EP1873289A1

EP1873289A1 - Perforated non-woven fabric and manufacturing method

Info

Publication number: EP1873289A1
Application number: EP06012939A
Authority: EP
Inventors: Marco Maranghi
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-06-23
Filing date: 2006-06-23
Publication date: 2008-01-02

Abstract

A perforated non-woven fabric, constituted by natural and/or synthetic fibers, such as cotton and/or viscose and/or Lyocell, containing thermoplastic fibers. The non-woven fabric is treated so as to make it hydrophobic and subsequently perforated with a roller provided with hot needles.

Description

The present invention relates to a perforated non-woven fabric and to the method for manufacturing it.
The non-woven fabric according to the present invention can be applied to the production of products in which it is necessary to have a layer which allows the flow of liquid through perforations provided therein.
In particular, the present invention can be advantageously used in the fields of sanitary towels and diapers in general, both for children and for incontinent adults.
Methods for producing perforated material, to be used in the production of diapers and the like, in which the perforation allows the flow of liquids to the underlying absorbent surfaces, are known.
According to a known method, heated rollers provided with protrusions, which simply compress the underlying material until they pierce it, are used for perforation.
A drawback of such method is that a certain difficulty is encountered in piercing the material by means of a simple passage below the pressure of a roller with protrusions having a square, circular, elliptical or rectangular profile, as revealed by the attempt to accelerate the operation by preheating the material before it enters below the rollers, described in WO2004/087384 .
Another drawback of such method is that the holes are produced by pressing and squeezing the material, and therefore the perforated material remains deformed and the perforations are uneven and poorly defined.
According to other known methods, systems for perforation with water jets or by heating and subsequent aspiration on perforated rollers, are used.
The drawback of those water-jet systems is that if small fibrils become interposed at the hole to be provided, which is on the order of 0.5 mm to a few millimeters, and pass through it, during the treatment the jet of water widens the fibers, forming the perforation, but since total control of hole quality is not possible, some fibrils may remain within the internal diameter of the hole, consequently preventing or damaging the perforation and causing a lack of uniformity of the hole.
The drawback that arises from the non-optimum quality of the hole produced according to all the known methods is observed during the hydrophobicity treatment, for which a single fibril can prevent the passage of the fluid, but especially during use it may occur that even if a single small fibril passes through the diameter of the hole, the fibril is able to prevent the sought correct flow of liquids through the hole in order to reach the underlying absorbent layers. The penetration of the liquid through holes which are even only partially obstructed by fluff is hindered also by the surface tension of the liquid itself, which is supported by the hydrophobicity of the non-woven fabric.
The drawbacks observed when using any of the methods of the prior art are that the perforations are uncertain, irregular and different.
All the cited drawbacks have been overcome by using the perforated non-woven fabric provided with the manufacturing method according to the present invention.
The aim of the present invention is to provide a non-woven fabric in which holes are provided which are certainly regular, uniform, clearly defined, identical to each other, and are bonded in a heat-sealed three-dimensional structure, in order to obtain an article which is solid and withstands friction and use.
For this purpose, a non-woven fabric which contains to a minimum extent thermoplastic fibers and is treated with hydrophobicity systems by means of techniques which are known in the textile field, and the corresponding perforation method, are provided.
In order to achieve this aim, a non-woven fabric has been used which is constituted by cotton and/or viscose and/or Lyocell and contains bonding agents such as polypropylene or polyethylene or polylactic acid, and the perforation has been provided by means of a roller provided with V-shaped hot needles.
Some of the many advantages that are achieved with the present invention are as follows.
The main advantage is that the hot needles inserted in the fabric with thermoplastic fibrous do not press the fibers but widen them, and since the needles are hot, the holes melt and solidify.
This leads to the advantage that the resulting holes are all identical, since they are obtained easily by means of the perforation of a hot needle in a non-woven fabric characterized by the presence of the thermoplastic fibers.
Another advantage is that by perforating the fabric with the V-shaped hot needle, a funnel-shaped hole is formed in the fabric with the thermoplastic fibers and remains impressed within the fabric, consequently providing a one-way hole which facilitates the entry of the liquid but hinders its return.
Another advantage of the perforation method according to the invention is that a certain three-dimensional effect is obtained in the non-woven fabric, increasing the thickness of the material proximate to the holes, and this fact allows a spacing of the perforated non-woven fabric from the underlying layers, which are normally moist during use. An air pocket is thus provided between the liquid storage region and the upper perforated non-woven fabric, providing a more pleasant sensation for the user and giving the user the perception of dryness more effectively.
Not least important is the great advantage achieved with the perforation method according to the present invention, i.e., the simplicity of the apparatus that is needed and the swiftness of the entire perforation process, by virtue of the limited time for which the fabric is required to remain below the roller with the heated needles.
In order to manufacture the perforated non-woven fabric according to the invention, a non-woven fabric is used which has a high percentage of natural fibers of cotton or viscose or a mixed fabric of cotton and viscose is used which contains a small portion of polypropylene or of thermoplastic synthetic fibers, such as polyethylene or polyesters or polyolefins in general, or polylactic acid, which is preferred because it is biodegradable.
Cotton and viscose are absorbent materials, and therefore upon contact with the skin, if soaked with liquid, they would give a feeling of wetness. In order to avoid this drawback, the fabric is treated so as to make it hydrophobic. A minimal amount of known water-repellent chemical products, such as silicone or fluorocarbon resins, is applied to the non-woven fabric, with a thickness on the order of a few microns. Preferably, plasma treatments can be used, because they reduce significantly the quantity of chemical products used. This operation renders the underlying material, cotton or other, impermeable. The treatment should be extremely delicate, because a large quantity would make the non-woven fabric completely water-repellent and no longer able to perform its absorption task.
This treatment can be performed with known methods suitable to allow a minimum application of impermeabilizing chemicals to adjust the hydrophobicity of the surface fibers, such as for example machines for surface plasma spreading, impregnation, spraying, or by means of a bath with silicone or fluorocarbon resins, or with a surface treatment by means of a graining print.
The fabric thus treated is passed, after drying, between two rollers, one of which is provided with heated needles, which preferably have a length on the order of 6 to 10 mm and a diameter from 1 to 1.2 mm at their base, which becomes zero at the tip, having a V-like shape. The other roller is covered on its surface with bristles or with a soft material such as silicone rubber, in order to allow the needles to penetrate the non-woven fabric.
The treatment with the water-repellent products makes the non-woven fabric impermeable. Perforation with the needle roller allows the mechanical inward flow of the liquid, preserving the dryness effect externally.
In order to obtain the required effects of heat-sealability in non-woven fabrics, it is possible to use thermoplastic fibers in a mixture of 2 to 50%, but lower percentages, from 2 to 15%, are preferably adopted. The non-woven fabric can weigh from 15 to 70 g/m2.
According to a preferred embodiment, the non-woven fabric has been provided with 95% cotton and 5% polylactic acid, with a weight of 35 g/m2, in order to obtain a product which is 100% biodegradable.
By changing the position of the needles on the perforation rollers it is also possible to obtain patterns on the fabric.
All these advantages and others will become evident from the description of the figures that follow, given merely by way of non-limiting example, and wherein:

Figure 1 is a schematic sectional view of the perforated non-woven fabric;
Figure 2 is a view of the two rollers, with the perforated non-woven fabric interposed;
Figure 3 shows a flap of the lower part of the perforated non-woven fabric, obtained with the present invention;
Figure 4 is an enlarged-scale view of a portion of the needle roller.

In the various figures, similar elements have been designated by the same numeric symbols.
Figure 1 is a sectional view of the result of a non-woven fabric 10 perforated according to the invention.
As shown in the figure, funnel-shaped holes 11 that form in the non-woven fabric 10 have a wider inlet 15 and a narrower outlet 16, which hinders the unwanted reverse flow of the liquid.
Figure 2 illustrates a roller 12 with radial needles 13. A roller 14 is arranged opposite the roller 12 and is covered by a flexible surface layer with bristles or soft material. The non-woven fabric 10 is inserted between the two rollers 12 and 14, and by virtue of the flexibility of the covering of the roller 14 the needles 13 can penetrate the non-woven fabric 10, passing through it.
Since the needles 13 are hot and thermoplastic materials are present in the non-woven fabric 10, the provided holes 11 remain permanent, because they are provided by melting, with a clearly solidified perimetric surface.
During perforation, material contained in the holes 11 is expelled from them and collects externally in the vicinity of the outlet 16, forming small protrusions 17.
The protrusions 17 keep the non-woven fabric 10 raised with respect to the underlying liquid absorption layer, giving the user a constant sensation of dryness even when the underlying layer is moist or even wet.
The protrusions 17 are clearly visible in the reproduction shown in Figure 3.
Figure 4 illustrates an arc of a roller with the needles, according to the present invention. One can see the needles 13 arranged radially on the perimeter of the roller. The needles are arranged in rows along radial planes, i.e., planes which pass through the axis of the roller 12, in succession, for example at a distance of 2 mm, the rows being mutually spaced in a perimetric direction, for example at a distance of 2 mm.
According to a preferred embodiment, the present invention uses a non-woven fabric made of natural fibers such as cotton, preferably anallergic cotton, and/or with the addition of thermoplastic fibers such as PLA in order to obtain a ply of fibers which is bonded in the most natural manner and with the softest textile handle (spunlace), and therefore the naturally absorbent fibers are prevented from getting wet with a water-repellent treatment; then the non-woven fabric is perforated mechanically in order to make the liquids flow out into the underlying absorbent seat.
The present invention comprises all the detail variations and modifications that can be obvious to a person skilled in the art and are within the scope of the claims that follow.

Claims

A perforated non-woven fabric, characterized in that it is constituted by natural and/or synthetic fibers, such as cotton and/or viscose and/or Lyocell, containing thermoplastic fibers, treated so as to make it hydrophobic and subsequently perforated with a roller provided with hot needles.
The perforated non-woven fabric according to claim 1, characterized in that it is provided with a high percentage of natural fibers of cotton and/or viscose and/or Lyocell containing a small part of polypropylene or thermoplastic synthetic fibers such as polyethylene (PE), or polyesters (PET), or polyolefins, or polylactic acid (PLA).
The perforated non-woven fabric according to the preceding claims, characterized in that the needles have a length of 6 to 10 mm and a diameter of 1 to 1.2 mm at the base, which then becomes zero at the tip, having a V-like shape, and in that the holes that form in the non-woven fabric are melted and solidified, in a funnel-like shape, with a wider inlet and a narrower outlet.
The perforated non-woven fabric according to the preceding claims, characterized in that the thermoplastic fibers used in the mixture are from 2 to 50%, and in that the perforated non-woven fabric weighs between 15 and 70 g/m2.
The perforated non-woven fabric according to the preceding claims, characterized in that it is provided with 95% cotton and 5% polylactic acid, with a weight of 35 g/m2.
A method for manufacturing the perforated non-woven fabric according to the preceding claims, characterized in that it is rendered hydrophobic by spreading on its surface a minimal quantity of water-repellent chemicals, such as silicone or fluorocarbon resins, with a thickness on the order of a few microns, and is then passed between two rollers, of which one is provided with radial heated needles and the other is covered with a flexible surface layer with bristles or with a soft material.