Sheet for absorbent article and absorbent article including same

Abstract

To provide a sheet for an absorbent article capable of suppressing return of permeated liquid to the surface.SOLUTION: A sheet for an absorbent article in an embodiment is a sheet for an absorbent article having a film-like shape memory layer containing a shape memory polymer. The shape memory layer has a principal surface and multiple recesses, and the recesses are recessed from the principal surface, and have an aperture. The area of the aperture is reduced by contact of warm water with the recesses.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sheet for absorbent articles used as a topsheet or the like for absorbent articles such as disposable diapers, sanitary napkins, panty liners (discharge sheets), and urine absorption pads, and to an absorbent article provided with the same. [Background technology]

[0002] As surface sheets for absorbent articles such as disposable diapers and sanitary napkins, those having concave and convex portions formed on the surface that comes into contact with the wearer's skin are known. Furthermore, sheets having perforations formed in the concave portions for the purpose of absorbing liquids are also known.

[0003] For example, Patent Document 1 describes a top sheet of an absorbent article that has liquid-passing channels that have upper and lower openings and are arranged to extend downward, and a skin-contact area that is continuous with the edges of the upper openings of these liquid-passing channels. For example, Patent Document 2 describes a three-dimensional sheet in which a first fiber sheet and a second fiber sheet that are stacked on top of each other are partially heat-fused to form heat-fused portions, the first fiber sheet protrudes in areas other than the heat-fused portions to form numerous convex portions, and the heat-fused portions have openings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-58950 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-175688 Summary of the Invention [Problem to be solved by the invention]

[0005] When the sheets shown in Patent Documents 1 and 2 are used as topsheets for absorbent articles, there is a possibility that liquid that passes through the perforations will return to the skin-facing surface due to the wearer's body pressure, etc. Furthermore, when excreted liquid is repeatedly excreted, the excreted liquid repeatedly passes through some of the perforations near the excretion area, causing it to concentrate in a certain region of the absorbent body. This can cause that certain region of the absorbent body to be unable to retain the liquid, and the overflowing liquid may return to the surface via the perforations, etc.

[0006] The present invention relates to a sheet for absorbent articles that can prevent permeated liquid from returning to the surface, and to an absorbent article including the same. [Means for solving the problem]

[0007] A sheet for absorbent articles according to one embodiment of the present invention is a sheet for absorbent articles that includes a film-like shape-memory layer containing a shape-memory polymer. The shape memory layer has a main surface and a plurality of recesses, The recess is recessed from the main surface and has an opening. The area of the opening decreases as hot water comes into contact with the recess. [Effects of the Invention]

[0008] The absorbent article sheet of the present invention can prevent the permeated liquid from returning to the surface. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of a sheet for absorbent articles according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic plan view of the absorbent article sheet. [Figure 3] 3 is a schematic plan view of the absorbent article sheet, showing a state in which the recesses shown in FIG. 2 are brought into contact with warm water. FIG. [Figure 4] 3A and 3B are diagrams illustrating the shape memory and shape recovery processes in the absorbent article sheet, showing a schematic diagram of each process and the temperature transition thereof. [Figure 5] 1A and 1B are schematic cross-sectional views illustrating the effect of using the above-mentioned absorbent article sheet as a top sheet of an absorbent article, where (A) shows the state when the above-mentioned absorbent article sheet comes into contact with excrement, and (B) shows the state after the excrement has permeated the above-mentioned absorbent article sheet. [Figure 6] This is a schematic cross-sectional view illustrating other effects when the above-mentioned absorbent article sheet is used as a top sheet of an absorbent article, and shows a state in which excreted liquid has penetrated a part of the above-mentioned absorbent article sheet, and then further excreted liquid has been excreted. [Figure 7] FIG. 10 is a schematic plan view of a sheet for absorbent articles according to a modified example of the first embodiment. [Figure 8] 10A to 10C are diagrams illustrating the manufacturing process of the absorbent article sheet, and are schematic cross-sectional views illustrating a step of forming recesses and apertures. [Figure 9] FIG. 3 is a schematic cross-sectional view of a sheet for absorbent articles according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] First Embodiment [Overall structure of absorbent article sheet] 1 and 2 show a sheet 10 for absorbent articles according to a first embodiment of the present invention. The sheet 10 for absorbent articles is a sheet used in absorbent articles, and will be referred to as the sheet 10 hereinafter. The absorbent article is an article capable of absorbing the excrement of a wearer, and may be, for example, a disposable diaper, a sanitary napkin, a panty liner (panty liner), or an incontinence pad. The sheet 10 is preferably a sheet that is placed closer to the skin than the absorbent core of the absorbent article. The sheet 10 shown in Figures 1 and 2 is used, for example, as a topsheet of the absorbent article. The excrement refers to the liquid excrement of the wearer, such as urine, menstrual blood, vaginal discharge, and the like. In each drawing, the thickness direction Z indicates the thickness direction of the sheet 10, and the first planar direction X and the second planar direction Y indicate directions that are perpendicular to the thickness direction Z and intersect with each other. In the illustrated example, the first planar direction X and the second planar direction Y are directions that are perpendicular to each other. The upward direction in the thickness direction Z is the direction toward the skin when the sheet 10 is used in an absorbent article. The downward direction in the thickness direction Z is the direction away from the skin when the sheet 10 is used in an absorbent article. "Planar view" refers to a planar view seen from the thickness direction Z. The "planar shape" refers to the shape in a planar view. "Area" refers to the area in a planar shape.

[0012] In this embodiment, the sheet 10 includes a shape memory layer 11. As will be described in detail later, in the sheet 10 of this embodiment, the area of the openings 15 in the shape memory layer 11 is configured to decrease after the excreted liquid has permeated through, thereby making it possible to prevent the excreted liquid from returning to the surface (liquid return). In the cross-sectional views of FIG. 1 and the like, the shape memory layer 11 is shown by oblique hatching, and this hatching is intended to schematically indicate the range of the shape memory layer 11.

[0013] [Configuration of shape memory layer] The shape memory layer 11 contains a shape memory polymer and is configured in a film form. From the viewpoint of obtaining liquid permeability, the shape memory layer 11 has a main surface 12 and a plurality of recesses 13. The recesses 13 are recessed from the main surface 12 and have openings 15. The shape memory layer 11 is formed by molding a material containing a shape memory polymer into a thin film, and then forming recesses 13 and openings 15. The shape memory layer 11 does not have a fibrous structure, and in the example shown in Figures 1 and 2, it does not have any holes or gaps visible to the naked eye other than the recesses 13 and openings 15. However, the shape memory layer 11 may have fine holes such as ventilation holes that are not visible to the naked eye other than the openings 15. By forming the shape memory layer 11 into a film, the number of steps during manufacturing can be reduced.

[0014] 1, the main surface 12 is a surface located upward in the thickness direction Z, and when used in an absorbent article, can be configured as a skin-facing surface that faces the skin of a wearer. The main surface 12 extends around the recess 13 in a plan view as shown in FIG. The major surface 12 may include a substantially flat portion, as illustrated in FIG. The "substantially flat portion of the main surface 12" refers to the portion of the main surface 12 in which, when the sheet 10 is placed on a flat XY plane without applying external force, the undulations in the thickness direction Z are 25% or less of the entire thickness of the shape memory layer 11.

[0015] The recess 13 is recessed, for example, downward in the thickness direction Z from the main surface 12. This allows the excretory liquid flowing from the main surface 12 side to be guided downward in the thickness direction Z by the recess 13. The part of the recess 13 that is farthest from the main surface 12 in the thickness direction Z, i.e., the part located furthest downward in the thickness direction Z, is defined as the bottom 14. In the recess 13, the opening area in the upper part in the thickness direction Z in a plan view is preferably larger than the opening area in the bottom part 14 in a plan view. This can improve the liquid guideability downward in the thickness direction Z. The planar shape of the recess 13 is not particularly limited and can be determined based on the planar shape of the aperture 15. In the example shown in FIG.

[0016] From the viewpoint of allowing excreted liquid that has flowed into the recess 13 to pass through effectively, the opening 15 is preferably formed in the bottom 14 of the recess 13 as shown in FIG. The planar shape of aperture 15 is not particularly limited and can be appropriately selected from, for example, a circle, an ellipse, an oval, a polygon, similar shapes, and other shapes. As shown in Fig. 2, by making the planar shape of aperture 15 a circle or a similar shape, tearing around the periphery during the formation of aperture 15 can be suppressed, making it easier to form aperture 15 into the desired shape. The planar shapes of the apertures 15 may be the same as shown in FIG. 2, or may be different.

[0017] In this embodiment, the shape memory polymer causes the area of the apertures 15 to decrease upon contact of the warm water with the recesses 13. Figure 3 shows the sheet 10 in which the area of the apertures 15 has decreased after contact of the warm water with the recesses 13. The method for bringing the recesses 13 into contact with the warm water is not particularly limited, but for example, at least a portion of the sheet 10 may be immersed in the warm water. Alternatively, the warm water may be dripped onto the recesses 13. When dripping the warm water onto the recesses 13, it is preferable to drip an amount of warm water that will completely wet at least one recess 13.

[0018] A method for determining the reduction in area of the opening 15 will be described. First, the area of the apertures 15 of the sheet 10 before contact with the hot water, that is, in the state shown in FIG. 2, is calculated. The area of the perforations 15 can be calculated, for example, by placing the sheet 10 on an arbitrary flat surface (XY plane) and analyzing an image of the sheet 10 taken from above in the thickness direction Z. Alternatively, if the perforations 15 are circular, the area can also be calculated by measuring their diameter. The areas of any five or more (e.g., ten) perforations 15 in the sheet 10 are calculated and their average value is calculated. This average value is defined as the "area of the perforations before contact with hot water." Next, after 15 seconds or more have passed since the recesses 13 were brought into contact with the hot water, the area of the openings 15 is calculated in the same manner as before contact with the hot water. The areas of five or more (e.g., ten) openings 15 having the same or similar shape as the openings 15 for which the opening area before contact with the hot water was calculated are calculated, and the average value of these is measured. This average value is defined as the "area of the openings after contact with the hot water." If the area of the opening after contact with hot water is smaller than the area of the opening before contact with hot water, it is determined that the area of the opening 15 has decreased due to contact with hot water.

[0019] In this specification, warm water refers to water at a temperature similar to the body temperature of the wearer, for example, water between 35° C. and 42° C., and preferably between 36° C. and 41° C. As a result, the area of the openings 15 can be reduced by contacting the excretory liquid having a temperature similar to the body temperature of the wearer with the recesses 13. The shape memory polymer of the shape memory layer 11 of this embodiment memorizes an original shape that does not have the recesses 13 and the openings 15, and is shaped under a predetermined temperature condition into a primary shape that has the recesses 13 and the openings 15. The shape memory polymer shaped into the primary shape is configured to return to the original shape when stimulated by warm water.

[0020] Shape memory polymers generally consist of a reversible phase, which becomes fluid above a certain temperature, and a fixed phase, which has a higher melting temperature than the reversible phase. The fixed phase contains physical or chemical bonding sites (crosslinking points) that do not deform at the temperature at which the reversible phase deforms. Hereinafter, the melting temperature of the fixed phase is referred to as the "melting temperature (of the shape memory polymer)," and the melting temperature of the reversible phase is referred to as the "deformation temperature" at which the shape memory polymer softens and becomes deformable. The deformation temperature may be, for example, the glass transition temperature of the shape memory polymer. When a shape memory polymer is heated above its melting temperature, it melts entirely and is molded into its original shape. Then, when the shape memory polymer is cooled and maintained in its original shape, it is molded at a temperature below its melting temperature but above its deformation temperature, where it softens and is molded into a temporary shape. When the shape memory polymer is cooled and maintained in its temporary shape, it is heated to a temperature close to its deformation temperature, where the reversible phase softens again, returning it to a shape close to its original shape.

[0021] In this embodiment, a shape memory polymer having a deformation temperature close to the temperature of the warm water can be selected as the shape memory polymer contained in the shape memory layer 11. Specifically, the deformation temperature of the shape memory polymer contained in the shape memory layer 11 in a moisture-free condition is preferably equal to or slightly higher than the body temperature of the wearer, i.e., 35°C or higher and 47°C or lower, more preferably 35°C or higher and 42°C or lower, and even more preferably 36°C or higher and 41°C or lower. The shape memory layer 11 may contain one type of shape memory polymer having a deformation temperature in the above range, or may contain two or more types of shape memory polymers adjusted to have a deformation temperature in the above range. The shape memory polymer can be appropriately selected based on the deformation temperature within the above range, and preferably contains one or more polymers selected from, for example, polyester resins (see, for example, JP-A-5-279922), polyurethane resins (see, for example, JP-A-2-118178), polytransisoprene resins (see, for example, JP-A-55-93806), polynorbornene resins (see, for example, JP-A-59-53528), and mixtures of vinyl resins and acrylic resins or synthetic rubbers (see, for example, JP-A-63-17952).

[0022] From the viewpoint of fully exerting the shape-recovery effect, shape memory layer 11 preferably contains a shape memory polymer as a main component, but may also contain other polymers and / or additives. From the viewpoint of more reliably reducing the area of openings 15 with warm water, the content of shape memory polymer in shape memory layer 11 is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 100% by mass. In other words, it is more preferable that shape memory layer 11 is made of a shape memory polymer.

[0023] The shape memory and shape recovery processes in the shape memory layer 11 of this embodiment will be described with reference to Figure 4. In Figure 4, the vertical axis indicates temperature, and the order of each process is indicated by arrows. Note that the temperature on the vertical axis is a schematic representation of the temperature levels of each process, and does not reflect the actual temperature differences between each process.

[0024] First, as shown in Fig. 4(A), the raw material of the shape memory layer 11 containing a shape memory polymer is heated to a first temperature T1 higher than the melting temperature Ta of the shape memory polymer to form the original shape sheet 10a. The first temperature T1 is preferably 100°C or higher, more preferably 150°C or higher. To form the original shape sheet 10a, a general resin film forming method can be used, such as extrusion molding, heat press molding, or calendar molding. The original sheet 10a has a first shape as an original shape having no apertures. The first shape preferably has no irregularities visible to the naked eye and is substantially flat. 4(B), the original shape sheet 10a is then cooled to room temperature RT (e.g., 25°C), which is lower than the deformation temperature Tb of the shape memory polymer, so that the original shape sheet 10a maintains the first shape. In this state, the fixed phase of the shape memory polymer is solidified, thereby memorizing the first shape.

[0025] Next, as shown in Figures 4(C) and (D), the original shape sheet 10a is heated at a second temperature T2 lower than the first temperature T1, and an external force is applied to form the original shape sheet 10a into a second shape sheet 10 having the above-mentioned recesses 13 and openings 15. The second temperature T2 is higher than the deformation temperature Tb of the shape memory polymer and lower than its melting temperature Ta. During this molding, the fixed phase of the shape memory polymer does not melt, and only the reversible phase has fluidity, which allows only the reversible phase to deform while the fixed phase remains unchanged. 4(E), the formed sheet 10 is cooled to about room temperature RT, thereby maintaining the second shape of the sheet 10. The sheet 10 is mounted in the absorbent article in the second shape.

[0026] In this embodiment, as shown in Figures 4(F) and (G), by bringing the recesses 13 of the sheet 10 having the second shape into contact with hot water W, the recesses 13 that have come into contact with the hot water W return to a shape close to the first shape. Specifically, when the hot water W comes into contact with the recesses 13, the recesses 13 are heated and softened, and the reversible phase of the shape memory polymer regains fluidity. As a result, the shape memory polymer that constitutes the recesses 13 regains its elasticity and returns to a shape close to its original first shape without the need for an external force. As a result, the recess 13 is flattened, and the area of the opening 15 is accordingly reduced. After contact with the hot water, the sheet 10 is cooled to about room temperature RT, as shown in FIG. 4(H), and is fixed in its restored shape.

[0027] The effects based on the above-mentioned action will be described assuming that the sheet 10 is used in an absorbent article. Fig. 5 shows an example in which the sheet 10 is placed on an absorbent body 30 as a topsheet of the absorbent article.

[0028] As shown in Figure 5(A), the excreted liquid WL from the wearer excreted on the sheet 10 flows into the recesses 13 and passes through the openings 15. This allows the excreted liquid WL to be absorbed into the absorber 30. By forming the openings 15 in the bottoms 14 of the recesses 13, the openings 15 are brought closer to the absorber 30, allowing the absorber 30 to more reliably absorb the excreted liquid WL.

[0029] The recesses 13 around the holes 15 are heated and softened by contact with the excreta WL. As a result, as shown in FIG. 5(B), the recesses 13 are flattened so that they return to their first shape due to their elasticity. As a result, the area of the holes 15 also decreases. FIG. 5(B) shows an example in which the holes 15 are completely closed after the excreta WL has passed through them. In the sheet 10, the region where the area of the pores 15 is reduced by contact with the excrement WL is referred to as the shape-recovery region R. After the excrement WL passes through, the shape-recovery region R is cooled by the surrounding air and maintains its original shape. As shown in Figure 5(B), the excreted liquid WL held in the absorbent body 30 is less likely to return to the main surface 12 due to the reduced area of the perforations 15. This makes it possible to prevent the liquid from returning to the main surface 12 even when an external force such as the wearer's body pressure is applied to the absorbent article. Therefore, the sheet 10 can prevent discomfort caused by the liquid returning and leakage of the liquid to the outside of the absorbent article.

[0030] Furthermore, in this embodiment, the apertures 15 are formed in the recesses 13 that have distortion due to shaping. That is, the apertures 15 can be formed not in the portions where a part of the shape memory polymer has been removed by punching or the like, but in the portions where the distortion of the recesses 13 has increased and the recesses 13 have been broken by shear force. This makes it easier for the sheet 10 to return to the first shape without apertures 15, and the area of the apertures 15 can be more reliably reduced in this embodiment.

[0031] Furthermore, when the absorbent article is worn for a long period of time, it may absorb excreted liquid WL multiple times. 6, the excreted liquid WL excreted the second time or later does not easily pass through the shape-recovery region R, and therefore may flow over the shape-recovery region R and move to other regions. The excreted liquid WL then passes through the non-shape-recovery openings 15 and may be absorbed in a different position in the absorber 30 from the previous excreted liquid WL. This prevents the excreted liquid WL from concentrating in one part of the absorber 30, even when worn for a long period of time, and allows the excreted liquid WL to be dispersed and absorbed over a wide area of the absorber 30. Therefore, it is possible to prevent the absorber 30 from locally absorbing a large amount of liquid, thereby preventing the liquid from overflowing, and effectively suppressing backflow and leakage that accompany the overflow.

[0032] [Example of pore size after immersion in warm water] In order to fully exert the above-mentioned function of preventing liquid backflow, it is preferable that the area of the openings 15 is sufficiently reduced by the stimulation of the warm water. For this reason, it is preferable that the area of the open pores 15 be reduced to 90% or less of the area before immersion, for example, by immersing the entire shape memory layer 11 in hot water at 40°C. In other words, the ratio of the open pore area after immersion to the open pore area before immersion in hot water is preferably 90% or less. The ratio of the open pore area after immersion to the open pore area before immersion in hot water is also referred to as the "open pore ratio after immersion in hot water." In this configuration, the openings 15 become sufficiently small due to the stimulation of the warm water, so that the return of liquid can be prevented more effectively.

[0033] The pore opening rate after immersion in hot water can be calculated as follows. First, the sheet 10 before immersion in hot water is cut into a 10 cm x 10 cm rectangle to prepare a measurement sample. The areas of any 5 or more (e.g., 10) openings 15 in this sample are calculated, and the average value is measured. This average value is defined as the "open opening area before immersion in hot water." A container large enough to hold the entire sample is filled with 40°C warm water in an amount sufficient to immerse the entire shape memory layer 11, preferably the entire sample. The entire sample is then immersed in the container containing the warm water for 15 seconds or more. After removing the sheet 10 from the warm water, the areas of five or more (e.g., ten) openings 15 having the same or similar shape as the openings 15 from which the opening area before immersion was calculated are calculated, and the average value of these openings is measured. This average value is the "open opening area after immersion in warm water." The ratio of the open opening area after immersion to the open opening area before immersion ((open opening area after immersion) / (open opening area before immersion)) is calculated as the "open opening rate after immersion in warm water."

[0034] In order to more reliably obtain the above-mentioned effect of preventing liquid return, the pore size after immersion in warm water is more preferably 70% or less, and even more preferably 65% or less. The area of the openings 15 before immersion in hot water is preferably 3.1 mm from the viewpoint of obtaining good liquid permeability and adjusting the opening rate after immersion in hot water to the above range. 2 More than 3.2mm, preferably 3.2mm 2 or more, preferably 4.5 mm 2 Less than or equal to 3.5mm, preferably 2 The following is the result.

[0035] [Example of recess and hole placement] The recesses 13 and the openings 15 can be arranged taking into consideration the permeability of excreted fluids and the like. In the example shown in FIG. 2, the apertures 15 are arranged in a plurality of first rows L1 along a first planar direction X and a plurality of second rows L2 along a second planar direction Y. In the illustrated example, the first planar direction X and the second planar direction Y are directions that are orthogonal to each other, but are not limited to this and may be directions that intersect each other. "The first row L1 is along the first planar direction X" is not limited to a case where a line connecting the center points of the apertures 15 is linear, but may be any case where the plurality of apertures 15 are arranged at intervals along any direction in the XY plane. Similarly, "the second row L2 is along the second planar direction Y" is not limited to a case where a line connecting the center points of the apertures 15 is linear, but may be any case where the plurality of apertures 15 are arranged at intervals along a direction intersecting the first row L1 in the XY plane.

[0036] In this case, the apertures 15 may be arranged in a grid pattern, with the apertures 15 being arranged at positions where the first row L1 and the second row L2 intersect, as shown in Fig. 2. Alternatively, without being limited thereto, the apertures 15 belonging to adjacent first rows L1 may be arranged shifted from each other in the first planar direction X, as shown in Fig. 7. In this way, by regularly arranging the apertures 15, it is possible to suppress variations in liquid permeability within the XY plane of the sheet 10. Therefore, even during repeated excretion, excreted liquid can be dispersed more effectively.

[0037] In order to arrange the apertures 15 more regularly, it is preferable that the intervals between adjacent apertures 15 in the first row L1 are substantially constant. Similarly, it is preferable that the intervals between adjacent apertures 15 in the second row L2 are substantially constant. "Substantially constant spacing" means that when the spacing between any three apertures 15 in each row is measured and the narrowest spacing is taken as 100%, the difference between the widest spacing and the narrowest spacing is 20% or less.

[0038] In addition, in the area where the openings 15 of the sheet 10 are formed, a 10 cm x 10 cm (100 cm 2 The ratio of the area of the openings 15 to the area of the sheet 10 is preferably 3% or more, more preferably 10% or more, and is preferably 50% or less, more preferably 40% or less, from the viewpoint of obtaining good liquid permeability and maintaining the shape of the sheet 10. The apertures 15 are not limited to being distributed over the entire sheet 10, but may be disposed in only a part of the sheet 10. When the area in which the apertures 15 are formed is smaller than the above-mentioned 10 cm × 10 cm area, it is preferable that the ratio of the area of the apertures 15 to the area in which the apertures 15 are formed is within the above-mentioned range.

[0039] [Examples of thickness and basis weight of shape memory layer] The thickness in the thickness direction Z of the region including the recess 13 of the shape memory layer 11 is preferably 2.0 mm or more, more preferably 2.5 mm or more, and preferably 4.5 mm or less, more preferably 3.0 mm or less, from the viewpoint of obtaining liquid conductivity through the recess 13 and improving the wearing comfort. The thickness in the thickness direction Z of the region including the main surface 12 of the shape memory layer 11 (i.e., the thickness of the film itself) is preferably 0.1 mm or more, more preferably 0.2 mm or more, and preferably 0.4 mm or less, more preferably 0.3 mm or less. The basis weight of the shape memory layer 11 is preferably 50 g / m 2 More preferably, 100 g / m 2 or more, and preferably 350 g / m 2 Less than 300 g / m 2 The following is the result. The above values are measured at room temperature (25° C.) using the shape memory layer 11 before contact with hot water.

[0040] A method for measuring the thickness of the shape memory layer 11 will be described. The sheet 10 to be measured is cut into a 10 cm x 10 cm rectangle to obtain a measurement sample. If a 10 cm x 10 cm rectangle cannot be obtained, cut it into as large an area as possible. Using a laser thickness meter (Omron Corporation ZSLD80), the thickness of a predetermined point in the sample is measured. Regarding the thickness of the region including the recesses 13, the thickness is measured at three points on the cross section including the recesses 13 in the sample, and the average value is taken as the thickness including the recesses 13 of the sheet 10 to be measured. Regarding the thickness of the region including the main surface 12, the thickness is measured at three points on a cross section including the main surface 12 (excluding the recesses 13) in the above sample, and the average value of these measurements is used as the thickness of the region including the main surface 12 of the sheet 10 being measured.

[0041] A method for measuring the basis weight of the shape memory layer 11 will be described. The sheet 10 to be measured is cut to a predetermined size to obtain small pieces for measurement. The mass of each small piece is measured, and the calculated mass is divided by the area of each small piece to calculate the basis weight of the small piece. The average basis weight of the five small pieces is taken as the basis weight of the sheet 10.

[0042] [Examples of methods for forming recesses and openings] The recesses 13 and the openings 15 are preferably formed by a method of stretching and distorting a portion of the original shape sheet 10a in the first shape. Specifically, the recesses 13 and the openings 15 can be formed by, for example, deep drawing or hot needle punching, in which a heated needle is used to punch holes in the original shape sheet 10a. Among these, from the viewpoint of forming recesses 13 with sufficient depth with high precision, it is preferable to form them by using deep drawing.

[0043] In the example shown in FIG. 8, the sheet 10 having the second shape is formed by deep drawing an original sheet 10a having the first shape using a lower mold K1 and an upper mold K2. 8(A), for example, the lower mold K1 has a convex portion K11 that protrudes upward in the thickness direction Z and a concave portion K12 that is recessed downward in the thickness direction Z. The convex portion K11 includes a flat upper surface K13. The upper surface K13 contributes to the formation of the main surface 12. The concave portion K12 contributes to the formation of the concave portion 13 of the shape memory layer 11. For example, the upper mold K2 has a convex portion K21 that protrudes downward in the thickness direction Z and a concave portion K22 that is recessed upward in the thickness direction Z. The convex portion K21 includes a flat lower surface K23. The lower surface K23 of the convex portion K21 fits into the concave portion K12 of the lower mold K1 and contributes to the formation of the concave portion 13 and the opening 15 of the shape memory layer 11. The convex portion K11 of the lower mold K1 fits into the concave portion K22.

[0044] During processing, as shown in FIG. 8(A), a lower mold K1 and an upper mold K2 are arranged opposite each other in the thickness direction Z, and an original sheet 10a, which is the workpiece, is placed between them. Then, as shown in FIG. 8(B), the upper mold K2 is pressed downward in the thickness direction Z relative to the lower mold K1, causing the convex portions K21 of the upper mold K2 to enter the concave portions K12 of the lower mold K1. As a result, the original sheet 10a is deformed along the convex portions K21 of the upper mold K2, and the portions that enter the concave portions K12 are significantly elongated. This elongated portion forms the concave portions 13. Furthermore, as the convex portions K21 of the upper mold K2 strongly press against the original sheet 10a, the elongated portions of the original sheet 10a are broken along the periphery of the lower surface K23, forming openings 15.

[0045] By forming the recesses 13 and the openings 15 by such deep drawing, the recesses 13 can be sufficiently stretched and distorted. This makes it easier for the recesses 13 to return to their original shape from the stretched state when stimulated by warm water. Furthermore, the openings 15 are formed by breaking based on shear force, rather than by removing part of the polymer. Therefore, the openings 15 are more likely to close as the recesses 13 return to their original shape. Furthermore, the shapes of the recesses 13 and the openings 15 can be adjusted with precision by the shapes of the lower mold K1 and the upper mold K2. For example, the planar shape of the openings 15 can be controlled by the shape of the lower surfaces K23 of the protrusions K21 of the upper mold K2. Furthermore, the opening shape of the recesses 13 can be controlled by the opening shape of the recesses K12 of the lower mold K1. Furthermore, the depth of the recesses 13 can be controlled by the dimension in the thickness direction Z of the protrusions K21 of the upper mold K2.

[0046] As described above, in this embodiment, a sheet 10 can be formed that has high liquid permeability due to the recesses 13 and openings 15, and that can effectively suppress liquid return after excretory liquid has passed through due to the reduced area of the openings 15.

[0047] Second Embodiment The absorbent sheet of the present invention may have other layers in addition to the shape-memory layer 11 described in the first embodiment, from the viewpoint of improving the feel when it touches the skin, absorbency, and the like. For example, a sheet (sheet) 20 for absorbent articles according to a second embodiment of the present invention includes a shape-memory layer 11 and a nonwoven fabric layer 21. This example is shown in FIG. In this embodiment, the shape memory layer 11 has the same configuration as in the first embodiment. Therefore, the configuration of the nonwoven fabric layer 21 will be mainly described below.

[0048] [Nonwoven fabric layer composition] The nonwoven fabric layer 21 can be adjacent to the main surface 12 of the shape-memory layer 11. The nonwoven fabric layer 21 includes a plurality of fibers F that are fused or entangled with each other. As a result, gaps are formed between the fibers F in the nonwoven fabric layer 21, which can impart flexibility and a pleasant feel to the sheet 20. The nonwoven fabric layer 21 can also quickly absorb and diffuse excreted liquid by capillary action. Therefore, the nonwoven fabric layer 21 can prevent liquid from remaining on the sheet 20 and reduce discomfort to the wearer. Furthermore, breathability can be ensured by including the nonwoven fabric layer 21 having gaps between the fibers F. This makes it possible to prevent stuffiness even in the sheet 20 having a multi-layer structure.

[0049] Furthermore, after a portion of the shape memory layer 11 has permeated the excreted liquid and the shape-recovery region R has been formed, the nonwoven fabric layer 21 can retain the excreted liquid above the shape-recovery region R where the area of the openings 15 has decreased, while diffusing the liquid into the open openings 15. Therefore, the excreted liquid can be dispersed and absorbed while suppressing discomfort felt by the wearer due to the movement of the excreted liquid.

[0050] The nonwoven fabric layer 21 includes an upper surface 22 located at an upper side in the thickness direction Z and a lower surface 23 located at a lower side in the thickness direction Z. When the sheet 20 is used as a topsheet of an absorbent article, the upper surface 22 can be the surface that can contact the wearer's skin. The lower surface 23 can be the surface that contacts the main surface 12. The shapes of the upper surface 22 and the lower surface 23 are not particularly limited. In the example shown in Fig. 9, the upper surface 22 and the lower surface 23 are configured to be substantially flat. By making the lower surface 23 substantially flat, the lower surface 23 is stably adjacent to the main surface 12. The upper surface 22 may be substantially flat, or may have irregularities. Here, "the upper surface 22 or the lower surface 23 is substantially flat" means that when the sheet 20 is placed on a flat XY plane without applying external force, the undulations in the thickness direction Z of the upper surface 22 or the lower surface 23 are 25% or less of the total thickness of the nonwoven fabric layer 21.

[0051] The nonwoven fabric layer 21 is preferably composed of one or more nonwoven fabric sheets, and is preferably composed of a single nonwoven fabric sheet from the viewpoints of liquid permeability and limiting the sheet thickness. As the nonwoven fabric that constitutes the nonwoven fabric layer 21, various nonwoven fabrics can be used, such as air-through nonwoven fabric, spunbond nonwoven fabric, resin-bond nonwoven fabric, spunlace nonwoven fabric, air-laid nonwoven fabric, melt-blown nonwoven fabric, and needle-punched nonwoven fabric. The basis weight of the nonwoven fabric layer 21 is preferably higher than that of the shape-memory layer 11, from the viewpoint of providing sufficient flexibility and a good feel to the sheet 20 and also obtaining a liquid diffusing effect. Specifically, the basis weight of the nonwoven fabric layer 21 is preferably 20 g / m 2 More preferably, 50 g / m 2 or more, and preferably 100 g / m 2 Less than 80 g / m 2 The following is the result. The basis weight of the nonwoven fabric layer 21 can be measured in the same manner as that of the shape-memory layer 11.

[0052] From the viewpoint of preventing slippage and creases during wear, the nonwoven fabric layer 21 is preferably bonded to the main surface 12. Bonding is performed at a temperature that does not cause the recesses 13 to return to their original shape (deform), and can be performed, for example, by bonding with an adhesive or by local heat fusion bonding to the main surface 12. For example, an adhesive such as a hot melt adhesive can be applied to the lower surface 23 of the nonwoven fabric layer 21 in a linear pattern such as a spiral or stripe pattern, and this lower surface 23 can be bonded to the main surface 12. This can prevent the effects of heat on the recesses 13 while also preventing the adhesive from hindering absorption of excretory fluids.

[0053] <Other embodiments> Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the gist of the present invention.

[0054] The arrangement of the apertures 15 is not limited to the example shown in FIG. 2 or 7, and may be, for example, another regular arrangement or a random arrangement. Furthermore, the openings 15 are not limited to being formed in the bottom 14 of the recess 13, but may be formed, for example, on the side surface of the recess 13. In this case, after the recess 13 without the openings 15 is formed by, for example, deep drawing or the like, the openings 15 can be formed in the recess 13 by hot needle punching or the like. In the second embodiment, the sheet 20 may have a plurality of nonwoven fabric layers.

[0055] The shape of the mold used to mold the shape memory layer 11 is not limited to the above example either. For example, the lower or upper surface of the convex portion of the mold may be formed in a convex shape. Furthermore, the molding method is not limited to the example using two molds described above. For example, two plate-like members each having a through hole formed therein and sandwiching the sheet from above and below, and a pressing member inserted into the through hole and pressing the sheet downward, may be used. In this way, recesses and openings can be formed in the sheet by pressing down the pressing member.

[0056] In the above embodiment, the absorbent article sheet is used as a top sheet of an absorbent article, but is not limited thereto. The absorbent article sheet of the present invention may be used, for example, as an intermediate sheet disposed between the top sheet and the absorbent core of an absorbent article. [Example]

[0057] [Test Example 1: Examination of reduction in open area of shape memory layer] In test example 1, multiple recesses with openings at the bottom were created using a film made of a shape memory polymer and a resin film that did not contain a shape memory polymer, and it was examined whether the area of the openings would decrease when exposed to warm water.

[0058] Example 1 As a sample of Example 1, a sheet made of a shape memory layer as explained in the first embodiment was produced. First, a commercially available polyurethane-based shape memory polymer ("SMP55", manufactured by Kyoraku Corporation) was prepared and melted to form a substantially flat film without pores. The film was formed by hot press molding at a molding temperature of 180°C. The formed film was cooled to room temperature to produce the original sheet of the first shape described in Embodiment 1. The original sheet had a thickness of 0.3 mm and a size of 10 cm x 10 cm.

[0059] Next, deep drawing was performed using a lower mold and an upper mold as shown in FIG. The multiple protrusions on the upper mold were arranged in a first row along one direction and a second row along the other direction in a plan view. The protrusions were arranged at the positions where these rows intersected, forming a so-called lattice pattern. The shapes of the protrusions and recesses in each mold were the same. The height of the convex portion of the upper mold was 8 mm. The shape of the lower surface of the upper mold was a circle with a diameter of 2 mm. The height of the protrusion of the lower die was 10 mm. The original sheet was placed between the lower and upper molds, and the upper mold was pressed downward at a pressure of 20 kPa for 20 seconds to form holes where the sheet came into contact with the lower surface of the upper mold. The heating temperature of the original sheet during molding was 50°C.

[0060] The formed sheet was cooled to room temperature to produce the sheet of the second shape described in the first embodiment. As shown in Figures 1 and 2, the sheet had a main surface and a plurality of recesses with openings formed in the bottom. The thickness of the sheet, including the recesses, was 3.0 mm. The basis weight of the sheet was 270 g / m 2 It was decided. The number of apertures in the rectangular sheet of 10 cm x 10 cm was set to 400. The average area of any five openings in the sheet is 3.1 mm 2 This average value was defined as the "open pore area before immersion in hot water."

[0061] (Comparative Example 1) As a sample of Comparative Example 1, a film made of a polymer not containing a shape-memory polymer was produced in the same manner as in Example 1, and was shaped into a shape having recesses including apertures. The polymer used for the film was polyethylene, whose glass transition temperature was -125°C. This material was melted at 130° C., and a sheet of the first shape was produced in the same manner as in Example 1. The thickness and size of the sheet of the first shape were the same as in Example 1.

[0062] Subsequently, this film was heated to 100°C and deep-drawn in the same manner as in Example 1. This produced a sheet having a main surface 12 and a plurality of recesses with openings formed in the bottom portions. The size, basis weight, thickness and number of apertures of the sheet were the same as those in Example 1. The average area of any five openings in the sheet is 3.1 mm 2 This average value was defined as the "open pore area before immersion in hot water."

[0063] (Evaluation of pore opening rate after immersion in warm water) Warm water at 40°C was added to a tray (container) large enough to hold the sheets of Example 1 and Comparative Example 1. The entire sheets of Example 1 and Comparative Example 1 were immersed in the warm water in this tray for 30 seconds. After removing the sheets from the warm water, the average value of the area of five randomly selected openings was measured. This average value was designated as the "open hole area after immersion in warm water." The ratio of the open hole area after immersion in warm water to the open hole area before immersion in warm water ((open hole area after immersion) / (open hole area before immersion)) was calculated as the "open hole rate after immersion in warm water." The results are shown in Table 1.

[0064] [Table 1]

[0065] As shown in Table 1, the sheet of Comparative Example 1 was softened somewhat by immersion in hot water, but the pore rate after immersion in hot water was 100%, and there was no change in the open pore area. On the other hand, the pore rate after immersion in hot water of Example 1 was 64.5%, and the open pore area was definitely reduced. From these results, it was found that the sheet having the above-mentioned structure returned to its first shape when exposed to warm water at 40°C due to the action of the shape memory polymer, and the area of the open pores was reliably reduced.

[0066] [Test Example 2: Examination of the influence of the shape memory layer configuration on the pore size after immersion in hot water] Next, as Test Example 2, sheets (see the second embodiment) having shape memory layers and nonwoven fabric layers with different configurations were produced, and the pore size, amount of liquid return, and liquid diffusion area after immersion in warm water were evaluated.

[0067] Example 2 A concave-convex film constituting a shape-memory layer was produced using the same materials and method as the sample of Test Example 1. The mold used to form the concave portions was the same as that of Test Example 1. The basis weight of the shape memory layer 11 is 270 g / m 2 It was decided. The thickness of the shape memory layer 11 including the recesses was set to 2.5 mm. The rectangular sheet of 100 cm x 100 cm had 400 apertures. The average area of any five openings in the shape memory layer 11 is 3.2 mm 2 This average value was defined as the "open pore area before immersion in hot water." Before immersion in hot water, the ratio of the sum of the areas of all the open holes to the entire area of the shape memory layer 11 (area ratio of the open holes before immersion in hot water) was 12.8%.

[0068] A sheet made of an air-through nonwoven fabric manufactured by Kao Corporation was prepared as the nonwoven fabric layer. The surface of this nonwoven fabric sheet was flat except for minute irregularities caused by the fibers. The basis weight of the nonwoven fabric sheet (nonwoven fabric layer) was 78 g / m 2 It was decided. A hot melt adhesive was spirally applied to one surface of this nonwoven fabric sheet, and the sheet was adhered to the main surface 12 of the shape memory layer 11. At this time, no deformation of the recesses was observed. This produced a sheet of Example 2 having a shape-memory layer and a nonwoven fabric layer. The structure of the sheet of Example 2 is shown in Table 2.

[0069] [Table 2]

[0070] [Example 3] A sheet of Example 3 having a shape memory layer and a nonwoven fabric layer was produced in the same manner as in Example 2, except that the planar shapes of the convex and concave portions of the mold used to form the concave portions were changed. As shown in Table 2, the shape memory layer of the sheet of Example 3 had concave portions and open holes. The nonwoven fabric layer was the same as in Example 2. In this example, the diameter of the circular lower surface of the upper mold was 2.1 mm. The upper and lower molds were arranged with convex and concave portions so as to have the same number of openings as in Example 2. The basis weight, thickness and size of the shape memory layer were the same as those in Example 2. The average area of any five openings in the shape memory layer (opening area before immersion) was 3.5 mm 2 It was. The area ratio of open pores before immersion in hot water was 14.0%.

[0071] [Example 4] A sheet of Example 4 having a shape memory layer and a nonwoven fabric layer was produced in the same manner as in Example 2, except that the planar shapes of the convex and concave portions of the mold used to form the concave portions were changed. As shown in Table 2, the shape memory layer of the sheet of Example 4 had concave portions and open holes. The nonwoven fabric layer was the same as in Example 2. In this example, the diameter of the circular lower surface of the upper mold was 2.4 mm. The upper and lower molds were arranged with convex and concave portions so as to have the same number of openings as in Example 2. The basis weight, thickness and size of the shape memory layer were the same as those in Example 2. The average area of any five openings in the shape memory layer (opening area before immersion) was 4.5 mm 2 It was. The area ratio of open pores before immersion in hot water was 18.0%.

[0072] Comparative Example 2 A sheet of Comparative Example 2 having a shape memory layer and a nonwoven fabric layer was produced in the same manner as in Example 2, except that the pressure of the upper mold during the formation of the recesses was reduced to 10 kPa. As shown in Table 2, the shape memory layer of the sheet of Comparative Example 2 had recesses but no open holes. The nonwoven fabric layer was the same as in Example 2. The thickness of the shape memory layer including the recesses was 2.0 mm. The basis weight and size of the shape memory layer were the same as those in Example 2.

[0073] Comparative Example 3 A sheet of Comparative Example 3 having a shape memory layer and a nonwoven fabric layer was produced in the same manner as in Example 2, except that no recesses were formed and only perforations were formed. As shown in Table 2, the shape memory layer of the sheet of Comparative Example 3 had no recesses but perforations. The nonwoven fabric layer was the same as in Example 2. In Comparative Example 3, the shape memory layer was punched without using the mold, removing the film at the portions corresponding to the holes. Specifically, the position of the film (shape memory layer) in the first shape was fixed with a fixture, and punched at the same positions as in Example 2 using a punch. This resulted in multiple circular holes. No recesses were formed by this punching process. The basis weight, size and number of apertures of the shape memory layer were the same as those in Example 2. The average area of any five openings in the shape memory layer (opening area before immersion) was 3.1 mm 2 It was. The area ratio of open pores before immersion in hot water was 12.4%.

[0074] [Evaluation of pore opening rate after immersion in hot water] The entire sheets of Examples 2 to 4 and Comparative Examples 2 to 3 were immersed in 40°C warm water for 15 seconds. After removing the sheets from the warm water, the average area of any five open holes was measured. The measured value was taken as the open hole area after immersion in warm water, and the open hole rate after immersion in warm water was calculated in the same manner as in Test Example 1. The results are shown in Table 2. Naturally, the pore rate could not be evaluated for the sheet of Comparative Example 2, which had no pores. In addition, in the sheet of Comparative Example 3 in which openings were formed without forming recesses, the opening rate was 100%, and no reduction in the opening area was observed. In contrast, in Examples 2 to 4, the pore area was 90% or less, and it was found that the pores were sufficiently closed after immersion in hot water. Also, it was observed that the larger the pore area before immersion, the greater the amount of pore closure after immersion in hot water, and the tendency for the pore area to decrease. These results show that when the shape memory layer has recesses containing pores, the area of the pores is sufficiently reduced by the stimulation of 40°C warm water.

[0075] [Evaluation of the amount of liquid returning] Using the sheets of Examples 2 to 4 and Comparative Examples 2 and 3 after immersion in hot water, the amount of liquid returning to the nonwoven fabric layer side was evaluated. First, the surface material of commercially available Merry's Tape (medium size) manufactured by Kao Corporation was peeled off, and the sheets of the Examples and Comparative Examples were placed on the absorbent core. Then, 50 g of ion-exchanged water heated to 40°C was poured over 15 seconds at a position 85 mm from the ventral edge of the diaper. 15 seconds after the pouring, a stack of 10 sheets of filter paper (quantitative filter paper No. 5C manufactured by Advantec Toyo Co., Ltd.) cut into a 10 cm x 10 cm rectangle was placed on top of the pouring point, and the amount of water absorbed after applying a pressure of 3 kPa for 30 seconds was measured using an electronic balance. This measurement was performed three times, and the average values are shown in Table 2. As shown in Table 2, Comparative Example 2, which had no pores, had a larger amount of liquid wetting compared to the other samples. In Examples 2 to 4, the lower the pore rate after immersion in hot water, the smaller the amount of liquid wetting tended to be. This shows that the amount of liquid wetting can be reduced by reducing the pore rate after immersion in hot water.

[0076] [Evaluation of liquid diffusion area] The liquid diffusion area was evaluated using the sheets of Examples 2 to 4 and Comparative Examples 2 and 3 when hot water was dripped onto them multiple times. First, the surface material of a commercially available Merry's Tape (medium size) manufactured by Kao Corporation was peeled off, and the sheet of each Example / Comparative Example was placed on top of the absorbent core. 50 g of ion-exchanged water heated to 40°C was injected over 15 seconds at a position 85 mm from the ventral end of the diaper. 15 seconds after the injection, 50 g of ion-exchanged water heated to 40°C was injected again over 15 seconds. 15 seconds after the second injection, the sheet of each Example / Comparative Example was removed, and the area of the absorbent core where the liquid had diffused was measured. This measurement was performed three times, and the average value is shown in Table 2 as the measurement data. As shown in Table 2, Examples 2 to 4, which had recesses and apertures, had a larger liquid diffusion area than Comparative Example 3, which had no recesses. For this reason, in Examples 2 to 4, some apertures closed after the first injection of hot water, and when the second injection of hot water was performed, hot water passed through the remaining apertures that had not yet closed. This demonstrates that the sheets of Examples 2 to 4 suppress localized concentration of liquid in the absorbent core. [Explanation of symbols]

[0077] 10, 20... Sheet for absorbent article (sheet) 11...Shape memory layer 12...Main surface 13...Recess 15...Open hole

Claims

1. A sheet for absorbent articles having a film-like shape memory layer containing a shape memory polymer, the shape memory layer has a main surface and a plurality of recesses; the recess is recessed from the main surface and has an opening, The area of the opening is reduced by contact of hot water with the recess. Sheet for absorbent articles.

2. further comprising a nonwoven layer adjacent to the major surface. The sheet for absorbent articles according to claim 1.

3. The opening is formed in the bottom of the recess. The sheet for absorbent articles according to claim 1 or 2.

4. The shape memory layer contains 90% by mass or more of the shape memory polymer. The sheet for absorbent articles according to any one of claims 1 to 3.

5. The area of the pores is reduced to 90% or less of the area before immersion by immersing the entire shape memory layer in hot water at 40°C. The sheet for absorbent articles according to any one of claims 1 to 4.

6. An absorbent article comprising the sheet for absorbent articles according to any one of claims 1 to 5.

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