JP7835605B2 - Composite sheets and absorbent articles - Google Patents

Description

This invention relates to a stretchable composite sheet in which a stretchable porous moisture-permeable film and a non-stretchable nonwoven fabric are laminated and integrated.

As a moisture-permeable film, a resin-based moisture-permeable film having micropores is known. Such a moisture-permeable film is generally manufactured by stretching a resin film containing a filler and additives to form numerous micropores. Patent Document 1 describes a moisture-permeable film containing linear low-density polyethylene, branched low-density polyethylene, a filler, and a dispersant for the filler.

Absorbent articles such as disposable diapers and sanitary napkins typically include a surface sheet that forms the skin-facing side, a back sheet that forms the non-skin-facing side, and an absorbent material placed between the two sheets. It is well known that a composite sheet, in which a resin film and nonwoven fabric are laminated and integrated, is used as the leak-proof sheet forming the non-skin-facing side (outer surface) of the absorbent article, such as the back sheet (Patent Documents 2-5). In such composite sheets, from the viewpoint of providing a good feel against the skin, the resin film is often placed on the inside (skin-facing side) and the nonwoven fabric on the outside (non-skin-facing side).

Patent Document 2 describes the use of a composite sheet consisting of a stretchable sheet made of a thermoplastic synthetic resin elastomer film and a non-stretchable nonwoven fabric as a leak-proof sheet for disposable diapers. Patent Document 2 does not describe imparting moisture permeability to the film. Patent Document 3 describes the use of a composite sheet consisting of a non-porous moisture-permeable film and a stretchable nonwoven fabric as a leak-proof sheet for absorbent articles. Patent Document 4 describes a stretchable composite sheet usable as a component of absorbent articles, in which a moisture-permeable film is fully bonded to one side of a stretchable nonwoven fabric. The composite sheets described in Patent Documents 2 to 4 have an uneven structure in which convex and concave portions extending in one direction are alternately arranged in a direction perpendicular to that direction, when no external force is applied.

Japanese Patent Application Publication No. 1-144432 Japanese Patent Application Publication No. 10-99373 Japanese Patent Publication No. 2004-305771 Japanese Patent Publication No. 2008-284717 Japanese Patent Publication No. 2019-201691

In absorbent materials such as leak-proof sheets, components positioned relatively far from the wearer's skin are required to have excellent breathability and moisture permeability to prevent stuffiness during wear, excellent leak-proof properties to prevent leakage of excrement, excellent elasticity to improve the fit of the absorbent material, a small number of components, and a good feel and appearance. Conventional composite sheets have room for improvement in terms of these required performance aspects.

The object of this invention is to provide a composite sheet that is excellent in breathability, moisture permeability, leak resistance, elasticity, feel, and appearance.

The present invention involves a stretchable, moisture-permeable film having micropores and a non-stretchable nonwoven fabric overlapping, and being joined to each other at multiple joints scattered between the overlapping surfaces.
The aforementioned moisture-permeable film is expandable and contractible, and the non-jointed portion of the nonwoven fabric with the moisture-permeable film expands and contracts in accordance with the expansion and contraction of the moisture-permeable film, forming a composite sheet.

Furthermore, the present invention relates to an absorbent article comprising the composite sheet described above.

According to the present invention, a composite sheet is provided that is excellent in breathability, moisture permeability, leak resistance, elasticity, feel, and appearance.

Figure 1 is a schematic perspective view of one embodiment of the composite sheet of the present invention in its natural state. Figure 2 is a schematic cross-sectional view showing the section along line I-I in Figure 1 (a section along the thickness direction and the expansion/contraction direction). Figure 3 is a schematic perspective view of another embodiment of the composite sheet of the present invention in its natural state. Figure 4 is a schematic perspective view of yet another embodiment of the composite sheet of the present invention in its natural state. Figure 5 is a photograph corresponding to Figure 2 of yet another embodiment of the composite sheet of the present invention. Figure 6 is a schematic cross-sectional view of the crotch area of a disposable diaper, which is one embodiment of the absorbent article of the present invention, along the transverse and thickness directions. Figure 7 is a schematic exploded perspective view of the diaper shown in Figure 6.

The present invention will be described below with reference to the drawings, based on preferred embodiments. In the following drawings, identical or similar parts are denoted by the same or similar reference numerals. The drawings are generally schematic, and the proportions of dimensions may differ from those of actual objects.

Figures 1 and 2 show a composite sheet 1, which is one embodiment of the composite sheet of the present invention. The composite sheet 1 includes a stretchable moisture-permeable film 2 having micropores and a non-stretchable nonwoven fabric 3. In the composite sheet 1, the moisture-permeable film 2 and the nonwoven fabric 3 overlap and are joined to each other at a plurality of joints 4 scattered between their overlapping surfaces. The moisture-permeable film 2 is stretchable, and as the moisture-permeable film 2 stretches, the non-jointed portions 31 of the nonwoven fabric 3 with the moisture-permeable film 2 also stretch.
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.

The composite sheet 1 has excellent breathability, moisture permeability, leak resistance, elasticity, texture, and appearance. The breathability, moisture permeability, leak resistance, and elasticity of the composite sheet 1 are mainly due to the moisture permeable film 2, and the texture and appearance are mainly due to the nonwoven fabric 3.
Conventional composite sheets of this type include, for example, 1) a combination of a non-porous stretchable moisture-permeable film and a non-stretchable nonwoven fabric, 2) a combination of a perforated non-stretchable moisture-permeable film and a non-stretchable nonwoven fabric, and 3) a combination of a moisture-permeable film and a stretchable nonwoven fabric. However, 1) has poor breathability because the moisture-permeable film is non-porous, 2) has poor stretchability, and 3) has poor texture due to the nonwoven fabric. In contrast, the composite sheet of the present invention, represented by composite sheet 1, achieves the above-mentioned excellent properties by having at least one perforated stretchable moisture-permeable film and one non-stretchable nonwoven fabric (one layer) each.
As will be described later, one embodiment of the composite sheet of the present invention employs an olefin resin and an inorganic filler as the main raw materials for the moisture-permeable film, which can also provide secondary effects such as a) reduction of manufacturing costs by using relatively inexpensive raw materials, b) improvement of bonding strength with synthetic rubber-based materials (e.g., adhesives, smudges, shear stabilizers, etc.) that are commonly used in absorbent articles such as disposable diapers and sanitary napkins, c) improvement of breathability by expanding micropores when the composite sheet is stretched, and d) reduction of environmental burden by reducing the amount of resin used. The aforementioned d) means that because the moisture-permeable film is perforated and contains an inorganic filler, the amount of resin used can be reduced by the volume of the inorganic filler and the volume of the pores compared to a case where the moisture-permeable film is non-porous and consists only of resin, thus reducing the burden on the environment.

In this invention, "stretchability" means the property of being able to stretch in a predetermined direction and contracting when the stretching is released.
In this invention, whether or not an object is stretchable is evaluated by its degree of flexible deformation or residual strain after stretching. Specifically, the following tensile test is performed on the object to be evaluated for stretchability (moisture-permeable film, nonwoven fabric, etc.). If the measured degree of flexible deformation is 0.060 N/(mm·(g/ ^m² )) or less, or if the measured residual strain after 30% stretching is 11% or less, the object is evaluated as having stretchability in the tensile direction. On the other hand, if the measured degree of flexible deformation is greater than 0.060 N/(mm·(g/ ^m² )) and the measured residual strain after 30% stretching is greater than 11%, the object is evaluated as not having stretchability in the tensile direction and is considered non-stretchable.
The "stretchable moisture-permeable film" used in this invention is a moisture-permeable film that is stretchable in at least one direction, and the "non-stretchable nonwoven fabric" is a nonwoven fabric that is not stretchable in the machine direction (the flow direction during the manufacturing of the object being evaluated).

(Tensile test: Measurement of degree of flexible deformation and residual strain after 30% elongation)
A rectangular shape in plan view is cut from the object under evaluation, with a length of 150 mm in the machine direction (the flow direction during the manufacturing of the object under evaluation) and a length of 30 mm in the width direction perpendicular to the machine direction, to be used as a test specimen. The test specimen is fixed to a tensile testing machine (product name: AG-1S, manufactured by Shimadzu Corporation) between a pair of gripping fixtures provided by the tensile testing machine so that the machine direction of the test specimen is the tensile direction. At that time, the length between the pair of gripping fixtures, i.e., the length of the test specimen in the machine direction before the tensile test (initial length) _L0 , is fixed to 100 mm. After fixing, the load read by the tensile testing machine is set to zero, and the test specimen is stretched to 1.3 times _L0 (i.e., stretched by 30%) at a deformation speed of 200 mm/min, and then immediately contracted back to _L0 at a deformation speed of 200 mm/min in a cycle test. From the data obtained in the aforementioned cycle test, the load at 1.03 times deformation during the elongation process (F _3% ) is read, and the degree of flexible deformation of the test specimen [N/(mm・(g/ ^m² ))] is calculated using the following formula.
Degree of flexibility deformation [N/(mm·(g/ ^m² ))] = F _3% [N] / (0.03 × 30 [mm] × basis weight of test specimen [g/ ^m² ])
Furthermore, in the cycle test, the length _L1 of the test specimen in the mechanical direction is measured when the load becomes 0.01 [N] or less during the process of shrinking the test specimen, and the residual strain after 30% elongation of the test specimen is calculated using the following formula.
Residual strain after 30% elongation (%) = {(L ₁ [mm] - L ₀ [mm])/L ₀ }× 100
For each type of object to be evaluated, three test specimens are prepared, and the cycle test described above is performed on each specimen to calculate the degree of flexible deformation and the residual strain after 30% elongation. The arithmetic mean of the degrees of flexible deformation of each of the three test specimens is taken as the degree of flexible deformation of the object to be evaluated, and the arithmetic mean of the residual strain after 30% elongation of each of the three test specimens is taken as the residual strain after 30% elongation of the object to be evaluated.
If the size of the object to be evaluated is too small to fix the test specimen in a rectangular shape in plan view with a mechanical length L _{0 of} 100 mm and a width length of 30 mm, the test specimen shall be fixed in such a way as to create the most similar rectangular shape in plan view. In that case, the value of L ₀ shall be measured, and the deformation speed shall be set so that the deformation speed per unit sample length is equal, and a tensile test shall be performed. When calculating the degree of flexible deformation, the width length shall be changed to match the test specimen.

In composite sheet 1, as shown in Figures 1 and 2, in the natural state of the moisture-permeable film 2,
A protrusion 5 is formed on the side opposite to the moisture-permeable film 2, and part or all of the protrusion 5 is the non-jointed portion 31 of the nonwoven fabric 3. In the present invention, "natural state" means a state in which no external force is applied to the object (moisture-permeable film, composite sheet, 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, in the natural state of the moisture-permeable film 2, a plurality of pleated protrusions 5 (non-jointed portions 31 of the nonwoven fabric 3) extend in a direction intersecting the expansion and contraction direction (direction Y) of the moisture-permeable film 2, and between adjacent protrusions 5, 5, recesses 6 having joint portions 4 at their bottoms extend in the same direction as the protrusions 5. In the illustrated embodiment, the direction of extension of the protrusions 5 and recesses 6 is perpendicular to the expansion and contraction direction (direction X) of the moisture-permeable film 2.
In its natural state, the composite sheet 1 has an uneven surface on the nonwoven fabric 3 side, with multiple protrusions 5 and recesses 6 extending in direction X and alternately arranged in direction Y, whereas the moisture-permeable film 2 side is substantially flat with no unevenness.
The protrusion 5 of the composite sheet 1 is formed by the non-joint portion 31 of the nonwoven fabric 3 protruding in a direction away from the moisture-permeable film 2, and has a hollow portion 7 consisting of the gap between the non-joint portion 31 and the moisture-permeable film 2.
A composite sheet 1 having such a hollow structure with protrusions 5, that is, a composite sheet 1 in which the non-jointed portion 31 of the nonwoven fabric 3 separates from the moisture-permeable film 2 in its natural state to form the protrusions 5, can be manufactured, for example, by overlapping the nonwoven fabric 3 with the moisture-permeable film 2 in an extended state and joining them together at the joint portion 4, and then releasing the moisture-permeable film 2 from its extended state to its natural state.
Thus, in the composite sheet 1, the bonding of the moisture-permeable film 2 and the nonwoven fabric 3 is performed under the stretched state of the moisture-permeable film 2. In the natural state of the moisture-permeable film 2, the unbonded portion 31 of the nonwoven fabric 3 separates from the moisture-permeable film 2, forming a hollow structure with protrusions 5.

Furthermore, in the composite sheet of the present invention, it is not essential that the unjointed portion 31 of the nonwoven fabric 3 protrudes on the side opposite to the moisture-permeable film 2 to form a protrusion 5 in its natural state. The composite sheet of the present invention includes a configuration in which, in its natural state, the unjointed portion 31 does not substantially separate from the moisture-permeable film 2, and no protrusion 5 is formed; that is, a configuration in which both the moisture-permeable film 2 side and the nonwoven fabric 3 side are substantially flat without an uneven structure.

Furthermore, in the composite sheet of the present invention, the pattern of the joint portion 4 (specifically, the position and plan view shape of the joint portion 4) is not particularly limited, and any pattern can be adopted. The pattern of the joint portion 4 determines the pattern of the recess 6 formed at the position corresponding to the joint portion 4, and consequently, the pattern of the uneven structure consisting of the convex portion 5 and the recess 6.
Figures 3 and 4 show other embodiments of the uneven structure that can be used in the composite sheet of the present invention. In the other embodiments described later, configurations different from those of the composite sheet 1 described above will be explained, and configurations similar to those of the composite sheet 1 will be denoted by the same reference numerals and their descriptions will be omitted. For configurations not specifically described in the other embodiments described later, the description of the composite sheet 1 will be applied as appropriate.
The composite sheet 1A shown in Figure 3 differs from the composite sheet 1 in that the protrusions 5 and recesses 6 (joints 4) are arranged irregularly. Furthermore, while the protrusions 5 of the composite sheet 1 are continuous along the entire length in the direction X of the composite sheet 1, the protrusions 5 of the composite sheet 1A, although elongated in the direction X, do not extend along the entire length in the direction X of the composite sheet 1A, and recesses 6 exist between the protrusions 5, 5.
The composite sheet 1B shown in Figure 4 differs from the composite sheet 1, in that the convex portion 5 has a closed shape in plan view and the concave portion 6 surrounds the convex portion 5, while the convex portion 5 extends in one direction from one end of the sheet to the other. The plan view shape of the convex portion 5 in the composite sheet 1B is not particularly limited and can be, for example, circular, elliptical, or rectangular.
Among the embodiments of the composite sheet described above, composite sheet 1 in particular has a good texture and appearance because the convex portions 5 and concave portions 6 are regularly arranged as shown in Figure 1. Therefore, it is suitable for applications where a good texture and appearance are required, such as a leak-proof sheet for absorbent articles.

Figure 5 shows a photograph corresponding to Figure 2 of another embodiment of the composite sheet of the present invention. The protrusions 5 of the aforementioned composite sheets 1, 1A, and 1B had a hollow structure with a hollow portion 7, but the protrusions of the composite sheet shown in Figure 5 do not have a hollow portion 7 and have a solid structure with the constituent fibers of the nonwoven fabric 3 filled inside.
A composite sheet having such a solid structure with protrusions 5 can be manufactured, for example, by obtaining a composite sheet precursor by overlapping a nonwoven fabric 3 with a non-stretched moisture-permeable film 2 and joining them at a joint 4, and then introducing the composite sheet precursor into the interlocking portion of a pair of processing members that interlock with each other, such as a pair of toothed rolls, and subjecting the composite sheet precursor to stretching (tooth groove stretching). The composite sheet precursor introduced into the interlocking portion is given "stretchability" because the bonds between the constituent fibers are partially broken by the interlocking of one tooth and the tooth root of the pair of processing members, resulting in the moisture-permeable film 2 and the nonwoven fabric 3 being partially separated to form a non-jointed portion 31, and also gaining elasticity in the direction of introduction into the interlocking portion (the flow direction during composite sheet manufacturing). The solid structure with protrusions 5 is the portion to which the stretchability is given by the interlocking of the tooth grooves, and is more flexible than other parts.
Thus, in the composite sheet shown in Figure 5, the bonding of the moisture-permeable film 2 and the nonwoven fabric 3 is performed under the non-stretched state of the moisture-permeable film 2, and in the natural state of the moisture-permeable film 2, the unbonded portion 31 of the nonwoven fabric 3 becomes part of the solid structure's protrusion 5.

The composite sheet of the present invention can also be manufactured by methods other than the two manufacturing methods described above, namely, 1) a method comprising the step of joining a stretchable moisture-permeable film and a non-stretchable nonwoven fabric while the stretchable moisture-permeable film is in an elongated state, and then releasing the moisture-permeable film from its elongated state (hereinafter also referred to as "manufacturing method A"), and 2) a method comprising the step of joining a stretchable moisture-permeable film and a non-stretchable nonwoven fabric while the stretchable moisture-permeable film is in an un-elongated state to obtain a composite sheet precursor, and then subjecting the composite sheet precursor to tooth groove stretching (hereinafter also referred to as "manufacturing method B").
For example, the following manufacturing method C can be cited. Manufacturing method C includes a shaping step in which a non-stretchable nonwoven fabric is made to conform to the circumferential surface of a roll with irregularities on its circumferential surface while rotating the roll, and a step in which the non-stretchable nonwoven fabric, which has been deformed into an irregular shape, is conveyed while being held on the circumferential surface of the roll, and a step in which a stretched moisture-permeable film is superimposed on the non-stretchable nonwoven fabric during conveyance, and the two are joined by adhesive or fusion. In manufacturing method C, as with manufacturing method A, the joining of the moisture-permeable film and the nonwoven fabric is performed while the moisture-permeable film is in an stretched state, so in the natural state of the composite sheet 1 manufactured by manufacturing method C, the unjointed portion 31 of the nonwoven fabric 3 is separated from the moisture-permeable film 2, forming a hollow structure with protrusions 5. For manufacturing method C, for example, the manufacturing method of a composite sheet described in Japanese Patent Application Publication No. 2021-79106 may be appropriately adopted.

The moisture-permeable film 2 typically consists mainly of an olefin resin and also contains an inorganic filler. The inorganic filler is a substance that forms micropores in the moisture-permeable film 2. Details of the moisture-permeable film 2 will be described later.

As the nonwoven fabric 3, various nonwoven fabrics manufactured by different methods can be used, provided that they are non-stretchable. Examples of nonwoven fabrics 3 include spunbond nonwoven fabrics, air-through nonwoven fabrics, needle-punched nonwoven fabrics, etc. The nonwoven fabric 3 may have a single-layer structure or a laminated structure in which one or more types of nonwoven fabrics are laminated together.
Various synthetic fibers, regenerated fibers, and natural fibers can be used as constituent fibers of the nonwoven fabric 3. Examples of synthetic fibers include polyester such as polyethylene, polypropylene, polyethylene terephthalate, and polybutylene terephthalate, and polyamides. Examples of regenerated fibers include fibers made from rayon or cupro. Examples of natural fibers include fibers made from cotton, linen, or silk. The constituent fibers of the nonwoven fabric 3 may be short fibers or long fibers, and may be hydrophilic or hydrophobic. In addition, core-sheath type or side-by-side type composite fibers, split fibers, irregular cross-section fibers, crimped fibers, heat-shrinkable fibers, etc., can also be used. These fibers can be used individually or in combination of two or more types.

The nonwoven fabric 3 preferably contains an olefin resin. As described later, the moisture-permeable film 2 is typically mainly composed of an olefin resin. By including an olefin resin in the nonwoven fabric 3 joined to the moisture-permeable film 2, the bonding strength between the two is improved when an adhesive containing synthetic rubber is used, effectively preventing problems such as peeling during use of the composite sheet 1. As the synthetic rubber, for example, a styrene-based thermoplastic elastomer can be used. Therefore, the nonwoven fabric 3 preferably mainly consists of synthetic fibers made of olefin resins such as ethylene, propylene, and butene.

The basis weight of the moisture-permeable film 2 and the nonwoven fabric 3 is not particularly limited and can be adjusted as appropriate depending on the intended use of the composite sheet 1.
For example, when the composite sheet 1 is used as a leak-proof sheet for absorbent articles, the basis weight of the moisture-permeable film 2 is preferably 5 g/ ^m² or more, more preferably 6 g/ ^m² or more, and preferably 100 g/ ^m² or less, and more preferably 90 g/ ^m² or less. Also, the basis weight of the nonwoven fabric 3 is preferably 5 g/ ^m² or more, more preferably 6 g/ ^m² or more, and preferably 100 g/ ^m² or less, and more preferably 90 g/ ^m² or less.

The means for forming the joint 4 are not particularly limited, and known joining methods such as adhesives and fusion (e.g., heat sealing, ultrasonic sealing, etc.) can be used. Generally, adhesives cause less damage to the moisture-permeable film 2 and nonwoven fabric 3 compared to fusion; therefore, adhesives are preferred as the joining method. That is, it is preferable that the moisture-permeable film 2 and nonwoven fabric 3 are joined by an adhesive at the joint 4. As the adhesive, known adhesives such as hot-melt adhesives can be used.

When using an adhesive as a means of joining the moisture-permeable film 2 and the nonwoven fabric 3 at the joint 4, it is preferable that the adhesive contains synthetic rubber. The reason for this is the same as the reason why it is preferable for the nonwoven fabric 3 to contain olefin resin, as described above.

The adhesive used to form the joint 4 is applied to either or both of the moisture-permeable film 2 and the nonwoven fabric 3. While the adhesive application pattern is not particularly limited, from the viewpoint of maintaining high breathability and moisture permeability derived from the moisture-permeable film, it is preferable to apply the adhesive intermittently so that areas of the surface remain uncoated, rather than applying it to the entire surface (i.e., solid coating). Examples of such intermittent adhesive application patterns include spiral, summit, omega, curtain, and stripe patterns.

The composite sheet of the present invention is useful in applications requiring these properties due to its excellent breathability, moisture permeability, leak-proof properties, and elasticity. Suitable applications of the composite sheet include leak-proof sheets for absorbent articles such as disposable diapers and sanitary napkins; and waterproof sheets for rain gear. The composite sheet of the present invention is particularly useful as a component of absorbent articles.

The present invention includes absorbent articles equipped with the composite sheet of the present invention described above. The absorbent articles of the present invention broadly include articles used to absorb bodily fluids (urine, loose stools, menstrual blood, sweat, etc.) discharged from the human body, and include, for example, disposable diapers, sanitary napkins, sanitary shorts, incontinence pads, etc.
The absorbent article of the present invention typically comprises a surface sheet forming a skin-facing surface, a back sheet forming a non-skin-facing surface, and a liquid-retaining absorbent body disposed between these two sheets. The absorbent article may further have leak-proof cuffs on both sides along the longitudinal direction of the skin-facing surface. The absorbent article of the present invention also includes a pant-type absorbent article comprising an absorbent body including the surface sheet, absorbent body, and back sheet, and an outer casing disposed on the non-skin-facing side of the absorbent body. The diaper 10 described later is a pant-type absorbent article. The surface sheet is typically liquid-permeable. The absorbent body typically includes an absorbent core and a core-wrap sheet enclosing it. The surface sheet, absorbent core, and core-wrap sheet can each be any material commonly used in this type of absorbent article without particular limitation.

In this specification, "skin-facing surface" refers to the surface of an absorbent article or its components (e.g., backing sheet, outer casing) that faces the wearer's skin when the absorbent article is worn, i.e., the side relatively closer to the wearer's skin. "Non-skin-facing surface" refers to the surface of an absorbent article or its components that faces the opposite side from the skin when the absorbent article is worn, i.e., the side relatively further away from the wearer's skin.

In the absorbent article of the present invention, the composite sheet of the present invention described above is preferably used as a leak-proof sheet, and is particularly useful as a leak-proof sheet forming the outer surface (non-skin-facing surface) of the absorbent article. Examples of such leak-proof sheets include the backing sheet and the outer casing.
One embodiment of the absorbent article of the present invention comprises a composite sheet of the present invention as a leak-proof sheet forming the outer surface (non-skin-facing surface) of the absorbent article.
Furthermore, in the absorbent article of the present invention, when the composite sheet of the present invention is used as a leak-proof sheet, the composite sheet itself may be used as the leak-proof sheet, or a laminated sheet of the composite sheet and another sheet material (e.g., nonwoven fabric) may be used as the leak-proof sheet.

Figures 6 and 7 show a disposable pant-type diaper 10, which is one embodiment of the absorbent article of the present invention. The diaper 10 has a longitudinal direction X extending from the wearer's ventral side through the crotch area to the back, and a transverse direction Y perpendicular to the longitudinal direction X. The diaper 10 is divided into three parts: a crotch area located at the wearer's crotch, an abdominal area located further ventral (front) than the crotch area, and a dorsal area located further back (rear) than the crotch area. The diaper 10 comprises an absorbent body 11 and an outer covering 20, which serves as a leak-proof sheet, positioned on the non-skin-facing side of the absorbent body 11. The diaper 10 is a pant-type diaper with a pair of side seals, a waist opening, and a pair of leg openings, formed by joining the side edges of the outer covering 20 along the longitudinal direction X in the abdominal and dorsal areas, respectively.

The absorbent body 11 includes a surface sheet 12 positioned relatively close to the wearer's skin, a back sheet 13 positioned relatively far from the wearer's skin, and an absorbent core 14 positioned between the two sheets 12 and 13. The absorbent core 14 includes an absorbent core 15 and a core wrap sheet 16 surrounding it. A pair of leak-proof cuffs 17, 17 are provided on both the left and right sides of the absorbent body 11, along the longitudinal direction X, and stand upright against the wearer's skin when worn.

As shown in Figure 7, the outer casing 20 includes a laminate of an outer layer sheet 21 that forms the non-skin-facing surface (outer surface) of the diaper 1 when worn, and an inner layer sheet 22 positioned opposite the skin-facing surface of the outer layer sheet 21. The two sheets 21 and 22 are joined to each other via bonding means such as adhesive. The inner layer sheet 22 is made up of a single continuous sheet, while the outer layer sheet 21 is made up of multiple sheets combined together. Specifically, the outer layer sheet 21 includes a ventral outer layer sheet 21A that constitutes the ventral side, a dorsal outer layer sheet 21C that constitutes the dorsal side, and a crotch outer layer sheet 21B that is located between the two sheets 21A and 21C and constitutes the crotch area. The sheets 21A, 21B, and 21C that make up the outer layer sheet 21 are joined to each other and integrated at the overlapping portion by known bonding means such as adhesive, heat seal, high-frequency seal, or ultrasonic seal. In the outer casing 20, elastic members 23 for forming waist gathers are arranged to be expandable and contractible in the lateral direction Y, corresponding to the wearer's waist circumference. Elastic members 24 for forming leg gathers are also arranged to be expandable and contractible in the outer casing 20 corresponding to the wearer's legs. The elastic members 23 and 24 are sandwiched and fixed between the outer layer sheet 21 and the inner layer sheet 22 by a bonding means such as an adhesive.

The crotch outer layer sheet 21B, which is part of the outer casing 20, is formed from the composite sheet 1 described above. In the diaper 10, the crotch outer layer sheet 21B made of the composite sheet 1 is stretchable in the lateral direction Y of the diaper 10, and in the natural state of the composite sheet 1 (moisture-permeable film 2), the nonwoven fabric 3 side has an uneven structure in which a plurality of convex portions 5 and concave portions 6 extending in the vertical direction X of the diaper 10 are alternately arranged in the lateral direction Y.
Furthermore, the crotch outer layer sheet 21B, which is made of composite sheet 1, may be stretchable in the longitudinal direction X of the diaper 10. In this case, in the natural state of the composite sheet 1 (moisture-permeable film 2), the nonwoven fabric 3 side has an uneven structure in which a plurality of convex portions 5 and concave portions 6 extending in the transverse direction Y of the diaper 10 are alternately arranged in the longitudinal direction X.
For leak-proof sheets in the crotch area of absorbent articles, such as the crotch outer layer sheet 21B, good breathability, moisture permeability, leak-proof properties, elasticity, feel against the skin, and appearance are required. Therefore, the composite sheets of the present invention, represented by composite sheet 1, are useful as leak-proof sheets in the crotch area of absorbent articles.

The composite sheet of the present invention is useful not only as the crotch outer layer sheet 21B, but also as the ventral outer layer sheet 21A and the dorsal outer layer sheet 21C. The ventral outer layer sheet 21A and the dorsal outer layer sheet 21C, particularly the areas around the wearer's waist, may require higher breathability than the crotch outer layer sheet 21B. One way to improve the breathability of the composite sheet in such cases is to form pores with a larger opening diameter than the micropores in the moisture-permeable film constituting the composite sheet, in addition to the micropores. While forming such pores in the moisture-permeable film may raise concerns about a decrease in the leak-proof properties of the composite sheet, leak-proof properties are not usually required for components placed around the wearer's waist in absorbent articles. Therefore, if the composite sheet is used in an application where such a low level of leak-proof requirement is needed, there is room to form pores in the moisture-permeable film constituting the composite sheet, in addition to the micropores.
From this perspective, the moisture-permeable film constituting the composite sheet of the present invention may have pores with a larger opening diameter than the micropores, in addition to the micropores. This can improve the breathability of the moisture-permeable film and, consequently, the breathability of the composite sheet.
From the viewpoint of air permeability and strength, the pore diameter in the moisture-permeable film is preferably 0.5 mm or more, more preferably 0.6 mm or more, and preferably 10 mm or less, and more preferably 8 mm or less.
On the other hand, the pore diameter of the micropores in the moisture-permeable film is usually preferably 0.001 μm or more, more preferably 0.005 μm or more, and preferably 500 μm or less, and more preferably 300 μm or less.
The aforementioned pore diameter refers to the length of the pore or micropore at its narrowest point (or diameter if the pore or micropore is circular in plan view). The aforementioned pore diameter can be determined from a microscopic photograph of the pore or micropore.
Forming pores with a larger opening diameter than micropores in a moisture-permeable film can be achieved, for example, by physically creating holes in the moisture-permeable film by pressing the circumferential surface of a roll having an uneven surface against the film.

The composite sheet of the present invention can be used not only as the outer casing 20 (outer layer sheet 21) but also as the backing sheet 13 in the diaper 10. Furthermore, the composite sheet of the present invention can be used not only in pull-up diapers like the diaper 10 but also in unfoldable diapers. In the latter case, it is preferable to use it as the backing sheet forming the outer surface (non-skin-facing surface) of the unfoldable diaper. Typically, unfoldable diapers have a pair of fastening tapes extending laterally on the dorsal side, and when worn, these fastening tapes are fastened to a fastening area provided on the outer surface of the ventral side.

The moisture-permeable film constituting the composite sheet of the present invention will be described in detail below based on a preferred embodiment.
Moisture-permeable films possess breathability, moisture permeability, leak-proof properties, and elasticity. These films are primarily resin-based resin films with numerous micropores; their breathability is mainly due to these micropores. While moisture permeability can sometimes be attributed to the resin itself, it can be improved by the presence of micropores regardless of the resin's moisture permeability. Furthermore, the elasticity of these films is primarily due to the resin (for example, olefin-based resins, as described later).

A moisture-permeable film typically contains a resin and an inorganic filler. Such a film is manufactured by stretching a resin product containing the resin and inorganic filler, thereby forming numerous micropores in the resin product.

As the main raw material for the moisture-permeable film, resins that exhibit elasticity when formed into a film can be used. Examples include olefin resins, ester resins (polyethylene terephthalate, polybutylene terephthalate, etc.), amide resins (nylon, etc.), acrylonitrile resins, vinyl resins, vinylidene resins, and urethane resins. One of these can be used alone or in combination of two or more. Among these resins, olefin resins are particularly suitable as resins for moisture-permeable films because they allow for the production of high-quality moisture-permeable films at a relatively low cost.
Olefin resins used in moisture-permeable films typically consist mainly of polymers and copolymers of monoolefins such as ethylene, propylene, and butene. Specific examples include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and polypropylene.

From the viewpoint of improving the flexibility of the moisture-permeable film, and consequently the flexibility of the composite sheet of the present invention, it is preferable that the moisture-permeable film contains a low-density olefin-based resin composition.
In this specification, "olefin resin composition" encompasses both cases where it contains only one type of olefin resin and cases where it contains two or more types. Furthermore, "olefin resin composition" is a concept that consists solely of various olefin resins and does not contain other resins or non-resin components. It should be noted that the moisture-permeable film used in the present invention may contain resins other than olefin resins.

The olefin resin composition contained in the moisture-permeable film preferably has a density of less than 0.900 g/ ^cm³ , more preferably 0.895 g/ ^cm³ or less, and even more preferably 0.885 g/ ^cm³ or less.
Furthermore, the olefin resin composition contained in the moisture-permeable film preferably has a density of 0.840 g/ ^cm³ or higher, which reduces the likelihood of blocking in the moisture-permeable film. A density of 0.850 g/ ^cm³ or higher is more preferable, and a density of 0.860 g/ ^cm³ or higher is even more preferable.
In summary, 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.

The olefin resin composition contained in the moisture-permeable film preferably contains a low-melting-point olefin resin with a melting point of less than 90°C (hereinafter also simply referred to as "low-melting-point olefin resin") and a high-melting-point olefin resin with a melting point of 95°C or higher (hereinafter also simply referred to as "high-melting-point olefin resin"). 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 allowing the moisture-permeable film obtained by melt molding to solidify in a short time, enabling high-speed molding.
To further enhance the aforementioned advantages, the melting point of the low-melting-point olefin resin is preferably 80°C or lower, more preferably 70°C or lower. Furthermore, to obtain morphological 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 aforementioned advantages, the melting point of the high-melting-point olefin resin is preferably 100°C or higher, and more preferably 110°C or higher.

The melting point of the olefin resin composition contained in the moisture-permeable film is measured by the following method.
Approximately 2.0 mg of moisture-permeable film was used as a sample, and differential scanning calorimetry (DSC) was performed using a differential scanning calorimetry meter (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) under the following conditions: measurement temperature range of 10°C to 260°C, heating rate of 10°C/min, and in an air environment. The obtained DSC curve showed an endothermic peak that occurs when the olefin resin melts, and the melting point of the olefin resin was the temperature at the peak of the observed endothermic peak. It is possible to distinguish between the melting point of the additive contained in the moisture-permeable film and the melting point of the olefin resin 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 a moisture-permeable film. First, the moisture-permeable film is kneaded using a Laboplast Mill (manufactured by Toyo Seiki) at 160°C and 30 rpm for 10 minutes to obtain a resin mass. Next, the resin mass is pressed using a Lab Press (manufactured by Toyo Seiki) at 150°C and 13 MPa for 1 minute, and then cooled and pressed at room temperature and 13 MPa for 1 minute 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 one week. This allows more additives to bleed out onto the surface of the pressed film than in the moisture-permeable film, enabling efficient collection of the additives. Methods for collecting additives from the surface of the pressed film 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, the olefin resin composition), in order to give the moisture-permeable film satisfactory flexibility while keeping residual strain after stretch deformation small. More preferably, it is 35 parts by mass or more, and even more preferably 40 parts by mass or more. Furthermore, it is preferable that the content be 95 parts by mass or less, in order to prevent blocking from occurring in the moisture-permeable film. More preferably, it is 92 parts by mass or less, and even more preferably 90 parts by mass or less.
The content of high-melting-point olefin resin in the moisture-permeable film is preferably 5 parts by mass or more per 100 parts by mass of the resin in the moisture-permeable film (specifically, for example, the olefin resin composition), from the viewpoint of further imparting heat resistance, morphological stability, and processability to the moisture-permeable film, more preferably 8 parts by mass or more, and even more preferably 10 parts by mass or more. Furthermore, it is preferable that the content be 70 parts by mass or less from the viewpoint of achieving compatibility with the flexibility of the moisture-permeable film, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

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/ ^cm³ or less, more preferably 0.885 g/ ^cm³ or less, and even more preferably 0.875 g/ ^cm³ or less.
Furthermore, 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/ ^cm³ or higher, more preferably 0.850 g/ ^cm³ or higher, and even more preferably 0.860 g/ ^cm³ or higher.
In summary, assuming that the density of the low-melting-point olefin resin is lower than that of the high-melting-point olefin resin used in combination, the density is preferably 0.840 g/ ^cm³ to 0.895 g/ ^cm³ , more preferably 0.850 g/ ^cm³ to 0.885 g/ ^cm³ , and even more preferably 0.860 g/ ^cm³ to 0.875 g/ ^cm³ .
A preferred example of a low-melting-point olefin resin is a copolymer of ethylene and α-olefin, where α-olefins include, for example, propylene, 1-butene, 1-pentene, and 1-hexene. From the viewpoint of reliably adjusting the melting point and density of the low-melting-point olefin resin to the aforementioned preferred ranges, it is preferable that the low-melting-point olefin resin is a random copolymer. In particular, a copolymer of ethylene and α-olefin polymerized with a metallocene catalyst is more preferable because it further improves the strength of the film against tearing and penetration.

The density of the high-melting-point olefin resin is preferably relatively low, from the viewpoint of achieving compatibility with the flexibility of the moisture-permeable film, 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.
Furthermore, from the viewpoint of suppressing blocking, the density of the high-melting-point olefin resin is preferably 0.900 g/ ^cm³ or higher, more preferably 0.905 g/ ^cm³ or higher, and even more preferably 0.910 g/ ^cm³ or higher.
In summary, assuming that the density of the high-melting-point olefin resin is higher than that of the low-melting-point olefin resin used in combination, the density is preferably 0.900 g/ ^cm³ to 0.950 g/ ^cm³ , more preferably 0.905 g/ ^cm³ to 0.940 g/ ^cm³ , and even more preferably 0.910 g/ ^cm³ to 0.930 g/ ^cm³ .
As the high-melting-point olefin resin, low-density polyethylene and linear low-density polyethylene are preferred, and the use of linear low-density polyethylene is particularly preferred from the viewpoint of improving heat resistance during stretching and enabling uniform stretching. Linear low-density polyethylene polymerized with a metallocene catalyst is especially preferred because it further improves the strength of the film against tearing and puncture.

In a moisture-permeable film, the inorganic filler is a substance that causes delamination at the interface with the resin used in combination, thereby forming micropores. From the viewpoint of ensuring that such an inorganic filler reliably exhibits its function, 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, and more preferably 10 μm or less.
The average particle size D50 of an inorganic filler refers to the cumulative particle size at 50% by weight, as measured by laser diffraction scattering particle size distribution analysis.

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 dioxide, alumina, mica, zeolite, and carbon black, as well as mixtures thereof. Calcium carbonate is particularly preferred because it easily adjusts the average particle size D50 to the aforementioned preferred range.

The inorganic filler content in a moisture-permeable film is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 80 parts by mass or more, and preferably 400 parts by mass or less, more preferably 350 parts by mass or less, and even more preferably 200 parts by mass or less, per 100 parts by mass of resin in the moisture-permeable film, from the viewpoint of balancing the breathability, moisture permeability, and leak-proof properties of the film. If the inorganic filler content is too low, the size and number of micropores may be insufficient, potentially resulting in insufficient breathability and moisture permeability. Conversely, if the inorganic filler content is too high, it may lead to a decrease in leak-proof properties.

The moisture-permeable film may further contain a pore-opening accelerator in addition to the aforementioned resin (preferably an olefin-based resin composition) and inorganic filler. The pore-opening accelerator is used to facilitate the stretching of the resin sheet containing the resin and inorganic filler to form micropores. As mentioned above, from the viewpoint of improving the flexibility of the moisture-permeable film, it is preferable to include a low-melting-point olefin-based resin in the moisture-permeable film. Since low-melting-point olefin-based resins are resins that are relatively less prone to interfacial delamination with inorganic fillers, using a pore-opening accelerator in addition to a low-melting-point olefin-based resin as a raw material for the moisture-permeable film can promote such interfacial delamination.
Suitable pore-opening accelerators include substances known as release agents for metals and resins. Specifically, these include metal soaps, silicones, fluororesins, fatty acid amides, and hydrocarbon paraffin waxes. In particular, metal soaps are preferred because they facilitate the formation of micropores more smoothly.
As the aforementioned metal soap, metal salts of fatty acids are preferably used. Examples of fatty acids include caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, and lauric acid. Examples of metal salts include salts of calcium, aluminum, magnesium, and zinc of these fatty acids.
In particular, it is preferable that the chain length of the hydrocarbon chain in the fatty acid added to hydrophobize the surface of the inorganic filler (described later) is the same as the chain length of the hydrocarbon chain in the fatty acid constituting the metal soap, because this allows the metal soap to migrate more smoothly to the inorganic filler surface-modified with fatty acids. In particular, it is preferable that both the fatty acid and the fatty acid constituting the metal soap are stearic acid.
It should be noted that 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 improve the dispersibility of inorganic fillers. However, fatty acids do not have the function of promoting interfacial delamination between the resin and the inorganic filler. Therefore, in this invention, metal salts of fatty acids and fatty acids are clearly distinguished both materially and functionally.

In particular, using a metal soap with a melting point of 200°C or lower is preferable from the viewpoint that the metal soap will melt sufficiently and be uniformly mixed into the molten resin during the kneading of the resin-containing compound in the manufacturing process of the moisture-permeable film. From this viewpoint, it is even more preferable that the melting point of the metal soap be 180°C or lower, and even more preferable that it be 160°C or lower.

Furthermore, in relation to the aforementioned resin, it is preferable to use a metal soap whose precipitation temperature is higher than the solidification temperature of the resin. This is preferable from the viewpoint of successfully forming micropores and obtaining a moisture-permeable film with high moisture permeability and high water resistance. Specifically, because 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 release properties between the inorganic filler and the resin during stretching are improved, and micropores are smoothly formed. From the viewpoint of further enhancing this advantage, when the precipitation temperature of the metal soap is Ts (°C) and the solidification temperature of the resin is Tp (°C), it is preferable that the value of Ts-Tp is greater than 0°C, more preferably 1°C or higher, and even more preferably 2°C or higher. Furthermore, it is preferable that the value of Ts-Tp is 50°C or lower.

Provided that the value of Ts-Tp is within the aforementioned 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 to 130°C, more preferably 70°C to 120°C, and even more preferably 80°C to 115°C, provided that the value of Ts-Tp is within the aforementioned range.

The precipitation temperature Ts of metal soap is measured using a hot stirrer and thermocouple in the following manner: Using a hot stirrer, 0.43 g of metal soap is added to 5.0 g of paraffin oil and heated while stirring until the metal soap dissolves. After stopping the stirring of the liquid with the stirrer, 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 precipitates is read using a thermocouple, and this temperature is defined as the precipitation temperature of the metal soap. If the metal soap does not dissolve in the paraffin oil even after heating it to 210 °C, the precipitation temperature is defined as 210 °C.
On the other hand, the solidification temperature Tp of the resin is measured in accordance with JIS K 7121 (Method for determining the end temperature of extrapolation crystallization) by the following method. A sample of approximately 2.0 mg of moisture-permeable film is used, and differential scanning calorimetry (DSC7000X, manufactured by Hitachi High-Tech Science Corporation) is performed using a differential scanning calorimetry (DSC7000X) with a measurement temperature range of 30°C to 260°C, a heating rate of 10°C/min, a cooling rate of 50°C/min, in an air environment, and a data sampling period of 0.5 s. In the cooling process of the obtained DSC curve, an exothermic peak that occurs when the resin solidifies (crystallizes) is observed. The solidification temperature of the resin is defined as the temperature at the intersection of a straight line drawn from the baseline on the lower side of the peak temperature to the higher side, and an approximate straight line drawn between the two data points where the slope is maximum on the lower side of the peak curve, with respect to the peak with the greatest amount of exothermic heat during the cooling process. If two or more heat-generating peaks overlap, the solidification temperature is determined using the method described above after peak separation, for example, by using the software PeakFit v4.12 (manufactured by Huelinks Co., Ltd.).

The content of the pore-opening promoter in the moisture-permeable film is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of resin in the moisture-permeable film, from the viewpoint of promoting the formation of micropores. From the viewpoint of obtaining good film moldability, 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 accelerator in the moisture-permeable film is a metal soap, the amount of 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. And, in order to maintain good moldability, it 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 triglycerides in addition to the aforementioned resin (preferably an olefin-based resin composition) and inorganic filler, and optionally a pore-opening accelerator. The triglycerides can function as water repellents in the moisture-permeable film to improve water repellency and leak resistance.
In the field of the breathable film used in the present invention, it has been common practice to incorporate triglycerides into breathable films. However, it is preferable that the triglycerides used in the present invention be of a different type from those previously used in this field. Specifically, the triglycerides preferably used in the present invention are "triglycerides containing a group derived from a fatty acid having 16 to 22 carbon atoms, wherein the group is a hydrocarbon group without unsaturated bonds or substituents" (hereinafter also referred to as "specific triglycerides"). The inventors' research has revealed that using specific triglycerides improves the water repellency of the breathable film containing the specific triglycerides, thereby improving the leak-proof properties of the breathable film.

From the viewpoint of making the aforementioned advantages even more pronounced, the content of specific triglycerides in the moisture-permeable film is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of resin.
Furthermore, from the viewpoint of film moldability, the content of specific triglycerides 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 resin.
In summary, the content of specific triglycerides is preferably 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of resin, more preferably 0.5 parts by mass or more and 25 parts by mass or less, and even more preferably 1.0 part by mass or more and 20 parts by mass or less.

Furthermore, from the viewpoint of fully utilizing both the effect of the metal soap used as a pore-opening accelerator and the effect of the water-repellent agent, and from the viewpoint of preventing deterioration of processability due to excessive additive content, the ratio of specific triglycerides to metal soaps contained in the moisture-permeable film is preferably 30 to 300 parts by mass of metal soap per 100 parts by mass of specific triglycerides. From the viewpoint of further enhancing this advantage, it is even more preferable that the metal soap be used in an amount of 35 to 230 parts by mass, and even more preferable that it be used in an amount of 40 to 220 parts by mass, per 100 parts by mass of specific triglycerides.

The following describes specific triglycerides. Specific triglycerides are represented by the following formula (1).

In formula (1) above, ^R1 , ^R2 , and ^R3 represent the same or different hydrocarbon groups. At least one of ^R1 , ^R2 , and ^R3 is a group derived from a fatty acid having 16 to 22 carbon atoms, and this group is a hydrocarbon group without unsaturated bonds or substituents. Note that the alkyl group of palmitic acid, a fatty acid with 16 carbon atoms, has 15 carbon atoms.
The term "hydrocarbon group without an unsaturated bond" refers to a hydrocarbon group that does not have either a carbon-carbon double bond or a triple bond. In other words, it refers to an alkyl group. Furthermore, the term "hydrocarbon group without substituents" means that the hydrogen atoms contained in the hydrocarbon group are not substituted by other atoms or groups of atoms (e.g., hydroxyl groups). Therefore, the term "hydrocarbon group without an unsaturated bond and substituents" is synonymous with an unsubstituted alkyl group.

In the specific triglyceride represented by formula (1) above, from the viewpoint of obtaining a moisture-permeable film with even higher water repellency, it is preferable that at least one of ^R1 , ^R2 , and ^R3 is a group derived from a fatty acid having 16 to 20 carbon atoms, and that this group is a hydrocarbon group without unsaturated bonds or substituents.
Furthermore, in the specific triglyceride represented by formula (1), if one or two of ^R1 , ^R2 , and ^R3 are groups other than a group derived from a fatty acid having 16 to 22 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents), there are no particular restrictions on the type of group as long as it is derived from a fatty acid. However, from the viewpoint of obtaining a moisture-permeable film with even higher water repellency, it is preferable that these groups do not have unsaturated bonds and substituents.

The specific triglyceride is preferably one in which the number of carbon atoms in the fatty acid residue has been adjusted. Doing so can improve the water repellency of the moisture-permeable film. More specifically, the specific triglyceride is preferably either (A) or (B) below.
(A) A triglyceride comprising a mixture of a triglyceride containing at least one group derived from a fatty acid with 18 carbon atoms and a triglyceride containing at least one group derived from a fatty acid with 16 to 22 carbon atoms (excluding fatty acids with 18 carbon atoms).
(B) A triglyceride containing at least one group derived from a saturated fatty acid with 18 carbon atoms and at least one group derived from a saturated fatty acid with 16 to 22 carbon atoms (excluding fatty acids with 18 carbon atoms) in one molecule.
In particular, from the viewpoint of further enhancing liquid repellency, it is preferable that the triglyceride contains at least one group derived from a saturated fatty acid with 18 carbon atoms in each molecule, and at least one group derived from a saturated fatty acid with 16 to 22 carbon atoms (excluding fatty acids with 18 carbon atoms).
As a specific example, the combination of a fatty acid with 18 carbon atoms and a fatty acid with 16 carbon atoms is as shown in (C) or (D) below.
(C) A triglyceride comprising a mixture of a triglyceride containing at least one group derived from a fatty acid having 18 carbon atoms (i.e., stearic acid) (the group is a hydrocarbon group without unsaturated bonds and substituents) in one molecule and a triglyceride containing at least one group derived from a fatty acid having 16 carbon atoms (i.e., palmitic acid) (the group is a hydrocarbon group without unsaturated bonds and substituents) in one molecule.
(D) A triglyceride containing at least one group derived from a fatty acid having 18 carbon atoms (the group is a hydrocarbon group without unsaturated bonds and substituents) and at least one group derived from a fatty acid having 16 carbon atoms (the group is a hydrocarbon group without unsaturated bonds and substituents) in one molecule.

In the case of (C) above, if 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 with 16 carbon atoms in each molecule (this triglyceride is also called "triglyceride 16"). Triglyceride 16 may contain one group derived from a saturated fatty acid with 16 carbon atoms in each molecule (this triglyceride is also called "triglyceride P"), two groups (this triglyceride is also called "triglyceride PP"), or three groups (this triglyceride is also called "triglyceride PPP").
Furthermore, there are no particular restrictions on the types of remaining fatty acid residues in triglyceride P and triglyceride PP; for example, they may be saturated fatty acid residues having 12 to 24 carbon atoms.

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

In the case of (C) above, if the specific triglyceride includes multiple types of triglycerides, it is also preferable that at least one of the triglycerides contains at least one group derived from a saturated fatty acid with 18 carbon atoms in one molecule (this triglyceride is also called "triglyceride 18"). Triglyceride 18 may contain one group derived from a fatty acid with 18 carbon atoms in one molecule (this triglyceride is also called "triglyceride S"), two groups (this triglyceride is also called "triglyceride SS"), or three groups (this triglyceride is also called "triglyceride SSS").
Furthermore, there are no particular restrictions on the types of remaining fatty acid residues in triglyceride S and triglyceride SS; for example, they may be saturated fatty acid residues with 12 to 24 carbon atoms.

Triglyceride 18 may consist only of triglyceride S, or only of triglyceride SS, or only of triglyceride SSS.
Triglyceride 18 may be a combination of two or more types 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 the case of (C) above, the specific triglyceride may consist only of triglyceride 16 and triglyceride 18, or it may consist of triglyceride 16 and triglyceride 18 plus other triglycerides. Examples of other triglycerides include triglycerides that do not have any 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 we denote a group derived from a saturated fatty acid with 16 carbon atoms as "P", a group derived from a saturated fatty acid with 18 carbon atoms as "S", and groups derived from fatty acids other than saturated fatty acids with 16 carbon atoms and saturated fatty acids with 18 carbon atoms as "X" and "Y", then combinations of aliphatic groups constituting a specific triglyceride include, for example, PPP, SSS, PPX, SSX, PXY, SXY, PPS, PSS, and PSX. The structures of the triglycerides represented by PPX, SSX, PXY, SXY, and PSX are shown in (a) through (m) below. Note that the structures of PPS and PSS are not shown, but the structure of PPS is similar to the structure of PPX, and the structure of PSS is similar to the structure of SSX.

The specified triglycerides can be any of the aforementioned triglycerides used individually. For example, in case (D) above, the specified triglyceride may consist of a molecule containing at least one group derived from a saturated fatty acid with 16 carbon atoms, at least one group derived from a saturated fatty acid with 18 carbon atoms, and no groups derived from other fatty acids. Alternatively, the specified triglyceride may consist of a triglyceride containing one group derived from a saturated fatty acid with 16 carbon atoms, one group derived from a saturated fatty acid with 18 carbon atoms, and one group derived from another fatty acid.

The specified triglyceride may be a combination of two or more of the various triglycerides described above. For example, the specified triglyceride may be a combination of (C) and (D), or a combination of two or more of (D).
Furthermore, the specified triglycerides may be a combination of one or more of the aforementioned triglycerides and other triglycerides. Examples of other triglycerides include triglycerides containing a group derived from a fatty acid having 14 to 22 carbon atoms (excluding triglycerides 16 and 18).
In the present invention, it is preferable to use the various triglycerides described above individually, or to use a combination of two or more of the various triglycerides described above, from the viewpoint of further improving the water repellency of the moisture-permeable film.

In the present invention, it is preferable that the triglycerides contained in the moisture-permeable film consist of groups derived from fatty acids with 18 carbon atoms (hydrocarbon groups without unsaturated bonds or substituents), with a proportion of 28% to 96% by mass, particularly 28% to 70% by mass, and especially 29% to 67% by mass, based on the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film. This is preferable from the viewpoint of obtaining a moisture-permeable film with even higher water repellency.
Furthermore, the term "all triglycerides" as used above refers to all triglycerides other than the specified triglycerides contained in the moisture-permeable film (the same applies hereafter unless otherwise specified).

Furthermore, from the viewpoint of further increasing the water repellency of the breathable film and shortening the time it takes for water repellency to manifest, it is preferable that the triglycerides contained in the breathable film used in the present invention consist of, with respect to the total amount of fatty acid-derived groups contained in all triglycerides in the breathable film, 28% to 68% by mass being groups derived from fatty acids with 18 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents) and 26% to 70% by mass being groups derived from fatty acids with 16 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents). However, the sum of the proportion of groups derived from fatty acids with 18 carbon atoms and the proportion of groups derived from fatty acids with 16 carbon atoms does not exceed 100% by mass.
In this case, the proportion of groups derived from fatty acids with 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 with 16 carbon atoms is 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. A higher proportion of groups derived from fatty acids with 16 carbon atoms makes it easier for triglycerides to precipitate on the surface of the moisture-permeable film, shortening the time it takes for water repellency to develop.

Furthermore, from the viewpoint of improving the thermal stability of the moisture-permeable film and further enhancing the water repellency of the moisture-permeable film, it is preferable that the triglycerides contained in the moisture-permeable film of the present invention consist of, with respect to the total amount of fatty acid-derived groups contained in all triglycerides, 28% to 47% by mass being groups derived from fatty acids with 18 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents), and 40% to 60% by mass being groups derived from fatty acids with 22 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents). However, the sum of the proportion of groups derived from fatty acids with 18 carbon atoms and the proportion of groups derived from fatty acids with 22 carbon atoms does not exceed 100% by mass.
In this case, the proportion of groups derived from fatty acids with 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 with 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. A higher proportion of groups derived from fatty acids with 22 carbon atoms results in a higher melting point of the triglyceride and improved thermal stability of the molded product. Furthermore, it can reduce contamination of the processing machine's rolls.

The proportions of fatty acid-derived groups in all triglycerides, based on the total amount of fatty acid-derived groups, of groups derived from 16-carbon fatty acids, 18-carbon fatty acids, and 22-carbon fatty acids are measured by the following method.
Triglycerides that have bled out onto the surface of the film are wiped away and collected with a cellulose wiper.
The ester bonds in the obtained triglycerides are hydrolyzed with alkali, and the methyl-esterified fatty acids are quantitatively analyzed by gas chromatography.

Furthermore, whether or not alkyl chains with different numbers of carbon atoms are present in a single triglyceride molecule can be determined by TOF-MS (Time-of-Flight Mass Spectrometry). Specifically, the molecular weight distribution of the triglyceride is measured by TOF-MS, and the presence or absence of alkyl groups with different numbers of carbon atoms within the molecule is determined from the molecular weight of a single molecule. For compounds with the same molecular weight, whether or not alkyl chains with different numbers of carbon atoms are present in a single molecule can be determined using a tandem mass spectrometer (MS/MS). This is done by selecting a specific ion in the first mass separation unit, colliding it with an inactivating gas, and then separating and detecting the resulting fragment ions in the second mass separation unit.

In this invention, it is preferable that the triglycerides used do not contain groups derived from unsaturated fatty acids, from the viewpoint of further enhancing the water repellency of the moisture-permeable film. "Not containing groups derived from unsaturated fatty acids" encompasses both cases: the complete absence of such groups, and the unavoidable presence of small amounts of unsaturated fatty acids. The case of unavoidable small amounts of unsaturated fatty acids refers, for example, to a situation where the proportion of groups derived from unsaturated fatty acids is 2% by mass or less, based on the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film.

Similarly, from the viewpoint of further enhancing the water repellency of the moisture-permeable film, it is preferable that the triglycerides used in the present invention do not contain groups derived from fatty acids having hydroxyl groups. A fatty acid having hydroxyl groups refers to a fatty acid in which at least one hydrogen atom in the hydrocarbon group of the fatty acid is replaced by a hydroxyl group. "Not containing groups derived from fatty acids having hydroxyl groups" includes both cases where no groups derived from fatty acids having hydroxyl groups are present at all, and cases where a small amount of groups derived from fatty acids having hydroxyl groups is inevitably present. The case where a small amount of groups derived from fatty acids having hydroxyl groups is inevitably present is, for example, when the proportion of groups derived from fatty acids having hydroxyl groups is 2% by mass or less, based on the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film.

From the viewpoint of further enhancing the water repellency of the moisture-permeable film used in this invention, it is preferable that the groups derived from fatty acids contained in all triglycerides in the moisture-permeable film are hydrocarbon groups without unsaturated bonds. Furthermore, it is preferable that the groups derived from fatty acids contained in all triglycerides are hydrocarbon groups without substituents.

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

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

As a dispersant, one that can hydrophobize the surface of the inorganic filler is preferably used. From this viewpoint, it is preferable to use a fatty acid as a dispersant. Examples of fatty acids include caprylic acid, palmitic acid, stearic acid, capric acid, oleic acid, myristic acid, and lauric acid.

Plasticizers are used to impart flexibility and pliability to moisture-permeable films, and to prevent rustling noises from occurring in the films. Preferred plasticizers include monoesters, polyesters, ethylene-α-olefin co-oligomers, low molecular weight polyethylene, olefin oligomers, liquid polyisoprene, and liquid polybutadiene.
Monoesters are compounds obtained from a monobasic acid and a monohydric alcohol.
On the other hand, polyesters are compounds obtained from any combination of a polybasic acid and a monohydric alcohol, a monobasic acid and a polyhydric alcohol, or a polybasic acid and a polyhydric alcohol.
Ethylene-α-olefin co-oligomers are low molecular weight copolymers of ethylene with α-olefins such as propylene, 1-butene, 1-pentene, and 1-hexene.
The following are examples of commonly used basic acids, polybasic acids, monohydric alcohols, and polyhydric alcohols.
Examples of monobasic acids include monocarboxylic acids, which are long-chain hydrocarbons having 10 to 22 carbon atoms.
Examples of polybasic acids include dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids.
Examples of monohydric alcohols include monoalcohols of long-chain hydrocarbons having 10 to 22 carbon atoms.
Examples of polyhydric alcohols include diols, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol, and sucrose.

Among polyesters used as plasticizers, particularly preferred examples include polyesters in which the carboxylic acids or alcohols at both ends of a diethylene glycol and dimer acid polyester are partially or completely encapsulated with stearyl alcohol or stearic acid; polyesters of 1,3-butanediol and adipic acid; hexaesters consisting of trimethylolpropane-adipic acid-stearic acid; octaesters consisting of pentaerythritol-adipic acid-stearic acid; and dodecaesters consisting of dipentaerythritol-adipic acid-stearic acid.

Furthermore, among monoesters used as plasticizers, particularly preferred examples include esters with a total of 30 or more carbon atoms obtained by dehydrating a monocarboxylic acid having 1 to 40 carbon atoms and a monoalcohol having 1 to 40 carbon atoms. Among these, monoesters with a total of 30 or more carbon atoms obtained from a monocarboxylic acid and a monoalcohol are preferred, and monoesters with 38 or more carbon atoms and having a branched chain are more preferred. Specifically, 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 (18 to 40 carbon atoms) and monoalcohols (6 to 36 carbon atoms).

The content of dispersants and plasticizers in the moisture-permeable film is preferably 0.01 parts by mass or more, more preferably 0.10 parts by mass or more, even more preferably 2.0 parts by mass or more, and preferably 18.0 parts by mass or less, and more preferably 16.0 parts by mass or less, per 100 parts by mass of resin in the moisture-permeable film, from the viewpoint of clearly defining the purpose of their use while suppressing the adverse effects of excessive use (e.g., a decrease in the moldability and strength of the film).

Other additives (such as pore-opening promoters, dispersants, and plasticizers) that may be contained in the moisture-permeable film may include at least a first additive whose SP value difference from that of the specific triglyceride is less than 0.37. The first additive is preferably included in an amount of 3.5 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler, and specific triglyceride, in order to allow the additive to be incorporated without inhibiting the water repellency exhibited by the specific triglyceride. From the viewpoint of improving leak prevention without impairing water repellency, the first additive is preferably included in an amount of 0.01 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler, and specific triglyceride, more preferably in an amount of 0.03 parts by mass or more and 3.3 parts by mass or less, and even more preferably in an amount of 0.06 parts by mass or more and 3.2 parts by mass or less.
Furthermore, the additive may include at least a second additive whose SP value difference from that of the specific triglyceride is 0.37 or more. The second additive is preferably included in an amount of 10 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler and specific triglyceride, in order to enable the formulation of the additive without inhibiting the water repellency exhibited by the specific triglyceride. When the second additive is included as an additive, from the viewpoint of improving leak prevention without impairing water repellency, the second additive is preferably included in an amount of 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler and specific triglyceride, more preferably 1 part by mass or more and 8 parts by mass or less, and more preferably 1.5 parts by mass or more and 6 parts by mass or less.
As mentioned earlier, in the 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' research has revealed that randomly adding additives to a moisture-permeable film containing triglycerides inhibits the water repellency caused by the triglycerides. In contrast, if the first additive is used in an amount of 3.5 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler, and specific triglycerides, or if the second additive is used in an amount of 10 parts by mass or less per 100 parts by mass of the total of the resin, inorganic filler, and specific triglycerides, the additives can be incorporated without inhibiting the water repellency exhibited by the specific triglycerides. From the viewpoint of making this advantage even more pronounced, it is more preferable that the difference in SP values between the specific triglycerides and the second additive is 0.50 or more, and even more preferable that it is 0.60 or more. Furthermore, 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 called the solubility parameter. Two substances with similar SP values tend to mix well. In other words, two substances with similar SP values have high compatibility. Therefore, when comparing the SP value of a specific triglyceride with that of an additive, the SP value of the specific triglyceride may be larger, or the SP value of the additive may be larger. From the viewpoint of minimizing the inhibition of the water repellency of the specific triglyceride due to the additive, it is preferable that the SP value of the specific triglyceride is larger than that of the additive.

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

Examples of second additives selected such that the difference in SP value with a 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 this 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 alone may be used.

The SP value is calculated using Fedors' method [R. F. FEDORS, POLYM. ENG. SCI. 14, 147 (1974)], and is expressed in units of (cal/ ^cm³ ) ^1/2 .

If the moisture-permeable film contains multiple types of specific triglycerides, the SP value δmix of the mixture shown below should be 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.

The moisture-permeable film is preferably evaluated as having leak-proof properties in the leak-proof evaluation test described below. This allows the composite sheet of the present invention to have high leak-proof properties. The aforementioned moisture-permeable film may be evaluated as having leak-proof properties in the leak-proof evaluation test described below.
In the leak-proof evaluation test described below, the moisture-permeable film is fixed in its natural state and its leak-proof properties are evaluated. However, it is more preferable that the moisture-permeable film used in the present invention is evaluated as having leak-proof properties even when its leak-proof properties are evaluated in the same manner as the leak-proof evaluation test described below, except that it is fixed in an elongated state, such as a 30% elongated state, as shown in the examples described later. Moisture-permeable films with elasticity tend to allow liquid to permeate more easily and have reduced leak-proof performance when elongated than in their natural state. However, by exhibiting a certain level of leak-proof performance even in such an elongated state where leak-proof performance tends to be low, the composite sheet of the present invention can be given high leak-proof properties.

(Leakage resistance evaluation test)
The material to be evaluated and a pulp sheet (Lion Corporation, Lead Healthy Cooking Paper Double (product name), basis weight 40 g/ ^m² ) are placed on top of a filter paper (Advantec Toyo Co., Ltd., No. 2, diameter 70 mm) in that order. The material to be evaluated is fixed in its natural state and its size is adjusted in plan view so that its entirety overlaps with the filter paper. The pulp sheet is a rectangular shape in plan view of 25 mm x 30 mm. 0.265 g of a wettability test mixture (Kanto Chemical Co., Ltd.), with a surface tension of 44 mN/m at 25°C, is injected into the center of the top surface of the pulp sheet using a dropper. Immediately after injection, a cylindrical acrylic resin plate with a diameter of 60 mm and a thickness of 5 mm is placed on top of the pulp sheet, and a 500 g weight is placed on the plate and pressurized for 1 hour. After 1 hour has elapsed since the weight was placed, the weight is removed, and the presence or absence of seepage of the test solution onto the filter paper is visually observed. The above series of operations is performed three times on the object to be evaluated. If no leakage of the test liquid is observed onto the filter paper in any of the three attempts, the object to be evaluated is evaluated as having leak-proof properties. Otherwise, it is evaluated as not having leak-proof properties.

To elaborate on the aforementioned leak-proof evaluation test, the object to be evaluated (moisture-permeable film) can be 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 for reasons such as the object to be evaluated being too small, the largest similar square shape in plan view should be cut out to be used as a test piece, and the pulp sheet and test liquid should be adjusted so that the surface pressure on the pulp sheet and the amount of test liquid per unit area are equal, and the test should be conducted. Furthermore, if the object to be evaluated is part of a product such as an absorbent article, the object to be evaluated should be removed from the product with sufficient care to avoid tearing, etc., and then subjected to the test.
Furthermore, if the test solution injected onto the top surface of the pulp sheet overflows from the pulp sheet during pressurization and seeps into the filter paper from the edges of the object being evaluated, a polyethylene film or similar material that is impermeable to the test solution should be used to prevent the test solution from seeping into the filter paper from the edges of the object being evaluated.

The moisture-permeable film has a degree of flexible deformation in the stretching direction (mechanical direction of the moisture-permeable film) measured by the tensile test described above, 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. As a result, the composite sheet of the present invention has high elasticity and can be particularly stretchable. Furthermore, when the composite sheet of the present invention is used as a component of an absorbent article, it can be stretched without hindering the wearer's movement, thus reducing discomfort to the wearer. The moisture-permeable film described above may have a degree of flexible deformation in the stretching direction within the above range. On the other hand, the lower limit of the degree of flexible deformation in the stretching direction of the moisture-permeable film is preferably 0.005 N/(mm·(g/ ^m² )) or more, from the viewpoint of maintaining the strength of the composite sheet of the present invention.

The moisture-permeable film has a residual strain after 30% elongation, as measured by the tensile test, preferably 11% or less, more preferably 10% or less, and even more preferably 9% or less. This results in the composite sheet of the present invention having high elasticity, and in particular, being easily shrinkable. 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, thus reducing discomfort to the wearer. The aforementioned moisture-permeable film can have a residual strain after 30% elongation within the aforementioned range. On the other hand, the lower limit of the residual strain after 30% elongation of the moisture-permeable film is preferable as small as possible, most preferably 0%.

The moisture-permeable film is permeable and can allow moisture to pass through. The moisture-permeable film has a moisture permeability of preferably 0.4 g/(100 ^cm² ·h) or more, more preferably 0.45 g/(100 ^cm² ·h) or more, and even more preferably 0.8 g/(100 cm²·h) or more, as measured in accordance with JIS L 1099 ^A -2. As a result, the composite sheet of the present invention has high moisture permeability, and when the composite sheet is used as a component of an absorbent article, moisture inside the absorbent article can be appropriately released to the outside. The moisture-permeable film described above 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 cm²·h) or less, more preferably 3.5 g/(100 ^cm² ·h) or less, and even more preferably 3.0 g/( ^{100 cm²} ·h) or less, from the viewpoint of preventing loss of leak-proof properties due to excessive porosity. The moisture permeability is measured by the following method.

(Method for measuring moisture permeability)
This measurement method conforms to JIS L 1099 A-2. Approximately 25 mL of deionized water is placed in a glass bottle (Laboran screw-cap bottle No. 8, manufactured by AS ONE) with a diameter of 2.03 cm (area of 3.23 ^cm² ). The mouth of the glass bottle is covered with one test piece so as to leave no gaps, and the test piece (e.g., a moisture-permeable film) is secured to the glass bottle with a rubber band to serve as the evaluation sample. After measuring the mass (W1) of the evaluation sample, the sample is stored in a constant temperature bath 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 natural air permeability of the moisture-permeable film is preferably 3000 seconds or less, more preferably 2500 seconds or less. The air permeability is measured by the following method. This air permeability is an indicator of the time required for 25 cc of air to pass through the moisture-permeable film in the thickness direction. The smaller the value of the air permeability, the higher the air permeability of the moisture-permeable film. A composite sheet equipped with a moisture-permeable film having an air permeability within the above range can have high air permeability. The aforementioned moisture-permeable film can have an air permeability within the above range. On the other hand, the lower limit of the natural air permeability of the moisture-permeable film is preferably 1 second or more, from the viewpoint of maintaining the strength of the moisture-permeable film. Furthermore, since the moisture-permeable film used in this invention has micropores and is expandable and contractible, stretching the moisture-permeable film in its mechanical direction (stretching direction) can widen the micropores of the moisture-permeable film, improving air permeability (the value of the air permeability may decrease). Therefore, a preferred embodiment of the moisture-permeable film used in the present invention is a moisture-permeable film that has been stretched in the mechanical direction (stretching direction). This stretching treatment can be carried out according to conventional methods. Furthermore, the stretching ratio is not particularly limited, but for example, it can be 1.3 times.

(Method for measuring air permeability)
This measurement method conforms to JIS P8117. Using an air permeability tester (product name: Garre Densometer, manufactured by Kumagai Riki Kogyo Co., Ltd.), the time required for 25 cc of air to permeate the object under evaluation (moisture-permeable film) in the thickness direction is measured. The state of the object under evaluation during the test shall be in its natural state or in an elongated state (e.g., 30% elongation). If 25 cc of air does not completely permeate the moisture-permeable film after 10,000 seconds or more, and the measurement cannot be completed, the measurement is deemed impossible, and the moisture-permeable film is evaluated as having no air permeability.

Next, a preferred method for manufacturing the moisture-permeable film used in the present invention will be described.
A suitable method for manufacturing a moisture-permeable film includes a step of stretching a resin sheet, which is obtained by melt-molding a compound containing a resin, an inorganic filler, and an additive, in at least one axial direction.
The details of the resin, inorganic filler, and additives contained in the compound are as previously described. Furthermore, the proportions of the resin, inorganic filler, and additives contained in the compound are the same as those of these components contained in the breathable film. In addition, the types and amounts of optional components contained in the compound are the same as those of optional components contained in the breathable film.

The moisture-permeable film used in this invention can be efficiently manufactured, for example, by the following method.
First, the components constituting the compound are pre-mixed using a Henschel mixer or super mixer, and then kneaded into pellets using a single-screw or twin-screw extruder. Next, the resulting pellets are used to form a film using a molding machine to obtain a resin sheet. For example, a T-die type or an inflation type molding machine can be used.

Regarding the dispersant, it may be used alone or mixed with other components of the compound. However, it is preferable to pre-apply the dispersant to the surface of the inorganic filler to produce a surface-modified inorganic filler, and then mix this surface-modified inorganic filler with other components of the compound to prepare the compound. This method allows for successful stretching of the resin sheet while suppressing the occurrence of unintended pinholes, resulting in a moisture-permeable film with high moisture permeability and high water resistance.

The aforementioned resin sheet undergoes uniaxial or biaxial stretching, which causes interfacial delamination between the resin and the inorganic filler, forming micropores. This stretching can be performed using methods such as the roll method, which allows stretching in the machine direction, or the 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. The resin sheet is preferably stretched at least 1.1 times in one axis direction, more preferably 1.5 times, and even more preferably 2 times, so that its area increases with stretching. Furthermore, from the viewpoint of avoiding a decrease in tear strength due to excessive molecular orientation associated with excessive stretching, it is preferable to stretch it to 5.0 times or less, more preferably 4.5 times or less, and even more preferably 4 times or less.

In both uniaxial and biaxial stretching, the temperature of the resin film during stretching is preferably set to 30°C to 100°C, more preferably 35°C to 95°C, and even more preferably 40°C to 90°C, from the viewpoint of uniformly stretching the film without tearing it.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited in any way to the above embodiments and can be modified as appropriate without departing from the spirit of the invention.
With regard to the embodiments of the present invention described above, the following additional information is disclosed.

<1>
A stretchable, moisture-permeable film with micropores and a non-stretchable nonwoven fabric are overlapped and joined to each other at multiple joints scattered between the overlapping surfaces.
A composite sheet wherein the moisture-permeable film is stretchable, and the non-jointed portion of the nonwoven fabric with the moisture-permeable film expands and contracts as the moisture-permeable film expands and contracts.
<2>
The composite sheet according to <1>, wherein, in the natural state of the moisture-permeable film, it has a protrusion that protrudes on the side opposite to the moisture-permeable film, and part or all of the protrusion is the non-jointed portion of the nonwoven fabric.
<3>
The composite sheet according to <2>, wherein, in the natural state of the moisture-permeable film, a plurality of pleated protrusions extend in a direction intersecting the expansion and contraction direction of the moisture-permeable film, and between adjacent protrusions, recesses having the joint at the bottom extend in the same direction as the protrusions.
<4>
The composite sheet according to <2> or <3>, wherein the protrusion is formed by the non-joint portion of the nonwoven fabric protruding in a direction away from the moisture-permeable film, and has a hollow portion consisting of the gap between the non-joint portion and the moisture-permeable film.
<5>
The composite sheet according to <2> or <3>, wherein the protrusion has a solid structure in which the constituent fibers of the nonwoven fabric are filled inside the protrusion.
<6>
The nonwoven fabric is a composite sheet according to any one of the above items <1> to <5>, comprising an olefin resin.
<7>
The composite sheet according to any one of the above <1> to <6>, wherein the moisture-permeable film and the nonwoven fabric are joined together by an adhesive at the joint.
<8>
The composite sheet according to <7> above, comprising the adhesive, synthetic rubber.
<9>
The moisture-permeable film is a composite sheet according to any one of the above <1> to <8>, wherein, in addition to the micropores, it has pores with a larger opening diameter than the micropores.
<10>
The composite sheet according to <9>, wherein the diameter of the opening of the pores is preferably 0.5 mm or more, more preferably 0.6 mm or more, and preferably 10 mm or less, and more preferably 8 mm or less.
<11>
The composite sheet according to any one of the above <1> to <10>, wherein the opening diameter of the micropores is preferably 0.001 μm or more, more preferably 0.005 μm or more, and preferably 500 μm or less, and more preferably 300 μm or less.

<12>
The breathable film is a composite sheet as described in any one of items <1> to <11> above, which is evaluated as having leak-proof properties in a natural state in the leak-proof evaluation test.
<13>
The composite sheet according to any one of items <1> to <12>, wherein the degree of flexible deformation of the moisture-permeable film in the expansion and contraction direction (mechanical direction) is preferably 0.060 N/mm or less, more preferably 0.057 N/(mm·(g/ ^m² )) or less, even more preferably 0.055 N/mm or less, and preferably 0.005 N/mm or more.
<14>
The composite sheet according to any one of the above <1> to <13>, wherein the residual strain after 30% elongation of the moisture-permeable film is preferably 11% or less, more preferably 10% or less, even more preferably 9% or less, and preferably 0%.
<15>
The composite sheet according to any one of items <1> to <14>, wherein the air permeability of the moisture-permeable film in its natural state, as measured by the method described above, is 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 pass through the moisture-permeable film in the thickness direction.
<16>
The composite sheet according to any one of the above <1> to <15>, wherein the basis weight of the moisture-permeable film is preferably 5 g/ ^m² or more, more preferably 6 g/ ^m² or more, and preferably 100 g/ ^m² or less, and more preferably 90 g/ ^m² or less.
<17>
The composite sheet according to any one of the above <1> to <16>, wherein the basis weight of the nonwoven fabric is preferably 5 g/ ^m² or more, more preferably 6 g/ ^m² or ^more , and preferably 100 g/ ^m² or less, and more preferably 90 g/m² or less.

<18>
The aforementioned moisture-permeable film contains a resin and an inorganic filler,
The composite sheet according to any one of the above <1> to <17>, 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.
<19>
The composite sheet according to <18>, wherein the resin comprises an olefin-based resin composition having a density of 0.840 g/ ^cm³ or more and less than 0.900 g/ ^cm³ .
<20>
The composite sheet according to <19>, wherein the density of the olefin resin composition is preferably 0.850 g/ ^cm³ or more and 0.895 g/ ^cm³ or less, more preferably 0.860 g/ ^cm³ or more and 0.885 g/ ^cm³ or less.
<21>
The composite sheet according to <19> or <20>, wherein the olefin resin composition 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.
<22>
The composite sheet according to any one of the above <18> to <21>, wherein the moisture-permeable film contains 0.1 parts by mass or more and 20 parts by mass of a pore-opening accelerator per 100 parts by mass of resin in the moisture-permeable film, and the pore-opening accelerator is a metal soap.

<23>
The composite sheet according to any one of the above <18> to <22>, wherein the moisture-permeable film contains triglycerides in an amount of 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of resin in the moisture-permeable film, and the triglycerides include a group derived from a fatty acid having 16 to 22 carbon atoms, and the group is a hydrocarbon group without unsaturated bonds or substituents.
<24>
The composite sheet according to <23>, wherein the triglyceride is a mixture of a triglyceride containing at least one group derived from a fatty acid having 18 carbon atoms and a triglyceride containing at least one group derived from a fatty acid having 16 to 22 carbon atoms (excluding the fatty acid having 18 carbon atoms).
<25>
The composite sheet according to <23>, wherein the triglyceride is a triglyceride that contains at least one group derived from a saturated fatty acid having 18 carbon atoms in one molecule, and at least one group derived from a saturated fatty acid having 16 to 22 carbon atoms (excluding fatty acids having 18 carbon atoms).
<26>
The composite sheet according to any one of the above <23> to <25>, wherein, with respect to the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film, preferably 28% to 96% by mass, more preferably 28% to 70% by mass, and even more preferably 29% to 67% by mass are groups derived from fatty acids having 18 carbon atoms (the group is a hydrocarbon group without unsaturated bonds and substituents).
<27>
A composite sheet according to any one of the above <23> to <26>, wherein, with respect to the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film, 28% by mass or more and 68% by mass or less are groups derived from fatty acids having 18 carbon atoms, and 26% by mass or more and 70% by mass or less are groups derived from fatty acids having 16 carbon atoms.
<28>
The composite sheet according to any one of the above <23> to <26>, wherein, with respect to the total amount of fatty acid-derived groups contained in all triglycerides in the moisture-permeable film, 28% by mass to 47% by mass are groups derived from fatty acids having 18 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents), and 40% by mass to 60% by mass are groups derived from fatty acids having 22 carbon atoms (these groups are hydrocarbon groups without unsaturated bonds and substituents).
<29>
The composite sheet according to any one of the above <23> to <28>, wherein the fatty acid-derived groups contained in all the triglycerides in the moisture-permeable film are hydrocarbon groups that do not have unsaturated bonds.
<30>
The composite sheet according to any one of the above <23> to <29>, wherein the fatty acid-derived groups contained in all the triglycerides in the moisture-permeable film are unsubstituted hydrocarbon groups.
<31>
An absorbent article comprising a composite sheet as described in any one of items <1> to <30> above.
<32>
The absorbent article has a longitudinal direction extending from the wearer's abdominal side through the groin area to the dorsal side, and a transverse direction perpendicular to the longitudinal direction.
The composite sheet is an absorbent article as described in <31>, having elasticity in the longitudinal or transverse direction.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

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

The details of the raw materials used in the manufacture of moisture-permeable films A through E are as follows.
• Olefin resin A (corresponding to the low-melting-point olefin resin): Ethylene-α-olefin copolymer produced with a metallocene catalyst, melting point 44°C, resin density 0.864 g/ ^cm³
• Olefin resin B (corresponding to the high-melting-point olefin resin mentioned above): Linear low-density polyethylene produced with a metallocene catalyst, melting point 116°C, resin density 0.924 g/ ^cm³
Inorganic filler: Calcium carbonate, average particle size D50: 1.8 μm
• Dispersant: Stearic acid • Specific triglycerides: Palm oil (C14: 1%, C16: 42%, C18: 57%)
• Pore opening accelerator (metal soap): Zinc stearate, precipitation 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 Industries Co., Ltd., Silklon ES85), which has no micropores and is stretchable, were also measured. The results are shown in Table 1.
The degree of air permeability was measured using the air permeability measurement method described above. The evaluated material (moisture-permeable film) was in two states during measurement: its natural state and a state of being stretched 1.3 times in one direction (machine direction) (30% stretched state). Note that the air permeability of moisture-permeable film F could not be measured because its air permeability was too low. Furthermore, since moisture-permeable film E does not have elasticity, its air permeability was not evaluated in the stretched state.
Leak resistance was evaluated by the aforementioned leak resistance evaluation test. However, the moisture-permeable film to be evaluated was in its natural state or in a 30% stretched state. In addition to a test solution with a surface tension of 44 mN/m at 25°C, a test solution with a surface tension of 35 mN/m at 25°C was used as a test solution under more severe conditions. The wettability test mixture manufactured by Kanto Chemical Co., Ltd. was used for these test solutions. In the "Leak Resistance" column of Table 1, "A" means leak-proof and "B" means leak-proof. Note that since moisture-permeable film E does not have elasticity, the evaluation of its leak resistance in the stretched state was not performed.

[Examples 1-2, Comparative Example 1: Manufacturing of Composite Sheets]
Using a moisture-permeable film C or F and a non-stretchable nonwoven fabric, a composite sheet was manufactured by the aforementioned manufacturing method A or B, that is, "a composite sheet in which, in the natural state of the film, the non-joint portions of the nonwoven fabric with the film form a plurality of pleated protrusions, some or all of which protrude in one direction on the opposite side from the film, and between adjacent protrusions, recesses with the joint portion between the film and the nonwoven fabric at the bottom extend in the same direction as the protrusions."
In the manufacturing method of the composite sheet according to manufacturing method A, the moisture-permeable film was stretched to 60% in the direction of the machine, and the one side of a non-stretchable nonwoven fabric, on which 10 g/ ^m² of adhesive had been intermittently applied in a summit-like manner to one side of the stretched moisture-permeable film, was superimposed on the stretched moisture-permeable film and the two were joined together, and then the moisture-permeable film was released from the stretched state to produce the target composite sheet.
In the manufacturing method of the composite sheet according to manufacturing method B, a composite sheet precursor was obtained by overlapping a moisture-permeable film in an unstretched state with one side of a non-stretchable nonwoven fabric on which an adhesive of 4 g/ ^m² was intermittently applied in a summit-like manner. The target composite sheet was then manufactured by subjecting the composite sheet precursor to tooth groove stretching using a pair of toothed rolls with a pressing depth of 3.7 mm and a conveying speed of 10 m/min after tooth grooves.
In manufacturing method A, a spunbond nonwoven fabric with a basis weight of 17 g/ ^m² , whose constituent fibers are made of olefin resin, was used as the non-stretchable nonwoven fabric. In manufacturing method B, an air-through nonwoven fabric with a basis weight of 29 g/ ^m² , whose constituent fibers are made of olefin resin, was used as the non-stretchable nonwoven fabric. A hot-melt adhesive containing synthetic rubber was used as the adhesive.

[Performance evaluation of composite sheets]
The breathability, moisture permeability, leak resistance, and elasticity of the composite sheets of each example and comparative example were evaluated using the method described below. The results are shown in Table 2 below.

(Method for evaluating the breathability of composite sheets)
The air permeability of the composite sheet (the time required for 25 cc of air to pass through the composite sheet in the thickness direction) was measured according to the air permeability measurement method described above. However, the composite sheet was in a state of being stretched 1.3 times in one direction that is expandable and contractible (30% stretched state) during the measurement. An air permeability of 3000 seconds or less was designated as A (highest rating for air permeability), and all other cases were designated as B.

(Method for evaluating the breathability of composite sheets)
The moisture permeability of the composite sheet was measured in accordance with the moisture permeability measurement method described above. Specifically, the composite sheet was used as the test specimen in the moisture permeability measurement method described above. A value of 0.4 g/(100 ^cm² ·h) or higher was designated as A (highest evaluation of moisture permeability), and all other cases were designated as B.

(Method for evaluating the leak-proof properties of composite sheets)
The leak-proof properties of the composite sheet were evaluated in accordance with the aforementioned leak-proof evaluation test. Specifically, in the aforementioned leak-proof evaluation test, the composite sheet was used as the object to be evaluated, and the test was conducted with the composite sheet stretched to 1.3 times its original length (30% stretch) in one direction (machine direction) where it is expandable and contractible. Three tests were performed for each type of object to be evaluated, and if no leakage of the test liquid was observed onto the filter paper in any of the three tests, it was classified as A (highest rating for leak-proof properties), and all other cases were classified as B.

(Method for evaluating the elasticity of composite sheets)
The residual strain after 30% elongation of the composite sheet was measured in accordance with the cycle test described above in the tensile test. That is, the composite sheet was used as the object to be evaluated in the cycle test described above. For each type of object to be evaluated, the residual strain after 30% elongation was measured in two directions: the "machine direction" (the flow direction during the manufacturing of the object to be evaluated) and the "direction perpendicular to the machine direction". If the residual strain after 30% elongation in either of these two directions was 11% or less, it was classified as A (highest evaluation of elasticity), and otherwise as B.

As shown in Table 2, the composite sheets of each embodiment exhibited superior breathability compared to Comparative Example 1, where the moisture-permeable film F was non-porous and completely impermeable, because the moisture-permeable film C constituting the composite sheet had micropores. Furthermore, the composite sheets of each embodiment and comparative example, like composite sheet 1 shown in Figure 1, had regularly arranged convex and concave portions (non-jointed portions of the nonwoven fabric) on the nonwoven fabric side, resulting in a good texture and appearance.

1, 1A, 1B Composite sheet 2 Breathable film 3 Nonwoven fabric 31 Non-jointed part of nonwoven fabric 4 Joint part 5 Convex part 6 Concave part 7 Hollow part 10 Disposable diaper (absorbent item)
11 Absorbent body 20 Outer body 21 Outer layer sheet 21A Ventral outer layer sheet 21B Crotch outer layer sheet 21C Back outer layer sheet 22 Inner layer sheet

Claims (16)

A stretchable, moisture-permeable film with micropores and a non-stretchable nonwoven fabric are overlapped and joined to each other at multiple joints scattered between the overlapping surfaces.
The aforementioned micropores have an opening diameter of 0.001 μm or more and 500 μm or less.
The moisture-permeable film contains a resin and a triglyceride,
The triglyceride contains a group derived from a fatty acid having 16 to 22 carbon atoms, and the group is a hydrocarbon group without unsaturated bonds and substituents.
The triglyceride content in the moisture-permeable film is 2.84 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin in the moisture-permeable film.
The nonwoven fabric does not have elasticity in the flow direction during manufacturing, its degree of flexible deformation in the flow direction is greater than 0.060 N/(mm(g/ ^m² )), and its residual strain after 30% elongation in the flow direction is greater than 11%.
A composite sheet wherein the moisture-permeable film is stretchable, and the non-jointed portion of the nonwoven fabric with the moisture-permeable film expands and contracts as the moisture-permeable film expands and contracts. The composite sheet according to claim 1, wherein, in the natural state of the moisture-permeable film, it has a protrusion projecting on the side opposite to the moisture-permeable film, and part or all of the protrusion is the non-jointed portion of the nonwoven fabric. The composite sheet according to claim 2, wherein, in the natural state of the moisture-permeable film, a plurality of pleated protrusions extend in a direction intersecting the expansion and contraction direction of the moisture-permeable film, and between adjacent protrusions, recesses having the joint portion at their bottom extend in the same direction as the protrusions. The composite sheet according to claim 2, wherein the protrusion is formed by the non-jointed portion of the nonwoven fabric protruding in a direction away from the moisture-permeable film, and has a hollow portion formed by the gap between the non-jointed portion and the moisture-permeable film. The composite sheet according to claim 2, wherein the protrusion has a solid structure in which the constituent fibers of the nonwoven fabric are filled inside the protrusion. The composite sheet according to claim 1, wherein the nonwoven fabric contains an olefin resin. The composite sheet according to claim 1, wherein the moisture-permeable film and the nonwoven fabric are joined together by an adhesive at the joint. The composite sheet according to claim 7, wherein the adhesive includes synthetic rubber. The composite sheet according to claim 1, wherein the moisture-permeable film has pores with a larger opening diameter than the micropores, in addition to the micropores. The composite sheet according to claim 1, wherein the moisture-permeable film has a degree of flexible deformation in the flow direction during manufacturing of the moisture-permeable film of 0.020 N/(mm(g/ ^m² )) or more and 0.060 N/(mm(g/ ^m² )) or less, and the residual strain after 30% elongation in the flow direction is 11% or less. The aforementioned moisture-permeable film contains 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 11, wherein the resin comprises an olefin-based resin composition having a density of 0.840 g/ ^cm³ or more and less than 0.900 g/ ^cm³ . The composite sheet according to claim 12, wherein the olefin resin composition 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 according to claim 11, wherein the moisture-permeable film contains a pore-opening accelerator in an amount of 0.1 to 20 parts by mass per 100 parts by mass of the resin in the moisture-permeable film, and the pore-opening accelerator is a metal soap. An absorbent article comprising a composite sheet as described in any one of claims 1 to 14. The absorbent article has a longitudinal direction extending from the wearer's abdominal side through the groin area to the dorsal side, and a transverse direction perpendicular to the longitudinal direction.
The absorbent article according to claim 15, wherein the composite sheet is stretchable in the longitudinal or transverse direction.