Note: Descriptions are shown in the official language in which they were submitted.
'` X005~
Composite material which i8 capable of swelling ln the
presence of water, supports which can be used for
manufacture of same and uses thereof
The invention relates to a composite material capable
of swelling in the presence of water or an aqueous
solution.
More precisely, the ob~ect of the invention is a
composite "sandwich" type materlal, comprising essentially
a mixture of hydroexpandable powder and thermobonding
powder fixing two layers of identical or different
materials one on the other, one at least of which is at
least partially hydrosoluble, a material at least
partially hydrosoluble for manufacturing this composite
and the applications of this composite.
Composite materials are already known capable of
swelling, without appreciable dissolution, in the presence
of water. Such materials are generally used in the
electric cable industry. In this case they are introduced,
; 20 in the form of a ribbon, into the sheath of the cable to
provide longitudinal sealing, by swelling and forming a
plug if water penetrates accidentally into the cable not
only at its ends but at a position where the sheath may be
pierced, thus preventing the propagation of water inside
the cable.
Among ribbons of this type may be mentioned the one
commercialized by the firm Freundenberg, Weinheim, G.F.R.
under the name VILEDON-FIBREX~ and the references known up
to date : K 3310, K 3312, K 3313, K 3303C and K 3002C, the
one commercialized by the firm LANTOR, Veenendaal,
Netherlands, under the references known to date : 3C 115,
3C 116, 3E 110, 3E 111, 3E 113, 3E 114, 3E 115 and 3E 116
to which reference is made in the patent FR 81 02863 and
the one commercialized by the firm GECA TAPES, BAARLE
NASSEAU, NETHERLANDS, under the references known to date :
GT 100, GT 101, GT 200, GT 201, GT 1000, GT 205.
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These rlbbons are essentially formed of a
hydroexpandable polymer powder sandwiched between two
conventional non-woven fabric layers.
Cohesion of the composite ls obtained by incorporating
a thermoplastic substance (powder, fibre or other) in the
hydroexpandable polymer powder. Under the combined action
of pressure and heat, the thermoplastic substance softens,
becomes sticky and thus provides cohesion of the
composite.
During this bonding action, the nature of the non-woven
fabrics and their association with the thermobonding
substance cause an unfavourable effect : in fact, the two
non-woven fabric layers are firmly and durably bonded
together by the molten thermoplastic powder mass. This
: 15 limits the swelling of the hydroexpandable polymer in the
presence of water or an aqueous solution.
According to the invention, it has now been discovered
that the properties of such a composite material could be
considerably increased by replacing one at least of the
two conventional non-woven fabric layers by one or two
flat solid supports, partially or completely soluble in
water or aqueous solutions (hereafter to simplify
water).
Among other things an object of the invention is the
composite material thus obtained.
The invention relates more particularly to a composite
material comprising essentially a mixture of
hydroexpandable powder and thermobonding powder,
sandwiched between two solid flat supports, one at least
30 of which is at least partially hydrosoluble.
In a preferred embodiment, said mixture is formed of :
- 80 to 60~ by weight of hydroexpandable powder, and
- 20 to 40~ by weight of thermobonding powder.
Such a material allows the water to be held at the
35 position where it is introduced and thus has numerous
appl1cat1ons.
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Thus, it may be used as a seallng rlbbon ln cables,
partlcularly electrlc or telecommunicatlons cables, but
also as germination activator or for the transplantation
of young shoots, in medicine or surgery as "sponge", or ln
the field of hygiene, for example ln dlsposable nappies.
The supports and ln partlcular the at least partlally
hydrosoluble support or supports of this materlal are
chosen essentially as a function of the final use thereof.
They may be formed particularly of a non-woven fabric,
a textile, paper, or a synthetlc film. For most
applications, particularly in the energy transporting and
telecommunications cable industry, they are preferably
flexible.
The hydroexpandable polymer may be formed from any
polymer or mixture of polymers compatible with the support
and the final use thereof and capable of considerable
swelling in the presence of water or of aqueous solutions
by "storing" them, yet insoluble therein, i.e. having a
solubility in these liquids less than 5%.
Advantageously, the hydroexpandable polymer is chosen
so that it is capable of absorbing at least 15 times its
own weight of water.
The hydroexpandable polymer may be chosen particularly
from modified acrylic polymers, grafted starches,
polyacrylamides, carboxymethylcellulose and its
derivatives and adyantageously generally from polymers
corresponding to the definition of "superabsorbents",
namely polymers which are "insoluble" (in the above
mentioned meaning) in the fluids which they absorb and
30 absorbing at least 15 times their own weight of water or
of aqueous solution.
As superabsorbent polymers, there may be mentioned by
way of lndicatlon but ln no wlse limiting :
- the acrylic polymer commercialized by the firm JAPAN
35 CATALYTIC CHEMICAL under the name AQUALIC,
- the acrylamide polymer commerclalized by the firm
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CYANIMID under the name HYDROBLOCXO,
- the carboxymethylcellulose polymer commercialized by She
firm HERCULES under the name AQUASORB,
- the starch/polyacrylic acid polymer obtained by grafting
- 5 and commercialized by the firm LION under the name LION-
POLYMER, and
- the sodium polyacrylate polymer commercialized by the
firm GRAIN PROCESSING under the name WATER-LOCK J~.
The thermobonding powder is chosen from the
thermoplastic polymers capable of bonding two fibrous or
solid surfaces together and compatible with the other
~materials used and for the contemplated use.
Among the thermobonding polymer powders which may be
advantageously used in the scope of the invention, there
may be mentioned by way of non limitative examples :
- the polyethylenes commercialized by the firm CDF CHIMIE
" under the trademark LOTRENE,
- the polyethylenes commercialized by the firm EXXON under
the trademark ESCORENE, and
- the polyamides commercialized by the firm EMS under the
trademark GRILTEXq.
For use as sealing agent in the industry manufacturing
electric cables for transporting medium and high voltage
energy, it is advantageous to make the composite material
25 electrically conducting, so as to obtain acceptable
conductivity in its thickness and on the surface.
To achieve this, at least one of the two flat solid
supports is charged previously with a material for
obtaining surface and transverse resistance adapted to the
30 type of cable manufactured. In general, for this, 5 to
20g/m2 of conducting carbon black is introduced into said
support or each of said supports during manufacture
thereof.
Conducting carbon black may also be introduced into the
35 hydroexpandable powder and the thermobonding powder
mixture in proportlons such that a distribution of 8 to 20
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- 5 --
g/m2 of carbon black is obtalned in the sandwiched
mixture.
: In a preferred embodiment of the invention, a composite
material is thus obtained comprising essentially a mixture
of 80 to 60~ by weight of hydroexpandable powder and 20 to
40% by weight of thermobonding powder, sandwiched between
two flat solid supports, one at least of which is at least
partially hydrosoluble and 5 to 60 g/m2 of conducting
carbon black.
The composite material according to the invention may
be produced in a way known per se by sprinkling, on a flat
solid support, the hydroexpandable powder and
thermobonding powder mixture containing, if required,
conducting carbon black. This assembly is then heated to a
sufficient temperature to cause the thermobonding powder
to melt. Such heating may be carried out in a drier, an
oven, for example a pulsed hot alr oven, or under lnfrared
heating ramps. The second flat solid support iæ then
applied and pressed on the heated assembly by means of
rollers.
This assembly may also be formed directly by means of
two heated rollers (calender).
In an advantageous embodiment, at least one of the
supports of the composite of the invention is formed of a
partially hydrosoluble non-woven fabric. Non-woven fabrics
of this type ars new.
The lnvention has further as object a partially
hydrosoluble non-woven fabric which may be used for
manufacturing the composite material of the inventlon,
characterized in that it essentlally comprises by weig~t :
- 95 to 55% of non hydrosoluble fibres;
- 5 to 35% of hydrosoluble binder; and
- 0 to 10% of surface-active agent.
Such a non-woven fabric may further comprise conducting
carbon black, particularly for use in electric cables.
A further obJect of the invention, in an advantageous
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embodiment, is a partially hydrosoluble non-woven fabric
characterized in that it essentially comprises by weight :
- 76 to 28% of non hydrosoluble fibres;
- 4 to 18% of hydrosoluble binder;
- O to 4% of surface-active agent; and
- 20 to 50% of conducting carbon black.
The non hydrosoluble fibres may be natural, artificial
or synthetic. They may be viscose fibres, polyester
fibres, acrylic fibres or mixtures of such fibres.
As examples of such fibres may be mentioned, purely by
way of illustration, :
- the polyester fibres commercialized by the firm EMS,
under the tradename GRILENE~; -
- the polyester fibres commercialized by the firm DU PONT
DE NEMOURS under the tradename DACRON~;
- the polyamide fibres commercialized by the firm EMS
under the name GRILON;
- the polypropylene fibres commercialized by the firm
STEEN under the name POLYSTEEN; and
- the viscose fibres commercialized by the firm LENZING.
The hydrosoluble binder is chosen from the hydrosol~ble
binders capable of fixing flat fibrous masses, without
substantially modifying their physico-chemical properties.
Among binders of this type which may be advantageously
used in the scope of the invention, may be mentioned by
way of non limitative examples :
- the polyvinylpyrrolidones commercialized by the firm -
GAF, under the tradenames PVP K 30 and PVP K 90~;
- the polyvinylpyrrolidones and vinylpyrrolidone-vinyl
acetate copolymers commercialized by the firm BASF (GFR)
under the tradenames of LW ISKOL K30-K90; and
- the hydropropylcelluloses commercialized by the firm
HERCULES (USA) under the tradenames KLUCEL H, M, G, J, L
and E~.
Although the presence of a surface-active agent is not
indispensable, it has been discovered that it plays a
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favorable role, particularly in the dlstrlbutlon of the
binder during manufacture of the non-woven fabric.
Preferably an anionic or non ionlc surface-active agent
is used as surface-active agent.
Among the surface-active agents whlch may be used
wlthln the scope of the invention there may be mentioned
by way of non limitative examples :
- the product commercialized by the firm ROHM AND HAAS
(USA) under the tradenames of TRITON X 100~ and TRITON GR
5 M;
- the product commercialized by the firm BYKMALLINCKRODT
under the name ANTI-TERRA-U;
- the product commercialized by the firm PETROCHEMICALS
: CO., INC. under the name of MORWET EFN;
- the products commercialized by the firm AIR PRODUCTS
under the name SURFYNOL-; and
- the product commercialized by the firm 8ASF ~GFR) under
the name LEOPHEN RA.
Such a partially hydrosoluble non-woven fabric may be
manufactured conventionally using the so-called "dry
process". Thls process conslsts of an operation for
carding the fibres, to make thesefibres parallel with each
other and produce an homogeneous layer. This layer is then
fixed by means of the hydrosoluble binder, used for
;- 25 example in the form of an aqueous phase solution whose
concentration is dosed so as to obtain a sufficiently
strong non-woven fabric for the application contemplated~
whlle permitting the most rapid dissolution possible when
the complex plays its role in contact with water or an
aqueous solution.
This concentration depends particularly on the nature
and on the physical characteristics of the fibres to be
bonded together and on the binder used. In most cases it
may be from 3 to 20%, advantageously 7%. The hydrosoluble
binder solution is deposited on the layer, for example in
the form of foam using a device known as a "foamer".
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Possible addltives (such as surface-active agent,
conductlng carbon black) may be incorporated in the
solution before or durlng foaming.
The layer thus impregnated is then dried, for example
S using a rotary through air drier, a system of heated
rollers, called ~maniques", a heating tunnel or any other
device suitable for this application.
The non-woven fabric may then be either wound for
subsequent use or fed immediately into the manufacturing
process of the composite of the invention.
In another advantageous embodlment, at least one of the
~supports of the composite of the invention is formed from
a non-woven fabric, at least partially hydrosoluble,
formed wholly or partially of fibres which are at least
partially hydrosoluble and thermobonding, the bonding of
the fibres being then achieved by heat bonding.
- In this context, by way of example, the non-woven
fabric may be formed of :
- 50 to 100% of PVA (polyvinyl alcohol) fibres ; and
- 50 to 0% of natural, artificial or synthetic fibres,
such for example as those mentioned above by way of
examples.
As PYA fibres, those commercialized by the firm KURARAY
under the trademark KURALON~ may be mentioned.
In yet another embodiment, the composite of the
invention may comprise as support at least one textile, at
least partially hydrosoluble which is woven or knitted.
As new textile of this type may be mentioned a woven or
knitted textile, at least partially hydrosoluble, which is
e8sentially formed of :
- 50 to 100% of PVA (polyvinyl alcohol) threads,
- 50 to 0% of conventional natural, artificial or
synthetic threads, obtained for example from the fibres
mentioned above by way of examples.
The paper, at least partially hydrosoluble, which may
also be used as support in the composite of the invention
;~00~ 4
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may be formed conventlonally by dlspersing natural,
artificlal or synthetic flbres ln a bath with a high
concentratlon of hydrosoluble blnder.
As paper of this type, may be mentloned the paper
commerclallzed by the flrm NEDI (France) under the name
"Hydro dispersable paper".
As hydrosoluble support film a synthetic polyvinyl
alcohol film may be used. In thls context, the films
commercialized by the firm NEDI (France) under the name
NEDOL may be mentioned.
As was lndlcated above, the composite material of the
~invention may have various uses.
Thus, it may be used as water or physiological liquid
absorbent, particularly in medicine and surgery or in the
field of sanitary products such as dlsposable nappies,
etc..
It may in particular be lncorporated in the manufacture
of nappies for babies, in the form of strips or cut
pieces, thus reinforcing absorption and urine retention,
especially at particular positions depending on the
morphology of the bables.
The composite of the invention may also be used in
agrlculture as germinatlon activator for holdlng water at
the position where the grain is deposited : such precise
localization ls particularly interesting when the water is
enriched wlth growth promoting substances, such as
nutrltional substances. In addition, substances su~h as
anticryptogamic compounds, fungicides, fertilizers may be
readily incorporated in the composite material at the time
of powdering.
The composite material of the invention may also be
used for the transplantation of young shoots. They are
packed with their clod of earth in the composite materlal
and may be transplanted without risk after soaking in
water.
As mentioned above, another important appllcation of
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the composlte material of the lnvention i8 its use in
cables for providing longitudinal sealing thereof.
In the case of contact with water, one at least o the
two supports is decomposed, at leaQt partially, uncovering
the hydrophilic sites of the hydroexpandable polymer.
The result is compact and rapid swelling. At the ~ame
time, the hydroexpandable polymer is released by
decomposition of the support or supports. Such release
allows displacement of the gel which may be oriented
towards the zones of preferential passage of the water,
thus providing excellent efficiency in situ.
~ Referring to figures 1 and 2 of the accompanying
; drawings, the behaviour of the composite material of the
invention will be described hereafter when it is
incorporated in the sheath of a cable, in the presence of
water passing accldentally through the external sheath of
- the cable.
The composite material of the invention 1, formed of
two flat solid supports 10 and 11, one 11 at least of
which is completely or partially hydrosoluble, bonded
together by a mixture 12 of hydroexpandable polymer powder
and thermobonding polymer powder, is placed between the
external sheath 2 and the core, or more generally the
internal sheath 3 of the cable. Because of the
construction of the cable, its parts 2 and 3 are often
separated by a slight empty space. In addition, they move
away from each other to a greater or lesser extent during
use of the cable (figure 1).
If water penetrates accidentally into the cable (figure
2) through the external sheath 2 and passes through the
flat solid support 11, which is at least partially
hydrosoluble, of the composite material 1, it dissolves
this flat and solld support at least partially and
practically instantaneously and enters into contact with
the hydroexpandable polymer powder, about the position at
whlch lt penetrated into the cable.
" : ' ,-
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-- 11 --
The hydroexpandable polymer which was held between the
two supports ls then released at this position and thus
has the possibility of moving, while gelling, 80 as to
form about the water penetration zone a pad 13 which
prevents propagation of the water in the cable.
The hydroexpandable polymer which is no longer a
prisoner of the supports may develop all its swelling
capacity for blocking the accidental entry of water into
the cable. Such capacity and such rapidity are improved
with respect to the prior art where the hydroexpansion
force must first of all unstick the two non hydrosoluble
~supports, between which the gel remained prisoner for an
appreciable period of time.
In addition, with the composite of the invention 1, the
gel created is completely efficient for it is free and
accumulates close to the infiltration zone.
It is obvious that such a description is only given by
way of illustration and that in particular other
arrangements could be provided inside the cable without
departing from the scope of the invention.
Figures 3 and 4 show what happens when prior art
composites such as defined above are used.
The composite material 4 ls formed of a layer of a
mixture 42 of a hydroexpandable polymer and a
thermoplastic substance sandwiched between two non
hydrosoluble non-woven fabric layers 40 and 41. When water
penetrates accidentally into the cable, the
hydroexpandable polymer swells, at the point of
penetration of the water, without being separated from the
supports : it causes "swelling" 43 Just at this level, but
cannot form a pad about this zone.
The protection conferred is therefore less efficient
than with the invention and, since this polymer cannot
develop all its swelling capacity, particularly because of
the strong and durable bond between the two non
hydrosoluble supports due to the thermoplastic polymer, it
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ls necessary to use a larger amount.
The following examples are given to better illustrate
and explain the invention without however limitlng the
scope thereof.
` EXAMPLE 1
.
Partially hydrosoluble non-woven fabric having a
conventional non hydrosoluble fibre basis
- Polyester fibres GRILENE HTB of
the firm EMS (Switzerland)73% by weight
- Polyvinylpyrrolidone binder PVP K30
15 from the firm GAF (USA)25% by weight
., .
- Wettlng agent TRITON GR 5 M-
from the firm ROHM AND HAAS (USA)2~ by weight
; 20
EXAMPLE 2
Manufacture of a partially hydrosoluble non-woven fabric
comprising thermobonding hydrosoluble fibres.
- KURALON~ PVA fibres from the firm
KURARAY (Japan) 70% by weight
- Polyester GRILENE HTB fibres
30 from the firm EMS (Switzerland)30% by weight
The fibre layer is damped then heat bonded by
calendering.
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EXAMPLE 3
Manufacture of a composite materlal accordlng to the
invention
: 5
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COMPONENTS WEIGHT
10 Non woven non hydrosoluble support
. Ref : 42040 from INTISSEL (France) 40 g/m2
Hydroexpandable powder
ref : 10 SHP from NORSOLOR (France) 35 g/m2
.. Thermoplastic polyethylene powder
ESCORENE-, ref : MP 654 from EXXON (USA) 10 g/m2
...
: Non woven fabric support, at least
partially hydrosoluble, according to
the invention (in particular with the
compositions described above and
particularly in examples 1 and 2) 15 g/m2
-,
: 25 -
The non hydrosoluble support is a conventional non-
woven fabric, which may be conducting or not, manufactured
using the so-called ~dry process~, from polyester fibres
and a butadiene acrylonitrile binder, charged or not with .
-30 conducting carbon black. These fibres are oriented ~ ~
preferably parallel. .
On this non woven non hydrosoluble support is then
deposited the hydroexpandable powder and thermobonding
powder mixture using a sprinkler formed of a powder
storage tank at the bottom of which is situated an
engraved roller whl d dellvors the powder and whooe epeed ¦~
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of rotatlon determlnes the welght of powder deposlted. It
: is in this example 45 ~/m2.
The powdered non hydrosoluble non-woven fabric support
then enters an oven comprislng lnfrared radiatlon ramps,
: 5 adJusted to a sufflclent temperature to cause the
thermobondlng powder to melt.
On leavlng thls oven, the at least partially
hydrosoluble non-woven fabric support, which is conducting
or not, ls unwound and applled with pressure to the first
powdered support by means of two rollers whose pressure
force may be adJusted.
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