GB2216774A

GB2216774A - Disposable diaper having stiffened waistbelt

Info

Publication number: GB2216774A
Application number: GB8807940A
Authority: GB
Inventors: John Allen Chang
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1988-04-05
Filing date: 1988-04-05
Publication date: 1989-10-18
Also published as: GB8807940D0

Abstract

At least one waist portion 31, 41 of the diaper is reinforced by a waistbelt strip 32, 42 to provide a waistbelt system that has a machine direction (i.e. lengthwise of the diaper) cantilever stiffness of at least 60 cNcm<2>. The waistbelt system reduces rollover at the waist, thereby reducing waist leakage. <IMAGE>

Description

ABSORBENT GARMENT HAVING STIFFENED WAISTBELT TECHNICAL FIELD The present invention relates to integral disposable absorbent garments such as disposable diapers, and in particular to disposable diapers having a stiffened waistbelt system.

BACKGROUND OF THE INVENTION Absorbent garments of the general type described are well-known. Typically, such garments comprise a liquid pervious topsheet, a liquid impervious backsheet. and an absorbent core interposed between said topsheet and said backsheet. Such garments usually have a front waist portion, a back waist portion and a center portion.

Typically, the garment is closed around the wearer by attaching the back waist portion to the front waist portion, e.g. by means of adhesive tape tabs extending outwardly from the side edges to the back waist portion.

Such garments frequently exhibit leakage problems in the waist area, particularly in the front waist area. Means have been described to reduce such leakage, for example waistshields enclosing the end portions of the absorbent core, or means for elasticating the waist portions.

Even garments having such waistshield features do not fully solve the problem of waist leakage. Waist elastication is a very expensive feature, and is not a complete solution of waist leakage. An important reason is that. in use, the waist portions of the garment deform resulting in a poor fit of the garment in the waist area after some time of usage. In particular, the waist portions of the garment tend to roll outwardly, thus exposing the topsheet, or even the end portions of the absorbent core. It is therefore an object of the present invention to provide absorbent garments having a stiffened waist portion, providing an improved fit around the waist even after several hours of wear. It is another object of the present invention to provide an absorbent garment exhibiting reduced waist leakage.

SUMMARY OF THE INVENTION The present invention relates to a disposable absorbent garment, such as a disposable diaper, comprising a liquid pervious topsheet, a liquid impervious backsheet, and an absorbent core interposed between said topsheet and said backsheet. The backsheet, and optionally also the topsheet, extend beyond the absorbent pad in the machine direction of the diaper so as to form an end flap in at least one waist portion of the diaper. In this end flap, the diaper is provided with a waistbelt strip which, in cooperation with the backsheet and, if present in the end flap, the topsheet, provides a waistbelt having a machine direction Canliver stiffness of at least 60 cNcm2.

In a preferred embodiment both topsheet and backsheet extend beyond the absorbent pad in both the front waist portion and the back waist portion, and the waistbelt strip is interposed between topsheet and backsheet in the endflaps. In a further preferred embodiment, the waisbelt strip extends over at least 608 of the length and 60% of the width of the endflap. In a highly preferred embodiment, the waistbelt strip overlaps with the absorbent core, so as to avoid any areas between the waistbelt and the absorbent core having a stiffness less than that of the stiffened endflap or the core, whichever is the smaller.

In a highly preferred embodiment, the waistbelt system is combined with a fastening means that is wide enough to achieve a full side closure.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following descriptions which are taken in conjunction with the accompanying drawings in which like designations are used to designate substantially identical elements and in which: Fig. 1 is a plan view of a disposable diaper showing both a preferred and a less preferred embodiment of the waistbelt system.

Fig. 2 is a cross section view taken along line 2-2 of Fig. 1.

Fig. 3 is a plan view of two parts of a disposable diaper, showing the full side closures system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to integral disposable absorbent garments such as disposable diapers and more particularly to integral disposable absorbent garments having an improved waistbelt system. As used herein, the term "integral disposable absorbent garment" refers to articles which absorb and contain body exudates and more specifically refers to articles which are placed against or in proximity to the body of a wearer to absorb and contain the various exudates discharged from the body and which are intended to be discarded after a single use (i.e. they are not intended to be laundered or otherwise restored or reused), and which are unitary in that they do not require separate manipulative parts like a separate holder and liner.A preferred embodiment of the integral disposable absorbent garment of the present invention is shown in Fig. 1 as it would be used in a diaper 10. As used herein, the term "diaper" refers to a garment generally worn about the lower torso by infants or other incontinent persons.

Figure 1 shows a plan view of a diaper showing two different embodiments of the waistbelt system. As can be seen in Fig. 1, diaper 10 basically comprises a topsheet 11, a backsheet 12 and an absorbent core 20 interposed between the topsheet 11 and the backsheet 12. The absorbent core 20 has core side edges 21 and core waist edges 22. Disposable diaper 10 has a front waist portion 30, a rear waist portion 40 and a center portion 50.

Impervious backsheet 12 and liquid pervious topsheet 11 extend in the machine direction of the diaper beyond the core waist edges 22, thus forming endflaps 31 and 41.

Diaper 10 has a liquid receiving top surface which is generally defined by the topsheet 11, and a back surface which is generally defined by the backsheet 12.

Preferably the topsheet and the backsheet have length and width dimensions generally larger than the absorbent core 20 so that they extend beyond the core side edges 21 and core waist edges 22 of the absorbent core 20 where they are associated together in a suitable manner. As used herein, the term "associated" encompasses configurations whereby the topsheet 11 is directly joined to the backsheet 12 by affixing the topsheet 11 directly to the backsheet 12 and configuations whereby the topsheet 11 is indirectly joined to the backsheet 12 by affixing the topsheet 11 to intermediate members which in turn are affixed to the backsheet 12.

Examining some of the elements of the diaper 10 in more detail, the topsheet 11 is positioned adjacent the body surface 23 of the absorbent core 20 and overlays a major portion of the absorbent core 20 so that when exudates are discharged onto the topsheet 11 they penetrate through the topsheet where they are absorbed by the absorbent core 20. Topsheet 11 is compliant, soft feeling and non-irritating to the wearer's skin. Further, the topsheet 11 is liquid pervious, permitting liquids to readily penetrate through its thickness. A suitable topsheet may be manufactured from a wide range of materials. such as porous foams, reticulated foams, apertured plastic films, natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or polypropylene fibers)or from a combination of natural and synthetic fibers. Preferably, it is made of hydrophobic material to isolate the wearer's skin from liquids in the absorbent core 20. A particularly preferred topsheet comprises staple length polypropylene fibers having a denier of about 1.5, such as Hercules Type 151 polyproylene marketed by Hercules, Inc. of Wilmington, Delaware. As used herein, the term "staple length fibers" refers to those fibers having a length of at least about 15.9 millimeters (0.625 inches).

There are a number of manufacturing techniques which may be used to manufacture the topsheet 11. For example, the topsheet 11 may be woven, non-woven, spunbonded, carded, or the like. A preferred topsheet 11 is carded and thermally bonded by means well known to those skilled in the fabrics art. Preferably, the topsheet has a weight from about 18 to about 25 grams per square meter, a minimum dry tensile strength of at least about 400 g/cm in the machine direction and a wet tensile strength of at least 38 g/cm in the cross-machine direction of the sheet.

The absorbent core 20 may be any means which is generally compressible, conformable, non-irritating to the wearer's skin, and capable of absorbing and containing liquids and certain body exudates. A preferred absorbent core 20 has a body surface 23 and a garment surface 24 and comprises an absorbent layer and first and second tissue layers (not shown). The first and second tissue layers overlay the major surfaces of the absorbent layer to form the body surface 23 and the garment surface 24 of the absorbent core 20.

The absorbent core 20 may be manufactured in a wide variety of sizes and shapes (e.g. rectangular, hourglass, etc.) and from a wide variety of liquid absorbent materials commonly used in disposable diapers and other absorbent articles, such as comminuted wood pulp which is generally referred to as airfelt. Examples of other suitable absorbent materials include creped cellulose wadding, absorbent foams, absorbent sponges, superabsorbent polymers, absorbent gelling materials, or any equivalent materials or combination of materials. The total absorbent capacity of the absorbent core 20 should, however, be compatible with the design exudate loading for the intended use of the diaper 10. Further, the size and absorbent capacity of the absorbent core 20 may be varied to accomodate wearers ranging from infants to adults.

The backsheet 12 is positioned adjacent the garment surface 24 of the absorbent core 20 and is preferably attached thereto by attachments means (not shown) such as those well known in the art. For example, the backsheet 12 may be secured to the absorbent core 20 by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines or spots of adhesive. Adhesives which have been found to be satisfactory are manufactured by Eastman Chemical Products Company of Kingsport, Tennessee, and marketed under the tradename EASTOBOND A-3 and by Century Adhesives, Inc. of Columbus, Ohio and marketed under the tradename CENTURY 5227.

The backsheet 12 is impervious to liquids and is preferably manufactured from a thin plastic film,although other flexible liquid impervious materials may also be used. The backsheet 12 prevents the exudates absorbed and contained in the absorbent core 20 from wetting articles which contact the diaper 10 such as bedsheets and undergarments. Preferably, the backsheet 12 is a polyethylene film having a thickness of from about 0.012 mm to about 0.051 mm,although other flexible, liquid impervious materials may be used. As used herein, the term "flexible" refers to materials which are compliant and which will readily conform to the general shape and contours of the human body.

A suitable polyethylene film is manfuactured by Monsanto Chemical Corporation and marketed in the trade as Film No. 8020. The backsheet 12 is preferably embossed and/or matte finished to provide a more clothlike appearance. Further, the backsheet 12 may permit vapors to escape from the absorbent core 20 while still preventing exudates from passing through the backsheet 12.

The machine direction of the diaper is from rear waist portion 40 to front waist portion 30. The cross machine direction is perpendicular to the machine direction.

Shown in front waist portion 30 is a less preferred embodiment of the waistbelt. Backsheet 12 and topsheet 11 extend beyond absorbent core 20 in the machine direction of the diaper to form endflap 31. Interposed between the top sheet 11 and the backsheet 12 in this endflap 31 is waistbelt strip 32. The stiffness of the material used for waistbelt strip 32 is such that the Cantilever stiffness of the assembley formed by topsheet 11, backsheet 12 and waistbelt strip 32 in the machine direction of the diaper is at least 60cNcm2. Preferably, this stiffness does not exceed 600 cNcm2.

In this less preferred embodiment of the waistbelt system the waistbelt strip 32 and the absorbent core 20 do not overlap.

The cross machine direction dimension of the endflap 31 will be referred to as the "width' of the endflap 31.

The machine direction dimension 35 of the endflap 31 will be referred to as the "length" of the endflap 31. This length preferably is in the range of from 2 cm to 8 cm.

In this embodiment of the waistbelt system, the machine direction dimension 34, or width of the waistbelt strip 32 is preferably at least 80%, most preferably close to 100%, of the length of endflap 31. Likewise, the cross machine direction dimension 36, or length of waistbelt strip 32 is preferably at least 60%, more preferably close to 100%, of the width of the endflap 31.

Shown in endflap 41 is a more preferred embodiment of the waistbelt system. Waistbelt strip 42 is interposed between topsheet 11 backsheet 12. Waistbelt strip 42 is positioned in such a way that there is overlap with the end portion 25 of the absorbent core 20. Like in the earlier described embodiment, the stiffness of the waistbelt strip material is such that the resulting machine direction stiffness of the ensemble topsheet 11, backsheet 12 and waistbelt strip 42 is at least 60 cNcm2. The overlap of the waistbelt strip 42 and the absorbent core 20 is such that there is no area of reduced stiffness in the transition area from waistbelt strip 42 to the absorbent core.This means that if the Cantilever stiffness of the ensemble absorbent core 20, topsheet 11 and backsheet 12 is S1, and the Cantilever stiffness of the ensemble topsheet 11, backsheet 12 and waistbelt strip 42 is Sa, there is no area where the Cantilever stiffness is less than S1, if S1 is smaller than or equal to 52, or less than S2 if S2 is smaller than S1. In the former described embodiment shown in endflap 31, there is an area 37 where the stiffness is likely to be less than the smaller of S1 and S2.

In the preferred waistbelt system shown in endflap 41, width 44 of waistbelt strip 42 is preferably at least 80% of the length 45 of endflap 41, and the length 46 of waistbelt strip 42 preferably is at least 60%, more preferably close to 100%. of the cross machine direction dimension, or width, of the endflap 41.

Materials used for waistbelt strips 32 and 42 are sufficicently stiff so as to impart a Cantilever stiffness 2 of at least 60 cNcm2 to the waistbelt system, yet are preferably also compliant and soft and compressible.

Examples of suitable materials include open cell foams, closed cell foams. and air cushion films. Suitable examples of open cell foams are the so-called polyurethane foams, as are commonaly used in bedding and furniture and the like. Suitable for use in the waistbelt systems of this invention are polyurethane foams having a thickness of from 2 to 5 mm, and a density in the range from 10 to 3 30 kg/m Examples of suitable closed cell foams are closed cell foams of polyethylene. Suitable foams include those having a thickness of from 1 to 5 mm and a density of from 10 to 30 kg/m3. Closed cell foams are more preferred than the open cell foams because the former have a higher stiffness at a given density.

Air cushion films are well-known as disposable packaging materials. They typically comprise at least 2 thin films of e.g. polyethylene. laminated onto each other. Prior to lamination, one of the films is deformed so as to form bubble shaped cavities. After lamination air is trapped within these cavities, providing stiffness to the material. An example of a suitable air cushion film for the purpose of the present invention is a polyethylene film having a bubble size of about 5 mm, and a ratio of entrapped air to free air of about 50/50. Air cushion films also exist in 3-layer executions which have a higher stiffness than 2-layer versions.

Cantilever stiffness test. The machine direction stiffness of the waistbelt system is measured in the Cantilever stiffness test, by the method described in DIN norm 53362, substantially equivalent to norm ISO 4604-1978. This test determines the stiffness of a film or fabric material in bending, by the method according to Cantilever. The method gives stiffness readings in cNcm2.

The stiffness of the waistbelt system is measured as is, that is, the stiffness of the ensemble topsheet 11, backsheet 12 and waistbelt strip 32, 42 is measured as a whole. If other materials are present in the endflap, as for example a waistshield, or a tissue, such a material will not be removed for the determination of stiffness of the waistbelt, as it is the stiffness of the waistbelt that is the key feature of the present invention, regardless as to how the stiffness is obtained.

Generally, the dimensions of a diaper do not permit measurement of the machine direction stiffness of the waistbelt system on a finished diaper. When homogeneous materials are used for waistbelt strip 32, 42,the cross machine direction stiffness is a reliable measure of its machine direction stiffness. In other cases, samples of the proper dimensions for Cantilever testing may be prepared by assembling samples of the constituting materials a and measuring the Cantilever stiffness of such samples.

Since stiffness is needed to prevent rollover of the endflap of the diaper, it is the stiffness in the machine direction of the diaper that is of importance. It is possible to use waistbelt strip materials that have Cantilever stiffnesses that are different in the machine direction and the cross machine direction. In a way, it is desirable to provide a waistbelt system that is less stiff in the cross machine direction so as to provide easely complying waist fit. This kind of effect can also be obtained by stiffening the waistbelt in the machine direction during manufacture of the diaper, for example by providing glue lines in the machine direction of the diaper in the waistbelt area.

The benefits of the waistbelt system are particularly important in an hour glass-shaped diaper, having full side closure. The term "hour glass-shaped diaper", as used herein, signifies a diaper having a width, or cross machine direction dimension, in the center portion which is smaller than the cross machine direction dimension in the front waist and back waist portions. The diapers shown in Figs. 1 and 3 are examples of such diapers. This construction results in the diaper having chassis ears 33, 34, 43, 44 which have a machine direction dimension, or width. By "full side closure", as used herein, is meant fastening means 60, 61 provided at the rear waist portion having a machine direction dimension, or width, of at least 40% of the width of the ears 43, 44.

Fastening means 60, 61 should have an overlap 62, 63 with the waistbelt strip 42 of at least 10% of the width of the waistbelt strip 42. Preferably, there is a target means 70, 71 for the closure means in the front waist portion, having a machine direction dimension 73 of at least 40% of the machine direction dimension 72 of the front waist ears 33, 34 and having an overlap 74, 75 with waistbelt strip 32 of at least 10% of the width of waistbelt strip 32.

The fastening means 60, 61 can be, for example, adhesive tape tabs of the required width or a combination of two or more tape tabs on each side, having a combined width resulting in the full side closure described hereinabove.

Preferred target means 70, 71 for such adhesive tape tabs are reinforcement strips of a polymeric film material, for example a biaxially oriented polypropylene, which are provided on the outside of the backsheet 12 of the diaper. Target means 70, 71 can consist of 2 separate strips, or 1 strip extending over a substantial part of the width of the diaper 10.

In an alternate embodiment, the fastening means 60.

61, 70, 71 consist of a hook and loop mechanical fastening system. Preferably, the hooks 60, 61 are provided at the rear waist ears 43, 44 and the loop target means are provided at the front waist ears 33, 34 of the diaper 10.

Suitable materials for these and other embodiments of the closure means will be apparent to those skilled in the art. The important feature of the closure means in the context of the present invention is that it cooperates with the waistbelt system to provide a good fit throughout the use lifetime of the diaper. If used with a full side closure, the machine direction stiffness of the waistbelt system preferably is less than 170 cNcm2. Shown in Fig. 3 is a mechanical fastening system. Hook parts 60, 61 are affixed to topsheet 11: loop parts 70, 71 are affixed to backsheet 12.

Tape tabs are generally affixed to the backsheet in the rear waist portion of the diaper, and folded over to temporary landing areas affixed at the topsheet. When the diaper is applied to the wearer, the tape tabs are removed from the temporary landing areas, so that the tabs extend outwardly laterally, and may be folded around the front ears and affixed to target means (70, 71), or directly to the backsheet (12), in the front waist portion of the diaper.

Claims

1. A disposable diaper (10), comprising a liquid pervious topsheet (11), a liquid impervious backsheet (12) and an absorbent core (20) interposed between said topsheet (11) and said backsheet (12), said diaper having a center portion (50), a front waist portion (30) and a rear waist portion (40), a machine direction running from front waist portion (30) to rear waist portion (40) and a cross machine direction perpendicular to the machine direction in the plane of the diaper, characterized in that at least one waist portion is reinforced in an area extending beyond the absorbent core (20), resulting in a machine direction Cantilever stiffness in at least one point of that waist portion of at least 60 cNcm2.

2. A disposable diaper according to Claim 1, character ized in that each waist portion (30, 40) has, in at least one point in an area extending beyond absorbent core (20), a machine direction Cantilever stiff 2 ness of at least 60 cNcm2.

3. A disposable diaper according to claim 1 or 2, wherein said topsheet (11) and said backsheet (12) extend beyond said absorbent pad (20) in the machine direction so as to form a first end flap (31) and a second end flap (41), characterized in that waistbelt strip (32, 42) is interposed between topsheet (11) and backsheet (12) in the endflaps (31, 41), creating a waistbelt having a machine direction Cantilever stiffness of at least 60 cNcm2.

4. A disposable diaper according to Claim 3, wherein the waistbelt strip (32, 42) extends over at least 60% of the cross machine direction dimension, or width, of the endflap (31, 41).

5. A disposable diaper according to claim 3 or 4, wherein the waistbelt strip (32, 42) has a machine direction dimension (34, 44), or width. of at least 60t of the machine direction dimension (35, 45), or length, of the endflap (31, 41).

6. A disposable diaper according to Claim 5, wherein the waistbelt strip (42) extends beyond the endflap (41) so as to overlap with absorbent pad (20).

7. A disposable diaper according to Claim 5, wherein the waistbelt strip (32) does not overlap with absorbent pad (20) and has a machine direction dimension (34), or width, of at least 80% of the machine direction dimension (35), or length, of the endflap (31).

8. A disposable diaper according to any one of the preceding claims, wherein the center portion (50) has a cross machine direction dimension which is smaller than the cross machine direction of the front waist and back waist portions, resulting in rear chassis ears (43,44) having machine direction dimension (46), characterized in that the rear waist portion has fastening means (60, 61) having machine direction dimension (64), or width, of at least 40% of (46), and having overlap (62, 63) with waistbelt strip (42) of at least 10t of the width of waistbelt strip (42).

9. A disposable diaper according to Claim 8, having target means (70, 71) for closure means (60, 61) in the front waist portion, having machine direction dimension (73) of at least 80% of machine direction dimension (74) of front ears (33, 34), and having overlap (74, 75) with waistbelt strip (32) of at least 10%.

10. A disposable diaper according to any one of the preceding claims, wherein the waistbelt strip (32, 42) is of an open cell foam material, preferably a polyurethan open cell foam.

11. A disposable diaper according to any one of claims 1-9, wherein the waistbelt strip (32, 42) is an air cushion film, preferably a polyethylene air cushion film.

12. A disposable diaper according to any one of claims 1-9, wherein the waistbelt strip (32, 42) is a closed cell foam material, preferably a polyethylene closed cell foam material.