U.S. patent application number 14/106101 was filed with the patent office on 2014-04-10 for polymer webs having enhanced softness.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. The applicant listed for this patent is Kimberly-Clark Worldwide, Inc.. Invention is credited to Frank Paul Abuto, David G. Biggs, Deborah Joy Calewarts, Virginia Lee Day, Michael J. Faulks, Jian Qin, Ray A. Sterling, Donald Eugene Waldroup.
Application Number | 20140099469 14/106101 |
Document ID | / |
Family ID | 50432873 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140099469 |
Kind Code |
A1 |
Abuto; Frank Paul ; et
al. |
April 10, 2014 |
Polymer Webs Having Enhanced Softness
Abstract
The present invention provides a nonwoven substrate comprising a
fibrous web defining a surface; and a layer of a benefit agent
wherein said benefit agent is selected from an additive
composition, an enhancement component and combinations thereof;
wherein said benefit agent is frothed and bonded to the fibrous web
surface through a creping process and wherein said nonwoven
substrate demonstrates improvements selected from enhanced tactile
feel, enhanced printing, a decrease in hysteresis, an increase in
bulk, an increase in elasticity/extensibility, an increase in
retractability, a reduction in rugosities and combinations thereof
when compared to an untreated substrate.
Inventors: |
Abuto; Frank Paul; (Johns
Creek, GA) ; Day; Virginia Lee; (Woodstock, GA)
; Sterling; Ray A.; (Woodstock, GA) ; Faulks;
Michael J.; (Neenah, WI) ; Waldroup; Donald
Eugene; (Roswell, GA) ; Biggs; David G.; (New
London, WI) ; Qin; Jian; (Appleton, WI) ;
Calewarts; Deborah Joy; (Winneconne, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kimberly-Clark Worldwide, Inc. |
Neenah |
WI |
US |
|
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
Neenah
WI
|
Family ID: |
50432873 |
Appl. No.: |
14/106101 |
Filed: |
December 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13718709 |
Dec 18, 2012 |
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14106101 |
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13330440 |
Dec 19, 2011 |
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13718709 |
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12979852 |
Dec 28, 2010 |
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13330440 |
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Current U.S.
Class: |
428/88 ;
428/152 |
Current CPC
Class: |
B32B 5/022 20130101;
B32B 2555/00 20130101; Y10T 428/24446 20150115; D04H 1/4326
20130101; B32B 5/20 20130101; B32B 2555/02 20130101; D04H 1/488
20130101; Y10T 428/23929 20150401; D04H 1/552 20130101; B32B 38/145
20130101; A61Q 19/00 20130101; B32B 27/12 20130101; B32B 2307/75
20130101; B32B 37/12 20130101; A61K 8/0208 20130101; D04H 3/08
20130101; D04H 1/4291 20130101; A61F 13/51121 20130101; A61K 8/8111
20130101; B32B 2307/51 20130101; A61K 9/70 20130101; D04H 11/00
20130101; A61Q 19/10 20130101; D04H 3/16 20130101; A61F 13/513
20130101; B32B 2305/20 20130101; B32B 5/245 20130101 |
Class at
Publication: |
428/88 ;
428/152 |
International
Class: |
D04H 3/16 20060101
D04H003/16; D04H 3/08 20060101 D04H003/08; D04H 11/00 20060101
D04H011/00 |
Claims
1. A nonwoven material comprising: a web containing fibers
comprised of a synthetic thermoplastic polymer, the web defining a
creped surface; and an additive composition present on the creped
surface of the fibrous web, the additive composition comprising a
polyolefin copolymer.
2. A nonwoven material as defined in claim 1, wherein the creped
surface of the web has a Fuzz on Edge of greater than about 1.5
mm/mm.
3. A nonwoven material as defined in claim 1, wherein the creped
surface of the web has a Fuzz on Edge of greater than about 2.0
mm/mm to less than about 10 mm/mm.
4. A nonwoven material as defined in claim 1, wherein the web has a
bulk of greater than 25 cc/g.
5. A nonwoven material as defined in claim 1, wherein the web has a
bulk of greater than 28 cc/g and up to about 50 cc/g.
6. A nonwoven material as defined in claim 1, wherein the fibers
contained in the web comprise continuous filaments.
7. A nonwoven material as defined in claim 1, wherein the web
comprises a spunbond web.
8. A nonwoven material as defined in claim 1, wherein the web
comprises a hydroentangled web, a meltblown web, a SMS web, or a
coform web.
9. A nonwoven material as defined in claim 1, wherein the additive
composition forms a collapsed foam film layer on the creped
surface.
10. A nonwoven material as defined in claim 1, wherein the additive
composition further comprises a copolymer of ethylene and acrylic
acid.
11. A nonwoven material as defined in claim 1, wherein the
polyolefin copolymer in the additive composition comprises a
copolymer of ethylene or propylene and an alkene.
12. A nonwoven material as defined in claim 9, wherein the
collapsed foam film layer is discontinuous.
13. A nonwoven material as defined in claim 1, wherein the additive
composition further comprises a nonionic surfactant.
14. A nonwoven material as defined in claim 13, wherein the
nonionic surfactant comprises an ethoxylate of an alkyl
polyethylene glycol ether.
15. A nonwoven material as defined in claim 13, wherein the
nonionic surfactant comprises an ethylene oxide adduct of a linear
lauryl myristyl alcohol.
16. A nonwoven material as defined in claim 1, wherein the material
comprises a laminate, the web being combined with a film.
17. An absorbent article including an outer cover and an absorbent
structure and wherein the outer cover comprises the laminate of
claim 16.
18. A nonwoven material as defined in claim 1, wherein the web has
a basis weight of from about 10 gsm to about 40 gsm.
19. A nonwoven material as defined in claim 1, wherein the web
comprises a spunbond web, the spunbond web having a basis weight of
from about 10 gsm to about 25 gsm, the additive composition further
comprising a nonionic surfactant comprising an ethoxylate of an
alkyl polyethylene glycol ether, the additive composition further
comprising a copolymer of ethylene and acrylic acid, the web having
a bulk of at least 25 cc/g and wherein the creped surface of the
web has a Fuzz on Edge greater than about 1.5 mm/mm.
20. A nonwoven material comprising: a web containing fibers
comprised of a synthetic thermoplastic polymer, the fibers
comprising filaments, the web having a basis weight of from about 5
gsm to about 25 gsm, the web having less than about 5% bond area,
the web defining groove lines extending generally along a common
direction, the web defining a first surface and a second and
opposite surface, the first surface having a Fuzz on Edge of at
least about 1.5 mm/mm.
21. A nonwoven material as defined in claim 20, wherein the groove
lines are generally parallel and wherein the first surface of the
web has a groove density of about 5 grooves per inch to about 15
grooves per inch.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 13/718,709 filed Dec. 18, 2012, which was a
continuation-in-part of U.S. application Ser. No. 13/330,440 filed
Dec. 19, 2011 which was a continuation-in-part of U.S. application
Ser. No. 12/979,852 filed Dec. 28, 2010, and wherein all of the
above applications are hereby incorporated by reference in their
entireties.
BACKGROUND
[0002] Absorbent nonwoven products such as paper towels, tissues,
diapers, and other similar products are designed to have desired
levels of bulk, softness and strength. For example, in some tissue
products, softness is enhanced by a topical additive composition
such as a softening agent to the outer surface(s) of a tissue web.
Such additive composition may be a bonding agent that is topically
applied to a substrate, such as a nonwoven, alone or in combination
with creping operations. Creping may be part of a nonwoven
manufacturing process wherein tissue is adhered to the hot surface
of a rotating dryer drum by an additive composition. The dried
tissue and additive composition are together scraped off the dryer
drum via a doctor blade assembly. Creping adds bulk to tissue base
sheets which in turn, increases softness as determined by hand
feel. Other properties are affected as well, such as strength,
flexibility, crepe folds and the like.
[0003] In addition to tissue products, material softness is also a
desired and important characteristic for materials, particularly
nonwovens, that are used to construct personal care products, such
as diapers, feminine hygiene products, baby wipes, adult
incontinence products, training pants, and the like. The outer
cover materials and the inside linings of such products, for
instance, come in contact with the user's skin. Thus, such
materials must not only be aesthetically pleasing but must also be
soft when contacted with the wearer.
[0004] Bonded carded webs currently used as outercovers in some
diapers are known to be very soft and have a desired cotton-like
tactile feel. Unfortunately, bonded carded webs are relatively
expensive materials thus prohibiting their use in some
applications. In view of the above, a need exists for a nonwoven
material having enhanced softness properties that is less expensive
to produce than bonded carded webs.
SUMMARY
[0005] In one embodiment, the present disclosure provides a
nonwoven substrate comprising a fibrous web defining a surface; and
a layer of a benefit agent wherein said benefit agent is selected
from an additive composition, an enhancement component and
combinations thereof; wherein said benefit agent is frothed and
bonded to the fibrous web surface through a creping process and
wherein said nonwoven substrate demonstrates improvements selected
from enhanced tactile feel, enhanced printing, a decrease in
hysteresis, an increase in bulk, an increase in
elasticity/extensibility, an increase in retractability, a
reduction in rugosities and combinations thereof when compared to
an untreated substrate.
[0006] In one embodiment, the present disclosure is directed to a
nonwoven material comprising a web. The web contains fibers
comprised of a synthetic thermoplastic polymer. The fibers may
comprise filaments, such as continuous filaments. In accordance
with the present disclosure, the web defines a creped surface. An
additive composition is present on the creped surface of the web.
The additive composition may comprise a polyolefin copolymer. The
polyolefin copolymer may be present in an aqueous dispersion when
initially applied to the web. The additive composition may serve as
a creping aid and/or a softness enhancing agent.
[0007] In one embodiment, the additive composition comprises a
polyolefin copolymer in combination with a dispersing agent. The
dispersing agent may comprise a copolymer of ethylene and acrylic
acid. The polyolefin copolymer may comprise a copolymer of
propylene or ethylene and an alkene. In one particular embodiment,
for instance, the polyolefin copolymer may comprise a
polyethylene-octene copolymer.
[0008] The additive composition may also comprise a combination of
the polyolefin copolymer and a nonionic surfactant. The nonionic
surfactant may comprise an ethoxylate of an alkyl polyethylene
glycol ether. For instance, the nonionic surfactant may comprise an
ethylene oxide adduct of a linear lauryl myristyl alcohol.
[0009] The creped surface of the web may have Fuzz on Edge
characteristics that indicate enhanced softness. For instance, the
creped surface can have a Fuzz on Edge of greater than about 1.5
mm/mm, such as greater than about 2 mm/mm, such as greater than
about 2.5 mm/mm, such as greater than about 2.6 mm/mm, such as
greater than about 2.7 mm/mm. The Fuzz on Edge is generally less
than about 15 mm/mm, such as less than about 10 mm/mm.
[0010] The web can also have enhanced bulk characteristics. For
instance, the bulk of the web can be greater than about 25 cc/g,
such as greater than about 26 cc/g, such as greater than about 27
cc/g, such as greater than about 28 cc/g, such as greater than
about 29 cc/g, such as greater than about 30 cc/g, such as greater
than about 31 cc/g, such as greater than about 32 cc/g. The bulk of
the web is generally less than about 50 cc/g. Although the web may
comprise a hydroentangled web, a meltblown web, a
spunbond-meltblown-spunbond (SMS) web or a coform web, in one
particular embodiment, the web comprises a spunbond web. The
spunbond web may have a basis weight of from about 10 gsm to about
40 gsm.
[0011] In an alternative embodiment, the present disclosure is
directed to a nonwoven material comprising a web. The web contains
fibers comprised of a synthetic thermoplastic polymer. The fibers
may comprise filaments. The web has a basis weight of from about 5
gsm to about 25 gsm and may comprise a spunbond web that has less
than about 15%, or less than 8% or even less than 2% bond area. The
web has a first surface and a second and opposite surface. At least
the first surface defines groove lines that extend generally along
a common direction. The first surface of the web has a Fuzz on Edge
of at least 1.5 mm/mm, such as at least 1.7 mm/mm, such as at least
2.0 mm/mm.
[0012] The groove lines can be generally parallel and the first
surface of the web can have a groove density of from about 3
grooves per inch to about 15 grooves per inch, such as from about 5
grooves per inch to about 10 grooves per inch.
[0013] Other features and aspects of the present disclosure are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For the purpose of illustrating the invention, there is
shown in the drawings a form that is exemplary; it being
understood, however, that this invention is not limited to the
precise arrangements and instrumentalities shown.
[0015] FIG. 1 is a schematic view of process steps used to create
one embodiment of a froth according to the present invention.
[0016] FIG. 2 shows a SEM Image of untreated spunbond with printed
ink.
[0017] FIG. 3 shows a SEM Image of one embodiment of the present
invention wherein spunbond has been used as the substrate which has
been treated according to the present invention and printed with
ink.
[0018] FIG. 4 shows a graphical representation of elastic strain
versus applied strain for embodiments of hydroknit materials that
have been treated according to the present invention along with
comparative data of an untreated substrate.
[0019] FIG. 5 shows a graphical representation of elastic strain
versus applied strain for embodiment of spunbond materials that
have been treated according to the present invention along with
comparative data of an untreated substrate.
[0020] FIG. 6 is a series of SEM photographs showing the structural
change of a tissue material after being treated by an embodiment of
the present invention.
[0021] FIG. 7 shows the mechanical direction (MD) elastic strain
versus the applied strain of an embodiment of a tissue substrate
that has been treated according to the present invention along with
comparative data of an untreated tissue substrate.
[0022] FIG. 8 shows the cross-directional (CD) elastic strain
versus the applied strain of an embodiment of a tissue substrate
that has been treated according to the present invention along with
comparative data of an untreated tissue substrate.
[0023] FIG. 9 shows SEM Images of an untreated control film.
[0024] (a) shows a SEM Image of one side of the untreated control
film.
[0025] (b) shows a SEM Image of the opposite side of the untreated
control film.
[0026] (c) shows a SEM Image of the cross-sectional view of the
untreated control film.
[0027] (d) shows a SEM Image of the cross-sectional view of an
untreated control film at 5.times. the magnification of FIG.
9(c).
[0028] FIG. 10 shows SEM Images of a collapsed foam film layer of
one embodiment of a benefit agent according to the present
invention wherein such embodiment comprises a HYPOD.RTM.
dispersion.
[0029] (a) shows a SEM Image of one side of the collapsed foam film
layer.
[0030] (b) shows a SEM Image of the opposite side of the collapsed
foam film layer.
[0031] (c) shows a SEM Image of the cross-sectional view of the
collapsed foam film layer.
[0032] (d) shows a SEM Image of the cross-sectional view of the
collapsed foam film layer at almost 2.times. the magnification of
FIG. 10(c).
[0033] (e) shows a SEM Image of the cross-sectional view of the
collapsed foam film layer at almost 7.times. the magnification of
FIG. 10(c).
[0034] (f) shows a SEM Image of the cross-sectional view of the
collapsed foam film layer at 25.times. the magnification of FIG.
10(c).
[0035] FIG. 11 is a perspective view of one embodiment of a groove
rolling arrangement.
DETAILED DESCRIPTION
[0036] While the specification concludes with the claims
particularly pointing out and distinctly claiming the invention, it
is believed that the present invention will be better understood
from the following description.
[0037] All percentages, parts and ratios are based upon the total
weight of the compositions of the present invention, unless
otherwise specified. All such weights as they pertain to listed
ingredients are based on the active level and, therefore, do not
include solvents or by-products that may be included in
commercially available materials, unless otherwise specified. The
term "weight percent" may be denoted as "wt. %" herein. Except
where specific examples of actual measured values are presented,
numerical values referred to herein should be considered to be
qualified by the word "about".
[0038] As used herein, "comprising" means that other steps and
other ingredients which do not affect the end result can be added.
This term encompasses the terms "consisting of" and "consisting
essentially of". The compositions and methods/processes of the
present invention can comprise, consist of, and consist essentially
of the essential elements and limitations of the invention
described herein, as well as any of the additional or optional
ingredients, components, steps, or limitations described
herein.
[0039] "Additive composition" as used herein refers to chemical
additives (sometimes referred to as chemical, chemistry, chemical
composition and add-on) that are applied topically to a substrate.
Topical applications in accordance with the method of the present
invention may occur during a drying process, or a converting
process. Additive compositions according to the present invention
may be applied to any substrate (e.g. tissues or nonwovens) and may
include, but are not limited to, polymer dispersions, polymer
solutions or mixtures thereof.
[0040] "Airlaid web" as used herein is made with an air forming
process, wherein bundles of small fibers, having typical lengths
ranging from about 3 to about 52 millimeters (mm), are separated
and entrained in an air supply and then deposited onto a forming
screen, usually with the assistance of a vacuum supply. The
randomly deposited fibers are then bonded to one another using, for
example, hot air or a spray adhesive. The production of airlaid
nonwoven composites is well defined in the literature and
documented in the art. Examples include, but are not limited to,
the DanWeb process as described in U.S. Pat. No. 4,640,810 to
Laursen et al. and assigned to Scan Web of North America Inc.; the
Kroyer process as described in U.S. Pat. No. 4,494,278 to Kroyer et
al.; and U.S. Pat. No. 5,527,171 to Soerensen assigned to Niro
Separation a/s; and the method of U.S. Pat. No. 4,375,448 to Appel
et al. assigned to Kimberly-Clark Corporation, or other similar
methods.
[0041] "Benefit Agents" are compositions or components that provide
benefits to the overall treated substrate such as softness,
smoothness, moisture, scents, and the like. Benefit agents of the
present invention include, but are not limited to "additive
compositions" and "enhancement components".
[0042] "Bonded Carded Web" or "BCW" refers to a nonwoven web formed
by carding processes as are known to those skilled in the art and
further described, for example, in U.S. Pat. No. 4,488,928, which
is incorporated herein by reference to the extent it is consistent
to the present invention. In the carding process, one may use a
blend of staple fibers, bonding fibers, and possibly other bonding
components, such as an adhesive. These components are formed into a
bulky ball that is combed or otherwise treated to create a
substantially uniform basis weight. This web is heated or otherwise
treated to activate any adhesive component, resulting in an
integrated, lofty, nonwoven material.
[0043] "Coform" as used herein is a meltblown polymeric material to
which fibers or other components may be added. In the most basic
sense, coform may be made by having at least one meltblown die head
arranged near a chute through which other materials are added to
the meltblown materials as the web is formed. These "other
materials" may be natural fibers, superabsorbent particles, natural
polymer fibers (for example, rayon) and/or synthetic polymer fibers
(for example, polypropylene or polyester). The fibers may be of
staple length. Coform material may contain cellulosic material in
an amount from about 10% by weight to about 80% by weight, such as
from about 30% by weight to about 70% by weight. For example, in
one embodiment, a coform material may be produced containing pulp
fibers in an amount from about 40% by weight to about 60% by
weight.
[0044] "Creping" as defined herein occurs when a web that is
adhered to a dryer surface is scraped off with a blade, such as a
doctor blade.
[0045] "Enhancement Components" of the present invention are
benefit agents that are additional components that may be added to
the additive composition in order to impart other tactile or
additional benefits that cannot be achieved by the additive
composition alone. The enhancement components include, but are not
limited to, microparticles, expandable microspheres, fibers,
additional polymer dispersions, scents, anti-bacterials,
moisturizers, medicaments, soothers, and the like.
[0046] "Froth" as defined herein is a liquid foam. According to the
present invention, when the frothable composition of the present
invention is heated on the dryer's surface, it will not form a
solid foam structure. Instead, when applied to a heated surface,
the frothable composition turns into a substantially continuous
film with air bubbles inside the film.
[0047] "Hydroentangled web" according to the present invention
refers to a web that has been subjected to columnar jets of a fluid
causing the web fibers to entangle. Hydroentangling a web typically
increases the strength of the web. In one aspect, pulp fibers can
be hydroentangled into a continuous filament material, such as a
"spunbond web." The hydroentangled web resulting in a nonwoven
composite may contain pulp fibers in an amount from about 50% to
about 80% by weight, such as in an amount of about 70% by weight.
Hydroentangled composite webs as described above are commercially
available from the Kimberly-Clark Corporation under the name
HYDROKNIT.RTM.. Hydraulic entangling is described in, for example,
U.S. Pat. No. 5,389,202 to Everhart.
[0048] "Nonwoven" is defined herein as a class of fabrics generally
produced by attaching fibers together. Nonwoven fabric is made by
mechanical, chemical, thermal, adhesive, or solvent means, or any
combination of these. Nonwoven manufacture is distinct from
weaving, knitting, or tufting. Nonwoven fabrics may be made from
synthetic thermoplastic polymers or natural polymers such as
cellulose. Cellulosic tissue is one example of a nonwoven
material.
[0049] "Meltblowing" as used herein is a nonwoven web forming
process that extrudes and draws molten polymer resins with heated,
high velocity air to form fine filaments. The filaments are cooled
and collected as a web onto a moving screen. The process is similar
to the spunbond process but meltblown fibers are much finer and
generally measured in microns.
[0050] "Processing Aids" as used herein refer to compositions that
may help in the process of forming the treated substrate of the
present invention. For example, foaming agents may serve as
suitable processing aids of the present invention. Additionally,
creping aids may help with additional adhesion or release
properties for creping the substrate from a dryer drum.
[0051] "Rugosities" as used herein describes the behavior of an
elastic laminate to appear as channeled wrinkles as a result of an
elastic material (film or filaments) that is pre-stretched while
being attached to a non-stretchy material substrate (such as a
nonwoven). Rugosities may depend on how the laminate is attached or
bonded to the non-stretchy material substrate. When the laminate is
relaxed or released, the substrate appears as grooved or channeled
wrinkles similar to that of an accordion instrument. Such effect is
common in personal care articles wherein the cuffs and waistbands
are often bunched in order to provide a better fit to the wearer.
Rugosities are also described in further detail according to U.S.
Pat. No. 6,475,600 to Morman, et al, issued Nov. 5, 2002.
[0052] "Spunbond" as used herein is a nonwoven web process in which
the filaments have been extruded, drawn and laid on a moving screen
to form a web. The term "spunbond" is often interchanged with
"spunlaid," but the industry has conventionally adopted the
spunbond or spunbonded terms to denote a specific web forming
process. This is to differentiate this web forming process from the
other two forms of the spunlaid web forming, which are meltblowing
and flashspinning.
[0053] "Spunbond/Meltblown composite" as used herein is a laminar
composite defined by a multiple-layer fabric that is generally made
of various alternating layers of spunbond ("S") webs and meltblown
("M") webs: SMS, SMMS, SSMMS, etc.
[0054] "Tissue" as used herein generally refers to various paper
products, such as facial tissue, bath tissue, paper towels, table
napkins, sanitary napkins, and the like. A tissue product of the
present invention can generally be produced from a cellulosic web
having one or multiple layers. For example, in one embodiment, the
cellulosic or "paper" product can contain a single-layered paper
web formed from a blend of fibers. In another embodiment, the paper
product can contain a multi-layered paper (i.e., stratified) web.
Furthermore, the paper product can also be a single-or multi-ply
product (e.g., more than one paper web), wherein one or more of the
plies may contain a paper web formed according to the present
invention.
[0055] The present invention is an alternative to the current
method of spraying onto a dryer surface (e.g. the drum of a Yankee
dryer or a hot calendar) an aqueous dispersion or a solution of
creping chemicals. In contrast to liquid chemistry, the frothed
chemistry has enough structural integrity to reach the dryer
surface against gravity due to significant high viscosity. By
creating a frothed chemistry according to the present invention, a
chemistry applicator can be placed in much closer proximity to the
dryer surface. Additionally, by utilizing the frothed chemistry of
the present invention, it is feasible to incorporate additional
benefits that were otherwise more difficult to apply.
[0056] Another advantage of the present invention is that less
energy is consumed by the dryer. The close proximity of the
chemistry applicator to the dryer surface improves chemical mass
efficiency (i.e., decrease waste in application process) and energy
efficiency. Efficiency is increased because the air introduced into
the froth of the present invention acts as a diluter. As a result,
less heat is required to remove water from the frothed creping
chemistry (i.e., benefit agents) during the drying process. This is
an improvement over the spraying process which uses water to dilute
the benefit agent.
[0057] Further, after the creping step, a layer of the benefit
agent remains on the nonwoven substrate surface in order to add
more bulk and softness. This increase in bulk is due to the
entrapped air inside the coated layer. The enhanced softness is due
to the benefit agents that can be frothed onto the dryer surface
and subsequently transferred or adhered to the surface of the
substrate through the creping process. Though the frothed benefit
agents become a film during the drying step, not all of the air
entrapped in the froth is lost during the drying step due to the
higher viscosity associated with higher solid-levels in the frothed
additive composition.
[0058] The "film" of the benefit agent is more appropriately and
accurately described as a "collapsed foam film layer". To better
understand this distinction, FIG. 9 shows the view of a traditional
film (such as cast, extruded or blown film). As shown in FIG. 9a
the film is relatively smooth with a few voids on one side and
completely smooth on the other side as shown in FIG. 9b. In viewing
the cross-sectional views of FIGS. 9c and 9d, voids of the film can
be seen relatively parallel to the horizontal axis of the film. By
contrast, FIG. 10 shows the view of a layer of the collapsed foam
film of the present invention. Both sides (as shown in FIG. 10a and
FIG. 10b of the collapsed foam film layer show a unique cellular
structure that allow it to possess a difference in both mechanical
and tactile properties when compared to traditional films. FIG.
10c-FIG. 10f show magnified cross-sectional views of an embodiment
of a collapsed foam film layer of the present invention. As shown,
the frothed benefit layer possesses voids of air entrapped due to
the froth which leads to advantages provided by the present
invention. Additionally, the cellular structure in the Z direction
can be easily seen wherein the voids of the layer are more
perpendicular to the horizontal axis of the layer. Thus, the
present invention does not just provide a film in the traditional
sense of the word but provides an advantageous collapsed foam film
layer via frothing and creping that provides the enhancements and
improvements as described herein.
[0059] Various substrates other than tissue may be treated in
accordance with the present disclosure. Examples include, but are
not limited to, wet-laid webs, airlaid webs, spunbond webs,
meltblown webs, coform webs, bonded & carded webs (BCW),
continuous film, spunlace, film/laminate sheets, and hydroentangled
webs. The benefit agent is typically applied on one side of any
substrate, but could be applied to both sides as desired.
Benefit Agents
1. Additive Composition
[0060] In a desired application, the additive composition may be
present at a level from about 50 mg/m.sup.2 to about 10,000
mg/m.sup.2, or from about 50 mg/m.sup.2 to about 1000 mg/m.sup.2 or
from about 100 mg/m.sup.2 to about 1000 mg/m.sup.2. The difference
between these suggested ranges is dependent on whether or not the
additive composition is applied to a substrate either in-line (such
as a tissue machine), or an off-line machine (such as a non-woven
converting line). Additive compositions of the present invention
may be in the form of a polymer dispersion or a polymer solution as
set forth below.
[0061] A. Polymer Dispersions
[0062] Frothable compositions of water insoluble polymers may be in
the form of dispersions. The water insoluble polymer materials that
are solids, such as powder, granules, and the like, may be
converted into a frothable dispersion by mixing it with water and
surfactant(s) under certain processing conditions such as high
pressure extrusion at an elevated temperature. The polymer
dispersion may then be mixed with air and a foaming agent to
convert it into a froth.
[0063] Examples of dispersions according to the present invention
include, but are not limited to, a polyolefin dispersion such as
HYPOD 8510.RTM., commercially available from Dow Chemical,
Freeport, Tex., U.S.A.; polyisoprene dispersion, such as
KRATON.RTM., or styrene-ethylene/butylene-styrene (SEBS)
copolymers, commercially available from Kraton Polymers U.S. LLC,
Houston, Tex., U.S.A.; polybutadiene-styrene block copolymer
dispersion such as Butanol.RTM., commercially available from BASF
Corporation, Florham Park, N.J., USA; latex dispersion such as
E-PLUS.RTM., commercially available from Wacker, Munich, Germany;
polyvinyl pyrrolidone-styrene copolymer dispersion and polyvinyl
alcohol-ethylene copolymer dispersion, both are available from
Aldrich, Milwaukee, Wis., U.S.A.
[0064] In one embodiment, the additive composition generally
contains an aqueous dispersion comprising at least one
thermoplastic resin, water, and, optionally, at least one
dispersing agent. The thermoplastic resin is present within the
dispersion at a relatively small particle size. For example, the
average volumetric particle size of the polymer may be less than
about 5 microns. The actual particle size may depend upon various
factors including the thermoplastic polymer that is present in the
dispersion. Thus, the average volumetric particle size may be from
about 0.05 microns to about 5 microns, such as less than about 4
microns, such as less than about 3 microns, such as less than about
2 microns, such as less than about 1 micron. Particle sizes can be
measured on a Coulter LS230 light-scattering particle size analyzer
or other suitable device. When present in the aqueous dispersion,
the thermoplastic resin is typically found in a non-fibrous
form.
[0065] The particle size distribution (polydispersity) of the
polymer particles in the dispersion may be less than or equal to
about 2.0, such as less than 1.9, 1.7 or 1.5.
[0066] The thermoplastic resin contained within the additive
composition may vary depending upon the particular application and
the desired result. In one embodiment, for instance, thermoplastic
resin is an olefin polymer. As used herein, an olefin polymer
refers to a class of unsaturated open-chain hydrocarbons having the
general formula C.sub.nH.sub.2n. The olefin polymer may be present
as a copolymer, such as an interpolymer. As used herein, a
substantially olefin polymer refers to a polymer that contains less
than about 1% substitution.
[0067] In one particular embodiment, for instance, the olefin
polymer may comprise an alpha-olefin interpolymer of ethylene or
propylene with at least one comonomer selected from the group
consisting of a C.sub.4-C.sub.20 linear, branched or cyclic diene,
or an ethylene vinyl compound, such as vinyl acetate, and a
compound represented by the formula H.sub.2C.dbd.CHR wherein R is a
C.sub.1-C.sub.20 linear, branched or cyclic alkyl group or a
C.sub.6-C.sub.20 aryl group. Examples of comonomers include an
alkene, such as propylene, 1-butene, 3-methyl-1-butene,
4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene,
1-octene, 1-decene, and 1-dodecene. In some embodiments, the
interpolymer of ethylene has a density of less than about 0.92
g/cc.
[0068] In other embodiments, the thermoplastic resin comprises an
alpha-olefin interpolymer of propylene with at least one comonomer
selected from the group consisting of ethylene, a C.sub.4-C.sub.20
linear, branched or cyclic diene, and a compound represented by the
formula H.sub.2C.dbd.CHR wherein R is a C.sub.1-C.sub.20 linear,
branched or cyclic alkyl group or a C.sub.6-C.sub.20 aryl group.
Examples of comonomers include an alkene, such as ethylene,
1-butene, 3-methyl-1-butene, 4-methyl-1-pentene,
3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, and
1-dodecene. In some embodiments, the comonomer is present at about
5% by weight to about 25% by weight of the interpolymer. In one
embodiment, a propylene-ethylene interpolymer is used.
[0069] In one particular embodiment, the thermoplastic resin
comprises an alpha-olefin interpolymer of ethylene with a comonomer
comprising an alkene, such as 1-octene. The ethylene and octene
copolymer may be present alone in the additive composition or in
combination with another thermoplastic resin or dispersing agent,
such as ethylene-acrylic acid copolymer. Of particular advantage,
the ethylene-acrylic acid copolymer not only is a thermoplastic
resin, but also serves as a dispersing agent. When present
together, the weight ratio between the ethylene and octene
copolymer and the ethylene-acrylic acid copolymer may be from about
1:10 to about 10:1, such as from about 3:2 to about 2:3.
[0070] The aqueous dispersion also contains water. Water may be
added as tap water or as deionized water. The pH of the aqueous
dispersion is generally less than about 12, such as from about 5 to
about 11.5, such as from about 7 to about 11. The aqueous
dispersion may have a solids content of less than about 75%, such
as less than about 70%. For instance, the solids content of the
aqueous dispersion may range from about 5% to about 60%.
[0071] The additive composition of the present invention may be
commercially available, such as HYPOD 8510.RTM. dispersion, from
the Dow Chemical Corporation and consists of water, a
polyethylene-octene copolymer, and a copolymer of ethylene and
acrylic acid. The polyethylene-octene copolymer may be obtained
commercially from the Dow Chemical Corporation under the name
AFFINITY.RTM. (type 2980I) and the copolymer of ethylene and
acrylic acid may be obtained commercially from the Dow Chemical
Corporation under the name PRIMACOR.RTM. (type 59081).
PRIMACOR.RTM. acts as a surfactant to emulsify and stabilize
AFFINITY.RTM. dispersion particles. The acrylic acid co-monomer of
PRIMACOR.RTM. is neutralized by potassium hydroxide to a degree of
neutralization of around 80%. Therefore, in comparison,
PRIMACOR.RTM. is more hydrophilic than is AFFINITY.RTM.. In a
dispersion, PRIMACOR.RTM. acts as a surfactant or a dispersant.
Unlike PRIMACOR.RTM., AFFINITY.RTM., as suspended in a dispersion,
takes on a form of tiny droplets with a diameter of a few microns.
PRIMACOR.RTM. molecules surround the AFFINITY.RTM. droplets to form
a "micelle" structure that stabilizes the droplets. HYPOD 8510.RTM.
contains about 60% AFFINITY.RTM. and 40% PRIMACOR.RTM..
[0072] When the dispersion becomes a molten liquid on the dryer's
hot surface, AFFINITY.degree. forms a continuous phase and
PRIMACOR.RTM. a dispersing phase forming islands in the
AFFINITY.RTM. "ocean." This phase change is called phase inversion.
However, occurrence of this phase inversion depends upon external
conditions such as temperature, time, molecular weight of solids,
and concentration. Ultimately, phase inversion only occurs when the
two polymers (or two phases) have enough relaxation time to allow
phase inversion completion. In the present invention, HYPOD
8510.RTM. coated film retains a dispersion morphology which
indicates there is an incompletion of phase inversion. Benefits of
the remaining dispersion morphology include, but are not limited
to, a more hydrophilic coating layer due to the exposure of the
PRIMACOR.RTM. phase; and more improved softness of the coated
product due to entrapped air bubbles inside the coated HYPOD
8510.RTM. layer which provide extra bulkiness.
[0073] The diluted dispersion may have a very low viscosity (around
1 cp, just like water). A low viscosity dispersion, when applied
onto a hot dryer drum, will undergo a process of water evaporation
and a complete phase inversion of AFFINITY.RTM.. The resulting
continuous molten film then has PRIMACOR.RTM. dispersion islands
embedded therein. The film formed after completely evaporating the
water is solid without any air bubbles entrapped therein. After
transferring the molten film onto a the web through the creping
process, the thin film covering the surface of the treated tissue
is discontinuous yet interconnected, see FIG. 6c, discussed
infra.
[0074] The process of the present invention may use a high solid,
high viscosity dispersion of (about 10% to about 30%) and may
contain a large amount of air bubbles (air volume is at least 10
times more than the dispersion volume). Desirably, the commercially
available HYPOD 8510.RTM. dispersion (about 42% solids, including
both AFFINITY.RTM. and PRIMACOR.RTM.) has a viscosity around about
500 cps whereas water has a viscosity of around about 1 cps. A
dispersion containing about 20% HYPOD 8510.RTM. may have a
viscosity of around 200 cps, a relatively high viscosity, while a
dispersion having less than about 1% HYPOD 8510.RTM. may have a
viscosity closer to water's viscosity (1 cp). After entrapping a
high ratio of air, the viscosity of the frothed HYPOD 8510.RTM.
dispersion has been increased exponentially compared to the
dispersion before being frothed.
[0075] Referring to FIG. 1, when a frothed dispersion is applied
onto the non-porous dryer surface 23, a limited amount of water
will be quickly evaporated therefrom. It is thought that the
dispersion's slow evaporation due to high solids combined with its
high viscosity will prevent the AFFINITY.RTM.-PRIMACOR.RTM.
dispersion from completing a phase inversion (wherein the
AFFINITY.RTM. becomes continuous and the PRIMACOR.RTM. becomes a
dispersion) and entrapped air from escaping. This results in a
unique micro-structured molten film on the hot dryer surface.
[0076] Referring to FIG. 6, the SEM photos confirm the foregoing
hypothesis. Two immediate benefits can be observed when comparing
the prior art surface-treated tissues and the surface-treated
tissues of the present invention. First, the method of the present
invention yields a tissue that is more bulky and has a softer hand
feel due to entrapment of air bubbles 21 (see FIG. 6b). Second, the
tissue of the present invention has a more wettable surface due to
incomplete phase inversion, which in turn results in surface
exposure of the hydrophilic component.
[0077] Visually compare FIGS. 6a, 6b, 6c to FIGS. 6a', 6b', 6c'.
The coated layer having dispersion beads 19 and entrapped air
bubbles 21 shown in FIG. 6b, is softer than the melted film shown
in FIG. 6b' as determined by the In Hand Ranking Test disclosed
herein.
[0078] B. Polymer Solutions
[0079] Frothable compositions of water soluble polymers may also be
in the form of solutions. The water-soluble polymer materials that
are solids, such as powder, granules, and the like, may be
dissolved into a solution. The polymer solution may then be mixed
with air and a foaming agent to convert it into a froth.
[0080] Examples of polymer solutions according to the present
invention include both synthetic and natural based water soluble
polymers. The synthetic water soluble polymers include, but are not
limited to, polyalcohols, polyamines, polyimines, polyamides,
polycarboxlic acids, polyoxides, polyglycols, polyethers,
polyesters, copolymers and mixtures of the listed above.
[0081] The natural based water soluble polymers include, but are
not limited to, modified cellulose, such as cellulose ethers and
esters, modified starch, chitosan and its salts, carrageenan, agar,
gellan gum, guar gum, other modified polysaccharides and proteins,
and combinations thereof. In one particular embodiment, the water
soluble polymers also include: poly(acrylic acid) and salts
thereof, poly(acrylate esters), and poly(acrylic acid) copolymers.
Other suitable water soluble polymers include polysaccharides of
sufficient chain length to form films such as, but not limited to,
pullulan and pectin. For example, the water soluble polymers may
contain additional monoethylenically unsaturated monomers that do
not bear a pendant acid group, but are copolymerizable with
monomers bearing acid groups. Such compounds include, for example,
the monoacrylic esters and monomethacrylic esters of polyethylene
glycol or polypropylene glycol, the molar masses (Mn) of the
polyalkylene glycols being up to about 2,000, for example.
[0082] In another particular embodiment, the water soluble polymers
may be hydroxypropyl cellulose (HPC) sold by Ashland, Inc. under
the brand name of KLUCEL.RTM.. The water soluble polymers can be
present in the additive composition in any operative amount and
will vary based on the chemical component selected as well as on
the end properties that are desired. For example, in the exemplary
case of KLUCEL.RTM., the biodegradable, water soluble polymers can
be present in the additive composition in an amount of about 1% to
about 75%, or at least about 1%, at least about 5%, or at least
about 10%, or up to about 30%, up to about 50% or up to about 75%,
based on the total weight of the additive composition, to provide
improved benefits. Other examples of suitable water soluble
polymers include methyl cellulose (MC) sold by Ashland, Inc. under
the brand name BENECEL.RTM.; hydroxyethyl cellulose sold by
Ashland, Inc. under the brand name NATROSOL.RTM.; and hydroxypropyl
starch sold by Chemstar (Minneapolis, Minn., U.S.A.) under the
brand name GLUCOSOL 800.RTM.. Any of these chemistries, once
diluted in water, are disposed onto a hot, non-porous dryer surface
to ultimately transfer the chemistry to the web surface. The water
soluble polymers in these chemistries include, but are not limited
to, polyvinyl alcohol, polyethylene glycol, polyethylene oxide,
hydroxypropyl starch, hydroxypropyl cellulose, and combinations
thereof.
[0083] Conventional creping chemistries for tissue manufacturing
may include water-soluble polymer solutions, such as an aqueous
mixture comprising polyvinyl alcohol and a polyamide-epihalohydrin
resin. While these conventional creping chemistries comprise
water-soluble polymer solutions, these are not able to provide the
benefits of the present invention, which include enhanced softness
without compromising the strength of the tissue sheet.
II. Enhancement Components
[0084] The present invention not only provides a substrate with
improved softness due to the benefit agents and process described
herein, but it also provides for an improved hand feel. Enhancement
components are added to the dispersions of the present invention to
provide a cottony/fluffy feel to the substrate instead of the
silky/slippery feel that may often be felt with the use of the
dispersions alone. It may be understood that the improved hand feel
produced by the present invention may also include properties such
as velvety, suede-like, hairy, smooth, fuzzy and like descriptors
used to describe soft tactile properties. While the silky/slippery
feel may be desirable for some substrates, the present invention
provides other options in order that a variety of textures and
aesthetics can be provided. Enhancement components of the present
invention include, but are not limited to, micro-particles such as
silica gel particles, thermally expandable microspheres such as
EXPANCEL.RTM., fibers such as cotton linter flocks, polymer
dispersions such as poly(vinylpyrrolidone-styrene), and
combinations thereof. When cotton linter flocks or other types of
fibers are used, they may be from about 0.1 mm fiber length to
about 5 mm fiber length.
[0085] In addition to the enhancement components providing a
contrasting hand feel, the enhancement components may also provide
additional benefits that could not be appreciated with the use of
the dispersion alone. Enhancement components of the present
invention may also include fragrances, anti-bacterials,
moisturizers, soothers, coloring agents, hydroxyethyl cellulose,
medicaments and combinations thereof. Such components will provide
an overall substrate that has improved feel from the dispersion in
combination with benefits that may have not otherwise been provided
without the present technology. The present invention may utilize
any or a combination of enhancement components to be included
within the additive composition of the present invention. For
example, enhancement components may be added to a dispersion of the
present invention in an amount of from about 0.5% to about 30%,
from about 1% to about 20% or from about 2% to about 10%, by weight
of the dispersion composition.
[0086] The enhancement components can be added into the frothed
chemistry either before or after the chemistry has been frothed. In
a desired application, the enhancement component level is about
from about 0.5% to about 30%, or from about 1% to about 20%, or
from about 2% to about 10%, based on total dry weight of the
additive composition.
[0087] When enhancement components are used in combination with the
additive compositions of the present invention, they allow for
enhanced softness without compromising strength. For example, when
facial tissue is used as the substrate of the present invention,
there is an overall log odds increase of from about 0.5 to about 18
and a GMT level of from about 800 to about 1200 when compared to
substrates that have not been processed in the same manner as the
present invention. "GMT" as used herein refers to the combination
of machine and cross-machine directions in determining tensile
strength. Expanded microspheres stay on the surface of both film
and tissue to contribute to hand feel improvement when consumers
touch them in use conditions.
III. Processing Aids
[0088] Processing aids of the present invention include chemicals
that may help in the process of forming the treated substrate of
the present invention. The processing aids may slightly appear or
may dissipate in the final, treated substrate. While they are
included to solely aid in the process of producing the treated
substrates, they may also impart slight benefits to the substrate
that are desired of the present invention. For the purposes of this
application, "processing aids" are those used in the process of
frothing or applying the benefit agents to the substrate and are
not used in the process of making the precursor substrate.
[0089] A. Foaming Agents
[0090] Most commercial foaming agents are suitable for creating the
froth of the present invention. Suitable foaming agents include,
but are not limited to, either low molecular or polymeric materials
in liquid form. The foaming agents can be anionic, cationic or
nonionic. These foaming agents can be divided into four groups
depending on function: [0091] 1. Air Entrapment Agent--used to
enhance a liquid's (dispersion, solution, or a mixture, etc.)
capability to entrap air which can be measured by determining a
"blow ratio." An exemplary list of foaming agents include but is
not limited to potassium laurate, sodium lauryl sulfate, ammonium
lauryl sulfate, ammonium stearate, potassium oleate, disodium
octadecyl sulfosuccinimate, hydroxypropyl cellulose, etc. [0092] 2.
Stabilization Agent--used to enhance stability of froth's air
bubbles against time and temperature; examples include, but are not
limited to, sodium lauryl sulfate, ammonium stearate, hydroxypropyl
cellulose, etc. [0093] 3. Wetting Agent--used to enhance the
wettability of a film-coated dried surface. Examples include, but
are not limited to, sodium lauryl sulfate, potassium laurate,
disodium octadecyl sulfosuccinimate, etc. [0094] 4. Gelling
Agent--used to stabilize air bubbles in the froth by causing the
additive composition to take the form of a gel which serves to
reinforce cell walls.
[0095] Examples include, but are not limited to, hydroxypropyl
cellulose, hydroxyethyl cellulose, carboxymethyl cellulose and
other modified cellulose ethers.
[0096] Some foaming agents can deliver more than one of the
functions listed above. Therefore, it is not necessary to use all
four foaming agents in a frothable additive composition. Selection
of the foaming agents is dependent upon the chemistry of the
additive composition. For example, when the additive composition
comprises an anionic component, such as HYPOD 8510.RTM., suitable
foaming agents have to be selected from either anionic or non-ionic
groups. If a cationic foaming agent is used to enhance frothability
of an anionic additive composition, the cationic components in the
foaming agent will form ionic bonds with the anionic components in
the additive composition and cause both cationic foaming agent and
anionic additive composition to become water insoluble due to
formation of the bonds. On the other hand, if an additive
composition comprises cationic components, anionic foaming agents
are not suitable to use.
[0097] B. Creping Aids
[0098] Creping Aids are chemistries that are added to the benefit
agents of the present invention to optimize the adhesion and
release properties of the tissue substrate to the dryer surface.
These fall broadly into the following groupings: [0099] 1. Adhesion
Aid--used to increase adhesion of the tissue sheet to the dryer
surface. Examples include, but are not limited to, polyvinyl
alcohol, polyacrylate, hydroxypropy starch, carboxymethy cellulose,
kymene, polyvinyl amine, copolymers or mixtures thereof. [0100] 2.
Release Aid--used to decrease adhesion (enhance release) of the
tissue sheet to (from) the dryer surface. Examples include, but are
not limited to, polyethylene glycol, polypropylene glycol,
polyethylene oxide, polypropylene oxide, polyolefin, fluorinated
polyolefin, copolymer and blends comprising the above. [0101] 3.
Curing Aid--used to hasten or retard curing of the creping package
such as a plasticizer or toughener. [0102] 4. Lutensol A 65 N
Iconol 24 7.RTM., hereinafter "Lutensol.RTM." (from the BASF.RTM.
Chemical Company) may also be used to aid in creping within the
present invention.
Froth Generating Process
[0103] In general, preparing frothed chemicals utilizes a system
that pumps both liquid and air into a mixer. The mixer blends the
air into the liquid to produce a froth which inherently includes a
plurality of small air bubbles. The froth exits the mixer and flows
to an applicator.
[0104] One parameter to define the quality of frothed chemistry is
the blow ratio, which is defined by ratio of volume of small air
bubbles entrapped by dispersion chemical to the volume of the
dispersion before mixing. For example, at a blow ratio of 10:1, a
dispersion flow rate of 1 liter/minute will be able to entrap 10
liters/minute of air into its liquid and produce a total froth flow
rate of 11 liters per minute.
[0105] To achieve a high blow ratio, both the mechanical mixing and
the frothing capability of the additive composition are determining
factors. If a chemical can only hold or entrap air volume up to a
blow ratio of 5, no matter how powerful a froth unit is, it won't
be able to produce a stable froth having a blow ratio of 10. Any
extra air beyond the blow ratio of 5 will release out of the froth
system once the mechanical force is removed. In other words, any
entrapped air higher than the dispersion's air containment
capability will become instable. Most of such instable air bubbles
will escape from the froth (debubbling) immediately after
mechanical agitation is stopped.
[0106] Referring to FIG. 1, shown schematically, is a system 10
that can generate the frothed chemistry according to the present
invention. To begin, frothable chemicals (e.g. HYPOD 8510.RTM.,
KRATON.RTM., and the like) are placed in a chemical tank 12. The
chemical tank 12 is connected to a pump 14. It may be desirable to
modify piping 13 between the chemical tank 12 and pump 14 so that
one may transmit the frothable chemicals to two different sizes of
pumps. Desirably the chemical tank 12 is situated at an elevated
level above the pump 14 in order to keep the pump primed.
[0107] One optional small secondary pump (not shown) may be used
for running the frothing process at slow speeds relative to the
pump 14. The larger primary pump 14 is capable of producing flow
rates up to 25 liters/minute liquid flow-rate for high application
speeds and/or high amounts of additive composition. The smaller,
secondary pump (not shown) is capable of liquid flow rates up to
about 500 cc/min. for low application speeds and/or low additive
composition.
[0108] A flow meter 16 is situated between the pump(s) 14 and a
foam mixer 18. Liquid flow rates are calculated from desired
additive composition, chemical solids, line-speed and applicator
width. The flow rate may range from about 5:1 to about 50:1. When
using the small secondary pump, its flow rate ranges from about 10
cc/min to about 500 cc/min. When using the large pump 14, its flow
rate ranges from about 0.5 liter/min to about 25 liter/min. A 20
liter/min air flow meter is selected when using the small secondary
pump. There is a 200 liter/min air flow meter to use when running
the larger primary pump 14.
[0109] In one aspect, the foam mixer 18 is used to blend air into
the liquid mixture of frothable chemicals to create small air
bubbles in the froth. Air is metered into the system 10 using
certain liquid flow rates and blow ratios as discussed above.
Desirably, the foam mixer 18 having a size of 25.4 cm (10 inches)
may be used to generate froth. One possible foam mixer 18 is a
CFS-10 inch Foam Generator from Gaston Systems, Inc. of Stanley,
N.C., U.S.A.
[0110] Desirably, the rotational speed of the foam mixer 18 is
limited to about 600 rpm. The rpm speed for the mixer in this
process is dependent upon the additive composition's ability to
foam (i.e., its capability of entrapping air to form stable
bubbles). If the additive composition foams easily, a lower rpm is
generally required. If the additive composition does not foam
easily, a higher rpm is generally required. The higher mixer speed
helps to speed up the foam equilibrium or optimal blow ratio. A
normal rpm for the mixer is about 20%-60% of the maximum rpm speed.
The type of and/or amount of foam agent in addition to the additive
composition also has an effect on the mixer speed requirement.
[0111] The froth is checked for bubble uniformity, stability and
flow pattern. If bubble uniformity, stability and flow pattern are
not to desired standards, adjustments may be made to flow rates,
mixing speeds, blow ratio, and/or chemical compositions of the
solutions/dispersions before directing the froth to the applicator
24.
[0112] In one aspect of the invention, HYPOD 8510.RTM., or other
chemistries to be frothed and used for creping are blended and
added to the chemical tank 12. Dilute solutions of HYPOD 8510.RTM.
(<10% total solids) and other hard-to-froth chemistries
generally require something added to the formulation to increase
viscosity and foamability. For example, hydroxypropyl cellulose or
other foaming agents or surfactants, can be used to produce a
stable froth for uniform application onto the heated and
non-permeable surface of a rotating drum of a dryer surface. The
enhancement components, such as silica gel particles or cotton
linter flocks, can be added into the additive composition in
various ways, including, but not limited to: added into the
additive composition before the additive composition is pumped into
a frothing machine; introduced into the frothed additive
composition after the additive composition is coming out of the
frothing machine but before the frothed additive composition is
applied onto the dryer's surface; or applied to the dryer before
the substrate contacts the additive composition. When the
enhancement components are introduced into the additive
composition, it is necessary to constantly agitate the mixture
before adding it into the frothing machine in order to prevent the
solid enhancement component from being settled down at the bottom
of the container. When the enhancement components are introduced
into the frothed additive composition, a suitable device, which
ensures a uniform mixing of the enhancement components and the
frothed additive composition, is needed.
Substrates
[0113] Suitable substrate materials include but are not limited to
facial tissue; uncreped through air-dried tissue (UCTAD); paper
toweling; HYDROKNIT.RTM. nonwoven material from Kimberly Clark
Corporation, Neenah, Wis., U.S.A., wet-laid webs, airlaid webs,
spunbond webs, meltblown webs, SMS webs, coform webs, bonded &
carded webs (BCW), continuous film, spunlace, film/laminate sheets,
hydroentangled webs, and all types of paper, tissue and other
nonwoven products.
[0114] In the non-limiting examples discussed herein, the frothed
chemistry may be applied to a nonwoven such as a tissue. As used
herein, nonwovens are meant to include facial tissue, bath tissue,
paper towels, spunbond, diaper or feminine care body side liners
and outer covers, napkins (such as for hands and face) and the
like. Tissue may be made in different ways, including but not
limited to conventionally felt-pressed tissue paper; high bulk
pattern densified tissue paper; and high bulk, uncompacted tissue
paper. Tissue paper products made therefrom can be of a single-ply
or multi-ply construction such as in US Patent Publication No.
2008/0135195. Another embodiment for forming a tissue of the
present invention utilizes a papermaking technique known as
uncreped through-air dried ("UCTAD"). Examples of such a technique
are disclosed in U.S. Pat. No. 5,048,589 to Cook, et al.; U.S. Pat.
No. 5,399,412 to Sudall, et al.; U.S. Pat. No. 5,510,001 to
Hermans, et al.; U.S. Pat. No. 5,591,309 to Rugowski, et al.; and
U.S. Pat. No. 6,017,417 to Wendt, et al.
Surface Coating Process
[0115] Unlike a process that sprays a dilute dispersion or solution
onto a dryer surface such as a Yankee dryer surface 23 (or other
suitable dryer drum surface (not shown)), the process of the
present invention can apply high-solid frothed chemistry onto the
dryer surface 23. In the present invention, air is used to dilute a
benefit agent comprising any level of solids wherein the viscosity
is within a range that can be pumped by the foaming machine. For
example, having up to about 65% of solids, up to about 50% solids,
up to about 35%, or up to about 20% solids.
[0116] The high-solid coating process of the present invention may
exhibit product or process benefits including but not limited to
softer surface due to the unique micro-structure of the collapsed
foam film layer, less chemical waste due to close and direct
application of the frothed chemistry, and no need to use soft or
deionized water due to the high ratio of chemistry to water (for
example, a chemical such as HYPOD 8510.RTM. becomes instable when
it is exposed to a large quantity of hard water, i.e., a solid
level of 1% or less); and less drying energy required to dry the
frothed chemistry as well as the base sheet. Additional benefits
due to the addition of enhancement components include, but are not
limited to uniformity of the overall Benefit Agent film coating on
the nonwoven substrate; enhanced adhesion of the overall Benefit
Agent coating to the nonwoven substrate; enhance mechanical
strength of the overall Benefit Agent coating film; and enhanced
stability of the Benefit Agent froth from the foam generator unit
to the dryer surface.
[0117] The frothed benefit agents may be applied onto a substrate
by two ways: an inline application or an offline application. In
the inline processes a foam generator and an applicator will be
incorporated into a tissue manufacturing and the frothed chemicals
will be applied onto any substrate during the manufacture of same.
An offline application enables application of the froth chemistry
to those substrates which are produced by a non-creping process.
For example, uncreped through air dried ("UCTAD") bath tissue and
melt-spun nonwoven materials are suitable for use with the offline
application method.
[0118] Referring to FIG. 1, in one aspect of the invention, the
frothed chemicals are applied to the dryer surface 23 via an
applicator 24. The froth applicator 24 is placed close to the dryer
surface (0.64 cm or 1/4 inch) for uniform froth distribution onto
the dryer surface 23. Such positioning allows for better, direct
contact of the frothed chemistry to the dryer surface 23,
especially during high speed operations.
[0119] It is most desirable to use a single parabolic applicator 24
to apply chemistry to a rotating dryer drum surface 23. However, if
varying levels of chemical application are required across the
width of the dryer surface due to dryer or basesheet variability,
applicators (not shown) with multiple zones of miniature parabolic
applicators may be used.
[0120] In general, the enhancement component makes the additive
composition coating (i.e., the ocean layer) exhibit a novel and
improved hand feel. For example, HYPOD 8510.RTM. may be used as an
additive composition and is frothed/surface coated onto a substrate
without an enhancement component. When its surface is touched, it
provides significant softness improvement in comparison to the same
tissue with a conventional creping chemistry. However, at the same
time, it also feels slightly waxy or slippery.
[0121] Some types of consumers may like this slippery feel, but
others may not want to have the feel. Adding an enhancement
component can change the feel without compromising the softness
improvement. The hand feel obtained through this approach includes,
but is not limited to, cottony, velvety, fluffy, and/or hairy.
Another benefit of adding the enhancement component(s) is that the
additive composition HYPOD 8510.RTM. coating layer has an improved
strength which was important when the benefit agents were applied
onto pre-prepared substrates, such as thermoplastic nonwovens. This
improved strength enables the coated film of the benefit agents to
have a uniform and complete coverage on the substrate.
[0122] Additionally, it can be shown that enhancement components
and the method of application could be used to enhance surface
feel, such as softness or improve surface properties, such as
absorbency, friction, bulk, etc. Additionally, other surface
benefits, such as scents, anti-bacterial, moisturizing, soothing
agents, etc., could be applied better than the additive composition
HYPOD 8510.RTM. alone could provide. Substrates comprising both
HYPOD 8510.RTM. and polyvinylpyrrolidone-styrene was perceived to
be almost 1.5 log odds softer (significant) than the use of HYPOD
8510.RTM. without any enhancement components.
[0123] Applicants found that the IHR results for the HYPOD
8510.RTM. frothed substrate with 6% silica gel particles as the
enhancement components resulted in having the softest perceived
results with a greater than 5 log-odds difference from the
non-frothed substrate with conventional creping chemistry. The
HYPOD 8510.RTM. frothed control without any enhancement components
was next at over 4 log-odds difference. All other frothed
substrates were perceived to be at least 3 log odds softer than the
control non-frothed substrate.
[0124] Another benefit to adding enhancement components is the
tremendous caliper increase that can be achieved while generally
maintaining or having greater tensile strength than the non-frothed
surface treated substrate. These substrates were all calendered at
the same nip pressure for the facial converting process. The
percentages listed next to the data points are the amounts of the
enhancement components added based on HYPOD 8510.RTM. dry weight in
the formulation before frothing. It has been shown that frothed and
creped substrates showed an added increase in bulk over the
non-frothed and creped substrates with the highest level increases
at almost 35%. The majority of the substrates with the enhancement
components increased bulk over the frothed substrate comprising
only HYPOD 8510.RTM.. All of the processing conditions, such as
blade types, bevel, and pressure loadings, were the same.
Creping Process
[0125] Creping is part of the substrate manufacturing process
wherein the substrate is scraped off the surface of a rotating
dryer (e.g. a Yankee Dryer) via a blade assembly. Creping may be
done as described in U.S. application Ser. No. 13/330,440 to Qin,
et al., filed Dec. 19, 2011
Other Benefitting Factors
[0126] Benefit agents of the present invention can be used to
provide a variety of advantages that may be used to coat a
substrate and provide the aforementioned advantages. Additionally,
there are other advantages that the present invention provides that
can be distinctly called out and described according to the
following.
[0127] Enhanced Printing
[0128] A unique advantage that the present invention, as described
herein, provides is that it allows for improved capabilities for
printing on a nonwoven substrate. The additive composition can be
applied such that it essentially forms a surface on the substrate
that is more like a film so that printing is more consistent and in
some instances more vibrant. For example, spunbond is appreciated
for its cloth-like tactile properties or feel, however, it is not a
favored substrate over a film laminate when it comes to printing as
the ink tends to spread or absorb into the material reducing the
ink coverage that is shown on the substrate. Of course, a film
laminate is optimal for printing graphics but it is not optimal as
a substrate that will be close to the skin. Prior to the present
invention, a solution for printing onto a nonwoven substrate has
been to adhesively laminate a printed film to the substrate.
Although this has worked well, it can add to the manufacturing
process and costs. The present invention therefore provides a
unique compromise wherein the cloth-like tactile properties or feel
of the substrate is not removed, yet it also provides a surface
that allows for enhanced printing capabilities relative to the
substrates. The present invention provides for a relatively smooth
surface eliminating the pixilated appearance of current outer cover
materials. Additionally, ink adhesion is improved. Substrates of
the present invention will have improved ink coverage of at least
about 25%, at least about 50% or at least about 75% when compared
to an untreated substrate. The present invention provides for an
improved surface area so that more of the substrate can be covered
by the printed ink thereby improving the appearance or clarity of
printing on the substrate as compared to an untreated substrate.
Currently surface printing of outer cover laminates require the use
of specialized inks to avoid potential issues with ink rub off. The
present invention may accommodate any commercially available ink
used for printing onto substrates. Additionally, any conventional
techniques useful for printing may be used within the present
invention. Such techniques may include, but are not limited to,
gravure coating, offset printing, screen printing, flexography,
inkjet printing, laser printing, digital printing, and the like.
The dispersions of the present invention provide polar moieties
that are anticipated to improve ink adhesion and thus improve
printing onto nonwoven substrates directly.
[0129] FIG. 2 shows an untreated spunbond that has been printed
with ink. (The white splotches are the ink printed onto the fibers
of the spunbond). By comparison, FIG. 3 shows a spunbond substrate
that has been treated with the benefit agent of the present
invention and printed with ink. It can be seen that the treated
sample (FIG. 3) has a film like coating on the surface which gives
it a greater area for the ink to cover the surface leading to
enhanced visual aesthetics in terms of print clarity and vividness.
Only approximately 20% of the surface was covered by ink in the
untreated spunbond, FIG. 2, as compared to the 50% ink coverage of
the spunbond, FIG. 3, which was treated with the present invention.
This data was obtained quantifying the SEM images using image
analysis software. The ink is able to adhere more consistently and
smoothly on the treated substrate and therefore improves the
overall look of the printing.
[0130] Enhanced Bulk and Stretch
[0131] In addition to improving the overall tactile feel of the
nonwoven substrate, the present invention also enables an increase
in both bulk and basis weight when compared to an untreated
substrate. Without being limited by theory, bulk may be
proportional to the basis weight of the fibers within the
substrates of the present invention. As the basis weight increases,
the corrugation of the fibers may expand the caliper of the fibers
in the Z direction and thus expand the bulk of the fibers. The
fibers will loft thereby increasing the bulk of the fibers. The
benefit agents of the present invention may alone or in combination
with certain creping mechanisms within the present invention
contribute to said increase in bulk and increase in basis weight.
For example, without being limited, when compared to an untreated
spunbond substrate with a basis weight of 12 gsm and a bulk of 13
cc/g, the present invention may allow for the spunbond to
demonstrate a basis weight of 16 gsm and a bulk of 27 cc/g (or a
33% and 108% increase respectively). Similarly, the creping
mechanism and process can demonstrate an even greater advantage and
allow the spunbond to demonstrate a basis weight of 25 gsm and 25
cc/g (or a 108% and 92% increase respectively). For example, the
present invention allows for nonwoven materials with varying
cellulosic content to have a basis weight increase of greater than
at least about 20% to about 250% as compared to an untreated
substrate. For example, an untreated cellulose substrate has been
shown to have a basis weight of about 56 gsm and 84% hysteresis. A
nonwoven cellulose substrate of the present invention, however, can
demonstrate a basis weight of about 95 gsm (about a 70% increase in
basis weight) and about a 74% hysteresis.
[0132] In addition to the benefit agent, such as the frothed HYPOD
8510.RTM. dispersion used in the present invention, a second
component such as a nonionic surfactant like Lutensol.RTM. may
further aid in the success of increasing bulk in substrates of the
present invention. In one embodiment, the nonionic surfactant may
comprise an alkoxylated polyalkylene glycol ether, such as an
ethoxylate of an alkyl polyethylene glycol ether. In one
embodiment, the nonionic surfactant may comprise an ethoxylate of
one or more fatty alcohols. The fatty alcohols may comprise linear
alcohols having a carbon chain length of from about 8 carbon atoms
to about 28 carbon atoms, such as from about 10 carbon atoms to
about 18 carbon atoms, such as from about 12 carbon atoms to about
14 carbon atoms. For example, the nonionic surfactant may comprise
an ethylene oxide adduct of linear lauryl myristyl alcohol.
Lutensol.RTM. is composed of a seven mole ethylene oxide adduct of
a linear lauryl myristyl alcohol that is also readily
biodegradable. Additionally, with the use of a nonionic surfactant
such as Lutensol.RTM., the present invention allows for the frothed
benefit agent such as the HYPOD 8510.RTM. dispersion to be used at
a low add-on level yet still uniformly spread over the entire area
of the substrate. The present invention, however, enables an
increase in bulk without or up to about 50% addition of a nonionic
surfactant such as Lutensol.RTM.. For example, about 500 mg/m.sup.2
of the frothed benefit agent, for example, HYPOD 8510.RTM.
dispersion may be combined with about 250 mg/m.sup.2 of a nonionic
surfactant such as Lutensol.RTM. in some embodiments of the present
invention (i.e. a ratio of nonionic surfactant to benefit agent of
about 1:2).
[0133] As used herein, the "hysteresis" value of a sample maybe
determined by first stretching the sample to the desired elongation
and then allowing the sample to retract in a controlled manner at
the same speed. The hysteresis value is the decrease or loss of
energy during this cyclic loading. The percent hysteresis (%
hysteresis) is calculated by integrating the area under the loading
(A.sub.L) and unloading curve (A.sub.UL); taking their difference
and dividing it by the area under the loading curve. %
Hysteresis=(A.sub.L-A.sub.UL)*100/(A.sub.L). These measurements are
performed using a "strip elongation test which is substantially in
accordance with the specifications in ASTM D5035-95. Specifically
the test uses two clamps each having two jaws with each jaw having
a facing in contact with the sample. The clamps hold the material
in the same plane usually vertically, separated by 3 inches and
move the cross head at a specific rate of extension. The sample
size is 3 inches by 6 inches with a jaw facing height of 1 inch and
width of 3 inches and a constant rate of 10 in/min. The specimen is
clamped in a MTS (Mechanical Test Systems) electromechanical test
frame which has data acquisition capability. The test is conducted
at ambient condition both in cross direction and machine direction
(CD & MD). Results are reported as an average of at least five
specimens.
[0134] Without being limited by the data shown, FIG. 4 gives an
example of the present invention, frothed and creped using
hydroknit as the substrate, has about a 22% to about a 25% elastic
strain at about 100% applied strain before showing any breakage.
Comparatively, the control hydroknit only has about a 15% elastic
strain and breaks at about 25% applied strain. Similarly, without
being limited by the data shown in FIG. 5, the present invention,
frothed and creped using spunbond as the substrate, has about a 27%
to about a 55% elastic strain at about a 100% stretch compared to
the control that only extends up to about 18% elastic strain at
about a 50% stretch before break. Without being limited by the data
shown, FIG. 7 shows the mechanical direction (MD) elastic stretch
(the recovery) versus the applied stretch. The present invention
shows an increase in stretch due to the presence of the frothed
HYPOD 8510.RTM. dispersion combined with Lutensol.RTM. frothed onto
a tissue substrate. The present invention shows a surprising about
30% elastic stretch at about 80% applied strain=while the basic
cellulose tissue shows no more than an only about an 8% elastic
stretch at about a 18% applied strain. Without being limited by the
data shown, FIG. 8 shows the cross-directional (CD) strain versus
the applied strain comparison of a tissue of the present invention
versus an untreated tissue substrate. As shown, the present
invention, using the frothed benefit agent as a HYPOD 8510.RTM.
dispersion combined with Lutensol.RTM. on a tissue substrate, has
the most elastic stretch up to failure compared to the basic
cellulose tissue.
[0135] Thus, while untreated nonwoven substrates may demonstrate a
stretch or elongation at break, they generally do so at earlier
stages of stretch. Generally, traditional untreated substrates may
demonstrate of from about 8% to about 45% elongation at break. The
present invention, however, allows for substrates that are treated
as described herein, to demonstrate elongation at break of above
about 45% elongation at break. For example, the present invention
may demonstrate from about 45%, or from about 47% to about 55%, to
about 80%, to about 280%, to about 337%, or to about 350%
elongation at break. Particularly for certain substrates wherein
the elongation at break is usually low, the present invention may
provide for elongation at break to be about 25%, about 30%, about
35%, about 38%, about 45% or about 47%. Such stretch can be
especially exemplified in tissue substrates according to the
present invention.
[0136] Nonwoven substrates of the present invention will
demonstrate at least about a 5%, at least about a 20%, at least
about a 30%, at least about a 40%, at least about 50%, at least
about 60%, at least about 70%, or at least about 100% decrease in
hysteresis when compared to a similarly untreated substrate. It
will also demonstrate at least about a 20%, at least about a 25%,
at least about a 50%, at least about a 70%, at least about a 80%,
at least about a 90%, at least about a 100%, at least about a 110%,
at least about a 125%, at least about a 200%, at least about a
225%, or at least about a 250% increase in bulk as compared to an
untreated substrate as determined by the bulk test described
herein.
[0137] Again, the present invention will increase bulk and/or
elasticity in a substrate with or without the presence of
Lutensol.RTM. and may demonstrate bulk and/or elasticity with the
frothed HYPOD 8510.RTM. dispersion alone. Without being limited, an
untreated hydroknit substrate can demonstrate about 87% hysteresis
and about 25% elongation at break. A hydroknit substrate of the
present invention, however, can demonstrate about 67% hysteresis
and about 337% elongation at break. Similarly, an untreated
spunbond substrate can demonstrate 100% hysteresis and about 45%
elongation at break while a spunbond substrate of the present
invention can demonstrate about 40% hysteresis and about 280%
elongation at break. Thus, the present invention provides enhanced
versatility by allowing substrates that usually provide no
elasticity to not only be able to stretch but also recover with
ease and go beyond the normal and expected nature of a similar
substrate that has not been processed by the present invention.
[0138] A material which has more elastic strain has more elasticity
or elastic energy. Substrates of the present invention can
demonstrate an increased ability to withstand stretches of at least
about 25%, at least about 50%, at least about 75% or at least about
100% of applied strain as compared to an untreated substrate. While
various substrates will vary, it is clear that the present
invention allows for enhanced stretching compared to substrates
that have not been treated accordingly. For example, untreated
hydroknit can withstand about a 15% stretch with about 25% applied
strain. At about 50% applied strain, that same untreated hydroknit
is unable to sustain stretching without breaking. Hydroknit of the
present invention can withstand about a 12% stretch at about 25%
applied strain, about a 18% stretch at about a 50% applied strain,
about a 21% stretch at about 75% applied strain and about a 23%
stretch at about 100% applied strain. Similarly, untreated spunbond
can withstand about a 10% stretch at about a 25% applied strain and
about a 16% stretch at about a 50% applied strain. At about 75%
applied strain, however, that same untreated spunbond is unable to
sustain stretching without breaking. Spunbond of the present
invention, however, can withstand about a 17% stretch at about 25%
applied strain, about 36% stretch at about 50% stretch applied
strain, about 46% stretch at about 75% applied strain and about 54%
stretch at about 100% applied strain.
[0139] Enhanced Stretch with Elastic Retractibility
[0140] Current existing elastic film laminates such as those
described in U.S. Pat. No. 8,287,677 to Lake et al, issued Oct. 16,
2012, are incorporated into personal care products utilize facings
that are not elastic or extensible. As a result, the elastic film
(and this is also the case in elastic filament executions) must be
extended prior to lamination of the facings and then relaxed. As a
result of the film extension/relaxation, the elastic laminates tend
to be bulkier when compared to traditional textile materials. In
addition to the increase in bulk, the elastic laminate visual
appearance is dictated by the bond pattern used for the lamination.
The visual effect is more like an accordion with peaks and valleys
bunched up in succession. Rugosities, as they are technically
known, are commonly seen along the cuffs and waistbands of
disposable personal care products such as, but not limited to,
feminine articles, incontinence products and diapers. Consumer
feedback indicates that materials that are thin, able to drape and
possess cloth-like visual and tactile aesthetics are highly
desired. Thus, a smoother elastic area that appears more like
underwear due to the reduced or absent rugosities is more
desirable. In addition, elastic film laminates rely on the
non-elastic facing to drive the perception of cloth-like aesthetics
(visual and tactile). Currently, approaches to modify the
aesthetics of the facings of laminates rely on post-lamination
treatment (for example, groove rolling) or the use of high basis
weight materials (bonded carded webs in particular which are not
cost effective). Thus, a facing material that is extensible, has a
relatively low basis weight, and provides bulk conveys a more
cloth-like appearance and tactile properties and provides an
excellent opportunity to possess film laminates that mimic
traditional textiles, i.e. appears more like cloth underwear. The
present invention provides such a solution by providing a creped
nonwoven substrate that has enhanced stretching capabilities and
increased bulk to deliver a product, specifically an elastic film
laminate for a product with reduced or no rugosities. Nonwoven
substrates, when combined with a non-pre-stretched elastic film to
create an elastic laminate of the present invention may demonstrate
an elimination of rugosities (100% reduction in rugosities) or at
the very least a reduction in rugosities from at least about 5%,
from at least about 10%, from at least about 25% or from at least
about 50% as compared to an untreated substrate. The creped facings
could also be used in work wear and Health Care garments
(particularly on the body side of the garment) to enhance the
perception of softness and more cloth-like texture for improved
visual and tactile feel. The creping may also provide opportunities
for improved moisture wicking depending on the nonwoven substrate
used as the facing.
[0141] Therefore, in addition, to the aforementioned softness and
bulk enhancing improvements, the present invention enables the
creping of nonwoven substrates such as spunbond, bonded carded web,
spunlace etc. leading to the development of structures with
improvements such as higher bulk and improved tactile and visual
aesthetics. Because the present invention delivers a collapsed foam
film benefit agent layer on the nonwoven substrates, it helps the
nonwoven retain a creped structure that should be advantageous
during the lamination process. Structural evaluation of nonwoven
materials, for example, spunbond, utilizing the present invention
shows that the benefit agent layer coating essentially stays on one
side of, specifically the surface of the nonwoven material. The
benefit agent of the present invention is concentrated primarily on
the peaks of the creped material which may coincide with the
nonwoven material bond points. The creped nonwoven has machine
direction extensibility (with some level of recovery) and a more
cloth-like visual aesthetic because the appearance of the bond
points (if present) on the nonwoven material is minimized and
thereby reduces the rugosities. When laminated to an elastic
film/filaments (without the need to pre-stretch the elastic), the
result is a laminated web that can be incorporated into a product,
for example, a disposable personal care article that looks and
feels like underwear but provides the protection and manageable
care qualities of a disposable article. Although not limited to
such articles, this can be especially desirable in disposable
incontinence articles where adults desire a less diaper-appearing
product that bunches at the waist and legs in order to wear a
product that gives a more discreet wear and feel.
[0142] The ability to crepe an extensible and retractable nonwoven
material facing has been leveraged to produce non-pre-stretched (no
or less rugosities) elastic laminates. To produce the laminates,
the creped nonwoven materials of the present invention, for example
(a spunbond material layered with the benefit agent comprising
HYPOD.RTM. 8510) was laminated to one or both sides of an elastic
film using adhesive. As a result, the benefit agent may be layered
on the side of the creped substrate that is attached to the film to
produce tactile and visual cues of laminates that are a more bulky,
cloth-like material. As the film layer is not stretched and
retracted, the basis weight of the film can be adjusted to meet
physical property requirements rather than process requirements.
The present invention provides creped nonwoven substrates produced
from a variety of raw materials. Of particular interest are
nonwovens produced from polypropylene, polyamides, polyesters,
polyethylene, propylene/ethylene copolymers and other polyolefin
blends. In addition, the level of crepe may be adjusted to provide
varying degrees of MD extensibility allowing for elastic laminates
with varying amounts of stretch/recovery.
[0143] Use of the creped substrates of the present invention also
provides the opportunity to enhance the visual and tactile
aesthetics of elastic film laminates such as those used as outer
cover materials in personal care products such as, but not limited
to, feminine articles, incontinence products and diapers. Adhesive
lamination of the creped facings provides a more bulky, cloth-like
appearance and tactile properties without requiring the use of high
basis weight materials.
[0144] The present invention demonstrates improvements unfounded in
substrates that have not been treated by means provided by the
present invention. As described, improvements of the present
invention as compared to untreated substrates may be selected from,
enhanced tactile feel such as softness and the like, enhanced
printing, a decrease in hysteresis, an increase in bulk, an
increase in elasticity/extensibility, an increase in
retractability, a reduction in rugosities, and combinations
thereof.
[0145] Other Additives
[0146] The nonwoven substrates of the present invention may have
additional compositions added to provide additional benefits beyond
the aforementioned such as softness, printing enhancement,
elasticity and bulk. Compositions may be added to the benefit agent
treated substrates to aid in the overall substrate performance.
Specifically, in products such as personal care articles,
additional compositions may help the performance or the users
experience with the product overall.
[0147] Body Fluid Rheological Modifiers
[0148] The advantage in providing a body fluid rheological modifier
is to aid the nonwoven substrates of the present invention in the
handling of fluids comprising blood components such as, but not
limited to, feminine care products and wound dressings. Body fluid
rheological modifiers include, but are not limited to mucolytic
agents, mucin modifiers, red blood cell modifiers, the like, and
combinations thereof. Body fluid rheological modifiers of the
present invention comprise a variety of composition or agents that
are able to interact with body fluids in order to better aid body
fluid interaction with the substrate. For example, mucolytic agents
are known to break down critical disulfide intramolecular and/or
intermolecular bonds in the mucus glycol-protein or mucin component
of the menstrual fluid, thereby significantly decreasing the
viscoelasticity of the mucus. Such agents have been described in
U.S. Pat. No. 7,687,681 to DiLuccio et al, issued Mar. 30, 2010 and
are useful herein. Mucolytic agents can also modify the mucin by
cleaving the protein backbone, modifying the 3D structure and
decreasing the entanglement within the structure of the mucin.
These include non-ionic surfactants, such as Lutensolo, enzymes,
such as Papain, and carbohydrates, such as Dextran as further
described in U.S. Pat. No. 8,044,255 to Potts et al, issued Oct.
25, 2011, U.S. Pat. No. 6,060,636 to Yahiaoui, et al., issued May
9, 2000 and U.S. Pat. No. 7,928,282 to Dibb, et al., issued Apr.
19, 2011, respectively. Mucolytic agents of the present invention
include, but are not limited to, L-cysteine, thioglycolates,
dithiotriacol and combinations thereof. Body fluid rheological
modifiers can be used within the present invention in amounts of
from about 0.1% or from about 0.2% to about 5% or to about 20% or
based on the weight of the benefit agent composition.
[0149] In some substrates, the nonwoven material may exhibit a
blockage of pores caused by the red blood cells which results in a
decrease in the fluid intake and the wicking capabilities of the
substrate. Red blood cell modifiers also exist that can reduce the
viscosity as well as reduce pore blockage. These include, but are
not limited to, Glucopon 220.RTM., PLURONIC.RTM., and those
described in U.S. Pat. No. 6,350,711 to Potts, et al., issued Feb.
26, 2002. Additionally, wherein the substrate is used for capturing
body fluids, including, but not limited to red blood cells, the
blockage of pores may result in an increase of leakage. Thus,
adding such a composition to the nonwoven substrate of the present
invention may enhance the end user experience thereby creating an
advantageous substrate product.
[0150] Anti-Adherence Agents
[0151] In order to prevent viscoelastic fluids, such as menses and
feces, from attaching to the skin, anti-adherence agents may be
added. Anti-adherence agents may comprise at least one
viscoelastant material, at least one anti-adherent material, or
combinations thereof and may be added to the nonwoven substrate of
the present invention. Anti-adherent agents are described in U.S.
Pat. No. 7,642,396 to Schroeder et al, issued Jan. 5, 2010.
Specifically, anti-adherent agents act to prevent the adherence of
menses and/or fecal material to the skin in the labial and perianal
regions during and after menstruation or defecation, respectively.
Suitable viscoelastant materials include, but are not limited to,
linked enzymes, alkyl polyglycosides having 8-10 carbon atoms in
the alkyl chain, bovine lipid extract surfactant, dextrans, dextran
derivatives and combinations thereof. Suitable anti-adherent
compounds of the present invention include, but are not limited to,
alginic acid, beta-benzal-butyric acid, botanicals, casein,
farnesol, flavones, fucans, galactolipid, kininogen, hyaluronate,
inulin, iridoid glycosides, nanoparticles, perlecan,
phosphorothioate oligodeoxynucleotides, poloxamer 407,
polymethylmethacrylate, silicone, sulphated exopolysaccharides,
tetrachlorodecaoxide, and combinations thereof. Anti-adherence
agents may be added to the nonwoven substrates of the present
invention in an amount of from about 0.01% to about 25% by weight
of the viscoelastant material or the anti-adherent material. Other
variant amounts include from about 0.05% to about 10% or from about
0.1% to about 8% or from about 0.1% to about 5% by weight of the
viscoelastant material or the anti-adherent material.
[0152] Odor Control Materials
[0153] Any variety of odor control materials may be used in
accordance with the present invention that are capable of imparting
odor control to a nonwoven substrate. Such odor control uses are
especially useful in personal care absorbent articles. For example,
odor control materials may be a deodorizing mixture of an anhydrous
mixture of basic, pH neutral and acidic odor absorbing particles as
described in U.S. Pat. No. 5,342,333 to Tanzer et al., issued Aug.
30, 1994 or U.S. Pat. No. 5,364,380 to Tanzer et al, issued Nov.
15, 1994. Suitable odor control materials of the present invention
may also comprise odor control systems that reduce odor by action
on malodorous substances in a substrate (such as an absorbent
article) or by reducing the odor by acting on the user's nose
receptors as described in US Application No. 2008249490 to Carlucci
et al, filed Oct. 9, 2008. Other odor control materials of the
present invention may also comprise odor control systems that
provide prolonged odor control by focusing on materials with high
and low volatility such as those described in US Application No.
2008071238 to Sierri et al, filed Mar. 26, 2008. Odor control
materials are further described in U.S. Pat. No. 8,066,956 to Do,
et al, issued Nov. 29, 2011 and U.S. Pat. No. 6,926,862 to
Fontenot, et al, issued Aug. 9, 2005. Odor control materials of the
present invention include, but are not limited to, ammonia
neutralizers, functional fragrances, chelating agents, inorganic
oxide particles, such as silica, alumina, zirconia, magnesium
oxide, titanium dioxide, iron oxide, zinc oxide, copper oxide,
baking soda (sodium bicarbonate), activated charcoal, activated
carbon, diatomaceous earths, zeolites, clays (e.g., smectite clay)
and combinations thereof. Odor control materials may be present
from about 2 gsm to about 80 gsm, from about 8 gsm to about 40 gsm,
or from about 12 gsm to about 30 gsm depending on the basis weight
of the nonwoven substrate.
[0154] Embodiment of Creped Nonwoven Material Having Enhanced
Softness
[0155] In one particular embodiment of the present disclosure, a
nonwoven material is creped using an additive composition. The
nonwoven material contains fibers or filaments made from a
thermoplastic synthetic polymer. In one embodiment, the nonwoven
material contains continuous filaments. For instance, the nonwoven
material may comprise a spunbond web. In other embodiments,
however, the nonwoven material may comprise a meltblown web, a
coform web, a SMS web or a hydroentangled web.
[0156] The basis weight of the nonwoven material can vary depending
upon the particular application. In general, the basis weight is
less than about 50 gsm, such as less than about 40 gsm, such as
less than about 30 gsm, such as less than about 25 gsm. The basis
weight, for instance, can be from about 5 gsm to about 30 gsm, such
as from about 10 gsm to about 25 gsm.
[0157] In accordance with the present disclosure, at least one side
of the nonwoven material is creped. In one embodiment, both sides
of the nonwoven material may be creped. The nonwoven material may
be creped by applying an additive composition to a creping drum,
adhering the nonwoven material to the creping drum and then creping
the nonwoven material from the drum. In an alternative embodiment,
the additive composition may be applied first to a surface of the
nonwoven material, such as in a pattern, and then adhered to a
creping surface and creped.
[0158] In one embodiment, the additive composition comprises a
polyolefin copolymer, a dispersing agent, and a nonionic
surfactant. The polyolefin copolymer may comprise a copolymer of
ethylene or propylene and an alkene. In one embodiment, the
polyolefin copolymer comprises a copolymer of ethylene and octene.
The dispersing agent, on the other hand, may comprise a copolymer
of ethylene and acrylic acid. The nonionic surfactant may comprise
an ethoxylated alkyl polyethylene glycol ether. For instance, the
nonionic surfactant may comprise one or more ethoxylated fatty
alcohols. In one particular embodiment, for instance, the nonionic
surfactant comprises an ethylene oxide adduct of a linear lauryl
myristyl alcohol.
[0159] The relative amounts of components contained in the additive
composition can vary depending upon many factors including the
nonwoven material being creped and the desired result. In one
embodiment, the ratio of the polyolefin copolymer to the dispersing
agent can be from about 80:20 to about 40:60, such as from about
70:30 to about 50:50. In one embodiment, the polyolefin copolymer
and the dispersing agent are present in the additive composition at
a weight ratio of from about 65:35 to about 55:45. The nonionic
surfactant may be present in the aqueous dispersion in an amount of
from about 0.5% to about 10% by weight, such as in an amount from
about 1% to about 8% by weight, such as in an amount from about 2%
to about 5% by weight.
[0160] In accordance with the present disclosure, the additive
composition is formed into a froth or foam and used to crepe at
least one surface of the nonwoven material from a creping surface.
After creping, the additive composition forms a collapsed foam
layer. The collapsed foam layer may be discontinuous.
[0161] Creping the nonwoven material dramatically increases the
softness properties of the material. For instance, the resulting
creped product can have a bulk of greater than 25 cc/g, such as
greater than 26 cc/g, such as greater than 27 cc/g, such as greater
than 28 cc/g, such as greater than 29 cc/g, such as greater than 30
cc/g, such as greater than 31 cc/g, such as even greater than 32
cc/g. The bulk is generally less than about 50 cc/g.
[0162] In addition to bulk, the creped surface of the nonwoven
material can have excellent Fuzz on Edge characteristics. Fuzz on
Edge is a measure of softness, especially tactile softness. The
Fuzz on Edge of the creped surface, for instance, can be greater
than about 1.5 mm/mm, such as greater than 2.0 mm/mm, such as
greater than 2.5 mm/mm, such as greater than 2.6 mm/mm, such as
even greater than 2.7 mm/mm. The Fuzz on Edge is generally less
than 10 mm/mm, such as less than about 5 mm/mm.
[0163] Alternative Embodiment of Nonwoven Material with Enhanced
Softness
[0164] In an alternative embodiment of the present disclosure, a
nonwoven web with enhanced softness can be produced by groove
rolling or ring-rolling a nonwoven material, and particularly a
nonwoven material made from synthetic thermoplastic polymer fibers
that is lightly bonded.
[0165] In this embodiment, the nonwoven material is particularly a
spunbond web comprised of continuous filaments. The web can have a
basis weight of less than about 50 gsm, such as less than about 30
gsm, such as less than about 25 gsm, such as less than about 20
gsm, such as less than about 18 gsm. For instance, the basis weight
of the nonwoven material can be from about 5 gsm to about 25 gsm,
such as from about 5 gsm to about 20 gsm. In one embodiment, the
filaments can be made from a polypropylene polymer.
[0166] In accordance with the present disclosure, the nonwoven web
is low bonded or lightly bonded. For instance, the nonwoven web can
have less than about 10% bond area, such as less than about 5% bond
area, such as less than about 2% bond area, such as even less than
about 1% bond area.
[0167] The nonwoven web can be optionally treated with an additive
composition as described above. In one embodiment, however, the
nonwoven web is not treated with an additive composition and
instead subjected to groove rolling. In particular, the web is fed
between a first roller and a second roller where at least one of
the rollers defines grooves. The web is fed in between the two
rollers with sufficient nip pressure to form grooves into at least
one surface of the web.
[0168] Referring to FIG. 11, one embodiment of groove rolls that
may be used in accordance with the present disclosure is
illustrated. As shown, for example, satellite rolls 102 may engage
an anvil roll 104, each of which include a plurality of ridges 103
defining a plurality of grooves 105 positioned across the grooved
rolls in the cross-machine direction. The grooves 105 may be
oriented in the machine direction. The grooves 105 may likewise be
oriented in the cross-machine direction. The ridges 103 of
satellite roll 102 intermesh with the grooves 105 of anvil roll
104, and the grooves 105 of satellite roll 102 intermesh with the
ridges 103 of anvil roll 104.
[0169] The dimensions and parameters of the grooves 105 and ridges
103 may vary. For example, the number of grooves 105 contained on a
roll may vary. The grooves 105 may also have a certain depth "D",
which generally ranges from about 2 mm to about 20 mm, and in some
embodiments, from about 8 mm to about 15 mm. In addition, the
peak-to-peak distance "P" between the grooves 105 is typically from
about 1 mm to about 50 mm, and in some embodiments, from about 2 mm
to about 10 mm.
[0170] In general, the groove rolls can include grooves that are
evenly spaced along the length of the groove face or unevenly
spaced. In various embodiments, the density of grooves can be from
about 1 groove per about 50 mm to about 1 groove per about 1 mm. In
other embodiments, the grooves can be spaced such that there is 1
groove per about 2 mm to about 1 groove per about 7 mm.
[0171] If desired, heat may be applied to the web just prior to or
during the application of the grooves. Heat may be applied by any
suitable method known in the art, such as heated air, infrared
heaters, heated nipped rolls, or partial wrapping of the laminate
around one or more heated rolls or steam canisters, etc. Heat may
also be applied to the grooved rolls themselves. It should also be
understood that other grooved roll arrangement are equally
suitable, such as two grooved rolls positioned immediately adjacent
to one another. In another embodiment, the process may include a
grooved roll that contacts a flat anvil roll which may have a
deformable surface.
[0172] In one embodiment, the nonwoven material is subjected to
groove rolling without heat.
[0173] Groove rolling the very low bonded nonwoven material can
dramatically increase the bulk and Fuzz on Edge properties of the
nonwoven web. The resulting web can have a substantially improved
tactile softness feel when rubbed between the fingers. It is
believed that the increased bulk is due to the loosening or
displacement of fibers contained within the web.
[0174] Webs made according to the present disclosure, for instance,
can have a bulk of generally greater than 15 cc/g, such as greater
than about 16 cc/g. The bulk is generally less than about 30 cc/g.
The Fuzz on Edge characteristics of the grooved surface, on the
other hand, can be greater than about 1.5 mm/mm, such as greater
than about 1.6 mm/mm, such as greater than about 1.7 mm/mm. The
Fuzz on Edge is generally less than about 5 mm/mm, such as less
than about 3 mm/mm.
EXAMPLES
[0175] The following examples further describe and demonstrate
embodiments within the scope of the present invention. The examples
are given solely for the purpose of illustration and are not to be
construed as limitations of the present invention, as many
variations thereof are possible without departing from the spirit
and scope of the invention.
Example 1
[0176] Commercial HYPOD.RTM. dispersion was diluted with water to a
30% HYPOD.RTM. solid level and then frothed by the Gaston unit. The
stable froth was applied to the hot drum surface of the 60 inch
calendar dryer. The cured HYPOD.RTM. dispersion was creped off the
dryer surface. Spunbond basesheets were creped using the froth
process of the present invention as described herein. The
HYPOD.RTM. coated basesheets were then printed with Cyan ink
wherein 100 parts of the ink were mixed with 4.5 parts of the
cross-linker by weight. The samples were hand printed using an
anilox roller of 10.8 bcm (billion cubic microns).
[0177] Froth Process Conditions:
Solids in dispersion: 10-30% HYPOD 8510.RTM.
Dryer Temperature: 260-300 deg F.
[0178] Dispersion Flow rate: 100-500 cc/min
Mixer Speed: 20%-60%
[0179] Blow ratio: 5-30
[0180] Image analysis was performed on the SEM images to quantify
surface ink coverage on both the untreated spunbond and the
spunbond treated with the benefit agent of the present invention.
The treated samples show higher % surface ink coverage than the
untreated spunbond as shown in Table 1.
TABLE-US-00001 TABLE 1 Substrate % Ink Coverage Spunbond Control A
(8 gsm) 14.00 Spunbond Control B (12 gsm) 17.00 Spunbond Frothed (8
gsm) 61.00
Example 2
[0181] Commercial HYPOD 8510.RTM. polyolefin dispersion was diluted
with water to varied HYPOD 8510 solids levels with no or up to 50%
additions of Lutensol.RTM. A 65 N ICONOL.RTM. 24 7 based on HYPOD
8510.RTM. solids. This chemistry was then frothed by the Gaston
Systems foam unit and the stable froth was applied to the hot
surface of a 60 inch dryer. The basesheet was then pressed onto the
collapsed foam coated dryer surface, creped off the dryer surface,
and wound up on a reel drum.
[0182] Basesheets namely cellulose based towel, Hydroknit.RTM.,
spunbond were used to create stretchy materials using the process
by controlling the creping blade geometry and/or the draw
ratio.
Froth Process Conditions:
[0183] % Solids in dispersion: 5%-30% HYPOD 8510.RTM.
Dryer Temperature: 230-300 deg F.
[0184] Dispersion Flow rate: 50-500 cc/min
Mixer Speed: 20-60%
[0185] Blow ratio: 5-30
Mechanical Testing--% Hysteresis:
[0186] Testing was performed using MTS tensile tester model
#Insight Model EL1. A 3'' inch wide test specimen was pulled at 10
in/min up to 20% strain and then retracted at the same rate to 0%
strain. The area under the loading and unloading curve was measured
as % hysteresis as shown in tables 2 and 3. Additionally, table 3
shows elongation at break for each of the tested substrates.
TABLE-US-00002 TABLE 2 % Hysteresis for creped cellulose towel %
Hysteresis Basis Weight (gsm) Average Std. Dev Control 56 84
.+-.0.6 Cellulose Frothed 95 74 .+-.0.7
TABLE-US-00003 TABLE 3 % Hysteresis for creped spunbond and
hydroknit and cellulose facial tissue % Hysteresis % Elongation at
break Control Hydroknit 87 25 Hydroknit A Frothed 70 153 Hydroknit
B Frothed 66 337 Control Spunbond 100 45 Spunbond A Frothed 42 124
Spunbond B Frothed 40 280 Control Facial Tissue 95 29 Frothed
Facial Tissue 65 47
Mechanical Testing--Elastic Energy:
[0187] Testing was performed using MTS tensile tester model
#Insight Model EL1. A 3'' inch wide test specimen was pulled at 10
in/min through numerous cyclic loading and unloading curves up to
increasing % strains (25, 50, 75 and 100). The amount of permanent
deformation was measured after each cycle according to the applied
strain (in/in) for each cycle as shown in Table 4.
TABLE-US-00004 TABLE 4 Elastic Strain at given applied strain
Applied strain (in/in) 0.25 0.50 0.75 1.00 Control Hydroknit 0.15
0.00 0.00 0.00 Hydroknit A Frothed 0.12 0.18 0.21 0.23 Hydroknit B
Frothed 0.10 0.17 0.22 0.25 Control spunbond 0.10 0.16 0.00 0.00
Spunbond A Frothed 0.16 0.28 0.30 0.28 Spunbond B Frothed 0.17 0.36
0.46 0.54 Control Facial Tissue 0.06 0.00 0.00 0.00 Frothed Facial
Tissue 0.12 0.16 0.03 0.00
Example 3
[0188] Bulk was measured by quantifying the basis weight (gsm) and
bulk (cc/g) by measuring the weight and the thickness of the
material. The results are as shown in Table 5.
TABLE-US-00005 TABLE 5 Code Number Basis Weight (gsm) Bulk (cc/g)
Control Spunbond 12 13 Spunbond A Frothed 16 27 Spunbond B Frothed
25 25
Test Methods
[0189] (1) In-Hand Ranking Test for Tactile Properties (IHR
Test):
[0190] The In-Hand Ranking Test (IHR) is a basic assessment of
in-hand feel of fibrous webs and assesses attributes such as
softness. This test is useful in obtaining a quick read as to
whether a process change is humanly detectable and/or affects the
softness perception, as compared to a control. The difference of
the IHR softness data between a treated web and a control web
reflects the degree of softness improvement.
[0191] A panel of testers was trained to provide assessments more
accurately than an average untrained consumer might provide. Rank
data generated for each sample code by the panel were analyzed
using a proportional hazards regression model. This model
computationally assumes that the panelist proceeds through the
ranking procedure from most of the attribute being assessed to
least of the attribute. The softness test results are presented as
log odds values. The log odds are the natural logarithm of the risk
ratios that are estimated for each code from the proportional
hazards regression model. Larger log odds indicate the attribute of
interest is perceived with greater intensity.
[0192] Because the IHR results are expressed in log odds, the
difference in improved softness is actually much more significant
than the data indicates. For example, when the difference of IHR
data is 1, it actually represents 10 times (10.sup.1=10)
improvement in overall softness, or 1,000% improvement over its
control. In another example, if the difference is 0.2, it
represents 1.58 times (10.sup.0.2=1.58) or a 58% improvement.
[0193] The data from the IHR can also be presented in rank format.
The data can generally be used to make relative comparisons within
tests as a product's ranking is dependent upon the products with
which it is ranked. Across-test comparisons can be made when at
least one product is tested in both tests.
[0194] (2) Bulk Test
[0195] Sheet bulk is calculated as the quotient of the sheet
caliper of a conditioned fibrous sheet, expressed in microns,
divided by the conditioned basis weight, and expressed in grams per
square meter. The resulting sheet bulk is expressed in cubic
centimeters per gram (cc/g). More specifically, the sheet caliper
is the representative thickness of a single sheet measured in
accordance with TAPPI test methods T402 "Standard Conditioning and
Testing Atmosphere For Paper, Board, Pulp Handsheets and Related
Products" and T411 om-89 "Thickness (caliper) of Paper, Paperboard,
and Combined Board" with Note 3 for stacked sheets. The micrometer
used for carrying out T411 om-89 is an Emveco 200-A Tissue Caliper
Tester available from Emveco, Inc., Newberg, Oreg., U.S.A. The
micrometer has a load of 2 kilo-Pascals, a pressure foot area of
2500 square millimeters, a pressure foot diameter of 56.42
millimeters, a dwell time of 3 seconds and a lowering rate of 0.8
millimeters per second.
[0196] (3) Viscosity Test
[0197] Viscosity is measured using a Brookfield Viscometer, model
RVDV-II+, available from Brookfield Engineering Laboratories,
Middleboro, Mass., U.S.A. Measurements are taken at room
temperature (23 C), at 100 rpm, with either spindle 4 or spindle 6,
depending on the expected viscosity. Viscosity measurements are
reported in units of centipoise.
[0198] (4) Quantity of HYPOD 8510.RTM. Additive Composition
Test
[0199] In one aspect of the invention, HYPOD add-on is determined
by using acid digestion. Samples are wet ashed with enough
concentrated sulfuric and nitric acid to destroy the carbonaceous
material and isolate the potassium ions from the cellulosic matrix.
The potassium concentration is then measured by atomic absorption.
HYPOD 8510.RTM. add-ons are determined by referencing the potassium
concentration of the HYPOD 8510.RTM. on the sample to bulk HYPOD
8510.RTM. measurements from a control HYPOD 8510.RTM. dispersion
solution (LOTVB1955WC30, 3.53%).
[0200] (5) Method for Determining Content of Additive Composition
in Tissue.
[0201] Samples were digested following EPA method 3010A. The method
consists of digesting a known amount of material with Nitric Acid
in a block digester and bringing it up to a known volume at the end
of the digestion.
[0202] Analysis was performed on a flame atomic absorption
spectrophotometer using EPA method 7610 dated July 1986, which is a
direct aspiration method using an air/acetylene flame. The
instrument used was a VARIAN AA240FS available from Aligent
Technologies, Santa Clara, Calif., U.S.A.
[0203] The analysis was performed in the following manner: The
instrument was calibrated with a blank and five standards.
Calibration was followed with analyzing a second source standard to
confirm the calibration standards. In this particular case,
recovery was 97% (90-110% being acceptable). Next a digestion blank
and a digestion standard were analyzed. In this particular case,
the blank was less than 0.1 mg/l and the standard recovery was 93%
(85-115% being acceptable). Samples were then analyzed and after
every tenth sample a standard was run (90-110% being acceptable).
At the end of entire analysis, a blank and standard were run.
[0204] (6) Basis Weight
[0205] The Basis Weight of the tissue sheet specimens was
determined using a modified TAPPI T410 procedure. The pre-plied
samples were conditioned at 23.degree. C..+-.1.degree. C. and
50.+-.2% relative humidity for a minimum of 4 hours. After
conditioning a stack of 16-3''.times.3'' pre-plied samples was cut
using a die press and associated die. This represents a tissue
sheet sample area of 144 in.sup.2 or 0.0929 m.sup.2. Examples of
suitable die presses are TMI DGD die press manufactured by Testing
Machines, Inc. located at Islandia, N.Y., or a Swing Beam testing
machine manufactured by USM Corporation, located at Wilmington,
Mass. Die size tolerances are +/-0.008 inches in both directions.
The specimen stack is then weighed to the nearest 0.001 gram on a
tared analytical balance. The basis weight in grams per square
meter (gsm) is calculated using the following equation:
Basis weight(conditioned)=stack wt. in grams/(0.0929 m.sup.2)
[0206] (7) Geometric Mean Tensile Strength (GMT)
[0207] The Geometric Mean Tensile Strength (GMT) is the square root
of the product of the dry machine direction (MD) tensile strength
multiplied by the dry cross-machine direction (CD) tensile strength
and is expressed as grams per 3 inches of sample width. The MD
tensile strength is the peak load per 3 inches of sample width when
a sample is pulled to rupture in the machine direction. Similarly,
the CD tensile strength is the peak load per 3 inches of sample
width when a sample is pulled to rupture in the cross-machine
direction. The tensile curves are obtained under laboratory
conditions of 23.0.degree. C..+-.1.0.degree. C., 50.0.+-.2.0%
relative humidity and after the tissue samples have equilibrated to
the testing conditions for a period of not less than four
hours.
[0208] The samples for tensile strength testing are cut into strips
3 inches wide (76 mm) by at least 5 inches (127 mm) long in either
the machine direction (MD) or cross-machine direction (CD)
orientation using a JDC Precision Sample Cutter (Thwing-Albert
Instrument Company, Philadelphia, Pa., Model No. SC130). The
tensile tests are measured on an MTS Systems Synergie 100 run with
TestWorks.RTM. 4 software version 4.08 (MTS Systems Corp., Eden
Prairie, Minn.).
[0209] The load cell is selected from either a 50 Newton or 100
Newton maximum, depending on the strength of the sample being
tested, such that the majority of peak load values fall between
10-90% of the load cell's full scale value. The gauge length
between jaws is 4+/-0.04 inches (102+/-1 mm). The jaws are operated
using pneumatic-action and are rubber coated. The minimum grip face
width is 3 inches (76 mm), and the approximate height of a jaw is
0.5 inches (13 m). The crosshead speed is 10+/-0.4 inches/min
(254+/-10 mm/min), and the break sensitivity is set at 65%.
[0210] The sample is placed in the jaws of the instrument, centered
both vertically and horizontally. The test is then started and ends
when the specimen breaks. The peak load is recorded as either the
"MD tensile strength" or the "CD tensile strength" of the specimen
depending on direction of the sample being tested. Ten (10)
specimens per sample are tested in each direction with the
arithmetic average being reported as either the MD or CD tensile
strength value for the product. The geometric mean tensile strength
is calculated from the following equation:
GMT=(MI)Tensile*CD Tensile).sup.1/2
[0211] 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".
[0212] All documents cited in the Detailed Description of the
Invention 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. To the
extent that any meaning or definition of a term in this written
document conflicts with any meaning or definition of the term in a
document incorporated by reference, the meaning or definition
assigned to the term in this written document shall govern.
Example 4
[0213] The following example demonstrates the enhanced softness
properties of nonwoven materials made in accordance with the
present disclosure.
[0214] A 17 gsm polypropylene spunbond was creped using HYPOD
8510.RTM. polyolefin dispersion, commercially available from Dow
Chemical, Freeport, Tex., U.S.A. containing water, a
polyethylene-octene copolymer, and a copolymer of ethylene and
acrylic acid. The polyethylene-octene copolymer may be obtained
commercially from the Dow Chemical Corporation under the name
AFFINITY.RTM. (type 29801) and the copolymer of ethylene and
acrylic acid may be obtained commercially from the Dow Chemical
Corporation under the name PRIMACOR.RTM. (type 59081).
PRIMACOR.RTM. acts as a surfactant to emulsify and stabilize
AFFINITY.RTM. dispersion particles. The acrylic acid co-monomer of
PRIMACOR.RTM. is neutralized by potassium hydroxide to a degree of
neutralization of around 80%. In a dispersion, PRIMACOR.RTM. acts
as a surfactant or a dispersant. Unlike PRIMACOR.RTM.,
AFFINITY.RTM., as suspended in a dispersion, takes on a form of
tiny droplets with a diameter of a few microns. HYPOD 8510.RTM.
contains about 60% AFFINITY.RTM. and 40% PRIMACOR.RTM. as received
from DOW with solids concentration of about 42%. The HYPOD
8510.RTM. was diluted down to about 20% solids and Lutensol A65N
available from BASF was added to the dispersion in the amount as a
creping processing aid. Lutensol A65N is a nonionic surfactant
comprising a 7 mol ethylene oxide adduct of a linear lauryl
myristyl alcohol. HYPOD8510.RTM./Lutensol dispersion formulation
was prepared by mixing 3.6 kg of HYPOD8510.RTM., 0.6 kg of
Lutensol, and 10.8 kg of water or 24%, 4% and 72% HYPOD8510.RTM.,
Lutensol and water respectively. The dispersion was froth-foamed by
introducing air into it and the frothy foam applied to a .about.240
degrees F. heated dryer surface. The foam formed a film-like
coating on the dryer, and the nonwoven (17 gsm spunbond) material
was pressed onto the foam coated dryer surface and then creped off
of the dryer by a creping blade. The creping speed was about 50
ft/min and the sheet temperature at creping blade was about
.about.165 degrees F. The creped material basis weight increased
from 17 gsm to about 21 gsm and the bulk increased by over 150%.
The creped sheet comprised the HYPOD 8510.RTM./Lutensol chemistry
solids add-on of about 1 gsm (5%) total of which about 70% (0.7
gsm) was HYPOD 8510.RTM. and 30% or (0.3 gsm) was Lutensol
A65N.
[0215] In addition to the above creped nonwoven material, various
groove rolled spunbond webs were produced. Specifically, low bonded
(2% bond area or less) polypropylene spunbond webs having basis
weights of 10 gsm, 14 gsm, 15 gsm, and 20 gsm were subjected to a
groove-rolled process. The webs were fed through a nip of a pair of
rolls comprising 8 grooves per inch at a speed of about 50 ft/min.
The groove engagement depth was about 0.13 inches.
[0216] For purposes of comparison, a polypropylene spunbond web was
produced having a basis weight of 17 gsm. In addition, a bonded
carded web having a basis weight of 25 gsm was analyzed.
[0217] The above webs were tested for Fuzz-on-Edge and for
bulk.
[0218] The Fuzz on Edge methodology measures the amount of fibers
that protrude from the surface of a fibrous material. The
measurement is performed using image analysis to detect and then
measure the total perimeter of protruding surface fibers observed
when the material in question is wrapped over an "edge" to allow
the fibers to be viewed from the side using transmitted light. An
image analysis algorithm was developed to detect and measure the
perimeter length (mm) of the fibers per edge length (mm) of
material, where the perimeter length is defined as the total length
of the boundaries of all of the protruding fibers (i.e.
Perimeter/Edge Length or PR/EL for short). For example, an edge
along the majority of the length of a fibrous material (e.g. facial
tissue) can be measured by acquiring and analyzing multiple,
adjacent fields-of-view to arrive at a single PR/EL value.
Typically, several such material specimens are analyzed for a
sample to arrive at a mean PR/EL value.
[0219] The Fuzz on Edge was determined using the method described
in US Publication No. 2010/0155004 with the following
modifications. A Leica DFX-300 camera (Leica Microsystems Ltd,
Heerbrugg, Switzerland) is mounted on a Polaroid MP-4 Land Camera
(Polaroid Resource Center, Cambridge, Mass.) standard support. The
support is attached to a Kreonite macro-viewer (Kreonite, Inc.,
Wichita, Kans.). An auto-stage, DCI Model HM-1212, is placed on the
upper surface of the Kreonite macro-viewer and the sample mounting
apparatus was placed atop the auto-stage (commercially available
from Design Components Incorporated, Franklin, Mass.). The
auto-stage is used to move the sample in order to obtain 15
separate and distinct, non-overlapping images from the specimen.
The sample mounting apparatus is placed on the auto macro-stage
(DCI 12.times.12 inch) of an image analysis system controlled by
Leica Microsystems QWIN Pro software, under the optical axis of a
60-mm AF Micro Nikon lens (Nikon Corp., Japan) fitted with a 20-mm
extension tube. The lens focus is adjusted to provide the maximum
magnification and the camera position on the Polaroid MP-4 support
is adjusted to provide optimum focus of the tissue edge. The sample
is illuminated from beneath the auto-stage using a Chroma Pro 45
(Circle 2, Inc., Tempe, Ariz.). The Chroma Pro settings are such
that the light is `white` and not filtered in any way to bias the
light's spectral output. The Chroma Pro may be connected to a
POWERSTAT Variable Auto-transformer, type 3PN117C, which may be
purchased from Superior Electric, Co. having an office in Bristol,
Conn. The auto-transformer is used to adjust the Chroma Pro's
illumination level.
[0220] The following results were obtained. As shown below, creping
a spunbond web as described above or subjecting a lightly bonded
spunbond web to a groove roll process significantly increased Fuzz
on Edge properties in comparison to a control.
TABLE-US-00006 Sample FOE (mm/mm) S. Dev. Creped 21 gsm
polypropylene spunbond 2.73 0.20 Groove roll 15 gsm polypropylene
spunbond 1.77 0.50 Control 17 gsm polypropylene spunbond 0.37 0.13
Bonded Carded Web 5.14 0.52
[0221] The samples were also tested for bulk. The following results
were obtained.
TABLE-US-00007 Thickness Density Bulk Sample Basis Wt. (mm) g/cc
cc/g Control 1 17.6 0.284 0.062 16.17 17 gsm 2 16.0 0.242 0.066
15.11 Spunbond 3 18.6 0.269 0.069 14.46 4 18.6 0.373 0.050 20.05 5
17.1 0.264 0.065 15.48 Average 17.6 0.29 0.061 16.30 17 gsm 1 22.2
0.722 0.031 32.50 Spunbond 2 22.7 0.673 0.034 29.60 Creped to 3
22.2 0.774 0.029 34.84 23 gsm 4 23.8 0.720 0.033 30.29 5 23.8 0.792
0.030 33.32 Average 22.9 0.74 0.031 32.09 Basis Weight Width
Thickness Bulk Sample g/M2 (mm) (mm) Density g/cc cc/g 1 10 gsm
10.3 445 0.17 0.061 16.49 polypropylene spunbond control, 2% bond
area Polypropylene 9.1 521 0.17 0.053 18.94 spunbond groove-rolled,
2% bond area % Change -11.7 17 0.0 -13.1 14.9 2 14 gsm 14.6 445
0.24 0.06 16.77 polypropylene spunbond control, 2% bond area 14 gsm
11.2 635 0.21 0.053 18.71 polypropylene spunbond groove-rolled, 2%
bond area % Change -23.3 43 -12.5 -11.7 11.6 3 20 gsm 21.7 445 0.34
0.06 16.6 polypropylene spunbond control, 2% bond area 20 gsm 20.5
521 0.28 0.06 16.73 polypropylene spunbond groove-rolled, 2% bond
area % Change -5.5 17 -17.6 0.0 0.8 4 20 gsm 21.4 548 0.39 0.055
18.27 polypropylene spunbond control, less than 2% bond area 20 gsm
17.7 625 0.33 0.054 18.68 polypropylene spunbond groove-rolled,
less than 2% bond area % Change -17.3 14 -15.4 -1.8 2.2
[0222] 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.
* * * * *