Note: Descriptions are shown in the official language in which they were submitted.
CA 02552621 1997-12-15
la
A SOFT AND RESILIENT WEB COMPRISING MICRO-APERTURES AND
MACRO-APERTURES
ZO
FIELD Oi= INVENTION
The present invention relates to a process of forming a soft and resilient
web and a soft and resilient web formed by the process. More particularly, the
15 present invention relates to a process utilizing a locally heating process
to form a
soft and resilient web exhibiting a substantially continuous pattern of
debossments
or apertures. The present invention also relates to a soft and resilient web
exhibiting a substantially continuous pattern of debossrnents or apertures.
20 . eACKGROUhtD
tn processes disclosed in prior art for producing a web such as a formed
film, a web ofi heat-softened film is provided on the patterned, perforated
outer
surface (referred to herein as a forming surface) of a structure such as an
endless
25 beat or a drum cylindrical surface. A vacuum beneath the forming surface
pulls the
heat sot~ened ntm info conformity with the forming surface. Alternatively, a
positive
pressure may be used to force the heat softened film against the forming
surface.
Whether the web of film is simply embossed or is debossed and perforated will
depend on the size of the holes in the forming surface, the softness and
thickness
30 of the film being fomned, and the fluid pressure d'rf'rerentiaE across the
film.
Processes for producing webs of embossed thermoplastic film are disclosed
in U.S. Pat. Nos. Re 23,9'f0 issued to Smith & Smith on Dec. 12, 9954;
2,776,451
and 2,776,452 both issued to Chavannes on Jan. 8, 1957; and 2,905,969 issued
to
Giibert & Prendergast on Sept. 29, 1959. Processes for the production of webs
of
35 debossed and perforated thermoplastic films are disclosed in U.S. Pat. Nos.
CA 02552621 1997-12-15
3.038,198 issued to Shaar on June 12, 1962; 3.054,148 issued to Zimmer(i on
Sept. 18, 1962; 4,151,240 issued to t_ucas & Van Coney on Apr. 24, 1979;
4,155,693 issued to Raley on May 22, 1979; 4,226.828 issued to Halt on Oct. 7,
1980; 4,259.286 issued to t-ewis, Sorensen & Baltard on Mar. 31, 1981;
4,280,978
issued to Dannheim & McNaboe on July 28, 1981; 4,317,792 issued to Ra(ey &
Adams on Mar. 2, 1982; 4,342,314 issued to Radei & Thompson on Aug. 3, 1982;
and 4,395,215 issued to Bishop on July 26, i 983. A process for the production
of
perforated seamless tubular film is disclosed in U.S. Pat No. 4,303,609 issued
to
Hureau, Hureu 8~ Gaillard on Dec. 1, 1981.
I0 The processes disclosed in the references cited above require that the
thermoplastic film be heat-softened in order to achieve the desired embossing
or
debossing and perforation of the film. This can be achieved as disclosed in
many
of the above references by heating an existing web of film to a temperature
above
its melt temperature range such that it is in a molten state and will readily
flow and
IS attain a new configuration. Alternatively, the motten film may be achieved
by
feeding a web of film directly from a film extruder onto the forming surface.
Such a
process is disclosed in U.S. Pat. No. 3,685,930 issued to Davis & Etiiot on
Aug. 22,
1972, where a web of them~oplastic film is extruded directly onto the outer
surface
of an endless belt and a vacuum is pulled beneath the belt to make the molten
web
20 of film assume the confguration of the outer heft surface. Similarly, U.S.
Pat. No.
3,709,647 issued to Barnhart on Jan. 9, 1973 discloses a web of molten
thermoptastic film extruded directly onto the outer cylindrical surface of a
vacuum
forming drum.
It is known to shape molten thermoptastic sheet materiat by the use of a
25 fluid pressure forcing the sheet against a mold; such processes are
disclosed in
U.S. Pat. Nos. 2,'!23,552 issued to t-iefwig on July 12, '3938; and 3,084,389
issued
to Doyle on Apr. 9, 1963.
When webs of embossed or debossed and perforated thermoplastic film are
produced on a patterned surface by the above prior art processes, it is
generally
30 necessary to cool the film below its melting temperature range to set its
three
dimensional structure prior to removing the web of formed film from the
fom~ing
surface. This mattes the web of formed film much less susceptible to
distortion of
its bulk conformation.
To make webs of formed film by these prior art processes, it is necessary to
35 have the fim within or above its melting temperature range in order to form
the frlm.
CA 02552621 1997-12-15
This limits the range of desired properties that can be engineered into the
formed
film since all previous thermo-mechanical history of the film is erased.
Other attempts to produce a web, such as a formed film, are to apply a
liquid pressure to the web on the forming surface. The liquid pressure has
S sufficient force and mass flux to cause the web to be deformed toward the
forming
surface such that the material acquires a substantial three-dimensional
conformation. The temperature of the web of material is controlled such that
it
remains below the transformation temperature range of the material throughout
the
process. Such process is disclosed in U.S. Pat. No. 4.695,422 issued to Curro
et
al. on September 22, 1987.
Jn the process disclosed in the reference, the web is exposed to the liquid
pressure, however, the temperature is below the transformation temperature
range
of the material which does not melt the material. When the material defom~s by
the
liquid pressure, the material substantially ruptures and the some
°spring-back" of
the material generally occurs after it passes the zone of liquid pressure.
This
"spring-back" of the material causes dimensionally unstable, three-dimensional
apertures on the web which results in poor resiliency of the web.
Therefore, it is an objective of the present invention to provide a process
of forming a soft and resilient web utilizing a locally heating process to
form a
substantially continuous pattern of debossments or apertures on the web.
It is a further objective of the present invention to provide a soft and
resilient web formed by the process utilizing a locally heating process to
form a
substantially continuous pattern of debossments or apertures on the web.
SUMMARY
The present invention provides a process of forming a soft and resilient web
exhibiting a substantially continuous pattern of debossments or apertures
being
formed by locally heated at predetermined points along the surface of the web.
The process comprises. continuously bringing the web in contact relation with
a
forming structure exhibiting a substantially continuous pattern of apertures
corresponding to the debossments or apertures of the web, the continuous
pattern
of the apertures extending from the outermost to the innermost surface of the
forming structure; locally heating the region of the web at the predetermined
points
along the surface of the web by an energy source, the energy source heating
the
CA 02552621 1997-12-15
region of the web above its melting temperature range; applying a
substantially
uniform fluid pressure differential to the locally heated web at least in
those regions
to be debossed or apertured while the web is in contact with the fom~ing
structure,
whereby the web is debossed or apertured at the predetermined points and
generally maintains its surface structure at least in those areas in which the
web is
not debossed or apertured; and removing the debossed or apertured web from the
forming structure.
The present invention also provides a soft and resilient web exhibiting a
substantially continuous three-dimensional pattern of macro-apertures. The web
comprises a fluid impermeable plastic material. The web has a first surface, a
second surface, a multiplicity of micro-apertures and a multiplicity of macro-
apertures. The web has a land area on the first surface and a wall protruding
beyond the second surface of the land area. The land area includes a pattern
of
fine-scale, volcano-like micro-apertures comprising discrete volcano-like
surface
1 S aberrations and micro-openings. The aberrations protrude from the land
area
beyond the first surface of the land area. The micro-opening locates at the
top of
each aberration. The macro-apertures are defined by the wall, an opening on
the first surface surrounded by the waft and an apex opening. The wall has the
micro-apertures thereon. The size of the micro-apertures on the wall is
generally
smaller than that of the micro-apertures on the land area.
The present invention further provides a soft and resilient web exhibiting a
substantially confinuous three-dimensional pattern of macro-apertures. The web
comprises a fluid impermeable plastic material. The web has a first surface, a
second surface, a multiplicity of micro-apertures and a multiplicity of macro-
apertures. The web has a land area on the first surface and a wall protruding
beyond the second surface of the land area. The land area includes a pattern
of
fine-scale, volcano-#ike micro-apertures comprising discrete volcano-tike
surface
aberrations and micro-openings. The aberrations protrude from the land area
beyond the first surface of the land area. The micro-opening locates at the
top of
the aberration. The macro-apertures ace defined by the wall, an opening on the
frrst surface surrounded by the waif and an apex opening. The wa#! has the
micro-apertures thereon. The number of the micro-apertures on the wall is less
than the number of the micro-apertures on the land area, per a unit area.
The present invention further provides a soft and resilient web exhibiting a
substantialty continuous three-dimensional pattern of apertures. The web
CA 02552621 1997-12-15
J
comprises fiber aggregation. The web has a first surface, a second surface,
and
a multiplicity of apertures. The web has a land area on the first surface and
a
wall protruding beyond the second surface of the Land area. The apertures are
defined by the wall, an opening on the first surface surrounded by the wail
and
an apex opening. The land area on the first surface comprises the fiber
aggregation. At least a portion of the wait comprises the fiber aggregation,
and
at least a portion of the fiber aggregation is melted to each other at least
adjacent
the apex opening of the apertures.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the present invention, it is believed that the present
invention wilt
be better understood from the following description in conjunction with the
t 5 accompanying drawings, in which like reference numbers identify tike
elements,
and wherein:
FfG. 1 is a simplifed schematic view of a web forming process of the
present invention including two phase process;
FIG. 2 is an enlarged fragmentary perspective view of the first forming
structure utilized to support the web when the web is subjected to a first
phase
shown in FIG. 1;
FiG. 3 is an enlarged cross-sectional view of the web which is supported on
the surface of the first forming structure of the first phase shown in FIG. 1
when the
web is subjected to a fluid pressure differential and a locally heating
energy;
F1G. 4 is an enlarged inset of the web after it has been removed from the
frrst forming structure of the first phase shown in FIG. 1;
FIG. 5 is an entarged fragmentary perspective view of the second forming
structure utilized to support the web when the web is subjected to a second
phase
shown in FIG. 1;
FIG. 6 is an enlarged cross-sectional view of the web which is supported on
the surface of the second forming structure of the second phase shown in FIG.
1
when the web is subjected to a fluid pressure differential and a locally
heating
energy;
FIG. 7 is an enlarged cross-sectional view of the alternative embodiment of
the forming structure;
CA 02552621 1997-12-15
6
FIG. 8 is an enlarged cross-sectional view of the alternative embodiment of
the forming structure;
FIG. 9 is a simplified schematic view of the alternative embodiment which
may be utilized for a part of the two phase process shown in FIG. 1;
FIG. 10 is an enlarged cross-sectional view of the web which is supported
on the surface of the forming structure of the alternative embodiment shown in
FIG.
9 when the web is subjected to a fluid pressure differential and a locally
heating
energy;
FIG. 11 is an enlarged fragmentary perspective view of a plastic film after
completion of the web forming process;
FIG. 12 is an enlarged cross-sectional view of the plastic film after
completion of the web forming process;
FIG. 13 is a greatly enlarged fragmentary perspective view of the plastic film
after completion of the web forming process;
FLG. 14 is an enlarged fragmentary perspective view of a web comprising
fiber aggregation after completion of the web forming process;
FIG. 15 is an enlarged cross-sectional view of the web comprising fiber
aggregation after completion of the web forming process; and
FLG. 16 is an enlarged cross-sectional view of a web comprising fiber
aggregation and a plastic film after completion of the web forming process.
DETAILED DESCRIPTION OF THE INVENTLON
While the present invention will be described in the context of providing
three dimensional, apertured webs particularly suited for use as a wearer
contacting surface on absorbent bandages such as disposable diapers, sanitary
napkins, wound dressings and the like, the present invention is in no way
Limited to
such applLCations. The patterns created rnay be of any desired shape, they may
be
regulated or random, reticulated or non-reticulated, continuous or
interrupted, or
any desired combination thereof. The detailed description of the structures
disclosed herein and their suggested use as topsheets and/or backsheets in a
disposable absorbent bandage context wilt allow one skilled in the art to
readily
adapt the invention to produce webs weft suited to other applications.
A particularly preferred multi-phase, continuous forming process of the
present invention is schematically illustrated in FIG 1. tn the embodiment
shown in
CA 02552621 1997-12-15
7
FIG. 1, a substantially planar web 10 which may be comprised of, e.g., a
thermoplastic film, a fiber aggregation, or a combination of a fiber
aggregation and
a thermoplastic film is fed from a supply roll 1 onto the surface of a first
forming
drum 18 about which a forming structure 15 continuously rotates at
substantially
the same speed as the incoming web. The forming drum 18 preferably includes an
internally located vacuum chamber 20 and an energy source 21 such as a radiant
energy source which is preferably stationary relative to the moving forming
structure 15. The forming drum 18 may further include a reflector 23. An air
jet
means 22 is also provided adjacent the outside surface of the forming
structure 15
opposite the vacuum chamber 20.
Forming structure 15, a greatly enlarged fragmentary segment of which is
illustrated in FtG. 2, includes a multiplicity of relatively small apertures
16 across all
or any desired portion of its surface. For disposable absorbent article
topsheet
applications these apertures typically range in site between about 0.05 mm and
about 0.5 mm in diameter. Their spacing may be in a regular pattern or it may
vary
randomly, as desired, in the resultant plastic ftfm 10. Methods for
constructing
suitable three-dimensional tubular forming members of this general type are
disclosed in commonly assigned U.S. Pat. No. 4,503,256 issued to Radel et at.
On
Apr. 2, 1985 and commonly assigned U.S. Pat. No. 4,509,908 issued to Multane,
Jr. on Apr. 9, 1985.
The apertures 16 in the forming structure 15 may be of any desired shape or
cross-section when the forming structure is fabricated utilizing the laminar
construction techniques generally disclosed in the aforementioned commonly
assigned patents. Attematively, the tubular shaped forming structure 15 may be
comprised of non-laminar construction and the desired pattern of apertures 16
created by means of laser drilling or the like. It is also possible to use
belts or the
like comprised of pliable material and operating continuously about a pair of
rolls.
In the latter circumstance, it is generally desirable to provide suitable
support
beneath the pliable belt while it is subjected to the fluid pressure
differential in order
to avoid distortion.
tt is preferable that the physics! characteristics of the incoming web be
substantially maintained in the regions of the web that overlay the area of
the
forming structure that are not aligned with the apertures 16. This is, at
least in part
achieved by ensuring that the outer surface of the forming structure 15 is not
. heated to the temperature above the melting temperature of the incoming web.
CA 02552621 1997-12-15
g
This may be achieved by coating the inside surface 15A of the forming
structure 15
with a reflective material 19 to reflect the radiant energy 21A generated by
the
energy source 21 as shown in FiG. 3. The aperture walls 16A may also be coated
with this reflective material. The reflective material 19 may, for example be
nickel
plating or any other coating that effectively adheres to the inside surface
15A while
substantially reflecting the type of energy being used as a source.
Alternately, the
inside surface 15A and/or the wall 16A may be laminated using a reflective
material. it is preferable to select appropriate reflective coatings based on
their
absorbency to the frequency spectrum of the energy source. To minimize
conductive heat transfer from the inside surface 15A to the outside surface
15B,
layers of the forming structure 15 can be constructed of low thermal
conductivity
materials such as ceramics or high service temperature plastics. A semi-
continuous layer internal to the forming structure 15 may be used to create
interior
voids further reducing thermal conduction to the outer surface 15B. Other
approaches to reduce conductive heat transfer to the web may include texturing
of
the outer surface of the forming structure 15B to minimize physical contact
with the
web. Additionally, the forming structure 15 may be precooled as it rotates in
order
to further reduce the peak temperature that the outer surface 15B reaches
during
the forming process. This may take the form of an air jet of cool air incident
on the
forming structure 15 immediately upstream of the location where the plastic
film 10
is introduced. Alternatively, an additional vacuum plenum may be added
internally
to the forming structure 15 in a similar location to the above example to draw
air
through the forming structure thus cooling it prior to introduction of the
plastic film
10.
The energy source 21 generates the radiant energy 21A and the radiant
energy source 21A melts at feast a part of the plastic web 10. The radiant
energy
21A reaches the part of the plastic film 10 which is supported on the surface
of the
forming structure 15 through the apertures 16 of the forming structure 15. The
radiant energy 21A heats a part of the plastic film 10 to a temperature above
its
melting temperature range such that a part of the plastic film 10 is in a
molten
andlor flowable state. The energy source 21 may take the form of a
substantially
targeted flux of electromagnetic radiation such as that provided by an infra-
red
radiant heater. This type of heater may be used to direct an electromagnetic
energy flux towards a targeted area on the inside surface 15A of the forming
structure 15. Radiant thermal heaters of this type are commercially available,
CA 02552621 1997-12-15
9
emitting infra-red radiation at a predetermined and preferred wavelength.
Further,
these heaters can be equipped with variously shaped parabolic reflectors. The
parabolic reflector serves to provide a concentrated parallel flux of radiant
energy
in a confined beam or, alternately, can target the energy flux at a
predetermined
focal point thus further intensifying the energy flux over this region. The
energy flux
incident on the plastic film 10 at the points co-incident with the apertures
16 must
be sufficient to melt the plastic film 10 such that it can be induced to
substantially
conform to the apertures 16 by the fluid pressure differential. Although the
above
is one preferred embodiment of the energy source, the source can take many
IO alternate forms. These may include lasers or other frequencies of
electromagnetic
radiation.
ft is desired that the temperature of the outside surface 15B be maintained
below the melting temperature of the plastic film 10 so as to maintain the
physical
structure of the incoming web in the areas not located above the apertures 16.
It is
therefore preferable that the energy flux be targeted on a limited arc or
region of
the inside surface 15A. This minimizes the opportunity for substantial thermal
conduction to the outside surface 15B, which would result in an undesirable
increase in temperature for this surface. The energy flux should be of
sufficient
intensity so as to melt the plastic film 10 through the apertures 16 while
permitting
the duration of the energy incident on the inside surface 15A to be minimized.
It is
known that the absorption co-effrcient of polymers varies as a function of the
frequency of the incident electromagnetic energy source. Therefore, the
frequency
of the energy source should typically be selected to maximize the energy
absorbed
by the plastic film 10. At the same time, the reflective coating 15A on the
inner
surface of the forming structure 15, should be selected such that the maximum
amount of energy incident on this surface 15A is reflected. Appropriate
selection
and balancing of these two design parameters contributes to a robust process.
A reflector 23 directs a part of the radiant energy 21A towards a desired
region on the inner surface 15A of the forming structure 15. The reflector 23
preferably has a parabolic shape with an opening 24 which faces the inside
surface
15A of the forming structure 15 and extends along the length of the energy
source
21. The reflector 23 may focus the radiant energy 21A onto a very narrow
region
on the inner surface 15A of the forming structure 15 in a circumferential
direction.
It may focus the radiant energy 21A into a predetermined area on the inner
surface
15A of the forming, structure 15. The reflector 23 may have any preferred
cross-
CA 02552621 1997-12-15
t t)
sectional prafife, such as a parabola. The reflector 23 is preferably made of
metal
coated with a highly emissive material such as nickel so as to reflect the
radiant
energy 21 A very effectively. The reflector 23 may for example, be made by
electroplating a pre-formed thin metal plate. Such reflectors are commercially
available from suppliers such as OGDEN Mfg. Co. (USA) and are often an
integral
component of a radiant heater.
A differential pressure is applied across the plastic film 10 between the air
jet
means 22 and inner chamber 20 and in the region along the circumference of the
forming structure 15 where the plastic flm 10 is Locally melted. The air jet
means
22 approximatety coincides with the beginning and the end of the inner chamber
20
and is located adjacent the outside surface 15B of the forming structure 15.
tn this
region, a substantially uniform fluid pressure differential is applied to the
plastic film
10. This may be applied by means of a positive pressure (high pressure) within
the
air jet means 22, a partial vacuum {low pressure) within the chamber 20 or a
combination of these two conditions. Thus, a substantial differential pressure
is
applied to the substantially planar web of the polymeric web 10 as it passes
across
the suction chamber. The high pressure air 22A which is generated by the air
jet
means 22 may be preheated to a temperature below the softening temperature of
the plastic film 10 to help to make more dimensionally stable micro-apertures
50.
Alternatively, the high pressure air 22A may be precooled to help further
maintain
the thermo-mechanical history given to the plastic film 10 which is not
located on
the apertures 16 of the fomzing structure 15. The high pressure air 22A may be
precooled to a temperature below the plastic film temperature before the
plastic film
10 is provided on the fomZing structure i 5.
As shown in FIG. 3, the forming structure i 5 rotates in the direction D with
the plastic film i 0. FiG. 3 shows four sequential apertures 16B, 16C, 16D and
16E
of the forming structure 15 as it rotates in the downstream direction D. At
the
aperture 16B at the upstream end, the energy source 21 gives the radiant
energy
21A to the plastic ftIm 10 from the inside of the forming structure 15 through
the
aperture 16B to soften the plastic film 10. Since there is an inward pressure
differential 22A applied in this region, the softened plastic film 10 is
deformed
slightly inward. While the forming structure 15 rotates toward the position
ofi the
aperture 16C shown in FIG. 3, the plastic fi#m 10 receives more radiant energy
21A
and the softened plastic film 10 deforms further into the aperture 16. As the
fom~ing structure 15 further rotates, the softened plastic film 10 locally
melts,
CA 02552621 1997-12-15
rupturing and debossing as shown at the position of the aperture 16D matting
the
aperture 50 in the plastic film 10. While the forming structure 15 continues
to rotate
from the position of the aperture 16D to 16E, the plastic film 10 receives
more
radiant energy 21A and high air pressure 22A flowing through the newly formed
film aperture 50. This causes the plastic film 10 to further conform to the
shape of
the aperture 16 of the forming structure 15 and the aperture 50 to become more
stable to form a ftne-scale, three-dimensional, volcano-tike micro-aperture
50.
During the process, regions of the polymeric film 10 not located above the
apertures i6 of the forming structure 15 are not heated beyond the melting
~ 0 temperature range of the resin. Therefore, the thermo-mechanical history
previously existing in the film is maintained in these regions.
After the plastic film 10 is apertured, the finely apertured plastic film 10
is
removed from the surface of the first fine-scale forming structure 15 about an
idler
roil 39 in the condition ittustrated in greatly enlarged form in the inset of
FIG. 4.
Because the plastic film 10 is molten only at a portion over the apertures 16
of the
forming structure 15 during the forming process, it can be more easily removed
from the forming structure 15 requiring only a shorter time period for cooling
the
plastic film 10. This has the further advantage of permitting increased
processing
speeds and web stability and/or a broader range of plastic webs that would
otherwise tack stability in atternate processes. This further increases the
flexibility
to obtain finished webs of greater wearer acceptance by using, for example,
incoming webs of lower basis weight or tower density resins to increase
flexibility
and thus softness of the micro-apertures.
Because of the presence of the fine-scale, three-dimensional, volcano-like
~5 micro-apertures 50 and ftne cusps 53, the first surface 57 which contacted
forming
structure 15 exhibits a much softer tactile impression than the second surface
54
which was contacted by the high pressure air 22A. Accordingly, the first
surface 57
of the plastic frlm 10 is generally preferred as the wearer contacting surface
over
the second surface 54.
As will be appreciated by those skilled in the art, the degree of conformance
of the plastic web 10 to the surface of the forming structure 15 and the size
of the
apertures created therein will be in#luenced by factors such as the
temperature of
the film 10 at the time it is subjected to the high pressure air 22A, the
pressure at
which the air jet means 22 is applied to the surface of the film, the
temperature of
the air, the mass flux of the air, etc. More importantly, the degree of
conformance
CA 02552621 1997-12-15
1~
and the size of the apertures may be influenced by the type of radiant energy,
intensity of radiant energy, flux of radiant energy, etc. in general, when the
fluid
pressure differential is applied to the web, the lower the viscosity of the
plastic film
being locally heated, the greater will be the degree of confom~ance and
5 aperturing. In addition, the less the temperature of the plastic film 10 in
the regions
not located above the apertures 16 is altered from its original state, the
less the
thermo-mechanical history is altered.
After completion of the first phase of the web forming process disclosed in
FIG. 1, the finely apertured plastic film 10 may be fed to the second phase of
the
10 forming process for macroscopic expansion or to a rewind station for
temporary
storage. In the latter circumstance, application of the second phase of the
process
may be deferred until a later date, perhaps at .a different location.
Alternatively, the
finely apertured plastic t~lm 10 may be utilized without further processing in
an end
product wherein fluid permeability and a soft tactile impression are
particularly
1 S desirable, but a macroscopically expanded, three-dimensions! cross-section
is not
essential.
Because of the desirable tactile impression imparted to the first surface 57
of
the plastic film 10 in the embodiment illustrated in F1G. 1, the plastic film
10 which
is to undergo macroscopic, three-dimensional expansion is preferably fed onto
a
second forming structure 35 which operates about forming drum 38 so that its
opposite second surface 54 is placed in contact with the second forming
structure
35. The forming drum 38, which may be generally similar to the forming drum 18
includes a stationary vacuum chamber 40 located adjacent the interior of the
forming structure 35 and an energy source 41, both of which may be generally
similar structure to the chamber 20 and the energy source 21 respectively. The
forming drum 38 may further include a reflector 43, which also may be
generally
similar to the reflector 23. An air jet means 42 is also provided adjacent the
outside
surface of the forming structure 35 opposite the vacuum chamber 40. Because
the
macroscopic cross-section of forming structure 35 is considerably different
than
that of forming structure 15, the pressure and mass flux rates of the air jet
means
42 are preferably adjusted independently of the pressure and mass flux rates
used
for the air jet means 22. The radiant energy generated by the energy source 41
is
also preferably adjusted independently of the radiant energy of the radiant
energy
source 21.
CA 02552621 1997-12-15
I _',
The macroscopic cross-section of forming structure 35 is visible in the
greatly enlarged fragmentary perspective of FIG 5. The forming structure 35
exhibits a substantiatty continuous three-dimensional pattern including a
multiplicity
of apertures 36. Although not limited to these dimensions, for disposable
absorbent article topsheet applications, these macro-apertures typically range
in
size from 0.3 to 3.Omm and are typically at least 4 times as big as the fine-
scale
small apertures 16 of the forming structure 15. The forming structure 35 has
the
outside surface 35B and the inside surface 35A. The forming structure 35 may
comprise a plurality of layers. In the embodiment shown in FIG. 5, the forming
structure 35 includes three layers L1, L2 and L3. Each of the layers may have
a
different thermal conductivity from layer to layer in order to minimize heat
transfer
to the plastic film 10 supported on the outer surfaces 35B. This is so that
the outer
surface of the forming structure 35B is not heated above the melting
temperature
range of the plastic film 10. Alternatively, the inside surface 35A of the
forming
structure 35 may be coated with a reflective material in order to reflect the
radiant
energy generated by the energy source 41. The wall of the apertures 36A also
may be coated by the reflective material or laminated with the reflective
material.
As shown in FtG. 6, the wail of the apertures 36A may be generally at a right
angle
to the outside surface 35B and the inside surface 35A. Alternatively, the wait
36A
of the apertures 36 may be angled relative to the inner surface such that the
size of
the apertures 36 becomes smatter from the outside surface 35B towards the
inside
surface 35A as shown in FIG. 7. Alternatively, the wall 36A of the apertures
36
may be angled relative to the inner surface such that the size of the
apertures 36
becomes larger from the outside surface 35B towards the inside surface 35A as
shown in FIG. 8.
As is more readily apparent from the inset of FtG. 6, the plastic film 10
containing the fine-scale, volcano-like micro-apertures 50 is fed onto the
outside
surface 35B of the forming structure 35 such that its second surface 54
contacts
the forming structure 35, while its first surface 57 is oriented toward the
air jet
means 42. Accordingly, the small cusps 53 of the micro-apertures 50 are
oriented
toward the air jet means 42.
The regions of the plastic flm 10 with the fne-scale, volcano-tike micro-
apertures 50, which are located above the apertures 36 of the forming
structure 35,
receive the radiant energy 41 A generated by the energy source 41. Thereby,
the
3~ regions of the pias~ic film 10 receiving the radiant energy 41A are locally
heated
CA 02552621 1997-12-15
l
above the film softening temperature. The region of the plastic film 10
locally
heated is also exposed to high pressure air 42A and deforms toward the inside
of
the forming structure 35. As the forming structure 35 rotates, the region of
the
plastic film 10 receives more radiant energy 41A and high pressure air 42A.
The
region of the plastic film 10 further deforms into the aperture 36 and finally
ruptures
to form the macro-apertures 60 surrounded by a wall 61 on the plastic film 10.
As
the forming structure 35 rotates further, the region of the plastic film 10
further
melts, and the plastic film 10 substantialty conforms to the shape of the
apertures
36. Since the plastic film 10 is melted and conforms to the shape of the
apertures
36, the shape of the macro-apertures 60 corresponding to the apertures 36
become substantially regular and thus the plastic film 10 with the
dimensionally
stable macro-apertures 60 becomes substantially dimensionally stable and
resilient. During this process, because a region of the wall 61 of the plastic
film 10
melts, the fine scale, volcano-like micro-apertures 50 on the wall 61 tend to
IS disappear such that the wall 61 of the plastic film 10 conforms to the
apertures 36
of the forming structure 35 and is substantially without micro-apertures. On
the
other hand, the region of the plastic film 10 which contacts the outside
surface 35B
of the forming structure 35 does not receive the radiant energy 41A, the
forming
structure 35 also being constructed so as to minimize heat transfer to these
portions of the plastic film 10. The high pressure air 42A also does not
change the
surface structure of the plastic film 10. Therefore, the fine-scale volcano-
like micro-
apertures 50 which are oriented toward the air jet means 42 do not disappear
and
remain on the surface of the plastic film 10.
After completion of the second phase the macroscopically expanded, three
dimensional, apertured plastic web 10 is removed from the forming structure 35
and wrapped about idler rolls 110 and 120 from where it may be fed either to a
rewinding station for temporary storage or directly to converting lines where
it may
be applied to making finished product structures, such as disposable absorbent
articles.
!n the above mufti-phase forming process, the first phase may comprise any
conventional process which forms apertures on incoming web, such as a process
using a liquid pressure differential across the web or a process using an air
pressure differential across the web while the entire web is in the molten
state.
The first phase may be directly coupled to the second phase to form an
integral
CA 02552621 1997-12-15
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mufti-phase process, or may be conducted separately and a roll ofi material
unwound into the second phase described above for final forming.
FIGS. 9 and 10 show alternative embodiment of a forming process of the
present invention which may be used for either or both of the first or second
phases in the above two-phase forming process. The alternative shown in FIGS.
9
and 10 is suitable especially for the second process. in the embodiment shown
in
FIG. 9, the plastic film 10 may be fed onto the surface of a forming drum 7 00
about
which a forming structure 101 continuously rotates at substantially the same
speed
as the incoming web 10. The forming drum 100, which may be generally similar
to
the forming drum 38, may include a stationary vacuum chamber 102, which may be
generally similar structure to the chamber 40, located adjacent the interior
of the
forming structure 101. An energy source 7 03 with a reflector 104 may be
disposed
outside the forming structure 101. The energy source 103 may be covered by a
shield screen 705 with a pattern of apertures and air jet means 106 may be
provided adjacent the outside surface of the forming structure 101.
The forming structure 101 has a pattern of apertures 110 which may be
generally similar to the pattern of the apertures 36 on the forming structure
35. The
shield screen 105 which has a cylindrical shape rotates at substantially the
same
speed as the forming structure 101. The shield screen 105 may have a pattern
of
apertures 111 on the surface generally identical to the pattern of the
apertures 110
on the forming structure 7 01. As the shield screen 105 rotates with the
forming
structure 101, each of the apertures 1 t 1 on the shield screen 105 and each
of the
apertures 110 on the forming structure 101 correspond to each other as shown
in
FIG. 10. The shield screen 105 comprises a material which reflects at least a
part
of the radiant energy 103A generated by the energy source 103. Alternatively,
at
least the inside 105A of the shield screen 105 may be coated by the
ret'lective
material or laminated with the reflective material. The energy source 103
provides
radiant energy 103A to the region of the plastic film 10 through the aperture
111
from the inside of the shield screen 105 such that the region of the plastic
film 10 is
locally heated. As the region of the plastic film 10 receives more radiant
energy
103A, the region of the plastic film 10 softens and melts. The air jet means
106
applies high pressure air 106A to the plastic fim 10 and/or the vacuum chamber
102 draws air to pul! the softened region of the plastic film 10. Thereby, a
fluid
pressure differential is provided across the plastic f~im 10 by a pressure
gradient
from the air jet means 106 toward the vacuum chamber 102. While the energy
CA 02552621 1997-12-15
16
source 103 locally heats and melts the region of the plastic flm 10 which
corresponds to the apertures 111 of the shield screen 105, the shield screen
105
prevents the region of the plastic film 10, which is shielded from the radiant
energy
103A, from being substantially heated, thereby retaining its original form.
After
completion of the process, the plastic web 10 is removed from the forming
structure
107 and may be forwarded down stream. The high pressure air 106 may be pre-
heated or pre-cooled in order to further stabilize the process as previously
described.
FIGS. 11 - 13 show the fully processed plastic film 10. The plastic film 10
shown in FIGS. 11 - 13 may be used for a body-facing material for an absorbent
article. As will be apparent from the enlarged fragmentary perspective view of
the
plastic film 10 shown in FIG. 11, the fully processed plastic film 10 exhibits
dimensionally stable, three-dimensional macro-apertures 60 and fine-scale,
volcano-tike micro-apertures 50. The plastic film 10 has a first surface 57
and a
IS second surface 54. The plastic film 10 has a land area 56 which faces the
wearer's
body when the plastic film 10 is used as a topsheet of an absorbent article.
The
plastic film 10 also has volcano-like aberrations 58.
The land area 56 has a pattern of frne scale, volcano-like surface micro
apertures 50. The fine scale, voicano-tike micro-apertures 50 comprise the
?0 volcano-like aberrations 58 and the micro-opening 62 at the top of the
aberrations
58. The size of the micro-apertures 50 on the land area 56 may be defined by
either of the average height of the aberrations 58 or the average area of the
micro-
openings 62 or by both of these. The micro-openings 62 on the land area 56
have
an average aperture area which typically may be from 0.002 mm2 and 0.2 mm2.
25 The aberrations 58 on the land area 56 protrude from the land area 56
beyond the
first surface 57 of the land area 56. The aberrations 58 have an average
height
which typically may be from 0.05 mm and 0.5 mm. Each of the fine-scale,
voicano-
like micro-apertures 50 actually forms a small capillary network resembling a
tiny
volcano, the outermost edges of which end in silky and soft feeling cusps 53.
Due
30 to the tactile impression imparted to the plastic film 7 0 by cusps 53, the
land area
56 of the plastic fili~r~ 10 is normally perceived as well suited for
sustained contact
with the skin. As explained in the above process description, the fine-scale,
volcano-tike micro-apertures 50 are maintained on the first surface 57
generally
without changing its shape.
CA 02552621 1997-12-15
17
The macro-apertures 60 are defined by the wall 61, an opening 60A located
on the first surface 57 and the apex opening 60B. The size of the macro-
apertures
60 is generally bigger than the size of the fine-scale, volcano-like micro-
apertures
50 located on the (and area 56. Preferably, the size of the macro-apertures 60
may
be at least 4 times as big as the size of the micro-apertures 50. The wall 61
extends and protrudes beyond the second surface 54 of the tand area 56. The
wall
61 may have the fine-scale, volcano-like micro-apertures 50 on its surface.
The
fine-scale, volcano-like micro-apertures 50 on the wall 61 may also comprise
the
volcano-like aberrations 58 and the micro-opening 62 at the top of the
aberrations
1 Q 58. The size of the micro-apertures 50 on the wall 61 may be defined by
either of
the average height of the aberrations 58 or the average area of the micro-
openings
62 or by both of these. The size of micro-apertures 50 on the watt 61 is
generally
smaller than that of the micro-apertures on the land area 56. As shown in
FIGS. 12
and 13, both the height of the aberrations 58 and the aperture area of the
micro-
openings 62 are generally decreasing toward the apex opening 60B because the
wall 61 of the plastic film 10 is heated and melted during the process as
described
above. While the micro-apertures 50 on the wail 61 shown in FIGS. 12 and 13
loses both the height and the area of the micro-apertures 50, they may
maintain
either of these. The micro-apertures 50 on the wail 61 may lose only its
height of
the aberrations 58. Aitematively, the micro-apertures 50 on the watt 61 may
lose
only its aperture area of the micro-openings 62. Consequently, the wail 61
becomes dimensionally stable and becomes stiffer than the land area 56 which
has
many micro-apertures 50 thereon. The wall 61 also becomes more resilient to be
capable of withstanding and rebounding from a pressure which is given by the
wearer when the plastic film 90 is used for an absorbent article topsheet.
Further,
losing the height of the volcano-like aberrations 58 and the area of the micro-
openings 62, the wall 61 may have no micro-apertures at the region adjacent
the
apex opening 60B, or most or all region of the wall 61. Therefore, the number
of
the micro-apertures 50 per a unit area may be less on the wall 61 than the
land
area 56. In the embodiment shown in FIG. 13, although there is still
aberrations
adjacent the apex opening 60B, the aberrations 58A have lost the micro-opening
on the top of the aberrations.
When the plastic film 10 is used for the absorbent article topsheet, the
plastic frlm 10 shown in FIGS. 11 - 13 gives softer tactile impression to the
wearer
because the plastic fiirn 10 has the fine-scale, volcano-like micro-apertures
50 with
CA 02552621 1997-12-15
18
the cusps 53 on the land area 56. The plastic film 10 also shows good fluid
acpuisition because the macro-apertures 60 have a dimensionally stable shape
of
apertures which makes fluid penetrate easily. In addition, the plastic ftlm 10
shows
good rewet performance because the wall 61 of the macro-apertures has
resiliency
so that the wearer's skin is maintained at a distance away from an absorbent
core
which absorbs body fluid by interposing the resilient plastic flm 10
therebetween.
FIGS. 14 - 15 show alternative embodiment of the fully processed web 150
comprising fiber aggregation 152. The fibrous web 150 can be made from a fiber
aggregation 152 which is formed as a nonwoven. The nonwoven may be
processed only by the second process shown in FIG. 1 since the fibrous web 150
may not have micro-apertures on the land area. However, if desired, the
nonwoven may be processed by both the first process and the second process
shown in FIG. 1. Alternatively, a nonwoven may be processed by the process
shown in FIG. 9 in order to get the processed ftbrous web 150.
The fully processed fibrous web 150 exhibits dimensionally stable, three-
dimensional macro-apertures 154. The fbrous web 150 may be used for a body-
facing material for an absorbent article. The fibrous web 150 has a fast
surface
156 and a second surface 158. The fibrous web 150 has a land area 160 which
upwardly faces the wearer's body when the ftbrous web 150 is used as a
topsheet
of an absorbent article and a wall 162 which protrudes beyond the second
surface
158 of the land area 160. The macro-apertures 154 are defined by the wail 162,
an
opening 164 on the first surface surrounded by the wall 162 and an apex
opening
166.
The fibrous web 150 comprises ftber aggregation 152 which may include
one fibrous layer or more layers. Each Layer may comprise any type of
thermoplastic fibers using such as polyethylene, polypropylene, polyester or
any
combination thereof. The thermoplastic fibers may be bi-component fibers using
the above materials. The thermoplastic fbers may be of varying the cross-
section.
When the ftber aggregation 152 includes at least two layers having the ftrst
layer
which is disposed adjacent the ftrst surface 156 and the second layer which is
disposed adjacent the second surface 158, each layer may comprise different
types of thermoplastic ftbers from each other. Further each layer may comprise
different types of forming processes from each other, such as spunbond, carded
or
meltbiown layers. Alternatively, they may comprise the same type of fibers.
Optionally, the first layer disposed adjacent the first surtace 156 may
comprise less
CA 02552621 1997-12-15
1~
hydrophilic fibers than the secand layer disposed adjacent the second surface
158
whereby the first layer becomes less hydrophilic than the second layer.
The land area 160 of the fibrous web 150 comprises fiber aggregation 152
and exhibits capillary network therein. The land area 160 of the fbrous web
150
gives soft tactile impression to the wearer and a soft feeling when the Eand
area
160 touches the wearer's body.
A portion of the wall 162 also comprises the fiber aggregation 152. At
least a portion of the fibers forming the wall 162 are melted and bonded to
each
other by, e.g., the above process whereby the fiber aggregation 152 on the
wall
IO 162 is densified at least at a portion. Preferably the fiber aggregation
152 may
be melted and densified at least at a portion adjacent to the apex opening
166.
Thereby the ftber aggregation 152 on the watt 162 may have a positive fiber
density gradient from the opening 164 toward the apex opening 166 as
schematically shown in FIGS. 14 and 15. Alternatively, most or alt of the
fiber
IS aggregation 152 of the wall i62 may be melted and densified. The melted and
densified fiber aggregation 152 becomes stiffer than the other portion of the
fiber
aggregation 152, such as the fiber aggregation 152 on the land area 160. The
stiff watt also has more resiliency. Therefore, the wall 162 is capable of
withstanding and/or rebounding from pressure given by the wearer when the
20 fibrous web 150 is used as a topsheet of an absorbent article.
When the fibrous web 150 is used for the absorbent article topsheet, the
fibrous web 150 shown in FIGS. 14 and 15 gives soft tactile impression to the
wearer because the frbrous web 10 comprises the fiber aggregation 152 on the
Land area 760. The fibrous web 150 atso shows good fluid acquisition because
?5 the macro-apertures 154 has a dimensionally stable shape of apertures which
makes r'iuid penetrate easily. In addition, the fibrous web 150 shows good
rewet
performance because the wall 162 of the macro-apertures has resiliency so that
the wearer's skin is maintained at a distance away from an absorbent core
which
absorbs body fluid by interposing the resilient fibrous web 150 therebetween.
30 FIG. 16 shows a further alternative embodiment of the fully processed
composite web 180 comprising fiber aggregation 182 and a plastic film 183. The
composite web 180 can be made from a fiber aggregation 182 which is formed as
a nonwoven and a plastic f im 183. The nonwoven and the plastic film may be
processed only by the second process shown in FIG. 1 since the composite web
35 180 may not have micro-apertures on the Land area. However, if desired, a
CA 02552621 1997-12-15
U
nonwoven and a plastic film which form the composite web '180 may be processed
by both the fist process and the second process shown in F1G. 1.
Alternatively, a
nonwoven and a plastic film may be processed by the process shown in FIG. 9 in
order to get the composite web 180.
S The fully processed composite web 180 exhibits dimensionally stable, three-
dimensional macro-apertures 184. The composite web 180 may be used for a
body-facing material for an absorbent article. The composite web 180 has a
first
surface 186 and a second surface 188. The composite web 180 has a land area
. 190 which upwardly faces the wearer's body when the composite web 180 is
used
as a topsheet of an absorbent article and a wall 192 which protrudes beyond
the
second surface 188 of the land area 190. The macro-apertures 184 are defined
by
the wall 192, an opening 194 on the first surface surrounded by the wall and
an
apex opening 196.
The composite web 180 may include fiber aggregation 182 which may
t 5 have one fibrous layer or more layers. Each layer may comprise
thermoplastic
fibers which may be the same materials for the fiber aggregation 162 above.
Further, the composite web 180 may include at least one thermoplastic film
layer
183 which may comprise various materials, such as polyethylene, low density
polyethylene, linear low density polyethylene, or polypropylene. Preferably,
the
materials for the fiber aggregation 182 and the thermoplastic film may
comprise
the chemically same or chemically similar type of materials such that the
fiber
aggregation 182 and the thermoptastic film 183 can be bonded when they are
melted to each other. Preferably, the fcber aggregation 182 is disposed on the
first surface 186 of the composite web '180 and the plastic fitm 183 is
disposed on
the second surtace 188. The fiber aggregation 182 may be less hydrophilic than
the plastic fslm 183 so that the composite web 180 has posi ive hydrophilici y
gradient from the fiber aggregation 182 towards the plastic film 183.
The land area 190 of the composite web 180 comprises the fiber
aggregation 182 and the plastic film 183, and exhibits capillary network
therein.
The fiber aggregation 182 on the first surface 186 of the land area 190 can be
directly seen by the wearer, therefore gives soft tactile impression to
wearer.
The plastic film 183 on the second surface 188 of the land area 190 prevents
body fluid, which is held in an absorbent core of an absorbent article, from
leaking out toward the wearer's skin through the land area 190. Further, the
CA 02552621 1997-12-15
~1
plastic film 183 also serves to mask the color of the body fluid held in the
absorbent core.
A portion of the wall 192 also comprises the fiber aggregation 182 and the
plastic film 183. At least a portion of the fiber aggregation 182 on the wall
192 is
S melted and bonded to each other by, e.g., the above process whereby the
fiber
aggregation 182 on the wall 162 is densified at least at a portion. Preferably
the
ftber aggregation 182 may be melted and densified at least at a portion
adjacent
the apex opening 196. Thereby the fiber aggregation 182 on the wail 192 may
have a positive fiber density gradient from the opening 194 toward the apex
opening 196 as schematically shown in FIG. 16. Alternativety, most or ail of
the
fiber aggregation 182 of the wall 192 may be melted and densified. Preferably,
at least a portion of the fiber aggregation 182 on the watt 192 is melted and
bonded to the plastic film 183. The plastic frlm 183 also may be melted and
bonded with the fibers of the fiber aggregation 182. As schematically shown in
1 S FIG. 16, the fiber aggregation 182 and the plastic film 183 are melted to
each
other at least adjacent the apex opening 196. If desired, the fiber
aggregation
182 and the plastic film 183 may be melted and bonded to each other on most or
all portion of the watt 192. The melted and densifieed fiber aggregation 152
and
the plastic film 183 which are bonded together become stiffer than the other
portion of the fiber aggregation 152 and the plastic film 183, such as on the
land
area 190. The stiff wall also has more resiliency. Therefore, the wall 192 is
capable of withstanding andJor rebounding from pressure given by the wearer
when the fibrous web 180 is used as a topsheet of an absorbent article.
When the composite web 180 is used for the absorbent article topsheet,
the composite web 180 shown in FIG. 16 gives a soft impression to the wearer
because of the fiber aggregation 182 on the land area 790. The composite web
180 also shows good fluid acquisition because the macro-apertures 184 have a
dimensionally stable shape of apertures which makes fluid penetrate easily. In
addition, the composite web 180 shows good rewet performance because the
wail 192 of the macro-apertures has resiliency so that the wearer's skin is
maintained at a distance away from an absorbent core which absorbs body fluid
by interposing the resilient composite web 180 therebetween. The composite
web 180 also helps mask the color of body fluid which is held in the absorbent
core.
CA 02552621 1997-12-15
While particular embodiments of the present invention have been illustrated
and described, it woufd be obvious to those skilled in the art that various
other
changes and modifications can be made without departing from the spirit and
scope of the invention. 1t is therefore intended to cover in the appended
claims aff
S such changes and modifications that are within the scope of this invention.
