WO1990014813A1

WO1990014813A1 - Nonwoven material, in particular composite nonwoven material

Info

Publication number: WO1990014813A1
Application number: PCT/DE1990/000413
Authority: WO
Inventors: Heinz-Horst Boich; Tarek Fahmy
Original assignee: Corovin Gmbh
Priority date: 1989-06-01
Filing date: 1990-05-29
Publication date: 1990-12-13
Also published as: DE3917791A1; DE3917791C2

Abstract

A nonwoven material, in particular a composite nonwoven material (12) consisting of two layers, conveys liquid in one direction to an absorbent body (23) which absorbs liquid. In contrast to other known embodiments, the inherently hydrophobic nonwoven material is not permeable to water over its whole surface but only at a plurality of discrete, interspaced, hydrophilized points (16).

Description

Nonwoven material, in particular composite material

The invention relates to a nonwoven material, in particular a composite nonwoven material with at least two layers according to the preamble of claim 1.

Such nonwoven materials are produced according to the known spunbonded nonwoven processes and are used to transport liquid in only one direction from the outside inwards, with a storage body or an absorbent body being located on the inside which absorbs and stores the liquid transported through the nonwoven material. A preferred use of such a nonwoven material is given in diapers for children or also in incontinent diapers for adults. As is known, such diapers comprise an absorbent body which is coated on one side with a polymer film to prevent the escape of the liquid stored in the absorbent body. On its other inner use side, the absorbent body is covered with the nonwoven material made of synthetic fibers, which serves here as a covering nonwoven and which is intrinsically hydrophobic. As a result, the fleece material, i.e. the covering fleece, appears dry even when the absorbent body in a diaper is soaked with urine.

In order to ensure that the liquid is adequately quickly transported to the absorbent when the urine is absorbed, it is known to provide the hydrophobic covering fleece with suitable wetting agents, as is described, for example, in German specification 27 22 860. By applying a wetting agent, ie by hydrophilizing the nonwoven material, the previously hydrophobic covering nonwoven is now permeable to water. However, it must be ensured that the application of the wetting agent must be controlled in a certain way. Too much application accelerates the transport of the urine to the absorbent body, but there is then the danger that the urine stored in the absorbent body can also be transported back outwards, thereby reducing the feeling of dryness.

On the other hand, if the wetting agent is completely dispensed with or if the wetting agent is applied too weakly, the result is that the urine is not transported to the absorbent body quickly enough, which also impairs the desired feeling of dryness.

In principle, the hydrophilization of the non-woven material, which is hydrophobic per se, does not pose any difficulty, but in practice the comfort of the non-woven material thus prepared leaves something to be desired.

The invention is based on the object of providing a nonwoven material of the type assumed, which enables improved liquid transport in a preferred direction and at the same time undesired return transport of the liquid prevented.

The invention achieves this aim in the nonwoven material mentioned in the preamble of claim 1 by the features of the characterizing part of claim 1.

While it is provided in the prior art to hydrophilize the entire surface of the nonwoven material and to provide it with a wetting agent and thus to make it water-permeable over the entire surface, the invention surprisingly describes the way of using the nonwoven material only on a large number of discrete, from one another separate hydrophilized areas to be water-permeable. A pattern with discrete areas is generated on the nonwoven material, so to speak, only these discrete areas being water-permeable, while the remaining surface area of the nonwoven material remains hydrophobic.

The invention is based on the knowledge that with a nonwoven material that has been hydrophilized over the entire surface, there is a risk that the liquid stored in the storage body can be transported back through the nonwoven material if the storage body is a Has absorbed maximum of liquid and soaked up.

In the case of such a full absorbent body, there is local saturation at the points at which further liquid is supplied, since the absorbent body is no longer capable of being absorbed. Such local saturation can also result from the fact that too much liquid is fed to the absorbent body at a certain point and the latter is not able to distribute the liquid quickly enough as a result of wicking within the entire absorbent body.

At pressure points, such as occur repeatedly when the diaper user is moving, there is then the risk that the liquid will be transported back through the known nonwoven material, thereby impairing the feeling of dryness.

In contrast, this disadvantage can be largely avoided in the embodiment of the nonwoven material according to the invention with a large number of discrete hydrophilized and water-permeable points. Due to the many hydrophilized areas of the nonwoven material, it occurs when the nonwoven material is covered with urine is already a distribution of the liquid on the nonwoven material, with the result that the penetration or the liquid transport occurs only at the discrete locations and not over the entire surface. As has been shown in experiments, this surprisingly results in a substantially increased suction capacity and also an increased absorption speed for the liquid.

Another advantage is that due to the targeted liquid transport at discrete locations, the absorbent body is also supplied with liquid only at discrete locations, and that the absorbent body is capable of being supplied to it at discrete locations due to its suction effect It is better to distribute liquid over its entire cross-sectional content. The risk of the nonwoven material feeling damp, which the user of a diaper feels as uncomfortable, is thus largely eliminated.

In an expedient embodiment of the invention, the hydrophilized, water-permeable points can be formed in a dot or circular shape, rectangular or even in a strip shape. In any case, it is crucial that the nonwoven material does not cover the entire surface, but is designed to be permeable to water only at discrete, spatially separated locations.

In a further advantageous embodiment of the invention, the nonwoven material is formed in two layers with an upper outer layer made of relatively coarse fibers (coarse layer) and a lower inner layer (fine layer) facing the absorbent body with finer fibers.

A fiber diameter gradient is thereby formed over the cross section of this two-layer nonwoven material with regard to the diameter of the fibers of the individual layers. In the desired manner, this fiber diameter gradient ensures a directed liquid transport in the direction from the outer layer downward over the inner layer to the absorbent body, because the liquid storage capacity and the transport speed of the coarse outer layer are lower than that of the inner fine layer.

If, by the way, the disadvantageous return transport of the liquid from the absorbent body to the outside is avoided in the invention, this is due to the novel design of the nonwoven material. ren, which is not hydrophilized over the entire surface, but only at a large number of discrete points. In the case of a full absorbent body, the return transport is thereby limited to an overall smaller surface level than if - as is provided in the known nonwoven material - the entire surface of the nonwoven material is hydrophilized.

The upper outer layer can be regarded as a spacer, since the outer layer is only suitable to a limited extent for storing liquid because of its coarse structure.

The configuration of the nonwoven material according to claim 1 thus fulfills the function of distributing the liquid and ensures that the liquid is rapidly penetrated to the absorbent body.

According to a further expedient embodiment of the invention, the multiplicity of discrete, hydrophilized, water-permeable points is not distributed over the entire surface of the nonwoven material, but rather is only provided within a surface area forming a window, while the area outside the window remains hydrophobic. This configuration of the nonwoven material enables even better targeted control of the wetting agent application and the liquid transport at desired areas. In relation to the total area of a diaper, it is sufficient if the covering fleece is only provided with the window with the discrete hydrophilized areas between about 6 and 50%. It is assumed that in practice - in particular in the case of diapers - the liquid does not appear on the entire outer surface, but only in some areas and has to be transported to the absorbent body. Moreover, this embodiment of the invention ensures that the urine emerging from the user can be sucked up in a targeted manner and can be quickly transported to the absorbent body in the region of the part provided with the hydrophilized points.

Due to the wicking action of the absorbent body, the urine is then drained on all sides, even to areas above which the nonwoven material is still hydrophobic. Experiments have shown that this significantly restricts the tendency of urine to be transported back can be, because in those areas in which the nonwoven material or the covering nonwoven is still hydrophobic, such a return transport is practically completely excluded.

The selected area, which specifies the area with the discrete hydrophilized areas, can preferably be provided in the form of a strip in the middle of a disposable diaper. In any case, it is sufficient if a strip is equipped with the hydrophilized areas in the middle of the step in the folded diaper. In the case of a profiled diaper, a width which corresponds to that of the narrow web is sufficient.

In a further expedient embodiment of the invention, the discrete water-permeable points are produced by printing on the nonwoven material with a wetting agent. In this way, the discrete points can be implemented in a method-simple manner. It is also possible to produce the discrete water-permeable points by intermittently spraying the nonwoven material with a wetting agent. In another expedient embodiment of the invention, the discrete water-permeable points are formed by holes made in the nonwoven material, the holes being wetted on their outer edges with a wetting agent.

This type of producing the discrete, water-permeable points can be carried out in a simple manner with a spiked roller which is provided with spikes on its circumference and is known per se for other purposes. The fleece material is guided over the spiked roller, the spikes of which then produce the holes, preferably 5-50 holes per cm ^{2 being} provided.

The spikes are provided with a wetting agent so that the outer edges of the holes are then covered with the wetting agent when the holes are made in the nonwoven material.

In a further expedient embodiment, it is provided for the convenience and convenience of the user and the processor to make the individual discrete water-permeable points visible, for example by adding a color to the wetting agent. Other advantageous developments and refinements of the invention result from the subclaims and the following description.

The invention is explained in more detail below on the basis of the exemplary embodiments shown in the drawing. Show it:

Fig. 1 is a plan view of a

Diaper in which a surface area of the covering fleece is provided with a multiplicity of discrete water-permeable points,

Fig. 2 is a partial representation as

Top view of a diaper, in which the discrete, water-permeable areas of the cover fleece are formed by holes,

3 is a schematic cross-sectional view of a diaper according to FIG. 2, Fig. 4 shows a further schematic

Cross-sectional view in a different scale of a diaper according to FIG. 2, and

Fig. 5 shows another embodiment of a nonwoven material.

1 shows a diagrammatic view of a diaper 10 as a top view, which in a manner known per se has an absorbent body 24 (cf. FIG. 3), which is also on its rear side in a manner known and not shown here is surrounded with a water-impermeable polymer film in order to prevent the liquid stored in the absorbent body 24 from escaping.

On the side of the absorbent body 24 opposite the polymer film mentioned, that is to say on the user side, a cover fleece 12 is provided as the fleece material. This cover fleece 12 is formed by hydrophobic fibers and extends over the entire surface area of the diaper 10.

Within a space formed by a window 14 rich is a plurality of discrete hydrophilized and thus water-permeable points 16 which are formed by applying a wetting agent at the respective points 16.

As such, these hydrophilized, water-permeable points 16 are not visible, but for better clarification of the invention, these points are shown hatched in the drawing. For the rest, an advantageous embodiment of the invention provides that these hydrophilized areas 16 can also be made visible to the user by means of a color.

While the hydrophilized water-permeable points 16 are formed by small rectangles in FIG. 1, FIG. 2 illustrates an embodiment in which the hydrophilized points 16 are formed by a large number of holes, preferably 5-50 holes per cm ² .

In the cross-sectional view of a nonwoven material designed as a cover nonwoven 12 according to FIG. 3, these holes 26 are shown in a schematic view. For the sake of better Visibility of the drawing shows the absorbent body 24 at a distance from the covering fleece 12.

The cover nonwoven 12 has a two-layer structure with a coarse outer layer 18 and an inner fine layer or inner layer 20. The cover nonwoven 12 is here designed as a composite nonwoven material with two layers.

The holes 26 shown are provided on their outer edges 28 with a wetting agent. The outer layer 18 here consists of continuous fibers with an average diameter of 10-30 μm. The inner layer here also consists of continuous fibers with an average diameter of 4 to 10 μm. In a further embodiment of the invention, the inner layer can also be formed by short finite fibers with an average diameter of 1-5 μm.

As can be seen in FIG. 3, the outer layer 18 and the inner layer 20 are separated from one another by a functional boundary 22 shown as a broken line. As a result of the rough structuring of the outer layer 18 and the fine inner layer 20 with the thinner fiber diameters A fiber diameter gradient is formed over the entire cross-section of the cover fleece 12, which enables a liquid to be transported in the direction of the absorbent body 24.

To further clarify the invention, an area with water 30 is shown in FIG. 3 on the upper outer layer 18. As a result of the effect of the large number of individual discrete hydrophilized spots in the form of the holes 26, the liquid supply of the water 30 on the surface of the cover fleece 12 is distributed over the holes 26 in the manner illustrated by the arrows.

Below the holes 26, spatially limited water accumulations 32 form in the area of the holes 26 within the absorbent body 24. As is indicated by the arrows, each of these water accumulations 32 thus ver the liquid through the known wicking action of the absorbent body 24 ¬ shares.

To further clarify the invention, FIG. 4 shows a schematic cross-sectional view the two-layer cover fleece 12 with the outer layer 18 and the inner layer 20, which are connected to one another in a manner known per se at the fastening points 34 by thermal welding. Here too the functional limit 22 can be seen.

The holes 26, which are only partially and not to scale to simplify the drawing, extend through the outer layer 18 and the inner layer 20.

These holes 26 can be produced, for example, with a spiked roller (not shown here) provided with spikes on its outer circumference. The diameter of the holes is so small at 0.2-2 mm that the holes 26 as such are not necessarily visible in the upper coarse outer layer, while they actually penetrate the lower fine layer or inner layer 20 because of the finer structure .

As a further embodiment, FIG. 5 schematically shows a cross-sectional view of a two-layer cover fleece with an outer layer 18 and an inner layer 20, which is not shown here. provided suction body is facing.

The entire surface of the cover fleece 12 is here hydrophilized and thus made water-permeable overall, while only the lower inner layer 20 is hydrophilized at a number of discrete locations 16, for example through the holes 26 already mentioned.

Although in this embodiment the upper outer layer 18 is designed to be water-permeable over the entire surface, the advantages sought by the invention can also be achieved here because of the lower layer which is hydrophilized only at discrete points.

Claims

Patent claims

1. Nonwoven material, in particular composite nonwoven material with at least two layers, for a liquid or moisture transport in a preferred direction, preferably to a storage body for the liquid covered by the nonwoven material on its suction side, the nonwoven material originally being hydrophobic trained and then hydrophilized by treatment with agents, characterized in that the nonwoven material (12) is water-permeable only at a plurality of discrete, separate hydrophilized points (16).

2. Nonwoven material according to claim 1, characterized in that only a selected area

(14) of the total area of the nonwoven material (12) is provided with the hydrophilized points (16).

3. Nonwoven material according to claim 1 and / or 2, characterized in that the hydrophilized Stel¬ len (16) are circular or point-shaped or in a freely selectable geometric shape.

4. Nonwoven material according to claim 1 and / or 2, characterized in that the hydrophilized Stel¬ len (16) are rectangular.

5. Nonwoven material according to claim 1 and / or 2, characterized in that the hydrophilized Stel¬ len are strip-shaped.

6. Nonwoven material according to one of the preceding claims 1-5, characterized in that the Vlies¬ material (12) in two layers with an upper outer layer

(18) is constructed of coarse fiber and a lower inner layer (20) with finer ^fibers'.

7. fleece material according to claim 6, characterized ge indicates that the outer layer (18) flat hydro- is philicated, while the inner layer (20) is permeable to water only at discrete locations (16).

8. Nonwoven material according to claim 6, characterized ge indicates that the outer layer (18) and the inner layer (20) together are water-permeable at discrete locations (16).

9. Nonwoven material according to one of the preceding claims 1-8, characterized in that the discrete water-permeable points (16) are produced by printing the nonwoven material (12) with wetting agent.

10. Nonwoven material according to one of the preceding claims 1-8, characterized in that the discrete water-permeable points (16) are produced by intermittent spraying with wetting agent.

11. Nonwoven material according to one of the preceding claims 1-8, characterized in that the discrete water-permeable points (16) through small holes (26) are made in the nonwoven material (12), which on their outer edges (28) with a Wetting agents are wetted and partially or completely penetrate the nonwoven material.

12. Nonwoven material according to one of the preceding claims 1-5, characterized in that the Vlies¬ material (12) is designed as a single-layer cover fleece (cover stock) of a diaper (10), a sanitary napkin or other incontinence products.

13. Nonwoven material according to one of the preceding claims 6 - 12, characterized in that the dis¬ crete hydrophilized areas (16) are made visible in color.

14. Nonwoven material according to one of the preceding claims 6-11 or 13, characterized in that the fibers of the coarse outer layer are continuous fibers and have an average diameter of about 10 - 30 microns and that the fibers of the fine inner layer (20) are predominantly continuous fibers and have an average diameter of about 4 - 10 μm.

15. Nonwoven material according to claim 14, characterized ge indicates that the fibers of the inner layer (20) are finite and / or infinite fibers with an average diameter of about 1-5 microns.

16. Nonwoven material according to claim 11, characterized in that the average diameter of the holes (26) be about 0.2-2 mm.