SPUNBONDED LAMINATE AND METHOD OF MAKING SAME

Abstract

A laminate has first and second spunbonded nonwoven layers at least one of which comprises or consists essentially of crimped continuous filaments that are bicomponent filaments having a first component based on polypropylene and a second component based on polypropylene. A specific density ρ (g/cm.sup.3) of the spunbonded nonwoven laminate depending on the surface density of the spunbonded nonwoven laminate lies below a density limit ρ.sub.G defined by the following equation:

ρ.sub.G=9 cm.sup.−1×surface density g/cm.sup.2+0.0393 g/cm.sup.3.

Claims

1. A laminate comprising first and second spunbonded nonwoven layers at least one of which comprises or consists essentially of crimped continuous filaments that are bicomponent filaments having a first component based on polypropylene and a second component based on polypropylene, a specific density ρ in g/cm.sup.3 of the spunbonded nonwoven laminate depending on the surface density of the spunbonded nonwoven laminate lying below a density limit ρ.sub.G defined by the following equation:
ρ.sub.G=9 cm.sup.−1×surface density g/cm.sup.2+0.0393 g/cm.sup.3.

2. The laminate according to claim 1, wherein the first component consists or substantially consists of a polypropylene mixture or consists or substantially consists of a polypropylene copolymer.

3. The laminate according to claim 1, wherein the second component consists or substantially consists of a polypropylene.

4. The laminate according to claim 1, wherein at least one spunbonded nonwoven layer of the laminate comprises crimped continuous filaments having a titer of up to 2 denier.

5. The laminate according to claim 1, wherein at least one spunbonded nonwoven layer is comprises of crimped continuous filaments having a core-sheath configuration and the first component is the sheath and the second component is the core.

6. The laminate according to claim 1, wherein at least 25% of all the continuous filaments of the laminate are crimped continuous filaments having an eccentric core-sheath configuration.

7. The laminate according to claim 6, wherein, in the crimped continuous filaments having an eccentric core-sheath configuration, the sheath of the filaments has a constant thickness D or a substantially constant cross-sectional thickness D over at least 20% of the filament circumference and a thickness of the sheath in the region of its constant or substantially constant thickness D is 0.1 to 4 μm.

8. The laminate according to claim 1, wherein the laminate further comprises a third spunbonded nonwoven layer, at least one of the spunbonded nonwoven layers comprising crimped continuous filaments having an eccentric core-sheath configuration and on an outer side of the laminate and a titer of the continuous filaments of this one spunbonded nonwoven layer is up to 2 denier.

9. The laminate according to claim 1, wherein at least one of the spunbonded nonwoven layer comprises crimped continuous filaments with side-by-side configuration.

10. The laminate according to claim 1, wherein the laminate has a surface density of 10 to 40 g/m.sup.2.

11. The laminate according to claim 1, wherein the first component comprises at least one polypropylene copolymer that has a fraction of the co-monomer of 1 to 6 wt. %.

12. The laminate according to claim 1, wherein the first and the second component have different melt-flow rates and the continuous filaments have a core-sheath configuration and the second component forms the core component and has a higher melt-flow rate than the first component forming the sheath component.

13. The laminate according to claim 12, wherein a ratio of the melt-flow rate of the second component to the melt-flow rate of the first component is 0.9 to 2.2.

14. The laminate according to claim 1, wherein a ratio of a polydispersity index of the first component to a polydispersity index of the second component is 0.9 to 1.4.

15. The laminate according to claim 1, wherein a melting temperature of the first component is lower than a melting temperature of the second component and a difference between the melting temperatures is 0 to 20° C.

16. The laminate according to claim 1, wherein, wherein the second component comprises at least 1000 ppm relative to the total filament of at least one lubricant.

17. A method of making a spunbonded nonwoven laminate, the method comprising the steps of sequentially: making first and second spunbonded nonwoven layers of which at least one has crimped bicomponent filaments having a first component based on polypropylene and a second component based on polypropylene; preconsolidating at least one spunbonded nonwoven layer with at least one hot roller or at least one calender roller or at least one hot air oven; final consolidating the first and second spunbonded nonwoven layers into the spunbonded nonwoven laminate by at least one calender roller such that the laminate has a specific density dependent on its surface density and below a density limit ρ.sub.G according to the equation:
ρ.sub.G=9 cm.sup.−1×Surface density g/cm.sup.2+0.0393 g/cm.sup.3.

18. The method according to claim 17, wherein the final consolidation is performed using at least one calender roller having an open dot engraving.

19. The method according to claim 17, further comprising the step after the final consolidation of: compressing the laminate such that it has a residual compression set when relaxed of a maximum of 30% and a specific density ρ of the laminate is a maximum of 30% above the density

Description

BRIEF DESCRIPTION OF THE DRAWING

[0057] 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:

[0058] FIG. 1 is a vertical section through a device for making a spunbonded nonwoven layer of a spunbonded nonwoven laminate according to the invention,

[0059] FIG. 2 is a cross-section through a preferred continuous filament with eccentric core-sheath configuration and

[0060] FIG. 3 is a diagram of density versus surface density,

[0061] FIG. 4 is the diagram of the melt-flow rate quotient versus the polydispersity index quotient.

SPECIFIC DESCRIPTION OF THE INVENTION

[0062] FIG. 1 shows a system for making a spunbonded nonwoven layer for the spunbonded nonwoven laminate according to the invention according to the spunbond method. Using this device or using this method preferably also the at least one spunbonded nonwoven layer with crimped continuous filaments is produced for the spunbonded nonwoven laminate. The device comprises a spinneret 1 for spinning continuous filaments 2 for a spunbonded nonwoven layer of the spunbonded nonwoven laminate according to the invention. The continuous filaments 2 spun by the spinneret 1 are introduced into a cooler with a cooling chamber 4. Preferably and in the embodiment air supply cabins 5, 6 arranged one above the other are arranged on two opposite sides of the cooling chamber 4. Expediently air at different temperature is introduced into the cooling chamber 4 from the air supply cabins 5, 6 arranged one above the other. Preferably and in the embodiment, a monomer extraction device 7 is arranged between the spinneret 1 and the cooler 3. With this monomer extraction device 7 perturbing gases produced during the spinning process can be removed from the device.

[0063] It is recommended that and in the embodiment a stretcher 8 for elongating the continuous filaments 2 is located downstream of the cooler 3 in the filament flow direction. Expediently and in the embodiment the stretcher 8 comprises an intermediate passage 9 that connects the cooler 3 to a stretching shaft 10 of the stretcher 8. Preferably and in the embodiment the unit comprising the cooler 3 and the stretcher 8 or the unit comprising the cooler 3, the intermediate passage 9 and the stretching shaft 10 is configured as a closed unit and apart from the supply of cooling air in the cooler 3, no further air is supplied from outside into this unit.

[0064] Expediently and in the experimental embodiment, in the filament flow direction the stretcher 8 is adjoined by a diffuser 11 through which the continuous filaments 2 are guided. After running through the diffuser 11, preferably and in the embodiment the continuous filaments 2 are deposited on a depositing device configured as a depositing foraminous belt 12. The depositing foraminous belt 12 is expediently and in the embodiment configured as a continuously circulating depositing foraminous belt 12. It lies within the scope of the invention that the depositing foraminous belt 12 is air-permeable so that it is possible to extract process air from below through the depositing foraminous belt 12. To this end, expediently and in the embodiment an extraction device 13 is disposed below the depositing foraminous belt 12.

[0065] FIG. 2 shows a section through a continuous filament 2 with an eccentric core-sheath configuration. Such continuous filaments 2 are preferably used for a spunbonded nonwoven layer with crimped continuous filaments in the spunbonded nonwoven laminate according to the invention. These comprise a bicomponent filament having a first component based on polypropylene in the sheath 14 and having a second component based on polypropylene in the core 15. It can be seen in FIG. 2 that in the preferred continuous filaments 2 the sheath 14 of the filaments 2 in the filament cross-section preferably and in the embodiment has a constant thickness D over more than 50% of the filament circumference. Preferably and in the embodiment the core 15 of the filaments 2, when viewed in the filament cross-section, is configured to be circular-segment-shaped. The sheath 14 in its region of constant thickness D preferably has a thickness D of 0.1 to 0.9 μm.