VOLUMINOUS MELTBLOWN NONWOVEN FABRIC WITH IMPROVED STACKABILITY AND STORABILITY

Abstract

The present invention relates to a meltblown nonwoven in the form of a sheet-like formation with a weight per unit area of 100 to 600 g/m.sup.2 and with a density of 5 to 50 kg/m.sup.3, wherein the meltblown nonwoven (10) has at least one spacer (12), extending at least on one of the surfaces thereof and/or at least partially in the direction of the thickness of the meltblown nonwoven (10) and arranged in such a way that the meltblown nonwoven (10) has a compressibility of less than 10% when a pressure of 50 Pa is applied to its surface.

Claims

1. A meltblown nonwoven fabric (10) in the form of a planar structure with a weight per unit area of from 100 to 600 g/m.sup.2 and with a density of from 5 to 50 kg/m.sup.3, the meltblown nonwoven fabric (10) having at least one spacer (12) extending on at least one of its surfaces and/or partially in the direction of thickness of the meltblown nonwoven fabric (10) that is arranged such that the meltblown nonwoven fabric (10) has a compressibility of less than 10% when a pressure of 50 Pa is applied to its surface.

2. The meltblown nonwoven fabric as set forth in claim 1, wherein the meltblown nonwoven fabric (10) has a compressibility of less than 10% when a pressure of 75 Pa is applied to its surface.

3. The meltblown nonwoven fabric as set forth in claim 1, wherein the at least one spacer (12) is made of compressed nonwoven fabric that is a depression (14) formed in the meltblown nonwoven fabric (10) through application of mechanical pressure, wherein the side surfaces and bottom of the depression (14) are delimited by compressed nonwoven fabric (16), and wherein the bottom of the depression (14) that is delimited by the compressed nonwoven fabric (10) is between 0% and up to 10% of the thickness of the meltblown nonwoven fabric below the lower side of the meltblown nonwoven fabric as seen in the direction of thickness, or it protrudes beyond the lower side of the nonwoven fabric (10).

4. The meltblown nonwoven fabric as set forth in claim 2, wherein the depression (14) has a width of from 0.1 to 5 times the thickness of the nonwoven fabric (10).

5. The meltblown nonwoven fabric as set forth in claim 3, wherein it has a plurality of depressions (14) that are spaced apart from one another by 50 to 500 mm as seen on the nonwoven fabric plane.

6. The meltblown nonwoven fabric as set forth in claim 1, wherein the at least one spacer (12) is an element that is made of a material other than nonwoven fabric, with the element being a material that is selected from one among metals, plastics, ceramics, wood, glass and any combination of two or more of the aforementioned materials.

7. The meltblown nonwoven fabric as set forth in claim 6, wherein the at least one spacer (12) can be placed onto the upper side and/or lower side of the nonwoven fabric (10) and is affixed with adhesive, with a connecting element, by thermal welding, or by mechanical pressing.

8. The meltblown nonwoven fabric as set forth in claim 6, wherein the at least one spacer (12) extends through an opening (18) that was previously introduced in a pressure-free manner into the nonwoven fabric (10) and has at least a dimension that is 90% to 100% of the thickness of the meltblown nonwoven fabric (10) as viewed in the direction of thickness or protrudes beyond the upper side and/or the lower side of the nonwoven fabric (10).

9. The meltblown nonwoven fabric as set forth in claim 6, wherein it has a plurality of spacers (12) that are spaced apart from one another by 50 to 500 mm as seen on the nonwoven fabric plane.

10. The meltblown nonwoven fabric as set forth in claim 1, wherein additional nonwoven fabric (20) is applied to the nonwoven fabric (10) in some regions as a spacer (12), so that the total thickness in this region or in these regions is greater than that of the rest of the nonwoven fabric (10), the additional nonwoven fabric (20) being affixed to the nonwoven fabric (10) by means of adhesive, thermal welding, or mechanical pressing.

11. The meltblown nonwoven fabric as set forth in claim 10, wherein the additional nonwoven fabric (10) is applied to at least a portion of the edge region of the nonwoven fabric (10) as a spacer (12), so that the total thickness in this edge region is greater than that of the rest of the nonwoven fabric (10).

12. The meltblown nonwoven fabric as set forth in claim 10, wherein the additional nonwoven fabric (20) is placed onto at least a portion of the edge region of the meltblown nonwoven fabric (10) by folding over the meltblown nonwoven fabric (10) and affixed to the edge region of the meltblown nonwoven fabric (10) by means of adhesive, thermal welding, or mechanical pressing.

13. The meltblown nonwoven fabric as set forth in claim 1, wherein the meltblown nonwoven fabric (10) has a weight per unit area of from 100 to 400 g/m.sup.2.

14. The meltblown nonwoven fabric as set forth in claim 1, wherein the meltblown nonwoven fabric (10) is a voluminous meltblown nonwoven fabric (10) having a density of from 8 to 25 kg/m.sup.3.

15. The meltblown nonwoven fabric as set forth in claim 1, wherein the thickness of the meltblown nonwoven fabric (15) is from 6 to 50 mm.

Description

[0041] Hereinafter, the present invention will be described below with reference to the clarifying but non-limiting drawing.

[0042] In the drawing:

[0043] FIG. 1 shows a schematic view of a meltblown nonwoven fabric without spacers according to the prior art.

[0044] FIG. 2 shows a schematic view of a meltblown nonwoven fabric according to FIG. 1 that has been irreversibly deformed as a result of applied mechanical pressure.

[0045] FIG. 3 shows a schematic view of a meltblown nonwoven fabric with spacers arranged in the direction of thickness of the meltblown nonwoven fabric according to a first exemplary embodiment of the present invention.

[0046] FIG. 4 shows a schematic view of a meltblown nonwoven fabric with spacers arranged in the direction of thickness of the meltblown nonwoven fabric according to a second exemplary embodiment of the present invention.

[0047] FIG. 5 shows a schematic view of a meltblown nonwoven fabric with spacers arranged in the direction of thickness of the meltblown nonwoven fabric according to a third exemplary embodiment of the present invention.

[0048] FIG. 1 shows a schematic view of a meltblown nonwoven fabric 10 without spacers according to the prior art that has been manufactured according to the method described in DE 17 85 712 C3. The C-shaped structure within the meltblown nonwoven fabric 10 that is caused by the high-frequency reciprocation of the filament curtain that occurs in the manufacturing method described in DE 17 85 712.

[0049] If a meltblown nonwoven fabric 10 according to the prior art is acted upon by pressure for example as a result of stacking the meltblown nonwoven fabric 10 with multiple layers of the meltblown nonwoven fabric 10 the meltblown nonwoven fabric 10 is irreversibly compressed and remains deformed as shown in FIG. 2.

[0050] In order to increase the resistance to compression and thus the stackability of the meltblown nonwoven fabric 10, it is proposed according to the invention that at least one and preferably a plurality of spacers 12 be provided in the meltblown nonwoven fabric 10. The spacers 12 shown in FIG. 3 are depressions 14 formed through application of mechanical pressure whose side surfaces and bottom are delimited by compressed nonwoven fabric 16, with the bottom of the depression 14 that is delimited by the compressed nonwoven fabric 16 protruding beyond the lower side of the nonwoven fabric 10 by the distance L as seen in the direction of thickness. By virtue of the much higher mechanical stability of compressed nonwoven fabric 16 compared to the non-compressed nonwoven fabric 10, these spacers 12 can accommodate the pressure of overlying nonwoven fabric layers without deformation and thus allow stackability of the meltblown nonwoven fabric 10.

[0051] In the embodiment shown in FIG. 4, the spacers 12 that are arranged in the direction of thickness of the meltblown nonwoven fabric 10 are made of material other than nonwoven fabric, namely plastic mushroom-shaped elements 12. The spacers extend through an opening 18 that was previously introduced in a pressure-free manner into the nonwoven fabric 10 and, in this example, protrude beyond the lower side of the nonwoven fabric 10 by the distance L.

[0052] In the embodiment shown in FIG. 5, an additional nonwoven fabric 20 is applied to the left edge and to the right edge of the meltblown nonwoven fabric 10 as a spacer, so that the total thickness in these regions of the meltblown nonwoven fabric 10 is greater than that of the rest of the nonwoven fabric. In this case, the additional nonwoven fabric 20 has been applied to both edges through folding-over of the meltblown nonwoven fabric 10, compression, and attachment by means of adhesive.

[0053] By virtue of the fact that spacers 12 are provided in the meltblown nonwoven fabric 10 that extend on at least one of the surfaces of the meltblown nonwoven fabric 10 and/or at least partially in the direction of thickness of the meltblown nonwoven fabric 10 and are arranged such that the meltblown nonwoven fabric 10 has a compressibility of less than 10% when a pressure of 50 Pa is applied to its surface, various layers of the meltblown nonwoven fabric 10 can be easily stacked on top of one another without causing unacceptable deformation and particularly compression of the meltblown nonwoven fabric 10, since the various layers each contact their spacers 12 and are mutually spaced apart by these in such a way that the upper layers do not compress the lower layers by their weight. Easy storability of the meltblown nonwoven fabric 10 is thus achieved.

[0054] The present invention will be described below with reference to clarifying but non-limiting examples.

EXAMPLE 1

[0055] A meltblown nonwoven fabric having a weight per unit area of 300 g/m.sup.2 and a thickness of 15 mm was prepared from filaments of isotactic polypropylene with a mean filament fineness of 5 m. Spacers made of polystyrene having the shape shown in FIG. 4 and a maximum resistance to compression of greater than 2 kg were introduced into this meltblown nonwoven fabric as described previously in connection with this embodiment, particularly in such a way that the grid dimension i.e., the spacing between the individual spacers was 20 cm20 cm.

[0056] Sixty-six layers of this nonwoven fabric were stacked on top of one another so that the total stack height was about 1 meter. The compressive load for the lowermost layer was therefore 20 kg/m.sup.2, corresponding to about 200 Pa, meaning that the compressive load for each of the 25 spacers per square meter was 800 g. Since each spacer is dimensionally stable at this pressure, no change in the thickness of the lowermost layer could be identified. Therefore, the compressibility of the meltblown nonwoven fabric of the lowermost layer was 0% under a load of 200 Pa applied to its surface.

LIST OF REFERENCE SYMBOLS

[0057] 10 meltblown nonwoven fabric [0058] 12 spacer [0059] 14 depressions [0060] 16 compressed nonwoven fabric [0061] 18 opening [0062] 20 additional nonwoven fabric [0063] L distance by which the bottom of the depression that is delimited by the compressed nonwoven fabric protrudes beyond the lower side of the nonwoven fabric as seen in the direction of thickness.