Disposable diaper having a puff bonded facing layer

A disposable absorbent bandage such as a diaper has a nonwoven fibrous facing layer which includes side portions flanking a median portion, at least the side portions thereof being impregnated with a volatile liquid containing a binder to secure the interfiber connections to maintain the fiber superstructure and at least the side portions being heated to explosively puff at least the side portions of the web into a gossamer web in which the side portions have a density less than about 0.02 gm./cm..sup.3, and in which the median portion has a density of at least 0.04 gm./cm..sup.3. The differential in fiber densities between the median portion and the side portion results in substantially greater wickability in the median portion than in the side portions and reduces the tendency for leakage at the sides of the diaper.

BACKGROUND OF THE INVENTION 
Disposable diapers have met with increased commercial acceptance in recent 
years primarily because of their convenience, as opposed to cloth diapers, 
which need to be laundered once soiled. Many different constructions have 
been proposed and used, and some have met with widespread commercial 
success. 
One of the most serious prior art problems has been the inability to 
provide a suitable construction that would keep moisture away from the 
surface of the diaper which comes into contact with the infant's skin and 
thereby avoid skin irritation and infection. Commonly assigned Mesek et 
al., U.S. Pat. No. 3,612,055 discloses several diaper constructions that 
function extremely well in keeping moisture away from an infant's skin 
while at the same time handling a full volume discharge of urine. 
These functions are accomplished by a multilayer diaper comprising, in 
order, a fibrous facing layer which is to be brought into contact with the 
infant's skin, a layer of highly porous, loosely compacted cellulosic 
batt, a paperlike, densified, highly compacted cellulosic fibrous layer 
integral with the loosely compacted batt and an impervious backing sheet 
adhered to the densified layer throughout the interface therebetween. The 
facing layer is of porous construction and its fibers have less 
wettability for water than the fibers of the loosely compacted batt, 
resulting in a tendency for liquid to flow from the facing web into the 
batt. The densified fibrous layer has a smaller average pore size than the 
loosely compacted batt, resulting in a tendency for liquid to flow 
preferentially from the batt into the underlying densified layer rather 
than to other areas of the batt, thus tending to restrict wetting in the 
batt to an area of moderate size. Liquid flowing into the densified layer 
tends to spread laterally because of its wicking action and liquid which 
might pass through the densified layer during discharge (when flow is 
rapid) is held back by the impervious backing sheet for sufficient time to 
permit absorption to take place. Liquid in excess of the absorptive 
capacity of the densified layer is forced back by the impervious layer 
into the dry portion of the loosely compacted batt, thus utilizing the 
additional absorptive capacity therein. 
The facing layer in the above described diaper is comprised of a mixture of 
long and short fibers that are held together by a binder having a wetting 
agent therein which reduces the water repellency of the facing layer, so 
that urine may readily pass therethrough and into the loosely compacted 
batt. The binder and wetting agent are uniformly applied across the width 
and thickness of the facing layer so that the facing layer has uniform 
functioning properties. While the above type of facing layer has 
functioned satisfactorily in use, in certain circumstances, particularly 
when the diaper becomes saturated, there has been a tendency for urine to 
wick along the facing layer and cause leakage at the sides of the diaper. 
It has been proposed to obviate this problem by spraying, or otherwise 
applying, a water-repellent agent on the edges of the facing layer in an 
effort to prevent urine from wicking outwardly; and commonly assigned U.S. 
Pat. No. 3,730,184 to Mesek discloses a facing layer which is treated to 
impart the desired degree of water repellency to the marginal side 
portions of the facing layer. 
SUMMARY OF THE INVENTION 
The present invention provides another approach and another solution to the 
problems of edge leakage in a disposable diaper. In one embodiment it also 
provides a diaper which can be fitted more closely about the thighs of an 
infant. 
According to the present invention, the marginal side portions of an 
integral nonwoven web are provided with a controlled and lesser degree of 
water absorbency than the median portion by expanding and puffing the 
marginal side portions of the web to a density substantially lower than 
that of the median portion. Preferably the side portion density is not 
greater than about 0.02 gm./cm..sup.3, and no more than about half as 
great as the density of the median portion of the web. Due to a 
substantially lower fiber density, the side portions of the web have less 
wickability for liquids than the median portion of the web. 
The side portions of the web comprise haphazardly arranged fibers secured 
together at their junctions by a binder and formed into a cellular 
structure comprising chambers substantially free of fibers and surrounded 
by fiber strata. A complete description of webs having an overall 
structure similar to the structure of the side portions of the web 
comprising the facing layer of this invention, and of the method of making 
such webs may be found in Shepherd U.S. Pat. No. 3,759,775, the disclosure 
of which is hereby incorporated herein by reference. 
The median portion of the diaper may be of a noncellular structure or may 
be a cellular structure having chambers of smaller average size than the 
chambers in the cellular structure of the side portions. 
The method of making a diaper according to the present invention includes 
the steps of impregnating a nonwoven web of discrete fibers having side 
portions flanking a median portion with a volatile liquid containing a 
binder capable of stabilizing the fibers as an interconnected web. The 
volatile liquid is rapidly vaporized by applying heat substantially to an 
internal portion of the impregnated web at a rate sufficient to cause 
expanding vaporized liquid to form liquid membranes within the web and to 
exert expansive forces on the liquid membranes between the fibers and to 
thereby separate portions of the web and produce a puffed web portion. The 
application of the volatile liquid and the heat are correlated to separate 
and puff the side portions of the web substantially more than the median 
portion of the web. The binder is set while fibers are in the puffed 
condition to secure the fibers to one another at interconnections 
therebetween and thereby to produce a stabilized puffed web with a 
structure including chambers within the interior of the web surrounded by 
more dense fiber strata. 
One face of the web is brought into face to face contact with one face of 
an absorbent batt with areas of the web overlapping the edges of the batt, 
and an opposite face of the batt and the overlapping areas of the web are 
brought into contact with an impervious flexible layer. The impervious 
flexible layer is adhered to the opposite face of the batt and to the 
overlapping areas of the web. 
In addition to the differential in wickability between the median and side 
portions of the web, a further feature of one embodiment of the present 
invention is the provision of additional bulk at the side edges of a 
diaper where it serves a useful function. In a typical disposable diaper 
comprising a facing sheet and a backing sheet of equal dimensions and an 
absorbent batt of smaller dimension positioned therebetween, the present 
invention can provide greater thickness at the edges of the diaper where 
the batt does not extend. Due to this additional thickness, or bulk, at 
the side edges of the diaper, a better seal is provided at the thighs 
where tape tabs are used with the present invention. 
In an alternate embodiment, the precursor web has a greater thickness in 
the median portion than in the side portions and, after puffing, the 
entire web is about equal in thickness at all portions of its width.

DETAILED DESCRIPTION OF THE INVENTION 
While this invention is susceptible of embodiment in many different forms, 
there is shown in the drawings and will herein be described in detail 
preferred embodiments of the invention with the understanding that the 
present disclosure is to be considered as an exemplification of the 
principles of the invention and is not intended to limit the invention to 
the embodiments illustrated. The scope of the invention will be pointed 
out in the appended claims. 
Referring to FIG. 1, disposable diaper 10, having a substantially 
rectangular configuration, is provided with moisture-impermeable backing 
sheet 11 which forms an outside surface for direction away from an infant 
and with an absorbent pad or batt 12 situated on backing sheet 11 and 
attached thereto by means of adhesive beads 13. Moisture-pervious facing 
sheet or web 14, forming an inside surface for direction toward an infant, 
overlies batt 12 and is substantially coextensive with backing sheet 11. 
Batt 12 is smaller in dimension than backing sheet 11 and facing sheet 14, 
and facing sheet 14 has a median portion 15 overlying batt 12 and side 
portions 16 and 17 which flank the median portion and overlie marginal 
portions of backing sheet 11. Facing sheet 14 is similarly attached to 
backing sheet 11 by adhesive beads 13 which extend beyond the ends of the 
batt, as shown, and by adhesive beads 18 which run along the side margins 
of the diaper. Diaper 10 can be provided with adhesive tab fasteners 19 as 
shown in FIG. 9. 
The diaper of this invention may be assembled in equipment such as that 
schematically shown in FIG. 4. A roll of compacted wood pulp 21 is 
provided to feed a source of short cellulosic fibers to grinding mill 22 
from which a stream of fibers is blown onto belt 23 as a layer 24 weighing 
between about 2 and about 10 oz./yd..sup.2. The pulpboard normally has a 
moisture content of 5 to 10 percent by weight, but if it is lower (as from 
prolonged exposure to a dry atmosphere) the pulpboard may be slightly 
moistened before grinding in mill 22 to bring its moisture content within 
the desired range. 
Mill 22 grinds the pulpboard into individual short fibers. However, in one 
preferred embodiment, some of the pulpboard fibers are not completely 
comminuted and remain joined to other fibers in small clumps, generally 
smaller than about one-fourth inch across. It has been found that the 
presence of such small clumps of fibers in the body of batt 12 provides 
islands of increased tenacity for holding liquid. When an infant's weight 
on one portion of the batt densifies that portion and tends to concentrate 
the liquid in the densified portion, the presence of clumps of fibers 
elsewhere in the batt tends to hold the liquid in place. Preferably from 
about 2 to about 10 percent by weight of the fibers should be in the form 
of such clumps. 
The air blown layer is passed under compacting roll 26 from which it 
emerges with enough integrity to sustain itself as a web without the 
support of belt 23. The web then passes through a pair of calendar rolls 
27 for further compression and then under nozzle 28 which deposits a fine 
spray of moisture on the upper surface of the web. The moistened web then 
passes between another set of calendar rolls 29 which exert heavy pressure 
on it to form a skin 31 on its upper surface. 
The amount of moisture applied to the web may vary suitably from about 
0.005 to about 0.03 cc. of H.sub.2 O/cm..sup.2 of web surface, depending 
on the thickness of the web and the thickness of the paper-like densified 
skin desired, with lesser amounts of moisture being used for thinner webs 
and very thin, papery skins and greater amounts for thicker webs and skins 
of greater thickness. 
The amount of pressure applied by rolls 29 may vary from about 5 to about 
100 or more lbs./in..sup.2, with the commercially preferable range being 
from about 10 to about 50 lbs./in..sup.2. In a typical embodiment, the web 
is sprayed with about 0.0015 cc. of H.sub.2 O/cm..sup.2 of web surface and 
subjected to a pressure of about 40 lbs./in..sup.2 to obtain a densified, 
coherent papery skin on the surface of the web which has been moistened. 
In the absorbent web and in the batts cut therefrom, there are weak 
hydrogen bonds in the body of the batt providing sufficient strength to 
maintain the integrity of the batt in ordinary handling, and there are 
strong hydrogen bonds in the densified layer or skin to increase the 
cohesive strength of the composite. After the skin is formed, the 
absorbent web comes into contact with a web of facing material 32 and is 
supported thereby while being cut by cutter 33 into individual batts 12. 
Facing material 32, comprises a nonwoven fibrous web, which is more porous 
in its marginal side portions than in its median portion and at least a 
portion of which contains a small amount of binder. 
As illustrated in FIG. 4, facing material 32 may be prepared by initially 
feeding a source 34 of short fibers and a source 35 of textile length 
fibers to a fiber individualizing and mixing means 36, which separates the 
fibers from their respective sources, mixes them, and deposits them on a 
foraminous belt 37. The web forming means may be similar to a Rando-Webber 
made by the Curlator Co. The web of facing material 32 is thereafter 
impregnated throughout with an acrylic binder which is dispersible in a 
vaporizable liquid, such as water, contained in hopper 38 by applying the 
same to at least side portions 16 and 17 of the top surface of the web and 
then passing the web over a suction box 39 by virtue of which the binder 
and water are distributed relatively uniformly throughout the thickness of 
the web. The vaporizable liquid may flow freely onto web 32 from hopper 38 
and suction box 39 may be used to remove excess liquid from the web. 
The impregnated web is next passed through a heating means 40 which may 
comprise one or more dielectric dryers. By virtue of its high loss factor, 
the water solution rapidly absorbs energy from the heating means, thus 
causing the liquid in the interior of the web to rapidly heat, vaporize, 
and expand explosively causing the web to puff as shown at 41 in FIG. 4. 
As the web of facing material 32 is thus dried, the liquid activated 
binder sets and the web at 41 is stabilized in its puffed condition. 
As shown in schematic plan view in FIG. 5, described below, both hopper 38 
and heating means 40 are divided into three separate sections (i.e., a 
median section and two flanking sections) so that either the amount of 
liquid applied to each width portion of the web, or the amount of heat 
applied, or both, can be controlled to provide puffing, or different 
degrees of puffing, so that the median portion of the web is denser than 
the side portions. 
Polyethylene film 42, which is later cut into a plurality of backing sheets 
11, is fed to the assembly from roll 43, lines of adhesive being applied 
from applicator 44. As described above, the adhesive is applied as 
parallel lines or beads between the impervious sheet and the densified 
layer of the batt (or the facing layer in the marginal portion of the 
diaper). Adhesive may, if desired, be applied as a continuous layer 
between the polyethylene and the batt, but such application tends to 
provide excessive stiffness. The adhesive may also be applied in other 
patterns, such as spaced dots or other forms of so-called "island" bonds, 
but fairly close overall adhesion between the sheet and the batt is 
required and no portion of the polyethylene should be more than about 2 
inches from a point of adhesion. In the absence of such close overall 
adhesion, the polyethylene film may be separated from the densified layer 
to create substantial space in which uncontrollably large amounts of free 
liquid can accumulate. 
After the facing material and polyethylene are brought into contact with 
opposite faces of the absorbent batts, the assembly is subjected to 
compression by rolls 45 and 46 to shape the diaper assembly, and the 
individual diapers are cut off by cutter 47. 
If desired, adhesive applicator 44 may be omitted and adhesion between the 
polyethylene layer and the fibrous layers may be achieved by heat sealing, 
employing a suitable sealing element in the production line. 
The term "vaporizable liquid" contemplates a liquid capable of generating 
gases at a very rapid rate at temperatures which can be tolerated by the 
common synthetic and natural fibers. The vaporizable liquid with which 
portions of web 32 are impregnated is heated rapidly internally of the web 
to explosively vaporize the same and to puff the previously impregnated 
portions of the web to an expanded though structurally weak, low density 
condition. The binder, which has been activated and made adhesive, is then 
set while the previously impregnated portion of the web is in its puffed 
or expanded state. This secures the fibers together where they intersect 
and provides substantial structural integrity. 
It is preferred that the liquid have a relatively low surface tension so 
that it will tend to adhere to the fibers as it partially is vaporized, 
thus forming discrete, rapidly expanding bubbles of vapor or walls 
interconnecting the fibers to lift the fibers. It is thought that the 
bubbles cannot immediately escape from the web where the interfiber 
membranes extend during the explosive action. Therefore, the gases expand 
more or less in situ until the bubbles or membranes release the vapor 
entrapped therein, which then readily escapes through and from the web. 
The more rapid the vaporization, the greater will be the number of these 
expanding bubbles thrust into a given interstitial volume within the web 
at a given moment. It is thought that if the total volume of these 
expanding bubbles in a given web portion at any moment is greater than the 
interstitial volume of that web portion, that web portion expands, or 
becomes puffed in an explosive manner. 
Dielectric heating means 40 are preferably used to vaporize the liquid 
because of the speed of the action and the internal nature of the heating. 
Dielectric heating occurs generally through the absorption of electrical 
energy in a dielectric material exposed to a rapidly changing 
electromagnetic field. Thus, when using dielectric heating means, 
generally only dielectric substances having a substantial loss factor 
within the web absorb electrical energy and are heated directly. The 
amount of heat generated in the fibrous web and the fluids held in the web 
depends upon the frequency of the electromagnetic field applied to the 
product, the applied voltage, the effective capacitance of the plates and 
dielectric material and the power factor or loss factor of the web. The 
power dissipated in the fibrous web can be calculated in watts from the 
equation: 
##EQU1## 
where f= frequency in Hertz 
C= capacitance in microfarads 
E= applied r.m.s. voltage 
PF= power factor. 
The dielectric liquid throughout the web will be rapidly heated fairly 
uniformly according to this equation rather than being heated much more 
slowly from the outside inwardly as is the case with conventional steam, 
hot air, or infrared dryers. 
As will be described, certain additives will substantially improve the loss 
factor (lower the power factor) of the fiber web and thus enhance the 
rapid heating. These may also be conductive but no detrimental effect 
results therefrom provided there is an air gap between the heater plates. 
If the vaporizable liquid is in fact a solvent for the binder, as the 
liquid is vaporized and the web dried of the liquid, the binder 
simultaneously becomes set to interconnect the discrete fibers and 
stabilize the puffed web. The binder may also be present in the form of 
thermoplastic fibers or powder, such as plasticized cellulose acetate, and 
the like, dispersed throughout the web and having an activation 
temperature at or near the vaporization temperature of the vaporizable 
liquid. When using a thermoplastic binder and dielectric heating means, 
the binder activation and deactivation steps may again suitably be 
combined with the vaporization of the liquid. When the liquid is heated by 
virtue of the absorption of electric energy from the dielectric dryer and 
vaporized, the hot vapor within the web is sufficient to cause activation 
of the thermoplastic fibers or powder. As the web is dried and the 
conductive liquid is driven off, the loss factor goes down and there is 
less and less absorption of energy within the web and, therefore, less 
heating of the web. Thus, the thermoplastic fibers or powder becomes 
deactivated and bonds the nonthermoplastic fibers together at points of 
contact with the thermoplastic material. 
Although as previously described, the liquid may act as an activating agent 
for the binder, the primary purpose of the liquid is to provide the vapor 
to puff the web. When using a volatile liquid and dielectric heating, the 
degree of puffing may be controlled by varying certain parameters, 
including the thickness of the web, the loss factor of the liquid, the 
surface tension or foamability of the liquid, the amount of liquid in the 
web, and the energy level of the dielectric dryer. 
If the liquid used is tap water, in order that most of the vapor produced 
will be in the form of discrete expanding vapor bubbles or constrained by 
interfiber membranes, it is necessary to add a foaming or wetting agent to 
the water. These agents are generally those substances which significantly 
lower the surface tension of water, such as the polyoxyethylene sorbitan 
fatty acids esters and sorbitan fatty acid esters. Usually, only small 
amounts of these agents, on the order of from about 1/10 of 1% to about 1% 
by weight of the water need be used. However, in the case of a weak 
foaming agent or if substances which retard foaming are present, 10% or 
more of the foaming agent by weight of the water may be required. A 
particularly suitable agent is Triton GR-5, a sulfonated alkyl ester, sold 
by Rohm & Haas. 
The higher the loss factor of the liquid solution, the more rapid is the 
heating and rate of vaporization. Likewise, the higher the energy level of 
the dielectric dryer and the higher the web liquid pick-up weight, the 
more rapid is the rate of vapor-evolution. If the web is very thin, 
vaporization will occur essentially on the surface of the web, there will 
be little vapor entrapment by the liquid films and, thus, the vapor will 
rapidly escape from the web without effecting puffing. Thus, by varying 
any or all of these factors, the web is puffed to a greater or lesser 
extent as desired. 
In order to heat and vaporize the volatile liquid with commercially 
available dielectric heaters, having an energy output of about 1 kw./inch 
width/100 feet (web velocity) /minute, rapidly enough to cause puffing of 
an impregnated web having a fiber weight of between about 3 and about 19 
ounces/yard.sup.2 and a thickness of between about 0.05 and about 0.30 
inch, the web suitably has a liquid pick-up weight of from about 100% to 
about 600% and the liquid must have a substantial loss factor. In the case 
of water, this level of loss factor or power factor may be provided by 
adding small amounts, on the order of from about 1/100 of 1 to 5% by 
weight of the weight of the water, of an electrolytic salt, such as 
ammonium chloride. For example, if tap water is the volatile liquid, the 
addition of a particular acrylic binder (sold as Hycar 2,600 .times. 120) 
in an amount of about 3% solids by weight to the water provides the 
necessary interfiber stabilization and increases the loss factor 
substantially. The addition of about 1/10 of 1% by weight of ammonium 
chloride further increases the loss factor and provides explosive 
vaporization in a dielectric heater as described. The resistance of an 
ammonium chloride water solution becomes asymptotic with a salt 
concentration of about 5% solids by weight and, therefore, there is little 
advantage in using salt concentrations above this level. 
The amount of binder should be selected to provide the desired interfiber 
bonds while maintaining the absorbent interstices. In the preferred 
embodiments, the binder comprises between about 4 and 10% of the fabric, 
by weight on a dry solids basis and with this amount, there is an optimum 
structural stability and minimum tendency to collapse while still 
maintaining light weight and high absorbency. Binder add-on in the range 
of about 1 to about 30% of dry solids by weight can be used. The lower 
range is acceptable where increased structural collapse under compression 
is not excessively detrimental, and the upper range is useful where 
increased rigidity is desired although some increase in cost and weight 
and some decrease in absorptive capacity may be detected. 
Referring now specifically to FIGS. 2, 6 and 7, there are shown magnified 
transverse cross sections of the puffed facing sheet (web) 14. The total 
thickness of these webs is actually about 1/2 inch or less. The puffed web 
has a cellular or honey-combed appearance throughout most of the 
stabilized portion and essentially comprises longitudinally and 
transversely extending haphazardly arranged fiber strata 50 and fiber 
chambers 51. The fiber chambers 51 separate fiber strata 50 and act 
essentially as pores within the body of the fabric. Most of the fiber 
strata 50 have a fiber density approaching that of the unexpanded web, and 
the fiber chambers 51 have a considerably lower fiber density than the 
surrounding fiber strata 50. Some portions of the fiber chambers 51 are 
essentially devoid of fibers, and the chambers are defined by a large 
number of small fibers secured together at their junctions by a small 
amount of binder. The chambers defined by the strata are larger than the 
expected interstitial spaces. The portion 53 of the web 32 near the 
surfaces of the same, is usually of more nearly uniform and higher 
density. This is thought to be due to the fact that the bubbles formed in 
the surface adjacent web portions 53 escape relatively rapidly from the 
web and do not carry many fibers with them. Thus, little or no puffing 
occurs in this area. 
During heating and drying of webs, most binders which are solvent 
activated, tend to migrate somewhat toward the surface of the web, 
especially if the binder pick-up weight is relatively high; and, 
therefore, the surface adjacent portions 53 of the web may have a higher 
binder content than the center portions 56 of the web. As a result, a 
relatively hard "skin" 57 may be formed on the web surfaces. The web 
portions 56 interposed between the surface adjacent portions 53 tend to be 
less dense and remain softer and somewhat springy. Thus, a low density 
high bulk absorbent web may be provided which has a hard enough surface to 
provide improved scuff resistance, thus minimizing the fluffing off of the 
surface fibers. 
The present invention contemplates selective wickability along various 
width portions of an integral nonwoven fibrous web. More specifically, it 
is desired to provide a web including side portions 16 and 17 having an 
overall density substantially lower than the density of median portion 15. 
Preferably, the density of the median portion will be at least twice as 
great as the density of the side portions. Since wickability increases 
with decreasing interfiber distances, due to increased capillarity with a 
greater number of fibers per unit volume, the median portion 15 of the web 
is substantially more absorbent than side portions 16 and 17. Reduced 
wickability is desired along side portions 16 and 17 of the web in a 
diaper to minimize any tendency for urine to wick along the facing layer 
to the marginal side edges thereof. 
Various means are contemplated for producing the integral nonwoven webs of 
the present invention having varying densities therein, with median 
portion 15 of the web having a substantially greater density than side 
portions 16 and 17. At least the side portions 16 and 17 of the web are 
impregnated with a volatile liquid containing a binder capable of 
stabilizing the fibers in the web as an interconnected web, and the 
volatile liquid in at least the side portions of the web is rapidly 
vaporized by applying heat substantially to an internal portion of the web 
to produce a puffed web portion. The application of the volatile liquid 
and the heating are correlated to puff only the side portions 16 and 17 of 
the web, or to puff them substantially more than median portion 15. Only 
side portions 16 and 17 are puffed in the embodiment of FIGS. 2 and 6; and 
the entire web is puffed, with side portions 16 and 17 being puffed to a 
substantially greater extent than median portion 15 in the embodiment of 
FIG. 3. In the embodiments illustrated in FIGS. 2, 3 and 6, the median 
portion 15 (115 in FIG. 3) of web 32 has approximately the same fiber 
weight per unit area as side portions 16 and 17 (116 in FIG. 3), and the 
side portions are therefore thicker than the median portion. In the 
embodiment illustrated in FIG. 8, median portion 15 has a higher fiber 
weight per unit area than side portions 16 and 17 and the entire web is of 
approximately equal thickness in all width portions after puffing. 
As shown in FIG. 5, hopper 38 is divided into median portion 60 and side 
portions 61 and 62; and heating means 40 comprises a dielectric heater 
having median portion 63 and side portions 64 and 65. The power to each 
portion of the dielectric heater is separately controlled by rheostats 
63a, 64a and 65a, respectively. 
The median portions of the hopper and heater are positioned above the 
median portion 15 of the web, and the side portions of the hopper and 
heater are positioned above side portions 16 and 17 of the web. The amount 
of liquid supplied by the portions of the hopper and the amount of heat 
produced by each dielectric heater portion are independently adjustable 
and are variable. If desired, hopper 38 may comprise a plurality of 
separate hoppers, and heating means 40 may comprise a plurality of 
separate dielectric heaters. 
To puff only the side portions 16 and 17 of the web to produce the web 
illustrated in FIG. 2, either the volatile liquid is supplied from side 
portions 61 and 62 of the hopper to only the portions 16 and 17 of the web 
while the entire web is heated; or the entire web is wetted while only the 
side portions of the web are heated by side portions 61 and 62 of the 
dielectric heater. Or, if desired, both the wetting and the dielectric 
heating may be restricted to the side portions. Where the volatile liquid 
is supplied to only the side portions of the web, it is desirable to 
provide binder to the median portion 15 of the web through median portion 
60 of the hopper so that the median portion of the web will be a binder 
stabilized uniform mixture of fibers. 
The present invention also contemplates a web which is entirely puffed, but 
wherein side portions 16 and 17 are expanded substantially more than 
median portion 15. In the following portion of the description, the same 
last two digits in each numeral designate similar elements in the various 
embodiments. Referring to FIGS. 3 and 5, the entire web 132 is impregnated 
with liquid from hopper 38 and the entire web is heated by dielectric 
heater 40 to puff the entire web. To puff side portions 116 and 117 of the 
web substantially more than median portion 115 of the web, a greater 
quantity of volatile liquid is provided to side portions 116 and 117 of 
the web from side portions 61 and 62 of the hopper than is provided to 
median portion 115 of the web from median portion 60 of the hopper. 
Alternatively, or in addition, more heat is applied to side portions 116 
and 117 of the web from side portions 64 and 65 of dielectric heater 40 
than is applied to median portion 115 of the web from median portion 63 of 
the dielectric heater. A greater amount of puffing in side portions 116 
and 117 of the web than in median portion 115 of the web can also be 
accomplished by applying salt to the side portions 116 and 117 of the web 
through the side portions 61 and 62 of the hopper, and then heating the 
entire web evenly or applying more heat to the side portions of the web 
than to the median portion. An ionizing material comprising an 
electrolytic salt, such as ammonium chloride, increases the heating rate 
of the liquid in the side portions of the web. 
As illustrated in FIG. 8, web 214, after it is puffed, may have 
approximately the same thickness in side portions 216 and 217 and median 
portion 215. This is accomplished by starting with a precursor web having 
a median portion 215 which is thicker than side portions 216 and 217. 
After the web is puffed, the entire web has about the same thickness due 
to a substantially greater amount of puffing in side portions 216 and 217 
than in median portion 215. 
Referring to FIGS. 1, 2 and 5, median portion 15 of web 14 preferably runs 
lengthwise along diaper 10, and is uniform in construction throughout its 
length. As shown in FIG. 1, median portion 15 may comprise a central 
portion 70 and end portions, such as 71, at opposite ends of diaper 10. If 
desired, end portions 71 are puffed and have a density lower than that of 
central portion 70 and no greater than about 0.02 gm./cm..sup.3. End 
portions 71 and side portions 16 and 17 may comprise haphazardly arranged 
fibers secured together at their junctions by a binder and formed into a 
cellular structure comprising chambers substantially free of fibers and 
surrounded by fiber strata. 
Webs having end portions as well as side portions of lower density than the 
central portions may be produced in the same general manner as described 
above, by restricting the application of the volatile liquid to a hollow, 
rectangular, "picture-frame" pattern, by restricting the dielectric 
heating to such a pattern, or both. 
The fiber assemblies used in the manufacture of the improved puffed 
nonwoven fabrics described herein may advantageously use the fiber 
combination described in detail in commonly assigned U.S. Pat. No. 
3,663,348, the various examples and teachings thereof being incorporated 
herein by reference. The fabric is preferably predominately fibers under 
about 1/4 inch in length, with a minor proportion of long fibers in excess 
of about 3/4 inch in length. A combination of about 70% or more by weight 
of short fibers under about 1/4 inch and about 30% or less long fibers of 
about 3/4 inch or more have proven especially advantageous and economical. 
The practice of the invention is not limited to any particular type, length 
or denier fibers and includes the use of waste fibers, such as chopped 
threads and the like. Thus, any of the natural fibers such as cotton, 
linen, hemp, silk, wool, or wood pulp; or synthetic fibers such as rayon, 
acetate, polyester, acrylic or modacrylic fibers may be used. The method 
may also be used with fibers of any length, though short fibers are of 
particular usefulness. Short fibers such as cotton linters or wood pulp 
are particularly desirable for use in a low cost absorbent product due to 
their low cost and their ease of handling. In the past, the production of 
webs of these short fibers have presented the greatest problems with 
respect to providing low density, high bulk webs. Therefore, it is in 
producing webs of these short fibers that one may benefit most from the 
puffing which may be obtained through use of this invention. 
The invention has been described with respect to its preferred embodiment 
in connection with diapers and the preparation of diapers. It will be 
understood, however, that the fibrous web of this invention may also be 
used as a facing layer in other absorbent bandages, such as surgical 
dressings and sanitary napkins, in which a facing layer is in face to face 
contact with an absorbent batt. 
Other modifications and variations will be apparent to those skilled in the 
art.