Shield for absorbent products

The invention relates to absorbent products (1) like baby diapers, adult incontinence products and particularly to sanitary napkins or pantyliners. These absorbent products all have absorbent cores (4) which according to the present invention comprise absorbent gelling materials (5) in granular form or other particles. A problem associated with such cores is that these particles can migrate out of the article along the paths of liquid entry into the product. Therefore, a shield (8) positively separating the paths of liquid transport into the product from the particles is provided for absorbent structures according to the invention.

FIELD OF THE INVENTION 
The present invention relates to absorbent products like baby diapers, 
adult incontinence products and particularly to sanitary napkins or 
pantyliners. These absorbent products all have absorbent cores which 
according to the present invention comprise absorbent gelling materials in 
granular form or other particles. A problem associated with such cores is 
that these particles can migrate out of the article along the paths of 
liquid entry into the product and then become recognisable to the user 
while also being lost for the absorptive capacity of the article. 
Therefore a shield positively separating the paths of liquid transport 
into the product from the particles is provided for absorbent structures 
according to the invention. 
BACKGROUND OF THE INVENTION 
The problem of migrating particles of highly absorbent material has been 
considered in several publications but to the knowledge of the inventors 
it has not yet been satisfactorily resolved. For example U.S. Pat. No. 
4,321,924 discloses a sanitary napkin which comprises a fibrous layer as 
part of the topsheet to improve strike through characteristics of the 
absorbent article. However no disclosure of the appropriate size of pores 
in the topsheet is given and the problem of particle migration in 
absorbent structures is not touched upon. 
U.S. Pat. No. 4,752,349 discloses a sanitary napkin wherein a wicking layer 
adjacent to the topsheet extends beyond the periphery of the absorbent 
core. It therefore would serve as a barrier along a straight line between 
particles in said absorbent core and the liquid passage ways in the 
topsheet of the sanitary napkin. However no barrier against migration 
around the edge of the tissue is foreseen or considered since this 
disclosure does not relate to the same problem underlying the present 
invention. 
U.S. Pat. No. 5,009,653 shows absorbent gel material containment structures 
interposed between topsheet and backsheet of absorbent articles. This 
patent addresses the problem of particle migration from the absorbent 
structure through the liquid passage ways in the topsheet and implies that 
a wetlaid tissue between the topsheet and the absorbent structure would 
reduce absorbent gel material particles migration. However as in the above 
cited prior art no shielding at the edge of the wetlaid tissue is provided 
for. 
EP-A-248 584 also discloses sanitary napkins which have fully enclosed 
absorbent structures by providing several layers of tissue around the 
particle containing absorbent structure. However these tissues are not 
joined to each other along an endless peripheral line such that particle 
migration paths remain open for particles to ultimately migrate through 
the liquid passage ways in the topsheets employed in these articles. 
It is therefore an objective of the present invention to fully shield 
absorbent structures comprising absorbent particles from the liquid 
passage ways in the topsheet of absorbent articles. In particular tissues 
having pore sizes smaller than the smallest particle are desirable since 
they simultaneously perform as wicking and distribution layers while 
serving as particle migration shields.

BRIEF DESCRIPTION OF THE INVENTION 
The present invention relates to an absorbent product comprising a topsheet 
with liquid passage ways, a liquid impervious backsheet and an absorbent 
core enveloped between the topsheet and the backsheet. The core comprises 
dry absorbent particles or other particles which are capable of permeating 
in their dry state through the topsheet along the liquid passage ways. The 
absorbent product further comprises a permeation blockage means to 
restrict permeation of the particles to the liquid passage ways of the 
topsheet. The permeation blockage means is placed between the topsheet and 
the absorbent core and is joined to the backsheet, topsheet or both such 
that it is shielding the particles from the liquid passage ways. 
Preferably the permeation blockage means is a non-woven substrate with a 
maximum pore size of less than 60 micro meters. In a preferred embodiment 
the permeation blockage means extends beyond the core and is attached to 
the backsheet while it can or can not extend to the full size of the 
backsheet itself. 
The permeation blockage means can also be joined to the topsheet such that 
all liquid passage ways are encircled by the line of joining between said 
permeation blockage means and the topsheet such that the objective of 
shielding the particles from the liquid passage ways is achieved. 
Finally in a particularly preferred embodiment the permeation blockage 
means extends beyond the perimeter of the core of the absorbent article 
and is joined simultaneously to the topsheet and the backsheet of the 
absorbent article most preferably along a single endless line which 
simultaneously forms the peripheral edge of the absorbent product itself. 
In this embodiment, however, the joining has to be such that wicking 
through the side seal of the absorbent product is prevented or 
alternatively the permeation blockage means does not support liquid 
transport within its own plane. 
Definitions 
As used herein, the term "aqueous body fluids" includes urine, menses and 
vaginal discharges. 
As used herein, the term "absorbent product" refers to articles which are 
capable of absorbing aqueous body fluids like disposable baby, children or 
adult diapers, incontinence products like inserts or bed pads and sanitary 
napkins. 
As used herein, the term "sanitary napkin" refers to an absorbent article 
that is worn by females adjacent to the pudendal region, generally 
external to the urogenital region, and which is intended to absorb and 
contain aqueous body fluids and other vaginal discharges from the wearer's 
body. It should be understood, however, that the present invention is also 
applicable to other feminine hygiene or catamenial pads such as 
pantyliners, or other absorbent articles such as incontinence pads, and 
the like. 
All percentages, ratios and proportions used herein are by weight unless 
otherwise specified. 
DETAILED DESCRIPTION OF THE INVENTION 
According to the present invention the absorbent product comprises three 
main elements: a topsheet, a core and a backsheet. Typically the topsheet 
is worn next to the skin of the user while the backsheet is worn next to 
the undergarment of the user with the core enveloped between both. This 
structure as known from the prior art is principally shown in FIG. 1 where 
a liquid permeable topsheet (2) overlays a core (4), which comprises 
particles (5). The backsheet (3) is joined to the topsheet (2) by joining 
means (7), preferably by crimping seals or adhesive seals. The particles 
(5) are capable of permeating in their dry state through the topsheet (2) 
as indicated by arrows (6) in the prior art embodyment of FIG. 1. Each of 
the three main elements of the absorbent product can be selected from a 
wide variety of alternatives and can also comprise several elements 
contributing to the individual function of each of the main elements. 
According to the invention the absorbent product further comprises a 
permeation blockage means (8) which is joined to either the backsheet (3), 
the topsheet (2) or both in order to shield the particles (5) form the 
liquid passage ways in the topsheet (2). This can be achieved for example 
by an endless line of attachment (9) shown in FIGS. 2, 3, 4 which can be 
separate from the joining means (7). 
In the following non-limiting embodiments of the main elements of the 
absorbent product are described. 
Absorbent core 
This absorbent core is shown as a single entity (4) in all Figures. It 
typically includes the following components: (a) optionally a primary 
fluid distribution layer; (b) optionally, but preferably, a secondary 
fluid distribution layer; (c) a fluid storage layer, (d) optionally a 
fibrous ("dusting") layer underlying the storage layer; and (e) other 
optional components. 
a. Primary Fluid Distribution Layer 
One optional component of the absorbent cores according to the present 
invention is the primary fluid distribution layer. This primary 
distribution layer typically underlies the topsheet and is in fluid 
communication therewith. The topsheet transfers the acquired menstrual 
fluid to this primary distribution layer for ultimate distribution to the 
storage layer. This transfer of fluid through the primary distribution 
layer occurs not only in the thickness, but also along the length and 
width directions of the absorbent product. 
b. Optional Secondary Fluid Distribution Layer 
Also optional but preferred component of the absorbent cores according to 
the present invention is a secondary fluid distribution layer. This 
secondary distribution layer typically underlies the primary distribution 
layer and is in fluid communication therewith. The purpose of this 
secondary distribution layer is to readily acquire menstrual fluid from 
the primary distribution layer and transfer it rapidly to the underlying 
storage layer. This helps the fluid capacity of the underlying storage 
layer to be fully utilized. 
c. Fluid Storage Layer 
Positioned in fluid communication with, and typically underlying the 
primary or secondary distribution layers, is a fluid storage layer 
comprising certain absorbent gelling materials usually referred to as 
"hydrogels," "superabsorbent" "hydrocolloid" materials. Absorbent gelling 
materials are those materials that, upon contact with aqueous fluids, 
especially aqueous body fluids, imbibes such fluids and thus form 
hydrogels. These absorbent gelling materials are typically capable of 
absorbing large quantities of aqueous body fluids, and are further capable 
of retaining such absorbed fluids under moderate pressures. These 
absorbent gelling materials are also typically in the form of discrete, 
nonfibrous particles. 
This fluid storage layer can comprise solely absorbent gelling materials, 
or these absorbent gelling materials can be dispersed homogeneously or 
non-homogeneously in a suitable carrier. Suitable carriers include 
cellulose fibers, in the form of fluff, such as is conventionally utilized 
in absorbent cores. Modified cellulose fibers such as the stiffened 
cellulose fibers can also be used. Synthetic fibers can also be used and 
include those made of cellulose acetate, polyvinyl fluoride, 
polyvinylidene chloride, acrylics (such as Orlon), polyvinyl acetate, 
non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides 
(such as nylon), polyesters, bicomponent fibers, tricomponent fibers, 
mixtures thereof and the like. Preferred synthetic fibers have a denier of 
from about 3 denier per filament to about 25 denier per filament, more 
preferably from about 5 denier per filament to about 16 denier per 
filament. Also preferably, the fiber surfaces are hydrophilic or are 
treated to be hydrophilic. The storage layer can also include filler 
materials, such as Perlite, diatomaceous earth, Vermiculite, etc., that 
lower rewet problems. 
If dispersed non-homogeneously in a carrier, the storage layer can be 
locally homogeneous, i.e. have a distribution gradient in one or several 
directions within the dimensions of the storage layer. Non-homogeneous 
distribution can also refer to laminates of carriers enclosing absorbent 
gelling materials partially or fully (i.e. with or without migration 
possibilities). 
Generally, the storage layer comprises from about 15 to 100% absorbent 
gelling materials and from 0 to about 85% carrier. Preferably, the storage 
layer comprises from about 30 to 100%, most preferably from about 60 to 
100% absorbent gelling materials and from 0 to about 70%, most preferably 
from 0 to about 40%, carrier. 
Suitable absorbent gelling materials for use herein will most often 
comprise a substantially water-insoluble, slightly crosslinked, partially 
neutralized, polymeric gelling material. This material forms a hydrogel 
upon contact with water. Such polymer materials can be prepared from 
polymerizable, unsaturated, acid-containing monomers. Suitable unsaturated 
acidic monomers for use in preparing the polymeric absorbent gelling 
material used in this invention include those listed in U.S. Pat. No. 
4,654,039 (Brandt et al), issued Mar. 31, 1987, and reissued as RE 32,649 
on Apr. 19, 1988. Preferred monomers include acrylic acid, methacrylic 
acid, and 2-acrylamido-2-methyl propane sulfonic acid. Acrylic acid itself 
is especially preferred for preparation of the polymeric gelling material. 
The polymeric component formed from the unsaturated, acid-containing 
monomers can be grafted onto other types of polymer moieties such as 
starch or cellulose. Polyacrylate grafted starch materials of this type 
are especially preferred. Preferred polymeric absorbent gelling materials 
that can be prepared from conventional types of monomers include 
hydrolyzed acrylonitrile grafted starch, polyacrylate grafted starch, 
polyacrylates, maleic anhydride-based copolymers and combinations thereof. 
Especially preferred are the polyacrylates and polyacrylate grafted 
starch. 
Whatever the nature of the basic polymer components of the hydrogel-forming 
polymeric absorbent gelling materials, such materials will in general be 
slightly crosslinked. Crosslinking serves to render the hydrogel-forming 
polymer gelling materials substantially water-insoluble, and cross-linking 
thus in part determines the gel volume and extractable polymer 
characteristics of the hydrogels formed from these polymeric gelling 
materials. Suitable crosslinking agents are well known in the art and 
include, for example, those described in greater detail in U.S. Pat. No. 
4,076,663 (Masuda et al), issued Feb. 28, 1978. Preferred crosslinking 
agents are the di- or polyesters of unsaturated mono- or polycarboxylic 
acids with polyols, the bisacrylamides and the di- or triallyl amines. 
Other preferred crosslinking agents are N,N'-methylenebisacrylamide, 
trimethylol propane triacrylate and triallyl amine. The crosslinking agent 
can generally constitute from about 0.001 mole percent to 5 mole percent 
of the resulting hydrogel-forming polymer material. More preferably, the 
crosslinking agent will constitute from about 0.01 mole percent to 3 mole 
percent of the hydrogel-forming polymeric gelling material. 
The slightly crosslinked, hydrogel-forming polymeric gelling materials are 
generally employed in their partially neutralized form. For purposes of 
the present invention, such materials are considered partially neutralized 
when at least 25 mole percent, and preferably at least 50 mole percent of 
monomers used to form the polymer are acid group-containing monomers that 
have been neutralized with a salt-forming cation. Suitable salt-forming 
cations include alkali metal, ammonium, substituted ammonium and amines. 
This percentage of the total monomers utilized which are neutralized acid 
group-containing monomers is referred to herein as the "degree of 
neutralization." 
While these absorbent gelling materials are typically in particle form, it 
is also contemplated that the absorbent gelling material can be in the 
form of macrostructures such as fibers, sheets or strips. These 
macrostructures are typically prepared by forming the particulate 
absorbent gelling material into an aggregate. treating the aggregated 
material with a suitable crosslinking agent, compacting the treated 
aggregate to densify it and form a coherent mass, and then curing the 
compacted aggregate to cause the crosslinking agent to react with the 
particulate absorbent gelling material to form a composite, porous 
absorbent macrostructure. Such porous, absorbent macrostructures are 
disclosed, for example, in U.S. Pat. No. 5,102,597 (Roe et al), issued 
Apr. 7, 1992. 
d. Optional Fibrous ("Dusting") Layer 
An optional component for inclusion in the absorbent cores according to the 
present invention is a fibrous layer adjacent to, and typically underlying 
the storage layer. This underlying fibrous layer is typically referred to 
as a "dusting" layer since it provides a substrate on which to deposit 
absorbent gelling material in the storage layer during manufacture of the 
absorbent core. Indeed, in those instances where the absorbent gelling 
material is in the form of macrostructures such as fibers, sheets or 
strips, this fibrous "dusting" layer need not be included. However, 
because this "dusting" layer provides some additional fluid-handling 
capabilities such as rapid wicking of fluid along the length of the pad, 
its inclusion is typically preferred in absorbent cores according to the 
present invention. 
e. Other Optional Components 
The absorbent cores according to the present invention can include other 
optional components normally present in absorbent webs. For example, a 
reinforcing scrim can be positioned within the respective layers, or 
between the respective layers, of the absorbent cores. Such reinforcing 
scrims should be of such configuration as to not form interfacial barriers 
to fluid transfer, especially if positioned between the respective layers 
of the absorbent core. Given the structural integrity that usually occurs 
as a result of thermal bonding, reinforcing scrims are usually not 
required for the absorbent structures according to the present invention. 
Another component which can be included in the absorbent core according to 
the invention and preferably is provided close to or as part of the 
primary or secondary fluid distribution layer are odor control agents. 
Typically active carbon coated with or in addition to other odor control 
agents, in particular suitable zeolite or clay materials, are optionally 
incorporated in the absorbent core. These components can be incorporated 
in any desired form but often are included as discrete, non-fibrous 
particles. 
Topsheet 
The topsheet (2) is compliant, soft feeling, and non-irritating to the 
wearer's skin. The topsheet also can have elastic characteristics allowing 
it to stretch in one or two directions. Further, the topsheet is fluid 
pervious permitting fluids (e.g., menses and/or urine) to readily 
penetrate through its thickness. A suitable topsheet can 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. 
Preferred topsheets for use in the present are selected from high loft 
nonwoven topsheets and aperture formed film topsheets. Apertured formed 
films are especially preferred for the topsheet because they are pervious 
to body exudates and yet non-absorbent and have a reduced tendency to 
allow fluids to pass back through and rewet the wearer's skin. Thus, the 
surface of the formed film that 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. Pat. No. 3,929,135 
(Thompson), issued Dec. 30, 1975, U.S. Pat. No. 4,324,246 (Mullane, et 
al.), issued Apr. 13, 1982, U.S. Pat. No. 4,342,314 (Radel, et al.), 
issued Aug. 3, 1982; U.S. Pat. No. 4,463,045 (Ahr et al.), issued Jul. 31, 
1984; and U.S. Pat. No. 5,006,394 (Baird), issued Apr. 9, 1991. 
Particularly preferred microapetured formed film topsheets are disclosed 
in U.S. Pat. No. 4,609,518 (Curro et al), issue Sep. 2, 1986 and U.S. Pat. 
No. 4,629,643 (Curro et al), issued Dec. 16, 1986. The preferred topsheet 
for the present invention is the formed film described in one or more of 
the above patents and marketed on sanitary napkins by The Procter & Gamble 
Company of Cincinnati, Ohio as "DRI-WEAVE." 
Topsheets having not a homogeneous distribution of liquid passage ways but 
only a portion of the topsheet comprising liquid passage ways are also 
contemplated by the present invention. Typically such topsheets would have 
the liquid passage ways oriented such that they result in a centrally 
permeable and peripherally impermeable topsheet for liquids. 
The body surface of the formed film topsheet can be hydrophilic so as to 
help liquid to transfer through the topsheet faster than if the body 
surface was not hydrophilic. In a preferred embodiment, surfactant is 
incorporated into the polymeric materials of the formed film topsheet such 
as is described in U.S. patent application Ser. No. 07/794,745, "Absorbent 
Article Having A Nonwoven and Apertured Film Coversheet" filed on Nov. 19, 
1991 by Aziz, et al. Alternatively, the body surface of the topsheet can 
be made hydrophilic by treating it with a surfactant such as is described 
in the above referenced U.S. Pat. No. 4,950,254. 
Backsheet 
The backsheet prevents the exudates absorbed and contained in the absorbent 
core from wetting articles that contact the sanitary napkin such as pants, 
pajamas and undergarments. The backsheet (3) is impervious to liquids 
(e.g., menses and/or urine) and is preferably manufactured from a thin 
plastic film, although other flexible liquid impervious materials can also 
be used. As used herein, the term "flexible" refers to materials that are 
compliant and will readily conform to the general shape and contours of 
the human body. The backsheet also can have elastic characteristics 
allowing it to stretch in one or two directions. 
The backsheet can 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. Preferably, the 
backsheet is a polyethylene film having a thickness of from about 0.012 mm 
(0.5 mil) to about 0.051 mm (2.0 mils). 
Exemplary polyethylene films are manufactured by Clopay Corporation of 
Cincinnati, Ohio, under the designation P18-0401 and by Ethyl Corporation, 
Visqueen Division, of Terre Haute, Ind., under the designation XP-39385. 
The backsheet is preferably embossed and/or matte finished to provide a 
more clothlike appearance. Further, the backsheet can permit vapors to 
escape from the absorbent structure (i.e., be breathable) while still 
preventing exudates from passing through the backsheet. 
Permeation Blockage Means 
The purpose of the permeation blockage means is to positively shield all 
particles from possible migration out of the absorbent product. The 
permeation blockage means (8) as shown in FIG. 2, 3 and 4 is a structural 
part of the absorbent product according to the invention. As such it can 
be considered part of the topsheet which then could be called a 
multi-layer topsheet or composite topsheet. It also could be considered 
part of the core, for example as the primary or optional distribution 
layers. 
The permeation blockage means can be made of a variety of materials as long 
as its main function is satisfied. The materials for the permeation 
blockage means can be woven or non-woven materials or even films. 
Naturally, since the permeation blockage means is interim the topsheet (2) 
and the absorbent core (4), a liquid communication through it must be 
possible, at least in the direction from the topsheet towards the 
absorbent core. 
Preferred material for the permeation blockage means is a non-woven tissue 
made of natural or synthetic fibres like those mentioned when describing 
the absorbent core above. Particularly preferred are tissues of natural 
fibres such as cellulose, or modified natural fibres such as cross-linked 
cellulosic materials. It should also be mentioned that for permeation 
blockage means having the same periphery as the topsheet or the backsheet 
it is advantageous that their fluid communication capability does not lead 
to undesired wicking of fluids within the absorbent product towards the 
peripheral edge of the product. Therefore, permeation blockage means are 
desired which have directional wicking such that peripheral leakage 
induced by wicking within the permeation blockage means is prevented. 
In order to assess whether an absorbent product is susseptible to the 
present invention it first has to be assessed whether particles could 
migrate to the liquid passage ways. For example a sanitary napkin can 
comprise an absorbent core consisting entirely of a fluid storage layer 
which is provided as a laminate. The laminate encloses particulate 
absorbent gelling material as indicated above. It now has to be reviewed 
whether absorbent gelling material particles could migrate from the 
laminate to the liquid passage ways in the topsheet. If the laminate for 
example is cut at its longitudinal or lateral edges particles can escape 
there. If, however, the laminate is formed such that it fully encloses the 
absorbent gelling material particles, these particles would not benefit 
from a permeation blockage means and the product would not be susceptible 
to the present invention. 
An endless seal (9) has to limit the possible migration paths of the 
particles from the liquid passage ways in the topsheet. If there is only a 
limited area in which liquid passage ways are present in the topsheet, 
this can be accomplished by joining the permeation blockage means only to 
the topsheet. It also is possible to join the permeation blockage means 
only to the backsheet outside the periphery of the core but inside the 
periphery of the backsheet. However, it is preferred to seal the 
permeation blockage means to the topsheet as well as to the backsheet, and 
preferably, indicated as number 7, 9 in FIG. 2 and 3. along a common 
endless peripheral edge. 
This joining of the permeation blockage means to the absorbent product can 
be accomplished by adhesive, by welding or as indicated in FIG. 3 by 
crimping. In general the same means which are common for joining the 
compounds of the absorbent product together can be used for the permeation 
blockage means. 
The permeation blockage means preferably is used in absorbent products 
comprising absorbent gelling materials in particulate form. For example, 
the particle size distribution of commercially available particles, 
designated Shokubai L74, of the Shokubai Company, Tokyo, Japan, has 90% 
particles greater than 160 micro meters. In other samples even less than 
1% of particles have been found to be smaller than 45 micro meters. 
Particle size is measured by a sieve test series well known in the art end 
e.g. disclosed in European Application EP-A-0 576 738. It has been found 
to be satisfactory for the permeation blockage means if particles of the 
size of about 60 micro meters and less, and even more so for the size of 
about 45 micro meters and less, can still migrate through the permeation 
blockage means. This is believed to be so because they are neither 
contributing substantially to the absorbent capacity of absorbent products 
and are also not necessarily noticed by users of absorbent products. 
Therefore, permeation blockage means having a maximum pore size smaller 
than 60 micro meters, preferably smaller than 45 micro meters, are 
especially useful in embodiments of the present invention. 
Optional components of the absorbent products 
Optionally, the absorbent product of the present invention can comprise all 
those components typical for the particularly intended product use. For 
example catamenials, panty liners and sanitary napkins often comprise 
components such as wings and panty fastening adhesives in order to improve 
their positioning and soiling protection performance. Baby diapers 
comprise adhesive or mechanical closure systems such as tapes and 
dedicated fastening surfaces or velcro (TM) systems. Elasticated 
waistbands, waistbelts and other waist features are also common in baby 
diapers or adult incontinence products. Leg elastication by one or several 
elastic strands is also common in the art of absorbent products. In 
general, all typically used components in absorbent products can also be 
comprised in the absorbent products according to the present invention as 
long as a particle blockage means is present.