Sanitary napkin

Abstract: A sanitary napkin (1) comprises a pair of grooves (5) being formed in a top surface (2) of the napkin (1) by compression-molding along transversely opposite sides of the napkin (1). Each of these grooves (5) has lower and higher density compressed zones (8,9) arranged on the bottom (5A) thereof alternately in a longitudinal direction thereof.

Description: The present invention relates generally to a sanitary napkin and more particularly to a female sanitary napkin or pad to absorb and retain body exudates such as menses. Japanese Utility Model Application Publication No. Hei5-39691 and also EP-A-267059 each discloses a sanitary napkin formed on an upper surface thereof along transversely opposite sides thereof with a pair of longitudinally extending compression-molded grooves spaced from each other by a distance gradually increasing from the minimum at longitudinally middle points thereof to the maximum at longitudinally opposite ends thereof. Such grooves provide enhanced fit of the napkin against the wearer's private parts. In addition, the presence of such grooves is effective to prevent a twist possibly occurring in a central region of the napkin, when it is worn on the wearer's body, from extending to the transversely opposite side edges of the napkin. In this way, it is possible to avoid a problem that a quantity of body exudates might flow along the twist to the side edges of the napkin and cause sideway leakage onto the wearer's undergarments. EP-A-0291316 discloses an absorbent pad having a densification pattern to improve liquid distribution comprising relatively low density tuft regions which are separated and surrounded by channels. The channels comprise storage regions and transport regions wherein one of the storage or transport regions surround the other of the storage or transport regions. The density of the transport regions is higher than that of the storage regions, which have a higher density than the tuft regions. However, in a liquid-absorbent core incorporated in the napkin, the compression-molded grooves have a density substantially higher than the density in the central region of the napkin and the quantity of body exudates once having flowed into the grooves tend to spread too rapidly along their lengths. In view of the fact that the grooves are usually formed adjacent the transversely opposite side edges of the liquid-absorbent core, such rapid spread of body exudates stains the side edges of the napkin, and therefore the wearer's undergarments being in contact with the stained side edges of the napkin are also stained more often than in a napkin without such grooves. Accordingly, it is a principal object of the invention to suppress spread of body exudates along the grooves formed in a sanitary napkin as well as avoiding undesirable sideways leakage while the advantageous effect of such grooves is maintained. According to the invention, there is provided a sanitary napkin comprising the features of the claim. The invention will be described in more detail by way of example with reference to the accompanying drawings, in which:- Fig. 1 is a perspective view, partially broken away, showing an embodiment of the inventive sanitary napkin; Fig. 2 is a fragmentary plan view showing the sanitary napkin in partially enlarged scale; and Fig. 3 is a sectional view taken along a line III-III in Fig. 1. A sanitary napkin 1 shown by Fig. 1 in a perspective view as partially broken away comprises a liquid-permeable topsheet 2, a liquid-impermeable backsheet 3 and a liquid-absorbent core 4. The topsheet 2 and the backsheet 3 are placed one upon another with inner surfaces opposed to each other and water-tightly bonded together over portions extending outward beyond a peripheral edge of the core 4. The napkin 1 is formed on an upper surface thereof with a pair of compression-molded grooves 5 longitudinally extending along transversely opposite sides thereof, respectively. At a longitudinally middle region of the napkin 1, these compression-molded grooves 5 are spaced apart from each other by the minimum distance and this distance is progressively enlarged toward longitudinally opposite ends of the napkin 1. The grooves 5 effectively serve to provide enhanced fit of the napkin 1 against the wearer's private parts. Figs. 2 and 3 are respectively a plan view showing a fragment of Fig. 1 in enlarged scale and a sectional view taken along line III-III in Fig. 1. As shown, a bottom 5A of each groove 5 comprises a plurality of lower density compressed zones 8 each having a thickness (height) B and a plurality of higher density compressed zones 9 each having a thickness (height) C wherein these zones 8, 9 alternate longitudinally of the groove 5. The groove 5 has an upper opening 5B of a width larger than that of the bottom 5A and upper opening edges 5C describing circular arcs. Both the lower density compressed zones 8 and the higher density compressed zones 9 extend transversely across the bottom 5A, more specifically, obliquely of a longitudinal axis x of the napkin 1 (as seen in Figs. 1 and 2). The respective zones 8, 9 thus transversely extending across the bottom 5A are narrower than the bottom 5A. The groove 5 is compression-molded to produce a dimensional relationship of B = 0.7 to 0.2 X A, C = 0.5 to 0.05 X A and B > C, where A represents a thickness of the napkin 1 at the non-compressed region, and preferably the higher density compressed zone 9 presents a density of 0.1g/cm 3 or higher while the lower density compressed zone 8 presents a density lower than that in the higher density compressed zone 9. Preferably, the groove 5 has a length corresponding to 1/2 to 4/5 of the full length of the core 4 and a width of 1 to 5mm. Both the lower density compressed zone 8 and the higher density compressed zone 9 preferably have a width of 0.8 to 4mm as measured longitudinally of the groove 5. It will be understood that the portions of the core 4 extending respectively along and adjacent inner and outer side walls 5D 1 , 5D 2 defining the groove 5 are also more or less influenced by compression-molding of the groove 5 and, as a result, have a density lower than the densities of the compressed zones 8, 9 but higher than the density of the other regions which were not subjected to any compressive force at all. Referring to Fig. 3, a portion of an upper opening edge 5C continuous with the inner side wall 5D 1 describes a circular arc which is more gentle, i.e. longer than a circular arc described by a portion of the other upper opening edge 5C continuous with the outer side wall 5D 2 , and therefore the portion of the core 4 lying under the former is compressed over a larger extent and at a higher density compared to the portion of the core 4 lying under the latter. Accordingly, a quantity of body exudates flowing into the groove 5 tends to be predominantly absorbed by this groove 5 and to spread thereinto on the inner side wall 5D 1 , so the quantity of body exudates will not spread through the outer side wall 5D 2 toward the outer side edges of the napkin causing undesirable sideway leakage. As will be readily understood from such effect, the groove 5 is compression-molded so that the portion of the core 4 lying on the inner side wall 5D 1 presents a density higher than in the portion of the core 4 lying on the outer side wall 5D 2 . Such configuration of the groove 5 can be obtained by compressing the napkin 1 in an appropriate mold under a high pressure and can be stabilized by, for example, immersing the region of the napkin 1 to be compressed with a small quantity of water or disposing hot melt adhesive between the topsheet 2 and the core 4 followed by compression under heating. With the napkin 1 constructed as described above, body exudates rapidly spread from the higher density compressed zones 9 as soon as the body exudates are discharged and flow into the grooves 5 in directions as indicated by arrows P, Q in Fig. 1. The surroundings of the zones 9, on the other hand, are of relatively lower density, so the quantity of body exudates once having been absorbed by the zones 9 hardly spreads into the surroundings. In this manner, the inventive napkin 1 allows body exudates once having flowed into the grooves 5 to be prevented not only from rapidly spreading longitudinally thereof but also from spreading outward toward the transversely opposite side edges of the napkin 1. To implement the invention, the core 4 may be made of fluff pulp mixed with superabsorptive polymer powder and/or thermoplastic synthetic fiber. Assuming that the groove 5 is compression-molded under heating, the thermoplastic synthetic fiber can serve to stabilize the resultant configuration of the groove 5. Preferably, the topsheet 2 is made of nonwoven fabric or perforated plastic film and the backsheet 3 is made of plastic film. Bonding of the respective components to form the napkin 1 may be achieved by using suitable adhesive agent, e.g. of hot melt type or so-called heat-sealing technique so far as the components to be bonded together are of a heat-sealable nature. It should be noted that no specific means of bonding is illustrated. The inventive sanitary napkin has a pair of grooves formed on the top surface thereof so as to extend respectively along the transversely opposite sides thereof and these grooves not only provide enhanced fit of the napkin against the wearer's private parts but also practically prevent a twist possibly occurring in the middle region of the napkin from reaching the peripheral region of the napkin. On the bottom of each groove, there are arranged the relatively high density compressed zones and the relatively low density compressed zones alternately in the longitudinal direction of the bottom. This feature serves to suppress a phenomenon that the quantity of body exudates once having flowed into the grooves might too rapidly spread longitudinally of the grooves and thereby to prevent the transversely opposite side edges of the napkin as well as the wearer's undergarments contacted by these side edges from being stained with any quantity of body exudates. The groove is formed by compression-molding but presents an upper opening edge describing a circular arc in cross-section which makes the wearer's private parts free from uncomfortable irritation and allows body exudates to flow smoothly into the groove. The napkin of such type is generally folded at a right angle to the longitudinal direction thereof for individually packaging, resulting in generation of many fine transverse wrinkles in the proximity of the fold. The fine transverse wrinkles may cause sideway leakage of body exudates. However, it has been found that the invention can alleviate generation of the fine transverse wrinkles compared to the case in which there are provided neither the grooves nor their bottoms comprising the higher and lower density compressed zones arranged alternately in the longitudinal direction of the grooves, depending on factors such as the particular material of the topsheet. The portion of the core lying along the inner side wall coextensive with the outer side wall to define each of the grooves has a density higher than in the portion of the core lying along the outer side wall, so body exudates are predominantly absorbed by and spread into the portion of the core lying along the inner side wall and thus sideway leakage of body exudates are effectively avoided.

Claims: A sanitary napkin (1) comprising a liquid-permeable topsheet (2), a liquid-impermeable backsheet (3) and a liquid-absorbent core (4) disposed therebetween and having a pair of grooves (5) formed by compression-molding in a top surface of an absorbing region defined by the presence of said core (4), wherein said grooves (5) longitudinally extend along transversely opposite sides of said absorbing region and said grooves (5) are spaced apart from each other by a distance gradually increasing from the minimum at longitudinally middle points thereof to the maximum at longitudinally opposite ends thereof, said sanitary napkin being characterized in that : each of said grooves (5) is defined by inner and outer side walls (5D 1 , 5D 2 ) and has higher and lower density compressed zones (9,8) on the bottom (5A) thereof alternately arranged in a longitudinal direction thereof, each of said higher and lower density compressed zones (9, 8) extending transversely across the bottom (5A) continuously from said inner side wall (5D 1 ) to said outer side wall (5D 2 ), said higher and lower density compressed zones also extending parallel to each other and obliquely to a longitudinal axis (X) of said napkin (1), and said lower density compressed zone (B) has a vertical dimension (B) larger than the corresponding dimension (C) of said higher density compressed zone (9) as measured from said bottom (5A); wherein said groove (5) has a width at an upper opening (5B) thereof larger than a width at the bottom (5A) thereof and an edge (5C) of said upper opening (5B) describes a circular arc in cross-section, wherein said vertical dimension (B) of said lower density compressed zone (8) is 0.7 to 0.2 times a thickness (A) of the non-compressed region of the sanitary napkin (1) in a location where said edge (5c) continuous with said inner side wall (5D 1 ) terminates inward along the transverse direction in the middle of said sanitary napkin (1) and said corresponding dimension (C) of said higher density compressed zone (9) is 0.5 to 0.05 times said thickness (A) and a portion of said core (4) lying along said inner side wall (5D 1 ) has a density higher than the density in a portion of said core (4) lying along said outer side wall (5D 2 ) and a portion of said upper opening edge (5c) continuous with the inner side wall (5D 1 ) describes a circular arc more gentle than a circular arc described by a portion of the upper opening edge continuous with the outer side wall (5D 2 ).

Inventors: HISADA KENICHI, MIZUTANI SATOSHI, HISADA, KENICHI, MIZUTANI, SATOSHI
Applicants: UNI CHARM CORP, UNI-CHARM CORPORATION
Application year: 1996
Main classification: A61F13
IPC codes: A61F13