Note: Descriptions are shown in the official language in which they were submitted.
CA 02756555 2011-10-21
FIBROUS STRUCTURE AND PROCESS FOR MAKING SAME
FIELD OF THE INVENTION
The present invention relates to fibrous structures, especially TAD ("TAD")
fibrous
structures incorporated into sanitary tissue products such as facial tissue,
toilet tissue and paper
towels, that comprise a short fiber furnish comprising a short fiber having a
length of from about 0.4
mm to about 1.2 mm and a coarseness of from about 3.0 mg/100 in to about 7.5
mg/100 m, and
processes for making such fibrous structures.
BACKGROUND OF THE INVENTION
Typically, fibrous structures used for sanitary tissue products contain two or
more fiber
furnishes. Such fibrous structures typically contain one furnish comprised of
relatively long fibers,
i.e. fibers with length-weighted average fiber length exceeding about 2 mm.
This furnish is intended
as reinforcement or strength generation within the sanitary tissue products.
Additionally, the fibrous
structures typically further comprise at least one relatively short fiber
furnish, i.e. fibers having a fiber
length less than about 1.2 mm. These short fibers improve the softness of the
sanitary tissue products
since they are relatively unbonded. The unbonded fibers allow free ends, which
impart a velvety
smoothness to the structure. See US Patent No. 4,300,981 to Carstens for a
disclosure of such velvety
structures.
It is well known to those skilled in the art that the use of the short fibers
is limited however
from the point of view that a certain minimum average fiber length of that
furnish is required and
from the point of view that there is a maximum rate of inclusion of that
furnish relative to the longer-
fibered furnish or furnishes used in the sanitary tissue paper structure. This
limitation is due to the
fact that strength is lost. A certain amount of strength is necessary to be
present in the product for
the manufacturer to be able to handle the web which ultimately is converted
into the sanitary tissue
product. It is also necessary that the user of the end product be provided
with a certain amount of
strength to prevent/inhibit fingers poking through the product during use for
example.
This problem with strength development is heightened when the tissue paper
product is made
by the so-called TAD papermaking process. This is because strength development
is improved when
the tissue paper web is pressed against the surface of a Yankee dryer. In some
TAD processes, this
pressing is changed from pressing over 100% of the area, typical of
conventional non-TAD processes,
to less than 50%, more preferably even less than 40% of the surface. While the
strength development
is surprisingly good, it necessarily suffers relative to conventional web
making. Furthermore in some
TAD processes, the Yankee dryer has been eliminated completely which obviously
totally eliminates
this means of strength generation.
1
CA 02756555 2011-10-21
Today's art limits the short-fibered furnish used in TAD processes to greater
than about 0.75
mm.
Inventors have now found that, when accompanied by low coarseness and a
physical property
modifier which can comprise either a permanent wet strength agent or a
chemical softening agent,
surprisingly low fiber length, i.e. less than about 1.2 mm fibers can be used
in the production and use
of TAD tissue paper structures and realizing a softness benefit from such
fibers which would not
hereinbefore be predicted.
No prior art reference teaches a TAD fibrous structure comprising a short
fiber furnish
comprising a short fiber having a length of from about 0.4 mm to about 1.2 mm
and a coarseness of
from about 3.0 mg/100 in to about 7.5 mg/100 m, and a physical property
ingredient selected from the
group consisting of permanent wet strength resins, chemical softeners and
mixtures thereof.
SUMMARY OF THE INVENTION
The present invention provides a TAD fibrous structure that comprises a short
fiber furnish
and a physical property ingredient selected from the group consisting of
permanent wet strength
resins, chemical softeners and mixtures thereof.
In one aspect of the present invention, a TAD fibrous structure comprising a
short fiber
furnish comprising a short fiber having a length of from about 0.4 mm to about
1.2 mm and a
coarseness of from about 3.0 mg/100 in to about 7.5 mg/100 in, and a physical
property ingredient
selected from the group consisting of permanent wet strength resins, chemical
softeners and mixtures
thereof, is provided.
In another aspect of the present invention, a paper product comprising a TAD
fibrous
structure according to the present invention is provided.
In yet another aspect of the present invention, a sanitary tissue product
comprising a TAD
fibrous structure wherein the sanitary tissue product is selected from the
group consisting of facial
tissue products, toilet tissue products, paper towel products and mixtures
thereof, is provided.
In yet still another aspect of the present invention, a process for making a
through-air dried
fibrous structure comprising the steps of
a. preparing a fibrous furnish comprising a short fiber furnish comprising a
short fiber
having a length of from about 0.4 mm to about 1.2 mm and a coarseness of from
about
3.0 mg/ 100 in to about 7.5 mg/ 100 in, by mixing the short fiber with water
to form the
short fiber furnish;
b. depositing the fibrous furnish on a foraminous forming surface to form an
embryonic
fibrous web;
c. adding a permanent wet strength resin to the fibrous furnish and/or the
embryonic fibrous
web; and
2
CA 02756555 2011-10-21
d. through-air drying said embryonic fibrous web such that the through-air
dried fibrous
structure is formed, is provided.
In even yet another aspect of the present invention, a process for making a
through-air dried,
chemical softener-containing fibrous structure comprising the steps of-
a. preparing a fibrous furnish comprising a short fiber furnish comprising a
short fiber
having a length of from about 0.4 mm to about 1.2 mm and a coarseness of from
about
3.0 mg/100 in to about 7.5 mg/100 in, by mixing the short fiber with water to
form the
short fiber furnish;
b. depositing the fibrous furnish on a foraminous forming surface to form an
embryonic
fibrous web;
c. through-air drying said embryonic fibrous web such that a through-air dried
fibrous
structure is formed; and
d. applying a chemical softener to the fibrous furnish and/or embryonic
fibrous web and/or
through-air dried fibrous structure such that the through-air dried, chemical
softener-
containing fibrous structure is formed, is provided.
DETAILED DESCRIPTION OF THE INVENTION
"Fiber" as used herein means a elongate particulate having an apparent length
greatly
exceeding its apparent width, i.e. a length to diameter ratio of at least
about 10. More specifically, as
used herein, "fiber" refers to papermaking fibers. The present invention
contemplates the use of a
variety of paper-making fibers, such as, for example, natural fibers or
synthetic fibers, or any other
suitable fibers, and any combination thereof. Papermaking fibers useful in the
present invention
include cellulosic fibers commonly known as wood pulp fibers. Applicable wood
pulps include
chemical pulps, such as Kraft, sulfite, and sulfate pulps, as well as
mechanical pulps including, for
example, groundwood, thermomechanical pulp and chemically modified
thermomechanical pulp.
Chemical pulps, however, may be preferred since they impart a superior tactile
sense of softness to
tissue sheets made therefrom. Pulps derived from both deciduous trees
(hereinafter, also referred to as
"hardwood") and coniferous trees (hereinafter, also referred to as "softwood")
may be utilized. The
hardwood and softwood fibers can be blended, or alternatively, can be
deposited in layers to provide a
stratified web. U.S. Pat. No. 4,300,981 and U.S. Pat. No. 3,994,771 disclose
layering of hardwood
and softwood fibers. Also applicable to the present invention are fibers
derived from recycled paper,
which may contain any or all of the above categories as well as other non-
fibrous materials such as
fillers and adhesives used to facilitate the original papermaking.
In addition to the various wood pulp fibers, other cellulosic fibers such as
cotton linters,
rayon, and bagasse can be used in this invention. Synthetic fibers, such as
polymeric fibers, can also
be used. Elastomeric polymers, polypropylene, polyethylene, polyester,
polyolefin, and nylon, can be
3
CA 02756555 2011-10-21
used. The polymeric fibers can be produced by spunbond processes, meitblown
processes, and other
suitable methods known in the art.
The embryonic web can be typically prepared from an aqueous dispersion of
papermaking
fibers, though dispersions in liquids other than water can be used. The fibers
are dispersed in the
carrier liquid to have a consistency of from about 0.1 to about 0.3 percent.
It is believed that the
present invention can also be applicable to moist forming operations where the
fibers are dispersed in
a carrier liquid to have a consistency less than about 50 percent, more
preferably less than about 10%.
"Sanitary tissue product" as used herein means a soft, low density (i.e. <
about 0.15 g/cm3)
web useful as a wiping implement for post-urinary and post-bowel movement
cleaning (toilet tissue),
for otorhinolaryngolical discharges (facial tissue), and multi-functional
absorbent and cleaning uses
(absorbent towels).
"Weight average molecular weight" as used herein means the weight average
molecular
weight as determined using gel permeation chromatography according to the
protocol found in
Colloids and Surfaces A. Physico Chemical & Engineering Aspects, Vol. 162,
2000, pg. 107-121.
"Wet Burst Strength" as used herein is a measure of the ability of a fibrous
structure and/or a
paper product incorporating a fibrous structure to absorb energy, when wet and
subjected to
deformation normal to the plane of the fibrous structure and/or paper product.
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 eight (8) fibrous structures
according to the present
invention and staking them in four pairs of two (2) samples each. Using
scissors, cut the samples so
that they are approximately 228 mm in the machine direction and approximately
114 mm in the cross
machine direction, each two finished product units thick. First, age the
samples for two (2) hours by
attaching the sample stack together with a small paper clip and "fan" the
other end of the sample
stack by a clamp in a 107 C ( 3 C) forced draft oven for 5 minutes ( 10
seconds). After the heating
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
4
CA 02756555 2011-10-21
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.
"Basis Weight" as used herein is the weight per unit area of a sample reported
in lbs/3000 ft2
or g/m2. Basis weight is measured by preparing one or more samples of a
certain area (m) and
weighing the sample(s) of a fibrous structure according to the present
invention and/or a paper
product comprising such fibrous structure on a top loading balance with a
minimum resolution of
0.01 g. The balance is protected from air drafts and other disturbances using
a draft shield. Weights
are recorded when the readings on the balance become constant. The average
weight (g) is calculated
and the average area of the samples (m). The basis weight (g/m2) is calculated
by dividing the
average weight (g) by the average area of the samples (m).
"Machine Direction" or "MD" as used herein means the direction parallel to the
flow of the
fibrous structure through the papermaking machine and/or product manufacturing
equipment.
"Cross Machine Direction" or "CD" as used herein means the direction
perpendicular to the
machine direction in the same plane of the fibrous structure and/or paper
product comprising the
fibrous structure.
"Total Dry Tensile Strength" or "TDT" of a fibrous structure of the present
invention and/or a
paper product comprising such fibrous structure is measured as follows. One
(1) inch by five (5) inch
(2.5 cm X 12.7 cm) strips of fibrous structure and/or paper product comprising
such fibrous structure
are provided. The strip is placed on an electronic tensile tester Model 1122
commercially available
from Instron Corp., Canton, Massachusetts in a conditioned room at a
temperature of 73 F 4 F
(about 28 C 2.2 C) and a relative humidity of 50% 10%. The crosshead speed
of the tensile
tester is 2.0 inches per minute (about 5.1 cm/minute) and the gauge length is
4.0 inches (about 10.2
cm). The TDT is the arithmetic total of MD and CD tensile strengths of the
strips.
"Caliper" as used herein means the macroscopic thickness of a sample. Caliper
of a sample
of fibrous structure according to the present invention is determined by
cutting a sample of the fibrous
structure such that it is larger in size than a load foot loading surface
where the load foot loading
surface has a circular surface area of about 3.14 int. The sample is confined
between a horizontal flat
surface and the load foot loading surface. The load foot loading surface
applies a confining pressure
to the sample of 15.5 g/cm2 (about 0.21 psi). The caliper is the resulting gap
between the flat surface
and the load foot loading surface. Such measurements can be obtained on a VIR
Electronic
Thickness Tester Model II available from Thwing-Albert Instrument Company,
Philadelphia, PA.
The caliper measurement is repeated and recorded at least five (5) times so
that an average caliper can
be calculated. The result is reported in millimeters.
5
CA 02756555 2011-10-21
"Apparent Density" or "Density"as used herein means the basis weight of a
sample divided
by the caliper with appropriate conversions incorporated therein. Apparent
density used herein has
the units g/cm'.
"Softness" of a fibrous structure according to the present invention and/or a
paper product
comprising such fibrous structure is determined as follows. Ideally, prior to
softness testing, the
samples to be tested should be conditioned according to Tappi Method #T4020M-
88. Here, samples
are preconditioned for 24 hours at a relative humidity level of 10 to 35% and
within a temperature
range of 22 C to 40 C. After this preconditioning step, samples should be
conditioned for 24 hours at
a relative humidity of 48% to 52% and within a temperature range of 22 C to 24
C. Ideally, the
softness panel testing should take place within the confines of a constant
temperature and humidity
room. If this is not feasible, all samples, including the controls, should
experience identical
environmental exposure conditions.
Softness testing is performed as a paired comparison in a form similar to that
described in
"Manual on Sensory Testing Methods", ASTM Special Technical Publication 434,
published by the
American Society for Testing and Materials 1968. Softness is evaluated by
subjective testing using
what is referred to as a Paired Difference Test. The method employs a standard
external to the test
material itself. For tactile perceived softness two samples are presented such
that the subject cannot
see the samples, and the subject is required to choose one of them on the
basis of tactile softness. The
result of the test is reported in what is referred to as Panel Score Unit
(PSU). With respect to softness
testing to obtain the softness data reported herein in PSU, a number of
softness panel tests are
performed. In each test ten practiced softness judges are asked to rate the
relative softness of three
sets of paired samples. The pairs of samples are judged one pair at a time by
each judge: one sample
of each pair being designated X and the other Y. Briefly, each X sample is
graded against its paired Y
sample as follows:
1. a grade of plus one is given if X is judged to may be a little softer than
Y, and a grade of
minus one is given if Y is judged to may be a little softer than X;
2. a grade of plus two is given if X is judged to surely be a little softer
than Y, and a grade of
minus two is given if Y is judged to surely be a little softer than X;
3. a grade of plus three is given to X if it is judged to be a lot softer than
Y, and a grade of
minus three is given if Y is judged to be a lot softer than X; and, lastly:
4. a grade of plus four is given to X if it is judged to be a whole lot softer
than Y, and a grade
of minus 4 is given if Y is judged to be a whole lot softer than X.
The grades are averaged and the resultant value is in units of PSU. The
resulting data are
considered the results of one panel test. If more than one sample pair is
evaluated then all sample
pairs are rank ordered according to their grades by paired statistical
analysis. Then, the rank is shifted
up or down in value as required to give a zero PSU value to which ever sample
is chosen to be the
6
CA 02756555 2011-10-21
zero-base standard. The other samples then have plus or minus values as
determined by their relative
grades with respect to the zero base standard. The number of panel tests
performed and averaged is
such that about 0.2 PSU represents a significant difference in subjectively
perceived softness.
"Ply" or "Plies" as used herein means an individual fibrous structure
optionally to be
disposed in a substantially contiguous, face-to-face relationship with other
plies, forming a multiple
ply fibrous structure. It is also contemplated that a single fibrous structure
can effectively form two
"plies" or multiple "plies", for example, by being folded on itself.
As used herein, the articles "a" and "an" when used herein, for example, "an
anionic
surfactant" or "a fiber" is understood to mean one or more of the material
that is claimed or described.
All percentages and ratios are calculated by weight unless otherwise
indicated. All
percentages and ratios are calculated based on the total composition unless
otherwise indicated.
Unless otherwise noted, all component or composition levels are in reference
to the active
level of that component or composition, and are exclusive of impurities, for
example, residual
solvents or by-products, which may be present in commercially available
sources.
TAD Fibrous Structure:
The TAD fibrous structure of the present invention may comprise a fibrous
furnish
comprising a short fiber furnish comprising a short fiber having a length of
from about 0.4 mm to
about 1.2 mm and a coarseness of from about 3.0 mg/100 in to about 7.5 mg/l00
in.
In addition to the short fiber, the TAD fibrous structure may comprise a wet
strength resin,
preferably a permanent wet strength resin. Also, in addition to the short
fiber, the TAD fibrous
structure may comprise a chemical softener. The fibrous furnish used to make
the TAD fibrous
structure may further comprise a permanent wet strength resin.
The short fibers having a length of from about 0.4 mm to about 1.2 mm and a
coarseness of from about 3.0 mg/l00 m to about 7.5 mg/100 m may be present in
the TAD fibrous
structure at a level of at least 10% by weight of the total fibers, and/or at
a level of at least 20% up to
100% by weight of the total fibers of the TAD fibrous structure.
In addition to the short fiber, the TAD fibrous structure of the present
invention may include
optional ingredients, which are described in more detail below.
In addition to the short fiber furnish, the fibrous furnish of the present
invention may further
comprise a long fiber furnish comprising a long fiber having a length of
greater than 1.2 mm.
Nonlimiting examples of these long fibers include fibers derived from wood
pulp. Other cellulosic
fibrous pulp fibers, such as cotton linters, bagasse, etc., can be utilized
and are intended to be within
the scope of this invention. Synthetic fibers, such as rayon, polyethylene and
polypropylene fibers,
can also be utilized in combination with natural cellulosic fibers. One
exemplary polyethylene fiber
that can be utilized is Pulpex(R), available from Hercules, Inc. (Wilmington,
Del.).
7
CA 02756555 2011-10-21
Applicable wood pulps include chemical pulps, such as Kraft, especially
Northern Softwood
Kraft ("NSK"), sulfite, and sulfate pulps, as well as mechanical pulps
including, for example,
groundwood, thermomechanical pulp and chemically modified thennomechanical
pulp. Chemical
pulps, however, are preferred since they impart a superior tactile sense of
softness to tissue sheets
made therefrom. Pulps derived from both deciduous trees (hereafter, also
referred to as "hardwood")
and coniferous trees (hereafter, also referred to as "softwood") can be
utilized. Also useful in the
present invention are fibers derived from recycled paper, which can contain
any or all of the above
categories as well as other non-fibrous materials such as fillers and
adhesives used to facilitate the
original papermaking.
In addition to wood pulps, fibers may be produced/obtained from vegetable
sources such as
corn (i.e., starch).
The TAD fibrous structures of the present invention are useful in paper,
especially sanitary
tissue paper products in general, including but not limited to conventionally
felt-pressed tissue paper;
high bulk pattern densified tissue paper; and high bulk, uncompacted tissue
paper. The tissue paper
can be of a homogenous or multi-layered construction; and tissue paper
products made therefrom can
be of a single-ply or multi-ply construction. The tissue paper may have a
basis weight of between
about 10 g/m2 to about 65 g/m2, and a density of from about 0.6 g/cc or less.
Conventionally pressed tissue paper and methods for making such paper are well
known in
the art. Such paper is typically made by depositing a papermaking furnish on a
foraminous forming
wire, often referred to in the art as a Fourdrinier wire. Once the furnish is
deposited on the forming
wire, it is referred to as a web. The web is dewatered by pressing the web and
drying at elevated
temperature. The particular techniques and typical equipment for making webs
according to the
process just described are well known to those skilled in the art. In a
typical process, a low
consistency pulp furnish is provided from a pressurized headbox. The headbox
has an opening for
delivering a thin deposit of pulp furnish onto the Fourdrinier wire to form a
wet web. The web is then
typically dewatered to a fiber consistency of between about 7% and about 25%
(total web weight
basis) by vacuum dewatering and further dried by pressing operations wherein
the web is subjected to
pressure developed by opposing mechanical members, for example, cylindrical
rolls. The dewatered
web is then further pressed and dried by a steam drum apparatus known in the
art as a Yankee dryer.
Pressure can be developed at the Yankee dryer by mechanical means such as an
opposing cylindrical
drum pressing against the web. Multiple Yankee dryer drums can be employed,
whereby additional
pressing is optionally incurred between the drums. The tissue paper structures
that are formed are
referred to hereafter as conventional, pressed, tissue paper structures. Such
sheets are considered to be
compacted since the entire web is subjected to substantial mechanical
compressional forces while the
fibers are moist and are then dried while in a compressed state.
8
CA 02756555 2011-10-21
The TAD fibrous structure may be made with a fibrous furnish that produces a
single layer
embryonic fibrous web or a fibrous furnish that produces a multi-layer
embryonic fibrous web. One
or more short fibers may be present in a fibrous furnish with one or more long
fibers. Further, one or
more short fibers may be present in a furnish layer with one or more long
fibers.
The TAD fibrous structures of the present invention and/or paper products
comprising such
TAD fibrous structures may have a basis weight of from about 12 g/m2 to about
120 g/m2 and/or from
about 14 g/m2 to about 80 g/m2 and/or from about 20 g/m2 to about 60 g/m2.
The TAD fibrous structures of the present invention and/or paper products
comprising such
TAD fibrous structures may have a total dry tensile of greater than about 150
g/in and/or from about
200 g/in to about 1000 g/in and/or from about 250 g/in to about 850 g/in.
The TAD fibrous structures of the present invention and/or paper products
comprising such
TAD fibrous structures may have a wet burst strength of greater than about 25
g/in and/or from about
30 g/in to about 200 g/in and/or from about 150 g/in to about 500 g/in.
Short Fibers:
The short fibers of the present invention may have a length of from about 0.4
mm to about
1.2 mm and/or from about 0.5 mm to about 0.75 mm and/or from about 0.6 mm to
about 0.7 mm and
a coarseness of from about 3.0 mg/100 in to about 7.5 mg/100 in and/or from
about 5.0 mg/100 m to
about 7.5 mg/100 m and/or from about 6.0 mg/100 m to about 7.0 mg/100 m.
The short fibers of the present invention may be derived 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, Bagasse, Flax, Hemp, Kenaf and mixtures thereof.
In one embodiment, the short fibers are derived from tropical hardwood.
In another embodiment, the short fibers are derived from a fiber source
selected from the
group consisting of Acacia, Eucalyptus, Gmelina and mixtures thereof.
In another embodiment, the short fibers are derived from a fiber source
selected from the
group consisting of Acacia, Gmelina and mixtures thereof.
In yet another embodiment, the short fibers are derived from Acacia.
Nonlimiting examples of suitable short fibers having a length of from about
0.4 mm to about
1.2 mm and a coarseness of from about 3.0 mg/100 m to about 7.5 mg/100 m are
commercially
available from PT Tel of Indonesia.
The short fibers of the present invention may comprise cellulose and/or
hemicellulose.
Preferably, the fibers comprise cellulose.
The length and coarseness of the short fibers may be determined using a
Kajaani FiberLab
Fiber Analyzer commercially available from Metso Automation, Kajaani Finland.
As used herein,
fiber length is defined as the "length weighted average fiber length". The
instructions supplied with
9
CA 02756555 2011-10-21
the unit detail the formula used to arrive at this average. However, the
recommended method used to
determine fiber lengths and coarseness of fiber specimens essentially the same
as detailed by the
manufacturer of the Fiber Lab. The recommended consistencies for charging to
the Fiber Lab are
somewhat lower than recommended by the manufacturer since this gives more
reliable operation.
Short fiber furnishes, as defined herein, should be diluted to 0.02-0.04%
prior to charging to the
instrument. Long fiber fuurnishes, as defined herein, should be diluted to
0.15% - 0.30%.
Alternatively, the length and coarseness of the short fibers may be determined
by sending the short
fibers to an outside contract lab, such as Integrated Paper Services,
Appleton, Wisconsin.
Permanent Wet Strength Resins
The TAD fibrous structure of the present invention may comprise a permanent
wet strength
resin. The permanent wet strength resin may be present in the fibrous furnish,
particularly, the short
fiber furnish used to form the TAD fibrous structure and/or can be deposited
onto the embryonic
fibrous web prior to through-air drying of the embryonic fibrous web.
The permanent wet strength resins act to control tinting and also to offset
the loss in tensile
strength, if any, resulting from the any chemical softeners added to the
fibrous structure. Further, the
permanent wet strength resins give the fibrous structure or paper product it
is incorporated into a
property such that when it is placed in an aqueous medium it retains a
substantial portion of its initial
wet strength over time
Nonlimiting examples of permanent wet strength resins include: polyamide-
epichlorohydrin
resins, polyacrylamide resins, styrenebutadiene resins; insolubilized
polyvinyl alcohol resins; urea-
formaldehyde resins; polyethyleneimine resins; chitosan resins and mixtures
thereof. Preferably, the
permanent wet strength resins are selected from the group consisting of
polyamide-epichlorohydrin
resins, polyacrylamide resins and mixtures thereof.
Polyamide-epichlorohydrin resins are cationic wet strength resins which have
been found to
be of particular utility. Suitable types of such resins are described in U.S.
Pat. Nos. 3,700,623, issued
on Oct. 24, 1972, and 3,772,076, issued on Nov. 13, 1973, both issued to Keim.
One commercial
source of a useful polyamide-epichlorohydrin resins is Hercules, Inc. of
Wilmington, Del., which
markets such resin under the trade-mark KYMENE 557H.
Polyacrylamide resins have also been found to be of utility as wet strength
resins. These
resins are described in U.S. Pat. Nos. 3,556,932, issued on Jan. 19, 1971, to
Coscia, et at. and
3,556,933, issued on Jan. 19, 1971, to Williams et al. One commercial source
of polyacrylamide
resins is CYTEC Co. of Stanford, Conn., which markets one such resin under the
trade-mark PAREZ
631 NC. Still other water-soluble cationic resins finding utility in this
invention are urea
formaldehyde and melamine formaldehyde resins.
Chemical Softeners:
The TAD fibrous structure of the present invention may comprise a chemical
softener.
CA 02756555 2011-10-21
As used herein, the term "chemical softener" and/or "chemical softening agent"
refers to any
chemical ingredient which improves the tactile sensation perceived by the user
whom holds a
particular paper product and rubs it across her skin. Although somewhat
desirable for towel products,
softness is a particularly important property for facial and toilet tissues.
Such tactile perceivable
softness can be characterized by, but is not limited to, friction,
flexibility, and smoothness, as well as
subjective descriptors, such as a feeling like lubricious, velvet, silk or
flannel.
Chemical softening agent is any chemical ingredient which imparts a lubricious
feel to tissue.
This includes, for exemplary purposes only, basic waxes such as paraffin and
beeswax and oils such
as mineral oil and silicone oils and silicone gels as well as petrolatum and
more complex lubricants
and emollients such as quaternary ammonium compounds with long (C 10 - C22)
hydrocarbyl chains,
functional silicones, and long (C 10 - C22) hydrocarbyl chain-bearing
compounds possessing
functional groups such as amines, acids, alcohols and esters.
The field of work in the prior art pertaining to chemical softeners has taken
two paths. The
first path is characterized by the addition of softeners to the tissue paper
web during its formation
either by adding an attractive ingredient to the vats of pulp which will
ultimately be formed into a
tissue paper web, to the pulp slurry as it approaches a paper making machine,
or to the wet web as it
resides on a Fourdrinier cloth or dryer cloth on a paper making machine.
The second path is categorized by the addition of chemical softeners to tissue
paper web after
the web is partially or completely dried. Applicable processes can be
incorporated into the paper
making operation as, for example, by spraying onto the embryonic web and/or
dried fibrous structure
before it is wound into a roll of paper, extruding, especially via slot
extrusion, onto the embryonic
web and/or dried fibrous structure, and/or by gravure printing onto the
embryonic web and/or dried
fibrous structure.
Exemplary art related to the former path categorized by adding chemical
softeners to the
tissue paper prior to its assembly into a web includes U.S. Pat. 5,264,082
issued to Phan and Trokhan
on Nov. 23, 1993. Such methods have found broad use in the industry especially
when it is desired to
reduce the strength which would otherwise be present in the paper and when the
papermaking
process, particularly the creping operation, is robust enough to tolerate
incorporation of the bond
inhibiting agents.
Further exemplary art related to the addition of chemical softeners to the
tissue paper web
during its formation includes U.S. Pat. No. 5,059,282 issued to Ampulski, et.
al. on Oct. 22, 1991.
The Ampulski patent discloses a process for adding a polysiloxane compound to
a wet tissue web
(preferably at a fiber consistency between about 20% and about 35%). Such a
method represents an
advance in some respects over the addition of chemicals into the slurry vats
supplying the
papermaking machine. For example, such means target the application to one of
the web surfaces as
opposed to distributing the additive onto all of the fibers of the furnish.
11
CA 02756555 2011-10-21
Considerable art has been devised to apply chemical softeners to already-dried
paper webs
either at the so-called dry end of the papermaking machine or in a separate
converting operation
subsequent to the papermaking step. Exemplary art from this field includes
U.S. Pat. No. 5,215,626
issued to Ampulski, et al. on Jun. 1, 1993; U.S. Pat. No. 5,246,545 issued to
Ampulski, et al. on Sep.
21, 1993; and U.S. Pat. No. 5,525,345 issued to Warner, et al. on Jun. 11,
1996. U.S. Pat. No.
5,215,626 discloses a method for preparing soft tissue paper by applying a
polysiloxane to a dry web.
U.S. Pat. No. 5,246,545 discloses a similar method utilizing a heated transfer
surface. Finally, the
Warner Patent discloses methods of application including roll coating and
extrusion for applying
particular compositions to the surface of a dry tissue web.
Particularly preferred chemical softening ingredients are further detailed as
follows:
i_Ouaternary Ammonium Softeners
Preferably, quaternary ammonium compounds suitable to serve as chemical
softening agents
of the present invention have the formula:
(R' )4-m N+- [R2 I. X-
wherein:
in is 1 to 3; each R' is independently a C1 -C6 alkyl group, hydroxyalkyl
group, hydrocarbyl or
substituted hydrocarbyl group, alkoxylated group, benzyl group, or mixtures
thereof; each R2 is
independently a C14 -C22 alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted hydrocarbyl
group, alkoxylated group, benzyl group, or mixtures thereof; and X" is any
softener-compatible anion
are suitable for use in the present invention.
Preferably, each R' is methyl and Y is chloride or methyl sulfate. Preferably,
each R2 is
independently C16 -C18 alkyl or alkenyl, most preferably each R2 is
independently straight-chain C18
alkyl or alkenyl.
Particularly preferred variants of these softening agents are what are
considered to be mono
or diester variations of these quaternary ammonium compounds having the
formula:
(R')4-m N+- [(CH2)n Y R3 ]m X
wherein:
Y is -0-- (O)C-, or -C(O) ---4-, or NH-C(O) -, or -C(O) -NH-; in is 1 to 3; n
is
Oto 4; each R' is independently a C1 -C6 alkyl group, hydroxyalkyl group,
hydrocarbyl or substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; each
R3 is independently a
C13 -C21 alkyl group, hydroxyalkyl group, hydrocarbyl or substituted
hydrocarbyl group, alkoxylated
group, benzyl group, or mixtures thereof, and X- is any softener-compatible
anion.
Preferably, Y is -0- (O)C-, or ----C(O) - 0-; m=2; and n=2. Each R' is
independently
preferably a C, -C3, alkyl group, with methyl being most preferred.
Preferably, each R3 is
independently C13 -C17 alkyl and/or alkenyl, more preferably R3 is
independently straight chain C15 -
12
CA 02756555 2011-10-21
C17 alkyl and/or alkenyl, C15 -C17 alkyl, most preferably each R3 is
independently straight-chain Cn
alkyl.
As mentioned above, X can be any softener-compatible anion, for example,
acetate, chloride,
bromide, methyl sulfate, formate, sulfate, nitrate and the like can also be
used in the present
invention. Preferably X' is chloride or methyl sulfate.
One particularly preferred material is so-called DEEDMAMS (diethyl ester
dimethyl
ammonium methyl sulfate), further defined herein wherein the hydrocarbyl
chains are derived from
tallow fatty acids optionally partially hardened to an iodine value from about
10 to about 60.
ii. Emollient Lotion Composition
Suitable chemical softening agents as defined herein may include emollient
lotion
compositions. As used herein, an "emollient lotion composition" is a chemical
softening agent that
softens, soothes, supples, coats, lubricates, or moisturizes the skin. An
emollient typically
accomplishes several of these objectives such as soothing, moisturizing, and
lubricating the skin.
Emollients useful in the present invention can be petroleum-based, fatty acid
ester type, alkyl
ethoxylate type, or mixtures of these emollients. Suitable petroleum-based
emollients include those
hydrocarbons, or mixtures of hydrocarbons, having chain lengths of from 16 to
32 carbon atoms.
Petroleum based hydrocarbons having these chain lengths include mineral oil
(also known as "liquid
petrolatum") and petrolatum (also known as "mineral wax," "petroleum jelly"
and "mineral jelly").
Mineral oil usually refers to less viscous mixtures of hydrocarbons having
from 16 to 20 carbon
atoms. Petrolatum usually refers to more viscous mixtures of hydrocarbons
having from 16 to 32
carbon atoms. Petrolatum is a particularly preferred emollient for use in
fibrous structures that are
incorporated into toilet tissue products. and a suitable material is available
from Witco, Corp.,
Greenwich, Conn. as White Protopet IS. Mineral oil is also a preferred
emollient for use in fibrous
structures that are incorporated into facial tissue products. Such mineral oil
is commercially available
also from Witco Corp.
Suitable fatty acid ester type emollients include those derived from C12 -C28
fatty acids,
preferably C16 -C22 saturated fatty acids, and short chain (C1 -Cg, preferably
CI -C3) monohydric
alcohols. Representative examples of such esters include methyl palmitate,
methyl stearate, isopropyl
laurate, isopropyl myristate, isopropyl palmitate, and ethylhexyl palmitate.
Suitable fatty acid ester
emollients can also be derived from esters of longer chain fatty alcohols (C12
-C2S, preferably C12 -
C16) and shorter chain fatty acids e.g., lactic acid, such as lauryl lactate
and cetyl lactate.
Suitable alkyl ethoxylate type emollients include C12 -CI8 fatty alcohol
ethoxylates having an
average of from 3 to 30 oxyethylene units, preferably from about 4 to about
23. Representative
examples of such alkyl ethoxylates include laureth-3 (a lauryl ethoxylate
having an average of 3
oxyethylene units), laureth-23 (a lauryl ethoxylate having an average of 23
oxyethylene units), ceteth-
10 (acetyl ethoxylate having an average of 10 oxyethylene units) and steareth-
10 (a stearyl ethoxylate
13
CA 02756555 2011-10-21
having an average of 10 oxyethylene units). These alkyl ethoxylate emollients
are typically used in
combination with the petroleum-based emollients, such as petrolatum, at a
weight ratio of alkyl
ethoxylate emollient to petroleum-based emollient of from about 1:1 to about
1:3, preferably from
about 1:1.5 to about 1:2.5.
Emollient lotion compositions may optionally include an "immobilizing agents",
so-called
because it is believed to act to prevent migration of the emollient so that it
can remain primarily on
the surface of the paper structure to which it is applied so that it may
deliver maximum softening
benefit as well as be available for transferability to the user's skin.
Suitable immobilizing agents for
the present invention can comprise polyhydroxy fatty acid esters, polyhydroxy
fatty acid amides, and
mixtures thereof. To be useful as immobilizing agents, the polyhydroxy moiety
of the ester or amide
has to have at least two free hydroxy groups. It is believed that these free
hydroxy groups are the ones
that co-crosslink through hydrogen bonds with the cellulosic fibers of the
tissue paper web to which
the lotion composition is applied and homo-crosslink, also through hydrogen
bonds, the hydroxy
groups of the ester or amide, thus entrapping and immobilizing the other
components in the lotion
matrix. Preferred esters and amides will have three or more free hydroxy
groups on the polyhydroxy
moiety and are typically nonionic in character. Because of the skin
sensitivity of those using paper
products to which the lotion composition is applied, these esters and amides
should also be relatively
mild and non-irritating to the skin.
Suitable polyhydroxy fatty acid esters for use in the present invention will
have the formula:
O
I I
R C-OY
n
wherein R is a C5 -C31 hydrocarbyl group, preferably straight chain C7 -C19
alkyl or alkenyl, more
preferably straight chain C9 -C17 alkyl or alkenyl, most preferably straight
chain C11 -C17 alkyl or
alkenyl, or mixture thereof; Y is a polyhydroxyhydrocarbyl moiety having a
hydrocarbyl chain with
at least 2 free hydroxyls directly connected to the chain; and n is at least
1. Suitable Y groups can be
derived from polyols such as glycerol, pentaerythritol; sugars such as
raffinose, maltodextrose,
galactose, sucrose, glucose, xylose, fructose, maltose, lactose, mannose and
erythrose; sugar alcohols
such as erythritol, xylitol, malitol, mannitol and sorbitol; and anhydrides of
sugar alcohols such as
sorbitan.
One class of suitable polyhydroxy fatty acid esters for use in the present
invention comprises
certain sorbitan esters, preferably the sorbitan esters of C16 -C22 saturated
fatty acids. Because of the
manner in which they are typically manufactured, these sorbitan esters usually
comprise mixtures of
mono-, di-, tri-, etc. esters. Representative examples of suitable sorbitan
esters include sorbitan
palmitates (e.g., SPAN 40), sorbitan stearates (e.g., SPAN 60), and sorbitan
behenates, that comprise
one or more of the mono-, di- and tri-ester versions of these sorbitan esters,
e.g., sorbitan mono-, di-
14
CA 02756555 2011-10-21
and tri-palmitate, sorbitan mono-, di- and tri-stearate, sorbitan mono-, di
and ri-behenate, as well as
mixed tallow fatty acid sorbitan mono-, di- and tri-esters. Mixtures of
different sorbitan esters can
also be used, such as sorbitan palmitates with sorbitan stearates.
Particularly preferred sorbitan esters
are the sorbitan stearates, typically as a mixture of mono-, di- and tri-
esters (plus some tetraester)
such as SPAN 60, and sorbitan stearates sold under the trade name GLYCOMUL-S
by Lonza, Inc.
Although these sorbitan esters typically contain mixtures of mono-, di- and
tri-esters, plus some
tetraester, the mono-and di-esters are usually the predominant species in
these mixtures.
iii. Polysiloxanes and/or other Silicone Materials
Other suitable chemical softening agents suitable for the invention include
silicone materials,
such as polysiloxane compounds, cationic silicones, quaternary silicone
compounds and/or
aminosilicones. In general, suitable polysiloxane materials for use in the
present invention include
those having monomeric siloxane units of the following structure:
R
C
120t
t
R
wherein, R' and R2, for each independent siloxane monomeric unit can each
independently be
hydrogen or any alkyl, aryl, alkenyl, alkaryl, arakyl, cycloalkyl, halogenated
hydrocarbon, or other
radical. Any of such radicals can be substituted or unsubstituted. R' and R2
radicals of any particular
monomeric unit may differ from the corresponding functionalities of the next
adjoining monomeric
unit. Additionally, the polysiloxane can be either a straight chain, a
branched chain or have a cyclic
structure. The radicals R' and R2 can additionally independently be other
silaceous functionalities
such as, but not limited to siloxanes, polysiloxanes, silanes, and
polysilanes. The radicals R' and R2
may contain any of a variety of organic functionalities including, for
example, alcohol, carboxylic
acid, phenyl, and amine functionalities.
Exemplary alkyl radicals are methyl, ethyl, propyl, butyl, pentyl, hexyl,
octyl, decyl,
octadecyl, and the like. Exemplary alkenyl radicals are vinyl, allyl, and the
like. Exemplary aryl
radicals are phenyl, diphenyl, naphthyl, and the like. Exemplary alkaryl
radicals are toyl, xylyl,
ethylphenyl, and the like. Exemplary aralkyl radicals are benzyl, alpha-
phenylethyl, beta-phenylethyl,
alpha-phenylbutyl, and the like. Exemplary cycloalkyl radicals are cyclobutyl,
cyclopentyl,
cyclohexyl, and the like. Exemplary halogenated hydrocarbon radicals are
chloromethyl, bromoethyl,
tetrafluorethyl, fluorethyl, trifluorethyl, trifluorotloyl, hexafluoroxylyl,
and the like.
Preferred polysiloxanes include straight chain organopolysiloxane materials of
the following
general formula:
CA 02756555 2011-10-21
Rt R7 R9 1R4
I I I I R2-Si-0--Si-&- Si-0--Si-R'
3 Rs R10 JR6
b
a
wherein each R' -R9 radical can independently be any C1 -C10 unsubstituted
alkyl or aryl radical, and
R10 of any substituted C1 -C10 alkyl or aryl radical. Preferably each R' -R9
radical is independently
any C1 -C4 unsubstituted alkyl group. those skilled in the art will recognize
that technically there is no
difference whether, for example, R9 or R10 is the substituted radical.
Preferably the mole ratio of b to
(a+b) is between 0 and about 20%, more preferably between 0 and about 10%, and
most preferably
between about 1% and about 5%.
In one particularly preferred embodiment, R' -R9 are methyl groups and R1 is
a substituted or
unsubstituted alkyl, aryl, or alkenyl group. Such material shall be generally
described herein as
polydimethylsiloxane which has a particular functionality as may be
appropriate in that particular
case. Exemplary polydimethylsiloxane include, for example,
polydimethylsiloxane having an alkyl
hydrocarbon R10 radical and polydimethylsiloxane having one or more amino,
carboxyl, hydroxyl,
ether, polyether, aldehyde, ketone, amide, ester, thiol, and/or other
functionalities including alkyl and
alkenyl analogs of such functionalities. For example, an amino functional
alkyl group as R10 could be
an amino functional or an aminoalkyl-functional polydimethylsiloxane. The
exemplary listing of
these polydimethylsiloxanes is not meant to thereby exclude others not
specifically listed.
Viscosity of polysiloxanes useful for this invention may vary as widely as the
viscosity of
polysiloxanes in general vary, so long as the polysiloxane can be rendered
into a form which can be
applied to the tissue paper product herein. This includes, but is not limited
to, viscosity as low as
about 25 centistokes to about 20,000,000 centistokes or even higher.
While not wishing to be bound by theory, it is believed that the tactile
benefit efficacy is
related to average molecular weight and that viscosity is also related to
average molecular weight.
Accordingly, due to the difficulty of measuring molecular weight directly,
viscosity is used herein as
the apparent operative parameter with respect to imparting softness to tissue
paper.
References disclosing polysiloxanes include U.S. Pat. No. 2,826.551, issued to
Geen on Mar.
11, 1958; U.S. Pat. No. 3,964,500, issued to Drakoff on Jun. 22, 1976; U.S.
Pat. No. 4,364,837,
issued to Pader on Dec. 21, 1982; U.S. Pat. No. 5,059,282, issued to Ampulski;
U.S. Pat. No.
5,529,665 issued to Kaun on Jun 25, 1996; U.S. Pat. No. 5,552,020 issued to
Smithe et al. on Sep. 3,
1996; and British Patent 849,433, published on Sep. 28, 1960 in the name of
Wooston. Silicone
Compounds, pp. 181-217, distributed by Petrach Systems, Inc. contains an
extensive listing and
description of polysiloxanes in general.
16
CA 02756555 2011-10-21
In one embodiment, the chemical softeners may be mixed with the fibers,
especially the short
fibers to form the fibrous furnish, especially the short fiber furnish.
In another embodiment, the chemical softeners may be applied to the embryonic
fibrous web
and/or the TAD fibrous structure. Application of the chemical softener to the
embryonic fibrous web
and/or TAD fibrous structure may be by any suitable process known to those of
ordinary skill in the
art. Nonlimiting examples of such application processes include spraying the
chemical softener onto
the embryonic fibrous web and/or TAD fibrous structure and/or extruding the
chemical softener onto
the embryonic fibrous web and/or TAD fibrous structure. Other application
processes include
brushing the chemical softener onto the embryonic fibrous web and/or TAD
fibrous structure and/or
dipping the embryonic fibrous web and/or TAD fibrous structure in the chemical
softener.
Optional Ingredients:
The TAD fibrous structure of the present invention may comprise an optional
ingredient
selected from the group consisting of temporary wet strength resins, dry
strength resins, wetting
agents, lint resisting agents, absorbency-enhancing agents, immobilizing
agents, especially in
combination with emollient lotion compositions, antiviral agents including
organic acids, antibacterial
agents, polyol polyesters, antimigration agents, polyhydroxy plasticizers and
mixtures thereof. Such
optional ingredients may be added to the fiber furnish, the embryonic fibrous
web and/or the TAD
fibrous structure.
Such optional ingredients may be present in the TAD fibrous structure at any
level based on
the dry weight of the TAD fibrous structure.
The optional ingredients may be present in the TAD fibrous structure at a
level of from about
0.001 to about 50% and/or from about 0.001 to about 20% and/or from about 0.01
to about 5% and/or
from about 0.03 to about 3% and/or from about 0.1 to about 1.0% by weight, on
a dry TAD fibrous
structure basis.
i. Temporary Wet Strength Additives
One method of delivering fugitive wet strength is to provide for the formation
of acid-catalysed
hemiacetal formation through the introduction of ketone or, more specifically
aldehyde functional
groups on the papermaking fibers or in a binder additive for the papermaking
fibers. One binder
material that have been found particularly useful for imparting this form of
fugitive wet strength is
Parez 750 offered by Cytec of Stamford, CT.
Other additives can also be used to augment this wet strength mechanism. This
technique for
delivering fugitive wet strength is well known in the art. Exemplary showing
methods of delivering
the fugitive wet strength to the web, includes the following: US Patent No.
5,690,790; 5,656,746;
5,723,022; 4,981,557; 5,008,344; 5,085,736; 5,760,212; 4,605,702; 6,228,126;
4,079,043; 4,035,229;
4,079,044; and 6,127,593.
17
CA 02756555 2011-10-21
While the hemiacetal formation mechanism is one suitable technique for
generating
temporary wet strength, there are other methods, such as providing the sheet
with a binder mechanism
which is more active in the dry or slightly wet condition than in the
condition of high dilution as
would be experienced in the toilet bowl or in the subsequent sewer and septic
system. Such methods
have been primarily directed at web products which are to be delivered in a
slightly moist or wet
condition, then will be disposed under situation of high dilution. The
following references show
exemplary systems to accomplish this, and those skilled in the art will
readily recognize that they can
be applied to the webs of the present invention which will be supplied
generally at lower moisture
content than those described therewithin: US Patent Nos. 4,537,807; 4,419,403;
4,309,469; and
4,362,781.
ii. Dry Strength Additives
Nonlimiting examples of dry strength resins include polyacrylamides (such as
combinations
of CYPRO 514 and ACCOSTRENGTH 711 produced by Cytec of Stamford CT; starch,
for
example corn starch and/or potato starch (such as REDMOND 5320 and 2005)
available from
National Starch and Chemical Company, Bridgewater, N.J.; polyvinyl alcohol
(such as AIRVOL
540 produced by Air Products Inc of Allentown, Pa.); guar or locust bean gums;
and/or
carboxymethyl cellulose (such as CMC from Hercules, Inc. of Wilmington, Del.).
Dry strength
additives are used in more or less amounts to control tensile strength and
lint levels.
iii. Wetting Agents
Nonlimiting examples of wetting agents suitable for use in the present
invention include
polyhydroxy compounds, such as glyercol and polyglycols, and nonionic
surfactants, such as addition
products of ethylene oxide and, optionally, propylene oxide, with fatty
alcohols, fatty acids and fatty
amines.
The above listing of optional ingredients is intended to be merely exemplary
in nature, and is
not meant to limit the scope of the invention.
Processes of the Present Invention:
The TAD fibrous structure of the present invention may be made by any suitable
TAD
papermaking process.
A nonlimiting example of a suitable TAD papermaking process for making the TAD
fibrous
structure of the present invention is described as follows.
In one embodiment, a short fiber furnish is prepared by mixing a short fiber
with water. One
or more additional ingredients such as a physical property ingredient and/or
optional ingredients may
be added to the short fiber furnish. The short fiber furnish may then be put
into a headbox of a
papermaking machine. The short fiber furnish may then be deposited on a
foraminous surface to
form a single layer embryonic fibrous web. Physical property ingredients
and/or optional ingredients
may be added to the embryonic fibrous web by spraying and/or extruding and/or
by any other suitable
18
CA 02756555 2011-10-21
process known to those of ordinary skill in the art. The embryonic web may
then be transferred to a
through-air drying belt such that the embryonic fibrous web is dried via
through-air drying. From the
through-air drying belt, the TAD fibrous structure may be transferred to a
Yankee dryer. From the
Yankee dryer, the TAD fibrous structure may be wound into a roll.
From the through-air drying belt, or after transfer to a Yankee dryer, if such
a dryer is
employed, the TAD fibrous structure may be wound into a roll. Physical
property ingredients and/or
optional ingredients may be applied to the TAD fibrous structure while it is
semi-dry or after dried
completely. The TAD fibrous structure may be converted into various paper
products, particularly
sanitary tissue products, both in single-ply forms and/or in multi-ply forms.
In another embodiment, a TAD fibrous structure is prepared from a short fiber
furnish and a
long fiber furnish. The long fiber furnish may be made by mixing a long fiber
with water. The long
fiber furnish may include one or more additional ingredients such as a
physical property ingredient
and/or optional ingredients. These one or more additional ingredients may be
present in the long
and/or short fiber furnish. The fibrous furnish may be placed in a layered
headbox of a papermaking
machine. The fibrous furnishes may then be deposited on a foraminous surface
to form a multi-
layered embryonic fibrous web wherein the long fiber furnish is directed into
one or more layers and
the short fiber furnish is directed into one or more layers.
Preferred layering methodology for structures which will be assembled into two-
ply products
include two-layered structures wherein the short fiber furnish is applied into
a surface layer, i.e. the
layer which will be in contact with a user of the product. In this case, the
long fiber furnish layer will
be directed toward the inside of the two-ply assembly.
Preferred layering methodology for structures which will be converted into
single-ply
products include three-layered structures wherein the short fiber furnish is
applied into the surface
layers surrounding a central long fibered layer.
Physical property ingredients and/or optional ingredients may be added to the
embryonic
fibrous web by spraying and/or extruding and/or by any other suitable process
known to those of
ordinary skill in the art. The embryonic web may then be transferred to a
through-air drying belt such
that the embryonic fibrous web is dried via through-air drying.
Physical property ingredients and/or optional ingredients may be added to the
semi-dry or dry
fibrous web by spraying and/or extruding and/or by any other suitable process
known to those of
ordinary skill in the art.
From the through-air drying belt, or after transfer to a Yankee dryer, if such
a dryer is
employed, the TAD fibrous structure may be wound into a roll. Physical
property ingredients and/or
optional ingredients may be applied to the TAD fibrous structure while it is
semi-dry or after dried
completely. The TAD fibrous structure may be converted into various paper
products, particularly
sanitary tissue products, both in single-ply forms and/or in multi-ply forms.
The paper products may
19
CA 02756555 2011-10-21
be designed such that the surface of the paper product that is intended to
contact a human's skin
comprises a short fiber furnish and/or a short fiber.
Example 1
This Example illustrates a process incorporating a preferred embodiment of the
present
invention using the pilot scale Fourdrinier to make a facial tissue product.
An aqueous slurry of Northern Softwood Kraft (NSK) of about 3% consistency is
made up
using a conventional pulper and is passed through a stock pipe toward the
headbox of the Fourdrinier.
In order to impart a permanent wet strength to the finished product, a 1%
dispersion of
Hercules' Kymene 557 LX is prepared and is added to the NSK stock pipe at a
rate sufficient to
deliver 0.7% Kymene 557 LX based on the dry weight of the ultimate paper. The
absorption of the
permanent wet strength resin is enhanced by passing the treated slurry through
an in-line mixer.
Carboxymethyl cellulose (CMC) is added next to the NSK stock pipe after the in-
line mixer. CMC is
first dissolved in water and diluted to a solution strength of 1% by weight.
Hercules CMC-7MT is
used to make-up the CMC solution. The aqueous solution of CMC is added to the
aqueous slurry of
NSK fibers at a rate of 0.15% CMC by weight based on the dry weight of the
ultimate paper. The
aqueous slurry of NSK fibers passes through a centrifugal stock pump to aid in
distributing the CMC.
The chemical softening composition is added next. The chemical softening
composition is DiTallow
DiMethyl Ammonium Methyl Sulfate (DTDMAMS). Pre-heated DTDMAMS (170 F.) is
first
slurried in water conditioned by pre-heating to 170 F. The water is agitated
during addition of the
DTDMAMS to aid in its dispersion. The concentration of the resultant DTDMAMS
dispersion is 1%
by weight, and it is added to the NSK stock pipe at a rate of 0.2% by weight
DTDMAMS based on
the dry weight of the ultimate paper. The NSK slurry is diluted with white
water to about 0.2%
consistency at the fan pump.
An aqueous slurry of acacia fibers (from PT Tel - Indonesia) of about 3% by
weight is made
up using a conventional repulper. The Acacia furnish has a weighted average
fiber length of 0.66mm
and a coarseness of 7.1 mg/100m. The Acacia slurry passes to the second fan
pump where it is
diluted with white water to a consistency of about 0.2%.
The slurries of NSK and acacia are directed into a multi-channeled headbox
suitably
equipped with layering leaves to maintain the streams as separate layers until
discharged onto a
traveling Fourdrinier wire. A three-chambered headbox is used. The acacia
slurry containing 64% of
the dry weight of the ultimate paper is directed to the chambers leading to
the outer layer, while the
NSK slurry comprising 36% of the dry weight of the ultimate paper is directed
to the chamber leading
to the layer in contact with the wire and to the central layer. The NSK and
acacia slurries are
combined at the discharge of the headbox into a composite slurry.
The composite slurry is discharged onto the traveling Fourdrinier wire and is
dewatered
assisted by a deflector and vacuum boxes. The embryonic wet web is transferred
from the
CA 02756555 2011-10-21
Fourdrinier wire, at a fiber consistency of about 17% by weight at the point
of transfer, to a patterned
drying fabric. The drying fabric is designed to yield a pattern-densified
tissue with discontinuous
low-density deflected areas arranged within a continuous network of high
density (knuckle) areas.
This drying fabric is formed by casting an impervious resin surface onto a
fiber mesh supporting
fabric. The supporting fabric is a 48 x 52 filament, dual layer mesh. The
thickness of the resin cast is
about 12 mil above the supporting fabric. The knuckle area is about 30% and
the open cells remain at
a frequency of about 68 per square inch.
Further de-watering is accomplished by vacuum assisted drainage until the web
has a fiber
consistency of about 22% by weight. While remaining in contact with the
patterned forming fabric,
the patterned web is pre-dried by air blow-through pre-dryer to a fiber
consistency of about 58% by
weight.
The semi-dry web is then adhered to the surface of a Yankee dryer with a
sprayed creping
adhesive comprising a 0.250% aqueous solution of polyvinyl alcohol. The
creping adhesive is
delivered to the Yankee surface at a rate of 0. 1% adhesive solids based on
the dry weight of the web.
The fiber consistency is increased to about 98% before the web is dry creped
from the
Yankee with a doctor blade. The doctor blade has a bevel angle of about 20
degrees and is
positioned with respect to the Yankee dryer to provide an impact angle of
about 76 degrees. The
Yankee dryer is operated at a temperature of about 350 F (177 C) and a speed
of about 800 fpm (feet
per minute) (about 244 meters per minute). The paper is wound in a roll using
a surface driven reel
drum having a surface speed of about 680 fpm (about 207 meters per minute),
thus resulting in a
crepe of about 15%.
After the doctor blade, the web is calendered across all its width with a
steel to rubber
calendar roll operating at a loading of 400 psi. Resulting tissue has a basis
weight of about 20 g/m2; a
1-ply total dry tensile between 210 and 240 g/in, a I-ply wet burst between 35
and 65 g/in and a 2-ply
caliper of about 0.020 inches. Resulting tissue is then plied together with a
like sheet to form a two-
ply, creped, pattern densified tissue so that the acacia fibers face the
outside. The resulting two-ply
tissue has a) a total basis weight of about 39 g/m2; b) a 2-ply total dry
tensile between 350 and 420
g/in; c) a 2-ply wet burst between 90 and 130 g/in; and d) a 4-ply caliper of
about 0.028 inches.
Example 2
The same 2-ply, creped, pattern densified tissue, with the acacia fibers
facing outside
presented in Example #1, adding CM849 - an amino functional dimethyl
polysiloxane sold by
General Electric Silicones of Waterford, N.Y. - via slot extrusion onto both
sides in contact with a
human's skin, at an add-on amount of approximately 0.3-0.5 percent of silicone
per ply based on the
total weight of fibers. A comparative product is made in the same manner as
this example except that
a Eucalyptus bleached kraft fibrous pulp is substituted for the Acacia
bleached kraft fibrous pulp.
21
CA 02756555 2011-10-21
The Eucalyptus pulp furnish has a fiber length of 0.73mm and a coarseness of
8.0 mg/100m. The
resultant tissue paper using the comparative furnish is judged less soft by a
panel of expert judges.
Example 3
This Example illustrates another process incorporating a preferred embodiment
of the present
invention using the pilot scale Fourdrinier to make a facial tissue product.
An aqueous slurry of
Northern Softwood Kraft (NSK) of about 3% consistency is made up using a
conventional pulper and
is passed through a stock pipe toward the headbox of the Fourdrinier.
In order to impart a permanent wet strength to the finished product, a 1%
dispersion of
Hercules' Kymene 557 LX is prepared and is added to the NSK stock pipe at a
rate sufficient to
deliver 0.9% Kymene 557 LX based on the dry weight of the ultimate paper. The
absorption of the
permanent wet strength resin is enhanced by passing the treated slurry through
an in-line mixer.
Carboxymethyl cellulose (CMC) is added next to the NSK stock pipe after the in-
line mixer. CMC is
first dissolved in water and diluted to a solution strength of 1% by weight.
Hercules CMC-7MT is
used to make-up the CMC solution. The aqueous solution of CMC is added to the
aqueous slurry of
NSK fibers at a rate of 0.15% CMC by weight based on the dry weight of the
ultimate paper. The
aqueous slurry of NSK fibers passes through a centrifugal stock pump to aid in
distributing the CMC.
The bonding inhibitor composition is added next. The bonding inhibitor
composition is DiTallow
DiMethyl Ammonium Methyl Sulfate (DTDMAMS). Pre-heated DTDMAMS (170 F.) is
first
slurried in water conditioned by pre-heating to 170 F. The water is agitated
during addition of the
DTDMAMS to aid in its dispersion. The concentration of the resultant DTDMAMS
dispersion is 1%
by weight, and it is added to the NSK stock pipe at a rate of 0.125% by weight
DTDMAMS based on
the dry weight of the ultimate paper.
An aqueous slurry of acacia fibers (from PT Tel - Indonesia) of about 1.5% by
weight is
made up using a conventional repulper and is passed through a stock pipe
toward the headbox of the
Fourdrinier. The Acacia furnish has a weighted average fiber length of 0.66 mm
and a coarseness of
7.1 mg/100m. This Acacia furnish joins the NSK slurry at the fan pump where
both are diluted with
white water to about 0.2% consistency.
An aqueous slurry of acacia fibers (from PT Tel - Indonesia) of about 3% by
weight is made
up using a conventional repulper. The Acacia slurry passes to the second fan
pump where it is diluted
with white water to a consistency of about 0.2%.
The slurries of NSK/acacia and acacia are directed into a multi-channeled
headbox suitably
equipped with layering leaves to maintain the streams as separate layers until
discharged onto a
traveling Fourdrinier wire. A three-chambered headbox is used. The acacia
slurry containing 53% of
the dry weight of the ultimate paper is directed to the chambers leading to
the outer layer, while the
NSK/aeacia slurry comprising 47% (30% NSK and 17% acacia) of the dry weight of
the ultimate
paper is directed to the chamber leading to the layer in contact with the wire
and to the chamber
22
CA 02756555 2011-10-21
leading to the layer between the outer layer and the layer in contact with the
wire. The NSK/acacia
and acacia slurries are combined at the discharge of the headbox into a
composite slurry.
The composite slurry is discharged onto the traveling Fourdrinier wire and is
dewatered
assisted by a deflector and vacuum boxes. The embryonic wet web is transferred
from the
Fourdrinier wire, at a fiber consistency of about 18% by weight at the point
of transfer, to a patterned
drying fabric. The drying fabric is designed to yield a pattern-densified
tissue with discontinuous
low-density deflected areas arranged within a continuous network of high
density (knuckle) areas.
This drying fabric is formed by casting an impervious resin surface onto a
fiber mesh supporting
fabric. The supporting fabric is a 48 x 52 filament, dual layer mesh. The
thickness of the resin cast is
about 9 mil above the supporting fabric. The knuckle area is about 40% and the
open cells remain at
a frequency of about 68 per square inch.
Further de-watering is accomplished by vacuum assisted drainage until the web
has a fiber
consistency of about 26%. While remaining in contact with the patterned
forming fabric, the
patterned web is pre-dried by air blown through to a fiber consistency of
about 59% by weight.
The semi-dry web is then adhered to the surface of a Yankee dryer with a
sprayed creping
adhesive comprising a 0.250% aqueous solution of polyvinyl alcohol. The
creping adhesive is
delivered to the Yankee surface at a rate of 0.1 % adhesive solids based on
the dry weight of the web.
The fiber consistency is increased to about 98% before the web is dry creped
from the
Yankee with a doctor blade. The doctor blade has a bevel angle of about 20
degrees and is positioned
with respect to the Yankee dryer to provide an impact angle of about 76
degrees. The Yankee dryer is
operated at a temperature of about 300oF and a speed of about 800 fpm (feet
per minute) (about 244
meters per minute). The paper is wound in a roll using a surface driven reel
drum having a surface
speed of about 680 fpm (about 207 meters per minute), thus resulting in a
crepe of about 15%.
After the doctor blade, the web is calendared across all its width with a
steel to rubber
calendar roll operating at a loading of 450 psi.
Resulting tissue has a basis weight of about 22 g/m2; a 1-ply total dry
tensile between 280
and 320 g/in, a 1-ply wet burst between 45 and 65 g/in and a 2-ply caliper of
about 0.020 inches.
Resulting tissue is then plied together with a like sheet to form a two-ply,
creped, pattern
densified tissue so that the acacia fibers face the outside. The resulting two-
ply tissue has a) a total
basis weight of about 42-45 g/m2; b) a 2-ply total dry tensile between 550 and
600 g/in; c) a 2-ply
wet burst between 90 and 120 glin; and d) a 4-ply caliper of about 0.028
inches.
Example 4
This Example illustrates a process incorporating a preferred embodiment of the
present
invention using the pilot scale Fourdrinier to make a toilet tissue product.
An aqueous slurry of
Northern Softwood Kraft (NSK) of about 3% consistency is made up using a
conventional pulper and
the furnish is passed through a stock pipe toward the headbox of the
Fourdrinier.
23
CA 02756555 2011-10-21
In order aid in delivering a temporary wet strength to the finished product, a
1% dispersion of
Cytec's Parez 750C is prepared and is added to the NSK stock pipe at a rate
sufficient to deliver 0.2%
of the resin based on the dry weight of the ultimate paper. The absorption of
the temporary wet
strength resin is enhanced by passing the treated slurry through an in-line
mixer.
The NSK slurry furnish is diluted with white water to about 0.2% consistency
at the fan
pump.
An aqueous slurry of Acacia bleached haft fibrous pulp (from PT Tel -
Indonesia) of about
3% by weight is made up using a conventional repulper and the furnish is
passed through a stock pipe
toward the headbox of the Fourdrinier. The Acacia furnish has a weighted
average fiber length of
0.66mm and a coarseness of 7.1 mg/100m. In order to aid in delivering
temporary wet strength to the
finished product, the I% dispersion of Cytec's Parez 750C is also added to the
Acacia stock pipe at a
rate sufficient to deliver 0.05% of the resin based on the dry weight of the
ultimate paper. The
absorption of the temporary wet strength resin is enhanced by passing the
treated slurry through an in-
line mixer. The Acacia slurry furnish passes to the second fan pump where it
is diluted with white
water to a consistency of about 0.2%.
The slurries of NSK and acacia are directed into a multi-channeled headbox
suitably
equipped with layering leaves to maintain the streams as separate layers until
discharged onto a
traveling Fourdrinier wire. A three-chambered headbox is used. The acacia
slurry containing 70% of
the dry weight of the ultimate paper is directed to the chambers leading to
the outer layers, while the
NSK slurry comprising 30% of the dry weight of the ultimate paper is directed
to the chamber leading
to the central layer.
The NSK and acacia slurries are combined at the discharge of the headbox into
a composite
slurry and the composite slurry is discharged onto the traveling Fourdrinier
wire and is dewatered
assisted by a deflector and vacuum boxes.
The embryonic wet web is transferred from the Fourdrinier wire, at a fiber
consistency of about
15% at the point of transfer, to a patterned drying fabric. The drying fabric
is designed to yield a
pattern-densified tissue with discontinuous low-density deflected areas
arranged within a continuous
network of high density (knuckle) areas. This drying fabric is formed by
casting an impervious resin
surface onto a fiber mesh supporting fabric. The supporting fabric is a 45 x
52 filament, dual layer
mesh. The thickness of the resin cast is about 10 mil above the supporting
fabric. The knuckle area is
about 40% and the open cells remain at a frequency of about 78 per square
inch.
Further de-watering is accomplished by vacuum assisted drainage until the web
has a fiber
consistency of about 30%. While remaining in contact with the patterned
forming fabric, the
patterned web is pre-dried by air blow-through pre-dryers to a fiber
consistency of about 65% by
weight. The semi-dry web is then transferred to the Yankee dryer and adhered
to the surface of the
Yankee dryer with a sprayed creping adhesive comprising a 0.125% aqueous
solution of polyvinyl
24
CA 02756555 2011-10-21
alcohol. The creping adhesive is delivered to the Yankee surface at a rate of
0.1% adhesive solids
based on the dry weight of the web. The fiber consistency is increased to
about 98% before the web
is dry creped from the Yankee 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 a
temperature of about 350 F (177 C) and a speed of about 800 fpm (feet per
minute) (about 244 meters
per minute). The paper is wound in a roll using a surface driven reel drum
having a surface speed of
about 656 feet per minute. In a free span between the doctor blade and the
reel in a position at which
the web is essentially horizontal, an applicator comprising an extrusion slot
applies an aqueous
dispersion of DEEDMAMS having 44% cationic actives onto the top side of the
tissue web such that
the actives are uniformly distributed onto the tissue web surface. A
sufficient flow of the
DEEDMAMS slurry is maintained so that I% DEEDMAMS is applied to the tissue web
surface.
The resulting tissue paper web is converted into a single-ply toilet tissue
paper product using a
conventional tissue winding stand. The finished product has a basis weight of
about 21 lb/3000ft2; a
total dry tensile of 450 g/in and a density of 0.065 g/cm3. A comparative
product is made in the same
manner as this example except that a Eucalyptus bleached kraft fibrous pulp is
substituted for the
Acacia bleached kraft fiberous pulp. The Eucalyptus pulp furnish has a fiber
length of 0.73mm and a
coarseness of 8.0 mg/100m. The resultant tissue paper using the comparative
furnish is judged less
soft by a panel of expert judges.
Example 5
Example 4 is repeated except that the furnish flow rates are adjusted in order
to reduce the
basis weight of the fibrous web in order to make a two ply tissue web product.
Preparation of the
two ply product is completed by simultaneously unwinding two rolls of fibrous
web combining them
into a two-ply bath by a narrow, approximately 'h" stripe of pressure
sensitive adhesive which allows
the plies to maintain their ability to slip relative to one another. The
combining is completed so that
the respective Yankee-side surfaces of each ply contact each other. The
finished product has a basis
weight of about 28 lb/3000ft2; a total dry tensile of 500g/in and a density of
0.055 g/cm3. Again, a
comparative product is made in the same manner as this example except that the
Eucalyptus bleached
kraft fibrous pulp is substituted for the Acacia bleached kraft fibrous pulp.
Again, the resultant tissue
paper using the comparative furnish is judged less soft by a panel of expert
judges.
While particular embodiments and/or individual features 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. Further, all combinations of embodiments and
features which are
possible, can result in preferred executions of the invention. Therefore, the
appended claims are
intended to cover all such changes and modifications that are within this
invention.
