Note: Descriptions are shown in the official language in which they were submitted.
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ANTIMICROBIAL-COATED HYDROGEL FORMING ABSORBENT POLYMERS
BACKGROUND
A wide variety of disposable absorbent articles designed' not only to be
efficient in the absorption of body fluids such as urine, blood, menses and
the
like) but also to be sanitary and comfortable in-use, are known in the
literature.
Disposable absorbent products of this type generally comprise a fluid-
permeable
topsheet material) an absorbent core) and a fluid-impermeable backsheet
material. Various shapes, sizes and thicknesses of such articles have been
explored in an attempt to make their use more comfortable and convenient.
For some time now, studies for such disposable absorbent articles have
been primarily focused on the absorptive capacity of the article. As a result,
various absorbent polymers with high absorptive power have been developed.
Such known absorbent polymers (also known as hydrogel-forming absorbent
polymers) are capable of absorbing from about thirty to sixty grams of water
per
gram of polymer.
More recently, research has been focused on the removal of foul odors
and the prevention of skin diseases such as dermatitis, rash and redness
caused
by wearing a disposable absorbent article for a relatively long time. Many
body
fluids have an unpleasant odor, or develop such odors when in contact with air
and/or bacteria for prolonged periods. Additionally, urine and/or other
exudates
absorbed into the absorbent article are converted to ammonia by urease
produced by skin-flora, i.e., a group of normal microorganisms on the skin.
This
ammonia, in turn, causes dermatitis) rash andlor other forms of skin
irritation.
Such disease of the skin in infants can be a serious medical matter which, in
extreme cases) can result in death.
Antimicrobial agents and bactericides are chemical compositions that are
used to prevent microbiological contamination and deterioration of products,
materials, and systems. Particular areas of application of antimicrobial
agents
au
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and compositions are, for example, cosmetics, disinfectants, sanitizers, wood
preservation, food, animal feed, cooling water, metalworking fluids, hospital
and
medical uses, plastics and resins, petroleum, pulp and paper, textiles, latex,
adhesives, leather and hides, paint slurries) and disposable diapers.
For example, Japanese Patent 4-17058 discloses a disposable diaper
which is said to prevent the occurrence of diaper rash caused by the growth of
saprophytes such as the bacteria colibacilius and Candida. The disclosed
disposable diaper consists of a water-permeable top sheet, a water-impermeable
back sheet, and a water-absorbent layer sandwiched between these sheets. The
water-absorbent layer is further disclosed as consisting of a) an ammonia-
adsorbent, water-absorbent organic polymer selected from the group consisting
of polyacrylate polymers, starch-acrylonitrile graft copolymer hydrolizates,
starch-
acrylic acid graft copolymers, polyvinyl alcohol-acrylate copolymers, polymers
produced by further crosslinking of a crosslinked acrylate with a crosslinking
agent) and modified carboxymethyl cellulose; and b) benzalkonium chloride
and/or chlorhexidine gluconate, contained within the water-absorbent organic
polymer. The reference further discloses forming the organic polymer
bactericide material by combining the starting materials of the organic
polymer
(e.g., microparticulate silicon dioxide, a copolymer such as crosslinked
potassium
polyacrylate, and a cross-linking agent such as ethylene glycol diglycidyl)
and the
bactericide. The resulting mixture is then heated to bring about a
crosslinking
reaction, thereby forming a crosslinked structure, the bactericide being
incorporated within the structure.
While the diaper disclosed by Japanese Patent No. 4-17058 is said to
result in absorption by the organic polymer of ammonia contained in the
wearer's
urine, and the bactericide is said to inhibit the production ammonia (formed
by
decomposition of the urea contained in the urine) by bacteria, we have
discovered certain disadvantages with this technology.
For example, because the bactericide is incorporated within the polymer,
the bactericide does not begin acting until the polymer swells with the urine.
In
other words, the product does not provide immediate efficacy upon) e.g.,
urination.
In addition, water-absorbent polymers (whether manufactured as set forth
in Japanese Patent No. 4-17058, or without incorporating a bactericide within
the
polymer) tend to produce dust during manufacture. Such dust production has
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several disadvantages including, health risks to workers who inhale the dust,
increased cleanings of the machinery to remove the dust, and loss of product
in
the form of unclaimed dust.
Based on the foregoing, there is a need for an antimicrobial hydrogel-
forming absorbent polymer ("A-HFAP") that provides immediate efficacy, when
employed in a disposable absorbent article, upon excretion of body fluid by
the
user. There is also a need for a process for making such an A-HFAP that
results
in minimal dust production. There is also a need for an absorbent article
product
containing such an A-HFAP, which maintains the antimicrobial in a region away
from the wearer's skin, even after wetting.
SUMMARY
The present invention is directed to an antimicrobial hydrogel-forming
absorbent polymer comprising a hydrogel-forming absorbent polymer) and an
antimicrobial; wherein the hydrogel-forming absorbent polymer is coated with
the
antimicrobial. Such a material satisfies the need for a hydrogel-forming
absorbent polymer and antimicrobial combination which) when employed in a
disposable absorbent article, provides immediate effrcacy upon excretion of
body
fluid by the user.
The present invention further relates to a process for making such an
antimicrobial hydrogel-forming absorbent polymer) the process comprising
coating a hydrogei-forming absorbent polymer with an antimicrobial. Such a
process satisfies the need for process which minimizes dust production
otherwise
associated with the manufacture of hydrogei-forming absorbent polymers.
The present invention further relates to a disposable absorbent article
comprising an antimicrobial hydrogel-forming absorbent polymer. Such a
structure satisfies the need for an absorbent article which efficaciously
reduces
malodor and rash, yet maintains the active ingredients away from the user's
skin.
These and other features, aspects, and advantages of the present
invention will become evident to those skilled in the art from a reading of
the
present disclosure and accompanying drawings with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims which particularly point out
and distinctly claim the invention, it is believed the present invention will
be better
understood from the following description of preferred embodiments taken in
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conjunction with the accompanying drawings, in which like reference numerals
identify identical elements and wherein:
Figure 1 is a plan view of a disposable diaper embodiment of the present
invention, having portions cut away to reveal underlying structure, the inner
surface of the diaper facing the viewer;
Figure 2 is a cross-sectional view of one embodiment of the disposable
diaper of Figure 1, taken along transverse center line 110 of Figure 1;
Figure 3 is an enlarged view of an alternative embodiment of the
disposable diaper of Figure 1, the view corresponding to a portion of Figure
2;
and
Figure 4 shows the key elements of the finished product acquisition test.
DETAILED DESCRIPTION
The following is a list of definitions for terms used herein.
"A-HFAP" means antimicrobial hydrogel-forming absorbent polymer.
"Body fluids" includes urine) menses and vaginal discharges.
"Comprising" means that other steps and other ingredients which do not
affect the end result can be added. This term encompasses the terms
"consisting
of and "consisting essentially of'.
"Disposable" describes 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).
"HFAP" means hydrogel-forming absorbent polymer.
"Unitary" absorbent article refers to an absorbent article which is formed of
separate parts united together to form a coordinated entity so that they do
not
require separate manipulative parts like a separate holder and liner.
All percentages are by weight of total composition unless specifically
stated otherwise.
All ratios are weight ratios unless specifically stated otherwise.
The present invention, in its product and process aspects) is described in
detail as follows.
The present invention relates to an antimicrobial hydrogel-forming
absorbent polymer comprising a HFAP, and an antimicrobial; wherein the HFAP
is coated with the antimicrobial.
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in preferred embodiments, the weight ratio of HFAP to antimicrobiai is from
about 100:0.01 to about 100:2, more preferably from about 100:0.02 to about
100:1, more preferably still from about 100:0.05 to about 100:0.5.
Hydrocel-ForminqAbsorbent Polymer
5 The water-insoluble, water-swellable absorbent polymers useful in the
present invention are commonly referred to as "hydrogel-forming absorbent
polymers" (HFAPs), "hydrocoiloids", or "superabsorbent" polymers and can
include polysaccharides such as carboxymethyl starch, carboxymethyl cellulose,
and hydroxypropyl cellulose; nonionic types such as polyvinyl alcohol, and
polyvinyl ethers; cationic types such as polyvinyl pyridine, polyvinyl
morpholinione, and N,N-dimethylaminoethyl or N,N-diethylaminopropyl acrylates
and methacrylates, and the respective quaternary salts thereof. Typically)
HFAPs
useful in the present invention have a multiplicity of anionic) functional
groups,
such as sulfonic acid, and more typically carboxy, groups. Examples of
polymers
suitable for use herein include those which are prepared from polymerizable,
unsaturated) acid-containing monomers. Thus, such monomers include the
olefinically unsaturated acids and anhydrides that contain at least one carbon
to
carbon olefinic double bond. More specifically, these monomers can be selected
from olefinically unsaturated carboxylic acids and acid anhydrides,
olefinically
unsaturated sulfonic acids, and mixtures thereof.
Some non-acid monomers can also be included, usually in minor amounts,
in preparing the HFAPs herein. Such non-acid monomers can include, for
example; the water-soluble or water-dispersible esters of the acid-containing
monomers) as well as monomers that contain no carboxylic or sulfonic acid
groups at all. Optional non-acid monomers can thus include monomers
containing the following types of functional groups: carboxylic acid or
sulfonic
acid esters, hydroxyl groups, amide-groups, amino groups, nitrite groups)
quaternary ammonium salt groups, aryl groups (e.g., phenyl groups, such as
those derived from styrene monomer). These non-acid monomers are well-
known materials and are described in greater detail) for example, in U.S.
Patent
4,076,663 (Masuda et al), issued February 28, 1978; and in U.S. Patent
4,062,817 (Westerman), issued December 13) 1977.
Olefinically unsaturated carboxylic acid and carboxylic acid anhydride
monomers include the acrylic acids typified by acrylic acid itself)
methacrylic acid,
ethacrylic acid, 3-chloroacrylic acid) cyanoacrylic acid, methacrylic acid
(crotonic
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acid), phenylacrylic acid, acryloloxypropionic acid, sorbic acid, chlorosorbic
acid,
angelic acid, cinnamic acid, p-chlorocinnamic acid, sterylacrylic acid,
itaconic
acid, citroconic acid, mesaconic acid, glutaconic acid, aconitic acid, malefic
acid,
fumaric acid, tricarboxyethylene and malefic acid anhydride.
Olefnically unsaturated sulfonic acid monomers include aliphatic or
aromatic vinyl sulfonic acids such as vinylsulfonic acid, allyl suifonic acid,
vinyl
toluene sulfonic acid and styrene sulfonic acid; acrylic and methacrylic
sulfonic
acid such as sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl
acrylate,
sulfopropyl methacrylate, 2-hydroxy-3-methacryloxypropyl sulfonic acid and 2-
acrylamide-2-methylpropane sulfonic acid.
Preferred HFAPs for use in the present invention contain carboxy groups.
These polymers include hydrolyzed starch-acrylonitrile graft copolymers,
partially
neutralized hydrolyzed starch-acrylonitrile graft copolymers) starch-acrylic
acid
graft copolymers, partially neutralized starch-acrylic acid graft copolymers,
saponified vinyl acetate-acrylic ester copolymers, hydrolyzed acryionitrile or
acrylamide copolymers, slightly network crosslinked polymers of any of the
foregoing copolymers, partially neutralized polyacrylic acid, and slightly
network
crosslinked polymers of partially neutralized poiyacrylic acid. These polymers
can be used either solely or in the form of a mixture of two or more different
polymers. Examples of these polymer materials are disclosed in U.S. Patent
3,661,875, U.S. Patent 4,076,663, U.S. Patent 4,093,776, U.S. Patent
4,666,983,
and U.S. Patent 4,734,478.
More preferred polymer materials for use in making the HFAPs are slightly
network crosslinked polymers of partially neutralized polyacrylic acids and
starch
derivatives thereof. More preferably, the HFAPs comprise from about 50 to
about
95%, preferably about 75%, neutralized, slightly network crosslinked)
polyacrylic
acid (i.e.) poly (sodium acrylatelacrylic acid) ). Network crosslinking
renders the
polymer substantially water-insoluble and, in part, determines the absorptive
capacity and extractable polymer content characteristics of the HFAPs.
Processes for network crosslinking these polymers and typical network
crosslinking agents are described in greater detail in U.S. Patent 4,076,663.
Further, surface crosslinked HFAPs can be preferably used in the present
invention. They have a higher level of crosslinking in the vicinity of the
surface
than in the interior. As used herein, "surface" describes the outer-facing
boundaries of the particle, fiber, etc. For porous HFAPs (e.g.) porous
particles,
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etc.), exposed internal boundaries can also be included. By a higher level of
crossiinking at the surface, it is meant that the level of~functional
crosslinks for the
HFAP in the vicinity of the surface is generally higher than the level of
functional
crosslinks for the polymer in the interior.
The gradation in crosslinking from surface to interior can vary, both in
depth and profile. Thus, for example, the depth of surface crosslinking can be
shallow, with a relatively sharp transition to a lower level of crosslinking.
Alternatively, for example, the depth of surface crosslinking can be a
significant
fraction of the dimensions of the HFAP, with a broader transition.
Depending on size, shape, porosity as well as functional considerations,
the degree and gradient of surface crosslinking can vary within a given HFAP.
For particulate HFAPs, surface crosslinking can vary with particle size)
porosity,
etc. Depending on variations in surface:volume ratio within the HEAP {e.g.,
between small and large particles}, it is not unusual for the overall level of
crosslinking to vary within the material (e.g., be greater for smaller
particles).
Surface crossiinking is generally accomplished after the final boundaries of
the HEAP are essentially established (e.g., by grinding, extruding) foaming,
etc.)
However, it is also possible to effect surface crosslinking concurrent with
the
creation of final boundaries. Furthermore, some additional changes in
boundaries can occur even after surface crosslinks are introduced.
A number of processes for introducing surface crosslinks are disclosed in
the art. These include those where: (i) a di- or poly-functional reagent{s)
(e.g.,
glycerol, 1,3-dioxolan-2-one, polyvalent metal ions, polyquaternary amines)
capable of reacting with existing functional groups within the HFAP is applied
to
the surface of the HEAP; (ii) a di- or poly-functional reagent that is capable
of
reacting with other added reagents and possibly existing functional groups
within
the HEAP such as to increase the level of crosslinking at the surface is
applied to
the surface (e.g.) the addition of monomer plus crosslinker and the initiation
of a
second polymerization reaction); (iii) no additional poiyfunctional reagents
are
added, but additional reactions) is induced amongst existing components within
the HFAP either during or after the primary polymerization process such as to
generate a higher level of crosslinking at or near the surface (e.g., heating
to
induce the formation of anhydride and or esters crosslinks between existing
polymer carboxylic acid andlor hydroxyl groups and suspension polymerization
processes wherein the crosslinker is inherently present at higher levels near
the
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surface); and (iv) other materials are added to the surface such as to induce
a
higher level of crosslinking or otherwise reduce the surface deforrnability of
the
resultant hydrogel. Combinations of these surface crosslinking processes
either
concurrently or in sequence can also be employed. In addition to crosslinking
reagents, other components can be added to the surface to aidlcontrol the
distribution of crosslinking (e.g., the spreading and penetration of the
surface
crosslinking reagents.)
Suitable general methods for carrying out surface crosslinking of HFAPs
according to the present invention are disclosed in U.S. Patent 4,541,871
(Obayashi), issued September 17, 1985; published PCT application W092I165fi5
(Stanley), published October 1, 1992, published PCT application W090!08789
(Tai)) published August 9) 1990; published PCT application W093105080
(Stanley), published March 18, 1993; U.S. Patent 4,824,901 (Alexander), issued
April 25, 1989; U.S. Patent 4,789,8fi1 (Johnson), issued January 17, 1989;
U.S.
Patent 4,587,308 (Makita), issued May 6, 1986; U.S. Patent 4,734,478
(Tsubakimoto), issued March 29) 1988; U.S. Patent 5) 164,459 (Kimura et. al.),
issued November 17, 1992; published German patent application 4,020,780
(Dahmen), published August 29, 1991; and published European patent
application 509,708 {Gartner), published October 21, 1992.
While the HFAP is preferably of one type (i.e., homogeneous), mixtures of
polymers can also be used in the present invention. For example, mixtures of
starch-acrylic acid graft copolymers and slightly network crosslinked polymers
of
partially neutralized polyacrylic acid can be used in the present invention.
The HFAP particles used in the present invention can have a size, shape
andlor morphology varying over a wide range. The HFAP particles do not have a
large ratio of greatest dimension to smallest dimension (e.g.) granules)
flakes,
pulverulents, interparticle aggregates) interparticle crosslinked aggregates,
and
the Like) and can be in the form of fibers) foams, and the like. The HFAPs can
also comprise mixtures with low levels of one or more additives) such as for
example powdered silica) surfactants, glue, binders) and the like. The
components in this mixture can be physically andlor chemically associated in a
form such that the hydrogel-forming polymer component and the non-hydrogel-
forming polymer additive are not readily physically separable.
The HFAPs can be essentially non-porous or have substantial internal
porosity.
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For particles as described above, particle size is defined as the dimension
determined by sieve size analysis. Thus, for example, a particle that is
retained
on a U.S.A. Standard Testing Sieve with 710 micron openings (e.g., No. 25 U.S.
Series Alternate Sieve Designation) is considered to have a size greater than
710
microns; a particle that passes through a sieve with 710 micron openings and
is
retained on a sieve with 500 micron openings (e.g., No. 35 U.S, Series
Alternate
Sieve Designation) is considered to have a particle size between 500 and 710
microns; and a particle that passes through a sieve with 500 micron openings
is
considered to have a size less than 500 microns. The mass median particle size
of a given sample of hydrogel-forming absorbent polymer particles is defined
as
the particle size that divides the sample in half on a mass basis, i.e., one-
half of
the sample by weight will have a particle size less than the mass median size
and
one-half of the sample will have a particle size greater than the mass median
size. A standard particle-size plotting method {wherein the cumulative weight
percent of the particle sample retained on or passed through a given sieve
size
opening is plotted versus sieve size opening on probability paper) is
typically
used to determine mass median particle size when the 50% mass value does not
correspond to the size opening of a U.S.A. Standard Testing Sieve. These
methods for determining particle sizes of the hydrogel-forming absorbent
polymer
particles are further described in U.S. Patent 5,061,259 (Goldman et. an,
issued
October 29, 1991.
For particles of HFAPs useful in the present invention, the particles will
generally range in size from about 1 to about 2000 microns, more preferably
from
about 20 to about 1000 microns. The mass median particle size will generally
be
from about 20 to about 1500 microns, more preferably from about 50 microns to
about 1000 microns, and even more preferably from about 100 to about 800
microns.
Within these size ranges) it can be preferable to choose either larger or
smaller particles depending on the need for faster or slower absorption
kinetics.
For example, for non-porous particles) the swelling rate will generally
decrease
with increasing particle size. It can also be preferable to choose either
larger or
smaller particles or narrower size cuts (fractions) of larger or smaller
particles
from the bulk polymer in order to increase the gel layer permeability (i.e.)
increase
the Saline Flow Conductivity (SFC) value). For particles of some HFAPs, it has
been found that narrower size range cuts containing generally larger particle
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sizes within the above specified size ranges have higher SFC values without
any
significant degradation in other HFAP properties such as Performance Under
Pressure (PUP) capacity and level of extractable polymer. Thus, for example)
it
can be useful to use a size cut having a mass median size in the range of from
5 about 5D0 to about 710 microns wherein only minimal mass fractions of the
particulates have sizes either greater than about 710 microns or less than
about
500 microns. Alternatively) a broader size cut wherein the particles generally
have a size in the range of from about 150 microns to about 800 microns can be
useful.
10 Antimicrobial
The antimicrobiai agent useful in the present invention may be any
chemical capable of preventing the growth of or killing microorganisms, and is
capable of binding to an HFAP; more preferably, capable of binding to the
surface of an HFAP. Preferred antimicrobiais are those that can prevent the
growth of or kill microorganisms typically found in body fluids, more
preferably
those body fluids typically collected by a disposable absorbent article.
Preferred
antimicrobials include, but are not limited to, quaternary ammonium, phenolic,
amide, acid, and vitro compounds, and mixtures thereof; more preferably
quaternary ammonium, acid and phenolic; more preferably still quaternary
ammonium compounds.
Preferred quaternary ammonium compounds include, but are not limited
to, 2-(3-anilinovinylul)3,4-dimethyl-oxazolinium iodide, alkylisoquinolium
bromide,
benzalkonium chloride, benzethonium chloride, cetylpyridium chloride,
chforhexidine gluconate, chlorhexidine hydrochloride, lauryl trimethyl
ammonium)
methylbenzethonium chloride, stearltrimethylammonium chloride, 2,4,5-trichloro
phenoxide) and mixtures thereof; more preferably benzalkonium chloride and
chiorhexidine gluconate; more preferably still benzalkonium chloride.
Preferred phenolic compounds include) but are not limited to, benzyl
alcohol, p-chlorophenol, chloreocresol, chloroxylenol, cresol, o-cymene-5-o!
(BIOSOL), hexachlorophene, hinokitiol, isopropylmethylphenol, parabens (having
methyl, ethyl) propyl) butyl, isobutyl, isopropyl, and/or sodium methyl
substituents), phenethyl alcohol, phenol, phenoxyethanol, o-phynylphenol,
resorcin, resorcin monoacetate) sodium parabens, sodium phenolsulfonate,
thioxolone, 2,4,4'-trichloro-2'-hydroxydiphenyl ether, zinc phenolsulfonate,
and
mixtures thereof; more preferably sodium parabens.
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Preferred amides include, but are not limited to, diazolidinyl urea, 2,4
imidazolidinedione (HYDATOIN), 3,4,4'-trichlorocarbanilide, 3-trifluoromethyl-
4-4'
dichlorocarbanilide, undecylenic acid monoethanolamide, and mixtures thereof;
more preferably diazolidinyl urea and 2,4-imidazolidinedione; more preferably
still
2,4-imidazolidinedione.
Preferred acids include, but are not limited to, benzoate, benzoic acid,
citric acide, dehydroacetic acid, potassium sorbate, sodium citrate, sodium
dehydroacetate, sodium salicylate, sodium salicylic acid, sorbic acid,
undecylenic
acid, zinc undecylenate, and mixtures thereof; more preferably benzoic acid)
citric
acid, salicylic acid and sorbic acid, more preferably still citric acid and
sorbic acid.
Preferred nitro compounds include, but are not limited to, 2-bromo-2-nitro
2,3-propanediol (BRONOPOt), and methyldibromo glutaronitrile and propyulene
glycol (MERGUARD), and mixtures thereof.
Process for Producing an Antimicrobial Hydrogel-Forming Absorbent Polymer
The invention further relates to a process for making an antimicrobial
hydrogel-forming absorbent polymer, the process comprising coating HFAP
particles with an antimicrobial. As used herein, "coating" means that the
antimicrobial will be on at least a portion of the surface area of the HFAP.
Preferably, the antimicrobial is applied onto all of the surface of the HFAP.
Without wishing to be bound by theory) it is believed that the antimicrobial
is
bonded to the surface of the HFAP by Coulumb interaction. When the A-HFAP is
hydrated, most of the antimicrobial remains ionically attracted to the HFAP.
However, some antimicrobial may diffuse to interparticuiate space and fibers.
In a case where the antimicrobial is in the form of a small particle or
powder, the antimicrobial can be applied by any of various techniques and
apparatus used for applying (e.g., coating) a material to another material. In
another case where the antimicrobial is in the form of a liquid) the
antimicrobial
can be applied (e.g., coated onto the HFAP) by any of various techniques and
apparatus used for applying a liquid to a material. As a result, A-HFAPs of
the
present invention can be obtained as described above.
In a preferred embodiment, an antimicrobial is dissolved into a solvent to
make a solution. The antimicrobial can be dissolved in the solvent by any of
various techniques and apparatus used for dissolving a material to a solvent
known in the art. In more preferred embodiments, an inorganic solvent is used
as
the solvent; preferably water. Preferably, the concentration of the
antimicrobial in
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the solution by weight is from about 2% to 25%, more preferably) from about 5%
to 15%.
In certain embodiments) an antimicrobial which is insoluble in an organic
solvent can be used. In more preferred embodiments, a polar organic solvent is
used as the solvent. In such embodiments, a mixture solvent of a hydrophilic
organic solvent and water is used as the solvent for the antimicrobiai. Non-
limiting examples of the preferred organic solvent includes: the low molecular
weight alcohols such as methanol, ethanol, or propanol; acetone;
dimethylformamide(DMF); dimethylsulfoxide(DMSO); hexyimethylphosphoric
triamide(HMPT); and mixtures thereof. (n alternative preferred embodiments,
non-polar solvents such as hexane, toluene, xylene, and benzene can be used
as one of the organic solvents.
After preparing the solution, the solution is applied onto the HFAP thereby
making an intermittent mixture. More specifically, an amount of the solution
is
applied onto the HFAP. The solution can be applied by any of various
techniques
and apparatus used for applying a solution to a material including coating,
dumping, pouring) dropping, spraying, atomizing, condensing, or immersing the
liquid mixture onto the absorbent gelling particles; to cause partial or
complete
coating of the HFAP with the antimicrobial. Thus, in' the intermittent mixture
the
solution will be on (e.g., coat) at least a portion of the surface area of the
HFAP.
Preferably, the solution will be on all of the surface of the HFAP particles.
The amount of the antimicrobial which is sufficient to effect an efficacious
antimicrobial properties can vary based on a number of factors such as the
chemical composition of the HFAP and the physical forms of the HFAP, e.g.,
particle size of the HFAP, and the chemical composition and molecular weight
of
the antimicrobial, as well as on the method of applying the antimicrobial.
After making the intermittent mixture, at least a portion of the solvent is
removed from the intermittent mixture. Preferably, at least about 80%, more
preferably more than 95%, most preferably about 100% of the solvent is removed
from the intermittent mixture. The removal of the solvent can be made by any
of
various techniques and apparatus used for separating or removing liquids from
liquid-solid mixtures, including evaporation, filtration, washing) or a
combination
thereof.
In a preferred embodiment, the antimicrobial is applied onto the HEAP
after the treatment of the surface crosslinking of the HFAP particles. On the
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other hand, in another embodiment the antimicrobial is applied onto the HFAP
before the treatment of the surface crosslinking of the HFAP. In addition, in
a
further embodiment the application of the antimicrobial and the treatment of
the
cross linking can be carried out at the same time.
In preferred embodiments, the resultant A-HFAP can have a number of
shapes and sizes. For example, the absorbent materials can be typically in the
form of particles, sheets) films, cylinders) blocks, fibers, filaments, or
other
shaped elements. More preferably, the absorbent material is particulate.
Absorbent Articles Employing the Antimicrobial Hydroq_el-Forming- Absorbent
Polymer
The A-HFAPs according to the present invention can be used for many
purposes in many fields of use. For example, the A-HFAPs can be used for
packing containers; drug delivery devices; wound cleaning devices; burn
treatment devices; ion exchange column materials; construction materials;
agricultural or horticultural materials such as seed sheets or water-retentive
materials; and industrial uses such as sludge or oil dewatering agents,
materials
for the prevention of dew formation, desiccants, and humidity control
materials.
Because of the unique absorbent and antimicrobial properties of the
A-HFAPs of the present invention, they are especially suitable for use as
absorbent cores in absorbent articles, especially disposable absorbent
articles.
As used herein, the term "absorbent article" refers to articles which absorb
and
contain body fluids and more specifically refers to articles which are placed
against or in proximity to the body of the wearer to absorb and contain the
various fluids discharged from the body.
In general, an absorbent article comprises: (a) a liquid pervious topsheet
which is located adjacent to the wearer's body; (b) a liquid impervious
backsheet
which is located distant from the wearer's body and adjacent to the wearer's
clothing; and (c) an absorbent core positioned between the topsheet and the
backsheet. The absorbent core comprises at least one of the above described A-
HFAPs of the present invention. Preferably) the absorbent core further
comprises
a substrate web wherein the absorbent material is attached to the substrate
web.
Alternatively, the absorbent core further comprises an envelope web encasing
the absorbent material. In a further alternative embodiment, the absorbent
core
further comprises two layered tissues wherein the absorbent material is
distributed between the two layered tissues.
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14
In more preferred embodiments, the A-HFAP in the absorbent core has a
basis weight of from about 60 glm2 to about 1500 g/m2, more preferably from
about 100 g/m2 to about 1000 g/m2, most preferably from about 150 glm2 to
about 500 g/m2 of the absorbent material.
In some preferred embodiments, the absorbent core or absorbent member
can further comprise fibers or fluff pulp (fibrous or fiber material), more
specifically, non-absorbent-gelling fibers. Such fiber material can be used as
reinforcing members in the absorbent core, improving fluid handling of the
core,
as well as a co-absorbent with the absorbent polymers. Preferably, the
absorbent core or member includes from about 40% to about 100% by weight of
the A-HFAP and from about 60% to about 0% by weight of such non-absorbent-
gelling fiber material distributed within the absorbent material.
In a preferred embodiment, the A-HFAP is in a concentration of at least
40%, more preferably from about 60 to 100% by weight in at least one region of
the core or absorbent member. In a more preferred embodiment, the absorbent
member comprises fibrous matrix wherein the A-HFAP is distributed in the
frbrous
matrix.
Any type of fiber material which is suitable for use in conventional
absorbent products can be used in the absorbent core or absorbent member
herein. Specific examples of such fiber material include cellulose fibers,
improved cellulose fibers, rayon) polypropylene, and polyester fibers such as
polyethylene terephthalate (DACRON), hydrophilic nylon (HYDROFIL), and the
like. Examples of other fiber materials for use in the present invention
include
hydrophilized hydrophobic fibers) such as surfactant-treated or silica-treated
thermoplastic fibers derived) for example, from polyolefins such as
polyethylene
or polypropylene, polyacrylics, polyamides, polystyrenes, polyurethanes and
the
Eike. In fact, hydrophiiized hydrophobic fibers which are in and of themselves
not
very absorbent and which, therefore, do not provide webs of sufficient
absorbent
capacity to be useful in conventional absorbent structures, are suitable for
use in
the absorbent core by virtue of their good wicking properties. This is
because, in
the absorbent core herein, the wicking propensity of the fibers is as
important, if
not more important, than the absorbent capacity of the fiber material itself
due to
the high rate of fluid uptake and lack of gel blocking properties of the
absorbent
core. Synthetic fibers are generally preferred for use herein as the fiber
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component of the absorbent core. Most preferred are polyolefin fibers,
preferably
polyethylene fibers.
Other cellulosic fiber materials which can be useful in certain absorbent
cores or absorbent members herein are chemically stiffened cellulosic fibers.
5 Preferred chemically stiffened cellulosic fibers are the stiffened, twisted,
curled
cellulosic fibers which can be produced by internally crosslinking cellulose
fibers
with a crosslinking agent. Suitable stiffened, twisted, curled cellulose
fibers
useful as the hydrophilic fiber material herein are described in greater
detail in
U.S. Patent 4,888,093 (Dean et al), issued December 19, 1989; U.S. Patent
10 4,889,595 (Herron et al)) issued December 26) 1989; U.S. Patent 4,889,596
(Schoggen et al), issued December 26, 1989; U.S. Patent 4,889,597 (Bourbon et
al), issued December 26, 1989; and U.S. Patent 4,898,647 (Moore et al), issued
February 6, 1990.
A preferred embodiment of the disposable absorbent article is a diaper.
15 As used herein, the term "diaper" refers to a garment generally worn by
infants
and incontinent persons that is worn about the lower torso of the wearer. A
preferred diaper configuration for a diaper comprising an absorbent core is
described generally in U.S. Patent 3,860,003 (Buell)) issued January 14, 1975.
Alternatively preferred configurations for disposable diapers herein are also
disclosed in U.S. Patent 4,808,178 (Aziz et al), issued February 28, 1989;
U.S.
Patent 4,695,278 (Lawson), issued September 22, 1987; U.S. Patent 4,816,025
(Foreman), issued March 28, 1989; and U.S. Patent 5,151,092 (Buell et al.),
issued September 29, 1992.
A preferred embodiment of an absorbent article of the present invention is
the unitary disposable absorbent article, diaper 20, shown in Figure 1. Figure
1 is
a plan view of the diaper 20 of the present invention 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 the wearer, the inner
surface
40, facing the viewer. As shown in Figure 1, the diaper 20 preferably
comprises a
containment assembly 22 comprising a liquid pervious topsheet 24; a liquid
impervious backsheet 26 joined to the topsheet; and an absorbent core 28
positioned between the topsheet 24 and the backsheet 26. The absorbent core
28 has a pair of opposing longitudinal edges 60, an inner surface 62 and an
outer
surface 64. The diaper preferably further comprises side panels 30;
elasticized
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16
leg cuffs 32; elasticized waistbands 34; and a fastening system 36 preferably
comprising a pair of securement members 37 and a landing member 38.
The diaper 20 is shown in Figure 1 to have an inner surface 40 (facing the
viewer in Figure 1 ), an outer surface 42 opposed to the inner surface 40, a
rear
waist region 44, a front waist region 46 opposed to the rear waist region 44,
a
crotch region 48 positioned between the rear waist region 44 and the front
waist
region 46, and a periphery which is defined by the outer perimeter or edges of
the
diaper 20 in which the side edges are designated 50 and the end edges are
designated 52. The inner surface 40 of the diaper 20 comprises that portion of
the diaper 20 which is positioned adjacent to the wearer's body during use
(i.e.,
the inner surface 40 generally is formed by at least a portion of the topsheet
24
and other components joined to the topsheet 24). The outer surface 42
comprises that portion of the diaper 20 which is positioned away from the
wearer's body (i.e., the outer surface 42 is generally formed by at least a
portion
of the backsheet 26 and other components joined to the backsheet 26). As used
herein, the term "joined" encompasses corifigurations 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 members) which in turn
are
affixed to the other element. The rear waist region 44 and the front waist
region
46 extend from the end edges 52 of the periphery to the crotch region 48.
The diaper 20 also has two centerlines, a longitudinal centerline 100 and a
transverse centerline 110. The term "longitudinal", as used herein, refers to
a
line, axis, or direction in the plane of the diaper 20 that is generally
aligned with
(e.g. approximately parallel with) a vertical plane which bisects a standing
wearer
into left and right halves when the diaper 20 is worn. The terms "transverse"
and
"lateral", as used herein, are interchangeable and refer to a line, axis or
direction
which lies within the plane of the diaper that is generally perpendicular to
the
longitudinal direction (which divides the wearer into front and back body
halves).
The containment assembly 22 of the diaper 20 is shown in Figure 1 as
comprising the main body (chassis) of the diaper 20. The containment assembly
22 preferably comprises a topsheet 24, a backsheet 26 and an absorbent core 28
having a pair of opposing longitudinal edges 60, an inner surface 62, an outer
surface 64. The inner surface 62 generaify faces the body of the wearer while
the outer surface 64 generally faces away from the body of the wearer. When
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17
the absorbent article comprises a separate holder and a liner, the containment
assembly 22 generally comprises the holder and the liner (i.e., the
containment
assembly 22 comprises one or more layers of material to define the holder
while
the liner comprises an absorbent composite such as a topsheet, a backsheet,
and an absorbent core.) For unitary absorbent articles, the containment
assembly 22 preferably comprises the topsheet 24, the backsheet 26 and the
absorbent core 28 of the diaper with other features added to form the
composite
diaper structure.
Figure 1 shows a preferred embodiment of the containment assembly 22
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 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,
exemplary containment assembly configurations are described generally in U.S.
Patent 3,860,003 entitled "Contractible Side Portions for Disposable Diaper"
which issued to Kenneth B. Bueil on January 14, 1975; and U.S. Patent
5,151,092 entitled "Absorbent Article With Dynamic Elastic Waist Feature
Having
A Predisposed Resilient Flexural Hinge" which issued to Kenneth B. Buell et
al.)
on September 29) 1992; each of which is incorporated herein by reference.
The absorbent core 28 may be any absorbent member which 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.
As shown in Figure 1, the absorbent core 28 has a garment-facing side, a body-
facing side, a pair of side edges, and a pair of waist edges. The absorbent
core
28 may be manufactured in a wide variety of sizes and shapes (e.g.,
rectangular,
hourglass, "T'-shaped, asymmetric, etc.) and, in addition to including an A-
HFAP
of the present invention, may also include 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 airfelt. Examples of
other suitable absorbent materials include creped cellulose wadding; meltblown
polymers including coform; chemically stiffened, modified or cross-linked
cellulosic fibers; tissue including tissue wraps and tissue laminates;
absorbent
foams; absorbent sponges; superabsorbent polymers; absorbent gelling
materials; or any equivalent material or combinations of materials.
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18
The configuration and construction of the absorbent core 28 may vary
(e.g., the absorbent core 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).
Further, the size and absorbent capacity of the absorbent core 28 may also be
varied to accommodate wearers ranging from infants through adults. However,
the total absorbent capacity of the absorbent core 28 should be compatible
with
the design loading and the intended use of the diaper 20.
One embodiment of the diaper 20 has an asymmetric, modified T-shaped
absorbent core 28 having ears in the front waist region but a generally
rectangular shape in the rear waist region. Exemplary absorbent structures for
use as the absorbent core 28 of the present invention that have achieved wide
acceptance and commercial success are described in U.S. Patent 4,610,678
entitled "High-Density Absorbent Structures" issued to Weisman et al. on
September 9, 1986; U.S. Patent 4,673,402 entitled "Absorbent Articles With
Dual-Layered Cores" issued to Weisman et al. on June 16) 1987; U.S. Patent
4,888,231 entitled "Absorbent Core Having A Dusting Layer" issued to Angstadt
on December 19, 1989; and U.S. Patent 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. The absorbent core may
further comprise the dual core system containing an acquisition/distribution
core
of chemically stiffened fibers positioned over an absorbent storage core as
detailed in U.S. Patent 5,234,423, entitled "Absorbent Article With Elastic
Waist
Feature and Enhanced Absorbency" issued to Alemany et al.) on August 10,
1993; and in U.S. Patent 5,147,345, entitled "High Efficiency Absorbent
Articles
For Incontinence Management" issued to Young, LaVon and Taylor on
September 15, 1992.
The topsheet 24 is preferably positioned adjacent the inner surface 62 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. In a preferred embodiment of the present invention, the
topsheet 24 and the backsheet 26 are joined directly to each other in the
diaper
periphery and are indirectly joined together by directly joining them ~ to the
absorbent core 28 by any suitable attachment means.
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19
The topsheet 24 is preferably compliant, soft feeling, and non-irritating to
the wearer's skin. Further, the topsheet 24 is preferably liquid pervious
permitting
liquids (e.g., urine) to readily penetrate through its thickness. A suitable
topsheet
24 may be manufactured from a wide range of materials such as woven and
nonwoven materials; polymeric materials such as apertured formed thermoplastic
films, apertured plastic films, and hydroformed thermoplastic films; porous
foams;
reticulated foams; reticulated thermoplastic films; and thermoplastic scrims.
Suitable woven and nonwoven materials can be comprised of natural fibers
(e.g.,
wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as
polyester,
polypropylene, or polyethylene fibers) or from a combination of natural and
synthetic fibers. The topsheet 24 is preferably made of a hydrophobic material
to
isolate the wearer's skin from liquids which have passed through the topsheet
24
and are contained in the absorbent core 28 (i.e. to prevent rewet). If the
topsheet
24 is made of a hydrophobic material, at least the upper surface of the
topsheet
24 is treated to be hydrophilic so that liquids will transfer through the
topsheet
more rapidly. This diminishes the likelihood that body exudates will flow off
the
topsheet 24 rather than being drawn through the topsheet 24 and being absorbed
by the absorbent core 28. The topsheet 24 can be rendered hydrophilic by
treating it with a surfactant. Suitable methods for treating the topsheet 24
with a
surfactant include spraying the topsheet 24 material with the surfactant and
immersing the material into the surfactant. A more detailed discussion of such
a
treatment and hydrophilicity is contained in U.S. Patents 4,988,344 entitled
"Absorbent Articles with Multiple Layer Absorbent Layers" issued to Reising,
et al
on January 29, 1991 and U.S. Patent 4,988,345 entitled "Absorbent Articles
with
Rapid Acquiring Absorbent Cores" issued to Reising on January 29, 1991.
An alternative preferred topsheet comprises an apertured formed film.
Apertured formed films are preferred for the topsheet because they are
pervious
to body exudates and yet non-absorbent and have a reduced tendency to allow
liquids to pass back through and rewet the wearer's skin. Thus, the surface of
the formed film which is in contact with the body remains dry, thereby
reducing
body soiling and creating a more comfortable feel for the wearer. Suitable
formed
films are described in U.S. Patent 3,929,135, entitled "Absorptive Structures
Having Tapered Capillaries", which issued to Thompson on December 30, 1975;
U.S. Patent 4,324,246 entitled "Disposable Absorbent Article Having A Stain
Resistant Topsheet", which issued to Mullane, et al. on April 13, 1982; U.S.
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Patent 4,342,314 entitled "Resilient Plastic Web Exhibiting Fiber-Like
Properties",
which issued to Radel. et al. on August 3, 1982; U.S. Patent 4,463,045
entitled
"Macroscopically Expanded Three-Dimensional Plastic Web Exhibiting Non-
Glossy Visible Surface and Cloth-Like Tactile Impression", which issued to Ahr
et
5 al. on July 31, 1984; and U.S. 5,006,394 "Multilayer Polymeric Film" issued
to
Baird on April 9, 1991.
The backsheet 2fi of the present invention is that portion of the diaper 20
which is generally positioned away from the wearer's skin and which prevents
the
exudates absorbed and contained in the absorbent core 28 from wetting articles
10 which contact the diaper 20 such as bedsheets and undergarments. Thus, the
backsheet 26 is preferably impervious to liquids (e.g., urine) and is
preferably
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 ace compliant and will readily conform to the general shape
arid
15 contours of the human body.) However, the backsheet 26 permits vapors to
escape from the diaper 20. A suitable material for the backsheet 26 is a
thermoplastic film having a thickness of from about 0.012 mm (0.5 mil) to
about
0.051 mm (2.0 mils), preferably comprising polyethylene or polypropylene.
The backsheet 26 of the present invention may comprise a single member
20 such as the film described above, or may comprise a number of materials
joined
together to form the backsheet 26. For example, the backsheet may have a
central region 74 comprising one film or other member and one or more outer
regions 76 joined to the central region 74 comprising the same or different
films
or other materials. In one preferred embodiment, the backsheet 26 comprises a
central region 76 comprising a liquid impervious, non-apertured film and two
opposing outer regions 76 comprising an air pervious, apertured film. The
means
by which any portions of such a backsheet are joined my include any means
known in the art such as adhesives, heat, pressure, heat and pressure and
ultrasonic bonds. Further) the backsheet 26 may comprise any number of layers
of material joined together to form a laminate. If the backsheet 26 is a
laminate,
the layers need not be uniform throughout the backsheet. For example, the
central region 74 of the backsheet 26 may comprise more layers or layers of
different material than the outer regions 76.
The backsheet 26 is preferably positioned adjacent the outer surface 64 of
the absorbent core 28 and is preferably joined thereto by any suitable
attachment
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21
means 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, Minnesota and marketed as HL-1258. An example of a
suitable attachment means comprising an open pattern network of filaments of
adhesive is disclosed in U.S. Patent 4,573,986 entitled "Disposable
Waste-Containment Garment", which issued to Minetola et al. on March 4, 1986.
Another suitable attachment means comprising several lines of adhesive
filaments swirled into a spiral pattern is illustrated by the apparatus and
methods
shown in U.S. Patent 3,911,173 issued to Sprague, Jr. on October 7, 19T5; U.S.
Patent 4,785,996 issued to Ziecker, et al. on November 22) 1978; and U.S.
Patent 4,842,666 issued to Werenicz on June 27, 1989. Each of these patents
are incorporated herein by reference. 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.
Embodiments of the present invention are also contemplated wherein the
absorbent core is not joined to the backsheet 26) and/or the topsheet 24 in
order
to provide greater extensibility in the front waist region 46 and the rear
waist
region 44. Alternative embodiments are contemplated wherein an additional
member, such as a liquid impervious barrier materiai(s) (not shown), is
positioned
between the outer surface 64 of the absorbent core 28 and the backsheet 28.
Any such barrier member may or may not be joined to the absorbent core 28.
Further, the backsheet 26 may or may not be joined to any barrier materials)
that
are positioned between the backsheet 26 and the absorbent core 28.
Another preferred embodiment of the disposable absorbent article is a
catamenial product. Preferred catamenial products comprise a formed-film,
apertured topsheet as disclosed in U.S. Patent 4,285,343 (McNair), issued
August 25) 1981; U.S. Patent 4,608,047 (Mattingiy), issued August 26, 1986;
and
U.S. Patent 4,687,478 (Van Tilburg), issued August 18, 1987.
Preferred catamenial products can comprise wings, side flaps, and other
structures and elements, as described in co-pending) commonly-assigned U.S.
application serial No. 984,071, to Yasuko Morita, entitled "Absorbent Article
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22
Having Elasticized Side Flaps", Attorney Docket No. JA-09RM, filed November
30, 1992.
A particularly preferred disposable absorbent article comprising the
A-HFAP has a reduced tendency for surface wetness. Such an article facilitates
maintaining the antimicrobial away from the user's skin, even after wetting. A
disposable absorbent article comprising a backsheet, a topsheet, an
acquisition/distribution layer, and an absorbent core; the absorbent core
comprising the A-HFAP of the present invention. Such an absorbent article
preferably has a total finished product acquisition rate (test method
discussed
below} greater than or equal to about 1.9 ml/sec at first gush and greater
than or
equal to about 0.3 mllsec at fourth gush. The folded stackheight of such an
absorbent article is preferably less than about 9.9 mm per pad, more
preferably
less than about 6 mm. Preferably the topsheet of such a product retains no
more
than about 0.05 g to about 1 g of fluid as measured by the finished product
wetness test (discussed below); more preferably no more than about 0.5 g of
fluid; more preferably, no more than about 0.2 g of fluid; more preferably
still, no
more than about 0.15 g of fluid.
Referring to Figure 2, an exemplary embodiment of such a disposable
absorbent article in the form of a diaper is provided. Figure 2 is a cross-
sectional
view of such an embodiment of the disposable diaper of Figure 1, taken along
transverse center line 110 of Figure 1. This view shows fragmentary cross
sectional views of the backsheet 2fi, core cover 22, absorbent core 28)
topsheet
24, and elasticized leg cuffs 32. This embodiment differs from that shown in
Figure 1, in that an additional element, acquisitionldistribution layer 105
has been
added.
Figure 3 is an enlarged view of an alternative embodiment of the
disposable diaper of Figure 1, the view corresponding to a portion of Figure
2. In
this embodiment, topsheet 24 comprises first topsheet layer 115 and second
topsheet layer 120. First topsheet layer 115 and second topsheet layer 120 are
preferably heat bonded together. Acquisitionldistribution layer 105 comprises
a
first acquisition/distribution layer 125 and a second acquisitionldistribution
layer
130. First acquisition/distribution layer 125 is preferably spiral glue bonded
to
second topsheet layer 120. Preferably first acquisitionldistribution layer 125
and
second acquisitionldistribution layer 130 are not bonded together.
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23
Either embodiment set forth in Figure 2 or Figure 3 provides reduced
tendency for surface wetness; and consequently facilitates maintaining the
antimicrobial away from the user's skin, even after wetting. In other words,
such
an embodiment reduces the chance that liquid) e.g., urine having come in
contact
with the A-HFAP and now possibly containing antimicrobial, will flow back to
the
user's skin, bringing the antimicrobial in contact with the user's skin.
Preferred topsheet 24 and acquisitionldistribution layer 105 materials for
such a reduced surface wetness absorbent article include the following:
Preferred topsheet 24 material is P-8 nonwoven available from Fiberweb
North America, Inc. (Simpsonville) South Carolina, U.S.A.). It is a
conventional
thermobonded carded web of about 20 to 22 g/m2. made of polypropylene fibers
of about 2.2 dtex and an easily removable surfactant (spin finish), i.e., at a
first
fluid insult, it is very hydrophilic, but at repeated wetting it is
essentially as
hydrophobic as the base polypropylene.
More preferably, the topsheet 24 material is S-2355, available from Havix
Co., Japan. This is a bi-layer composite material, and made of two kinds of
synthetic surfactant treated bicomponent fibers by using carding and air-
through
technologies. First topsheet layer 115 is preferably a
polypropylenelpoiypropylene bicomponent fiber, e.g., a lower melting
temperature
polypropylene in sheath and a higher melting temperature polypropylene in the
core of the fiber. Second topsheet layer 120 is preferably a
polyethylene/polyethylene telephthalate bicomponent fiber) e. g. , a lower
melting
temperature polyethylene in the sheath and a higher melting temperature and
more resilient polyethylene telephthalate in the core of the fiber. The first
topsheet layer 115 preferably has a weak hydrophilic surfactant and the second
topsheet layer preferably has a normal hydrophilic surfactant. The total basis
weight of a typical material is about 20 to 22 glm2.
Preferably the acquisitionldistribution layer 105 comprises carded, resin
bonded hiloft nonwoven materials such as, for example, FT-6860, available from
Polymer Group) Inc., North America (Landisiville, New Jersey, U.S.A.). They
are
made of polyethylene teiephthaiate fibers of 6 dtex, and has a basis weight of
about 43 g/m2. Alternatively, acquisition/distribution layer 105 comprises
chemically treated stiffened cellulosic fiber material, available from
Weyerhaeuser
Co. (United States) under the trade designation of CMC. In another preferred
embodiment) the acquisitionldistribution layer 105 comprises conventional
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24
cellulosic fluff material, also known as wood pulp fiber, available from
Weyerhaeuser Co. (United States) under the trade name FLINT RIVER.
It should be further understood that the present invention is also applicable
to other absorbent articles known commercially by other names, such as
incontinent briefs, adult incontinent products) training pants, diaper
inserts, facial
tissues, paper towels, and the like.
Test Methods
a. General
All tests are carried out at about 23 +I- 2°C and at about 50 +I-
10%
relative humidity
Unless specified explicitly, the specific synthetic urine used in the test
methods is commonly known as JAYCO SYNURINE and is available from Jayco
Pharmaceuticals Company of Camp Hill, Pennsylvania. The formula for the
synthetic urine is: 20g11 of KC1) 2.0 gll of Na2S04, 0.85 g/l of (NH4)H2P04;
0.15
gll (NH4)2HP04, 0.19 g/l of CaCl2, and 0.23 gll of MgCl2. All of the chemicals
are of reagent grade. The pH of the synthetic urine is in the range of from
about
6.0 to about 6.4.
b. Finished Product Acguisition Test
Referring to Figure 4, 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
forms.
The test sample, which comprises an absorbent 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 50 glcm2 is typically utilized for
this test.
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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
5 electrodes is broken.
The acquisition rate is defined as the gush volume absorbed (ml) per unit
time (seconds). 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.
10 This test is primarily designed to evaluate products having an absorbent
capacity of about 300 ml to about 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.
15 c. Finished Product Wetness Test
A disposable absorbent article is placed on the apparatus set forth in
Figure 4, as discussed under the finished product acquisition test, above,
with the
following differences. 225 ml of synthetic urine is loaded into the absorbent
article sample. The load occurs via 3 gushes, of 75 ml each) at 3 min.
intervals.
20 No additional pressure is applied, other than any negligible pressure that
may
come from the perspex plate.
Following completion of 225 ml of synthetic urine loading) the perspex
plate is removed. Two pieces of filter paper {supplied by Hollingsworth &
Vose,
United Kingdom, of the type ERT FF3.WlS), having dimensions of 12 cm by 12
25 cm, are weighed) and then placed on the urine loaded diaper. A load of 2 kg
over
a 10 cm by 10 cm area is applied to the flter paper {i.e., 0.28 psi) for 2
minutes.
The filter paper is removed and weighed a second time. The diaper rewet value
is defined as the increase in weight (g) of the filter paper.
d. In Bag Stack Height
Essentially, the in bag stack height is measured by measuring the height of
a stack of absorbent products as it is packed into cartons or bags as supplied
to
the market, and dividing the height by the number of articles in this stack.
It either can be measured by taking one of the bags and carrying out the
measurement) or by simulating the pressure of a packed bag in a suitable
device
1 I
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(such as a stress-strain measurement device such as provided by INSTRON
Instruments).
This test has primarily been developed for "bi-folded" products, i.e.,
products which have only one folding line in the cross {width) direction of
the
article at about the middle part of the article, such that the front and rear
part of
the article overlay in the bag. For non-folded or tri-folded products (with
three
layers overlying), the results need to be corrected accordingly.
e. Basis Weight
Basis weights are often referred to for various materials. These can be
generated by essentially dividing the weight of a specimen by the area of it.
The
size of the area as well as the number of rewired replicates depend on the
homogeneity of the specimen.
f. Hydrophilicity l Hydrophobicity
Hydrophilicity (and hence, wettability) are typically defined in terms of
contact angle and the surtace tension of the fluids and solids involved. This
is
discussed in detail in, e.g., the American Chemical Society publication
entitled
"Contact Angle, Wettability and Adhesion", edited by R.F. Gould (copyright
1964).
In the context of the current invention, materials can be categorized into
three
groups:
Materials which are "highly hydrophilic" (abbreviated "h+"): These
generally have a contact angle of less than about 80 degrees. Examples include
cellulosic fibers and olefinic polymers when they are treated with an
effective and
strong surfactant (at least when exposed the first time to wetting).
Materials which are "essentially hydrophobic" (abbreviated "h"): These
generally have a contact angle of more than about 100 degrees. Examples
include pure oiefines (polyethylenelpolypropylene) without surfactants
(neither at
the surface, nor resin incorporated).
Materials which are "moderately hydrophilic" (abbreviated "ho"): These
have a contact angle of about 90 degrees. Examples include
polypropylene/polyethyiene with less effective resin incorporated surfactants,
and
other less hydrophilic surfactants applied to the surface of such olefins.
The following examples further describe and demonstrate the preferred
embodiments within the scope of the present invention. The examples are given
solely for the purpose of illustration, and are not to be construed as
limitations of
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the present invention since many variations thereof are possible without
departing from its spirit and scope.
Example 1
This example shows how to manufacture a HFAP for use in the present
invention.
4,000 parts of an aqueous solution of 37% acrylic monomer composed of
74.95 mol% of sodium acrylate, 25 mol% of acrylic acid, and 0.05 mol% of
trimethylolpropane triacrylate is polymerized by being stirred with 2.0 parts
of
sodium persuifate and 0.08 part of 1-ascorbic acid, to produce a gel hydrated
polymer finely divided in a particle diameter of about 5 mm. The gel hydrated
polymer is dried with a hot air dryer at 150°C, pulverized with a
hammer type
pulverizing device, and sifted with a 20-mesh metallic gauze to separate a 20-
mesh pass powder as an absorbent polymer A (having an average particle
diameter of about 350 microns).
By mixing 100 parts of the absorbent polymer A with 0.5 part of glycerol, 2
parts of water, and 2 parts of ethyl alcohol and then heat treating the
resultant
mixture at 210°C, an absorbent polymer B having the surtace region
thereof
secondarily cross-linked is obtained.
Example 2
This example shows how to manufacture an A-HFAP of the present
invention.
10 g of benzalkonium chloride (available, e.g., from Wako Chemical
(Osaka, Japan) is dissolved into 100 ml of distilled ionized water. After
complete
dissolution, the solution is introduced to an air tank which is connected to a
spray
nozzle and air pump. 500g of the absorbent polymer B from Example 1 is evenly
placed on a stainless steel plate to form thin layers of ca. 3 mm thickness.
25 g
of the benzalkonium chloride aqueous solution is sprayed onto the 500 g of
absorbent polymer B particles at room temperature. The particles are then
placed into a food mixer and agitated for 15 minutes. The benzalkonium
chloride-coated absorbent polymer B particles are subsequently subjected to
drying at 95°C in a dynamic oven for one hour, or through hot air
drying for 10
minutes to reduce the moisture level to less than 1 % of the absorbent polymer
B
particles. The dry particles are gently ground into granules of equal or less
than
800 wm in size, resulting in nominal production of polymer dust. The resulting
particles contain 0.5% benzalkonium chloride.
i
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Example 3
This example shows how to manufacture another embodiment of an A-
HFAP of the present invention.
In this case) the same procedure as in Example 2 is followed, except that
the absorbent polymer B is replaced with Aquatic CA-L76 (a cross-linked sodium
polyacrylate; available from Nippon Shokubai Co. Ltd, Osaka, Japan). The
process results in nominal production of polymer dust, following coating with
the
benzalkonium chloride.
Examt~le 4
This example shows the an absorbent core comprising an A-HFAP of the
present invention, for use in a disposable absorbent article.
Wood pulp of Southern Pine is disintegrated and opened in an air flowing
chamber. Fibers having an average length of about 3 mm are allowed to fall on
a
vacuum plate. During the fiber laydown procedure, the A-HFAP of Example 3 is
sprinkled into the wood pulp fibers. A core containing 230 to 400 g/m2 of wood
pulp fibers and 160 to 360 g/m2 of the A-HFAP is formed. The core is suitable
for use in infant and/or adult incontinent diaper applications. A typical
composition of an L-size infant diaper application is as follows:
Component Weight (gm) Percent (wt)
Wood pulp fiber 15 55
Hydrogel-forming absorbent polymer 12 44
Antimicrobial 0.024 0.09
Example 5
This example shows a disposable baby diaper comprising an A-HFAP of
the present invention.
The dimensions listed are for a diaper intended for use with a child in the
6-10 kilogram size range. These dimensions can be modifed proportionately for
different size children) or for adult incontinence briefs, according to
standard
practice.
1. Backsheet 0.020-0.038 mm fluid-impermeable film manufactured
per U.S. Patent No. 4,687,478; width at top and bottom 33cm; notched inwardly
on both sides to a width-at-center of 28.5 cm; length 50.2 cm.
2. Topsheet: carded and thermally bonded staple-length
polypropylene fibers (Hercules type 151 polypropylene); width at top and
bottom
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29
33 cm; notched inwardly on both sides to a width-at-center of 28.5 cm; length
50.2 cm.
3. Absorbent core: comprises 28.6 g of cellulose wood pulp and 4.9 g
of the A-HFAP of Example 3; 8.4 mrn thick) calendered; width at top and bottom
28.6 cm; notched inwardly at both sides to a width-at-center of 10.2 cm;
length
44.5 cm.
4. Elastic leg bands: four individual rubber strips (2 per side); width
4.77 mm; length 370 mm; thickness 0.178 mm (all the foregoing dimensions
being in the relaxed state).
The diaper is prepared in standard fashion by positioning the core material
covered with the topsheet on the backsheet and gluing.
The elastic bands (designated "inner" and "outer", corresponding to the
bands ctosest to, and farthest from, the core) respectively) are stretched to
ca.
50.2 cm and positioned between the topsheetlbacksheet along each longitudinal
side (2 bands per side) of the core. The inner bands along each side are
positioned ca. 55 mm from the narrowest width of the core (measured from the
inner edge of the elastic band). this provides a spacing element along each
side
of the diaper comprising the flexible topsheetlbacksheet material between the
inner elastic and the curved edge of the core. The inner bands are glued down
along their length in the stretched state. The topsheet/backsheet assembly is
flexible, and the glued-down bands contract to elasticize the sides of the
diaper.
The resulting diaper provides combined fluid adsorption and antimicrobial
properties.
Example 6
This example shows an adult incontinent product comprising an A-HFAP
of the present invention.
Following the preparation procedures of Example 4, a heavy weight core is
formed having 24 to 40 g of wood pulp fiber and 10 to 20 g of the A-HFAP. The
core is subsequently interposed between a fluid-impermeable poly backsheet and
a fluid-permeable topsheet to form an adult incontinent product.
Example 7
This example shows a light weight pantiliner product comprising an A-
HFAP of the present invention.
A light weight pantiliner suitable for use between menstrual periods
comprises a pad. The pad has a surface area 117 cm2; and contains 3 g of
m
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wood pulp fiber and 1.5 g A-HFAP of Example 3. The pad is subsequently
interposed between a porous formed-film topsheet according to U.S. Patent No.
4,463,045 and a fluid-impermeable backsheet is manufactured per U.S. Patent
No. 4,687,478, to form a light weight pantiliner product. The resulting
pantiiiner
5 provides combined fluid adsorption and antimicrobial properties.
Example 8
This example shows a sanitary pad comprising an A-HFAP of the present
invention.
A catamenial product in the form of a sanitary napkin having two flaps
10 extending outward from its absorbent core is prepared per the design of
U.S.
Patent No. 4,687,478, Van Tillburg, issued Aug. 18, 1987. However, the pad
utilized has a surface are of 117 cm2; and containing 6 to 12 g of wood pulp
fiber
and 1 to 3 g of the A-HFAP of Example 2. The fluid-permeable topsheet is
manufactured per U.S. Patent No. 4,463,045. The fluid-impermeable backsheet
15 is manufactured per U.S. Patent No. 4,687,478. The resulting sanitary pad
provides combined fluid adsorption and antimicrobial properties.
The aspects and embodiments of the present invention set forth in this
document have many surprising advantages, including improved efficacy and
improved processability. For example, by coating the surface area of the HFAP
20 with the antimicrobial, rather than incorporating the antimicrobial within
the HFAP,
the antirnicrobial will act immediately upon fluid entering the absorbent
core. In
contrast, if the antimicrobial were incorporated within the HFAP, its efficacy
would
be delayed until the HFAP began swelling with the fluid.
In addition, the coating of HFAP with) e.g., the antimicrobial, results in
25 reducing the release of HFAP dust particles into the air. This reduction of
HFAP
dust particles produces a safer environment for workers, less downtime spent
cleaning processing equipment, and prevention of loss of material.
All publications, patent applications, and issued patents mentioned
hereinabove are hereby incorporated in their entirety by reference.
30 It is understood that the examples and embodiments described herein are
for illustrative purposes only and that various modifications or changes in
light
thereof will be suggested to one skilled in the art and are to be included in
the
spirit and purview of this application and scope of the appended claims.
