Sanitary napkin

Abstract: A sanitary napkin comprises a liquid-permeable surface material, a liquid-impermeable leakproof material and an absorber inserted between said surface material and said leakproof material, said absorber comprising a first absorbent paper, a second absorbent paper and an absorbent material inserted beween both papers, said first absorbent paper covering at least a part of said second absorbent paper, said first absorbent paper being fixed at the portion thereof covering the second absorbent paper onto said leakproof material.

Description: The present device relates to a sanitary napkin for use in menstruation. A purpose of the invention and device is to provide a sanitary napkin which exhibits an improvement of shape-retentivity, in the production thereof without scattering the materials constituting its absorber and is excellent in absorbency. Figures 5 to 7 are transverse cross-sectional views of the napkin according to the prior art. 1 - surface material 2, 2' - absorbent paper 21 - first absorbent paper 22 - second absorbent paper 3 - leakproof material 4 - cottony pulp 5 - polymeric absorbent material 6 - cottony staple 7 - shift-inhibiting material 8 - bonded area Figure 8 is a transverse cross-sectional view of an example of a sanitary napkin according to the present device. Figure 9 shows another example of a sanitary napkin according to the present device, wherein (a) is a plan view thereof and (b) is a cross-sectional view thereof taken along the line X-X'. Figure 10 is a transverse cross-sectional view of another example of a sanitary napkin according to the present device. Figure 11 is a perspective view of the form after the application to the crotch of the sanitary napkin according to the prior art. 31 - first absorber 32 - second absorber 33 - bonding between the first absorber and the second absorber 34 - leakproof material 35 - surface material 36, 36' - bonding between the surface material and the leakproof material 37 - bonding between the leakproof material and the first absorber 38 - pressure-sensitive adhesive tape 39 - flap 40, 40' - absorbent paper 41 - cottony pulp 42 - highly absorbent polymer 43 - rayon staple cotton. PRIOR ART An ordinary napkin comprises an absorber made of absorbent paper and/or fluff pulp, called also cottony pulp, a liquid-impermeable leakproof material covering the bottom and bottom sides of the absorber, a liquid-permeable surface material covering the whole of the absorber covered with the leakproof material and a shift-inhibiting tape attached on the non-use surface, as shown, for example, in Figure 5 wherein numeral 1 is surface material, numeral 2 is absorbent paper, numeral 3 is leakproof material and numeral 7 is shift-inhibiting tape. Recently, a polymeric absorbent material has been frequently used as a component constituting the absorber of a sanitary napkin for the purpose of enhancing the absorption capacity of the napkin, as shown, for example, in Figures 6 and 7 wherein numeral 2' is absorbent paper for piling cottony pulp, numeral 4 is cottony pulp, numeral 5 is polymeric absorbent material and numeral 6 is cottony staple. Although a sanitary napkin containing a polymeric absorbent material as described above has been generally thought to exhibit an enhanced absorption capacity, the following problems have not been solved as yet. For example, with respect to the napkin shown in Figure 6, a polymeric absorbent material 5 is present at a position near the non-use surface. Therefore, when the amount of menstrual blood is small, the blood is absorbed and kept by only the cottony pulp 4 or the absorbent paper 2', which is an ordinary absorbent material according to the prior art, so that the blood does not reach the polymeric absorbent material 5 to result in an ineffective use of the polymeric absorbent material 5. Further, when the cottony pulp 4 and the absorbent paper 2' are piled to produce an absorber, these constituent members each tend to shift and the cottony pulp tends to scatter from the edge thereof. The scattering cottony pulp adheres to some area of the processing line or falls down to give a product contaminated therewith which is unfavourable for sanitary reasons. On the other hand, the napkin shown in Figure 7 contains an absorber produced by spraying a cottony pulp 4 with a polymeric absorbent material 5 and folding the resulting pulp at both ends into an "e"-shape. In this napkin, the shifting of the constituent members caused in the production of the absorber is remarkably reduced as compared with that of the napkin shown in Figure 6. However, the scattering of cottony pulp still occurs from the area b, and thus the problem cannot be solved completely. The napkin shown in Figure 7 exhibits absorbency more excellent than that of the one shown in Figure 6, because the relative position of the polymeric absorbent material 5 to the use surface in the former is nearer than that in the latter. The former is superior to the latter in the effective utilisation of a polymeric absorbent material. Accordingly, when the amount of menstrual blood is small, the napkin shown in Figure 7 exhibits sufficiently excellent absorbency unlike the napkin shown in Figure 6. However, when the amount of menstrual blood is large, the amount of the menstrual blood to be absorbed per unit volume of the absorber exceeds the absorption capacity of the absorber, because the absorber does not contain any material which can diffuse blood, for example, absorbent paper. This problem can be solved to some extent by increasing the content of a polymeric absorbent material or the amount of cottony pulp. However, these means bring about enhancement in cost and increase in thickness to lower the feeling in service, so that they are not substantially effective solution. In other words, the napkin shown in Figure 7 has a disadvantage in that not the whole thereof can be utilised. However, the devisers of the present device think that such a napkin will still exhibit insufficient absorption characteristics, particularly poor proofness against side leakage, even if a highly absorbent polymer functions effectively. That is because a sanitary napkin is significantly deformed by pressure brought about by the application thereof to the crotch to cause side leakage. That is to say, when a sanitary napkin is applied to the crotch, it is in a deformed (twisted) state as shown in Figure 11, so that most of the leakage occurs from the sides in the central part of the longitudinal direction. More precisely, when pressure due to the closing of feet or walking is applied to a wet sanitary napkin containing absorbed blood therein, the napkin is twisted in the central part of the longitudinal direction, so that the distance between both sides and the blood-absorbing area (the central part of the width direction, when the napkin is accurately worn) is reduced to cause leakage, though there are still parts wherein no blood is absorbed. GB-A-2151488 discloses sanitary towels comprising multiple layers of absorbent material comprising a primary absorbent paper, a mixture of a fluffy pulp and super-absorbent polymer, and a second absorbent paper, the secondary absorbent paper being covered at least partly by the primary absorbent paper. US 4540414 discloses the use of a non-woven polypropylene fabric having the fibres on one side fused and on the opposite side unfused, as in diapers, wrist bands and bandages. The fabric is used in conjunction with an absorbent layer to transfer moisture to the absorbing layer. SUMMARY OF THE INVENTION In view of the above problems, the devisers of the present device have extensively studied on the constitution of a sanitary napkin which is protected from deformation and twisting in service without lowering the feeling and exhibits effectively reduced side leakage by enhancing the fitness of the napkin to the crotch and the pubic region and have accomplished the present device. The inventor provides a sanitary napkin which comprises a liquid-permeable surface material 35 and an absorber assembly between the surface material 35 and the leakproof material 34, the absorber assembly comprising juxtaposed first and second absorbers 31, 32 respectively, fixing means being provided between the first absorber 31 and the second absorber 32 and between the leakproof material 34 and the first or the second absorber 32, the surface material 35 covering a part of the leakproof material 34, characterised in that the first absorber 31 extends bilaterally beyond the second absorber 32 to provide laterally-extending flaps 39 and the leakproof material 34 covers at least the bottom surface, both side surfaces and a part of the top surface of the first absorber and extends to cover a part of the side surfaces of the second absorber 32. Figure 8 is a transverse cross-sectional view of an example showing the constituent members of the sanitary napkin according to the present device. The constituent members can be arranged as follows: (1) The absorber comprises the first absorber 31 as lower layer and the second absorber 32 having a width smaller than that of the first absorber 31 present on the first absorber 31 nearly in the centre of the first absorber. (2) The first absorber 31 is fixed to the second absorber 32 by some means, so that they are unified by a bonding 33 which spreads over at least a part of the interfacial boundary. (3) The bottom, the sides and a part of the top surface of the first absorber 31 and a part of the sides of the second absorber are covered with a leakproof material 34 and at least a part of the leakproof material and the top surface of the second absorber are covered with surface material 35. Thus, a flap 39 is formed. (4) In the flap 39, the surface material 35 is fixed to the leakproof material 34 by some means to form a bonding 36 and the leakproof material 34 is fixed to the first absorber by some means to form a bonding 37. The both bondings may each spread over at least a part of the interfacial boundary. (5) The sanitary napkin is provided with a shift-inhibiting material 38 on the non-use surface and a part of the material 38 reaches the leakproof material 34 through the surface material 35 to form the bonding 36' between the surface material and the leakproof material. The constituent members will be each described below together with effect thereof. Examples of the material constituting the first absorber 31 and the second absorber 32 include ordinary absorbent materials such as cottony pulp, absorbent paper and highly absorbent polymer and synthetic fibres such as polyethylene, polypropylene, polyester, acrylic polymer and hot-melt fibre as typified by ES fibre. These materials can be used alone or as a combination thereof and neither the construction nor the mixing method are linked. The first absorber and the second absorber are unified by a bonding 33, so that they cannot be separated from each other even by pressure brought about by the application of the napkin to the crotch, thus serving to protect the napkin from deformation and twisting. The difference in width between the first absorber and the second absorber is preferably at least 10 mm, most preferably about 30 mm. It is generally effective that the second absorber has a width of 30 to 70 mm. However, the width varies depending upon the object of the application. For example, it is suitable that the width of the second absorber of the napkin of ordinary type is 40 to 50 mm and the width of the one for the treatment of light bleeding is 30 to 45 mm, while the width of the one for long application or night is 50 to 70 mm. It has been confirmed that the napkin exhibits excellent fitness to the crotch and less deformation even under vivid motion, when the first absorber thereof has a width of 70 to 85 mm and the second absorber thereof has a width of 40 to 55 mm. The bonding 36 of the surface material 35 to the leakproof material 34 and the bonding 37 of the leakproof material 34 to the first absorber 31 may be formed in the flap 39 by either heat sealing or hot melt process. The bonding 36 is preferably present at a distance of 2 to 10 mm, most preferably 3 to 5 mm, from the end of the second absorber 32. If the bonding 36 is too near the second absorber, the absorber will be influenced by the formation of the bonding to lower the absorbency, touch and appearance. On the contrary, if the bonding 36 is too far from the second absorber, the space between the surface material and the absorber will hinder rapid transfer of the menstrual blood from the surface material to the absorber to unfavourably cause side leakage. It is preferred that the bonding 37 is present at a distance of at least 3 mm, preferably about 5 mm, from the end of the leakproof material. When it is present at a distance of about 5 mm from the leakproof material, the menstrual blood which has been absorbed and reached the end of the second absorber can be effectively prevented from diffusing or spreading in the transverse direction to be introduced into the end of the first absorber 31. It is preferred that the material to be used for constituting the first absorber has an absorption capacity of at least 7 g/g (at least 7 g per gram of the material) and an absolute absorption capacity of at least 3 g (one side). The leakproof material 34 to be used in the present device may be not only an ordinary polyaminated waterproof paper obtained by laminating polyethylene or the like on one surface of a waterproof paper, but also laminated waterproof paper obtained by laminating a resin having a relatively low melting point of 150°C or below on one surface of a waterproof paper or by double-laminating two resins on the both surfaces. Further, it is preferable in the napkin according to the present device that the shift-inhibiting pressure-sensitive adhesive 38, which is present on the non-use surface and is a pressure-sensitive adhesive tape or a hot melt, reaches the back surface of the leakproof material through the surface material. In this case, the surface material 35 is fixed to the leakproof material 34 by the bonding 36' under the back surface of the first absorber 31. The bond strength of the bonding 36' is preferably enough to stand loading of at least 30 g as a whole of the napkin. As described above, the sanitary napkin according to the present device is characterised in that it is essentially constituted by a main absorber (second absorber) which has a small width and therefore is fit to the crotch and a flap-forming absorber (first absorber) and that the fixation of the first absorber to the second absorber, that of the surface material to the leakproof material and that of the leakproof material to the first and second absorber is to tight as not to undergo separation thereof from each other. Accordingly, the deformation and twisting of the sanitary napkin according to the present device is lighter than those of the one according to the prior art wherein the constituent members are partially fixed to each other or not unified, so that the members must each alone resist the deformation. Further, the constitution of the sanitary napkin according to the present device also serves to make the surface material adhere to the absorber to thereby allow rapid transfer of menstrual blood to the absorber. Thus, the sanitary napkin according to the present device exhibits excellent proofness against side leakage and is excellent in fitness without giving feeling as a foreign substance. Example : A sanitary napkin shown in Figure 9 relates to the embodiment of the invention in which the first absorber and the second absorber are used. In the drawing, (a) is a plan view and (b) is a cross-sectional view taken along the line X-X'. In the sanitary napkin shown in Figure 9, the first absorber is made of absorbent paper 40 and the second absorber is made of cottony pulp 41 containing a highly absorbent polymer 42 and the both absorbers are covered with an absorbent paper 40', while the first absorber is fixed to the absorbent paper 40' by a bonding 33. Rayon staple cotton 43 is laid on the above absorbers and the bottom and the sides of the resulting laminate is covered with leakproof material 34 and wrapped in a surface material 35. Further, the non-use surface is provided with a pressure-sensitive adhesive tape 38. The surface material 35 is fixed to the leakproof material 34 by bonding 36, 36', while the leakproof material 34 is fixed to the absorbent paper 40' by a bonding 37. Figure 10 is a transverse cross-sectional view of another example of the napkin according to the present device.

Claims: A sanitary napkin which comprises a liquid-permeable surface material (35) and an absorber assembly between the surface material (35) and the leakproof material (34), the absorber assembly comprising juxtaposed first and second absorbers (31, 32), fixing means being provided between the first absorber (31) and the second absorber (32) and between the leakproof material (34) and the first or the second absorber (32), the surface material (35) covering a part of the leakproof material (34), characterised in that: the first absorber (31) extends bilaterally beyond the second absorber (32) to provide laterally-extending flaps (39) and the leakproof material (34) covers at least the bottom surface, both side surfaces and a part of the top surface of the first absorber and extends to cover a part of the side surfaces of the second absorber (32).

Inventors: SAKURAI AKIRA, SHIROSE TOSHIHIRO, SAKURAI, AKIRA, SHIROSE, TOSHIHIRO
Applicants: KAO CORP, KAO CORPORATION
Application year: 1987
Main classification: A61F13
IPC codes: A61F13