US20130269154A1

US20130269154A1 - Method and apparatus for producing a composite nonwoven

Info

Publication number: US20130269154A1
Application number: US13/880,861
Authority: US
Inventors: Norbert Kühl; Markus Hones
Original assignee: Individual
Current assignee: Hi Tech Textile Holding GmbH
Priority date: 2010-10-21
Filing date: 2011-10-21
Publication date: 2013-10-17
Also published as: WO2012052535A1; EP2630287B1; EP2630287A1; CN103180501B; CN103180501A

Abstract

A method for producing a composite nonwoven in a continuous process sequence, and an apparatus for carrying out the method are provided. A fibrous web is formed by a carding device from a fiber strand, on the surface of which fibrous web subsequently a nonwoven layer of synthetic fibers is laid. To this end, the fibrous web is guided within a suction zone on a laydown belt to a melt-blowing device, in which the synthetic fibers are laid on the surface of the fibrous web by melt-blowing. The fibrous web which is covered with the nonwoven layer is subsequently laid by a nonwoven laying device in a plurality of layers to form the composite nonwoven.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a United States National Phase application of International Application PCT/EP2011/068408 filed Oct. 21, 2011 and claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2010 049 180.2 filed Oct. 21, 2010, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention pertains to a method for producing a composite nonwoven in a continuous process sequence as well as to a device for carrying out the method.

BACKGROUND OF THE INVENTION

It is generally known in connection with the production of composite nonwovens that the properties of the composite nonwoven are determined essentially by the interaction of a plurality of different types of nonwoven layers. Thus, it was found, for example, in the case of composite nonwovens that are used for soundproofing that it is especially the differences in the densities of the materials of the nonwoven layers that cause sound waves to be compensated and reflected to a reduced extent. Such composite nonwovens, which are used for insulation and soundproofing, have a relatively low area weight, so that special requirements are imposed on their production.
A sound-absorbing thin-layer laminate, which comprises a foam or a fibrous web and melt-blown fibers connected thereto, is known from EP 1 058 618 B1. The foam or the fibrous web is pulled off in the form of a web from a first roller, then sprayed with a contact adhesive and partially dried with an infrared radiator and subsequently brought together with a second web of melt-blown fibers. The two webs are then guided together through pinching rollers and bonded to one another. Another cover layer consisting of a fiber web may optionally be applied to the thin-layer laminate. This fibrous web cover layer may consist of melt-blown spun yarns, which are temporarily bonded by ultrasound. The thin-layer laminate is subsequently cut into green pieces and fed to a molding press.
It is known from WO 2006/108364 A1 that a single-layer or multilayered textile can be produced from polymeric nanofibers, which are obtained by electrospinning.
EP 0 501 842 B1 and DE 692 09 703 T2 pertain to the production of a fabric covering textile for the manufacture of clothing. A first nonwoven layer consisting of microfibers is produced by melt blowing, while a second, carded nonwoven layer is formed and then arranged under the first layer. The two layers are knitted and bonded to one another by fluid jets and then dried. The second carded nonwoven layer is preferably pre-needled. In addition, an adhesive applied in a distributed manner is used to bond the two layers. Furthermore, a third nonwoven layer may be added. In one embodiment, a melt-blown microfiber layer may be applied directly and formed on a second carded layer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a better production technique for composite nonwovens.
Another object of the present invention is to bring a fibrous web produced by a carding device to a composite nonwoven at the highest belt speed possible. Furthermore, one object of the present invention is to form a multilayered soundproofing nonwoven element.
According to the invention, a method is provided for producing a composite nonwoven in a continuous process sequence in a plurality of steps. The steps include feeding of a continuous fiber strand consisting of fibers or fiber blends to a carding device, carding and doffing of the fibers to form at least one fibrous web and guiding of the fibrous web to a holding zone and holding of the fibrous web at a running conveying means within the holding zone. The method further comprises melt blowing of a plurality of synthetic fibers extruded from a polymer melt and laying of the synthetic fibers to form a nonwoven layer on the fibrous web in the area of the holding zone. The fibrous web, with nonwoven layer, is led out of the holding zone to a further processing device, especially a nonwoven laying device.
According to another aspect of the invention a soundproofing nonwoven element having a composite nonwoven is manufactured in accordance with the described method.
According to another aspect of the invention, a device is provided for producing a composite nonwoven. The device comprises a carding device, a doffer device, a conveying device and a further processing device, especially a nonwoven laying device. A station for producing a nonwoven layer, is provided between the doffer device and the further processing device. The station comprises a melt-blowing device. A holding device is arranged at the conveying device. The holding device is associated with the melt-blowing device.
In EP 0501842 B1, a composite nonwoven is produced in a production process from a fibrous web produced by a carding device and a nonwoven layer produced by melt blowing. In melt blowing, the fibers are produced with the lowest possible air pressure and the greatest possible distance from the fibrous web. However, it is not possible to produce fine fibers in this manner. The prior-art method and prior-art device are therefore suitable essentially for producing composite nonwovens with relatively high area weights only.
The technique according to the invention has the advantage that even very loose and lightweight laid fibrous webs can be combined with certainty with a nonwoven layer produced by melt blowing. The fibrous web is prevented from being swirled and altered by the fiber strand of melt blowing by the fibrous web being led into a holding zone, e.g., a suction zone, so that the fibrous web becomes fixed, e.g., by the suction current on the laydown belt. The synthetic fibers produced during melt blowing are laid directly on the fibrous web in the area of the holding or suction zone to form a nonwoven layer and bonded hereto to form a compound. The excess blowing air occurring in the process can likewise be taken up and removed via a suction zone. To make it possible to embed the nonwoven layer produced as a cover layer in a structure comprising a plurality of fibrous webs, the fibrous web with the nonwoven layer may be led out of the suction zone and sent to a nonwoven laying device. The nonwoven laying device then combines a plurality of layers of the fibrous web or compound into a composite nonwoven.
To ensure reliable entry of the fibrous web into the laying area of the melt-blowing device and to lead the fibrous web combined with the nonwoven layer out of the laying area, the variant of the present invention, in which the fibrous web passes through a plurality of suction areas located one after another with separately adjustable suction capacities within the suction zone, is especially advantageous. Pressure conditions adapted to the particular state of the fibrous web can thus be generated at the laydown belt in order to minimize a suction current generated from the environment, on the one hand, and to take up the blowing air generated by the melt blowing with certainty, on the other hand. In addition, the direct laying of the synthetic fibers can be affected, moreover, by different pressure settings in order to produce certain structures within the nonwoven layers.
The fibrous web can be formed, in principle, from fibers and fiber blends consisting of synthetic or natural fibers. However, it was found to be especially advantageous for binding and bonding if the fibers or fiber blends used to form the fibrous web are formed with a weight percentage of synthetic fibers in the range of 10% to 100%.
The method variant in which the fibrous material of the synthetic fibers and the polymer melt for extruding the synthetic fibers are formed from an identical basic material is preferably used. The recycling of such composite nonwovens can thus be considerably improved.
The nonwoven layer on the surface of the fibrous web is preferably laid with fine fibers in order to obtain the properties advantageous for soundproofing. The method variant in which the synthetic fibers are laid on the fibrous web during melt blowing with a fine fiber cross section in the range of 0.2μ to 3μ to form the nonwoven layer is thus preferably used. However, depending on the application, the composite nonwoven may also be produced with coarser synthetic fibers.
The performance capacity of the carding device is exhausted especially with the method variant in which the fibrous web is guided continuously at a belt speed in the range of 50 m/minute to 200 m/minute after doffing until laying. The belt speed is limited essentially by the capacity of the nonwoven laying device.
To make it possible to produce different types of composite nonwovens, another method variant is proposed, in which a plurality of fibrous webs are doffed in parallel next to each other from the carding device and are combined in a sandwich-like pattern after melt blowing and the laying of the synthetic fibers, with the nonwoven layer forming an intermediate layer between the fibrous webs. Such double fibrous web layers are especially suitable for protecting the nonwoven layer of synthetic fibers obtained as an intermediate layer from further processing. The structure and distribution of the synthetic fibers within the nonwoven layers remain unchanged and can thus be set to the necessary specific properties already in the production process.
However, it is also possible, in principle, to cover the two fibrous webs in parallel with a respective nonwoven layer each, which are brought together into a multilayered nonwoven.
To guarantee cohesion of the fibrous webs laid one on the other in a plurality of layers, it is proposed, furthermore, to feed the composite nonwoven laid by the nonwoven laying device continuously to a bonding device and to bond it. Bonding may be carried out here mechanically, chemically or thermally.
In order to obtain the respective nonwoven layers within the composite nonwoven consisting of synthetic fibers as completely as possible, the method variant is especially advantageous, in which the composite nonwoven is bonded by a heat treatment in a belt type drier, wherein the composite nonwoven is led during bonding through a calibration zone, in which a calibrating belt adjustable relative to a guide belt acts on the free top side of the composite nonwoven. Besides bonding, it is also possible to set a certain thickness of the composite nonwoven. The melting of the synthetic fibers within the nonwoven layers can be advantageously avoided now by the fiber material of the synthetic fibers having a slightly higher melting point than the synthetic fibers of the fibrous web. This can advantageously also be achieved in the same basic polymer by means of additives.
For the further processing of such composite nonwovens, provisions are, furthermore, made for the composite nonwoven to be stored in a storage device in a roll or, as an alternative, in a stack. In case of stack formation, the storage device additionally has a cutting device in order to cut the composite nonwoven into individual pieces of nonwoven, which are then stacked lying one on top of another.
The device according to the present invention is provided for carrying out the method being claimed. This device preferably has a carding device, a doffer device, a conveying device and a further processing device, especially a nonwoven laying device, with a station for producing a nonwoven layer from synthetic fibers being provided between the doffer device and the further processing device or nonwoven laying device. To accomplish the object according to the present invention, the station is designed as a melt-blowing device, with which a holding device, especially suction device, is associated. The suction device is preferably arranged under a laydown belt of the conveying device, so that the fibrous web being led on the laydown belt is held on the laydown belt fixed by means of suction effect.
The suction device for applying suction to the laydown belt is formed according to an advantageous variant of the device according to the present invention by a plurality of suction chambers, which are connected to a vacuum source, wherein separate control means are associated with the suction chambers for setting an individual vacuum. Both the position of the fibrous web and the laying of the synthetic fibers into the nonwoven layer can thus be affected.
To produce the smallest possible amount of waste material during the production of the composite nonwoven, the variant of the device according to the present invention is preferably used, in which the melt-blowing device has a movable spinning head, which can be guided between an operating position above the laydown belt and an inoperative position on the side next to the laydown belt. Spinning and the melt-blowing device can thus be started outside the operating position, so that the spinning head being held in the operating position can be used exclusively for producing the composite nonwoven.
To make it possible to produce combinations of fibrous webs, the device according to the present invention is varied especially such that the doffer device has two separate doffing sites, which cooperate with two belt arrangements of the conveying device for receiving and doffing a plurality of fibrous webs. The variant of the device in which one of the belt arrangements cooperates with the laydown belt and the second belt arrangement is arranged with a conveying section in parallel to the laydown belt above the spinning head is used to produce a sandwich-like fibrous web combination with a nonwoven layer arranged between them. The fibrous webs doffed from the calibrating device can thus be guided in one plane without deflection.
However, it is also possible as an alternative for the second belt arrangement to have a second laydown belt and for a second spinning head of the melt-blowing device to be associated with the second laydown belt. A plurality of fibrous webs with a combined nonwoven layer can thus be produced.
The further processing of the composite nonwoven takes place within the device by a conveyor belt device, which connects the nonwoven laying device to a bonding device and to a storage device. The composite nonwoven can thus be stored in the form of a roll or stack within the storage device.
For bonding, it is proposed that the device have a belt type drier with a guide belt and with a calibrating belt arranged above the guide belt, wherein the calibrating belt is designed such that it is adjustable in height relative to the guide belt. Specific material thicknesses of the composite nonwoven can thus also be produced besides bonding.
The method according to the present invention will be explained in more detail below on the basis of some exemplary embodiments of the device according to the present invention for producing a composite nonwoven with reference to the figures attached. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic first partial view of a first exemplary embodiment of a device according to the present invention;

FIG. 2 is a schematic second partial view of the exemplary embodiment from FIG. 1;

FIG. 3.1 is a schematic cross-sectional view of the melt-blowing device of the exemplary embodiment from FIG. 1 in one of a plurality of operating positions;

FIG. 3.2 is a schematic cross-sectional view of the melt-blowing device of the exemplary embodiment from FIG. 1 in another of a plurality of operating positions;

FIG. 4 schematic partial view of another exemplary embodiment of the device according to the present invention; and

FIG. 5 is a schematic partial view of another exemplary embodiment of the device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, the present invention pertains to a method and a device for producing a composite nonwoven (36) and a sound-absorbing nonwoven element produced therefrom.
FIGS. 1 and 2 show a first exemplary embodiment of the device according to the present invention for carrying out the method according to the present invention. FIG. 1 shows a partial view of the front half of the machine and FIG. 2 shows a partial view of the rear half of the machine.
The device according to the present invention has a carding device (1) in the front half of the machine according to FIG. 1. The carding device (1) cooperates with a feeding device (2) at one end and with a doffer device (7) at the opposite end. A breast roller (4) and a main cylinder (5), on the circumference of which a plurality of carding elements (6) act, are arranged between the feeding device (2) and doffer device (7). A plurality of feeding systems (3) are provided between the feeding device (2) and breast roller (4) in order to take up a fiber strand made continuously available by the feeding device (2) and to move same to the breast roller (4). The fibers are carded at the breast roller (4) and main cylinder (5) and doffed as a fibrous web via the doffer device (7) associated in the main cylinder (5).
It shall be expressly mentioned here that the design and number of cylinders and carding elements used in the carding device are indicated as examples only. It is also possible, in principle, to use carding devices with only one cylinder.
The doffer device (7) is formed in this exemplary embodiment by a doffing cylinder system (8), which directly cooperates with a conveyor belt (10.1) of a conveying device (9). The conveying device (9) is formed in this exemplary embodiment by a first conveyor belt (10.1), a laydown belt (11) and a second conveyor belt (10.2), which cooperate together to take up and doff a fibrous web (32) continuously from the carding device (1).
A melt-blowing device (12) is associated with the laydown belt (11) on a top side and a holding device (17) is associated with it on an underside. A nonwoven layer (35) consisting of melt-blown synthetic fibers (33) is applied, e.g., with a stream of compressed gas, to the surface of the fibrous web (32) with the melt-blowing device (12). The composite of fibrous web (32) and nonwoven layer (35) will hereinafter be called compound.
The holding device (17) can act on the fibrous web (32) and/or on a stream of compressed gas of the melt-blowing device (12). It can hold, e.g., the fibrous web (32) on the laydown belt (11) and stabilize same against the incident stream of compressed gas with the melt-blown fibers (33). It can also act guidingly on the stream of compressed gas and the fiber strand. It can, e.g., draw off the compressed gas stream in a controlled manner after the release of the fibers (33) to the fibrous web (32). The holding device (17) may also be designed, e.g., as a suction device.
The laydown belt (11) is designed as a gas-permeable belt and is led over a total of three suction chambers (18.1, 18.2, 18.3) of the suction device (17). The suction chambers (18.1, 18.2 and 18.3) of the suction device (17) are connected to a vacuum source (not shown here) via separate suction lines (19.1, 19.2 and 19.3) independently from each other and their suction capacity can be set independently from each other by means of associated control means (20.1, 20.2, 20.3).
Above the middle suction chamber (18.2), the melt-blowing device (12) has a spinning head (13), which is coupled by a melt line (34) with an extruder (14). The spinning head (13) also has a port to a compressed gas supply unit (15), e.g., a compressed air supply unit, which is connected to a compressed air source (not shown here) via a control valve (16). On its underside, the spinning head (13) has a melt blowing nozzle, which extends essentially over the entire width of the laydown belt (11). The width of the melt blowing nozzle of the spinning head (13) is identical to the working width of the carding device (1). The working widths of the carding device (1) can thus be designed in the range of 2 m to 4 m and more. The width of the melt blowing nozzle is correspondingly likewise in the range of 2 m to 4 m.
The spinning head (13) as well as the extruder (14) are held in this exemplary embodiment at a movable carrier (21), by which the spinning head (13) can be moved back and forth between an operating position and an inoperative position. A cross section of the melt-blowing device (12) is shown for illustration in the operating position in FIG. 3.1 and in the inoperative position in FIG. 3.2. Reference is therefore made here additionally to FIGS. 3.1 and 3.2.
In the operating position, the spinning head (13) of the melt-blowing device (12) is located directly above the laydown belt (11), to which suction is applied on its underside by the suction chamber (18.2). The suction chamber (18.2) is connected to a vacuum source, not shown here, via a suction line (19.2) and a control means (20.2).
The carrier (21) of the spinning head (13) and of extruder (14) is designed as a movable carrier and can be displaced to and fro, for example, via a rail system or a roller system at right angles to the laydown belt (11). The ports on the spinning head (13) remain unchanged. Thus, the spinning head (13) is connected to the extruder (14) via the melt line (34). Connection to a pressure source is provided via the compressed air supply unit (15) and control valve (16).
As is shown in FIG. 3.2, carrier (21) can be displaced such that the spinning head (13) is maintained in an inoperative position on the side next to the laydown belt (11). Maintenance operations and, when starting the process, spinning start operations can be performed in this position without a fibrous web (32) being led at the laydown belt (11).
As is shown in the view in FIG. 1, a nonwoven laying device (22) is arranged next to the melt-blowing device (12), and the conveyor belt (10.2) of the conveying device (9) is held between the melt-blowing device (12) and nonwoven laying device (22). The nonwoven laying device (22) has laying means, not shown here in more detail, for laying the fibrous web (32) or compound being fed by means of the conveyor belt (10.2) in a steady and, e.g., uniform to and fro motion on a conveyor belt of a conveyor belt device (23) in a plurality of layers and with a selectable number of layers and for forming a composite nonwoven (36). The area weight of the multilayered composite nonwoven (36) may be possibly controlled and regulated here as needed and changed globally or locally in the transverse and/or longitudinal direction (so-called profiling).
The conveyor belt is operated correspondingly depending on the number of layers and the laying width with a low belt speed. The conveying direction of the conveyor belt device (23) is thus directed at right angles to the conveying direction of the conveying device (9). The following units of the device according to the present invention which are arranged downstream form a second longitudinal side of the machine, on which the devices are arranged one after another for the further processing of a composite nonwoven.
Thus, it is shown in FIG. 2 that the nonwoven laying device (22) is followed over the further course by a bonding device (24) and a storage device (28). The bonding device (24) is formed in this exemplary embodiment by a belt type drier (25), which has a guide belt (26) and a calibrating belt (27) arranged above the guide belt in a calibration zone. The calibrating belt (27) is designed as a belt that is adjustable in height in relation to the position of the guide belt (26), so that a composite nonwoven (36) being guided on the guide belt (26) can be bonded with a defined material thickness. Bonding is carried out here by means of heat treatment and is called thermobonding by persons skilled in the art. Stable cohesion of all fibers is generated here by partially melting the fiber material of some fibers within the composite nonwoven.
The multilayered composite nonwoven (36) laid by the nonwoven laying device (22) is fed to this end continuously to the bonding device (24) by the conveyor belt device (23).
The storage device (28), which is formed by a winding station (29) in this exemplary embodiment, is provided on the outlet side of bonding device (24). The winding station (29) produces a roll of nonwoven material (30) from the composite nonwoven (36) being fed continuously.
The device according to the present invention, shown in FIGS. 1 and 2, is especially suitable for carrying out the method for producing a composite nonwoven (36) that is used as an insulating material. Such composite nonwovens usually have a relatively low area weight and a relatively loose structure of the fibers contained within the composite nonwoven.
As is shown in FIG. 1 and FIG. 2, a continuous fiber strand of fibers or fiber blends is charged at first in the method to the carding device (1). The fibers (31) are fed via the feeding device (1) and carded by means of one or more cylinder systems and doffed as a fibrous web (32). The fibrous web (32) is taken up by means of the conveying device (9) and doffed continuously. The conveyor belts (10.1) and (10.2) of the conveying device (9) are operated in this process at a belt speed in the range of 50 m/minute to 200 m/minute. The belt speed is determined by the carding device (1) or the nonwoven laying device (22).
The fibrous web (32) is transferred in the further course from the first conveyor belt (10.1) to the laydown belt (11), which delivers the fibrous web (32) to the melt-blowing device (12), in which a nonwoven layer (35) of synthetic fibers (33) is laid on the surface of the fibrous web (32) and the compound is formed. To take up and produce the nonwoven layer (35) on the surface of fibrous web (32), the fibrous web (32) is guided on the laydown belt (11) through a holding zone, e.g., a suction zone. The suction zone is formed by the three suction chambers (18.1, 18.2 and 18.3) in this exemplary embodiment. Suction is applied in the suction zone to the underside of the laydown belt (11), which is designed as a gas-permeable belt and may be, for example, a screen belt or fabric belt. As a result, a holding force is generated at the fibrous web (32), so that the structure of the fibrous web (32) is preserved in the laying zone of the synthetic fibers (33) despite the air streams generated during melt blowing.
A polymer melt is melted during melt blowing by means of an extruder (14) and fed to a spinning head (13). A melt blowing nozzle is provided on the underside of the spinning head (13), and a plurality of synthetic fibers (33) are extruded through said melt blowing head and pulled off by means of compressed gas, e.g., compressed air, which is likewise fed in the spinning head (13), and blown in the direction of the laydown belt (11). The melt blowing nozzle, melt throughput as well as setting of the compressed air are preferably selected here to be such that relatively fine synthetic fibers (33) are produced. The synthetic fibers (33) preferably have a fine fiber cross section in the range of 0.5μ to 3μ in order to form the nonwoven layer (35) on the surface of the fibrous web (32).
The synthetic fibers (33) are preferably laid on the fibrous web (32) in the middle area of the suction zone, so that different settings of the suction capacity are possible in an inlet area, in a contact area and in an outlet area of the fibrous web (32) due to the separately adjustable suction capacities of the suction chambers (18.1 through 18.3). On the one hand, a sufficient holding force can be generated on the fibrous web (32) during the entry of the fibrous web (32). On the other hand, the laying of the synthetic fibers (33) can be affected by means of different suction capacities. Besides, the blowing air produced during melt blowing can also be integrated by the ambient air of the suction chambers into the synthetic fiber laying process. Additional effects and structures can thus be produced in the nonwoven layer.
After the nonwoven layer (35) has been laid on the surface of the fibrous web (32), the fibrous web (32) of the nonwoven layer (35), i.e., the compound, is fed by the conveyor belt (10.2) to the nonwoven laying device (22). The fibrous web (32) with the nonwoven layer (35) is laid by the nonwoven laying device (22) in a plurality of layers to form the desired composite nonwoven (36). The composite nonwoven (36) has, e.g., at least two layers of fibrous web (32) laid one over the other or a plurality of double layers of fibrous web (32) or compound. The composite nonwoven (36) is doffed continuously by the conveyor belt device (23) and fed to the bonding device (24). The belt speed of the conveyor belt device (23) depends on the number of layers and the laying width of the nonwoven laying device (22).
The composite nonwoven (36) is thermally bonded within the bonding device (24), where the material thickness of the composite nonwoven (36) is determined especially in a calibration zone by the interaction of the guide belt (26) and calibrating belt (27).
The composite nonwoven (36) is wound up into the nonwoven roll (30) after bonding.
Preferably 100% synthetic fibers are used to form the fibrous web (32) in the method and device shown in FIGS. 1 and 2. The fiber material of the synthetic fibers and the polymer melt for extruding the synthetic fibers (33) are preferably formed from an identical basic material here. For example, a polyester or a polypropylene would be a suitable basic material. The specific properties of the fiber material of the synthetic fibers and of the material of the polymer melt are coordinated here with one another such that essentially only the synthetic fibers in the fibrous web are melted for bonding during thermobonding. The fiber material of the synthetic fibers, which may also be formed from biofibers, is thus provided with a somewhat lower melting point than the polymer melt.
However, the exemplary embodiment according to FIG. 1 and FIG. 2 could also be expanded such that a second carding device with a doffer device is arranged between the melt-blowing device (12) and nonwoven laying device (22) in order to produce a second fibrous web. The second fibrous web would be laid on the nonwoven layer, so that the nonwoven layer is held in a sandwich-like manner between lower and upper fibrous web layers.
It is possible, in principle, to form one of the fibrous webs or both fibrous webs from a fiber blend consisting of synthetic fibers and natural fibers. To obtain sufficient strength during thermobonding, at least 10% of the fibers are formed by synthetic fibers.
A single-layer fibrous web (32) is doffed from the carding device (1) for producing the composite nonwoven (36) in the exemplary embodiment shown in FIGS. 1 and 2. However, it is also possible, in principle, to provide the doffer device (7) with a plurality of doffer sites. Thus, a partial view of another exemplary embodiment of the device according to the present invention for carrying out the method according to the present invention is shown schematically in FIG. 4. The exemplary embodiment is essentially identical to the above-mentioned exemplary embodiment according to FIGS. 1 and 2, so that only the differences will be explained here and reference will otherwise be made to the above-mentioned description.
In the exemplary embodiment shown in FIG. 4, the doffer device (7) forms two doffer sites (37.1) and (37.2). A doffing roller system (8) each is provided in each of the doffing sites (37.1) and (37.2) in order to take up a fibrous web (32.1) and (32.2) each and feed it to the conveying device (9). Conveying device (9) has a lower belt arrangement (38.1) and an upper belt arrangement (38.2) in this exemplary embodiment. The belt arrangement (38.1) has a design identical to that in the exemplary embodiment according to FIGS. 1 and 2. The upper belt arrangement (38.2) has a conveying section (10.3), which is led in parallel to the laydown belt (11) above spinning head (13). The upper belt arrangement (38.2) may be of a multipart design here in the form of a plurality of conveyor belts or also of a one-part design formed by an endlessly running conveyor belt.
The two belt arrangements (38.1) and (38.2) of the conveying device (9) are brought together in the area between the melt-blowing device (12) and nonwoven laying device (22) such that the two fibrous webs (32.1) and (32.2) are put together in a sandwich-like manner and enclose the nonwoven layer (35) between them. The multilayered nonwoven or multilayered compound thus formed is then fed to the nonwoven laying device (22) and laid in a plurality of layers to form the composite nonwoven (36).
The suction zone is formed by one suction chamber (18) of the suction device (17) only in this exemplary embodiment when the nonwoven layer (35) is formed by the melt-blowing device (12). The suction chamber (18) preferably extends here in the longitudinal direction of the laydown belt (11) such that a holding force is produced at the fibrous web (32) by the suction effect of the suction chamber (18) immediately before or during the entry of the fibrous web (32) into the laying zone of the melt-blowing device (12).
A multilayered fibrous web (32.1, 32.2) with a nonwoven layer (35) located inside can thus be produced with the exemplary embodiment shown in FIG. 4.
However, it is also possible, in principle, that both fibrous webs (32.1) and (32.2) are covered with a nonwoven layer (35.1, 35.2) consisting of synthetic fibers. Thus, a partial view of another exemplary embodiment, which is essentially identical to the exemplary embodiment in FIG. 4, is shown schematically in FIG. 5. Unlike in the above-mentioned exemplary embodiment according to FIG. 4, the belt arrangements (38.1) and (38.2) have an identical design, so that the belt arrangement (38.1) has a lower laydown belt (11.1) and the belt arrangement (38.1) has an upper laydown belt (11.2). A suction chamber (18.1) and (18.2) each, which apply suction to the respective laydown belts (11.1) and (11.2) independently from one another, is associated with each of the laydown belts (11.1) and (11.2). A spinning head (13.1) and (13.2) each of the melt-blowing device (12) is arranged above the laydown belts (11.1) and (11.2). The spinning heads (13.1) and (13.2) are coupled together with an extruder (14).
Unlike in the exemplary embodiment according to FIG. 4, one nonwoven layer (35.1) and (35.2) each is produced at each of the fibrous webs (32.1) and (32.2) in the exemplary embodiment according to FIG. 5. The structures and designs of the nonwoven layers (35.1) and (35.2) may be identical or different.
The two fibrous webs (32.1) and (32.2) are subsequently brought together with the nonwoven layers (35.1) and (35.2) laid on the surfaces and fed as a multilayered nonwoven or multilayered compound to the nonwoven laying device (22). The method being shown and the device being shown can thus be expanded in a flexible manner in order to produce single-layer or multilayered fibrous webs for producing composite nonwovens.
For example, three fibrous webs, which are put together by means of three conveyor belt systems to form a multilayered nonwoven or multilayered compound and fed to a nonwoven laying device, could be produced simultaneously in an advantageous variant of the present invention by means of a carding device by three separate doffer sites. Two melt-blowing devices, which are associated with the conveyor belt system, could be arranged between the carding device and the nonwoven laying device, so that two of the three fibrous webs are covered with a nonwoven layer made of synthetic fibers prior to bringing together. Multilayered nonwovens, which contain synthetic fibers from two different polymers, can be produced with this variant of the present invention.
As an alternative, the melt-blowing devices could also be associated one after another with a conveyor belt system in order to lay two nonwoven layers on a fibrous web.
The devices for producing the composite nonwoven, which are shown especially in FIGS. 1 and 2, are examples. The method according to the present invention and the device according to the present invention are, in principle, also suitable for producing composite nonwovens in which bonding is brought about by chemical agents or by mechanical means, for example, needling. In addition, the composite nonwoven may also be cut into individual pieces of nonwoven for storage and then stacked up into a stack. The winding station could thus be replaced with a stacking station.
Various further variants of the embodiments shown and described above are possible. The holding device (17) may have a different design and be arranged differently, e.g., as an electrostatic or mechanical holding device, which holds the fibrous web (32) with electrostatic forces, hooks or needles or the like on the laydown belt (11, 11.1, 11.2) and stabilizes it against being blown away. The laydown belt (11, 11.1, 11.2) may again be permeable to gas. A suction device can be eliminated in these cases. A suction device may be present as an alternative, but it may be designed for a lower capacity. Furthermore, it is possible to arrange a suction device elsewhere. In the exemplary embodiments being shown, it sucks from the laydown belt (11, 11.1, 11.2) and acts on the underside of the carrying run located there. As an alternative, it may be arranged elsewhere and outside the laydown belt.
Other conveying means may be used for the fibrous web (32) instead of the conveyor belts described.
In the exemplary embodiments shown and described, the further processing (device) (22) is a nonwoven laying device (22), e.g., designed as a crosslapper, especially as a belt type laying device, which lays the single-layer or multilayered compound fed on the laydown belt (23) in a zigzag and scale-like layer pattern. As an alternative, a nonwoven laying device (22) may also be designed as a carriage type laying device, camelback laying device or the like. In another variation, the single-layer or multilayered compound may be cut and divided into pieces before laying, and the pieces are laid one on top of another individually and optionally flush one on top of another to form a multilayered composite nonwoven (36). The nonwoven laying device (22) is designed in a correspondingly modified manner for this.
In the preferred exemplary embodiments shown, the single-layer or multilayered compound is fed to a nonwoven laying device (22) immediately after it has been formed. In a variation of this, an intermediate step may be inserted between the formation of the compound and a nonwoven laying device (22). For example, the single-layer or multilayered compound may be taken up and stored temporarily, and it is fed to a nonwoven laying device (22) or to another further processing process only later. Said compound may, e.g., be stabilized in a suitable manner and wound up in an intermediate step.
The further processing may be designed in another manner. For example, a multilayered design of the composite nonwoven (36) may be eliminated by the single-layer or multilayered compound being fed directly to another further processing, e.g., bonding, especially needling, thermobonding or the like and possibly fed to a storage unit.
Mat-like, shell-like soundproofing parts or sound-absorbing nonwoven elements or soundproofing parts or sound-absorbing parts of other forms can be manufactured from the single-layer or multilayered composite nonwoven (36). A shaping process with pressing and possibly heating may possibly be used for this. A multilayered composite nonwoven (36) with a nonwoven layer (35, 35.1, 35.2) located on the outside and/or on the inside has special advantages for soundproofing. The exemplary embodiments shown for a multilayered or sandwich type composite nonwoven (36) are especially advantageous for this. A composite nonwoven may also be produced with a single-layer design in the above-mentioned manner and used for insulation purposes.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

Claims

1. A method for producing a composite nonwoven in a continuous process sequence the method comprising the steps of:

feeding a continuous fiber strand formed of fibers or fiber blends to a carding device;

carding and doffing of the fibers to form at least one fibrous web;

guiding of the fibrous web to a holding zone and holding the fibrous web at a running conveying means within the holding zone;

melt blowing a plurality of synthetic fibers extruded from a polymer melt and laying of the synthetic fibers to form a nonwoven layer on the fibrous web in the area of the holding zone;

leading the fibrous web with nonwoven layer out of the holding zone to a further processing device.

2. A method in accordance with claim 1, wherein the fibrous web is sucked onto the conveying means in a holding zone designed as a suction zone.

3. A method in accordance with claim 1, wherein the fibrous web passes through a plurality of suction areas located one after another with separately adjustable suction capacities within a suction zone.

4. A method in accordance with claim 1, wherein the fibrous web with nonwoven layer is laid in a nonwoven laying device in a plurality of layers to form a composite nonwoven.

5. A method in accordance with claim 1, wherein the fibers or fiber blends for forming the fibrous web are formed from synthetic fibers at a weight percentage in the range of 10% to 100%.

6. A method in accordance with claim 1, wherein the fiber material of the synthetic fibers and the polymer melt for extruding the synthetic fibers are formed from an identical basic material.

7. A method in accordance with claim 1, wherein the synthetic fibers are laid on the fibrous web with a fine fiber cross section in the range of 0.2μ to 3μ to form the nonwoven layer during melt blowing.

8. A method in accordance with claim 1, wherein the fibrous web is led continuously at a belt speed in the range of 50 m/minute to 200 m/minute after doffing until laying.

9. A method in accordance with claim 1, wherein a plurality of fibrous webs are doffed from the carding device one on top of another and put together in a sandwich pattern after melt blowing and laying of the synthetic fibers, the nonwoven layer forming an intermediate layer between the fibrous webs.

10. A method in accordance with claim 1, wherein a plurality of fibrous webs are covered with a nonwoven layer each and the fibrous webs are brought together with the nonwoven layers before the further processing device comprising a nonwoven laying device, to form a multilayered nonwoven.

11. A method in accordance with claim 1, wherein a composite nonwoven laid by a nonwoven laying device is fed continuously to a bonding device and bonded.

12. A method in accordance with claim 1, wherein a composite nonwoven is bonded by heat treatment in a belt type drier, wherein the composite nonwoven is passed, during bonding, through a calibration zone, in which a calibrating belt, that is adjustable relative to a guide belt, acts on a free surface of the composite nonwoven.

13. A method in accordance with claim 1, wherein a composite nonwoven is fed to a storage device and stored as a roll or as a stack.

14. A device for producing a composite nonwoven, the device comprising:

a carding device;

a doffer device;

a conveying device;

a further processing device

a station, for producing a nonwoven layer, provided between the doffer device and the further processing device, wherein the station comprises a melt-blowing device; and

a holding device arranged at the conveying device, the holding device being associated with the melt-blowing device.

15. A device in accordance with claim 14, wherein the holding device comprises a suction device.

16. A device in accordance with claim 15, wherein the suction device is arranged under a laydown belt, of the conveying device.

17. A device in accordance with claim 16, wherein the suction device has a plurality of suction chambers for applying suction to the laydown belt and further comprising a separate control means associated with the suction chambers for setting a vacuum.

18. A device in accordance with claim 16, wherein the melt-blowing device has a movable spinning head, which can be guided between an operating position above the laydown belt, and an inoperative position on a side next to the laydown belt.

19. A device in accordance with claim 14, wherein the doffer device has two separate doffing sites, which cooperate with two belt arrangements of the conveying device for picking up and doffing a plurality of fibrous webs.

20. A device in accordance with claim 19, wherein:

the conveying device comprises a laydown belt; and

one of the belt arrangements cooperates with the laydown belt and that a second belt arrangement is arranged with a conveying section above the spinning head in parallel to the laydown belt.

21. A device in accordance with claim 20, wherein the second belt arrangement has a second laydown belt and that a second spinning head of the melt-blowing device is associated with the second laydown belt.

22. A device in accordance with claim 14, wherein the further processing device comprises a nonwoven laying device that cooperates with a conveyor belt device, a bonding device and a storage device, wherein the composite nonwoven laid by the nonwoven laying device is led to a roll or a stack in a storage station.

23. A device in accordance with claim 22, wherein the bonding device has a belt type drier with a guide belt and with a calibrating belt arranged above the guide belt and that the calibrating belt is designed as a height-adjustable belt relative to the guide belt.

24. A soundproofing nonwoven element, wherein the nonwoven element has a composite nonwoven and is manufactured by a method comprising the steps of:

carding and doffing of the fibers to form at least one fibrous web;