JP7818442B2 - Composite sheet and absorbent article - Google Patents

Description

The present invention relates to a stretchable composite sheet in which a stretchable porous moisture-permeable film and an absorbent body capable of absorbing body fluids are laminated together.

Absorbent articles such as disposable diapers and sanitary napkins typically include a topsheet that forms the skin-facing surface, a backsheet that forms the non-skin-facing surface, and an absorbent body placed between the two sheets. The absorbent body is required to follow the movements of the wearer of the absorbent article and provide high conformity to the body. To meet these required characteristics, a conventional approach is to impart stretchability to the absorbent body by bonding a stretchable sheet to one side of the absorbent body.

For example, Patent Document 1 describes a stretchable liquid-absorbent article having a plurality of absorbers discretely arranged and fixed on one surface of a stretchable sheet. In the stretchable liquid-absorbent article, when the stretchable sheet is in an unstretched state (natural state), each of the plurality of absorbers forms an overlapping portion where it overlaps with at least one adjacent absorber. As the stretchable sheet stretches, each absorber slides in the stretching direction, reducing the size of the overlapping portion and expanding the effective absorption area of the entire plurality of absorbers. Patent Document 1 does not specifically describe the material of the stretchable sheet.
Patent document 2 describes a stretchable absorbent body that has a plurality of individually independent absorbent sections fixed via fixing points to one side of a liquid-permeable or liquid-impermeable or liquid-slightly permeable stretchable sheet, and that exhibits stretchability between the fixing points.
Patent Document 3 describes an absorbent article comprising an absorbent body having a large number of individually independent block-shaped absorbent portions, and a backsheet joined to the non-skin-facing surface of the absorbent body and stretchable in the longitudinal direction corresponding to the front-to-rear direction of the wearer. Patent Document 3 exemplifies materials for the backsheet, such as a liquid-impermeable or water-repellent olefin-based elastomer film and a resin porous film having micropores.

Japanese Patent Application Laid-Open No. 2003-126144 JP 2009-136498 A JP 2013-385 A

The absorbent bodies described in Patent Documents 1 to 3 are given stretchability by being joined to a stretch sheet, and therefore, compared to absorbent bodies not joined to a stretch sheet, the absorbent article is better able to follow the movements of the wearer, but there is room for improvement in the leakproofness of the stretch sheet. The leakproofness of a stretch sheet joined to an absorbent body is particularly important when the stretch sheet is used as a backsheet of an absorbent article.
Furthermore, even if the absorbent body is provided with stretchability by a stretchable sheet, if a relatively large external force is required to exhibit that stretchability, this may cause stress to the wearer of the absorbent article, and therefore it is preferable that the stretchability can be exhibited with a relatively small external force. The absorbent bodies described in Patent Documents 1 to 3 also have room for improvement in terms of stretchability.

The objective of the present invention is to provide a composite sheet that is suitable as a component of absorbent articles, comprising a moisture-permeable film with excellent leak-proofing and stretchability properties and an absorbent body capable of absorbing body fluids.

The present invention relates to a composite sheet in which a stretchable breathable film having micropores and an absorbent body capable of absorbing bodily fluids are overlapped and joined to each other at a joint between the overlapping surfaces, the breathable film being stretchable and evaluated as having leakproof properties in the breathable film leakproofness evaluation test described below (at 30% elongation), and the absorbent body stretches and contracts in conjunction with the stretching and contraction of the breathable film.

The present invention also relates to an absorbent article equipped with the composite sheet of the present invention.

The present invention provides a composite sheet that is suitable as a component of absorbent articles, comprising a moisture-permeable film with excellent leak-proofing and stretchability and an absorbent body capable of absorbing body fluids.

FIG. 1 is a schematic perspective view of one embodiment of the composite sheet of the present invention, showing the natural state of the moisture-permeable film provided in the composite sheet. FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II in FIG. 1 (a cross section along the thickness direction and the expansion/contraction direction). FIG. 3 is a view corresponding to FIG. 1 showing another embodiment of the composite sheet of the present invention. FIG. 4 is a cross-sectional view schematically showing a cross section of still another embodiment of the composite sheet of the present invention in its natural state along the thickness direction and the stretching direction. FIG. 5 is a view corresponding to FIG. 4 showing a composite sheet according to still another embodiment of the present invention. FIG. 6 is an explanatory view of an example of a method for producing the composite sheet shown in FIG. 5, and is a schematic plan view of a composite sheet precursor used in the production method. FIG. 7 is a view corresponding to FIG. 4 showing a composite sheet according to still another embodiment of the present invention.

The present invention will now be described based on preferred embodiments with reference to the drawings. Note that in the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. The drawings are essentially schematic, and the proportions of each dimension may differ from those of the actual product.

The composite sheet of the present invention comprises a stretchable moisture-permeable film with micropores and an absorbent body capable of absorbing bodily fluids (aqueous fluids) such as urine, menstrual blood, and sweat. The moisture-permeable film and absorbent body overlap and are joined to each other at a joint between the overlapping surfaces. The moisture-permeable film is stretchable, and the absorbent body stretches in response to the stretching of the moisture-permeable film.

The moisture-permeable film according to the present invention is a resin film mainly made of a resin, typically an olefin-based resin, and further contains an inorganic filler. The inorganic filler is a substance that forms micropores in the moisture-permeable film.
The absorbent body according to the present invention typically comprises at least an absorbent core mainly made of a water-absorbing material, and optionally further comprises a liquid-permeable core wrap sheet covering the outer surface of the absorbent core.
When the composite sheet of the present invention is used as a constituent member of absorbent articles such as disposable diapers and sanitary napkins, the absorbent body side is usually the skin-facing side, and the moisture-permeable film side is usually the non-skin-facing side.
In this specification, the "skin-facing side" refers to the side of an absorbent article or its constituent member (e.g., absorbent body) that faces the skin side of the wearer when the absorbent article is worn, i.e., the side that is relatively closer to the wearer's skin, and the "non-skin-facing side" refers to the side of an absorbent article or its constituent member that faces the opposite side to the skin side when the absorbent article is worn, i.e., the side that is relatively farther from the wearer's skin.

In the present invention, "stretchable" means the property of being stretchable in a predetermined direction and shrinking when the stretch is released.
In the present invention, whether an object has stretchability is evaluated based on the object's degree of flexibility or residual strain after elongation. Specifically, the following tensile test is performed on an object to be evaluated for stretchability (such as a moisture-permeable film or an absorbent), and if the measured degree of flexibility is 0.060 N/(mm·(g/m ² )) or less, or the measured residual strain after 30% elongation is 11% or less, the object is evaluated as having stretchability in the tensile direction. On the other hand, if the measured degree of flexibility is more than 0.060 N/(mm·(g/m ² )) and the measured residual strain after 30% elongation is more than 11%, the object is evaluated as not having stretchability in the tensile direction and as being inelastic.
The "stretchable moisture-permeable film" used in the present invention is a moisture-permeable film that is stretchable in at least one direction. On the other hand, the absorbent body according to the present invention includes a "stretchable absorbent body" and a "non-stretchable absorbent body," the former being an absorbent body that is stretchable in at least one direction, and the latter being an absorbent body that is not stretchable in any direction.

(Tensile test: measurement of flexibility and residual strain after 30% elongation)
A rectangular test piece in plan view, measuring 150 mm in length in the machine direction (the flow direction during the manufacture of the test piece) and 30 mm in length in the short direction perpendicular to the machine direction, was cut out from the test piece to prepare a test piece. The test piece was fixed between a pair of gripping jigs in a tensile tester (product name: AG-1S, manufactured by Shimadzu Corporation) so that the machine direction of the test piece was the tensile direction. The test piece was fixed so that the length between the pair of gripping jigs, i.e., the machine direction length (initial length) _L0 of the test piece before the tensile test, was 100 mm. After fixing, the load read by the tensile tester was set to zero, and the test piece was stretched to 1.3 times _L0 (i.e., 30% stretch) at a deformation rate of 200 mm/min, and then immediately contracted to _L0 at a deformation rate of 200 mm/min, in a cyclic test. From the data obtained in the cycle test, the load (F _3% ) at 1.03 times deformation during the elongation process is read, and the degree of flexible deformation [N/(mm·(g/m ² ))] of the test piece is calculated using the following formula.
Degree of flexible deformation [N/(mm·(g/m ² ))]=F _3% [N]/(0.03×30 [mm]×basis weight of test piece [g/m ² ])
In the cycle test, the length _L1 of the test piece in the machine direction when the load becomes 0.01 [N] or less in the process of shrinking the test piece is measured, and the residual strain after 30% elongation of the test piece is calculated using the following formula.
Residual strain after 30% elongation (%) = {(L ₁ [mm] - L ₀ [mm])/L ₀ }×100
For each evaluation object, three test pieces are prepared, and the cycle test is carried out on each test piece to calculate the degree of flexible deformation and the residual strain after 30% elongation. The arithmetic mean value of the degrees of flexible deformation of each of the three test pieces is taken as the degree of flexible deformation of the evaluation object, and the arithmetic mean value of the residual strain after 30% elongation of each of the three test pieces is taken as the residual strain after 30% elongation of the evaluation object.
If the size of the evaluation object is too small to cut out a rectangular shape in plan view that is 150 mm long in the machine direction and 30 mm long in the lateral direction, the test piece is cut out taking into consideration the size of the area to be clamped by the gripping jigs so that the extension area between the gripping jigs is the largest possible similarity to the rectangular shape in plan view of the evaluation object that is 100 mm long in the machine direction and 30 mm long in the lateral direction perpendicular to the machine direction. In this case, the value of _L0 is measured, and the tensile test is performed by setting the deformation rate so that the deformation rate per unit sample length is equal.

The moisture-permeable film of the present invention is evaluated as having leakproof properties in the following moisture-permeable film leakproofness evaluation test at 30% elongation. This allows the composite sheet of the present invention to have high leakproof properties. The leakproof properties of the composite sheet of the present invention are primarily due to the moisture-permeable film. A moisture-permeable film having the composition described below can be evaluated as having leakproof properties in the following moisture-permeable film leakproofness evaluation test.

(Evaluation test of moisture-permeable film leak prevention at 30% elongation)
The evaluation object (moisture-permeable film) and a pulp sheet with a 40 g/m² basis weight and a rectangular shape in plan view (25 mm x 30 mm) were stacked on top of filter paper (Advantec Toyo Co., Ltd., No. ² , diameter 70 mm). The evaluation object was stretched 1.3 times in the machine direction (30% stretched), and its size in plan view was adjusted so that it completely overlapped the filter paper. 0.265 g of a test liquid with a surface tension of 44 mN/m at 25°C was injected into the center of the upper surface of the pulp sheet. Immediately after injection, a cylindrical acrylic resin plate with a diameter of 60 mm and a thickness of 5 mm was placed on the pulp sheet, and a 500 g weight was placed on the plate and pressure was applied for 1 hour. After 1 hour had passed since the weight was placed, the weight was removed, and the presence or absence of the test liquid seeping into the filter paper was visually observed. The above series of operations is carried out three times for the evaluation object, and if no seepage of the test liquid into the filter paper is observed in any of the three times, the evaluation object is evaluated as having leak-proof properties; otherwise, it is evaluated as not having leak-proof properties.

To add to the above (Test for Evaluating the Leakproofness of Moisture-Permeable Films in a 30% Elongated State), the object to be evaluated (moisture-permeable film) is to have a rectangular shape in plan view that is larger than the size of the pulp sheet (25 mm x 30 mm). If this size cannot be prepared due to reasons such as the object being small, a test piece is cut out of the largest similar shape to the rectangular shape in plan view, and the test is performed using a pulp sheet and test liquid so that the surface pressure received by the pulp sheet and the amount of test liquid per unit area of the pulp sheet are equal. Furthermore, if the object to be evaluated is part of a product such as an absorbent article, the object to be evaluated is removed from the product with great care to avoid tears, etc., and then subjected to the test.
The pulp sheet used may be, for example, "Lead Healthy Cooking Paper Double" manufactured by Lion Corporation. If necessary, the rectangular shape in plan view is cut out from the pulp sheet and used for the test.
The test liquid used has a surface tension of 44 mN/m at 25°C and is a mixture for wetting tension testing manufactured by Kanto Chemical Co., Inc. The test liquid is injected into the pulp sheet using a dropper. If the test liquid injected onto the upper surface of the pulp sheet overflows from the pulp sheet during pressure application and flows around the edge of the evaluation object into the filter paper, the size of the evaluation object is expanded using a polyethylene film or the like that is impermeable to the test liquid.

The moisture-permeable film according to the present invention has a flexibility deformation degree in the stretch direction (machine direction of the moisture-permeable film) measured by the tensile test of preferably 0.060 N/(mm·(g/ ^m2 )) or less, more preferably 0.057 N/(mm·(g/ ^m2 )) or less, and even more preferably 0.055 N/(mm·(g/ ^m2 )) or less. This makes the composite sheet of the present invention highly stretchable and particularly easy to stretch. Furthermore, when the composite sheet of the present invention is used as a component of an absorbent article, it can be stretched without interfering with the movement of the wearer of the absorbent article, thereby reducing discomfort to the wearer. A moisture-permeable film having a composition described below can have a flexibility deformation degree in the stretch direction within the above range. On the other hand, the lower limit of the flexibility deformation degree in the stretch direction of the moisture-permeable film is preferably 0.005 N/(mm·(g/ ^m2 )) or more, from the viewpoint of maintaining the shape of the composite sheet and ensuring the transportability of the composite sheet during processing.

The moisture-permeable film of the present invention preferably has a residual strain after 30% elongation measured by the tensile test of 11% or less, more preferably 10% or less, and even more preferably 9% or less. This gives the composite sheet of the present invention high stretchability and can be particularly prone to shrinkage. Furthermore, when the composite sheet of the present invention is used as a component of an absorbent article, the composite sheet follows the movements of the wearer of the absorbent article, thereby reducing discomfort to the wearer. A moisture-permeable film having the composition described below can have a residual strain after 30% elongation within the above range. Meanwhile, the lower limit of the residual strain after 30% elongation of the moisture-permeable film is the better, with 0% being the most preferred.

The moisture-permeable film according to the present invention is moisture-permeable and can transmit moisture. The moisture-permeable film according to the present invention has a moisture permeability measured in accordance with JIS L 1099 A-2 of preferably 0.4 g/(100 cm ² ·h) or more, more preferably 0.45 g/(100 cm ² ·h) or more, and even more preferably 0.8 g/(100 cm ² ·h) or more. This allows the composite sheet of the present invention to have high moisture permeability, and when used as a component of an absorbent article, the composite sheet can appropriately dissipate moisture inside the absorbent article to the outside. A moisture-permeable film having the composition described below can have a moisture permeability within the above range. On the other hand, the upper limit of the moisture permeability of the moisture-permeable film is preferably 4.5 g/(100 cm ² ·h) or less, more preferably 3.5 g/(100 cm ² ·h) or less, and even more preferably 3.0 g/(100 cm ² ·h) or less, from the viewpoint of preventing loss of leakproofness due to excessive porosity. The moisture permeability is measured by the following method.

(Method for measuring moisture permeability)
This measurement method complies with JIS L 1099 A-2. Approximately 25 mL of ion-exchanged water is placed in a glass bottle (Labolan screw cap bottle No. 8, manufactured by AS ONE) with a diameter of 2.03 cm (area 3.23 cm2), and the mouth of the glass bottle is covered with a single test piece, leaving no gaps. The test piece (e.g., a moisture-permeable film) is then secured to the glass bottle with a rubber band to form an evaluation sample. After measuring the mass (W1) of the evaluation sample, the sample is stored in a thermostatic chamber controlled at 40°C and 20% RH for 10 to 15 hours. After storage, the mass (W2) of the evaluation sample is measured, the storage time (T1, unit: h) is recorded, and the moisture permeability is calculated using the following formula:
Moisture permeability [g/( ^100cm2・h)]={(W1-W2)/(T1×3.23)}×100

The breathability of the moisture-permeable film of the present invention in its natural state is preferably 3000 seconds or less, more preferably 2500 seconds or less. This breathability is measured using the time required for 25 cc of air to permeate the moisture-permeable film in the thickness direction. The smaller the breathability value, the more breathable the moisture-permeable film is evaluated to be. This allows the composite sheet of the present invention to have high breathability. The breathability of the moisture-permeable film described above can be within the above range. Furthermore, since moisture-permeable films are stretchable, stretching the moisture-permeable film in the machine direction enlarges the micropores, and stretching by, for example, 30% has the advantage of achieving even higher breathability. On the other hand, the lower limit of the breathability of the moisture-permeable film in its natural state is preferably 1 second or more, from the perspective of maintaining the strength of the moisture-permeable film. Typically, the breathability of a moisture-permeable film stretched in the machine direction (e.g., 30% stretched) is higher than that in its natural state. Breathability is measured by the following method.

(Method for measuring air permeability)
This measurement method complies with JIS P8117. Using an air permeability tester (product name: Gurley Densometer, manufactured by Kumagai Riki Kogyo Co., Ltd.), the time required for 25 cc of air to permeate through the evaluation object (moisture-permeable film) in the thickness direction is measured. The state of the evaluation object during the test is in a natural state or an elongated state (e.g., 30% elongation state). If 25 cc of air has not permeated the moisture-permeable film completely even after 10,000 seconds or more have elapsed and the measurement is not completed, the measurement is deemed impossible, and the moisture-permeable film is evaluated as having no breathability.

The basis weight of the moisture-permeable film according to the present invention is not particularly limited and may be adjusted appropriately depending on the application of the composite sheet of the present invention, etc. For example, when the composite sheet of the present invention is used as a component of an absorbent article, the basis weight of the moisture-permeable film is preferably 5 g/ ^m2 or more, more preferably 10 g/ ^m2 or more, and preferably 100 g/ ^m2 or less, more preferably 50 g/ ^m2 or less.

The absorbent body according to the present invention can be any absorbent body usable as an absorbent body for absorbent articles such as disposable diapers, sanitary napkins, etc. The absorbent body typically includes at least an absorbent core mainly made of a water-absorbent material.
Examples of the water-absorbing material include hydrophilic fibers and water-absorbing polymers, and these may be used alone or in combination of two or more.
The hydrophilic fibers may be inherently hydrophilic fibers or hydrophobic fibers that have been subjected to a hydrophilization treatment. Examples of inherently hydrophilic fibers include natural fibers such as pulp fibers, regenerated or semi-synthetic cellulose fibers, and hydrophilic synthetic fibers.
The water-absorbing polymer is generally in the form of particles, but may also be in the form of fibers. The shape of the particulate water-absorbing polymer is not particularly limited, and may be, for example, spherical, blocky, bale-like, or irregular. The water-absorbing polymer is typically mainly composed of a polymer or copolymer of acrylic acid or an alkali metal salt of acrylic acid.

The absorbent body according to the present invention may further include, in addition to the absorbent core, a core wrap sheet that covers the outer surface of the absorbent core. The absorbent core and the core wrap sheet may be joined by a joining means such as adhesive or fusion. The core wrap sheet is preferably a liquid-permeable sheet, such as paper or nonwoven fabric.

The absorbent core can be roughly divided into a pile type and a sheet type, and either type can be used in the present invention.
Fiber-stacking absorbent cores typically consist primarily of an aggregate of fibrous materials such as hydrophilic fibers, with absorbent polymer particles supported on the aggregate as needed. Fiber-stacking absorbent cores can be manufactured in accordance with conventional methods using a known fiber-stacking device equipped with a rotating drum. The fiber-stacking device typically includes a rotating drum having an accumulation recess formed on its outer circumferential surface and a duct having an internal flow path for transporting absorbent core forming materials (fibers, water-absorbent polymer particles) to the accumulation recess. While the rotating drum is rotated around its rotation axis along the drum circumferential direction, the forming materials are transported on an airflow generated in the flow path by suction from the inside of the rotating drum, and are stacked in the accumulation recess.
Sheet-type absorbent cores typically have a structure in which water-absorbent polymer particles are fixed inside or on the surface of a fiber sheet, and are also called absorbent sheets. Sheet-type absorbent cores are thinner and more flexible than stacked-fiber absorbent cores. For example, sheet-type absorbent cores may have a structure in which water-absorbent polymer particles are interposed between two opposing fiber sheets. As sheet-type absorbent cores, those described in Japanese Patent No. 2963647 and Japanese Patent No. 2955223 may also be used.

The absorbent body according to the present invention may be stretchable or non-stretchable. The absorbent body having the above-mentioned absorbent core is typically a non-stretchable absorbent body.
An example of a stretchable absorbent body is one that includes an absorbent core and a core wrap sheet that covers the outer surface of the absorbent core, and the core wrap sheet includes a stretchable sheet. The absorbent core in such a stretchable absorbent body may be of a stacked fiber type or a sheet type.
Examples of the stretchable sheet include (1) a nonwoven fabric made of elastic fibers, (2) a stretchable sheet in which a stretchable fiber layer is integrated on one or both sides of an elastic fiber layer, (3) a stretchable sheet in which a stretchable fiber layer is integrated on one or both sides of an elastic sheet made of a net-like elastic sheet, (4) a stretchable sheet in which a large number of elastic filaments arranged so as to extend in one direction without crossing each other are integrated into an stretchable fiber layer, and (5) a composite stretchable member in which an elastic member extending in one direction is fixed in a non-stretched or stretched state between two sheet materials such as nonwoven fabrics with irregularities. The "stretchable fiber layer" includes not only a fiber layer that is stretchable before being integrated with an elastic material, but also a fiber layer that is made stretchable by mechanical processing or the like after being integrated with an elastic material. Examples of methods for integrating the elastic fiber layer and the extensible fiber layer include a method of laminating them and entangling the fibers by hydroentangling or air-through, or a method of bonding them by heat embossing, adhesive, ultrasonic waves, etc. As the composite elastic member of (5), for example, those described in WO 2018/189781 can be used.

The basis weight of the absorbent body according to the present invention is not particularly limited and may be adjusted appropriately depending on the application of the composite sheet of the present invention, etc. For example, when the composite sheet of the present invention is used as a component of an absorbent article, the basis weight of the absorbent body is preferably 40 g/ ^m2 or more, more preferably 150 g/ ^m2 or more, and preferably 750 g/ ^m2 or less, more preferably 650 g/ ^m2 or less.

In the composite sheet of the present invention, the moisture-permeable film and the absorbent body overlap and are joined to each other at a joint between the overlapping surfaces. The means for forming the joint in the present invention is not particularly limited, and known joining means such as adhesives or fusion (e.g., heat sealing, ultrasonic sealing, etc.) can be used. Generally, adhesives cause less damage to the moisture-permeable film 2 and the absorbent body 3 than fusion, and therefore adhesives are preferred as the joining means. That is, in the joint in the present invention, it is preferable that the moisture-permeable film and the absorbent body (absorbent section) are joined with an adhesive. Known adhesives such as hot-melt adhesives can be used as the adhesive. The adhesive to be used for forming the joint in the present invention is applied to one or both of the moisture-permeable film and the absorbent body. The adhesive application pattern is not particularly limited, but from the perspective of preventing the adhesive from impairing the moisture permeability or breathability or the stretchability of the composite sheet, it is preferable to apply the adhesive intermittently so that there are areas of the surface to be applied where the adhesive is not applied, rather than applying it solidly across the entire surface to be applied. Examples of such intermittent adhesive application patterns include ladder, spiral, summit, omega, curtain, and stripe patterns.

The composite sheet of the present invention includes a configuration in which the surface of the absorbent body that contacts the moisture-permeable film has an uneven structure when the moisture-permeable film is in its natural state. Figures 1 and 2 show a composite sheet 1 that is one embodiment of such a composite sheet. In the illustrated composite sheet 1, the uneven structure of the absorbent body 3 is formed not only on the surface that contacts the moisture-permeable film 2, but also on the opposite surface (the outer surface of the composite sheet 1).
The composite sheet 1 includes a stretchable moisture-permeable film 2 having micropores and an absorbent body 3 capable of absorbing bodily fluids. The absorbent body 3 includes at least the aforementioned stack-type or sheet-type absorbent core, and may further include a core wrap sheet covering the outer surface of the absorbent core. In the composite sheet 1, the moisture-permeable film 2 and the absorbent body 3 overlap and are joined to each other at a joint 4 located between their overlapping surfaces (contact surfaces). The moisture-permeable film 2 is stretchable, and the absorbent body 3 stretches in accordance with the stretching of the moisture-permeable film 2. In the composite sheet 1, the moisture-permeable film 2 is stretchable in one direction indicated by the symbol Y in the figure, and the composite sheet 1 is also stretchable in the same direction Y.

In this specification, "natural state" refers to a state in which no external force is applied to the object (composite sheet, moisture-permeable film, etc.). The natural state of the moisture-permeable film 2 is also the natural state of the composite sheet 1.

In the composite sheet 1, the uneven structure is formed in the absorbent body 3 at least when the moisture-permeable film 2 is in its natural state, and is formed by pleated convex portions 5 and concave portions 6 extending in a direction intersecting the stretch direction (direction Y) of the moisture-permeable film 2 and being arranged alternately in direction Y. More specifically, in the composite sheet 1, the joints 4 extend in direction X perpendicular to direction Y and are arranged intermittently in direction Y, with the portions of the absorbent body 3 that overlap with the joints 4 in a planar view being convex portions 5, and the portions of the absorbent body 3 sandwiched between adjacent convex portions 5, 5 in direction Y being concave portions 6.
In the composite sheet 1, when the uneven structure is formed (when the moisture-permeable film 2 is in its natural state), the portions of the absorbent body 3 corresponding to the convex portions 5 have different effective thicknesses (thickness of only the portions of the absorbent body 3 where the forming material is present) than the portions of the absorbent body 3 corresponding to the concave portions 6, with the portions corresponding to the convex portions 5 having a greater effective thickness than the portions corresponding to the concave portions 6. Such a composite sheet in which the effective thickness of the absorbent body 3 varies depending on the portion when the moisture-permeable film 2 is in its natural state is easily obtained when an absorbent body 3 having a stacked fiber type absorbent core is used.
In the composite sheet 1, when the moisture-permeable film 2 is in its natural state, the absorbent body 3 has an uneven structure in which a plurality of convex portions 5 and concave portions 6 extending in direction X are alternately arranged in direction Y, whereas the moisture-permeable film 2 is flat and substantially free of unevenness. When the composite sheet 1 in its natural state is stretched in the stretch direction (direction Y) of the moisture-permeable film 2, the unevenness of the absorbent body 3 is eliminated during the stretching process, and the uneven structure that the absorbent body 3 had in its natural state is eliminated.

As mentioned above, when the moisture-permeable film 2 is in its natural state, the surface of the absorbent 3 that abuts the moisture-permeable film 2 has an uneven structure. This allows the non-stretchable absorbent 3 to be stretched and contracted in response to the expansion and contraction of the moisture-permeable film 2. Furthermore, this effect can be more reliably achieved when, as in the composite sheet 1 shown in the figure, the uneven structure is formed by alternating pleated convex portions 5 and concave portions 6 that extend in a direction intersecting the expansion and contraction direction (direction Y) of the moisture-permeable film 2. In the composite sheet 1 shown in the figure, an uneven structure is also formed on the surface of the absorbent 3 opposite the surface that abuts the moisture-permeable film 2, but this is not essential to achieving this effect. As long as there is sufficient slack to withstand expansion on the surface of the absorbent 3 opposite the surface that abuts the moisture-permeable film 2 when the moisture-permeable film 2 is in its natural state, this will not pose a problem in achieving the desired effect of the present invention.

Figures 3 to 7 show other embodiments of the composite sheet of the present invention. In the other embodiments described below, configurations that differ from the composite sheet 1 described above will be described, and configurations that are similar to those in composite sheet 1 will be given the same reference numerals and will not be described again. For configurations that are not specifically described in the other embodiments described below, the description of composite sheet 1 will be applied as appropriate.

In the composite sheet 1A shown in Figure 3, the absorbent body 3 has a uniform effective thickness when the uneven structure is formed (when the moisture-permeable film 2 is in its natural state). Such a composite sheet, in which the absorbent body 3 has a uniform effective thickness when the moisture-permeable film 2 is stretched, is easily obtained when the absorbent body 3 uses a sheet-type absorbent core.

In the composite sheet 1B shown in Figure 4, the absorbent body 3 includes an absorbent core 30 and a core wrap sheet 31 that covers the absorbent core 30 and forms the outer surface (the surface opposite the surface facing the moisture-permeable film 2) and inner surface (the surface facing the moisture-permeable film 2) of the absorbent body 3. When the moisture-permeable film 2 is in its natural state, the core wrap sheet 31 has mountain folds 32 formed by partial mountain folds of the core wrap sheet 31 that extend in a direction perpendicular to the stretch direction (direction Y) of the moisture-permeable film 2 (the direction corresponding to direction X in Figure 1) and are arranged intermittently in multiple locations in direction Y. The moisture-permeable film 2 and the absorbent body 3 are joined via multiple joints 4 arranged intermittently in direction Y. When the moisture-permeable film 2 (composite sheet 1B) is in its natural state as shown in Figure 4, the surface of the composite sheet 1B facing the absorbent body 3 has an uneven structure in which pleated convex portions 5 formed by the mountain folds 32 and concave portions 6 formed by non-positioned portions of the mountain folds 32 are arranged alternately in direction Y. When the moisture-permeable film 2 is stretched in direction Y from the natural state of the composite sheet 1B shown in Figure 4, the portion of the core wrap sheet 31 that forms the mountain fold 32 stretches in direction Y, causing the absorbent body 3 to stretch in direction Y. In this way, the mountain fold 32 functions as an "extensibility" for the absorbent body 3.

With regard to the aforementioned composite sheets 1, 1A, and 1B, when the composite sheet is stretched to a state where the uneven structure of the absorbent body 3 completely disappears in the natural state of the moisture-permeable film 2, the elongation of the composite sheet (hereinafter also referred to as the "unevenness disappearance elongation") is preferably equal to or less than the elongation at which the moisture-permeable film 2 can maintain its leakproofness (hereinafter also referred to as the "moisture-permeable film limit elongation"). The "state where the uneven structure completely disappears" refers to a state in which the convex portions 5 (mountain folds 32 in the composite sheet 1B) and concave portions 6 of the absorbent body 3 have disappeared, leaving the absorbent body 3 essentially flat. The establishment of this relationship, "unevenness disappearance elongation ≦ moisture-permeable film limit elongation," prevents a decrease in the leakproofness of the composite sheet due to the moisture-permeable film being stretched beyond the limit elongation at which it can maintain leakproofness. In particular, the establishment of "unevenness disappearance elongation = moisture-permeable film limit elongation" is preferable because it allows the composite sheet to maximize its stretchability without compromising the leakproofness of the moisture-permeable film.

As described above, in the composite sheet of the present invention, the moisture-permeable film is stretchable, and the absorbent body stretches and contracts in accordance with the stretching of the moisture-permeable film, and the absorbent body may be separable into a plurality of individually independent absorbent sections when the moisture-permeable film is in an extended state. Hereinafter, such a separable absorbent body will be referred to as a "separable type" and an inseparable absorbent body will be referred to as a "non-separable type".
FIG. 5 shows a composite sheet 1C, an example of a composite sheet with a segmented absorbent body. The absorbent body 3 of the composite sheet 1C includes a plurality of independent absorbent sections 35. The absorbent sections 35 are configured similarly to the absorbent body 3 except for their size and shape, and include at least an absorbent core. The absorbent core of the absorbent section 35 may be a stacked fiber type or a sheet type. The absorbent section 35 may include a core wrap sheet covering the outer surface of the absorbent core. In this case, the plurality of absorbent sections 35 may be individually covered with the core wrap sheet, or the plurality of absorbent sections 35 may be collectively covered with the core wrap sheet. FIG. 5 shows the natural state of the moisture-permeable film 2 (composite sheet 1C). The plurality of absorbent sections 35 are intermittently arranged on one side of the moisture-permeable film 2 in the stretch direction (direction Y) of the moisture-permeable film 2 in the natural state, and are each fixed to the moisture-permeable film 2 via a joint 4. A non-absorbent section 36 is formed between adjacent absorbent sections 35 in direction Y. The outer surface of the absorber 3 has an uneven structure in which convex portions 5 made up of absorbent sections 35 and concave portions 6 made up of non-absorbent sections 36 are arranged alternately in direction Y. When the moisture permeable film 2 is stretched in direction Y from the natural state shown in Figure 5, the portions of the moisture permeable film 2 corresponding to the non-absorbent sections 36 and the portions of the moisture permeable film 2 corresponding to the regions not joined to the moisture permeable film 2 in the positions of the absorbent sections 35 each stretch in direction Y, and the lengths of these portions in direction Y increase.

The composite sheet 1C can be manufactured, for example, by cutting the composite sheet precursor 10 shown in FIG. 6 along the planned cutting lines indicated by CL in FIG. 2. The composite sheet precursor 10 includes a strip-shaped moisture-permeable film 2 that is elongated in the stretch direction (direction Y) and a strip-shaped absorbent 37 that is elongated in direction Y and bonded to one side of the moisture-permeable film 2. The strip-shaped absorbent 37 has multiple absorbent-free sections 36 that are linear in plan view and extend in direction X, perpendicular to direction Y, and are arranged intermittently in direction Y. The absorbent-free sections 36 are through-holes that penetrate the absorbent strip 37 in the thickness direction. The multiple absorbent-free sections 36 have the same length in direction X and the same positions in direction X at both ends of their longitudinal lengths. By cutting the composite sheet precursor 10 configured in this way along two planned cutting lines CL that extend in direction Y through the multiple absorbent-free sections 36, the absorbent strip 37 is divided into multiple absorbent sections 35, resulting in the composite sheet 1C shown in FIG. 5.

The multiple absorbent sections 35 only need to be independent when the moisture-permeable film 2 is stretched, and may be integrated when the moisture-permeable film 2 has never been stretched (when the composite sheet 1C is unused). For example, when the composite sheet 1C is unused, the multiple absorbent sections 35 are connected to each other in the stretch direction of the moisture-permeable film 2 via connecting sections of relatively low basis weight to form a single absorbent body 3; when the moisture-permeable film 2 is stretched in the stretch direction, the connecting sections break, and from that point onwards the multiple absorbent sections 35 exist independently. To ensure that the connecting sections break easily when the moisture-permeable film 2 is stretched, the connecting sections may include breakage guide lines.

In the composite sheet 1C, the multiple absorbent sections 35 are always spaced apart in the stretch direction (direction Y) of the moisture-permeable film 2, regardless of whether the moisture-permeable film 2 is in a natural state or a stretched state, but in the composite sheet 1D, as shown in Fig. 7 , the absorbent body 3 has an overlapping portion 38 where adjacent absorbent sections 35 in direction Y partially overlap with each other, at least when the moisture-permeable film 2 is in a natural state. Further explaining the composite sheet 1D, one of the two side edges of each of the multiple absorbent sections 35 along direction X (the left edge in Fig. 7 ) is joined to the moisture-permeable film 2 via a joint 4, and the rest of the absorbent section 35 is not joined to the moisture-permeable film 2. The non-joined portion of each of the multiple absorbent sections 35 with respect to the moisture-permeable film 2 overlaps with a portion of another absorbent section 35 adjacent to the non-joined portion that corresponds to the joint 4, thereby forming an overlapping portion 38 at a position overlapping with the joint 4 in a planar view. The joints 4 extend in a direction perpendicular to the direction Y (a direction corresponding to the direction X in FIG. 1 ). Thus, in the natural state of the moisture-permeable film 2, the surface of the composite sheet 1C facing the absorbent body 3 has an uneven structure in which convex portions 5 consisting of overlapping portions 38 and concave portions 6 consisting of non-overlapping portions 38 are alternately arranged in the direction Y. When the moisture-permeable film 2 is stretched in the direction Y from the natural state shown in FIG. 7 , the spacing between adjacent joints 4, 4 in the direction Y increases, the overlapping portions 38 disappear, and multiple absorbent portions 35 may be arranged intermittently in the direction Y. The composite sheet 1D also achieves the same effects as the composite sheet 1. In particular, with the composite sheet 1D, the presence of the overlapping portions 38 in the natural state allows the absorbent portions 35 to be arranged on the moisture-permeable film regardless of the stretched state of the moisture-permeable film, thereby realizing a product design with minimal liquid return.
In a configuration in which multiple absorbent sections 35 partially overlap each other in the natural state of the moisture-permeable film 2, such as the composite sheet 1D, the pattern (shape and arrangement) of the absorbent sections 35 is not limited to that shown in Figure 7, and can be set as appropriate within the range in which the desired effects of the present invention are achieved.

The pattern of the uneven structure (shape and arrangement of the protrusions 5) is not particularly limited and can be set as desired. In the patterns of the uneven structure of the composite sheets 1 and 1A to 1D described above, the protrusions 5 are regularly arranged, but in the present invention, the protrusions 5 may be irregularly arranged. An uneven structure in which the protrusions 5 are regularly arranged has the advantage of providing a good feel and appearance.
The pattern of the concave-convex structure can be controlled to some extent by the pattern of the joints 4, although it depends on the basis weight of the absorbent body 3 and the like. For example, while all of the patterns of the concave-convex structure in the composite sheet described above are patterns in which convex portions and concave portions are arranged alternately in one direction, such a regular pattern can be obtained by adopting, as the pattern of the joints 4, a pattern in which "a plurality of joints 4 extending in one direction are arranged intermittently in a direction intersecting (perpendicular to) that one direction."

The composite sheet of the present invention can be produced, for example, by a method (hereinafter also referred to as "Production Method A") that includes a step of joining a moisture-permeable film and an absorbent body while the moisture-permeable film is in an elongated state, and then releasing the moisture-permeable film from the elongated state. Another method for producing the composite sheet of the present invention includes a step (hereinafter also referred to as "Production Method B") that includes a step of joining the moisture-permeable film and an absorbent body while the moisture-permeable film is in an unelongated state. In either Production Method A or B, the method for joining the moisture-permeable film and the absorbent body (the method for forming the joint according to the present invention) is not particularly limited, and known joining methods such as adhesives and fusion (e.g., heat sealing, ultrasonic sealing, etc.) can be used. In either Production Method A or B, it is preferable to arrange multiple bonded regions between the moisture-permeable film and the absorbent body at intervals in the direction of expansion and contraction of the moisture-permeable film. The composite sheet obtained in this manner can exhibit the stretchability of the moisture-permeable film without inhibiting its inherent stretchability.

The composite sheet of the present invention comprises a moisture-permeable film that is excellent in leakproofness and stretchability, and an absorbent that can absorb bodily fluids such as urine, menstrual blood, and sweat, and is therefore particularly useful as a constituent member of absorbent articles such as disposable diapers and sanitary napkins.
For example, when the composite sheet of the present invention is used as an absorbent body and a back sheet in an absorbent article, i.e., when the composite sheet of the present invention is used in place of the absorbent body and back sheet in an absorbent article, the excellent stretchability of the moisture-permeable film of the composite sheet allows the absorbent body of the composite sheet to follow the movements of the wearer and fit the shape of the wearer's body, whether in a dry state before absorbing body fluids or in a swollen state after absorbing body fluids, and the excellent leak-proof properties of the moisture-permeable film prevent body fluids from leaking out of the absorbent article while it is being worn.
As will be described later, one embodiment of the composite sheet of the present invention employs an olefin-based elastomer and an inorganic filler as the main raw materials of the moisture-permeable film, which can achieve the following secondary effects: a) reduction in manufacturing costs due to the use of relatively inexpensive raw materials, b) improvement in the bonding strength with olefin-based resin components (e.g., adhesives, pressure-sensitive adhesives, anti-slip agents, etc.) conventionally used in absorbent articles, and c) reduction in the environmental burden due to the reduction in the amount of resin used. The effect of c) is that the burden on the environment is reduced because it is not necessary to use a separate elastic material to achieve the stretchability of the moisture-permeable film.

The present invention includes an absorbent article comprising the composite sheet of the present invention. The absorbent article of the present invention broadly includes articles used to absorb body fluids (urine, loose stools, menstrual blood, sweat, etc.) discharged from the human body, such as disposable diapers, sanitary napkins, sanitary shorts, and incontinence pads.
The absorbent article of the present invention typically comprises a topsheet forming the skin-facing surface, a backsheet forming the non-skin-facing surface, and a liquid-retaining absorbent core disposed between these two sheets. The absorbent article may further have leakage-proof cuffs on both sides along the longitudinal direction of the skin-facing surface. The absorbent article of the present invention also includes pants-type absorbent articles comprising an absorbent main body including the above-mentioned topsheet, absorbent core, and backsheet, and an outer body disposed on the non-skin-facing side of the absorbent main body. The topsheet may be any sheet commonly used in this type of absorbent article, without any particular restrictions.

In the absorbent article of the present invention, the composite sheet of the present invention described above is suitable as a component that combines the functions of both an absorbent body and a backsheet. The composite sheet of the present invention functions by itself as both an absorbent body capable of absorbing bodily fluids and a leakproof sheet (backsheet, outer body, etc.) placed on its non-skin-facing side. Therefore, by placing a liquid-permeable sheet such as a topsheet on the skin-facing side of the composite sheet, it can be used as an absorbent article.

One embodiment of the absorbent article of the present invention comprises the composite sheet of the present invention described above and a liquid-permeable sheet disposed on the skin-facing side of the absorbent body of the composite sheet. In this embodiment, the composite sheet of the present invention is disposed so that the absorbent body side is the skin-facing side and the moisture-permeable film side is the non-skin-facing side. The liquid-permeable sheet corresponds to the sheet-like member disposed on the skin-facing side of the absorbent body in this type of absorbent article, and may have a single-layer structure or a laminate structure of multiple sheets. The liquid-permeable sheet of a single-layer structure may be, for example, a topsheet that can come into contact with the wearer's skin while the absorbent article is being worn. The liquid-permeable sheet of a laminate structure may, for example, include the topsheet and a sublayer disposed on the non-skin-facing side of the topsheet.

The absorbent article of the present invention may include a moisture-permeable film and/or an absorbent body in addition to the composite sheet of the present invention. For example, in the absorbent article of the present invention, a separate absorbent body may be placed on the skin-facing side of the absorbent body in the composite sheet of the present invention, and the liquid-permeable sheet may be placed on the skin-facing side of the separate absorbent body. Furthermore, in the absorbent article of the present invention, a separate moisture-permeable film may be placed on the non-skin-facing side of the moisture-permeable film in the composite sheet of the present invention.

In one embodiment of the absorbent article of the present invention, the absorbent article has a longitudinal direction extending from the wearer's abdomen through the crotch region to the back, and a transverse direction perpendicular to the longitudinal direction, and the composite sheet of the present invention included in the absorbent article has stretchability in the longitudinal direction or the transverse direction. In a typical absorbent article, the longitudinal direction coincides with the longitudinal direction of the absorbent article.
In the absorbent article of the present invention, when the composite sheet of the present invention has stretchability in the longitudinal direction, and when the moisture-permeable film provided in the composite sheet is in an extended state, the surface of the composite sheet facing the absorbent body has an uneven structure, the uneven structure can have multiple convex portions and concave portions extending in the horizontal direction arranged alternately in the longitudinal direction.
Furthermore, in the absorbent article of the present invention, when the composite sheet of the present invention has stretchability in the horizontal direction, and when the moisture-permeable film provided in the composite sheet is in an extended state, the surface of the composite sheet facing the absorbent body has an uneven structure, the uneven structure can have multiple convex portions and concave portions extending in the vertical direction arranged alternately in the horizontal direction.

The moisture-permeable film constituting the composite sheet of the present invention will be described in detail below based on preferred embodiments thereof.
The moisture-permeable film has breathability, moisture permeability, leakproofness, and stretchability. The moisture-permeable film is a resin film mainly made of resin and has many micropores, and the breathability and moisture permeability of the moisture-permeable film are mainly due to these micropores. The stretchability of the moisture-permeable film is mainly due to the resin.

Moisture-permeable films typically contain a resin and an inorganic filler. Such moisture-permeable films are produced by stretching a resin sheet obtained by molding a compound containing a resin and an inorganic filler into a film, thereby forming numerous micropores in the resin sheet.

The resin that is the main raw material of the moisture-permeable film can be a resin that exhibits stretchability when formed into a film, and examples thereof include olefin-based resins, ester-based resins (polyethylene terephthalate, polybutylene terephthalate, etc.), amide-based resins (nylon, etc.), acrylonitrile-based resins, vinyl-based resins, vinylidene-based resins, urethane-based resins, etc., and these can be used alone or in combination of two or more. Among these resins, olefin-based resins are particularly suitable as resins for moisture-permeable films because they can be used to produce high-quality moisture-permeable films relatively inexpensively.
The olefin resin used in the moisture-permeable film typically contains as its main component a polymer or copolymer of a monoolefin such as ethylene, propylene, or butene, etc. Specific examples include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.

From the viewpoint of improving the flexibility of the moisture-permeable film, and therefore the flexibility of the composite sheet of the present invention, the moisture-permeable film preferably contains an olefin-based resin composition having a low density.
The olefin resin composition contained in the moisture-permeable film preferably has a density of less than 0.900 g/cm ³ , more preferably 0.895 g/cm ³ or less, and even more preferably 0.885 g/cm ³ or less.
Furthermore, if the olefin resin composition contained in the moisture-permeable film has a density of preferably 0.840 g/ ^cm3 or more, blocking in the moisture-permeable film is less likely to occur, more preferably 0.850 g/ ^cm3 or more, and even more preferably 0.860 g/ ^cm3 or more.
Taking all of the above into consideration, the olefin resin composition contained in the moisture-permeable film preferably has a density of 0.840 g/ ^cm3 or more and less than 0.900 g/ ^cm3 , more preferably 0.850 g/ ^cm3 or more and 0.895 g/ ^cm3 or less, and even more preferably 0.860 g/ ^cm3 or more and 0.885 g/ ^cm3 or less.

From the viewpoint of improving the flexibility of the moisture-permeable film, and therefore the flexibility of the composite sheet of the present invention, the olefin resin composition contained in the moisture-permeable film preferably contains a low-melting-point olefin resin having a melting point of less than 90° C. and a high-melting-point olefin resin having a melting point of at least 95° C. The low-melting-point olefin resin has the advantage of imparting flexibility to the moisture-permeable film, while the high-melting-point olefin resin has the advantage of being able to solidify the moisture-permeable film obtained by melt molding in a short period of time, enabling high-speed molding.
To further enhance the above-mentioned advantages, the melting point of the low-melting-point olefin resin is preferably 80° C. or lower, more preferably 70° C. or lower. In addition, to obtain dimensional stability of the moisture-permeable film, the melting point of the low-melting-point olefin resin is preferably 40° C. or higher.
From the viewpoint of further enhancing the above-mentioned merits, the melting point of the high-melting-point olefin resin is preferably 100° C. or higher, more preferably 110° C. or higher.

The melting points of the olefin resin and its composition contained in the moisture-permeable film are measured by the following method.
Using approximately 2.0 mg of moisture-permeable film as a sample, differential scanning calorimetry (DSC) was performed using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) at a measurement temperature range of 10°C to 260°C, a heating rate of 10°C/min, and in an air environment. An endothermic peak that occurs when the olefin-based resin melts is observed in the resulting DSC curve, and the melting point of the olefin-based resin is the temperature at the apex of the observed endothermic peak. The melting points of the additives contained in the moisture-permeable film and the olefin-based resin can be distinguished by collecting the additive that bleeds out from the moisture-permeable film and measuring its melting point.
The following method can be used to efficiently collect additives from moisture-permeable films. First, the moisture-permeable film is kneaded for 10 minutes at 160°C and 30 rpm using a Labo Plastomill (manufactured by Toyo Seiki Seisakusho) to obtain a resin mass. Next, the resin mass is pressed for 1 minute at 150°C and 13 MPa using a Labo Press (manufactured by Toyo Seiki Seisakusho), and then cold-pressed for 1 minute at room temperature and 13 MPa to obtain a pressed film with a thickness of approximately 0.5 mm. Finally, the pressed film is stored in a 50°C environment for 1 week. By doing so, more additives bleed out onto the pressed film surface than in the moisture-permeable film, allowing the additives to be efficiently collected. Methods for collecting additives from the pressed film surface include, for example, wiping with a wipe or scraping with a spatula.

The content of the low-melting-point olefin resin in the moisture-permeable film is preferably 30 parts by mass or more per 100 parts by mass of the resin in the moisture-permeable film (specifically, for example, an olefin-based resin composition) in order to provide the moisture-permeable film with satisfactory flexibility while maintaining small residual strain after elongation deformation, more preferably 35 parts by mass or more, and even more preferably 40 parts by mass or more. The content is preferably 95 parts by mass or less in order to make the moisture-permeable film less susceptible to blocking, more preferably 92 parts by mass or less, and even more preferably 90 parts by mass or less.
The content of the high-melting point olefin resin in the moisture-permeable film is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the resin in the moisture-permeable film (specifically, for example, an olefin-based resin composition), from the viewpoint of further imparting heat resistance, dimensional stability, and processability to the moisture-permeable film. Furthermore, the content is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less, from the viewpoint of achieving both flexibility and heat resistance, dimensional stability, and processability of the moisture-permeable film.

From the viewpoint of improving the flexibility of the moisture-permeable film, the density of the low-melting-point olefin resin is preferably 0.895 g/cm ³ or less, more preferably 0.885 g/cm ³ or less, and even more preferably 0.875 g/cm ³ or less.
From the viewpoint of maintaining the strength of the moisture-permeable film, the density of the low-melting-point olefin resin is preferably 0.840 g/cm ³ or more, more preferably 0.850 g/cm ³ or more, and even more preferably 0.860 g/cm ³ or more.
Considering the above, on the premise that the density of the low-melting-point olefin resin is lower than the density of the high-melting-point olefin resin used in combination, the density is preferably 0.840 g/cm ^or more and 0.895 g/cm ^{or less} , more preferably 0.850 g/cm ^or more and 0.885 g/cm ^or less, and even more preferably 0.860 g/cm or ^more and 0.875 g/cm ^or less.
A preferred example of the low-melting-point olefin-based resin is a copolymer of ethylene and an α-olefin, and examples of the α-olefin include propylene, 1-butene, 1-pentene, and 1-hexene. In order to achieve both the preferred density range and the preferred melting point range, the low-melting-point olefin-based resin is preferably a random copolymer.

From the viewpoint of achieving a balance between flexibility, heat resistance, dimensional stability, and processability of the moisture-permeable film, the density of the high-melting-point olefin resin is preferably relatively low, and is preferably 0.950 g/ ^cm3 or less, more preferably 0.940 g/ ^cm3 or less, and even more preferably 0.930 g/ ^cm3 or less.
From the viewpoint of suppressing blocking, the density of the high-melting-point olefin resin is preferably 0.900 g/cm ³ or more, more preferably 0.905 g/cm ³ or more, and even more preferably 0.910 g/cm ³ or more.
Considering the above, assuming that the density of the high-melting-point olefin resin is higher than the density of the low-melting-point olefin resin used in combination, it is preferably 0.900 g/cm ³ or more and 0.950 g/cm ³ or less, more preferably 0.905 g/cm ³ or more and 0.940 g/cm ³ or less, and even more preferably 0.910 g/cm ³ or more and 0.930 g/cm ³ or less.
As the high-melting-point olefin resin having the above density, low-density polyethylene and linear low-density polyethylene are preferably used, and linear low-density polyethylene is particularly preferred from the viewpoints of improving heat resistance during stretching and enabling uniform stretching. In particular, linear low-density polyethylene polymerized with a metallocene catalyst is more preferred because it further improves the strength of the film against tearing, puncture, etc.

In the moisture-permeable film, the inorganic filler is a substance that causes peeling at the interface with the resin used in combination to form micropores. From the viewpoint of ensuring that the inorganic filler functions as described above, the average particle size D50 of the inorganic filler is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 30 μm or less, more preferably 10 μm or less.
The average particle size D50 of the inorganic filler is the weight cumulative particle size at a cumulative weight of 50% by mass as determined by a laser diffraction scattering particle size distribution measurement method.

Examples of inorganic fillers include calcium carbonate, gypsum, talc, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium phosphate, aluminum hydroxide, zinc oxide, titanium oxide, alumina, mica, zeolite, carbon black, and mixtures thereof. Calcium carbonate is particularly preferred because its average particle size D50 can be easily adjusted to fall within the preferred range mentioned above.

From the perspective of balancing the breathability, moisture permeability, and leak resistance of the moisture permeable film, the content of inorganic filler in the moisture permeable film is preferably at least 50 parts by mass, more preferably at least 60 parts by mass, even more preferably at least 80 parts by mass, and preferably at most 400 parts by mass, more preferably at most 350 parts by mass, and even more preferably at most 200 parts by mass, per 100 parts by mass of resin in the moisture permeable film. If the content of inorganic filler is too low, the size and number of micropores may be insufficient, resulting in insufficient breathability and moisture permeability, while if the content of inorganic filler is too high, it may result in reduced leak resistance.

Typically, moisture-permeable films contain a dispersant for the inorganic filler. Dispersants that can hydrophobize the surface of the inorganic filler are preferably used. From this perspective, it is preferable to use fatty acids as the dispersant. Examples of fatty acids include caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, and lauric acid.

The moisture-permeable film may further contain a pore-opening promoter in addition to the above-mentioned resin (preferably an olefin-based resin) and inorganic filler. The pore-opening promoter is used for the purpose of smoothly forming micropores by stretching a resin sheet obtained by molding a compound containing a resin and an inorganic filler into a film. As mentioned above, from the viewpoint of improving the flexibility of the moisture-permeable film, it is preferable to contain a low-melting-point olefin-based resin in the moisture-permeable film. However, since the low-melting-point olefin-based resin is a resin that is relatively unlikely to undergo interfacial peeling with the inorganic filler, using a pore-opening promoter in addition to the low-melting-point olefin-based resin as a raw material for the moisture-permeable film can promote such interfacial peeling.
As the pore opening promoter, a substance known as a mold release agent between metal and resin is preferably used. Specific examples include metal soap, silicone, fluororesin, fatty acid amide, hydrocarbon paraffin wax, etc. In particular, it is preferable to use metal soap because it can more smoothly form micropores.
The metal soap is preferably a metal salt of a fatty acid. Examples of the fatty acid include caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, and lauric acid. Examples of the metal salt include salts of calcium, aluminum, magnesium, zinc, etc., of these fatty acids.
In particular, it is preferable that the hydrocarbon chain length of the fatty acid serving as a dispersant is the same as that of the fatty acid constituting the metallic soap, since this allows the metallic soap to be more smoothly transferred to the inorganic filler surface-modified with the fatty acid. In particular, it is preferable that both the fatty acid and the fatty acid constituting the metallic soap are stearic acid.
Fatty acids themselves are known as substances similar to metal salts of fatty acids and are incorporated into moisture-permeable films. Fatty acids are used to enhance the dispersibility of inorganic fillers. However, fatty acids do not promote interfacial delamination between resins and inorganic fillers. Therefore, in the present invention, metal salts of fatty acids and fatty acids are clearly distinguished from each other both physically and functionally.

In particular, it is preferable to use a metal soap with a melting point of 200°C or less, as this allows the metal soap to melt sufficiently and be uniformly mixed into the molten resin when the compound is kneaded during the moisture-permeable film manufacturing process. From this perspective, it is more preferable for the melting point of the metal soap to be 180°C or less, and even more preferable for it to be 160°C or less.

In addition, in relation to the resin described above, it is preferable to use a metal soap whose precipitation temperature is higher than the solidification temperature of the resin, as this allows for the successful formation of micropores and results in a moisture-permeable film with high moisture permeability and high water resistance. Specifically, when the precipitation temperature of the metal soap is higher than the solidification temperature of the resin, the metal soap precipitates faster than the resin solidifies, allowing the metal soap to smoothly migrate to the surface of the inorganic filler. As a result, the releasability between the inorganic filler and the resin during stretching is improved, and micropores are smoothly formed. To further enhance this advantage, when the precipitation temperature of the metal soap is Ts (°C) and the solidification temperature of the resin is Tp (°C), the value of Ts - Tp is preferably greater than 0°C, more preferably 1°C or greater, and even more preferably 2°C or greater. Furthermore, it is preferable that the value of Ts - Tp is 50°C or less.

Provided that the value of Ts-Tp is within the above-mentioned range, the deposition temperature Ts of the metal soap is preferably 80°C or higher and 180°C or lower, more preferably 90°C or higher and 170°C or lower, and even more preferably 100°C or higher and 160°C or lower.
On the other hand, the solidification temperature Tp of the resin is preferably 60°C or higher and 130°C or lower, more preferably 70°C or higher and 120°C or lower, and even more preferably 80°C or higher and 115°C or lower, provided that the value of Ts-Tp is within the above-mentioned range.

The precipitation temperature Ts of the metal soap is measured using a hot stirrer and a thermocouple as follows. Using a hot stirrer, 0.43 g of the metal soap is added to 5.0 g of paraffin oil, and the mixture is heated while stirring until the metal soap dissolves. After stirring the liquid with the stirrer is stopped, the temperature of the paraffin oil is lowered at a rate of 0.2°C/min, and the temperature of the paraffin oil when the metal soap begins to precipitate is read with a thermocouple, and this temperature is defined as the precipitation temperature of the metal soap. Note that if the metal soap does not dissolve in the paraffin oil even after the paraffin oil is heated to 210°C, the precipitation temperature is defined as 210°C.
On the other hand, the resin solidification temperature Tp is measured in accordance with JIS K 7121 (method of determining the extrapolated crystallization end temperature) using the following method. Approximately 2.0 mg of moisture-permeable film is used as a sample, and differential scanning calorimetry (DSC) is performed using a differential scanning calorimeter (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) under the following conditions: a measurement temperature range of 30 ° C to 260 ° C, a heating rate of 10 ° C/min, a heating rate of 50 ° C/min, an air environment, and a data sampling period of 0.5 s. During the cooling process of the obtained DSC curve, an exothermic peak that occurs when the resin solidifies (crystallizes) is observed. The resin solidification temperature is the temperature at the intersection of a straight line extending the baseline on the lower side of the peak temperature toward the higher side, relative to the peak with the greatest heat release during the cooling process, and an approximation line drawn between the two data points where the slope of the curve on the lower side of the peak is greatest. When two or more overlapping exothermic peaks exist, the peaks are separated using, for example, software PeakFit v4.12 (manufactured by Hulinks Co., Ltd.), and then the solidification temperature is determined by the above-mentioned method.

From the viewpoint of promoting the formation of micropores, the content of the pore opening promoter in the moisture-permeable film is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the resin in the moisture-permeable film; and from the viewpoint of obtaining good film formability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

Furthermore, when the moisture-permeable film contains an inorganic filler and the pore-opening promoter in the moisture-permeable film is a metal soap, the content of the metal soap in the moisture-permeable film is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more per 100 parts by mass of the inorganic filler in the moisture-permeable film, in order to successfully generate micropores. Furthermore, in order to maintain good moldability, the content is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less.

The moisture-permeable film may further contain a triglyceride in addition to the resin (preferably an olefin-based resin composition), inorganic filler, and, if necessary, a pore-opening promoter. The triglyceride can function as a water-repellent agent that improves the water pressure resistance and leak-proofness of the moisture-permeable film.
In the technical field of moisture-permeable films used in the present invention, triglycerides have been blended into moisture-permeable films up to now, but the triglyceride used in the present invention is preferably a different type from the triglycerides that have been used up to now in the technical field. In particular, the triglyceride preferably used in the present invention is a "triglyceride that contains a group derived from a fatty acid having from 16 to 22 carbon atoms, and this group is a hydrocarbon group that has no unsaturated bond or substituent" (hereinafter also referred to as a "specific triglyceride"). As a result of investigations by the present inventors, it was found that the use of a specific triglyceride improves the water repellency of moisture-permeable films containing the specific triglyceride, and improves the leak-proofness of the moisture-permeable films more than ever before.

In order to make the above-mentioned advantages even more pronounced, the content of the specific triglyceride in the moisture-permeable film is preferably 0.1 parts by mass or more per 100 parts by mass of the resin, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more.
Furthermore, from the viewpoint of film formability, the content of the specific triglyceride is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the resin.
Taking all of the above into consideration, the content of the specific triglyceride is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1.0 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the resin.

In addition, from the perspective of fully utilizing the effects of both the metal soap used as a pore-opening promoter and the water repellent, and from the perspective of preventing deterioration of processability due to excessive additive content, the ratio of the specific triglyceride to the metal soap contained in the moisture-permeable film is preferably 30 to 300 parts by weight of the metal soap per 100 parts by weight of the specific triglyceride. To further enhance this advantage, the metal soap is preferably used in an amount of 35 to 230 parts by weight, and even more preferably 40 to 220 parts by weight, per 100 parts by weight of the specific triglyceride.

The specific triglyceride is described below. The specific triglyceride is represented by the following formula (1):

In the formula (1), R ¹ , R ² , and R ³ represent the same or different hydrocarbon groups. At least one of ^{R 1} , R ² , and R ³ is a group derived from a fatty acid having 16 to 22 carbon atoms, and this group is a hydrocarbon group having no unsaturated bond or substituent. The alkyl group of palmitic acid, a fatty acid having 16 carbon atoms, has 15 carbon atoms.
The "hydrocarbon group having no unsaturated bonds" refers to a hydrocarbon group having neither a carbon-carbon double bond nor a triple bond. In other words, it refers to an alkyl group. Furthermore, the "hydrocarbon group having no substituents" refers to a hydrocarbon group in which the hydrogen atoms contained in the hydrocarbon group are not substituted with other atoms or atomic groups (for example, hydroxyl groups). Therefore, the "hydrocarbon group having no unsaturated bonds or substituents" is synonymous with an unsubstituted alkyl group.

In the specific triglyceride represented by the formula (1), from the viewpoint of obtaining a moisture-permeable film with even higher water repellency, it is preferable that at least one of R ¹ , R ² , and R ³ is a group derived from a fatty acid having from 16 to 20 carbon atoms, and that this group is a hydrocarbon group having no unsaturated bonds or substituents.
Furthermore, in the specific triglyceride represented by formula (1), when any one or two of R ¹ , R ² , and R ³ is a group other than a group derived from a fatty acid having from 16 to 22 carbon atoms (the group is a hydrocarbon group having no unsaturated bond and no substituent), the type of the group is not particularly limited as long as it is a group derived from a fatty acid, but from the viewpoint of obtaining a moisture-permeable film with even higher water repellency, it is preferable that the group has no unsaturated bond and no substituent.

The specific triglyceride is preferably one in which the number of carbon atoms in the fatty acid residue is adjusted. By doing so, the water repellency of the moisture-permeable film can be improved. Specifically, the specific triglyceride is preferably (A) or (B) below.
(A) A triglyceride containing a mixture of a triglyceride containing at least a group derived from a fatty acid having 18 carbon atoms in one molecule and a triglyceride containing at least a group derived from a fatty acid having 16 to 22 carbon atoms in one molecule (excluding fatty acids having 18 carbon atoms).
(B) A triglyceride containing, in one molecule, at least one group derived from a saturated fatty acid having 18 carbon atoms and at least one group derived from a saturated fatty acid having 16 to 22 carbon atoms (excluding fatty acids having 18 carbon atoms).
In particular, from the viewpoint of further enhancing the liquid repellency, it is preferable that the triglyceride contains, in one molecule, at least one group derived from a saturated fatty acid having 18 carbon atoms and at least one group derived from a saturated fatty acid having 16 to 22 carbon atoms (excluding fatty acids having 18 carbon atoms).
As a specific example, a combination of a fatty acid having 18 carbon atoms and a fatty acid having 16 carbon atoms is as shown in (C) or (D) below.
(C) A triglyceride containing a mixture of a triglyceride containing at least a group (the group is a hydrocarbon group having no unsaturated bonds and no substituents) derived from a fatty acid having 18 carbon atoms (i.e., stearic acid) in one molecule, and a triglyceride containing at least a group (the group is a hydrocarbon group having no unsaturated bonds and no substituents) derived from a fatty acid having 16 carbon atoms (i.e., palmitic acid) in one molecule.
(D) A triglyceride containing, in one molecule, at least one group derived from a fatty acid having 18 carbon atoms (the group is a hydrocarbon group having no unsaturated bonds or substituents) and at least one group derived from a fatty acid having 16 carbon atoms (the group is a hydrocarbon group having no unsaturated bonds or substituents).

As in the case of (C) above, when the specific triglyceride includes multiple types of triglycerides, it is preferable that at least one of the triglycerides contains at least one group derived from a saturated fatty acid having 16 carbon atoms in one molecule (this triglyceride is also referred to as "triglyceride 16"). Triglyceride 16 may contain one group derived from a saturated fatty acid having 16 carbon atoms in one molecule (this triglyceride is also referred to as "triglyceride P"), two groups (this triglyceride is also referred to as "triglyceride PP"), or three groups (this triglyceride is also referred to as "triglyceride PPP").
The type of the remaining fatty acid residue in triglyceride P and triglyceride PP is not particularly limited, and may be, for example, a residue of a saturated fatty acid having 12 to 24 carbon atoms.

Triglyceride 16 may consist solely of triglyceride P, may consist solely of triglyceride PP, or may consist solely of triglyceride PPP.
The triglyceride 16 may be a combination of two or more selected from triglyceride P, triglyceride PP, and triglyceride PPP. For example, the triglyceride 16 may be a combination of triglyceride P and triglyceride PP, a combination of triglyceride P and triglyceride PPP, a combination of triglyceride PP and triglyceride PPP, or a combination of triglyceride P, triglyceride PP, and triglyceride PPP.

As in the case of (C) above, when the specific triglyceride includes multiple types of triglycerides, it is also preferred that at least one of the triglycerides contains at least one group derived from a saturated fatty acid having 18 carbon atoms in one molecule (this triglyceride is also referred to as "triglyceride 18"). Triglyceride 18 may contain one group derived from a saturated fatty acid having 18 carbon atoms in one molecule (this triglyceride is also referred to as "triglyceride S"), two groups (this triglyceride is also referred to as "triglyceride SS"), or three groups (this triglyceride is also referred to as "triglyceride SSS").
The type of the remaining fatty acid residue in triglyceride S and triglyceride SS is not particularly limited, and may be, for example, a residue of a saturated fatty acid having 12 to 24 carbon atoms.

Triglycerides 18 may consist solely of S triglycerides, may consist solely of SS triglycerides, or may consist solely of SSS triglycerides.
Triglyceride 18 may be a combination of two or more selected from triglyceride S, triglyceride SS, and triglyceride SSS. For example, triglyceride 18 may be a combination of triglyceride S and triglyceride SS, a combination of triglyceride S and triglyceride SSS, a combination of triglyceride SS and triglyceride SSS, or a combination of triglyceride S, triglyceride SS, and triglyceride SSS.

In case (C) above, the specific triglyceride may consist solely of triglyceride 16 and triglyceride 18, or may contain other triglycerides in addition to triglyceride 16 and triglyceride 18. Examples of other triglycerides include triglycerides that have no groups derived from fatty acids having 14 to 22 carbon atoms, and triglycerides that contain groups derived from fatty acids having 14 to 22 carbon atoms (excluding triglyceride 16 and triglyceride 18).

If "P" denotes a group derived from a saturated fatty acid having 16 carbon atoms, "S" denotes a group derived from a saturated fatty acid having 18 carbon atoms, and "X" and "Y" denote groups derived from a saturated fatty acid having 16 carbon atoms and a fatty acid other than a saturated fatty acid having 18 carbon atoms, examples of combinations of aliphatic groups that make up specific triglycerides include PPP, SSS, PPX, SSX, PXY, SXY, PPS, PSS, and PSX. The structures of triglycerides represented by PPX, SSX, PXY, SXY, and PSX are (a) to (m) below. Note that the structures of PPS and PSS are not shown, but the structure of PPS conforms to the structure of PPX, and the structure of PSS conforms to the structure of SSX.

The specific triglyceride may be any of the various triglycerides described above. For example, in the case of (D) above, the specific triglyceride may be composed of a triglyceride containing, in one molecule, at least one group derived from a saturated fatty acid having 16 carbon atoms and at least one group derived from a saturated fatty acid having 18 carbon atoms, but no groups derived from other fatty acids. Alternatively, the specific triglyceride may be composed of a triglyceride containing one group derived from a saturated fatty acid having 16 carbon atoms, one group derived from a saturated fatty acid having 18 carbon atoms, and one group derived from another fatty acid.

The specific triglyceride may be a combination of two or more of the various triglycerides described above. For example, the specific triglyceride may be a combination of the triglycerides (C) and (D). Alternatively, the specific triglyceride may be a combination of two or more of the triglycerides (D).
Furthermore, the specific triglyceride may be a combination of one or more of the above-mentioned triglycerides with other triglycerides, such as triglycerides containing a group derived from a fatty acid having 14 to 22 carbon atoms (excluding triglyceride 16 and triglyceride 18).
In the present invention, it is preferred to use the above-mentioned various triglycerides alone or to use a combination of two or more of the above-mentioned various triglycerides, from the viewpoint of further increasing the water repellency of the moisture-permeable film.

From the viewpoint of obtaining a moisture-permeable film with even higher water repellency, it is preferred that the triglycerides contained in the moisture-permeable film used in the present invention have 28% by mass or more and 96% by mass or less, particularly 28% by mass or more and 70% by mass or less, and especially 29% by mass or more and 67% by mass or less, of the total amount of groups derived from fatty acids contained in all triglycerides in the moisture-permeable film, be groups derived from fatty acids having 18 carbon atoms (these groups are hydrocarbon groups having no unsaturated bonds and no substituents).
The above-mentioned "all triglycerides" is a general term for the specific triglycerides contained in the moisture-permeable film and triglycerides other than the specific triglycerides (hereinafter the same unless otherwise specified).

Furthermore, from the viewpoint of further increasing the water repellency of the moisture-permeable film and shortening the time until water repellency is achieved, it is preferable that the triglycerides contained in the moisture-permeable film used in the present invention have, relative to the total amount of groups derived from fatty acids contained in all triglycerides in the moisture-permeable film, 28% by mass to 68% by mass of groups derived from fatty acids having 18 carbon atoms (these groups are hydrocarbon groups having no unsaturated bonds or substituents) and 26% by mass to 70% by mass of groups derived from fatty acids having 16 carbon atoms (these groups are hydrocarbon groups having no unsaturated bonds or substituents), provided that the sum of the proportion of groups derived from fatty acids having 18 carbon atoms and the proportion of groups derived from fatty acids having 16 carbon atoms does not exceed 100% by mass.
In this case, the proportion of groups derived from fatty acids having 18 carbon atoms is more preferably 29% by mass or more and 66% by mass or less, and even more preferably 30% by mass or more and 64% by mass or less.
On the other hand, the proportion of groups derived from fatty acids having 16 carbon atoms is more preferably 27% by mass or more and 69% by mass or less, and even more preferably 28% by mass or more and 68% by mass or less. The higher the proportion of groups derived from fatty acids having 16 carbon atoms, the more easily triglycerides are precipitated on the surface of the moisture-permeable film, and the shorter the time until water repellency is achieved.

Furthermore, from the viewpoint of improving the thermal stability of the moisture-permeable film and further increasing the water repellency of the moisture-permeable film, it is preferable that the triglycerides contained in the moisture-permeable film used in the present invention have, relative to the total amount of groups derived from fatty acids contained in all triglycerides, 28% by mass to 47% by mass of groups derived from fatty acids having 18 carbon atoms (these groups are hydrocarbon groups having no unsaturated bonds or substituents) and 40% by mass to 60% by mass of groups derived from fatty acids having 22 carbon atoms (these groups are hydrocarbon groups having no unsaturated bonds or substituents), provided that the sum of the proportion of groups derived from fatty acids having 18 carbon atoms and the proportion of groups derived from fatty acids having 22 carbon atoms does not exceed 100% by mass.
In this case, the proportion of groups derived from fatty acids having 18 carbon atoms is more preferably 30% by mass or more and 45% by mass or less, and even more preferably 32% by mass or more and 43% by mass or less.
On the other hand, the proportion of groups derived from fatty acids having 22 carbon atoms is more preferably 42% by mass or more and 58% by mass or less, and even more preferably 44% by mass or more and 56% by mass or less. The higher the proportion of groups derived from fatty acids having 22 carbon atoms, the higher the melting point of the triglyceride and the higher the thermal stability of the molded product. Furthermore, contamination of the rolls of the processing machine can be reduced.

The proportions of groups derived from fatty acids having 16 carbon atoms, groups derived from fatty acids having 18 carbon atoms, and groups derived from fatty acids having 22 carbon atoms, based on the total amount of groups derived from fatty acids contained in all triglycerides, are measured by the following method.
The triglycerides that bleed out from the surface of the film to be measured are wiped with a cellulose wiper and collected. The ester bonds in the collected triglycerides are hydrolyzed with alkali, and the methyl-esterified fatty acids are quantitatively analyzed by gas chromatography.

Whether or not alkyl chains with different carbon numbers exist within a single triglyceride molecule can be determined using TOF-MS (time-of-flight mass spectrometry). Specifically, the molecular weight distribution of triglycerides is measured using TOF-MS, and whether or not alkyl groups with different carbon numbers exist within the molecule can be determined from the molecular weight of each molecule. Whether or not alkyl chains with different carbon numbers exist within a single molecule of a compound with the same molecular weight can be determined using a tandem mass spectrometer (MS/MS). Specific ions are selected in the first mass separation section, and the fragment ions generated by colliding with an inert gas are separated and detected in the second mass separation section to determine the presence of alkyl chains.

The triglycerides used in the present invention preferably do not contain groups derived from unsaturated fatty acids, from the perspective of further increasing the water repellency of the moisture-permeable film. "Doing not contain groups derived from unsaturated fatty acids" encompasses both cases where no groups derived from unsaturated fatty acids are contained at all, and cases where a small amount of unsaturated fatty acids is unavoidably contained. An example of a case where a small amount of unsaturated fatty acids is unavoidably contained is when the proportion of groups derived from unsaturated fatty acids is 2% by mass or less, based on the total amount of groups derived from fatty acids contained in all triglycerides in the moisture-permeable film.

As mentioned above, it is preferable that the triglyceride used in the present invention does not contain any groups derived from fatty acids having hydroxyl groups, from the viewpoint of further enhancing the water repellency of the moisture-permeable film. A fatty acid having a hydroxyl group is a fatty acid in which at least one hydrogen atom in the hydrocarbon group of the fatty acid is substituted with a hydroxyl group. "Not containing any groups derived from fatty acids having hydroxyl groups" encompasses both cases in which no groups derived from fatty acids having hydroxyl groups are contained at all, and cases in which small amounts of groups derived from fatty acids having hydroxyl groups are unavoidably contained. An example of a case in which small amounts of groups derived from fatty acids having hydroxyl groups are those in which the proportion of groups derived from fatty acids having hydroxyl groups is 2% by mass or less, based on the total amount of groups derived from fatty acids contained in all triglycerides in the moisture-permeable film.

From the perspective of further increasing the water repellency of the moisture-permeable film used in the present invention, it is preferable that in the moisture-permeable film, the groups derived from fatty acids contained in all triglycerides are hydrocarbon groups without unsaturated bonds. It is also preferable that the groups derived from fatty acids contained in all triglycerides are hydrocarbon groups without substituents.

The moisture-permeable film used in the present invention may contain only triglycerides as glycerides, or may contain monoglycerides and/or diglycerides in addition to triglycerides, as long as the desired effects of the present invention are achieved.

The moisture-permeable film may contain components other than the aforementioned olefin-based resins and other resins, inorganic fillers, dispersants, pore-opening promoters, and specific triglycerides. Examples of such components include plasticizers, antioxidants, UV absorbers, and colorants. Dispersants and plasticizers are particularly useful in imparting various additional properties to the moisture-permeable film.

The plasticizer is used to impart flexibility and suppleness to the moisture-permeable film and to prevent rustling noise from occurring in the moisture-permeable film. Preferred plasticizers include monoesters, polyesters, ethylene-α-olefin co-oligomers, low-molecular-weight polyethylenes, olefin oligomers, liquid polyisoprene, and liquid polybutadiene.
Monoesters are compounds obtained from monobasic acids and monohydric alcohols.
On the other hand, polyester is a compound obtained by combining any one of polybasic acid and monohydric alcohol, monobasic acid and polyhydric alcohol, and polybasic acid and polyhydric alcohol.
Ethylene-alpha olefin co-oligomers are low molecular weight copolymers of ethylene with an alpha olefin such as propylene, 1-butene, 1-pentene, and 1-hexene.
As the basic acid, polybasic acid, monohydric alcohol, and polyhydric alcohol, for example, the following are preferably used.
Examples of monobasic acids include monocarboxylic acids of long-chain hydrocarbons having 10 to 22 carbon atoms.
Examples of polybasic acids include dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids.
Examples of the monohydric alcohol include monoalcohols of long chain hydrocarbons having 10 to 22 carbon atoms.
Examples of polyhydric alcohols include diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, and sucrose.

Particularly preferred polyesters as plasticizers include, for example, polyesters of diethylene glycol and dimer acid in which the carboxylic acid or alcohol at both ends is partially or completely blocked with stearyl alcohol or stearic acid, polyesters of 1,3-butanediol and adipic acid, hexaesters of trimethylolpropane-adipic acid-stearic acid, octaesters of pentaerythritol-adipic acid-stearic acid, and dodecaesters of dipentaerythritol-adipic acid-stearic acid.

Furthermore, particularly preferred monoesters as plasticizers include, for example, esters with a total of 30 or more carbon atoms obtained by dehydration of a monocarboxylic acid having 1 to 40 carbon atoms and a monoalcohol having 1 to 40 carbon atoms. Of these, those with a total of 30 or more carbon atoms obtained from a monocarboxylic acid and a monoalcohol are preferred, and monoesters with a total of 38 or more carbon atoms and having a branched chain are even more preferred. Specific examples include isodecyl stearate, isodecyl behenate, isotridecyl stearate, 2-octadecyl stearate, 2-decyltetradecyl laurate, 2-decyltetradecyl stearate, 2-octadecyl behenate, stearyl isostearate, esters of stearic acid and C20 Guerbet alcohol, and esters of α-branched fatty acids (having 18 to 40 carbon atoms) and monoalcohols (having 6 to 36 carbon atoms).

The content of dispersant and plasticizer in the moisture-permeable film is preferably at least 0.01 parts by mass, more preferably at least 0.10 parts by mass, even more preferably at least 2.0 parts by mass, and preferably at most 18.0 parts by mass, more preferably at most 16.0 parts by mass, per 100 parts by mass of resin in the moisture-permeable film, from the standpoint of clarifying the purpose of their use and suppressing the adverse effects that result from excessive use (for example, a decrease in the formability and strength of the film).

Additives other than the specific triglyceride (such as pore-opening promoters, dispersants, and plasticizers) that can be contained in the moisture-permeable film may include at least a first additive whose SP value differs from that of the specific triglyceride by less than 0.37. The first additive is preferably contained in an amount of 3.5 parts by mass or less per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined, since this allows the additive to be incorporated without inhibiting the water repellency exhibited by the specific triglyceride. From the viewpoint of improving leakproofness without impairing water repellency, the first additive is preferably contained in an amount of 0.01 to 3.5 parts by mass, more preferably 0.03 to 3.3 parts by mass, and even more preferably 0.06 to 3.2 parts by mass, per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined.
The additive may also contain at least a second additive whose SP value differs from that of the specific triglyceride by 0.37 or more. The second additive is preferably contained in an amount of 10 parts by mass or less per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined, since this allows the additive to be incorporated without inhibiting the water repellency exhibited by the specific triglyceride. When the second additive is contained as an additive, the second additive is preferably contained in an amount of 0.01 to 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 1.5 to 6 parts by mass, per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined, from the viewpoint of improving leakproofness without impairing water repellency.
As mentioned above, in the technical field of moisture-permeable films such as the moisture-permeable film used in the present invention, triglycerides have been incorporated into moisture-permeable films. However, the inventors' investigations have revealed that randomly incorporating additives into a moisture-permeable film containing triglycerides inhibits the water repellency inherent to the triglycerides. In contrast, by using the first additive in an amount of 3.5 parts by mass or less per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined, or by using the second additive in an amount of 10 parts by mass or less per 100 parts by mass of the resin, inorganic filler, and specific triglyceride combined, the additives can be incorporated without inhibiting the water repellency exhibited by the specific triglyceride. To further enhance this advantage, the difference in SP value between the specific triglyceride and the second additive is preferably 0.50 or more, and even more preferably 0.60 or more. Moreover, the difference is preferably 4.00 or less, more preferably 3.00 or less, and even more preferably 1.50 or less.

The SP value is a physical property known as the solubility parameter, and two substances with similar SP values tend to mix well together. In other words, two substances with similar SP values are highly compatible. Therefore, when comparing the SP value of a specific triglyceride with the SP value of an additive, the SP value of the specific triglyceride may be higher, or the SP value of the additive may be higher. From the perspective of preventing the additive from interfering with the water repellency of the specific triglyceride, it is preferable that the SP value of the specific triglyceride be higher than the SP value of the additive.

Examples of the first additive selected so that the difference in SP value from the specific triglyceride is less than 0.37 include fatty acids, alcohols, monoesters, polyesters, and metal soaps, which are exemplified above as dispersants, plasticizers, and pore-opening promoters.

Examples of the second additive selected so that the difference in SP value from the specific triglyceride is 0.37 or more include olefin oligomers, ethylene-α-olefin co-oligomers, low-molecular-weight polyethylene, silicone rubber, fluororubber, fluororesin, and polystyrene. In the present invention, the second additive may be used alone, or the second additive and the first additive may be used in combination. In some cases, the first additive may be used alone.

The SP value is calculated by the Fedors method [R. F. FEDORS, POLYM. ENG. SCI. 14, 147 (1974)] and is expressed in units of (cal/cm ³ ) ^1/2 .

When the moisture-permeable film contains multiple types of specific triglycerides, the SP value δmix of the mixture shown below is calculated.
δmix=Σδiφi (cal/cm ³ ) ^1/2
In the above formula, δi represents the SP value of each component constituting the mixture, and φi represents the volume fraction of that component.

Next, a preferred method for producing the moisture-permeable film used in the present invention will be described.
A suitable method for producing a moisture-permeable film includes a step of stretching, at least uniaxially, a resin sheet obtained by melt-molding a compound containing a resin, an inorganic filler, and an additive.
The details of the resin, inorganic filler, and additives contained in the compound are as described above. The blending amounts of the resin, inorganic filler, and additives contained in the compound are the same as the blending amounts of these components contained in the moisture-permeable film. Furthermore, the types and amounts of optional components contained in the compound are the same as the types and amounts of optional components contained in the moisture-permeable film.

The moisture-permeable film used in the present invention can be efficiently produced, for example, by the following method.
First, the components constituting the compound described above are premixed using a Henschel mixer, a supermixer, or the like, and then kneaded and pelletized using a single-screw or twin-screw extruder. The pellets are then used to form a film using a molding machine to obtain a resin sheet. Examples of molding machines that can be used include T-die and inflation types.

The dispersant may be used alone or mixed with the other components that make up the compound, but it is preferable to first attach it to the surface of the inorganic filler to produce a surface-modified inorganic filler, and then mix this surface-modified inorganic filler with the other components that make up the compound to prepare the compound. This allows the resin sheet to be successfully stretched while suppressing the occurrence of unintended pinholes, resulting in a moisture-permeable film that combines high moisture permeability and high water resistance.

By stretching the aforementioned resin sheet uniaxially or biaxially, interfacial delamination between the resin and inorganic filler occurs, forming micropores. This stretching can be achieved using a roll method, which allows stretching in the machine direction, or a tenter method, which allows stretching in both the machine direction and the film width direction. In this way, the moisture-permeable film used in the present invention is obtained. To increase the area of the resin sheet as it is stretched, it is preferable to stretch the resin sheet at least uniaxially by 1.1 times or more, more preferably by 1.5 times or more, and even more preferably by 2 times or more. Furthermore, to avoid a decrease in tear strength due to excessive molecular orientation caused by excessive stretching, it is preferable to stretch the resin sheet by 5.0 times or less, more preferably by 4.5 times or less, and even more preferably by 4 times or less.

Whether uniaxially or biaxially stretched, the temperature of the resin film during stretching is preferably set to 30°C or higher and 100°C or lower, more preferably 35°C or higher and 95°C or lower, and even more preferably 40°C or higher and 90°C or lower, in order to ensure that the film can be stretched uniformly without breaking.

The present invention has been described above based on its preferred embodiments, but the present invention is not limited to the above embodiments and can be modified as appropriate within the scope of the invention.
The following supplementary notes are further disclosed regarding the above-described embodiment of the present invention.

<1>
a stretchable moisture-permeable film having micropores and an absorbent body capable of absorbing body fluids are overlapped and joined to each other at a joining portion present between the overlapping surfaces;
The moisture-permeable film is stretchable and is evaluated as having leak-proofness in the moisture-permeable film leak-proofness evaluation test at 30% elongation,
The composite sheet is such that the absorbent body expands and contracts in accordance with the expansion and contraction of the moisture-permeable film.
<2>
The composite sheet according to <1>, wherein the moisture-permeable film has a flexibility deformation in a stretching direction of 0.060 N/(mm·(g/m ² )) or less.
<3>
The composite sheet according to <2>, wherein the flexibility deformation of the moisture-permeable film in the stretch direction is preferably 0.057 N/(mm·(g/m ² )) or less, more preferably 0.055 N/(mm·(g/m ² )) or less, and preferably 0.005 N/(mm·(g/m ² )) or more.
＜4＞
The composite sheet according to any one of <1> to <3>, wherein the moisture-permeable film has a residual strain of 11% or less after 30% elongation.
<5>
The composite sheet according to any one of <1> to <4>, wherein the moisture-permeable film has a residual strain after 30% elongation of preferably 10% or less, more preferably 9% or less, and preferably 0%.
＜6＞
The composite sheet according to any one of <1> to <5>, wherein the moisture-permeable film has a moisture permeability of 0.4 g/(100 ^cm2 ·h) or more as measured in accordance with JIS L 1099 A-2.
＜７＞
The composite sheet according to any one of <1> to <6>, wherein the moisture permeability of the moisture permeable film measured in accordance with JIS L 1099 A-2 is preferably 0.45 g/(100 cm ² ·h) or more, more preferably 0.8 g/(100 cm ^{2 ·} h) or more, and preferably 4.5 g/(100 cm ² ·h) or less, more preferably 3.5 g/(100 cm ² ·h) or less, and even more preferably 3.0 g/(100 cm 2 ·h) or less.
＜8＞
The composite sheet according to any one of <1> to <7>, wherein the moisture-permeable film has an air permeability in a natural state, measured by the above method, of preferably 3000 seconds or less, more preferably 2500 seconds or less, and preferably 1 second or more, as the time required for 25 cc of air to permeate the moisture-permeable film in the thickness direction.
＜９＞
The composite sheet according to any one of <1> to <8>, wherein the moisture-permeable film has a basis weight of preferably 5 g/m ² or more, more preferably 10 g/m ² or ^more , and preferably 100 g/m ² or less, more preferably 50 g/m 2 or less.

<10>
The composite sheet according to any one of <1> to <9>, wherein the absorbent body is stretchable.
<11>
The composite sheet according to any one of <1> to <9>, wherein the absorbent body is non-stretchable.
<12>
The composite sheet according to any one of <1> to <11>, wherein the absorbent body has a basis weight of preferably 40 g/ ^m2 or more, more preferably 150 g/ ^m2 or more, and preferably 750 g/ ^m2 or ^less , more preferably 650 g/m2 or less.
<13>
<13> The composite sheet according to any one of <1> to <12>, wherein the moisture-permeable film and the absorbent body are joined at the joint with an adhesive.
<14>
The composite sheet according to any one of <1> to <13>, wherein the absorbent body is separable into a plurality of independent absorbent sections when the moisture-permeable film is in a stretched state.
＜15＞
The composite sheet according to <14>, wherein the absorbent body has overlapping portions where adjacent absorbent sections partially overlap each other when the moisture-permeable film is in a natural state.
<16>
<16> The composite sheet according to any one of <1> to <15>, wherein, in the natural state of the moisture-permeable film, the surface of the absorber that contacts the moisture-permeable film has an uneven structure.
＜17＞
The composite sheet according to <16>, wherein the uneven structure is formed by pleated convex portions and concave portions extending in a direction intersecting the stretching direction of the moisture-permeable film and being alternately arranged in the stretching direction.
＜18＞
The composite sheet according to <17>, wherein the convex portions are regularly arranged in the concave-convex structure.

＜19＞
The moisture-permeable film contains a resin and an inorganic filler,
<1><18> The composite sheet according to any one of the above items <1> to <18>, wherein the content of the inorganic filler in the moisture-permeable film is 50 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the resin in the moisture-permeable film.
＜20＞
The composite sheet according to <19>, wherein the content of the inorganic filler in the moisture-permeable film is preferably 60 parts by mass or more, more preferably 80 parts by mass or more, and preferably 350 parts by mass or less, more preferably 200 parts by mass or less, relative to 100 parts by mass of the resin in the moisture-permeable film.
＜21＞
The composite sheet according to <19> or <20>, wherein the inorganic filler contains calcium carbonate.
<22>
<22> The composite sheet according to any one of <19> to <21>, wherein the resin contains an olefin-based resin composition having a density of 0.840 g/cm ³ or more and less than 0.900 g/cm ³ .
＜23＞
The moisture-permeable film contains a low-melting-point olefin-based resin having a melting point of less than 90°C and a high-melting-point olefin-based resin having a melting point of 95°C or higher. The composite sheet according to any one of <1> to <22>.
＜24＞
The composite sheet according to <23>, wherein the density of the low-melting-point olefin-based resin is lower than the density of the high-melting-point olefin-based resin, and is preferably 0.840 g/cm ^{or more} and 0.895 g/cm ^or less, more preferably 0.850 g/cm or ^more and 0.885 g/cm or less, and even more preferably 0.860 g/cm ^or more and 0.875 g/cm ^or less.
＜25＞
The composite sheet according to <23> or <24>, wherein the density of the high-melting-point olefin-based resin is higher than the density of the low-melting-point olefin-based resin, and is preferably 0.900 g/cm ³ or more and 0.950 g/cm ³ or less, more preferably 0.905 g/cm ³ or ^more and 0.940 g/cm 3 or less, and even more preferably 0.910 g/cm ³ or more and 0.930 g/cm ³ or less.
<26>
The composite sheet according to <25>, wherein the high-melting-point olefin-based resin contains linear low-density polyethylene.

＜27＞
The moisture-permeable film contains a pore-opening promoter in an amount of 0.1 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the resin in the moisture-permeable film, and the pore-opening promoter is a metal soap. The composite sheet according to any one of <1> to <26>.
＜28＞
The composite sheet according to <27>, wherein the metal soap contains zinc stearate.
＜29＞
The composite sheet according to <27> or <28>, wherein the moisture-permeable film contains the metal soap in an amount of 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic filler in the moisture-permeable film.
＜30＞
The moisture-permeable film contains 0.1 parts by mass or more and 30 parts by mass or less of a triglyceride relative to 100 parts by mass of a resin in the moisture-permeable film, and the triglyceride contains a group derived from a fatty acid having 16 to 22 carbon atoms, and the group is a hydrocarbon group having no unsaturated bond and no substituent. The composite sheet according to any one of <1> to <29>.
＜31＞
An absorbent article comprising the composite sheet according to any one of <1> to <30>.
＜32＞
The absorbent article has a vertical direction extending from the wearer's abdomen side through the crotch region to the back side, and a horizontal direction perpendicular to the vertical direction,
The absorbent article according to <31>, wherein the composite sheet has stretchability in the longitudinal direction or the lateral direction.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

[Production of moisture-permeable films A to E]
The components listed in the "Raw Materials" column of Table 1 below were weighed out in the amounts shown in the table. These were mixed in a Henschel mixer (manufactured by Kawata Co., Ltd.). The resulting mixture was kneaded in a twin-screw extruder (manufactured by Toyo Seiki Seisakusho) at a set temperature of 180°C and a screw rotation speed of 180 rpm to obtain a pelletized compound.
The obtained compounds were used to produce moisture-permeable films A to E. Specifically, first, using the resin composition as a raw material, a resin sheet was molded from the molten compound at a blow ratio of 2.5 using an inflation molding machine with a slit diameter of 100 mm and a gap of 0.9 mm at the die discharge section. The die temperature was set to 200°C, and the take-up speed was 10 m/min. Next, the molded film was uniaxially stretched in the machine direction using a roll stretching machine to obtain moisture-permeable films A to E with the basis weights shown in Table 1. Moisture-permeable films A to D all have micropores and are stretchable in the stretching direction. On the other hand, moisture-permeable film E has micropores but is not stretchable.

Details of the raw materials used in the production of moisture-permeable films A to E are as follows.
Olefin resin A (corresponding to the low-melting-point olefin resin): ethylene-α-olefin copolymer produced using a metallocene catalyst, melting point 44°C, resin density 0.864 g/cm ³
Olefin-based resin B (corresponding to the high-melting-point olefin-based resin): linear low-density polyethylene produced using a metallocene catalyst, melting point 116°C, resin density 0.924 g/cm ³
Inorganic filler: calcium carbonate, average particle size D50: 1.8 μm
Dispersant: stearic acid Specific triglyceride: palm oil (C14: 1%, C16: 42%, C18: 57%)
Pore opening promoter (metal soap): zinc stearate, deposition temperature 102°C, melting point 124°C

The physical properties of moisture-permeable films A to E were measured. The physical properties of moisture-permeable film F (urethane elastomer film, manufactured by Okura Kogyo Co., Ltd., Silklon ES85), which does not have micropores and has elasticity, were also measured. The results are shown in Table 1.
The air permeability was measured by the above-mentioned method for measuring air permeability. The state of the evaluation object (moisture-permeable film) during measurement was two types: a natural state and a state stretched 1.3 times in one direction (machine direction) in which it can stretch (30% stretch state). Note that the breathability of moisture-permeable film F was too low, so the air permeability could not be measured.
The leakproofness was evaluated in the same manner as in the (Test for Evaluating Leakproofness of Moisture-Permeable Films in a 30% Elongated State) described above. Furthermore, the leakproofness of the moisture-permeable films was evaluated in the same manner as in the (Test for Evaluating Leakproofness of Moisture-Permeable Films in a 30% Elongated State) described above, except that the moisture-permeable film to be evaluated was in its natural state and/or the test liquid was changed to a test liquid having a surface tension of 35 mN/m at 25°C, a test liquid having a surface tension of 40 mN/m at 25°C, or a test liquid having a surface tension of 44 mN/m at 25°C. Wet tension test mixtures manufactured by Kanto Chemical Co., Inc. were used as these test liquids. In the "Leakproofness" column of Table 1, "A" indicates leakproofness and "B" indicates no leakproofness. Since moisture-permeable film E does not have stretchability, leakproofness in a stretched state was not evaluated.

[Examples 1 to 5 and Comparative Examples 1 and 2: Production of Composite Sheets]
A composite sheet was produced using moisture-permeable film C or E and an absorbent body by the above-mentioned production method A or B. Of the composite sheets produced in each of the examples and comparative examples, all of the composite sheets except for Example 1 had an uneven structure on the absorbent body side surface of the moisture-permeable film in its natural state, and this uneven structure was formed by pleated convex and concave portions extending in a direction intersecting the stretching direction of the moisture-permeable film and being arranged alternately in the stretching direction.
In the manufacturing method for a composite sheet by manufacturing method A, the moisture-permeable film was stretched in the direction of 40% expansion and contraction (in the case where the moisture-permeable film was obtained by uniaxial stretching, in the machine direction of the uniaxial stretching), and one side of an absorbent body, one side of which had been intermittently coated with adhesive in advance, was superimposed on the stretched moisture-permeable film to bond the two together, and the moisture-permeable film was then released from its stretched state to produce the desired composite sheet.
In the manufacturing method for the composite sheet using manufacturing method B, the desired composite sheet was manufactured by superposing one side of an absorbent body, one side of which had previously been intermittently coated with adhesive, onto an unstretched moisture-permeable film.
In the manufacturing methods A and B, the absorbent body was one of the following types A to D. A hot melt adhesive containing synthetic rubber was used to bond the moisture-permeable film and the absorbent body, and the coating pattern was a stripe pattern with spaced apart coated areas, each having a coated length of 2 mm in the stretch direction and a non-coated length of 8 mm, and the adhesive basis weight of the coated area was 30 g/ ^cm2 .

(Absorbent type)
1) Type A1 (stacked fiber, non-separable type): An absorbent body having a stacked fiber type absorbent core (basis weight: mixed stacked fiber of wood pulp 300 g/ ^m2 and water-absorbent polymer 50 g/ ^m2 ) and which cannot be separated into multiple independent absorbent sections. The outer surface of the absorbent core was covered with a stretchable core wrap sheet made of a 10 g/ ^m2 meltblown nonwoven fabric made of styrene-ethylene-propylene-styrene (SEPS) copolymer, and the absorbent body had stretchability in the same direction as the stretch direction of the core wrap sheet.
2) Type A2 (Stacked fiber, non-separable type): An absorbent body having a stacked fiber type absorbent core (basis weight: mixed stacked fiber of wood pulp 300 g/ ^m2 and water-absorbent polymer 50 g/ ^m2 ) and which cannot be separated into multiple independent absorbent sections. The outer surface of the absorbent core was covered with a non-stretchable core wrap sheet made of paper with a basis weight of 16 g/ ^m2 , and the absorbent body was non-stretchable.
3) Type B (Stacked/Divided Type): An absorbent body having a stacked type absorbent core, which is divided into a plurality of independent absorbent sections (basis weight: mixed stacked fibers of wood pulp 300 g/ ^m2 and water-absorbent polymer 50 g/ ^m2 ). Each of the plurality of absorbent sections was individually covered with a non-stretchable core wrap sheet made of 16 g/ ^m2 paper, and the absorbent body was non-stretchable.
4) Type C (sheet, non-divisible type): An absorbent body having a sheet-type absorbent core and not divisible into multiple, individually independent absorbent sections. The absorbent body was non-stretchable. The absorbent core's water-absorbent material was a fiber aggregate made of wood pulp carrying water-absorbent polymer particles (basis weight: wood pulp 50 g/ ^m2 , water-absorbent polymer 30 g/ ^m2 ). The sheet-type absorbent core had a configuration in which water-absorbent polymer particles (basis weight 30 g/ ^m2 ) were sandwiched between ^two opposing fiber sheets (paper, each 25 g/m2).
5) Type D (sheet/divided type): An absorbent body having a sheet-type absorbent core, which was divided into a plurality of individually independent absorbent sections (basis weight 80 g/ ^m2 ). The absorbent body was non-stretchable. The absorbent core's water-absorbent material was a fiber aggregate made of wood pulp carrying water-absorbent polymer particles (basis weight: wood pulp 50 g/ ^m2 , water-absorbent polymer 30 g/ ^m2 ). The sheet-type absorbent core had a configuration in which water-absorbent polymer particles (basis weight 30 g/ ^m2 ) were sandwiched between two opposing fiber sheets (paper, each 25 g/ ^m2 ).

[Performance evaluation of composite sheets]
The composite sheets of the examples and comparative examples were evaluated for leak-proofness by the composite sheet leak-proofness evaluation test described below. The results are shown in Table 2 below.

(Composite sheet leak prevention evaluation test)
The composite sheet to be evaluated is placed with the moisture-permeable film side of the composite sheet facing up, and a pulp sheet measuring 25 mm x 30 mm in plan view and having a basis weight of 40 g/ ^m² is placed on top of it. The composite sheet is in its natural state or in a state of 30% elongation. 0.265 g of test liquid is poured into the center of the upper surface of the pulp sheet. Immediately after the pouring, a cylindrical acrylic resin plate with a diameter of 60 mm and a thickness of 5 mm is placed on the pulp sheet, and a 500 g weight is placed on the plate to apply pressure for 1 hour. The poured test liquid migrates in the following order: pulp sheet → moisture-permeable film of the composite sheet → absorbent body of the composite sheet. The test liquid used is a test liquid with a surface tension of 35 mN/m at 25°C, a test liquid with a surface tension of 40 mN/m at 25°C, or a test liquid with a surface tension of 44 mN/m at 25°C. These test liquids are mixtures for wetting tension tests manufactured by Kanto Chemical Co., Inc. One hour after placing the weight, the weight is removed, the absorbent body constituting the composite sheet is disassembled, and the presence or absence of exudation of the test liquid into the moisture-permeable film-side surface layer of the absorbent body (the layer forming the contact surface with the moisture-permeable film) is visually observed. The above series of operations is performed three times for the composite sheet. If no exudation of the test liquid is observed into the moisture-permeable film-side surface layer of the absorbent body in any of the three times, the composite sheet is evaluated as having leakproof properties; otherwise, it is evaluated as not having leakproof properties. In the "Leakproofness" column of Table 2, "A" means having leakproof properties, and "B" means not having leakproof properties. For points not specifically explained in this evaluation test, the explanation for the above (Moisture-Permeable Film Leakproofness Evaluation Test at 30% Elongation) applies as appropriate.

As shown in Table 2, the composite sheets of each example had superior leak-proofing properties because the moisture-permeable film constituting the composite sheets was moisture-permeable film C, which had elasticity, compared to the comparative examples in which the moisture-permeable film was moisture-permeable film E, which had no elasticity.
In the composite sheets of each Example that were evaluated as having leakproof properties in the above (Composite Sheet Leakproofness Evaluation Test), it is presumed that the moisture-permeable film constituting the composite sheet functioned as a barrier layer that prevented the test liquid from permeating. Therefore, it can be said that the composite sheets of each Example have the ability to prevent body fluid from permeating the moisture-permeable film from the absorbent body and leaking to the outside, even when the absorbent body constituting the composite sheet absorbs a body fluid with a surface tension equivalent to that of the test liquid.

REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D Composite sheet 2 Moisture-permeable film 3 Absorbent body 30 Absorbent core 31 Core wrap sheet 32 Mountain fold portion 35 Absorbent portion 36 Absorbent body non-positioning portion 37 Strip-shaped absorbent body 38 Overlapping portion 4 Joint portion 5 Convex portion 6 Concave portion 10 Composite sheet precursor

Claims (14)

a stretchable moisture-permeable film having micropores and an absorbent body capable of absorbing body fluids are overlapped and joined to each other at a joining portion present between the overlapping surfaces;
The moisture-permeable film is produced by stretching a resin sheet obtained by molding a compound containing a resin and an inorganic filler into a film, and forming a large number of micropores in the resin sheet;
The inorganic filler has an average particle size D50 of 0.5 μm or more and 30 μm or less,
The moisture-permeable film further contains 2.84 parts by mass or more and 30 parts by mass or less of triglyceride per 100 parts by mass of the resin in the moisture-permeable film,
The triglyceride contains a group derived from a fatty acid having from 16 to 22 carbon atoms, and the group is a hydrocarbon group having no unsaturated bond and no substituent;
The moisture-permeable film is stretchable and is evaluated as having leak-proofness in the following moisture-permeable film leak-proofness evaluation test in a 30% elongated state,
The moisture-permeable film has a flexibility deformation in the stretch direction of 0.060 N/(mm·(g/m ² )) or less and a residual strain after 30% elongation of 11% or less;
The composite sheet is such that the absorbent body expands and contracts in accordance with the expansion and contraction of the moisture-permeable film.
(Evaluation test of moisture-permeable film leak prevention at 30% elongation)
The moisture-permeable film to be evaluated and a pulp sheet (Lion Corporation, product name "Lead Healthy Cooking Paper Double") with a basis weight of 40 g/ ^m² and a rectangular shape in plan view of 25 mm x 30 mm were layered on top of filter paper (Advantec Toyo Co., Ltd., No. 2, diameter 70 mm) . The evaluation object was stretched 1.3 times in the machine direction, and its size in plan view was adjusted so that it completely overlapped the filter paper. 0.265 g of a test liquid (Kanto Chemical Co., Ltd., wet tension test mixture) with a surface tension of 44 mN/m at 25°C was poured into the center of the upper surface of the pulp sheet. Immediately after the pouring, a cylindrical acrylic resin plate with a diameter of 60 mm and a thickness of 5 mm was placed on top of the pulp sheet, and a 500 g weight was placed on the plate and pressure was applied for 1 hour. After 1 hour had passed since the weight was placed, the weight was removed, and the presence or absence of the test liquid seeping into the filter paper was visually observed. The above series of operations is carried out three times for the evaluation object, and if no seepage of the test liquid into the filter paper is observed in any of the three operations, the evaluation object is evaluated as having leak-proof properties; otherwise, it is evaluated as not having leak-proof properties. 2. The composite sheet according to claim 1, wherein the moisture-permeable film has a moisture permeability of 0.4 g/(100 cm ² ·h) or more as measured in accordance with JIS L 1099 A-2. 2. The composite sheet according to claim 1, wherein the absorbent body is inelastic, the degree of flexible deformation of the absorbent body in any one direction is greater than 0.060 N/(mm·(g/m ² )), and the residual strain after 30% elongation in the one direction is greater than 11% . The composite sheet according to claim 1, wherein, when the moisture-permeable film is in its natural state, the surface of the absorbent body that contacts the moisture-permeable film has an uneven structure. The composite sheet according to claim 4 , wherein the uneven structure is formed by pleated convex portions and concave portions extending in a direction intersecting the stretching direction of the moisture-permeable film and arranged alternately in the stretching direction. The composite sheet according to claim 1, wherein the absorbent body is separable into a plurality of independent absorbent sections when the moisture-permeable film is in an extended state. The composite sheet according to claim 6 , wherein the absorbent body has overlapping portions where adjacent absorbent sections partially overlap each other when the moisture-permeable film is in its natural state. The moisture-permeable film contains a resin and an inorganic filler,
The composite sheet according to claim 1 , wherein the content of the inorganic filler in the moisture-permeable film is 50 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the resin in the moisture-permeable film. The composite sheet according to claim 8 , wherein the resin comprises an olefin-based resin composition having a density of 0.840 g/cm ³ or more and less than 0.900 g/cm ³ . The composite sheet according to claim 1, wherein the moisture-permeable film contains a low-melting-point olefin resin having a melting point of less than 90°C and a high-melting-point olefin resin having a melting point of 95°C or higher. The composite sheet of claim 1, wherein the moisture-permeable film contains a pore-opening promoter in an amount of 0.1 to 20 parts by mass per 100 parts by mass of resin in the moisture-permeable film, and the pore-opening promoter is a metal soap. The composite sheet according to claim 11 , wherein the moisture-permeable film contains the metal soap in an amount of 0.5 parts by mass to 10 parts by mass relative to 100 parts by mass of the inorganic filler in the moisture-permeable film. An absorbent article comprising the composite sheet according to any one of claims 1 to 12 . The absorbent article has a vertical direction extending from the wearer's abdomen side through the crotch region to the back side, and a horizontal direction perpendicular to the vertical direction,
The absorbent article according to claim 13 , wherein the composite sheet has stretchability in the longitudinal direction or the transverse direction.