METHOD OF MAKING A SPUN-BONDED NONWOVEN FOR PACKAGING

Abstract

A package has walls formed of a weldable spun-bonded nonwoven and having welded wall regions. The spun-bonded nonwoven has continuous filaments of a thermoplastic plastic each with a thermoplastic core surrounded by a thermoplastic sheath. The sheaths of the continuous multicomponent filaments of both components contain at least 3 wt % of at least one filler so that weldability of the spun-bonded nonwoven is improved by reducing a welding temperature in thermal welding of the spun-bonded nonwoven. A first plastic component forming the sheaths of the multicomponent filaments has the same or a lower melting point than a second plastic component forming the cores of the filaments.

Claims

1. A method of making a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven comprising the steps of: spinning endless filaments having sheaths of a first thermoplastic surrounding respective cores of a second thermoplastic wherein the sheaths contain at least 3 wt % of at least one filler, the first thermoplastic forming the sheaths of the multicomponent filaments has the same or a lower melting point than the second thermoplastic forming the cores of the filaments such that filaments are weldable to each other by fusing together the sheaths, a mass ratio of the first plastic component forming the sheaths to the second plastic component forming the cores is 25:75 to 50:50 and in welded regions 35:65 to 50:50; depositing the filaments to form a spun-bonded nonwoven web; calendering an outer face of the spun-bonded nonwoven web smooth and without engraving; and engraving an inner face of the spun-bonded nonwoven web 15 to 35% and to an embossing depth of 0.1 to 0.6 mm.

2. The method according to claim 1, wherein the first plastic of the continuous filaments has 4 to 25 wt % of the filler.

3. The method according to claim 1, wherein the filler is a metal salt.

4. The method according to claim 1, further comprising after the step of spinning and before the step of depositing the steps of sequentially: cooling the filaments in a cooler; and stretching the cooled filaments in a stretcher.

5. The method according to claim 1, wherein during calendering the spun-bonded nonwoven is pressed with a calender having an embossing surface of 10 to 90% to 30%.

6. The method according to claim 1, wherein a number of engraved points of the calender is greater than 30/cm.sup.2.

7. The method according to claim 1, wherein the first component of the continuous filaments has 4 to 25 wt % of the filler.

8. The method according to claim 1, wherein the melting point of the second plastic of the cores is above that of first thermoplastic of the sheaths, the method further comprising the steps after engraving of: cutting pieces of the web, and welding the pieces together at edges thereof by applying sufficient heat to melt only the sheaths of the filaments, whereby the melted sheets fuse together.

9. A package having walls formed of a weldable spun-bonded nonwoven and having welded wall regions, wherein the spun-bonded nonwoven has continuous multicomponent filaments of a thermoplastic plastic of both components each have a thermoplastic core surrounded by a thermoplastic sheath, the sheaths of the continuous multicomponent filaments of both components contain at least 3 wt % of at least one filler, whereby weldability of the spun-bonded nonwoven is improved by reducing a welding temperature in thermal welding of the spun-bonded nonwoven, a first plastic component forming the sheaths of the multicomponent filaments has the same or a lower melting point than a second plastic component forming the cores of the filaments, a mass ratio of the first plastic component forming the sheaths to the second plastic component forming the cores is 25:75 to 50:50 and in the welded wall regions 35:65 to 50:50, an outer face of the spun-bonded nonwoven is calendered smooth and without engraving, and an inner face of the spun-bonded nonwoven is engraved 15 to 35% and to an embossing depth of 0.1 to 0.6 mm.

10. The package according to claim 9, wherein the first component of the continuous filaments has 4 to 25 wt % of the filler.

13. The package according to claim 9, wherein the filler is a metal salt.

14. The package according to claim 9, wherein the package is formed of a plurality of pieces of the calendered and engraved nonwoven joined together at seams where the first thermoplastic of the sheaths are fused together but the second thermoplastic of the cores is not fused.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0040] The invention will be explained in greater detail below in conjunction with drawings that depict only one exemplary embodiment. In the drawings:

[0041] FIG. 1 is a schematic, perspective view of a package according to the invention in the form of a bag,

[0042] FIG. 2 is a schematic vertical section through am apparatus for carrying out a method of making a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven according to the invention, and

[0043] FIGS. 3A and 3B are a schematic cross-sections through a bicomponent filament of a spun-bonded nonwoven or packaging spun-bonded nonwoven respectively used in the side wall region of the packaging bag and in the bottom wall and/or top wall of the packaging bag.

SPECIFIC DESCRIPTION OF THE INVENTION

[0044] FIG. 1 shows a package according to the invention in the form of a packaging bag 1 for bulk materials, in particular for cement.

[0045] The package wall of this packaging bag 1 contains weldable spun-bonded nonwovens 2 according to the invention. These spun-bonded nonwovens 2 or packaging spun-bonded nonwovens are of endless filaments 3 of a thermoplastic plastic. The endless filaments 3 contain at least 3 wt % of a filler 4 in the form of calcium carbonate to improve the weldability of the filaments and of the spun-bonded nonwoven 2 and in particular to reduce the welding temperature during thermal welding of the filaments or of the spun-bonded nonwoven 2.

[0046] The packaging bag 1 shown in FIG. 1 has a side wall 5 of a spun-bonded nonwoven according to the invention that has been welded at its side edges 6 into a tube, so to speak. A flat bottom wall 7 in the form of a spun-bonded nonwoven 2 according to the invention is positioned at the bottom of the packaging bag 1 and is welded to the side wall 5 of the packaging bag 1. A flat top wall 8 in the form of a spun-bonded nonwoven 2 according to the invention is likewise positioned at the top of the packaging bag 1 and welded to the side wall 5. On an inner face of the package wall of the packaging bag 1, an additional plastic film can be provided, but this is not shown in the embodiment according to FIG. 1. The spun-bonded nonwovens used for the side wall 5, the bottom wall 7, and the top wall 8 of the packaging bag 1 are preferably, and in this embodiment, of bicomponent filaments with a core/sheath configuration (also see FIG. 3). Of the two plastic components of these bicomponent filaments, the lower-melting-point plastic component is the sheath 9 and the higher-melting-point plastic component is the core 10. the filler 4 in the form of calcium carbonate is preferably, and in this embodiment, only contained in the sheath 9 of the bicomponent filaments.

[0047] FIG. 2 shows a particularly preferred apparatus for manufacturing the spun nonwovens 2 (spun-bonded nonwovens) according to the invention. The endless filaments 3 in this case are first spun by a spinneret 11 and are then conveyed through a monomer aspirator 12. Then the endless filaments 3 are chilled in the cooler 13. The cooler 13 preferably, and in this embodiment, has two compartments 14, 15 one above another or one after another in the filament flow direction from which cooling air with different temperatures is introduced into the filament flow chamber. After the cooler 13, the endless filaments 3 travel into an intermediate conduit 16 that converges in the filament flow direction. This intermediate conduit 16 is followed by a pull-down conduit 17 of the stretcher 18. This design serves to stretch the endless filaments 3. The endless filaments 3 emerging from the pull-down conduit 17 then preferably, and in this embodiment, pass through two diffusors 19, 20 one above the other or one after another in the filament flow direction. In a recommended embodiment, and here, an ambient air entry gap 25 is provided between the diffusors 19, 20 for drawing in ambient air. Advantageously, and in this embodiment, the endless filaments 3 are then deposited on a mesh belt 21 to form the spun-bonded nonwoven 2. The spun-bonded nonwoven 2 is advanced in the machine direction M by the mesh deposition belt 21.

[0048] Preferably, and in this embodiment, the spun-bonded nonwoven 2 is calendered and prehardened/hardened by a calender 22. According to one variant, a calender roller 23 is provided with an engraving, not shown in detail, and a calender roller 24 of the calender 22 that cooperates with and is works with it is preferably, and in this embodiment, equipped with a smooth surface. A spun-bonded nonwoven 2 made in the above-explained manner can be simply and easily used for a package wall (side wall 5 and/or bottom wall 7 and/or top wall 8) of the packaging bag 1.

[0049] FIG. 3A and 3B show bicomponent filaments for a weldable spun-bonded nonwoven 2 according to the invention. In the FIG. 3A, the percentage of the core 10 is higher in comparison to the sheath 9. In the bicomponent filaments according to FIG. 3B, the filler in the form of calcium carbonate is contained only in the sheath 9 that corresponds to the lower-melting-point plastic component. The bicomponent filaments according to FIG. Aa are primarily suitable for spun-bonded nonwovens 2 that form the side wall 5 of a packaging bag 1.

[0050] By contrast, the bicomponent filaments according to FIG. 3B have a significantly higher percentage of sheath 9 of the lower-melting-point plastic component. Here, too, the filler preferably, and in this embodiment, is completely contained in the sheath 9. The bicomponent filaments according to FIG. 3B are primarily suitable for spun-bonded nonwovens 2 or spun-bonded nonwoven regions that must be welded. The sheath 9 with the lower-melting-point plastic component provides enough welding material for this purpose. Welding is preferably carried out in that only or mainly the sheath 9 melts and is welded. Consequently, the bicomponent filaments according to FIG. 3B are primarily suitable for the bottom wall 7 and/or the top wall 8 that is to be welded of a packaging bag according to the invention 1.

[0051] The mass ratio of the lower-melting-point plastic component (sheath 9) to the higher-melting-point plastic component (core 10) may be 20:80 in the embodiment according to FIG. 3A. By contrast, in this embodiment according to FIG. 3B, the mass ratio of the lower-melting-point plastic component 5 (sheath 9) to the higher-melting-point plastic component (core 10) is 40:60.