U.S. patent application number 13/848116 was filed with the patent office on 2013-08-29 for soft and strong fibrous structures and methods for making same.
This patent application is currently assigned to The Procter & Gamble Company. The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Khosrow Parviz MOHAMMADI.
Application Number | 20130220563 13/848116 |
Document ID | / |
Family ID | 43608655 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220563 |
Kind Code |
A1 |
MOHAMMADI; Khosrow Parviz |
August 29, 2013 |
SOFT AND STRONG FIBROUS STRUCTURES AND METHODS FOR MAKING SAME
Abstract
Soft and strong fibrous structures and more particularly soft
and strong fibrous structures that contains less softwood fibers
than known fibrous structures and methods for making such soft and
strong fibrous structures are provided.
Inventors: |
MOHAMMADI; Khosrow Parviz;
(Liberty Township, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company; |
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US |
|
|
Assignee: |
The Procter & Gamble
Company
Cincinnati
OH
|
Family ID: |
43608655 |
Appl. No.: |
13/848116 |
Filed: |
March 21, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13217466 |
Aug 25, 2011 |
8425722 |
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13848116 |
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12987330 |
Jan 10, 2011 |
8029645 |
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13217466 |
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61294909 |
Jan 14, 2010 |
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Current U.S.
Class: |
162/146 ;
162/141 |
Current CPC
Class: |
D21H 11/12 20130101;
D21H 27/30 20130101; Y10T 428/27 20150115; A61F 2013/530014
20130101; D21H 13/00 20130101; D21H 15/00 20130101; Y10T 428/24612
20150115; A61F 2013/530021 20130101; Y10T 428/249966 20150401; D21H
11/14 20130101 |
Class at
Publication: |
162/146 ;
162/141 |
International
Class: |
D21H 11/14 20060101
D21H011/14 |
Claims
1. A fibrous structure exhibiting a basis weight of from about 10
to about 120 g/m.sup.2, wherein the fibrous structure comprises
greater than 50% by weight on a dry fiber basis of pulp fibers,
wherein greater than 0% and less than 20% by weight on a dry fiber
basis of the pulp fibers are softwood fibers, and wherein the
weight ratio of softwood fibers to non-softwood fibers within the
fibrous structure is less than 1:4.
2. The fibrous structure of claim 1, comprising greater than 75% by
weight on a dry fiber basis of pulp fibers.
3. The fibrous structure of claim 1, comprising greater than 90% by
weight on a dry fiber basis of pulp fibers.
4. The fibrous structure of claim 1, wherein the pulp fibers
comprise trichome fibers, and wherein one of trichome fibers is
derived from a plant in the Stachys genus.
5. The fibrous structure of claim 4, wherein one of the trichome
fibers is derived from a plant Stachys byzantina.
6. The fibrous structure of claim 1, comprising tropical hardwood
fibers selected from the group consisting of: eucalyptus fibers,
acacia fibers, and mixtures thereof.
7. The fibrous structure of claim 1, comprising less than 50% by
weight on a dry fiber basis of hardwood fibers.
8. The fibrous structure of claim 1, wherein the fibrous structure
is void of hardwood fibers.
9. The fibrous structure of claim 1, wherein the softwood fibers
comprise one of northern softwood kraft fibers and southern kraft
fibers.
10. The fibrous structure of claim 1, comprising one or more
synthetic fibers.
11. The fibrous structure of claim 1, wherein the fibrous structure
comprises layers, and wherein the pulp fibers in an exterior layer
of the fibrous structure comprise one or more trichome fibers.
12. The fibrous structure of claim 1, comprising a softening
agent.
13. The fibrous structure of claim 1, exhibiting a basis weight of
greater than 21 g/m.sup.2.
14. The fibrous structure of claim 1, wherein the pulp fibers
comprise trichome fibers.
15. The fibrous structure of claim 1, wherein the fibrous structure
is a sanitary tissue product.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to soft and strong fibrous
structures and more particularly to soft and strong fibrous
structures that comprise less softwood fibers than known fibrous
structures and methods for making such soft and strong fibrous
structures.
BACKGROUND OF THE INVENTION
[0002] Historically, fibrous structures, such as fibrous structures
that are used to make sanitary tissue products, have been made with
softwood fibers and hardwood fibers. For example, softwood fibers
have typically made up greater than 20% by weight on a dry fiber
basis of through-air-dried fibrous structures. The softwood fibers
are longer fibers than the hardwood fibers and they provide greater
strength properties to the fibrous structures than do the hardwood
fibers. However, softwood fibers negatively impact the softness of
the fibrous structures.
[0003] Formulators have for years attempted to balance the level of
softwood fibers in their fibrous structures to ensure adequate
strength of the fibrous structures while at the same time trying to
minimize the level of softwood fibers to avoid negatively impacting
the softness of the fibrous structures. The problem has been that
formulators have been unable to reliably make fibrous structures,
especially through-air-dried ("TAD") fibrous structures that are
used to make sanitary tissue products that contain less than 20% by
weight of softwood fibers on a dry fiber basis of the fibrous
structure, due to lower resulting strength in the fibrous
structures which can lead to product quality issues and/or sheet
breaks during processing. If formulators use less than 20% by
weight on a dry fiber basis of softwood fibers to make fibrous
structures and/or sanitary tissue products, the softwood fibers
would need to have excessive refining and/or chemical strength
agents to achieve the desired level of strength needed for product
quality and/or reliability (avoid sheet breaks during making and/or
processing). Both of these actions negatively impact softness of
the fibrous structure and/or sanitary tissue product.
[0004] Accordingly, there is a need for a fibrous structure that
comprises less softwood fibers, for example a 5% or more by weight
reduction on a dry fiber basis, than traditional fibrous
structures, especially traditional through-air-dried fibrous
structures, without negatively impacting the strength of the
resulting fibrous structures and reducing machine reliability,
sanitary tissue products comprising same and methods for making
same.
SUMMARY OF THE INVENTION
[0005] The present invention fulfills the need described above by
providing a fibrous structure that comprises less softwood fibers,
for example a 5% or more by weight reduction on a dry fiber basis,
than traditional fibrous structures, especially traditional
through-air-dried fibrous structures, without negatively impacting
the strength and/or softness of the fibrous structures and
optionally, positively impacting the softness of the fibrous
structures, sanitary tissue products comprising such fibrous
structures and methods for making such fibrous structures.
[0006] In one example of the present invention, a fibrous
structure, for example a through-air-dried fibrous structure,
exhibiting a basis weight of from about 10 to about 120 g/m.sup.2,
wherein the fibrous structure comprises greater than 50% by weight
on a dry fiber basis of pulp fibers, wherein greater than 0% but
less than 20% by weight on a dry fiber basis of the pulp fibers are
softwood fibers, is provided.
[0007] In another example of the present invention, a single- or
multi-ply sanitary tissue product comprising one or more fibrous
structures of the present invention, is provided.
[0008] In yet another example of the present invention, a sanitary
tissue product, for example a sanitary tissue product comprising a
through-air-dried fibrous structure, comprising greater than 50% by
weight on a dry fiber basis of pulp fibers, wherein less than 20%
by weight on a dry fiber basis of the pulp fibers are softwood
fibers, optionally, wherein the sanitary tissue product comprises
trichome fibers, and wherein the sanitary tissue product exhibits a
total dry tensile of at least 300 g/in as measured according to the
Total Dry Tensile Test Method described herein, is provided.
[0009] In even another example of the present invention, a fibrous
structure, for example a through-air-dried fibrous structure,
comprising a plurality of pulp fibers, wherein greater than 0% but
less than 20% by weight on a dry fiber basis of the pulp fibers are
softwood fibers and wherein the fibrous structure comprises fibers
derived from a fiber-producing source that has a growing cycle of
less than 800 and/or less than 400 and/or less than 200 and/or less
than 100 days. By using fibers derived from fiber-producing sources
that have a growing cycle of less than 800 and/or less than 400
and/or less than 200 and/or less than 100 days, these fibrous
structures are significantly more sustainable than fibrous
structures that do not use such fibers.
[0010] In still another example of the present invention, a fibrous
structure, for example a through-air-dried fibrous structure,
comprising a plurality of fibers and being void of surface
softening agents, such as quaternary ammonium surface softening
agents and silicones, wherein the fibrous structure exhibits a
Slip-and-Stick Coefficient of Friction of less than 0.8 and/or less
than 0.75 and/or less than 0.7 as measured according to the
Slip-and-Stick Coefficient of Friction Test Method as described
herein.
[0011] In yet another example of the present invention, a fibrous
structure, for example a through-air-dried fibrous structure,
comprising individualized trichomes and greater than 0% but less
than 20% by weight on a dry fiber basis of softwood fibers and
wherein the fibrous structure exhibits a Slip-and-Stick Coefficient
of Friction as measured according to Slip-and-Stick Coefficient of
Friction Test Method of less than 20% compared to the same fibrous
structure void of the individualized trichomes, is provided.
[0012] In even still another example of the present invention, a
fibrous structure, for example a through-air-dried fibrous
structure, comprising fibers, wherein the weight ratio of softwood
fibers to non-softwood fibers within the fibrous structure is less
than 1:4 and/or less than 1:5 and/or less than 1:6 and/or less than
1:7 and/or less than 1:8 and/or less than 1:9, is provided.
[0013] Accordingly, the present invention provides fibrous
structures that comprise less softwood fibers than previously
known, sanitary tissue products comprising such fibrous structures
and methods for making such fibrous structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a light micrograph of a leaf and leaf stem
illustrating trichomes present on red clover, Trifolium pratense
L;
[0015] FIG. 2 is a light micrograph of a lower stem illustrating
trichomes present on red clover, Trifolium pratense L.
[0016] FIG. 3 is a light micrograph of a leaf illustrating
trichomes present on dusty miller, Centaurea gymnocarpa;
[0017] FIG. 4 is a light micrograph of individualized trichomes
individualized from a leaf of dusty miller, Centaurea
gymnocarpa;
[0018] FIG. 5 is a light micrograph of a basal leaf illustrating
trichomes present on silver sage, Salvia argentiae;
[0019] FIG. 6 is a light micrograph of a bloom-stalk leaf
illustrating trichomes present in silver sage, Salvia
argentiae;
[0020] FIG. 7 is a light micrograph of a mature leaf illustrating
trichomes present on common mullein, Verbascum thapsus;
[0021] FIG. 8 is a light micrograph of a juvenile leaf illustrating
trichomes present on common mullein, Verbascum thapsus;
[0022] FIG. 9 is a light micrograph of a perpendicular view of a
leaf illustrating trichomes present on wooly betony, Stachys
byzantina;
[0023] FIG. 10 is a light micrograph of a cross-sectional view of a
leaf illustrating trichomes present on wooly betony, Stachys
byzantina; and
[0024] FIG. 11 is a light micrograph of individualized trichomes in
the form of a plurality of trichomes bound by their individual
attachment to a common remnant of a host plant, wooly betony,
Stachys byzantina.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0025] "Trichome" as used herein means an epidermal attachment of a
varying shape, structure and/or function of a non-seed portion of a
plant. In one example, a trichome is an outgrowth of the epidermis
of a non-seed portion of a plant. The outgrowth may extend from an
epidermal cell. In one embodiment, the outgrowth is a trichome
fiber. The outgrowth may be a hairlike or bristlelike outgrowth
from the epidermis of a plant.
[0026] Trichomes may protect the plant tissues present on a plant.
Trichomes may for example protect leaves and stems from attack by
other organisms, particularly insects or other foraging animals
and/or they may regulate light and/or temperature and/or moisture.
They may also produce glands in the forms of scales, different
papills and, in roots, often they may function to absorb water
and/or moisture.
[0027] A trichome may be formed by one cell or many cells.
[0028] The term "individualized trichome" as used herein means
trichomes which have been artificially separated by a suitable
method for individualizing trichomes from their host plant. In
other words, individualized trichomes as used herein means that the
trichomes become separated from a non-seed portion of a host plant
by some non-naturally occurring action. In one example,
individualized trichomes are artificially separated in a location
that is sheltered from nature. Primarily, individualized trichomes
will be fragments or entire trichomes with essentially no remnant
of the host plant attached. However, individualized trichomes can
also comprise a minor fraction of trichomes retaining a portion of
the host plant still attached, as well as a minor fraction of
trichomes in the form of a plurality of trichomes bound by their
individual attachment to a common remnant of the host plant.
Individualized trichomes may comprise a portion of a pulp or mass
further comprising other materials. Other materials includes
non-trichome-bearing fragments of the host plant.
[0029] In one example of the present invention, the individualized
trichomes may be classified to enrich the individualized trichomal
content at the expense of mass not constituting individualized
trichomes.
[0030] Individualized trichomes may be converted into chemical
derivatives including but not limited to cellulose derivatives, for
example, regenerated cellulose such as rayon; cellulose ethers such
as methyl cellulose, carboxymethyl cellulose, and hydroxyethyl
cellulose; cellulose esters such as cellulose acetate and cellulose
butyrate; and nitrocellulose. Individualized trichomes may also be
used in their physical form, usually fibrous, and herein referred
to "trichome fibers", as a component of fibrous structures.
[0031] Trichome fibers are different from seed hair fibers in that
they are not attached to seed portions of a plant. For example,
trichome fibers, unlike seed hair fibers, are not attached to a
seed or a seed pod epidermis. Cotton, kapok, milkweed, and coconut
coir are non-limiting examples of seed hair fibers.
[0032] Further, trichome fibers are different from nonwood bast
and/or core fibers in that they are not attached to the bast, also
known as phloem, or the core, also known as xylem portions of a
nonwood dicotyledonous plant stem. Non-limiting examples of plants
which have been used to yield nonwood bast fibers and/or nonwood
core fibers include kenaf, jute, flax, ramie and hemp.
[0033] Further trichome fibers are different from monocotyledonous
plant derived fibers such as those derived from cereal straws
(wheat, rye, barley, oat, etc), stalks (corn, cotton, sorghum,
Hesperaloe funifera, etc.), canes (bamboo, bagasse, etc.), grasses
(esparto, lemon, sabai, switchgrass, etc), since such
monocotyledonous plant derived fibers are not attached to an
epidermis of a plant.
[0034] Further, trichome fibers are different from leaf fibers in
that they do not originate from within the leaf structure. Sisal
and abaca are sometimes liberated as leaf fibers.
[0035] Finally, trichome fibers are different from wood pulp fibers
since wood pulp fibers are not outgrowths from the epidermis of a
plant; namely, a tree. Wood pulp fibers rather originate from the
secondary xylem portion of the tree stem.
[0036] "Fiber" as used herein means an elongate physical structure
having an apparent length greatly exceeding its apparent diameter,
i.e. a length to diameter ratio of at least about 10. Fibers having
a non-circular cross-section and/or tubular shape are common; the
"diameter" in this case may be considered to be the diameter of a
circle having cross-sectional area equal to the cross-sectional
area of the fiber. More specifically, as used herein, "fiber"
refers to fibrous structure-making fibers. The present invention
contemplates the use of a variety of fibrous structure-making
fibers, such as, for example, natural fibers, such as trichome
fibers and/or wood pulp fibers, or synthetic fibers, or any other
suitable fibers, and any combination thereof.
[0037] Natural fibrous structure-making fibers useful in the
present invention include animal fibers, mineral fibers, other
plant fibers (in addition to the trichomes of the present
invention) and mixtures thereof. Animal fibers may, for example, be
selected from the group consisting of: wool, silk and mixtures
thereof. The other plant fibers may, for example, be derived from a
plant selected from the group consisting of: wood, cotton, cotton
linters, flax, sisal, abaca, hemp, hesperaloe, jute, bamboo,
bagasse, kudzu, corn, sorghum, gourd, agave, loofah and mixtures
thereof.
[0038] Wood fibers; often referred to as wood pulps include
chemical pulps, such as kraft (sulfate) and sulfite pulps, as well
as mechanical and semi-chemical pulps including, for example,
groundwood, thermomechanical pulp, chemi-mechanical pulp (CMP),
chemi-thermomechanical pulp (CTMP), neutral semi-chemical sulfite
pulp (NSCS). 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 and/or layered 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.
[0039] The wood pulp fibers may be short (typical of hardwood
fibers) or long (typical of softwood fibers). Non-limiting examples
of short fibers include fibers 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, and Magnolia. Non-limiting examples of long
fibers include fibers derived from Pine, Spruce, Fir, Tamarack,
Hemlock, Cypress, and Cedar. Softwood fibers derived from the kraft
process and originating from more-northern climates may be
preferred. These are often referred to as northern softwood kraft
(NSK) pulps.
[0040] Synthetic fibers may be selected from the group consisting
of: wet spun fibers, dry spun fibers, melt spun (including melt
blown) fibers, synthetic pulp fibers and mixtures thereof.
Synthetic fibers may, for example, be comprised of cellulose (often
referred to as "rayon"); cellulose derivatives such as esters,
ether, or nitrous derivatives; polyolefins (including polyethylene
and polypropylene); polyesters (including polyethylene
terephthalate); polyamides (often referred to as "nylon");
acrylics; non-cellulosic polymeric carbohydrates (such as starch,
chitin and chitin derivatives such as chitosan); polylactic acids,
polyhydroxyalkanoates, polycaprolactones, and mixtures thereof. In
one example, synthetic fibers may be used as binding agents.
[0041] The web (fibrous structure) of the present invention may
comprise fibers, films and/or foams that comprises a hydroxyl
polymer and optionally a crosslinking system. Non-limiting examples
of suitable hydroxyl polymers include polyols, such as polyvinyl
alcohol, polyvinyl alcohol derivatives, polyvinyl alcohol
copolymers, starch, starch derivatives, chitosan, chitosan
derivatives, cellulose derivatives such as cellulose ether and
ester derivatives, gums, arabinans, galactans, proteins and various
other polysaccharides and mixtures thereof. For example, a web of
the present invention may comprise a continuous or substantially
continuous fiber comprising a starch hydroxyl polymer and a
polyvinyl alcohol hydroxyl polymer produced by dry spinning and/or
solvent spinning (both unlike wet spinning into a coagulating bath)
a composition comprising the starch hydroxyl polymer and the
polyvinyl alcohol hydroxyl polymer.
[0042] "Fiber Length", "Average Fiber Length" and "Weighted Average
Fiber Length", are terms used interchangeably herein all intended
to represent the "Length Weighted Average Fiber Length" as
determined for example by means of a Kajaani FiberLab Fiber
Analyzer commercially available from Metso Automation, Kajaani
Finland. The instructions supplied with the unit detail the formula
used to arrive at this average. The recommended method for
measuring fiber length using this instrument is essentially the
same as detailed by the manufacturer of the FiberLab in its
operation manual. The recommended consistencies for charging to the
FiberLab 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, fiber length may be
determined by sending the short fibers to a contract lab, such as
Integrated Paper Services, Appleton, Wis.
[0043] Fibrous structures may be comprised of a combination of long
fibers and short fibers.
[0044] Non-limiting examples of suitable long fibers for use in the
present invention include fibers that exhibit an average fiber
length of less than about 7 mm and/or less than about 5 mm and/or
less than about 3 mm and/or less than about 2.5 mm and/or from
about 1 mm to about 5 mm and/or from about 1.5 mm to about 3 mm
and/or from about 1.8 mm to about 4 mm and/or from about 2 mm to
about 3 mm.
[0045] Non-limiting examples of suitable short fibers suitable for
use in the present invention include fibers that exhibit an average
fiber length of less than about 5 mm and/or less than about 3 mm
and/or less than about 1.2 mm and/or less than about 1.0 mm and/or
from about 0.4 mm to about 5 mm and/or from about 0.5 mm to about 3
mm and/or from about 0.5 mm to about 1.2 mm and/or from about 0.6
mm to about 1.0 mm.
[0046] The invidividualizes trichomes used in the present invention
may include trichome fibers. The trichome fibers may be
characterized as either long fibers or short fibers.
[0047] "Fibrous structure" as used herein means a structure that
comprises one or more fibers. Non-limiting examples of processes
for making fibrous structures include known wet-laid papermaking
processes and air-laid papermaking processes. Such processes
typically include steps of preparing a fiber composition in the
form of a suspension in a medium, either wet, more specifically
aqueous medium, or dry, more specifically gaseous, i.e. with air as
medium. The aqueous medium used for wet-laid processes is
oftentimes referred to as a fiber slurry. The fibrous suspension is
then used to deposit a plurality of fibers onto a forming wire or
belt such that an embryonic fibrous structure is formed, after
which drying and/or bonding the fibers together results in a
fibrous structure. Further processing the fibrous structure may be
carried out such that a finished fibrous structure is formed. For
example, in typical papermaking processes, the finished fibrous
structure is the fibrous structure that is wound on the reel at the
end of papermaking, and may subsequently be converted into a
finished product, e.g. a sanitary tissue product.
[0048] Non-limiting types of fibrous structures according to the
present invention include conventionally felt-pressed fibrous
structures; pattern densified fibrous structures; and high-bulk,
uncompacted fibrous structures. The fibrous structures may be of a
homogenous or multilayered (two or three or more layers)
construction; and the sanitary tissue products made therefrom may
be of a single-ply or multi-ply construction.
[0049] In one example, the fibrous structure of the present
invention is a pattern densified fibrous structure characterized by
having a relatively high-bulk region of relatively low fiber
density and an array of densified regions of relatively high fiber
density. The high-bulk field is characterized as a field of pillow
regions. The densified zones are referred to as knuckle regions.
The knuckle regions exhibit greater density than the pillow
regions. The densified zones may be discretely spaced within the
high-bulk field or may be interconnected, either fully or
partially, within the high-bulk field. Typically, from about 8% to
about 65% of the fibrous structure surface comprises densified
knuckles, the knuckles may exhibit a relative density of at least
125% of the density of the high-bulk field. Processes for making
pattern densified fibrous structures are well known in the art as
exemplified in U.S. Pat. Nos. 3,301,746, 3,974,025, 4,191,609 and
4,637,859.
[0050] The fibrous structures comprising a trichome in accordance
with the present invention may be in the form of through-air-dried
fibrous structures, differential density fibrous structures,
differential basis weight fibrous structures, wet laid fibrous
structures, air laid fibrous structures (examples of which are
described in U.S. Pat. Nos. 3,949,035 and 3,825,381), conventional
dried fibrous structures, creped or uncreped fibrous structures,
patterned-densified or non-patterned-densified fibrous structures,
compacted or uncompacted fibrous structures, nonwoven fibrous
structures comprising synthetic or multicomponent fibers,
homogeneous or multilayered fibrous structures, double re-creped
fibrous structures, foreshortened fibrous structures, co-form
fibrous structures (examples of which are described in U.S. Pat.
No. 4,100,324) and mixtures thereof.
[0051] In one example, the air laid fibrous structure is selected
from the group consisting of thermal bonded air laid (TBAL) fibrous
structures, latex bonded air laid (LBAL) fibrous structures and
mixed bonded air laid (MBAL) fibrous structures.
[0052] The fibrous structures may exhibit a substantially uniform
density or may exhibit differential density regions, in other words
regions of high density compared to other regions within the
patterned fibrous structure. Typically, when a fibrous structure is
not pressed against a cylindrical dryer, such as a Yankee dryer,
while the fibrous structure is still wet and supported by a
through-air-drying fabric or by another fabric or when an air laid
fibrous structure is not spot bonded, the fibrous structure
typically exhibits a substantially uniform density.
[0053] "Sanitary tissue product" as used herein means a soft, low
density (i.e. <about 0.15 g/cm.sup.3) web useful as a wiping
implement for post-urinary and post-bowel movement cleaning (toilet
tissue), for otorhinolaryngological discharges (facial tissue), and
multi-functional absorbent and cleaning uses (absorbent towels).
The sanitary tissue product may be convolutedly wound upon itself
about a core or without a core to form a sanitary tissue product
roll.
[0054] In one example, the sanitary tissue product of the present
invention comprises a fibrous structure according to the present
invention.
[0055] The sanitary tissue products of the present invention may
exhibit a basis weight between about 10 g/m.sup.2 to about 120
g/m.sup.2 and/or from about 15 g/m.sup.2 to about 110 g/m.sup.2
and/or from about 20 g/m.sup.2 to about 100 g/m.sup.2 and/or from
about 30 to 90 g/m.sup.2. In addition, the sanitary tissue product
of the present invention may exhibit a basis weight between about
40 g/m.sup.2 to about 120 g/m.sup.2 and/or from about 50 g/m.sup.2
to about 110 g/m.sup.2 and/or from about 55 g/m.sup.2 to about 105
g/m.sup.2 and/or from about 60 to 100 g/m.sup.2 as measured
according to the Basis Weight Test Method described herein.
[0056] The sanitary tissue products of the present invention may
exhibit a total dry tensile of at least 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 as measured according to the Total Dry Tensile Test Method
described herein.
[0057] In another example, the sanitary tissue product of the
present invention may exhibit a total dry tensile of at least 300
g/in and/or at least 350 g/in and/or at least 400 g/in and/or at
least 450 g/in and/or at least 500 g/in and/or from about 500 g/in
to about 1000 g/in and/or from about 550 g/in to about 850 g/in
and/or from about 600 g/in to about 800 g/in as measured according
to the Total Dry Tensile Test Method described herein. In one
example, the sanitary tissue product exhibits a total dry tensile
strength of less than 1000 g/in and/or less than 850 g/in as
measured according to the Total Dry Tensile Test Method described
herein.
[0058] In another example, the sanitary tissue products of the
present invention may exhibit a total dry tensile of at least 500
g/in and/or at least 600 g/in and/or at least 700 g/in and/or at
least 800 g/in and/or at least 900 g/in and/or at least 1000 g/in
and/or from about 800 g/in to about 5000 g/in and/or from about 900
g/in to about 3000 g/in and/or from about 900 g/in to about 2500
g/in and/or from about 1000 g/in to about 2000 g/in as measured
according to the Total Dry Tensile Test Method described
herein.
[0059] "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 sanitary tissue 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) is measured. 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).
[0060] "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.
[0061] 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:
[0062] 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;
[0063] 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;
[0064] 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:
[0065] 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.
[0066] 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.
Trichomes
[0067] Essentially all plants have trichomes. Those skilled in the
art will recognize that some plants will have trichomes of
sufficient mass fraction and/or the overall growth rate and/or
robustness of the plant so that they may offer attractive
agricultural economy to make them more suitable for a large
commercial process, such as using them as a source of chemicals,
e.g. cellulose, or assembling them into fibrous structures, such as
disposable fibrous structures. Trichomes may have a wide range of
morphology and chemical properties. For example, the trichomes may
be in the form of fibers; namely, trichome fibers. Such trichome
fibers may have a high length to diameter ratio.
[0068] The following sources are offered as non-limiting examples
of trichome-bearing plants (suitable sources) for obtaining
trichomes, especially trichome fibers.
[0069] Non-limiting examples of suitable sources for obtaining
trichomes, especially trichome fibers, are plants in the Labiatae
(Lamiaceae) family commonly referred to as the mint family.
[0070] Examples of suitable species in the Labiatae family include
Stachys byzantina, also known as Stachys lanata commonly referred
to as lamb's ear, woolly betony, or woundwort. The term Stachys
byzantina as used herein also includes cultivars Stachys byzantina
`Primrose Heron`, Stachys byzantina `Helene von Stein` (sometimes
referred to as Stachys byzantina `Big Ears`), Stachys byzantina
`Cotton Boll`, Stachys byzantina `Variegated` (sometimes referred
to as Stachys byzantina `Striped Phantom`), and Stachys byzantina
`Silver Carpet`.
[0071] Additional examples of suitable species in the Labiatae
family include the arcticus subspecies of Thymus praecox, commonly
referred to as creeping thyme and the pseudolanuginosus subspecies
of Thymus praecox, commonly referred to as wooly thyme.
[0072] Further examples of suitable species in the Labiatae family
include several species in the genus Salvia (sage), including
Salvia leucantha, commonly referred to as the Mexican bush sage;
Salvia tarahumara, commonly referred to as the grape scented Indian
sage; Salvia apiana, commonly referred to as white sage; Salvia
funereal, commonly referred to as Death Valley sage; Salvia
sagittata, commonly referred to as balsamic sage; and Salvia
argentiae, commonly referred to as silver sage.
[0073] Even further examples of suitable species in the Labiatae
family include Lavandula lanata, commonly referred to as wooly
lavender; Marrubium vulgare, commonly referred to as horehound;
Plectranthus argentatus, commonly referred to as silver shield; and
Plectranthus tomentosa.
[0074] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers are plants in the
Asteraceae family commonly referred to as the sunflower family.
[0075] Examples of suitable species in the Asteraceae family
include Artemisia stelleriana, also known as silver brocade;
Haplopappus macronema, also known as the whitestem goldenbush;
Helichrysum petiolare; Centaurea maritime, also known as Centaurea
gymnocarpa or dusty miller; Achillea tomentosum, also known as
wooly yarrow; Anaphalis margaritacea, also known as pearly
everlasting; and Encelia farinose, also known as brittle bush.
[0076] Additional examples of suitable species in the Asteraceae
family include Senecio brachyglottis and Senecio haworthii, the
latter also known as Kleinia haworthii.
[0077] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers, are plants in the
Scrophulariaceae family commonly referred to as the figwort or
snapdragon family.
[0078] An example of a suitable species in the Scrophulariaceae
family includes Pedicularis kanei, also known as the wooly
lousewort.
[0079] Additional examples of suitable species in the
Scrophulariaceae family include the mullein species (Verbascum)
such as Verbascum hybridium, also known as snow maiden; Verbascum
thapsus, also known as common mullein; Verbascum baldaccii;
Verbascum bombyciferum; Verbascum broussa; Verbascum chaixii;
Verbascum dumulsum; Verbascum laciniatum; Verbascum lanatum;
Verbascum longifolium; Verbascum lychnitis; Verbascum olympicum;
Verbascum paniculatum; Verbascum phlomoides; Verbascum phoeniceum;
Verbascum speciosum; Verbascum thapsiforme; Verbascum virgatum;
Verbascum wiedemannianum; and various mullein hybrids including
Verbascum `Helen Johnson` and Verbascum `Jackie`.
[0080] Further examples of suitable species in the Scrophulariaceae
family include Stemodia tomentosa and Stemodia durantifolia.
[0081] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include Greyia
radlkoferi and Greyia flanmaganii plants in the Greyiaceae family
commonly referred to as the wild bottlebrush family.
[0082] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include members of
the Fabaceae (legume) family. These include the Glycine max,
commonly referred to as the soybean, and Trifolium pratense L,
commonly referred to as medium and/or mammoth red clover.
[0083] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include members of
the Solanaceae family including varieties of Lycopersicum
esculentum, otherwise known as the common tomato.
[0084] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include members of
the Convolvulaceae (morning glory) family, including Argyreia
nervosa, commonly referred to as the wooly morning glory and
Convolvulus cneorum, commonly referred to as the bush morning
glory.
[0085] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include members of
the Malvaceae (mallow) family, including Anoda cristata, commonly
referred to as spurred anoda and Abutilon theophrasti, commonly
referred to as velvetleaf.
[0086] Non-limiting examples of other suitable sources for
obtaining trichomes, especially trichome fibers include Buddleia
marrubiifolia, commonly referred to as the wooly butterfly bush of
the Loganiaceae family; the Casimiroa tetrameria, commonly referred
to as the wooly leafed sapote of the Rutaceae family; the Ceanothus
tomentosus, commonly referred to as the wooly leafed mountain
liliac of the Rhamnaceae family; the `Philippe Vapelle` cultivar of
renardii in the Geraniaceae (geranium) family; the Tibouchina
urvilleana, commonly referred to as the Brazilian spider flower of
the Melastomataceae family; the Tillandsia recurvata, commonly
referred to as ballmoss of the Bromeliaceae (pineapple) family; the
Hypericum tomentosum, commonly referred to as the wooly St. John's
wort of the Hypericaceae family; the Chorizanthe orcuttiana,
commonly referred to as the San Diego spineflower of the
Polygonaceae family; Eremocarpus setigerus, commonly referred to as
the doveweed of the Euphorbiaceae or spurge family; Kalanchoe
tomentosa, commonly referred to as the panda plant of the
Crassulaceae family; and Cynodon dactylon, commonly referred to as
Bermuda grass, of the Poaceae family; and Congea tomentosa,
commonly referred to as the shower orchid, of the Verbenaceae
family.
[0087] Suitable trichome-bearing plants are commercially available
from nurseries and other plant-selling commercial venues. For
example, Stachys byzantina may be purchased and/or viewed at
Blanchette Gardens, Carlisle, Mass.
[0088] The trichome-bearing material may be subjected to a
mechanical process to liberate its trichomes from its plant
epidermis to enrich the pulp or fiber mass' content of
individualized trichomes. This may be carried out by means of
screening or air classifying equipment well known in the art. A
suitable air classifier is the Hosokawa Alpine 50ATP, sold by
Hosokawa Micron Powder Systems of Summit, N.J. Other suitable
classifiers are available from the Minox Siebtechnik.
[0089] In one example, a trichome suitable for use in the fibrous
structures of the present invention comprises cellulose.
[0090] In yet another example, a trichome suitable for use in the
fibrous structures of the present invention comprises a fatty
acid.
[0091] In still another example, a trichome suitable for use in the
fibrous structures of the present invention is hydrophobic.
[0092] In yet another example, a trichome suitable for use in the
fibrous structures of the present invention is less hydrophilic
that softwood fibers. This characteristic of the trichome may
facilitate a reduction in drying temperatures needed to dry fibrous
structures comprising such trichome and/or may facilitate making
the fibrous structures containing such trichome at a faster
rate.
[0093] As shown in FIG. 1, numerous trichomes 10 are present on
this red clover leaf and leaf stem. FIG. 2 shows numerous trichomes
10 present on a red clover lower stem.
[0094] As shown in FIG. 3, a dusty miller leaf is contains numerous
trichomes 10. FIG. 4 shows individualized trichomes 10' obtained
from a dusty miller leaf.
[0095] As shown in FIG. 5, a basal leaf on a silver sage contains
numerous trichomes 10. FIG. 6 shows trichomes 10 present on a
bloom-stalk leaf of a silver sage.
[0096] As shown in FIG. 7, trichomes 10 are present on a mature
leaf of common mullein. FIG. 8 shows trichomes 10 present on a
juvenile leaf of common mullein.
[0097] FIG. 9 shows, via a perpendicular view, trichomes 10 present
on a leaf of wooly betony. FIG. 10 is a cross-sectional view of a
leaf of wooly betony containing trichomes 10. FIG. 11 shows
individualized trichomes 10' obtained from a wooly betony leaf.
[0098] Table 1 below shows a comparison of fiber morphology for a
hardwood fiber (Eucalyptus pulp fiber), a softwood fiber (NSK pulp
fiber) and a trichome fiber.
TABLE-US-00001 TABLE 1 Property Eucalyptus Fiber NSK Fiber Trichome
Fiber Fiber Length (mm) 0.76 2.18 1.352 Fiber Width (.mu.m) 19.1
27.6 18.1 Coarseness (mg/m) 0.0895 0.1386 0.0995 Bendability 3.4
6.4 0.5 Kinks/mm 0.82 0.47 0.77 Kajaani Cell Wall 6.6 9.6 6.44
[0099] As is evident from Table 1, trichome fibers are greater in
length than Eucalyptus fibers, but shorter than NSK fibers.
However, other properties of trichome fibers are more closely
associated with properties of Eucalyptus fibers than to NSK
fibers.
Fibrous Structures
[0100] The fibrous structures of the present invention may comprise
greater than 50% and/or greater than 75% and/or greater than 90%
and/or 100% or less by weight on a dry fiber basis of pulp
fibers.
[0101] In one example, the fibrous structures of the present
invention comprise less than 22% and/or less than 21% and/or less
than 20% and/or less than 19% and/or less than 18% and/or to about
5% and/or to about 7% and/or to about 10% and/or to about 12%
and/or to about 15% by weight on a dry fiber basis of softwood
fibers.
[0102] In one example, the fibrous structures of the present
invention may exhibit a basis weight between about 10 g/m.sup.2 to
about 120 g/m.sup.2 and/or from about 15 g/m.sup.2 to about 110
g/m.sup.2 and/or from about 20 g/m.sup.2 to about 100 g/m.sup.2
and/or from about 30 to 90 g/m.sup.2. In addition, the sanitary
tissue product of the present invention may exhibit a basis weight
between about 40 g/m.sup.2 to about 120 g/m.sup.2 and/or from about
50 g/m.sup.2 to about 110 g/m.sup.2 and/or from about 55 g/m.sup.2
to about 105 g/m.sup.2 and/or from about 60 to 100 g/m.sup.2 as
measured according to the Basis Weight Test Method described
herein.
[0103] In another example, the fibrous structures of the present
invention may exhibit a basis weight of at least 21 g/m.sup.2
and/or at least 23 g/m.sup.2 and/or at least 25 g/m.sup.2.
[0104] In yet another example, the fibrous structures of the
present invention may comprise a plurality of pulp fibers, wherein
greater than 0% but less than 20% by weight on a dry fiber basis of
the pulp fibers are softwood fibers and wherein the fibrous
structure comprises pulp fibers derived from a pulp fiber-producing
source that has a growing cycle of less than 800 and/or every 400
and/or every 200 and/or every 100 or less days.
[0105] The fibrous structures of the present invention may comprise
one or more individualized trichomes, especially trichome fibers.
In one example, a trichome fiber suitable for use in the fibrous
structures of the present invention exhibit a fiber length of from
about 100 .mu.m to about 7000 .mu.m and a width of from about 3
.mu.m to about 30 .mu.m.
[0106] In addition to a trichome, other fibers and/or other
ingredients may also be present in the fibrous structures of the
present invention.
[0107] Fibrous structures according to this invention may contain
from about 0.1% to about 100% and/or from about 0.5% to about 90%
and/or from about 0.5% to about 80% and/or from about 0.5% to about
50% and/or from about 1% to about 40% and/or from about 2% to about
30% and/or from about 5% to about 25% by weight on a dry fiber
basis of trichome fibers.
[0108] In addition to a trichome, the fibrous structure may
comprise other additives, such as wet strength additives, softening
additives, solid additives (such as starch, clays), dry strength
resins, wetting agents, lint resisting and/or reducing 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 other additives may be added to the fiber furnish,
the embryonic fibrous web and/or the fibrous structure.
[0109] Such other additives may be present in the fibrous structure
at any level based on the dry weight of the fibrous structure.
[0110] The other additives may be present in the 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 fibrous structure basis.
[0111] The fibrous structures of the present invention may be
subjected to any suitable post processing including, but not
limited to, printing, embossing, calendaring, slitting, folding,
combining with other fibrous structures, and the like.
[0112] Table 2 below shows a comparison of fibrous structures
according to the present invention that comprise trichome fibers
that have been classified using a classifier from Minox Siebtechnik
and a control fibrous structure without any trichome fibers.
TABLE-US-00002 TABLE 2 2.5% 5% 7.5% Control Trichome Trichome
Trichome Property 1 Fibers Fibers Fibers Basis Weight 29.4 29.2
29.0 30.0 Softwood/Hardwood/ 26/74/0 19/78.5/2.5 17/78/5
17/75.5/7.5 Trichome (%) Total Dry Tensile 550.7 550.7 535.3 663.3
(g/in) Softness (PSU) 0.5 1.06 1.49 1.39
[0113] Table 3 below shows a comparison of fibrous structures
according to the present invention that comprise trichome fibers
that have been classified using a classifier from Hosokawa and a
control fibrous structure without any trichome fibers.
TABLE-US-00003 TABLE 3 2.5% 5% 7.5% Control Trichome Trichome
Trichome Property 1 Fibers Fibers Fibers Basis Weight 28.9 28.8
28.1 28.6 Softwood/Hardwood/ 24/76/0 19/78.5/2.5 17/78/5
18/74.5/7.5 Trichome (%) Total Dry Tensile 566.0 523.0 523.0 544.7
(g/in) Softness (PSU) -0.44 0.67 1.05 1.66
[0114] As shown in Tables 2 and 3, the use of trichome fibers in
the fibrous structure making process permits the reduction of
softwood fibers in the fibrous structure. In one example, the
inclusion of trichome fibers permits at least a 5% by weight on a
dry fiber basis reduction of softwood fibers while maintaining a
total dry tensile strength of greater than 500 g/in and/or greater
than 520 g/in and increasing the softness (PSU) to at least 0.67
and/or at least 1.00.
[0115] In one example, the replacement of softwood fibers with
trichome fibers produces a fibrous structure and/or sanitary tissue
product that exhibits a softness (PSU) increase of at least 0.5
and/or at least 0.67 and/or at least 1.00 compared to the same
fibrous structure and/or sanitary tissue product without the
trichome fibers.
[0116] In addition to the reduction of softwood fibers, the
inclusion of trichome fibers, may result, especially when they are
added to an outer layer or in a homogeneous fibrous structure, in a
surface that has a "fuzzy" feel to consumers. In addition, the
trichome fibers may also provide surface smoothness increases,
strength increases and flexibility increases to the fibrous
structures. The trichome fibers in one example at 5% inclusion,
results in a reduction of Slip-and-Stick Coefficient of Friction of
at least 15% and/or at least 17% and/or at least 20% and/or at
least 22% as shown in Table 4 below. These Slip-and-Stick
Coefficients of Friction are significant and large and indicate a
very smooth surface feel versus substrates without trichome
fibers.
TABLE-US-00004 TABLE 4 CONTROL W/O WITH TRICHOME TRICHOME % FIBERS
(AVG) FIBERS (AVG) change COF frit kinetic-out 0.968 0.770 20.41%
COF frit kinetic-in 1.003 0.784 21.80% COF frit kinetic-AVG 0.985
0.777 21.12% COF frit slipstick-out 250 201 19.60% COF frit
slipstick-in 281 194 30.84% COF frit slipstick-AVG 265 198 25.54%
COF kinetic*slipstick 261 153 41.27%
Processes for Making Trichome-Containing Fibrous Structures
[0117] Any suitable process for making fibrous structures known in
the art may be used to make trichome-containing fibrous structures
of the present invention.
[0118] In one example, the trichome-containing fibrous structures
of the present invention are made by a wet laid fibrous structure
making process.
[0119] In another example, the trichome-containing fibrous
structures of the present invention are made by an air laid fibrous
structure making process.
[0120] In one example, a trichome-containing fibrous structure is
made by the process comprising the steps of: a) preparing a fiber
furnish (slurry) by mixing a trichome with water; b) depositing the
fiber furnish on a foraminous forming surface to form an embryonic
fibrous web; and c) drying the embryonic fibrous web.
[0121] In one example, a fiber furnish comprising a trichome, such
as a trichome fiber, is deposited onto a foraminuous forming
surface via a headbox.
NON-LIMITING EXAMPLES
Example 1
Fibrous Structure without Trichomes
[0122] The following example illustrates a non-limiting example for
the preparation of a non-trichome containing fibrous structure on a
pilot-scale Fourdrinier paper making machine.
[0123] A sheet with 33%.times.34%.times.33% layering consist of
fabric layer, center layer and wire layer. The entire sheet has 70%
by weight on a dry fiber basis of Eucalyptus and 30% by weight on a
dry fiber basis of NSK pulp fibers is made.
[0124] An aqueous slurry of eucalyptus fibers is prepared at about
3% by weight using a conventional repulper. Separately, an aqueous
slurry of NSK fibers of about 3% by weight is made up using a
conventional repulper.
[0125] In order to impart temporary wet strength to the finished
fibrous structure, a 1% dispersion of temporary wet strengthening
additive (e.g., Parez.RTM. commercially available from Kemira) is
prepared and is added to the NSK fiber stock pipe at a rate
sufficient to deliver 0.3% temporary wet strengthening additive
based on the dry weight of the NSK fibers. The absorption of the
temporary wet strengthening additive is enhanced by passing the
treated slurry through an in-line mixer.
[0126] The eucalyptus fiber slurry is diluted with white water at
the inlet of a fan pump to a consistency of about 0.15% based on
the total weight of the eucalyptus fiber slurry. The NSK fibers,
likewise, are diluted with white water at the inlet of a fan pump
to a consistency of about 0.15% based on the total weight of the
NSK fiber slurry. The eucalyptus fiber slurry and the NSK fiber
slurry are both directed to a layered headbox capable of
maintaining the slurries as separate streams until they are
deposited onto a forming fabric on the Fourdrinier.
[0127] "DC 2310" (Dow Corning, Midland, Mich.) antifoam is dripped
into the wirepit to control foam to maintain whitewater levels of
10 ppm.
[0128] The paper making machine has a layered headbox with a top
chamber, a center chamber, and a bottom chamber. The eucalyptus
fiber slurry is pumped through the top and bottom headbox chambers
and, simultaneously, the NSK fiber slurry is pumped through the
center headbox chamber and delivered in superposed relation onto a
Fourdrinier wire to form thereon a three-layer embryonic web, of
which about 70% is made up of the eucalyptus fibers and about 30%
is made up of the NSK fibers. Dewatering occurs through the
Fourdrinier wire and is assisted by a deflector and vacuum boxes.
The Fourdrinier wire is of a 5-shed, satin weave configuration
having 87 machine-direction and 76 cross-machine-direction
monofilaments per inch, respectively. The speed of the Fourdrinier
wire is about 750 fpm (feet per minute).
[0129] 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 speed of the patterned drying
fabric is about the same as the speed of the Fourdrinier wire. 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
98.times.62 filament, dual layer mesh. The thickness of the resin
cast is about 12 mils above the supporting fabric. A suitable
process for making the patterned drying fabric is described in
published application US 2004/0084167 A1.
[0130] Further de-watering is accomplished by vacuum assisted
drainage until the web has a fiber consistency of about 30%.
[0131] While remaining in contact with the patterned drying fabric,
the web is pre-dried by air blow-through pre-dryers to a fiber
consistency of about 65% by weight.
[0132] After the pre-dryers, the semi-dry web is transferred to the
Yankee dryer and adhered to the surface of the Yankee dryer with a
sprayed creping adhesive. The creping adhesive is an aqueous
dispersion with the actives consisting of about 22% polyvinyl
alcohol, about 11% CREPETROL A3025, and about 67% CREPETROL R6390.
CREPETROL A3025 and CREPETROL R6390 are commercially available from
Hercules Incorporated of Wilmington, Del. The creping adhesive is
delivered to the Yankee surface at a rate of about 0.15% adhesive
solids based on the dry weight of the web. The fiber consistency is
increased to about 97% before the web is dry creped from the Yankee
with a doctor blade.
[0133] 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. and a speed of about 800 fpm.
The fibrous structure is wound in a roll using a surface driven
reel drum having a surface speed of about 656 feet per minute. The
fibrous structure may be subsequently converted into a two-ply
sanitary tissue product having a basis weight of about 50 lbs/3000
ft.sup.2.
[0134] The resulting total dry tensile strength for the fibrous
structure product having no trichomes is 566 g/in.
Example 2
Fibrous Structure with Trichome Fibers
[0135] This following example illustrates a non-limiting example
for the preparation of a fibrous structure according to the present
invention on a pilot-scale Fourdrinier paper making machine with
the addition of trichome fibers providing a strength increase.
[0136] The following Example illustrates a non-limiting example for
the preparation of sanitary tissue product comprising a fibrous
structure according to the present invention on a pilot-scale
Fourdrinier fibrous structure making machine.
[0137] Individualized trichome are first prepared from Stachys
byzantina bloom stalks consisting of the dried stems, leaves, and
pre-flowering buds, by passing dried Stachys byzantina plant matter
through a knife cutter (Wiley mill, manufactured by the C. W.
Brabender Co. located in South Hackensack, N.J.) equipped with an
attrition screen having 1/4'' holes. Exiting the Wiley mill is a
composite fluff constituting the individualized trichome fibers
together with chunks of leaf and stem material. The individualized
trichome fluff is then passed through an air classifier (Hosokawa
Alpine 50ATP); the "accepts" or "fine" fraction from the classifier
is greatly enriched in individualized trichome fibers while the
"rejects" or "coarse" fraction is primarily chunks of stalks, and
leaf elements with only a minor fraction of individualized trichome
fibers. A squirrel cage speed of 9000 rpm, an air pressure
resistance of 10-15 mbar, and a feed rate of about 10 g/min are
used on the 50 ATP. The resulting individualized trichome material
(fines) is mixed with a 10% aqueous dispersion of "Texcare 4060" to
add about 10% by weight "Texcare 4060" by weight of the bone dry
weight of the individualized trichomes followed by slurrying the
"Texcare"-treated trichome in water at 3% consistency using a
conventional repulper. This slurry is passed through a stock pipe
toward another stock pipe containing a eucalyptus fiber slurry.
[0138] Special care must be taken while processing the trichomes.
60 lbs. of trichome fiber is pulped in a 50 gallon pulper by adding
water in half amount required to make a 1% trichome fiber slurry.
This is done to prevent trichome fibers over flowing and floating
on surface of the water due to lower density and hydrophobic nature
of the trichome fiber. After mixing and stirring a few minutes, the
pulper is stopped and the remaining trichome fibers are pushed in
while water is added. After pH adjustment, it is pulped for 20
minutes, then dumped in a separate chest for delivery onto the
machine headbox. This allows one to place trichome fibers in one or
more layers, alone or mixed with other fibers, such as hardwood
fibers and/or softwood fibers. During this particular run, the
trichome fibers are added exclusively on the wire outer layer as
the product is converted wire side up; therefore it is desirable to
add the trichome fibers to the wire side (the side where the
tactile feel senses paper the most).
[0139] The aqueous slurry of eucalyptus fibers is prepared at about
3% by weight using a conventional repulper. This slurry is also
passed through a stock pipe toward the stock pipe containing the
trichome fiber slurry.
[0140] The 1% trichome fiber slurry is combined with the 3%
eucalyptus fiber slurry in a proportion which yields about 13.3%
trichome fibers and 86.7% eucalyptus fibers. The stockpipe
containing the combined trichome and eucalyptus fiber slurries is
directed toward the wire layer of headbox of a Fourdrinier
machine.
[0141] Separately, an aqueous slurry of NSK fibers of about 3% by
weight is made up using a conventional repulper.
[0142] In order to impart temporary wet strength to the finished
fibrous structure, a 1% dispersion of temporary wet strengthening
additive (e.g., Parez.RTM. commercially available from Kemira) is
prepared and is added to the NSK fiber stock pipe at a rate
sufficient to deliver 0.3% temporary wet strengthening additive
based on the dry weight of the NSK fibers. The absorption of the
temporary wet strengthening additive is enhanced by passing the
treated slurry through an in-line mixer.
[0143] The trichome fiber and eucalyptus fiber slurry is diluted
with white water at the inlet of a fan pump to a consistency of
about 0.15% based on the total weight of the eucalyptus and
trichome fiber slurry. The NSK fibers, likewise, are diluted with
white water at the inlet of a fan pump to a consistency of about
0.15% based on the total weight of the NSK fiber slurry. The
eucalyptus/trichome fiber slurry and the NSK fiber slurry are both
directed to a layered headbox capable of maintaining the slurries
as separate streams until they are deposited onto a forming fabric
on the Fourdrinier.
[0144] "DC 2310" antifoam is dripped into the wirepit to control
foam to maintain whitewater levels of 10 ppm of antifoam.
[0145] The fibrous structure making machine has a layered headbox
having a top chamber, a center chamber, and a bottom chamber. The
eucalyptus/trichome combined fiber slurry is pumped through the top
headbox chamber, eucalyptus fiber slurry is pumped through the
bottom headbox chamber, and, simultaneously, the NSK fiber slurry
is pumped through the center headbox chamber and delivered in
superposed relation onto the Fourdrinier wire to form thereon a
three-layer embryonic web, of which about 83% is made up of the
eucalyptus/trichome fibers and 17% is made up of the NSK fibers.
Dewatering occurs through the Fourdrinier wire and is assisted by a
deflector and vacuum boxes. The Fourdrinier wire is of a 5-shed,
satin weave configuration having 87 machine-direction and 76
cross-machine-direction monofilaments per inch, respectively. The
speed of the Fourdrinier wire is about 750 fpm (feet per
minute).
[0146] 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 speed of the patterned drying
fabric is the same as the speed of the Fourdrinier wire. 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 12 mils above the supporting fabric. A suitable
process for making the patterned drying fabric is described in
published application US 2004/0084167 A1.
[0147] Further de-watering is accomplished by vacuum assisted
drainage until the web has a fiber consistency of about 30%.
[0148] While remaining in contact with the patterned drying fabric,
the web is pre-dried by air blow-through pre-dryers to a fiber
consistency of about 65% by weight.
[0149] After the pre-dryers, the semi-dry web is transferred to the
Yankee dryer and adhered to the surface of the Yankee dryer with a
sprayed creping adhesive. The creping adhesive is an aqueous
dispersion with the actives consisting of about 22% polyvinyl
alcohol, about 11% CREPETROL A3025, and about 67% CREPETROL R6390.
CREPETROL A3025 and CREPETROL R6390 are commercially available from
Hercules Incorporated of Wilmington, Del. The creping adhesive is
delivered to the Yankee surface at a rate of about 0.15% adhesive
solids based on the dry weight of the web. The fiber consistency is
increased to about 97% before the web is dry creped from the Yankee
with a doctor blade.
[0150] 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. The fibrous structure is wound in a roll using a
surface driven reel drum having a surface speed of about 656 feet
per minute. The fibrous structure may be subsequently converted
into a two-ply sanitary tissue product having a basis weight of
about 50 g/m.sup.2.
[0151] 5% by weight of trichome fibers on the outer layer of the
sheet produced a product with considerable softness. To control
tensile, softwood fibers had to be removed by 7% to compensate for
5% addition of trichome fibers. The base product had a softness of
-0.44 PSU compared to our standard but the fibrous structure made
with trichome fibers had 1.05 PSU at a comparable wet and dry
tensile. Adjusting for the base softness deficit the condition with
trichome fibers softness would be at about 1.5 PSU. Other benefits
of trichome fiber addition is that the pre-dryer temperatures may
be reduced by at least 30.degree. F., and in one example at least
30.degree. F. to about 50.degree. F. This is a significant
temperature reduction that can be used for energy saving or
increase machine capacity if it is drying limited. In addition to
the benefits described above, the use of trichome fibers to reduce
the use of pulp fibers, especially softwood pulp fibers, in making
fibrous structures, such as sanitary tissue products, also has
environmental benefits, such as reducing carbon footprint of
fibrous structures, especially paper products that have
historically been made from wood pulp, by reducing the usage wood
pulp and thus tree usage while maintaining or increasing the
softness of the fibrous structures. In addition, as is always clear
from the above description, the use of trichome fibers in fibrous
structure breaks the strength/softness contradiction that has
historically plagued the fibrous structure, especially the sanitary
tissue product industry by increasing strength while increasing
softness of the fibrous structure.
[0152] The following table, Table 5, shows the results for the
fibrous structure of Example 2:
TABLE-US-00005 TABLE 5 Control (No 5% Trichome Trichome Fibers)
Fibers SW % used 24 17 Total Tensile (gm/in) 566 523 Softness -0.4
1.05
Test Methods
[0153] Unless otherwise specified, all tests described herein
including those described under the Definitions section and the
following test methods are conducted on samples that have been
conditioned in a conditioned room at a temperature of 73.degree.
F..+-.4.degree. F. (about 23.degree. C..+-.2.2.degree. C.) and a
relative humidity of 50%.+-.10% for 2 hours prior to the test. All
tests are conducted in such conditioned room. Do not test samples
that have defects such as wrinkles, tears, holes, and like.
Total Dry Tensile Strength Test Method
[0154] Cut at least eight 1 inch wide strips of the fibrous
structure and/or sanitary tissue product to be tested in the
machine direction. Cut at least eight 1 inch wide strips in the
cross direction. If the machine direction and cross direction are
not readily ascertainable, then the cross direction will be the
strips that result in the lower peak load tensile. For the wet
measurements, each sample is wetted by submerging the sample in a
distilled water bath for 30 seconds. The wet property of the wet
sample is measured within 30 seconds of removing the sample from
the bath.
[0155] For the actual measurements of the properties, use a
Thwing-Albert Intelect II Standard Tensile Tester (Thwing-Albert
Instrument Co. of Philadelphia, Pa.). Insert the flat face clamps
into the unit and calibrate the tester according to the
instructions given in the operation manual of the Thwing-Albert
Intelect II. Set the instrument crosshead speed to 4.00 in/min and
the 1st and 2nd gauge lengths to 4.00 inches. The break sensitivity
is set to 20.0 grams and the sample width is set to 1.00 inch. The
energy units are set to TEA and the tangent modulus (Modulus) trap
setting is set to 38.1 g.
[0156] After inserting the fibrous structure sample strip into the
two clamps, the instrument tension can be monitored. If it shows a
value of 5 grams or more, the fibrous structure sample strip is too
taut. Conversely, if a period of 2-3 seconds passes after starting
the test before any value is recorded, the fibrous structure sample
strip is too slack.
[0157] Start the tensile tester as described in the tensile tester
instrument manual. When the test is complete, read and record the
following with units of measure:
[0158] Peak Load Tensile (Tensile Strength) (g/in)
[0159] Peak Elongation (Elongation) (%)
[0160] Peak CD TEA (Wet CD TEA) (in-g/in.sup.2)
[0161] Tangent Modulus (Dry MD Modulus and Dry CD Modulus) (at 15
g/cm)
[0162] Test each of the samples in the same manner, recording the
above measured values from each test. Average the values for each
property obtained from the samples tested to obtain the reported
value for that property.
Total Dry Tensile (TDT)=Peak Load MD Tensile (g/in)+Peak Load CD
Tensile (g/in)
Slip-and-Stick Coefficient of Friction Test Method
[0163] The Slip-and-Stick Coefficient of Friction is defined as the
mean deviation of the coefficient of friction. It is dimensionless.
This test is performed on a KES-FB4 Surface Analyzer from Kato
Tekko Co. of Karato-Cho, Nishikiyo, Minami-Ku, Koyota, Japan, with
a modified friction probe. The probe sled is a two centimeter
diameter, 40 to 60 micron glass frit obtained from Ace Glass
Company. The normal force of the probe was 12.5 grams. The details
of the procedure are described in "Methods for the Measurement of
the Mechanical Properties of Tissue Paper" by Ampulski, et. al.,
1991 International Paper Physics Conference, page 19, incorporated
herein by reference. When a sample is scanned, the instrument
senses the lateral force on the stylus as the sample is scanned.
The lateral force is called the frictional force; and the ratio of
the frictional force to stylus weight is the coefficient of
friction, mu. The instrument then solves the following equation to
determine Slip-and-Stick Coefficient of Friction for each scan of
each sample.
Slip - and - Stick Coefficient of Friction = 1 / X .intg. 0 X m
.mu. avg - m .mu. x ##EQU00001##
in which m.mu. is the ratio of frictional force to probe loading;
m.mu..sub.avg is the average value of m.mu.; and X is 2 cm.
[0164] The samples are scanned in both the forward and reverse
direction. The average values from the forward and reverse scans of
multiple samples were obtained and reported.
[0165] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0166] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0167] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *