U.S. patent application number 12/647969 was filed with the patent office on 2011-06-30 for bulk enhancement for airlaid material.
Invention is credited to Clayton Bunyard, Jian Qin, Donald E. Waldroup, Jun G. Zhang.
Application Number | 20110155338 12/647969 |
Document ID | / |
Family ID | 44186024 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155338 |
Kind Code |
A1 |
Zhang; Jun G. ; et
al. |
June 30, 2011 |
Bulk Enhancement For Airlaid Material
Abstract
An airlaid substrate may have a positive increase in thickness
through the addition of thermally expandable microspheres into the
substrate. In one application, the substrate may be converted to
sheets used as wet or dry wipes.
Inventors: |
Zhang; Jun G.; (Appleton,
WI) ; Qin; Jian; (Appleton, WI) ; Waldroup;
Donald E.; (Roswell, GA) ; Bunyard; Clayton;
(DePere, WI) |
Family ID: |
44186024 |
Appl. No.: |
12/647969 |
Filed: |
December 28, 2009 |
Current U.S.
Class: |
162/158 |
Current CPC
Class: |
D21H 21/54 20130101;
D21H 27/42 20130101 |
Class at
Publication: |
162/158 |
International
Class: |
D21H 23/00 20060101
D21H023/00 |
Claims
1. A sheet comprising: an airlaid material having a thickness and
comprising fibers; a plurality of thermally expandable microspheres
distributed at least partially through the material thickness; and
a binder material applied to the sheet.
2. The sheet of claim 1 wherein the microspheres have an initial
state and an expanded state, wherein the microspheres have an
average diameter of about 80 micrometers when in the expanded
state.
3. The sheet of claim 1 wherein the total adhesive binder material
within the sheet is about 15 to 20 percent by weight.
4. The sheet of claim 3 wherein the thermally expandable
microspheres content in the sheet is about 1 to about 10 percent by
weight.
5. The sheet of claim 4 wherein the sheet is a thermally-bonded
airlaid in the form of a wet wipe, the sheet having about a 46 to
about 58 percent increase in sheet bulk as determined by the
caliper measurement and bone-dry basis-weight test methods as
described herein.
6. The sheet of claim 5 wherein the sheet is a multi-bonded airlaid
material in the form of a wet wipe, wherein the wet wipe has about
80 to about 132 percent increase in sheet bulk as determined by the
caliper measurement and bone-dry basis-weight test methods as
described herein, and wherein the multi-bonded airlaid further
comprises a thermal binder of about 16 percent by weight.
7. The sheet of claim 5 wherein the sheet is an adhesively-bonded
airlaid in the form of a dispersible wet wipe, the sheet with 1 to
5% thermally expandable micropsheres by weight, and having about 10
to about 110 percent increase in sheet bulk as determined by the
caliper measurement and bone-dry basis-weight test methods as
described herein.
8. The sheet of claim 1 wherein the sheet is an adhesively-bonded
airlaid in the form of a non-dispersible wet wipe, the sheet with 1
to 5% thermally expandable microspheres by weight and having about
a 35 to about 120 percent increase in sheet bulk as determined by
the caliper measurement and bone-dry basis-weight test methods as
described herein.
9. The sheet of claim 1 wherein the binder is salt responsive.
10. The sheet of claim 1 wherein the binder is water
dispersible.
11. A method of making an airlaid sheet having a thickness, the
method comprising the steps of: (a) spraying an airlaid sheet with
a bonding material; and (b) spraying the thermally expandable
microspheres onto the airlaid sheet.
12. The method of claim 11 further comprising the step of applying
a vacuum to the sheet so that the microspheres are distributed at
least partially through the sheet thickness.
13. The method of claim 11 wherein step (b) is performed before
step (a).
14. The method of claim 11 wherein steps (a) and (b) are
accomplished simultaneously by mixing the bonding material with the
thermally expandable microspheres prior to the spraying step.
15. A method of making an airlaid sheet comprising the step of
disposing the thermally expandable microspheres and fibers for
airlaying into a forming station so that the airlaid sheet has
thermally expandable microspheres distributed throughout the sheet
thickness prior to spraying the sheet with a binder.
16. The method of claim 15 wherein the thermally expandable
microspheres have an average diameter of about 80 micrometers when
in an expanded state.
17. The method of claim 16 comprising the step of heating the sheet
after distributing the thermally expandable microspheres into the
sheet so that the microspheres expand to the average diameter.
Description
[0001] The present invention generally relates to a method of
incorporating thermally expandable microspheres into a material so
that the resulting products have increased bulk. More particularly,
the present invention is directed to the incorporation of thermally
expandable microspheres into an airlaid material.
BACKGROUND OF THE INVENTION
[0002] Most consumers have a perception that the thickness of a
non-dispersible or dispersible wipe is related to hand protection
and cleaning. Specifically, it is thought that thicker airlaid
sheet products provide better hand protection and cleaning effect.
In the current technology, the addition of a binder into a sheet of
an airlaid substrate causes the substrate to collapse in the
z-direction, and thus reducing the stack thickness. Therefore, it
is desirable to recover the thickness of an airlaid substrate to
improve consumer perception.
SUMMARY OF THE INVENTION
[0003] It has now been discovered that the thickness reduction in
airlaid substrates can be reversed by adding a thermally expandable
thermoplastic microspheres to a formed sheet of airlaid material.
Thermally expandable microspheres are spherically formed particles
with a gas-proof shell encapsulating a drop of liquid hydrocarbon.
When exposed to heat, the microsphere volume expands about 50
times. The thermally expandable microspheres can be used for bulk
enhancement of dispersible moist wipes and other airlaid-based
products.
[0004] In one aspect of the invention there is a sheet of airlaid
material made from fibers and having a thickness. There is a
plurality of thermally expandable microspheres distributed at least
partially into the material thickness. A binder material is applied
to the sheet to keep the microspheres in place.
[0005] In another aspect of the invention is a method of making an
airlaid sheet having a thickness, the method including the steps
of: (a) spraying an airlaid sheet with a bonding material; and (b)
spraying the thermally expandable microspheres onto the airlaid
sheet.
[0006] In yet another aspect of the invention is a method of making
an airlaid sheet including the step of incorporating the thermally
expandable microspheres into a forming station along with fibers
for airlaying so that the airlaid sheet has thermally expandable
microspheres distributed at least partially through the sheet
thickness prior to spraying the sheet with a binder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a scanning electron microscopic (SEM) view of a
cross section of a wetted airlaid substrate (a control).
[0008] FIG. 2 is a plan view of the wetted airlaid substrate of
FIG. 1.
[0009] FIG. 3 is a SEM view of a cross section airlaid substrate
showing the distribution of expanded thermally-expandable
microspheres within the substrate.
[0010] FIG. 4 is a plan view of the airlaid substrate of FIG.
3.
[0011] FIG. 5 is a schematic representation of one embodiment of an
airlaying forming station.
[0012] FIG. 6 is a schematic representation of an airlaying process
suitable for making the substrate of the present invention as
formed in FIG. 5.
DETAILED DESCRIPTION OF THE ENCLOSED EMBODIMENTS
[0013] Reference now will be made in detail to the embodiments of
the invention, and the examples of which are set forth below. Each
example is provided by way of explanation of the invention, not
limitation of the invention. In fact, it will be apparent to those
skilled in the art that various modifications and variations can be
made in the present invention without departing from the scope or
spirit of the invention. For instance, features illustrated or
described as part of one embodiment, can be used on another
embodiment to yield a still further embodiment.
[0014] Thus, it is intended that the present invention cover such
modifications and variations as come within the scope of the
appended claims and their equivalents. Other features and aspects
of the present invention are disclosed in the following detailed
description. Examples of commercial products that are being
produced via air forming include but are not limited to industrial
wipers, disposable hospital underpads, disposable tablecloths and
napkins, pre-moistened baby wipes, and absorbent cores for diapers,
feminine pads and the like.
[0015] One aspect of the present invention is an airlaid substrate
for wet wipes that is treated with a binder and thermally activated
microspheres. When heated, the microsperes expand thereby causing
the airlaid substrate to expand in the z-direction (thickness). The
result of the expansion is added bulk which gives the consumer a
better hand feel and the perception that the wet wipes are more apt
to clean better.
[0016] Airlaid Substrate
[0017] "Airlaying" is a well-known process by which a fibrous
nonwoven layer can be formed. In the airlaying process, bundles of
small fibers having typical lengths ranging from about 3 to about
52 millimeters (mm) are separated and entrained in an air supply
and then deposited onto a forming screen, usually with the
assistance of a vacuum supply. The randomly deposited fibers then
are bonded to one another using, for example, hot air to activate a
binder component or a latex adhesive. Airlaying is taught in, for
example, U.S. Pat. No. 4,640,810 to Laursen et al.
[0018] The production of airlaid nonwoven composites is well
defined in the literature and documented in the art. Examples
include the DANWEB process as described in U.S. Pat. No. 4,640,810
to Laursen et al assigned to Scan Web of North America Inc; the
Kroyer process as described in U.S. Pat. No. 4,494,278 to Kroyer et
al. and U.S. Pat. No. 5,527,171 to Soerensen assigned to Niro
Separation a/s; the method of U.S. Pat. No. 4,375,448 Appel et al.
assigned to Kimberly-Clark Corporation, or other similar methods.
The webs produced by these methods may subsequently be bonded
together to form an adequate tensile strength web by thermal
fusing, latex bonding or combinations thereof, which are well known
in the art. Webs produced in this text are best exemplified but not
limited to the DANWEB process.
[0019] The fibrous material may be formed from a single layer or
multiple layers. In the case of multiple layers, the layers are
generally positioned in a juxtaposed or surface-to-surface
relationship and all or a portion of the layers may be bound to
adjacent layers. The fibrous material may also be formed from a
plurality of separate fibrous materials wherein each of the
separate fibrous materials may be formed from a different type of
fiber. In those instances where the fibrous material includes
multiple layers, the binder composition of the present invention
may be applied to the entire thickness of the fibrous material, or
each individual layer may be separately treated and then combined
with other layers in a juxtaposed relationship to form the finished
fibrous material.
[0020] Airlaid nonwoven fabrics are particularly well suited for
use as wet wipes. The basis weights for airlaid nonwoven fabrics
may range from about 30 to about 350 grams per square meter (gsm)
with staple fibers having a denier of about 0.5-10 and a length of
about 6-15 millimeters. Wet wipe substrates may generally have a
fiber dry density of about 0.025 g/cc to about 0.2 g/cc.
[0021] Bonding
[0022] Generally, there are three ways to bond fibers: (a) with an
adhesive (b) thermally, or (c) a combination of adhesive and
thermal bonding. Of the binders there are two types, namely,
dispersible and non-dispersible binders. A non-dispersible adhesive
binder, such as a latex adhesive, used on an airlaid substrate is
used to create a cohesive web which does not disperse/degrade when
exposed to water. A dispersible adhesive binder and optional
dispersible cobinder composition ("binder(s)") may be a component
of a web which enhances bonding of the fibers and/or filaments
within a nonwoven web to provide wet strength to a wet wipe or the
like. The binder(s) composition for a dispersible wipe is desirably
ion-sensitive such that in the presence of water it becomes
soluble, thus allowing the nonwoven web to disperse.
[0023] Thermally activated binders can be used in airlaid
structures to help provide mechanical integrity and stabilization.
Such binders include fiber, liquid or other binder means that may
be thermally activated. These binders may be dispersible or
non-dispersible.
[0024] Without the presence of the thermally expanding microspheres
of the present invention, these types of dispersible and
non-dispersible binder(s) cause the substrate to collapse in the
z-direction (a direction perpendicular to a plane defining a
surface of the nonwoven web).
[0025] In some aspects, the total amount of dispersible adhesive
binder(s) composition present in the nonwoven web can range from
about 5 to about 65 wt %, such as between about 7 to about 35 wt %,
or between about 10 to about 25 wt % or between about 15 to 20 wt %
based on the total weight of the nonwoven web. A sufficient amount
of the binder(s) composition results in a nonwoven web that has
desirable in-use integrity, but quickly disperses when disposed in
tap water.
[0026] One particular example of thermally activated binder fibers
are polyolefin fibers. Lower melting point polymers, such as
polyolefin polymers, provide the ability to bond the fabric
together at fiber cross-over points upon the application of heat.
In addition, fibers of a lower melting polymer, like conjugate and
biconstituent fibers are suitable for practice of this invention.
Fibers having a lower melting polymer are generally referred to as
"fusible fibers." By "lower melting polymers" what is meant are
those fibers having a glass transition temperature less than about
175.degree. C. Thermally activated fibers are available from many
manufacturers such as Chisso of Tokyo, Japan and Fibervisions,
L.L.C. of Wilmington, Del.
[0027] Regardless of the type of binder used, it is desirable that
the binder(s) composition can be processed on a commercial scale
(i.e., the binder(s) may be capable of rapid application on a large
scale, such as by spraying). Further, the binder(s) composition can
further provide acceptable levels of sheet wetability. In addition,
it is desirable that all components of the wet wipe, including the
binder(s) composition, are non-toxic and relatively economical.
[0028] Thermally Expandable Microspheres
[0029] The microspheres may be added anywhere in the manufacturing
of the airlaid making process. For example, the microspheres may be
added to the forming chamber in an airlaying forming station as
described herein (see FIG. 5).
[0030] Many brands of microspheres may be utilized, such as AQUA
SLURRY from Polytex Environmental Inks and MATSUMOTO MICROSPHERE
from Matsumoto Yushi-Seiyaku Co., Ltd. One desireable brand of
microspheres is sold under the name EXPANCEL by Akzo Nobel. In
particular, EXPANCEL 091 DU 80 microspheres consist of hollow,
white, spherically-formed polymer particles encapsulating a blowing
agent (for example, liquid isobutane) under pressure. The EXPANCEL
091 DU 80 microspheres generally have a mean diameter of about 80
micrometers after expansion.
[0031] The density of the microspheres is about 1000-1300
kg/m.sup.3. The thermoplastic shell softens when heated so that the
gasification of the blowing agent expands the microspheres to a
final volume that is from 30 to more than 60 times larger than the
original volume at constant weight. The density of the expanded
microsphere is then below about 30 kg/m.sup.3.
[0032] The microspheres start to expand upon heating above a given
temperature, depending on the chemistry of the shell copolymer. It
is the shell that determines how and when the sphere will expand.
In a particular embodiment of the present invention, EXPANCEL 091
DU 80 was expanded in the airlaid drying process. Other grades of
EXPANCEL products (and other brands of expandable microspheres) may
expand at lower or higher temperatures and may, thus, be suitable
for engineered applications. Cooling causes the expanded
microsphere shells to stiffen and thus remain in the expanded
state. It is noted that the temperature range of the airlaid
heating process governs the expansion of the microspheres.
Desirably, suitable microspheres are selected by considering the
temperature of the airlaid heating process.
[0033] Desirably, the amount of thermally expandable microspheres
disposed in or on an airlaid substrate is from about 0.05 percent
to about 20 percent based on the substrate basis weight. In another
aspect, the microspheres disposed in or on an airlaid substrate is
from about 0.5 percent to about 10 percent based on the substrate
basis weight. In yet another aspect, the microspheres disposed in
or on an airlaid substrate is from about 1 percent to about 5
percent based on the substrate basis weight.
[0034] In one example, absorbent cores are typically composed of
superabsorbent particles and/or pulp. A newer class of absorbents
also uses a binder to improve wet stability and to ease converting
into final products. Binders can be liquid adhesive or thermally
expandable fibers typically present in amounts between 10 and 25
weight percent.
[0035] The Airlaid Process
[0036] For an adhesive binder process, in one aspect of the
invention the microspheres are sprayed onto one surface of the
airlaid web before the adhesive binder(s) is applied to that
surface. In another aspect of the invention, the binder(s) and
microspheres are mixed and simultaneously applied to a surface of
the airlaid web. In a further aspect of the invention, the
microspheres are applied to the surface of the airlaid web after
the adhesive binder(s) is applied to the same surface. In yet
another aspect of the invention, the airlaid web is impregnated
with microspheres during the forming of the airlaid web and the
adhesive binder(s) is subsequently sprayed onto the impregnated
web. The binder(s) and/or microspheres can be applied to both
surfaces of the airlaid web in any combination or sequence.
[0037] FIG. 5 schematically illustrates an airlaying forming
station useful for airlaying a web of fibers to make an airlaid
sheet in accordance with the Example below.
[0038] If desired, there are different ways of imparting texture
patterns to the tissue sheet for purposes of this invention. Fabric
texture patterns associated with airlaying is one such method. The
airlaying forming station 30 produces an airlaid web 32 on a
forming fabric or screen 34. The forming fabric 34 can be in the
form of an endless belt mounted on support rollers 36 and 38. A
suitable driving device, such as an electric motor 40 rotates at
least one of the support rollers 38 in a direction indicated by the
arrows at a selected speed. As a result, the forming fabric 34
moves in a machine direction indicated by the arrow 42.
[0039] The forming fabric 34 can be provided in other forms as
desired. For example, the forming fabric can be in the form of a
circular drum which can be rotated using a motor as disclosed in
U.S. Pat. No. 4,666,647, U.S. Pat. No. 4,761,258, or U.S. Pat. No.
6,202,259, which are incorporated herein by reference.
[0040] As shown, the airlaying forming station 30 includes a
forming chamber 44 having end walls and side walls. Within the
forming chamber 44 are a pair of material distributors 46 and 48
which distribute fibers and/or other particles inside the forming
chamber 44 across the width of the chamber. The material
distributors 46 and 48 can be, for instance, rotating cylindrical
distributing screens.
[0041] In the embodiment shown in FIG. 5, a single forming chamber
44 is illustrated in association with the forming fabric 34. It
should be understood, however, that more than one forming chamber
can be included in the system. By including multiple forming
chambers, layered webs can be formed in which each layer is made
from the same or different materials.
[0042] Airlaying forming stations as shown in FIG. 5 are available
commercially through Dan-Webforming Int. LTD. of Aarhus, Denmark.
Other suitable airlaying forming systems are also available from M
& J Fibretech of Horsens, Denmark. As described above, however,
any suitable airlaying forming system can be used in accordance
with the present invention.
[0043] As shown in FIG. 5, below the airlaying forming station 30
is a vacuum source 50, such as a conventional blower, for creating
a selected pressure differential through the forming chamber 44 to
draw the fibrous material against the forming fabric 34. If
desired, a blower can also be incorporated into the forming chamber
44 for assisting in blowing the fibers down on to the forming
fabric 34.
[0044] In one embodiment, the vacuum source 50 is a blower
connected to a vacuum box 52 which is located below the forming
chamber 44 and the forming fabric 34. The vacuum source 50 creates
an airflow indicated by the arrows positioned within the forming
chamber 44. Various seals can be used to increase the positive air
pressure between the chamber and the forming fabric surface.
[0045] During operation, typically a fiber stock is fed to one or
more defibrators (not shown) and fed to the material distributors
46 and 48. The material distributors distribute the fibers evenly
throughout the forming chamber 44 as shown. Positive airflow
created by the vacuum source 50 and possibly an additional blower
force the fibers onto the forming fabric 34 thereby forming an
airlaid non-woven web 32.
[0046] When wood pulp fibers are present in the airlaid web of the
present invention, the pulp fibers may be in a rolled and fluffed
form. As is known to those skilled in the art, fluffed fibers
generally refer to fibers that have been shredded.
[0047] In one embodiment, the debonding agent can be an organic
quaternary ammonium chloride and particularly a silicone based
amine salt of a quaternary ammonium chloride. For example, the
debonding agent can be PROSOFT TQ1003 marketed by the Hercules
Corporation.
[0048] When forming the airlaid web 32 from different materials and
fibers, the forming chamber 44 can include multiple inlets for
feeding the materials to the chamber. Once in the chamber, the
materials can be mixed together if desired. Alternatively, the
different materials can be separated into different layers in
forming the web.
[0049] Referring to FIG. 6, shown is a schematic diagram of an
entire web forming system useful for making wipes in accordance
with the present invention. In this embodiment, the system includes
three separate airlaying forming chambers 44A and 44B and 44C. As
described above, the use of multiple forming chambers can serve to
facilitate formation of the airlaid web at a desired basis weight.
Further, using multiple forming chambers can allow the formation of
layered webs. As shown, forming stations 44A, 44B and 44C
contribute to the formation of the airlaid web 32.
[0050] Airlaid web 32, after exiting the forming chambers 44A, 44B
and 44C, is conveyed on a forming fabric 34 to a compaction device
54A. Compaction device 54A can be, for instance, a pair of opposing
rolls that define a nip through which the airlaid web and forming
fabric are passed. For example, in one embodiment, the compaction
device can comprise a steel roll positioned above a rubber-coated
roll. The compaction device moderately compacts the airlaid web to
generate sufficient strength for transfer of the airlaid web to a
transfer fabric such as, for instance, via an open gap arrangement.
In general, the compaction device increases the density of the web
over the entire surface area of the web as opposed to only creating
localized high density areas.
[0051] After exiting the compaction device 54A, the airlaid web 32
is transferred to a transfer fabric 52. A suitable transfer fabric
is ElectroTech 56 manufactured by Albany International. Once placed
upon the transfer fabric, the airlaid web can be fed through a
second compaction device 54B and further compacted against the
transfer fabric to generate a texture pattern in the sheet. The
compaction device 54B can also be used to improve the appearance of
the web, to adjust the caliper of the web, and/or to increase the
tensile strength of the web.
[0052] Next, the airlaid web 32 is transferred to a spray fabric
53A and fed to a spray chamber 56. Within the spray chamber 56,
microspheres and binder(s) may be applied to the airlaid web. Under
fabric vacuum may also be used to regulate and control penetration
of the bonding material into the web. The binder(s) may add dry
strength, wet strength, stretchability, and tear resistance. The
expanded microspheres add bulk, resiliency, wet firmness and
improved hand feel.
[0053] The bonding material and microspheres can be applied so as
to uniformly cover the entire surface area of one side of the web.
For instance, the bonding material and microspheres can be applied
to the first side of the web so as to cover at least about 80% of
the surface area of one side of the web, such as at least about 90%
of the surface area of one side of the web. In other embodiments,
the bonding material and microspheres can cover greater than about
95% of the surface area of one side of the web. It is possible that
the microspheres will penetrate the web as seen in FIG. 4.
[0054] The bonding material and microspheres can be applied so as
to cover only part of the entire surface area of one side of the
web. This covered area can have certain patterns and designs
disposed on the web, such as lines, circles, etc.
[0055] Once the binder(s) and microspheres are applied to at least
one side of the web, as shown in FIG. 6, the airlaid web 32 is
transferred to drying fabric 55A and fed to a drying apparatus 58.
In the drying apparatus 58, the web is subjected to heat causing
the bonding material and microspheres to dry and/or cure and cause
the microspheres to expand. In one aspect, when using an ethylene
vinyl acetate copolymer bonding material, the drying apparatus can
be heated to a temperature of from about 120.degree. C. to about
170.degree. C.
[0056] The use of such expandable microspheres allows the opening
up of the fiber structure so as to create a bulkier (i.e., less
dense) web. Accordingly, when expandable microspheres are utilized
in an airlaid product, the resulting airlaid product will have a
bulkier structure than the same airlaid product at the same weight
basis.
[0057] From the drying apparatus 58, the airlaid web is then
transferred to a second spray fabric 53B and fed to a second spray
chamber 60. In the spray chamber 60, a second bonding material is
applied to the untreated side of the airlaid web. In general, the
first bonding material and the second bonding material can be
different bonding materials or the same bonding material. The
second bonding material may be applied to the nonwoven web as
described above with respect to the first bonding material.
[0058] From the second spray chamber 60, the nonwoven web is then
transferred to a second drying fabric 55B and passed through a
second drying apparatus 62 for drying and/or curing the second
bonding material.
[0059] From the second drying apparatus 62, the airlaid web 32 is
transferred to a return fabric 59 and may optionally be fed to a
further compaction device 64 prior to being wound on a reel 66. The
compaction device 64 can be similar to the first compaction device
and may comprise, for instance, calendar rolls. Alternatively, the
compaction device 64 can be a pair of embossing rolls used for the
purpose of softening and further texturizing the sheet.
[0060] Wetting Composition for Wet Wipe Examples.
[0061] The wetting composition for use in combination with the
dispersible ion-sensitive nonwoven materials may desirably comprise
an aqueous composition containing insolubilizing agent that
maintains the coherency of the binder composition, and thus, the
in-use strength of the wet-wipe steady until the insolubilizing
agent is diluted with sufficient water to provide strength
loss.
[0062] Desirably, a salt triggerable binder composition may be
insoluble in a wetting composition, wherein the wetting composition
comprises at least about 0.3 weight percent of an insolubilizing
agent which may be comprised of one or more inorganic and/or
organic salts containing monovalent and/or divalent ions. More
desirably, the binder composition may be insoluble in the wetting
composition, wherein the wetting composition comprises from about
0.3% to about 10% by weight of an insolubilizing agent which may be
comprised of one or more inorganic and/or organic salts containing
monovalent and/or divalent ions. Even more desirably, the binder
composition may be insoluble in the wetting composition, wherein
the wetting composition comprises from about 0.5% to about 5% by
weight of an insolubilizing agent which comprises one or more
inorganic and/or organic salts containing monovalent and/or
divalent ions. Most desirably, the binder composition may be
insoluble in the wetting composition, wherein the wetting
composition comprises from about 1.0% to about 4.0% by weight of an
insolubilizing agent which comprises one or more inorganic and/or
organic salts containing monovalent and/or divalent ions.
[0063] Suitable monovalent ions include, but are not limited to,
Na.sup.+ ions, K+ ions, Li+ ions, NH.sub.4+ ions, low molecular
weight quaternary ammonium compounds (e.g., those having fewer than
5 carbons on any side groups), and a combination thereof. Suitable
divalent ions include, but are not limited to, Zn.sup.2+, Ca.sup.2+
and Mg.sup.2+. These monovalent and divalent ions may be derived
from organic and inorganic salts including, but not limited to,
NaCl, NaBr, KCl, NH.sub.4Cl, Na.sub.2SO.sub.4, ZnCl.sub.2,
CaCl.sub.2, MgCl.sub.2, MgSO.sub.4, and combinations thereof.
Typically, alkali metal halides are the most desirable monovalent
or divalent ions because of cost, purity, low toxicity, and
availability. A particularly desirable salt is NaCl.
[0064] The wetting composition may include a variety of additives
or components, including those disclosed in U.S. Patent Publication
No. 2002/0155281, which is hereby incorporated by reference in a
manner that is consistent herewith. Possible additives may include,
but are not limited to skin-care additives, odor control additives,
wetting agents and/or cleaning agents; surfactants, pH control
agents, preservatives and/or anti-microbial agents.
[0065] The wet wipes, as disclosed herein, do not require organic
solvents to maintain in-use strength, and the wetting composition
may be substantially free of organic solvents. However, a small
amount of organic solvents may be included in the wetting
composition for different purposes other than maintaining in-use
wet strength.
[0066] After the airlaid substrate has been heated so that the
microspheres expand, the wetting composition may be applied to the
airlaid substrate in several ways (e.g. spraying or dipping).
[0067] General Procedures for Sample Preparation and Test
Methods
[0068] Lab Preparation of Thermally-Bonded Airlaid Nonwoven
Material Basesheets
[0069] A thermally-bonded airlaid (TBAL) nonwoven basesheet was
prepared using Weyerhaeuser CF405 bleached softwood Kraft pulp
fiber, available from Weyerhaeuser Company, Federal Way, Wash., and
TENCEL.RTM. H400 945 synthetic fiber, available from Lenzing Group,
Lenzing, Austria. The ratio of CF405 to TENCEL.RTM. is 85:15. In
addition to the pulp and TENCEL.RTM., thermal binder fiber is added
to the air former to an overall level of 50% by weight. The thermal
binder fiber used is a bicomponent core/sheath-type fiber available
from ES FiberVisions Inc., located in Athens, Ga. The bicomponent
fiber is a Polyethylene terephthalate-core/Polypropylene-sheath
(PET-core/PP-sheath) with dimensions of 2.2 dtex and 6 mm fiber
length. Enough materials are used in a laboratory-scale air former
to prepare 50 gsm handsheets.
[0070] For codes that include thermally-expandable microspheres,
EXPANCEL microspheres, available from Akzo Nobel, Sundsvall,
Sweden, were also added to the air former, in addition to the pulp
and TENCEL.RTM..
[0071] The resulting lab-prepared TBAL basesheet is then compressed
using a heated Carver press, model 4531, available from Carver,
Inc., located in Wabash, Ind. The compression force is set to 30000
lb and the temperature of the plates is set to 175 degrees F., for
duration of 1 minute.
[0072] Lab Preparation of Adhesively-Bonded Airlaid Nonwoven
Material Basesheets
[0073] Basesheets of the nonwoven web, used to prepare samples of
adhesively-bonded airlaid (ABAL), were produced on a Dan-Web pilot
line, available from Dan-Web, Risskov, Denmark. The un-bonded
basesheet was prepared using Weyerhaeuser CF405 bleached softwood
Kraft pulp fiber, available from Weyerhaeuser Company, Federal Way,
Wash., and TENCEL.RTM. H400 945 synthetic fiber, available from
Lenzing Group, Lenzing, Austria. The ratio of CF405 to TENCEL.RTM.
is 85:15. The basis weight of this material is 58.5 gsm.
[0074] Aqueous adhesive binder solutions are then topically applied
to both sides of the un-bonded airlaid basesheet. The binder
solutions can be dispersible or non-dispersible in nature. First,
the basesheet is placed on a screen which is under vacuum
conditions during the spraying operation. Then the basesheet is
sprayed on each side equally to achieve a final binder add-on of 18
to 20% by weight, in the handsheet. The binder composition is
typically approximately 15 to 16% solids level. A Quick VEEJET.RTM.
nozzle, type 8001, manufactured by Spraying Systems Co., Wheaton,
Ill., operating at approximately 80 psi was employed to spray the
binder composition onto the fibrous material. The distance from the
nozzle tip to the basesheet is 8 inches.
[0075] For codes that include thermally-expandable microspheres,
EXPANCEL microspheres, available from Akzo Nobel, Sundsvall,
Sweden, were also sprayed onto the basesheet, either before, in
combination with, or after, the adhesive binder solution, depending
on the sample code.
[0076] The resulting adhesive binder-sprayed airlaid basesheet is
then transferred to and dried in a Werner Mathis Model LTV
Through-Air Dryer, available from Mathis AG, located in Oberhasli,
Switzerland. The Through-Air Dryer is set to 180 degrees C. for 23
seconds at 100% fan speed.
[0077] Lab Preparation of Multi-Bonded (Thermally and Adhesively)
Airlaid Nonwoven
[0078] Material Basesheets
[0079] Multi-bonded airlaid (MBAL) nonwoven basesheet was prepared
using Weyerhaeuser CF405 bleached softwood Kraft pulp fiber,
available from Weyerhaeuser Company, Federal Way, Wash., and
TENCEL.RTM. H400 945 synthetic fiber, available from Lenzing Group,
Lenzing, Austria. The ratio of CF405 to TENCEL.RTM. is 85:15. In
addition to the pulp and TENCEL.RTM., thermal binder fiber is added
to the air former to an overall level of 20% by weight. The thermal
binder fiber used is a bicomponent core/sheath-type fiber available
from ES FiberVisions Inc., located in Athens, Ga. The bicomponent
fiber is a polyethylene terephthalate-core/polypropylene-sheath
(PET-core/PP-sheath) with dimensions of 2.2 dtex and 6 mm fiber
length. Enough materials are used in a laboratory-scale air former
to prepare 50 gsm handsheets.
[0080] The resulting lab-prepared basesheet is then compressed
using a heated Carver press, model 4531, available from Carver,
Inc., located in Wabash, Ind. The compression force is set to 15000
lb and the temperature of the plates is set to 175 degrees F., for
duration of 1 minute.
[0081] Aqueous adhesive binder solutions are then topically applied
to both sides of the airlaid basesheet. First, the basesheet is
placed on a screen which is under vacuum conditions during the
spraying operation. Then the basesheet is sprayed on each side
equally to achieve a final binder add-on of 18 to 20% by weight, in
the handsheet. The binder composition is typically approximately 15
to 16% solids level. A Quick VEEJET.RTM. nozzle, type 8001,
manufactured by Spraying Systems Co., Wheaton, Ill., operating at
approximately 80 psi was employed to spray the binder composition
onto the fibrous material. The distance from the nozzle tip to the
basesheet is 8 inches.
[0082] For codes that include thermally-expandable microspheres,
EXPANCEL microspheres, available from Akzo Nobel, Sundsvall,
Sweden, were also sprayed onto the basesheet, either before, in
combination with, or after, the adhesive binder solution, depending
on the sample code.
[0083] The resulting adhesive binder-sprayed airlaid basesheet is
then transferred to and dried in a Werner Mathis Model LTV
Through-Air Dryer, available from Mathis AG, located in Oberhasli,
Switzerland. The Through-Air Dryer is set to 180 degrees C. for 23
seconds at 100% fan speed.
[0084] Lab-Prepared Wet Wipe Preparation Protocol
[0085] Each 10''.times.13'' lab-prepared airlaid nonwoven material
was die-cut into two 7.5''.times.5.5'' dry wipes, with the shorter
direction being the machine-direction (MD) direction. Each dry wipe
was then sprayed with a 235% add-on of a wetting composition that
is used on commercially available wet wipes under the trade
designation KLEENEX.RTM. COTTONELLE FRESH.RTM. Folded Wipes
(Kimberly-Clark Corporation of Neenah, Wis.) containing 2 wt %
sodium chloride to yield lab-prepared wet wipes. A stack of 10
lab-prepared wet wipes was formed and placed inside a re-sealable
plastic bag. The stack of 10 lab-prepared wet wipes in the
re-sealable plastic bag was compressed with a 22 lb metal roller,
where the open bag containing the wipes is rolled four times each
in both the MD and cross-direction (CD). The bag is sealed and then
compressed under 1000 g of weight for 48 hours.
[0086] Lab-Prepared Dry Wipe Preparation Protocol
[0087] Each 10''.times.13'' lab-prepared airlaid nonwoven material
was die cut into two 7.5''.times.5.5'' dry wipes, with the shorter
direction being the machine-direction (MD) direction. The wipes are
then conditioned at 23 degrees C. and 50% relative humidity.
[0088] Wet or Dry Wipe Caliper (Thickness) Measurements
[0089] As used herein, the "thickness" of a web is measured with a
3-inch diameter, 5/8'' thick, acrylic plastic disk connected to the
spindle of a SONY Digital Indicator U60A (SONY Corporation, Tokyo,
Japan) and which delivers a net load of 0.05 psi to the sample
being measured. The SONY Digital Indicator is zeroed when the disk
rests on a flat surface. When a sample having a size at least as
great as the acrylic disk is placed under the disk, a thickness
reading can be obtained from the digital readout of the indicator.
Stacks of 10 wet or dry wipes are measured in this manner with
three replicates and averaged. The average is divided by 10 to
obtain a caliper on a per-sheet basis.
[0090] Bone Dry Basis Weight Measurements
[0091] Bone Dry Basis Weight measurements were taken by weighing
the basesheet samples immediately after removal from the
Through-Air Dryer or the Carver Press, at the completion of the lab
preparation process. The sample weights were then converted to
grams per square meter (gsm) values.
EXAMPLES
Example 1
TBAL
[0092] Thermally-bonded airlaid (TBAL) basesheets were prepared as
described in the section "Lab Preparation of Thermally-Bonded
Airlaid Nonwoven Material Basesheets".
[0093] Samples were made with and without EXPANCEL
thermally-expandable microspheres. The type of EXPANCEL used for
these samples was "009 DU 80", available from Akzo Nobel,
Sundsvall, Sweden.
[0094] Additionally, Dry and Wet Wipe samples were prepared from
these TBAL basesheets as described in the sections "Lab-Prepared
Dry Wipe Preparation Protocol" and "Lab-Prepared Wet Wipe
Preparation Protocol."
[0095] These samples are coded A1, A2, A3, and A4. Pertinent
information related to their composition is described in Table
1.
TABLE-US-00001 TABLE 1 Type Type of Type of Type of Wt % Wt % Dry
of Thermal Adhesive EXPANCEL Thermal Adhesive Wt % Wt % Wt % or
Code Airlaid Binder Binder microspheres Binder Binder CF405 TENCEL
EXPANCEL Wet A1 TBAL bico PET- NA NA 50 0 42.5 7.5 0 Dry core/PP-
sheath A2 TBAL bico PET- NA 009 DU 80 45.4 0 38.6 6.8 9.1 Dry
core/PP- sheath A3 TBAL bico PET- NA NA 50 0 42.5 7.5 0 Wet
core/PP- sheath A4 TBAL bico PET- NA 009 DU 80 45.4 0 38.6 6.8 9.1
Wet core/PP- sheath
[0096] Stacks of 10 wet or dry wipes were then measured as
described in the section "Wet or Dry Wipe Caliper (Thickness)
Measurements". This resulted in single sheet calipers after
dividing the average measurements by 10. Additionally, the single
sheet bulk can be calculated as the quotient of the single sheet
caliper, expressed in microns, divided by the bone dry basis
weight, expressed in grams per square meter (gsm). The resulting
sheet bulk is expressed in cubic centimeters per gram. This allows
the calipers to be compared after being normalized by basis weight.
This information is detailed in Table 2.
TABLE-US-00002 TABLE 2 Overall Bone Dry Single Sheet Sheet Bulk %
Thickness Code Basis Weight (gsm) Caliper (mm) (cc/g) Improvement
A1 50 0.93 18.6 NA A2 55 1.49 27.1 45.7 A3 50 0.49 9.8 NA A4 55
0.85 15.5 57.7
[0097] As can be seen, the sheet bulk increases by 45.7% for the
dry TBAL wipes, while the sheet bulk increases by 57.7% for the wet
TBAL wipes.
Example 2
MBAL
[0098] Multi-bonded airlaid (MBAL) basesheets were prepared as
described in the section "Lab Preparation of Multi-Bonded
(Thermally and Adhesively) Airlaid Nonwoven Material Basesheets".
The adhesive binder was an ion-sensitive dispersible binder
composition, comprising a 70/30 combination of binder and co-binder
mixed with de-ionized water to a solids level of 15.5%.
[0099] The binder was a cationic ion-sensitive polyacrylate. More
specifically, the cationic ion-sensitive polyacrylate is a
copolymer of methyl acrylate (96 mol %) and
[(2-acryloyloxy)ethyl]trimethyl ammonium chloride (4 mol %) with a
weight average molecular weight between 140,000 to 200,000 g/mol as
determined by gel permeation chromatography in a
dimethylformamide/LiCl mobile phase. The co-binder was
VINNAPAS.RTM. EZ123 (formerly known as AIRFLEX.RTM. EZ123),
available from Wacker Chemie AG, Munich, Germany.
[0100] Samples were made with and without EXPANCEL
thermally-expandable microspheres. The type of EXPANCEL used for
these samples are "091 DU 80", available from Akzo Nobel,
Sundsvall, Sweden. These were mixed into the binder composition
prior to spraying on the basesheet samples.
[0101] Additionally, Dry and Wet Wipe samples were prepared from
these MBAL basesheets as described in the sections "Lab-Prepared
Dry Wipe Preparation Protocol" and "Lab-Prepared Wet Wipe
Preparation Protocol".
[0102] These samples are coded B1, B2, B3, and B4. Pertinent
information related to their composition is described in Table
3.
TABLE-US-00003 TABLE 3 Type Type of Type of Type of Wt % Wt % Dry
of Thermal Adhesive EXPANCEL Thermal Adhesive Wt % Wt % Wt % or
Code Airlaid Binder Binder microspheres Binder Binder CF405 TENCEL
EXPANCEL Wet B1 MBAL bico PET- Dispersible NA 16.4 18 55.7 9.8 0
Dry core/PP- sheath B2 MBAL bico PET- Dispersible 091 DU 80 15.4 18
52.4 9.2 4.9 Dry core/PP- sheath B3 MBAL bico PET- Dispersible NA
16.4 18 55.7 9.8 0 Wet core/PP- sheath B4 MBAL bico PET-
Dispersible 091 DU 80 15.4 18 52.4 9.2 4.9 Wet core/PP- sheath
[0103] Stacks of 10 wet or dry wipes were then measured as
described in the section "Wet or Dry Wipe Caliper (Thickness)
Measurements." This resulted in single sheet calipers after
dividing the average measurements by 10. Additionally, the single
sheet bulk can be calculated as the quotient of the single sheet
caliper, expressed in microns, divided by the bone dry basis
weight, expressed in grams per sqare meter (gsm). The resulting
sheet bulk is express in cubic centimeters per gram. This allows
the calipers to be compared after being normalized by basis weight.
This information is detailed in Table 4.
TABLE-US-00004 TABLE 4 Overall Bone Dry Single Sheet Sheet Bulk %
Thickness Code Basis Weight (gsm) Caliper (mm) (cc/g) Improvement
B1 61 0.92 15.1 NA B2 64.9 1.76 27.1 79.8 B3 61 0.34 5.6 NA B4 64.9
0.84 12.9 132.2
[0104] As can be seen, the sheet bulk increases by 79.8% for the
dry MBAL wipes, while the caliper/bdbwt increases by 132.2% for the
wet MBAL wipes.
Example 3
ABAL Dispersible
[0105] Adhesively-bonded airlaid (ABAL) basesheets were prepared as
described in the section "Lab Preparation of Adhesively-Bonded
Airlaid Nonwoven Material Basesheets". The adhesive binder was an
ion-sensitive dispersible binder composition, comprising a 70/30
combination of binder and co-binder mixed with de-ionized water to
a solids level of 15.5%.
[0106] The binder was a cationic ion-sensitive polyacrylate. More
specifically, the cationic ion-sensitive polyacrylate is a
copolymer of methyl acrylate (96 mol %) and
[(2-acryloyloxy)ethyl]trimethyl ammonium chloride (4 mol %) with a
weight average molecular weight between 140,000 to 200,000 g/mol as
determined by gel permeation chromatography in a
dimethylformamide/LiCl mobile phase. The co-binder was
VINNAPAS.RTM. EZ123 (formerly known as AIRFLEX.RTM. EZ123),
available from Wacker Chemie AG, Munich, Germany.
[0107] Samples were made with and without EXPANCEL
thermally-expandable microspheres. The type of EXPANCEL used for
these samples are "009 DU 80", available from Akzo Nobel,
Sundsvall, Sweden. These were mixed into the binder composition
prior to spraying on the basesheet samples.
[0108] Additionally, Dry and Wet Wipe samples were prepared from
these dispersible ABAL basesheets as described in the sections
"Lab-Prepared Dry Wipe Preparation Protocol" and "Lab-Prepared Wet
Wipe Preparation Protocol."
[0109] These samples are coded C1, C2, C3, . . . , C12. Pertinent
information related to their composition is described in Table
5.
TABLE-US-00005 TABLE 5 Type Type of Type of Type of Wt % Wt % Dry
of Thermal Adhesive EXPANCEL Thermal Adhesive Wt % Wt % Wt % or
Code Airlaid Binder Binder microspheres Binder Binder CF405 TENCEL
EXPANCEL Wet C1 ABAL NA Dispersible NA 0 18 69.7 12.3 0.0 Dry C2
ABAL NA Dispersible 009 DU 80 0 18 68.9 12.2 1.0 Dry C3 ABAL NA
Dispersible 009 DU 80 0 18 68.0 12.0 2.0 Dry C4 ABAL NA Dispersible
009 DU 80 0 18 67.2 11.9 3.0 Dry C5 ABAL NA Dispersible 009 DU 80 0
18 66.3 11.7 4.0 Dry C6 ABAL NA Dispersible 009 DU 80 0 18 65.5
11.6 5.0 Dry C7 ABAL NA Dispersible NA 0 18 69.7 12.3 0.0 Wet C8
ABAL NA Dispersible 009 DU 80 0 18 68.9 12.2 1.0 Wet C9 ABAL NA
Dispersible 009 DU 80 0 18 68.0 12.0 2.0 Wet C10 ABAL NA
Dispersible 009 DU 80 0 18 67.2 11.9 3.0 Wet C11 ABAL NA
Dispersible 009 DU 80 0 18 66.3 11.7 4.0 Wet C12 ABAL NA
Dispersible 009 DU 80 0 18 65.5 11.6 5.0 Wet
[0110] Stacks of 10 wet or dry wipes were then measured as
described in the section "Wet or Dry Wipe Caliper (Thickness)
Measurements". This resulted in single sheet calipers after
dividing the average measurements by 10. Additionally, the single
sheet bulk can be calculated as the quotient of the single sheet
caliper, expressed in microns, divided by the bone dry basis
weight, expressed in grams per square meter (gsm). The resulting
sheet bulk is expressed in cubic centimeters per gram. This allows
the calipers to be compared after being normalized by basis weight.
This information is detailed in Table 6.
TABLE-US-00006 TABLE 6 Overall Bone Dry Single Sheet Sheet Bulk %
Thickness Code Basis Weight (gsm) Caliper (mm) (cc/g) Improvement
C1 67.1 1.11 16.5 NA C2 67.9 1.33 19.6 18.4 C3 68.8 1.56 22.7 37.1
C4 69.6 1.80 25.9 56.3 C5 70.5 2.06 29.2 76.6 C6 71.4 2.17 30.4
83.7 C7 67.1 0.37 5.5 NA C8 67.9 0.42 6.2 12.2 C9 68.8 0.53 7.7
39.7 C10 69.6 0.65 9.3 69.4 C11 70.5 0.80 11.3 105.8 C12 71.4 0.81
11.3 105.7
[0111] As can be seen, the sheet bulk increases from 18.4% to 83.7%
for the dry dispersible ABAL wipes, depending on the amount of
EXPANCEL added to the basesheet, while the sheet bulk increases
from 12.2% to 105.8% for the wet dispersible ABAL wipes.
[0112] The moist wipes corresponding to code C12 were imaged by SEM
to investigate the distribution of expanded microspheres in the
wipes. Code C7, which did not contain any microspheres, were also
imaged by SEM to represent a "control" code.
[0113] FIGS. 1 and 2 show the SEM images of the control code C7 in
cross-section and on the surface, respectively. There are no
microspheres in this code and the sheet is thin and compact.
[0114] FIGS. 3 and 4 show the SEM images of code C12 in the
cross-section and on the surface, respectively. This code includes
expanded microspheres and it can be observed that the microspheres
are well-distributed in both the planar x-y surface and the
z-direction thickness.
Example 4
ABAL Non-Dispersible
[0115] Adhesively-bonded airlaid (ABAL) basesheets were prepared as
described in the section "Lab Preparation of Adhesively-Bonded
Airlaid Nonwoven Material Basesheets." The adhesive binder was a
non-dispersible binder composition, comprising a non-dispersible
binder mixed with de-ionized water to a solids level of 15.5%. The
binder was VINNAPAS.RTM. 192 available from Wacker Chemie AG,
Munich, Germany.
[0116] Samples were made with and without EXPANCEL
thermally-expandable microspheres. The type of EXPANCEL used for
these samples are "091 DU 80", available from Akzo Nobel,
Sundsvall, Sweden. These were mixed into the binder composition
prior to spraying on the basesheet samples.
[0117] Additionally, Dry and Wet Wipe samples were prepared from
these non-dispersible ABAL basesheets as described in the sections
"Lab-Prepared Dry Wipe Preparation Protocol" and "Lab-Prepared Wet
Wipe Preparation Protocol". These samples are coded D1, D2, D3, . .
. , D12. Pertinent information related to their composition is
described in Table 7.
TABLE-US-00007 TABLE 7 Type Type of Type of Type of Wt % Wt % Dry
of Thermal Adhesive EXPANCEL Thermal Adhesive Wt % Wt % Wt % or
Code Airlaid Binder Binder microspheres Binder Binder CF405 TENCEL
EXPANCEL Wet D1 ABAL NA Non- NA 0 18 69.7 12.3 0.0 Dry dispersible
D2 ABAL NA Non- 091 DU 80 0 18 68.9 12.2 1.0 Dry dispersible D3
ABAL NA Non- 091 DU 80 0 18 68.0 12.0 2.0 Dry dispersible D4 ABAL
NA Non- 091 DU 80 0 18 67.2 11.9 3.0 Dry dispersible D5 ABAL NA
Non- 091 DU 80 0 18 66.3 11.7 4.0 Dry dispersible D6 ABAL NA Non-
091 DU 80 0 18 65.5 11.6 5.0 Dry dispersible D7 ABAL NA Non- NA 0
18 69.7 12.3 0.0 Wet dispersible D8 ABAL NA Non- 091 DU 80 0 18
68.9 12.2 1.0 Wet dispersible D9 ABAL NA Non- 091 DU 80 0 18 68.0
12.0 2.0 Wet dispersible D10 ABAL NA Non- 091 DU 80 0 18 67.2 11.9
3.0 Wet dispersible D11 ABAL NA Non- 091 DU 80 0 18 66.3 11.7 4.0
Wet dispersible D12 ABAL NA Non- 091 DU 80 0 18 65.5 11.6 5.0 Wet
dispersible
[0118] Stacks of 10 wet or dry wipes were then measured as
described in the section "Wet or Dry Wipe Caliper (Thickness)
Measurements." This resulted in single sheet calipers after
dividing the average measurements by 10. Additionally, single sheet
bulk can be calculated as the quotient of the single sheet caliper,
expressed in microns, divided by the bone dry basis weight,
expressed in grams per square meter (gsm). The resulting sheet bulk
is expressed in cubic centimeters per gram. This allows the
calipers to be compared after being normalized by basis weight.
This information is detailed in Table 8.
TABLE-US-00008 TABLE 8 Overall Bone Dry Single Sheet Sheet Bulk %
Thickness Code Basis Weight (gsm) Caliper (mm) (cc/g) Improvement
D1 67.1 1.13 16.8 NA D2 67.9 1.28 18.9 11.9 D3 68.8 1.38 20.1 19.1
D4 69.6 1.46 21.0 24.6 D5 70.5 1.58 22.4 33.1 D6 71.4 1.56 21.8
29.7 D7 67.1 0.44 6.6 NA D8 67.9 0.61 9.0 37.0 D9 68.8 0.71 10.3
57.4 D10 69.6 0.80 11.5 75.3 D11 70.5 0.98 13.9 112.0 D12 71.4 1.02
14.3 117.9
[0119] As can be seen, the sheet bulk increases from 11.9% to 33.1%
for the dry non-dispersible ABAL wipes, depending on the amount of
EXPANCEL added to the basesheet, while the sheet bulk increases
from 37.0% to 117.9% for the wet non-dispersible ABAL wipes.
[0120] Overall Results
[0121] As can be seen from the combined data from the above
examples, the addition of EXPANCEL thermally-expandable
microspheres increases the thickness of wet wipes by at least about
12%, when added at the 1% level, to as much as about 132%, when
added at the 5% level.
* * * * *