Disposable diaper

Abstract: A disposable diaper includes an absorbent unit 8 and a breathable sweat-absorbent sheet 9. An end flap 13 formed in a rear waist region 3 of the absorbent unit B is arranged to be breathable and the breathable sweat-absorbent sheet 9 is bonded to the inner surface of the end flap 13. The diaper thus constructed improves breathability and sweat absorbability in the waist region of the absorbent unit.

Description: This invention relates to a disposable diaper adapted to absorb and contain body wastes, known, for instance, from US-A-5 019 066. Such a diaper is usually provided along the end flaps defining the waist band region with the elastic members so that contraction of these elastic members may function to press the diaper against a wearer's skin and thereby to prevent the diaper from getting out of its shape or from slipping down during use of the diaper. Consequently, perspiration occurs along the region of the wearer's skin against which the end flaps are pressed. Such oppression and perspiration give the wearer unpleasant feeling and may cause various skin diseases such as eczema, eruption and heat rash. To overcome this adverse affection of perspiration, it is well known, for example, from Japanese Utility Model Application Disclosure Gazette (Kokai) No. Hei5-41525 to detachably attach a sweat-absorbent sheet of cotton cloth to the inner surface of the rear waist region. The Japanese Utility Model Application Disclosure Gazette (Kokai) No. Hei5-41525 certainly discloses an idea of providing the rear waist band region with the sweat-absorbent sheet of cotton cloth. However, it is difficult for such a diaper to avoid the unpleasant feeling and skin diseases merely by providing the sweat-absorbent sheet because the inventors have found that the waist band region of the diaper should be sweat-absorbable and, at the same time, sufficiently breathable to avoid the problems. It is an object of this invention to compose at least one of the end flaps in the front and rear waist regions defining the waist band region in such a manner that the end flap may have not only a ventilating function but also a sweat-absorbing function. According to this invention, there is provided a disposable diaper having a front waist region, a rear waist region and a crotch region, the diaper comprising an absorbent unit comprising a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent core disposed between said topsheet and said backsheet, and, in said front and rear waist regions, a pair of end flaps extending outward beyond longitudinally opposite ends of said absorbent core; at least one of said end flaps in said front and rear waist regions including a region defined between a longitudinal end of said at least one end flap and a longitudinal end of said absorbent core opposed to said longitudinal end of said at least one end flap, said at least one end flap being provided on an inner surface thereof with a breathable and sweat-absorbent sheet bonded thereto so as to cover said topsheet in said region; characterised in that said backsheet includes a breathable outer layer and a liquid-impervious inner layer laminated to an inner surface of said breathable outer layer, and in that said region is formed by a portion of said outer layer that extends outward beyond a longitudinal end of said liquid-impervious inner layer, a portion of said topsheet that extends outward beyond said longitudinal end of said absorbent core and said breathable and sweat-absorbent sheet. This invention includes alternative embodiments wherein the breathable sweat-absorbent sheet contains hydrophilic fibers of at least 20% by weight; wherein the breathable sweat-absorbent sheet comprises a laminate of an upper layer containing hydrophilic fibers of at least 20% by weight and intended to come in contact with a wearer's skin and a lower layer formed by hydrophilic fibers and intended not to come in contact with the wearer's skin; wherein the breathable sweat-absorbent sheet has a plurality of pores each having a diameter of 0.1 - 3 mm; wherein the breathable sweat-absorbent sheet is bonded to the end flap intermittently at least in a circumferential direction of the diaper; the end flap having the breathable sweat-absorbent sheet bonded thereto is provided with elastic members adapted to be stretchable and contractable in the circumferential direction of the diaper; and the outer layer of the backsheet is formed by a nonwoven fabric and the inner layer of the backsheet is formed by a plastic film. Fig. 1 is a perspective view of a pull-on disposable diaper as a specific embodiment of this invention; Fig. 2 is a plan view showing the partially cutaway and developed diaper; Fig. 3 is a sectional view showing, in an enlarged scale, a rear waist region and its vicinity; Fig. 4 is a view similar to Fig. 3 showing a rear waist region and its vicinity according to an embodiment differing from the embodiment shown in Fig. 3; Fig. 5 is a sectional view showing an embodiment of a breathable sweat-absorbent sheet; and Fig. 6 is a view similar to Fig. 5 showing another embodiment of the breathable sweat-absorbent sheet. Details of this invention will be more fully understood from the description of a disposable pull-on diaper as a specific embodiment of this invention given hereunder with reference to the accompanying drawings. Referring to Fig. 1, a diaper is bilaterally configured about a center line 1 extending in its longitudinal direction and has a front waist region 2, a rear waist region 3 and a crotch region 4. The front and rear waist regions 2, 3 are bonded to each other intermittently along their transversely opposite side edges 5, 5 to define an elastic waist-opening 6 and a pair of elastic leg-openings 7, 7. Referring to Figs. 2 and 3, the diaper comprises of an absorbent unit 8 and a breathable sweat-absorbent sheet 9. The absorbent unit 8 comprises a liquid-pervious topsheet 10, a liquid-impervious backsheet 11 and a liquid-absorbent core 12 disposed between these two sheets 10, 11. The backsheet 11 comprises, in turn, a breathable outer layer 11a and a liquid-impervious inner layer 11b integrally laminated on the inner surface of the breathable outer layer 11a by suitable means (not shown) such as the well known sealing technique or use of adhesive. The topsheet 10 and the backsheet 11 extending outward beyond a peripheral edge of the absorbent core 12 and these extensions of the sheets 10, 11 cooperate with each other to form longitudinally opposite end flaps 13 serving as waist-band regions for the front and rear waist regions, respectively, and transversely opposite side flaps 19 (See Fig. 1). It should be understood that the end flaps 13 substantially comprise the outer layer 11a of the backsheet 11 and the topsheet 10 because the extension of the inner layer 11b of the backsheet 11 beyond the peripheral edge of the absorbent core 12 is extremely small. Along the end flap 13 in the rear waist region, the breathable sweat-absorbent sheet 9 extends circumferentially of the diaper. The sweat-absorbent sheet 9 is bonded to the upper surface of the topsheet 10 utilizing the well known bonding means 14 such as hot melt adhesive, heat-emboss/deboss or heat-sealing intermittently in the circumferential direction as well as in the longitudinal direction of the diaper. The outer layer 11a of the backsheet 11 as one component of the end flap 13 has a longitudinal dimension larger than that of the topsheet 10 and is folded back onto and bonded to the topsheet 10 by the means (not shown) similar to those as have been described above. Between an extension 11c of the outer layer 11a and an extension 10a of the topsheet 10 forming together the end flap 13, a plurality of elastic members 15 adapted to be stretchable and contractable circumferentially of the diaper are bonded to the extensions 11c, 10a by hot melt adhesive of well known art (not shown). The embodiment shown in Fig. 4 is similar to the embodiment shown in Fig. 3 except that a breathable sweat-absorbent sheet 29 is wider than the breathable sweat-absorbent sheet 9 and bonded to substantially the entire inner surface of the end flap 13 including a portion of the extension 11c of the outer layer 11a making a part of the backsheet 11 which has been folded back onto the topsheet 10. Without departing from the scope of this invention, the embodiments shown in Figs. 3 and 4 may be modified so that not only the inner layer 11b of the backsheet 11 but also the topsheet 10 extend slightly into the region defined by the end flap 13 and the breathable sweat-absorbent sheet 9, 29 is directly bonded to the extension 11c of the outer sheet 11a making a part of the backsheet 11 substantially over the entire region the sheet 9, 29. Referring to Figs. 5 and 6, the breathable sweat-absorbent sheet 9, 29 preferably comprises an upper layer 9a, 29a containing hydrophilic fibers at least of 20% by weight and a lower layer 9b, 29b of hydrophobic fibers laminated integrally with the upper layer 9a, 29a taking account of desired breathability, sweat-absorbability and cushioning property. Alternatively, the breathable sweat-absorbent sheet 9, 29 may be formed by a single layer containing hydrophilic fibers of at least 20% by weight. The hydrophilic fibers useful for this purpose includes cellulose fibers such as rayon and sweat-absorbent polyester fibers or the like having a fiber surface subjected to any hydrophiling treatment. The fiber other than the hydrophilic fiber, i.e., the hydrophobic fibers useful for this purpose includes polypropylene, polyester, and crimped or not crimped polyethylene/polyester conjugated fibers. The breathable sweat-absorbent sheet 9, 29 may be provided in optional forms, for example, in the form of a spun lace, needle punched, thermal bond, spun bond, melt blown or chemical bond nonwoven fabric having a basis weight of 10 - 100 g/m 2 and a fineness of 0.1 - 10 d. The breathable sweat-absorbent sheet 9, 29 is preferably formed with a plurality of pores having a diameter of 0.1 - 3 mm in order to improve its breathability. While Fig. 2 shows the breathable sweat-absorbent sheet 9 as provided only in the rear waist region 3 of the diaper taking account of sweating occurring more significantly in a rear waist region than in a front waist region of a wearer, it is possible to provide the front waist region with the similar breathable sweat-absorbent sheet 9, if desired. This is true for the breathable sweat-absorbent sheet 29. Referring again to Fig. 2, the topsheet 10 and the backsheet 11 in the crotch region 4 are formed along transversely opposite side edges with cutouts 17, 17 intended to define the pair of leg-openings 7, 7 as shown in Fig. 1. Along the cutouts 17, 17, elastic members 18, 18 are respectively bonded by means of well known hot melt (not shown) between the topsheet 10 and the backsheet 11 so that these elastic members 17, 17 extend and are stretchable/contractable circumferentially around the respective legs. The absorbent core 12 is semi-rigid and substantially fixed by means of well known hot melt adhesive between the topsheet 10 and the backsheet 11 in order to ensure that the absorbent core 12 should be protected from getting out of its initial shape. The topsheet 10 and the backsheet 11 have a high flexibility and therefore the end flaps 13 as well as the side flaps 19 also have a relatively high flexibility. Accordingly, soft and good fitness of the diaper can be ensured around the wearer's torso and legs. While both the outer layer 11a and the inner layer 11b of the backsheet 11 are shown to extend beyond the side edges of the absorbent core 12 into the respective side flaps 19, 19 by the same dimension (See Fig. 3), an alternative arrangement is possible, in which the side edges of the inner layer 11b lie inside the side edges of the outer layer 11a. The inner layer 11b is preferably liquid-pervious and moisture-pervious so that, in addition to the breathability offered by the end flaps 13, moisture possibly accumulated within the diaper can be positively exhausted to the exterior of the diaper to avoid undesirable stuffiness. The topsheet 10 is made of a breathable nonwoven fabric, porous plastic film or the like , the outer layer 11a of the backsheet 11 is made of a breathable nonwoven fabric or the like, the inner layer 11b of the backsheet 11 is made of a plastic film or the like and the absorbent core 12 is made of a mixture of fluff pulp and superabsorbable polymer particles covered with an absorbent/diffusive sheet or the like. These stock materials are those usually used for disposable diapers or sanitary napkins. While the breathable sweat-absorbent sheet 9, 29 formed by any one of the above-mentioned materials effectively functions, the breathable sweat-absorbent sheet 9, 29 is preferably formed by an upper layer 9a, 29a and a lower layer 9b, 29b. The upper layer 9a, 29a is formed by a mixture of rayon fibers of 50% by weight and polypropylene fibers of 50% by weight and the lower layer 9b, 29b is formed by a mixture of polypropylene fibers of 80% by weight and core-sheath-type polyethylene/polyester conjugated fibers of 20% by weight. The breathable sweat-absorbent sheet 9, 29 may contain crimped fibers to improve its cushioning property and breathability. The absorbent unit 8 may be realized also in the form of a so-called open type unit. By wearing the diaper according to this invention as has been described heretofore, sweat spreading around the wearer' torso is effectively absorbed by the breathable sweat-absorbent sheet 9, 29 and vapor generated from evaporation of sweat is ventilated out through the outer layer 1a of the backsheet 11 in the regions of the end flaps 13, 13 where the inner layer 11b of the backsheet 11 is absent. Particularly, the unique arrangement such that the breathable sweat-absorbent sheet 9, 29 is intermittently bonded to the end flap 13 cooperates with elastic contraction of the elastic members 15 to generate many spaces between the breathable sweat-absorbent sheet 9, 29 and the extension 11c of the outer layer 11a. As a result, the ventilation through the end flap 13 is further improved and the breathable sweat-absorbent sheet 9, 29 is always maintained in a relatively high dryness. As will be apparent from the foregoing description, the diaper according to this invention has end flaps defining the waist band region adapted to offer a high breathability and at the same time to effectively absorb the wearer's sweat so that the wearer can be protected not only from discomfort due to a stuffiness within the diaper but also against being affected with various skin diseases as have previously been described. These features enable the diaper of this invention to be advantageously used in practice.

Claims: A disposable diaper having a front waist region (2), a rear waist region (3) and a crotch region (4), the diaper comprising an absorbent unit (8) comprising a liquid-pervious topsheet (10), a liquid-impervious backsheet (11) and a liquid-absorbent core (12) disposed between said topsheet and said backsheet, and, in said front and rear waist regions, a pair of end flaps (13) extending outward beyond longitudinally opposite ends of said absorbent core (12); at least one of said end flaps (13) in said front and rear waist regions (2, 3) including a region defined between a longitudinal end of said at least one end flap and a longitudinal end of said absorbent core(12) opposed to said longitudinal end of said at least one end flap (13), said at least one end flap (13) being provided on an inner surface thereof with a breathable and sweat-absorbent sheet (9) bonded thereto so as to cover said topsheet (10) in said region; characterised in that said backsheet includes a breathable outer layer (11a) and a liquid-impervious inner layer (11b) laminated to an inner surface of said breathable outer layer, and in that said region is formed by a portion (11c) of said outer layer (11a) that extends outward beyond a longitudinal end of said liquid-impervious inner layer, a portion (10a) of said topsheet (10) that extends outward beyond said longitudinal end of said absorbent core (12) and said breathable and sweat-absorbent sheet (9). A disposable diaper according to Claim 1, wherein said breathable sweat-absorbent sheet (9) contains hydrophilic fibers of at least 20% by weight. A disposable diaper according to Claim 1, wherein said breathable sweat-absorbent sheet (9) comprises a laminate of an upper layer (9a) containing hydrophilic fibers of at least 20% by weight and intended to come in contact with a wearer's skin and a lower layer (9b) formed by hydrophilic fibers and intended not to come in contact with the wearer's skin. A disposable diaper according to Claim 1, wherein said breathable sweat-absorbent sheet (9) has a plurality of pores (14) each having a diameter of 0.1 - 3 mm. A disposable diaper according to Claim 1, wherein said breathable sweat-absorbent sheet (9) is bonded to said end flap (13) intermittently at least in a circumferential direction of said diaper. A disposable diaper according to Claim 1, wherein said end flap (13) having said breathable sweat-absorbent sheet (9) bonded thereto is provided with elastic members (15) adapted to be stretchable and contractable in said circumferential direction of said diaper. A disposable diaper according to Claim 1, wherein said outer layer (11a) of said backsheet is formed by a nonwoven fabric and said inner layer (11b) of said backsheet is formed by a plastic film.

Inventors: SHIMADA TAKAAKI, SUZUKI SEIJI, SHIMADA, TAKAAKI, SUZUKI, SEIJI
Applicants: UNI CHARM CORP, UNI-CHARM CORPORATION
Application year: 1999
Main classification: A61F13
IPC codes: A61F13