U.S. patent application number 10/271767 was filed with the patent office on 2003-02-20 for non woven textile structure incorporating stabilized filament assemblies.
This patent application is currently assigned to Lohmann GmbH & Co KG. Invention is credited to Barth, Georg Martin, Carus, Edmund Hugh.
Application Number | 20030034115 10/271767 |
Document ID | / |
Family ID | 9884183 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030034115 |
Kind Code |
A1 |
Barth, Georg Martin ; et
al. |
February 20, 2003 |
Non woven textile structure incorporating stabilized filament
assemblies
Abstract
A plurality of substantially parallel continuous filaments, e.g.
of cellulose acetate or rayon, and preferably newly formed, are
consolidated or partially stabilised, e.g. by application of
solvent and pressure, by hydroentanglement, by embossing, or by
crimping and stretching. The filament assembly or subassemblies
thus produced are further stablised by folding, bundling, twisting
or intertwining, e.g. to form braids (10), and are then bonded to a
carrier layer or sandwiched between outer layers (12, 14), e.g. by
hydroentanglement, melt blowing, spinbonding etc. The stablised
filament assemblies may be arranged spaced transversely and may be
cut just prior to bonding so as also to provide longitudinally
spaced three dimensionally thicker regions, ready for conversion to
finished products such as absorbant feminine hygiene products or
medical swabs or the like.
Inventors: |
Barth, Georg Martin;
(Rengsdorf, DE) ; Carus, Edmund Hugh; (Clitheroe,
GB) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Lohmann GmbH & Co KG
Neuwied
DE
|
Family ID: |
9884183 |
Appl. No.: |
10/271767 |
Filed: |
October 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10271767 |
Oct 17, 2002 |
|
|
|
PCT/GB00/01510 |
Apr 18, 2000 |
|
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|
Current U.S.
Class: |
156/148 ;
156/296 |
Current CPC
Class: |
B32B 5/26 20130101; D04H
3/11 20130101; B32B 38/06 20130101; D04H 3/04 20130101; D04H 13/00
20130101; B32B 2262/04 20130101; B32B 7/04 20130101; D04H 3/07
20130101; D04H 3/14 20130101; Y10T 442/643 20150401; Y10T 442/659
20150401; Y10T 428/2913 20150115; B32B 2305/20 20130101; D02G 1/00
20130101; B32B 2038/0028 20130101; B32B 2307/73 20130101; Y10T
442/608 20150401 |
Class at
Publication: |
156/148 ;
156/296 |
International
Class: |
B32B 001/00 |
Claims
1. A method of producing a nonwoven textile structure comprising
the steps of initially stretching a plurality of substantially
parallel continuous tow filaments to provide a partially stabilized
filament assembly, further constraining said filament assembly by
folding, bundling or twisting operations, subjecting this
constrained filament assembly to low hydroentangling pressures and
bonding the resulting filament assembly to a carrier layer or
layers so as to maintain substantially uninterrupted capillarity
along the entire length of the said resulting filament
assembly.
2. A method as set forth in claim 1 wherein the resulting filament
assembly is cut at intervals and deposited at spaced intervals on
the carrier layer prior to bonding to the carrier layer or
layers.
3. A method as set forth in claim 1 wherein a plurality of spaced
apart fully stabilized filament assemblies are bonded to the
carrier layer or between carrier layers.
4. A nonwoven textile structure produced by the method set forth in
claim 3 and comprising a plurality of spaced apart stabilized
filament assemblies bonded between respective outer layers, each
assembly being composed of filaments having substantially
uninterrupted capillarity.
5. A nonwoven textile structure as set forth in claim 4 wherein the
filament assemblies comprise cellulose acetate.
6. A nonwoven textile structure as set forth in claim 4 wherein the
filament assemblies comprise solvent spun rayon.
7. A nonwoven textile structure as set forth in claim 4 wherein the
outer layers extend beyond the filament assemblies at the edges
thereof and are bonded only to each other in these locations.
8. A method of producing a nonwoven textile structure comprising
the steps of initially stretching a plurality of substantially
parallel continuous tow filaments to provide a partially stabilized
filament assembly, further constraining said filament assembly by
folding, bundling or twisting operations, subjecting this
constrained filament assembly to light tacking by means of thermal
spot calendaring or by ultrasonic means and bonding the resulting
filament assembly to a carrier layer or layers so as to maintain
substantially uninterrupted capillarity along the entire length of
the said resulting filament assembly.
9. A method as set forth in claim 8 wherein the resulting filament
assembly is cut at intervals and deposited at spaced intervals on
the carrier layer prior to bonding to the carrier layer or
layers.
10. A method as set forth in claim 8 wherein a plurality of spaced
apart fully stabilized filament assemblies are bonded to the
carrier layer or between carrier layers.
11. A nonwoven textile structure produced by the method set forth
in claim 10 and comprising a plurality of spaced apart stabilized
filament assemblies bonded between respective outer layers, each
assembly being composed of filaments having substantially
uninterrupted capillarity.
12. A nonwoven textile structure as set forth in claim 11 wherein
the filament assemblies comprise cellulose acetate.
13. A nonwoven textile structure as set forth in claim 11 wherein
the filament assemblies comprise solvent spun rayon.
14. A nonwoven textile structure as set forth in claim 11 wherein
the outer layers extend beyond the filament assemblies at the edges
thereof and are bonded only to each other in these locations.
15. A method of producing a nonwoven textile structure comprising
the steps of: (a) drawing a bundle of crimped filaments, i.e. tow,
from a bale; (b) stretching said bundle lengthways and across its
width; (c) folding or corrugating said stretched bundle in a
stuffer box process which includes air injection so as to increase
its bulk and loft; and (d) subjecting the resulting material to a
hydroentangling process.
16. A method as set forth in claim 15 wherein step (d) comprises
directly subjecting the corrugated and bulked material to a process
of hydroentanglement employing widely spaced water injection
manifolds.
17. A method as set forth in claim 15 wherein step (d) comprises
directly subjecting the corrugated and bulked material to a process
of hydroentanglement at lower water pressure.
18. A method as set forth in claim 17 including the further step of
feeding the resulting material between upper and lower layers of
nonwoven textile web and subjecting this layered structure to a
process of hydroentanglement at lower water pressure and/or using
widely spaced water injunction manifolds.
19. A method as set forth in claim 18 including the additional step
of cutting the resulting material and feeing the cut pieces in a
spaced array between the upper and lower layers of nonwoven textile
web.
20. A bandage formed by the method set forth in claim 18.
21. Dressings or pads for medical and surgical purposes formed by
the method set forth in claim 19.
Description
[0001] This application is a continuation-in-part of International
Patent Application No. PCT/GB00/01510 filed Apr. 18, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to nonwoven textile materials
and in particular to composite absorbent textile materials.
[0003] The present invention has particular application to
absorbent textile materials or structures for uses in the medical
field, for example in or as dressings, sponges or swabs and
laparotomy sponges. There are applications also in the fields of
sanitary protection, infant care and adult incontinence
protection.
BACKGROUND ART
[0004] Nonwoven materials made by many different processes have
been utilised as components to produce absorbent materials for use
in feminine hygiene, infant diapers and incontinence products.
Modern technologies utilising fluff pulp structures often combined
with other non-woven materials to form multilayer composites, have
been used to facilitate fluid capture, distribution and
containment. Other materials such as superabsorbent polymers are
often incorporated in these composites to maximise fluid
containment.
[0005] WO 99/27876, WO 99/27879, WO 99/30661, WO 00/56258 and WO
01/72253 A1, (SCA Hygiene Products AB) and US 2002/0026699A1, US
2002/0029026A1, US 2002/0028624A1, US 2002/0029023A1, US
2002/0029024A1, US 2002/0029025A1 and US 2002/0049419A1 (Uni-Charm
Corporation) all describe use of filament "tows" as a fluid
acquisition material in infant diapers and the like but as only one
component in the absorbent matrices specified. More particularly,
these specifications disclose production of a layer or layers of
continuous "tow" filaments which are bonded in various ways and
which may be of cellulose acetate, or of polyethylene,
polypropylene, polyamide, polyester, polyvinyl acetate, viscose or
rayon, or bi-component polymers. Steps in production of said layer
can include crimping or curling, then stretching and distributing
the "tow" filaments in various ways, then bonding same in a pattern
of lines, spots or points by any suitable technique including
thermal or ultrasonic bonding, calendering, laser or print-bonding
or undefined hydroentanglement. The filaments are cut to length
either before or after the aforesaid bonding. Optionally in some
cases, the "tow" filaments can be bonded, at the same time as the
pattern of bonding mentioned above, to a liquid containment layer
which can be a non-woven composite material. In some cases, some
further details are provided of the method of handling the "tow"
filaments to produce a finished layer or layers. The prior art
describes conventional bonding of tow filaments by various
techniques, all of which depress the performance of such tow
assemblies by capillary blockage at points of bonding.
OBJECT OF THE INVENTION
[0006] The present object is to provide an improved manner of
handling continuous filaments to facilitate their incorporation
into a finished product, which has enhanced properties, e.g. of
absorbency and/or fluid management, compared to known products.
SUMMARY OF THE INVENTION
[0007] A method of producing a non-woven textile structure is now
proposed which comprises the steps of initially stretching a
plurality of substantially parallel continuous tow filaments to
provide a partially stabilized filament assembly, further
constraining said filament assembly by folding, bundling or
twisting operations, subjecting this constrained filament assembly
to low hydroentangling pressures, and bonding the resulting
filament assembly to a carrier layer or layers. An alternative to
hydroentangling is light tacking.
[0008] In the finished product, where the filament material is
absorbent, significant improvements in fluid management, notably
wicking and fluid containment are apparent over existing materials
currently utilised and known to those skilled in the art. This is
because the processing of the filament assembly is such as to
maintain substantially uninterrupted capillary along its entire
length.
[0009] In more detail, the initial stages of the method of the
invention require tow stretching followed by a carefully controlled
corrugation or compaction procedure using for example, overfeed
technology such as forced fluid or air injection stuffer box
processes. These latter processes enhance the coherence and
integrity of multifilament tow assemblies and also impart a degree
of loft, bulk, airiness and/or three dimensionality to the
assembly.
[0010] Other comparable techniques known to those skilled in the
art and optional layering operations can also or alternatively be
used at this stage.
[0011] Subsequent to these processes is a second, full
consolidation operation preferably using controlled very light
hydroentangling. This may mean low water pressure and/or widely
spaced water injection manifolds. Alternatively, very light but
highly controlled tacking using simplified thermal spot calendering
or ultrasonic means can be employed. Either technique should
provide sufficient strength and integrity to these tow assemblies
to facilitate further processing without disrupting the inherent
capillarity of such structures.
[0012] From such a multi-stage process, three-dimensional tow
structures of chosen size and shape result with properties that can
be selected for optimum end-use performance.
[0013] One or more of the resulting three dimensional stabilized
tow assemblies can then be incorporated into simple composite
structures by appropriate highly controlled light bonding means
such as, but not limited to, controlled light hydroentangling. In
this way one or more such stabilized tow assemblies can be bonded
to a carrier layer of nonwoven fabric, or between respective outer
layers of nonwoven fabric. Such bonding retains the capillary
structures in these consolidated tow assemblies. Any capillary
tortuosity as a result of controlled light hydroentangling can be
accepted since the capillary matrices remain substantially intact
and functional.
[0014] Surprisingly, it has been discovered that the presence of
such nonwoven fabric outer layers serves to preserve the
capillarity of the three dimensional tow assemblies by lessening
the impact of resultant hydroentangling water jets on these
assemblies by a shielding action. At the same time though, the
nonwoven fabrics are lightly mechanically adhered to the tow
assemblies to form the completed desired composite assemblies.
Naturally, in specific locations where the tow assemblies are
absent in the composite structures, the outer nonwoven fabric
layers adhere to each other as a consequence of the controlled
hydroentangling procedure.
[0015] Such composite structures can, of course, contain more than
or less than three layers of material, and these layers may
include, in addition to fully consolidated tow assemblies, the
nonwoven fabrics already mentioned and/or other materials
appropriate to the desired end-use.
[0016] The materials or structures described in this disclosure can
be made into converted pieces with controlled tow assembly
deposition. The simplest product envisaged is a single elongate
stabilized tow assembly of the type already described and of
somewhat flattened cross-sectional shape bonded to a nonwoven
fabric web. This could serve as or be incorporated with other
layers as a bandage. In a preferred, modified version, the tow
assembly would be sandwiched between respective outer layers of
nonwoven fabric and bonded thereto, by hydroentanglement or
tacking, as already outlined. In either form, there may be free
edge margins where no tow assembly is present and there is only a
marginal strip of carrier material, or the outer layers are bonded
to each other.
[0017] In a further development, favourable for mass production,
several such stabilized tow assemblies are spaced apart
transversely and bonded to a carrier layer or between outer layers.
Again there may be free edge margins also, with no tow present. The
composite formed can be cut, if required, only at the end of the
procedure. That cutting can be along the strips between the
presence of the tow assemblies, to provide several elongate
bandages, but it could also be transversely of the composite to
provide individual dressings.
[0018] Another way of obtaining smaller individual products, like
dressings, is to cut the single stabilized tow assembly, mentioned
above, into short sections and spaced these apart longitudinally
before sandwiching between outer layers and further bonding.
[0019] In a more favourable further development, particularly for
production of individual medical dressings or surgical sponges,
several such filament assemblies may be spaced apart transversely
and also cut and the resulting sections spaced apart longitudinally
on a carrier nonwoven web and then subjected to controlled
hydroentangling possibly following the addition of an upper carrier
nonwoven web.
[0020] This yields areas of carrier material around each island of
filament tow, and the individual pieces can be cut apart at each
end of the procedure.
[0021] The fully consolidated filament assemblies can be secured
during their preparation and/or prior to the final composite
assembly procedure by a degree of "moistening". This acts to secure
the filaments by a combination of hydrogen bonding between these
filaments possibly combined with light mechanical filament cohesion
by surface tension forces imparted by the presence of this added
moisture. Such a moistening procedure enhances the quality of the
nonwoven composites produced by hydroentangling by retaining the
shape and geometry of the filament assemblies.
[0022] Whilst any polymer filament system which can be rendered
hydrophilic can be considered applicable for production of these
three-dimensional stabilized filament assemblies, either alone or
with other polymers to form blended filament assemblies, the
preferred polymer is cellulose acetate which achieves outstanding
fluid take up and wicking properties. Staple cellulose acetate
fibre has been used in non-woven fabrics in the past and reported
in literature by Celanese Acetate LLC and other sources such as
Kimberly-Clark but such non-woven materials have been conventional
web-like structures. Solvent spun rayons as described in the
literature by Acordis plc and Lenzing AG are also a favoured option
since such materials exhibit excellent fluid handling properties
particularly in fully stabilized three-dimensional tow formats
[0023] The fluid management performance of filament assemblies
produced in accordance with the invention can be optimised by the
careful selection of filament diameters and packing density.
Mixtures of coarser and finer filaments may be advantageous since
filament spacing and the presence of capillaries are required for
optimum fluid management. In this regard, the use, in the
assemblies of filaments which have a "Y" shaped or "stellar" shaped
cross-section or the like may be advantageous since the crevices
running along such shaped filaments act like fine capillary
structures thus enhancing fluid wicking and full utilisation of the
composite structures.
[0024] A preferred nonwoven material for use in the outer layers of
such composites surrounding the fully stabilized filament
assemblies is solvent spun cellulose. Such cellulose exhibits
excellent hydroentangling properties yielding strong composites
with excellent tactile and absorbency properties, essential in
medical applications such as swabbing or laparotomy. Such
hydroentangled structures also exhibit excellent fibre retention
(i.e. minimal loose fibres) in both wet and dry states, again vital
in medical uses.
[0025] The stabilized filament assemblies can be cut by heat,
ultrasonic or laser technologies prior to their deposition onto a
carrier nonwoven web to produce nonwoven composites. These forms of
cutting prevent filament loss which is highly undesirable in many
end use applications, such as medical swabs and the like.
[0026] All the nonwoven structures described can be laminated to
suitable backing sheets either during manufacture or as an after
process to provide for extra security in use by preventing fluid
leakage through the thickness of the absorbent composites. Such
backing sheets include polymeric films, preferably those having
water vapour permeability to optimise skin wellness in use.
Preferred backing sheets such as, for example, those made from
cellulose or cellulose acetate exhibit environmentally responsible
disposability.
[0027] The nonwoven composites disclosed in this current invention
are suitable as a novel and innovative alternative to traditional
gauze, as used in medical dressings, sponges, laparotomy sponges
and bandages. In particular, due to their capillarity, the
composites are highly absorbent. Moreover, by correct material
usage in the outer nonwoven component or components they can
possess a non-adherent surface for single sided or double sided
dressings, respectively. Because of the high absorbency of these
composites, there is no need for folding or use in multiple plies
as is the case with all woven and nonwoven sponges used to date. It
is also possible to produce shaped sponges which are advantageous
to the end-user and which are difficult to produce when folding is
involved.
[0028] The composites described can possess chosen tactile
properties dependent on the ingredients used. Furthermore, it is
possible to reproduce the feel and three-dimensionality of
conventional woven products. The texture, absorbency performance
and appearance of the finished composites are dependent on the
number, size, morphology and spacing of the filament assemblies
incorporated into the composites coupled with the composition of
the outer nonwoven layers surrounding these filament
assemblies.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The invention will be exemplified by reference to the
accompanying drawings, in which:
[0030] FIG. 1 is a sketch illustrating apparatus used for the three
step production of a practical embodiment of newly formed fully
stabilized three-dimensional filament assembly in accordance with
the present invention;
[0031] FIG. 2 is a sketch illustrating one type of apparatus for
the production of composite material incorporating cut sections of
the fully stabilized three-dimensional filament assembly resulting
from the apparatus shown I FIG. 1; and
[0032] FIG. 3 is a sketch illustrating a version of a completed
composite article or product containing a cut section of the
filament assembly resulting from the apparatus of FIG. 1, as
produced, for example, by the apparatus of FIG. 2.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] FIG. 1 illustrates a three step in-line consolidation
procedure for the formation of a stabilized three dimensional
multifilament assembly with substantially continuous capillarity
from, in this case, cellulose acetate spun filaments. Spun
filaments (1) from a bale (2) of crimped filamentary tow as is
commercially available are subjected to a longitudinal stretching
process using textile drafting rollers (3) coupled with a degree of
lateral stretching using bowed "Mount Hope" rollers (4).
Corrugation and compaction of these stretched filaments (5) is
achieved using a stuffer box (6) with forced air injection (7).
[0034] The initially consolidated three-dimensional compacted
filaments are then subjected to a very light and highly controlled
specialist hydroentangling operation. In this respect, an extremely
light, minimal water pressure, preferably in the region of only
10-15 bars, is used in the hydroentangling operation. Portions of
two pairs of hydroentangling manifolds 8 are shown. Water jets
issue from apertures in these manifolds 8 directed upwards and
downwards onto the compacted filament assembly. This is sufficient
to impart handling integrity to the resultant filament assembly (9)
without interfering with the capillarity of said structure.
[0035] FIG. 2 illustrates a typical process whereby such formed
fully stabilized filament assemblies 9 can be incorporated into
finished absorbent nonwoven composites. Fully stabilized filament
assemblies (9), production of which was described in relation to
FIG. 1, are positioned onto a prepared nonwoven fabric (12). Three
such assemblies 9 are shown spaced apart transversely across the
width of the apparatus and of the fabric 12, with a margin at each
transverse edge of the fabric 12. The assemblies 9 are cut at
intervals so as also to produce a longitudinal array of filament
assembly sections 10.
[0036] The fabric 12 is pre-moistened at a preliminary station 13
to facilitate positioning of the filament assemblies' sections 10
by drum-like apparatus 14 in a controlled manner and specifically
to prevent movement of the assembly sections 10 on the base
nonwoven material 12.
[0037] A second nonwoven fabric 15, in this case identical to the
base nonwoven material 12 is placed onto the assembly of fully
stabilized filament assembly sections 10 and base nonwoven 12. The
total structure thus formed is subjected to light but controlled
hydroentangling by further pairs of hydroentangling manifolds 16.
This should be sufficient to hold the composite 17 securely
together but insufficient to destroy the capillarity and three
dimensionality of the fully stabilized filament assembly sections
10. Suitable hydroentangling pressures at this stage may be between
40 and 200 bars, optimally possibly between 50 and 100 bars. The
completed composite 17 is then subjected to drying, in this case
using through-air technology in enclosure 18.
* * * * *