Note: Descriptions are shown in the official language in which they were submitted.
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1
METHODS OF BONDING MATERIALS, ESPECIALLY MATERIALS
USED IN ABSORBENT ARTICLES
FIELD OF THE IIWENT10N
The present invention relates generally to methods of bonding materials for
use in
absorbent articles, although the techniques described herein may be used to
bond
materials used in other types of articles. In preferred embodiments, the
present invention
relates to methods which are used in the manufacture of absorbent articles
such as
sanitary napkins, pantiliners, tampons, absorbent interlabial devices,
diapers,
incontinence devices, and the like.
BACKGROUND OF THE 1IWENTION
Absorbent articles such as sanitary napkins, pantiliners, tampons, absorbent
interlabial devices, disposable diapers, incontinence products, and bandages
are designed
to absorb and retain liquid and other discharges from the human body and to
prevent
body and clothing soiling.
In the manufacture of absorbent articles, it is generally necessary to bond
the
components that will form the absorbent article together in order to form the
finished
product. Typical methods for bonding such material include adhesives, heat
and/or
pressure, and uitrasonics.
Some materials, however, cannot be bonded by these typical bonding techniques
because of their structural integrity or composition. One such type of
material are
absorbent foam materials made from high internal phase emulsions (or "HIPS"
foams)
such as those described in U.S. Patent 5,260,345 issued to DesMarais, et al.
on
November 9, 1993; U.S. Patent 5,268,224 issued to DesMarais, et al. on
December 7,
1993; and U.S. Patent 5,387,207 issued to Dyer, et al. on February 7, 1995.
Such
materials typically have a low tensile strength and/or low structural
integrity. It is
difficult to bond to such materials using adhesives because the structural
integrity is often
not as strong as the adhesive bond. As a result, only the portions of these
materials that
are in direct contact with the adhesive will remain bonded to other materials.
The
remainder of the material will readily separate from the material to which it
is bonded.
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Such materials cannot be bonded using heat bonds because such foams are
thermoset
polymers. Once they are formed, they cannot be remelted. Instead, when heat is
applied
to such foam materials, they will char rather than melt and flow, which is
needed for heat
bonding. Such foam material likewise cannot be pressure bonded since the
thermoset
foam material has no ability to flow and be fused under pressure.
U.S. Patent 4,473,611 entitled "Porous Polymeric Material Containing a
Reinforcing and Heat-Sealable Material" issued to Haq on September 25, 1984
describes
one prior effort to bond materials to a highly porous polymeric material
prepared by
polymerization of a high-internal phase emulsion. The Haq reference discloses
providing
such a material with the ability to form heat seals by incorporating
thermoplastic fibrous,
particulate, or foraminous material therein. An article such as a wipe is
formed by
sandwiching the modified porous polymeric material between two heat sealable
substrates, and heat sealing the first and second substrates to the heat-
sealable reinforcing
material in the intermediate highly porous polymeric material. The method of
making
the porous polymeric material described in the Haq patent, however, requires
the addition
of thermoplastic material. This complicates the process of making the porous
polymeric
material.
Other types of materials used in the manufacture of absorbent articles
frequently
comprise thermoplastic materials. U.S. Patent 4,854,984 entitled "Dynamic
Mechanical
Bonding Method and Apparatus" issued to Ball, et al. on August 8, 1989
discloses a
method and apparatus for dynamically mechanically bonding together a plurality
of
laminae by feeding the laminae through a pressure biased nip between a pair of
rolls, at
least one of which has a relief pattern thereon. The method described in the
Ball, et al.
patent has been used with great commercial success. Still, the search for
improved
methods of bonding materials has continued.
Thus, a need exists for improved methods of bonding materials, especially
those
used in absorbent articles. For example, a need exists for an improved method
of
bonding materials for use in absorbent articles that cannot be bonded by known
bonding
techniques, and in particular for a method that does not require the addition
of
thermoplastic materials to the material in issue in order to bond other
materials thereto.
A need also exists for a method of bonding through relatively thick materials
during the
manufacture of absorbent articles. In addition, a need also exists for methods
of bonding
which are able to create a virtually unlimited number of bonding patterns in
the materials
to be bonded.
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SUMMARY OF THE INVENTION
The present invention is directed generally to methods of bonding materials
for
use in absorbent articles, although the techniques described herein may also
be used to
bond materials used in other types of articles. All of such uses of the
methods described
herein may be considered to be within the scope of the present invention. In
preferred
embodiments, the present invention relates to such a method which is used in
the
manufacture of absorbent articles such as sanitary napkins, pantiliners,
tampons,
absorbent interlabial devices, diapers, incontinence devices, and the like.
There are numerous aspects of the present invention. In one aspect, the
present
invention relates to a method of bonding through incompatible materials during
the
process of making a composite structure comprising several materials. As used
herein,
the term "incompatible materials" refers to materials to which it is difficult
to bond other
materials to using conventional bonding techniques. In another aspect, the
present
invention relates to improvements that allow the method to be used to bond
through
relatively thick materials (e.g., materials having a thickness of greater than
or equal to
about 2, 3, or 4 mm). In another aspect, the present invention relates to
methods of
bonding which are able to create a virtually unlimited number of bonding
patterns in the
materials to be bonded. In still another aspect, the present invention relates
to methods
of bonding that utilize a compression step to improve bond formation. In still
another
aspect, the present invention relates to methods of bonding that utilize a
step of slitting a
material through which the bonds are made.
It should be understood that the embodiments described in the specification
are
expressed in terms of preferred embodiments so that the length of this
specification is not
excessive. It should be understood that the present invention is not intended
to be limited
to such embodiments. It should also be understood that the aspects of the
methods
described herein can be combined in a single process, or they can be used
individually, or
in any desired combination. It should fiuther be understood that the inventors
consider
all such uses or combinations of these aspects to potentially comprise
separate patentable
inventions, and that the scope of such inventions is intended to be as broad
as the prior
art permits. The scope of such inventions is intended to be limited by the
claims only,
and not by the preferred embodiments described herein.
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The aspect of the method of bonding through incompatible materials
preferably comprises the steps o~
(a) providing a material that has at least a degree of incompatibility with
bonding using conventional techniques, the incompatible material
having a first bondability, a first surface, and a second surface;
(b) providing at least one other material having bondability that is higher
than the first bondability;
(c) covering at least a portion of the first and second surfaces of the
incompatible material with at least one material having a bondability
that is higher than the first bondability; and
(d) bonding the material having the higher bondability that covers at least
a portion of the first surface of the incompatible material to the
material having the higher bondability that covers at least a portion of
the second surface of the incompatible material using bonds that
penetrate the incompatible material.
According to an aspect of the present invention, there is provided a method of
bonding materials during the process of making an absorbent article, the
method
comprising the steps o~
(a) providing a first material, the first material having a first bondability,
a
first surface, and a second surface;
(b) providing at least one other material having a bondability that is higher
than the first bondability;
(c) covering at least a portion of the first and second surfaces of the first
material with the at least one material having a bondability that is
higher than the first bondability; and
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4a
(d) bonding the material having a higher bondability that covers at least a
portion of the first surface of the first material to the material having a
higher bondability that covers at least a portion of the second surface
of the first material, wherein the higher bondability materials are in
contact with each other and the first material is displaced
therebetween.
According to another aspect of the present invention, there is provided a
composite structure comprising an absorbent material that has at least a
degree of
incompatibility with conventional bonding processes, the incompatible material
having a first bondability and first and second surfaces that are at least
partially
covered by at least one material having a higher bondability than the first
bondability,
the composite structure comprising one or more autogenous bonds that bond a
portion
of the covering material that at least partially covers the first surface of
the
incompatible material to a portion of the covering material that at least
partially
covers the second surface of the incompatible material, the composite
structure having
a quilted appearance in the area of the bonds.
According to a further aspect of the present invention, there is provided a
method of bonding through an absorbent material that has at least a degree of
incompatibility with conventional bonding processes during the process of
making an
absorbent article, the method comprising the steps of:
(a) providing an absorbent material that has at least a degree of
incompatibility with conventional bonding processes, the absorbent
material having a first bondability, a first surface, and an opposed
second surface;
(b) providing at least one other material having a bondability that is higher
than the first bondability;
(c) covering at least a portion of the first and second surfaces of the
absorbent material with at least one material having a bondability that
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4b
is higher than first the bondability; and
(d) applying a localized force to the covered absorbent material to displace
the absorbent material at the place where the force was applied, the
force causing the materials having a bondability that is higher than the
first bondability which lie on opposite surfaces of the absorbent
material to come into contact with each other where the absorbent
material was displaced; and
(e) bonding the materials having the higher bondability together where the
absorbent material was displaced.
In this aspect of the methods described herein, the incompatible material
preferably comprises an absorbent material. In one particularly preferred
embodiment,
the incompatible material comprises a thermoset polymeric absorbent foam
material.
The material having the higher bondability can comprise a number of suitable
materials, including, but not limited to: one or more webs of material, a
layer of glue,
or a silicone coating. In one particularly preferred embodiment in which the
incompatible material comprises a thermoset polymeric absorbent foam material,
the
material having the higher bondability comprises a nonwoven web.
The present invention also provides a method of shaping materials,
particularly compressible materials, such as absorbent materials, for use in
absorbent
articles such as sanitary napkins, pantiliners, tampons, absorbent interlabial
devices,
diapers, incontinence devices, wipes, and the like. In this aspect of the
present
invention, a bond pattern is impressed into the compressible incompatible
material to
isolate a portion of the incompatible material from the remainder of the
incompatible
material and form the isolated portion into a distinct shape. The shaping
aspect of the
method described herein may involve one or more folding steps. Numerous other
uses
of the methods described herein will also become apparent.
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BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the subject matter which is regarded as forming the
present invention,
it is believed that the invention will be better understood from the following
description
which is taken in conjunction with the accompanying drawings in which:
Fig. 1 is a perspective view of a composite web of material comprising an
incompatible absorbent foam material that will be bonded and shaped into an
absorbent
tube for a sanitary napkin using the method of the present invention.
Fig. 2 is a perspective view of an apparatus used to form the absorbent
material in
the composite web shown in Fig. 1 into particulate material in an optional,
but preferred
step of making the absorbent tube.
Fig. 3 is a partially fragmented perspective view of the composite web shown
in
Fig. 1 after it has been fed through the apparatus shown in Fig. 2 and the
incompatible
absorbent foam material has been formed into particulate material.
Fig. 4 is a perspective view of the composite web shown in Fig. 3 after the
side
margins have been folded in a first optional folding operation.
Fig. S is a schematic perspective view of the composite web shown in Fig. 3
after
it has been folded in a second optional folding operation.
Fig. 6 is a schematic perspective view of the composite web shown in Fig. 5
after
portions thereof have been bonded together.
Fig. 7 is a simplified cross-sectional view of the web shown in Fig. 6 taken
through one of the bond sites along line 7-7 of Fig. 6.
Fig. 8 is a schematic perspective view of one embodiment of a step of the
method
which is used to bond the tube of absorbent material for a sanitary napkin,
with the
patterned roll shown in a simplified manner.
Fig. 9 is a simplified fragmentary schematic view showing a relatively high
caliper material in the nip between a patterned roll and an anvil roll in
which the
patterned roil is not provided with a compressible material around its raised
element.
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Fig. 10 is a simplified fragmentary schematic view showing a relatively high
caliper material in the nip between a patterned roll and an anvil roll in
which the
patterned roll is provided with a compressible material around its raised
element.
Fig. 11 is a perspective view showing the surface of a prior dynamic bonding
roll
with intermittent load bearing members thereon.
Fig. 12 is a perspective view showing the surface of a patterned roll used in
one
embodiment of the method of the present invention with continuous load bearing
members thereon.
Fig. 13 is a perspective view of a compound sanitary napkin having a tube of
absorbent material on the body-facing side thereof, which was bonded and
shaped by the
method of the present invention.
Fig. 14 is a schematic view showing an alternative way of bonding two
incompatible materials together using the method of the present invention.
Fig. 15 is a perspective view of an absorbent interlabial device that is
bonded and
shaped by the method of the present invention.
Fig. 16 is a perspective view of a variation of the method of the present
invention
which is used to make an interlabial device.
Fig. 17 is a partially fragmented plan view of a sanitary napkin that is made
by
the method of the present invention.
Fig. 18 is a schematic cross section of a portion of the sanitary napkin shown
in
Fig. 17.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a method of bonding materials for use in
absorbent articles, although the techniques described herein may be used to
bond
materials used in other types of articles. In preferred embodiments, the
present invention
relates to such a method which is used in the manufacture of absorbent
articles such as
sanitary napkins, pantiliners, tampons, absorbent interlabial devices,
diapers,
incontinence devices, wipes, and the like.
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There are numerous aspects of the present invention. In one aspect, the
present
invention relates to a method of bonding through incompatible materials during
the
process of making a composite structure comprising several materials. As used
herein,
the term "incompatible materials" refers to materials to which it is difficult
to bond other
materials to using conventional bonding techniques. In another aspect, the
present
invention relates to improvements that allow the method to be used to bond
through
relatively thick materials (e.g., materials having a thickness of greater than
or equal to
about 2, 3, or 4 mm). In another aspect, the present invention relates to
methods of
bonding which are able to create a virtually unlimited number of bonding
patterns in the
materials to be bonded. In still another aspect, the present invention relates
to methods
of bonding that utilize a compression step to improve bond formation. In still
another
aspect, the present invention relates to methods of bonding that utilize a
step of slitting a
material through which the bonds are made.
It should be understood that the embodiments described in the specification
are
expressed in terms of preferred embodiments so that the length of this
specification is not
excessive. It should be understood that the present invention is not intended
to be limited
to such embodiments. It should also be understood that the aspects of the
methods
described herein can be combined in a single process, or they can be used
individually, or
in any desired combination. It should further be understood that the inventors
consider
all such uses or combinations of these aspects to potentially comprise
separate patentable
inventions, and that the scope of such inventions is intended to be as broad
as the prior
art permits. The scope of such inventions is intended to be limited by the
claims only,
and not by the preferred embodiments described herein.
In particularly preferred embodiments, the methods of bonding materials
described herein may also be used to provide the absorbent articles (or other
types of
articles), or portions thereof, with unique three dimensional shapes by using
the bonding
process to apply external forces to portions of the articles to shape the
same.
1. Description of One Non-Limiting Embodiment of the Method of The Present
Invention: For Use In Making A Tube of Absorbent Material for a Compound
Sanitary Napkin.
The method of the present invention can be used to bond many different
materials
for use in many different types of articles, including absorbent articles.
Figs. 1-8 show
one particularly preferred use of the method of the present invention. Figs. 1-
8 show a
process for making a tube of absorbent material for placement on the body-
facing side of
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a base pad to form a compound sanitary napkin. A compound sanitary napkin
comprises
a primary menstrual pad (the tube of absorbent material) which is joined to a
panty
protector (the base pad). The tube of absorbent material is bonded and shaped
by the
method of the present invention. The final product is shown in Fig. 13.
The drawings show a number of steps that take place before (and after) the
step of
bonding the materials comprising the tube of absorbent material. It should be
understood
that a number of these steps are optional, and are shown since they are useful
in making
the absorbent product shown in Fig. 13. All uses of the method of the present
invention
need not include these optional steps. It should be understood that the method
of the
present invention is not limited to the method shown in Figs. 1-8, and that
the method
shown in Figs. 1-8 is merely exemplary.
A. Assembline the Components.
Fig. 1 shows a composite web of material 20 that will be bonded using the
method of the present invention, and shaped into the absorbent tube for use in
the
sanitary napkin shown in Fig. 13. The composite web of material 20 shown in
Fig. 1
comprises a first material, such as first web of material 22 that is
incompatible with
bonding using conventional techniques, such as adhesives, heat and/or
pressure, and
ultrasonics. The first web of material 22 may, thus, also be referred to as
the "bonding
incompatible material" or "web of incompatible material". The web of
incompatible
material 22 has a first surface 22A and a second surface 22B.
The incompatible first material 22 can be any suitable material. Preferably,
the
web of incompatible material 22 is an absorbent material, although
substantially non-
absorbent incompatible materials can be bonded using the method of the present
invention. The web of incompatible material 22 may, but need not be,
compressible
and/or resilient. Preferably, in this aspect of the invention, the first
material 22
comprises a compressible and resilient, porous absorbent material. The first
material 22
is also not limited to materials in the form of webs. The first material 22
can be in any
suitable form. For instance, the first material 22 can be in the form of a
mass of particles
or fibers, a laminate, one or more layers, strips, sheets, blocks, or webs.
Preferably, to
make the tube of absorbent material shown in the drawings, it is in the form
of a web.
The web of incompatible material 22 has a first bondability (ease, or degree
to
which it is capable of bonding to other materials or having other materials
bond to it).
The web of incompatible material 22 may, but need not be, completely
incompatible with
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conventional bonding techniques. For example, it may be a material to which
other
materials are merely not readily bondable using such techniques. The
bondability of a
material can be determined by measuring the force required to separate the
material from
a bond, or attempted bond with another material. For the purpose of this
definition, the
separation occurs under the forces at which the two materials can be peeled
apart, or the
force at which the incompatible material's structural integrity breaks down
during the
process of attempting to separate the materials, whichever occurs first.
The web of incompatible material 22 may be a material that other materials are
not readily bondable to for one or more reasons. Most often, such materials
are
incompatible with conventional bonding techniques because of their structural
integrity
or composition. One type of incompatible material is a porous polymeric
absorbent foam
material made from a high internal phase emulsion (or "HIPE" foam). Absorbent
foam
materials that have these characteristics are described in the patent
literature, and include,
but are not limited to the following patents: U.S. Patent 5,260,345 issued to
DesMarais,
et al. on November 9, 1993; U.S. Patent 5,268,224 issued to DesMarais, et al.
on
December 7, 1993; and U.S. Patent 5,387,207 issued to Dyer, et al. on February
7, 1995.
Such materials may have a low tensile strength and/or low structural integrity
and/or low
level of elongation before breaking.
It is difficult to bond other materials to these absorbent foam materials
using
adhesives because the structural integrity of such materials is often not as
strong as the
adhesive bond. As a result, only the portions of the incompatible material
that are in
direct contact with the adhesive will remain bonded to other materials. The
remainder of
the incompatible material will readily separate from the material to which it
is bonded.
In addition, the foam materials described in the patents listed above cannot
be bonded to
other materials using heat bonds because these foams are thermoset polymers.
Once they
are formed, they cannot be remelted. Instead, when heat is applied to these
foam
materials, they will char rather than melt and flow, which is needed for heat
bonding.
These foam materials cannot be pressure bonded to other materials since the
thermoset
foam material does not have the ability to flow and be fused under pressure.
The web of incompatible material 22 may, thus, also be referred to as a
material
that is not readily bondable. In some instances, it may also be referred to as
being non-
heat sealable, free of thermoplastic material, and/or as a material having a
low structural
integrity. It should also be understood that the use of an incompatible
material is only
important in the aspect of the present invention that deals with a method of
bonding
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incompatible materials. In other aspects of the method described herein, it is
not
necessary to use an incompatible material. In such other aspects, any suitable
material,
including a wide variety of absorbent materials, can be used.
In the embodiment shown in the drawings, the web of incompatible material 22
is
a web of absorbent foam material such as one of those foam materials described
in the
foregoing patents. The web of incompatible material 22 in the embodiment shown
in
Fig. 1 is at least partially wrapped in a second web of material 24. The
second web of
material 24 has a second bondability that is higher than the bondability of
the web of
incompatible material 22. That is, it can be more readily bonded to other
materials (or to
itself) using conventional bonding techniques. The second web of material 24
may also
be referred to herein as a "carrier web" or a "bondable web". In the
embodiment shown
in Fig. 1, the second web of material 24 is preferably completely wrapped
around the
web of incompatible material 22 so that the second web of material 24 has an
"e"-folded
configuration in cross-section.
The second web of material 24 can be any material that is capable of being
bonded to itself, or to at least some other materials used in the types of
absorbent articles
described herein by heat or pressure, adhesives, or ultrasonics. The second
web of
material 24 may be manufactured from a wide range of materials such as woven
and
nonwoven materials; polymeric materials such as apertured formed thermoplastic
films,
apertured or unapertured 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
o~ cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester,
polypropylene,
or polyethylene fibers); bicomponent fibers (that is, fibers having a core of
one material
which enclosed in a sheath made of another material), or from a combination of
natural
and synthetic fibers. Preferably, in the embodiment shown, the second web of
material
24 at least partially comprises thermoplastic material. In other embodiments,
however,
particularly if adhesives or other types of bonding are used, the second
material 24 need
not comprise thermoplastic material. For instance, second material 24 can be a
cellulosic
material that can be bonded to itself by hydrogen bonding.
In still other embodiments, the second web of material 24 can be replaced by a
material that is in a form other than a web of material. For example, the
second web of
material 24 may be replaced by a bondable layer or coating such as an extruded
glue
coating or a polymeric coating that is applied to the web of incompatible
material 22.
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11
Glues, particularly hot melt adhesives, are similar to thermoplastic materials
in that they
are capable of being bonded using this aspect of the method of the present
invention.
Certain silicones, particularly if they have low enough melting points, will
also be
capable of being bonded as described herein. For this reason, the second web
of material
24 may be referred to as the "second material" so that it is clear that
materials other than
webs are included.
In the preferred embodiment shown in the drawings, the second material 24
preferably comprises a material that is also suitable for use as a wrapping
for the
absorbent material in an absorbent article. For example, the second material
24 can serve
as a containment web for containing absorbent material in the absorbent
article, as a
cover or topsheet for the absorbent article, or as a backsheet for the
absorbent article. For
the embodiment shown in Figs. 1-8 and 13, the second material 24 comprises a
containment web made of spunbonded nonwoven material. One particularly
preferred
spunbonded nonwoven material is a 19 g/yd2 (22.5 g/m2) spunbonded
polypropylene
nonwoven material referred to as product No. 065MLPV60U (or "P-9") obtained
from
Fiberweb, North America of Washougal, WA. Another particularly preferred
nonwoven
material is a spunbonded polyethylene nonwoven material known as COROLINDTM
sold
by Corovin GmbH, Peine, Germany, which can be obtained in two basis weights,
23 gsm
and 30 gsm.
_ Although the second web of material 24 is wrapped around the web of
incompatible material 22 in an e-folded configuration, it should be understood
that if a
web of material is used, the second web of material 24 is not limited to
wrapping the web
of incompatible material 22 in an "e"-folded configuration. The relationship
between the
web of incompatible material 22 and the second web of material 24 is
preferably one in
which a web of material having a higher bondability than the web of
incompatible
material 22 is merely at least adjacent to two opposing surfaces (e.g., 22A
and 22B
shown in Fig. I ) of the web of incompatible material 22. Thus, in other
embodiments,
the second web of material 24 may only be partially folded or wrapped around
the web of
incompatible material 22. The second web of material 24 can be folded or
wrapped
around the incompatible material 22 in any other suitable configurations.
Other suitable
configurations include, but are not limited to C-folded configurations, and
the like.
It is_ also not necessary that the second web of material 24 be limited to a
single
web that wraps the web of incompatible material 22. One (or more) webs of
material
may be placed adjacent to each surface 22A and 22B of the web of incompatible
material
CA 02311393 2004-O1-21
12
22. For example, in other embodiments, there may be two separate webs of
second
material 24, one of which is placed adjacent to each surface 22A and 22B of
the web of
incompatible material 22: The two webs of second material 24 may be the same
type of
material and have the same characteristics. In other embodiments, the two webs
of
material that are placed adjacent to each surface 22A and 22B of the web of
incompatible
material 22 may differ. For example, they may be different types of materials,
or they
may be the same basic types of materials, but have different characteristics
(such as
caliper, etc.).
In still other embodiments, the second material 24 need not be a web that is
as
wide or as long as the web of incompatible material 22. For instance, the
second
material 24 can be in the form of strips, stripes, patches, or pieces located
at the desired
location for the bond points. Thus, the second material 24 need only cover a
portion of
the first and second surfaces 22A and 22B of the web of incompatible material
22.
B. Optional Intermediate SteQs
(1) Formine the Incompatible Material Into Particulate Material.
In the preferred embodiment of the process of making the tube of absorbent
material shown in Figs. 1-8, before the bonding and shaping take place, the
web of
incompatible material 22 will be formed into particulate material while it is
inside the
' second web of material 24. This will be done by the process described in the
commonly-
assigned U.S. Patent No. 6,203,654 entitled "Method of Making Slitted or
Particulate
Absorbent Materials" issued in the name of Ronald R. McFall, et al. on March
20, 2001.
In such a case, it is preferable that the second web of material 24, not only
be
more bondable than the web of incompatible material 22, but also that it have
a higher
yield to break point than the web of incompatible material 22. This operation
(forming
the incompatible material into particulate material) is an optional step that
is preferably
performed prior to carrying out the step of bonding, which is highly preferred
for making
the tube of absorbent material for the sanitary napkin shown in Fig. 13. It
should also be
understood that the step of forming the incompatible material into particulate
material is
not limited to being carried out before the bonding step. The step of forming
the
incompatible material into particulate material can alternatively be carried
out at the
same time as, or after, the bonding step, if desired. The reasons for this
optional step
being preferred are discussed in greater detail below.
CA 02311393 2000-OS-24
WO 99/26769 PCT/US98/25222
13
The optional process of forming the incompatible material 22 into particulate
material comprises several steps. Although there are several embodiments of
this
optional process (and the apparatus used therein), a preferred embodiment of
the process
and apparatus are shown in Fig. 2. The process and apparatus shown in Fig. 2
are used to
form the incompatible material 22 into particulate material by mechanically
straining the
incompatible material 22.
A first step involves providing a "carrier web" having a first yield to break
point
under tensile forces is provided. (In the embodiment described herein, the
second web of
material 24 serves as the carrier web.) The web of material for forming into
particulate
material (which in this case is the web of incompatible material, foam
absorbent material
22) and the Garner web are then formed into a composite structure, such as
composite
web 20. The foam absorbent material 22 has a second yield to break point under
tensile
forces that is lower than the yield to break point of the nonwoven Garner web
24. Thus,
the first two steps of forming the incompatible material 22 into particulate
material have
already been performed in preparation for the method of bonding described
herein.
An apparatus for mechanically straining the composite web 20 is provided. The
apparatus preferably comprises a device that has at least one component with a
patterned
surface thereon. The composite web 20 is then preferably subjected to a
mechanical
straining process using the apparatus by impressing the patterned surface
thereon into the
composite web 20 so that the foam absorbent material 22 is at least partially
formed into
particulate material without forming the carrier web (the second web of
material) 24 into
particulate material.
The apparatus 30 for mechanically straining the composite web 20 shown in Fig.
2 comprises two pairs of cylindrical rolls, a first pair of rolls 32 and a
second pair of rolls
62. Each of the rolls has a patterned surface thereon. The patterns are
preferably formed
by a plurality of ridges and valleys on the rolls that define a plurality of
triangularly
shaped teeth. Suitable patterned rolls for use as the first and second pair of
rolls 32 and
62 of the apparatus shown in Fig. 2 (though not for this purpose of forming
incompatible
material into particulate material) are described in greater detail in U.S.
Patent 5,518,801
entitled "Web Materials Exhibiting Elastic-Like Behavior" issued to Chappell,
et al. on
May 21, 1996.
In the preferred embodiment shown, the rolls in the first pair of rolls 32
preferably have triangularly-shaped teeth that are formed by ridges and
valleys that are
oriented around the circumference of the rolls. The teeth preferably have
cross-sections
CA 02311393 2000-OS-24
WO 99/26769 PCT/US98/25212
14
in the form of isosceles triangles. The apex of the teeth may be slightly
rounded, if
desired. The top roll 34 and the bottom roll 36 in the first pair of rolls 32
are aligned so
that the ridges 38 of the top roll 34 align with the valleys 40 on the bottom
roll 36. The
triangular-shaped teeth that form the ridges on the top roll 34 and the
valleys on the
bottom roll are spaced so that these teeth do not touch each other or fully
"engage".
The teeth can be of any suitable size and pitch. The term "pitch", as used
herein,
refers to the distance between the apexes of adjacent teeth. In the preferred
embodiment
shown in the drawings, the depth (or height) of the teeth is preferably
between about 0. I
inches and about 0.17 inches (about 2.5 mm to about 4.3 mm). The pitch is
preferably
between about 1 mm and about 5 mm, and more preferably is between about 1.5 mm
and
about 2.5 mm. The pitch of the teeth establishes the width of pieces into
which the
absorbent material is cut or chopped.
The bottom roll 3b may also comprises several evenly-spaced thin planar
channels 44 on the surface of the bottom roll 36 that are oriented parallel to
the axis, X,
of the bottom roll. In this embodiment, the spaced apart channels 44 in the
bottom roll
36 preferably have a width of 2 mm. The "length" of the teeth in the bottom
roll 36
measured around the circumference of the bottom roll between the spaced apart
channels
is 8 mm. The rolls 34 and 36 are preferably driven in opposite directions.
The triangularly-shaped teeth on the top roll 34 and the valleys 40 on the
bottom
roll 36 should preferably be spaced so that they are partially intermeshing.
The degree to
which the teeth on the opposing rolls intermesh is referred to herein as the
"engagement"
cf the teeth. The engagement of the teeth is the distance between a position
where the
apexes of the teeth on the respective rolls are in the same plane (0%
engagement) to a
position designated by plane where the apexes of the teeth of one roll extend
inward
beyond the plane toward the valleys on the opposing roll. The engagement of
the teeth
can be expressed as a percentage of the pitch (distance between the apexes of
the teeth on
one of the rolls), or in terms of a measured distance. Since the height of the
teeth may be
greater than the pitch, the engagement may be a value that is greater than
100% (for
instance, if the engagement is greater than the pitch length). Preferably, the
engagement
is between about 15% and about 120% of the pitch length. The engagement
expressed in
terms of a measured distance is preferably between about 0.01 inch to about
0.07 inch
(about 0.25 mm to about 1.8 mm), and more preferably is between about 0.04
inch to
about 0.06 inch (about 1 mm to about 1.5 mm).
CA 02311393 2000-OS-24
WO 99/2669 PCT/US98l25222
As shown in Fig. 2, at the stage designated A, the composite web 20 is fed in
a
machine direction (MD) into the nip between the rolls 34 and 36. The second
web of
material 24 at this stage of the process is serving as a carrier web. As a
carrier web it
holds and contains the web of incompatible material 22 which is about to be
slit and
formed into particulate material. The second web of material 24 wraps the
outside of the
web of incompatible material 22 so that the second web of material 24 faces
the
patterned surfaces on the rolls 34 and 36.
The rolls 34 and 36 subject the composite web 20 to a mechanical straining
process by impressing the patterned surfaces thereon into the composite web
20. The
mechanical straining process applies a force that is greater than the yield to
break point
of the web of incompatible foam absorbent material 22, but less than the yield
to break
point of the nonwoven carrier web (the second web of material (having the
higher
bondability)) 24 so that the web of incompatible foam absorbent material 22 is
at least
partially slit without slitting the carrier web 24.
Fig. 2 shows the condition of the composite web at stage B, after it passes
through the nip between the first pair of rolls 32. As shown in Fig. 2, the
carrier web 24
will have a pattern of corrugations formed therein that corresponds to the
combination of
the patterns on the adjacent rolls, 34 and 36. The carrier web 24, however, is
not slit or
cut. The intermediate web of foam absorbent material 22 has a plurality of
slits 50
formed therein. The slits 50 are oriented in the machine direction (or "MD").
In the
particular embodiment shown, the slits 50 are intermittent and separated by
cross-
machine direction (or "CD") bands of unslit material 52. This is due to the
presence of
the channels 44 on the bottom roll 36. The web of foam absorbent material 22
is slit
while the Garner web 24 is not slit because the web of foam absorbent material
22 has a
lower yield to break point than the carrier web 24, and breaks, under tensile
forces (the
straining process) while the carrier web 24 does not.
At this point in the process, (at stage B, between the first and second sets
of rolls,
32 and 62) it is possible to perform additional operations on the composite
web 20. For
example, the composite web 20 can be cut into discrete lengths between the
first and
second sets of rolls 32 and 62. In other embodiments, the composite web 20 can
be cut
into discrete lengths by a cutting blade located on one of the rolls in the
first set of rolls
32. The composite web 20 would be cut into lengths that correspond to the
length of the
tube desired for the sanitary napkin shown in Fig. 13.
CA 02311393 2000-OS-24
WO 99126769 PCT/LS98/25222
16
Further, an additional web (or webs) of material, such as a continuous web of
apertured film topsheet material 56, can be joined to the composite web 20
between the
first and second sets of rolls, 32 and 62. Alternatively, such an additional
material could
be cut into individual pieces and joined to the composite web 20 between the
first and
second set of rolls. The joinder of the apertured film topsheet material 56 to
the
composite web 20 is shown in Fig. 3. It has also been omitted from Fig. 2 for
simplicity
of illustration. The apertured film topsheet material 56 is preferably joined
to the
composite web 20 by adhesives. This forms a structure that will be referred to
herein as
the "tube forming composite" (or "tube forming composite web") 88.
The second set of rolls 62 of the apparatus 30 for mechanically straining the
composite web comprises top and bottom rolls, 64 and 66, respectively. Each of
these
rolls also has a pattern on its surface. As shown in Fig. 2, the top roll 64
has ridges that
run parallel to the axis, X, of the top roll 64. The ridges define a plurality
of triangular-
shaped teeth 68. The top roll 64 may also have several spaced apart channels
70 that are
oriented around the circumference of the cylindrical roll.
Fig. 2 shows that when the composite web 20 leaves the nip between the second
set of rolls 62, at least a portion of the foam absorbent material 22 is
further provided
with a plurality of slits 80 that are oriented in the cross-machine direction.
This initial
slitting in the machine direction and subsequent slitting in the cross machine
direction
results in the absorbent material 22 being formed or chopped into a plurality
of particles
82. The foam absorbent material 22 can optionally have unslit strips 84 left
therein due
to the presence of the channels 70 in the second pair of rolls 62, in addition
to any cross-
machine direction bands of unslit material due to the presence of the channels
44 on the
bottom roll 36 in the first pair of rolls 32.
Again, the nonwoven carrier web 24 is not slit, but has another pattern formed
therein. The overall pattern formed therein resembles a grid with a
combination of the
impressions created by the first and second sets of rolls 32 and 62. The
apertured film
topsheet 56 will have a pattern formed therein that resembles that of the
second pair of
rolls 62.
Fig. 3 shows the composite web 20 after it has been fed through the apparatus
shown in Fig. 2. As discussed above, a sheet of apertured film topsheet
material 56 has
preferably been joined to the individual lengths of the composite web 20
between the
first and second pairs of rolls. Fig. 3 shows that the sheet of apertured film
topsheet
material 56 is preferably of a size that is about the same width as, but
longer than, the
CA 02311393 2000-OS-24
WO 99/26769 PCT/US98/25222
17
individual lengths that the composite web 20 was cut into. The apertured film
56 extends
beyond the ends of the individual lengths of composite web material so that
the tube of
absorbent material, once formed, can be more easily attached to the sanitary
napkin, by
attaching only the ends of the same to the sanitary napkin.
It should be understood that in Fig. 3, the pattern impressed into the
nonwoven
material 24 by the first and second sets of rolls has been omitted or
simplicity. In
addition, the incompatible foam absorbent material 22 is shown as comprising
only
particles 82 for simplicity (that is, no unslit strips are shown as being left
in the
incompatible material 22). Such an embodiment could be created by providing
the rolls
on the first and second sets of rolls 62 with continuous teeth and omitting
the valleys 40
and channels 70 between the teeth.
(2) Optional Step of Folding-The Tube Forming_Composite Web.
The next step in making the tube of absorbent material for the sanitary napkin
shown in Fig. 13, is folding the combination of the composite web 20 and the
sheet of
apertured film topsheet material 56, the tube forming composite web 88. These
optional
but preferable folding steps are shown in the next few drawing figures.
Fig. 3 shows the longitudinally-oriented folding lines, F, about which the
longitudinal side margins 90 of the tube forming composite web 88 will
initially be
folded. Fig. 4 shows the tube forming composite web 88 after the side margins
90
thereof have been folded along folding lines F in a first folding operation to
form a "C"-
folded structure.
Fig. 5 shows the tube forming composite web 88 after it has been folded in a
second folding operation. As shown in Fig. 5, the tube forming composite web
88 has
been folded along its longitudinal centerline, L. As a result, the previously-
folded
longitudinal side margins 90 are brought adjacent to each other, and the
longitudinal side
margins 90 of the tube foaming composite web 88 are tucked inside the folded
tube
forming composite web 88. As shown in Fig. 5, the folded longitudinal side
margins 90
lie adjacent to the longitudinal centerline, L, of the tube forming composite
web 88. The
folded tube forming composite web 88 shown in Fig. 5 is now ready to be bonded
using
the method of the present invention. (The steps shown in Figs. 2-5 were all
optional, but
preferred steps for making a tube of absorbent material for the sanitary
napkin shown in
Fig. 13.)
CA 02311393 2000-OS-24
WO 99/26769 PCT/iiS98/25222
18
C. Bonding (and Shapingl The Incompatible Material.
( 1 ) In General.
In order to bond (and shape) the incompatible absorbent foam material 22, in
the
most general sense, the web of material having the higher second bondability
(the
nonwoven) 24 is positioned to the outside of the incompatible material (the
absorbent
foam material) 22. The cross-section of the actual structure being bonded (as
shown in
Fig. 7) is somewhat more complicated than that, but for the purposes of the
present
description, the above-described general relationship (with the web of
material having
the higher second bondability positioned outside of the web of incompatible
material) is
preferably present.
The incompatible material, absorbent foam material 22, with the web of
material
having the second higher bondability, the nonwoven web 24, on the outside of
the same,
is preferably bonded with a plurality of autogenous bonds 94. The term
"autogenous", as
used herein, refers to bonding without adhesives or some other additional
material (that
is, additional to the components to be bonded) such as a stitched thread. The
method
described herein, however, is not intended to be limited to methods which
preclude
adhesive augmentation of such autogenous bonding, or adhesive bonding per se.
The bonds 94 preferably penetrate the incompatible absorbent foam material 22.
The bonds 94 preferably join one portion of the nonwoven web 24 to another
portion of
the nonwoven web 24 on the opposite side of the incompatible foam material 22.
In the
embodiment shown in the drawings, the bonding serves as a step in the method
of the
present invention directed to bonding incompatible materials, and also serves
to provide
the tube of absorbent material with a unique three dimensional shape.
In carrying out the method of the present invention, any suitable number of
bonds
94 can be used. The bonds 94 can also be placed in any suitable location. For
making
the tube of absorbent material for the sanitary napkin in Fig. 13, two to five
bonds 94 are
preferably used. In the embodiment shown in the drawings, three bonds 94 are
used.
The bonds 94 are preferably spaced about 1.75 inches (about 4.4 cm) apart, and
are
located about 17 mm from the fold made along the longitudinal centerline, L,
of the tube
forming composite web 88.
The preferred autogenous bonding process can be accomplished using heat and/or
pressure; or by ultrasonics. Suitable techniques for heat and/or pressure
bonding, and
CA 02311393 2004-O1-21
19
dynamic bonding in particular, are described in greater detail below. Suitable
techniques
for ultrasonically bonding are described in Procter & Gambles U.S. Patent
4,430,148
entitled "Ultrasonic Bonding Process" issued to Schaefer on February 7, 1984
and U.S.
Patent 4,823,783 entitled "Adhesive-Free Bonding of Continuously Moving Webs
to
form Laminate Web and Products Cut Therefrom" issued to Willhite, Jr. et al.
on April
25, 1989. Suitable equipment for ultrasonic bonding is available from Branson
UltrasonicsTM of Danbury, CT. The ultrasonic bonding apparatus is preferably
equipped
with a plate which has pattern elements similar to those described below for
the dynamic
bonding process. It should be understood, however, that ultrasonic bonding may
be less
preferred (than the dynamic bonding process) for use in bonding some of the
higher
caliper structures described herein.
A dynamic bonding process has several other advantages over ultrasonic bonding
processes. First, it can be a continuous process which is capable of operating
at high
speeds. By contrast, ultrasonics generally require the use of an apparatus
having at least
one static head which provides a fixed dwell time to form the bond. Thus, in
ultrasonic
bonding processes, the web to be bonded has to be stopped for a period to
complete the
bond. Second, ultrasonic bonding processes are not as suitable for bonding
through
materials having thicknesses over certain amounts (e.g., up to, or greater
than or equal to,
about 4 mm). The dynamic bonding process described herein, in the other hand.
can
easily bond through materials having such thicknesses.
The slitting or forming the absorbent material 22 into particulate material in
the
prior step is advantageous in the bonding process. This is because the method
used to
form the slit or particulate material may provide a continuous clear path for
the bonds to
penetrate through the absorbent material. This is particularly the case if the
bonds are
aligned with the slits or the spaces between the particles. This is most
likely to occur
where the slit or particulate material is adhered to a carrier web. Prior
methods of
chopping absorbent material which merely chop the absorbent material and blow
it by
compressed air into a closed tube will result in a random distribution of the
chopped
particles. Such methods will not form the clear path for the bonding process
described
herein.
The dynamic bonding process, as discussed above, involves bonding portions of
the second web of material (nonwoven covering) 24 on each side of the
absorbent foam
material 22 together. The apertured film topsheet material 56 can also have
portions
which are dynamically bonded together. The apertured film topsheet material 56
can be
CA 02311393 2004-O1-21
ZU
bonded in addition to, or alternatively to bonding portions of the nonwoven
covering 24
together. In the dynamic bonding process, at least one of the materials to be
bonded (the
nonwoven covering 24 or the apertured film topsheet 56 material) preferably
comprises
thermoplastic material. (It should be understood that, for simplicity, the
bonding will be
expressed below in terms of bonding portions of the nonwoven covering 24
together,
even though portions of the apertured film topsheet material may be similarly
bonded in
the process.)
Fig. 8 shows the process in which a first portion 24A of the cover material 24
is
preferably bonded through the tube forming composite web 88 to a second
portion 24B
of the cover material. The apparatus used for bonding the tube forming
composite web
88 preferably comprises a pair of cylindrical rolls 110 and 112. Preferably,
at least one
of the rolls, patterned roll 110, has a relief pattern on its surface. The
patterned roll 110
is shown in a simplified manner in Fig. 8, and in greater detail in Fig. 12.
(Fig. I2,
however, shows a roll with a relief pattern thereon that is slightly different
from the
pattern shown in Fig. 8.)
As shown in Fig. 12, the patterned roll 110 has a cylindrical surface 11 S,
and a
plurality of protruberances or pattern elements (or "pattern element
segments",
"projections", or "nubs'' 116 which extend outwardly from the surface 115. The
relief
pattern formed by the pattern elements 116 can be in any suitable
configuration. It can
be linear, curvilinear, or it can be comprised of linear segments and
curvilinear segments.
The relief pattern can be continuous or intermittent. The relief pattern can
define an
unlimited number of patterns and other types of designs. For example, it can
define
geometric shapes, arrows, words, etc. The land surfaces 118 on the pattern
elements can _
also be provided -in a wide variety of possible shapes. Suitable shapes for
the land
surfaces 118 include, but are not limited to, oval and circular.
In the embodiment of the apparatus shown, the relief pattern comprises a
plurality
of spaced apart pattern elements 116 having circular land surfaces 118. In the
embodiment of the method shown in Fig. 8, the pattern elements 116 are
arranged in ao
intermittent linear configuration.
While the present invention is intended to apply to bonds of any suitable
shape
and size, bond sizes that have been found to be suitable have a circular plan
view
configuration with a diameter of between about 0.25 mm to about 5 mm or more.
In one
preferred embodiment, the bonds have a diameter of about 3 mm and an area of
about 8
mm2.
CA 02311393 2000-OS-24
WO 99/26769 PCT/US98/25222
21
The pattern elements 116 have side walls 119 that are preferably not
perpendicular
with the surface of the cylindrical roll. Preferably, the side walls 119 of
the pattern
elements 116 form an angle of greater than 45° and less than
90°, preferably between
about 70 - 90 degrees, with surface 11 S of the cylindrical roll. Modifying
the orientation
of the side walls 119 of the pattern elements 116 is preferred due to the
thickness of the
materials being bonded, and the desire to avoid tearing the cover material 24.
The other roll 112, serves as an anvil member and, thus, may be referred to as
anvil
roll 112. The patterned roll 110 and the anvil roll 112 define a pressure
biased nip 114
therebetween. Preferably, the anvil roll 112 is smooth surfaced. In other
embodiments,
however, both rolls 110 and 112 may have a relief pattern and/or pattern
elements
thereon. The patterned roll 110 and anvil roll 112 are preferably biased
toward each
other with a pre-determined pattern element loading of from about 20,000 psi
(about 140
Mpa) to about 200,000 psi (about 1,400 MPa). In the embodiment shown in Fig.
8, the
rolls are baised toward each other so that pressure in the nip 114 is
preferably maintained
at about 93,700 psi (about 656 Mpa). In this embodiment, the materials to be
bonded are
preferably being fed through the nip 114 at a relatively high rate of speed.
The speed of
the line is preferably about 383 feet/minute (about 117 m/minute).
The patterned roll 110 and the anvil roll 112 are preferably driven in the
same
direction at different speeds so that there is a surface velocity differential
therebetween.
The surface velocity differential preferably has a magnitude of from about 2
to about 40
percent of the roll having the lower surface velocity, more preferably between
about 2 to
about 20 percent. The anvil roll 112 is preferably operated at a surface
velocity that is
greater than the surface velocity of the patterned roll 110. It is also
possible, however, at
high line velocities, for the bonding to occur at zero velocity differential
(that is, with the
nip defining rolls having equal surface velocities).
The plural laminae comprising the tube forming composite web 88 is bonded by
feeding it into the nip 114 between rolls 110 and 112. The preferred bonding
process
shown in the drawings penetrates through the tube forming composite web 88 and
autogenously bonds the first portion 24A of the nonwoven cover material to the
second
portion 24B of the cover material 24. The bonds 94 are formed between the
opposed
portions of the nonwoven web of material 24 having the higher second
bondability that
are positioned outside the foam material 22.
Without wishing to be bound to any particular theory, the mechanism by which
the bonding of the incompatible material is believed to occur is as follows.
The pattern
CA 02311393 2004-O1-21
22
elements 116 of the bonding mechanism compress the incompatible absorbent foam
material 22. This localized compression causes the incompatible absorbent foam
material 22 to fracture and separate (move away from the pressure point) from
the area of
the pattern elements 116. The bonding mechanism slices through the
incompatible
material 22 or displaces the particles of incompatible material 22 so that
there is a clear
path for the bondable materials to bond together. Preferably, very little (if
any) of the
foam material 22 is actually left in the bond sites.
In addition to the penetration of the incompatible material by the bonds, the
method described herein has several other important features. These features
allow high
caliper materials to be bonded, and enable the process to create a virtually
unlimitc
number of bonding patterns in the materials to be bonded. The patterned roll
110
preferably has a compliant (or compressible) material 120 on its surface 11 ~
. The
patterned roll 110 preferably also has a pair of load bearing members 122 on
its surface
115. The purposes of these components are described below.
The purpose of the compliant material 120 is to compress the materials to be
bonded so that the pattern elements 116 are less likely to puncture the cover
materials)
24. If the cover materials) are punctured, the bonds will either not form, or
a weak bond
will form because the cover material will not be melted to form the bond. The
compression step may occur prior to, or simultaneously with the .bonding. The
use of a
compliant material is particularly preferred when the materials to be bonded
are
relatively thick. The complaint material can be omitted when the materials to
be bonded
are thinner. Fig. 12 shows that the compliant material 120 preferably
surrounds the
pattern elements 116.
A comparison of Figs. 9 and 10 shows the manner in which the compliant
material 120 is believed to function. Fig. 9 shows a relatively thick material
passing
through the nip 114 between the patterned roll 110 and the anvil roll 112
without a
compliant material surrounding the pattern element 116. As shown in Fig. 9,
the pattern
element 116 tends to puncture the materials to be bonded due to the high
localized
stresses in the materials to be bonded, particularly the cover material 24.
Fig. 10 shows the same relatively thick material passing through the nip 114
between the patterned roll 110 and the anvil roll 112 with a compliant
material 120
surrounding the pattern element 116. As shown in Fig. 10, the compliant
material 120
occupies space between the patterned roll 110 and the anvil roll 112_ The
compliant
material 120 causes the materials to be bonded to be gradually compressed in
the area of
CA 02311393 2004-O1-21
23
the pattern element 116. This brings both of the layers of the cover material
24 closer
together during the bonding without applying added strain to the cover
material 24. This
allows the bond 94 to be made without tearing the cover material 24, or
punching a hole
through the foam material 22 situated between the layers of cover material 24.
.
The way this works can be visualized by thinking of the following analogy :
The
principle involved is similar to the problem of attempting to secure a six
inch (1~ cm)
thick piece of fiberglass housing insulation to another material using a nail
gun. If this is
attempted when the fiberglass is uncompressed, when the nail is ejected, it
will pierce the
insulation and pass completely through the insulation. However, if the
fiberglass
insulation is compressed prior to attempting to secure it with a nail gun,
this will not
occur, and the nail will be capable of securing the insulation.
The compliant material 120 preferably has certain characteristics. The
compliant
material 120 is preferably less compressible than the materials to be bonded,
and more
compressible than the surface 115 of the patterned roll 110. Therefore, the
compliant
material 120 should preferably have a hardness of less than that of the
surface 115 of the
patterned roll 110. Preferably, the compliant material 120 has a hardness
(which is
measured using a durometer) of between about 50 on the Shore A scale to about
62 on
the Rockwell C scale, more preferably has a hardness of between about 50 to
about 100
on the Shore A scale, and most preferably has a hardness of about 90 on the
Shore A
scale. (A hardness of 62 on the Rockwell C scale is the hardness of the D2
steel
comprising the surface 1 I S of patterned roll 110.) (Wlvle the surface of the
anvil roll can
have any suitable hardness, the surface of the anvil roll 112 preferably has a
hardness that
is equal to or greater than that of the patterned roll 110.)
The compliant material 120 can comprise any suitable type of material.
Suitable
materials include brass, rubber, and polymeric materials such as polyurethane.
In a
particularly preferred embodiment, the compliant material 120 comprises
polyurethane.
The compliant material 120 is preferably wider in width than the materials to
be
bonded. This allows it to equalize the pressure over the entirety of the
materials to be
bonded. The compliant material 120 can have any suitable caliper. Preferably,
the
caliper of the compliant material 120 is great enough to have some appreciable
effect on
avoiding the problem of punching holes through the cover material 24. The
caliper of
the compliant material 120 is preferably no greater than the height of the
pattern elements
116. The pattern elements may, for example, have a height of about 2 mm. In
one non-
limiting embodiment, it has been found that a compliant polyurethane material
having a
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24
hardness of about 90A on the Shore A scale which has a height of about 1.5 mm
is
suitable.
The compliant material 120 is preferably adhered to the surface 115 of the
patterned roll. The complaint material 120 can be adhered to the patterned
roll 110 in
any suitable manner, such as by welding, or by adhesives.
The purpose of the load bearing members 122 is to balance the patterned roll
110
(that is, to equalize the forces on the patterned roll 110 when the materials
to be bonded
pass between the patterned roll 110 and the anvil roll 112). The use of the
load bearing
members 122 is particularly preferred when the pattern on the patterned roll
110 is
"unbalanced" or "imbalanced." By "unbalanced" or "imbalanced", it is meant
that the
pattern elements l l6 are distributed in a manner in which the pressure in the
nip 114
between the patterned roll 1 IO and the anvil roll 112 varies around the
circumference of
the patterned roll I 10 due to differences in the surface area of the lands I
18 of the pattern
elements I I6 and/or due to the distribution of the pattern elements 116.
The load bearing members 122 can be omitted when the bonding pattern is
balanced. However, as will be discussed in greater detail below, it may be
desirable to
use load bearing members 122 even when the bonding pattern is balanced to
provide
greater flexibility in using pattern elements 116 that have a greater height.
The load bearing members 122 may be in any suitable configuration. The load
bearing members 122 may be in the form of continuous rings around the
patterned roll
110. It also possible for the load bearing members 122 to be in the form of
intermittent
elements. If the load bearing members 122 are in the form of intermittent
elements,
however, they are preferably in an arrangement that is staggered around the
circumference of the patterned roll l I0 in such a manner that they
effectively form a
continuous ring around the circumference of the patterned roll 110. As shown
in Fig. 12,
the load bearing members 122 are preferably in the form of continuous rings
around the
patterned roll 110.
In the embodiment shown in the drawings, the load bearing members 122 are
preferably located adjacent to each side edge of the patterned roll 110. The
load bearing
members are preferably located laterally outboard of the portion of the
surface 115 of the
patterned roll 110 along which the materials to be bonded will contact (that
is, they are
preferably located between the central portion of the patterned roll 110 and
the side edges
of the patterned roll 110). This ensures that the anvil roll 112 will be
capable of making
CA 02311393 2004-O1-21
25
direct contact with the load bearing members 122. It is believed that this
contact will
even occur when the materials to be bonded are fed into the nip 114 between
the rolls.
This contact is believed to occur due to the compression of the materials to
be bonded in
the nip 114 and deformation of the rolls under the high forces that are being
applied to
bias the rolls toward each other.
A comparison of Figs. 11 and 12 shows the manner in which the load bearing
members 122 are believed to function in greater detail. Fig. 11 shows an
example of a
patterned roll 1110 which does not have bearing members of the type described
herein.
The distribution of pattern elements 1116 on the patterned roll 1110 is both
"nested" and
balanced. The term "nested" as used herein refers to distributions of pattern
elements
1116 that exhibit a degree of overlap as one looks at the pattern proceeding
around the
circumference of the patterned roll 1110. This ensures that the anvil roll 112
will be
continuously riding over the tops of the pattern elements 1116 in the nip area
114, and
will not drop or dip down between each pattern element 1116. If the pattern
elements
1116 were not nested, and the anvil roll 112 did dip down between pattern
elements
1116, the rolls, which are being held closely together at very high pressures
and are
rotating at high speeds, would operate in an extremely rough manner, akin to a
flat tire on
an automobile.
In the roll 1110 shown in Fig. 11, there are identical groups of pattern
elements
similar to the group shown on other parts of the roll. There are also bearers
or bearer
strips 1124 between the groups of pattern elements. The other identical groups
of pattern
elements cannot be seen in Fig. 11 since only a portion of the surface of the
roll is
shown. However, the single group of pattern elements and the bearers 1124 are
shown
sufficiently to describe the concept in issue. As shown in Fig. 11, when the
pattern is
balanced, any bearers or bearing strips 1124 need only be provided in a non-
continuous
(or intermittent) arrangement around the circumference of the patterned roll
1110. The
bearers 1124 are provided in those locations where no pattern elements 1116
are present.
This is because the total force from the loading mechanism is transferred from
the pattern
elements to the bearers 1124 when the patterned roll 1110 rotates. Balanced
patterns are
required, meaning that the bonding area in the nip (that is, the surface area
of the portions
of the rolls which are in contact within the nip) at any point around the roll
must remain
constant. If it were allowed to vary, the bonding pressure would also vary and
inconsistent bonds would result.
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26
Fig. 12 shows an example of a patterned roll 110 that can be used in
embodiments
of the method described herein which have a non-nested and an imbalanced
pattern of
pattern elements 116.thereon. Although only a portion of the roll 110 with a
single
group of pattern elements 116 is shown in Fig. 12, the patterned roll 110
preferably
comprises several similar patterns of dots spaced around the circumference of
the roll
110. (By "dots", it is meant that the pattern elements have circular land
areas.) Each
group of dots is distributed in the desired arrangement to form bonds on the
product in
issue. For example, to bond the tube forming composite web shown in Fig. 8,
each
group of dots may be arranged in a linear pattern of three dots. To bond the
interlabial
device 1020 shown in Fig. 15, each group of dots may be in a semi-circular
arrangement
of four or five dots as in the case of the group of pattern elements shown in
Fig. 16.
For purposes of this discussion, it will be assumed that there are six groups
of dots
around the circumference of the roll 110. All of the pattern elements 116 in
this example
are of the same height. Three of the dot patterns have pattern elements 116
with lands
defining a circular bonding surface having a diameter of 2 mm. The other three
dot
patterns have pattern elements 116 with a circular bonding surface having a
diameter of 3
mm. The groups of pattern elements 116 alternate around the surface of the
patterned
roll 110 with each group of 3 mm diameter pattern elements following a group
of 2 mm
diameter pattern elements.
There was no convenient way known to the inventors to form bonds using both
the
2 mm diameter pattern elements and the 3 mm diameter pattern elements, prior
to the
invention of the bearing members 122 described herein. For example, using a
conventional roll arrangement, it was possible to form bonds with the 2 mm
diameter
elements, but not with the 3 mm diameter elements. If the proper pressure was
selected
to form bonds with the 2 mm diameter elements, there would not be sufficient
pressure to
form bonds using the 3 mm diameter elements. The opposite was also true (it
was
possible to form bonds with the 3 mm diameter elements, but not with the 2 mm
diameter elements). If the proper pressure was selected to form bonds with the
3 mm
diameter elements, the pressures would be too high for bonding with the 2 mm
diameter
elements, and holes be punched through the materials to be bonded.
The bearing members 122 described herein were then developed. As described
above, the bearing members I22 are preferably provided in the form of
continuous rings
around the circumference of the patterned roll 110. To ensure dynamic
balancing of the
patterned roll I 10, an amount of material equal to the surface area of the
pattern element
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27
is removed from the bearing members. As shown in Fig. 12, the bearing members
122
preferably have small cut out areas 126 on each side. The cut out areas I26
are
preferably located along the same longitudinal axis on the surface of the roll
on which
the pattern elements 116 are located. There are two cut out areas 126 for each
pattern
element 116. The cut out areas 126 shown in Fig. 12 are each semi-circular in
shape.
The size of each of the cut out areas 126 is preferably equal to one-half the
size of the
surface of the pattern elements 116 that are located on the common
longitudinal axis.
The bearing members 122 should have a hardness of greater than or equal to the
surface of the patterned roll 110 and the pattern elements 116. The bearing
members 122
can comprise any suitable type of material. The bearing members 122, like the
surface of
the patterned roll 110 and the pattern elements 116, are preferably comprised
of D2 steel.
The bearing members 122 may have a caliper that is less than, greater than, or
equal to the height of the pattern elements 116. Preferably, to simplify the
process set
up, the caliper of the bearing members 122 is the same as the height of the
pattern
elements 116. The pattern elements 116 may, for example, have a height of
about 2 mm.
In one non-limiting embodiment, it has been found that bearing members 122
also
having a height of about 2 mm is suitable. The bearing members 122 can be of
any
suitable width. The bearing members 122 are preferably of a width that
provides them
with a surface area along each portion of a longitudinally oriented zone taken
along the
surface of the patterned roll 110 (that is, oriented parallel to the axis of
the roll) which is
equal to or greater than that of the total surface area of the lands 118 on
the pattern
elements 116 that lie within the same zone. In the embodiment shown in Fig.
12. the
bearing members 122 have a width of about 6 mm (as measured through a portion
of the_
bearing members 122 that does not include the cut out areas 126).
The bearing members 122 can be integrally formed on the patterned roll 110, or
they can comprise separate elements that are adhered to the surface 115 of the
patterned
roll 110. The bearing members 122 are preferably integrally formed on the
surface I 15
of the patterned roll 1 I0. If the bearing members 122 are adhered to the
patterned roll
I 10, they can be adhered in any suitable manner, such as by welding.
Without wishing to be bound by any particular theory, it is believed that the
bearing members 122 allow for bonding using unbalanced patterns because the
pressure
in the bonding area is no longer solely a function of the surface area of the
pattern
elements or a function of the presence or absence of the pattern elements.
With the
bearing members 122, the pressure in the bonding area becomes controlled by
the
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28
material properties of the rolls, particularly the patterned roll 110, and the
materials to be
bonded, as well as the geometry (that is, the height and surface area) of the
pattern
elements 116 and the bearing members 122. It is believed that as bonding takes
place
under the relatively high pressures used, there is deformation of the rolls,
particularly of
the pattern elements 116. The pressure in the bonding area is believed to
result in a
compressive deflection in the pattern elements 116. The pressure in the
bonding area
may also result in a degree of deflection in the surface of the patterned roll
110 around
the base of the pattern elements. Localized deformation on the anvil roll 112
at the
location of the points of contact with the pattern elements 116 is also
possible.
It is believed that the magnitude of the deformations in the pattern elements
116
and the surrounding areas is on the order of the thickness of the bonds formed
by this
process. In the preferred embodiment described herein, the bonds have a
thickness in the
range of about 0.0015 to about 0.002 inches (about 0.038 mm to about 0.05 mm).
This
deformation allows the anvil roll 112 to maintain constant contact with the
bearing
members 122, even in the areas where there are pattern elements 116 present
and the
intervening materials to be bonded are being fed into the nip 114 between the
patterned
roll 110 and the anvil roll 112. For this to be possible, the loading force
must be
sufficiently high to ensure constant contact between the bearing members 122
and the
anvil roll 112. The bearing members 122, thus act as a "stop" for the anvil
roll 112 to
prevent further compressive deflection of the pattern elements 116.
The bearing members 122 can be designed to be sufficiently strong so that once
the anvil roll 112 is in contact with the bearing members 122, no further
increase in the
bonding pressure on the pattern elements 116 would be possible. If the loading
force
were to increase, only the load acting on the bearing members 122 would
increase,
assuming they were very rigid.
The balancing of the patterned roll 110 has particularly important
implications.
This aspect of the bonding method can be used to produce bonding patterns with
pattern
elements having different size lands around the circumference of the patterned
roll. This
aspect of the bonding method can also be used to that are not subject to the
previous
mechanical limitations. The bond patterns do not have to have nested pattern
elements,
and the bond patterns do not have to be balanced. For example, in prior
bonding
processes, creation of complex patterns, such as a pattern like that shown in
Fig. 17,
which is nested and balanced, involves an extremely complicated designing
process. The
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29
balancing of the patterned roll eliminates the need to go through complex
design work to
assure that the bond pattern is nested and balanced.
In addition, bonding patterns can be created which are tailored to suit some
particular bonding need, or to suit consumer preference, rather than process
limitations.
In addition, the method described herein can be used to create an unlimited
number of
bond designs for aesthetic purposes or for other purposes. For example, using
the
techniques described herein could be used to write a script or emboss a
picture into the
materials to be bonded.
i; urther, the use of the bearing members 122 in the method permits pattern
elements 116 having much greater heights to be used. Previous pattern elements
were
typically about 0.015 inches (about 0.38 mm) in height. As discussed herein,
the pattern
elements 116 can range in height up to 2 mm, or more. This allows thicker
materials to
be bonded. Providing a patterned roll with pattern elements having a greater
height,
however, is not limited to use in bonding thick materials. It also can be used
to bond
through thin materials because the bearing members 122 will keep the pattern
elements
116 from puncturing the materials to be bonded.
This aspect of the method is also believed to result in increased life of the
patterned roll 110. Generally, relief patterned rolls wear out because of
stresses on the
pattern elements. The use of the bearing members is believed to reduce
stresses by
bearing a portion of these stresses and relieving the pressure on the pattern
elements. As
discussed above, the bearing members may also act as a "stop" to prevent
further
compressive deflection of the pattern elements. It is believed, that because
the bearing
members may act as a "stop" to prevent further compressive deflection of the
pattern
elements, the pattern elements will not be strained beyond their plastic
deformation
point.
(2) Non-Limiting Variations of the Bonding Process.
There are many possible variations of the bonding process described herein. A
non-limiting number of these variations are set out below.
For example, the methods described herein are not limited to use in bonding
materials for use in absorbent articles. The methods described herein, may for
instance,
be used to bond materials for use in making packages, or any other types of
articles,
particularly where incompatible materials, polymeric materials, or the like
are used. In
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addition, the center laminae of the materials to be bonded does not have to
comprise an
incompatible material. It can comprise any suitable type of material,
including, but not
limited to a thermoplastic material.
In addition, the method of bonding described herein is not limited to the
arrangement of rolls shown in the drawings. In other embodiments, for example,
both of
the rolls can be provided with pattern elements. In embodiments where both of
the rolls
are provided with pattern elements, the pattern elements can be arranged to
make contact
with each other. Alternatively, the pattern elements on one of the rolls can
be arranged to
make contact with the surface of the opposite roll at locations between the
pattern
elements on the surface of the other roll. In addition, the load bearing
members are not
limited to being positioned only on the patterned roll. The load bearing
members can be
provided on the anvil roll, or on both the patterned roll and the anvil roll.
Numerous variations of the bearing members shown in Fig. 12 are also possible.
For example, it is possible that the bearing members can have at least some
portions that
are not continuous, and the patterned roll 110 may still provide some or all
of the benefits
described herein. In addition, the shape of the cut out areas in ~.he bearing
members need
not be the same as one half of the shape of the pattern elements.
.The preferred method of dynamically bonding these materials may further
comprise the step of heating one or both of the rolls, 110 and 112. If the
rolls are heated,
they are preferably heated to a surface temperature that is a predetermined
number of
degrees below the melting temperature of the thermoplastic material in the
cover material
24.
In other embodiments, the materials to be bonded can be compressed (or "pre-
compressed") before they are fed into the nip 114 for bonding. For example,
the
materials to be bonded can be fed through a pressurized nip between another
pair of rolls
prior to the set of rolls 110 and 112 to pre-compress the materials to be
bonded. The pre-
compression may involve compressing the entirety of the materials to be
bonded. or it
may comprise a localized compression in those areas of the tube forming
composite web
88 at which the bonds 94 will be formed.
The pre-compression step can also occur in conjunction with the bonding in
other
types of bonding processes. For example, if ultrasonics are used, the
ultrasonic welder or
"staker" will generally cause the material to be bonded undergo a degree of
compression
for the dwell time needed to form the ultrasonic bond. Thus, in the case of
conventional
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31
ultrasonic welding, a pre-compression step that is separate from the bonding
process
generally used, is not required.
In addition, for simplicity and clarity of the invention, the apparatus used
in the
bonding process is described herein as comprising cylinders 110 and 112.
However,
cylinders are but exemplary nip defining members. Accordingly, it is not
intended to
thereby limit the present invention to an apparatus comprising cylinders per
se. In the
same vein, use of the term ''pattern element" is not intended to limit the
method
described to bonding patterns consisting of only discrete, spaced pattern
elements to the
exclusion of other patterns: e.g., reticulated patterns or patterns comprising
continuous
or elongate lines of bonding.
The methods described herein can further comprise any of the process
limitations
or steps described in U.S. Patent 4,854,984 issued to Ball, et al on August 8,
1989.
Another factor that should be taken into consideration when forming bonds
using
a dynamic bonding process is evenly distributing the load on the pattern
elements. This
is most significant when a single bonding roll or surface is used to bond a
material
having portions with different thicknesses. The different thicknesses may
occur in
several different situations. For example, the material to be bonded could be
profiled or
calendered so that it has regions with different thicknesses. Alternatively,
the material to
be bonded may comprise a laminate wherein the length and/or width of all the
layers is
not the same. In such a case, some of the bonds may have to pass through more
layers
than the other bonds.
One way of evenly distributing the load on the pattein elements in such
situations, is to vary the angle of the side walls 119 of the pattern elements
116. The
angle of the side walls 119 of the pattern elements 116 that will be
penetrating the
portions of the material or materials to be bonded which have a greater
thickness should
be greater than that of the pattern elements 116 that will be penetrating the
portions of
the materials) which have a lesser thickness. For example, the angle of the
side walls
119 of the pattern elements 116 that will be penetrating the thinner portions
of the
materials) to be bonded may form an angle of about 50°, and the angle
of the side walls
119 of the pattern elements 116 that will be penetrating the thicker portions
of the
materials) to be bonded may be about 70°. The pattern elements 116 that
will be
penetrating the thicker portions of the materials) to be bonded may also have
a greater
height, if desired (or the other pattern elements can be made shorter).
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32
As discussed above, the method of the present invention can be carried out
using
adhesives, cohesives, hydrogen bonding (for example, if one of the materials
to be
bonded comprises cellulose), heat and/or pressure, or ultrasonics. Preferably,
however,
either the dynamic bonding process or ultrasonics are used. Such processes are
particularly preferred if the bondable material, such as second web of
material 24 is
treated by a chemical or composition that interferes with usual bonding
methods
(particularly adhesives). For example, these bonding processes would be
preferred if the
second material is treated with a skin care composition, or a material that
alters the
hydrophilicity of the second material.
Examples of the latter types of surface treatments are described in P&G U.S.
Patent 5,693,037 entitled "Absorbent Articles Having Improved Surfactant-
Treated
Hydrophilic Topsheets", issued to Yan-Per Lee, et al. on December 2, 1997. The
dynamic bonding process and the ultrasonic bonding processes described herein
are
capable of either bonding through such treatments, or transferring enough heat
through
such coatings or surface treatments that the bond can be formed with the
underlying
material. Alternatively, if such surface treatments are intermittently
applied, the pattern
on the bonding device may be designed so that the bonds penetrate the
untreated portions
of the material.
Fig. 7 shows that the bonding compresses, or more preferably, displaces the
compressible foam absorbent material 22 in localized areas where the bonds 94
are
formed. This isolates a three-dimensionally shaped portion 100 of the tube
forming
composite web 88 from the remainder of the tube forming composite web 102 and
forms
the isolated portion 100 (as well as the entire tube forming composite web 88)
into a
distinct shape. The tube forming composite web 88 is shaped, preferably
symmetrically,
on both sides. This is possible because the bonding exerts pressure on only a
portion of
the tube forming composite web 88 where the tube forming composite web 88 is
compressed by the pattern elements 116 against the curved surface of the anvil
roll. This
embodiment of the method of the present invention, thus, differs from
embossing
processes which would create a structure with one embossed side and one flat
side.
D. Attachine The Tube of Absorbent material To A Base Pad To Form A
Compound Sanitary Napkin.
After the bonding process, the bonded tube forming composite web 88 is
preferably cut into a plurality of individual tubes of absorbent material,
each of which
will be placed on top of a base pad to form a compound sanitary napkin.
CA 02311393 2004-O1-21
33
As shown in Fig. 8, the apparatus used for cutting the bonded tube forming
composite web 88 comprises a pair of rolls 130 and 132. One of the rolls, roll
130, has at
least one, and preferably a plurality of knife elements 134 on its surface.
The knife
elements 134 are preferably configured to make a continuous, generally
transverse
direction cut in the continuous bonded tube forming composite web 88. The
other roll
132 serves as an anvil member, and, thus, may be referred to as anvil roll
132. The knife
roll 130 and anvil roll 132 also define a nip 136 therebetween. After the
cutting step, the
individual tube of absorbent material 88 which are sent to a conveyor 140 for
attachment
to the base pad to form a compound sanitary napkin.
In the case of the individual tube of absorbent material shown in Fig. 7, the
remainder 102 of the tube forming composite web 88, which is not held together
by
bonds, is unfolded and spread out prior to attachment of the tube forming
composite web
88 to the base pad. The bonding and the unfolding of the remainder 102 of the
tube
forming composite web 88 forms the tube forming composite web 88 into a
profiled
shape in which the portion of the tube forming composite web 88 that will form
the top
of the absorbent tube on the finished product, is given a narrower width.
Preferably, as
shown in Fig. 13, the portion of the composite web 88 that will form the top
of the
absorbent tube on the finished product defines a ridge 106 that projects
perpendicularly
from the top of the remainder of the forming composite tube 102 (and the
remainder of
the sanitary napkin). As shown in Fig. 13, the bonding also provides the tube
forming
composite web 88 with a quilt-like pattern where the tube forming composite
web 88 is
puckered around the bond sites 94.
Fig. 13 shows a compound sanitary napkin 800 having the tube of absorbent
material 88 on the body-facing side thereof, which was bonded by the method of
the
present invention.
To form the compound sanitary napkin 800, a sanitary napkin can serve as the
panty protector (or "base pad") 820 and the tube of absorbent material 88,
which will
serve as the "primary menstrual pad is placed on top of the base pad 820 and
attached
thereto at least at its ends. Sanitary napkins suitable for use as the base
pad 820 include
ALWAYS ULTRAS sanitary napkins marketed by The Procter & Gamble Company of
Cincinnati, Ohio.
In a particularly preferred embodiment, the base pad 820 comprises a variation
of
such an ALWAYS ULTRATM sanitary napkin which has an absorbent core comprising
a
tissue laminate with superabsorbent hydrogel-forming material particles
therebetween,
CA 02311393 2004-O1-21
34
and a tissue and a DRI-WEAVETM apertured film overlying the absorbent core.
Suitable
tissues are manufactured by Merfin~ Hygienic Products. The tissue overlying
the
absorbent core is preferably joined to the absorbent core by a spiral pattern
of adhesive.
The tube of absorbent material 88 can be joined to the base pad 820 in any
suitable
manner. The attachment of the tube 88 to the sanitary napkin 820 is preferably
achieved
by fusion bonding extensions 58 of the topsheet material 56 at the ends of the
tube to the
base pad 820. In some preferred embodiments of such a compound sanitary
napkin,
there may also be attachment to the base pad 820 between the ends of the tube
of
absorbent material 88 and the base pad 820. The tube of the compound sanitary
napkin
can be attached to the base pad between its ends by any suitable attachment
means. such
as by adhesives.
The sanitary napkin 800 has a first (or front) end region 828, a second (or
rear) end
region 830, and a central region 832 positioned between the first and second
end regions.
As shown in Fig. 13, the tube of absorbent material 88 is profiled from the
front end
region 828 of the sanitary napkin 800 to the rear end region 830 of the
sanitary napkin as
a result of the bonding. More specifically, the tube of absorbent material 88
has its
highest caliper in the center of the sanitary napkin along the transverse
centerline, T, and
tapers to a lesser caliper at the ends of the sanitary napkin.
The bond patterns can be varied to create a tube of absorbent material with
increased caliper along all or any portion of the length of the sanitary
napkin 800. Foi
example, the bonding can be such that the increased caliper is confined to the
central
region 832 of the sanitary napkin 800. Alternatively, the bond pattern can be
used to
provide increased caliper in the end regions, or in a portion of central
region and a
portion of the end regions.
2. Alternative Embodiments of the Method of the Present Invention.
Numerous alternative embodiments of the present invention exist. For example,
in
one alternative embodiment, the absorbent material in the tube of absorbent
material
need not be formed into particulate material before it is bonded. That is, a
solid piece of
absorbent material can be used. However, the bonding through a solid absorbent
material, such as an absorbent foam material, may be more difficult,
particularly if it is
over about 4 mm thick.
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It is also possible to bond through other types of materials, such as low
density
absorbent materials, using the method of the present invention. For example,
the method
of the present invention can be used to bond through non-calendered airfelt.
If it is
desired that the airfelt be calendered, the airfelt can be calendered after it
has been
enveloped in the bondable material and bonded according to the method of the
present
invention.
The method of the present invention, however, provides several advantages in
comparison to merely embossing an absorbent article, such as an absorbent
article
comprising an embossed airfelt absorbent core. In such absorbent articles, the
topsheet
may be adhesively bonded to the airfelt absorbent core. The backsheet may be
adhesively bonded to the airfelt as well. The cellulosic fibers in the airfelt
are held
together by hydrogen bonds. These hydrogen bonds suffer from the disadvantage
that
they will tend to be released by liquids. Adhesives also suffer from the
disadvantage that
they may tend to be released by liquids and if certain surface treatments are
applied to the
components of the absorbent article, such as the topsheet.
Fig. 14 shows another use of the method of the present invention. In the prior
embodiments, the method of the present invention involved placing materials
that were
capable of being bonded on the outside surfaces of an incompatible material
and bonding
these materials together by penetrating through the incompatible material. In
Fig. 14, the
method of the present invention is used to bond two incompatible materials to
materials
that are capable of being bonded, which lie inside the incompatible materials.
Fig. 14 shows two webs of incompatible material 22. The webs of incompatible
material 22 may comprise any of the incompatible materials described herein.
Preferably, the webs of incompatible material comprise an absorbent foam
material.
Although it is difficult to attach such absorbent foam materials to other
materials using
adhesives, in this embodiment, a layer of adhesive 98 is used to bond each of
the webs of
absorbent foam material 22 to a web of material 24 that has a higher
bondability. This
adhesive bond is, however, subject to the risk that the absorbent foam
material may
separate therefrom due to the low structural integrity of the absorbent foam
material.
The webs of material 24 having the higher bondability can be any of the second
materials
described herein. Preferably, the webs of material 24 having the higher
bondability
comprise nonwoven webs.
As shown in Fig. 14, the webs of absorbent foam material 22, with the nonwoven
webs 24 adhesively attached thereto are placed in a face-to-face relationship
with the
CA 02311393 2004-O1-21
36.
nonwoven webs 24 adjacent to each other. The entire composite structure thus
formed is
then bonded together by the method described herein. The composite structure
can be
bonded by passing it through a nip between a pair of rolls such as those in
the apparatus
shown in Fig. 8. This will cause a bond 94 to be formed between the two
nonwoven
webs 24.
The bond 94 in this embodiment, may be a "hidden" bond which is not visible
from outside the absorbent foam material 22. The bond 94 may be hidden because
that
pattern element which formed the bond will typically displace a small amount
of the
foam material. In addition, after the bonding, the foam material 22 may expand
over the
bend area to make the places where the foam material was displaced, less
visible.
In addition, the method described herein can be used for other purposes and to
make other types of absorbent articles. For instance, Fig. 15 shows an
absorbent
interlabial device 1020 that is bonded and shaped by the method of the present
invention.
The absorbent interlabial device 1020 may comprise any suitable absorbent
material,
including any of the incompatible materials described herein. In the
embodiment shown
in Fig. 15, the absorbent interlabial device 1020 comprises a rayon core 1044
that is
wrapped with a nonwoven web cover material 1046. Rayon is typically
incompatible
using conventional bonding techniques. As shown in Fig. 16, however, the
method of
the present invention can be used to bond and shape the rayon core 1044 by
providing
bonds 94 between the nonwoven cover 1046 on opposite sides of the absorbent
interlabial device that penetrate the rayon.
As shown in Fig. 16, a first portion 1044A of the cover material 1046 is
preferably bonded through the absorbent rayon material 1044 to a second
portion 1044B
of the cover material. The apparatus used for bonding the covered absorbent
material
1044 preferably comprises a pair of cylindrical rolls, patterned roll and
anvil roll, 110 and
112. The cylindrical rolls 110 and 112 are similar to those shown in Fig. 8.
As in the
embodiment shown in Fig. 8, preferably, at least one of the rolls, roll 110,
has a relief
pattern on its sdrface. The patterned roll 110 is configured to have a
circular cylindrical
surface 115, and a plurality of protruberances or pattern elements 116 which
extend
outwardly from the surface 115. The relief pattern and the land surfaces 118
on the
pattern elements 116 can be in any suitable configuration. The side walls 119
of the
pattern elements 116 preferably form an angle similar to that described
relative to the roll
110 shown in Fig. 8.
The rolls 110 and 112 are preferably operated in a manner that is the same or
similar to that described above for the apparatus shown in Fig. 8 (including,
but not
CA 02311393 2004-O1-21
37
limited to, ranges of surface velocity differential between the rolls, range
of nip pressures
between the rolls, optional possibility of heating one or both rolls, and
replacement of the
rolls by other types of nip defining members.
The relief pattern, in the embodiment of the apparatus shown in Fig. 16, also
comprises a plurality of spaced apart pattern elements (or "pattern element
segments")
116 having circular land surfaces 118. In the embodiment of the method shown
in Fig.
16, however, the pattern elements 116 are arranged in a "half moon"
configuration. The
pattern elements 116 are provided in an alternating pattern wherein every
other
application of the bonding pattern, bonds 94 are formed on opposite sides of
the
longitudinal axis, A1, of the covered "rope" of absorbent material.
The bonding process shown in the drawings penetrates through the sliver of
absorbent material 1044 and autogenously bonds the first portion 1044A of the
cover
material to the second portion 1044B of the cover material 1046.
The embodiments of the absorbent articles shown in the drawings demonstrate
other advantages of the method of the present invention. The bonds 94 can be
placed in a
virtually unlimited number of patterns. These bonds 94 can be used to create
products
having a virtually unlimited number of possible geometric shapes. The bonding
patterns
can also be used to add structural stability as well as shaping the absorbent
article by
adding a degree of stiffness to the product along a line that passes through
the bonds.
This line can be rectilinear, curvilinear, or partially rectilinear and
partially curvilinear.
Deep quilted impressions can be created for liquid handling or appearance. The
method
of the present invention can also be used on a manufacturing line running at
high speeds
(e.g. 700 - 1,000 feet per minute), and is not limited to particular patterns,
as are sewing
processes.
Figs. 17 and 18 show a sanitary napkin 1320 that can be produced with several
different features using the method of the present invention. Fig. 17 shows an
absorbent
article (an extensible sanitary napkin designated 1320) in which the method of
the
present invention was used to simultaneously perform several different
operations in the
process of making the absorbent article. The sanitary napkin 1320 comprises a
main
body portion 1322. The main body portion 1322 comprises a liquid pervious
topsheet
1324, a liquid impervious backsheet 1326 joined to the topsheet, and an
absorbent core
1328 positioned between the topsheet 1324 and the backsheet 1326. These
components
can be joined in any suitable manner that allows the assembled sanitary napkin
1320 to
be extended. The sanitary napkin 1320 may comprise a pair of end seals 1329
that are
CA 02311393 2000-OS-24
WO 99126769 PCT/US98/25222
38
formed by fusing the topsheet and backsheet together. The sanitary napkin 1320
also has
wings or flaps 1330 extending from each longitudinal side edge of the main
body portion
1322 thereof.
The sanitary napkin 1320 shown in Fig. 17 has an absorbent core 1328 with
regions 1334 that have been formed into particulate material 1336 by the
method
described herein. As shown in Fig. 17, the regions 1334 comprising the
particulate
material are separated by unformed bands 1338 that are oriented in both the
longitudinal
direction and the transverse direction. In addition, the method of the present
invention
was preferably also used to form strainable network regions into the topsheet
1324 and
the backsheet 1326. The term "strainable network region" is described in
greater detail
in U.S. Patent No. 5,518,801 entitled Web Materials Exhibiting Elastic-Like
Behavior,
which issued to Chappell, et al. on May 21, 1996. The formation of the
strainable
network regions into the topsheet 1324 and backsheet 1326 provides these
components
of the sanitary napkin with extensibility. The unformed bands of the
strainable network
in the topsheet 1324 and backsheet 1326 provide these extensible components
with
elastic-like properties. The formation of the absorbent core 1328 into
particulate material
places the absorbent core 1328 into a form that will not interfere with the
extensibility of
the topsheet 1324 and backsheet 1326.
The topsheet 1324 and backsheet 1326 can be provided with extensibility in one
direction, in more than one direction, or in all directions in the X-Y plane,
depending on
the pattern of the strainable network formed therein. In the embodiment shown
in Fig.
17, the sanitary napkin 1320 is extensible in both the longitudinal and
transverse
directions. The sanitary napkin 1320 shown in Fig. 17 is preferably extensible
in the
amounts specified in the disclosure of U.S. Patent 5,611,790 entitled
"Stretchable
Absorbent Articles", which issued to Osborn, et al. on March 18, 1997.
Fig. 17 shows that the methods described herein can also be used to provide
the
wings or flaps 1330 with extensibility. The wings 1330 can be provided with
extensibility in any of the directions specified above for the topsheet and
backsheet. It is
also possible to provide the wings 1330 with extensibility in a direction or
amount that
differs from that of the topsheet and backsheet by passing the sanitary napkin
1320
through an apparatus that has a different pattern on the portion of the
patterned surface
that contacts the wings 1330 from the portion of the apparatus that contacts
the main
body portion of the absorbent article. The portions of the rolls that will be
used to
provide the wings with extensibility, if mating rolls are used, may also be
positioned
CA 02311393 2004-O1-21
39
closer together, or engage to a greater extent, if the wings 1330 do not have
as many
layers as the main body portion 1322 does.
The method of the present invention is also used to emboss and/or bond the
components of the sanitary napkin together. Fig. 17 shows that the body-facing
surface
of the sanitary napkin 1320 may be provided with a plurality of embossments in
the form
of fusion bonds 1340. The fusion bonds 1340 can be formed by providing a
plurality of
bonding elements on the patterned surface of the apparatus used to form the
absorbent
core 1328 into particulate material. The bonding elements may optionally be
heated if
desired. Typically, in order to bond the components together, at least those
components
that are bonded together will preferably comprise at least some thermoplastic
material.
In other embodiments, it may be desirable for the patterned surface to be
provided with
elements that merely emboss the body-facing surface of the sanitary napkin,
and do not
form fusion bonds between the components thereof.
The method of the present invention can, thus, be used to form the absorbent
core
1328 into particulate material, provide the. topsheet 1324 and backsheet 1326
with
extensibility, provide the wings or flaps 1330 with extensibility, to emboss
and/or bond
the components together, and seal the ends of the sanitary napkin 1320. This
can all be
accomplished in a single pass through an apparatus similar to that shown in
the drawings.
Further, as shown in Fig. 18, the bonding pattern can penetrate the topsheet
all the way to
the backsheet to provide the absorbent material with integrity by
compartmentalizing the
same. For example, the absorbent material can comprise a thermally bonded
airlaid
material. In such an embodiment, it may not be necessary to provide
conventional binder
fibers or powder binders to maintain the integrity of the material.
While particular embodiments of the present invention have been illustrated
and
described, it would 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.
