Note: Descriptions are shown in the official language in which they were submitted.
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UNITED STATES PATENT APPLICATION
Inventors: Nikhil P. Dani, Joerg Hendrix, Scott Wood, Hubert Chan,
Mark Pszczolkowski and Daniela Fritter
PROCESS FOR MANUFACTURING MULTI-LAYER SUBSTRATES
COMPRISING SANDWICH LAYERS AND POLYETHYLENE
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The
present application claims the benefit of United States Provisional Patent
Application No. 62/860,655 filed on June 12, 2019 and United States
Provisional Patent
Application No. 62/828,301 filed on April 2, 2019. The disclosure of each of
the
foregoing is herein incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. The Field of the Invention
[0002] The
present invention relates to methods for manufacturing cleaning wipes, more
particularly to pre-moistened cleaning wipes that are formed from multi-layer
substrates.
2. Description of Related Art
[0003] Numerous cleaning wipes are available, e.g., such as CLOROX
DISINFECTING WIPES. While such wipes provide good overall cleaning and
disinfection characteristics, versatility, and convenience, there is a
continuing need for
improved cleaning wipes, as well as methods for their manufacture.
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BRIEF SUMMARY
[0004] The present invention relates methods of manufacturing wipes that may
typically be pre-moistened during manufacture or use, where the wipe includes
a multi-
layer substrate comprising at least three layers, where the wipe as a whole
may include a
significant fraction of pulp fibers, and where such can be achieved in a
relatively simple,
high speed (350 meter per minute (mpm) or more), low capital investment
process, where
the process does not employ loose pulp fibers within the process, does not
require use of
process water to aid in maneuvering fibers (pulp or otherwise present in any
of the layers)
along the plane of the wipe or through the thickness of the wipe, does not
require a drying
step to remove such process water, does not require use of chemical binders to
achieve
bonding between the three layers, and which facilitates use of synthetic
fibers (e.g., staple
or continuous synthetic fibers) having particular properties, for the middle
layer of the
multi-layer substrate without the fibers of the middle layer protruding
through the
external surface of either the top or bottom layers.
[0005] An embodiment may be directed to a method for manufacturing a multi-
layer
substrate, including providing both top and bottom surface layers, e.g., both
comprised of
pulp fibers, providing a thermoplastic material that comprises polyethylene
and/or has a
tan delta value of 0.2 to 0.4 within the temperature range of 100 F to 350 F,
positioning
the thermoplastic material so as to be sandwiched between the top and bottom
surface
layers, and heating the thermoplastic material to a temperature at which the
thermoplastic
material heat softens. During such heating there may also be application of
pressure to the
sandwich structure. In any case, such heating results in bonding of the
thermoplastic
material to groups of fiber in the top and bottom surface layers that are in
contact with the
sandwiched thermoplastic layer as it softens, such that no chemical adhesives
are used to
adhere the top and bottom surface layers to the thermoplastic material.
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[0006] In
addition, after heat softening, the thermoplastic material includes pores
therethrough, providing a fluid pathway therethrough such that any liquid
loaded into the
top surface layer is able to pass through the pathway, into the bottom surface
layer. Such
is the case, even where the thermoplastic layer may initially have been an
initially liquid
impervious film layer, prior to the heating and bonding portion of the
process. Once so
formed, the multi-layer substrate can be loaded with a cleaning composition,
e.g., by
applying the cleaning composition to the top and/or bottom surface layer(s).
Because of
the fluid pathway, fluid communication is possible from one surface layer to
the other,
through the fluid pathway in the thermoplastic film layer. The multi-layer
substrate may
be void of any chemical adhesives for holding the plurality of layers
together. Binders
may technically be present in tissue paper or other pulp layers (e.g., in
relatively small
amounts) because such binders are frequently used as processing aids in
processing pulp
material layers, although the purpose of such included materials, like kymene,
is to impart
strength to the pulp fiber structures (better holding such fibers together, in
the fixed web),
rather than for any purpose of actually adhering a layer of pulp material to a
thermoplastic
material layer. Instead, the melted thermoplastic material bonds to groups of
fibers (e.g.,
pulp fibers) in the top and bottom layers that were in contact with the
thermoplastic
material as it melted.
[0007] The
referenced tan delta value is defined as the ratio of viscous modulus
divided by elastic modulus. It therefore provides information relative to the
ratio of a
material's viscous liquid phase stiffness or flow characteristics relative to
the material's
solid phase stiffness characteristics. Different polymeric materials exhibit
different tan
delta characteristics, and this ratio also varies for a given material with
temperature.
Polyethylene is an exemplary material that exhibits a tan delta value in a
range of 0.2 to
0.4 within the temperature range of 100 F to 350 F. Other polymeric materials
(e.g.,
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polypropylene) do not necessarily exhibit such characteristics. Applicant has
found that
tan delta is a good indicator of whether a given polymeric material will
result in a melted
thermoplastic "sandwich" layer that effectively bonds to the exterior nonwoven
layers
both above and below the thermoplastic inner "sandwich" layer, while at the
same time
opening up fluid pathways through the thermoplastic layer, allowing liquids
(e.g., a
cleaning composition) to flow between the top and bottom layers, through the
thermoplastic layer.
[0008] Another embodiment is directed to a method of manufacturing a multi-
layer
substrate, comprising providing top and bottom surface layers in which fibers
of each
surface layer comprise at least 95% by weight pulp fibers, providing a
thermoplastic
material that comprises polyethylene or has a tan delta value of 0.2 to 0.4
within the
temperature range of 100 F to 350 F, positioning the thermoplastic material so
as to be
sandwiched between the top and bottom surface layers, creating a sandwich
structure
having at least 3 layers, and applying a calendaring process to the sandwich
structure by
heating the sandwich structure to a temperature at which the thermoplastic
material melt
softens, while applying pressure during such heating. This results in bonding
of the
thermoplastic material to pulp fibers in the top and bottom surface layers
that are in
contact with the thermoplastic material as it softens, such that no chemical
adhesives are
used to adhere the top and bottom surface layers to the thermoplastic
material. After
calendaring, the thermoplastic material includes open pores through the
thermoplastic
material, providing a fluid pathway therethrough such that any liquid loaded
into the top
surface layer is able to pass through the pathway to the bottom surface layer.
Once
formed, the 3-layer multi-layer substrate is loaded with a cleaning
composition.
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[0009] Further
features and advantages of the present invention will become apparent
to those of ordinary skill in the art in view of the detailed description of
preferred
embodiments below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] To
further clarify the above and other advantages and features of the present
invention, a more particular description of the invention will be rendered by
reference to
specific embodiments thereof which are illustrated in the drawings located in
the
specification. It is appreciated that these drawings depict only typical
embodiments of the
invention and are therefore not to be considered limiting of its scope. The
invention will
be described and explained with additional specificity and detail through the
use of the
accompanying drawings.
[0011] Figures
1A-1D show schematic views of exemplary multi-layer substrate
textures with various dot patterns.
[0012] Figure
1E is a photograph showing 4 different exemplary multi-layer substrate
textures that were actually formed, each with differently sized unbonded
raised texture
features (i.e., raised dots).
[0013] Figure 2 is an SEM image of the top surface of an exemplary multi-layer
substrate, showing two adjacent unbonded raised regions, with the bonded
region
extending there-between.
[0014] Figure 3 shows an SEM image of an cross-sectional or edge view through
an
exemplary multi-layer substrate such as that of Figure 2, showing the top
surface layer,
the bottom surface layer, and the thermoplastic film layer sandwiched there-
between,
where there are both bonded regions, and regions in which the thermoplastic
layer and the
adjacent exterior surface layer are unbonded relative to one another.
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[0015] Figure 4
is a chart showing elastic modulus and tan delta values versus
temperature for polyethylene, polypropylene, and for a polymer comprised of
"bicomponent" core/sheath type fibers, i.e., a ("bico") polymer.
[0016] Figures
5A-5B illustrate various exemplary wipes packages, showing how the
present multi-layer substrate wipes can be pulled through a typical wipe pack
orifice,
without significant shredding of the exterior layers, even where such layers
are pulp fiber
layers.
[0017] Figure 6 is an SEM image showing spunbond thermoplastic fibers
enveloping
adjacent pulp fibers of the adjacent top surface layer.
[0018] Figures
7A-7F illustrate additional exemplary textures and patterns that could
be applied during calendaring.
[0019] Figure 8
schematically illustrates an exemplary calendaring process by which
the thermoplastic layer having particular tan delta characteristics is melt
softened,
bonding it to the adjacent exterior surface layers in multi-layer substrates
according to the
present invention.
[0020] Figure
9A illustrates images comparing a conventional 1-sided texture (top of
Figure 9A), to a two-sided textured substrate (bottom of Figure 9A).
[0021] Figures
9B-9C illustrate profilometer data for the "bumpy" face and the "other"
face of a substrate without two-sided texturing.
[0022] Figures
9D-9E illustrate profilometer data for the first and second faces of a
substrate with two-sided texturing (both are "bumpy").
[0023] Figures
9F-91 illustrate additional profilometer data for the tested comparative
one-sided versus two-sided textured samples.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
I. Definitions
[0024] Before
describing the present invention in detail, it is to be understood that this
invention is not limited to particularly exemplified systems or process
parameters that
may, of course, vary. It is also to be understood that the terminology used
herein is for the
purpose of describing particular embodiments of the invention only, and is not
intended to
limit the scope of the invention in any manner.
[0025] All
publications, patents and patent applications cited herein, whether supra or
infra, are hereby incorporated by reference in their entirety to the same
extent as if each
individual publication, patent or patent application was specifically and
individually
indicated to be incorporated by reference.
[0026] The term "comprising" which is synonymous with "including,"
"containing,"
or "characterized by," is inclusive or open-ended and does not exclude
additional,
unrecited elements or method steps.
[0027] The term
"consisting essentially of" limits the scope of a claim to the specified
materials or steps "and those that do not materially affect the basic and
novel
characteristic(s)" of the claimed invention.
[0028] The term
"consisting of" as used herein, excludes any element, step, or
ingredient not specified in the claim.
[0029] It must
be noted that, as used in this specification and the appended claims, the
singular forms "a," "an" and "the" include plural referents unless the content
clearly
dictates otherwise. Thus, for example, reference to a "surfactant" includes
one, two or
more surfactants.
[0030] Unless
otherwise stated, all percentages, ratios, parts, and amounts used and
described herein are by weight.
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[0031] Numbers,
percentages, ratios, or other values stated herein may include that
value, and also other values that are about or approximately the stated value,
as would be
appreciated by one of ordinary skill in the art. As such, all values herein
are understood to
be modified by the term "about". Such values thus include an amount or state
close to the
stated amount or state that still performs a desired function or achieves a
desired result. A
stated value should therefore be interpreted broadly enough to encompass
values that are at
least close enough to the stated value to perform a desired function or
achieve a desired
result, and/or values that round to the stated value. The stated values
include at least the
variation to be expected in a typical manufacturing or other process, and may
include
values that are within 10%, within 5%, within 1%, etc. of a stated value.
[0032] Some
ranges may be disclosed herein. Additional ranges may be defined
between any values disclosed herein as being exemplary of a particular
parameter. All
such ranges are contemplated and within the scope of the present disclosure.
[0033] In the
application, effective amounts are generally those amounts listed as the
ranges or levels of ingredients in the descriptions, which follow hereto.
Unless otherwise
stated, amounts listed in percentage ("%'s") are in weight percent (based on
100% active)
of any composition.
[0034] The
phrase 'free of' or similar phrases if used herein means that the composition
or article comprises 0% of the stated component, that is, the component has
not been
intentionally added. However, it will be appreciated that such components may
incidentally form thereafter, under some circumstances, or such component may
be
incidentally present, e.g., as an incidental contaminant.
[0035] The
phrase 'substantially free of' or similar phrases as used herein means that
the composition or article preferably comprises 0% of the stated component,
although it
will be appreciated that very small concentrations may possibly be present,
e.g., through
incidental formation, contamination, or even by intentional addition. Such
components
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may be present, if at all, in amounts of less than 1%, less than 0.5%, less
than 0.25%, less
than 0.1%, less than 0.05%, less than 0.01%, less than 0.005%, less than
0.001%, or less
than 0.0001%. In some embodiments, the compositions or articles described
herein may be
free or substantially free from any specific components not mentioned within
this
specification.
[0036] As used
herein, -disposable" is used in its ordinary sense to mean an article that
is disposed or discarded after a limited number of usage events, preferably
less than 25,
more preferably less than about 10, and most preferably after a single usage
event. The
wipes disclosed herein are typically disposable.
[0037] As used
herein, the term "substrate" is intended to include any material that is
used to clean an article or a surface. Examples of cleaning substrates
include, but are not
limited to, wipes, mitts, pads, or a single sheet of material which is used to
clean a surface
by hand or a sheet of material which can be attached to a cleaning implement,
such as a
floor mop, handle, or a hand held cleaning tool, such as a toilet cleaning
device. The term
"substrate" is also intended to include any material that is used for personal
cleansing
applications. These substrates can be used for hard surface, soft surface, and
personal care
applications. Such substrates may typically be in the form of a wipe.
[0038] The
substrates contemplated herein are made up of at least 3 individual, distinct
layers, which are bonded together in the described calendaring process. Each
layer of the
substrate may be formed from individual fibers which are interlaid, typically
in a manner
that is not identifiable, similar to a nonwoven. Woven layers are also
possible. Films,
which may not necessarily be fibrous (e.g., for the middle thermoplastic
layer) may also be
possible (e.g., a cast or blown film that does not necessarily include fibers)
The top and
bottom surface layers included in the present substrates may be formed by any
suitable
process, typically through wetlaying, although airlaying may also be possible.
Where the
exterior surface layers are formed of pulp fibers, wetlaid and airlaid
exterior surface layers
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may be typical. Where synthetic fiber materials could be used for the exterior
surface
layers, other processes may be used to form such layers that are the starting
materials for
the present processes. For example, the layer(s) could be meltblown, spunbond,
spunlaid,
SMS (spunbond-meltblown-spunbond), coformed, carded webs, thermal bonded,
thermoformed, spunlace, hydroentangled, needled, or chemically bonded. Various
processes for foi ___________________________________________________ ming
such nonwovens will be apparent to those of skill in the art, many of
which are described in U.S. Patent No. 7,696,109, incorporated herein by
reference in its
entirety. Pulp fibers may generally be ribbon-shaped, rather than the
generally circular
cross section seen with synthetic fibers. Examples of synthetic fibers often
used in forming
nonwoven layers and that could be used in multi-layer wipes (e.g., as exterior
surface
layers) include, but are not limited to, polypropylene, PLA, PET, PVC,
polyacrylics,
polyvinyl acetates, polyvinyl alcohols, polyamides, polystyrenes, or the like.
Polyethylene
or other thermoplastic polymers having the desired tan delta characteristics
may be useful
as the interior thermoplastic material layer. PLA (e.g., a spunbond PLA
nonwoven layer,
a PLA film, etc.) is an example of another material that may also be suitable
for use in
one or more of the layers, including as a thermoplastic layer having the
desired tan delta
properties. It may also be possible to include polyethylene in the exterior
surface layers,
in some embodiments. The thermoplastic interior layer may be provided as a
synthetic
nonwoven, formed according to any desired process. The thermoplastic layer may
also be
a -cast" film, e.g., rather than being comprised of fibers. Such layer could
alternatively
comprise loose fibers of a material having the desired tan delta
characteristics, where a
layer of such loose fibers are placed on one of the exterior layers, covered
with the other
exterior layer, and then processed as described herein. Structured nonwoven
fixed fiber
forms that do not involve use of loose fibers may be preferred. Avoiding the
use of loose
pulp fibers in the exterior surface layers (using structured fixed fiber
forms) is particularly
beneficial. The basis weight of any of the layers of the substrate (and the
multi-layer
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substrate as a whole) may be expressed in grams per square meter (gsm). Basis
weight
may sometimes also be expressed in "pounds" (e.g., referring to 1bs/3000 ft2
of the sheet
material). The substrates as a whole may have basis weight values from 30-80
gsm.
[0039] The
terms "wipe", "substrate" and the like may thus overlap in meaning, and
while "wipe" may typically be used herein for convenience, it will be
appreciated that this
term may often be interchangeable with "substrate".
[0040] As used
herein, "wiping" refers to any shearing action that the wipe undergoes
while in contact with a target surface. This includes hand or body motion,
substrate-
implement motion over a surface, or any perturbation of the substrate via
energy sources
such as ultrasound, mechanical vibration, electromagnetism, and so forth.
[0041] The
cleaning compositions dosed onto the substrate as described herein may
provide sanitization, disinfection, or sterilization, other cleaning, or other
treatment. As
used herein, the term "sanitize" shall mean the reduction of "target"
contaminants in the
inanimate environment to levels considered safe according to public health
ordinance, or
that reduces a "target" bacterial population by significant numbers where
public health
requirements have not been established. By way of example, an at least 99%
reduction in
bacterial population within a 24 hour time period is deemed "significant."
Greater levels
of reduction (e.g., 99.9%, 99.99%, etc.) are possible, as are faster treatment
times (e.g.,
within 10 minutes, within 5 minutes, within 4 minutes, within 3 minutes,
within 2
minutes, or within 1 minute), when sanitizing or disinfecting.
[0042] As used
herein, the term "disinfect" shall mean the elimination of many or all
"target" pathogenic microorganisms on surfaces with the exception of bacterial
endospores.
[0043] As used
herein, the term "sterilize" shall mean the complete elimination or
destruction of all forms of "target" microbial life and which is authorized
under the
applicable regulatory laws to make legal claims as a "sterilant" or to have
sterilizing
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properties or qualities. Some embodiments may provide for at least a 2 or more
log
reduction (e.g., 3-log reduction, or 6-log reduction) in a bacterial
population within a
designated time period (e.g., 10 minutes, 5 minutes, 4 minutes, 3 minutes, 1
minute, 30
seconds, 10 seconds or the like). A 2-log reduction is equivalent to a 99%
reduction, a 3-
log reduction is equivalent to at least a 99.9% reduction, a 4-log reduction
is equivalent to
at least a 99.99% reduction, a 5-log reduction is equivalent to at least a
99.999%
reduction, etc. An example of a target microbe may be Staphylococcus aureus .
It will be
appreciated that microefficacy can also be achieved against other target
microbes,
numerous examples of which will be apparent to those of skill in the art. It
will also be
appreciated that the present cleaning compositions need not include an
antimicrobial
agent, where sanitization or disinfection is not necessarily desired.
[0044] The term
"texture" as used herein refers to the character or appearance of a
substrate as determined by the arrangement and thickness of its constituent
fibers. In at
least some instances, texture can be quantified using imaging techniques
and/or caliper
measurements at the local and macro scales, as described in Applicant's
Application Serial
No. 16/042,690, filed July 23, 2018 (Docket No. 510.174), herein incorporated
by
reference in its entirety. By way of explanation, "patterns" are typically
visual, with areas
of discernable contrast. "Texture" is typically tactile, and relates to
variations relative to
the normal plane of the substrate (i.e., 3-dimensional texture in the
substrate). Visual
pattern and tactile texture interact in a complex manner with a user's
visual/tactile sense of
sight and touch to produce a given aesthetic perception for a given substrate,
in addition to
other quantifiable technical characteristics associated with such.
[0045] Unless
defined otherwise, all technical and scientific terms used herein have the
same meaning as commonly understood by one of ordinary skill in the art to
which the
invention pertains. Although a number of methods and materials similar or
equivalent to
those described herein can be used in the practice of the present invention,
the preferred
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materials and methods are described herein.
Introduction
[0046] In an
aspect, the present invention is directed to methods for manufacturing
multi-layer substrates including at least 3 layers. In an embodiment, the
exterior faces of
the wipe are provided by structured plant based fibers (fixed fibers, rather
than loose
fibers), such as structured, fixed wood pulp fibers (e.g., tissue paper).
Where used, the
term "tissue" is used for convenience, and it will be appreciated that it is
intended to be
broadly construed, including tissue paper materials, as well as other similar
materials
formed from pulp. Synthetic exterior layers such as meltblown, spunbond,
spunlaid, SMS
(spunbond-meltblown-spunbond), coform, carded webs, thermal bonded,
thermoformed,
spunlace, hydroentangled, needled, or chemically bonded fibers may also be
suitable for
processing according to the present methods, e.g., as described in Applicant's
Application
bearing Clorox Docket No. 510.186. Configurations based on tissue exterior
layers re
described in Applicant's Application bearing Clorox Docket No. 510.188, each
of which
is herein incorporated by reference in its entirety.
[0047] An
interior "sandwich" layer comprising a thermoplastic material (e.g.,
different from the exterior layers) is provided, between the tissue or other
pulp layers (or
other top and bottom exterior layers), which adheres the entire multi-layer
substrate
together in a single mass, with low risk of delamination, while providing
desired
characteristics relative to hand-feel, stiffness, and absorbency (ability to
load the substrate
to a desired loading ratio with a cleaning composition), while also providing
a fluid
pathway through the thermoplastic layer through which the cleaning composition
can
migrate from the top surface layer, to the bottom surface layer, or vice
versa. Because the
thermoplastic layer melts in contact with fibers of the adjacent exterior
surface layers, and
particularly given the tan delta characteristics of the thermoplastic
material, the melt
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softened thermoplastic material encapsulates, envelops, wraps, or otherwise
coats
individual adjacent fibers of the exterior surface layer, providing a strong
bond between
the two adjacent layers, such that delamination does not readily occur. Even
if a synthetic
fiber were used in the exterior layers, the fibers of the exterior surface
layers may provide
differing characteristics, such that they do not melt soften in the same way
the interior
sandwich layer does, at the given processing conditions. In addition, the
thermoplastic
sandwich "cheese" layer typically does not penetrate through the exterior
"bread" surface
layers, so that none of the melt softened thermoplastic material with specific
tan delta
characteristics is on the exposed exterior faces of the wipe. This results in
the advantage
that relatively softer (e.g., pulp) fibers are used for wiping and cleaning
versus contact
with harder more abrasive synthetic melt softened fibers. The wipe may thus be
less harsh
on the surfaces being treated so as to reduce risk of undesirable mechanical
scratching,
abrasion, or erosion.
[0048] Such
multi-layer substrates may be formed through a thermal and pressure
calendaring process in which the top and bottom layers are provided preformed
(e.g., the
tissue or other layers are provided preformed, with the fibers already in a
structure, fixed
form, as a structured sheet, such as a nonwoven), and a thermoplastic material
comprising
polyethylene or another polymer having suitable tan delta values is also
provided. The
thermoplastic material may also be in the form of a structured sheet (e.g.,
also a
nonwoven, as a cast film, etc.), or may even be provided as loose fibers that
are
positioned onto a face of the bottom exterior layer, covered by the top
exterior layer, and
then calendared.
[0049] Many
commercially available multi-layer hard surface cleaning substrates have
external layers made of synthetic thermoplastic materials such as
polyethylene,
polypropylene, PET, and other commonly used synthetic materials, which can be
abrasive
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and harsh. Typically, a layer of pulp fibers is provided in the middle of the
synthetic
material layers so that the pulp fibers are not lost through abrasion during
the cleaning
process. In contrast, embodiment of the present invention including pulp
fibers have the
opposite configuration where the layers of pulp materials are in a top surface
layer and a
bottom surface layer and the thermoplastic material is between the pulp
material layers. In
any case, the described process and 3-layer configuration allows bonding of
the 3 layers
into an integral, single substrate structure, without the need for any
chemical adhesives.
[0050] The
layers may be assembled, e.g., with the tissue or other exterior layers as
"bread" sandwiching the thermoplastic film layer (as "cheese") therebetween,
followed
by subjecting the assembly to heat (and typically pressure) at a temperature
and time
period that melt softens the thermoplastic material. This heating may open up
pores
through the thermoplastic material, even if it was provided as a liquid
impervious film
layer prior to the treatment. Heat softening of the thermoplastic material
also causes it to
wrap around or otherwise coat and envelop the adjacent fibers of the top and
bottom
surface layers, effectively tying the adjacent layers to one another, without
any chemical
adhesive to prevent the layers from delaminating or pulling apart from one
another. As
mentioned, at the same time that this layer bonding occurs, any liquid
impervious film
characteristics that may have previously existed with respect to the interior
thermoplastic
layer are broken, so that a fluid pathway is created through the thermoplastic
layer,
through which a cleaning composition or other liquids applied to either the
top or bottom
layer can penetrate from one surface layer to the other surface layer, through
the
thermoplastic film layer.
[0051] Once the
dry substrate has been formed, a desired cleaning composition may be
loaded onto the multi-layer substrate. Because of the presence of the fluid
pathway, even
if the cleaning composition is loaded as a liquid into only one of the top or
bottom layers,
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it will flow through the substrate to the other exterior layer through the
broken
thermoplastic layer.
III. Exemplary Multi-Layer Substrates
[0052] Figures
1A-1D illustrate exemplary wipes 100a-100d, each with a different
applied surface texture and bonding pattern, but where each is configured as a
multi-layer
substrate including a melted thermoplastic layer sandwiched between top and
bottom pulp
fiber or other exterior surface layers. While shown with various textures, it
will be
appreciated that numerous other textures could be provided, or perhaps no
texture at all.
Additional exemplary textures are shown in Figures 7A-7F. Figure 1E shows
photographs
of 4 exemplary multi-layer wipes 100a-100d that were actually manufactured for
evaluation.
[0053] Figure 2
shows a close up of one of the raised ridges 102 of an exemplary wipe,
showing how the raised circular ridge 102 (a "dot") is unbonded to the
thermoplastic film
layer disposed therebelow, such that there is actually a gap there-between, at
the ridge
102. The region 104 surrounding the raised ridge 102 is bonded (and is so
labeled) to the
underlying thermoplastic film layer disposed therebelow. Depending on the
particular
applied textured pattern, the bonded region 104 may be contiguous, as shown
(i.e., there
is a single contiguous bonded region, rather than multiple bonded regions that
are fully
separated from one another). In other words, by "contiguous", one can reach
any
particular location in the bonded region from any other particular location in
the bonded
region, by traversing only other bonded regions, without any need to traverse
an
unbonded region. The bonded region 104 may thus be contiguous, even though it
does not
cover the entire top exterior face (or bottom exterior face) of the wipe,
because there are
spaced apart unbonded regions 102. Stated another way, by analogy, the
unbonded
regions may be configured as "islands" in a "sea" of the bonded region. It
will be
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appreciated that other configurations are of course possible.
[0054] The
texture may be an embossed texture that is applied during the thermal
calendaring or other manufacturing operation that laminates the 3 layers of
the
"sandwich" structure together. Alternatively, the texture could have been
introduced into
the substrate structure as a result of the geometry used in the forming screen
used during
the tissue making process, when depositing the pulp fibers that make up the
tissue or
other exterior surface layer(s).
[0055] From
Figure 2, it is apparent that the pulp fibers of the top surface layer (as
well as the bottom surface layer) are ribbon shaped, rather than being
generally circular in
cross-section, as is the case with typical synthetic fibers of non-woven
substrates. Such
ribbon-shaped fibers rather have a generally rectangular cross-section, as
opposed to
being circular in cross-section. Figure 3 is an SEM image of an end or cross-
section
through an exemplary multi-layer substrate, such as that of Figure 2, showing
the
thermoplastic film layer 106 (labeled "Bico") sandwiched between a through-air-
dried
("TAD") pulp fiber top surface layer 108a, and a TAD pulp fiber bottom surface
layer
108b. Also labeled in Figure 3 is a bonded region 104, as well as an unbonded
region,
adjacent a raised ridge "dot" of the bottom pulp fiber layer 108b. In this
labeled unbonded
region, there is a gap between the thermoplastic layer 106 and the bottom pulp
fiber layer
108b. While in this region the bottom pulp fiber layer 108b is unbonded, in
this same
region, the thermoplastic layer 106 may (or may not be) bonded to the top pulp
fiber layer
108a. In other words, the unbonded characteristic may apply to one or both
faces of the
thermoplastic layer.
a. Pulp Characteristics
[0056] The
fibrous portion of the top and bottom surface layers of the multi-layer
substrates may be formed predominantly, and in an embodiment entirely, from
pulp
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fibers, e.g., wood pulp or other plant fibers. Even where the thermoplastic
layer is clearly
not comprised of such pulp fibers (as it is instead a synthetic thermoplastic
polymeric
material, (e.g., having particular tan delta value characteristics), the
substrate as a whole
is one in which a majority of the fiber weight of the substrate may be pulp.
For example,
greater than 70% (by weight) of the fibers of the substrate may be pulp
fibers. In an
embodiment 75% to 90%, 75% to 85%, or 75% to 80% of the fibers in the
substrate may
be pulp fibers, by weight. In other words, synthetic fibers may account for
less than 30%,
such as 10% to 25%, 15% to 25%, or 20% to 25% by weight of the fibers. Such is
the
case where the thermoplastic interior layer is a fibrous film (e.g., a thin
spunbond film). It
will be appreciated that in another embodiment, the thermoplastic film may not
necessarily be fibrous, e.g., such as in the case of a cast or "bubble" blown
film that is not
made up of numerous fibers, but is simply a continuous thin (e.g., cast)
sheet. In such an
embodiment, the thermoplastic material may still account for less than 30%,
10% to 25%,
15% to 25%, or 20% to 25% of the dry substrate, but may simply be in non-
fibrous form
(e.g., a cast or blown sheet). In such a case, technically, 100% of the fibers
of the
substrate may be pulp fibers.
[0057] In an
embodiment, all fibers of the top surface layer and bottom surface layer
may consist of or consist essentially of pulp fibers. For example, these
layers may not
include any synthetic fibers, or any synthetic structural components (e.g., no
synthetic
fillers). By forming the multi-layer substrates from a high fraction of pulp,
the substrates
may be more sustainably sourced, e.g., where a higher fraction of the
components used
are derived from sustainable sources as compared to, e.g., existing wipes
formed from a
blend of pulp and synthetic fibers. In addition, the location of pulp versus
synthetic
materials in the wipe may differ in that all pulp may be in the exterior
surface layers,
rather than having pulp fibers intermixed (e.g., homogenously) through a given
(e.g.,
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interior) layer.
[0058] The pulp
fibers may typically be obtained from wood, although other possible
sources of pulp are also possible, e.g., from cotton, Esparto grass, bagasse,
hemp, flax,
jute or the like. Combinations of more than one material may be used. Various
exemplary pulp fibers may include, but are not limited to, thermomechanical
pulp fibers,
chemimechanical pulp fibers, chemithermomechanical pulp fibers, refiner
mechanical
pulp fibers, stone ground wood pulp fibers, peroxide mechanical pulp fibers,
and the like.
The fibers of the pulp substrate may generally comprise cellulosic fibers,
which are
typically hydrophilic. Such hydrophilicity differs from many synthetic fibers,
which are
typically hydrophobic, absent special treatment.
[0059]
Additional details relative to exemplary pulp fibers are found in Applicant's
Application Serial No. 16/042,690, filed July 23, 2018 (Docket No. 510.174),
already
herein incorporated by reference herein. Such characteristics can be
specifically selected
to ensure sufficient quat release, as well as other characteristics.
b. Other Top and Bottom Exterior Surface Layers
[0060] The top and bottom surface layers may alternatively be formed from a
material
that comprises synthetic fibers, or a blend of pulp and synthetic fibers. Any
of various
nonwoven materials may be used, which are widely available from various
commercial
sources. Such layers and fibers may be meltblown, spunbond, spunlaid, SMS
(spunbond-
meltblown-spunbond), coform, carded webs, thermal bonded, thermoformed,
spunlace,
hydroentangled, needled, or chemically bonded. In an embodiment, such surface
layers
may also incorporate a fraction of pulp fibers therein (e.g., as a homogenous
blend of
randomly distributed synthetic and pulp fibers, or where the pulp fibers are
positioned
non-randomly, e.g., at an exterior, or at an interior surface). In any case,
the fraction of
synthetic fibers within the top and bottom exterior surface layers may be at
least 50%, at
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least 60%, at least 70%, at least 80%, at least 90%, or at least 95%, by
weight, of the
fibers present in a given layer. In an embodiment, 100% of the fibers in a
given exterior
surface layer may be synthetic fibers.
[0061] A wide
variety of synthetic materials that can be formed into fibers, and laid
into a nonwoven substrate layer are appropriate for use in the contemplated
multi-layer
substrates. Examples of such polymeric synthetic materials include, but are
not limited to
polyethylene, polypropylene, PET, PVC, polyacrylics, polyvinyl acetates,
polyvinyl
alcohols, polyamides, polystyrenes, or the like. In an embodiment, the
external surface
layers may comprise a material other than polyethylene, and/or a material that
does not
have the tan delta characteristics possessed by the internal thermoplastic
layer, which is
configured to be melt-softened, bonding the 3 layers together.
[0062] No
matter the choice of materials in the top and bottom surface layers (e.g.,
pulp or synthetic), the top and bottom layers of the multi-layer substrate may
have a basis
weight of no more than 50 lbs, no more than 40 lbs, no more than 30 lbs, or no
more than
20 lbs, at least 3 lbs, at least 5 lbs, or at least 10 lbs, such as from 7 lbs
to 20 lbs, or 8 lbs
to 15 lbs. Such "lbs" values refer to the weight per /3000ft2, as will be
appreciated by
those of skill in the art. The multilayer substrate as a whole may have a
basis weight of
30-80 gsm.
[0063] In an
embodiment, the top and bottom layers comprise pulp fibers, and do not
include any added synthetic fibers, e.g., such as various polyolefins or other
fibers formed
from synthetic polymers, e.g., polyethylene, polypropylene, PET, PVC,
polyacrylics,
polyvinyl acetates, polyvinyl alcohols, polyamides, polystyrenes, or the like.
While such
synthetic fibers are widely used in the manufacture of nonwoven substrates,
such
embodiments may seek to reduce the use of such non-sustainable materials.
Furthermore,
by limiting or eliminating their use in the top and bottom exterior surface
layers,
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additional benefits can be provided. For example, the present wipes can
provide
functional parity, and sometimes advantages, over conventional nonwoven wipes
in
durability, safety for use on all surfaces, ease and convenience, ability to
clean and absorb
light liquid spills, ability to clean large areas effectively, and
microefficacy in the case of
sanitization or disinfection. Furthermore, the use of significant quantities
of synthetic
resins in existing pre-moistened nonwoven wipes represents a significant
expense, such
that cost savings, renewability and sustainability benefits, and
biodegradability benefits
can be achieved using pulp substrates, as described herein.
[0064] The
individual layers of the top and bottom (e.g., pulp fiber) layers that are
used in manufacturing the multi-layer substrate can be formed by any of a
number of
different techniques, e.g., such as any of those suitable for use in forming
tissue layers.
Examples include, but are not limited to wet-laying and air-laying, as well as
conventional press-drying, and through-air drying techniques. Methods of
making such
substrate layers will be apparent to those of skill in the art. Wet-laying
processes are
described in U.S. Patent Nos. 5,246,772 and 5,238,534 to Manning. Air-laying
processes
are described in U.S. Patent Publication No. 2003/0036741 to Abba et al. and
U.S. Patent
Publication No. 2003/0118825 to Melius et al. Conventional processes by which
a
manufactured substrate in a wet condition is pressed to remove process water,
as well as
through-air-drying processes will be familiar to those of skill in the art. In
an
embodiment, the top and bottom tissue layers are formed by through-air-drying.
[0065] Such
processes are typically carried out prior to the positioning and calendaring
processes described herein, e.g., where the inputs to the presently described
process are
nonwovens or similar structured sheet or web materials, already processed into
such
structured sheets, so that the present processes do not require use of loose
fibers
(particularly loose pulp fibers), do not require use of process water to
maneuver fibers
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along the plane or through a thickness of the given sheet or web (as the sheet
or web is
already formed in the material used as an input to the present process), do
not require
drying or another mechanism for removing process water, and do not require use
of
chemical binders to adhere the various layers to one another (as this is
achieved through
melt softening the interior thermoplastic layer).
[0066] Where
tissue layers are used as the exterior surface layers, one or both of the
tissue layers may comprise more than a single ply, or each may comprise only a
single
ply. Where multiple plies are provided, they may be adhered together, so as to
have
adequate peel strength, e.g., as described in Applicant's Application Serial
No.
16/042,690, filed July 23, 2018 (Docket No. 510. 74), already incorporated by
reference.
Where only a single ply is present in each of the top and bottom tissue
layers, no chemical
adhesive may be present anywhere in the multi-layer substrates. Where two
plies are used
in either or both of the tissue layers, a chemical adhesive may be present in
the tissue
layers (i.e., between plies), but may not be present between the thermoplastic
layer and
the adjacent top and bottom tissue layers.
c. Thermoplastic Layer
[0067] The
present multi-layer wipes include a sandwich structure in which a
thermoplastic layer is provided, on the inside of the wipe, sandwiched between
the top
and bottom surface layers (e.g., pulp layers). While in an embodiment, the
surface layers
could also be thermoplastic, these exterior layers may include different tan
delta
characteristics than the sandwiched thermoplastic layer. Where no chemical
adhesive is
used to adhere the 3 layers into an integral, single structure that does not
readily
delaminate between layers, but in which the thermoplastic sandwich "cheese"
layer itself
is used for this purpose, the Applicant has found that not just any
thermoplastic polymer
will be suitable for such a purpose. For example, in testing various
thermoplastic
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polymers, Applicant found that various materials, even upon heating, will not
readily
bond to the adjacent pulp fiber or other nonwoven top or bottom surface
layers, but will
form a very weak bond, if any at all. Such weak bonding is of course
unacceptable in a
multi-layer substrate to be used as a cleaning wipe, where delamination must
be avoided.
In the present invention, the multi-layer substrates have sufficient adhesion
between the
layers that they do not delaminate even when wet (e.g., allowed to soak for
weeks, in
storage) or when used for cleaning hard surfaces. The interior thermoplastic
layer not
only binds the multi-layer substrate together as it melts, but it also may
impart additional
strength to the exterior layers, where these layers may be relatively weak. It
is surprising
that this binding of the exterior layers occurs so well that there is not any
significant
shredding of the exterior surface layer, e.g., as the multi-layer substrate is
pulled through
a typical wipe dispensing orifice, even where such exterior layers consist
essentially of
pulp fibers (e.g., tissue). Values and testing protocols that may be
applicable to the peel
strength provided by the present bonding processes between the interior
thermoplastic
layer and the exterior surface layers are disclosed in Applicant's Application
bearing
Clorox Docket No. 425.372, herein incorporated by reference in its entirety.
[0068] Applicant found that while polypropylene may seem like a suitable
thermoplastic material to achieve sufficient bonding between the top and
bottom pulp
fiber or other nonwoven surface layers separated by the interior thermoplastic
material
layer, polypropylene did not provide good bonding, but resulted in weak
bonding and
delamination between the 3 layers. Applicant found a key characteristic or
indicator as to
whether a given thermoplastic material would work, is tan delta value. Tan
delta value is
an engineering characteristic that can be evaluated for thermoplastic
polymeric materials,
and gives information relative to how much "liquid" viscous phase
characteristics
dominate versus "solid" elastic phase characteristics, in a given material, at
a given
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temperature. Tan delta is simply calculated as the ratio of viscous modulus
divided by
elastic modulus for a given material, at a given temperature.
[0069] Figure 4
charts both tan delta and elastic modulus values for 3 tested
thermoplastic materials ¨ polyethylene, polypropylene, and a bicomponent
material that
comprises polyethylene. For example, the bicomponent material tested is
believed to be
comprised of bicomponent fibers, with a fiber core (that is not polyethylene),
and an
exterior coating or sheath on the core, that is polyethylene. Figure 4 charts
both elastic
modulus and the tan delta value for these 3 materials over the temperature
range of about
100 F to 350 F. Figure 4 shows how the elastic modulus (i.e., stiffness) of
the
polypropylene is the highest, followed by the "bico", followed by the
polyethylene, and
that the stiffness of each decreases with increasing temperature.
[0070] The tan
delta value for the polypropylene is very low, less than 0.2, and
remains less than 0.15 at temperatures from 100 F to over 300 F. It isn't
until nearly
350 F that the tan delta value increases somewhat, but only slightly, up to a
value of
about 0.15, and certainly still less than 0.2. The polyethylene tan delta
value is quite
different, being about 0.2 at a temperature of 100 F, and increasing to about
0.25 to 0.3 at
about 175 F-190 F. After peaking at around this temperature, the tan delta
value begins
to decrease, to 0.2 at about 250 F, and dropping somewhat below 0.2 (e.g.,
about 0.18) at
about 260 -270 F. Tan delta for the "bico" is between that of the
polypropylene and the
polyethylene for much of the temperature range, until about 250 F where it is
higher than
the polyethylene. Both the polyethylene and the "bico" material (which
comprises
polyethylene) include points along the temperature range of 100 F to 350 F
where tan
delta is at least 0.2 (e.g., greater than 0.2 to 0.4, or greater than 0.2 to
0.3), meeting the
stated requirement. The polypropylene tan delta never reaches 0.2 over this
temperature
range of 100 F to 350 F. Thus, in an embodiment, the selected thermoplastic
material for
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the interior "sandwich" layer has a tan delta value that is at least 0.2
(e.g., from 0.2 to 0.4,
or from 0.2 to 0.3) somewhere within the temperature range of 100 F to 350 F.
In an
embodiment, the selected thermoplastic material may have such a tan delta
value at the
particular temperature at which the thermal calendaring step is performed
(e.g., 150 F,
175 F, 200 F, 225 F, 250 F, 275 F, 300 F, 325 F, etc.) or at any narrower
range within
the temperature range of 100 F to 350 F.
[0071] The
selected thermoplastic material may advantageously have a melting
temperature that is less than 400 F, less than 375 F, less than 350 F, less
than 325 F, less
than 300 F, at least 150 F, at least 175 F, at least 200 F, or at least 225 F.
Having a
relatively lower melting temperature of course reduces energy requirements
needed in the
calendaring process, but may also be important depending on what materials are
used in
the top and bottom surface layers, to ensure they do not decompose, ignite, or
melt.
Where any pulp fiber content is included in the exterior surface layers, it
can be important
to ensure the temperature is low enough that such pulp fibers do not ignite,
or become
embrittled or discolored due to "burning", which may occur even below the
paper ignition
temperature of 451 F. As such, selection of lower melting temperature
thermoplastic
materials may be preferred, so long as they can provide a good bond to the
exterior top
and bottom layers.
[0072] The
interior thermoplastic layer may comprise, e.g., at least 25%, at least 30%,
at least 35%, at least 40%, at least 50%, at least 55%, at least 60%, at least
65%, at least
70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%,
from 25% to
100%, from 30% to 100%, or from 50% to 100% of a material having the desired
tan
delta characteristics. As illustrated by the bico fiber material, some portion
or component
of the thermoplastic material may not have the stated tan delta
characteristics, so long as
the thermoplastic material as a whole includes such characteristics. For
example, the bico
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fiber is believed to include a polypropylene core, which does not have the
stated tan delta
characteristics, although the sheath portion of the fiber is believed to be
polyethylene,
which does have the stated tan delta characteristics. As shown by Figure 4,
the bico
fibers as a whole do meet the stated tan delta characteristics. Where the
thermoplastic
material is a bicomponent fiber or other bicomponent (or other multicomponent)
structure, e.g., such as a layered film or the like, the polyethylene or other
material having
the stated tan delta characteristics may be positioned on the exterior of the
thermoplastic
material, so as to easily contact the adjacent exterior surface layers during
the calendaring
process.
[0073] Figures 5A-5B show how the present multi-layer substrates may be
packaged
within any of various exemplary flex packs (Figure 5A), cylinders (Figure 5B)
or other
containers for storage and dispensing. The wipes 100 may be pulled through an
orifice
such as typically provided with such containers, without fear of shredding or
delamination of the various layers. In particular, Applicant tested prototype
wipes such
as shown in Figure 1E by pulling them through orifices (e.g., as seen in
Figures 5A-5B),
and there was no significant shredding of the exterior tissue layers, or
delamination of the
layers from one another. Rather, each wipe was able to be pulled through the
orifice,
remaining fully intact, time after time. Figure 6 shows an SEM image at the
interface
between a spunbond fibrous thermoplastic layer 106 and an adjacent exterior
tissue layer
(e.g., 108a) showing how the pulp fibers at the interface are wrapped around,
enveloped,
or coated by the melt-softened thermoplastic material, that occurs during the
thermal
calendaring process. This strong connection between the pulp fiber layer and
the
thermoplastic layer provides a strong bond, so that shredding or delamination
does not
occur when pulling the wipe through a typical wipe pack orifice. These
characteristics are
believed to result because of the tan delta characteristics of the
thermoplastic material
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described above in conjunction with Figure 4.
[0074] Figure 5B further shows how such wipes may be packaged as a "donut",
e.g., in
a cylindrical container. The ability to package the wipes in such a donut
configuration is
somewhat surprising when the exterior surface layers are pulp, given the high
pulp
content (e.g., 75-80% pulp) of the substrate. For example, it is difficult to
package pre-
dosed 100% pulp substrates in such a configuration without the donut
collapsing or
creasing vertically, due to insufficient wet stiffness of the substrate.
[0075] The
thermoplastic film layer is not required to be particularly thick. For
example, the thermoplastic film layer may have a thickness of 0.01 mm to 0.1
mm, or
0.01 mm to 0.05 mm. It may be so thin as to be transparent or translucent,
prior to
assembly into the sandwich structure. That said, it will be apparent that if
desired, the
thermoplastic middle sandwich layer may be thicker. For example, it may have a
thickness that varies depending on the structural characteristics of such
layer (e.g.,
whether it is deposited as loose fibers (e.g., loose bico fibers, or loose
fibers otherwise
comprising a material having the desired tan delta characteristics), an intact
film, yarn
(e.g., loose yarn), an intact nonwoven layer, a woven layer, or the like). It
will be
apparent that the thermoplastic middle sandwich layer may thus have a
thickness ranging
from 0.01 mm to 5 mm, from 0.01 mm to 3 mm, from 0.01 mm to 2 mm, from 0.01 mm
to 1 mm, from 0.01 mm to 0.5 mm, or the like.
[0076] Strength
and/or stiffness characteristics of the wipe may be dictated at least in
part by the characteristics of the middle thermoplastic layer of the present
substrate. For
example, strength and stiffness of the substrate as a whole may progressively
increase as
one uses, respectively, fibers, a film, a yarn, a nonwoven (e.g., a bico
nonwoven), or a
woven structured material for the middle sandwich layer. Such materials are
listed
generally in order of increasing resiliency, where strength and/or stiffness
of the overall
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substrate increase with increasing resiliency of the middle layer. Of course,
thickness of
the middle layer will also affect the strength and/or stiffness of the
finished substrate. By
way of further explanation, at a given thickness, a woven structure for the
thermoplastic
middle sandwich layer may provide the greatest strength and/or stiffness to
the substrate,
while a nonwoven thermoplastic middle sandwich layer would typically provide
somewhat lower strength and/or stiffness. Use of a yarn, e.g., where multiple
fibers are
twisted or otherwise arranged together, providing a yarn diameter
significantly greater
than that of the individual fibers making up the yarn may provide somewhat
lower
stiffness and strength, and a film or simple deposition of individual, loose
fibers onto
either of the exterior surface layers to form the thermoplastic middle
sandwich layer may
provide even lower stiffness and/or strength.
[0077] It will
be apparent that numerous possible configurations are possible as to the
structure of the thermoplastic middle sandwich layer, and that numerous
possible methods
are possible for providing such (e.g., providing preformed layers, for
example, as a film,
nonwoven, or woven) that are simply placed between the exterior layers, or by
providing
one of the exterior surface layers, and then depositing individual loose
fibers, yarn or the
like onto the interior surface of such exterior layer, followed by positioning
the other
exterior surface layer there over, after which the 3-layer structure is then
subjected to heat
and/or pressure, to adhere the layers to one another, and cause the formation
of cracks,
fissures and the like through the thermoplastic middle sandwich layer, through
which a
cleaning lotion that eventually becomes loaded into the substrate can pass
from one
exterior surface layer, through the thermoplastic middle sandwich layer, to
the other
exterior surface layer. For example, one could provide a nonwoven exterior
surface layer
of any suitable material (e.g., pulp), which serves as a carrier to lay down
loose fibers (or
fibers formed into a yarn) of the thermoplastic material onto the pulp or
other suitable
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exterior surface layer. Finally, the opposite exterior surface layer (e.g.,
another pulp
nonwoven layer) may be positioned over the loose fibers or loose yarn, and the
3-layer
structure may be processed with appropriate heat and/or pressure to melt
soften the
thermoplastic middle sandwich layer, as described herein.
[0078] Another
benefit associated with use of pulp exterior layers is that the resulting
substrate exhibits lofted characteristics due to the "fuzzy", loose bulk
structure of the
nonwoven randomly laid pulp fibers in the exterior layers. When using
synthetic exterior
layers, it may be desirable to provide the substrate with a lofted structure,
so as to
increase the bulk and thickness of the substrate, where such lofted
characteristics may not
otherwise be provided with synthetic exterior layers. Such lofting may be
provided
through overfeeding one or more of the layers (e.g., exterior layers) into the
rollers which
heat and press the layered substrate. For example, the feed rate of one or
both exterior
surface layers may be greater than a pick up rate on the other side of such
rollers, which
causes the material of the overfed layers to bunch up or create pleats as it
enters the
rollers (e.g., the heated nip and the opposite roller) where the melt
softening of the middle
layer occurs. This causes a bunched up, pleated, or similar lofted
configuration including
air gaps to be locked in to the exterior layer as the middle layer melt
softens, and bonds to
the exterior overfed layer. Such a lofted configuration gives more cloth-like
hand feel
characteristics, and may provide "reservoirs" within which the cleaning lotion
may be
stored. This lofted configuration is durable after dosing and during use, akin
to what may
be provided with a fuzzy, lofted pulp containing (non-synthetic) layer. Other
techniques
for providing a lofted layer (e.g., particularly on either or both exterior
surface layers)
may also be used. For example, a pin roller could be used to pull portions of
the exterior
surface layer laterally outward from the substrate plane, creating a fuzzy,
lofted texture
with decreased density and increased volume and thickness to such layer.
Various other
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techniques will be apparent to those of skill in the art, in light of the
present disclosure.
[0079] Where
desired, any synthetic substrate layers or materials could be selected to
be biodegradable and/or compostable (e.g., meeting the standard of ASTM D6400
or
other applicable standard). Of course, pulp layers easily meet such criteria.
[0080] Figure 8
schematically illustrates an exemplary calendaring process 200 that
may be used to form the substrates including 3 or more distinctly identifiable
layers.
Figure 8 shows use of a rolled web of the 3 starting sheet materials, although
it will be
appreciated that they could be provided as distinct, separate sheets of
material, or that the
middle thermoplastic layer could be laid down as loose fibers, before
calendaring. Process
200 is shown as including a mechanism 202 for feeding thermoplastic material
204, as
well as mechanisms 206a, 206b for providing top and bottom exterior surface
layers
208a, 208b. As shown in Figure 8, the thermoplastic material 204 is sandwiched
between
exterior surface layers 208a, 208b as it is fed into calendaring portion of
process 100, e.g.,
along an optional conveyor belt 210. A 4th optional layer 207 is shown in
Figure 8. For
example, if desired, a layer having particular desired characteristics could
also be fed into
the sandwiching of such layers. Sandwiched structure 212 (thermoplastic
material layer
204 between exterior surface layers 208a, 208b) may pass under a roller 214
and then to
rollers 216a, 216b. Typically, one of rollers 216a, 216b is rubber, while the
other is metal.
The rollers may heat the sandwich structure 212 to the desired temperature,
for a desired
period of time, so as to melt soften the interior layer 204, causing it to
bond to the surface
exterior layers 208a, 208b.
[0081] The
pressure applied may be e.g., at about 10 bars, at least about 15 bars, or at
least about 25 bars. More generally, such pressure may be less than 300 bars,
less than
200 bars, less than 100 bars or less than 50 bars, from 1 to 500 bars, from 5
to 500 bars,
from 10 to 300 bars, or from 25 to 200 bars pressure. The thickness and weight
of the
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constituent layers, may have an effect on the required pressure and
temperature, and
contact time in order to achieve good bonding, as described herein.
[0082] After
passing through calendaring rollers 216a, 216b, the sandwich structure
212' which is now bonded between the interior layer and the exterior layers
passes to take
up roller 218.
[0083] It will
be appreciated that such a process is relatively simple, involving far less
capital investment than associated with typical wipe manufacturing operations,
which are
based on production of such wipe substrates using loose fiber starting
materials, and
which require use of process water, drying operations to remove such process
water, etc.
For example, typical processes that incorporate pulp fibers into a wipe
substrate are
complex processes, involving high capital investment, use of process water to
maneuver
the fibers either along the plane of the substrate being formed, or through
the thickness
thereof, subsequent drying to remove such process water, etc. The presently
described
process is far simpler, in that it uses pulp layers that are already provided
in structured
form, where the fibers are already fixed relative to the pulp layer, and
adhering two such
pulp layers so as to form the exterior surface layers, sandwiching
therebetween a
thermoplastic layer having particular characteristics that permit bonding of
the distinct 3
layers without use of any chemical adhesives that would require curing, etc.
[0084] While
principally described in the context of using rollers to perform the
heating and pressing, it will be appreciated that heated plates could
alternatively be used
(e.g., introducing the sandwich structure between platen plates and pressing
the
sandwich), although the rollers configuration may be preferred as allowing for
far higher
production volumes.
d. Cleaning Composition
[0085] Many cleaning composition components as known within the art may be
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suitable for use in the present pre-dosed wipes. In an embodiment, the
cleaning
composition is an aqueous composition, including at least 70%, at least 80%,
or at least
90% water by weight (e.g., 90% to 99% water). The composition may include
0.05% to
5% by weight of a quaternary ammonium compound, and/or 0.1% to 5% by weight of
a
glycol ether solvent. For example, the quaternary ammonium compound may be
included
from 0.05%, from 0.1%, up to 5%, up to 4%, up to 3%, up to 2%, or up to 1% by
weight
of the cleaning composition. The glycol ether solvent may be included from
0.1%, from
0.25%, up to 5%, up to 4%, up to 3%, up to 2%, or up to 1% by weight of the
cleaning
composition. Other solvents, surfactants, and various other adjuvants often
included in
cleaning compositions may optionally be present. While some embodiments may
include
lower alcohol solvents (e.g., C1-C4 alcohols), the amount of such volatile
solvents may be
limited, e.g., to less than 10%, less than 5%, less than 3%, less than 2%, or
less than 1%
by weight. In some embodiments, the composition may be free of, or
substantially free of,
such lower alcohol or other highly volatile solvents.
[0086] Quaternary ammonium compounds or other cationic biocides can have broad
spectrum antimicrobial properties. A variety of different quaternary ammonium
compounds can be used in the cleaning composition. Non-limiting examples of
quaternary ammonium compounds are typically halides (e.g., a chloride) of
alkyldimethylbenzylammonium,
alkyldimethylethylbenzylammonium,
alkyldimethylammonium, or the like. The alkyl groups of such quaternary
ammonium
compounds may typically range from C12 to C18. Quaternary ammonium compounds
are
described in more detail in U.S. Patent No. 6,825,158, incorporated by
reference herein,
and will already be familiar to those of skill in the art.
[0087] Organic
acids can also be used to provide antimicrobial properties. By way of
example, such an organic acid may be included in an amount of at least 0.1%,
or at least
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0.5%, up to 5%, up to 4%, up to 3%, up to 2%, or up to 1% by weight of the
cleaning
composition.
[0088] The
cleaning composition may include a glycol ether solvent. Exemplary
glycol ether solvents include, but are not limited to alkyl ethers of alkylene
glycols and
alkylene glycol ethers, such as ethylene glycol monopropyl ether, ethylene
glycol
monobutyl ether, propylene glycol n-propyl ether, propylene glycol monobutyl
ether,
propylene glycol t-butyl ether, diethylene glycol monoethyl or monopropyl or
monobutyl
ether, di- or tri-polypropylene glycol methyl or ethyl or propyl or butyl
ether, acetate
and/or propionate esters of glycol ethers.
[0089] Those of
skill in the art will appreciate that any among a wide variety of
surfactants (e.g., anionic, cationic, non-ionic, zwitterionic, and/or
amphoteric) may be
included in the cleaning composition, as desired. Where included, a surfactant
may be
present from 0.05%, from 0.1%, up to 10%, up to 5%, up to 4%, up to 3%, up to
2%, or
up to 1% by weight of the cleaning composition. Various surfactants and other
optional
adjuvants are disclosed in U.S. Pat. No. 3,929,678 to Laughlin and Heuring,
U.S. Pat. No.
4,259,217 to Murphy, U.S. Pat. No. 5,776,872 to Giret et al.; U.S. Pat. No.
5,883,059 to
Furman et al.; U.S. Pat. No. 5,883,062 to Addison et al.; U.S. Pat. No.
5,906,973 to
Ouzounis et al.; U.S. Pat. No. 4,565,647 to Llenado, and U.S. Publication No.
2013/0028990. The above patents and applications are each herein incorporated
by
reference in their entirety.
[0090] As used
herein the term "liquid" and "cleaning composition" includes, but is
not limited to, solutions, emulsions, suspensions and so forth. Thus, liquids
may comprise
and/or contain one or more of the following: disinfectants; antiseptics;
diluents;
surfactants, such as nonionic, anionic, cationic; waxes; antimicrobial agents;
sterilants;
sporicides; germicides; bactericides; fungicides; virucides; protozoacides;
algicides;
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bacteriostats; fungistats; virustats; sanitizers; antibiotics; pesticides; and
so forth.
Examples of some such components and exemplary compositions are disclosed in
U.S.
Patent Nos. 6,825,158; 8,648,027; 9,006,165; 9,234,165, 9,988,594 and U.S.
Publication
Nos. 2008/003906 and 2018/0216044, each of which is herein incorporated by
reference
in its entirety. In some embodiments, it may be possible to provide the
substrates in dry
form, where dosing with a selected cleaning composition may occur later (e.g.,
by the
user).
[0091] With
regard to pre-moistened substrates, a selected amount of liquid may be
added to the container or wipes during manufacture such that the cleaning
substrates
contain the desired amount of liquid. The substrates are not necessarily
loaded to their
saturation point, but are typically loaded with the cleaning composition to
some ratio less
than full saturation. For example, many substrates are capable of holding
about 8 to 14
times their weight in liquid. For various reasons, the substrates may be
loaded at a loading
ratio less than saturation, e.g., less than 6:1, less than 5:1, less than 4:1,
such as from 1:1
to 4:1, from 2:1 to 4:1, from 2.5:1 to 3.5:1, from 2.5:1 to 3:1 or from 2.5:1
to 3.75:1.
[0092] Where
the substrate may be configured so as to be all synthetic (e.g., without
pulp in the exterior surface layers), this may offer additional flexibility in
the chemistries
that may be dosed (e.g., during manufacture) onto such substrate for use,
while
minimizing or eliminating risk of undesired incompatibility that may result
between
components of such compositions and substrates that may include pulp, other
natural
fibers, or other natural components. By way of non-limiting example, a wide
variety of
bleaching agents (e.g., chlorine-based and otherwise, including peroxides,
hypochlorites,
etc.) may be used with such synthetic substrates. Compositions which achieve
disinfection based on acids (e.g., acetic acid) may also be used. Such acid
disinfectants
and bleaches are often incompatible with non-synthetic substrate materials.
Non-limiting
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examples of such compositions are disclosed in U.S. Patent Nos. 5,460,833 to
Andrews et
al.; 6,221,823 to Crisanti; 6,346,279 to Rochon et al.; 6,551,980 to
Wisniewski et al.;
6,699,825 to Rees et al.; 6,803,057 to Ramirez et al.; 6,812,196 to Rees et
al.; 6,936,597
to Urban; 7,008,600 to Katsigras et al.; 7,070,737 to Bains et al.; 7,354,604
to Ramirez et
al.; 7,598,214 to Cusack et al.; 7,605,096 to Tamarchio et al.; 7,658,953 to
Bobbert;
7,696,143 to McCue et al.; 7,915,207 to Chopskie et al.; 8,569,220 to
Gaudrealt;
8,575,084 to Gaudrealt; 10,064,409 to Hazenkamp et al.; 10,076,115 to Salminen
et al.;
U.S. Publication No. 2007/0190172 to Bobbert; PCT Publication Nos. WO 99/18180
to
Raso et al.; WO 99/53006 to Masotti et al.; WO 2004/067194 to Arrigoni et al.;
WO
2004/104147 to Rosiello et al.; WO 2017/174959 to Convery; and EPO Publication
EP
2843034 to Nedic et al.
e. Other Characteristics
[0093] The size
and shape of the wipe can vary with respect to the intended application
and/or end use of the same. The cleaning substrate can have a substantially
rectangular
shape of a size that allows it to readily engage standard cleaning equipment
or tools such
as, for example, mop heads, duster heads, brush heads, mitten shaped tools for
wiping or
cleaning, and so forth. In another embodiment, another shape, e.g., circular,
oval, or the
like) may be provided.
[0094] The
wipes or other cleaning substrates may be provided pre-moistened with a
cleaning composition. The wet cleaning substrates can be maintained over time
in a
sealable container such as, for example, within a bucket or tub with an
attachable lid,
sealable plastic pouches or bags, canisters, jars, and so forth. Desirably the
wet, stacked
cleaning substrates are maintained in a re-sealable container. The use of a re-
sealable
container is particularly desirable when using aqueous volatile liquid
compositions since
substantial amounts of liquid can evaporate while using the first sheets
thereby leaving
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the remaining sheets with little or no liquid. Exemplary re-sealable
containers and
dispensers include, but are not limited to, those described in U.S. Pat. No.
4,171,047 to
Doyle et al., U.S. Pat. No. 4,353,480 to McFadyen, U.S. Pat. No. 4,778,048 to
Kaspar et
al., U.S. Pat. No. 4,741,944 to Jackson et al., U.S. Pat. No. 5, 595,786 to
McBride et al =
the entire contents of each of the aforesaid references are incorporated
herein by
reference.
[0095]
Typically, the cleaning substrates are stacked and placed in the container and
the liquid subsequently added thereto, all during mass manufacturing. It is
advantageous
that the thermoplastic layer at the center of each wipe not be liquid
impervious, to
facilitate easier loading of the wipes. As described herein, even if the
thermoplastic film
as initially provided before lamination of the 3 layers together is liquid
impervious,
Applicant has found that cracks or other fluid pathways are opened up within
the film
during thermal calendaring, as contemplated herein. While this may not
necessarily occur
with any and all thermal calendaring operations, it does occur under the
conditions
contemplated herein.
[0096] The
presence of such cracks or other fluid pathways that are opened up during
manufacture of the multi-layer substrate advantageously allow liquid cleaning
composition dosed on either face of the substrate to migrate through the wipe,
to the
opposite exterior face, through the thermoplastic film layer. This similarly
allows the
dosed cleaning composition to migrate from one substrate to the next, e.g.,
where the
substrates are stacked (e.g., by wicking the liquid from one to the next). For
example, a
given volume or weight of the cleaning composition may simply be dosed into
the bottom
of the container, allowing it to wick into the stack of wipes. In the case of
a donut
configuration, by placing the cleaning composition into the bottom of the
cylindrical
container, an end of each wipe actually make simultaneous contact with the
cleaning
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composition in the bottom of the container, where it can be wicked up into the
height of
each wipe (and the height of the donut). This may actually occur with a donut
configuration whether the thermoplastic film layer were "broken" to include
the described
fluid pathways or not (i.e., if it remained impervious), as both the top and
bottom surface
layers will contact the cleaning composition at the bottom of the container
simultaneously. Where any initially liquid impervious characteristics of the
film are
"broken" by the thermal calendaring process, this may further aid the cleaning
composition in wicking upwards throughout the full height of each wipe, and
the donut as
a whole.
[0097] No matter the packaging and dosing process, once manufactured and
packaged,
the substrate can subsequently be used to wipe a surface. The moistened
cleaning
substrates can be used to treat various surfaces. As used herein "treating"
surfaces is used
in the broad sense and includes, but is not limited to, wiping, polishing,
swabbing,
cleaning, washing, disinfecting, scrubbing, scouring, sanitizing, and/or
applying active
agents thereto.
[0098] The
wipes or other cleaning substrates of the present invention can be provided
in a kit form, wherein a plurality of cleaning substrates and a cleaning tool
are provided in
a single package.
[0099] In
addition to material composition and construction (e.g., tissue substrates on
the exterior, thermoplastic layer having particular tan delta characteristics
only on the
inside, not on the exposed face, composition of the cleaning "lotion" and the
like), wipe
or other substrate dimensions can also be used to control dosing as well as
provide
ergonomic appeal. In one embodiment, substrate dimensions are from about 51/2
inches to
about 11 inches in length, and from about 51/2 inches to about 11 inches in
width to
comfortably fit in a hand. The substrate can have dimensions such that the
length and
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width differ by no more than about 2 inches. Larger substrates may be provided
that can
be used and then folded, either once or twice, so as to contain dirt within
the inside of the
fold and then the wipe can be re-used. Such larger substrates may have a
length from
about 51/2 inches to about 13 inches and a width from about 10 inches to about
13 inches.
Such substrates can be folded once or twice and still fit comfortably in the
hand.
[00100] While
most synthetic or blended nonwoven substrates used in wipe
manufacture exhibit significant differences in tensile strength in the machine
direction
(MD) versus the cross direction (CD), the present multi-layer substrates may
exhibit
values in each direction that result in a ratio of MD/CD that is relatively
close to 1, e.g.,
such as 0.5 to 1.5, 0.75 to 1.25, or 0.8 to 1.2. In other words, the
substrates may be
substantially isotropic with respect to their tensile strength. Such
substantially isotropic
characteristics reduce the likelihood of there being problems when folding
substrates into
stacks for packaging, or forming donuts for packaging.
[0101] Various
other characteristics relating to stiffness, strength, density of pulp
fibers, wet bulk factor, profile height, pore volume distribution
characteristics, retention
characteristics, lotion retention, MABDF, and others that may be provided by
the present
wipes are described in Applicant's Application Serial No. 16/042,690, filed
July 23. 2018
(Docket No. 510.174), already incorporated herein by reference.
f. Antimicrobial Efficacy & Other Characteristics
[0102]
Exemplary multi-layer substrates were tested for their ability to effectively
deliver an antimicrobial quaternary ammonium compound to a surface during
simulated
cleaning. Applicant notes that the generally anionic characteristics of
typical pulp
substrates lead to a tendency of the substrate to bind or otherwise retain the
cationic
quaternary ammonium compound, even when squeezing an aqueous cleaning
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composition including such a quat from the substrate. In other words,
typically, the
concentration of quaternary ammonium compound in the "squeezate" (the cleaning
composition as squeezed from the pre-loaded wipe) is less than the
concentration of
quaternary ammonium compound in the cleaning composition before it was loaded
into
the wipe. Since quaternary ammonium compounds are known to bind to pulp
substrates,
it was unexpected that the present wipes were able to release a significant
enough portion
of the quaternary ammonium compound to achieve disinfectancy and/or
sanitization on a
treated surface without the inclusion of any biocide release agent or latex
binder in the
substrate. Even more surprising was that even though the tested substrate was
comprised
of 78% pulp fibers by weight, when compared to a blended substrate including
60% pulp
fiber by weight, the present substrates exhibited greater quat release in the
"squeezate" as
compared to the comparative wipe, which included lower pulp content.
[0103] Because
of these interesting and advantageous characteristics, there may not be
a need to increase the quat concentration in the cleaning composition, in
order to achieve
a desired level of microefficacy, as compared to that used in the comparative
wipe. For
example, commercially available disinfecting wipes often contain about 0.1 to
5%, and
preferably 0.1 to 3%, and more preferably 0.1 to 2% by weight of quat in the
cleaning
composition. Surprisingly, despite the fact that the multi-layer substrates of
the present
invention have higher levels of pulp they also have good microefficacy
performance with
0.1 to 3%, and preferably 0.1 to 2% by weight of quat in the cleaning
composition. By
way of example, the multi-layer substrates of the present invention may be
loaded with
cleaning compositions including from 0.1% to 3%, such as 0.1% to 2% by weight
of quat.
In an embodiment, the wipes may release at least 40%, at least 50%, at least
55%, at least
60%, or at least 65% of the quaternary ammonium compound (i.e., quaternary
ammonium
compound in the squeezate as compared to the cleaning composition before
loading). The
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wipes may exhibit at least a 3-log reduction in a target microbe, such as
Staphylococcus
aureus, within a given time frame (e.g., such as 5 minutes, 4 minutes, 3
minutes, 1
minute, 30 seconds, 10 seconds, etc.).
[0104] Table 1
shows the results of testing in which a cleaning composition including
a quaternary ammonium compound was loaded into a substrate according to the
present
invention, and as compared to a conventional blended substrate. The cleaning
composition was squeezed from both substrates, and the squeezate was analyzed
to
determine the reduction in the concentration of the quaternary ammonium
compound in
the squeezate compared to the composition as loaded.
Table 1
Substrate % Quat Released
60/40 blended substrate ¨ 51%
comparative example
78/22 exemplary multi-layer 69%
substrate
[0105] The
ability to achieve higher quat release while including higher pulp content is
particularly surprising and unexpected. This characteristic advantageously
allows for
better relative microefficacy characteristics. This high quat release may be
due to the
presence of absorptive pockets or gaps, e.g., such as seen in Figure 3,
adjacent the
unbonded regions. Such gaps provide a significant absorptive region between
the
thermoplastic film layer and the unbonded raised region 102, which can serve
as a
reservoir for the cleaning composition. Such regions allow significant
quantities of the
cleaning composition to be stored within the substrate, to be released upon
squeezing,
wiping, or other compression, where there is reduced contact between the quat
in the
composition and any anionic binding sites associated with the pulp fibers of
the exterior
surface layer. This combination of the reservoirs being partially bounded by
the inert
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thermoplastic film material (which does not include significant concentration
of anionic
binding sites), in combination with the gaps associated with the reservoirs
themselves is
believed to at least partially account for the ability to release such high
fractions of the
quat upon squeezing the wipe.
[0106] Other characteristics of the comparative and exemplary substrates
are shown in
Table 2 below.
Table 2
Characteristic 60/40 blended 78/22 exemplary
substrate ¨ multi-layer substrate
comparative example
Basis weight 52 gsm 55 gsm (26 lb tissue
layers +12 gsm
thermoplastic layer
Composition (%pulp/%synthetic) 60/40 78/22
Caliper (wet ¨ mm) 0.6 0.76
Absorbency (g) 12 12
Tensile Strength (MD/CD ¨ lbf) 4.61/1.63 3.48/3.06
Dry Stiffness (mg. cm) 285 500
Carrier release total ¨ S1/S2 (g) 0.49/0.63 0.58/0.56
[0107] By way of further explanation the dot patterns and textures shown in
Figure 1E
included smallest dots (100b), small dots (100c), medium dots (100a), and
large dots
(100d). The wet thickness of the resulting substrates is affected by the dot
pattern or
texture. For example, a flat sample (not shown) had a wet thickness of 0.3 mm,
the
sample 100a (smallest dots) had a wet thickness of 0.39 mm, the sample 100b
(small
dots) had a wet thickness of 0.65 mm, the sample 100c (medium dots) had a wet
thickness
of 0.66 mm, and sample 100d (large dots) had a wet thickness of 0.83 mm. The
forgoing
values are for substrates with only one tissue layer textured. Two sided
samples include
somewhat higher wet thickness values.
[0108] The dosed exemplary multi-layer substrate was tested for
microefficacy against
Staphylococcus aureus at a loading ratio of 3.75:1, using an existing quat
cleaning
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composition, at a contact time of 3 min 30 sec. The control population of 6.1
log was
reduced to 0 in each of 60 replicates. Testing was performed under 5% soil
load
conditions. Such results indicated excellent efficacy against Staphylococcus
aureus at a
3:30 contact time.
[0109] The
dosed wipes were also tested for efficacy in various other household
cleaning tasks, including cleaning kitchen grease (KG) and bathroom scum (BS).
The
results of such testing demonstrated parity or near parity with the
comparative wipe, as
shown below in Table 3.
Table 3
Substrate % soil % soil Cycles
to 75% Cycles to 75%
removal at 30 removal at 30 removal - KG removal - BS
cycles - KG cycles - BS
60/40 blended 96.87 96.62 4 7
substrate ¨
comparative example
78/22 exemplary 97.92 96.2 6 9
multi-layer substrate
[0110] The small increase in cycles for 75% removal may be due to the absence
of
synthetic fibers on the exterior surface and reduced tendency of the present
wipes to
"dump" cleaning composition, as compared to the comparative example blended
wipe.
The reported values represent averages for two sides of the wipes. The
conventional wipe
"dumps" or releases more liquid from the first side, thereby requiring few
cycles to clean,
but also reducing mileage. This "dumping" characteristic is described in
Applicant's
Application Serial No. 16/042,690, filed July 23, 2018 (Docket No. 510.174),
previously
incorporated by reference.
[0111] As
mentioned, the present wipes do not include any synthetic fibers exposed at
the exterior faces of the wipe, but any synthetic fibers are rather located
only within the
interior of the wipe (and potentially incidentally exposed at the edges). As a
result, the
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exterior surface may be soft, rather than abrasive. While Applicant did
prepare some
prototype substrates that did include synthetic fibers on the exterior
surfaces (i.e., using a
blend of pulp and synthetic fibers to form the exterior "tissue layers", the
resulting wipes
did not provide the same desired hand-feel characteristics as were provided
where the
exterior pulp fiber or tissue layers did not include exposed synthetic fibers.
While 100%
pulp fibers on the exterior faces may thus be preferred, it will be
appreciated that some
small fraction of synthetic fibers (e.g., less than 10%, less than 5%, less
than 3%, or less
than 1%) may be included in some embodiments.
[0112] The
exterior tissue layers may be of a through-air dried configuration. While
conventional press-dried tissue was also tried in this exterior layer, this
also resulted in
less desirable hand-feel characteristics. Such conventional (not through-air-
dried) tissue
also undesirably presses out any initially included texture, while through-air-
dried
processing preserves such pre-existing texture. While these alternatives may
not be
preferred, they may still be suitable, for some uses. Various other possible
tissue or
nonwoven manufacturing techniques (e.g., dry crepe technique (DCT), structured
tissue
or new tissue technology (NTT), and others that will be apparent to those of
skill in the
art) may also be suitable in at least some embodiments.
[0113] While
use of polyethylene or another thermoplastic polymer having the
described tan delta characteristics eliminates any need for a chemical
adhesive to adhere
the top and bottom surface layer to the thermoplastic layer, it will be
appreciated that in
other embodiments, e.g., even using polypropylene or another material having
poor tan
delta characteristics, it may be possible to achieve a multi-layer substrate
that does not
delaminate, e.g., by using a chemical adhesive to provide the needed bonding.
[0114] The
degree of lamination and strength of the bond between adjacent layers
typically depends on the temperature, pressing or contact time, and applied
pressure
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associated with the calendaring operation. Temperature may be a primary
variable
responsible for bond strength achieved, although pressure and time may also
have an
effect, and may also affect the resulting texture that is "embossed" into the
pulp fiber
surface layer, and the resulting bond pattern. Where the pulp fiber or other
layers
provided on both exterior faces are embossed with a texture, the resulting
multi-layer
substrate exhibits a more "cloth-like" feel that is drapable and less stiff,
as compared to
where only one of the two faces is embossed with a texture. In addition, it
was observed
that all else being equal, heavier exterior layers (i.e., greater lb or gsm
weight) produces a
stiffer substrate. Figures 7A-7F illustrate various possible embossing
patterns that can be
applied by the calendar rollers. It will be apparent that the possibilities
are nearly
limitless.
[0115]
Temperatures applied during calendaring may be at least 150 F, at least 175 F,
at least 200 F, from 200 F to 400 F, or from 200 F to 350 F. Applied pressure
may be at
least 50 psi, at least 100 psi, at least 150 psi, at least 200 psi, from 100
psi to 1000 psi, or
from 300 psi to 600 psi. Contact time (time at the given pressure and/or
temperature) may
be at least 100 ms, at least 200 ms, from 100 ms to 5 s, from 200 ms to 1 s,
or from 200
ms to 500 ms.
[0116] Such a
manufacturing process may be attractive, e.g., as compared to
traditional non-woven substrate manufacture, as it may not require any
processing of
individual fibers not already provided in a nonwoven layer, water usage, water
filtration,
drying steps, loss of fibers during processing, and the like. In addition, the
present
calendaring process may allow for greater production line speeds (e.g., up to
900 m/min,
typically from 50 m/min to 600 m/min) as compared to SPINLACE manufacturing
conventional blended substrates (that are not multi-layer), which are at
significantly lower
line production speeds.
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[0117]
Increased line speed results in decreased contact time (all else being equal).
To
provide the desired good bonding, higher line speed may be accommodated by
increasing
web surface temperature (so shorter contact time is needed), increasing the
roller diameter
(thus increasing contact time), or increasing applied pressure (nip pressure).
By way of
example, for every 25 m/min increase in line speed, temperature can be
increased by
about 5% (in C) to maintain bonding level).
[0118] With
respect to embossed textures, it was observed that "pin" textures (e.g.,
associated with fine dots) can result in tearing of the top and bottom surface
layers, as the
fibers get caught on the pins. Thus, textures that are formed using more of a
"flat bar"
type contact versus a sharp "pin" may be preferred; as such larger features do
not result in
such tearing. In addition, it was observed that when manufacturing such
substrates
through a calendaring operation, that the thermoplastic "cheese" layer should
be narrower
in width than the top and bottom surface "bread" layers in order to further
minimize
complications during manufacture. From such a processed multi-layer laminated
web,
individual sized wipes may be cut to the desired size. Edges of the web that
may not
include the thermoplastic "cheese" layer could be cut away during such
cutting, if
desired. The present substrates also provide for the ability to modulate the
substrate
stiffness by changing the pattern applied during calendaring (e.g., see the
various patterns
of Figure lE or 7A-7F), as well as the ability to modulate stiffness and
tensile strength
characteristics by providing texturing on one or both of the substrate faces,
the ability to
provide for relatively higher quat release even at higher pulp fractions, and
more uniform
lotion release, with better mileage, as described in Applicant's Application
Serial No.
16/042,690, filed July 23, 2018 (Docket No. 510.174), due to the high pulp
content.
[0119] Table 4
below shows the results of additional testing conducted on exemplary
formed multi-layer wipes including exterior pulp layers and an interior
thermoplastic layer,
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relative to dry stiffness characteristics. As described in Applicant's
Application Serial No.
16/042,690, filed July 23, 2018 (Docket No. 510.174), the stiffness
characteristics of
wipes that are formed to include exterior pulp layers exhibit significantly
higher stiffness
than conventional, currently available wipes, even those that are blended
substrates, which
may include, e.g., up to 60% pulp fibers.
Table 4
Exemplary Exemplary Exemplary Comparative Comparative Comparative Comparative
substrate substrate substrate Example 1 Example 2
Example 3 Example 4
with Hex (no (large dot
texture texture) texture)
(Trial 1)
Composition Tissue ¨ Tissue ¨ Tissue ¨ SB
- loose SMS - loose SMS - loose 100% PET
Bico- Bico- Bico- pulp - SB pulp pulp
Tissue Tissue Tissue
%Pulp/%Synthetic 80/20 78/22 78/22 60/40 60/40 60/40
0/100
Basis Weight 58 54 54 52 52 52 52
(gsm)
Dry Stiffness 1222 379 868 174 70 86 62
(mg = cm)
[0120]
Stiffness values were measured using ASTM D-1388-96. As shown in Table 4,
the exemplary 3-layer substrate materials include approximately at least
double the dry
stiffness of wipes produced using current wipes technologies. Such increased
stiffness is
believed to be due at least in part to the use of fixed pulp fibers, where the
pulp layers
used in forming the substrates are already in structured form (e.g., as
nonwoven sheets,
similar to a paper towel).
[0121]
Additional testing was also performed to evaluate cantilever stiffness using
standard techniques e.g., where a substrate to be tested is evaluated by
placing it between
a stationary slide base, under a axially movable slide, and advancing the
substrate towards
a decline where the stationary slide base drops away from the axially movable
slide, at a
given angle (e.g., 45 ). During the test, the average length of the substrate
that is required
to cause the cantilevered substrate to bend so as to contact the declined
portion of the
stationary slide is measured. The stiffer the substrate, the longer the
cantilever length that
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will be needed to cause the substrate to bend, so as to touch the declined
surface of the
stationary slide. Applicant surprisingly found that cantilever stiffness
decreases with
increasing bond area, which is surprising as it would be thought that by
laminating the 3
layers of the substrate together, that they might act more in unison, as a
composite,
thicker, substrate. One hypothesis is that as the bond area is reduced by
having raised
features on the bonding plates or rollers, these features "break" some of the
original
structure of the tissue and thus lower the stiffness of the overall structure.
The results for
different bond areas (simply the fraction of surface area of the substrate
that is bonded
versus unbonded) are shown in Table 5.
Table 5
Bond Area Avg. Bending
Length (mm)
65% 109
73% 94
100% 83
[0122] Higher
bending length equates to lower stiffness (all else being equal). The
data indicates that as bonding area increases, stiffness decreases, and vice-
versa.
[0123] In
typical calendaring processes, only one of the rollers (e.g., 216a, 216b of
Figure 8) is embossed (e.g., one steel, one rubber or other elastomer). In
addition, typical
processes result in texture on only one of the two faces of the substrate,
where raised
texture features on one face are axially aligned with a corresponding
depression feature
on the opposite face. There are no substrates currently available, which are
textured in the
same way on both faces, so that raised texture features (bumps) on one face
would be
axially aligned with corresponding raised texture features (also bumps, not
depressions)
on the other face. With the presently described processes, it is possible to
achieve such
two-sided texturing. In an embodiment, two steel rollers (e.g., 216a, 216b)
could be used,
where both include the texture to be applied to the substrate, which can
result in two-
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sided texturing. Figure 9A illustrates images comparing a conventional 1-sided
texture
(top of Figure 9A), to a two-sided textured substrate, where the "bumps" can
be provided
in both faces, where the textured "bumps" are axially aligned with one another
through
the substrate thickness.
[0124] Such may
be important in providing a user of the wipe with the same hand feel
and other characteristics no matter which face of the wipe is oriented towards
the hand,
and which face is oriented towards the surface being cleaned (both have the
same tactile
characteristics, rather than differing from one another). In other words,
conventional
wipes are not the same on one face as compared to the other, while the present
processes
can be implemented in a way to provide the same user tactile experience no
matter the
orientation of the wipe in the user's hands, where two-sided texturing is
provided. Figures
9B-9C illustrate profilometer data for the "bumpy" face and the "other" face
of a
substrate without two-sided texturing, while Figures 9D-9E illustrate
profilometer data
for the first and second faces of a substrate with two-sided texturing (both
are "bumpy").
Figures 9F-9I illustrate additional profilometer data for the tested
comparative one-sided
versus two-sided textured samples.
[0125] Without
departing from the spirit and scope of this invention, one of ordinary
skill can make various modifications to the invention to adapt it to various
usages and
conditions. As such, these changes and modifications are properly, equitably,
and
intended to be, within the full range of equivalence of the following claims.
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