U.S. patent application number 10/374560 was filed with the patent office on 2004-08-26 for fibrous structure and process for making same.
Invention is credited to Edwards, Patrick Kip, Hernandez-Munoa, Diego Antonio, Kavalew, Dale Gary, Manifold, John Allen, Vinson, Kenneth Douglas.
Application Number | 20040163782 10/374560 |
Document ID | / |
Family ID | 32868900 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040163782 |
Kind Code |
A1 |
Hernandez-Munoa, Diego Antonio ;
et al. |
August 26, 2004 |
Fibrous structure and process for making same
Abstract
Through-air dried ("TAD") fibrous structures, especially TAD
fibrous structures incorporated into sanitary tissue products, that
comprise a short fiber furnish 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, and processes for making such TAD fibrous
structures are provided.
Inventors: |
Hernandez-Munoa, Diego Antonio;
(Liberty Township, OH) ; Vinson, Kenneth Douglas;
(Cincinnati, OH) ; Kavalew, Dale Gary;
(Cincinnati, OH) ; Edwards, Patrick Kip;
(Cincinnati, OH) ; Manifold, John Allen; (Milan,
IN) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
32868900 |
Appl. No.: |
10/374560 |
Filed: |
February 25, 2003 |
Current U.S.
Class: |
162/91 ; 162/123;
162/158; 162/96; 162/98 |
Current CPC
Class: |
D21H 21/22 20130101;
D21H 15/02 20130101; D21H 21/20 20130101; D21H 11/00 20130101; D21F
11/006 20130101; D21B 1/00 20130101; D21H 17/72 20130101; D21F
11/04 20130101; D21F 11/14 20130101; D21F 11/145 20130101 |
Class at
Publication: |
162/091 ;
162/096; 162/098; 162/158; 162/123 |
International
Class: |
D21F 011/00; D21H
011/12 |
Claims
What is claimed is:
1. A through-air dried fibrous structure comprising: a. a short
fiber furnish comprising a short fiber having a length of from
about 0.4 mm and about 1.2 mm and a coarseness of from about 3.0
mg/100 m to about 7.5 mg/100 m, and b. a physical property
ingredient selected from the group consisting of permanent wet
strength resins, chemical softeners and mixtures thereof.
2. The through-air dried fibrous structure according to claim 1
wherein said short fiber furnish comprises cellulose.
3. The through-air dried fibrous structure according to claim 2
wherein said short fiber furnish is 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.
4. The through-air dried fibrous structure according to claim 1
wherein the fibrous structure further comprises a long fiber
furnish comprising a long fiber having a length greater than 1.2
mm.
5. The through-air dried fibrous structure according to claim 4
wherein the fibrous structure comprises at least 10% by weight of
the total fiber composition of said short fiber furnish.
6. The through-air dried fibrous structure according to claim 4
wherein the fibrous structure has a basis weight greater than about
12 g/m.sup.2 to about 120 g/m.sup.2.
7. The through-air dried fibrous structure according to claim 4
wherein the fibrous structure has a total dry tensile greater than
about 150 g/in and a wet burst strength greater than about 25
g/in.
8. The through-air dried fibrous structure according to claim 4
wherein the fibrous structure comprises two or more fibrous furnish
layers.
9. The through-air dried fibrous structure according to claim 8
wherein at least one of the two or more fibrous furnish layers
comprises the short fiber furnish.
10. The through-air dried fibrous structure according to claim 9
wherein the at least one of the two or more fibrous furnish layers
when incorporated into a sanitary tissue product contacts a human's
skin upon use.
11. The through-air dried fibrous structure according to claim 1
wherein said physical property ingredient comprises a permanent wet
strength resin comprising a polyamide-epichlorohydrin resin.
12. The through-air dried fibrous structure according to claim 1
wherein said physical property ingredient comprises a chemical
softener selected from a group consisting of quaternary ammonium
compounds, silicones, emollient lotion compounds and mixtures
thereof.
13. The through-air dried fibrous structure according to claim 1
wherein the through-air dried fibrous structure further comprises
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, antiviral agents, antibacterial agents, polyol polyesters,
antimigration agents, polyhydroxy plasticizers and mixtures
thereof
14. A paper product comprising a fibrous structure according to
claim 1.
15. A one-ply sanitary tissue product selected from the group
consisting of facial tissue products, toilet tissue products, paper
towel products and mixtures thereof comprising a fibrous structure
according to claim 1.
16. A multi-ply sanitary tissue product selected from the group
consisting of facial tissue products, toilet tissue products, paper
towel products and mixtures thereof, wherein at least one ply of
the multi-ply sanitary tissue product comprises a fibrous structure
according to claim 1.
17. 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 m to about 7.5 mg/100 m, 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 d.
through-air drying said embryonic fibrous web such that the
through-air dried fibrous structure is formed.
18. The process according to claim 17 wherein the embryonic fibrous
web is formed from two or more furnish layers.
19. 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 m to about
7.5 mg/100 m, 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 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.
20. The process according to claim 19 wherein the embryonic fibrous
web is formed from two or more furnish layers.
Description
FIELD OF THE INVENTION
[0001] 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 m to about 7.5 mg/100 m,
and processes for making such fibrous structures.
BACKGROUND OF THE INVENTION
[0002] 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 U.S. Pat. No. 4,300,981 to
Carstens incorporated herein by reference for a disclosure of such
velvety structures.
[0003] 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.
[0004] 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.
[0005] Today's art limits the short-fibered furnish used in TAD
processes to greater than about 0.75 mm.
[0006] 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.
[0007] 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 m 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
[0008] 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.
[0009] 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 m 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, is provided.
[0010] In another aspect of the present invention, a paper product
comprising a TAD fibrous structure according to the present
invention is provided.
[0011] 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.
[0012] In yet still another aspect of the present invention, a
process for making a through-air dried fibrous structure comprising
the steps of:
[0013] 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 m to
about 7.5 mg/100 m, by mixing the short fiber with water to form
the short fiber furnish;
[0014] b. depositing the fibrous furnish on a foraminous forming
surface to form an embryonic fibrous web;
[0015] c. adding a permanent wet strength resin to the fibrous
furnish and/or the embryonic fibrous web; and
[0016] d. through-air drying said embryonic fibrous web such that
the through-air dried fibrous structure is formed, is provided.
[0017] 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:
[0018] 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 m to
about 7.5 mg/100 m, by mixing the short fiber with water to form
the short fiber furnish;
[0019] b. depositing the fibrous furnish on a foraminous forming
surface to form an embryonic fibrous web;
[0020] c. through-air drying said embryonic fibrous web such that a
through-air dried fibrous structure is formed; and
[0021] 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.
[0022] All documents cited are, in relevant part, incorporated
herein by reference; the citation of any document is not to be
construed as an admission that it is prior art with respect to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] "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 papermaking 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 are incorporated herein by reference for the purpose of
disclosing 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.
[0024] 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 used. The
polymeric fibers can be produced by spunbond processes, meltblown
processes, and other suitable methods known in the art.
[0025] 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%.
[0026] "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).
[0027] "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.
[0028] "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.
[0029] 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.degree. C. (.+-.3.degree. 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 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.
[0030] "Basis Weight" as used herein is the weight per unit area of
a sample reported in lbs/3000 ft.sup.2 or g/m.sup.2. Basis weight
is measured by preparing one or more samples of a certain area
(m.sup.2) 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.sup.2). The basis weight (g/m.sup.2) is calculated by
dividing the average weight (g) by the average area of the samples
(m.sup.2).
[0031] "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.
[0032] "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.
[0033] "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.times.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, Mass. in a
conditioned room at a temperature of 73.degree. F..+-.4.degree. F.
(about 28.degree. C..+-.2.2.degree. 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.
[0034] "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 in.sup.2. 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/cm.sup.2 (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.
[0035] "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.sup.3.
[0036] "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.degree. C. to 40.degree. 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.degree.
C. to 24.degree. 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.
[0037] 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 and is incorporated
herein by reference. 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:
[0038] 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;
[0039] 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;
[0040] 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:
[0041] 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.
[0042] 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 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.
[0043] "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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] TAD Fibrous Structure:
[0048] 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 m to about
7.5 mg/100 m.
[0049] 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.
[0050] 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/100 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.
[0051] 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.
[0052] 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.).
[0053] 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
thermomechanical 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.
[0054] In addition to wood pulps, fibers may be produced/obtained
from vegetable sources such as corn (i.e., starch).
[0055] 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.
[0056] 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 furnsh
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.
[0057] 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.
[0058] 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/m.sup.2 to about 120 g/m.sup.2
and/or from about 14 g/m.sup.2 to about 80 g/m.sup.2 and/or from
about 20 g/m.sup.2 to about 60 g/m.sup.2.
[0059] 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.
[0060] 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.
[0061] Short Fibers:
[0062] 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 m to about 7.5 mg/100 m 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.
[0063] 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.
[0064] In one embodiment, the short fibers are derived from
tropical hardwood.
[0065] In another embodiment, the short fibers are derived from a
fiber source selected from the group consisting of Acacia,
Eucalyptus, Gmelina and mixtures thereof.
[0066] In another embodiment, the short fibers are derived from a
fiber source selected from the group consisting of Acacia, Gmelina
and mixtures thereof.
[0067] In yet another embodiment, the short fibers are derived from
Acacia.
[0068] 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.
[0069] The short fibers of the present invention may comprise
cellulose and/or hemicellulose. Preferably, the fibers comprise
cellulose.
[0070] 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 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 furnishes, 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.
[0071] Permanent Wet Strength Resins
[0072] 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.
[0073] 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
[0074] 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.
[0075] 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. No. 3,700,623,
issued on Oct. 24, 1972, and U.S. Pat. No. 3,772,076, issued on
Nov. 13, 1973, both issued to Keim and both being hereby
incorporated by reference. One commercial source of a useful
polyamide-epichlorohydrin resins is Hercules, Inc. of Wilmington,
Del., which markets such resin under the trade-mark KYMENE.RTM.
557H.
[0076] Polyacrylamide resins have also been found to be of utility
as wet strength resins. These resins are described in U.S. Pat. No.
3,556,932, issued on Jan. 19, 1971, to Coscia, et al. and U.S. Pat.
No. 3,556,933, issued on Jan. 19, 1971, to Williams et al., both
patents being incorporated herein by reference. One commercial
source of polyacrylamide resins is CYTEC Co. of Stanford, Conn.,
which markets one such resin under the trade-mark PAREZ.RTM. 631
NC. Still other water-soluble cationic resins finding utility in
this invention are urea formaldehyde and melamine formaldehyde
resins.
[0077] Chemical Softeners:
[0078] The TAD fibrous structure of the present invention may
comprise a chemical softener.
[0079] 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.
[0080] 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 (C10-C22) hydrocarbyl
chains, functional silicones, and long (C10-C22) hydrocarbyl
chain-bearing compounds possessing functional groups such as
amines, acids, alcohols and esters.
[0081] 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.
[0082] 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.
[0083] 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. No. 5,264,082 issued to Phan and
Trokhan on Nov. 23, 1993, incorporated herein by reference. 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.
[0084] 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 incorporated herein by reference. 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.
[0085] 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, all incorporated herein by
reference. The U.S. Pat. No. 5,215,626 discloses a method for
preparing soft tissue paper by applying a polysiloxane to a dry
web. The U.S. Pat. No.5,246,545 Patent 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.
[0086] Particularly preferred chemical softening ingredients are
further detailed as follows:
i. Quaternary Ammonium Softeners
[0087] Preferably, quaternary ammonium compounds suitable to serve
as chemical softening agents of the present invention have the
formula:
(R.sup.1).sub.4-m--N+--[R.sup.2].sub.m X.sup.-
[0088] wherein:
[0089] m is 1 to 3; each R.sup.1 is independently a C.sub.1-C.sub.6
alkyl group, hydroxyalkyl group, hydrocarbyl or substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures
thereof; each R.sup.2 is independently a C.sub.14-C.sub.22 alkyl
group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl
group, alkoxylated group, benzyl group, or mixtures thereof; and
X.sup.- is any softener-compatible anion are suitable for use in
the present invention.
[0090] Preferably, each R.sup.1 is methyl and X.sup.- is chloride
or methyl sulfate. Preferably, each R.sup.2 is independently
C.sub.16-C.sub.18 alkyl or alkenyl, most preferably each R.sup.2 is
independently straight-chain C.sub.18 alkyl or alkenyl.
[0091] 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.sup.1).sub.4-m--N+--[(CH.sub.2).sub.n--Y--R.sup.3].sub.m
X.sup.-
[0092] wherein:
[0093] Y is --O--(O)C--, or --C(O)--O--, or --NH--C(O)--, or
--C(O)--NH--; m is 1 to 3; n is 0 to 4; each R.sup.1 is
independently a C.sub.1-C.sub.6 alkyl group, hydroxyalkyl group,
hydrocarbyl or substituted hydrocarbyl group, alkoxylated group,
benzyl group, or mixtures thereof; each R.sup.3 is independently a
C.sub.13-C.sub.21 alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted hydrocarbyl group, alkoxylated group, benzyl group, or
mixtures thereof, and X.sup.- is any softener-compatible anion.
[0094] Preferably, Y is --O--(O)C--, or --C(O)--O--; m=2; and n=2.
Each R.sup.1 is independently preferably a C.sub.1-C.sub.3, alkyl
group, with methyl being most preferred. Preferably, each R.sup.3
is independently C.sub.13-C.sub.17 alkyl and/or alkenyl, more
preferably R.sup.3 is independently straight chain
C.sub.15-C.sub.17 alkyl and/or alkenyl, C.sub.15-C.sub.17 alkyl,
most preferably each R.sup.3 is independently straight-chain
C.sub.17 alkyl.
[0095] As mentioned above, X.sup.- 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.sup.- is chloride or methyl
sulfate.
[0096] 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
[0097] 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.
[0098] 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.RTM. 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.
[0099] Suitable fatty acid ester type emollients include those
derived from C.sub.12-C.sub.28 fatty acids, preferably
C.sub.16-C.sub.22 saturated fatty acids, and short chain
(C.sub.1-C.sub.8, preferably C.sub.1-C.sub.3) 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 (C.sub.12-C.sub.28, preferably C.sub.12-C.sub.16) and
shorter chain fatty acids e.g., lactic acid, such as lauryl lactate
and cetyl lactate.
[0100] Suitable alkyl ethoxylate type emollients include
C.sub.12-C.sub.18 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
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.
[0101] 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 users 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.
[0102] Suitable polyhydroxy fatty acid esters for use in the
present invention will have the formula: 1
[0103] wherein R is a C.sub.5-C.sub.31 hydrocarbyl group,
preferably straight chain C.sub.7-C.sub.19 alkyl or alkenyl, more
preferably straight chain C.sub.9-C.sub.17 alkyl or alkenyl, most
preferably straight chain C.sub.11-C.sub.17 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.
[0104] One class of suitable polyhydroxy fatty acid esters for use
in the present invention comprises certain sorbitan esters,
preferably the sorbitan esters of C.sub.16-C.sub.22 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- 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
[0105] 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: 2
[0106] wherein, R.sup.1 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.sup.1 and R.sup.2 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.sup.1 and R.sup.2 can
additionally independently be other silaceous functionalities such
as, but not limited to siloxanes, polysiloxanes, silanes, and
polysilanes. The radicals R.sup.1 and R.sup.2 may contain any of a
variety of organic functionalities including, for example, alcohol,
carboxylic acid, phenyl, and amine functionalities.
[0107] 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.
[0108] Preferred polysiloxanes include straight chain
organopolysiloxane materials of the following general formula:
3
[0109] wherein each R.sup.1-R.sup.9 radical can independently be
any C.sub.1-C.sub.10 unsubstituted alkyl or aryl radical, and
R.sub.10 of any substituted C.sub.1-C.sub.10 alkyl or aryl radical.
Preferably each R.sup.1-R.sup.9 radical is independently any
C.sub.1-C.sub.4 unsubstituted alkyl group, those skilled in the art
will recognize that technically there is no difference whether, for
example, R.sup.9 or R.sub.10 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%.
[0110] In one particularly preferred embodiment, R.sup.1-R.sup.9
are methyl groups and R.sub.10 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 R.sup.10 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 R.sup.10 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.
[0111] 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.
[0112] 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.
[0113] 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. All of these patents are
incorporated herein by reference. Also incorporated herein by
reference is Silicone Compounds, pp. 181-217, distributed by
Petrach Systems, Inc., which contains an extensive listing and
description of polysiloxanes in general.
[0114] 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.
[0115] 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.
[0116] Optional Ingredients:
[0117] 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.
[0118] Such optional ingredients may be present in the TAD fibrous
structure at any level based on the dry weight of the TAD fibrous
structure.
[0119] 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
[0120] 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, Conn.
[0121] 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 art, incorporated
herein by reference for the purpose of showing methods of
delivering the fugitive wet strength to the web, includes the
following U.S. Pat. Nos. 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.
[0122] 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
are incorporated herein by reference for the purpose of showing
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: U.S. Pat. Nos.
4,537,807; 4,419,403; 4,309,469; and 4,362,781.
ii. Dry Strength Additives
[0123] Nonlimiting examples of dry strength resins include
polyacrylamides (such as combinations of CYPRO 514 and ACCOSTRENGTH
711 produced by Cytec of Stamford Conn.; starch, for example corn
starch and/or potato starch (such as REDIBOND 5320 and 2005)
available from National Starch and Chemical Company, Bridgewater,
N.J.; polyvinyl alcohol (such as AIRVOL.RTM. 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
[0124] 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.
[0125] 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.
[0126] Processes of the Present Invention:
[0127] The TAD fibrous structure of the present invention may be
made by any suitable TAD papermaking process.
[0128] A nonlimiting example of a suitable TAD papermaking process
for making the TAD fibrous structure of the present invention is
described as follows.
[0129] 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
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.
[0130] 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.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] 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.
[0135] 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.
[0136] 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 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
[0137] This Example illustrates a process incorporating a preferred
embodiment of the present invention using the pilot scale
Fourdrinier to make a facial tissue product.
[0138] 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.
[0139] 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.RTM. 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.degree.
F.) is first slurried in water conditioned by pre-heating to
170.degree. 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.
[0140] 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 0.66 mm and a
coarseness of 7.1 mg/100 m. The Acacia slurry passes to the second
fan pump where it is diluted with white water to a consistency of
about 0.2%.
[0141] 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.
[0142] 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 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.times.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.
[0143] 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.
[0144] 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.
[0145] 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.degree. F. (177.degree. 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%.
[0146] 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 1-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
[0147] 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. The Eucalyptus pulp furnish has a fiber length of 0.73 mm and
a coarseness of 8.0 mg/100 m. The resultant tissue paper using the
comparative furnish is judged less soft by a panel of expert
judges.
EXAMPLE 3
[0148] 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.
[0149] 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.RTM. 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.degree.
F.) is first slurried in water conditioned by pre-heating to
170.degree. 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.
[0150] 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/100 m. This Acacia furnish
joins the NSK slurry at the fan pump where both are diluted with
white water to about 0.2% consistency.
[0151] 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%.
[0152] 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/acacia 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
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.
[0153] 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.times.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.
[0154] 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.
[0155] 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.
[0156] 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
300.degree. F. 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%.
[0157] 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.
[0158] 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.
[0159] 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 g/in; and d) a 4-ply caliper of about 0.028 inches.
EXAMPLE 4
[0160] 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.
[0161] 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.
[0162] The NSK slurry furnish is diluted with white water to about
0.2% consistency at the fan pump.
[0163] An aqueous slurry of Acacia bleached kraft 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 0.66 mm and a coarseness of 7.1
mg/100 m. In order to aid in delivering temporary wet strength to
the finished product, the 1% 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%.
[0164] 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.
[0165] 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.
[0166] 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.times.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.
[0167] 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 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.
[0168] 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.degree. F. (177.degree. 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 1% DEEDMAMS is
applied to the tissue web surface.
[0169] 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/3000 ft2; a total dry tensile of 450 g/in and a density of 0.065
g/cm.sup.3. 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 0.73 mm and a
coarseness of 8.0 mg/100 m. The resultant tissue paper using the
comparative furnish is judged less soft by a panel of expert
judges.
EXAMPLE 5
[0170] 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 1/2" 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/3000 ft2; a total dry
tensile of 500 g/in and a density of 0.055 g/cm.sup.3. 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.
[0171] 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 without departing from the spirit and
scope of the invention. Further, it should be apparent that all
combinations of such embodiments and features are possible and can
result in preferred executions of the invention. Therefore, the
appended claims are intended to cover all such changes and
modifications that are within the scope of this invention.
* * * * *