GB2176388A - Disposable diaper - Google Patents

Abstract

A disposable diaper comprising an outer, moisture impervious layer (2), an inner, moisture permeable layer (7) and, enclosed by these two layers, an absorbent pad (3), the absorbent pad having one or more compression zones (24a, b and c) extending substantially the entire length of the longitudinal centre portion of the absorbent pad and symmetrically arranged along and/or on either side of the longitudinal centre line of the absorbent pad and/or the diaper, the diaper further comprising elastic members (5) disposed adjacent the absorbent pad at least in the leg areas of the diaper, the tension in the elastic members and the rigidity of the compression zone or zones being such that, in use, the compression zones form a keel and the diaper adopts a boat-like conformation and the pad substantially lacks rugosities extending across the compression zone or zones. <IMAGE>

Description

SPECIFICATION Disposable diaper The present invention relates to disposable diapers especially diapers intended for use on infants.

One of the major difficulties which has faced manufacturers of disposable diapers has been the problem of providing a garment which is comfortable for the wearer and affords a good seal at the legs and waist to prevent escape of body fluids. A number of solutions have been proposed for overcoming this problem but none has been entirely satisfactory. Thus U.K. Patent No. 1482677 proposes that the elastic members are spaced well away from the absorbent pad, at least in the leg area, and the flexible flaps in the impermeable backing sheet thus formed provide a seal against the legs of the wearer. Various objections to this design were addressed by U.K. Patent No. 1561021 which provided for the elastic members to be close to the edges of the leg area of the absorbent pad, thus avoiding the flexible flaps and causing transverse rugosities to form in the pad.Such rugosities were considered advantageous in providing increased thickness and absorbing capacity in the crotch area. However the rugosities also have the disadvantage, as pointed out in U.K.

Patent No. 2011778, of weakening the structure of the pad, especially because of the repeated folding and unfolding of the pad during manufacture, and thus causing tearing of the pad with consequent reduction in efficiency. It was also observed that in order to achieve the rugosities the elastics had to be so close to the edges of the pad that they did not provide a suitable seal with the wearers legs.

U.K. Patent 2011778 adopts an intermediate position of the elastic members thus purporting to avoid the flexible flap of U.K. Patent No. 1482677 and the rugosities of U.K. Patent No. 1561021.

However tests on such diapers have shown that, in fact, the elastic members still ';end to cause rugosities in the crotch portion of the absorbent pad with their associated disadvantages.

It has now been found that these problems can be avoided by constructing diapers in which one or more compression zones are applied longitudinally to the absorbent pad to afford a degree of rigidity to the pad and the elastic side members are tensioned such that the absorbent pad, and hence the rest of the diaper, is drawn into a boat-like shape of which the compression zone or zones corresponds with the "keel". This combination of features has been found to afford a diaper which conforms well to the anatomy of the wearer and avoids the formation of transverse rugosities whilst at the same time enabling appropriate spacing of the elastic from the absorbent pad to provide a good seal with the wearers legs.

U.K. Patent Application Publication No. A-2100130 discloses disposable diapers in which the absorbent pad is embossed to form densified regions to afford a "quilted" effect in orderto secure the permeable layer to the pad thus stabilising and reinforcing the pad. The "quilting" extends over substantially the whole area of the absorbent pad and is therefore unable to form the "keel" of the present diapers.

The present invention therefore provides a disposable diaper comprising an outer, moisture impervious layer, an inner, moisture permeable layer and, enclosed by these two layers, an absorbent pad, the absorbent pad having one or more compression zones extending substantially the entire length of the longitudinal centre portion of the absorbent pad and symmetrically arranged along and/or on either side of the longitudinal centre line of the absorbent pad and/or the diaper, the diaper further comprising elastic members disposed adjacent the absorbent pad at least in the leg areas of the diaper, the tension in the elastic members and the rigidity of the compression zone or zones being such that in use the compression zones form a keel and the diaper adopts a boat-like conformation and the pad substantially lacks rugosities extending across the compression zones or zones.

Suitably the absorbent pad is formed with from one to three compression zones, each being from 5 to 15 mm in width and arranged to form a keel area of from 5 to 25 mm in width disposed parallel to and symmetrically about the longitudinal centre line of the absorbent pad.

Preferably three compression zones are formed in the absorbent pad and most preferably each zone is about 5 mm wide and the three compression zones form a keel area not more than about 17 mm in width.

Apart from the provision of the compression zones and the corrent tension and spacing of the elastic members the diaper may be constructed from conventional materials and according to conventional designs. It has been found to be particularly advantageous to construct the diaper according to a "hour-glass" design having a generally rectangular absorbent pad from which leg portions have been cut-out and linear elastic members. Preferably the elastic members are disposed outwards of the absorbent pad and are spaced at 10 to 15 mm from the respective outer edges of the absorbent pad, although manufacturing tolerances of +2 mm in any chosen spacing mean that in practice spacings of from 8 to 17 mm might occasionally be found.Since in practice elastic members may be chosen from a variety of forms such as one or several thin filaments, tapes of broad ribbons and more complex structures such as those of European Patent Application Publication No. A-0023804, the spacings given herein refer to the distance between the outer edge of the absorbent pad and the centre line of the elastic member in question.

A particularly preferred design of diaper includes a second absorbent pad, the two absorbent pads being placed one above the other, the upper pad (the one adjacent the wearer) being narrower than the lower pad. The compression zone(s) may be formed in either the upper pad or the lower pad or both although preferably the compression zones are formed only in the lower pad.

Diapers according to the present invention may be produced in a conventional manner and the compression zone or zones may be formed in the absorbent pad at any convenient stage in the process, such as prior to assembling the diaper from its individual elements or even as a last stage once the diaper is fully assembled. The compression zone or zones may be produced by stamping or by passage between suitably formed rollers and may be performed as a separate operation or may be effected at the same time as other operations such as cutting out the absorbent pad or the final trimming to size of the diaper.

The invention will now be illustrated by reference to the Figures of the accompanying drawings in which: Figure 1 is a perspective view of the diaper according to the invention but with the upper, permeable layer removed to expose the absorbent pad.

Figure 2 is a plan view of a diaper as shown in Figure 1 in the fully extended position.

Figure 3 is a section of another embodiment of the invention taken on a line corresponding with the line A-A on Figure 2.

The diaper of the invention is illustrated in Figure 1 where it is generally indicated 1. The diaper comprises an impermeable backing sheet 2, absorbent pad 3 attached to the backing sheet 2 and a moisture permeable upper sheet (not shown).

Compression zones 4 formed in the absorbent pad 3 to provide a "keel" such that, under the influence of elastic members 5 the diaper 1 is drawn into a boat shape prior to application to an infant. After application to the infant the diaper is secured in place by tapes 6.

Figure 2 shows the same diaper as in Figure 1 but in the fully extended state. The absorbent pad 3 has three narrow and closely adjacent compression zones, 4a, 4b and 4c. Linear elastic members 5 are attached to the backing sheet to either side of the leg portion 9 of the absorbent pad 3. The absorbent pad 3 is covered by a permeable sheet 7, partially cut away to reveal the internal details of the diaper. Pad 3 and permeable sheet 7 are attached to the backing sheet 2 by glue-lines (not shown) and the backing sheet 2 is folded over at the waist portions 8 to further secure the permeable sheet 7.

Referring now to Figure 3, an alternative embodiment of the diaper has absorbent pad 20 with three compression zones 21a, b and 21 c along its longitudinal centre-line and is provided with a further absorbent pad 22. Pad 20 is secured by glue-lines (not shown) to an impermeable sheet 23 and pad 22 is held in place by the permeable sheet 24. Elastic members 25 are attached to the backing sheet 23 to the sides of pad 20 in the crotch region of the diaper.

The diapers are produced in conventional manner and compression zones in the absorbent pad or pads are formed by passing the pad(s) through, for instance, a nip roller. Suitable stiffness in the absorbent pad can be achieved by compressing the pad to a ratio of from 1:1.5 to 1:20 for instance about 1:5 or 1:10 between the relaxed thickness of compressed and uncompressed pulp. The elastics are applied to the impermeable backing sheet in conventional manner under tension which is normally expressed as a percentage elongation from the fully relaxed state of the elastic.

Elongations of 80 to 300%, preferably 100 to 200% are suitable.

The material in the absorbent pad can be any one known from literature or existing in practice.

However, according to a preferred embodiment of the invention the absorbent material consists of so called "fluff", manufactured by disintegration of pulp.

It is also possible to use so called "superabsorbent material", preferably in combination with fluff. This material absorbs much more liquid per gram than, for example, fluff. The superabsorbent material can be delivered in the form of powder, fiber or strip (ribbon). Powder and fiber are preferred. The material can be mixed with the fluff throughout the whole pad. However, it is preferred to concentrate the addition of the superabsorbent material at the compression zones. The material can be placed on the fluff before the compression is carried out or, after the compression step, it may be placed in the valleys formed by the compression.

As particular examples of superabsorbent material, those based on starch and acrylic ester can be mentioned. Also carboxymethyl cellulose and grafted (cross linked) cellulose materials can be used. As examples of acrylic ester based products, LuquasorbR and ArasorbR can be mentioned.

AqualonR and AkucellR are examples on ca rboxymethyl cellulose products.

Claims (18)

1. A disposable diaper comprising an outer, moisture impervious layer, an inner, moisture permeable layer and, enclosed by these two layer, an absorbent pad, the absorbent pad having one or more compression zones extending substantially the entire length of the longitudinal centre portion of the absorbent pad and symmetrically arranged along and/or on either side of the longitudinal centre line of the absorbent pad and/or the diaper, the diaper further comprising elastic members disposed adjacent the absorbent pad at least in the leg areas of the diaper the tension in the elastic members and the rigidity of the compression zone or zones being such that in use the compression zones form a keel and the diaper adopts a boat-like conformation and the pad substantially lacks rugosities extending across the compression zones or zones.

2. A disposable diaper according to claim 1 having from 1 to 3 compression zones.

3. A disposable diaper according to claim 1 or claim 2 wherein the or each compression zone is from 5 to 15 mm in width.

4. A disposable diaper according to any preceding claim wherein the compression zones form a keel area from 5 to 25 mm in width.

5. A disposable diaper according to any preceding claim having three compression zones each about 5 mm in width forming a keel area about 17 mm in width.

6. A disposable diaper according to any preceding claim wherein the absorbent pad is in hour-glass form.

7. A disposable diaper according to any preceding claim wherein the elastic members are disposed outwards of the absorbent pad.

8. A disposable diaper according to claim 7 wherein the elastic members are spaced at 10 to 15 mm from the outer edges of the absorbent pad.

9. A disposable diaper according to any preceding claim comprising a second absorbent pad narrower than the first absorbent pad and located above the first absorbent pad.

10. A disposable diaper according to claim 9 wherein the compression zones are formed only in the first absorbent pad.

11. A disposable diaper according to any preceding claim wherein the compression zones are formed by compressing the pad to a ratio of 1:1.5 to 1:20 between the relaxed thickness of compressed to uncompressed pad.

12. A disposable diaper according to claim 11 wherein the ratio is from 1:1.5 to 1:5.

13. A disposable diaper according to any preceding claim wherein the elastic members are applied to the impermeable backing sheet at a tension corresponding to an elongation of 80 to 300% of the fully relaxed length of the elastic.

14. A disposable diaper according to claim, 13 wherein the tension corresponds to an elongation of 100 to 200%.

15. A disposable diaper according to any preceding claim wherein the or each absorbent pad comprises fluff.

16. A disposable diaper according to any preceding claim wherein the or each absorbent pad comprises fluff and a superabsorbent material.

17. A disposable diaper according to claim 16 wherein the superabsorbent material is concentrated in the compression zones.

18. A disposable diaper substantially as hereinbefore described with reference to the figures of the drawings.