AU618778B2 - Disposable diaper - Google Patents

Description

12

AUSTRALIA

Patents Act 61sI COMPLETE SPECIFICATIN

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: APPLICAN LS REFERENcE: 63-10332 Name(s) of Applicant(s): Uni-Charm Corporation Address(es) of Applicant(s): 182, Shimobun, Kinsei-cho, Kawarioe -shi, Ehime-ken,

JAPAN.

SAdd~ress for Service is: PH~ILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: DISPOSABLE DIAPER Our Ref :121300 POF Code: 1647/76530 The following statement is a full description of this invention) including the best method of performuing it known to applicant(s): 6003q/ 1-1 I 2188Z 4. DISPOSABLE DIAPER BACKGROUND OF THE INVENTION The present invention relates to a disposable diaper perticularly characterized in side flaps provided with elastic members therein.

There have already been proposed various types of 0, disposable diaper. Concerning those of well known art 00S I including side flaps provided with elastic members 00 adapted to exert appropriate pressure around the wearer's 0 0o 0, legs, two types of diaposable diaper have been propos 0 0 0o0 the one comprising a liquid-absorbent core sandwiched between a liquid-permeable topsheet and a liquid-impermeable S00 0 backsheet and the side flaps formed by the areas of said two 0 0 0o00o0 sheets laterally extending from opposite outer side edges of ooo said core so as to contain in said side flaps to exert pressure around the wearer's legs, and the other employing as a part of said side flaps the third sheet made of material provided separately of said topsheet and said backsheet.

In such diaper of the prior art, said elastic member usually has a tensile strength of 100 to 600g so that the elastic member may exert effective pressure and establish desired seal around the wearer's leg.

Preferably, said elastic member should exhibit a high contraction percentage as being mounted on the diaper and 1Aeven the "onventional diaper has intended to achieve such a high contraction percentage of said elastic member. However, a relatively high rigidity of the side flap on which said elastic member is mounted disadvantageously has limited said contraction percentage. To solve such a problem, it may be contemplated that the elastic member permitting said desired contraction to be obtained, the elastic member being excellent in its elasticity and high in its stretching S.stress is employed. However, it is not easy to obtain such elastic member by the technique presently available and an I unacceptable cost will result even if such elastic member is obtained.

4 In the case of the diaper having said side flap at least partially formed by said topsheet, said problem will become Smore serious when said topsheet of a relatively high rigidity o. is employed in order to realize a desired characteristic thereof. Consequently, types and structures of said topsheet which may be adopted are limited.

An essential object of the present invention is to provide disposable diapers having said side flaps which at least alleviate the problems of the prior art.

SUMMARY OF THE INVENTION According to the present invention, the object as set forth above is achieved by a disposable diaper including a ~L~4 -2-

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liquid-permeable topsheet, a liquid-impermeable backsheet, a liquid-absorbent core sandwiched between these two sheets, and side flaps extending laterally from opposite side edges of said core and provided with associate elastic members, wherein each of said side flaps is disposed outside said topsheet and includes a third sheet forming at least a part of said side flap; wherein said third sheet has a rigidity as measured by the Clark rigidity tester according to The S.Japanese Industrial Standard(P8143) longitudinally of the :a: 0diaper lower than that of said topsheet; and wherein said 00 So9:. elastic member is adhered at least to said third sheet.

Ca So° To assure that said elastic member exhibits a predetermined contraction percentage even when said elastic member is adhered also to said backsheet forming a part of said side Sflaps, said topsheet has a rigidity of 90mm or higher as a.

a measured by said tester; said backsheet has a rigidity lower than 60mm as measured by said tester; said third sheet has a rigidity of 10 to 80mm as measured by said tester; said elastic member has a tensile strength of 70 to 700gC; and said third sheet has a water pressure resistance of 20mm or higher as measured by the water pressure resistance tester according to The Japanese Industrial Standard(L1092) (corresponding to ISO 811 standard) and is of air-permeable nature.

According to the present invention, the third sheet having a rigidity lower than that of the topsheet forms a -3

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part of the side flap and the elastic member for fitness around the wearer's leg is bonded at least to said third sheet. Such feature of the invention advantageously increases a contraction percentage, in other words, a contraction extent length) with respect to the case in which said part of the side flap is constructed by the area of said topsheet extending laterally from the outer side edge of the core. With a consequence, said side flap developing a shrinkage due to the presence of the elastic member therein well follows and accommodates movement of the wearer's leg and t exerts appropriate pressure around the leg for an effective seal, minizing possible leakage of fluids which would otherwise occur between the side flap and the leg. Furthermore, the present invention permits said topsheet of a relatively high 4 4 O 4 44 rigidity depending on factors such as quality and structure of its material to be selectively employed independently of said elastic member.

Further advantage of the diaper constructed according to Ut'' the present invention lies in that the rigidities not only of said third sheet but also of said topsheet and said backsheet as well as the tensile strength of said elastic member are respectively specified within the predetermined associated ranges and thereby it is assured to achieve the abovememtioned effect even when said elastin member is bonded to said backsheet.

4i Still another advantage of the diaper constructed according to the present invention lies in that the water pressure resistance of said third sheet is also specified within the predetermined range and thereby it is assured to minimize a possible trouble that a quantity of body fluids excreted on said topsheet might flow down onto the surface of said third sheet or permeate between said third sheet and said backsheet being in contact with said third sheet and result in leakage along the outer side edge of said side flap.

i 4; BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view showing an unfolded diaper as partially broken away; and Figs. 2A through 2H illustrate various manners in which important parts of the diaper may be arranged in accordance with the present invention.

4 PREFERRED EMBODIMENTS The invention will be described more in detail by way of example in reference with the accompanying drawing.

Referring to Fig. 1, a diaper comprises a liquidpermeable topsheet 1, a liquid-impermeable backsheet 2, a liquid-absorbent core 3 sandwiched between these two sheets, and a pair of side flaps 4 extending laterally from opposite II l 1 side edges of said core 3. Each of the side flaps 4 comprises an area la of the topsheet 1 extending from the associated outer side edge.of the core 3, an area 2a of the backsheet 2 extending from the outer side edge by an extent longer than the topsheet area la, and a third sheet 6 joined onto a zone of the backsheet area 2a on which the topsheet is absent. Between the backsheet area 2a and the third sheet 6 forming together a part of the side flap 4, there is Sprovided a longitudinally elastic member 5 adhered to the third sheet 6. It should be understood that this elastic member 5 may be adhered to both the backsheet 2 and the Sthird sheet 6.

Fig. 2 illustrates various manners in which the elastic member 5 and the third sheet 6 may be arranged. Fig. 2A illustrates an arrangement in which the inner side edge of the third sheet 6 is adhesively sandwiched between the topsheet area la and the backsheet area 2a adjacent the respective outer side edges thereof. Fig. 2B illustrates an arrangement in which the inner side edge of the third sheet 6 is joined onto the upper surface of the topsheet area la along the outer side edge thereof. Fig. 2C illustrates an arrangement in which the inner side edge of the third sheet 6 is joined not only onto the backsheet area 2a but also onto the topsheet area la along the outer side edge thereof which has been folded back down- and inwardly.

-6i, 1_ IC IIIOll--~ l~ l Fig. 2D illustrates an arrangement in which the inner side edge of the third sheet 6 is joined first onto the backsheet area 2a and then onto the topsheet area la along the outer side edge thereof which has been folded back up- and inwardly. Fig. 2E illustrates an arrangement in which the inner side edge of the third sheet 6 is joined onto the backsheet area 2a and at the same time to the outer side edge of the topsheet area la in abutting relationship. Fig.

2F illustrates an arrangement in which the inner side edge of the third sheet 6 is joined onto the backsheet area 2a with a gap maintained with respect to the outer side edge of the topsheet area la. Fig. 2G illustrates an arrangement in which the inner side edge of the third sheet 6 is joined onto the upper surface of the topsheet area la along its outer side edge and the outer side edge of said third sheet 6 is folded back up- and inwardly so as to wrap the elastic member 5 therein. Finally Fig. 2H illustrates an arrangement in which the inner side edge of the third sheet 6 is adhesively sandwiched between the respective outer side edges of the topsheet area la and the backsheet area 2a with the outer side edge of the third sheet being folded back up- and inwardly so as to wrap the elastic member 5 therein.

The topsheet 1 has a unique structure adapted to quickly guide a quantity of body fluids excreted thereon towards the core 3 and "hereby to effectively reduce a possible flowing -7i of the body fluids once absorbed by the core 3 back to the upper surface of the topsheet 1.

A preferable embodiment of such structure is a nonwoven fabric having a basic weight, a weight per unit area, of 25 to 35g/m 2 and a thickness of 1 to 2mm, comprising a top layer of a higher density and a back layer of a lower density melt-bonded together. Component fibers of such nonwoven fabric may be selectively combined from a group consisting of polypropyrene, polyethylene, conjugated polyethylene/polypropyrene, and conjugated polvester/ polyethylene. Such two-layered topsheet 1 has a rigidity of or higher as measured by the Clark rigidity tester according to The Japanese Industrial Standard(P8143) longitudinally of the diaper.

The third sheet 6 may be selectively used from a group consisting of a melt-bonded nonwoven fabric, a span-bonded nonwoven fabric, a water-jet treated nonwoven fabric, all these being made of hydrophobic fibers, such nonwoven fabric subjected to waterproofing treatment, hydrophobic plastic film, and such film provided with a plurality of apertures.

SThe third sheet 6 is air-permeable and has a water pressure resistance of 20mm or higher, preferably of 30mm or higher and most preferably of 40mm or higher as measured the water pressure resistance tester according to Japanese Industrial Standard(L1092). This third sheet 6 has a basic weight -8- L_ ~i i-i Ilr.r -I lower than that of the topsheet 1, a rigidity of 10 to as measured in said manner longitudinally of the diaper and a rigidity of 5 to 80mm as.measured transversely of the diaper.

The backsheet 2 is made of conventionally used material such as a polyethylene film and has a rigidity of 60mm or less both longitudinally and transversely of the diaper as measured according to said JIS.

44 It is preferred to adjust said rigidity longitudinall of the diaper to 50 to 100mm at a section consisting of the backsheet 2 and the third sheet 6.

The elastic member 5 comprises, for example, a plurality of rubber filaments, urethane rubber piece or urethane foam piece and a tensile strength thereof is adjusted to 70 to oP' 700g so as to exert appropriate pressure around the wearer's leg. The elastic member 5 has its outer side edge spaced by 3mm or longer from the outer side edge of the topsheet 1 having said rigidity which is relatively high.

Now the reason why said rigidity of the third sheet 6 longitudinally of the diaper has been set to 10 to 80mm will be explanined. A contraction percentage of the elastic member 5 is significantly influenced by said longitudinal rigidity in the side flap 4, particularly in the third sheet 6 which overlies the side flap 4 and, when the tensile strength of the elasitc member 5 is set to 70 to 700g in -9- L- L 1 II consideration of appropriate pressure to be exerted around the wearer's leg, the contraction percentage of the elastic member 5 adhesively sandwiched between the third sheet 6 and the backsheet 2 having said rigidity of 60mm or less optimally increases as indicated by an experimental result of an Example as will be described later so that the elastic member effectively accommodates movement of the wearer's leg and substantially no gap is developed between the region of the side flap 4 carrying the elastic member 5 and the wearer's leg, thus effectively preventing a quantity of body fluids from leakage.

When said rigidity of the third sheet 6 is higher than the contraction percentage of the elastic member adhesively sandwiched between the third sheet 6 and the o backsheet 2 would be as small as in the conventional diaper.

When said rigidity is lower than 10mm, on the contrary, said contraction percentage would certainly increase but the sheet material having said rigidity would exhibit a significantly low strength, and a basic weight of said sheet material would be too low to be agreeable to the touch, if said sheet material is fibrous nature.

(Example) A diaper construction (comparison) The diaper comprised a topsheet, a backsheet, a core sandwiched between said two sheets and elastic members disposed in respective side flaps consisting of said two sheets and extending from opposite outer side edges of said core.

Details of the respective members were following: Topsheet a nonwoven fabric consisting of top and bottom layers melt-bonded together, said top layer having a basic weight of 10g/m2 and made of conjugated polyethylene/ polypropyrene fibers and said bottom layer having a basic weight of 20g/m 2 and made of conjugated polyester/polyethylene fibers. Having a longitudinal rigidity of 140mm and a transverse rigidity of as measured by the Clark rigidity o tester according to JIS(P8143).

s Core fluffy pulp formed in a mat-like piece, oofO; having a rigidity of 10 5g cm as o 8 measured by the taber tester.

Backsheet a polyethylene film having a rigidity of both in longitudinal and transverse directions as measured by said Clark rigidity tester.

Elastic member a urethane film having a tensile strength of 250g. Mounted at a condition stretched twice as long as its original condition (150mm long and 20mm wide).

-11 It should be noted that said elastic member is bonded to said topsheet and said backsheet respectively by four lines of hot-melt adhesive applied on the top and bottom surface thereof, and the inner side edge of said elastic me,,ber is spaced from the outer side edge of said core.

A diaper construction (present invention) The diaper was constructed as has been described in reference with Fig. 2B.

4o #4 As the third sheet, a polypropyrene span-bonded nonwoven e0 fabric was used, which has a basic weight of 20g/m 2 a 0 0longitudinal rigidity of 50mm and a transverse rigidity of o 40mm as measured by said Clark rigidity tester. The other details were same as in said Experimental result on the contraction percentage of the elastic member oo~o Opposite ends of the respective side flaps on the 0 opposite extensions of said elastic members respectively ru mounted in diapers constructed according to said and (2) were gripped by hands and the side flaps were stretched until gathers which had been formed by the respective side flaps disappeared. Length of each elastic member after the hold on the opposite ends of the side flap had been loosed and the elastic member had contracted again from said stretched condition twice the original length of 150mm) was measured. Then, ratio of the length in the -12-

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contracted condition of each elastic member to its stretched length (150mm) was determined. The diaper of said (1) exhibited a contraction percentage of 40% and the diaper of said exhibited a contraction percentage of 13

Claims (4)

1. A disposable diaper including a liquid-permeable topsheet, a liquid-impermeable backsheet, a liquid-absorbent core sandwiched between these twc sheets, and side flaps extending laterally from opposite side edges of said core and provided with associated elastic members, wherein each of said side flaps is disposed outside said topsheet and includes a third sheet forming at least a part of said side flap; wherein said third sheet has a rigidity longitudinally of the diaper lower than that of said topsheet; and wherein said elastic member is adhered at least to said third sheet.

2. The disposable diaper according to claim 1, wherein said topsheet has a rigidity of 90mm or higher; said 15 backsheet has a rigidity lower than 60mm; said third sheet 0 0 has a rigidity of 10 to 80mm; and said elastic member has a tensile strength of 70 to 700gf. e0,4

3. The disposable diaper according to claim 1 or claim 2, wherein said third sheet has a water pressure 20 resistance of 20mm or higher and is of air-permeable nature.

4. The disposable diaper according to claim 1, substantially as herein described with reference to any one of the embodiments of the accompanying drawings. 2 DATED: 14 August, 1991 PHILLIPS ORMONDE FITZPATRICK Attorneys For: UNI-CHARM CORPORATION 0745Z 4R~ -4