EP1954859A1

EP1954859A1 - Process for producing sheath-core staple fibre with a three-dimensional crimp, and corresponding sheath-core staple fibre

Info

Publication number: EP1954859A1
Application number: EP06806673A
Authority: EP
Inventors: Hendrik Tiemeier; Ekkehard Labitzke
Original assignee: Oerlikon Textile GmbH and Co KG
Current assignee: Oerlikon Textile GmbH and Co KG
Priority date: 2005-11-07
Filing date: 2006-11-03
Publication date: 2008-08-13
Also published as: WO2007051633A1; JP2009515061A; DE102005052857A1; US20090124155A1; CN101305118A

Abstract

The invention relates to a process for producing sheath-core staple fibre with a three-dimensional crimp, and to corresponding sheath-core staple fibre. In this process the fibre, with a symmetrical sheath-core arrangement, is extruded from two different polymer melts, with one polymer component, A, for the core and one polymer component, B, for the sheath. In order to maximize the intensity of the three-dimensional crimping in the fibre, the fibre is cooled with a sharp stream of cooling air, with a quench air velocity of at least 3 m/sec, and, after the fibres have been bundled to a tow, the multi-stage treatment takes place in a fibre line at a maximum temperature load which is below the glass transition temperature of the polymer component B in the sheath of the fibre. In this way it is possible, after the multi-stage treatment and before the cutting of the fibre, to achieve a high degree of three-dimensional crimp.

Description

A process for producing core-sheath staple fibers having a three-dimensional crimp, and such a core-sheath staple fiber

The invention relates to a method for the production of core-sheath staple fibers with a three-dimensional crimping by extruding and cooling the fiber and subsequent multi-stage treatment in a fiber strand to cut the fiber into staple fibers and a core-sheath staple with a three-dimensional crimp consisting of several polymer components.

Synthetic staple fibers are increasingly used for the production of nonwoven materials, wherein in particular the external nature as well as the possibility of joining the fibers represent special characteristic quantities. It has been found that the staple fibers with a core-sheath characteristic, in which the sheath of the fiber has a thermobondierbares polymer material, is particularly well suited to obtain by thermobonding a preconsolidated nonwoven layer. Such nonwoven layers are preferably used for multilayer nonwoven materials, as substantially intermixings of the fiber between the individual layers occur. Such a core-sheath fiber is known, for example, from JP 2-191717.

In the known core-sheath staple fiber, the fiber is extruded from two different polymer components in order to obtain a material favorable for thermobonding in the sheath of the fibers. Furthermore, the polymer components are chosen such that after cooling, these have different shrinkage behavior, resulting in the further treatment for self-crimping of the fiber. Such a property of the fiber, which is also known as so-called three-dimensional crimping, is particularly intensified in that the core is formed eccentrically within the fiber cross-section and thus a material supply which differs substantially on both sides of the fiber. which increases the self-curling effect. After melt-spinning the fiber, it is drawn, mechanically crimped and cut into staple fibers after shrinking at about 100 ° C.

However, the eccentric arrangement of the core within the fiber cross-section has the disadvantage that in places an insufficient sheathing with the respective second polymer component is formed, which hampers the further processing process, in particular with regard to the thermal bonding properties. A further disadvantage is that the generated 3D crimp is based essentially on the differences between the polymer components.

Such a core-sheath staple fiber and its production process are also known from US 2004, 0234757 A1, wherein the eccentric formation of the polymer components within the fiber cross-section to produce 3D crimping is to be improved by unilaterally forming the fiber Kühlluflstrom is acted upon. The subsequent thermal treatment to fix the crimp at temperatures up to 200 ⁰ C, the cooling and structural alterations are greatest extent canceled starting, so that the self-crimping remains substantially determined only by the differences of the polymer components. In addition, the fiber has an eccentrically formed core-shell structure, which leads to the disadvantages already mentioned above.

EP 0 891 433 B1 discloses a core-shell staple fiber in which the fiber has a symmetrical core-shell arrangement. However, the fiber consists of a polymer component which is decomposed by Oxidarion in the edge region and thus shows the core-shell structure. However, such fibers have very poor self-cockling properties, so mechanical crimping is inevitable. The mechanical crimping, also referred to as so-called two-dimensional crimping is basically leads to a lower bulk and bulk of the fiber.

It is an object of the invention to provide a method for producing a core-shell staple with a three-dimensional crimping and such a core-shell staple fiber, in which a good thermobondability is guaranteed despite high self-crimp.

This object is achieved by a method having the features of claim 1 and a core-shell staple fiber according to claim 12.

Advantageous developments of the invention are defined by the features and feature combinations of the respective subclaims.

The invention is characterized in that the core-shell staple fiber has at its periphery a uniformly distributed polymer component whose properties can be matched to the further processing process. Thus, it is advantageous to produce thermal bonds through individual melting points to each fiber safely. Surprisingly, it has been shown that the different crystallinity produced during the solidification of the fiber, in particular in the cladding region, due to the sharp blowing, leads to a high degree of self-crimping, which is further intensified by the material difference resulting between the cladding and the core. What is essential here, however, is that a multi-stage treatment carried out in a fiber web after melt-spinning of the fiber is carried out at temperatures which are below the glass transition temperature of the polymer component in the sheath of the fibers. This avoids a reduction of the structural changes due to the different cooling history of the fiber sides. The different crystallinities lead in the subsequent treatment in particular a stretching to a pronounced crimping of the fiber. For this purpose, the core-sheath staple fiber according to the invention has, in the symmetrically formed core-sheath structure, a fine crystalline structure on one side of the fiber and a substantially coarser crystalline structure on an opposite side of the fiber. Thus, after the multistage treatment, the fiber shows an intensely embossed 3D crimp, which leads to a bulky and voluminous character of the fiber. Thus, such fibers can also be used advantageously as a filler. Due to the excellent thermobondability, the staple fiber according to the invention is also preferably suitable for multilayer nonwoven products.

It has been found that the three-dimensional crimping in the core-sheath staple fiber can be further improved by extruding the fiber with a hollow core which has a center-formed hollow portion of at least 2% of the fiber cross-section. The hollow portion can assume a maximum size of 30% of the fiber cross section. By the hollow portion, a separation between the acted upon by the cooling air fiber side and the opposite fiber side is created, so that the structural changes caused by cooling form even more on the two sides of the fiber. In addition, the elasticity of the fiber increases with the same level of constancy.

The hollow cross-section of the fiber is preferably extruded through a nozzle bore having a C-shaped opening cross-section. In this way, a filling of a gaseous medium, preferably an ambient air, can be realized in the hollow portion of the fiber cross-section. The air contained in the hollow portion thus acts in addition insulating between the fiber sides, so that the one-sided cooling create structural change can emerge even more. Furthermore, the filling within the fiber causes an increase in the elasticity, so that in particular a relatively high elastic recovery on the fiber is detectable. Depending on the requirement of further processing, the core-coat staple fiber is extruded with a jacket which encloses the core with a substantially coaxially shaped annular surface in the range of 5 to 50% of the fiber cross-section. This provides a high level of flexibility in the design of the core-shell staple fiber in order to realize different combinations of polyermomponents in different proportions.

In order to increase the caused by the sharp Anblasung with a blast air velocity of at least 3 m / s Abkühlunterschieden between the blown fiber side and not blown fiber side is carried out according to an advantageous embodiment of the method, the cooling of the fiber with a cooling air, the air temperature in the range from 5 ° C to 30 ⁰ C. Preferably, the cooling air is introduced at a temperature of below 20 ° C to the freshly extruded fibers.

The extrusion of the fibers can be carried out both by rectangular spinning nozzles and by ring spinning nozzles. When using rectangular spinning nozzles with a plurality of nozzle openings, the filament bundle extruded through the nozzle openings is guided along a transverse flow blowing and cooled from the outside by the cooling air flow.

When using a ring spinneret having a plurality of nozzle orifices, the fibers extruded into a filament veil are preferably cooled by a spark plug blowing, in which the cooling air flow flows radially through the annular filament bundle from inside to outside.

The fibers are preferably removed after extrusion at a take-off speed in the range of 100 m / min, up to 1,000 m / min, so that the further processing of the fiber on a fiber strand can be carried out both continuously and discontinuously. In order to obtain the best possible thermobonding properties in the core-sheath staple fiber, the sheath is extruded from a low-melting polymer, for example a co-polyester or olefin. On the other hand, the core can preferably be extruded from a polyolefin, for example a PP polymer, which can be regarded as a cost-effective filling material.

The core-sheath staple fiber according to the invention is characterized not only by the high three-dimensional crimping but also by its high dimensional stability, since during processing into a nonwoven essentially only the polymer component in the cladding region of the fiber is used to produce a thermal bond. Essentially, the polymer component in the core of the fiber remains unaffected. The self-crimping produced in the fiber provides, in particular, a fiber structure which is relatively light in terms of volume, so that high-voluminous nonwovens having high porosity and good recovery properties can be produced.

The relatively light specific weight of the fiber is in particular on the one hand by a relatively large hollow portion of max. Achieved 30% of the fiber cross section and on the other hand by the choice of material, which has a material density, in particular in the shell, which is greater than the material density in the core. It has been found to be particularly advantageous if the material density in the jacket by a factor between 1 to 1.5 greater than the material density of the core.

The self-crimp of the fiber, which is due to unilaterally faster cooling and any desired unevenness in material distribution across the fiber cross-section of the fiber, is in the range of 5 to 12 loops of 1-inch fiber length, corresponding to 25.4-mm fiber length , Such crimps are particularly suitable for forming bulky nonwovens therefrom. It has been found that the use of such core-sheath staple fibers is preferably in the lower titer range, so that the process variant is particularly advantageous, in which after the multi-stage treatment, a fiber having a filament titer in the range of 2 to 20 den.

The nonwoven fabric product according to the invention is characterized in particular by the fact that a fiber composite can be produced in a simple manner by, for example, application of hot air. In addition, both multi-layer fiber webs can be produced as a molded part or semifinished product. Likewise, the fibrous products could be used as filling material due to their bulkiness.

The staple fibers according to the invention are preferably processed by kadding into a pile, wherein the solidification of the staple fibers within the pile can be effected in a simple manner by thermal consolidation by fusing the intersection points of the staple fiber. For this purpose, the pile can be heated, for example, by heated air or by radiant heating elements. However, it is also possible to carry out an ultrasonic solidification in which the fibers are merely heated up by friction at their points of intersection with other fibers, so that a fusion occurs.

Due to the relatively high degree of self-crimping, the fiber is preferably suitable for producing three-dimensional fiber structures in the web. The fleece has the special advantage that recovery takes place as far as possible even after mechanical stress. This effect can be used over a very long period of time due to the special property of the fiber.

The nonwoven fabric formed from the staple fibers is thus formed in particular as heat insulation, sound insulation or padding material. Such materials are characterized in particular by the small surface volume which is possible by the core-sheath staple fiber according to the invention. in this respect Such nonwovens can be produced with relatively little use of raw materials.

The method according to the invention will be explained in more detail below with reference to some embodiments with reference to the accompanying drawings.

They show:

Fig. 1 shows schematically a side view of a melt spinning apparatus for extruding a plurality of fibers

FIG. 2 schematically shows a cross-sectional view of the exemplary embodiment according to FIG.

1 ^■ Fig. 3 schematically shows a side view of a fiber line for Mehrstufenbehand- averaging a plurality of sheath-core fibers Fig. 4 schematically shows a cross section of an embodiment of a core-sheath staple fiber Fig. 5 schematically shows a cross section of another embodiment of the sheath-core staple fiber according to the invention

6 is a schematic cross-sectional view of another embodiment of a melt spinning apparatus for extruding a plurality of core-sheath fibers

The device parts shown in FIGS. 1 and 3 form an embodiment of a device for carrying out the method according to the invention. Such staple fiber production plants have the peculiarity that the fibers extruded by melt spinning are intermediately stored before a multi-stage treatment. In this way, during melt spinning of the fiber and in the multi-stage treatment of the fiber, different production speeds and different material flows can be realized and optimized for the respective process section. Thus, in a first stage of process a variety of core-sheath fibers extruded and stored as a so-called tow in a jug for intermediate storage.

In FIGS. 1 and 2, an embodiment of such a melt spinning device is shown schematically in several views. Fig. 1 shows the melt spinning apparatus in a side view, and Fig. 2 shows the melt spinning apparatus in a cross sectional view. Insofar as no explicit reference is made to one of the figures, the following description applies to both figures.

The melt spinning device has a spinning device 1, which is connected to a melt preparation 2. In this exemplary embodiment, the melt preparation 2 is formed by two melt sources 3.1 and 3.2, which are connected to the spinning device 1 via the melt distribution systems 4.1 and 4.2. The melt sources 3.1 and 3.2 are shown in this embodiment as extruders, which each melt a polymer material. Thus, a first polymer component A can be prepared by the melt source 3.1 and a second polymer component B can be processed by the melt source 3.2 to produce a polymer melt which is fed to the spinning device 1.

The spinning device 1 has a plurality of spinneret means 5.1, 5.2 and 5.3 juxtaposed in a spinning beam 7. The spinneret means 5.1, 5.2 and 5.3 are coupled to the melt distribution systems 4.1 and 4.2. Within the spinneret means 5.1, 5.2 and 5.3 conveying and guiding means are provided in order to extrude the supplied melt streams in each case through a multiplicity of nozzle openings in a rectangular nozzle plate attached to the underside of the spinneret means. Extrusion of core-sheath fibers is well known in the art, so detailed description and design of the device parts are omitted here. For extruding a core-sheath fiber with a hollow core, nozzle openings are used in particular, which exhibit a C-shaped opening cross section. Thus, the fiber can be produced with a filling of a gaseous fluid. The gaseous fluid is formed from the gas atmosphere prevailing in the vicinity of the fiber. Since this environment is essentially determined by the ambient air, thus air enters the hollow portion of the core of the fiber.

Each of the spinneret means 5.1 to 5.3 associated rectangular nozzle plates 6.1, 6.2 and 6.3 produces a plurality of core-sheath fibers that emerge as filament bundles in a fiber bundle and are deducted. Thus, the filament bundle 12.1 is extruded through the nozzle plate 6.1, the filament bundle 12.2 etc. through the nozzle plate 6.2. ^•

Below the spinning beam 7, a cooling device 8 is arranged. The cooling device 8 has for each filament bundle 12.1 to 12.3 in each case a cooling shaft 9.1, 9.2 and 9.3, through which the filament bundles are led to cool. On one side of the cooling ducts 9.1, 9.2 and 9.3, a blowing wall 10 is formed, which is directly coupled to a pressure chamber 11. The pressure chamber 11 is connected to a cooling air source (not shown here), through which a cooling air is supplied with overpressure in the pressure chamber 11, so that the blowing wall 10 generates a cooling air flow, which is directed substantially transverse to the direction of filament bundles 12.1 to 12.3.

Below the cooling device 8, a plurality of preparation rollers 13.1 to 13.6 and a plurality of deflection rollers 14.1 to 14.3 are provided, through which the filament bundles 12.1, 12.2 and 12.3 are brought together to form a tow 22. Wherein the deduction of the filament bundles 12.1 to 12.3 essentially takes place through the deduction mechanism 15, which has a plurality of draw-off rollers 16, on which the tow is guided. The discharge unit 15 is followed by a conveying means 17, which has a deflection roller 18 and two downstream coiling rollers 19.1 to 19.2. has. The reel rollers 19.1 and 19.2 are driven at the same peripheral speeds, wherein the guided between the reel rollers 19.1 and 19.2 tow is required in a held below the conveyor 17 can 20. The pot 20 is held in a can holder 21, which carries out a movement of the pot, so that the tow 22 can be stored evenly distributed within the pot 20.

For further treatment of the fibers, after filling the can 20, they are placed in a so-called can gate in order to carry out a multistage treatment on the fibers in a second process sequence. In Fig. 3, the device parts of an embodiment of a fiber line are shown to cut after a multi-stage treatment, the fiber strands to the core-sheath fiber according to the invention. At the beginning of the fiber line, a can gate 23 is arranged which holds a plurality of cans 20. The Kannengatter is associated with a collective deduction 24, through which the fibers stored in the cans are withdrawn as tow and merged. The tow strands 22 are then fed to a plurality of treatment devices and cut at the end by a cutter 29 into staple fibers of predetermined length. The treatment devices comprise a first drafting system 25.1, a treatment chamber 26, a second drafting system 25.2, a drying device 27 and an attachment device 28.

The first drafting system 25.1 is arranged directly next to the collective take-off unit 24. The drafting system 25.1 is followed by the second drafting system 25.2, wherein each of the drafting systems 25.1 and 25.2 has a plurality of drafting rollers. The tow strands 22 are guided with simple looping on the drafting rollers of the drafting systems 25.1 and 25.2. The drafting rollers of the drafting systems 25.1 and 25.2 are driven, the drafting rollers of the drafting systems 25.1 and 25.2 being operated at different peripheral speeds depending on the desired drawing ratio. For simultaneous thermal treatment of the fibers, the drafting rollers of the drafting systems 25.1 and 25.2 can be used as required. claim have a cooled roll shell or a heated roll shell.

For treatment, for example, to heat the fibers, a treatment channel 26 is formed between the first drafting system 25.1 and the second drafting system 25.2, in which the fiber is conditioned. Thus it is possible to temper the fiber strands to a predetermined temperature by means of hot air or by means of hot steam. Alternatively, the conditioning may include wetting the fiber strands.

The drafting system 25.2 is followed by a dryer 27 to reduce the moisture content in the fiber strands to obtain a final fixation of the crimp in the fiber.

At the end of the fiber line, an adjustment device 28 and the cutter 29 are provided to continuously cut the fiber strands of the core-sheath fiber into staple fibers having a predetermined fiber length.

The fiber line shown in FIG. 3 is exemplary in structure and arrangement of the treatment device. Thus, 29 can be added between the Kannengattergestell 23 and the cutting device 29 additional treatment facilities. For a Mehrstufenverstreckung example, the second drafting followed by a third drafting, between the second and third drafting additional steam treatment would be possible. In addition, the drying device 27 could be preceded by a laying device in order to change the guide widths of the tow 22 within the fiber line. In order to produce extreme crimp in the core-sheath fibers, it would also be possible to pre-allocate a crimper to the dryer.

In order to be able to carry out the method according to the invention, the following process settings necessary for the melt spinning device and the fiber line are needed to hang. Thus, to produce a three-dimensional crimp in the core-clad fiber after extrusion, the core-clad fiber is blown with a sharp stream of cooling air. For this purpose, a cooling air flow is generated by the blowing wall 10 with a blast air velocity of at least 3 m / s. It has been found that at take-off speeds in the range of 300 to 800 m / min, the blast air velocity in the range of 3 to 8 m / s is set. The sharp blow-off of the fiber strands after extrusion results in uneven cooling of the fiber, so that the directly blown fiber side cools faster than the opposite unbleached side of the fiber. This results in the crystalline structure, in particular of the cladding layer of the fiber, a differentiated structure, which leads, in particular after the multi-stage treatment, to an intensive three-dimensional crimping of the fiber. In this case, however, the Mehrstufenbehaπdlung be carried out with a temperature which is well below the glass transition temperature of the polymer component in the cladding of the fiber. This ensures that the molecular structure formed during cooling is not destroyed. In that regard, in particular, the sheath structure of the fiber for the formation of self-crimping is decisive. In the production of a core-sheath fiber in which the polymer component A for the core is formed by a polypropylene and the polymer component B for the sheath by a polyethylene tereftate, the multi-step treatment was carried out at a maximum temperature stress of the fibers of <70 ° C. The glass transition temperature T _g of the Polyethylentereftaltes is 75 ⁰ C so that the during the cooling is trained molecular structure of the multi-stage treatment was obtained. Thus, the stretching of the core-sheath fibers lead to non-uniform distortion of the inside of the fiber with respect to the outside of the fiber, which, in particular after relaxation in the drying device, leads to intensive three-dimensional crimping in the fiber.

FIG. 4 schematically shows a fiber cross-section of a core-sheath fiber. The fiber cross section of the core-sheath fiber 30 has a symmetrical arrangement between a core 31 and a sheath 32. The core 31 thus becomes gleichf _ö RMIG through the jacket 32 with an annular surface coated. To cool the fibers extruded at melt temperatures in the range from 220 to 300 ° C., a cooling air flow is applied to a front fiber side 38. The cooling air flow is at a blast air velocity in the range of 3 to 8 m / sec. blown toward the core-sheath fiber 30. The air temperature of the cooling air is in the range of 5 ° C to 30 ° C, preferably a temperature of below 18 ⁰ C is set. In the solidification of the core-sheath fiber 30, molecular differences now arise between the front fiber side 38 and the rear fiber side 39. In particular, the polymer component B in the sheath 32 forms a different crystallinity at the fiber sides 38 and 39. In the area of the front side of the fiber 38 relatively large numbers of small crystals are formed by the strong cooling. In the remote area on the Faserseit'e 39 formed by the slower cooling relatively few, but larger crystals. These internal structure of the polymer component B formed by the solidification and the material-specific differences between the polymer components B in the shell and the polymer component A in the core 31 are used in the subsequent multi-stage treatment to form a very intense and uniform three-dimensional crimp in the core-sheath fiber ,

The intensification of the three-dimensional crimping in the fiber can be further enhanced, in particular with hollow fibers, since even greater differences can be produced during cooling between the opposing fiber sides. Li Fig. 5 is an embodiment of such a core-sheath fiber shown. The core-sheath fiber 30 has a hollow core 33, which is surrounded symmetrically by a jacket 32. Due to the hollow portion within the hollow core 33, no substantial heat conduction takes place within the fiber cross-section during the cooling of the fiber, so that the cooling across the fiber cross-section takes place both faster and with greater differences between the front fiber side 38 and the rear fiber side 39. In that regard, the core-sheath fiber with hollow portion is particularly suitable to voluminous and To form bulky core-shell staple fibers. It has been shown that even a hollow portion of at least 2% of the fiber cross section results in a significant improvement over a solid cross section. On the one hand to obtain a required for the further treatment of the staple fiber sheathing of the core fiber and on the other hand to produce the greatest possible cooling deficits between the fiber sides, it has been found that the core can be extruded with a maximum hollow portion of 30% of the fiber cross-section. The advantageous properties for thermobonding in the further processing of the core-sheath staple fiber are ensured in the method according to the invention and the fiber according to the invention in that the sheath forms the core with a substantially coaxial annular surface in the range of 5 to 50% of the Fiber cross section encloses. This makes it possible to safely and adequately produce thermal compounds in the further processing process.

In particular, the core-shell structure with a hollow portion in the fiber results in a fiber having a relatively low specific gravity to produce large volume nonwoven fabrics. This effect can be further improved by selecting a polymer component for the core of the fiber which has a lower material density in relation to the cladding. Considering that in particular the shell component is formed from a low-melting polymer, considerable differences in density can be achieved. Thus, differences in the range of a factor of 1 to 1.5 are realizable, that is, the polymer component of the shell has a density that is greater by a factor of 1 to 1.5 than the density of the core component.

The enclosed in the cavity of the core-sheath fiber gaseous fluid also causes an increase in the elastic property of the fiber, which is particularly noticeable in the elastic re-expansion of the fiber. Thus, elastic back strains were measured on such a fiber, which were in the range of 60%. The dimensional stability of the fiber is further supported by the fact that during the further processing by the thermal consolidation process In essence, only the sheath component of the fiber is used to connect the fibers. Thus, a polymer is selected for the sheath component which has a low melting point or lower melt index values (MFI) in relation to the core polymer. Thus, even in the thermal bonding of nonwovens, the shape of the fiber in the core region is not substantially affected.

The enclosed in the hollow portion of the fiber gaseous fluid, which is particularly formed by an air, also provides during the cooling of the fiber is an advantageous insulation between the unevenly treated fiber sides of the fiber. In that regard, the effect of self-crimping is enhanced. The self-crimping of such fibers has a degree of crimp ranging from 7 to 10 sheets per fiber length of 1 inch.

In the fiber cross-section illustrated in Figs. 4 and 5, the polymer component A in the core of the fiber is preferably formed by a polyolefin and the polymer component B in the sheath of the staple fiber by a polyester. Here, modifications of such polymers can also be used. However, it is in principle possible for specific application cases to form the polymer component A from a polyester and the polymer component B from a polyolefin.

For the production of nonwoven products from such a fiber, in particular the combination has proven in which the core is formed of a PP polymer and the shell of a PET polymer. Thus, large fields of application of the nonwoven products can be developed both in the technical and in the hygienic field. Likewise, the core-sheath staple fiber according to the invention is particularly well suited to form very voluminous nonwovens, which are used, for example, as filling material for upholstered furniture, pillows or blankets. However, because of the excellent properties of the thermobonding of the fiber, applications as multi-layer nonwovens are also possible where especially mixing effects, as they occur for example during needling or Wasserstrahlvernadeln completely avoid. Thus, nonwoven products can be produced in a multilayer arrangement without substantial mixing of the layers.

The staple fiber according to the invention is preferably processed into a kadierten pile, wherein the subsequent thermal consolidation is feasible in a simple manner. Due to the comparatively low melting point of the outer material of the core-sheath staple fiber, the pile can already be heated by fabrication by flowing through a heated air. It is also possible to generate the heating of the pile by radiant heating elements. However, it is particularly advantageous to treat the pile by ultrasonic consolidation, so that the fibers are merely heated up by friction at their points of intersection with other fibers, so that a fusion occurs.

In particular, the core-sheath structure of the fiber produces dimensional stability in the nonwoven fabrics produced since the energy required to melt the fibers is low and thus the core of the fiber remains substantially unaffected. The elastic properties as well as the self-crimping of the fiber lead to high-voluminous nonwovens with high porosity and very good recovery properties, which remains essentially unchanged even with repeated mechanical loading. In that regard, the staple fiber is particularly suitable for producing a three-dimensional fiber structure in the web.

These produced nonwovens are preferably formed as a thermal insulation material or sound insulation material. However, due to the dimensional stability, they are also preferably suitable as upholstery material, for example, for an interior trim in the automotive sector. In this case, in particular, the temperature stability of the fiber is advantageously noticeable. The inventive method is described with reference to an exemplary embodiment of a device in which the fibers are guided discontinuously from melt spinning to cutting. In principle, it is also possible to produce such a core-sheath fiber in a continuous process flow. Here, the fiber strands are drawn immediately after the extrusion and peeling directly into the fiber line. The inventive method thus extends to all known for the production of staple fibers devices, in particular the settings of the cooling and the multi-stage treatment is designed according to the invention.

In particular, the cooling of the freshly extruded fibers can alternatively be influenced by other blows acting unilaterally on the fiber. Thus, the device shown in Fig. 1 is also to be carried out alternatively with a ring spinning nozzle. FIG. 6 shows an exemplary embodiment in which the spinneret means 5.1 has a ring spinneret plate 36 on its underside. The ring spinneret plate 36 leads to the extrusion of the core-sheath fiber into a filament veil 35. To cool the fiber strands in the filament veil 35, a blow candle 37 is arranged inside the filament veil 35, which produces a uniform flow of cooling air on its jacket. The cooling air flow thus passes from the inside to the outside through the filament curtain 35, so that the fiber strands are blown on one side. The connection of the blow candle 37 to a cooling air source can in this case be formed both from above through the spinning nozzle means 5.1 or alternatively below the spinning device.

LIST OF REFERENCE NUMBERS

1 spinning device

2 Melt preparation

3.1, 3.2 melt source

4.1, 4.2 Melt distribution system

5.1, 5.2, 5. 3 Spinneret agent

6.1, 6.2, 6. 3 Rectangular nozzle plate

7 spinning beams

8 cooling device

9.1, 9.2, 9. 3 Cooling shaft

10 blowing wall

11 pressure chamber

12.1, 12.2, 12.3 filament bundles

13.1, 13.2 ... 13.6 Preparation roller

14.1, 14.2, 14.3 pulley

15 deduction mechanism

16 take-off rolls

17 subsidies

18 deflecting roller

19.1,, 19.2 Winder rollers

20 jug

21 can holder

22 tow

23 can gates

24 collective deduction plant

25.1, 25.2 drafting system

26 treatment channel

27 dryer device

28 Zugstelleinrichtung

29 cutting device 30 core-sheath fiber

31 core

32 coat

33 hollow core 34 cooling air flow

35 filament veils

36 ring spinneret plate

37 blow candle

38 fiber side (front) 39 fiber side (rear)

Claims

claims

1. A process for the production of core-shell staple fibers with a three-dimensional crimping in the following steps: 1.1. Extruding the fibers with a symmetric core-shell

Arrangement of two different polymer melts with a polymer component A for the core and a polymer component B for the shell,

1.2. Blowing the fibers through a cooling air stream directed at the fibers on one side with a blast air velocity of at least 3 m / s,

1.3. Combining the fibers into a To w, r.4. Multi-stage treatment in a fiber line at temperatures below the glass transition temperature (Tg) of the polymer component B and

1.5. Cutting the fiber with predetermined cut length into staple fibers.

2. The method according to claim 1, characterized in that the fibers are extruded with a hollow core, which has a hollow portion formed in the center of at least 2% of the fiber cross section.

3. The method according to claim 2, characterized in that the hollow core of the fibers with a maximum hollow content of 30% of

Fiber cross section is extruded.

4. The method according to claim 2 or 3, characterized in that the fiber is extruded through a nozzle bore with a C-shaped opening cross-section.

5. The method according to any one of claims 1 to 4, characterized in that the fibers are extruded with a jacket which encloses the core with a substantially coaxial annular surface in the range of 5% to 50% of the fiber cross-section.

6. The method according to any one of claims 1 to 5, characterized in that for cooling the fibers, the cooling air has an air temperature in the range of 5 ⁰ C to 30 ° C.

7. The method according to any one of claims 1 to 6, characterized in that the fibers are extruded through a rectangular spinneret having a plurality of Düsenöffhungen to a filament bundle and cooled by a Querstromanblasung, wherein the cooling air flow is directed from the outside to the filament bundle.

8. The method according to any one of claims 1 to 6, characterized in that the fibers are extruded through a ring spinning nozzle having a plurality of Düsenöffhungen to a Filamentschleier and cooled by a Kerzenanblasung, wherein the cooling air flow is directed from the inside to the Filamentschleier.

9. The method according to any one of claims 1 to 8, characterized in that the fibers are removed after extrusion at a take-off speed in the range of lOOm / min to 1000 m / min.

10. The method according to any one of claims 1 to 9, characterized in that the polymer component A is essentially a polyolefin polyol and the polymer component B is essentially a polyester.

11. The method according to any one of claims 1 to 10, characterized in that the fiber after the multi-stage treatment Lament titer in the range of 2 to 20 den.

12. core-shell staple fiber with a three-dimensional crimp consisting of a polymer component A in the core and a polymer component B in the shell, characterized in that the two polymer components are extruded symmetrically in the fiber cross-section and that the polymer component B within the

Fiber cross-section has a fine crystalline structure on one side of the fiber and a coarse crystalline structure on the opposite side of the fiber.

13. core-shell staple fiber according to claim 12, characterized in that the core is hollow and has a filled with a gaseous fluid hollow portion of at least 2% of the fiber cross-section in the center.

14. core-shell staple fiber according to claim 13, characterized in that the core is extruded with a maximum hollow portion of 30% of the fiber cross-section.

15. core-shell staple fiber according to any one of claims 12 to 14, character- ized in that the sheath surrounds the core with a substantially coaxial annular surface in the range of 5% to 50% of the fiber cross-section.

16. Core-shell staple fiber according to one of claims 12 to 15, characterized in that the shell has a material density which is larger than the material density of the core by a factor of 1 to 1.5.

17. core-shell staple fiber according to any one of claims 12 to 16, character- ized in that the polymer component A by a

Polyolefin and the polymer component B is formed by a polyester.

18. core-shell staple fiber according to claim 17, characterized marked, that the core of a PP polymer and the shell are formed from a PET polymer.

The core-shell staple fiber of any one of claims 12 to 18, characterized in that the self-crimp of the fiber is in a range of 5 to 12 loops per 1 inch (25.4 mm) fiber length.

20. Nonwoven fabric product comprising at least a portion of a staple fiber, characterized in that the staple fibers are formed by core-sheath staple fibers according to any one of claims 12 to 19.

21. A nonwoven fabric product according to claim 20, characterized in that the staple fibers are in the form of a carded Flores, wherein the staple fibers in the pile by a thermal Verfesti- gungsverfahren in intersection points are fused together.

22. Nonwoven fabric product according to claim 20 or 21, characterized in that the staple fibers in the nonwoven fabric are connected to form a three-dimensional fiber structure.

3. Nonwoven product according to one of claims 20 to 22, characterized in that the nonwoven fabric formed from the staple fibers is formed in particular as heat insulation, sound insulation or Polste- approximately material.