METHOD OF MAKING A SPUNBOND LAMINATE

Abstract

A spunbond nonwoven laminate has a first spunbond nonwoven layer having crimped filaments formed by a first component on an outer surface of the filaments of the first layer consisting or substantially consisting of a polyolefin and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the first layer. A second outermost spunbond nonwoven layer on the first layer having filaments as a cover layer and formed by a first component on an outer surface of the filaments of the second layer consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the second layer.

Claims

1. A method of making a spunbond nonwoven laminate, the method comprising the steps of: providing a first spunbond nonwoven layer having crimped multicomponent or bicomponent filaments and formed by a first component on an outer surface of the filaments of the first layer consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the first layer preconsolidating the first layer with hot air and imparting to the filaments of the first layer a predetermined crimp; providing a second outermost spunbond nonwoven layer having multicomponent or bicomponent filaments as a cover layer and formed by a first component on an outer surface of the filaments of the second layer consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the second layer, a polyolefin portion of the first component of the filaments of the second layer being greater than a polyolefin portion of the first component of the filaments of the first layer; preconsolidating the second layer with hot air and imparting to the filaments of the second layer a degree of crimp equal to or less than the predetermined degree of crimp of the filaments of the first layer; and finally consolidating the spunbond nonwoven laminate formed by the first and second layers with hot air.

2. The method according to claim 1, wherein first the second spunbond nonwoven layer is made as a cover layer and is preconsolidated, and then the first spunbond nonwoven layer is formed on the second spunbond nonwoven layer is in turn preconsolidated.

3. The method according to claim 1, further comprising the step of using multicomponent or bicomponent filaments for the second spunbond nonwoven layer.

4. The method according to claim 1, further comprising the step of: imparting to the filaments of the second outermost layer a titer that is less than a titer of the filaments of the first layer.

5. The method according to claim 1, wherein the second component of the filaments of the first layer consists or substantially consists of polypropylene or polyester.

6. The method according to claim 1, wherein the polyolefin portion of the filaments of the first layer is less than 40% by weight.

7. The method according to claim 1, further comprising the step of: imparting to the filaments of the first layer a titer of more than 1.5 den, and to the filaments of the first layer a titer of 1.5 den to 2.5 den.

8. The method according to claim 1, wherein the polyolefin of the first component of the filaments of the first layer is polyethylene having a melt flow rate of less than 35 g/10 min.

9. The method according to claim 1, wherein the second component of the filaments of the first layer consists or substantially consists of polypropylene having a melt flow rate of more than 25 g/10 min.

10. The method according to claim 1, wherein the second component of the filaments of the second layer consists or substantially consists of polypropylene.

11. The method according to claim 1, wherein the polyolefin portion of the filaments of the second layer is more than 33 wt.-%, and the polyolefin portion is 40 wt.-% to 65 wt.-%.

12. The method according to claim 1, wherein the multicomponent or bicomponent filaments of the second layer have an eccentric core-sheath configuration or a side-by-side configuration.

13. The method according to claim 1, wherein the first component on the outer surface of the filaments of the second layer consists or substantially consists of polyethylene having a melt-flow rate greater than 15 g/10 min.

14. The method according to claim 13, wherein the melt flow rate of the polypropylene of the second component of the second layer is more than 25 g/10 min.

15. The method according to claim 1, further comprising the step of: imparting to the second layer a weight per unit area of less than a weight per unit area of the first layer.

16. The method according to claim 1, wherein a strength of the spunbond nonwoven laminate in the machine direction is greater than 25 N/5 cm, the spunbond nonwoven laminate in particular having a basis weight of 12 to 50 g/m.sup.2.

17. The method according to claim 1, wherein a thickness of the spunbond nonwoven laminate is more than 0.50 mm, and the spunbond nonwoven laminate has in particular a basis weight from 12 to 50 g/m.sup.2.

18. The method according to claim 1, wherein a difference between a titer of the filaments of the first layer and a titer of the filaments of the second layer is at least 0.2 den.

19. A method of making a spunbond nonwoven laminate, the method comprising the steps of: providing a first spunbond nonwoven layer having crimped multicomponent or bicomponent filaments of an eccentric core-sheath configuration and formed by a first sheath component forming at least 20% of a filament circumference a substantially constant thickness, and consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the first layer preconsolidating the first layer with hot air; providing a second outermost spunbond nonwoven layer having multicomponent or bicomponent filaments as a cover layer and formed by a first component on an outer surface of the filaments of the second layer consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the second layer, a polyolefin portion of the first component of the filaments of the second layer being greater than a polyolefin portion of the first component of the filaments of the first layer; preconsolidating the second layer with hot air; and finally consolidating the spunbond nonwoven laminate formed by the first and second layers with hot air.

20. A method of making a spunbond nonwoven laminate, the method comprising the steps of: providing a first spunbond nonwoven layer having crimped multicomponent or bicomponent filaments and formed by a first component on an outer surface of the filaments of the first layer consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the first layer preconsolidating the first layer with hot air; providing a second outermost spunbond nonwoven layer having multicomponent or bicomponent filaments of an eccentric core-sheath configuration as a cover layer and formed by a first sheath component forming over at least 20% of a filament circumference a substantially constant thickness, and consisting or substantially consisting of a polyolefin, and a second component consisting or substantially consisting of a plastic having a higher melting point than the polyolefin of the first component of the filaments of the second layer, a polyolefin portion of the first component of the filaments of the second layer being greater than a polyolefin portion of the first component of the filaments of the first layer; preconsolidating the second layer with hot air; and finally consolidating the spunbond nonwoven laminate formed by the first and second layers with hot air.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0048] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

[0049] FIG. 1 is a vertical section through an apparatus for making a layer of a spunbond nonwoven laminate according to the invention;

[0050] FIG. 2 is a schematic side view of a two-beam system with two spunbonding devices for making two layers of a spunbond nonwoven laminate according to the invention;

[0051] FIG. 3 is a section through a spunbond nonwoven laminate according to the invention; and

[0052] FIG. 4 is a section through a continuous filament preferably used according to the invention with an eccentric core-sheath configuration.

SPECIFIC DESCRIPTION OF THE INVENTION

[0053] FIG. 1 shows a spunbonding device for making a spunbond nonwoven layer 2 or 3 for an inventive spunbond nonwoven laminate 1. Such a spunbond nonwoven layer 2 or 3 made with the apparatus has crimped continuous filaments F or consists of crimped continuous filaments F, or substantially consists of crimped continuous filaments F. It is within the scope of the invention that the continuous filaments F are thermoplastic.

[0054] The apparatus shown in FIG. 1 comprises a spinneret 10 for spinning the continuous filaments F and these spun continuous filaments F are expediently introduced into a cooler 11 with a cooling chamber 12. Preferably, air supply manifolds 13 and 14 are one atop the other on two opposite sides of the cooling chamber 12. Air of different temperatures is expediently introduced into the cooling chambers from these air supply manifolds 13 and 14. As recommended, a monomer extractor 15 is provided between the spinneret 10 and the cooler 11. With this monomer extractor 15, disruptive gases occurring during the spinning process can be removed from the apparatus. These gases can be, for example, monomers, oligomers, or decomposition products and the like substances.

[0055] The cooler 11 preferably and, in the embodiment in the filament flow direction, is followed by a stretcher 16 for stretching the continuous filaments F. Preferably, 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, the assembly from the cooler 11 and the stretcher 16 or the assembly from the cooler 11, the intermediate passage 17, and the stretching shaft 18 is designed as a closed subassembly and, apart from the supply of cooling air in the cooler 11, there is no further air supply from outside in this aggregate.

[0056] The stretcher 16 is preferably in this embodiment in the filament flow direction by a diffuser 19 through which the continuous filaments F are passed. After passing through the diffuser 19, the continuous filaments F are preferably, deposited on a conveyor designed as a deposit mesh belt 20. The deposit mesh belt 20 is preferred and, in the embodiment, is designed as an endlessly rotating deposit mesh belt 20. This deposit mesh belt 20 is expediently air-permeable so that process air can be aspirated from below through the deposit mesh belt 20.

[0057] Preferably, the diffuser 19 has two lower diverging upstream and downstream diffuser walls 21 and 22. These diverging diffuser walls 21 and 22 are expediently asymmetrical with respect to the center plane M of the apparatus or the diffuser 19. As recommended, the upstream diffuser wall 21 forms a smaller angle β with the center plane M than the downstream diffuser wall 22. The angle β that the upstream diffuser wall 21 forms with the center plane M is recommended to be at least 1° smaller than the angle β that the downstream diffuser wall 22 forms with the center plane M.

[0058] It is within the scope of the invention that two opposite secondary air inlet gaps 24 and 25 are provided at the inflow end 23 of the diffuser 19, each of which is formed in part by a respective one of the two opposite diffuser walls. A smaller secondary air volume flow can preferably be introduced through the upstream secondary air inlet gap 24 than through the downstream secondary air inlet gap 25. It is recommended that the secondary air volume flow of the upstream secondary air inlet gap 24 is at least 5%, preferably at least 10% and in particular at least 15% lower than the secondary air volume flow through the downstream secondary air inlet gap 2.

[0059] FIG. 2 shows a two-beam system with two spunbonding devices corresponding to FIG. 1 for making two spunbond nonwoven layers 2 and 3 to form a spunbond nonwoven laminate 1 according to the invention. For the sake of simplicity, the apparatus components of the spunbonding devices have not been shown in full in FIG. 2, but only the lower region of the respective diffusers 19. According to a particularly preferred embodiment, continuous filaments F are first spun with the upstream spunbonding device for the two-beam system and deposited to form the second spunbond nonwoven layer 3 (cover layer). Continuous filaments F for the first spunbond nonwoven layer 2 are then spun with the spunbonding device downstream in the travel direction of the deposit mesh belt 20 on the right in FIG. 2 and deposited on the deposit mesh belt 20 or on the second spunbond nonwoven layer 3. This order of production of the spunbond nonwoven layers 2, 3 is particularly recommended in the scope of the invention.

[0060] Below the deposit region 26 for the continuous filaments F of each spunbonding device, process air is extracted through the deposit mesh belt 20 in a main suction area 27, with a suction velocity v.sub.H. The nonwoven layer [2,] 3 made with the first spunbonding device shown on the left in FIG. 2, preferably and here the second layer 3, is recommended to be supplied to the hot-air preconsolidaters with the deposit mesh belt 20. Preferably, this second layer 3 is first preconsolidated with a hot air knife 31 and then preferably further consolidated with a hot air oven 32 connected downstream in the machine direction (MD). In the recommended embodiment, process air is extracted by the deposit mesh belt 20 both below the hot air knife 31 and below the hot air oven 32, specifically in the case of the hot air knife 31 with a suction velocity v.sub.2 and in the case of the hot air oven with a suction velocity v.sub.3. For the suction velocities, it is preferably the case that the suction velocity v.sub.H is greatest in the main suction area 27 and the suction velocity v.sub.2 under the hot air knife 31 is the second largest and that the suction velocity v.sub.3 under the hot air oven 32 is the third largest. The suction velocity v thus decreases from the deposit region 26 of the filaments F to the hot air oven 32. The hot air knife 31 (left in FIG. 2) preferably preconsolidates the second layer 3 at a hot air temperature of 80° C. to 250° C., preferably at 120° C. to 190° C. The hot-air preconsolidation in the downstream hot air oven 32 is advantageously carried out at a hot air temperature of 110° C. to 180° C., preferably from 120° C. to 160° C. The hot air knife 31 (left in FIG. 2) is preferred and, in the embodiment, hot air is supplied at a higher speed than the hot air of the downstream hot air oven 32. The speed of the supplied hot air in the hot air knife 31 preferably has a speed that is greater by at least a factor of 1.5, preferably a factor of 1.8, than the speed of the hot air in the hot air oven 32. Furthermore, as recommended, the width in the machine direction (MD) in which hot air is applied is narrower for the first (in FIG. 2 left) hot air knife 31 than for the first (in FIG. 2 left) hot air oven 32. The width of the hot air exposure in the machine direction (MD) in the hot air oven 32 is larger by at least a factor of 1.5 than in the hot air knife 31.

[0061] A second spunbond nonwoven layer 2, 3, preferably and here the first layer 2, for the spunbond nonwoven laminate 1 is made with the right second spunbonding device shown in FIG. 2. This first layer 2 is recommended and, in the embodiment, deposited on the second spunbond nonwoven layer 3 already transported by the deposit mesh belt 20. Subsequently, it is preferred and here the aggregate from two layers 2, 3 is preconsolidated, specifically as recommended and here preconsolidated with hot air. For this purpose, a hot air knife 31 is first downstream of the second spunbonding device in the machine direction (MD) and a hot air oven 32 is in turn downstream of the hot air knife 31. In the case of the second spunbonding device and in the aforementioned hot-air preconsolidaters of the second spunbonding device, the suction operations explained for the first spunbonding device are expediently carried out with the corresponding suction velocities. The parameters mentioned there for the hot-air preconsolidaters, in particular temperatures and width parameters, also apply to the hot air knife 31 and to the hot air oven 32 behind the second spunbonding device. In the embodiment of FIG. 2, both layers 2, 3 of the spunbond nonwoven laminate 1 according to the invention are only preconsolidated with hot air.

[0062] It is within the scope of the invention that the preconsolidated aggregate from the two layers 2 and 3 is then finally consolidated, and is preferably finally consolidated by means of hot air. For this purpose, a hot air oven, not shown in the figures, is expediently used. According to one embodiment of the invention, the layers or the two layers 2, 3 of the spunbond nonwoven laminate 1 are both preconsolidated with hot air or only preconsolidated with hot air and also finally consolidated with hot air or only finally consolidated with hot air.

[0063] FIG. 3 schematically shows a section through an inventive spunbond nonwoven laminate 1 with the two layers 2 and 3.

[0064] FIG. 4 shows bicomponent filaments with an eccentric core-sheath configuration, which are very particularly preferred for the layers 2, 3 of the spunbond nonwoven laminate 1 according to the invention. According to one embodiment of the invention, both layers 2, 3 of the spunbond nonwoven laminate 1 consist of such bicomponent filaments with an eccentric core-sheath configuration. FIG. 4 shows a cross section through a continuous filament F with the preferred special core-sheath configuration. With these continuous filaments F, the sheath 37 preferably has a constant thickness d in the filament cross section and here over more than 50%, preferably over more than 55% of the filament circumference. Preferably, the core 4 of the filaments F takes up more than 65% of the area of the filament cross section of the filaments F. As recommended, the core 4, seen in the filament cross section, is designed in the shape of a segment of a circle. Expediently, this core 4 has an arcuate peripheral portion 5 and a secantal peripheral portion 6 with regard to its circumference. Preferably, the arcuate peripheral portion of the core 4 takes up over 50%, preferably over 55% of the circumference of the core 4. Expediently, the sheath 37 of the filaments F, seen in the filament cross section, is formed in the shape of a segment of a circle outside the sheath region with a constant thickness d. This circular segment 7 of the sheath 37 has, as recommended, an arcuate peripheral portion 8 and a straight peripheral portion 9 with regard to its circumference. The thickness d or the average thickness d of the sheath 37 in the region of its constant thickness is preferably 0.5% to 8%, in particular 2% to 10% of the filament diameter D. The thickness d or the average thickness d of the sheath is preferably 0.1 μm to 3 μm. FIG. 4 also shows the distance a of the center of gravity of the core 4 from the centroid of the sheath 3 of the continuous filament 2. The distance a between the centroid of the core 4 and the centroid of the sheath 3 is preferably 5% to 40% of the filament diameter D or the largest filament diameter D for the filaments F here.