U.S. patent application number 10/556750 was filed with the patent office on 2007-04-26 for method and apparatus for producing spunbonded fabrics of filaments.
Invention is credited to Henning Roettger, Ralf Sodemann, Michael Voges.
Application Number | 20070090555 10/556750 |
Document ID | / |
Family ID | 33440956 |
Filed Date | 2007-04-26 |
United States Patent
Application |
20070090555 |
Kind Code |
A1 |
Roettger; Henning ; et
al. |
April 26, 2007 |
Method and apparatus for producing spunbonded fabrics of
filaments
Abstract
The invention relates to a method and an apparatus for producing
a spunbonded fabric of a thermoplastic material, wherein the
filaments resulting from broken fibers are additionally tempered
and/or drawn, and have different diameters and different fiber
lengths.
Inventors: |
Roettger; Henning;
(Kaltenkirchen, DE) ; Sodemann; Ralf; (Peine,
DE) ; Voges; Michael; (Hoechst i. Odw., DE) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Family ID: |
33440956 |
Appl. No.: |
10/556750 |
Filed: |
May 12, 2004 |
PCT Filed: |
May 12, 2004 |
PCT NO: |
PCT/EP04/05056 |
371 Date: |
November 8, 2006 |
Current U.S.
Class: |
264/103 ;
264/210.8; 264/555; 425/72.2 |
Current CPC
Class: |
D04H 3/02 20130101; D04H
13/00 20130101; D04H 3/16 20130101; D04H 3/11 20130101; D04H 3/14
20130101; D04H 3/007 20130101; D01D 5/0985 20130101 |
Class at
Publication: |
264/103 ;
264/555; 264/210.8; 425/072.2 |
International
Class: |
D04H 3/02 20060101
D04H003/02; D01D 5/098 20060101 D01D005/098; D01D 10/02 20060101
D01D010/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2003 |
DE |
103 22 460.2 |
Claims
1. A method of producing a spunbonded fabric of a thermoplastic
material, comprising advancing fibers through a nozzle such that a
hydrostatic pressure is reached in the interior of the fibers which
is greater than the gas pressure surrounding them so that the
fibers break and separate at least in part into a plurality of
filaments, additionally tempering and drawing the filaments after
the thermoplastic material leaves the nozzle and before the
filaments get into contact on a web laying surface and imparting to
the filaments different filament diameters and different filament
lengths.
2. (canceled)
3. The method of claim 1 wherein the additional tempering and
drawing of the filaments of burst fibers occur in one or more open
and/or closed systems.
4. The method of claim 1, wherein the tempering and drawing occur
at least in one section simultaneously.
5. The method of claim 1, wherein upstream of the web laying
surface, the filaments are accelerated and additionally tempered
and drawn by a gaseous medium that is supplied after their exit
from the nozzle.
6. The method of claim 1, wherein the filaments are accelerated and
additionally tempered and drawn by generating a low pressure in a
region directly below the web laying surface.
7. The method of claim 6, wherein the filaments are advanced
through a channel-type device downstream of the nozzle, and
accelerated and drawn.
8. The method of claim 1, wherein the filaments are accelerated and
additionally drawn and tempered by a gaseous medium or an
air-liquid mixture.
9. The method of claim 8, wherein at least one liquid of the
mixture is used, which has a specific heat capacity that is greater
than or equal to the air under atmospheric pressure.
10. The method of claim 8, wherein the mixture uses liquid, water
vapor and/or an aerosol.
11. The method of claim 1, wherein before meeting upon the web
laying surface, the filaments are additionally mechanically
drawn.
12. The method of claim 1, wherein the filaments advance through at
least one pair of temperable rolls, the rolls of which have smooth
and/or structured surfaces.
13. An apparatus for producing a spunbonded fabric of a
thermosplastic material, comprising: a web laying surface, a
spinning device for producing fibers, a nozzle into which the
fibers enter, the nozzle being designed and constructed such that
the fibers advancing through the nozzle reach a hydrostatic
pressure in their interior which is greater than the gas pressure
that surrounds them so that the fibers burst and separate into a
plurality of filaments, and at least one tempering and drawing
system, arranged downstream of the nozzle and upstream of the web
laying surface.
14. The apparatus of claim 13, wherein the tempering and drawing
system is an open and/or a closed system.
15. The apparatus of claim 13, wherein the tempering and drawing
system downstream of the nozzle surrounds the filaments in
symmetric relationship in at least one region.
16. The apparatus of claim 13, wherein the tempering and drawing
system downstream of the nozzle surrounds the filaments in
asymmetric relationship in at least one region.
17. The apparatus of claim 13, wherein for drawing the filaments,
at least one device is provided for generating and conditioning a
medium that can be supplied to the filaments after their exit from
the nozzle.
18. The apparatus of claim 17, wherein the device supplies air or
an air-liquid mixture.
19. The apparatus of claim 13, wherein below the web laying surface
in the region of the filament receiving area, a device for
generating a low pressure is arranged, which causes the filaments
to undergo drawing.
20. The apparatus of claim 13, wherein a channel-type draw system
is arranged between the nozzle and the web laying surface.
21. The apparatus of claim 20, wherein the draw system includes at
least a nozzle geometry.
22. The apparatus of claim 13, wherein the web laying surface
includes downstream of the region of the filament receiving area at
least one pair of temperable rolls with smooth and/or structured
surfaces.
23. The apparatus of claim 13, wherein in that in the region of the
filament receiving area, the web laying surface is a conveyor
belt.
24. The apparatus of claim 13, wherein in that in the region of the
filament receiving area, the web laying surface is an air permeable
drum.
25. Filaments of burst fibers with different filament diameters and
different filament lengths, which are drawn, and produced by the
method of claim 1.
26. Filaments of burst fibers as in claim 25, wherein the filaments
are continuous and/or discontinuous.
27. Filaments of burst fibers of claim 25 wherein the filaments
have diameters in a range from smaller than or equal to 1 .mu.m, to
80 .mu.m.
28. Filaments of burst fibers as in claim 25, wherein the filaments
have fiber length/diameter ratios ranging from 100:1 to
100,000,000:1.
29. A nonwoven spunbonded fabric with filaments of burst fibers,
which are produced by the method of claim 1.
30. The nonwoven of claim 29, wherein the nonwoven is multilayered
and forms a laminate, with at least one film layer or a different
nonwoven.
31. The nonwoven of claim 29 that is water-jet bonded.
32. A disposable article of a spunbonded fabric with filaments of
burst fibers, which are produced by the method of claim 1.
33. A protective clothing of a spunbonded fabric with filaments of
burst fibers, which are produced by the method of claim 1.
34. Clothing of a spunbonded fabric with filaments of burst fibers,
which are produced by the method of claim 1.
Description
[0001] The present invention relates to a method and an apparatus
for producing spunbonded fabrics of a thermoplastic material,
wherein the filaments of the spunbonded fabric result from burst
fibers, and undergo an additional treatment after leaving a Laval
nozzle.
[0002] WO 0100909 A1 and WO 02/052070 A2 disclose methods and
apparatus for producing substantially endless fine filaments from
meltable polymers or polymer solutions, wherein polymer melts or
polymer solutions are spun from at least one spinneret hole, and
wherein the spun filament is drawn by gas flows that are
accelerated to a high velocity by means of a Laval nozzle. With a
given geometry of the melt bore and its position relative to the
Laval nozzle, the temperature of the polymer melt, its throughput
per spinneret hole, and the pressures that determine the velocity
of the gas flows, are controlled upstream and downstream of the
Laval nozzle in such a manner that before its solidification, the
yarn reaches in its interior a hydrostatic pressure, which is
greater than the gas pressure that surrounds it, such that the
filament bursts and separates into a plurality of fine filaments.
In this process, the gas flows that draw the filament have an
ambient temperature or a temperature that is caused by their feed.
The filament exiting from the Laval nozzle is heated in the region
of the Laval nozzle.
[0003] Furthermore, WO 02/099176 A1 discloses a process for
producing a bonded nonwoven from at least partly microfine endless
filaments of meltable polymers, wherein a polymer melt of only one
certain polymer is spun from a plurality of spinneret holes, and
the spun filaments are drawn by substantially cold gas flows that
are accelerated by an acceleration nozzle, for example, a Laval
nozzle, and wherein as a result of further production conditions,
each filament reaches, before solidifying, a hydrostatic inside
pressure, which is greater than the surrounding gas pressure, such
that each filament bursts in the longitudinal direction, and
separates into a plurality of fine endless filaments. The
microfibers are continuously laid to a nonwoven (web) of a desired
width, and the web is continuously subjected to hydrodynamic water
jets for entangling the microfibers, so as to bond the nonwoven of
the longitudinally separated endless fibers. Furthermore, the
entanglement and bonding occur, if need be, with other fibers,
which have previously been laid below the microfibers, or are
subsequently laid on top of the microfibers.
[0004] WO 92/10599 discloses a method and an apparatus for
producing finest fibers from thermoplastic polymers by the
meltblowing method, wherein a polymer melt flows through at least
one outlet hole in a meltblowndie, and wherein directly after its
emergence, the polymer melt is surrounded on both sides of the
outlet hole by a gas flow, and burst and separated into fibers in
such a manner that the gas is accelerated to ultrasonic speed in a
Laval nozzle, which extends in mirror-symmetric relationship with
the outlet hole, that downstream of the Laval nozzle, it is
decelerated in flow channels with a constant cross section or a
cross section narrowing in the flow direction, to a flow velocity
just below the ultrasonic speed, and that the polymer melt is
supplied into the gas flow that emerges from the flow channels.
[0005] Further known are apparatus and methods for flash spinning
plexifilamentary strands of film fibrils that consist of fiber
forming polymers.
[0006] EP 0 482 882 B1 discloses such a strand as a
three-dimensional, integral network of a plurality of thin,
tapelike film fibril elements having a statistic length and an
average thickness of less than about 4 m, which are in general
oriented in a far extending relationship along the longitudinal
axis of the strand. The film fibril elements temporarily combine
and separate at irregular intervals in different locations along
the length, width, and thickness of the strand, while forming the
three-dimensional network.
[0007] EP 0 431 801, for example, discloses a method, wherein
strands of film fibrils of an ethylene vinyl alcohol copolymer, if
need be, with polyolefin components develop by forming a spin
mixture of water, carbon dioxide, and the copolymer at a
temperature of at least 130.degree. C. and under a pressure, which
is greater than the autogenous pressure of the mixture, and by
subsequently flash spinning the mixture at substantially lower
temperatures and pressures.
[0008] Preferred uses for spunbonded fabrics of this type in the
area of disposable products, in particular protective garments are
disclosed in EP 0 669 994 B1. These nonwovens are produced on an
industrial scale by E.I. du Pont de Nemours and Co., and marketed
as a spunbonded olefin nonwoven under the trade name "Tyvek."
[0009] The nonwovens that are produced in the art, exhibit in part
undesired thick places in filament sections, which result not only
from spin discontinuities that enter the deposited filaments, in an
undrawn state, as polymer melt drops, namely so-called "spots," but
also in particular from relaxations of the filaments in the case of
inadequate drawing and lacking tempering. Disadvantageous in this
connection is in particular that the water column of such nonwovens
is reduced by 20% to 80%, when compared with, for example,
conventional meltblown nonwovens with a comparable basis weight.
Likewise, the achievable textile-mechanical properties, such as
strength and elongation are reduced by 10% to 50%, when compared
with a conventional spunbonded fabric with a comparable basic
weight. Essential characteristics of use, such as softness and
hand, are deteriorated to the same extent. A further disadvantage
lies in that the production of nonwovens, which contain both
discontinuous and continuous filaments, requires additional steps,
such as, for example, a separate supply and feed of discontinuous
filaments or fibers. At this point, the invention sets in.
[0010] It is an object of the invention to improve a process for
producing spunbonded fabrics of a thermoplastic material with
filaments of burst fibers.
[0011] This object is accomplished by a method with the steps of
claim 1, with an apparatus comprising the elements of claim 13,
with filaments having the characteristics of claim 25, and with a
nonwoven fabric having the characteristics of claim 29.
[0012] Advantageous further developments and improvements are
defined in the respective dependent claims.
[0013] The present invention provides a method and an apparatus for
producing a spunbonded fabric of a thermoplastic material, wherein
the filaments of the spunbonded fabric originate from burst fibers.
As to the production of the filaments, the entire contents of WO
01/00909 are herewith incorporated by reference.
[0014] However, it is also possible to use different methods and
different apparatus, which utilize a thermoplastic material by way
of forming fibers to filaments with the use of a pressure that
prevails in the interior of the fibers. In particular, it is
possible to use in this process a Laval nozzle. However, it is
possible to use any other nozzle geometry, for example, a slot die
or the like, as long as it remains ensured that from the fibers,
filaments are formed by advancing the thermoplastic material
through the nozzle.
[0015] Because of the action of the interior pressure in the
fibers, the latter burst at least in part into a plurality of
filaments. The filaments are tempered, in particular additionally
tempered, and/or drawn, in particularly additionally drawn.
Preferably, the filaments have different diameters and different
lengths.
[0016] A further development provides that pressure is regulated
via the nozzle such that the fibers burst in such a manner that
they form at least 80%, preferably at least more than 90%,
preferably at least approximately all filaments, in particular that
100% filaments are formed from the fibers.
[0017] Another development provides that only a certain percentage
of the fibers burst and separate to result in filaments. Thus, the
fibers form anchoring points for the individual filaments, so that
the filaments are not loose, but still have cohesion at least in
part among themselves. This is especially preferred, when the
filaments are to be used for enabling an engagement of, for
example, hooklike means, as may find a use, for example, in
Velcro-type closures.
[0018] The method and the apparatus for producing the spunbonded
fabric differ from methods and apparatus of the art, in that the
filaments are additionally tempered, and/or additionally drawn, and
that the filaments have different diameters.
[0019] Furthermore, the filaments may also have different lengths.
Possibly because of the formation of fibers, the filaments are
already surrounded by a gaseous fluid. Therefore, an additional
tempering or an additional drawing means that when, for example,
this gaseous fluid also continues to exert on the filaments a
temperature effect or a drawing action, the filaments will then
undergo in addition a tempering and/or a drawing downstream of the
nozzle. The tempering or drawing that is imparted downstream of the
nozzle has the advantage that it permits in this process exerting
directly on the filaments a purposeful action in the absence of an
influence by preceding process steps, in particular the formation
of the fibers. With that, it becomes possible to perform a
tempering or a drawing operation that is adapted to the filaments,
while avoiding disturbing influences.
[0020] The method and the apparatus permit producing both
continuous filaments (endless fibers) and discontinuous filaments
(short fibers). According to a further development, the spunbonded
fabrics comprise different properties of different spunbonding
processes, which are realizable in combination with one another in
one production process. With that, essential disadvantages of known
nonwovens are eliminated. On the one hand, the nonwoven has, for
example, dimensions, which are otherwise known only from meltblown
nonwovens. On the other hand, the plurality of fine filaments is
produced in particular by a different mechanism, which in turn
brings along freedoms with respect to the usable materials.
Preferably, by bursting, filaments are produced, which have a
diameter of less than 10 .mu.m, preferably less than 1 .mu.m.
[0021] A tempering and/or drawing of the filaments after the
thermoplastic material leaves the nozzle, and before the filaments
impact upon a web laying surface, make it possible to use the space
between the nozzle and the web laying surface. Preferably, the
tempering and/or the drawing steps can be differently adjustable
along this path. It is likewise possible to provide one or more
tempering steps or drawing steps along this path. A tempering may
occur by way of radiation, convection, or via other active
mechanisms. A drawing is possible in particular by frictional force
acting upon the filament surface, as can be imparted, for example,
by a moved medium that surrounds the filaments. Furthermore, there
exists the possibility that a tension is active in the filaments
themselves, for example, by a mechanical withdrawal from the
nozzle.
[0022] When using a medium for drawing and/or tempering, in
particular a gaseous medium, same may be both heated and cooled. In
particular, the draw unit comprises conditioning facilities for
this medium. Conditioning may, for example, relate to a moisture
content of the medium, a composition of the medium, in particular a
composition of one or more phases, different substances, as well as
an addition of solid, liquid, and gaseous media. For example, the
gaseous medium is supplied to the filaments at a velocity, which is
approximately equal to, preferably higher than the speed of the
filaments advancing from the nozzle. According to one embodiment,
the medium has a velocity higher than 400 m/min, in particular a
velocity higher than 300 m/min, preferably higher than 800
m/min.
[0023] An accurate adjustment of the apparatus makes it possible to
suppress undesired thick places in filament segments to at least
more than 95%, in particular more than 98%, in particular
approximately 100%. On the one hand, the apparatus permits avoiding
the classic "spots." On the other hand, a suitable adjustment of
the drawing or the tempering step makes it possible to cause the
filaments to burst and separate totally and to prevent an undesired
relaxation of the filaments.
[0024] According to one embodiment, it accomplished that a nonwoven
that is totally produced from the thus-obtained filaments, has a
water column, which is clearly above conventional water column
values with a comparable basis weight and identical bonding of
other nonwovens. In particular, it is accomplished that such a
nonwoven has at least a 20% higher water column than a comparable
nonwoven of this type on the basis of a meltblown or a spunbonded
nonwoven. Furthermore, it is accomplished that a nonwoven of these
filaments has an elongation, which is at least 10%, preferably at
least 20%, in particular more than 35% higher than that of a
comparable spunbonded nonwoven with the same basis weight and the
same bonding. Moreover, in comparison with such a spunbonded
fabric, the nonwoven of the filaments produced in accordance with
the invention has the advantage of a softer surface.
[0025] In particular, a nonwoven that comprises filaments of the
present invention, in particular consists of these filaments, is
suitable for a preferred application as surface. Such a surface may
come into contact with sensitive surfaces. These surfaces can be,
for example, the skin of humans or animals, as well as polished
surfaces or other scratch- and pressure-sensitive surfaces.
[0026] In the production of the fibers, the thermoplastic material
according to one embodiment is heated to a temperature ranging from
150.degree. C. to 350.degree. C., preferably from 280.degree. C. to
330.degree. C. According to another embodiment, the thermoplastic
material is heated to a temperature from more than 205.degree. C.
to about at least 280.degree. C. According to a further embodiment,
a temperature range from 250.degree. C. to 320.degree. C. is
preferred. The temperature range for heating the thermoplastic
material is influenced, for example, by the selection thereof. It
is possible to spin a single polymer material. Furthermore, there
exists the possibility that one or more polymers form the
thermoplastic material. It is likewise possible that additives are
present, which may be both meltable and solid. In particular, it is
possible to use homopolymers, copolymers, as well as block
polymers. The thermoplastic material may be both atactic and
syndiotactic. In the production, it is possible to use polyolefins,
such as polypropylene, polyisoprene, polystyrene, or polyethylene.
Likewise, there exists the possibility of using polyester and
polyamides, alone or in combination with other polymers or
additives. In particular, it is possible to add additives,
stabilizers, as well as pigments. There exists the possibility of
using master batches.
[0027] According to a further development, the fibers formed in the
spinneret are immediately surrounded after leaving the spinneret by
the flow of a medium, in particular an oxygen-containing medium.
The medium for tempering the fibers has, for example, a temperature
above the melting point of the thermoplastic material, in
particular the polymer or polymers in use.
[0028] By the method of the invention, the filaments of burst
fibers are accelerated after leaving, for example, the Laval nozzle
and before impacting upon a web laying surface, and/or additionally
tempered, and/or drawn in desired locations. The acceleration
and/or additional tempering and/or drawing may occur, for example,
by compressed air upstream of the web laying surface in a channel,
which preferably is a nozzle.
[0029] Besides the use of compressed air, which may in particular
be conditioned, it is also possible to make use of multiphase
mixtures. For example, a gas may be mixed with a liquid, a vapor,
in particular water vapor, may be added to a gas, and the use of an
aerosol may also be made possible. Preferably, this additional
medium is supplied directly into an inlet opening of the channel
for the filaments. A further embodiment provides for supplying the
medium inside the channel. A yet further embodiment provides for
distributing the supply of the medium. For example, a first volume
is supplied upstream of an opening of the channel, while at least a
second volume is supplied inside the channel. Both volumes may be
differently conditioned.
[0030] Preferably, the opening of the channel is arranged in spaced
relationship with the nozzle outlet, which enables an inflow of
ambient air. In particular, a channel opening is arranged at a
distance of preferably no more than 30 cm downstream of a nozzle
opening. A further development provides that the channel opening is
arranged, preferably no more than 15 cm, in particular less than 10
cm removed from the nozzle outlet. Likewise, it is possible to vary
the spacing.
[0031] A further development provides for using a channel-shaped
unit. The channel-shaped unit may be a closed channel in the form
of a shaft. Preferably, the shaft is made nozzle-shaped. It may
comprise an injector region and/or also a diffuser region.
According to a further development, the channel-shaped unit may
also be constructed to be at least similar to a spin beam. For
example, the channel-shaped unit may have a geometry, as is known
in meltblowing processes. A further embodiment provides that a
geometry is present, as is used, for example, in spunbonding
processes. Furthermore, the channel-shaped unit may be constructed
at least approximately like a Lurgi-Docan draw unit. A further
development provides that the channel-shaped unit enables an
electrostatic charging, so that the filaments can be separated from
one another on the one hand, and undergo themselves a lasting
electrostatic charging on the other hand. This will be
advantageous, for example, in industrial applications, such as for
filter materials and the like.
[0032] A further development of the process provides that by
generating a vacuum in a region directly below the web laying
surface, the filaments are accelerated in a channel, and
additionally tempered and/or drawn. According to the invention, it
is possible to use as media for accelerating and additionally
tempering and/or drawing the filaments not only air, but also
air-liquid mixtures, or liquids. Preferably, these media possess
specific heat capacities, which are greater than or equal to air
under atmospheric pressure. Use is made, for example, of water
vapor or aerosols.
[0033] According to a further embodiment, an additional mechanical
drawing of the filaments is generated by providing, for example,
pairs of temperable rolls, which have smooth and/or structured
surfaces.
[0034] For the mechanical drawing of the filaments, one or also
several pairs of rolls may be arranged one following the other.
Preferably, one pair of rolls is arranged downstream of the nozzle,
so that the filaments leaving the nozzle advance between the rolls,
and can then be drawn in a mechanical way. A further development
provides that both a system of paired rolls and individual rolls
are used for enabling a mechanical drawing downstream of the exit
from the nozzle, before a compacting, and in particular a
thermobonding step. Preferably, at least one of the rolls is
heatable to a temperature, which ranges from 30.degree. C. to
180.degree. C. A further development provides that at least one of
the rolls can be cooled. It is also possible that successively
arranged rolls are cooled on the one hand and heated on the other
hand. In particular, the use of a pair of rolls presents the
possibility that portions of the rolls engage and, in so doing,
draw the filaments. There also exists the possibility that the
filaments are crimped.
[0035] An additional tempering, for example, by a gaseous medium,
which surrounds the filaments, may assist a mechanical drawing.
There also exists the possibility that the filaments reach the
desired temperature or are maintained at this temperature by a
different application of energy. For example, this may occur by
means of heat radiation, as well as with the use of suitable
wavelengths for applying energy to the filaments.
[0036] For carrying out the method of producing a spunbonded fabric
from filaments, at least one device for additionally tempering
and/or drawing the filaments is provided in any spaced relationship
downstream of the Laval nozzle. In this case, both open and closed
systems or combinations of both are used, which may surround the
filaments both in symmetric and asymmetric relationship.
[0037] An open system means in particular a system of the type,
which allows ambient air to enter. A closed system, however, avoids
the entry of ambient air. This may occur, for example, by suitable
seals. For example, one may provide such a seal at the inlet of the
channel-shaped unit. In this instance, one should see that in
cooperation with the outlet, a required pressure difference remains
unchanged for causing the filaments to burst. In particular, a
closed system makes it possible to adjust a pressure in a
purposeful manner. With that, for example, it becomes possible to
use overpressures and vacuums for influencing in particular a burst
and separation of the filaments.
[0038] Depending on the polymer quality and the process conditions,
the devices for additionally tempering and/or drawing the filaments
are constructed as devices for generating a vacuum or pressure, or
as a mechanical unit. The web laying surface in the region of the
filament receiving area may be a belt, preferably a screen belt. It
has also been found advantageous to deposit the filaments on a
drum, preferably a screen drum.
[0039] The spunbonded fabrics produced by the method of the
invention and its apparatus from filaments of burst fibers are
continuous or discontinuous, or contain both fiber types, and have
a filament diameter of a range between smaller than or equal to 1
.mu.m and 80 .mu.m, preferably from 2 .mu.m to 5 .mu.m. The
filament length/filament diameter ratios are from 100:1 to
100,000,000:1, preferably 10,000:1 to 1,000,000:1.
[0040] The throughput rate of the production line is preferably
from 0.15 to more than 2.00 grams per minute and hole. The used
polymer may have an MFI from 1 to 500 g/10 min. (at 230.degree. and
a piston weight of 2.16 kg), preferably an MFI that ranges from 9
to 45 g/10 min.
[0041] Preferably, the method and apparatus are used to produce
nonwoven fabrics or laminates that have at least one layer of a
spunbonded fabric.
[0042] The laminates may include a nonwoven layer that entirely
consists of the filaments. At least one adjacent nonwoven layer is,
for example, a prefabricated nonwoven, for example, a spunbonded
fabric with a larger filament diameter. In particular, it is
possible to produce multilayer nonwovens, which have in each layer
a different average filament diameter. For example, a first
nonwoven layer has an average filament diameter from 0.3 .mu.m to
0.7 .mu.m. A second nonwoven layer has an average filament diameter
that is higher. This diameter may be in a range from 1 .mu.m to 3
.mu.m. When a further nonwoven layer is added, same may have an
average diameter, which ranges, for example, from 3 .mu.m to 20
.mu.m.
[0043] Furthermore, the apparatus may provide not only for the
production of burst and separated filaments, but may also include
at least one further spin beam and/or meltblown beam, so as to
enable a simultaneous production of at least two-layer materials.
To this end, at least the one spin beam and/or the meltblown beam
may be arranged upstream or downstream of the filament production
unit.
[0044] A further development provides that a film forms part of the
laminate. The film may be directly or indirectly laminated with
burst filaments, for example, on one side or both sides. To this
end, the film layer may be prefabricated or also be directly
produced in the apparatus. The film may be, for example, gas
permeable, in particular microporous.
[0045] The nonwoven or the laminate, which contains burst and
separated filaments, is made both as a semi-finished and a finished
product. For example, the nonwoven may be bonded prior to further
processing and be subsequently assembled.
[0046] The nonwoven or the laminate is used for clothing,
preferably protective apparel, for example, in protective masks,
protective suits, protective covers for shoes and hair. A further
applicability includes the area of cleaning cloths, packaging, and
household products, medical products, such as OR covers, smocks,
sterile packs, bandage materials or, however, the use of hygienic
products, such as sanitary pads, diapers, tampons, disposable
products of the general type, and the like.
[0047] A further field of application is the use in filters, in
particular microfilters for room air up to the highest degree of
safety. It may likewise be used as preliminary or end filter
material. Besides the filtration of gaseous media, in particular
filtration of dust particles, there is also the possibility of use
in filtering liquid media, such as, for example, oil. Furthermore,
the nonwoven or the laminate may be used in the field of
construction or as a geotextile. In particular, there is the
possibility of using it in pillows. Because of the very fine
filament diameters, it is possible to apply it as covering of
finely powdered materials.
[0048] The nonwoven may be made antibacterial and/or antistatic,
and likewise be finished in a different manner. It may also be used
to store a material, for example, a fluid. For example, a material
is absorbed and/or dispensed or released.
[0049] Further advantageous embodiments, features, and further
developments are described in greater detail in the following. The
therein described features, however, are not restricted or limited
to there embodiments, but may be combined with further, in
particular the above-described features to further embodiments. For
a better understanding, the invention is described in greater
detail with reference to drawings, in which:
[0050] FIG. 1 is a schematic view of an apparatus for drawing
filaments by means of suction air in an open system;
[0051] FIG. 2 is a schematic view of the apparatus for drawing
filaments by means of compressed air in an open system;
[0052] FIG. 3 is a schematic view of a combination of a spinneret
and a Laval nozzle unit with a device for tempering and
subsequently drawing the filaments by means of suction air and/or
in combination with the volume flow of the tempering medium in a
closed system;
[0053] FIG. 4 is a schematic view of the apparatus for tempering
and subsequently drawing the filaments with the use of suction air
and/or additional media in an open system;
[0054] FIG. 5 is a schematic view of the apparatus for a mechanical
subsequent drawing of the filaments;
[0055] FIG. 6 is a schematic view of the apparatus for unilaterally
tempering and subsequently drawing the filaments with the use of
suction air and/or additional media in an open system; and
[0056] FIG. 7 is a scanned electron-microscopic picture of a
nonwoven web with continuous filaments.
[0057] FIG. 1 is a schematic view of an apparatus 1.1 for drawing
filaments by means of suction air in an open system. Initially,
fibers 2 are spun from a spinneret 1. Upon leaving the spinneret 1,
these fibers are drawn in a known manner in a downstream Laval
nozzle 3 by means of gas flows that are accelerated to high
velocities. The fibers burst and separate into filaments 4 after
leaving the Laval nozzle 3 and before solidifying. Subsequently,
the filaments 4 of burst fibers advance before impacting upon a web
laying surface 5, through a channel 6, which is preferably
constructed as a nozzle, in particular as an open system. Inside
the channel 6, the filaments are accelerated and additionally drawn
by a suction air 7 that is generated by a source of vacuum 8, which
is arranged below the web laying surface 5. In the present
embodiment, the web laying surface 5 is advantageously constructed
as a screen belt that is driven via rolls 9. Upon their impact upon
web laying surface 5, the filaments 4 advance through a pair of
temperable rolls 10, and form a nonwoven layer 11. The nonwoven
layer 11 comprises predominantly continuous fibers, which may be in
part curled or crimped.
[0058] FIG. 2 is a schematic view of an apparatus 2.1 for drawing
filaments by means of compressed air in an open system. In this
process, the filaments 4 that are produced in a known manner from
burst fibers 2, are additionally tempered, after leaving the Laval
nozzle 3, by an air supply device 12. The temperature of the air
ranges from 0.degree. C. to 350.degree. C., preferably 5 to 50
degrees above the melting point of the polymers. To receive the
filaments 4, a nozzle unit 13 is provided. This nozzle unit 13 may
be constructed as a meltblown beam. Downstream of the meltblown
beam is a draw unit 14, which is height adjustable, and can be
arranged at any distance from the meltblown beam above the filament
web laying surface 5.
[0059] Upstream of this draw unit, a device 15 for generating
compressed air is arranged. Below the filament web laying surface,
a vacuum source 8 is arranged for generating suction air 7. The
tempered and drawn filaments 4 that are deposited on the web laying
surface 5, form a nonwoven web 11, which contains filaments with
filament length/filament cross section ratios from 100:1 to
100,000,000:1, preferably 10,000:1 to 100,000:1.
[0060] A further development of this apparatus may be equipped
without a nozzle unit 13. In this development, the filaments 4 are
accelerated and drawn by means of compressed air 15 and suction air
7, or by means of an injector. In this instance, the produced
nonwoven web 11 comprises either exclusively continuous filaments,
or continuous filaments with portions of discontinuous filaments.
Subsequently, a pair of rolls 10 bonds the nonwoven web.
[0061] FIG. 3 is a schematic view of a combination 3.1 of a
spinneret and Laval nozzle unit with a device for tempering and
subsequently drawing by means of suction air in a closed system. In
this arrangement, filaments 4 that are produced in a known manner,
advance after leaving the Laval nozzle 3, to a tempering and draw
unit 17 subjacent the Laval nozzle, which operates by the principle
disclosed, for example, in DE 3 713 862, DE 4 312 419, or DE 195 21
466. Via an air supply 16 and a source of vacuum 8, tempered air
advances through the tempering and draw unit 17, which is
preferably constructed as a channel. Preferably, the temperature of
the air is from 0.degree. C. to 100.degree. C., preferably
5.degree. to 30.degree. C. In this channel 17, the filaments 4 are
accelerated and additionally drawn and tempered, and deposited on
web laying surface 5. The web laying surface 5 may be a belt or a
drum, preferably a screen belt or screen drum. The nonwoven web 11
is bonded by means of device 10, which may be constructed as a
calender with embossing rolls and/or smooth rolls, or as a pair of
embossing and/or smooth rolls.
[0062] FIG. 4 is a schematic view of a device 4.1 for tempering and
subsequently drawing the filaments by means of suction air and/or
additional media in an open system. After leaving the Laval nozzle
3, the filaments 4 of burst and separated fibers immediately
undergo an additional tempering by means of air or air-liquid
mixtures 18. Advantageously, aerosols or air-water mixtures are
used as air-liquid mixtures. Subsequently, the filaments 4 are
advanced through a channel 6 by means of suction air 7. In so
doing, they are accelerated and drawn, and deposited on web laying
surface 5. Finally, the nonwoven web 11 advances through a pair of
rolls 10, and is compacted, and/or smoothed, and/or embossed.
[0063] FIG. 5 is a schematic view of a device 5.1 for mechanically
redrawing the filaments. The filaments 4 leave the Laval nozzle 3,
and advance through a pair of oppositely rotating rolls 19, or they
are advanced and additionally drawn through a calendar, which
comprises any desired arrangement of rolls 20 that are designed as
guide and deflecting rolls. The rolls may be both smooth and
embossed. Subsequently, suction air 7, which is generated by the
vacuum source 8, positions the filaments on web laying surface 5.
Downstream of the rolls are, for example, apparatus for producing
multilayer nonwovens 22 or laminates 24. The laminates 24 comprise
at least one layer of spunbond and, if need be, other components,
such as other nonwovens 21 or films 23. Each of these apparatus for
further developing the nonwoven may likewise follow and/or precede
the embodiments of the invention according to FIGS. 1-4.
[0064] FIG. 6 is a schematic view of an apparatus 6.1 for
unilaterally tempering and subsequently drawing the filaments by
means of suction air and/or additional media in an open system. Via
an extruder 25 and a melt line 26, a polymer melt advances to a
spin device 1. After leaving the Laval nozzle 3, the filaments 4 of
burst fibers are immediately cooled on one side by means of air or
air-liquid mixtures 18. Subsequently, the filaments 4 are advanced
through a channel 6 by means of suction air 7. In so doing, they
are accelerated and drawn, and deposited on web laying surface 5.
The nonwoven web 11 then advances through a pair of rolls 10, and
is compacted, and/or smoothed, and/or embossed.
[0065] FIG. 7 is a scanned electron-microscopic picture of a
nonwoven with continuous filaments of burst fibers. The filaments
have diameters in a range from 1 .mu.m to 50 .mu.m. They are
present either totally separated or joined to one another in
discrete points, and they have no undesired partial thick
places.
EXAMPLE 1
[0066] Via an extruder 25 and a melt line 26, a polymer melt of
polypropylene with an MFI of 13 g/10 min. (at 230.degree. C. and a
piston weight of 2.16 kg) advances to a spin device 1 (with spin
pack and spinneret). At a melt temperature of 325.degree. C., a
yarn 2 forms, which bursts in a known manner into filaments 4 after
leaving the Laval nozzle 3. The burst filaments 4 are unilaterally
cooled by means of a gas 18, preferably air or an air-liquid
aerosol at a temperature from about 5.degree. to 25.degree. C. In a
channel 6, the filaments are drawn, with a vacuum from -500 to
-3000 Pa being adjusted in the region upstream of the screen belt
by the vacuum source 8 depending on the desired filament fineness
or the desired textile-mechanical properties of the nonwoven. The
filaments are collected on the screen belt 5 and advanced through
pressure rolls 10. The nonwoven web 11 predominantly comprises
endless filaments with diameters ranging from 0.5 to 12 m, and it
is bonded in a usual manner by a thermal bonding (calendering)
step. Thus, after thermobonding, one obtains with a specific
nonwoven weight of 11 g/m.sup.2, a strength from 0.5 to 12.5 N
crosswise to the machine direction (CD) (according to DIN 53455
(German Industrial Standards), with a free clamping length of 100
mm; width of 50 mm; testing speed of 200 mm/min.). Without further
finish, this spunbonded nonwoven has a water column from 15 to 20
mbar, which normally corresponds to a meltblown nonwoven with a
basis weight of 9 g/m2.
EXAMPLE 2
[0067] Under the same conditions as used in Example 1, a nonwoven
web is produced with a basis weight of 20 g/m.sup.2. The nonwoven
has strength values in the MD from 25 to 30 N (according to DIN
53455, with a free clamping length of 100 mm; width of 50 mm;
testing speed of 200 mm/min.) In the case of this nonwoven, the
water column is 30 to 40 mbar, which normally corresponds to a
16-g/m.sup.2 meltblown nonwoven.
* * * * *