DE2012758C2 - Disposable diaper - Google Patents

Description

The invention relates generally to an infant disposable diaper having a porous hydrophobic top layer facing the child's skin and with an absorbent pad that The liquid excretion of the child absorbs you affects a disposable diaper, whose over her entire Length extending absorbent pad has a central portion and two end portions, the End sections of the abdomen and back and the middle section the area between the legs A disposable diaper of this type is known from US Pat. No. 3,430,629

Diapers which are provided with a porous hydrophobic topsheet and a hydrophilic backing are well known. The purpose of the combination is to reduce the amount of moisture in contact with the skin, causing irritation and leaching of the skin, clumping of the diaper and other inconveniences to reduce. The terms "hydrophobic" and "hydrophilic" used here are indicative in their brevity, but in reality denote relatively low or relatively high critical surface tensions of the materials to be identified. The hydrophobic nature of an upper diaper layer is clearly expressed by its lack of affinity for the liquid excretions of humans in contrast to the affinity of the hydrophilic or absorbent lower layer. In the sense used here, a material is hydrophobic if a drop of the liquid excretion applied to it does not spread significantly on the substrate. The threshold value of the water repellency of a diaper material is in the vicinity of about 40 to 50 dynes / cm at 20 ^° C. Thus, if a layer of a hydrophobic material is placed on a layer of a hydrophilic or less hydrophobic absorbent material to form a diaper and the hydrophobic When the layer is facing the skin, the excreted liquids pass through the hydrophobic layer and are preferably distributed and absorbed in the hydrophilic layer below, while the upper layer in contact with the skin remains relatively dry.

However, the effectiveness of the combination of materials described above is limited, and the wetness of the surface remains a problem. It is believed that the surface moisture of the hydrophobic upper layer in the middle part of the diaper the consequence of an insufficient transition of the out separated liquid from the middle into the total mass of the absorbent material and the repeated Compressing the absorbent material in the front and middle areas of the diaper Stresses and deformations caused by the

ίο causes movement of the child's thighs are squeezed by the pressure loads from the absorbent pad and consequently causing flooding of the surface of the topsheet. This flooding follows a relaxation of the pressure acting on the absorbent material and a slow renewed one Suction of the liquid The terms "flooding" and "renewed flooding" used here are synonymous and denote the wetting of the surface of the upper layer of the diaper with excreted Liquids that were previously absorbed in the absorbent pad.

Excessive wetness of the skin on the child's abdomen tends to soften and leach the skin and thereby their resistance to primary irritants that are present in or from the excretions arise to weaken. Even if the surface of a diaper is damp (as is the case when using a hydrophilic upper layer would be the case), it is

beneficial as far as possible the flooding of the Turn off the top of the top layer of the diaper. In the aforementioned US-PS 34 30 629 is a Described diaper construction in which the strength in the stressed zones improves the absorption capacity and the ability to disperse liquids in the diaper is increased. This is achieved by the in the longitudinal direction of the diaper extending pad has folded and compressed flanks so that it have a lower liquid absorption capacity than the middle of the diaper. Im uncompressed In the middle, there are also channels running in the longitudinal direction, which have the receiving surface in the middle and contribute to the faster and more even distribution of the liquid.

Where this problem of skin irritation has been recognized and taken into account in the construction of the diaper, One of the countermeasures is a concentration of absorbent materials in the central part or along one center lines run in the longitudinal direction of the diaper.

so this reasonable solution, d. H. the arrangement of the absorbent material where it is needed most is well known and often successful in practice, but does not solve the problem of skin wetness in the Middle of the diaper.

The object of the invention is to create a diaper which is more comfortable to wear than the known one Diapers because rewetting of the skin between the legs is caused by re-leakage of what has already been absorbed Liquid is avoided from this part as a result of compressive stress when the child moves. This task is based on the knowledge that a uniform distribution of the liquid throughout Absorbent pad has the disadvantage that in the parts that are between the legs of the child, as a result Compression when the child moves, liquid is again squeezed out of the cushioning material and comes into contact with the skin. This object is characterized by that in claim 1

Features solved

The diaper according to the invention or the absorbent pad has a different shape in the longitudinal direction Capacity for liquid in such a way that the two end parts have a high capacity, while an area of the intermediate piece has a low suction and absorption capacity for liquid has In the unstressed state, its pumping speed per unit area is lower than the average of the absorbency in other parts of the absorbent pad. The end parts of the pillow with up Absorption capacity have a constant cross-section, while the middle piece has a has uneven cross-section The lateral outer edges are not compressed, while the intermediate piece, which makes up 70% of the width, is compressed, so that the middle piece too in the transverse direction still has a different capacity, namely that the edges more Can absorb liquid than the middle. In use, the middle section of the diaper takes up a certain state of compression or compression for a given position of the legs of the Child. After the child has excreted liquids into the diaper, they penetrate the hydrophobic top layer. They saturate or almost saturate the middle section and wander through that Wicking towards the ends of the diaper. Most of the liquid is gone within a short time soaked so that a relatively dry area of the hydrophobic topsheet is adjacent the child's body is left behind. Then the child's normal movements cause one Compression and compression of the absorbent material in the section, so that for absorption available free space and thus the ability to hold back the liquid or the ability to absorb it be reduced. The liquid displaced by this compression moves back into the free space within the hydrophobic upper layer and, if the volume is large enough, flooded again the surface of the hydrophobic top layer. However, if the weight of the absorbent substrate that the Subject to compression multiplied by the difference in volumetric moisture content per Unit of weight of the absorbent material between the unstressed state and the stressed state State is less than the free space required for the retention of fluid for the overlying one If parts of the upper layer are available, flooding is avoided.

The invention will be explained below with reference to the drawing, in which the thickness of some materials of the Is exaggerated for the sake of clarity, explained in more detail. It shows

F i g. 1 is a perspective view of a diaper according to the invention, partially cut away,

F i g. FIG. 2 is a perspective view of the FIG. 1 shown diaper 1 in use, F i g. 3 is a section along line 3-3 of FIG. 2, fig. 4 schematically a test apparatus, F i g. 5 is a section along line 5-5 of FIG. 1, Fig. 6 is a section along line 6-6 of FIG. 5,

F i g. 7 shows a longitudinal section similar to FIG. 5 with a different structure,

8 shows a longitudinal section of a further embodiment the diaper.

According to FIG. 1, the diaper consists of the absorbent pad 20 and a top layer 21. The length and width of the diaper are chosen to enclose the lower part of a child's torso, with the End portions are formed so that they encompass the child's hips and the adjacent abdominal and Cover the back of the child. The illustration shows an optionally used waterproof pad 22, which for example consist of a thin plastic film made of polyethylene, polypropylene, polyvinyl chloride can. The waterproof pad is not required for the invention, since the pad 20 consists of absorbent material in connection with a separate diaper pant that covers the child's clothing protects can be used. The lower sheet 22, however, is particularly advantageous when in connection with a diaper of the type shown in FIG. 1 is used, which is used in the in F i g. 9 to 11 shown, has been pre-folded as explained below. The middle section 23 of the suction pad 20 has in Inside, an essentially uniform pumping speed per unit area, which is less than that Pumping speed of the adjacent material. This can be achieved by a middle part 23, the is thinner than the lengthwise adjacent material. The upper layer 21 is preferably hydrophobic, and the following description assumes that it is. The section 23 with relatively low absorbency, alone or in combination with the hydrophobic upper layer 21, facilitated the forwarding of the liquid excreta to the ends of the diaper and has one on the skin of the The child's surface is relatively dry. The middle section 23 with lower Absorbency acts as a saturated source of moisture after urine excretion, creating a proportionate large moisture gradient in relation to the ends of the diaper and in this way a greater one Driving force for the transmission of moisture to the ends of the diaper is created. In a short time This gradient is reduced by the mechanism of mass transfer to the ends of the diaper, thereby causing there is a lower total moisture content in the central part 23 of the diaper.

F i g. 2 shows the in FIG. 1 shown diaper in the form of use, with leg openings 24 and side parts 22a of the lower layer 22, which are folded in over the side of the suction pad 20.

Fig.3 shows the diaper shown in Fig.2 in section and illustrates the position of the thin central section 23. The section 23 extends over the full width of the absorbent pad 20 and is arranged so that it lies between the legs of the child when these are in any position within the normal range of motion. Preferably, portion 23 is placed so that, in use on the diaper, it extends from about 120 ° in front of the vertical centerline of the leg openings (angle A) to about 45 ° rearward therefrom (angle B) . However, it may be desirable from a consumer standpoint to center the central portion 23 in the longitudinal direction of the absorbent pad in order to avoid confusion between the front and back of the diaper. In this case, the middle section 23 can enclose the angle which extends from about 120 ° in front of the vertical center line of the leg openings 24 to about 120 ° backwards therefrom. The thin middle section 23 thus includes the point of urine discharge, and only the thin middle section 23

■ subject to repeated squeezing and relaxation through the movements of the child's legs. The section 23 does not have a uniform absorbency over its entire width. To achieve a Diaper construction that in terms of overall effectiveness is good fit, comfort and resistance to Re-flooding is significantly improved, it is necessary that the absorbency per unit area inside the section 23 is measurably and uniformly less than the average absorbency per Unit of area in other parts of the diaper. Instead of being thin across its entire width as shown, section 23 may be thin in the center with a full thickness strip on each side. In in this case, each side strip should be no more than about 15% of the total width of section 23, so that the thin interior, d. H. the area between the strip, at least about 70% of the full width Preferably and for the same reason should be the absorbency per unit area inside of section 23 can be at least about 10% less than in other parts of the diaper.

The stresses and forces to which the central portion 23 of a diaper is subjected are ^{equivalent to a range of about 0.0007 to 0.042 N / mm 2} uniformly applied to a rectangular sample of hydrophilic or hydrophobic material, a range of approximately 0.0035 to 0.021 N / mm ^2, most of the stresses and forces occurring during use are recorded. One method for determining the relevant parameters of the absorption capacity of diaper materials consists in placing a soaked sample 25 of each material on a slightly inclined (e.g. 10 °) surface 26, as shown in FIG. 4, and using different weights 27 lays on the surface in the manner shown. Since one knows the size of the sample 25, the dry weight, the weight when fully soaked and the weight of the sample after the application of the pressure load, one can determine the absorbency in the unloaded state and the change in the absorbency of the material under load per unit weight or, if desired, per unit area of the material to be determined. Examples of test results obtained with some hydrophilic and hydrophobic materials are shown in the table below.

Sample no.

number

the

Locations

Area absorbency ¹ ) for specified consecutive

Squeeze

N / mm ²

0.007

0.021 0

Change in the average absorbency ² ) over the range of the calculated stress

0-0.007 N / mm ² 0-0.021 N / mm ²

Calendered
and embossed
Fleece weight of the sample 3 g

Embossed creped cellulose wadding, 8 layers, surface weight, (air dry) 39-45.5 g / rr ^? after creping

Overlay, wet-laid layer of rayon, manila and kraft fibers, tied with latex binder ³ )

1 8th 58 20.6 8.3 13.1 5.1 12.4 2 8th 58 20.3 8.2 14.5 5.7 12.5 average 20.4 8.2 13.8 5.4 12.4 1 W U » 58 16.9 6.7 12.6 4.4 11.1 2 58 16.3 6.3 12.6 4.2 11.6 average 16.6 6.5 12.6 4.3 11.4 1
2
average 58
58 No valid values:
Sample went without
Do not wet the pressure application 7.2
7.2
7.2 3.6
3.7
3.6 7.3
7.4
7.4

5.6

6.1

7.0

7.1

about 3.6

3.8

Notes on the table:

') g HjO / g dry absorbent material.

² ) g fyO / g dry absorbent material. This is the change in the average absorbency at 0 N / mm ² after initial compression to the specified high pressure of the area (ie to 0.007 and 0.021 N / mm ^2, respectively). This reflects the conditions in use because some prior compression occurs during and soon after the diaper is put on.

³ ) Basis weight about 24.4 g / m ² .

On the basis of the above results or on the basis of similar results for materials not included in the table above, a functional combination of materials can be determined in which the absorbency of the material of the hydrophobic layer under the maximum calculated stress (e.g. 0.021 N / mm ² ) is sufficient to absorb a considerable amount of the liquid contained in the middle section 23, which tends to flood the surface of the pad 21 again when the diaper is subjected to a force that is in the arithmetical range (e.g. 0.0035 to 0.021 N / mm ² ) is compressed. For example, in a diaper having a single layer pad as described in the table above and a central section 23 comprised of a single ply of the cellulose wadding described herein, approximately 1/3 that of section 23 at a pressure of 0.021 N / mm ^{2 of the} squeezed out liquid is retained in the interstices of the support 21. As an optimum, a four-layer overlay 21 made of the material described in combination with a single-layer middle section 23 made of creped cellulose would rule out renewed flooding of the surface at all. As an alternative, a gauze paper, which has a basis weight of 10 to 13 g / m ² and is arranged under a single-ply overlay, would also preclude flooding.

F i g. Figures 5 and 6 illustrate in section the manner in which the thin central portion 23 can be arranged. The absorbent pad 20 is made of compressible absorbent material which is initially of substantially uniform thickness and in which the thin central portion 23 has been formed by locally compressing the sheet 20 beyond its elastic limit to a fraction of its density in the uncompressed state is. One of the materials that is easy to adapt to this construction and suitable for a disposable diaper is creped cellulose wadding. The material can also be a fleece made of cellulose fibers or a mixture of fleece and creped wadding. The thin middle section 23 can also be formed in such a way that the wadding is locally compressed up to above the elastic limit to a point at which the free space content is about 85 to 95% of the total volume Absorbent pad 20 in the thin section 23 in the above-mentioned stress range of 0.0035 to 0.021 N / mm ² 4 to 12 cm ³ / g of the suction pad (with a specific weight of 1.5). If the free space content is higher than 95%, too much moisture will be sucked up in it, causing re-flooding problems. If the free space is less than 85%, the material tends to stiffen and become undesirable from the standpoint of convenience.

The length and position of the section 23 should, as mentioned in connection with the description of FIG. 3, be chosen so that this corresponds to the normal range of motion of the child's legs when the diaper is in use. A diaper having the construction described above can for example, a total length of the absorbent pad 20 to 40.6 cm and, as shown in FIG. 5, a length L of the central section 23 of approximately 30 to 45% of this dimension, ie of approximately 13 to 18 cm. In the case described, the section 23 can have a distance Λ / νοη about 5 to 10 cm from the front edge 28 of the suction pad. A topsheet 21, which in combination with the above-described creped cellulose wadding retains a substantial amount of liquid which tends to flood its surface again when the diaper is stressed, may for example consist of a nonwoven material made of rayon staple fibers of 0.75 up to 3 den and 40 mm in length, with about

20 to 35% of a thermoplastic binder is set and has a weight of about 18 to 29 g / m ² . The support 21 in the embodiment described above can be attached to the absorbent pad 20 in any suitable manner, for example in the manner shown in FIGS. In Fig. 5, the ends of the support 21 are turned over to under the absorbent pad 20 and glued to its underside at 29. F i g. 6 illustrates how the pad 21 is folded over the sides of the absorbent pad 20 and glued at 30. The waterproof backing layer 22, which may be used, is expediently made of an opaque, 18 to 38 μm thick film made of low-density polyethylene, which is glued to the hydrophobic layer 21 along its folded-under parts at 30a, as shown in FIG. 6 shown. In the case of the following in connection with FIG. 8 to 11 of the preferred construction of the diaper according to the invention, the backsheet is preferably about 2.5 to 10 cm longer and about 5 to 10 cm wider than the absorbent pad 20.

F i g. Figure 7 illustrates another possibility of forming a thin central portion 43. In this alternative, the absorbent pad consists of a thin layer 31 of absorbent material that extends the full length of the diaper and thicker portions of one or more layers 32 of it consist of absorbent material and are attached to the layer 31 and to the support 21 by sewing or in another suitable manner. The layers 31 and 32 can consist of different materials. For example, in the case of a disposable diaper, the layer 31 can consist of a material which has a relatively small capillary size and a low ^{compressibility under the above-mentioned pressure loads of 0.0035 to 0.021 N / mm 2, e.g.} B. from a 12 to 18% creped soft Kraft paper, which has a basis weight of 16.26 g / m ^2. The layers 32 can be made of highly absorbent material with relatively large capillaries, for. B. made of nonwoven material or

so strongly creped cellulose wadding or mixtures of these materials. A hydrophobic pad 21, a waterproof backing 22 and attachment along areas 29 may be provided as shown in US Pat Connection with the in F i g. 1 to 3, 5 and 6 shown embodiment has been described.

The middle diaper part with relatively low absorbency can also be used in other ways be formed by diluting or compressing the absorbent pad in the manner described above.

Such a different structure is shown in FIG This diaper consists of an absorbent pad 33a made of an absorbent material or substrate 33 from practically uniform thickness, a pad 34, which is preferably hydrophobic, and a water-impermeable Insert 35. In addition, a waterproof backing layer 36 can optionally be used for those already mentioned Purposes are provided. The overlay 34 and the backing layer 36 can be made in this manner.

as in connection with the support 21 and the backing layer 22 of the FIG. 1 to 3, 5 and 6 illustrated embodiment described. The in F i g. The middle section 23 shown in FIG. 3 is formed here by the layer between the support 34 and the insert 35, the insert 35 being made of a suitable, water-impermeable, thin, supple film similar to the backing film 22, e.g. B. a 2.5 to 25 μίτι thick film made of polyethylene or polypropylene and extends over the greater part of the width of the absorbent pad 33, namely over 70% of this width. A diaper with the one shown in FIG. 8 can for example have a length of the suction pad 33 of 40.5 cm, and the length L 'of the insert 35 can be approximately 30 to 45% of this dimension, ie approximately 13 to 18 cm. In the case described, the distance M ′ of the insert 35 from the front edge 37 of the diaper can be approximately 5 to 10 cm.

The arrangement of an insert 35 in the absorbent pad 33 in Distance from the pushback ι 36 and the support 34, d. H. in relation to the relative thickness of the parts of the suction pad 33 above and below the insert 35 depends depends on whether the goal to be achieved is only improving the dryness of the diaper surface by improving wicking or suction to their ends and partially eliminating the problem the re-flooding of the surface, or whether a practically complete prevention of re-flooding Flooding of the surface is sought. Any distance of the insert 35 from the backing layer 36 that the Absorbency per unit area of the part of the absorbent pad 33 between the insert 35 and the support 34 compared to the absorbency of the full thickness of the absorbent pad is noticeably reduced, favors the Forwarding the wicking to the ends of the diaper. To this end and with the above described absorbent materials, the insert 35 should be about the middle of the thickness of the absorbent pad 33, preferably immediately under the top layer of absorbent cotton or paper, if that layer is needed, or just below the top two to 20% of the air cushion thickness if this material is used, lie.

If the goal to be achieved is practically complete prevention of re-flooding the surface, the distance between the insert 35 and the support 34 must be such that the relative Absorbency per unit area of the support 34 and that part of the absorbent pad lying above the insert 35 33 must be taken into account. With the combination of support 34 and absorbent pad 33, the insert 35 must be so be arranged that the absorbency per unit area of the hydrophobic pad 34 at the maximum The compressive stress that normally occurs in use is equal to or greater than the change in Liquid retention capacity per unit area of the part of the absorbent pad 33 lying above the insert 35 within the range of compressive stresses encountered during use. The determination these parameters and materials as exemplified above in connection with the embodiments from F i g. 1 to 7 also applies here. A special example! of the in FIG. 8 illustrated structure is a diaper in which the absorbent pad 33 is made from creped cellulose wadding and the pad 34 is made from a single There is a layer of rayon fleece, both of which are described above in connection with FIG. 5, with a individual wadding layer between the support 34 and the insert 35 is arranged.

The support 34 can be attached to the hydrophilic absorbent pad 33 in the same way as the support 21 to the absorbent pad 20 in Fig. 5 can be attached. The backing layer 36 can also be attached to the folded-over parts of the support 34 can be attached, thereby obtaining a cover around the absorbent pad 33, as also above in connection with FIG F i g. 5 has been described.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Disposable diaper, whose entire length extending absorbent pad has a central portion and two end portions, wherein the end sections the abdomen and back and the middle section the area between the Covered legs of the child, characterized by that the middle section (23,45) of the suction pad (20, 33a) has one of lateral edges limited area of 70% across the width of the pad (20, 33a), its absorbency is less than in the end sections 2. Diaper according to claim 1, characterized in that that the area between the lateral edges of the central section (23, 43) of the Suction pad (20, 33a) is compressed to 5 to 15% of its original volume