U.S. patent application number 09/155469 was filed with the patent office on 2002-03-14 for disposable absorbent articles with controlled skin hydration effect.
Invention is credited to DOMINGUEZ-STAEDKE, JOSE, HERRLEIN, MATHAIS KURT, LANKHOF, JOHN PETER, OLLIVER, IVAN JEAN, ROBERTSON, MUIR CHARLES, SCHUMANN, KARL MICHAEL.
Application Number | 20020032423 09/155469 |
Document ID | / |
Family ID | 8222623 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020032423 |
Kind Code |
A1 |
HERRLEIN, MATHAIS KURT ; et
al. |
March 14, 2002 |
DISPOSABLE ABSORBENT ARTICLES WITH CONTROLLED SKIN HYDRATION
EFFECT
Abstract
This invention is a disposable absorbent article (20) covering
certain parts of the body of the wearer and comprising a loading
area, a storage area, as well as a chassis area, whereby the
absorbent article has a specific skin hydration value, calculated
from the individual skin hydration values of the respective
areas.
Inventors: |
HERRLEIN, MATHAIS KURT;
(FRANKFURT, DE) ; LANKHOF, JOHN PETER; (KELKHEIM,
NL) ; ROBERTSON, MUIR CHARLES; (KONIGSTEIN, DE)
; DOMINGUEZ-STAEDKE, JOSE; (BAD SODEN, DE) ;
OLLIVER, IVAN JEAN; (FRANKFURT, DE) ; SCHUMANN, KARL
MICHAEL; (BAD SODEN, DE) |
Correspondence
Address: |
T DAVID REED
THE PROCTER & GAMBLE COMPANY
5299 SPRING GROVE AVENUE
CINCINNATI
OH
452171087
|
Family ID: |
8222623 |
Appl. No.: |
09/155469 |
Filed: |
September 29, 1998 |
PCT Filed: |
March 25, 1997 |
PCT NO: |
PCT/US97/04807 |
Current U.S.
Class: |
604/378 ;
604/368 |
Current CPC
Class: |
A61F 2013/8491 20130101;
A61F 13/84 20130101; A61F 13/535 20130101 |
Class at
Publication: |
604/378 ;
604/368 |
International
Class: |
A61F 013/15; A61F
013/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 1996 |
GB |
96105023.4 |
Claims
What is claimed is:
1. An absorbent article covering certain parts of the body and
comprising distinct areas including a loading area, a storage area
and a chassis area, characterized in that said article has a Skin
Hydration Value of less than less than 1300, calculated according
to the method described herein.
2. An absorbent article according to claim 1, characterized in that
said Skin Hydration Value is less than 600.
3. An absorbent article according to claims 1-2, characterized in
that said Skin Hydration Value is less than 300.
4. An absorbent article according to claim 1-3, characterized in
that said loading area has a Skin Hydration Value of less than 150,
according to the Post Acquisition Collagen Rewet Method described
herein.
5. An absorbent article according to claims 1-4, characterized in
that said storage area has a Skin Hydration Value of less than 20
according to the Post Acquisition Collagen Rewet Method described
herein.
6. An absorbent article according to claim 5, characterized in that
said chassis area has a Skin Hydration Value of less than 1250,
according to the Chassis Collagen Wetness Method described
herein.
7. An absorbent article according to claim 6 characterized in that
said chassis area has a Skin Hydration value of less than 500.
Description
[0001] The present invention relates to disposable absorbent
articles such as diapers, incontinence articles, sanitary towels,
training pants and the like, and in particular to the control of
their hydration effect on the human skin.
BACKGROUND OF THE INVENTION
[0002] Disposable, absorbent articles such as diapers, incontinence
articles, sanitary towels, training pants and the like are well
know in the art. Typically, disposable absorbent articles comprise
a liquid pervious topsheet that faces the wearers body, a liquid
impervious backsheet that faces the wearers clothing, an absorbent
core interposed between the liquid previous topsheet and the
backsheet, and means to keep the core in fixed relation to the
wearers body.
[0003] The absorbent core needs to be capable of acquiring,
distributing, and storing discharges initially deposited on the
topsheet of the absorbent article. Preferably the design of the
absorbent core is such that the core acquires the discharges
substantially immediately after they have been deposited on the
topsheet of the absorbent article, with the intention that the
discharges do not accumulate on or run off the surface of the
topsheet, since this may result in inefficient fluid containment by
the absorbent article which may lead to wetting of outer garments
and discomfort for the wearer. After the insult, it is an essential
functionality of the absorbent article to retain the discharged
fluids firmly so as to avoid over-hydration of the skin of the
wearer. If the absorbent article is not well functioning in this
respect, liquid coming from the absorbent core back to the skin -
also often called "rewet"-- can have detrimental effects on the
condition of the skin, which can for example be observed by skin
irritations.
[0004] There have been many attempts to improve the fluid handling
properties of absorbent articles or cores, in particular when
further requirements were brought up such as a desired reduction of
product bulkiness or thickness.
[0005] Several patent publications deal with such improvements by
adding specially treated cellulosic material. For example U.S. Pat.
No. 4,898,642 of Moore et al. discloses specially twisted,
chemically stiffened cellulosic fibres and absorbent structures
made therefrom. EP 0 640 330 (Bewick-Sonntag) et al. discloses the
use of such fibres in a specific arrangement with specific
superabsorbent materials. EP 0 397 110 (Latimer) discloses an
absorbent article comprising a surge management region for improved
fluid handling, having specific basis weights, acquisition times
and residual wetness.
[0006] EP 0 312 118 (Meyer) discloses an absorbent article with a
fibrous topsheet with larger pores than the pores of the underlying
transport layer, which in turn has lager pores than the underlying
absorbent body. Further, the transport layer has to have a
hydrophilicity which is less than the one of the absorbent core,
and may generally be characterized as being substantially
hydrophobic.
[0007] In EP 0 312 118 it is said that some liquid might remain in
the transport layer and in the topsheet, so as to cause a wet feel
on the surface. In order to overcome this problem, it is proposed
in EP 0 312 118 to exploit the resilient compressibility of the
transport layer, such that in use under the pressure exerted by the
baby, the 25 pores become smaller and then can dry out the topsheet
and transport the fluid away into the underlying absorbent
body.
[0008] In accordance with the development direction of these
various approaches, the tools to assess the performance of such
structures were generally aiming at measuring the liquid
transfer--either from the surface of the absorbent structure into
the structure itself often referred to as the acquisition, or
within the absorbent structure referred to as distribution.
[0009] On the other hand the rewetting from the absorbent structure
has been tested, either by using in-vivo methods or by using
laboratory tests.
[0010] The in-vivo methods have in common, that they asses directly
the condition of the skin of the wearer of an absorbent article
either under real in-use loadings or possibly with artificially
loaded articles, which are for example worn on the forearm of a
test person for a certain period.
[0011] Elsner et al. provides a comprehensive overview of such
methods in "Bio- engineering of the skin: Water and the Stratum
Corneum", CRC Press, 1994. The most relevant methods are the
"Transepidermal Water Loss" (often abbreviated TEWL) measuring the
moisture evaporation from the skin; methods to measure the
electrical properties like capacitance, impedance, or conductance
of the skin, which depend strongly on the moisture content, such as
with the NOVAMETER (capacitance of skin) the CORNEOMETER or other
instruments. Elsner further discusses in detail the negatives of
both too dry and too wet (overhydrated) skin, and the risks of
higher occurrence of skin irritations or even damages, which can be
most easily detected by "redmarking" of the skin, in particular,
when the over- hydration occurs in combination with mechanical
stress such as chafing.
[0012] However, all in-vivo methods have in also common, that the
comparison of absorbent structures or articles for development
purposes is cumbersome. Apart from the fact of needing test persons
as such, individual parameters of the test persons - such as
varying reaction to certain room conditions as temperature or
relative humidity - are responsible for a large variability in the
test results. In order to still get meaningful data, the number of
test persons must be increased to substantial amounts.
[0013] Hence, significant effort has already been put against
evaluating absorbent articles and structures under reproducible and
easy to execute laboratory conditions, whereby mostly the human
skin is replaced by standardized fluid pick- up filter paper.
Essentially, these methods are based on the "capillary rewet"
principle, whereby a test sample is loaded with a certain amount of
test fluid, such as synthetic urine. After a certain time such as
to allow for equilibration and preferably under a certain pressure,
the pick up filter paper as "skin replacement" is placed on top of
the surface of the loaded structure for a certain time, under a
certain pressure. The pick-up filter paper is well defined such as
by porosity, basis weight, or absorbency. Due to the capillary
forces of its pores, it is sucking up readily available moisture
(i.e. "free" moisture not being bound such as through
superabsorbent materials or in smaller pores than the ones of the
pick-up paper) from the surface of the test specimen and the weight
increase is a measure for the "rewet" performance of the absorbent
article.
[0014] Optionally, this test procedure can be combined with other
fluid handling evaluation protocols, for example a
"post-acquisition-rewet-test- " indicates, that during the first
part of the combined protocol the fluid acquisition behaviour of
the test specimen is studied, whereas the rewet assessment is then
carried out in the second part of the test.
[0015] A number of such tests have been described, such as in WO
93/02 188 (Guidotti et al.); EP-0 039 974 (Mullane); EP 0 278 601
(Kobayashi); EP 0 539 703 (Hanson).
[0016] However, these tests have significant drawback, in so far as
they are only sensitive to liquid moisture, which is present in
capillaries larger then the capillaries of the pick-up medium. In
particular upon development of better absorbent products, it has
been found that not only the small amounts of liquid in relatively
small pores (i.e. smaller than the pores of the filter pick up
paper) can still contribute significantly to the overhydration of
the skin of the wearer, but that also the moisture released by the
skin itself in the form of sweat can have significant negative
effects on overhydration of the skin, such as when covered with an
impermeable material. This latter situation is often referred to as
"occlusion", and of particular relevance for the non-absorbent
regions in the absorbent article, often referred to as "chassis" or
"peripheral" elements.
[0017] Another approach to assess the performance of such articles
has been proposed by Lask et al. in EP-B-312919, whereby the
surface moisture e.g. of an absorbent article is correlated to the
reflection and scattering of a light beam. However, also this test
is only directed towards the liquid moisture of the surface,
and--even if it might have less limitations with respect to
capillary size at the lower detection limit--is relying on
essentially isotropic and homogeneous properties throughout the
topsheet layer.
[0018] With improvements in the performance of absorbent articles,
the ability of the known methods above to distinguish different
products has decreased, such products achieving practically
identical performance in said test, even though significant
differences were detected by the user of the absorbent
articles.
[0019] It has now been discovered that absorbent articles can be
provided with hitherto unprecedented performance with respect to
controlling the impact of the absorbent article on the skin
hydration.
[0020] This is achieved by relying on a new tool for realistically
and efficiently differentiating the absorbent articles with respect
to their impact on the skin hydration. This is further achieved by
not only focusing on the skin hydration impact of the absorbent
article in zones which are either directly loaded with the liquid
bodily discharges such as urine, menstrual fluids, or fecal
materials of sufficiently high liquid content, but also in the
zones of the absorbent article which are generally not being wetted
by such liquids.
SUMMARY OF THE INVENTION
[0021] The present inventions aims at providing a disposable
absorbent article covering certain parts of the body of the wearer
and comprising distinct areas including a loading area, a storage
area and a chassis area, whereby the absorbent article has a Skin
Hydration Value of less than 1300, preferably less than 600, more
preferably less than 300 as defined by the method described
hereinafter; said Skin Hydration Value of the total article
reflects the impact of the individual Skin Hydration Values of the
respective areas of the articles; the definition of said individual
Skin Hydration Value according to methods specific to the area,
represents another aspect of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 exemplifies a simplified absorbent article,
exemplifying a diaper;
[0023] FIG. 2 describes an acquisition test, which can be carried
out before the Skin Hydration Value testing.
[0024] FIG. 3 shows the Skin Hydration Value test set up.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Absorbent Articles
[0026] As used herein, the term "absorbent articles" refers to
devices which absorb and contain body exudates, and, more
specifically, refers to devices which are placed against or in
proximity to the body of the wearer to absorb and contain the
various exudates discharged from the body.
[0027] Such exudates comprise the body discharges for the release
of which the absorbent article is primarily worn, such as urine and
faeces for baby diapers, faeces and/or urine for adult incontinence
products, menstrual fluids for catamenial products and so on.
However, in the context of this invention, also secondary
discharges can be subject of absorption of the articles, such
discharges being an effect of the article being worn, and which are
generally sweat.
[0028] The term "disposable" is used herein to describe absorbent
articles which are not intended to be laundered or otherwise
restored or reused as an absorbent article (i.e., they are intended
to be discarded after a single use and, preferably, to be recycled,
composted or otherwise disposed of in an environmentally compatible
manner).
[0029] An absorbent article generally comprises
[0030] an absorbent core (which may consist of sub-structures);
[0031] a fluid pervious topsheet;
[0032] a fluid impervious backsheet;
[0033] optionally further features like closure elements or
elastification.
[0034] A specific embodiment of an absorbent article of the present
invention is the disposable absorbent article, diaper 20, shown in
FIG. 1. As used herein, the term "diaper" refers to an absorbent
article generally worn by infants and incontinent persons that is
worn about the lower torso of the wearer. It should be understood,
however, that the present invention is also applicable to other
absorbent articles such as incontinent briefs, incontinent
undergarments, diaper holders and liners, feminine hygiene
garments, and the like. FIG. 1 is a plan view of the diaper 20 in
its flat-out, uncontracted state (i.e. with elastic induced
contraction pulled out) with portions of the structure being
cut-away to more clearly show the construction of the diaper 20 and
with the portion of the diaper 20 which faces or contacts the
wearer, the inner surface, oriented towards the viewer. As shown in
FIG. 1, the diaper 20 preferably comprises a liquid pervious
topsheet 24; a liquid impervious backsheet 26 joined with the
topsheet 24; an absorbent core 28 positioned between the topsheet
24 and the backsheet 26. If not specified differently, the term
"upper" refers to the part of a structure directed towards the
wearer of the article, "lower" directs away from the wearer
[0035] FIG. 1 shows a preferred embodiment of the diaper 20 in
which the topsheet 24 and the backsheet 26 have length and width
dimensions generally larger than those of the absorbent core 28.
The topsheet 24 and the backsheet 26 extend beyond the edges of the
absorbent core 28 to thereby form the periphery 22 of the diaper
20. While the topsheet 24, the backsheet 26, and the absorbent core
28 may be assembled in a variety of well known configurations,
preferred diaper configurations are described generally in U.S.
Pat. No. 3,860,003 entitled "Contractable Side Portions for
Disposable Diaper" which issued to Kenneth B. Buell on Jan. 14,
1975; and U.S. patent application Ser. No. 07/715,152, allowed,
"Absorbent Article With Dynamic Elastic Waist Feature Having A
Predisposed Resilient Flexural Hinge", Kenneth B. Buell et al.
filed Jun. 13, 1991.
[0036] The backsheet 26 is positioned adjacent the garment surface
of the absorbent core 28 and is preferably joined thereto by
attachment means (not shown) such as those well known in the art.
For example, the backsheet 26 may be secured to the absorbent core
28 by a uniform continuous layer of adhesive, a patterned layer of
adhesive, or an array of separate lines, spirals, or spots of
adhesive. Adhesives which have been found to be satisfactory are
manufactured by H. B. Fuller Company of St. Paul, Minn. and
marketed as HL-1258. The attachment means will preferably comprise
an open pattern network of filaments of adhesive as is disclosed in
U.S. Pat. No. 4,573,986 entitled "Disposable Waste-Containment
Garment", which issued to Minetola et al. on Mar. 4, 1986, more
preferably several lines of adhesive filaments swirled Into a
spiral pattern such as is illustrated by the apparatus and methods
shown in U.S. Pat. No. 3,911,173 issued to Sprague, Jr. on Oct. 7,
1975; U.S. Pat. No. 4,785,996 issued to Ziecker, et al. on Nov. 22,
1978; and U.S. Pat. No. 4,842,666 issued to Werenicz on Jun. 27,
1989. Alternatively, the attachment means may comprise heat bonds,
pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or any
other suitable attachment means or combinations of these attachment
means as are known in the art.
[0037] The backsheet 26 is impervious to liquids (e.g. urine) and
is often manufactured from a thin plastic film, although other
flexible liquid impervious materials may also be used. As used
herein, the term "flexible" refers to materials which are compliant
and will readily conform to the general shape and contours of the
human body. The backsheet 26 prevents the exudates absorbed and
contained in the absorbent core 28 from wetting articles which
contact the diaper 20 such as bed-sheets and undergarments. The
backsheet 26 may thus comprise a woven or nonwoven material,
polymeric films such as thermoplastic films of polyethylene or
polypropylene, or composite materials such as a film-coated
nonwoven material. Often, the backsheet is a thermoplastic film
having a thickness of from about 0.012 mm to about 0.051 mm.
Examples for films as backsheet materials include RR8220 blown
films and RR5475 cast films as manufactured by Tredegar Industries,
Inc. of Terre Haute, Ind., US. The backsheet film is preferably
embossed and/or matte finished to provide a more clothlike
appearance. Preferably, the backsheet 26 may permit vapors to
escape from the absorbent article while still preventing liquid
exudates from passing through the backsheet 26.
[0038] The absorbent article may further comprise elastification or
closure features (not shown if FIG. 1) which are well-known in the
art and--for example--described in E 0254476 (Alemany).
[0039] The topsheet 24 is positioned adjacent the body surface of
the absorbent core 28 and is preferably joined thereto and to the
backsheet 26 by attachment means (not shown) such as those well
known in the art. Suitable attachment means are described with
respect to joining the backsheet 26 to the absorbent core 28. As
used herein, the term "joined" encompasses configurations whereby
an element is directly secured to the other element by affixing the
element directly to the other element, and configurations whereby
the element is indirectly secured to the other element by affixing
the element to intermediate member(s) which in turn are affixed to
the other element.
[0040] Generally, the topsheet 24 is compliant, soft feeling, and
non-irritating to the wearer's skin. Further, the topsheet 24 is
liquid pervious permitting liquids (e.g. urine) to readily
penetrate through its thickness. A suitable topsheet may be
manufactured from a wide range of materials, such as porous foams;
reticulated foams; apertured plastic films; or woven or nonwoven
webs of natural fibres (e.g., wood or cotton fibres), synthetic
fibres (e.g., polyester or polypropylene fibres), or a combination
of natural and synthetic fibres. There are a number of
manufacturing techniques which may be used to manufacture the
topsheet 24.
[0041] For example, the topsheet 24 may be a nonwoven web of fibres
spunbonded, carded, wet-laid, meltblown, hydroentangled,
combinations of the above, or the like.
[0042] Alternatively, combination composites of both nonwoven and
apertured films may be used, and for the hydrophilicity adjustment
the respective options of both can be applied.
[0043] Preferably, the topsheet pore size should not be smaller
than the pores of the underlying layer, such that - in combination
with the hydrophilicity of both layers--the fluid within the
topsheet can be readily drained towards the underlying layer
through the hydraulic forces.
[0044] The pore size and pore size distribution of this uppermost
layer and its relation to the respective pick up materials is very
relevant for the conventional rewet tests, as these generally rely
on capillary transport from the absorbent article which is
subjected to the testing and the pick-up medium.
[0045] The absorbent cores should be 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. As shown in FIG. 1, the absorbent core 28 has a
garment surface ("lower" or "bottom" part), a body surface, side
edges, and waist edges. In order to fit best into the overall
absorbent article design, the absorbent core 28 may be manufactured
in a wide variety of overall sizes and shapes (e.g., rectangular,
hourglass, "T"-shaped, asymmetric, etc.) It further might
comprise--such as in an acquisition pad (29)--a wide variety of
liquid-absorbent materials commonly used in disposable diapers and
other absorbent articles such as--but not limited to--comminuted
wood pulp which is generally referred to as airfelt; meltblown
polymers including coform; chemically stiffened. modified or
cross-linked cellulosic fibres; tissue including tissue wraps and
tissue laminates.
[0046] The configuration and construction of the absorbent core 28
may also be varied (e.g., the absorbent core 28 may have varying
caliper zones, a hydrophilic gradient, a superabsorbent gradient,
or lower average density and lower average basis weight acquisition
zones; or may comprise one or more layers or structures). The total
absorbent capacity of the absorbent core 28 should, however, be
compatible with the design loading and the intended use of the
diaper 20, Further, the size and absorbent capacity of the
absorbent core 28 may be varied to accommodate wearers ranging from
infants through adults.
[0047] Exemplary absorbent structures for use as the absorbent core
28 are described in U.S. Pat. No. 4,610,678 entitled "High-Density
Absorbent Structures" issued to Weisman et al. on Sep. 9, 1986;
U.S. Pat. No. 4,673,402 entitled "Absorbent Articles With
Dual-Layered Cores" issued to Weisman et al. on Jun. 16, 1987; U.S.
Pat. No. 4,888,231 entitled "Absorbent Core Having A Dusting Layer"
issued to Angstadt on Dec. 19, 1989; and 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; Also EP 0 640 330 of Bewick-Sonntag et al.; U.S. Pat.
No. 5 180 622 (Berg et al.); U.S. Pat. No. 5 102 597 (Roe et
al.)
[0048] Skin Hydration Value
[0049] The present invention is based on the use of a specifically
defined index, the Skin Hydration Value, to characterize the
absorbent articles of the invention and directly reflect their
impact on skin hydration; this index is calculated using the
individual Skin Hydration indexes of each of the loading, storage,
and chassis area of the absorbent article, which in turn are
measured according to specific methods which as described
hereinafter.
[0050] Generally, an absorbent article can be separated into
distinct areas with respect to their functionality, and in relation
how these regions are positioned to the various body parts of the
wearer.
[0051] The loading area is represented by one or more zones, where
the body fluids are deposited on. The size of these zone is
depending on external factors, namely of the wearer, such as the
intended use of the absorbent article or the position of the wearer
while the article is being loaded and the like. It also depends on
the performance of the absorbent article itself, for example this
area will be larger for an article with poor "run-off" or
"acquisition" performance, whereby the discharged fluids do not
directly penetrate into the absorbent structure, but are
distributed on the surface of the absorbent article. From a fluid
transport point of view, the loading area is dominated by
"flooding" conditions with fluid flowing primarily under gravity
driven conditions and relatively large pore capillary
transport.
[0052] The storage area is represented by one or more zones in
which the liquid discharges are firmly bound by capillary and/or
osmotic forces. Samples for suitable materials are conventional
fluff, superabsorbent materials, or other highly porous materials,
including hydrophilic or hydrophilized foam structures. All these
have in common, that they retain water as the essential composition
of most body fluids firmly preferably also against external
pressures, such as applied by the wearer to the article when
sitting or when moving.
[0053] The chassis area is represented by zones of the absorbent
article, which have no significant absorbency function, at least
not with regard to the primary loadings fluids such as urine,
menstrual fluids or faeces. However, these zones can have an
important gasketting function, such at leg opening of the absorbent
articles, or at the waist openings. In other embodiments, "belt
like" structures around the waist exemplify such regions. In many
instances, these regions will comprise a liquid impermeable layer
to avoid liquid penetration from the first two zones to the
outside, such as to the clothing of the wearer.
[0054] When referring to FIG. 1, the loading area can be
represented by the area of the acquisition/distribution layer (29),
the storage area by the parts of the storage core (28) which are
not covered by the acquisition/distribution layer 29, and the
chassis or peripheral area corresponds to the area of the topsheet
(24) and backsheet (26) circumscribing the absorbent core (28).
[0055] The chassis area must meet breathability need, i.e.
permeability for gases and/or vapours, with liquid barrier
functionality . Conventional liquid barrier materials such as
conventional backsheets made of a thin polyethylene film have
generally good liquid barrier properties and do protect wearers
clothing from wetting through the absorbent article. However, in
such chassis areas, such materials prevent the natural evaporation
process of the skin and create the risk of occlusion, whereby sweat
as released by the perspiration glands cannot evaporate but is
retained in the space between the impermeable film and the skin.
This generally relatively small and confined volume can be rapidly
saturated with moisture, such that further sweat production will
soon oversaturate the atmosphere and thus result in liquid
moisture. The hydration state of the skin will the quickly increase
up to over- hydration. This over-hydrated skin is then prone to
redmarking or other undesired effects which can be further enhanced
by only low or moderate mechanical irritation.
[0056] Apart from occlusion of sweat, a further undesired effect on
skin hydration can occur via water vapour transfer, enhanced by
thermal gradients, from a generally wetter area to a drier region
of the absorbent article. For example, freshly released and hence
relatively warm urine might allow evaporative fluid transfer to
other parts of the article which are cooler and thus provide a
moisture sink. These other parts might of course also be the
"chassis zones".
[0057] The present invention now allows not only to provide optimal
liquid rewet performance in and around said loading and the storage
zones, but also provide skin hydration control from all parts of
the wearers body which are covered by the absorbent article,
including the chassis area.
[0058] The absorbent articles herein should have a Skin Hydration
Value of less than 1300, preferably less than 600, more preferably
less than 300, said Skin Hydration Value being calculating by
adding up the individual Skin Hydration Values measured on each
area of the article.
[0059] The loading area should have a Skin Hydration Value of less
than 150, determined according to the following method, which as
mentioned above, departs from the known evaluation method and
alleviates their drawbacks.
[0060] The method herein, whilst still adhering to the principle of
measuring the rewetting to a pick up material, does not rely on
capillary fluid transport, but primarily on other fluid transfer
mechanism simulating the non-porous structure of the skin in a
better way.
[0061] The key element of the pick up materials according to the
new method herein is that the moisture transfer is not based upon
capillary fluid transfer, but that moisture mechanism occur very
similar to the ones taking place in the human skin. This is
achieved by using "hydratable" materials, which on one side have
the ability to pick up moisture, but which maintain their generally
sheet like structure even at equilibrium saturation, and do not
disintegrate upon wetting. Thereby, the moisture pick up is
dominated by hydration mechanisms, i.e. in contrast to the
mechanisms of porous and/or fibrous structures, the fluid is
transferred to the pick-up materials according to the present
invention not by capillary transport through said pores, but rather
by directly diffusing into the molecular matrix of the pick up
materials, and by hydrogen bonding mechanisms dominating the
moisture adsorption in these materials.
[0062] A preferred material for being used in these tests has now
been found in "synthetic skin" as being used for other purposes
such as for wound coverings or for sausage or ham encasings can be
an extremely sensitive and accurate evaluation tool, if applied
together with the appropriate testing protocol.
[0063] Such synthetic skin is described in WO 94/04201 assigned to
NATURIN GmbH, Germany, with collagen as an essential element. These
films are produced starting from bovine skin skives and
transforming these into a gel-like dispersion, which then is
extruded into thin films with about 12% moisture content. This
material has indeed the ability to pick up moisture in a mechanism
very close to real living skin, but is readily available with
narrow property variability for laboratory testing. A preferred
execution of these films is "Collagen Food Film" manufactured and
sold by NATURIN under the designation "COFFI". Such embossed films
have a basis weight of about 28g/m2. With a closely monitored
moisture content of about 12% by weight, the film material is
flexible and easy to handle. Upon further drying, it starts to
become brittle. If in contact with moisture--be this in the form of
liquid or vapour--the material starts to further soften and swells
up to an equilibrium moisture of 150 % of its initial weight.
[0064] A testing protocol building on these properties has been
developed, for example, for evaluation of baby diapers, and more
specifically baby diapers of the widely distributed MAXI/MAXI PLUS
size (i.e. infants in the weight range from about 8 kg to about 18
kg).
[0065] General
[0066] All tests are carried out at about 22+/-2.degree. C. and at
35+/-15% relative humidity. The synthetic urine used in the test
methods is commonly known as Jayco SynUrine and is available from
Jayco Pharmaceuticals Company of Camp Hill, Pa. The formula for the
synthetic urine is: 2.0 g/: of KCI; 2.0 g/l of Na2SO4; 0.85 g/l of
(NH4)H2PO4; 0.15 g/l (NH4)H2PO4; 0.19 g/l of CaCl2; ad 0.23 g/l of
MgCl2. All of the chemicals are of reagent grade. The pH of the
synthetic Urine is in the range of 6.0 to 6.4.
[0067] Acquisition Test
[0068] Referring to FIG. 2, an absorbent structure (10) is loaded
with a 75 ml gush of synthetic urine at a rate of 15 ml/s using a
pump (Model 7520-00, supplied by Cole Parmer Instruments., Chicago,
U.S.A.), from a height of 5 cm above the sample surface. The time
to absorb the urine is recorded by a timer. The gush is repeated
every 5 minutes at precisely 5 minute gush intervals until the
article is sufficiently loaded. Current test data are generated by
loading four times.
[0069] The test sample, which comprises a core and includes a
topsheet and a backsheet, is arranged to lie flat on a foam
platform 11 within a perspex box (only base 12 of which is shown).
A perspex plate 13 having a 5 cm diameter opening substantially in
its middle is placed on top of the sample. Synthetic urine is
introduced to the sample through a cylinder 14 fitted, and glued
into the opening. Electrodes 15 are located on the lowest surface
of the plate, in contact with the surface of the absorbent
structure 10. The electrodes are connected to the timer. Loads 16
are placed on top of the plate to simulate, for example a baby's
weight. A pressure of 50g cm-2 (0.7 psi) is typically utilised in
this test.
[0070] As test fluid is introduced into the cylinder it typically
builds up on top of the absorbent structure thereby completing an
electrical circuit between the electrodes. This starts the timer.
The timer is stopped when the absorbent structure has absorbed the
gush of urine, and the electrical contact between the electrodes is
broken.
[0071] The acquisition rate is defined as the gush volume absorbed
(ml) per unit time (s). The acquisition rate is calculated for each
gush introduced into the sample. Of particular interest in view of
the current invention are the first and the last of the four
gushes.
[0072] This test is primarily designed to evaluate products having
an absorbent capacity of about 300 ml to 400 ml. If products with
significantly different capacities should be evaluated, the
settings in particular of the fluid volume per gush should be
adjusted appropriately to about 20% of the theoretical capacity,
and the deviations should be recorded.
[0073] Post Acquisition Collagen Rewet Method (refer to FIG. 3)
[0074] Before executing the test, the collagen film as purchased
from NATURIN GmbH, Weinhein, Germany, under the designation of
COFFI and at a basis weight of about 28 g/m2 this prepared by being
cut into sheets of 90 mm diameter e.g. by using a sample cutter
device, and by equilibrating the film in the controlled environment
of the test room (see above) for at least 12 hours (tweezers are to
be used for all handling of the collagen film).
[0075] At least 5 minutes, but not more than 6 minutes after the
last gush of the above acquisition test is absorbed, the cover
plate and weights are removed, and the test sample (320) is
carefully placed flat on a lab bench.
[0076] 4 sheets of the precut and equilibrated collagen material
(310) are weighed with at least one milligram accuracy, and then
positioned centred onto the loading point of the article, and
covered by perspex plate (330) of 90 mm diameter, and about 20 mm
thickness. A weight (340) of 15 kg is carefully added (also
centred). After 30+/-2 seconds the weight and perspex plate are
carefully removed again, and the collagen films are reweighed.
[0077] The Post Acquisition Collagen Rewet Method result is the
moisture pick up of the collagen film, expressed in mg. Such a
result should be inferior to 50 mg, when using the above test, for
the loading area of an absorbent article according to the present
invention.
[0078] THe Skin Hydration Value is then calculated by dividing the
Post Acquisition Collagen Rewet Method result by the area of the
collagen containing film used in the Post Acquisition Collagen
Rewet Method and multiplying with the total area of the loading
zone of the respective article.
[0079] The storage area of the absorbent articles of the invention
should have a Skin Hydration Value of less than 20, measured
according to the same method as described hereinabove, i. e. using
the Post Acquisition Collagen Rewet Method result; such a result
for the storage area of the absorbent articles of the invention
should be inferior to 5 mg, using the above test.
[0080] The chassis area should have a Skin Hydration Value of less
than 1250, preferably less than 500, according to the following
specific method:
[0081] Chassis Collagen Wetness Test
[0082] This test is based on similar principles as the Post
Acquisition Collagen Rewet Method test outlined above, namely the
liquid pick-up and retention capability of Collagen films. It is,
however, modified to better reflect the situation in areas of the
absorbent article, where no significant absorption capacity is
present, and where--in particular when using vapour permeable
materials--moisture content of a skin replica material can be
reduced by evaporation through the permeable layer.
[0083] First, two layers of the film are prepared as for the Post
Acquisition Collagen Rewet Method.
[0084] A load of about 100 mg of synthetic urine is carefully
applied to the first layer whilst avoid run-off, and weighed to an
accuracy of 1mg.
[0085] The second layer is accurately weighed, too, and placed on
to top of the first layer.
[0086] Both are then covered with the respective chassis materials,
e.g. with a layer of topsheet and a layer of plastic film backsheet
in the case of most conventional diapers, or with a layer of
hydrophilic topsheet and a layer of hydrophobic nonwoven as
backsheet for designs where such a combination can be found in the
periphery of diapers.
[0087] After 60 minutes waiting time, whereby air convections needs
to be minimized such as by placing cylindrical ring of 15 cm
diameter and 15 cm height around the sample, the cover layers are
removed and the collagen sheets are reweighed.
[0088] The result is then corrected for deviations of the added
amount from 100 mg (i.e. divided by the actually added weight and
multiplied by 100) The final result of the Chassis Collagen Wetness
Test is than expressed in mg. For the chassis areas of absorbent
articles according to the invention, this value should be inferior
to 40 mg, preferably inferior to 30 mg, when using the above
test.
[0089] The respective chassis Skin Hydration Value can be
calculated in analogy to the above procedure, namely dividing the
Chassis Collagen Wetness test result by the area of the collagen
sheets, and multiplying with the respective area in the absorbent
article.
[0090] Essentially, good results in this criterion can be reached
by either reducing the negative overhydration effects of the
individual zones, or by at least minimizing the area of zones with
relatively poor performance.
[0091] It should be noted, that both a larger and a smaller number
of zones can be taken into consideration, and the option of looking
at a large number of small areas giving almost a continuous mapping
of the properties of the absorbent article should also be regarded
as the wider scope of the present description. The most critical
distinction, however, needs to remain between zones of the
absorbent core and of the chassis or peripheral zone, as there the
different method applications need to be applied.
[0092] It should be noted further, that this testing protocol can
be adjusted easily according to specific product types, such as
different baby diaper sizes, or adult incontinence articles, or
catamenial articles, or by the variation in the type and amount of
loading fluid, the amount and size of the absorbent material, or by
variations in the applicable pressure. Having once defined these
relevant parameters, such modifications will be obvious to the man
skilled in the art. When considering the results from the adjusted
test protocol the products can easily be optimizing these
identified relevant parameter such as in a designed experiment
according to standard statistical methods with realistic in use
boundary conditions.
[0093] In order to further illustrate the benefits of this new
method in assessing absorbent articles, one of the conventional
rewet testing protocols has been use as follows:
[0094] Comparative capillary rewet test
[0095] A comparative test is executed according the following
procedure.
[0096] This test is also carried out 10 minutes (+/-5 sec) after
the acquisition test, but uses 10 sheets of blotting paper of 220
g/m2 as supplied by Hollinsworth & Vose, UK under the
designation of MEDIUM WHITE WIS, and cut to 20 by 10 cm. This is
equilibrated and preweighed, and positioned centred onto the
loading point. A circular weight of 4860 g (in total) with a
perspex plate of 18 cm by 6 cm is covered with a soft foam of a
basis weight of 500 g/m2 of 1 cm thickness and a Polyethylene film
is carefully positioned onto the filter paper and left on it for 15
seconds.
[0097] The value for rewetting is the weight increase of the
blotting papers.
[0098] In contrast to the conventional tests, the new testing tool
now allows to even distinguish relatively well performing products,
i.e. absorbent articles where only a too small amount of liquid
will not allow conventional testing tools to discern such products,
articles or structures. Consequently, new absorbent articles with
the ability to provide unprecedented skin hydration performance can
be designed.
[0099] Surprisingly, it has been found, that such a performance can
be achieved by starting from conventional designs, which however
need to be modified in an extreme way, e.g. by increasing the
superabsorbent content to extremely high levels. Heretofore, such
amounts were not considered to be justified, from an effort to
result relation, i.e. the undoubtedly extreme effort was not judged
to counterbalance positive effects. These latter, however, were
generally based upon conventional (capillary) rewet results, which
were not practically not able to discern such products. Of course,
the invention should not be viewed to be limited to the use of
conventional approaches, but also other designs can be used to
achieve the requirements as outlined herein.
[0100] Samples according to the invention as well as comparative
samples have been submitted to the conventional test protocols as
well as to the new Post Acquisition Collagen Rewet Method protocol
and the resulting Skin Hydration Values have been determined.
Further, some articles have been given to a panel of specially
recruited mothers, and their judgment of the performance in
particular with respect to skin dryness and skin health condition
has been monitored. For especially strenuous wearing conditions,
i.e. overnight conditions, additional testing of the skin hydration
in the genital region was performed by using a NOVAMETER equipment
(as descried in Elsner - see above).
EXAMPLES
[0101] In order to further exemplify the benefits of the current
invention, samples of different baby diapers have been submitted
various test protocols as outlined in the above.
[0102] Sample 1 is a commercially available product, PAMPERS Baby
Dry Maxi/MAXI PLUS size as marketed by Procter & Gamble in
Europe.
[0103] Sample 3 is a commercially available product, HUGGIES
FLEXIFIT as marketed by Kimberly-Clark in Europe
[0104] Sample 2 is identical to sample 1 except for the
following:
[0105] First, chemically treated stiffened cellulosic material (CS)
supplied by Weyerhaeuser Co., US under the trade designation of
"CMC" functioning as an acquisition/distribution layer is doubled
in basis weight, by an increase from about 295 g/m2 to 590
g/m2.
[0106] Second, an additional acquisition layer in introduced
between the topsheet and said chemically treated stiffened
cellulose layer, namely a high-loft chemically bonded nonwoven as
supplied by FIBERTECH, North America under the designation type
6852. It is a chemically bonded PET fibre web of a basis weight of
42g/m2 and a width of 110 mm over the full length of the absorbent
core.
[0107] Thirdly, the cellulose material usage in the storage core
underneath the chemically treated stiffened cellulosic material is
increased from about 20 g to 40 g per pad.
[0108] Fourth, the amount of superabsorbent material in this
storage core is increased from about 10 g to about 33 g per pad.
Superabsorbent material was supplied by Stockhausen GmbH, Germany
under the trade name FAVOR SXM, type T5318.
[0109] The results were as follows:
1 TABLE I Sample 1 Sample 2 Sample 3 Post Acquisition Collagen
Rewet Method results Loading area rewet [mg] 80 37 85 Storage area
rewet [mg] 20 2 22 Diaper surfaces Loading area [cm2] 187 187 198
Storage area [cm2] 341 341 463 Skin Hydration Values loading area
237 110 267 storage area 108 11 162 comparative filter paper rewet
protocol [g] 0.4 0.35 0.43 Overnight wear study NOVAMETER testing
genital area, [-] 540 366 548 number of babies tested 43 21 20 % of
mothers rating skin being . . . dry 61 63 55 slightly damp 29 37 30
damp 10 0 15 wet 0 0 0 number of babies tested 21 21 20
[0110] As can be seen from these test, the directional differences
between the two reference products could be made significant on a
statistical basis, and the test product showed a significant
improvement over the other products.
[0111] A further test has been performed to show the advantages of
air permeable materials such as for backsheet applications. For
this the test as described above was applied to a conventional
polyethylene backsheet. and in comparison to a "breathable"
backsheet, consisting of a hydrophobic polypropylene non-woven, of
23g basis weight made by spunbonding technology as supplied by the
same supplier as the topsheets described above.
2 TABLE 2 PE flim PP nonwoven Chassis Collagen Wetness test [mg] 95
37.5
[0112] Clearly, the breathable material exhibits a much lower
wetness than the conventional film backsheet material.
[0113] For the Products of example 1, containing a conventional
backsheet, the chassis Skin Hydration Value was measured, and
consequently also the total diaper Skin Hydration value was
calculated: Rewets were as follows:
3 TABLE 3 Sample 1 Sample 2 Sample 3 Chassis area [cm2] 731 731 643
Skin Hydration Values chassis area 1152 1152 1013 total 1497 1272
1442
* * * * *