Note: Descriptions are shown in the official language in which they were submitted.
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. 1
A COMPOSITE PLANE MATERIAL INCLUDING A PERFORATED FILM
AND THERMOPLASTIC FIBERS, USE THEREOF AND METHOD OF
MANUFACTURE
The present invention relates to a composite plane
fiber material in which a film is covered with fibers
which are bonded to one another and also to the film. It
also relates to the use of said material as an air-
permeable film that is preferably, but not exclusively,
capable of being impermeable to liquids, in particular in
hygiene articles, e.g. disposable diapers or nappies and
sanitary napkins or towels. It also relates to a method
of manufacture specially designed for producing said
composite plane fiber material.
In diapers, the absorbent wad is generally placed on
a film that is impermeable to liquids and that serves
both to support said wad, enabling it to be put in place
and closed on the user, and also serving as a barrier to
urine. When the article is left in place on the user and
the absorbent wad is wet with urine, the urine often
soaks through to come into contact with the skin of the
user, thereby giving rise to rashes or even to allergies.
Proposals have already been made to remedy this situation
by using a film to support the absorbent wad, where the
film is both impermeable to liquids while being also
permeable to air and to water vapor. The film thus acts
as a barrier to urine while allowing gas exchange to take
place between the inside of the article and the outside,
thereby enabling the urine contained in the absorbent wad
to be progressively eliminated in the form of water
vapor.
One such film, having the properties of being
impermeable to liquids and of being permeable to air and
water vapor is generally made from a microporous material
that is known cs~m~rcially under the name Goretex. The
cost of that material is very high. In addition, in the
opinion of the Applicant, its feel is not very agreeable.
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For sanitary napkins, the absorbent wad is
surrounded by a film that must enable blood to pass in,
but not back out. For this purpose, proposals have
already been made for a perforated film in which the
perforations are in the form of craters, with the
projections of the craters being on the face that comes
into contact with the absorbent wad. Here again, the
feel of such a material is not agreeable.
The object of the Applicant is to provide a
composite plane material that is capable of mitigating
the drawbacks of the above-mentioned films.
This object is fully achieved by the composite plane
material of the invention. In characteristic manner,
this material is constituted by a perforated
thermoplastic film which has a multiplicity of small-
sized perforation craters on one face and whose opposite
face is smooth and is covered with fibers, most of which
are thermoplastic fibers; the fibers are bonded to one
another and to the film in substantially continuous
r~nnPr,
The bonding of the fibers on the film must not give
rise to crushed spots of the kind described in document
EP 0 403 187, since they give rise to harmful deformation
of the craters and to non-uniformity in the fiber sheet.
In that document it should be observed that the sheet of
fibers is not bonded to the smooth face as in the present
invention, but to the face that has the craters.
The fibers are preferably bonded to one another and
to the film, even on the walls of said craters.
Permeability to air and to water vapor is obtained
by the presence of the perforations that allow gas
exchange to take place between the faces of said
material. The chosen dimensions, number, and shape of
the perforations serve, where appropriate, to ensure that
the thermoplastic film remains impermeable to liquids, or
to obtain permeability to liquids in one direction only.
The presence of fibers on the surface of the
21382~
thermoplastic film provides the material of the invention
with a fiber feel that is more agreeable.
The fibers cover the smooth face of the
thermoplastic film, i.e. the face which corresponds to
the inside walls of the craters. The concept of inside
wall and "outside" wall as applied to a crater will
become more clear from the description given below of a
particular embodiment.
The plane material of the invention preferably
includes perorations at a density lying in the range 10
per cm2 to 100 per cm2, with the size of said perforations
lying in the range 0.1 mm to 1.5 mm.
The fibers are bonded to one another and to the film
by virtue of the thermoplasticity of the raw materials
thereof. It is therefore necessary for most of the
fibers to be thermoplastic fibers, so that the composite
material of the invention has sufficient cohesion between
the film and the fibers.
The perforated thermoplastic film may also be
covered with thermoplastic fibers that are bonded to one
another and to the film in substantially continuous
manner on the opposite face, i.e. on the face that has
the perforations craters on its surface. Under such
circumstances, both faces present an agreeable fiber
feel.
The raw material from which the thermoplastic fibers
and the film are made is preferably the same, e.g.
polyethylene. Nevertheless, the film could be made of
some other material such as polyamide or polypropylene,
or a mixture of polyethylene and of ethylene vinyl
acetate (EVA). The thermoplastics fibers may be made of
polypropylene.
In a variant, the fibers are bonded to one another
and to the film by the presence of an adhesive, in
combination with the thermoplasticity of the raw
materials constituting the fibers and the film. Under
2l3e2~3
such ~i~um~tances, lt is possible to use raw materials
havin~ melting points that ~re si~nlficantly differen~.
The qu~ntity of adhesive must be relat~ely low so
as ~o avoid spoiling ~he ~le~ibility of the composite
material. It preferably lies in the range 0.2 gr~ms per
s~uare meter (~/m2) to 5 gJm2 fo~ a weight o~ fibers ly~ng
in the range 2 g/m2 ~o 20 g/m2~
The composite fiber ma~erial is advantageously used
as a "~reathing" film in the manufactu~e of ab orbent
hygiene articles, in p~rticular disposable diapers ~nd
s~nit~y napkins It rel~tes in particul~r to a
breathing fil~ serving as a support or coverlng ~or ~he
a~sorbent w~d~
The ~nvention also provides a fi~st m~thod of
mqnufacturing ~he above-specifi~d composite pl~ fiber
material Th~ method consis~s:
a) in dispe~sing ~ shee~ o~ ~ibers most 0~ whi~h 2re
thermoplast~c on a ther~oplasti~ film, optionally pre-
coa~ed with adhesive,
~) ~n p~esenting the a~embly made up in this w~y on
a $urface that is p~ovided with orifices; and
c~ in heating said assembly to ~ temperature ~lose
to the soft~n; n~ t~mperature of ~he the~opl~st~
materials constit~ting the fi~ers and the ~ n while
2S simultaneously establ;~hing suction throu~h the ori~ice,
so as to cause the film over caid orifices to punct~re.
The heating of ~he fil~fibe~ a~semhly serves bo~h
to sof~en the filla in the :zones con~espond~ to ~he
ori~i~e~ and also to obtain bonding between the fibers
and between the fibers ~nd the f~lm in su~stant1ally
continuous m~nne~ at the poin~s o~ conta~t be~wee~ those
various parts~ In part~cular, it is o~served that the
walls of the craters formed durin~ p~n~urin~ of the ~lm
under the effect of air being sucked th~ough the orlfices
can constitute privile~ed zones for bonding between the
f i~ers and the ~il~.
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The fibers can be dispersed in the form of a sheet
over the surface of the thermoplastic film by any
appropriate means, in particular by spraying on the
fibers using the cut fiber technique, or the spun
technique, or indeed using the melt-blown technique.
In a preferred version, the manufacturing method is
a continuous method and the surface on which the
film/fiber assembly is presented is constituted by the
peripheral surface of a rotary drum fitted with an
internal suction system.
The heating of the film/fiber assembly can be
performed in particular by means of radiant panels
located above the surface of the drum, over that portion
thereof that is fitted with the suction system.
A composite plane fiber material of the invention
can also be obtained using a second method in which a
sheet of thermoplastic fibers is dispersed over a
perforated thermoplastic film which has a multiplicity of
small-sized perforation craters on one of its faces, the
fibers being dispersed at least over the smooth other
face of the film while the fibers are at a temperature
that is high enough to cause them to adhere naturally to
the surface of the film after it has cooled.
Under such circumstances, the film is covered
uniformly by the sheet of fibers and the fibers are point
bonded to one another and to the film solely because of
the thermoplasticity of the materials, bonding taking
place on the surface of the film with the exception of
its craters.
In order to be certain that the fibers do indeed
bond to one another and to the surface of the film, a
variant of the above-specified method consists in pre-
coating the smooth face of the perforated thermoplastic
film with adhesive that withstands said temperature. The
adhesive is preferably likewise a thermoplastic polymer,
suitable for application by the melt-blown technique.
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The invention also provides a third method of
manufacturing the above-mentioned composite plane fiber
material. This method consists:
a) in extruding a thermoplastic film on a non-woven
fabric constituted by a sheet of fibers most of which are
thermoplastic;
b) in presenting the assembly constituted in this
way onto a surface that is provided with orifices; and
c) in heating said assembly to a temperature close
to the softening temperature for the thermoplastic
materials constituting the fibers and the film while
simultaneously establishing suction through the orifices
so as to cause the film overlying said orifices to
puncture.
Compared with the first above-mentioned method, the
first step makes use of a non-woven fabric instead of a
thermoplastic film as the pre-existing support medium.
In this case, it turns out that there is no longer any
need to consider coating with adhesive insofar as highly
effective bonding is obtained between the fibers and the
film merely by applying the film during extrusion
directly onto the non-woven fabric.
The present invention will be better understood on
reading the following description of two embodiments of a
film/fiber composite material of perforated polyethylene
shown in the accompanying drawings, in which:
Figure 1 is a diagrammatic section view of one type
of composite material;
Figures 2A, 2B, 2C, and 2D are diagrammatic section
views through different fiber configurations in a crater
zone;
Figures 3 and 4 are diagrams showing two
installations for manufacturing said composite material;
and
Figure 5 is a diagrammatic section view through
another type of composite material.
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The composite material 1 characteristic of the
invention is made up of a thermoplastic film 2 that is
covered on one of its faces with fibers 3 that are mostly
thermoplastic fibers. The composite material 1 includes
a multiplicity of perforations which are substantially
crater-shaped, as can be seen clearly from Figure 1.
The fibers 3 are bonded to one another and to the
film, at least in the smooth zones 24 of the film which,
on the face of the film opposite from the craters 4,
corresponds to the plane zones excluding the inside walls
5 of the craters 4. The fibers 3 are bonded to one
another and to the film 2 in substantially continuous
manner, i.e. without any spots where the fibers are
crushed or where the craters are deformed.
The fibers 3 may also be bonded to one another and
to the film 2 on the walls 5 of the craters 4.
More precisely, Figures 2A, 2B, 2C, and 2D are
diagrams showing four configurations that can be taken up
by the fibers 3 where they overlie a crater 4.
In the first configuration tFigure 2A), the fibers
3a overlie the walls 5 of the crater 4, while leaving the
orifice 6 of the crater open.
In the second configuration (Figure 2B), the fibers
3b overlie the walls 5 of the crater 4 and at least some
of them cross from one wall 5a to the opposite wall 5b,
thereby obstructing the orifice 6, at least in part, in a
zone 7 of the crater that corresponds to the apex of said
crater.
In a third configuration (Figure 2C), fibers 3a
overlie the walls 5 of the crater 4 as in the first
configuration. However, there are also other fibers 3c
that extend over the crater 4 substantially in the same
plane as the other fibers in the non-perforated zones of
the non-composite material 1.
In a fourth configuration (Figure 2D), the fibers 3d
extend solely over the crater 4, remaining substantially
~13~253
in the same plane as the other fibers in the smooth zones
24.
A single composite material 1 of the invention may
naturally include craters whose fiber coverings
correspond to one or more of the above-specified four
configurations, and indeed they may be covered in other
types of configuration, depending in particular on the
method of manufacture. For example, it is possible to
ensure that there are no fibers overlying a crater 4,
e.g. as shown in Figure 2a, and also that there are no
fibers on the inside walls of the crater 4.
The predominance of one or other of the
configurations depends on the conditions under which the
composite material is manufactured, as appears more
clearly from the description below.
Figure 3 is a highly diagrammatic representation of
a first installation 29 for manufacturing the composite
material shown in Figures 1 and 2.
The installation 29 includes means for feeding a
plastic film 2, e.g. a polyethylene film. These means
may be constituted by a shaft 8 rotated by drive means
(not shown) and having a roll 9 fitted thereon that is
constituted by a reel of film 2.
On the path of the film 2, the installation 29
includes apparatus 10 for spraying on fibers 3, said
apparatus being disposed above a conveyor 11 suitable for
supporting the film 2 during said operation of building
up a sheet of fibers 3 on the top face of said film 2.
The installation 29 also includes a rotary drum 12
that is rotatable about a shaft 13, and that is rotated
by conventional means (not shown). The periphery of the
drum includes a multiplicity of orifices 14.
The drum 12 is a hollow cylinder having a suction
chamber 15 formed therein. The chamber 15 is
substantially airtight and is defined by an inside wall
16 which is stationary and by a fraction 17 of the drum
2138~53
g
12. Known suction generation means (not shown), e.g. a
fan, communicate with said chamber 15.
The installation 29 also includes a set of radiant
panels 18 disposed in a circular arc above the portion 17
of the drum 12 that overlies the suction chamber 15.
Finally, the installation 29 includes reception
means 29 for taking up the composite material 1.
The installation 29 operates as follows. The
thermoplastic film 2 is placed on the conveyor 11. The
spray apparatus 10 builds up a continuous and uniform
sheet of fibers 3 on the top face of the film 2, which
fibers are merely placed on the film 2 without any
particular bonding to the film. The assembly constituted
by the film 2 and the sheet of fibers 3 is brought onto
the drum 12 and is pressed thereagainst substantially
over its entire portion 17 overlying the suction chamber
15, prior to being wound onto the reception device 19.
While the film/fiber assembly is moving over the drum 12
as the shaft 13 of the drum rotates, it is simultaneously
subjected to the heating action of the radiant panels 18
and to the suction action of the chamber 15.
The effect of the heating action is to raise the
film/fiber assembly to a temperature close to the
softening temperature of the thermoplastic raw materials
constituting both the film 2 and the fibers 3.
Because of the presence of orifices 14 in the drum
12, the effect of the suction is not only to press the
film 2 against the surface of said drum 12 but also to
create perforations through the film/fiber assembly.
Since the thermoplastic film 2 is very close to its
softening state, the suction forces cause the zones of
the film that overlie the orifices 14 to be deformed;
this deformation (which is a kind of blistering)
continues until the blisters burst and then take up a
crater shape. The film 2 is thus pierced merely under
the mechanical effect of the suction.
2138~S3
,_ 10
The fibers 3 situated on the surface of the film 2
are likewise softened while the craters 4 are being
formed and they are entrained to a greater or lesser
extent during deformation of the film 2. This entraining
of the fibers 3 occurs to a greater or lesser extent
depending on various operating conditions, in particular
the heating temperature, the pressure that may possibly
be exerted to press the fibers 3 onto the film 2, the
length of the fibers 3, the content of non-thermoplastic
fibers in the fiber mix, the difference between the
softening temperature of the fibers 3 and that of the
film 2, etc. Thus, while the blisters are being created,
a greater or less quantity of fibers remains bonded to
the inside walls of each blister, so that after the
blister has burst, a crater 4 is formed with said fibers
covering the inside walls 4 of the blister. That
explains the various different configurations shown in
Figures 2a, 2B, 2C, and 2D.
It may be preferable to place an adhesive spraying
apparatus 25 on the path of the thermoplastic film 2
upstream from the fiber spraying apparatus 10, thereby
depositing a small and uniform quantity of adhesive over
the entire top face of the film 2. The device may be of
the melt-blown type projecting adhesive 26 in the form of
an adhesive thermoplastic resin.
The amount of adhesive applied must be sufficient to
improve bonding between the fibers and between the fibers
and the film while nevertheless being small enough to
avoid spoiling the flexibility of the material of the
invention. It is also a function of the quantity of
fibers 3 deposited on the film 2; the preferred range of
adhesive is 0.2 grams per square meter (g/m2) to 5 g/m2
and corresponds to the weight of fibers being in the
range 2 g/m2 to 20 g/m2.
In a variant embodiment, the composite material of
the invention may be manufactured on a second
installation as shown diagrammatically in Figure 4. For
- ll
simplification purposes, the same references are used to
designate elements that are common to both installations
29 and 30.
The shaft 8 has a roll 31 fitted thereon that
comprises a reel of non-woven fabric 32 that comprises a
sheet of fibers, most of which are thermoplastic fibers.
On the path of the non-woven fabric 32, the
installation 30 includes apparatus 33 for extruding a
thermoplastic film 34. The extruder apparatus 33 is
disposed above a conveyor 11 suitable for supporting the
fabric 32 while the film 34 is being extruded on the top
face of said fabric 32.
The installation 30 includes the same rotary drum 12
that is perforated and provided with suction means and
the same radiant panels 18 as described above for the
installation 29. However, the drum 12 must be disposed
in such a manner that it is the thermoplastic film 34
that comes into contact with the portion 17 of the drum
12 overlying the suction chamber 15, so the relative
disposition is reversed as compared with the installation
29.
The installation 30 operates as follows. The non-
woven fabric 32 is placed on the conveyor 11. The
apparatus 33 extrudes the thermoplastic film 34 which is
immediately applied to the top face of the fabric 32
before it has had time to cool down completely. This
ensures a certain amount of bonding between the fibers of
the fabric 32 and the film 34.
The other steps are identical to those described
above for the installation 29.
In the present case, because the thermoplastic film
is extruded onto a sheet of fibers that have already been
consolidated, it is found that after the composite has
gone past the rotary drum, the fibers of the non-woven
fabric in zones that overlie the craters are not only
generally unconnected with the film on the inside walls
~ 1 3 ~
_ 12
of the craters, but also they are moved apart from one
another so as to form holes over the craters.
Naturally it would be possible to obtain the
composite material of the invention using techniques
other than those described above, for example by
implementing the needling technique. However, the method
described above has the advantage of making it possible,
by adjusting operating conditions, to obtain a variety of
different products all based on the same concept, which
variety is much larger than that which could be obtained
by implementing the needling technique.
It is also possible to disperse the fibers over a
film that has already been perforated. Under such
circumstances, the fibers must be dispersed over the face
of the film that does not include the craters, with the
fibers being under conditions of temperature such that
after cooling they adhere to one another and to the
smooth zones 24 of the film. Such conditions can be
obtained by extruding the fibers directly over the film
as it moves continuously and by projecting said fibers
onto the film while they are still at a temperature that
is above the melting temperature of the thermoplastic
material from which they are made. The resulting
material will be mostly of the configuration shown in
Figure 2D.
Under such circumstances, it is also preferable to
pre-coat an adhesive onto the face of the film onto which
the fibers are projected. By way of example, the
adhesive may be a thermoplastic adhesive resin that
reacts at the temperature at which the fibers come into
contact with the film.
In the above example, a fiber covering is applied
only to the face of the film which corresponds to the
inside walls 5 of the craters 4. The invention is not
limited to that configuration. Figure 5 shows an example
of a material in which a first fiber surface 20 lies on
the face 21a of the film 21 which corresponds to the
~13~
13
outside walls 22 of the craters 23, while a second fiber
surface 27 is to be found on the face 21b of the film 21
which corresponds to the inside walls 28 of the craters
23. Such a material can be implemented by a first pass
through the installation of Figure 3 followed by fibers
being sprayed onto the other face being spunbounded
directly onto the film.
The composite material of the invention is
advantageously used in the manufacture of disposable
absorbent hygiene articles. For disposable diapers, it
is used as a support sheet for the absorbent wad, with
the craters preferably being directed towards the inside
of the article. The support thus remains impermeable to
liquids and therefore serves as a barrier to prevent
urine passing out, however, because of the perforations
it is permeable to gas and therefore allows an
interchange of air and water vapor between the inside and
the outside of the article.
For sanitary napkins, it is used as a sheet that
surrounds the absorbent wad, with the craters being
directed towards the absorbent wad. The shapes and sizes
of the perforations are such that the composite material
of the invention is permeable to liquids flowing towards
the absorbent wad but not in the opposite direction. In
both cases, the presence of fibers confers an agreeable
feel to the material of the invention which is very
different from the plastic feel of films presently used
for supporting or covering the absorbent wad.
The size and density of the perforations depend on
the intended application. In a specific example for a
hygiene application, in a film having a thickness of
about 80 micrometers, perforations were provided at a
density of about 50 craters per cm2, with an open area
ratio of 25% (ratio of the apexes of the craters divided
by the total area of the film). The film preferably
weighs 30 g/m2 to 40 g/m2.
_ 14
It may be advantageous for the thermoplastic film to
have a degree of natural elasticity. Under such
circumstances, it is preferable for the bonding between
the fibers and the film to be performed while the film is
in a stretched state. Once the perorated plane fiber
material has been made, the film returns to its initial,
non-stretched state, so that the fiber covering increases
in volume and in bulk, and is in no danger of breaking
should the material be stretched again.
The fibers constituting the non-woven fabric may be
polymers such as polypropylene or polyethylene, for
example, or they may constitute a mix of different types
of polymers or a mix of synthetic fibers and natural or
artificial fibers, e.g. viscose. Bi-component fibers may
also comprise a solution for making up a fiber wad.
The present invention is not limited to the
embodiments described above by way of non-exhaustive
example. In particular, the thermoplastic film may be
made of polyethylene, of polyamide, of EVA, of
polypropylene, or of a mixture of those materials
obtained by coextrusion or in a single layer.
