U.S. patent application number 12/791498 was filed with the patent office on 2011-12-01 for dispersible wet wipes made using short cellulose fibers for enhanced dispersibility.
Invention is credited to Kroy Donald Johnson, Peter Shawn Lortscher, David James Sealy Powling, Nathan John Vogel, Kenneth John Zwick.
Application Number | 20110290437 12/791498 |
Document ID | / |
Family ID | 45021105 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110290437 |
Kind Code |
A1 |
Vogel; Nathan John ; et
al. |
December 1, 2011 |
Dispersible Wet Wipes Made Using Short Cellulose Fibers for
Enhanced Dispersibility
Abstract
The present disclosure generally relates to dispersible wet
wipes. More particularly, the disclosure relates to a dispersible
wet wipe constructed of a wipe substrate containing a tissue web
consisting of cellulose fibers and a binder composition for binding
said binder composition to said tissue web. The tissue web contains
cellulose fibers that have a fiber length of 3 mm or less. The
construction of the dispersible wipes may allow for a pass through
percentage value calculates via a dispersibility shake flask test
of at least about 70 percent for increased dispersibility. More
desirably, the single-ply dispersible wet wipes may have a pass
through percentage value of at least about 95 percent.
Inventors: |
Vogel; Nathan John; (Neenah,
WI) ; Zwick; Kenneth John; (Neenah, WI) ;
Powling; David James Sealy; (Combined Locks, WI) ;
Johnson; Kroy Donald; (Neenah, WI) ; Lortscher; Peter
Shawn; (Neenah, WI) |
Family ID: |
45021105 |
Appl. No.: |
12/791498 |
Filed: |
June 1, 2010 |
Current U.S.
Class: |
162/158 |
Current CPC
Class: |
D21H 17/20 20130101;
D21H 27/001 20130101 |
Class at
Publication: |
162/158 |
International
Class: |
D21H 17/00 20060101
D21H017/00 |
Claims
1. A dispersible wet wipe comprising: a wipe substrate containing a
tissue web consisting of cellulose fibers, wherein said cellulose
fibers have a fiber length of 3 mm or less, and a binder
composition for binding said binder composition to said tissue web,
wherein said binder composition is present at an add-on rate of
between about 1 percent and about 15 percent based on total weight
the wipe substrate, the binder composition comprising less than
about 18 percent by weight of binder composition solids; and a
wetting composition containing between 0.4 and 3.5 percent
salt.
2. The dispersible wet wipe of claim 1 wherein said binder
composition is present at an add-on rate of between about 1 and
about 8 percent based on total weight the wipe substrate.
3. The dispersible wet wipe of claim 1 wherein the binder
composition comprising less than about 16 percent by weight of
binder composition solids
4. The dispersible wet wipe of claim 1 wherein the fibrous
substrate comprises an uncreped through-air dried tissue web.
5. The dispersible wet wipe of claim 1 wherein the wet wipe has an
in-use machine direction tensile strength of greater than 300 grams
per linear inch.
6. The dispersible wet wipe of claim 1 wherein the wet wipe has an
post-use machine direction tensile strength of less than 200 grams
per linear inch.
7. The dispersible wet wipe of claim 1 wherein the wet wipe has a
ratio of machine direction tensile strength to cross-direction
tensile strength of less than 2.25.
8. The dispersible wet wipe of claim 1 wherein the wet wipe has a
geometric mean tensile strength of at least 300 grams per linear
inch.
9. The dispersible wet wipe of claim 1 wherein the wipe substrate
comprises a single layer.
10. The dispersible wet wipe of claim 1 wherein said wipe substrate
has a formation value of greater than 20.
11. A dispersible wet wipe comprising: a wipe substrate containing
a tissue web consisting of cellulose fibers, wherein said cellulose
fibers have a fiber length of 3 mm or less, and a binder
composition for binding said binder composition to said tissue web,
said binder composition is present at an add-on rate of between
about 1 and about 15 percent; and a wetting composition containing
between about 0.4 and about 3.5 percent salt; wherein said
dispersible wet wipe has a pass through percentage value of at
least about 70 percent.
12. The dispersible wet wipe of claim 11 wherein said dispersible
wet wipe has a pass through percentage value of at least about 95
percent.
13. The dispersible wet wipe of claim 11 wherein said binder
composition is present at an add-on rate of between about 1 and
about 8 percent based on total weight of the wipe substrate.
14. The dispersible wet wipe of claim 11 wherein the binder
composition comprising less than about 18 percent by weight of
binder composition solids.
15. The dispersible wet wipe of claim 11 wherein the fibrous
substrate comprises an uncreped through-air dried tissue web.
16. The dispersible wet wipe of claim 11 wherein the wet wipe has
an in-use machine direction tensile strength of greater than 300
grams per linear inch.
17. The dispersible wet wipe of claim 11 wherein the wet wipe has
an post-use machine direction tensile strength of less than 200
grams per linear inch.
18. The dispersible wet wipe of claim 11 a pass through percentage
value of at least about 70 percent.
19. The dispersible wet wipe of claim 11 wherein said wipe
substrate has a formation value of greater than 18.
20. The dispersible wet wipe of claim 11 wherein the wet wipe has a
ratio of machine direction tensile strength to cross-direction
tensile strength of less than 2.25.
21. The dispersible wet wipe of claim 11 wherein the wet wipe has a
geometric mean tensile strength of at least 300 grams per linear
inch.
Description
BACKGROUND
[0001] Dispersible flushable moist products must exhibit
satisfactory in-use strength, but quickly break down in sewer or
septic systems. Current flushable moist wipes do this by using a
triggerable salt sensitive binder on a substrate comprising
cellulose based fibers. The binder attaches to cellulose fibers
which form a network of in-use strength in a 2 percent salt
solution (used as the moist wipe formulation), but swells and falls
apart in the fresh water of the toilet and sewer system.
[0002] Additionally, flushable moist wipes need to easily pass
through current municipal sewer systems. For many years, the
problem of disposability has plagued industries that provide
disposable items, such as diapers, wet wipes, incontinence garments
and feminine care products. Ideally, when a flushable disposable
product is discarded in either sewer or septic systems, the
product, or designated portions of the product, should "disperse"
and thus sufficiently dissolve or disintegrate in water so as not
to present problems under conditions typically found in household
and municipal sanitization systems. Some products have failed to
properly disperse. Many current wipe manufacturers achieve
acceptable strength in flushable moist wipes by using long fibers
(>10 mm) which entangle with other fibers to develop a wet
strength network. However, these long fibers are not desirable
because they tend to collect on screens in waste water systems and
cause obstructions and blockages.
[0003] As a result, there has been a movement by municipalities to
define "flushable" through various regulations. Flushable moist
wipes must meet these regulations to allow for compatibility with
home plumbing fixtures and drain lines, as well as the disposal of
the product in onsite and municipal wastewater treatment systems.
By following these regulations, manufacturers can ensure that in
normal conditions products best disposed of via the waste water
systems for public health and hygiene reasons will not block
toilets, drainage pipes, water conveyance and treatments systems or
become an aesthetic nuisance in surface waters or soil
environments.
[0004] One challenge for flushable moist wipes is that it takes
much longer to break down when compared to dry toilet tissue
potentially creating issues in sewer or septic systems. Currently
dry toilet tissue quickly exhibits lower post-use strength when
exposed to tap water whereas current flushable moist wipes take
time and/or agitation.
[0005] To achieve faster dispersion times with current binder
technologies requires lower in-use strength that is deemed
unacceptable by current consumers. Dispersibility could also be
improved by curing/drying the binder less, but again provides
unacceptable in-use strength.
[0006] Unfortunately, these approaches to addressing the
dispersibility problems provide unacceptable strength or products
that do not disperse quickly enough. Thus, there is a need to
provide a wet wipe that provides proper in-use strength for
consumers, but disperses more like toilet paper to pass various
municipal regulations and be defined as a flushable product.
SUMMARY
[0007] The present disclosure generally relates to dispersible wet
wipes. More particularly, the disclosure relates to a dispersible
wet wipe constructed of a wipe substrate containing a tissue web
consisting of cellulose fibers and a binder composition for binding
said binder composition to said tissue web. The tissue web contains
cellulose fibers that have a fiber length of 3 mm or less.
[0008] The construction of the dispersible wipes may allow for a
pass through percentage value based on the INDA/EDANA
dispersibility shake flask test of at least about 70 percent for
increased dispersibility. More desirably, the single-ply
dispersible wet wipes may have a pass through percentage value of
at least about 95 percent. For purposes herein, the "pass through
percentage value" is equal to the amount of the substrate that
passes through the 3.18 mm perforated plate using the
Dispersibility Shake Flask Test described herein.
[0009] The amount of binder composition present in the single-ply
wipe substrates may desirably range from about 1 to about 15
percent by weight based on the total weight of the single-ply wipe
substrates. More desirably, the binder composition may range from
about 1 to about 8 percent by weight based on the total weight of
the single-ply wipe substrate.
[0010] The amount of solids in the binder composition may desirably
be less than about 18 percent by weight based on the total weight
of the binder composition. More desirably, the amount of solids
binder composition may be less than about 16 percent by weight
based on the total weight of the binder composition.
[0011] In exemplary embodiments, the wipes substrate is constructed
from a tissue web that may be an uncreped through-air dried tissue
web. Additionally, the wipes substrate may be a single layer.
[0012] The dispersible wet wipes must have the desired in-use
strength. As disclosed herein, the dispersible wipes may possess an
in-use wet tensile strength of at least about 300 grams per linear
inch. The sections of the dispersible wet wipe that have broken
apart when agitated in a slosh box for approximately ten minutes
soaked in tap water after about 50 minutes or less have a post-use
machine tensile strength of less than about 200 grams per linear
inch.
[0013] Desirably, the dispersible wet wipes have a ratio of machine
direction tensile strength to cross-direction tensile strength that
is less than 2.2. The dispersible wet wipe may also have a
geometric mean tensile strength of at least 300 grams per linear
inch. The dispersible wet wipe may also have a formation value of
greater than 18.
DETAILED DESCRIPTION
[0014] The present disclosure generally relates to dispersible wet
wipes. More particularly, the disclosure relates to a dispersible
wet wipe constructed of a wipe substrate containing a tissue web
consisting of cellulose fibers and a binder composition for binding
said binder composition to said tissue web. The tissue web contains
cellulose fibers that have a fiber length of 3 mm or less to
enhance the dispersibility of the wipes.
[0015] Desirably, the dispersible wipes are constructed from tissue
webs. Basesheets suitable for this purpose can be made using any
process that produces a high density, resilient tissue structure.
Such processes include uncreped throughdried, creped throughdried
and modified wet press processes. Exemplary processes to prepare
uncreped throughdried tissue is described in U.S. Pat. No.
5,607,551, U.S. Pat. No. 5,672,248, and U.S. Pat. No. 5,593,545,
U.S. Pat. No. 6,083,346 and U.S. Pat. No. 7,056,572, all herein
incorporated by reference. Typically, the tissue webs of the
present disclosure define a basis weight of from about 60 to about
120 grams per square meter (gsm) and desirably from about 60 gsm to
about 90 gsm. Most desirably, the wipes of the present disclosure
define a basis weight from about 65 to about 80 gsm.
[0016] For example, the tissue web may be made using an uncreped
through-air-dried tissue making process in which a single-layer
headbox deposits an aqueous suspension of papermaking fibers
between forming wires. The newly-formed web is transferred from the
forming wire to a slower moving transfer fabric with the aid of a
vacuum box. The web is then transferred to a throughdrying fabric
and passed over throughdryers to dry the web. After drying, the web
is transferred from the throughdrying fabric to a reel fabric and
thereafter briefly sandwiched between fabrics. The dried web
remains with fabric until it is wound up into a parent roll.
[0017] Desirably, the tissue web consists of fibers that have fiber
lengths that are less than 3 mm. By having fiber lengths of the
less than 3 mm and providing the proper cure to the dispersible
binder, it will bring the fibers closer together so the dispersible
binder can build an acceptable in-use network, but still break up
effectively to individual fibers. Therefore, the broken-down
product will be able to effectively pass through the smallest
wastewater treatment screens, or sieves, just like toilet paper.
Optimizing basesheet properties and process conditions allows above
average in-use strength generation while improving flushability of
the product, with less risk to wastewater treatment facilities.
[0018] To provide a wipe substrate with the requisite strength,
good formation of high basis weight tissue is beneficial. To
prepare a tissue web with better formation, a wide slice opening on
the headbox may be used to allow a lot of water through and operate
at a higher tensile ratio. Providing good formation of the
substrate provides the ability to deliver strength with
significantly less binder and without the need of longer
fibers.
[0019] Desirably, the wipe substrate of the present disclosure has
a formation value of greater than 18. Providing a wipe substrate
with a formation value of greater than 18, provides the necessary
strength for in-use, but also allows a wipe substrate that
disperses in water.
[0020] The wipe substrate may be formed from a single layer or
multiple layers. In the case of multiple layers, the layers are
generally positioned in a juxtaposed or surface-to-surface
relationship and all or a portion of the layers may be bound to
adjacent layers. The fibrous material may also be formed from a
plurality of separate fibrous materials wherein each of the
separate fibrous materials may be formed from a different type of
fiber. In those instances where the fibrous material includes
multiple layers, the binder composition may be applied to the
entire thickness of the fibrous material, or each individual layer
may be separately treated and then combined with other layers in a
juxtaposed relationship to form the finished fibrous material.
Desirably, the wipe may be formed from a single layer or ply.
[0021] As described above, the wipe substrate includes a binder
composition. In one embodiment the binder composition may include a
triggerable polymer. In another embodiment, the binder composition
may comprise a triggerable polymer and a cobinder polymer.
[0022] The amount of binder composition present in the single-ply
wipe substrate may desirably range from about 1 to about 15 percent
by weight based on the total weight of the single-ply wipe
substrate. More desirably, the binder composition may comprise from
about 1 to about 10 percent by weight based on the total weight of
the single-ply wipe substrate. Even more desirably, the binder
composition may comprise from about 1 to about 8 percent by weight
based on the total weight of the single-ply wipe substrate. Most
desirably, the binder composition may comprise from about 3 to
about 8 percent by weight based on the total weight of the
single-ply wipe substrate. The amount of the binder composition
results in a single-ply wipe substrate that has in-use integrity,
but quickly disperses when soaked in tap water.
[0023] The composition of tap water can vary greatly depending on
the water source. In the case of a dispersible wipe, the binder
composition may preferably be capable of losing sufficient strength
to allow the wet wipe to disperse in tap water covering the
preponderance of the tap water composition range found throughout
the United States (and throughout the world). Thus, it is important
to evaluate the dispersibility of the binder composition in aqueous
solutions which contain the major components in tap water and in a
representative concentration range encompassing the majority of the
tap water sources in the United States. The predominant inorganic
ions typically found in drinking water are sodium, calcium,
magnesium, bicarbonate, sulfate and chloride. Based on a recent
study conducted by the American Water Works Association (AWWA) in
1996, the predominance of the U.S. municipal water systems (both
ground water and surface water sources) surveyed have a total
dissolved solids of inorganic components of about 500 ppm or less.
This level of 500 ppm total dissolved solids also represents the
secondary drinking water standard set by the U.S. Environmental
Protection Agency. The average water hardness, which represents the
calcium and magnesium concentrations in the tap water source, at
this total dissolved solids level was approximately 250 ppm
(CaCO.sub.3 equivalent), which also encompasses the water hardness
for the predominance of the municipal water systems surveyed by the
AWWA. As defined by the United States Geological Survey (USGS), a
water hardness of 250 ppm CaCO.sub.3 equivalent would be considered
"very hard" water. Similarly, the average bicarbonate concentration
at 500 ppm total dissolved solids reported in the study was 12 ppm,
which also encompasses the bicarbonate, or alkalinity, of the
predominance of the municipal water systems surveyed. A past study
by the USGS of the finished water supplies of 100 of the largest
cities in the United States suggests that a sulfate level of about
100 ppm is sufficient to cover the majority of finished water
supplies. Similarly, sodium and chloride levels of at least 50 ppm
each should be sufficient to cover the majority of U.S. finished
water supplies. Thus, binder compositions which are capable of
losing strength in tap water compositions meeting these minimum
requirements should also lose strength in tap water compositions of
lower total dissolved solids with varied compositions of calcium,
magnesium, bicarbonate, sulfate, sodium, and chloride. To ensure
the dispersibility of the binder composition across the country
(and throughout the whole world), the binder composition may
desirably be soluble in water containing up to about 100 ppm total
dissolved solids and a CaCO.sub.3 equivalent hardness up to about
55 ppm. More desirably, the binder composition may be soluble in
water containing up to about 300 ppm of total dissolved solids and
a CaCO.sub.3 equivalent hardness up to about 150 ppm. Even more
desirably, the binder composition may be soluble in water
containing up to about 500 ppm total dissolved solids and a
CaCO.sub.3 equivalent hardness up to about 250 ppm.
[0024] To provide a wipe substrate with the necessary strength,
good distribution of the binder across the sheet is needed. Earlier
examples using a similar basesheet had coverage with a single
nozzle that gave poor distribution of binder. Improving
distribution is critical to generate optimum strength and for
proper sheet handling.
[0025] To measure the proper distribution of binder across the
sheet, a ratio of the machine direction tensile strength to cross
direction tensile strength can be measured. Having more similar
values between the machine direction tensile strength to cross
direction tensile strength indicates that there is better binder
distribution across the sheet.
[0026] Desirably, the wipe substrate of the present disclosure has
a ratio value of machine direction tensile strength to cross
direction tensile strength of less than 2.25. Providing a wipe
substrate with a formation value of less than 2.25, provides the
necessary strength for in-use, but also allows it to disperse in
water.
[0027] As previously disclosed, the binder composition may comprise
the triggerable polymer and a cobinder. A variety of triggerable
polymers may be used. One type of triggerable polymer is a dilution
triggerable polymer. Examples of dilution triggerable polymers
include ion-sensitive polymers, which may be employed in
combination with a wetting composition in which the insolubilizing
agent is a salt. Other dilution triggerable polymers may also be
employed, wherein these dilution triggerable polymers are used in
combination with wetting agents using a variety of insolubilizing
agents, such as organic or polymeric compounds.
[0028] Although the triggerable polymer may be selected from a
variety of polymers, including temperature sensitive polymers and
pH-sensitive polymers, the triggerable polymer may preferably be
the dilution triggerable polymer, comprising the ion-sensitive
polymer. If the ion-sensitive polymer is derived from one or more
monomers, where at least one contains an anionic functionality, the
ion-sensitive polymer is referred to as an anionic ion-sensitive
polymer. If the ion-sensitive polymer is derived from one or more
monomers, where at least one contains a cationic functionality, the
ion-sensitive polymer is referred to as a cationic ion-sensitive
polymer. An exemplary anionic ion-sensitive polymer is described in
U.S. Pat. No. 6,423,804, which is incorporated herein in its
entirety by reference.
[0029] Examples of cationic ion-sensitive polymers are disclosed in
the following U.S. Patent Application Publication Nos.:
2003/0026963, 2003/0027270, 2003/0032352, 2004/0030080,
2003/0055146, 2003/0022568, 2003/0045645, 2004/0058600,
2004/0058073, 2004/0063888, 2004/0055704, 2004/0058606, and
2004/0062791, all of which are incorporated herein by reference in
their entirety, except that in the event of any inconsistent
disclosure or definition from the present application, the
disclosure or definition herein shall be deemed to prevail.
[0030] Desirably, the ion-sensitive polymer may be insoluble in the
wetting composition, wherein the wetting composition comprises at
least about 0.3 weight percent of an insolubilizing agent which may
be comprised of one or more inorganic and/or organic salts
containing monovalent and/or divalent ions. More desirably, the
ion-sensitive polymer may be insoluble in the wetting composition,
wherein the wetting composition comprises from about 0.3 to about
3.5 percent by weight of an insolubilizing agent which may be
comprised of one or more inorganic and/or organic salts containing
monovalent and/or divalent ions. Even more desirably, the
ion-sensitive polymer may be insoluble in the wetting composition,
wherein the wetting composition comprises from about 0.5 to about
3.5 percent by weight of an insolubilizing agent which comprises
one or more inorganic and/or organic salts containing monovalent
and/or divalent ions. Especially desirable, the ion-sensitive
polymer may be insoluble in the wetting composition, wherein the
wetting composition comprises from about 1 to about 3 percent by
weight of an insolubilizing agent which comprises one or more
inorganic and/or organic salts containing monovalent and/or
divalent ions. Suitable monovalent ions include, but are not
limited to, Na.sup.+ ions, K.sup.+ ions, Li.sup.+ ions,
NH.sub.4.sup.+ ions, low molecular weight quaternary ammonium
compounds (e.g., those having fewer than 5 carbons on any side
group), and a combination thereof. Suitable divalent ions include,
but are not limited to, Zn.sup.2+, Ca.sup.2+ and Mg.sup.2+. These
monovalent and divalent ions may be derived from organic and
inorganic salts including, but not limited to, NaCl, NaBr, KCl,
NH.sub.4Cl, Na.sub.2SO.sub.4, ZnCl.sub.2, CaCl.sub.2, MgCl.sub.2,
MgSO.sub.4, and combinations thereof. Typically, alkali metal
halides are the most desirable monovalent or divalent ions because
of cost, purity, low toxicity and availability. A desirable salt is
NaCl.
[0031] In a preferred embodiment, the ion-sensitive polymer may
desirably provide the wipe substrate with sufficient in-use
strength (typically >300 grams per linear inch) in combination
with the wetting composition containing sodium chloride. These wipe
substrates may be dispersible in tap water, desirably losing most
of their wet strength (<200 grams per linear inch) in one hour
or less.
[0032] In another preferred embodiment, the ion-sensitive polymer
may comprise the cationic sensitive polymer, wherein the cationic
sensitive polymer is a cationic polyacrylate that is the
polymerization product of 96 mol % methyl acrylate and 4 mol %
[2-(acryloyloxy)ethyl]trimethyl ammonium chloride.
[0033] As previously discussed, the binder composition may comprise
the triggerable polymer and/or the cobinder. When the binder
composition comprises the triggerable polymer and the cobinder, the
triggerable polymer and the cobinder may preferably be compatible
with each other in aqueous solutions to: 1) allow for facile
application of the binder composition to the fibrous substrate in a
continuous process and 2) prevent interference with the
dispersibility of the binder composition. Therefore, if the
triggerable polymer is the anionic ion-sensitive polymer, cobinders
which are anionic, nonionic, or very weakly cationic may be
preferred. If the triggerable polymer is the cationic ion-sensitive
polymer, cobinders which are cationic, nonionic, or very weakly
anionic may be added. Additionally, the cobinder desirably does not
provide substantial cohesion to the wipe substrate by way of
covalent bonds, such that it interferes with the dispersibility of
the wipe substrate.
[0034] The presence of the cobinder may provide a number of
desirable qualities. For example, the cobinder may serve to reduce
the shear viscosity of the triggerable polymer, such that the
binder composition has improved sprayability over the triggerable
binder alone. By use of the term "sprayable" it is meant that these
polymers may be applied to the fibrous material or substrate by
spraying, allowing the uniform distribution of these polymers
across the surface of the substrate and penetration of these
polymers into the substrate. The cobinder may also reduce the
stiffness of the wipe substrate compared to the stiffness of a wipe
substrate to which only the triggerable polymer has been applied.
Reduced stiffness may be achieved if the cobinder has a glass
transition temperature, Tg, which is lower than the Tg of the
triggerable polymer. In addition, the cobinder may be less
expensive than the triggerable polymer and by reducing the amount
of triggerable polymer needed, may serve to reduce the cost of the
binder composition. Thus, it may be desirable to use the highest
amount of cobinder possible in the binder composition such that it
does not jeopardize the dispersibility and in-use strength
properties of the wet wipe. In a preferred embodiment, the cobinder
replaces a portion of the triggerable polymer in the binder
composition and permits a given strength level to be achieved,
relative to a wet wipe having approximately the same tensile
strength but containing only the triggerable polymer in the binder
composition, to provide at least one of the following attributes:
lower stiffness, better tactile properties (e.g. lubricity or
smoothness) or reduced cost.
[0035] In one embodiment, the cobinder present in the binder
composition, relative to the mass of the binder composition, may be
about 10 percent or less, more desirably about 15 percent or less,
more desirably 20 percent or less, more desirably 30 percent or
less, or more desirably about 45 percent or less. Exemplary ranges
of cobinder relative to the solid mass of the binder composition
may include from about 1 to about 45 percent, from about 25 to
about 35 percent, from about 1 to about 20 percent and from about 5
to about 25 percent.
[0036] The cobinder may be selected from a wide variety of
polymers, as are known in the art. For example, the cobinder may be
selected from the group consisting of poly(ethylene-vinyl acetate),
poly(styrene-butadiene), poly(styrene-acrylic), a vinyl acrylic
terpolymer, a polyester latex, an acrylic emulsion latex,
poly(vinyl chloride), ethylene-vinyl chloride copolymer, a
carboxylated vinyl acetate latex, and the like. A variety of
additional exemplary cobinder polymers are discussed in U.S. Pat.
No. 6,653,406 and U.S. Patent Application Publication No.
2003/00326963, which are both incorporated herein by reference in
their entirety. Particularly preferred cobinders include
Airflex.RTM. EZ123 and Airflex.RTM. 110.
[0037] To prepare the wipe substrates described herein, the binder
composition may be applied to the fibrous material by any known
process. Suitable processes for applying the binder composition
include, but are not limited to printing, spraying, electrostatic
spraying, the use of metered press rolls or impregnating. The
amount of binder composition may be metered and distributed
uniformly onto the fibrous material or may be non-uniformly
distributed onto the fibrous material.
[0038] Once the binder composition is applied to the fibrous
material, drying, if necessary, may be achieved by any conventional
means. Once dry, the wipe substrate may exhibit improved tensile
strength when compared to the tensile strength of the untreated
wet-laid or dry-laid fibrous material, and yet should have the
ability to rapidly "fall apart" or disintegrate when placed in tap
water.
[0039] For ease of application to the fibrous substrate, the binder
composition may be dissolved in water, or in a non-aqueous solvent,
such as methanol, ethanol, acetone, or the like, with water being
the preferred solvent. The amount of binder dissolved in the
solvent may vary depending on the polymer used and the fabric
application. Desirably, the binder solution contains less than
about 18 percent by weight of binder composition solids. More
desirably, the binder solution contains less than 16 percent by
weight of binder composition solids.
[0040] Unexpectedly, It was discovered that the a percentage binder
composition solids of less than about 18 percent, and preferably
less than about 16 percent ensure spray coverage is optimized with
acrylate-based binder. Unexpectedly, low solids spraying of the
binder on uncreped through air-dried tissue provided beneficial
strength benefits despite significantly high attachment points per
fiber volume (36,000 contacts/mm.sup.3) that, in theory, should not
require droplet size optimization. In addition, one skilled in the
art would prefer not to lower the percentage of solids in the
binder since the lower binder add-on made spraying at lower solids
difficult due to dispersible binder nozzle tip requirements.
[0041] Effective spray coverage will provide better strength to the
wipe. The "geometric mean tensile strength" (GMT) may be used to
define effective spray coverage by illustrating the strength across
the wipe. Desirably, the dispersible wet wipes have a geometric
mean tensile strength of at least 300 grams per linear inch.
[0042] A number of techniques may be employed to manufacture the
wet wipes. In one embodiment, these techniques may include the
following steps: [0043] 1. Providing the fibrous material (e.g., an
unbonded airlaid, a tissue web, a carded web, fluff pulp, etc.).
[0044] 2. Applying the binder composition to the fibrous material,
typically in the form of a liquid, suspension, or foam to provide
the wipe substrate. [0045] 3. The wipe substrate may be dried.
[0046] 4. Applying a wetting composition to the wipe substrate to
generate the wet wipe. [0047] 5. Placing the wet wipe in roll form
or in a stack and packaging the product.
[0048] In one embodiment, the binder composition as applied in step
2 may comprise the triggerable polymer. In a further embodiment,
the binder composition as applied in step 2 may comprise the
triggerable polymer and the cobinder.
[0049] The finished wet wipes may be individually packaged,
desirably in a folded condition, in a moisture proof envelope or
packaged in containers holding any desired number of sheets in a
water-tight package with a wetting composition applied to the wipe.
Some example processes which can be used to manufacture folded wet
wipes are described in U.S. Pat. Nos. 5,540,332 and 6,905,748,
which are incorporated by reference herein. The finished wipes may
also be packaged as a roll of separable sheets in a moisture-proof
container holding any desired number of sheets on the roll with a
wetting composition applied to the wipes. The roll can be coreless
and either hollow or solid. Coreless rolls, including rolls with a
hollow center or without a solid center, can be produced with known
coreless roll winders, including those of SRP Industry, Inc. of San
Jose, Calif.; Shimizu Manufacturing of Japan, and the devices
disclosed in U.S. Pat. No. 4,667,890. U.S. Pat. No. 6,651,924 also
provides examples of a process for producing coreless rolls of wet
wipes.
[0050] In addition to the wipe substrate, wet wipes also contain a
wetting composition described herein. The liquid wetting
composition can be any liquid, which can be absorbed into the wet
wipe basesheet and may include any suitable components, which
provide the desired wiping properties. For example, the components
may include water, emollients, surfactants, fragrances,
preservatives, organic or inorganic acids, chelating agents, pH
buffers, or combinations thereof, as are well known to those
skilled in the art. Further, the liquid may also contain lotions,
medicaments, and/or antimicrobials.
[0051] The wetting composition may desirably be incorporated into
the wipe in an add-on amount of from about 10 to about 600 percent
by weight of the substrate, more desirably from about 50 to about
500 percent by weight of the substrate, even more desirably from
about 100 to about 500 percent by weight of the substrate, and
especially more desirably from about 200 to about 300 percent by
weight of the substrate.
[0052] In the case of a dispersible, wipe, the wetting composition
for use in combination with the wipe substrate may desirably
comprise an aqueous composition containing the insolubilizing agent
that maintains the coherency of the binder composition and thus the
in-use strength of the wet wipe until the insolubilizing agent is
diluted with tap water. Thus the wetting composition may contribute
to the triggerable property of the triggerable polymer and
concomitantly the binder composition.
[0053] The insolubilizing agent in the wetting composition can be a
salt, such as those previously disclosed for use with the
ion-sensitive polymer, a blend of salts having both monovalent and
multivalent ions, or any other compound, which provides in-use and
storage strength to the binder composition and may be diluted in
water to permit dispersion of the wet wipe as the binder
composition transitions to a weaker state. The wetting composition
may desirably contain more than about 0.3 weight percent of an
insolubilizing agent based on the total weight of the wetting
composition. The wetting composition may desirably contain from
about 0.3 to about 10 weight percent of an insolubilizing agent
based on the total weight of the wetting composition. More
desirably, the wetting composition may contain from about 0.5 to
about 5 weight percent of an insolubilizing agent based on the
total weight of the wetting composition. More desirably, the
wetting composition may contain from about 1 to about 4 weight
percent of an insolubilizing agent based on the total weight of the
wetting composition. Even more desirably, the wetting composition
may contain from about 1 to about 2 weight percent of an
insolubilizing agent based on the total weight of the wetting
composition.
[0054] The wetting composition may desirably be compatible with the
triggerable polymer, the cobinder polymer, and any other components
of the binder composition. In addition, the wetting composition
desirably contributes to the ability of the wet wipes to maintain
coherency during use, storage and/or dispensing, while still
providing dispersibility in tap water.
[0055] In one example, the wetting compositions may contain water.
The wetting compositions can suitably contain water in an amount of
from about 0.1 to about 99.9 percent by weight of the composition,
more typically from about 40 to about 99 percent by weight of the
composition, and more preferably from about 60 to about 99.9
percent by weight of the composition. For instance, where the
composition is used in connection with a wet wipe, the composition
can suitably contain water in an amount of from about 75 to about
99.9 percent by weight of the composition.
[0056] The wetting compositions may further contain additional
agents that impart a beneficial effect on skin or hair and/or
further act to improve the aesthetic feel of the compositions and
wipes described herein. Examples of suitable skin benefit agents
include emollients, sterols or sterol derivatives, natural and
synthetic fats or oils, viscosity enhancers, rheology modifiers,
polyols, surfactants, alcohols, esters, silicones, clays, starch,
cellulose, particulates, moisturizers, film formers, slip
modifiers, surface modifiers, skin protectants, humectants,
sunscreens, and the like.
[0057] Thus, in one example, the wetting compositions may further
optionally include one or more emollients, which typically act to
soften, soothe, and otherwise lubricate and/or moisturize the skin.
Suitable emollients that can be incorporated into the compositions
include oils such as petrolatum based oils, petrolatum, mineral
oils, alkyl dimethicones, alkyl methicones, alkyldimethicone
copolyols, phenyl silicones, alkyl trimethylsilanes, dimethicone,
dimethicone crosspolymers, cyclomethicone, lanolin and its
derivatives, glycerol esters and derivatives, propylene glycol
esters and derivatives, alkoxylated carboxylic acids, alkoxylated
alcohols, and combinations thereof.
[0058] Ethers such as eucalyptol, cetearyl glucoside, dimethyl
isosorbic polyglyceryl-3 cetyl ether, polyglyceryl-3
decyltetradecanol, propylene glycol myristyl ether, and
combinations thereof, can also suitably be used as emollients.
[0059] In addition, the wetting composition may include an
emollient in an amount of from about 0.01 to about 20 percent by
weight of the composition, more desirably from about 0.05 to about
10 percent by weight of the composition, and more typically from
about 0.1 to about 5 percent by weight of the composition.
[0060] One or more viscosity enhancers may also be added to the
wetting composition to increase the viscosity, to help stabilize
the composition thereby reducing migration of the composition and
improving transfer to the skin. Suitable viscosity enhancers
include polyolefin resins, lipophilic/oil thickeners, polyethylene,
silica, silica silylate, silica methyl silylate, colloidal silicone
dioxide, cetyl hydroxy ethyl cellulose, other organically modified
celluloses, PVP/decane copolymer, PVM/MA decadiene crosspolymer,
PVP/eicosene copolymer, PVP/hexadecane copolymer, clays, starches,
gums, water-soluble acrylates, carbomers, acrylate based
thickeners, surfactant thickeners, and combinations thereof.
[0061] The wetting composition may desirably include one or more
viscosity enhancers in an amount of from about 0.01 to about 25
percent by weight of the composition, more desirably from about
0.05 to about 10 percent by weight of the composition, and even
more desirably from about 0.1 to about 5 percent by weight of the
composition.
[0062] The compositions of the disclosure may optionally further
contain humectants. Examples of suitable humectants include
glycerin, glycerin derivatives, sodium hyaluronate, betaine, amino
acids, glycosaminoglycans, honey, sorbitol, glycols, polyols,
sugars, hydrogenated starch hydrolysates, salts of PCA, lactic
acid, lactates, and urea. A particularly preferred humectant is
glycerin. The composition of the present disclosure may suitably
include one or more humectants in an amount of from about 0.05 to
about 25 percent by weight of the composition.
[0063] The compositions of the disclosure may optionally further
contain film formers. Examples of suitable film formers include
lanolin derivatives (e.g., acetylated lanolins), superfatted oils,
cyclomethicone, cyclopentasiloxane, dimethicone, synthetic and
biological polymers, proteins, quaternary ammonium materials,
starches, gums, cellulosics, polysaccharides, albumen, acrylates
derivatives, IPDI derivatives, and the like. The composition of the
present disclosure may suitably include one or more film formers in
an amount of from about 0.01 to about 20 percent by weight of the
composition.
[0064] The wetting compositions may also further contain skin
protectants. Examples of suitable skin protectants include
ingredients referenced in SP monograph (21 CFR .sctn.347). Suitable
skin protectants and amounts include those set forth in SP
monograph, Subpart B--Active Ingredients .sctn.347.10: (a)
Allantoin, 0.5 to 2%, (b) Aluminum hydroxide gel, 0.15 to 5%, (c)
Calamine, 1 to 25%, (d) Cocoa butter, 50 to 100%, (e) Cod liver
oil, 5 to 13.56%, in accordance with .sctn.347.20(a)(1) or (a)(2),
provided the product is labeled so that the quantity used in a
24-hour period does not exceed 10,000 U.S.P. Units vitamin A and
400 U.S.P. Units cholecalciferol, (f) Colloidal oatmeal, 0.007%
minimum; 0.003% minimum in combination with mineral oil in
accordance with .sctn.347.20(a)(4), (g) Dimethicone, 1 to 30%, (h)
Glycerin, 20 to 45%, (i) Hard fat, 50 to 100%, (j) Kaolin, 4 to
20%, (k) Lanolin, 12.5 to 50%, (l) Mineral oil, 50 to 100%; 30 to
35% in combination with colloidal oatmeal in accordance with
.sctn.347.20(a)(4), (m) Petrolatum, 30 to 100%, (o) Sodium
bicarbonate, (q) Topical starch, 10 to 98%, (r) White petrolatum,
30 to 100%, (s) Zinc acetate, 0.1 to 2%, (t) Zinc carbonate, 0.2 to
2%, (u) Zinc oxide, 1 to 25%.
[0065] The wetting compositions may also further contain quaternary
ammonium materials. Examples of suitable quaternary ammonium
materials include polyquaternium-7, polyquaternium-10, benzalkonium
chloride, behentrimonium methosulfate, cetrimonium chloride,
cocamidopropyl pg-dimonium chloride, guar hydroxypropyltrimonium
chloride, isostearamidopropyl morpholine lactate,
polyquaternium-33, polyquaternium-60, polyquaternium-79,
quaternium-18 hectorite, quaternium-79 hydrolyzed silk,
quaternium-79 hydrolyzed soy protein, rapeseed amidopropyl
ethyldimonium ethosulfate, silicone quaternium-7, stearalkonium
chloride, palmitamidopropyltrimonium chloride, butylglucosides,
hydroxypropyltrimonium chloride, laurdimoniumhydroxypropyl
decylglucosides chloride, and the like. The composition of the
present disclosure may suitably include one or more quaternary
materials in an amount of from about 0.01 to about 20 percent by
weight of the composition.
[0066] The wetting compositions may optionally further contain
surfactants. Examples of suitable additional surfactants include,
for example, anionic surfactants, cationic surfactants, amphoteric
surfactants, zwitterionic surfactants, non-ionic surfactants, and
combinations thereof. Specific examples of suitable surfactants are
known in the art and include those suitable for incorporation into
wetting compositions and wipes. The composition of the present
disclosure may suitably include one or more surfactants in an
amount of from about 0.01 to about 20 percent by weight of the
composition.
[0067] In addition to nonionic surfactants, the cleanser may also
contain other types of surfactants. For instance, in some
embodiments, amphoteric surfactants, such as zwitterionic
surfactants, may also be used. For instance, one class of
amphoteric surfactants that may be used in the present disclosure
are derivatives of secondary and tertiary amines having aliphatic
radicals that are straight chain or branched, wherein one of the
aliphatic substituents contains from about 8 to 18 carbon atoms and
at least one of the aliphatic substituents contains an anionic
water-solubilizing group, such as a carboxy, sulfonate, or sulfate
group. Some examples of amphoteric surfactants include, but are not
limited to, sodium 3-(dodecylamino)propionate, sodium
3-(dodecylamino)-propane-1-sulfonate, sodium 2-(dodecylamino)ethyl
sulfate, sodium 2-(dimethylamino)octadecanoate, disodium
3-(N-carboxymethyl-dodecylamino)propane-1-sulfonate, disodium
octadecyliminodiacetate, sodium 1-carboxymethyl-2-undecylimidazole,
and sodium
N,N-bis(2-hydroxyethyl)-2-sulfato-3-dodecoxypropylamine.
[0068] Additional classes of suitable amphoteric surfactants
include phosphobetaines and the phosphitaines. For instance, some
examples of such amphoteric surfactants include, but are not
limited to, sodium coconut N-methyl taurate, sodium oleyl N-methyl
taurate, sodium tall oil acid N-methyl taurate, sodium palmitoyl
N-methyl taurate, cocodimethylcarboxymethylbetaine,
lauryldimethylcarboxymethylbetaine,
lauryldimethylcarboxyethylbetaine,
cetyl-dimethylcarboxymethylbetaine,
lauryl-bis-(2-hydroxyethyl)carboxymethylbetaine,
oleyldimethylgammacarboxypropylbetaine,
lauryl-bis-(2-hydroxypropyl)-carboxyethylbetaine,
cocoamidodimethylpropylsultaine,
stearylamidodimethylpropylsultaine,
laurylamido-bis-(2-hydroxyethyl)propylsultaine, di-sodium oleamide
PEG-2 sulfosuccinate, TEA oleamido PEG-2 sulfosuccinate, disodium
oleamide MEA sulfosuccinate, disodium oleamide MIPA sulfosuccinate,
disodium ricinoleamide MEA sulfosuccinate, disodium undecylenamide
MEA sulfosuccinate, disodium lauryl sulfosuccinate, disodium wheat
germamido MEA sulfosuccinate, disodium wheat germamido PEG-2
sulfosuccinate, disodium isostearamideo MEA sulfosuccinate,
cocoamphoglycinate, cocoamphocarboxyglycinate, lauroamphoglycinate,
lauroamphocarboxyglycinate, capryloamphocarboxyglycinate,
cocoamphopropionate, cocoamphocarboxypropionate,
lauroamphocarboxypropionate, capryloamphocarboxypropionate,
dihydroxyethyl tallow glycinate, cocoamido disodium 3-hydroxypropyl
phosphobetaine, lauric myristic amido disodium 3-hydroxypropyl
phosphobetaine, lauric myristic amido glyceryl phosphobetaine,
lauric myristic amido carboxy disodium 3-hydroxypropyl
phosphobetaine, cocoamido propyl monosodium phosphitaine,
cocamidopropyl betaine, lauric myristic amido propyl monosodium
phosphitaine, and mixtures thereof.
[0069] In certain instances, it may also be desired to utilize one
or more anionic surfactants within the cleansers. Suitable anionic
surfactants include, but are not limited to, alkyl sulfates, alkyl
ether sulfates, alkyl ether sulfonates, sulfate esters of an
alkylphenoxy polyoxyethylene ethanol, alpha-olefin sulfonates,
beta-alkoxy alkane sulfonates, alkylauryl sulfonates, alkyl
monoglyceride sulfates, alkyl monoglyceride sulfonates, alkyl
carbonates, alkyl ether carboxylates, fatty acid salts,
sulfosuccinates, sarcosinates, octoxynol or nonoxynol phosphates,
taurates, fatty taurides, fatty acid amide polyoxyethylene
sulfates, isethionates, or mixtures thereof.
[0070] Particular examples of some suitable anionic surfactants
include, but are not limited to, C.sub.8-18 alkyl sulfates,
C.sub.8-18 fatty acid salts, C.sub.8-18 alkyl ether sulfates having
one or two moles of ethoxylation, C.sub.8-18 alkoyl sarcosinates,
C.sub.8-18 sulfoacetates, C.sub.8-18 sulfosuccinates, C.sub.8-18
alkyl diphenyl oxide disulfonates, C.sub.8-18 alkyl carbonates,
C.sub.8-18 alpha-olefin sulfonates, methyl ester sulfonates, and
blends thereof. The C.sub.8-18 alkyl group can be straight chain
(e.g., lauryl) or branched (e.g., 2-ethylhexyl). The cation of the
anionic surfactant can be an alkali metal (e.g., sodium or
potassium), ammonium, C.sub.1-4 alkylammonium (e.g., mono-, di-,
tri-), or C.sub.1-3 alkanolammonium (e.g., mono-, di-, tri-).
[0071] Specific examples of such anionic surfactants include, but
are not limited to, lauryl sulfates, octyl sulfates, 2-ethylhexyl
sulfates, decyl sulfates, tridecyl sulfates, cocoates, lauroyl
sarcosinates, lauryl sulfosuccinates, linear C.sub.10 diphenyl
oxide disulfonates, lauryl sulfosuccinates, lauryl ether sulfates
(1 and 2 moles ethylene oxide), myristyl sulfates, oleates,
stearates, tallates, ricinoleates, cetyl sulfates, and similar
surfactants.
[0072] Cationic surfactants, such as cetylpyridinium chloride and
methylbenzethonium chloride, may also be utilized.
[0073] The wetting compositions may also further contain additional
emulsifiers. As mentioned above, the natural fatty acids, esters
and alcohols and their derivatives, and combinations thereof, may
act as emulsifiers in the composition. Optionally, the composition
may contain an additional emulsifier other than the natural fatty
acids, esters and alcohols and their derivatives, and combinations
thereof. Examples of suitable emulsifiers include nonionic
emulsifiers such as polysorbate 20, polysorbate 80, anionic
emulsifiers such as DEA phosphate, cationic emulsifiers such as
behentrimonium methosulfate, and the like. The composition of the
present disclosure may suitably include one or more additional
emulsifier in an amount of from about 0.01 to about 10 percent by
weight of the composition.
[0074] For example, nonionic surfactants may be used as an
emulsifier. Nonionic surfactants typically have a hydrophobic base,
such as a long chain alkyl group or an alkylated aryl group, and a
hydrophilic chain comprising a certain number (e.g., 1 to about 30)
of ethoxy and/or propoxy moieties. Examples of some classes of
nonionic surfactants that can be used include, but are not limited
to, ethoxylated alkylphenols, ethoxylated and propoxylated fatty
alcohols, polyethylene glycol ethers of methyl glucose,
polyethylene glycol ethers of sorbitol, ethylene oxide-propylene
oxide block copolymers, ethoxylated esters of fatty (C.sub.8-18)
acids, condensation products of ethylene oxide with long chain
amines or amides, condensation products of ethylene oxide with
alcohols, and mixtures thereof.
[0075] Various specific examples of suitable nonionic surfactants
include, but are not limited to, methyl gluceth-10, PEG-20 methyl
glucose distearate, PEG-20 methyl glucose sesquistearate,
C.sub.11-15 pareth-20, ceteth-8, ceteth-12, dodoxynol-12,
laureth-15, PEG-20 castor oil, polysorbate 20, steareth-20,
polyoxyethylene-10 cetyl ether, polyoxyethylene-10 stearyl ether,
polyoxyethylene-20 cetyl ether, polyoxyethylene-10 oleyl ether,
polyoxyethylene-20 oleyl ether, an ethoxylated nonylphenol,
ethoxylated octylphenol, ethoxylated dodecylphenol, ethoxylated
fatty (C.sub.8-22) alcohol, including 3 to 20 ethylene oxide
moieties, polyoxyethylene-20 isohexadecyl ether, polyoxyethylene-23
glycerol laurate, PEG 80 sorbitan laurate, polyoxy-ethylene-20
glyceryl stearate, PPG-10 methyl glucose ether, PPG-20 methyl
glucose ether, polyoxyethylene-20 sorbitan monoesters,
polyoxyethylene-80 castor oil, polyoxyethylene-15 tridecyl ether,
polyoxy-ethylene-6 tridecyl ether, laureth-2, laureth-3, laureth-4,
PEG-3 castor oil, PEG 600 dioleate, PEG 400 dioleate, and mixtures
thereof.
[0076] The wetting compositions may also further contain
preservatives. Suitable preservatives for use in the present
compositions may include, for instance, Kathon CG, which is a
mixture of methylchloroisothiazolinone and methylisothiazolinone
available from Rohm & Haas of Philadelphia, Pa.; Neolone
950.RTM., which is methylisothiazolinone available from Rohm &
Haas of Philadelphia, Pa.; DMDM hydantoin (e.g., Glydant Plus
available from Lonza, Inc. of Fair Lawn, N.J.); iodopropynyl
butylcarbamate; benzoic esters (parabens), such as methylparaben,
propylparaben, butylparaben, ethylparaben, isopropylparaben,
isobutylparaben, benzylparaben, sodium methylparaben, and sodium
propylparaben; 2-bromo-2-nitropropane-1,3-diol; benzoic acid;
imidazolidinyl urea; diazolidinyl urea; and the like. Still other
preservatives may include ethylhexylglycerin, phenoxyethanol
caprylyl glycol, a blend of 1,2-hexanediol, caprylyl glycol and
tropolone, and a blend of phenoxyethanol and tropolone.
[0077] The wetting compositions may additionally include adjunct
components conventionally found in pharmaceutical compositions in
their art-established fashion and at their art-established levels.
For example, the compositions may contain additional compatible
pharmaceutically active materials for combination therapy, such as
antimicrobials, antioxidants, anti-parasitic agents, antipruritics,
antifungals, antiseptic actives, biological actives, astringents,
keratolytic actives, local anesthetics, anti-stinging agents,
anti-reddening agents, skin soothing agents, and combinations
thereof. Other suitable additives that may be included in the
compositions of the present disclosure include colorants,
deodorants, fragrances, perfumes, emulsifiers, anti-foaming agents,
lubricants, natural moisturizing agents, skin conditioning agents,
skin protectants and other skin benefit agents (e.g., extracts such
as aloe vera and anti-aging agents such as peptides), solvents,
solubilizing agents, suspending agents, wetting agents, humectants,
pH adjusters, buffering agents, dyes and/or pigments, and
combinations thereof.
[0078] The wet wipes, as disclosed herein, do not require organic
solvents to maintain in-use strength, and the wetting composition
may be substantially free of organic solvents. Organic solvents may
produce a greasy after-feel and cause irritation in higher amounts.
However, small amounts of organic solvents may be included in the
wetting composition for different purposes other than maintaining
in-use wet strength. In one embodiment, small amounts of organic
solvents (less than about 1 percent) may be utilized as fragrance
or preservative solubilizers to improve process and shelf stability
of the wetting composition. The wetting composition may desirably
contain less than about 5 weight percent of organic solvents, such
as propylene glycol and other glycols, polyhydroxy alcohols, and
the like, based on the total weight of the wetting composition.
More desirably, the wetting composition may contain less than about
3 weight percent of organic solvents. Even more desirably, the
wetting composition may contain less than about 1 weight percent of
organic solvents.
[0079] The wet wipes, as disclosed herein, desirably may be made to
have sufficient tensile strength, sheet-to-sheet adhesion,
calculated per layer stack thickness and flexibility.
[0080] The wet wipes may be prepared using a wipe substrate with a
fibrous material and a binder composition forming a nonwoven
airlaid web. These wet wipes made with wipe substrate may also be
made to be usable without breaking or tearing, to be consumer
acceptable, and provide problem-free disposal once disposed in a
household sanitation system. The wet wipes may also be prepared
using a coform substrate as described above.
[0081] The wet wipe formed with a wipe substrate desirably may have
a machine direction tensile strength ranging from at least about
300 to about 1000 grams per linear inch. More desirably, the wet
wipe may have a machine direction tensile strength ranging from at
least about 300 to about 800 grams per linear inch. Even more
desirably, the wet wipe may have a machine direction tensile
strength ranging from at least about 300 to about 600 grams per
linear inch. Most desirably, the wet wipe may have a machine
direction tensile strength ranging from at least about 350 to about
550 grams per linear inch.
[0082] The wet wipe may be configured to provide all desired
physical properties by use of a single or multi-ply wet wipe
product, in which two or more plies of wipe substrate are joined
together by methods known in the art to form a multi-ply wipe.
[0083] The total basis weight of the wipe substrate, consisting of
a single or multiple layers of wipe substrate in the final wet wipe
product, may be in the range of at least about 25 to about 120 gsm.
More desirably, the basis weight of the wipe substrate may be
between about 40 and 90 gsm. Even more desirably, the basis weight
of the wipe substrate may be between about 60 and 80 gsm.
Especially more desirably, the basis weight of the wipe substrate
may be between about 70 and 75 gsm.
[0084] As mentioned previously, the wet wipes formed from the wipe
substrate, may be sufficiently dispersible so that they lose enough
strength to break apart in tap water under conditions typically
experienced in household or municipal sanitation systems. Also
mentioned previously, the tap water used for measuring
dispersibility should encompass the concentration range of the
majority of the components typically found in the tap water
compositions that the wet wipe would encounter upon disposal.
Previous methods for measuring dispersibility of the wipe
substrates, whether dry or pre-moistened, have commonly relied on
systems in which the material was exposed to shear while in water,
such as measuring the time for a material to break up while being
agitated by a mechanical mixer. Constant exposure to such
relatively high, uncontrolled shear gradients offers an unrealistic
and overly optimistic test for products designed to be flushed in a
toilet, where the level of shear is extremely weak or brief. Shear
rates may be negligible, for example once the material enters a
septic tank. Thus, for a realistic appraisal of wet wipe
dispersibility, the test methods should simulate the relatively low
shear rates the products will experience once they have been
flushed in the toilet.
[0085] A static soak test, for example, should illustrate the
dispersibility of the wet wipe after it is fully submerged with
water from the toilet and where it experiences negligible shear,
such as in a septic tank. Desirably, the wet wipe may have less
than about 200 grams per linear inch of tensile strength after one
hour when soaked in tap water.
[0086] As mentioned previously, the wet wipes formed from the
singly-ply wipe substrate, may be sufficiently dispersible so that
they lose enough strength to break apart in tap water under
conditions typically experienced in household or municipal
sanitation systems. Also mentioned previously, the tap water used
for measuring dispersibility should encompass the concentration
range of the majority of the components typically found in the tap
water compositions that the wet wipe would encounter upon disposal.
The Dispersibility Shake Flask Test is the first of two options to
assess the dispersibility or physical break-up of a test product
during its transport through building drain lines, sewage pumps,
and sewer pipes in the INDA/EDANA Guidance Document for Assessing
the Flushabliity of Nowoven Consumer Products. It simulates the
physical forces acting to disintegrate the product during passage
through sewage pumps or through sewer pipes. The whole product is
placed in a flask containing tap water or raw wastewater and is
mechanically shaken under specified conditions. The contents of the
flask are passed through a series of screens with sizes of 12, 6, 3
and 1.5 mm and the various size fractions retained on the screens
are weighed so that the extent of disintegration can be determined.
Under this test, if greater than 95 percent of the product mass
passes through a 3.18-mm sieve (perforated plate) after agitation
for one hour, then it is deemed that the product will adequately
disperse during sewer conveyance. For purposes herein, the pass
through percentage value is equal to the amount of the wipe that
passes though the 3 mm perforated plate after one-hour of
agitation. Thus, wipes will be the necessary size or smaller to
allow the pieces to pass through the bar screens typically found in
municipal sanitary sewer treatment facilities and not cause
problems or blockages in households.
[0087] The Dispersibility Shake Flask Test should illustrate the
dispersibility of the wet wipe after it is fully wetted with water
from the toilet and where it experiences typical forces during its
transport through sewage pumps and municipal wastewater conveyance
systems.
[0088] In one embodiment, the dispersible wet wipe has a pass
through percentage value of at least 70 percent. More desirably,
the dispersible wet wipe has a pass through percentage value of at
least 90 percent. Even more desirably, the dispersible wet wipe has
a pass through percentage value of at least 95 percent.
[0089] Desirably, the wet wipes, as disclosed herein, may possess
an in-use wet tensile strength of at least about 300 grams per
linear inch, and a tensile strength of less than about 200 grams
per linear inch when soaked in tap water after about one hour.
[0090] Most desirably, the wet wipes, as disclosed herein, may
possess an in-use wet tensile strength greater than about 300 grams
per linear inch when wetted, and a post-use tensile strength of
less than about 150 grams per linear inch when soaked in tap water
desirably after about one hour.
[0091] The wet wipe preferably maintains its desired
characteristics over the time periods involved in warehousing,
transportation, retail display and storage by the consumer. In one
embodiment, shelf life may range from two months to two years.
[0092] The wet wipes, as disclosed herein, are illustrated by the
following examples, which are not to be construed in any way as
imposing limitations upon the scope thereof. On the contrary, it is
to be clearly understood various other embodiments, modifications,
and equivalents thereof, which, after reading the description
herein, may suggest themselves to those skilled in the art without
departing from the spirit and/or the scope of the appended
claims.
Test Methods
Wet Wipe Tensile Strength Measurements
[0093] For purposes herein, tensile strength may be measured using
a Constant Rate of Elongation (CRE) tensile tester using a 1-inch
jaw width (sample width), a test span of 3 inches (gauge length),
and a rate of jaw separation of 25.4 centimeters per minute after
maintaining the sample at the ambient conditions of 23.+-.2.degree.
C. and 50.+-.5% relative humidity for four hours before testing the
sample at the same ambient conditions. The wet wipes are cut with
1-inch wide strips cut from the center of the wipes in the
specified machine direction (MD) or cross-machine direction (CD)
orientation using a JDC Precision Sample Cutter (Thwing-Albert
Instrument Company, Philadelphia, Pa., Model No. JDC3-10, Serial
No. 37333). The "MD tensile strength" is the peak load in
grams-force per inch of sample width when a sample is pulled to
rupture in the machine direction. The "CD tensile strength" is the
peak load in grams-force per inch of sample width when a sample is
pulled to rupture in the cross direction.
[0094] The instrument used for measuring tensile strength is an MTS
Systems Sinergie 200 model. The data acquisition software is MTS
TestWorks.RTM. for Windows Ver. 4.0 commercially available from MTS
Systems Corp., Eden Prairie, Minn. The load cell is an MTS 50
Newton maximum load cell. The gauge length between jaws is
3.+-.0.04 inches. The top and bottom jaws are operated using
pneumatic-action with maximum 60 P.S.I. The break sensitivity is
set at 40 percent. The data acquisition rate is set at 100 Hz (i.e.
100 samples per second). The sample is placed in the jaws of the
instrument, centered both vertically and horizontally. The test is
then started and ends when the force drops by 40 percent of peak.
The peak load expressed in grams-force is recorded as the "MD
tensile strength" of the specimen. At least twelve representative
specimens are tested for each product and its average peak load is
determined. As used herein, the "geometric mean tensile strength"
(GMT) is the square root of the product of the dry machine
direction tensile strength multiplied by the dry cross-machine
direction tensile strength and is expressed as grams per inch of
sample width. All of these values are for in-use tensile strength
measurements.
[0095] To provide post-use tensile strength measurements, the
samples are submerged in tap water for a time period of one hour
and then measured for tensile strength.
Basis Weight
[0096] The dry basis weight of the basesheet material forming the
wet wipes can be obtained using the ASTM active standard D646-96
(2001), Standard Test Method for Grammage of Paper and Paperboard
(Mass per Unit Area), or an equivalent method.
Dispersibility Shake Flask Test
[0097] The Percentage Mass Loss of the wet wipes can be obtained
using the INDA/EDANA Guidance Document for Assessing the
Flushability of Nonwoven Consumer Products, Dispersibilty Shake
Flask Test. For purposes herein, samples were placed into tap water
and tested after shaking on the flask shaker for one hour.
[0098] As used herein, the Pass Through Percentage Value is equal
to Percentage Mass Loss, or the amount of the substrate that passes
through the 3 mm perforated plate.
[0099] This test is used to assess the dispersibility or physical
breakup of a flushable product during its transport through sewage
pumps (e.g., ejector or grinder pumps) and municipal wastewater
conveyance systems (e.g., sewer pipes and lift stations). This test
assesses the rate and extent of disintegration of a test material
in the presence of tap water or raw wastewater. Results from this
test are used to predict the compatibility of a flushable product
with household sewage pumps and municipal collection systems.
[0100] Materials and Apparatus: [0101] 1. Fernbach triple-baffled,
glass, culture flasks (2800 mL). [0102] 2. Orbital floor shaker
with 2-in (5-cm) orbit capable of 150 rpm. The platform for the
shaker needs clamps to be able to accommodate a bottom flask
diameter of 205 mm. [0103] 3. USA Standard Testing Sieve #18 (1 mm
opening): 8 in (20 cm) diameter. [0104] 4. Perforated Plate Screens
details
TABLE-US-00001 [0104] Hole Size Hole size % open (mm) (in) Hole
Center Pattern Gauge area 12.75 mm 1/2'' 11/16''.sup. Staggered
16SWG 48% 6.35 mm 1/4'' 5/16'' Staggered 16SWG 58% 3.18 mm 1/8''
3/16'' Staggered 20SWG 40% 1.59 mm 1/16'' 3/32'' Staggered 20SWG
41%
[0105] 5. Drying oven capable of maintaining a temperature of
40.+-.3.degree. C. for thermoplastic test materials and capable of
maintaining a temperature of 103.+-.3.degree. C. for non-plastic
test materials.
[0106] Test Initiation:
[0107] Each test product is run in triplicate so there are three
flasks prepared for each of the two predetermined destructive
sampling time points. Each flask contains one liter of prescreened
wastewater or room temperature tap water and the test product (see
section 6.1 Summary of Test Methods for guidance in choosing a
medium for test). Each test product should be pre-weighed in
triplicate (dry weight basis) on an analytical balance that
measures at least 2-decimal places and then these weights recorded
in a laboratory notebook for later use in the final percent
disintegration calculations. Control flasks with the reference
material are also run to accommodate two destructive sampling time
points. Each flask also contains one liter of prescreened
wastewater or tap water and an appropriate reference material.
Whatman #41 ashless filter paper if used should be folded into
quarters and reopened before placing in flask. For products that
are pre-moistened (e.g., wet wipes) sample preconditioning to
simulate product delivery to the sewer can be performed by flushing
the product through the toilet and drain line apparatus. This
should be documented in the study record. Measure one liter of
wastewater or tap water into each of the Fernbach flasks and place
them on the rotary shaker table. Add test product to the flasks
(either one article or for toilet tissue typically 1 to 3 grams on
dry weight basis). A minimum of one gram of test product should be
used to ensure accurate measurement of the disintegration loss. The
flasks are shaken at 150 rpm. For the sewage pump assessment test
and control products are observed after 30 and 60 minutes, and then
destructively sampled at three hours. For the sewer conveyance
assessment, visual observations of the test and control products
are made at one hour, and then destructively sampled at six hours.
These tests are incubated at room temperature (22.+-.3.degree.
C.).
[0108] Test Termination:
[0109] At the designated destructive sampling points a flask from
each set of products being tested and the control set is removed
and the contents poured through a nest of screens arranged from top
to bottom in the following order: 12 mm, 3 mm and 1.5 mm (diameter
opening). Additional screens can be added to better understand the
dispersibility characteristics of the sample. With a hand held
showerhead spray nozzle held approximately 10 to 15 cm above the
sieve, the material is gently rinsed through the nested screens for
two minutes at a flow rate of 4 L/min being careful not to force
passage of the retained material through the next smaller screen.
After the two minutes of rinsing the top screen is removed and
rinsing of the next smaller screen, still nested, continues for two
additional minutes using the same procedure as above. The rinsing
process is continued until all of the screens have been rinsed.
After rinsing is complete, the retained material is removed from
each of the screens using forceps or by backwashing into a smaller
sized sieve. The content from each screen is transferred to a
separate, labeled tared aluminum weigh pan and dried overnight at
103.+-.3.degree. C. Dried samples are cooled in a desiccator. After
cooling the materials are weighed and percentage of disintegration
based on the initial starting weight of the test material is
calculated.
[0110] Slosh Box Test
[0111] This method uses a bench-scaled apparatus to evaluate the
breakup or dispersibility of flushable consumer products as they
travel through the wastewater collection system. In this test
method, a clear plastic tank is loaded with a product and tap water
or raw wastewater. The container is then moved up and down by a cam
system at a specified rotational speed to simulate the movement of
wastewater in the collection system. The initial breakup point and
the time for dispersion of the product into pieces measuring 1
in.times.1 in (25 mm.times.25 mm) are recorded in the laboratory
notebook. This 1 in.times.1 in (25 mm.times.25 mm) size is a
parameter that is used because it reduces the potential of product
recognition. The testing can be extended until the product is fully
dispersed. The various components of the product are then screened
and weighed to determine the rate and level of disintegration.
[0112] Testing Parameters:
[0113] The slosh box water transport simulator consists of a
transparent plastic tank that is mounted on an oscillating platform
with speed and holding time controller. The angle of incline
produced by the cam system produces a water motion equivalent to 60
cm/s (2 ft/s), which is the minimum design standard for wastewater
flow rate in an enclosed collection system. The rate of oscillation
is controlled mechanically by the rotation of a cam and level
system and should be measured periodically throughout the test.
This cycle mimics the normal back-and forth movement of wastewater
as it flows through sewer pipe.
[0114] Test Initiation:
[0115] Room temperature tap water (softened and/or non-softened) or
raw wastewater (2000 mL) is placed in the plastic container/tank.
The timer is set for six hours (or longer) and cycle speed is set
for 26 rpm. The preweighed product is placed in the tank and
observed as it undergoes the agitation period. For toilet tissue,
add a number of sheets that range in weight from 1 to 3 grams. All
other products may be added whole with no more than one article per
test. A minimum of one gram of test product is recommended so that
adequate loss measurements can be made. The time to first breakup
and full dispersion are recorded in the laboratory notebook. Note:
For pre-moistened products it is recommended to flush them down the
toilet and drain line apparatus prior to putting them into the
slosh box apparatus or rinse them by some other means. Other
prerinsing techniques should be described in the study records.
[0116] Test Termination:
[0117] The test is terminated when the product reaches a dispersion
point of no piece larger than 1 in.times.1 in (25 mm.times.25 mm)
square in size or at the designated destructive sampling points. At
the designated destructive sampling points, remove the clear
plastic tank from the oscillating platform. Pour the entire
contents of the plastic tank through a nest of screens arranged
from top to bottom in the following order: 25.40 mm, 12.70 mm, 6.35
mm, 3.18 mm, 1.59 mm (diameter opening). Make sure that the
perforated plate screens are set with the smooth side up. With a
showerhead spray nozzle held approximately 10 to 15 cm (4 to 6 in)
above the sieve, gently rinse the material through the nested
screens for two minutes at a flow rate of 4 L/min (1 gal/min) being
careful not to force passage of the retained material through the
next smaller screen. The flow rate can be assessed by measuring the
time it takes to fill a 4 L beaker. The average of three flow rates
should be 60.+-.2 seconds. The procedure is similar to that used in
the INDA/EDANA spray impact test method (WSP 80.3). After the two
minutes of rinsing, remove the top screen and continue to rinse the
next smaller screen, still nested, for two additional minutes.
Again, be careful not to force passage of retained material to the
next smaller screen. After rinsing is complete, remove the retained
material from each of the screens using forceps and/or commercial
paintbrushes. Transfer the content from each screen to a separate,
labeled aluminum weigh pan. Place the pan in a drying oven
overnight at 103.+-.3.degree. C. (or some other appropriate
temperature depending on the thermostability of the test material).
Continue this procedure at each designated sampling time until all
the test products are sampled. Allow dried samples to cool down in
a desiccator. After all the samples are dry, weigh the materials
from each of the retained fractions and calculate the percentage of
disintegration based on the initial starting weight of the test
material.
Fiber Length
[0118] Fiber length may be tested by TAPPI test method T 271 om-02
entitled Fiber Length of Pulp and Paper by Automated Optical
Analyzer Using Polarized Light. The test method is an automated
method by which the fiber length distributions of pulp and paper in
the range of 0.1 to 7.2 mm can be measured using light polarizing
optics. Fiber length is measured and calculated as a length
weighted mean fiber length according to the test method.
Formation Value
[0119] The formation value is tested using the Paper PerFect
Formation Analyzer Code LPA07 from OPTEST Equipment Inc. (OpTest
Equipment Inc. 900 Tupper St., Hawkesbury, ON, Canada). The samples
are tested using the procedure outlined in Section 10.0 of the
Paper PerFect Code LPA07 Operation Manual
(LPA07_PPF_Operation_Manual.sub.--004.wpd 2009-05-20). The
formation analyzer gives PPF formation values calculated for ten
size ranges from C1 for 0.5 to 0.7 mm to C10 for 31 to 60 mm. The
smaller sizes are important for printing clarity and the larger
sizes are important for strength properties. For purposes herein,
the C9 PPF value for the formation size range from 18.5 to 31 mm is
used to generate a measurement for the strength of the basesheet.
The PPF values are based on a 1000 point scale with 1000 being
completely uniform. The C9 PPF values reported for each sample are
based on the average of ten tests on five samples (two tests per
sample).
EXAMPLES
Example 1
[0120] The basesheet is made using an uncreped through-air-dried
tissue making process in which a headbox deposits an aqueous
suspension of papermaking fibers between forming wires. The
newly-formed web is transferred from the forming wire to a slower
moving transfer fabric with the aid of a vacuum box. The web is
then transferred to a throughdrying fabric and passed over
throughdryers to dry the web. After drying, the web is transferred
from the throughdrying fabric to a reel fabric and thereafter
briefly sandwiched between fabrics. The dried web remains on the
fabric until it is wound up into a parent roll.
[0121] To form the tissue, a headbox was employed, through which
the 100 percent softwood fibers and broke are pumped in a single
layer. The fiber was diluted to between 0.19 and 0.29 percent
consistency in the headbox to ensure uniform formation. The
resulting single-layered sheet structure was formed on a twin-wire,
suction form roll. The speed of the forming fabric was 3304 feet
per minute (fpm). The newly-formed web was then dewatered to a
consistency of about 20 to 27 percent using vacuum suction from
below the forming fabric before being transferred to the transfer
fabric, which was traveling at 2800 fpm (18 percent rush transfer).
A vacuum shoe pulling about 9 to 10 inches of mercury vacuum was
used to transfer the web to the transfer fabric. A second vacuum
shoe pulling about 5 to 6 inches of mercury vacuum was used to
transfer the web to a t1207-12 throughdrying fabric manufactured by
Voith Fabrics Inc. The web was carried over a pair of Honeycomb
throughdryers operating at temperatures of about 400 to 430.degree.
F. and dried to a final dryness of about 97 to 99 percent
consistency. The dried cellulosic web was rolled onto a core to
form a parent roll of tissue.
[0122] A series of Unijet.RTM. nozzles, Nozzle type800050,
manufactured by Spraying Systems Co., Wheaton, Ill., operating at
approximately 70 to 120 psi were used to spray the binder
composition onto both sides of the fibrous material. Each binder
composition was sprayed at approximately 15 percent binder solids
with water as the carrier. The wet partially formed single-ply wipe
substrate was carried through a dryer operating at 350 to
400.degree. F. at a speed of 350 fpm to partially dry the
single-ply wipe substrate. The partially dry wipe substrate was
then wound on a core and then unwound and run through the 350 to
400.degree. F. dryer a second time at a speed between 300 and 650
fpm to raise the temperature of the wipe substrate to 250 to
350.degree. F. The total dry weight percent of binder add-on was 5
percent relative to the dry mass of the single-ply wipe substrate.
The basesheet was machine-converted into sections of continuous web
5.5 inches wide by 56 inches long with perforations every 7 inches
which were adhesively joined, fan-folded and applied with the
wetting composition at 235 percent add-on to yield a fan-folded
stack of wet wipes. A wetting composition that is used on
commercially available wet wipes under the trade designation
KLEENEX.RTM. COTTONELLE FRESH.RTM. Folded Wipes (Kimberly-Clark
Corporation of Neenah, Wis.) with the addition of 2 weight percent
sodium chloride in the converting process for Example A. A wetting
composition that is used on commercially available wet wipes under
the trade designation KLEENEX.RTM. COTTONELLE FRESH.RTM. Folded
Wipes (Kimberly-Clark Corporation of Neenah, Wis.) with the
addition of 2 weight percent sodium chloride and 2 percent
organopolysiloxane in the converting process for Example B.
[0123] The exemplary dispersible wipes were tested under the Shake
Flask Test with each sample was tested at screen sizes of 12.70 mm,
6.35 mm, 3.18 mm, 1.59 mm with mass measured after the wipes and
tensile strength test and compared to KLEENEX.RTM. COTTONELLE
FRESH.RTM. Flushable Moist Wipes and Natural Choice.RTM. Flushable
Moist Wipes. Illustrative results are set forth below in Table
1.
TABLE-US-00002 TABLE 1 In-Use Tensile In-Use Tensile Strength (MD)
Strength (CD) Shake Flask (% Pass Through) Example Tissue (g/linear
inch) (g/linear inch) 12.70 mm 6.35 mm 3.18 mm 1.59 mm A UCTAD 568
272 100 100 98 63 B UCTAD 513 264 100 100 97 51 Comparative A
KLEENEX .RTM. 374 271 100 85 63 28 COTTONELLE FRESH .RTM.
Comparative B Natural Choice .RTM. 560 205 20 20 20 10
[0124] As can be seen from these results, use of a basesheet made
with cellulose fibers of length less than 3.18 mm have the
necessary strength for use by consumers, but also more easily pass
through smaller sieves. The exemplary wipes had percentage mass
loss values of greater than 95 percent at 3.18 mm, while the
comparative examples do not. Thus, using smaller fibers makes a big
improvement in percent pass through of the shaker flask test versus
current wipes on the market. The results show clear advantages in
flushability.
Example 2
[0125] For example 2, a wipe substrate was prepared as described in
Example A. Example C was prepared as a basesheet that was produced
without converting and subsequently adding the wetting composition.
For comparative purposes, a basesheet of airlaid nonwoven web was
formed continuously on a commercial scale airlaid machine similar
to the pilot-scale machine. Weyerhaeuser CF405 bleached softwood
kraft fiber in pulp sheet form was used as the fibrous material.
This airlaid fibrous material was densified to the desired level by
heated compaction rolls and transferred to an oven wire, where it
was sprayed on the top side with the a binder composition of a
cationic polyacrylate that is the polymerization product of 96 mol
% methyl acrylate and 4 mol % [2-(acryloyloxy)ethyl]trimethyl
ammonium chloride and Airflex.RTM. EZ123 in a 70:30 ratio was used
to bond the substrate binder composition, applying approximately
half of the desired binder solids onto the dry fibrous material to
prepare Comparative Example C. The airlaid basesheet is commonly
used with KLEENEX.RTM. COTTONELLE FRESH.RTM. Flushable Moist
Wipes.
[0126] Example C and Comparative Example C were tested to find the
formation value as described above. Example C has a formation value
of about 20.36 and Comparative Example C has a formation value of
about 16.90. Example C has better formation, and provides the
necessary strength while still being able to provide a wipe that
disperses in the sewer system.
Example 3
[0127] Example 3 illustrates the affect of the amount of binder
solids present in the binder composition used for the wipe
substrate. The basesheet was produced as described above for
Example A, but with varying the percentage of solids within the
binder to prepare Example D, Comparative Example D and Comparative
Example E. To illustrate the affect of the amount of binder solids
present in the binder composition, Example D, Comparative Example D
and Comparative Example E were tested for in-use tensile strength
and are illustrated in Table 2.
TABLE-US-00003 TABLE 2 In-Use Tensile In-Use Tensile % Solids in
Strength (MD) Strength (CD) In-Use GMT Example Tissue Binder
(g/linear inch) (g/linear inch (g/linear inch) D UCTAD 15 716.7
179.7 358.8 Comparative D UCTAD 18 432.4 115.8 223.8 Comparative E
UCTAD 21 404.8 132.8 231.8
[0128] As can be seen by the results illustrated in Table 2, low
solids spraying of the binder significantly improved in-use
strength by creating better coverage of the binder on the sheet. It
was discovered that the percentage binder composition solids of
less than about 18 percent, and preferably less than about 16
percent ensure spray coverage is optimized with acrylate-based
binder. Unexpectedly, low solids spraying of the binder on UCTAD
provided beneficial strength benefits despite significantly high
attachment points per fiber volume (36,000 contacts/mm.sup.3) that,
in theory, should not require droplet size optimization. In
addition, one skilled in the art would prefer not to lower the
percentage of solids in the binder since the lower binder add-on
made spraying at lower solids difficult due to dispersible binder
nozzle tip requirements. Better coverage of the binder provides
better in-use GMT. As seen in Table 2, a lower amount of binder
solids increased the in-use GMT to about 300 grams/linear inch.
Example 4
[0129] Use of a better binder application on the wipe substrate
also led to better strength formation. A wipe substrate was
prepared as described for Example A to create Example E. For
comparative purposes, wipe substrates was prepared as described for
Example A but varying the method of binder application, the amount
of plies, the binder add-on and the percentage of binder solids to
prepare Comparative Example F, Comparative Example G, and
Comparative Example H. Comparative Example F is a two-ply tissue
with a printed binder. Comparative Example G is a single-ply tissue
with a printed binder. Comparative Example H is a single-ply tissue
with a sprayed binder but with only a single nozzle. To illustrate
the affect of these changes, Example D, Comparative Example D and
Comparative Example E were tested for in-use tensile strength, the
tensile strength ratio, and post-use and are illustrated in Table
3.
TABLE-US-00004 TABLE 3 Tensile Post-use In-Use Tensile In-Use
Tensile Strength Tensile % Add-On % Solids Strength (MD) Strength
(CD) Ratio Strength (MD) Example Tissue of Binder in Binder
(g/linear inch) (g/linear inch (MD/CD) (g/linear inch) E UCTAD 5 15
568 272 2.08 108.2 Comparative F UCTAD 10 22 397.5 156.2 2.54 344
Comparative G UCTAD 9 21 467 283 2.54 285 Comparative H UCTAD 5 20
567 247 2.30 315
[0130] As illustrated in Table 3, applying the binder composition
to the wipe substrate by printing or with a single nozzle provides
poor distribution of binder. Improving distribution is critical to
generate optimum strength and for proper sheet handling. This is
shown by the above data regarding MD/CD tensile ratio. The lower
tensile strength ratio which is less 2.25 for Example E illustrates
improvements to the binder application, the binder add-on, the
percentage solids in the binder composition have allowed the
invention to reduce binder content and curing so that they are more
fully dispersible.
[0131] Additionally, as can be seen by the post-use strength in
Table 3, the proper binder application, the percent add-on and the
percent solids in the binder provide a wipe substrate that is
strong enough in-use, but quickly lowers in strength in water to
provide a dispersible product. Example E provides a sheet that can
pass 95 percent of its weight or greater through the 3.18 mm sieve
in the shake flask task with an in-use MD tensile strength greater
than 300 grams/per linear inch. Comparative Examples F, G and H do
not pass through a 3.18 mm sieve.
[0132] Other modifications and variations to the appended claims
may be practiced by those of ordinary skill in the art, without
departing from the spirit and scope as set forth in the appended
claims. It is understood that features of the various examples may
be interchanged in whole or part. The preceding description, given
by way of example in order to enable one of ordinary skill in the
art to practice the claimed invention, is not to be construed as
limiting the scope of the invention, which is defined by the claims
and all equivalents thereto.
* * * * *