
was 165 C . The Kappa number of the screened pulp was 5.0, the
cooking yield was 56.8%, the yield of the screened pulp was 56.5%, total
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rejects was 0.2% (+ 0.010" screen), and the viscosity of the pulp was
101.2 mPa.s.
[00149] III) Pulp cleaning
[00150] The pulp obtained from the cooking step was cleaned with a
centricleaner using a consistency of 1.0%, 30 gpm flow, and pressure of
34 psi with lightning mixer. The cleaned pulp was further cleaned by
water at a consistency of 0.05%, 30 gpm flow, and pressure of 34 psi
with lightning mixer.
[00151] IV) Bleaching
[00152] Pulp 1.1503-2-Po was obtained by bleaching the cleaned pulp
by a TCF bleaching having a sequence of QP1QP0 having the following
reaction condition.
[00153] Q stage: A pulp having a consistency of 10% was treated with
DTPMPA (0.5% by weight of the weight of the dry pulp) and H2SO4
(0.35%) at 80 C for 30 minutes. The initial pH was 4Ø
[00154] P1 stage: The pulp obtained from the Q stage was treated
with hydrogen peroxide (1.0% by weight of the weight of the dry pulp),
sodium hydroxide (0.8% by weight of the weight of the dry pulp), MgSO4
(0.3% by weight of the weight of the dry pulp), NaSiO3 (4.0% by weight of
the weight of the dry pulp) at 85 C for 60 minutes. ISO brightness of the
obtained pulp was 73.5%, yield of P1 stage was 98.2%.
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[00155] Q-Stage. The pulp obtained from the P1Stage having a
consistency of 10% was treated with DTPMPA (0.5% by weight of the
weight of the dry pulp) and H2SO4 (0.35%) at 80 C for 30 minutes. The
initial pH was 4Ø
[00156] PO stage: The pulp obtained from the Q Stage was treated
with hydrogen peroxide (6.0% by weight of the weight of the dry pulp),
sodium hydroxide (2.8% by weight of the weight of the dry pulp), NaSiO3
(4.0% by weight of the weight of the dry pulp), 02 (pressure measured as
60 psi) at 120 C for 120 minutes. Final pH was 10.5, residual H202 was
0.37%, and ISO brightness was 90.8%, stage yield was 95.9%.
[00157] Benchmarking of Pulp his shown below in Table 5.
Table 5. Benchmarking of Pulp 11
Analysis Unit L1503-2-Po
24 grams, 0.2 mm gap
PFI, TAPP1 Revolutions 0 200 700
C.S. Freeness mL 486 352 270
Basis weight, conditioned g/m2 66.38
66.31 67.14
Bulk cc/g
1.35 1.31 1.28
Density A/cc 0.74
0.77 0.78
Burst factor 33 39 43
Burst index kPa.m2/g 3.23
3.82 4.17
Tear factor 66 61 60
Tear index mN.m2/g 6.43
6.02 5.92
Tensile km 6.21
7.01 7.25
Tensile index N.m/g 60.9 68.8
71.1
Stretch % 2.48
2.56 2.64
Tensile Energy Absorption J/nn2 71.5 81.7
88.8
Zero Span, Pulmac (dry) km 11.7 12.1 12.5
Porosity, Gurley sec/100m1 12 34
63
CIE color:
L* 96.10
95.89 95.92
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a* -0.54 -0.54 -0.48
b* 1.89 1.74 1.67
Hunter color:
95.01 94.73 94.77
a -0.57 -0.57 -0.51
1.93 1.78 1.71
Fiber Quality Analyzer;
Population fibers/mg 23,277
AFL, arithmetic mm 0.45
LWAFL mm 0.98
VVWAFL mm 1.80
Coarseness nrig/m 0.095
Curl, length weighted 0.152
Kink index 1/mm 1.59
Percent fines, <0.2 mm, arithmetic 38.00
Percent fines, <0.2 mm, length weighted 11.66
Bauer McNett Fiber Classification:
= retained on + 28 mesh
12.3
= retained on + 65 mesh
32.8
= retained on + 100 mesh
17.4
= retained on + 200 mesh
13.1
= total retained 75.6
= fines through - 200 mesh
24.4
[00158] The results showed that a pulp having very high ISO
brightness with desired strength parameters was obtained from corn
stover.
[00159] Example 12. Effect of AQ concentration in the cooking
process for ARF pulping
[00160] Raw bagasse was washed as described in Example 1 and
cooked as described in Example 2 with the parameters summarized in
Tables 6 (high H-factor, Cook Numbers L1483-1, L1483-2, L1483-3,
L1484-3, A4385) and 7 (low H-factor, Cook Numbers L1486-2, L1488-2,
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L1488-3, A4397, A4400) below. The effect of %AO applied in the
cooking process on the Kappa numbers of the obtained pulps shown in
Tables 6 and 7 is reflected in Figure 1.
Table 6. Effect of AQ concentration in a soda AQ cooking process
of bagasse (high H-factor (- 1000))
Pulp Number 12-1 12-2 12-3 12-4 12-5
Cook Number L1483-1 L1483-2 L1483-3 L1484-3 A4385
Cooking:
NaOH, % on OD fiber weight 20 20 20 20 20
AQ, % 0 0.05 0.1 0.1 0.3
LNV 7.0 7.0 7.0 7.0 7.0
Max. Temperature, C 175 175 175 175 175
Time to max., min from 90 C 60 60 60 47 60
Time at max., min. 34 34 34 37 34
End of Cook:
Residual EA, g/L as Na20 3.7 2.47 2.93 4.47 2.78
Residual AA, g/L as Na20 4.63 3.24 3.55 5.24 3.55
H-factor 1055 1067 1078 965 1080
Unbleached Pulp:
Cooking yield, % 54.9 62* 56.6 52.7 57.3
Total rejects, +0.010", % 0.66 0.50 1.07 0.5 1.00
Screened yield, % 54.2 55.5 52.1 56.3
Kappa, screened, Quick Dry 8.4 6.0 5.5 5.3 5.2
Viscosity, mPa.s 32.1 30.5 26.8 28.7 30.6
Table 7. Effect of AQ concentration in the cooking process (low H-
factor (- 300))
Pulp Number 12-6 12-7 12-8 12-9
12-10
Cook Number L1486-2 L1488-2
L1488-3 A4397 A4400
O.D. charge, g 400 372.6 400 1523
1513
O.D. solids, % 42.74 41.79 41.79 30.91
36.20
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Cooking:
NaOH, % on wood 20 20 20 20 20
AQ , `)/0 0 0 0.1 0.2 0.2
LNV 7.0 7.0 7.0 8.0 8.0
Max. Temperature, C 166 166 166 165 165
Time to max., min from 90 C 47 "Drop-In" cooks 49 36
Time at max., min. 17 20 25 15 21
End of Cook:
Residual EA, g/L as Na20 6.48 8.8 9.11 4.64
5.85
Residual AA, g/L as Na20 7.25 10.0 10.3 5.68
6.88
H-factor ,300 308 300
Unbleached Pulp:
Cooking yield, % 57.5 57.2 57.2 56.2
57.9
Total rejects, +0.010", % 4.5 9.2 4.6 3.2 3.1
Screened yield, % 53.0 48.0 52.6 53.0
54.8
Kappa, screened, Quick Dry 11.3 14.4 9.4 7.2 6.8
Viscosity, mPa.s 38.7 33.8 53.8 53.9
53.7
[00161] Example 13. Articles of Manufacture Made from Agricultural
Renewable Fiber Pulp
[00162] An ARF pulp made as described supra was made having a
fiber count per milligram of 19,000. A premium grade bath tissue
meeting North American Premium Specifications was manufactured
using the ARF Pulp by directly substituting minimal amounts of NBSK
with the ARF pulp without any refining.
[00163] Examples of other articles of manufacture that can be made
from the pulps set forth herein by partially or entirely substituting a prior
art wood pulp with an ARF pulp or other pulp composition as described
herein include, tissue, printing and writing papers, communication papers,
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bleached board, food contact packaging papers such as OGR, bleached
packaging grades, liquid packaging, the more exotic papers such as wet
strength papers and release liner, recycled linerboard and molded
packaging products.
[00164] Although the invention has been described with reference to
preferred embodiments and specific examples, it will be readily
appreciated by those skilled in the art that many modifications and
adaptations of the invention are possible without deviating from the spirit
and scope of the invention. Thus, it is to be clearly understood that this
description is made only by way of example and not as a limitation on the
scope of the invention. All references herein are hereby incorporated by
reference.
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