Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIBROUS STRUCTURES COMPRISING
ENZYMATICALLY TREATED HARDWOOD PULP FIBERS
FIELD OF THE INVENTION
The present invention relates to fibrous structures comprising non-naturally
occurring
hardwood pulp fibers, and more particularly, sanitary tissue products
comprising non-naturally
occurring hardwood pulp fibers and methods for making same.
BACKGROUND OF THE INVENTION
Fibrous structures and/or sanitary tissue products comprising hardwood pulp
fibers
including non-naturally occurring hardwood pulp fibers are known in the art.
However, the level
of hardwood pulp fibers that formulators have used in their fibrous structures
and/or sanitary
tissue products have been limited due to the fact that hardwood pulp fibers
conventionally have
not exhibited the tensile strengths desired by consumers of such fibrous
structures and/or sanitary
tissue products. Therefore, formulators have had to use a mixture of hardwood
pulp fibers and
softwood pulp fibers to achieve the tensile strengths needed in their fibrous
structures and/or
sanitary tissue products.
Due to the costs differences between softwood pulp fibers and hardwood pulp
fibers
(softwood pulp fibers typically being more expensive) formulators desire to
increase the
hardwood pulp fiber levels and decrease the softwood pulp fiber levels in
their fibrous structures
and/or sanitary tissue products. Formulators have not had success in doing so
due to the tensile
strength differences between softwood pulp fibers and conventional hardwood
pulp fibers and the
drainage properties (as represented by PFR) of conventional hardwood pulp
fibers.
It is known that hardwoods increase the softness of the fibrous structures in
which they
are present. Therefore, there is a continuing desire, especially for softer
fibrous structures, to
increase the level of hardwood present in fibrous structures.
Accordingly, there is a need for fibrous structures and/or sanitary tissue
products
comprising hardwood pulp fibers that overcome or at least partially overcome
the differences
between softwood pulp fibers and conventional hardwood pulp fibers and/or that
overcome the
negatives associated with conventional hardwood pulp fibers.
SUMMARY OF THE INVENTION
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The present invention fulfills the need described above by providing fibrous
structures
and/or sanitary tissue products comprising hardwood pulp fibers that overcome
or at least
partially overcome the differences between softwood pulp fibers and
conventional hardwood
pulp fibers and/or that overcome the negatives associated with conventional
hardwood pulp
fibers.
In one example of the present invention, a fibrous structure comprising a non-
naturally
occurring hardwood pulp fiber that exhibits a handsheet tensile strength as
measured according to
the Handsheet Tensile Strength Test Method described herein less than the
handsheet tensile
strength of the non-naturally occurring hardwood pulp fiber in its naturally
occurring state, is
provided.
In another example of the present invention, a sanitary tissue product
comprising a non-
naturally occurring hardwood pulp fiber that exhibits a handsheet tensile
strength as measured
according to the Handsheet Tensile Strength Test Method described herein less
than the
handsheet tensile strength of the non-naturally occurring hardwood pulp fiber
in its naturally
occurring state, wherein the sanitary tissue product exhibits a greater wet
burst strength as
measured according to the Wet Burst Strength Test Method described herein
and/or a greater
initial total wet tensile as measured by the Initial Total Wet Tensile Test
Method described herein
than a sanitary tissue product that comprises the non-naturally occurring
hardwood pulp fiber in
its naturally occurring state, is provided.
In yet another example of the present invention, a fibrous structure
comprising an enzyme
treated hardwood pulp fiber that exhibits a handsheet tensile strength as
measured according to
the Handsheet Tensile Strength Test Method described herein less than the
handsheet tensile
strength of the hardwood pulp fiber without the enzyme treatment, is provided.
In still another example of the present invention, a sanitary tissue product
comprising an
enzyme treated hardwood pulp fiber that exhibits a handsheet tensile strength
as measured
according to the Handsheet Tensile Strength Test Method described herein less
than the
handsheet tensile strength of the non-enzyme treated hardwood pulp fiber,
wherein the sanitary
tissue product exhibits a greater wet burst strength as measured according to
the Wet Burst
Strength Test Method described herein and/or a greater initial total wet
tensile as measured by
the Initial Total Wet Tensile Test Method described herein than a sanitary
tissue product that
comprises the non-enzyme treated hardwood pulp fiber, is provided.
In even yet another example of the present invention, a method for making a
fibrous
structure comprising the steps of:
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a. providing a fibrous composition comprising a non-naturally occurring
hardwood pulp
fiber that exhibits a handsheet tensile strength as measured according to the
Handsheet Tensile Strength Test Method described herein less than the
handsheet
tensile strength of the non-naturally occurring hardwood pulp fiber in its
naturally
occurring state; and
b. depositing the fibrous composition onto a collection device, such as a
fabric and/or a
belt, to form a fibrous structure.
Accordingly, the present invention provides fibrous structures and/or sanitary
tissue
products comprising novel non-naturally occurring hardwood pulp fibers and
method for making
such fibrous structures and/or sanitary tissue products.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
"Pulp fiber" as used herein means a virgin fiber obtained from a tree or
plant.
A specific type of pulp fiber is a wood fiber. "Wood fiber" as used herein
means a virgin
fiber obtained from a tree.
Pulp (one or more pulp fibers) may be chemical pulps, such as kraft (sulfate)
and sulfite
pulps, as well as mechanical and semi-chemical pulps including, for example,
groundwood,
thermomechanical pulp, chemi-mechanical pulp (CMP), chemi-thermomechanical
pulp (CTMP),
neutral semi-chemical sulfite pulp (NSCS).
The pulp fibers may be short (typical of hardwood fibers) or long (typical of
softwood
fibers).
"Hardwood pulp fiber" as used herein means pulp fibers obtained from deciduous
trees.
Non-limiting examples of deciduous trees include Northern hardwood trees and
tropical
hardwood trees. Non-limiting examples of hardwood pulp fibers include hardwood
pulp fibers
obtained from a fiber source selected from the group consisting of Acacia,
Eucalyptus, Maple,
Oak, Aspen, Birch, Cottonwood, Alder, Ash, Cherry, Elm, Hickory, Poplar, Gum,
Walnut,
Locust, Sycamore, Beech, Catalpa, Sassafras, Gmelina, Albizia, Anthocephalus,
Magnolia, and
mixtures thereof. In one example, the hardwood pulp fiber of the present
invention is obtained
from Eucalyptus.
"Tropical hardwood pulp fiber" as used herein means pulp fibers obtained from
a tropical
hardwood tree. Non-limiting examples of tropical hardwood trees include
Eucalyptus trees
and/or Acacia trees.
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"Naturally occurring hardwood pulp fiber" as used herein means a pulp fiber
that is found
in nature or that has only been subjected to conventional pulping and/or
bleaching processes
without the presence of enzymes.
"Non-naturally occurring hardwood pulp fiber" as used herein means a naturally
occurring hardwood pulp fiber that has been modified and/or treated by humans
through a
human-designed process and/or a human executed modifying and/or treating
process. A
naturally occurring hardwood pulp fiber that has been treated with an enzyme,
such as during the
pulping process, is a non-naturally occurring hardwood pulp fiber. In one
example, a non-
naturally occurring hardwood pulp fiber is a Eucalyptus pulp fiber that has
been treated with an
enzyme composition, for example an enzyme composition comprising xylanase.
"Fibrous structure" as used herein means a structure that comprises one or
more pulp
fibers. Non-limiting examples of processes for making fibrous structures
include known wet-laid
papermaking processes and air-laid papermaking processes. Such processes
typically include
steps of preparing a pulp fiber composition, oftentimes referred to as a fiber
slurry in wet-laid
processes, either wet or dry, and then depositing a plurality of fibers onto a
forming wire or belt
such that an embryonic fibrous structure is formed, drying and/or bonding the
fibers together
such that a fibrous structure is formed, and/or further processing the fibrous
structure such that a
finished fibrous structure is formed. For example, in typical papermaking
processes, the finished
fibrous structure is the fibrous structure that is wound on the reel at the
end of papermaking, but
before converting thereof into a sanitary tissue product.
Non-limiting types of fibrous structures according to the present invention
include
conventionally felt-pressed fibrous structures; pattern densified fibrous
structures; and high-bulk,
uncompacted fibrous structures. The fibrous structures may be of a homogeneous
or multilayered
(two or three or more layers) construction; and the sanitary tissue products
made therefrom may
be of a single-ply or multi-ply construction.
The fibrous structures may be post-processed, such as by embossing and/or
calendaring
and/or folding and/or printing images thereon.
The fibrous structures may be through-air-dried fibrous structures or
conventionally dried
fibrous structures.
The fibrous structures may be creped or uncreped.
The fibrous structures of the present invention may comprise, in addition to
non-naturally
occurring hardwood pulp fibers, naturally occurring pulp fibers, such as
naturally occurring
hardwood pulp fibers, naturally occurring softwood pulp fibers, synthetic
fibers and/or filaments,
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such as polypropylene filaments, naturally occurring animal fibers, other
naturally occurring
plant fibers, and other non-naturally occurring fibers. The fibers may be in
different layers
within the fibrous structure or may be blended together in a single layer.
"Sanitary tissue product" comprises one or more fibrous structures, converted
or not, that
5 is useful as a wiping implement for post-urinary and post-bowel movement
cleaning (toilet
paper), for otorhinolaryngological discharges (facial tissue and/or disposable
handkerchiefs), and
multi-functional absorbent and cleaning uses (absorbent towels and/or wipes).
The sanitary
tissue product may be convolutedly wound upon itself about a core or without a
core to form a
sanitary tissue product roll.
In one example, the sanitary tissue product of the present invention comprises
one or
more fibrous structures according to the present invention.
The sanitary tissue products of the present invention may exhibit a basis
weight between
about 10 g/m2 to about 120 g/m2 and/or from about 15 g/m2 to about 110 g/m2
and/or from about
g/m2 to about 100 g/m2 and/or from about 30 to 90 g/m2. In addition, the
sanitary tissue
15 product of the present invention may exhibit a basis weight between about
40 g/m2 to about 120
g/m2 and/or from about 50 g/m2 to about 110 g/m2 and/or from about 55 g/m2 to
about 105 g/m2
and/or from about 60 to 100 g/m2.
The sanitary tissue products of the present invention may be in the form of
sanitary tissue
product rolls. Such sanitary tissue product rolls may comprise a plurality of
connected, but
20 perforated sheets of fibrous structure, that are separably dispensable from
adjacent sheets.
The sanitary tissue products of the present invention may comprises additives
such as
softening agents, temporary wet strength agents, permanent wet strength
agents, bulk softening
agents, lotions, silicones, wetting agents, latexes, patterned latexes and
other types of additives
suitable for inclusion in and/or on sanitary tissue products.
"Ply" or "Plies" as used herein means an individual finished fibrous structure
optionally
to be disposed in a substantially contiguous, face-to-face relationship with
other plies, forming a
multiple ply finished fibrous structure product and/or sanitary tissue
product. It is also
contemplated that a single fibrous structure can effectively form two "plies"
or multiple "plies",
for example, by being folded on itself.
"Wet burst strength" as used herein is a measure of the ability of a fibrous
structure
and/or a sanitary tissue product incorporating a fibrous structure to absorb
energy, when wet and
subjected to deformation normal to the plane of the fibrous structure and/or
fibrous structure
product.
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Non-naturally Occurring Hardwood Pulp Fibers
The non-naturally occurring hardwood pulp fibers of the present invention
exhibit a
handsheet tensile strength as measured according to the Handsheet Tensile
Strength Test Method
described herein less than the handsheet tensile strength of the non-naturally
occurring hardwood
pulp fiber in its naturally occurring state.
Further, the non-naturally occurring hardwood pulp fibers of the present
invention exhibit
the lower handsheet tensile strength without increasing the PFR of the
hardwood pulp fibers as
measured in their naturally occurring state. As a result, the non-naturally
occurring hardwood
pulp fibers provide a weaker fiber with respect to its handsheet tensile
strength that dries and/or
drains as good or better, as measured according to the PFR Test Method
described herein, than
the same hardwood pulp fibers as measured in their naturally occurring state.
Unexpectedly, the non-naturally occurring hardwood pulp fibers of the present
invention,
which weaker than their naturally occurring state, result in a sanitary tissue
product comprising
such non-naturally occurring hardwood pulp fibers exhibiting a greater wet
burst strength and/or
initial total wet tensile than a sanitary tissue product comprising the non-
naturally occurring
hardwood pulp fibers in their naturally occurring state.
Table 1 below evidences the differences between the fibrous structures and/or
sanitary
tissue products (A-C) comprising the non-naturally occurring hardwood pulp
fibers of the present
invention compared to a fibrous structure and/or sanitary tissue product
(Control) comprising the
hardwood pulp fibers in their naturally occurring state. The non-naturally
occurring hardwood
pulp fibers used in A and B were treated with a xylanase. The non-naturally
occurring hardwood
pulp fibers used in C were treated with an enzyme composition comprising
xylanase and
cellulase.
Property Control A B C
Handsheet Tensile Strength
(g/in per lb/3,000 ft2) 428 353 290 401
PFR (s) 7.4 7.1 6.9 7.4
Sanitary Tissue Product Wet 418 465 Did not 464
Burst Strength (g) measure
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Sanitary Tissue Product 56.6 62.6 68.4 65.8
Initial Total Wet Tensile
(g/in)
Relative Softness compared - Softer Softer Less soft
to Control
Table 1
The non-naturally occurring hardwood pulp fibers for use in the fibrous
structures and/or
sanitary tissue products of the present invention may exhibit a PFR of 7.4 or
less and/or less than
7.3 and/or less than 7.2 and/or less than 7.1 and/or less than 7.0 to about 0
and/or to about 1
and/or to about 2 as measured according to the PFR Test Method described
herein.
Enzymes
In one example of the present invention, the non-naturally occurring hardwood
pulp
fibers of the present invention may be derived from enzymatically treating
naturally occurring
hardwood pulp fibers. The enzyme and/or enzyme composition useful in
enzymatically treating
the naturally occurring hardwood pulp fibers comprises a xylanase enzyme.
In one example, the enzyme composition used to enzymatically treat the
naturally
occurring hardwood pulp fibers comprises xylanase and cellulase.
Fibrous Structure
The fibrous structure of the present invention comprises one or more non-
naturally
occurring hardwood pulp fibers that exhibit a handsheet tensile strength less
than the handsheet
tensile strength of the non-naturally occurring hardwood pulp fiber in its
naturally occurring state
as measured according to the Handsheet Tensile Strength Test Method described
herein. In one
example, the fibrous structure comprises at least 5% and/or at least 10%
and/or at least 20%
and/or at least 30% and/or at least 40% to about 100% and/or to about 90%
and/or to about 80%
and/or to about 70% and/or to about 60% by weight on a dry fiber basis of non-
naturally
occurring hardwood pulp fibers that exhibit a handsheet tensile strength less
than the handsheet
tensile strength of the non-naturally occurring hardwood pulp fiber in its
naturally occurring state
as measured according to the Handsheet Tensile Strength Test Method described
herein.
In addition to the non-naturally occurring hardwood pulp fibers, the fibrous
structures of
the present invention may comprise softwood pulp fibers, such as Northern
Softwood Kraft pulp
fibers (NSK). In one example, the fibrous structure comprises from about 0 to
about 90% and/or
from about 10 to about 80% and/or from about 30 to about 70% by weight on a
dry fiber basis of
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softwood pulp fibers and from about 10 to about 100% and/or from about 20 to
about 90% and/or
from about 30 to about 70% by weight on a dry fiber basis of hardwood pulp
fibers at least a
portion of which comprises non-naturally occurring hardwood pulp fibers that
exhibit a
handsheet tensile strength less than the handsheet tensile strength of the non-
naturally occurring
hardwood pulp fiber in its naturally occurring state as measured according to
the Handsheet
Tensile Strength Test Method described herein.
In another example, the fibrous structure of the present invention comprises
one or more
enzyme treated hardwood pulp fibers that exhibit a handsheet tensile strength
less than the
handsheet tensile strength of the non-enzyme treated hardwood pulp fiber as
measured according
to the Handsheet Tensile Strength Test Method described herein. In one
example, the fibrous
structure comprises at least 5% and/or at least 10% and/or at least 20% and/or
at least 30% and/or
at least 40% to about 100% and/or to about 90% and/or to about 80% and/or to
about 70%
and/or to about 60% by weight on a dry fiber basis of enzyme treated hardwood
pulp fibers that
exhibit a handsheet tensile strength less than the handsheet tensile strength
of the non-enzyme
treated hardwood pulp fiber as measured according to the Handsheet Tensile
Strength Test
Method described herein.
In addition to the enzyme treated hardwood pulp fibers, the fibrous structures
of the
present invention may comprise softwood pulp fibers, such as Northern Softwood
Kraft pulp
fibers (NSK). In one example, the fibrous structure comprises from about 0 to
about 90% and/or
from about 10 to about 80% and/or from about 30 to about 70% by weight on a
dry fiber basis of
softwood pulp fibers and from about 10 to about 100% and/or from about 20 to
about 90% and/or
from about 30 to about 70% by weight on a dry fiber basis of hardwood pulp
fibers at least a
portion of which comprises enzyme treated hardwood pulp fibers that exhibit a
handsheet tensile
strength less than the handsheet tensile strength of the non-enzyme treated
hardwood pulp fiber
as measured according to the Handsheet Tensile Strength Test Method described
herein.
Sanitary Tissue Product
The sanitary tissue products of the present invention may exhibit a wet burst
strength of
greater than 420 g and/or greater than 430 g and/or greater than 440 g and/or
greater than 450 g
and/or greater than 460 g to about 2000 g and/or to about 1500 g and/or to
about 1000 g and/or to
about 900 g and/or to about 800 g.
The sanitary tissue products of the present invention may exhibit an initial
total wet
tensile of greater than 58 g/in and/or greater than 60 g/in and/or greater
than 62 g/in and/or
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greater than 64 g/in and/or greater than 66 g/in to about 500 g/in and/or to
about 450 g/in and/or
to about 400 g/in and/or to about 300 g/in and/or to about 200 g/in and/or to
about 100 g/in.
Method for Making Fibrous Structure
The fibrous structures of the present invention may be made by any suitable
method
known in the art so long as one or more non-naturally occurring hardwood pulp
fibers that
exhibit a handsheet tensile strength less than the handsheet tensile strength
of the non-naturally
occurring hardwood pulp fiber in its naturally occurring state as measured
according to the
Handsheet Tensile Strength Test Method described herein are used to make the
fibrous structure.
In one example, a method for making a fibrous structure according to the
present
invention comprises the steps of:
a. providing a fibrous composition comprising a non-naturally occurring
hardwood pulp
fiber that exhibits a handsheet tensile strength less than the handsheet
tensile strength
of the non-naturally occurring hardwood pulp fiber in its naturally occurring
state as
measured according to the Handsheet Tensile Strength Test Method described
herein;
and
b. depositing the fibrous composition onto a collection device, such as a
fabric and/or a
belt, to form a fibrous structure.
The method may further comprise one or more of the following steps: creping,
compressively dewatering, and through-air-drying the fibrous structure.
The fibrous composition may comprise any suitable level of non-naturally
occurring
hardwood pulp fibers, such as enzyme treated hardwood pulp fibers.
Method for Making Sanitary Tissue Product
The sanitary tissue product of the present invention may be made by any
suitable method
known in the art so long as one or more fibrous structures of the present
invention are used to
make the sanitary tissue product.
Test Methods
Unless otherwise indicated, all tests described herein including those
described under the
Definitions section and the following test methods are conducted on samples,
fibrous structure
samples and/or sanitary tissue product samples and/or handsheets that have
been conditioned in a
conditioned room at a temperature of 73 F 4 F (about 23 C 2.2 C) and a
relative humidity of
50% 10% for 2 hours prior to the test. Further, all tests are conducted in
such conditioned
room. Tested samples and felts and any equipment or materials should be
subjected to 73 F
4 F (about 23 C 2.2 C) and a relative humidity of 50% 10% for 2 hours
prior to testing.
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Sample Preparation
To run the tests described below, handsheets must be prepared. The handsheets
are
prepared as follows.
The handsheets are low density handsheets and are prepared essentially
according to
5 TAPPI Standard T205 with the following modifications which are believed to
more accurately
reflect the sanitary tissue product manufacturing process.
For the handsheets, a fibrous slurry comprising tap water (with no pH
adjustment) and pulp
fibers is used.
An embryonic web is formed by depositing the fibrous slurry into a 12 inch x
12 inch
10 handsheet making apparatus on a monofilament polyester wire supplied by
Appleton Wire Co. of
Appleton WI. The monofilament polyester wire has the following specifications:
dimensions of
13.5 inch x 13.5 inch; machine direction warp count of 84 1.5 fibers/inch;
cross direction warp
count of 76 3 fibers/inch; warp size/type of 0.17 mm/9FU; shute size/type of
0.17 mmIWP-
110; caliper of 0.016 0.0005 inch; and air permeability of 720 25 cubic
feet/minute.
The embryonic web is then transferred by vacuum from the monofilament
polyester wire to
a monofilament polyester papermaking fabric supplied by Appleton Wire Co. of
Appleton, WI
and dewatered by vacuum suction instead of pressing. The monofilament
polyester papermaking
fabric has the following specifications: dimensions 16 inch x 14 inch; machine
direction warp
count of 36 1 fibers/inch; cross direction warp count of 30 3 fibers/inch;
warp size/type of
0.40 mm/WP-87-12A-W; shute size/type of 0.40 mm/WP-801-12A-W; caliper of 0.027
0.001
inch; and air permeability of 397 25 cubic feet/minute.
The embryonic web and monofilament polyester wire are placed on top of
monofilament
polyester papermaking fabric such that the embryonic web contacts the
papermaking fabric (a
trilayer configuration of wire/web/fabric with fabric side down) is formed.
The trilayer
configuration is then passed lengthwise across a 13 inch x 1/16 inch wide
vacuum slot box with a
90 flare set at a peak gauge reading of approximately 4.0 inches of Hg
vacuum. The rate of the
trilayer configuration passing across the vacuum slot should be uniform at a
velocity of 16 5
inches/second. The vacuum is then increased to achieve a peak gauge reading of
approximately
9.0 inches of Hg vacuum and the trilayer configuration is passed lengthwise
across the same
vacuum slot at the same rate of 16 5 inches/second 2 more times to form a
handsheet. Note
that the peak gauge reading is the amount of vacuum measured as the trilayer
configuration
passes across the vacuum slot.
The monofilament polyester wire is then carefully removed from the handsheet
ensuring
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that no pulp fibers stick to the wire. The handsheet is then dried on a rotary
drum dryer with a
drying felt by passing the handsheet and the papermaking fabric between the
drying felt and
rotary drum dryer surface with the papermaking fabric against the rotary drum
dryer surface and
again with a second pass of the handsheet against the rotary drum dryer
surface. The rotary drum
dryer surface specifications are as follows: stainless steel polished finish
cylinder with internal
steam heating, horizontally mounted; 17 inches in length and 13 inches in
diameter; 230 5 F;
rotation speed of 0.90 0.05 revolutions/minute; dryer felt is endless, 80
inches circumference
by 16 inches wide, No. 11614, style X225, all wool from Noble Wood Lab Machine
Company,
Hoosick Falls, NY; dryer felt tension as low and even as possible without
slippage occurring
between the dryer felt and the rotary drum dryer surface and uniform tracking.
The dried handsheet is 12 inch x 12 inch with a resulting target basis weight
of 16.5 1
lb/3,000 ft2 and a target density of 0.15 0.06 g/cm3, unless otherwise
noted.
The dried handsheet is then conditioned as described above before conducting
any tests on
the handsheets.
It will be recognized that the test methods described in this section require
the making of
handsheets following the specific procedure described above. Where a given
product is in a form
that includes chemical additives or where the fibrous structure is subjected
to mechanical
manipulation in generating the product, it is to be recognized that the
determination of whether
that product is within the scope of the present invention is made by forming
handsheets in
accordance with the present description, and measuring the physical properties
of those
handsheets, not measuring the physical properties of the product itself. That
is, the fibers used to
construct the product are used to make the handsheets as described; no
application of additives or
mechanical manipulation, aside from that discussed above, should occur.
From one handsheet, carefully cut four 1 in. wide strips of sample 6.0 0.1
inches in length
in the "MD" direction. From a second handsheet of the same sample set,
carefully cut four 1 in.
wide strips of sample 6.0 0. 1 inches in length in the "Cl)" direction. It
is important that the cut
be exactly perpendicular to the long dimension of the strip. The strip should
also be free of
wrinkles or excessive mechanical manipulation which can impact flexibility.
Mark the direction
very lightly on one end, keeping the same surface of the sample up for all
strips. Later, the strips
will be turned over for testing, thus it is important that one surface of the
strip be clearly
identified, however, it makes no difference which surface of the sample is
designated as the
upper surface.
Handsheet Tensile Strength Test Method
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The Handsheet Tensile Strength Test is performed according to TAPPI Standards
T220
om-88 and T494 om-88 on 1 inch x 6 inch (about 2.5 cm x 15. 2 cm) strips of
handsheets
prepared as described above. An electronic tensile tester (Intellect II-STD,
Thwing Albert Corp.,
Philadelphia, Pa.) is used and operated at a crosshead speed of 4
inches/minute (about 10
cm/minute) and a starting gauge length of 4 inches (about 10 cm). A minimum of
n=8 tests are
performed on each handsheet sample (4 machine direction strips and 4 cross
direction strips).
The resulting tensile strength values are recorded in g/in. and are divided by
the average basis
weight of the handsheet sample. The handsheet tensile strength for purpose of
the present
invention is the average of the basis weight normalized tensile strength
values.
PFR Test Method
PFR (pulp filtration resistance) is measured using the following procedure. A
sample of
2543 mL of a fiber suspension, having 0.1% consistency, prepared in a 19
liters tank, through a
registry coupled to the bottom of a proportionate tank, returning it to the
tank through the top
portion. Repeat the procedure (note that the PFR must be carried out after
taking 2543 mL for
checking the consistency since the height of the water column inside the
proportionate tank
changes the measure value). Measure the suspension temperature. Record the
value in Celsius
degrees. Install the connection for PFR measuring in the inferior registry of
the proportionate
tank of sample; Put the 100 mL glass flask below the connection (note that
since it refers to a
dynamic measurement having a specific recipient to this end, there is no need
to calibrate it).
With a single and fast movement, open the valve for sample collection and at
the same time
activate the chronometer in order to measure the time, in seconds, required
for filling the 100 mL
flask up to its mark. Record the time "A", in seconds. Discard the filtrate
and without washing
the screen of the connection, measure the time needed for filling the flask
again. Record the time
"B" in seconds. Repeat the previous item, recording the time "C" in seconds.
Remove the
connection and wash it in counter flow so as to remove all the pulp retained,
checking that the
connection sieve is clean and free of fibers which may dry and change further
tests. Calculate the
PFR value as follows:
PFR E x (B + C - 2A) / 1,5
=
wherein:
A, B and C = time measurements in seconds.
E = 1 + 0.013 (T-75)
T = temperature in Fahrenheit degrees.
A short formula may be used:
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13
PFR K x B+C-2A
wherein:
\ E/1,5
K=
then:
K= \/[1+0,013(T-75)]
"K" values to temperatures ranging from 70 OF (21 C) and 77 F (25 C).
C OF "K" factor
21.0 69.8 0.7884
21.5 70.7 0.7933
22.0 71.6 0.7982
22.5 72.5 0.8031
23.0 73.4 0.8080
23.5 74.3 0.8128
24.0 75.2 0.8176
24.5 76.1 0.8223
25.0 77.0 0.8270
The pulp filtration resistance (PFR) can be obtained by measuring the Canadian
Standard
Freeness (CSF) according to TAPPI Standard T-227 om-09. CSF is related to PFR
by the
following equation: PFR = 78918*CSF-1.4688
Wet Burst Strength Test Method
Wet burst strength may be measured using a Thwing-Albert Burst Tester Cat. No.
177
equipped with a 2000 g load cell commercially available from Thwing-Albert
Instrument
Company, Philadelphia, PA.
Wet burst strength is measured by taking two sanitary tissue product samples.
Using
scissors, cut the samples in half in the MD so that they are approximately 228
mm in the machine
direction and approximately 114 mm in the cross machine direction, each two
(2) plies thick (you
now have 4 samples). First, condition the samples for two (2) hours at a
temperature of 73 F
2 F (about 23 C 1 C) and a relative humidity of 50% 2%. Next age the
samples by stacking
the samples together with a small paper clip and "fan" the other end of the
stack of samples by a
clamp in a 105 C ( 1 C) forced draft oven for 5 minutes ( 10 seconds). After
the heating
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14
period, remove the sample stack from the oven and cool for a minimum of three
(3) minutes
before testing. Take one sample strip, holding the sample by the narrow cross
machine direction
edges, dipping the center of the sample into a pan filled with about 25 mm of
distilled water.
Leave the sample in the water four (4) ( 0.5) seconds. Remove and drain for
three (3) ( 0.5)
seconds holding the sample so the water runs off in the cross machine
direction. Proceed with
the test immediately after the drain step. Place the wet sample on the lower
ring of a sample
holding device of the Burst Tester with the outer surface of the sample facing
up so that the wet
part of the sample completely covers the open surface of the sample holding
ring. If wrinkles are
present, discard the samples and repeat with a new sample. After the sample is
properly in place
on the lower sample holding ring, turn the switch that lowers the upper ring
on the Burst Tester.
The sample to be tested is now securely gripped in the sample holding unit.
Start the burst test
immediately at this point by pressing the start button on the Burst Tester. A
plunger will begin to
rise toward the wet surface of the sample. At the point when the sample tears
or ruptures, report
the maximum reading. The plunger will automatically reverse and return to its
original starting
position. Repeat this procedure on three (3) more samples for a total of four
(4) tests, i.e., four
(4) replicates. Report the results as an average of the four (4) replicates,
to the nearest g.
Initial Total Wet Tensile Test Method
The initial total wet tensile of sanitary tissue products of the present
invention is
determined using a Thwing-Albert EJA Material Tester Instrument, Cat. No.
1350, equipped with
5000 g load cell available from Thwing-Albert Instrument Company, 14 Collings
Ave. W.
Berlin, NJ 08091. 10% of the 5000 g load cell is utilized for the wet tensile
test.
i. Sample Preparation - A strip of sample to be tested [2.54 cm (1 inch) wide
by greater
than 5.08 cm (2 inches)] long is obtained.
ii. Operation - The test settings for the instrument are:
Crosshead speed - 10.16 cm/minute (4.0 in/minute)
Initial gauge length - 2.54 cm (1.0 inch)
Adjust the load cell to read zero plus or minus 0.5 gramsforee=
iii. Testing Samples - One end of the sample strip is placed between the upper
jaws of
the machine and clamped. After verifying that the sample strip is hanging
straight between the
lower jaws, clamp the other end of the sample strip in the lower jaws.
a. Pre-Test - Strain the sample strip to 25 gramsforee (+/- 10 gramsforee) at
a strain rate of
3.38 cm/minute (1.33 in/minute) prior to wetting the sample strip. The
distance between the
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upper and lower jaws now being greater than 2.54 cm (1.0 inch). This distance
now becomes the
new zero-strain position for the forthcoming wet test.
b. Wet Test - While the sample strip is still at 25 gramsf ree (+/- 10 gramsf
ree), it is
wetted, starting near the upper jaws, a water/0.1% Pegosperse ML200
(available from Lonza
5 Inc. of Allendale, NJ) solution [having a temperature of about 73 F 4 F
(about 23 C 2.2 C)]
is delivered to the sample strip via a 2 ml disposable pipet. Do not contact
the sample strip with
the pipet and do not damage the sample strip by using excessive squirting
pressure. The solution
is continuously added until the sample strip is visually determined to be
completely saturated
between the upper and lower jaws. At this point, the load cell is re-adjusted
to read zero plus or
10 minus 0.5 gramsf ree.
The sample strip is then strained at a rate of 10.16 cm/minute (4
inches/minute) and
continues until the sample strip is strained past its failure point (failure
point being defined as the
point on the force-strain curve where the sample strip falls to 50% of its
peak strength after it has
been strained past its peak strength). The straining of the sample strip is
initiated between 5-10
15 seconds after the sample is initially wetted. The initial result of the
test is an array of data points
in the form of load (gramsf ree) versus strain (where strain is calculated as
the crosshead
displacement (cm of jaw movement from starting point) divided by the initial
separation distance
(cm) between the upper and lower jaws after the pre-test.
The sample is tested in two orientations, referred to here as MD (machine
direction, i.e.,
in the same direction as the continuously wound reel and forming fabric) and
CD (cross-machine
direction, i.e., 90 from MD). The MD and CD wet tensile strengths are
determined using the
above equipment and calculations in the following manner:
ITWT (gf/inch) = Peak LoadMD (gf) / 1 (inchW,dd,) + Peak LoadcD (gf) / 1
(inchW,dd,)
Non-limiting Examples
Example 1 - Multi-ply Sanitary Tissue Product Using Non-Enzyme Treated
Hardwood
Pulp Fibers (Control)
A pilot scale Fourdrinier papermaking machine is used in the present example.
A 3% by
weight aqueous slurry of Northern Softwood Kraft (NSK) (50/50 mixture of
softwood pulp
marketed by Abitibi Bowater Incorporated of Montreal, PQ, Canada and by
Zellstof Celgar,
Mercer International from Castlegar, BC, Canada mill) is made up in a
conventional re-pulper.
The NSK slurry is refined gently and a 3% solution of a permanent wet strength
resin (i.e.
Kymene 1142 marketed by Hercules Incorporated of Wilmington, Del.) is added to
the NSK
stock pipe at a rate of 1% by weight of the dry fibers. The adsorption of
Kymene 1142 to NSK is
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enhanced by an in-line mixer. A 1% solution of Carboxy Methyl Cellulose (CMC)
(i.e. FinnFix
from CP Kelco U.S., Inc. of Atlanta, GA) is added after the in-line mixer at a
rate of 0.35% by
weight of the dry fibers to enhance the dry strength of the fibrous substrate.
A 3% by weight
aqueous slurry Eucalyptus fibers (from Fibria's Aracruz, Brazil mill) is made
up in a
conventional re-pulper. A 1% solution of defoamer (i.e. Advantage DF285
marketed by
Hercules Incorporated of Wilmington, Del.) is added to eucalyptus line before
the in-line mixer
at a rate of 0.05% by weight of the dry fibers.
The NSK furnish and the Eucalyptus fibers are fed to the head box and
deposited onto a
Fourdrinier wire as a homogenous mixture to form an embryonic web. Dewatering
occurs
through the Foudrinier wire and is assisted by a deflector and vacuum boxes.
The Fourdrinier
wire is of a 5-shed, satin weave configuration having 84 machine-direction and
76 cross-
machine-direction monofilaments per inch, respectively. The embryonic wet web
is transferred
from the Fourdrinier wire, at a fiber consistency of about 19% at the point of
transfer, to a photo-
polymer fabric having 150 SP cells per square inch, 25 percent knuckle areas
and 18.5 mils of
photo-polymer depth. Further de-watering is accomplished by vacuum assisted
drainage until the
web has a fiber consistency of about 23%. The patterned web is pre-dried by
air blow-through to
a fiber consistency of about 60% by weight. The web is then adhered to the
surface of a Yankee
dryer with a sprayed creping adhesive comprising aqueous solution of Polyvinyl
Alcohol (PVA)
(i.e. Vinylon 88-44 marketed by Wego Chemical and mineral corporation of Great
Neck, NY) at
a rate of 0.1% by weight and a crepe aid (i.e. Unicrepe 457T20 marketed by
Georgia Pacific
Chemicals LLC of Atlanta, GA) at a rate of 0.025% by weight of the dry fibers.
The fiber
consistency is increased to an estimated 96% before the dry creping the web
with a doctor blade.
The doctor blade has a bevel angle of about 25 degrees and is positioned with
respect to the
Yankee dryer to provide an impact angle of about 81 degrees; the Yankee dryer
is operated at
about 800 fpm (feet per minute) (about 244 meters per minute). The dry web is
formed into roll
at a speed of 760 fpm (232 meters per minutes).
Two plies of the web are formed into a 2-ply paper towel by embossing and
laminating
them together using PVA adhesive. The 2-ply paper towel has about 47 g/m2
basis weight and
contains 65% by weight Northern Softwood Kraft and 35% by weight Eucalyptus
furnish. The
2-ply towel exhibits a wet burst strength of about 418 g, total dry tensile of
about 2297 g/in and
wet burst strength to total dry tensile ratio of 0.18.
Example 2 - Multi-ply Sanitary Tissue Product Using Enzyme Treated Hardwood
Pulp
Fibers (Invention)
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A paper towel is made by a method similar to that of Example 1, but replacing
the
Eucalyptus fibers with enzyme treated Eucalyptus pulp fibers from Fibria,
Brazil. The
Eucalyptus pulp fibers are treated by Fibria as follows. A xylanase enzymatic
treatment stage is
carried out using a xylanase charge of 1 kilogram of xylanase / ton of
cellulose, pH of about 7,
temperature of 75 C, in a 3 hour treatment, using a suspension at 11%
consistency. An acid step
is then performed at 90 C, pH of about 3 to 4.5 using sulfuric or hydrochloric
acid to set the pH,
for 3 hours and 11 % consistency.
After the enzymatic treatment, a method to denature the enzyme was conducted,
which
consisted of washing the treated cellulose, dewatering until a consistency of
25 to 30% by weight
is achieved, and heating of the medium to 85 to 95 C for 10 to 15 minutes.
The xylanase can be obtained from Novozymes A/S of Bagsvwrd, Denmark. The
xylanase is used at a rate of 0.1% by weight of dry pulp fibers during the
bleaching sequence
having an acid step.
The 2-ply paper towel made has about 47 g/m2 basis weight and contains 65% by
weight
Northern Softwood Kraft and 35% by weight xylanase treated Eucalyptus. The 2-
ply towel
exhibits a wet burst strength of about 465 g, total dry tensile of about 2337
g/in and wet burst
strength to total dry tensile ratio of 0.20.
Example 3 - Multi-ply Sanitary Tissue Product Using Enzyme Treated Hardwood
Pulp
Fibers (Invention)
A paper towel is made by a method similar to that of Example 1, but replacing
the
Eucalyptus fiber with enzyme treated Eucalyptus pulp fibers from Fibria,
Brazil. The Eucalyptus
pulp fibers are treated by Fibria as follows. A first enzymatic treatment
stage is carried out using
a xylanase charge of 0.5 kilogram of xylanase / ton of cellulose, pH of about
7, temperature of
75 C, in a 3 hour treatment, using a suspension at 11 % consistency. A second
enzyme treatment
stage is performed using a cellulase charge of 1 kilogram of cellulase / ton
of cellulose, pH of
about 7. The acid step is performed at 90 C, pH of about 3 to 4.5 using
sulfuric or hydrochloric
acid to set the pH, for 3 hours and 11% consistency.
After the enzymatic treatment, a method to denature the enzyme was conducted,
which
consisted of washing the treated cellulose, dewatering until a consistency of
25 to 30% by weight
is achieved, and heating of the medium to 85 to 95 C for 10 to 15 minutes.
The xylanase and cellulase can be obtained from Novozymes A/S of Bagsvwrd,
Denmark.
The xylanase is used at a rate of 0.05% by weight of dry pulp fibers and the
cellulase is used at a
rate of 0.1% by weight of dry pulp fibers during the bleaching sequence having
an acid step.
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The 2-ply paper towel has about 47 g/m2 basis weight and contains 65% by
weight
Northern Softwood Kraft and 35% by weight xylanase and cellulase treated
Eucalyptus. The 2-
ply towel exhibits a wet burst strength of about 464 g, total dry tensile of
about 2331 g/in and wet
burst strength to total dry tensile ratio of 0.20.
Example 4 - Multi-ply Sanitary Tissue Product Using Non-Enzyme Treated
Hardwood
Pulp Fibers (Control)
A pilot scale Fourdrinier papermaking machine is used in the present example.
A 3% by
weight aqueous slurry of Northern Softwood Kraft (NSK) (marketed by
Weyerhaeuser Co.
Federal Way, WA) is made up in a conventional re-pulper. The NSK slurry is
passed through a
refiner at no load and a 1% solution of a aldehyde functionalized cationic
polyacrylamide
temporary wet strength resin (i.e. PAREZ 750C marketed by Kemira Chemicals,
Inc. of
Kennesaw, GA) is added to the NSK stock pipe at a rate of 0.125% by weight of
the dry fibers. A
3% by weight aqueous slurry Eucalyptus fibers (from Fibria's Aracruz, Brazil
mill) is made up in
a conventional re-pulper. A 1% solution of a aldehyde functionalized cationic
polyacrylamide
temporary wet strength resin (i.e. PAREZ 750C marketed by Kemira Chemicals,
Inc. of
Kennesaw, GA) is added to the Eucalyptus stock pipe at a rate of 0.025% by
weight of the dry
fibers.
The NSK furnish and the Eucalyptus fibers are layered in the head box and
deposited
onto a Fourdrinier wire as different layers to form an embryonic web.
Dewatering occurs
through the Foudrinier wire and is assisted by a deflector and vacuum boxes.
The Fourdrinier
wire is of a 5-shed, satin weave configuration having 84 machine-direction and
76 cross-
machine-direction monofilaments per inch, respectively. The embryonic wet web
is transferred
from the Fourdrinier wire, at a fiber consistency of about 19% at the point of
transfer, to a photo-
polymer fabric having 20 Structured Linearly Aligned Molding cells per square
inch, 40 percent
knuckle areas and 11.6 mils of photo-polymer depth. Further de-watering is
accomplished by
vacuum assisted drainage until the web has a fiber consistency of about 26%.
The patterned web
is pre-dried by air blow-through to a fiber consistency of about 54% by
weight. The web is then
adhered to the surface of a Yankee dryer with a sprayed creping adhesive
comprising aqueous
solution of Polyvinyl Alcohol (PVA) (i.e. Vinylon 88-44 marketed by Wego
Chemical and
mineral corporation of Great Neck, NY) at a rate of 0.1 % by weight and a
crepe aid (i.e.
Unicrepe 457T20 marketed by Georgia Pacific Chemicals LLC of Atlanta, GA) at a
rate of
0.025% by weight of the dry fibers. The fiber consistency is increased to an
estimated 96%
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before the dry creping the web with a doctor blade. The doctor blade has a
bevel angle of about
25 degrees and is positioned with respect to the Yankee dryer to provide an
impact angle of about
81 degrees; the Yankee dryer is operated at about 800 fpm (feet per minute)
(about 244 meters
per minute). The dry web is formed into roll at a speed of 672 fpm (205 meters
per minutes).
Two plies of the web are formed into toilet paper products by laminating them
together
using a hot melt adhesive (i.e. Cycloflex 34-121C marketed by Henkel
Corporation of
Bridgewater, NJ). A cationic quad based surfactant at a rate of 0.375% by
weight of the dry
fibers also applied to the product. The 2-ply toilet paper has about 50.4 g/m2
basis weight and
contains 35% by weight Northern Softwood Kraft and 65% by weight Eucalyptus
furnish. The
2-ply toilet paper exhibits an initial total wet tensile of about 56.6 g/in,
total dry tensile of about
475.6 g/in and initial total wet tensile to total dry tensile ratio of 0.119.
Example 5 - Multi-ply Sanitary Tissue Product Using Enzyme Treated Hardwood
Pulp
Fibers (Invention)
A toilet paper is made by a method similar to that of Example 4, but replacing
the
Eucalyptus fiber with enzyme treated Eucalyptus pulp fibers from Fibria,
Brazil. The Eucalyptus
pulp fibers are treated by Fibria as follows. A xylanase enzymatic treatment
stage is carried out
using a xylanase charge of 1 kilogram of xylanase / ton of cellulose, pH of
about 7, temperature
of 75 C, in a 3 hour treatment, using a suspension at 11% consistency. An acid
step is then
performed at 90 C, pH of about 3 to 4.5 using sulfuric or hydrochloric acid to
set the pH, for 3
hours and 11% consistency.
After the enzymatic treatment, a method to denature the enzyme was conducted,
which
consisted of washing the treated cellulose, dewatering until a consistency of
25 to 30% by weight
is achieved, and heating of the medium to 85 to 95 C for 10 to 15 minutes.
The xylanase can be obtained from Novozymes A/S of Bagsvwrd, Denmark. The
xylanase is used at a rate of 0.1% by weight of dry pulp fibers during the
bleaching sequence
having an acid step.
The 2-ply toilet paper has about 50.4 g/m2 basis weight and contains 35% by
weight
Northern Softwood Kraft and 65% by weight xylanase treated Eucalyptus. The 2-
ply toilet paper
exhibits an initial total wet tensile of about 62.6 g/in, total dry tensile of
about 475.4 g/in and
initial total wet tensile to total dry tensile ratio of 0.132.
Example 6 - Multi-ply Sanitary Tissue Product Using Enzyme Treated Hardwood
Pulp
Fibers (Invention)
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A toilet paper is made by a method similar to that of Example 4, but replacing
the
Eucalyptus fiber with enzyme treated Eucalyptus pulp fibers from Fibria,
Brazil. The Eucalyptus
pulp fibers are treated by Fibria as follows. A first enzymatic treatment
stage is carried out using
a xylanase charge of 0.5 kilogram of xylanase / ton of cellulose, pH of about
7, temperature of
5 75 C, in a 3 hour treatment, using a suspension at 11 % consistency. A
second enzyme treatment
stage is performed using a cellulase charge of 1 kilogram of cellulase / ton
of cellulose, pH of
about 7. The acid step is performed at 90 C, pH of about 3 to 4.5 using
sulfuric or hydrochloric
acid to set the pH, for 3 hours and 11% consistency.
After the enzymatic treatment, a method to denature the enzyme was conducted,
which
10 consisted of washing the treated cellulose, dewatering until a consistency
of 25 to 30% by weight
is achieved, and heating of the medium to 85 to 95 C for 10 to 15 minutes.
The xylanase and cellulase can be obtained from Novozymes A/S of Bagsvwrd,
Denmark.
The xylanase is used at a rate of 0.05% by weight of dry pulp fibers and the
cellulase is used at a
rate of 0.1% by weight of dry pulp fibers during the bleaching sequence having
an acid step.
15 The 2-ply toilet paper has about 50.4 g/m2 basis weight and contains 35% by
weight
Northern Softwood Kraft and 65% by weight xylanase and cellulase treated
Eucalyptus. The 2-
ply toilet paper exhibits an initial total wet tensile of about 65.8 g/in,
total dry tensile of about
519.6 g/in and initial total wet tensile to total dry tensile ratio of 0.127.
Example 7 - Multi-ply Sanitary Tissue Product Using Enzyme Treated Hardwood
Pulp
20 Fibers (Invention)
A toilet paper is made by a method similar to that of Example 4, but replacing
the
Eucalyptus fiber with enzyme treated Eucalyptus pulp fibers from Fibria,
Brazil. The Eucalyptus
pulp fibers are treated by Fibria as follows. A xylanase enzymatic treatment
stage is carried out
using a xylanase charge of 0.5 kilogram of xylanase / ton of cellulose, pH of
about 7, temperature
of 75 C, in a 3 hour treatment, using a suspension at 11% consistency. An acid
step is then
performed at 90 C, pH of about 3 to 4.5 using sulfuric or hydrochloric acid to
set the pH, for 3
hours and 11% consistency.
After the enzymatic treatment, a method to denature the enzyme was conducted,
which
consisted of washing the treated cellulose, dewatering until a consistency of
25 to 30% by weight
is achieved, and heating of the medium to 85 to 95 C for 10 to 15 minutes.
The xylanase can be obtained from Verenium Corporation of San Diego, CA. The
xylanase is used at a rate of 0.05% by weight of dry pulp fibers during the
bleaching sequence
having an acid step.
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The 2-ply toilet paper has about 50.4 g/m2 basis weight and contains 35% by
weight
Northern Softwood Kraft and 65% by weight xylanase treated Eucalyptus. The 2-
ply toilet paper
exhibits an initial total wet tensile of about 68.4 g/in, total dry tensile of
about 505 g/in and initial
total wet tensile to total dry tensile ratio of 0.135.
The dimensions and values disclosed herein are not to be understood as being
strictly
limited to the exact numerical values recited. Instead, unless otherwise
specified, each such
dimension is intended to mean both the recited value and a functionally
equivalent range
surrounding that value. For example, a dimension disclosed as "40 mm" is
intended to mean
"about 40 mm."
The citation of any document, including any cross referenced or related patent
or
application, is not an admission that it is prior art with respect to any
invention disclosed or
claimed herein or that it alone, or in any combination with any other
reference or references,
teaches, suggests or discloses any such invention. Further, to the extent that
any meaning or
definition of a term in this document conflicts with any meaning or definition
of the same term in
a document cited herein, the meaning or definition assigned to that term in
this document shall
govern.
While particular embodiments of the present invention have been illustrated
and
described, it would be obvious to those skilled in the art that various other
changes and
modifications can be made without departing from the invention described
herein.
