U.S. patent application number 10/758066 was filed with the patent office on 2004-08-12 for disposable absorbent article comprising a durable hydrophilic core wrap.
This patent application is currently assigned to The Procter & Gamble Company. Invention is credited to Carter, John David, Cramer, Ronald Dean, Ponomarenko, Ekaterina Anatolyevna, Schmidt, Mattias.
Application Number | 20040158212 10/758066 |
Document ID | / |
Family ID | 32869488 |
Filed Date | 2004-08-12 |
United States Patent
Application |
20040158212 |
Kind Code |
A1 |
Ponomarenko, Ekaterina Anatolyevna
; et al. |
August 12, 2004 |
Disposable absorbent article comprising a durable hydrophilic core
wrap
Abstract
A disposable absorbent article comprising an absorbent core, the
absorbent core comprising: (a) a storage layer; and (b) a durable
hydrophilic fluid pervious core wrap, the core wrap surrounding at
least a portion of the storage layer, said core wrap comprising:
(i) a core wrap substrate; and (ii) a hydrophilicity boosting
composition coated on the substrate, the hydrophilicity boosting
composition comprising a hydrophilicity boosting amount of
nanoparticles, wherein the nanoparticles have a particle size of
from about 1 to about 750 nanometers. Methods of preparing
disposable absorbent articles are also provided.
Inventors: |
Ponomarenko, Ekaterina
Anatolyevna; (Bad Soden am Taunus, DE) ; Carter, John
David; (Mason, OH) ; Cramer, Ronald Dean;
(Cincinnati, OH) ; Schmidt, Mattias; (Idstein,
DE) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Assignee: |
The Procter & Gamble
Company
|
Family ID: |
32869488 |
Appl. No.: |
10/758066 |
Filed: |
January 15, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60446311 |
Feb 10, 2003 |
|
|
|
Current U.S.
Class: |
604/367 |
Current CPC
Class: |
A61F 2013/53472
20130101; A61F 13/15203 20130101; A61F 13/49446 20130101; A61F
13/534 20130101; A61F 13/1565 20130101; A61F 2013/5315 20130101;
A61F 13/51 20130101; A61F 13/53708 20130101; A61F 13/53747
20130101 |
Class at
Publication: |
604/367 |
International
Class: |
A61F 013/15; A61F
013/20 |
Claims
What is claimed is:
1. A disposable absorbent article comprising an absorbent core,
said absorbent core comprising: (a) a storage layer; and (b) a
durable, hydrophilic fluid pervious core wrap, said core wrap
surrounding at least a portion of said storage layer said core wrap
comprising: (i) a core wrap substrate; and (ii) a hydrophilicity
boosting composition coated on said substrate, said hydrophilicity
boosting composition comprising a hydrophilicity boosting amount of
nanoparticles, wherein said nanoparticles have a particle size of
from about 1 to about 750 nanometers.
2. A disposable absorbent article according to claim 1 wherein said
substrate is selected from the group consisting of porous polymeric
films, nonwoven materials and combinations thereof.
3. A disposable absorbent article according to claim 2 wherein said
nonwoven material comprises fibers selected from the group
consisting of polyolefins, polyesters, cellulose and combinations
thereof.
4. A disposable absorbent article according to claim 3 wherein said
nonwoven material comprises fibers selected from the group
consisting of polypropylene, polyethylene, polyethylene
terepthalate, rayon and combinations thereof.
5. A disposable absorbent article according to claim 1 wherein said
nanoparticles are inorganic nanoparticles.
6. A disposable absorbent article according to claim 5 wherein said
nanoparticles are selected from the group consisting of titanium
dioxide, layered clay minerals, alumina oxide, silicates, and
combinations thereof.
7. A disposable absorbent article according to claim 6 wherein said
nanoparticles are selected from the group consisting of titanium
dioxide, Boehmite alumina, sodium magnesium lithium fluorosilicates
and combinations thereof.
8. A disposable absorbent article according to claim 1 wherein said
hydrophilicity boosting composition further comprises a
surfactant.
9. A disposable absorbent article according to claim 1 wherein said
surfactant is a nonionic surfactant.
10. A disposable absorbent article according to claim 1 wherein
said storage layer comprises material selected from the group
consisting of absorbent gelling material, fluff, and mixtures
thereof.
11. A disposable absorbent article according to claim 1 wherein
said disposable absorbent article further comprises a substantially
liquid pervious topsheet and a substantially liquid impervious
backsheet, wherein said storage layer is between said topsheet and
said backsheet, and at least a portion of said core wrap is between
said storage layer and said top sheet.
12. A disposable absorbent article according to claim 1 wherein
said core warp surrounds all of said storage layer.
13. A disposable absorbent article according to claim 12 wherein
said disposable absorbent article is selected from the group
consisting of diapers, adult incontinence products, training pant,
feminine hygiene pads, and panty liners.
14. A disposable absorbent article according to claim 1 wherein
said substrate has been treated with a high-energy surface
treatment.
15. A disposable absorbent article according to claim 14 wherein
said high-energy surface treatment is selected from the group
consisting of corona discharge treatment, plasma treatment, UV
radiation, ion beam treatment, electron beam treatment and
combinations thereof.
16. A process for making a disposable absorbent article comprising
an absorbent core, said absorbent core comprising a storage layer
and a durable hydrophilic core wrap, said core wrap surrounding at
least a portion of said storage layer and said process comprising
the step of: coating a core wrap substrate with a hydrophilicity
boosting composition, said hydrophilicity boosting composition
comprises a hydrophilicity boosting amount of nanoparticles,
wherein said nanoparticles having a particle size of from about 1
to about 750 nanometers.
17. A process for making a disposable absorbent article according
to claim 16 wherein prior to or concurrent with coating of said
substrate, said substrate is treated with a high energy surface
treatment said high-energy surface treatment is selected from the
group consisting of corona discharge treatment, plasma treatment,
UV radiation, ion beam treatment, electron beam treatment and
combinations thereof.
18. A process for making a disposable absorbent article according
to claim 17 wherein hydrophilicity boosting composition further
comprises a carrier and a surfactant.
19. A process for making a disposable absorbent article according
to claim 18 wherein said nanoparticles are inorganic
nanoparticles.
20. A process for making a disposable absorbent article according
to claim 16 wherein said substrate is selected from the group
consisting of porous polymeric films, nonwoven materials and
combinations thereof.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/446,311, filed Feb. 10, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to disposable absorbent
article comprising a durable hydrophilic core wrap, and methods of
producing same.
BACKGROUND OF THE INVENTION
[0003] Disposable absorbent articles such as diapers and adult
incontinence products are well known in the art. Such disposable
articles collect and retain urine and fecal material deposited
thereon by the wearer.
[0004] Nonwoven fabrics made of synthetic fibers and/or natural
fibers are commonly used in absorbent articles, for example, as
topsheet material or as core wrap to enclose the storage layer of
the absorbent core. Such nonwoven fabrics are usually hydrophobic.
However, for many applications in hygiene products it is necessary
to have hydrophilic nonwoven. Therefore the nonwoven fabric has to
be treated accordingly.
[0005] One typical component of disposable absorbent articles is
core wraps. A core wrap is typically a nonwoven material designed
to contain the storage layer and provide structural integrity when
the storage layer is wet or dry. They may be a tissue wrap, or more
typically they are a nonwoven material which has been rendered
hydrophilic.
[0006] A common method for rendering nonwoven fabrics hydrophilic
is coating the surface of the nonwoven with hydrophilic
surfactants. As this coating does not lead to a tight chemical bond
between the nonwoven and the surfactant, the surfactant can be
washed off during use when the absorbent article is wetted. The
decrease in liquid strike-through time is a desirable effect when
the nonwoven is coated with surfactant. Liquid strike-through
refers to liquid passing through the nonwoven fabric with liquid
strike-through time referring to the time it takes for a certain
amount of liquid to pass through the nonwoven. However, as the
surfactant is washed off when coated nonwoven fabrics are exposed
to the liquid, the strike-through time in the next gushes is
increased. This results in performance reduction during use on
diapers or other articles comprising such nonwoven fabrics.
Furthermore, at the same time as liquid strike-through time
decreases due to use of surfactants, surface tension of the liquid,
which was in contact with the nonwoven fabric, is reduced. This
reduction is undesirable, because it can cause increased urine
leakage in a diaper.
[0007] Another common method to render a nonwoven fabric
hydrophilic is by applying corona and/or plasma treatment. Plasma
is an ionized form of gas that can be obtained by ionizing a gas or
liquid medium. Plasmas are widely used for the treatment of organic
and inorganic materials to promote adhesion between various
materials. Polymers that have chemically inert surfaces with low
surface energies do not allow good coatings with bondings and
adhesives. Thus, these surfaces are treated to make them receptive
to bonding with other substrates, coatings, adhesives and printing
inks.
[0008] However, corona and plasma treatments lead to low coating
durability upon storage of the treated material, i.e.,
hydrophilicity decreases over time.
[0009] Thus, there is a need for a hydrophilic coating of a
nonwoven, which is durable upon storage, is not easily washed off
when wetted and allows the nonwoven to achieve fast liquid
strike-through in multiple exposures to liquid.
SUMMARY OF THE INVENTION
[0010] A first aspect of the present invention provides a
disposable absorbent article comprising an absorbent core, the
absorbent core comprising:
[0011] (a) a storage layer; and
[0012] (b) a durable hydrophilic fluid pervious core wrap, the core
wrap surrounding at least a portion of the storage layer, said core
wrap comprising:
[0013] (i) a core wrap substrate; and
[0014] (ii) a hydrophilicity boosting composition coated on the
substrate, the hydrophilicity boosting composition comprising a
hydrophilicity boosting amount of nanoparticles, wherein the
nanoparticles have a particle size of from about 1 to about 750
nanometers.
[0015] A second aspect of the present invention provides a process
for making a disposable absorbent article comprising an absorbent
core, the absorbent core comprising a storage layer and a durable
hydrophilic core wrap, the core wrap surrounding at least a portion
of the storage layer and said process comprising the step of:
[0016] coating a core wrap substrate with a hydrophilicity boosting
composition, the hydrophilicity boosting composition comprises a
hydrophilicity boosting amount of nanoparticles, wherein the
nanoparticles having a particle size of from about 1 to about 750
nanometers.
[0017] It should be understood that every limit given throughout
this specification will include every lower or higher limit, as the
case may be, as if such lower or higher limit was expressly written
herein. Every range given throughout this specification will
include every narrower range that falls within such broader range,
as if such narrower ranges were all expressly written herein.
[0018] All documents cited are, in relevant part, incorporated
herein by reference; the citation of any document is not to be
construed as an admission that it is prior art with respect to the
present invention. All percentages, ratios and proportions are by
weight, and all temperatures are in degrees Celsius (.degree. C.),
unless otherwise specified. All measurements are in SI units,
unless otherwise specified.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] While the specification concludes with claims which
particularly point out and distinctly claim the present invention,
it is believed that the present invention will be better understood
from the following description of preferred embodiments, taken in
conjunction with the accompanying drawing wherein:
[0020] FIG. 1 is a partial cut-away top plan view of a disposable
absorbent article including an absorbent core and a durable
hydrophilic core wrap.
[0021] FIG. 2 is a partial sectional view along 2-2 of one
alternative embodiment of the absorbent core 10 of the disposable
absorbent article of FIG. 1.
[0022] FIG. 3 is a sectional view along 2-2 of another alternative
embodiment of the absorbent core 10 of the disposable absorbent
article of FIG. 1.
[0023] FIG. 4 is a sectional view along 2-2 of another alternative
embodiment of the absorbent core 10 of the disposable absorbent
article of FIG. 1.
[0024] FIG. 5 is a sectional view along 2-2 of another alternative
embodiment of the absorbent core 10 of the disposable absorbent
article of FIG. 1.
[0025] FIG. 6 is a sectional view along 2-2 of another alternative
embodiment of the absorbent core 10 of the disposable absorbent
article of FIG. 1.
[0026] FIG. 7 is a schematic side view of a process for forming an
absorbent article according to the present invention.
[0027] FIG. 8 is a schematic top view of a strike-through plate
which may be used to measure Liquid Strike-through of a
substrate.
[0028] FIG. 9 is a sectional view along 9-9 of the strike-through
plate of FIG. 8.
[0029] FIG. 10 is a sectional perspective view along 10-10 of the
strike-through plate of FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
[0030] The term "coating", as used herein, includes coatings that
completely cover a surface, or portion thereof (e.g., continuous
coatings, including those that form films on the surface), as well
as coatings that may only partially cover a surface, such as those
coatings that after drying leave gaps in coverage on a surface
(e.g., discontinuous coatings). The later category of coatings may
include, but is not limited to, a network of covered and uncovered
portions and distributions of nanoparticles on a surface which may
have spaces between the nanoparticles. In some embodiments, the
coating preferably forms at least one layer of nanoparticles on the
surface which has been coated, and is substantially uniform.
However, when the coatings described herein are described as being
applied to a surface, it is understood that the coatings need not
be applied to, or that they cover the entire surface. For instance,
the coatings will be considered as being applied to a surface even
if they are only applied to modify a portion of the surface.
[0031] The term "hydrophilic" describes fibers or surfaces of
fibers, which are wettable by aqueous fluids (e.g., aqueous body
fluids) deposited on these fibers. Hydrophilicity and wettability
are typically defined in terms of contact angle and the
strike-through time of the fluids, for example through a nonwoven
fabric. This is discussed in detail in the American Chemical
Society publication entitled "Contact Angle, Wettability and
Adhesion", edited by Robert F. Gould (Copyright 1964). A fiber or
surface of a fiber is said to be wetted by a fluid (i.e.,
hydrophilic) when either the contact angle between the fluid and
the fiber, or its surface, is less than 90.degree., or when the
fluid tends to spread spontaneously across the surface of the
fiber, both conditions are normally co-existing. Conversely, a
fiber or surface of the fiber is considered to be hydrophobic if
the contact angle is greater than 90.degree. and the fluid does not
spread spontaneously across the surface of the fiber.
[0032] As used herein, the term "hydrophilicity boosting" means a
composition when coated on a core wrap substrate to make a durable
hydrophilic fluid pervious core wrap, produces a durable
hydrophilic fluid pervious core wrap which has a liquid
strike-through time for the first gush of less than or equal to
about 6 seconds, more preferably less than or equal to about 4
seconds, and has a liquid strike-through time for the fifth gush of
test liquid, of preferably less than or equal to about 6 seconds,
more preferably less than or equal to about 4 seconds, when tested
in accordance with the Strike-Through Test in the Test Methods
section and further described herein.
[0033] As used herein, the term "comprising" means that the various
components, ingredients, or steps can be conjointly employed in
practicing the present invention. Accordingly, the term
"comprising" is open-ended and encompasses the more restrictive
terms "consisting essentially of" and "consisting of".
[0034] The disposable absorbent articles of the present invention
comprise an absorbent core at least a portion of which is
surrounded by a durable hydrophilic fluid pervious core wrap.
Examples of illustrative disposable absorbent articles, include but
are not limited to, diapers, adult incontinence products, training
pant, feminine hygiene pads, panty liners and the like. The durable
hydrophilic fluid pervious core wrap comprises a core wrap
substrate which has been coated with a hydrophilicity boosting
composition. The substrate, and hydrophilicity boosting composition
are both exemplified in more detail herein.
[0035] FIG. 1 is a plan view of a disposable absorbent article,
specifically a diaper 20, which is a preferred embodiment of an
absorbent article according to the present invention. The diaper is
shown in its flat out, uncontracted state (i.e., without elastic
induced contraction). Portions of the structure are cut away to
show the underlying structure of the diaper 20, especially the
absorbent core 10. The portion of the diaper 20 that contacts a
wearer is facing the viewer. The chassis 22 of the diaper 20 in
FIG. 1 comprises the main body of the diaper 20. The chassis 22
comprises an outer covering including a liquid pervious topsheet 24
and/or a liquid impervious backsheet 26. The chassis may also
include most or all of the absorbent core 10 encased between the
topsheet 24 and the backsheet 26.
[0036] For unitary absorbent articles, the chassis 22 comprises the
main structure of the diaper with other features added to form the
composite diaper structure. While the topsheet 24, the backsheet
26, and the absorbent core 10 may be assembled in a variety of
well-known configurations, preferred diaper configurations are
described generally in U.S. Pat. No. 5,569,234 entitled "Disposable
Pull-On Pant" issued to Buell et al. on Oct. 29, 1996; and U.S.
Pat. No. 6,004,306 entitled "Absorbent Article With
Multi-Directional Extensible Side Panels" issued to Robles et al.
on Dec. 21, 1999.
[0037] The topsheet 24 in FIG. 1 may be fully or partially
elasticized or may be foreshortened to provide a void space between
the topsheet 24 and the absorbent core 10. Exemplary structures
including elasticized or foreshortened topsheets are described in
more detail in U.S. Pat. No. 5,037,416 entitled "Disposable
Absorbent Article Having Elastically Extensible Topsheet" issued to
Allen et al. on Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled
"Trisection Topsheets for Disposable Absorbent Articles and
Disposable Absorbent Articles Having Such Trisection Topsheets"
issued to Freeland et al. on Dec. 14, 1993.
[0038] The backsheet 26 in FIG. 1 is generally the portion of the
diaper 20 positioned with the absorbent core 10 between the
backsheet 26 and the topsheet 24. The backsheet 26 may be joined
with the topsheet 24. The backsheet 26 prevents the exudates
absorbed by the absorbent core 10 and contained within the article
20 from soiling other external articles that may contact the diaper
20, such as bed sheets and undergarments. In preferred embodiments,
the backsheet 26 is substantially impervious to liquids (e.g.,
urine) and comprises a laminate of a nonwoven and a thin plastic
film such as a thermoplastic film having a thickness of about 0.012
mm (0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheet films
include those manufactured by Tredegar Industries Inc. of Terre
Haute, Ind. and sold under the trade names X15306, X10962, and
X10964. Other suitable backsheet materials may include breathable
materials that permit vapors to escape from the diaper 20 while
still preventing exudates from passing through the backsheet 26.
Exemplary breathable materials may include materials such as woven
webs, nonwoven webs, composite materials such as film-coated
nonwoven webs, and microporous films such as manufactured by Mitsui
Toatsu Co., of Japan under the designation ESPOIR NO and by EXXON
Chemical Co., of Bay City, Tex., under the designation EXXAIRE.
Suitable breathable composite materials comprising polymer blends
are available from Clopay Corporation, Cincinnati, Ohio under the
name HYTREL blend P18-3097.
[0039] Diapers 20 according to the present invention may be
provided with a re-closable fastening system (not shown) or may
alternatively be provided in the form of pant-type diapers.
[0040] The diaper 20 may also include such other features (not
shown) as are known in the art including front and rear ear panels,
re-closable fastening system, lotion, waist cap features, pant type
diapers, elastics and the like to provide better fit, containment
and aesthetic characteristics. Additional illustrative, but
non-limiting, information on construction, assembly, and the
various components of disposable diapers may be found in U.S. Pat.
No. 3,860,003 to Buell; U.S. Pat. No. 5,151,092 to Buell; U.S. Pat.
No. 5,221,274 to Buell; U.S. Pat. No. 5,554,145 to Roe et al. on
Sep. 10, 1996; U.S. Pat. No. 5,569,234 to Buell et al.; U.S. Pat.
No. 5,580,411 to Nease et al.; U.S. Pat. No. 6,004,306 to Robles et
al.; U.S. Pat. No. 5,938,648 to LaVon et al.; U.S. Pat. No.
5,865,823 to Curro; U.S. Pat. No. 5,571,096 to Dobrin et al.; U.S.
Pat. No. 5,518,801 to Chappell, et al.; U.S. Pat. No. 4,573,986 to
Minetola et al.; U.S. Pat. No. 3,929,135, to Thompson; U.S. Pat.
No. 4,463,045 to Ahr, et al.; U.S. Pat. No. 4,609,518 to Curro et
al.; U.S. Pat. No. 4,629,643 to Curro et al.; U.S. Pat. No.
5,037,416 to Allen et al.; U.S. Pat. No. 5,269,775 to Freeland et
al.; U.S. Pat. No. 4,610,678 to Weisman et al.; U.S. Pat. No.
4,673,402 to Weisman et al.; U.S. Pat. No. 4,888,231 to Angstadt;
U.S. Pat. No. 5,342,338 to Roe; U.S. Pat. No. 5,260,345 to
DesMarais et al.; U.S. Pat. No. 5,026,364 to Robertson; U.S. Pat.
No. 3,848,594 to Buell; U.S. Pat. No. 4,846,815 to Scripps; U.S.
Pat. No. 4,946,527 to Battrell; U.S. Pat. No. 4,963,140 to
Robertson et al.; U.S. Pat. No. 4,699,622 to Toussant et al.; U.S.
Pat. No. 5,591,152 to Buell et al.; U.S. Pat. No. 4,938,753 to Van
Gompel, et al.; U.S. Pat. No. 5,669,897 to LaVon, et al.; U.S. Pat.
No. 4,808,178 to Aziz et al.; U.S. Pat. No. 4,909,803 to Aziz et
al.; U.S. Pat. No. 4,695,278 to Lawson; U.S. Pat. No. 4,795,454
issued to Dragoo; U.S. Pat. No. 5,607,760 to Roe on; U.S. Pat. No.
5,609,587 to Roe; U.S. Pat. No. 5,635,191 to Roe et al.; U.S. Pat.
No. 5,643,588 to Roe et al.; and U.S. Pat. No. 5,968,025 to Roe et
al.
[0041] The absorbent core 10 in FIG. 1 generally is disposed
between the topsheet 24 and the backsheet 26. The absorbent core 10
comprises a durable hydrophilic fluid pervious core wrap 42, (also
referred to herein as durable hydrophilic core wrap, or core wrap)
described in more detail herein, and a storage layer 60 as shown in
FIG. 2. The storage layer 60 may comprise any absorbent material
that is generally compressible, conformable, non-irritating to the
wearer's skin, and capable of absorbing and retaining liquids such
as urine and other certain body exudates. The storage layer 60 may
comprise a wide variety of liquid-absorbent materials commonly used
in disposable diapers and other absorbent articles such as
comminuted wood pulp, which is generally referred to as air felt or
fluff. Examples of other suitable absorbent materials include
creped cellulose wadding; melt blown polymers, including co-form;
chemically stiffened, modified or cross-linked cellulosic fibers;
tissue, including tissue wraps and tissue laminates, absorbent
foams, absorbent sponges, superabsorbent polymers (such as
superabsorbent fibers), absorbent gelling materials, or any other
known absorbent material or combinations of materials. Examples of
some combinations of suitable absorbent materials are fluff with
absorbent gelling materials and/or superabsorbent polymers, and
absorbent gelling materials and superabsorbent fibers etc. In one
optional embodiment the storage layer is air felt free, that is, it
contains no air felt. The storage layer may further comprise minor
amounts (typically less than 10%) of non-liquid absorbent
materials, such as adhesives, waxes, oils and the like.
[0042] Exemplary absorbent structures for use as the absorbent
assemblies are described in U.S. Pat. No. 4,834,735, entitled "High
Density Absorbent Members Having Lower Density and Lower Basis
Weight Acquisition Zones", issued to Alemany et al. on May 30,
1989; and U.S. Pat. No. 5,625,222 entitled "Absorbent Foam
Materials For Aqueous Fluids Made From high Internal Phase
Emulsions Having Very High Water-To-Oil Ratios" issued to DesMarais
et al. on Jul. 22, 1997.
[0043] FIG. 2 is a sectional view along 2-2 showing a section of
one alternative embodiment of the absorbent core 10 of the diaper
of FIG. 1. In FIG. 2 the storage layer 60 is wrapped by a core wrap
42 in a in a C-fold. The core wrap 42 comprises a substrate which
has been coated with a hydrophilicity boosting composition which
contains nanoparticles 75. The substrate may be a nonwoven, a
polymeric film or combinations thereof. The substrate,
hydrophilicity boosting composition, the nonwoven, and the porous
polymeric film are all exemplified in more detail herein.
[0044] The durable hydrophilic core wrap of the present invention
provides a substrate which has both an extended shelf life and wear
life. Prior high-energy treatments tended to have a short shelf
life. That is, during the time from purchase to ultimate use and
disposal by the consumer the substrate would trend to loose its
hydrophilicity. Surfactant treatments, such as those of the prior
art, on the other hand would often have an adequate shelf life, but
have an inadequate wear life. That is, upon contact with bodily
fluids, such as urine, the substrate would instantly being to loose
its hydrophilic properties. This may even lead to a surface which
repels the bodily fluids it is designed to absorb even though the
absorbent article has not reached its total absorbance
capacity.
[0045] The hydrophilic core wrap of the present invention suffers
neither of these limitations as the substrates treated with the
hydrophilicity boosting composition of the present invention have a
long shelf life and long wear life, that is the hydrophilic
properties of the core wrap are not substantially lost over time or
upon contact with bodily fluids such as urine.
[0046] In one optional embodiment of the present invention the
hydrophilic core wrap has a wash-off surface tension of greater
than about 65 mN/m, when tested in accordance with the
Determination of surface tension Test in the Test Methods section
and further described herein.
[0047] In one optional embodiment of the present invention the
absorbent core comprises, in addition to the storage layer and the
durable hydrophilic core wrap, an acquisition system, which
comprises an upper acquisition layer facing towards the wearer and
a lower acquisition layer. In one preferred embodiment the upper
acquisition layer comprises a nonwoven fabric whereas the lower
acquisition layer preferably comprises a mixture of chemically
stiffened, twisted and curled fibers, high surface area fibers and
thermoplastic binding fibers. In another preferred embodiment both
acquisition layers are provided from a non-woven material, which is
preferably hydrophilic. The acquisition layer preferably is in
direct contact with the storage layer. Furthermore, the storage
layer or parts thereof, such as the upper acquisition layer, may
optionally be coated with the hydrophilicity boosting
composition.
[0048] FIG. 3 is a sectional view along 2-2 showing a section of
one alternative embodiment of the absorbent core 10 of the diaper
of FIG. 1. In FIG. 3 the storage layer 60 is surrounded or
enveloped by the core wrap 42. The core wrap 42 comprises a
substrate which has been coated with a hydrophilicity boosting
composition, both of which are exemplified in more detail
herein.
[0049] FIG. 4 is a sectional view along 2-2 showing a section of
one alternative embodiment of the absorbent core 10 of the diaper
of FIG. 1. In FIG. 3 the storage layer 60 is surrounded or
enveloped by the core wrap 42. The core wrap 42 comprises a fluid
receiving top layer 70 and a bottom layer 80. The fluid receiving
top layer 70 and the bottom layer 80 can be same or different. That
is they may be the same substrate coated with the same
hydrophilicity boosting composition, the different substrates
coated with the same hydrophilicity boosting composition or
different substrates coated with different hydrophilicity boosting
composition, etc.
[0050] In one optional embodiment of the present invention the top
layer 70 and the bottom layer 80 may comprise non-woven material.
One preferred material is a so-called SMS material, comprising a
spunbonded, a melt-blown and a further spunbonded layers. The top
layer 70 and the bottom layer 80 may be provided from two or more
separate sheets of nonwoven materials or they may be alternatively
provided from a unitary sheet of material. SMS materials are
exemplified in more detail herein.
[0051] In one alternative embodiment of the present invention only
a portion of the substrate is coated with the hydrophilicity
boosting composition. This is optional embodiment is illustrated in
FIGS. 5 and 6. FIG. 5 is a sectional view along 2-2 showing a
section of the absorbent core 10 of the diaper of FIG. 1. In FIG. 5
the storage layer 60 is wrapped by a core wrap 42 in a in a C-fold.
The core wrap 42 comprises two portions: a portion which has been
coated with the hydrophilicity boosting composition, or coated
portion 90, and a portion which is not coated with the
hydrophilicity boosting composition, or uncoated portion 30.
[0052] An alternative embodiment to that illustrated in FIG. 5 may
be found in FIG. 6. FIG. 6 is a sectional view along 2-2 showing a
section of one alternative embodiment of the absorbent core 10 of
the diaper of FIG. 1. In FIG. 6 the storage layer 60 is surrounded
or enveloped the core wrap 42. The core wrap 42 comprises a top
layer 70, which has been coated with the hydrophilicity boosting
composition, and forms a coated portion 90; and a bottom layer 80
which is not coated with the hydrophilicity boosting composition,
and forms an uncoated portion 30.
[0053] In another alternative embodiment the uncoated portion 30
may be optionally coated with a different composition to give it
different physical properties the coated portion 90. For example,
the uncoated portion 30 may be coated with a composition to make it
more hydrophobic, or it is coated with a hydrophilicity boosting
composition different to that used to coat the coated portion
90.
[0054] The durable hydrophilic core wrap of the present invention
will preferably have a basis weight of between about 1 grams per
square meter (or gsm) and about 100 gsm, more preferably between
about 2 gsm and about 50 gsm, even more preferably between about 5
gsm and about 30 gsm.
[0055] Core Wrap Substrate--The durable hydrophilic core wrap of
the present invention comprises a core wrap substrate (substrate)
which has been coated with a hydrophilicity boosting composition.
The substrate of interest herein may comprise any known type of
substrate, including but not limited to fabrics, garments,
textiles, and films. In certain embodiments, the substrate may
comprise one or more fibers. A fiber is defined as a fine hairlike
structure, of animal, vegetable, mineral, or synthetic origin.
Commercially available fibers have diameters ranging from less than
about 0.001 mm (about 0.00004 in) to more than about 0.2 mm (about
0.008 in) and they come in several different forms: short fibers
(known as staple, or chopped), continuous single fibers (filaments
or monofilaments), untwisted bundles of continuous filaments (tow),
and twisted bundles of continuous filaments (yarn).
[0056] The substrate may comprise fibers made by nature (natural
fibers), made by man (synthetic or man-made), or combinations
thereof. Example natural fibers include but are not limited to:
animal fibers such as wool, silk, fur, and hair; vegetable fibers
such as cellulose, cotton, flax, linen, and hemp; and certain
naturally occurring mineral fibers. Synthetic fibers can be derived
from natural fibers or not. For example synthetic fibers which are
derived from natural fibers, include but are not limited to, rayon
and lyocell, both of which are derived from cellulose. Synthetic
fibers which are not derived from natural fibers can be derived
from other natural sources or from mineral sources. Exemplary
synthetic fibers derived from natural sources, include but are not
limited to, polysaccharides such as starch. Exemplary fibers from
mineral sources, include but are not limited to, polyolefin fibers
such as polypropylene and polyethylene fibers, which are derived
from petroleum, and silicate fibers such as glass and asbestos.
Synthetic fibers are commonly formed, when possible, by fluid
handling processes (e.g., extruding, drawing, or spinning a fluid
such as a resin or a solution). Synthetic fibers are also formed by
solid handling size reduction processes (e.g., mechanical chopping
or cutting of a larger object such as a monolith, a film, or a
fabric).
[0057] Examples of suitable synthetic fibers which may comprise all
or part of the core wrap substrates of the present invention
include but are not limited, to nylon (polyamide), acrylic
(polyacrylonitrile), aramid (aromatic polyamide), polyolefin
(polyethylene and polypropylene), polyester, butadiene-styrene
block copolymers, natural rubber, latex, spandex (polyurethane) and
combinations thereof.
[0058] Synthetic fibers that contain more than one type of repeat
unit can result from combining repeat units at the molecular level
within each macromolecular strand (co-polymer), between
macromolecular strands (homopolymer blends), or combinations
thereof (co-polymer blends); or they can result from combining
repeat units at a higher scale level with distinct nanoscopic,
microscopic, or macroscopic phases (e.g., multicomponent fibers).
Each component of a multicomponent fiber can comprise a
homopolymer, a co-polymer, or blends thereof. Bicomponent fibers
are common versions of multicomponent fibers. The two or more types
of repeat units in a copolymer can be arranged randomly or in
alternating blocks of each type. Blocks of different types of
repeat units can joined to one another at their respective ends
(block co-polymers) or between the respective end of at least one
block (graft co-polymers).
[0059] Nonwoven materials are a type of fabric typically made from
fibers in a web format. Nonwoven materials are described by Butler
I, Batra S K, et al, Nonwovens Fabrics Handbook, Association of the
Nonwoven Fabrics Industry, 1999, and by Vaughn E A, Nonwoven Fabric
Sampler and Technology Reference, Association of the Nonwoven
Fabrics Industry.
[0060] Substrates comprising nonwoven materials can be formed by
direct extrusion processes during which the fibers and the nonwoven
materials are formed at about the same point in time, or by
preformed fibers which can be laid into nonwoven materials at a
distinctly subsequent point in time. Exemplary direct extrusion
processes include but are not limited to: spunbonding, meltblowing,
solvent spinning, electrospinning, and combinations thereof
typically forming layers. Exemplary "laying" processes include
wetlaying and drylaying. Example drylaying processes include but
are not limited to airlaying, carding, and combinations thereof
typically forming layers. Combinations of the above processes yield
nonwovens commonly called hybrids or composites. Exemplary
combinations include but are not limited to
spunbond-meltblown-spunbond (SMS), spunbond-carded (SC),
spunbond-airlaid (SA), meltblown-airlaid (MA), and combinations
thereof, typically in layers. Combinations which include direct
extrusion can be combined at the about the same point in time as
the direct extrusion process (e.g., spinform and coform for SA and
MA), or at a subsequent point in time. In the above examples, one
or more individual layers can be created by each process. For
instance, SMS can mean a three layer, `sms` nonwoven materials, a
five layer `ssmms` nonwoven materials, or any reasonable variation
thereof wherein the lower case letters designate individual layers
and the upper case letters designate the compilation of similar,
adjacent layers.
[0061] The fibers in nonwoven materials are typically joined to one
or more adjacent fibers at some of the overlapping junctions. This
includes joining fibers within each layer and joining fibers
between layers when there is more than one layer. Fibers can be
joined by mechanical entanglement, by chemical bond or by
combinations thereof.
[0062] Fibers and nonwoven materials can be subjected to additional
treatment after formation. For nonwoven materials, additional
treatment commonly occurs after the fibers are joined to one
another (post-treatment). Examples of additional treatments include
but are not limited to mechanical stresses, chemical additives, or
combinations thereof.
[0063] It is also within the scope of the present invention that
the term "core wrap substrate" includes laminates of two or more
substrates or webs. Commercially available laminates, or purpose
built ones would also be within the scope of the present invention.
Additionally, the substrates may be flat or textured. The formation
of textured substrates and laminates forms no part of this
invention. The following discussion is for convenience of
formulation, but is not intended to limit the type of substrate
used herein.
[0064] In one optional embodiment of the present invention the
substrate is treated with a high-energy surface treatment. This
high-energy treatment may be prior to or concurrent with the
coating of the substrate with the hydrophilicity boosting
composition. The high-energy treatment may be any suitable
high-energy treatment for increasing the hydrophilicity of a
substrate. Suitable high-energy treatments, include but are not
limited to, corona discharge treatment, plasma treatment, UV
radiation, ion beam treatment, electron beam treatment and
combinations thereof.
[0065] High-energy surface treatments which increase surface energy
are useful in that in combination with the nanoparticles they can
provide the surface with durable hydrophilic properties. In turn,
increased surface energy increases the wettability of the substrate
without use of surfactants in the dispersion to achieve wetting.
Avoiding use of surfactant is useful for reasons previously
discussed. In a non-limiting example, corona treatment places
transient charges on fibrous thermoplastic surfaces. As discussed
earlier, partial or full charges dissipate over time, and
maintaining partial or full charges on fibrous thermoplastic
surfaces is a common limitation. However, it has been found that
corona treatment in combination with the nanoparticles can be used
to place a durable charge on the material so that water continues
to be attracted to the material after time elapses. The use of
nanoparticles in conjunction with high-energy surface treatments,
can convert the transient properties of such treatments to more
durable properties. In a non-limiting example, corona treatment of
a 13 gram per square meter hydrophobic SMS polypropylene nonwoven
subsequently treated with a hydrophilicity boosting compositions
and dried exhibited consistently fast strikethrough following
multiple gushes or insults. Without wishing to be bound by theory,
the corona treatment increased the surface energy for the fiber.
The hydrophilicity boosting compositions without a surfactant was
brought into contact with the fiber surfaces before the charges
could dissipate. The higher surface energy enabled the dispersion
to wet the fibrous surfaces better than would have been possible
without the corona treatment. On the surfaces which are wetted, the
nanoparticles associate with the partial or full charge on the
surface which would otherwise be transient. This association may
take the form of a van der Waals interaction or the form of some
other interaction or bond. The nanoparticles are sufficiently small
to render the associations sufficient strong to withstand multiple
strikethroughs. The nanoparticle is sufficiently large to resist
rotation away from oxygen into the polymer or dissipate in
general.
[0066] Additional illustrative, but non limiting, information on
mechanical entanglement and by chemical bonding of fiber, as well
as additional treatments to nonwoven material, such as high-energy
treatment, may be found in copending US Published Patent
Application No. 2002/0151634 (application Ser. No. 10/060,708)
filed on Jan. 30, 2002, published on Oct. 17, 2002, P&G Docket
No. 8408M; US Published Patent Application No. 2002/0192366
(application Ser. No. 10/060,694) filed on Jan. 30, 2002, published
on Dec. 19, 2002, P&G Docket No. 8837Q; US Published Patent
Application No. 2002/0150678 (application Ser. No. 10/060,582)
filed on Jan. 30, 2002, published on Oct. 17, 2002, P&G Docket
No. 8838Q; U.S. patent application Ser. No. 10/338,603 filed on
Jan. 8, 2003, P&G Docket No. 8857; and U.S. patent application
Ser. No. 10/338,610 filed on Jan. 8, 2003, P&G Docket No.
8858.
[0067] The following patents may referred to for their disclosures
related to the substrate: U.S. Pat. No. 3,862,472 issued Jan. 28,
1975; U.S. Pat. No. 3,982,302 issued Sep. 28, 1976; U.S. Pat. No.
4,004,323 issued Jan. 25, 1977; U.S. Pat. No. 4,057,669 issued Nov.
8, 1977; U.S. Pat. No. 4,097,965 issued Jul. 4, 1978; U.S. Pat. No.
4,176,427 issued Dec. 4, 1979; U.S. Pat. No. 4,130,915 issued Dec.
26, 1978; U.S. Pat. No. 4,135,024 issued Jan. 16, 1979; U.S. Pat.
No. 4,189,896 issued Feb. 26, 1980; U.S. Pat. No. 4,207,367 issued
Jun. 10, 1980; U.S. Pat. No. 4,296,161 issued Oct. 20, 1981; U.S.
Pat. No. 4,309,469 issued Jan. 25, 1982; U.S. Pat. No. 4,682,942
issued Jul. 28, 1987; and U.S. Pat. Nos. 4,637,859; 5,223,096;
5,240,562; 5,556,509; and 5,580,423.
[0068] Hydrophilicity Boosting Composition--The hydrophilicity
boosting compositions of the present invention comprise a
hydrophilicity boosting amount of nanoparticles. By hydrophilicity
boosting amount, it is intended that an amount of nanoparticles be
present in the hydrophilicity boosting compositions which are
sufficient to make a substrate to which it is applied more
hydrophilic. Such amounts are readily ascertained by one of
ordinary skill in the art and are based on many factors, including
but not limited to, the substrate used, the nanoparticles used, the
desired hydrophilicity of the durable hydrophilic core wrap, the
consumer product in which the absorbent core is used, etc.
Preferably the nanoparticles are present in the hydrophilicity
boosting compositions at levels of from about 0.0001% to about 20%,
preferably from about 0.001% to about 15%, and more preferably from
about 0.001% to about 10%, by weight of the composition.
[0069] Typically the amount of hydrophilicity boosting compositions
present on a core wrap substrate will vary depending upon many
factors, including but not limited to, the substrate used, the
nanoparticles used, the desired hydrophilicity of the durable
hydrophilic core wrap, the consumer product in which the absorbent
core is used, etc. Preferably, the amount of hydrophilicity
boosting compositions on the core wrap substrate will be present
invention will be between about 0.01 grams of hydrophilicity
boosting composition per square meter of substrate (or gsm
substrate) and about 30 gsm substrate, more preferably between
about 0.01 gsm substrate and about 20 gsm substrate, even more
preferably between about 0.1 gsm substrate and about 10 gsm
substrate. In one preferred embodiment of the present invention the
nanoparticles are applied to the substrate as a dispersion in a
carrier.
[0070] Nanoparticles are particles which have a particle size, that
is diameter, which is of the order of magnitude of nanometers. That
is, nanoparticles have a particle size ranging from about 1 to
about 750 nanometers. Such particles are technologically
significant since they are utilized to produce durable hydrophilic
core wraps that have novel and useful properties due to the very
small dimensions of their particulate constituents. Nanoparticles
with particle sizes ranging from about 2 nm to about 750 nm can be
economically produced. Non-limiting examples of particle size
distributions of the nanoparticles are those that fall within the
range from about 2 nm to less than about 750 nm, alternatively from
about 2 nm to less than about 200 nm, and alternatively from about
2 nm to less than about 150 nm.
[0071] The particle size of the nanoparticles is the largest
diameter of a nanoparticle.
[0072] The mean particle size of various types of nanoparticles may
differ from the particle size distribution of the nanoparticles
particles. For example, a layered synthetic silicate can have a
mean particle size of about 25 nanometers while its particle size
distribution can generally vary between about 10 nm to about 40 nm.
(It should be understood that the particle sizes that are described
herein are for particles when they are dispersed in an aqueous
medium and the mean particle size is based on the mean of the
particle number distribution. Non-limiting examples of
nanoparticles can include crystalline or amorphous particles with a
particle size from about 2 to about 750 nanometers. Boehmite
alumina can have an average particle size distribution from 2 to
750 nm.)
[0073] When the hydrophilicity boosting composition is present on
the substrate it will typically be a substantially uniform coating.
When the hydrophilicity boosting composition dries, for example any
water evaporates, the nanoparticles may aggregate together on the
substrate forming larger particles, or even appear film like,
depending upon the observation method used. In any event, the
application of a hydrophilicity boosting composition comprising
nanoparticles, provides for a uniform coat of the substrate.
[0074] Either organic or inorganic nanoparticles may be used in the
hydrophilicity boosting composition of the present invention.
Suitable organic nanoparticle include, but are not limited to,
nanolatexes. A "nanolatex", as used herein, is a latex with
particle sizes less than or equal to about 750 nm. A "latex" is a
colloidal dispersion of water-insoluble polymer particles that are
usually spherical in shape. Nanolatexes may be formed by emulsion
polymerization. "Emulsion polymerization" is a process in which
monomers of the latex are dispersed in water using a surfactant to
form a stable emulsion followed by polymerization. Particles are
produced with can range in size from about 2 to about 600 nm.
[0075] While organic nanoparticles are within the scope of the
present invention, inorganic nanoparticles are preferred. Inorganic
nanoparticles generally exist as oxides, silicates, carbonates and
hydroxides. Some layered clay minerals and inorganic metal oxides
can be examples of nanoparticles. The layered clay minerals
suitable for use in the present invention include those in the
geological classes of the smectites, the kaolins, the illites, the
chlorites, the attapulgites and the mixed layer clays. Typical
examples of specific clays belonging to these classes are the
smectices, kaolins, illites, chlorites, attapulgites and mixed
layer clays. Smectites, for example, include montmorillonite,
bentonite, pyrophyllite, hectorite, saponite, sauconite,
nontronite, talc, beidellite, volchonskoite and vermiculite.
Kaolins include kaolinite, dickite, nacrite, antigorite, anauxite,
halloysite, indellite and chrysotile. Illites include bravaisite,
muscovite, paragonite, phlogopite and biotite. Chlorites include
corrensite, penninite, donbassite, sudoite, pennine and
clinochlore. Attapulgites include sepiolite and polygorskyte. Mixed
layer clays include allevardite and vermiculitebiotite. Variants
and isomorphic substitutions of these layered clay minerals offer
unique applications.
[0076] Layered clay minerals may be either naturally occurring or
synthetic. An example of one non-limiting embodiment of the coating
composition uses natural or synthetic hectorites, montmorillonites
and bentonites. Another embodiment uses the hectorites clays
commercially available, and typical sources of commercial
hectorites are the LAPONITEs .TM. from Southern Clay Products,
Inc., U.S.A; Veegum Pro and Veegum F from R. T. Vanderbilt, U.S.A.;
and the Barasyms, Macaloids and Propaloids from Baroid Division,
National Read Comp., U.S.A.
[0077] In one preferred embodiment of the present invention the
nanoparticles comprise a synthetic hectorite a lithium magnesium
silicate. One such suitable lithium magnesium silicate is
LAPONITE.TM., which has the formula:
[Mg.sub.wLi.sub.xSi.sub.8O.sub.20OH.sub.4-yF.sub.y].sup.z-
[0078] wherein w=3 to 6, x=0 to 3, y=0 to 4, z=12-2w-x, and the
overall negative lattice charge is balanced by counter-ions; and
wherein the counter-ions are selected from the group consisting of
selected Na.sup.+, K.sup.+, NH.sub.4.sup.+, Cs.sup.+, Li.sup.+,
Mg.sup.++, Ca.sup.++, Ba.sup.++, N(CH.sub.3).sub.4.sup.+ and
mixtures thereof. (If the LAPONITE.TM. is "modified" with a
cationic organic compound, then the "counter-ion" could be viewed
as being any cationic organic group (R).)
[0079] Other suitable synthetic hectorites include, but are not
limited to isomorphous substitutions of LAPONITE.TM., such as,
LAPONITE B.TM., LAPONITE S.TM., LAPONITE XLS.TM., LAPONITE RD.TM.,
LAPONITE XLG.TM., and LAPONITE RDS.TM..
[0080] The nanoparticles may also be other inorganic materials,
including inorganic oxides such as, but not limited to, titanium
oxide silica, zirconium oxide, aluminum oxide, magnesium oxide and
combinations thereof. Other suitable inorganic oxides include
various inorganic oxides of alumina and silica.
[0081] In one preferred embodiment of the present invention the
nanoparticles comprise a Boehmite alumina ([Al(O)(OH)].sub.n) which
is a water dispersible, inorganic metal oxide that can be prepared
to have a variety of particle sizes or range of particle sizes,
including a mean particle size distribution from about 2 nm to less
than or equal to about 750 nm. For example, a boehmite alumina
nanoparticle with a mean particle size distribution of around 25 nm
under the trade name Disperal P2.TM. and a nanoparticle with a mean
particle size distribution of around 140 nm under the trade name of
Dispal.RTM. 14N4-25 are available from North American Sasol,
Inc.
[0082] Use of mixtures of nanoparticles in the hydrophilicity
boosting compositions is also within the scope of the present
invention.
[0083] In one preferred embodiment of the present invention the
nanoparticles are selected from the group consisting of titanium
dioxide, Boehmite alumina, sodium magnesium lithium fluorosilicates
and combinations thereof.
[0084] Optional ingredients--The hydrophilicity boosting
compositions of the present invention may also include optional
ingredients such as, a carrier, surfactant and adjunct
ingredients.
[0085] Optional ingredients, when present, are typically employed
in compositions at levels of from about 0.001% to about 99.9%,
preferably from about 0.01% to about 98%, and more preferably from
about 0.1% to about 96%, by weight of the composition.
[0086] Suitable carriers include liquids, solids and gases. One
preferred carrier is water, which can be distilled, deionized, or
tap water. Water is valuable due to its low cost, availability,
safety, and compatibility.
[0087] Optionally, in addition to or in place of water, the carrier
can comprise a low molecular weight organic solvent. Preferably,
the solvent is highly soluble in water, e.g., ethanol, methanol,
acetone, ethylene glycol, propanol, isopropanol, and the like, and
mixtures thereof. Low molecular weight alcohols can reduce the
surface tension of the nanoparticle dispersion to improve
wettability of the substrate. This is particularly helpful when the
substrate is hydrophobic. Low molecular weight alcohols can also
help the treated substrate to dry faster. The optional water
soluble low molecular weight solvent can be used at any suitable
level. The carrier can comprise any suitable amount of the
composition, including but not limited to from about 10% to about
99%, alternatively from about 30% to about 95%, by weight of the
coating composition.
[0088] Surfactants are an optional ingredient in some embodiments
of the present invention. Surfactants are especially useful in the
coating composition as wetting agents to facilitate the dispersion
of nanoparticles onto the substrate. Surfactants are preferably
included when the coating composition is used to treat a
hydrophobic substrate.
[0089] Suitable surfactants can be selected from the group
including anionic surfactants, cationic surfactants, nonionic
surfactants, amphoteric surfactants, ampholytic surfactants,
zwitterionic surfactants and mixtures thereof. Nonlimiting examples
of surfactants useful in the compositions of the present invention
are disclosed in McCutcheon's, Detergents and Emulsifiers, North
American edition (1986), published by Allured Publishing
Corporation; McCutcheon's, Functional Materials, North American
Edition (1992); U.S. Pat. Nos. 5,707,950 and 5,576,282; and U.S.
Pat. No. 3,929,678, to Laughlin et al., issued Dec. 30, 1975.
[0090] When a surfactant is used in the coating composition, it may
be added at an effective amount to provide facilitate application
of the coating composition. Surfactant, when present, is typically
employed in compositions at levels of from about 0.0001% to about
60%, preferably from about 0.001% to about 35%, and more preferably
from about 0.001% to about 25%, by weight of the composition.
[0091] Nonlimiting examples of surfactants, including preferred
nonionic surfactants, useful herein typically at levels from about
0.001% to about 60%, by weight, include nonionic and amphoteric
surfactants such as the C.sub.12-C.sub.18 alkyl ethoxylates ("AE")
including the so-called narrow peaked alkyl ethoxylates and
C.sub.6-C.sub.12 alkyl phenol alkoxylates (especially ethoxylates
and mixed ethoxy/propoxy), C.sub.12-C.sub.18 betaines and
sulfobetaines ("sultaines"), C.sub.10-C.sub.18 amine oxides, and
the like.
[0092] Another class of useful surfactants is silicone surfactants
and/or silicones. They can be used alone and/or alternatively in
combination with the alkyl ethoxylate surfactants described herein.
Nonlimiting examples of silicone surfactants are the polyalkylene
oxide polysiloxanes having a dimethyl polysiloxane hydrophobic
moiety and one or more hydrophilic polyalkylene side chains, and
having the general formula:
R.sup.1--(CH.sub.3).sub.2SiO--[(CH.sub.3).sub.2SiO].sub.a--[(CH.sub.3)(R.s-
up.1)SiO].sub.b--Si(CH.sub.3).sub.2--R.sup.1
[0093] wherein a+b are from about 1 to about 50, and each R.sup.1
is the same or different and is selected from the group consisting
of methyl and a poly(ethyleneoxide/propyleneoxide) copolymer group
having the general formula:
--(CH.sub.2).sub.nO(C.sub.2H.sub.4O).sub.c(C.sub.3H.sub.6O).sub.-
dR.sup.2, wherein n is 3 or 4; total c (for all polyalkyleneoxy
side groups) has a value of from 1 to about 100, alternatively from
about 6 to about 100; total d is from 0 to about 14; alternatively
d is 0; total c+d has a value of from about 5 to about 150,
alternatively from about 9 to about 100 and each R.sup.2 is the
same or different and is selected from the group consisting of
hydrogen, an alkyl having 1 to 4 carbon atoms, and an acetyl group,
alternatively hydrogen and methyl group. Each polyalkylene oxide
polysiloxane has at least one R.sup.1 group being a
poly(ethyleneoxide/propyleneoxide) copolymer group. Silicone
superwetting agents are available from Dow Corning as silicone
glycol copolymers (e.g., Q2-5211 and Q2-5212).
[0094] It is also within the scope of the present invention to use
a mixture of surfactants.
[0095] Adjunct ingredients--The compositions can contain other
optional adjunct ingredients, including but not limited to process
aids, antimicrobial preservatives, antioxidants, anti-static
agents, chelating agents, colorants, dyes, filler salts,
fungicides, insect and moth repellant agents, germicides,
hydrotropes, metallic salts. These optional ingredients may be
included at any desired level, but are typically added at a level
of from about 0.0001% to about 99.99% by weight of the
composition.
[0096] Applying the hydrophilicity boosting composition to the
substrate--The hydrophilicity boosting composition can be applied
to the substrate in any suitable manner. The hydrophilicity
boosting composition can be applied to the substrate when the
substrate is at least partially immersed in a bath of the
composition (immersive processes), or without immersing the
substrate in the coating composition (non-immersive processes).
[0097] In one embodiment of the present invention the
hydrophilicity boosting composition is applied by kiss-roll
coating. In kiss-roll coating, the composition is kept in a
suitable bath. A rotating cylinder or any other device suitable for
this process, is contacting the composition with at least a part of
its surface. Thus, the composition is spread on the surface of the
cylinder. The substrate is brought into contact with the cylinder
while the cylinder already has the composition spread on its
surface. In this process, the amount of composition applied on the
substrate can be controlled easily and it is possible to avoid
soaking the substrate with composition.
[0098] Alternatively to the kiss-roll coating, the composition can
also be sprayed on the surface of the plurality of fibers. Like the
kiss-roll coating, spraying enables low and easily controllable
add-on level of aqueous solution, which is preferred in the present
invention. Other alternative methods include, but are not limited
to, printing such as, rotary, gravure, flexographic printing, ink
jet printing, slot coating and the like.
[0099] Process for Making a Disposable Absorbent Article--FIG. 7
illustrates one optional embodiment of manufacturing a disposable
absorbent article, more specifically the step of producing an
absorbent core. From dispensing roller 110 a durable hydrophilic
core wrap 42 is dispensed onto a conveyer belt 120. The durable
hydrophilic core wrap 42 was previously formed by coating a
substrate with a hydrophilicity boosting composition. The durable
hydrophilic core wrap 42 moves along the conveyer belt 120 to a
point 130 where the components of the storage layer 60 are
dispensed from bins 140 and 150. Air felt 160 dispensed from bin
150 mixes with absorbent gelling material 170 prior to deposition
on the hydrophilic core wrap 42 at point 130.
[0100] At stage 170 a portion of the storage layer 60 is surrounded
by the durable hydrophilic core wrap 42. Examples surrounding the
storage layer 60, such as encapsulating or enveloping, this may be
found described herein with reference to FIGS. 2 to 6 inclusive.
Lastly, at stage 180 the ends of the durable hydrophilic core wrap
42 are sealed. Suitable methods of sealing include, but are not
limited to, adhesive, heat, ultrasonic and combinations thereof.
The formed absorbent core may then be further processed to
incorporate it into a disposable absorbent article, such as in
between the topsheet and backsheet of a disposable diaper.
EXAMPLES
[0101] Hydrophilicity boosting compositions, according to the
present invention, are prepared as follows:
1 % Wt of Component Component 1 2 3 4 5 6 7 8 9 10 11 12 13
Nanoparticle.sup.1 0.1 0.05 0.05 0.1 1 Nanoparticle.sup.2 0.1 0.05
0.05 0.1 Nanoparticle.sup.3 1 1 4 Nanoparticle.sup.4 1
Surfactant.sup.5 0.075 0.075 0.075 0.075 0.075 0.075
Surfactant.sup.6 0.025 0.025 Water quantity sufficient to 100%
.sup.1LAPONITE B .TM. is sodium magnesium lithium fluorosilicate
from Southern Clay Products, Inc. .sup.2LAPONITE RD .TM. is sodium
magnesium lithium silicate from Southern Clay Products, Inc.
.sup.3Disperal 14N4-25 is a boebmite alumina nanoparticle available
from North American Sasol, Inc .sup.4ZSM5 is a nanosized zeolite
with a particle size from 70 to about 400 nm. .sup.5Neodol 91-6
.sup.6Silwet L-77
[0102] Test Methods--Unless otherwise stated, all tests are
performed under standard laboratory conditions (50% humidity and at
73.degree. F. (23.degree. C.)).
[0103] Contact Angle--Dynamic contact angles are measured using the
FTA200 Dynamic Contact Angle Analyzer, made by First Ten Angstroms,
USA. A single drop of test solution is dispensed onto the sample
substrate. A digital video recording is made while the drop spreads
out across the surface of the substrate and the FTA200 software
measures the contact angle of the liquid with the substrate as a
function of time.
[0104] Determination of surface tension--The surface tension (unit:
mN/m) is determined according to the following test. Apparatus:
Equipment: K10 tensiometer provided by Kruiss GmbH, Germany or
equivalent. The vessel elevation speed should be 4 mm/min. Liquid
surface height should be sensed automatically when using a plate or
a ring. The equipment must be able to adjust the sample position
automatically to the correct height. Precision of test should be
+/-0.1 mN/m.
[0105] Procedure (i) Calibration: Pour 40 ml of saline (0.9 wt %
NaCl in deionized water) into a cleaned beaker. Test the surface
tension of the saline with a platinum ring or a platinum plate
using the method described in equipment instructions. The surface
tension should be 71-72 mN/m at 20.degree. C. (ii) Method: Clean
the beaker with deionized water and isopropanol, including burning
it out with a gas burner for a few seconds. Wait until the beaker
temperature equilibrates to room temperature is reached. Place ten
60.times.60 mm pieces of test nonwoven into a cleaned beaker. The
nonwoven should have a basis weight of at least 10 grams per square
meter (or gsm). Add 40 ml of saline (0.9 wt % NaCl in deionized
water) and stir by hand with a clean surfactant-free plastic stick
for 10 seconds. Let the solution with nonwoven stand for 5 minutes.
Stir again by hand for ten seconds. Remove the nonwovens from the
saline with a clean surfactant-free plastic stick. Let the solution
stand for ten minutes. Then test the liquids surface tension with a
platinum plate or platinum ring; using the method described in the
equipment instructions. The measured surface tension is the
wash-off surface tension.
[0106] Liquid Strike-Through Test--The liquid strike-through time
is measured using Lister-type strike-through equipment,
manufactured by Lenzing AG, Austria. Test procedure is based on
standardized EDANA (European Disposables And Nonwovens Association)
method 150.3-96, with the test sample placed on an absorbent pad
comprised of ten plies of filter paper (Ahlstrom Grade 632 obtained
from Empirical Manufacturing Co., Inc., or equivalent). In a
typical experiment, three consecutive 5 ml gushes of test liquid
(0.9% saline solution) are applied to a nonwoven sample at one
minute intervals and the respective strike-through times are
recorded without changing the absorbent pad.
[0107] In addition to measuring the strike-through time for the
first gush, as described in the Edana Method, the test described
below does not only measure the first gush but several subsequent
gushes, especially the fifth gush.
[0108] Apparatus--Lister Strike-through Equipment--(i) A Funnel
fitted with magnetic valve: Rate of discharge of 25 ml in 3,5
(.+-.0.25) seconds; (ii) A Strike-through plate: Constructed of 25
mm thick acrylic glass. The total weight of the plate must be 500
g. The electrodes should be of non-corrosive material. The
electrodes are set in (4.0 mm.times.7.0 mm) cross section grooves,
cut in the base of the plate and fixed with quick setting epoxy
resin. FIGS. 8 9, and 10 illustrate a Strike-through plate 200
containing electrodes 210. FIG. 8 is a top view of a Strike-through
plate 200, where as FIG. 9 is a sectional view along 9-9 of the
Strike-through plate 200 of FIG. 8. FIG. 10 is a sectional
perspective view along 10-10 of the Strike-through plate 200 of
FIG. 8; (iii) Base plate: A square of acrylic glass 125
mm.times.125 mm approximately; (iv) Ring stand to support the
funnel; (v) Electronic Timer measuring to 0.01 seconds; (vi)
Burette with 50 ml capacity; and (vii) Core filter paper Ahlstrom
Grade 989 or equivalent (average Strike-through time 1.7 s+-0.3 s,
dimensions: 10.times.10 cm).
[0109] Procedure: (1) Carefully cut the required number of samples,
12.5 cm.times.12.5 cm with touching the sample only at the edge of
the sample. (2) Taking 10 plies of Core filter paper place one
sample on the set of 10 plies of filter paper on the base plate.
The sample should be positioned on the filter paper in such a way
that the side of the nonwoven, which is intended to face the user's
skin (when applied in an absorbent article) is uppermost. (3) Place
the strike-through plate on top with the center of the plate over
the center of the test piece. Center the burette and the funnel
over the plate. (4) Ensuring that the electrodes are connected to
the timer, switch on the timer and set the clock to zero. (5) Fill
the burette with saline solution (0.9 wt % NaCl in deionized
water). (6) Keep the discharge valve of the funnel closed and run
5.0 ml of liquid (=one gush) from the burette into the funnel. (7)
Open the magnetic valve of the funnel to discharge 5.0 ml of
liquid. The initial flow of liquid will complete the electrical
circuit and start the timer. It will stop when the liquid has
penetrated into the pad and fallen below the level of the
electrodes in the strike-through plate. (8) Record the time
indicated on the electronic timer. (9) Wait 60 seconds and repeat
steps (4), and (6) to (9) for the second, the third gush and any
subsequent gush, with each gush comprising 5 ml of liquid. (e.g., 5
ml into funnel, open magnetic valve, etc.) Record the Time for the
1.sup.st, 2.sup.nd and any subsequent gush in seconds.
[0110] Strike-through results for SMS polypropylene nonwoven
materials (13 grams per square meter) exposed to a Laboratory
Corona Treater (Model# BD-20AC, manufactured by Electro-Technic
Products Inc., USA) and coating compositions according to the
present invention are reported in Table 2.
2TABLE 2 Strike-through Times Strike-through Time (seconds) Sample
1st Gush 2.sup.nd Gush 5th Gush 0.2% Laponite RD (Southern 2.5 2.8
3.0 Clay Products) 0.1% Disperal P2 (Condea) 2.4 2.6 2.1
[0111] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention.
[0112] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
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