SPUNBOND NONWOVEN OF CONTINUOUS FILAMENTS AND METHOD OF MAKING SAM3E

Abstract

The invention relates to a spunbond nonwoven material made of continuous filaments, in particular crimped continuous filaments, the filaments being in the form of bicomponent filaments or multicomponent filaments and having an eccentric sheath-core configuration. The sheath of the filaments, in the filament cross-section, has a constant thickness d over at least 20% of the filament circumference.

Claims

1. A spunbond nonwoven textile made of endless crimped bicomponent or multicomponent filaments having an eccentric core-sheath configuration, wherein the sheath of the filaments in the filament cross-section has a substantially constant thickness over at least 20% of the filament outer surface.

2. The spunbond nonwoven according to claim 1, wherein the core of the filaments occupies more than 50% of the area of the cross-section of the filaments.

3. The spunbond nonwoven according to claim 1, wherein the core of the filaments is of circularly segmental shape as viewed in cross-section and has, with respect to its outer surface, one substantially circularly arcuate outer-surface portion and has substantially planar outer-surface portion.

4. The spunbond nonwoven according to claim 3, wherein the circularly arcuate surface portion of the core covers over 50% of the outer surface of the core.

5. The spunbond nonwoven according to claim 1, wherein the sheath of the filaments as seen in the filament cross-section is formed except at the sheath region with the constant thickness substantially as at least one and in particular only one circle segment and has at least one, in particular only one planar or substantially planar inner-surface portion.

6. The spunbond nonwoven according to claim 1, wherein the sheath of the filaments has a constant thickness or a substantially constant thickness, as seen in the filament cross section, over 45%, in particular over 50%, preferably over 55% and preferably over 60% of the filament outer surface.

7. The spunbond nonwoven according to claim 1, wherein the thickness of the sheath in the region of its constant or substantially constant thickness is less than 10% of a filament diameter or of a largest filament diameter.

8. The spunbond nonwoven according to claim 1, wherein a thickness of the sheath in the region of its constant or substantially constant thickness is 0.1 to 5 μm.

9. The spunbond nonwoven according to claim 1, wherein a ratio of the mass of the core to the mass of the sheath is 90:10 to 50:50.

10. The spunbond nonwoven according to claim 1, wherein a spacing of a centroid of the core from a centroid of the sheath is 5% to 45% of the filament diameter or of the largest filament diameter.

11. The spunbond nonwoven according to claim 10, wherein the spacing of the centroids at a core:sheath mass ratio from 85:15 to 70:30 is between 5% and 45% of the filament diameter or the largest filament diameter or at a core:sheath mass ratio of 70:30 to 60:40 is between 12% and 40% of the filament diameter or of the largest filament diameter or at a core:sheath mass ratio of 60:40 to 45:55 is between 18% and 36% of the filament diameter or of the largest filament diameter.

12. The spunbond nonwoven textile according to claim 1, wherein both the core and the sheath of the filaments consist of at least one polyolefin.

13. The spunbond nonwoven textile according to claim 1, wherein the core consists of or substantially consists of a polyester, and the sheath consists of or essentially consists of a copolyester.

14. The spunbond nonwoven according to claim 1, wherein a titer of the filaments is 1.5 to 2.5.

15. The spunbond nonwoven textile according to claim 1, wherein the nonwoven textile is a thermally preconsolidated or thermally finished nonwoven textile that has bonding points between the filaments.

16. An apparatus for making a spunbond nonwoven textile from endless crimped continuous filaments, wherein at least one spinneret is present that makes multicomponent filaments or bicomponent filaments having an eccentric core-sheath configuration, wherein the sheath of the filaments, seen axially of the filament, has a constant thickness or a constant thickness or a constant thickness over at least 20%, in particular over 25%, preferably over at least 30%, preferably over 35%, and very preferably over 40% of its outer surface, and wherein the filaments can be deposited on a support, in particular on a deposition mesh belt.

17. The apparatus according to claim 16, wherein the apparatus has a cooler for cooling the filaments and a stretcher connected thereto for stretching the filaments and preferably has at least one diffuser connected to the stretcher.

18. The apparatus according to claim 17, wherein an assembly consisting of the cooler and the stretcher is closed, and, except for the supply of cooling air in the cooler, no further supply of air takes place from the outside.

19. The apparatus according to claim 16, wherein at least one thermal preconsolidater is provided that thermally preconsolidates the filament of the nonwoven web laid on the support or on the deposition mesh belt.

20. The apparatus according to claim 19, wherein the thermal preconsolidater operates with hot air.

Description

[0025] The invention is explained in more detail below on the basis of a drawing showing only one embodiment. The following are shown in schematic representation:

[0026] FIG. 1[A} is a cross-sectional view of an endless filament with conventional eccentric core-sheath configuration;

[0027] FIG. 1B b with an eccentric core-sheath configuration according to the invention;

[0028] FIG. 2 shows a section through an endless filament according to the invention in detail;

[0029] FIG. 3 schematically shows the dependence of the spacing a of the centroids of centers of the core and sheath of a continuous filament according to the invention depend on the thickness d of the sheath of the endless filaments in the region of the constant thickness d of the sheath; and

[0030] FIG. 4 is a vertical section through an inventive apparatus for making a spunbond nonwoven according to the invention.

[0031] FIGS. 1[A and B] show, in comparison sections through an endless filament 2 with a conventional eccentric core-sheath configuration (FIG. 1A) and by an endless filament 2 with an eccentric core-sheath configuration according to the invention (FIG. 1B). In both cases, it is an object of the present invention to provide a method and an apparatus for carrying out the method of the present invention

[0032] Bicomponent filaments have a first component made of thermoplastic material in the sheath 3 and with a second component made of thermoplastic material in the core 4. Expediently, the component in the sheath 3 has a lower melting point than the component in the core 4. FIG. 1B and FIG. 2 show that, in the case of the endless filaments 2 for a spunbond nonwoven textile 1 according to the invention, the sheath 3 of the filaments 2 in the filament cross-section preferably and here has a constant thickness d over more than 50% of the filament outer surface. Preferably, and here, the core 4 of the filaments 2 occupies more than 65% of the area of the filament cross-section of the filaments 2.

[0033] It is recommended that the core 4 of the filaments 2 according to the invention, as seen in the filament cross-section, is of circularly segmental shape. Expediently and here, the core 4 has, with respect to its outer surface, a circularly arcuate outer-surface portion 5 and a planar outer-surface portion 6. Actually and here, the circularly arcuate outer-surface portion of the core 4 occupies over 65% of the outer surface of the core 4. Expediently and here, the sheath 3 of the filaments 2—seen axially of the filament—is shaped to be circularly segmental outside the sheath region with the constant thickness d. This circular segment 7 of the sheath 3 has a circularly arcuate surface portion 8 as well as a planar surface portion 9 here with respect to its outer surface.

[0034] The thickness d or the average thickness d of the sheath 3 in the region of its constant thickness is preferably 1% to 8%, in particular 2% to 10% of the filament diameter D. Here, the thickness d of the sheath 3 may be 0.2 to 3 μm in the region of its constant thickness.

[0035] FIG. 2 shows the spacing a of the center of gravity of the core 4 from the center of gravity of the sheath 3 of an endless filament according to the invention 2. This spacing a between the centers of surface centers of the core 4 and the sheath 3 is regularly greater in the case of a given mass or surface ratio of the core and sheath material in the case of the endless filaments 2 according to the invention than in conventional endless filaments 2 having an eccentric core-sheath configuration. The spacing a of the center of gravity of the core 4 from the center of gravity of the sheath 3 in the filaments 2 according to the invention is preferably 5 to 40% of the filament diameter D or the largest filament diameter D.

[0036] FIG. 3 shows schematically for preferred embodiments of the invention the dependence of the spacing a between the centroids of the core 4 and the sheath 3 from the constant thickness d of the sheath 3 of the endless filaments 2 according to the invention. The dependence is shown here for a surface proportion of the core 4 of 75%, of 67% and of 50%. The spacing a and the constant sheath thickness d of the sheath 3 are each indicated in micrometers. The underlying endless filaments 2 according to the invention here have a filament diameter D of 18 μm.

[0037] In the table below, the spacings a between the centers of centers of the core 4 and the sheath 3 for endless filaments 2 with a filament diameter D of 18 μm are specified, specifically for different surface conditions: core:sheath (75:25, 67:33 and 50:50). On the left in the table, these spacings are listed for a constant sheath thickness d of 1 μm for the continuous filaments according to the invention having an eccentric core-sheath configuration (eC/S filaments according to the invention). To the right in the table are the spacings for a sheath thickness d′ of 1 μm at the location of the smallest spacing between the core 4 and the outer surface for the endless filaments 2 with conventional eccentric core-sheath configuration (prior-art eC/S filaments). The spacing a of the centroid centers is here in each case set absolutely in μm and relative to the filament diameter D in %.

TABLE-US-00001 Inventive eC/S filaments Prior-art eC/S filaments Surface ratio Relative to D Relative to D core/sheath Absolute μm (%) Absolute μm (%) 75:25 1.5 8 0.4 2 67:33 3.11 17 1.1 6 50:50 4.1 23 2.5 14

[0038] It can be seen from the table that the spacing a of the centroids with the same filament diameter D and the same area ratio core:sheath in the continuous filaments 2 according to the invention with an eccentric core-sheath configuration is in each case greater or significantly greater than in the case of the conventional continuous filaments 2 with an eccentric core-sheath configuration. Maintaining the spacing a between the centers of gravity of the core 4 and the sheath 3 is an essential feature of the invention that is of particular importance. The spacing between the surfaces of centers is representative of the lever arm with which the crimping forces from the two materials act and thus a substantial factor for the extent of crimping.

[0039] Preferably, and here, the core 4 of the filaments 2 according to the invention consists of polypropylene and the sheath 3 of the filaments 2 consists of polyethylene. This is a very particularly preferred embodiment that has proven very successful within the scope of the invention. It is fundamentally within the scope of the invention that the melting point of the thermoplastic plastic of the sheath 3 is less than the melting point of the thermoplastic material of the core 4 of the continuous filaments 2 according to the invention.

[0040] According to a preferred embodiment of the invention, the endless filaments 2 of a spunbond nonwoven textile 1 according to the invention have a titer of 1.5 to 2.5, preferably of 1.5 to 2.2, and preferably of 1.8 to 2.2. This titer has proven quite particularly successful with regard to the solution of the technical problem. It is furthermore within the scope of the invention that the spunbond nonwoven textile 1 according to the invention is a thermally preconsolidated spunbond nonwoven textile, to be precise with thermal bonding points or bonding points between the endless filaments 2. In a very particularly preferred embodiment, the spunbond nonwoven textile 1 according to the invention is a spunbond nonwoven textile 1 that is thermally preconsolidated with hot air. Such a spunbond nonwoven textile 1 has proven very successful with regard to the solution of the technical problem.

[0041] FIG. 4 shows an apparatus according to the invention for making a spunbond nonwoven textile 1 according to the invention and consisting in particular of crimped continuous filaments 2. The spunbond apparatus comprises a spinneret 10 or a spin head for spinning the endless filaments 2. The spinneret 10 or the apparatus is designed in such a way that the endless filaments 2 are multicomponent filaments or bicomponent filaments having an eccentric core-sheath configuration, preferably as continuous filaments 2, in which the sheath 3 has a constant thickness d, as seen in the filament cross-section, over at least 50% of the filament outer surface.

[0042] Preferably and here, the spun endless filaments 2 are introduced into a cooler 11 with a cooling chamber 12.

[0043] Expediently and here, air supplies 13, 14 one above the other are on two opposite sides of the cooling chamber 12. Air of different temperatures is expediently introduced into the cooling chamber 12 from the air supplies 13, 14 one above the other.

[0044] According to a preferred embodiment and here according to FIG. 4, a monomer extractor 15 is between the spinneret 10 and the cooler 11. With this monomer extractor 15, unwanted gases produced during the spinning process can be removed from the apparatus. These gases can be, for example, monomers, oligomers or decomposition products and similar substances.

[0045] In the filament travel direction [D], a stretcher 16 for stretching the endless filaments 2 is connected downstream of the cooler 11. Recommended and here, the stretcher 16 has an intermediate passage 17 that connects the cooler 11 to a stretching shaft 18 of the stretcher 16. According to a particularly preferred embodiment and here, the assembly composed of the cooler 11 and the stretcher 16 or the unit comprising the cooler 11, the intermediate passage 17 and the stretching shaft 18 is closed and, in addition to the supply of cooling air in the cooler 11, no further supply of air takes place from the outside into this assembly.

[0046] Here, a diffuser 19, through which the endless filaments 2 are guided, extends down from the stretcher 16 in the filament travel direction. After passing through the diffuser 19, the endless filaments 2 are preferably deposited, here on a support formed by a deposition mesh belt 20. The deposition mesh belt 20 is preferably an endlessly circulating belt 20. It is expediently designed to be foraminous, so that suction from below through the storage screen belt 20 is possible.

[0047] According to the recommended embodiment and here, the diffuser 19 or the diffuser 19 directly above the deposition screen band 20 has two opposite diffuser walls, two lower diverging diffuser wall sections 21, 22 being provided that are preferably formed asymmetrically with respect to the center plane M of the diffuser 19. Expediently and here, the diffuser wall section 21 on the inlet side forms a smaller angle β with the center plane M of the diffuser 19 than the outlet-side diffuser wall section 22. This, before the preferred embodiment, is of particular importance within the scope of the invention and has proven particularly successful with regard to the solution of the technical problem. The terms on the inlet side and on the outlet side otherwise relate to the running direction of the deposition mesh belt 20 or to the conveying direction of the nonwoven web.

[0048] According to a recommended embodiment of the invention, two opposite secondary air inlet gaps 24, 25 are provided at the inflow end 23 of the diffuser 19, each of which is on one of the two opposite diffuser walls. Preferably, a smaller secondary air volume flow can be introduced through the secondary air inlet gap 24 on the inlet side with respect to the conveying direction of the deposition mesh belt 20 than through the secondary air inlet gap 25 on the outlet side. This embodiment also has particular importance within the scope of the invention.

[0049] It is recommended here that at least one aspirator is provided to draw air or process air through the mesh belt 20 in the storage area 26 of the filaments 2 in a main suction area 27. The main suction region 27 is expediently bounded below the deposition mesh belt 20 in an inlet region of the deposition mesh belt 20 and in an outlet region of the deposition mesh belt 20 in each case by a suction separating wall 28. Preferably and here, a second suction region 29 is connected downstream of the main suction region 27 in the conveying direction [MD] of the deposition mesh belt 20, in which second suction region air or process air can be sucked through the deposition mesh belt 20. It is recommended that the suction speed V.sub.2 of the process air through the deposition mesh belt 20 in the second suction region 29 is less than the suction speed V.sub.H in the main suction region 27.

[0050] A particularly preferred embodiment is characterized in that the end of a suction partition 28 facing the storage screen belt 20 has a vertical spacing A from the storage screen belt 20 between 10 and 250 mm, in particular between 25 and 200 mm, preferably between 28 and 150 mm and preferably between 29 and 140 mm and very preferably between 30 and 120 mm. According to a very recommended embodiment, in the region of this suction separating wall 28 facing the deposition mesh belt 20, a separating wall section is connected that is a bent section 30 and comprises the above-mentioned end of the suction separating wall 28 facing the deposition mesh belt 20. It is within the scope of the invention that the end of this bent section 30 adjacent the storage screen belt 20 forms an imaginary extension of the remaining associated suction partition 28 with a horizontal spacing C that corresponds to at least 80% of the vertical spacing A. The spacings A and C are not shown in the figures. According to a recommended embodiment shown in FIG. 4, the suction partition 28 has on the screen belt side a partition section that is angled away from the rest of the suction partition 28 and is the bent section 30. Expediently and here, this bent section 30 is provided on the outlet-side suction separating wall 28 of the suction extraction region 27. According to a proven embodiment of the invention, the bent section 30 is more angled with respect to a vertical perpendicular to the storage screen belt surface than a partition section of the other, opposite suction partition 28 facing the storage screen belt 20. Expediently, the bent section 30 has a greater length than the corresponding projection of an angled or bent partition section of the further opposite suction partition 28 facing the storage screen belt 20 in its projection onto the storage screen belt surface. It is recommended that the bent section 30 has, with respect to its end on the screen belt side, a greater spacing from the deposition mesh belt 20 than that end of the separating wall section of the further opposite suction separating wall 28 that faces the deposition mesh belt 20. The embodiment with the bent section 30 ensures a very uniform and continuous transition of the suction speeds from the main suction region 27 to the region following in the conveying direction [MD] of the deposition mesh belt 20 and in particular to the second suction region 29. As a result of the arrangement of the bent section 30, a very continuous drop in the suction speed can be achieved. This makes it possible to largely avoid defects in the nonwoven web or in the spunbond nonwoven textile 1 according to the invention, which can occur due to abrupt changes in the suction speed, for example by back-flow effects (so-called blow-back effects) in the transition region between the main suction region TI and the second suction region 29. Here with the bent section 30, this is therefore a very preferred embodiment that contributes to attaining the object of the invention.

[0051] Expediently and here, at least one thermal preconsolidater for thermally preconsolidating the nonwoven web is provided downstream of the depositing region 26 in the conveying direction of the nonwoven web. Preferably, the thermal preconsolidater is at or above the second suction region 29. According to a particularly preferred embodiment, the thermal preconsolidater operates with hot air and, with particular preference, this thermal preconsolidater downstream of the main suction region 27 is a hot air knife 31. With the thermal preconsolidater, bonding points between the filaments 2 of the nonwoven web can be realized in a simple manner. In this case, the sheath 3 of the endless filaments 2 according to the invention covering the entire outer surface can be used very effectively to form thermal bonding points.

[0052] According to one embodiment of the invention, at least two thermal preconsolidaters are provided for preconsolidating the nonwoven web. Expediently, the first thermal preconsolidater in the conveying direction of the nonwoven web is the hot-air knife 31 and, preferably, a second thermal preconsolidater in the form of a hot-air oven 32 is connected downstream of this hot-air knife 31 in the conveying direction of the deposition mesh belt 20. It is within the scope of the invention that, even in the region of the hot air oven 32, air is sucked through the storage screen belt 20. In addition, it is within the scope of the invention that the suction speed of the air sucked down through the storage screen belt 20 decreases from the main suction region 27 to further suction regions in the conveying direction of the deposition mesh belt 20.

[0053] FIG. 4 shows a spunbond apparatus according to the invention with a spinneret 10 and thus with a spinning beam. It is also within the scope of the invention that a spunbond apparatus according to the invention can be used in the context of a 2-beam system or multi-beam system. According to one embodiment, several spunbond apparatuses according to the invention can be used one after the other.