Composite sheet for absorbent article

Abstract

Provided is a composite sheet for an absorbent article that is excellent in durability while maintaining the good properties of skin touch. A composite sheet (10A) for an absorbent article having a first direction (W), a second direction (L), and a thickness direction (T) orthogonal to each other, wherein the composite sheet has, in the thickness direction (T), in order, a first nonwoven fabric (11) and a second nonwoven fabric (14), and further has a plurality of joint portions (18) that thermally join the first nonwoven fabric (11) and the second nonwoven fabric (14) to each other, the first nonwoven fabric (11) has a first fiber layer (12) and a second fiber layer (13) disposed between the first fiber layer (12) and the second nonwoven fabric (14), the first fiber layer (12) contains composite fibers, the composite fibers include, in a cross section, a polypropylene-based resin portion (20) containing a polypropylene-based resin and a polyethylene-based resin portion (22) containing a polyethylene-based resin, the second fiber layer (13) contains single fibers composed of a polypropylene-based resin, and the second nonwoven fabric (14) contains a polypropylene-based resin on a surface on a side that contacts the second fiber layer (13).

Description

Technical Field

[0001] This invention relates to a composite sheet for absorbent articles. Background Technology

[0002] Studies have been conducted on improving the skin feel of composite sheets used in absorbent articles. For example, Patent Document 1 discloses an absorbent article comprising: a main body having a liquid-permeable surface sheet, a liquid-impermeable back side sheet, and an absorbent body existing between the surface sheet and the back side sheet; and an outer sheet covering the back side of the main body. The outer sheet is formed by laminating one or more sheets of nonwoven fabric, and the torsional strength of the outermost nonwoven fabric is 3.8 gf·cm / cm or less. It is disclosed that the outermost nonwoven fabric is composed of a single fiber of polypropylene and a core-sheath type composite fiber of polypropylene and polyethylene.

[0003] Furthermore, Patent Document 2 discloses an absorbent article having longitudinal and transverse directions, comprising an absorbent body with an absorbent core, and a pair of waist sections. Each waist section includes a skin-side sheet positioned closest to the skin. In at least one of the pair of waist sections, the flexural stiffness of the skin-side sheet, based on the KES method, is 0.0096 N·m. 2 / (m×10 -4 Below. An inner layer sheet is disposed at a position closer to the non-skin side than the skin side sheet. The bending stiffness of the inner layer sheet based on the KES method is higher than that of the skin side sheet. The inner layer sheet is disposed at the waist-side end edge of the absorbent body on the skin side, across the longitudinal direction of the absorbent body. The aforementioned skin side sheet is disclosed to mainly comprise polyethylene.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-131167

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-187744 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the case where the outermost nonwoven fabric of Patent Document 1 is composed of a single fiber of polypropylene, since polypropylene is relatively stiff, it is foreseeable that the overall outer sheet composed of this outermost nonwoven fabric and other nonwoven fabrics will have limitations in terms of improving the feel against the skin. In the case where the outermost nonwoven fabric of Patent Document 1 is composed of a core-sheath type composite fiber including a core formed of polypropylene and a sheath formed of polyethylene, regarding the outer sheet formed by bonding this outermost nonwoven fabric with other nonwoven fabrics made of polypropylene, the large difference in melting points between polyethylene and polypropylene leads to a lack of compatibility. Therefore, the bonding strength between the outermost nonwoven fabric composed of composite fibers and other nonwoven fabrics is insufficient, and under repeated use, the outermost nonwoven fabric and other nonwoven fabrics will peel off from each other.

[0010] The polyethylene mainly contained in the skin side sheet of Patent Document 2 is relatively soft, so it is difficult to have the strength suitable for composite sheets used in absorbent products, and there are concerns that it is difficult to reuse.

[0011] The purpose of this invention is to provide a composite sheet for absorbent articles that maintains a pleasant feel against the skin while exhibiting excellent durability.

[0012] Solution for solving the problem

[0013] This invention relates to a composite sheet for use in absorbent articles having mutually orthogonal first, second, and thickness directions. The composite sheet comprises a first nonwoven fabric and a second nonwoven fabric sequentially in the thickness direction, and also includes multiple joints for thermally bonding the first and second nonwoven fabrics together. The first nonwoven fabric has a first fiber layer and a second fiber layer disposed between the first fiber layer and the second nonwoven fabric. The first fiber layer comprises composite fibers, which in cross-section include a polypropylene resin portion containing polypropylene resin and a polyethylene resin portion containing polyethylene resin. The second fiber layer comprises a single fiber composed of polypropylene resin, and the surface of the second nonwoven fabric in contact with the second fiber layer contains polypropylene resin.

[0014] The effects of the invention

[0015] The composite sheet for absorbent articles of the present invention maintains a pleasant feel against the skin while exhibiting excellent durability. Attached Figure Description

[0016] Figure 1 This is a top view of the composite sheet of the embodiment.

[0017] Figure 2A This is a cross-sectional view schematically showing the situation when the composite sheet of the embodiment is elongated.

[0018] Figure 2B This is a cross-sectional view schematically showing the situation when the composite sheet of the embodiment is contracted.

[0019] Figure 3A This is a cross-sectional view of the fibers of the first and second nonwoven fabrics in the embodiment.

[0020] Figure 3B This is a cross-sectional view of the fibers of the first and second nonwoven fabrics in a modified embodiment.

[0021] Figure 4 This is a perspective view of an absorbent article made of a composite sheet according to an embodiment of its use.

[0022] Figure 5 This is a top view of the composite sheet of variant example (1).

[0023] Figure 6 It is a cross-sectional view schematically showing the situation when the composite sheet of modified example (2) is elongated. Detailed Implementation

[0024] The embodiments of the present invention relate to the following methods.

[0025] [Method 1]

[0026] A composite sheet is a composite sheet for use in absorbent articles having mutually orthogonal first, second, and thickness directions, wherein,

[0027] The composite sheet comprises a first nonwoven fabric and a second nonwoven fabric in sequence in the thickness direction.

[0028] It also includes multiple joints for thermally bonding the first nonwoven fabric and the second nonwoven fabric together.

[0029] The first nonwoven fabric has a first fiber layer and a second fiber layer disposed between the first fiber layer and the second nonwoven fabric.

[0030] The first fiber layer comprises composite fibers, which in cross-section include a polypropylene resin portion containing polypropylene resin and a polyethylene resin portion containing polyethylene resin.

[0031] The second fiber layer comprises a single fiber made of polypropylene resin.

[0032] The second nonwoven fabric contains polypropylene resin on the side of its surface that contacts the second fiber layer.

[0033] Because the composite sheet includes a second fiber layer containing a single fiber made of polypropylene resin, it has the strength suitable for a composite sheet for the waist area of ​​absorbent products.

[0034] The first fiber layer contains composite fibers, which include a polypropylene resin portion containing polypropylene resin and a polyethylene resin portion containing polyethylene resin, thus possessing the softness derived from polyethylene resin. Because the first fiber layer is disposed on the surface of the composite sheet, the composite sheet has an excellent skin-touch feel.

[0035] The first fiber layer, the second fiber layer, and the second nonwoven fabric are integrated through thermal bonding. Since the first and second fiber layers contain the same type of polypropylene resin, they exhibit excellent compatibility and bond well. The second nonwoven fabric, because its surface in contact with the second fiber layer contains the same type of resin (polypropylene resin) as the individual fibers contained in the second fiber layer, is easily thermally bonded to the second fiber layer. Due to the excellent thermal bonding between the second fiber layer and the second nonwoven fabric, the composite sheet exhibits excellent bond strength between the first and second nonwoven fabrics, suppressing peeling during repeated use and demonstrating excellent durability.

[0036] Therefore, the composite sheet maintains a pleasant feel on the skin while exhibiting excellent durability.

[0037] [Method 2]

[0038] For the composite sheet described in Method 1, the second nonwoven fabric is an elastic nonwoven fabric capable of stretching along the first direction.

[0039] Since the composite sheet stretches and contracts along the first direction, by arranging the first direction parallel to the wearer's waistline, the composite sheet can be applied, for example, to a composite sheet for the waist section of an absorbent article.

[0040] The first nonwoven fabric, due to its inclusion of a soft first fiber layer, easily shrinks to match the shrinkage of the elastic nonwoven fabric (the second nonwoven fabric).

[0041] The elastic nonwoven fabric has excellent thermal bonding with the second fiber layer because its surface in contact with the second fiber layer contains the same type of resin, namely polypropylene resin, as the single fibers contained in the second fiber layer. Therefore, in the composite sheet, the bonding strength between the first nonwoven fabric and the elastic nonwoven fabric (second nonwoven fabric) is excellent.

[0042] Therefore, the composite sheet has excellent shrinkage and durability.

[0043] [Method 3]

[0044] For the composite sheet described in Method 2, the composite sheet has a third nonwoven fabric on the opposite side of the side of the second nonwoven fabric that contacts the first nonwoven fabric.

[0045] In the composite sheet, a third nonwoven fabric, matching the intended use, is provided on the opposite side of the second nonwoven fabric that contacts the first nonwoven fabric. This further expands the range of options for placing the first nonwoven fabric on the skin-side or the non-skin-side. Furthermore, by adding the third nonwoven fabric, the mechanical strength of the composite sheet is increased, resulting in superior durability. Therefore, the composite sheet is more suitable for use as a waistband-type absorbent material.

[0046] [Method 4]

[0047] For the composite sheet described in Method 1, the composite sheet includes elastic filaments that stretch along a first direction between the first nonwoven fabric and the second nonwoven fabric.

[0048] Since the composite sheet stretches and contracts along the first direction, by configuring the first direction parallel to the wearer's waist, the composite sheet can be applied, for example, to a composite sheet for the waist portion of an absorbent article.

[0049] The first nonwoven fabric, due to its inclusion of a soft first fiber layer, easily shrinks to match the shrinkage of the elastic yarn.

[0050] In the composite sheet, a second nonwoven fabric is disposed on the side opposite to the first nonwoven fabric, sandwiching elastic yarns, and this second nonwoven fabric is well thermally bonded to the second fiber layer. That is, the second fiber layer and the second nonwoven fabric are well thermally bonded with elastic yarns sandwiched between them. Therefore, in the composite sheet, the bonding strength between the first nonwoven fabric and the second nonwoven fabric is excellent.

[0051] Therefore, the composite sheet has excellent shrinkage and durability.

[0052] [Method 5]

[0053] For the composite sheet described in any of methods 1 to 4, wherein,

[0054] The polypropylene resin comprises a propylene-α-olefin random copolymer.

[0055] The polyethylene resins include ethylene polymers.

[0056] Compared to the difference in melting points between polypropylene and polyethylene resins, the difference in melting points between propylene-α-olefin random copolymers and polyethylene resins is smaller. Therefore, propylene-α-olefin random copolymers are easier to thermally bond with polyethylene resins than polypropylene. Consequently, the fibers of the first fiber layer are thermally bonded to each other over a larger area at the joint. Therefore, for the composite sheet, by thermally bonding the fibers of the first fiber layer disposed on the surface to each other over a larger area, less fuzzing is generated, thus enabling longer service life.

[0057] [Method 6]

[0058] For the composite sheet described in method 5, wherein,

[0059] The melting point of the propylene-α-olefin random copolymer is below 155°C, and the melting point of the ethylene polymer is above 95°C and below 125°C.

[0060] By placing the melting points of the propylene-α-olefin random copolymer and the ethylene polymer within the aforementioned ranges, the fibers of the first fiber layer can be thermally bonded to each other more reliably over a wider range.

[0061] [Method 7]

[0062] For the composite sheet described in any of the methods 1 to 6, the ratio of the polypropylene resin portion to the polyethylene resin portion is 70:30 to 10:90 (polypropylene resin portion: polyethylene resin portion) on a mass basis.

[0063] The first fiber layer comprises composite fibers, which include a predetermined amount or more of polyethylene resin, i.e., polyethylene resin, thereby facilitating the deposition of polyethylene resin onto the surface of the first fiber layer. Because the first fiber layer is disposed on the surface side of the composite sheet, the composite sheet provides an excellent skin-touch feel.

[0064] [Method 8]

[0065] For the composite sheet described in any of the methods 1 to 7, wherein the polyethylene resin portion is present on the fiber surface of the composite fiber.

[0066] The composite fiber has a polyethylene resin portion on its fiber surface. For example, the composite fiber is an off-core core-sheath type or a side-by-side type, in which a polypropylene resin portion is used as the core and a polyethylene resin portion is used as the sheath, with the polypropylene resin portion partially exposed from the polyethylene resin portion. Because of the polyethylene resin portion on the fiber surface of the composite fiber, the composite fiber possesses a softness derived from polyethylene resin. For composite sheets, since the first fiber layer is disposed on the surface side of the composite sheet, it has an excellent skin feel.

[0067] [Method 9]

[0068] For the composite sheet described in any of the methods 1 to 8, the ratio of the first fiber layer to the second fiber layer is 33:67 to 67:33 (first fiber layer: second fiber layer) based on a mass standard.

[0069] The first nonwoven fabric includes a second fiber layer made of polypropylene resin in a predetermined amount or more. Because the second fiber layer is positioned in contact with the second nonwoven fabric, it is more reliably thermally bonded to the second nonwoven fabric. Therefore, in the composite sheet, the bonding strength between the first and second nonwoven fabrics is excellent.

[0070] [Method 10]

[0071] For the composite sheet described in any of the methods 1 to 9, wherein the polypropylene resin of the first fiber layer and the polypropylene resin of the second fiber layer are the same propylene-α-olefin random copolymer.

[0072] Compared to the difference in melting points between polypropylene and polyethylene resins, the difference in melting points between propylene-α-olefin random copolymers and polyethylene resins is smaller. Therefore, propylene-α-olefin random copolymers are easier to thermally bond with polyethylene resins than polypropylene. Consequently, the fibers of the first fiber layer are thermally bonded to each other over a larger area at the joint. Therefore, for the composite sheet, by thermally bonding the fibers of the first fiber layer disposed on the surface to each other over a larger area, less fuzzing is generated, thus enabling longer service life.

[0073] Since the polypropylene resins of the first and second fiber layers are the same propylene-α-olefin random copolymer, they exhibit excellent compatibility, and the first and second fiber layers are easily thermally bonded over a wider range. Consequently, the bonding strength between the first and second fiber layers in the composite sheet is excellent.

[0074] [Method 11]

[0075] For the composite sheet described in any of methods 1 to 10, wherein,

[0076] The composite sheet has multiple embossed joints on the surface of the first fiber layer, which join the first fiber layer and the second fiber layer without joining the second nonwoven fabric.

[0077] The total area of ​​the plurality of joints on the surface of the first fiber layer is smaller than the total area of ​​the plurality of embossed joints on the surface of the first fiber layer.

[0078] In the first nonwoven fabric, the total area of ​​the multiple joints is smaller than the total area of ​​the multiple embossed joints, thus allowing for easy separation from the second nonwoven fabric between the joints and deformation along the thickness direction. Because the first nonwoven fabric easily deforms along the thickness direction between the joints, the second nonwoven fabric, when the composite sheet has elastic components (elastic nonwoven fabric or elastic yarn), is not hindered by the first nonwoven fabric and easily shrinks. Therefore, the composite sheet easily deforms along the wearer's waistline, resulting in excellent skin feel.

[0079] <Overall Structure>

[0080] Embodiments of the present invention will now be described with reference to the accompanying drawings. Furthermore, the drawings schematically illustrate one example of an embodiment, and the present invention is not limited to the illustrated manner. Figure 1 This is a top view of the composite sheet of the embodiment.

[0081] Figure 2A This is a cross-sectional view schematically showing the situation when the composite sheet of the embodiment is elongated. Figure 2B This is a cross-sectional view schematically showing the situation when the composite sheet of the embodiment is contracted. Figure 3A This is a cross-sectional view of the fibers of the first and second nonwoven fabrics in the embodiment. Figure 1 The composite sheet 10A shown has mutually orthogonal first direction W, second direction L and thickness direction T (in Figure 1 (Not shown in the image). Figure 2A and Figure 2B As shown, the composite sheet 10A has a first nonwoven fabric 11 and a second nonwoven fabric 14 sequentially in the thickness direction T. When the composite sheet 10A is used as a composite sheet for the waist of an absorbent article, the configuration is as follows: the first nonwoven fabric 11 is disposed on the skin side, the second nonwoven fabric 14 is disposed on the non-skin side, and the first direction W is approximately parallel to the wearer's waist.

[0082] like Figure 1 As shown, the composite sheet 10A also includes a plurality of joints 18 for thermally bonding the first nonwoven fabric 11 and the second nonwoven fabric 14 together. The thermal bonding is performed by heating with heat or ultrasound until the melting point of the thermoplastic resin is exceeded to melt the first nonwoven fabric 11 and the second nonwoven fabric 14, thereby bonding the first nonwoven fabric 11 and the second nonwoven fabric 14 together.

[0083] The morphology of the plurality of joints 18 is such that, when viewed in cross-section, they are recessed along the thickness direction T, but when viewed from above, their shape is not particularly limited; for example, they can be linear or dot-shaped. At least one of the surface sides of the composite sheet 10A of the plurality of joints 18 is recessed along the thickness direction. Figure 1The plurality of joints 18 shown are point-like in top view. The shape, size, and distance between the joints 18 are not particularly limited and can be appropriately selected based on the size and thickness of the composite sheet 10A. For example, the shape of each joint 18 viewed from the thickness direction T can be a circle, a triangle, or a rectangle, etc. Regarding the size of the joint 18, for example, in the case of a circle, the diameter can be 0.1 mm or more and 5.0 mm or less; in the case of a rectangle, the length of one side can be 0.1 mm or more and 5.0 mm or less. The distance between the joints 18 can be 1 mm or more and 5 mm or less. Adjacent joints 18 in the first direction W can be offset along the second direction L. The distance between adjacent joints 18 in the first direction W and in the second direction L is preferably 2.0 mm or more, more preferably 3.7 mm or more. Figure 1 As shown, the joint 18 can also be arranged alternately along the first direction W and the second direction L, respectively.

[0084] The composite sheet 10A may also include a third nonwoven fabric 16. The third nonwoven fabric 16 is located on the opposite side of the side of the second nonwoven fabric 14 that contacts the first nonwoven fabric 11. The third nonwoven fabric 16 may also be integrally and thermally bonded to the first nonwoven fabric 11 and the second nonwoven fabric 14 at the aforementioned joint 18.

[0085] The thickness and weight per unit area of ​​the composite sheet 10A are not particularly limited as long as they do not impair the effect of the present invention, and any thickness and weight per unit area corresponding to the desired application can be adopted. The thickness of the composite sheet 10A when not elongated is preferably 1.0 mm or more and 3.5 mm or less, more preferably 1.0 mm or more and 3.0 mm or less. The weight per unit area of ​​the composite sheet 10A is preferably, for example, 60 g / m². 2 ) or above and 150 (g / m 2 ) or less, more preferably 70 (g / m 2 ) or above and 140 (g / m 2 )the following.

[0086] The bending stiffness in the second direction L of the composite sheet 10A, based on the KES method, in the CD direction is preferably 0.02 (N·m). 2 / (m×10 -4 )) or above and 0.38 (N·m 2 / (m×10 -4 )) or less, preferably 0.02 (N·m 2 / (m×10 -4 )) or more and 0.32 (N·m 2 / (m×10 -4 )) or less, more preferably 0.02 (N·m 2 / (m×10 -4 )) or more and 0.20 (N·m 2 / (m×10 -4 The bending stiffness in the second direction L, based on the KES method, is set to 0.38 (N·m). 2 / (m×10 -4 The following results in composite sheet 10A being soft and having an excellent feel against the skin.

[0087] Regarding the breaking strength in the CD direction of the composite sheet 10A, there are no particular limitations as long as it can be used as a composite sheet for absorbent articles. For example, it can be set to preferably be 14 (N / 50 mm) or more and 75 (N / 50 mm) or less, more preferably 17 (N / 50 mm) or more and 75 (N / 50 mm) or less, and even more preferably 20 (N / 50 mm) or more and 75 (N / 50 mm) or less. The breaking strength is the value obtained by dividing the maximum tensile load required to cause the specimen to break by the width of the specimen.

[0088] The peel strength between the first nonwoven fabric and the second nonwoven fabric of the composite sheet 10A is preferably 1.0 (N / 25mm) or more, more preferably 1.4 (N / 25mm) or more, and even more preferably 1.5 (N / 25mm) or more.

[0089] (First nonwoven fabric)

[0090] The first nonwoven fabric 11 forms the surface on the skin side of the wearer when wearing the absorbent article using the composite sheet 10A. The first nonwoven fabric 11 has: a first fiber layer 12 having a skin-side surface; and a second fiber layer 13 disposed between the first fiber layer 12 and the second nonwoven fabric 14.

[0091] The first fiber layer 12 and the second fiber layer 13 can be formed using spunbonding, carding, meltblowing, air-laid web forming, etc., and joined together using embossing. In addition to the aforementioned plurality of joining portions 18, the first nonwoven fabric 11 also has a plurality of embossed joining portions (not shown) formed by embossing and recessed along the thickness direction T. At least one of the surfaces of the first nonwoven fabric 11 is recessed along the thickness direction. Preferably, the surface of the first nonwoven fabric 11 on the side of the first fiber layer 12 is recessed along the thickness direction. Preferably, the total area of ​​the plurality of joining portions 18 when viewed from above on the surface of the first nonwoven fabric 11 is smaller than the total area of ​​the embossed joining portions when viewed from above on the surface of the first nonwoven fabric 11. The embossed joining portions join the first fiber layer 12 and the second fiber layer 13, but do not join the second nonwoven fabric 14. That is, the embossed joining portions do not join the first nonwoven fabric 11 and the second nonwoven fabric 14. In the case where the embossed joint is recessed along the thickness direction on the surface of the first fiber layer 12, it is preferable that, in the first nonwoven fabric 11, the total area of ​​the plurality of joints 18 on the surface of the first fiber layer 12 when viewed from above is smaller than the total area of ​​the embossed joint when viewed from above.

[0092] Preferably, when the total mass of the first fiber layer 12 and the second fiber layer 13 is set to 100, the ratio of the first fiber layer 12 to the second fiber layer 13 is 33:67 to 67:33 (first fiber layer: second fiber layer) based on a mass standard. By keeping the ratio of the first fiber layer 12 to the second fiber layer 13 within the above range, there is a tendency to achieve an excellent balance between strength and softness.

[0093] (First fiber layer)

[0094] The first fiber layer 12 comprises composite fibers. In cross-section, the composite fibers include a polypropylene resin portion containing polypropylene resin (hereinafter referred to as the "PP resin portion") and a polyethylene resin portion containing polyethylene resin (hereinafter referred to as the "PE resin portion"). The composite fibers may, for example, be... Figure 3A The core-sheath type composite fiber shown, which uses PP resin as the core 20 and PE resin as the sheath 22, can also be used as follows: Figure 3B The image shows an eccentric core-sheath type composite fiber in which a portion of the PP resin portion (core 20) is exposed from the PE resin portion (sheath 22). The composite fiber can also be a parallel composite fiber comprising both a PP resin portion and a PE resin portion.

[0095] Preferably, when the total mass of the PP resin portion and the PE resin portion is set to 100 units, the ratio of the PP resin portion to the PE resin portion is 70:30 to 10:90 (PP resin portion: PE resin portion) based on a mass standard. This ratio is more preferably 65:35 to 35:65, and even more preferably 65:35 to 55:45. The ratio of the PP resin portion to the PE resin portion in the composite fiber can be measured using known nuclear magnetic resonance (NMR) based on the ratio of the integrated intensities of hydrogen and carbon nuclei derived from polyethylene resin to those derived from polypropylene resin. The ratio of the PP resin portion to the PE resin portion in the composite fiber can also be determined based on... 13 The C-NMR spectra were obtained using conventional methods.

[0096] The average fiber diameter of the composite fiber is preferably 10 μm or more and 40 μm or less, more preferably 10 μm or more and 25 μm or less, even more preferably 12 μm or more and 20 μm or less, and particularly preferably 13 μm or more and 18 μm or less. If the average fiber diameter of the composite fiber is within the above range, it tends to have an excellent balance between strength and softness.

[0097] The thickness and weight per unit area of ​​the first fiber layer 12 are not particularly limited as long as they do not impair the effects of the present invention, and any thickness and weight per unit area corresponding to the desired application can be used. The thickness of the first fiber layer 12 is preferably 0.03 mm or more and 2.00 mm or less, more preferably 0.05 mm or more and 1.00 mm or less. The weight per unit area of ​​the first fiber layer 12 is preferably 3 g / m³. 2 ) or more and 20 (g / m 2 ) or less, more preferably 4 (g / m 2 ) or more and 16 (g / m 2 ) or less, more preferably 5 (g / m 2 ) or more and 12 (g / m 2 )the following.

[0098] (PP resin part)

[0099] The PP resin portion may contain a propylene-α-olefin random copolymer. The content of propylene-derived structural units in the propylene-α-olefin random copolymer is 50% by mass or more and less than 100% by mass, preferably 70% by mass or more and 99% by mass or less from the viewpoint of balancing flexibility and strength, more preferably 80% by mass or more and 98% by mass or less. The content of α-olefin-derived structural units in the propylene-α-olefin random copolymer is greater than 0% by mass and less than 50% by mass, preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less.

[0100] There are no particular limitations on the α-olefin in the propylene-α-olefin random copolymer, as long as it is an α-olefin other than propylene. Examples of α-olefins include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, and 4-methyl-1-hexene. Among these, from the viewpoint of further improving flexibility, ethylene is preferred as the α-olefin.

[0101] The content of propylene-α-olefin random copolymer in the PP resin portion is preferably 10% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, and particularly preferably 99% by mass or more and 100% by mass or less.

[0102] As for propylene-α-olefin random copolymers, preferred examples include propylene-1-butene random copolymers, propylene-ethylene random copolymers, and propylene-ethylene-1-butene random copolymers. From the viewpoint of balancing flexibility and strength, random copolymers of propylene and ethylene are more preferred.

[0103] From the perspective of further improving strength, the PP resin portion may also include propylene homopolymers and various types of propylene-α-olefin random copolymers.

[0104] The content of propylene homopolymer in the PP resin portion is preferably 1% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 80% by mass or less. Furthermore, it is preferable that when the PP resin portion contains propylene homopolymer within the above-mentioned range, the content of the propylene-α-olefin random copolymer is an amount in which the total content of the propylene-α-olefin random copolymer and the propylene homopolymer is 100% by mass.

[0105] The content of propylene-derived structural units in all resin components included in the PP resin portion is preferably 90% by mass or more and 99.5% by mass or less, more preferably 93% by mass or more and 99% by mass or less, and even more preferably 95% by mass or more and 98% by mass or less.

[0106] Preferably, the melting point of the propylene-α-olefin random copolymer is below 155°C. When the PP resin portion contains only the propylene-α-olefin random copolymer as a resin component, it is preferable that the melting point of the propylene-α-olefin random copolymer is above 125°C and below 155°C. In this specification, "melting point" refers to the "peak temperature" measured in a differential scanning calorimeter during the endothermic change from a solid to a liquid state at a heating rate of 10°C / min.

[0107] The melt flow rate (MFR; measurement conditions: 230°C, 2.16 kg load) of the propylene-α-olefin random copolymer, measured according to ASTM standard D-1238, is preferably 10 (g / 10 min) or more and 100 (g / 10 min) or more, more preferably 15 (g / 10 min) or more and 80 (g / 10 min) or less. If the melt flow rate (MFR) of the propylene-α-olefin random copolymer is within the above range, it tends to have excellent flexibility.

[0108] (PE resin part)

[0109] The PE resin portion may also contain ethylene polymers. The density of the PE resin portion is 900 kg / m³. 3 ) or above and 945 (kg / m 3 The density of the PE resin portion is preferably 910 kg / m³ or less. 3 ) or above and 940 (kg / m 3 ) or less, preferably 915 (kg / m 3 ) or above and 940 (kg / m 3 Below 920 (kg / m³), further preferably 920 (kg / m³) 3 ) or above and 940 (kg / m 3 The density is below 95°C. If the density is within the above range, it tends to have an excellent balance between softness and strength. The density of the PE resin portion can be adjusted by changing the density of the resin that constitutes the PE resin portion. The melting point of ethylene polymers is approximately 95°C or higher and 125°C or lower.

[0110] The content of ethylene-derived structural units in ethylene-based polymers is 50% by mass or more, preferably 70% by mass or more and 99.8% by mass or less, more preferably 90% by mass or more and 99% by mass or less. The content of other structural units in ethylene-based polymers is 0% by mass or more and 50% by mass or less, preferably 0.2% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 10% by mass or less. If the content of ethylene-derived structural units and / or other structural units in ethylene-based polymers is within the above ranges, there is a tendency to achieve both excellent strength and flexibility.

[0111] α-olefins can be cited as monomers constituting other structural units. There are no particular limitations on α-olefins other than ethylene; examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, and 4-methyl-1-hexene. From the viewpoint of balancing flexibility and strength, 1-butene and 4-methyl-1-pentene are preferred as α-olefins.

[0112] Preferably, the ethylene polymer comprises an ethylene-α-olefin copolymer. Furthermore, the ethylene-α-olefin copolymer is preferably at least one selected from the group consisting of ethylene-1-butene copolymers and ethylene-4-methyl-1-pentene copolymers. When the ethylene polymer is in the above-described form, it tends to have an excellent balance of strength and flexibility.

[0113] The melt flow rate (MFR) (ASTM D-1238, 190°C, 2.16 kg load) of ethylene polymers is preferably 10 g / 10 min or more and 100 g / 10 min or less, more preferably 15 g / 10 min or more and 60 g / 10 min or less, and even more preferably 20 g / 10 min or more and 60 g / 10 min or less. When the melt flow rate (MFR) of the ethylene polymer is within the above range, it tends to have an excellent balance between strength and flexibility.

[0114] The content of ethylene polymers in the PE resin portion is preferably 10% by mass or more and 100% by mass or less, more preferably 50% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 99% by mass or more and 100% by mass or less. When the content of ethylene polymers in the PE resin portion is within the above range, it tends to have an excellent balance between strength and flexibility.

[0115] (Hydrophilic agent)

[0116] Preferably, the first fiber layer 12 has high hydrophilicity. When the composite fibers constituting the first fiber layer 12 are of an eccentric core-sheath type or a side-by-side type, it is preferable that a hydrophilic agent is incorporated into the PP resin portion. In the case of the eccentric core-sheath type, a portion of the core 20, which is the PP resin portion incorporating the hydrophilic agent, is partially exposed from the sheath 22, thereby making the first fiber layer 12 hydrophilic.

[0117] Hydrophilic agents can be further classified into penetrants and wetting agents. The second nonwoven fabric 14 may contain both penetrants and wetting agents, or it may contain a wetting agent but not a penetrant. From the viewpoint of excellent hydrophilicity, it is preferable that the hydrophilic agent includes both penetrants and wetting agents.

[0118] Preferably, the hydrophilic agent comprises at least one of a sulfonate and a sulfate salt as a penetrant. Examples of sulfonates include alkylbenzene sulfonates, alkylnaphthalene sulfonates, α-olefin sulfonates, and alkyl sulfosuccinates. These sulfonates are preferably alkali metal salts. Examples of sulfate salts include higher alcohol sulfates and alkyl sulfates. These sulfate salts are preferably alkali metal salts. Preferably, the hydrophilic agent comprises a sulfonate as a penetrant; more preferably, the hydrophilic agent comprises an alkali metal salt of a sulfonic acid as a penetrant.

[0119] When a hydrophilic agent contains a wetting agent, the wetting agent is not particularly limited. For example, the hydrophilic agent may contain any of the following as a wetting agent: cationic surfactant, anionic surfactant, amphoteric surfactant, or nonionic surfactant.

[0120] The content of the hydrophilic agent is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 0.05% by mass or more and 1.0% by mass or less, and even more preferably 0.1% by mass or more and 0.5% by mass or less. As a method for incorporating the hydrophilic agent into the resin of the raw material of the core-sheath type composite fiber, for example, a method of adding the above-mentioned hydrophilic agent to the resin of the raw material of the core 20 and then spinning to form a fiber can be described.

[0121] (Second fiber layer)

[0122] The second fiber layer 13 comprises a single fiber made of polypropylene resin. The average fiber diameter of the single fiber is preferably 10 μm or more and 30 μm or less, more preferably 11 μm or more and 25 μm or less, and even more preferably 12 μm or more and 20 μm or less.

[0123] The second fiber layer 13 preferably contains 60% by mass or more of a single fiber made of polypropylene resin, more preferably 75% by mass or more of a single fiber made of polypropylene resin, and particularly preferably 95% by mass or more of a single fiber made of polypropylene resin.

[0124] The thickness and weight per unit area of ​​the second fiber layer 13 are not particularly limited as long as they do not impair the effects of the present invention, and any thickness and weight per unit area corresponding to the desired application can be used. The thickness of the second fiber layer 13 is preferably 0.03 mm or more and 2.00 mm or less, more preferably 0.05 mm or more and 1.00 mm or less. The weight per unit area of ​​the second fiber layer 13 is preferably, for example, 3 g / m³. 2 ) or more and 20 (g / m 2 ) or less, more preferably 4 (g / m 2 ) or more and 16 (g / m 2 ) or less, more preferably 5 (g / m 2 ) or more and 12 (g / m 2 )the following.

[0125] The polypropylene resin of the second fiber layer 13 may also include the aforementioned propylene-α-olefin random copolymer that constitutes the first fiber layer 12.

[0126] (Second nonwoven fabric)

[0127] When wearing an absorbent article using composite sheet 10A, the second nonwoven fabric 14 is positioned relative to the first nonwoven fabric 11 on the non-skin side of the wearer. In this embodiment, the second nonwoven fabric 14 is an elastic nonwoven fabric that stretches along the first direction W.

[0128] The second nonwoven fabric 14 can be any type of nonwoven fabric, such as hot-air nonwoven fabric, spunbond nonwoven fabric, dot-bonded nonwoven fabric, spunlace nonwoven fabric, needle-punched nonwoven fabric, meltblown nonwoven fabric, and combinations thereof (e.g., SMS). The second nonwoven fabric 14 can be exemplified by a nonwoven fabric obtained by performing a suitable stretching treatment, such as a gear stretching treatment, on a nonwoven fabric containing thermoplastic elastomer fibers exhibiting approximately elasticity and thermoplastic resin fibers exhibiting approximately inelasticity. That is, by performing this stretching treatment, the approximately inelastic thermoplastic resin fibers contained in the nonwoven fabric are plastically deformed, or the bonding points between the fibers are broken, etc., so that the nonwoven fabric can be made into a structure that does not easily hinder the approximately elastic stretching deformation of the thermoplastic elastomer fibers. In this way, the stretchability of the nonwoven fabric can be exhibited, making it suitable for use as an elastic nonwoven fabric.

[0129] Furthermore, examples of thermoplastic elastomers that are generally elastic include polyurethane elastomers, polystyrene elastomers, polyolefin elastomers, and polyamide elastomers. Additionally, thermoplastic resin fibers that are generally inelastic include polypropylene resins such as polypropylene (PP), and may also include polyethylene (PE).

[0130] The polypropylene resin contained in the generally inelastic thermoplastic resin fibers of the second nonwoven fabric 14 is exposed on the surface of the side in contact with the second fiber layer 13. The weight per unit area of ​​the second nonwoven fabric 14 is not particularly limited, but may be set to, for example, 10 g / m². 2 ) or above and 80 (g / m 2 The elongation ratio of the second nonwoven fabric 14 is not particularly limited; for example, it can be set to more than 1.5 times and less than 3.5 times. The elongation ratio is the ratio of the length of the second nonwoven fabric 14 after elongation when its unstretched length is set to 1.

[0131] The thickness and weight per unit area of ​​the second nonwoven fabric 14 are not particularly limited as long as they do not impair the effect of the present invention, and any thickness and weight per unit area corresponding to the desired application can be adopted. The thickness of the second nonwoven fabric 14 is preferably 0.05 mm or more and 2.00 mm or less, more preferably 0.10 mm or more and 1.50 mm or less. The weight per unit area of ​​the second fiber layer 13 is preferably, for example, 10 g / m³. 2 ) or above and 80 (g / m 2 ) or less, more preferably 12 (g / m 2 ) or above and 70 (g / m 2 ) or less, more preferably 14 (g / m 2 ) or above and 60 (g / m 2 )the following.

[0132] (Third nonwoven fabric)

[0133] When the absorbent article using composite sheet 10A is worn, the third nonwoven fabric 16 forms the surface on the non-skin side of the wearer. The nonwoven fabric used as the third nonwoven fabric 16 can be any type of nonwoven fabric, such as hot-air nonwoven fabric, spunbond nonwoven fabric, dot-bonded nonwoven fabric, spunlace nonwoven fabric, needle-punched nonwoven fabric, meltblown nonwoven fabric, and combinations thereof (e.g., SMS). The thickness and weight per unit area of ​​the third nonwoven fabric 16 are not particularly limited as long as they do not impair the effect of the present invention; any thickness and weight per unit area appropriate to the desired application can be used. The thickness of the third nonwoven fabric 16 is preferably 0.05 mm or more and 2.00 mm or less, more preferably 0.10 mm or more and 1.50 mm or less. The weight per unit area of ​​the third nonwoven fabric 16 is preferably, for example, 8 g / m³. 2 ) or more and 30 (g / m 2 ) or less, more preferably 10 (g / m 2 ) or more and 25 (g / m 2 ) or less, more preferably 12 (g / m 2 ) or more and 20 (g / m 2The third nonwoven fabric 16 may be the same as the first nonwoven fabric 11 or a different nonwoven fabric than the first nonwoven fabric 11.

[0134] <Manufacturing Method>

[0135] In manufacturing the composite sheet 10A, firstly, a first nonwoven fabric 11, a second nonwoven fabric 14, and a third nonwoven fabric 16 are prepared. The first nonwoven fabric 11 is formed by overlapping and embossing a first fiber layer 12 and a second fiber layer 13 along the thickness direction T. Multiple embossed joints with recesses along the thickness direction T are formed on the surface of the first nonwoven fabric 11 through the embossing process.

[0136] Next, the first nonwoven fabric 11, the second nonwoven fabric 14, and the third nonwoven fabric 16 are sequentially overlapped along the thickness direction T. In this case, the second nonwoven fabric 14 is in a stretched state due to the speed difference between the supply speed and the winding speed after the gear stretching process. The first nonwoven fabric 11 is arranged such that the second fiber layer 13 contacts the second nonwoven fabric 14. The first nonwoven fabric 11, the second nonwoven fabric 14, and the third nonwoven fabric 16 are thermally bonded in an overlapping state. Although not shown, thermal bonding can, for example, use an ultrasonic amplitude transformer and an anvil roller. The ultrasonic amplitude transformer generates ultrasonic vibrations on its outer peripheral surface. The anvil roller has a plurality of protrusions on its outer peripheral surface that protrude outward in the radial direction. The first nonwoven fabric 11, the second nonwoven fabric 14, and the third nonwoven fabric 16 are conveyed in an overlapping state between the ultrasonic amplitude transformer and the anvil roller along the MD direction (W direction), which is the conveying direction, and are sandwiched between the protrusions of the anvil roller and the ultrasonic amplitude transformer, thereby forming a plurality of joints 18. The joint 18 is formed by ultrasonic pressing, resulting in a T-shaped indentation along the thickness direction. Composite sheet 10A is formed as described above. Composite sheet 10A has an embossed joint and joint 18 on the surface of the first nonwoven fabric 11. Composite sheet 10A has joint 18 on the surface of the third nonwoven fabric 16.

[0137] <Functions and Effects>

[0138] Because the composite sheet 10A stretches and contracts along the first direction W, therefore... Figure 4As shown, by arranging the first direction W parallel to the wearer's waistline DW, the composite sheet 10A can be applied to the waist section of an absorbent article. For example, a disposable diaper 1, as an absorbent article, has a crotch section 2 covering the wearer's groin and a waist section 3 covering the wearer's waist. The waist section 3 is formed by the composite sheet 10A. The composite sheet 10A is configured such that a first nonwoven fabric 11 is disposed on the skin side, a second nonwoven fabric 14 is disposed on the non-skin side, and the first direction W is parallel to the wearer's waistline DW. When applied as a waist section composite sheet for the disposable diaper 1, the composite sheet 10A extends along the waistline direction DW and is pulled upwards to be worn by the wearer. The composite sheet 10A contracts in accordance with the length of the wearer's waistline DW while the first nonwoven fabric 11 is in contact with the wearer's skin.

[0139] Since the composite sheet 10A comprises composite fibers containing PP resin and PE resin portions, it has a first fiber layer 12 on its surface that is soft and derived from polyethylene resin. Therefore, the composite sheet 10A has an excellent skin feel.

[0140] Since the composite sheet 10A includes a second fiber layer 13 containing a single fiber made of polypropylene resin, the reduction in mechanical strength caused by the first fiber layer 12 containing polyethylene resin can be suppressed. The tensile strength of the composite sheet 10A in the CD direction (L direction) is 14 (N / 50mm) or more. Therefore, when the composite sheet 10A is used in the waistband of an absorbent article, it can suppress the breakage caused by the upward pulling force on the absorbent article during wear.

[0141] The second fiber layer 13 contacts the second nonwoven fabric 14 and is bonded to the second nonwoven fabric 14 by thermal bonding. Since the second fiber layer 13 contains a single fiber made of polypropylene resin, and the surface of the second nonwoven fabric 14 on the side in contact with the second fiber layer 13 contains polypropylene resin, a joint 18 is formed where the polypropylene resins bond to each other. Because the joint 18 where the polypropylene resins bond to each other has high compatibility, and because there is no polyethylene resin between the joint 18, the thermal bonding is excellent. Since the first nonwoven fabric 11 and the second nonwoven fabric 14 have the aforementioned joint 18 where the polypropylene resins bond to each other, the bonding strength is excellent. The peel strength of the composite sheet 10A is 1.0 (N / 25mm) or higher; therefore, when the composite sheet 10A is applied to the waist section of an absorbent article, the peeling of the first nonwoven fabric 11 from the second nonwoven fabric 14 due to repeated use can be suppressed. The second fiber layer 13 comprises more than 60% by mass of a single fiber made of polypropylene resin, thereby enabling more reliable formation of the joint 18 in which there is no polyethylene resin.

[0142] The composite sheet 10A has mutually orthogonal first direction W, second direction L and thickness direction T. A first nonwoven fabric 11 and a second nonwoven fabric 14 are sequentially provided in the thickness direction T. It also has a plurality of joints 18 for thermally bonding the first nonwoven fabric 11 and the second nonwoven fabric 14 together. The first nonwoven fabric 11 has a first fiber layer 12 and a second fiber layer 13 disposed between the first fiber layer 12 and the second nonwoven fabric 14. The first fiber layer 12 contains composite fibers. The composite fibers include, in cross-section, a polypropylene resin portion containing polypropylene resin and a polyethylene resin portion containing polyethylene resin. The second fiber layer 13 contains a single fiber made of polypropylene resin. The surface of the second nonwoven fabric 14 on the side in contact with the second fiber layer 13 contains polypropylene resin.

[0143] The first fiber layer 12, the second fiber layer 13, and the second nonwoven fabric 14 are integrated by heat bonding at the joint 18. Since the first fiber layer 12 and the second fiber layer 13 contain the same type of polypropylene resin, they exhibit excellent compatibility and are well bonded. The second nonwoven fabric 14, because its surface in contact with the second fiber layer 13 contains the same type of resin (polypropylene resin) as the single fibers contained in the second fiber layer 13, is easily heat-bonded to the second fiber layer 13. Due to the good heat bonding between the second fiber layer 13 and the second nonwoven fabric 14, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 14 is excellent for the composite sheet 10A, suppressing peeling between them under repeated use and exhibiting excellent durability. Therefore, the composite sheet 10A maintains a pleasant skin feel while exhibiting excellent durability.

[0144] Preferably, the second nonwoven fabric 14 is an elastic nonwoven fabric capable of stretching along the first direction W. Since the composite sheet 10A stretches along the first direction W, by arranging the first direction W parallel to the wearer's waist, the composite sheet 10A can be applied, for example, to a composite sheet for the waist portion of absorbent articles. Because the first nonwoven fabric 11 includes a soft first fiber layer 12, it easily shrinks to match the shrinkage of the second nonwoven fabric 14 (elastic nonwoven fabric). Because the second nonwoven fabric 14 (elastic nonwoven fabric) contains a resin of the same type as the single fiber contained in the second fiber layer 13—namely, a polypropylene resin—on its surface in contact with the second fiber layer 13, it is well thermally bonded to the second fiber layer 13. Therefore, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 14 (elastic nonwoven fabric) in the composite sheet 10A is excellent. As a result, the composite sheet 10A exhibits excellent shrinkage and durability.

[0145] Preferably, the composite sheet 10A has a third nonwoven fabric 16 on the opposite side of the second nonwoven fabric 14 that contacts the first nonwoven fabric 11. In the composite sheet 10A, by providing a third nonwoven fabric 16, which is appropriate for the intended use, on the opposite side of the second nonwoven fabric 14 that contacts the first nonwoven fabric 11, the range of options for placing the first nonwoven fabric 11 on the skin side or the non-skin side is further expanded. Furthermore, by adding the third nonwoven fabric 16, the mechanical strength of the composite sheet 10A is increased, resulting in superior durability. Therefore, the composite sheet 10A is more suitable for use as a composite sheet for the waist area of ​​absorbent articles.

[0146] Preferably, the polypropylene resin comprises a propylene-α-olefin random copolymer, and the polyethylene resin comprises an ethylene polymer. The difference in melting points between the propylene-α-olefin random copolymer and the polyethylene resin is smaller than the difference in melting points between the polypropylene and polyethylene resins. Therefore, the propylene-α-olefin random copolymer is easier to thermally bond with the polyethylene resin than polypropylene. Consequently, the fibers of the first fiber layer 12 are thermally bonded to each other over a larger area at the embossed joint and the joint 18. Therefore, for the composite sheet 10A, by thermally bonding the fibers of the first fiber layer 12 disposed on the surface of the composite sheet 10A to each other over a larger area, less fuzzing is generated, thus enabling longer service life.

[0147] Preferably, the melting point of the propylene-α-olefin random copolymer is below 155°C, and the melting point of the ethylene polymer is above 95°C and below 125°C. By placing the melting points of the propylene-α-olefin random copolymer and the ethylene polymer within the aforementioned ranges, the fibers of the first fiber layer 12 can be thermally bonded to each other more reliably over a wider range.

[0148] Preferably, when the total mass of the PP resin portion and the PE resin portion is set to 100 parts, the ratio of the PP resin portion to the PE resin portion is 70:30 to 10:90 (polypropylene resin portion: polyethylene resin portion) by mass. The first fiber layer 12 includes composite fibers, which contain a predetermined amount or more of polyethylene resin portion, i.e., polyethylene resin, thereby facilitating the deposition of polyethylene resin on the surface of the first fiber layer 12. Since the first fiber layer 12 is disposed on the surface side of the composite sheet 10A, the composite sheet 10A has an excellent skin feel.

[0149] Preferably, the polyethylene resin portion is present on the fiber surface of the composite fiber. For example, the composite fiber is an off-core core-sheath type or a side-by-side type, in which the polypropylene resin portion serves as the core 20 and the polyethylene resin portion serves as the sheath 22, with a portion of the polypropylene resin portion partially exposed from the polyethylene resin portion. Because the polyethylene resin portion is present on the fiber surface of the composite fiber, the composite fiber possesses a softness derived from the polyethylene resin. Since the first fiber layer 12 is disposed on the surface side of the composite sheet 10A, the composite sheet 10A has an excellent skin-touch feel.

[0150] Preferably, when the total mass of the first fiber layer 12 and the second fiber layer 13 is set to 100%, the ratio of the first fiber layer 12 to the second fiber layer 13 is 33:67 to 67:33 (first fiber layer: second fiber layer) based on a mass standard. The first nonwoven fabric 11 includes a predetermined amount or more of the second fiber layer 13 made of polypropylene resin. Since the second fiber layer 13 is disposed at a position in contact with the second nonwoven fabric 14, it is more reliably thermally bonded to the second nonwoven fabric 14. Therefore, in the composite sheet 10A, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 14 is excellent.

[0151] Preferably, the polypropylene resin of the first fiber layer 12 and the polypropylene resin of the second fiber layer 13 are the same propylene-α-olefin random copolymer. Compared with polypropylene, the propylene-α-olefin random copolymer has a lower melting point and a smaller difference in melting point with the polyethylene resin, thus it is easier to heat bond with the polyethylene resin than polypropylene. Therefore, at the embossed joint and the joint 18, the fibers of the first fiber layer 12 are heat-bonded to each other over a larger area. Consequently, for the composite sheet 10A, by heat-bonding the fibers of the first fiber layer 12 disposed on the surface of the composite sheet 10A to each other over a larger area, there is less fuzzing, thus enabling long-term use. Since the polypropylene resins of the first fiber layer 12 and the second fiber layer 13 are the same propylene-α-olefin random copolymer, the compatibility is excellent, and the first fiber layer 12 and the second fiber layer 13 are easily heat-bonded over a larger area. Therefore, in the composite sheet 10A, the bonding strength between the first fiber layer 12 and the second fiber layer 13 is excellent.

[0152] Preferably, the composite sheet 10A has multiple embossed joints on the surface of the first fiber layer 12, which join the first fiber layer 12 and the second fiber layer 13 without joining the second nonwoven fabric 14. The total area of ​​the multiple joints 18 on the surface of the first fiber layer 12 is smaller than the total area of ​​the multiple embossed joints on the surface of the first fiber layer 12. For the first nonwoven fabric 11, since the total area of ​​the multiple joints 18 is smaller than the total area of ​​the multiple embossed joints, it is easier to separate from the second nonwoven fabric 14 between the multiple joints 18 and deform along the thickness direction T. Because the first nonwoven fabric 11 is easily deformed along the thickness direction T between the joints 18, the second nonwoven fabric 14 is not hindered by the first nonwoven fabric 11 and can easily shrink. Therefore, the composite sheet 10A easily deforms along the wearer's waist, resulting in excellent skin feel.

[0153] <Variation Example>

[0154] This invention is not limited to the above-described embodiments, and appropriate modifications can be made within the scope of the invention's intent. For example, in the above-described embodiments, the dotted joints 18 are arranged in a grid pattern, but the invention is not limited thereto. It is also possible to... Figure 1 The same structures are labeled with the same reference numerals. Figure 5 They are arranged in a grid pattern as shown. Figure 5 The adjacent joints 18 shown in the first direction W are offset from each other by approximately 0.2 mm along the second direction L. Equipped with Figure 5 The composite sheet 10B with the dotted joint 18 shown can achieve the same effect as the above-described embodiment.

[0155] In the above embodiments, the case where the second nonwoven fabric 14 is an elastic nonwoven fabric has been described, but the present invention is not limited thereto. Regarding... Figure 2A The same structures are labeled with the same reference numerals. Figure 6The composite sheet 10C shown has, in the thickness direction T, a first nonwoven fabric 11, an elastic filament 24, and a second nonwoven fabric 26 sequentially. The elastic filament 24 can be an elastic filament obtained by molding a thermoplastic elastomer such as polyurethane or ethylene-vinyl acetate copolymer (EVA) into a filament. The surface of the second nonwoven fabric 26 in contact with the second fiber layer 13 of the first nonwoven fabric 11 contains a polypropylene resin. The nonwoven fabric used as the second nonwoven fabric 26 can be any nonwoven fabric such as hot-air nonwoven fabric, spunbond nonwoven fabric, dot-bonded nonwoven fabric, spunlace nonwoven fabric, needle-punched nonwoven fabric, meltblown nonwoven fabric, and combinations of these nonwoven fabrics (e.g., SMS). The thickness and weight per unit area of ​​the second nonwoven fabric 26 are not particularly limited as long as they do not impair the effect of the present invention, and any thickness and weight per unit area corresponding to the desired application can be used. The thickness of the second nonwoven fabric 26 is preferably 0.05 mm or more and 2.00 mm or less, more preferably 0.10 mm or more and 1.50 mm or less. The weight per unit area of ​​the second nonwoven fabric is preferably, for example, 10 g / m². 2 ) or more and 30 (g / m 2 ) or less, more preferably 12 (g / m 2 ) or more and 25 (g / m 2 ) or less, more preferably 14 (g / m 2 ) or more and 20 (g / m 2 The following describes the composite sheet 10C of this modified example, which is formed by thermal bonding with an elastic filament 24 disposed between the first nonwoven fabric 11 and the second nonwoven fabric 26. The elastic filament 24 is bonded to the first nonwoven fabric 11 and the second nonwoven fabric 26 in a stretched state due to the speed difference between the supply speed and the winding speed.

[0156] The composite sheet 10C includes elastic yarns 24 that stretch along a first direction W between the first nonwoven fabric 11 and the second nonwoven fabric 26. Because the composite sheet 10C stretches along the first direction W, by arranging the first direction W parallel to the wearer's waist, the composite sheet 10C can be applied, for example, to a composite sheet for the waist portion of an absorbent article 1. The first nonwoven fabric 11, due to including a soft first fiber layer 12, easily shrinks to match the shrinkage of the elastic yarns 24. The second nonwoven fabric 26 is arranged on the opposite side of the first nonwoven fabric 11, sandwiching the elastic yarns 24, and is well thermally bonded to the second fiber layer 13. That is, the second fiber layer 13 and the second nonwoven fabric 26 are well thermally bonded with the elastic yarns 24 sandwiched between them. Therefore, in the composite sheet 10C, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 26 is excellent. As a result, Composite Sheet 10C exhibits excellent shrinkage and durability.

[0157] <Measurement Method>

[0158] The measurement methods for each value described in the above embodiments will be explained below.

[0159] (Weight per unit area)

[0160] First, the composite sheet without elongation has a total area of ​​500 (cm²). 2 One or more test pieces are cut out as samples using the above method. Next, the total weight of the sample is measured using a direct-reading balance (e.g., an HF-300 electronic balance manufactured by Kensei Kogyo Co., Ltd.). Finally, the weight per unit area (g / m²) of the sample is calculated based on the measured total weight and the total area of ​​the sample. 2 The value of ) is used as the weight per unit area of ​​the composite sheet.

[0161] The unit area weights of the first, second, and third nonwoven fabrics are calculated as follows. First, after separating them from the composite sheet, the total area of ​​each material in the stretched-out state is 500 (cm²). 2 Cut one or more sample pieces using the above method. Measure the total weight of each material, and calculate the weight per unit area (g / m²) of each sample based on the total weight and total area. 2 ), which is the weight per unit area of ​​each material.

[0162] (thickness)

[0163] The thickness was measured using a thickness gauge FS-60DS (pressure foot diameter: 50.5 mm, measuring pressure: 0.3 kPa) manufactured by Daiei Scientific Precision Manufacturing Co., Ltd.

[0164] (Bending stiffness based on KES method)

[0165] Regarding the bending stiffness based on the KES method, the bending stiffness of the composite sheet in the second direction was measured using the KES-FB2-L large-scale bending tester manufactured by Kado Technology Co., Ltd. Samples were cut from the composite sheet with a length of 40 mm in the first direction and a length of 60 mm in the second direction.

[0166] The measurement conditions are as follows.

[0167] SENS: 4

[0168] SIZE: 4cm (set as the measurement width of the sample)

[0169] Pattern: One cycle

[0170] Curvature: 0.5cm -1

[0171] B: K = 0.1cm~0.3cm

[0172] (Tension strength)

[0173] The fracture strength was measured using a Shimadzu AG-1 universal testing machine manufactured by Shimadzu Corporation. First, a composite sheet in its elongated state without any wrinkles was cut into specimens with a length of 50 mm in the first direction and 70 mm in the second direction. Next, the fracture strength in the second direction of the composite sheet was measured with the chuck distance set to 50 mm and a tensile speed of 500 mm / min. "N / 50 mm" refers to the fracture strength (N) per 50 mm width.

[0174] (Average fiber diameter)

[0175] First, the first and second nonwoven fabrics were separated from the composite sheet. 10mm × 10mm samples of each nonwoven fabric were cut and prepared, and placed on a glass slide. Next, a suitable amount of glycerin was dripped onto each sample, so that the entire sample was impregnated with glycerin, and a coverslip was placed on top. Then, the samples were observed at 1000x magnification using a known optical microscope (e.g., Keyence VHC-100 digital microscope VH-Z450). The fiber diameters of 50 exposed fibers on the sample surface were measured, and the average value was taken as the average fiber diameter.

[0176] (Peel strength)

[0177] (1) Cut out a portion of the composite sheet, including the joint (including the first nonwoven fabric and the second nonwoven fabric), in the size of 70mm in the stretching direction and 25mm in the non-stretching direction, as a sample.

[0178] (2) Using a peel tester, peel the first and second nonwoven fabrics of the cut sample 20 mm apart along the stretching direction L, and hold the ends of the first and second nonwoven fabrics in the two chucks of the tester. The initial distance between the chucks is set to 30 mm.

[0179] (3) Using a tester, pull the two chucks at a certain speed (e.g., 50 mm / min) to widen the gap between them. While the first and second nonwoven fabrics at the joint are peeled off in the 180° direction, measure the gap between the two chucks and the load F applied to the two chucks.

[0180] (4) The peel strength of the joint is measured based on the relationship between the load F applied between the two chucks and the distance Dm between the two chucks. The maximum value of the measured load F is set as the peel strength (N / 25mm).

[0181] (Comparison of the area of ​​the joint and the area of ​​the embossed joint)

[0182] A 10mm × 10mm sample was cut from the nonwoven fabric. The sample was observed using an electron microscope at 100x magnification, and the area of ​​the joints and the area of ​​the embossed joints on the sample surface were measured and compared.

[0183] Example

[0184] The following examples illustrate the present invention, but the present invention is not limited to these examples.

[0185] (A) Sample

[0186] A composite sheet comprising a first nonwoven fabric, a second nonwoven fabric, and a third nonwoven fabric was prepared. The first nonwoven fabric was formed by spunbonding a first fiber layer composed of eccentric core-sheath type composite fibers and a second fiber layer composed of single fibers, and then embossing them together. As the polypropylene resin, a propylene-α-olefin random copolymer (α-olefin: ethylene) was used, and as the polyethylene resin, an ethylene-α-olefin copolymer (α-olefin: 1-butene) was used. The elastic nonwoven fabric was a spunbond nonwoven fabric containing polyurethane and polypropylene; the same materials were used in all samples. The third nonwoven fabric was a spunbond nonwoven fabric comprising an eccentric core-sheath type composite fiber layer and a single fiber layer. The detailed structures of each nonwoven fabric are shown in Table 1. Regarding the ratio of the first fiber layer to the second fiber layer (first fiber layer: second fiber layer), when the total of the first fiber layer and the second fiber layer is set to 100 units of mass, the ratio of the first fiber layer to the second fiber layer is 67:33 in Examples 1 to 3 and 33:67 in Examples 4 to 6.

[0187] The first nonwoven fabric, the elastic nonwoven fabric, and the third nonwoven fabric were sequentially overlapped along their thickness direction and then ultrasonically heat-bonded. Ultrasonic heat bonding was performed using equipment manufactured by Herrmann Ultrasonics. The ultrasonic amplitude transformers were set to: 161 mm width × 2 pieces, frequency 20 kHz, and pressure 500 N. The anvil roller speed was set to 200 m / min, the unwinding speed of the elastic nonwoven fabric was set to 80 m / min, and the unwinding speeds of the first and third nonwoven fabrics were set to 199 m / min.

[0188] As a reference example, composite sheets were prepared, including a first nonwoven fabric composed of a single fiber, the aforementioned elastic nonwoven fabric, and a third nonwoven fabric composed of a single fiber (Reference Example 1), and composite sheets were prepared, including a first nonwoven fabric composed of a spunbond nonwoven fabric composed of an eccentric core-sheath type composite fiber, the aforementioned elastic nonwoven fabric, and a third nonwoven fabric composed of an eccentric core-sheath type composite fiber (Reference Examples 2 and 3). The composite sheets were obtained by heat bonding using ultrasonic waves under the same conditions as in the above embodiments.

[0189] (B) Results

[0190] The fracture strength, bond strength, and flexural stiffness in the CD direction of the composite sheets in the embodiments and reference examples were measured. As shown in Table 1, in Examples 1 to 6, since a first fiber layer comprising composite fibers containing PP resin and PE resin portions is provided, the flexural stiffness is 0.31 (N·m). 2 / (m×10 -4 Since it has a second fiber layer containing a single fiber formed of polypropylene resin, the tensile strength is 17.39 (N / 50mm) or higher. Furthermore, since the second fiber layer is thermally bonded to the elastic nonwoven fabric, a tensile strength of 1.47 (N / mm) or higher is obtained.

[0191] In contrast, in Reference Example 1, since the first nonwoven fabric is composed of a single polypropylene fiber, the resulting tensile strength and bond strength in the CD direction are high, but the flexural stiffness in the CD direction is also high. In Reference Examples 2 and 3, since the elastic nonwoven fabric and the first nonwoven fabric, which is composed of composite fibers including PP resin and PE resin portions, are thermally bonded, the resulting bond strength is low.

[0192] [Table 1]

[0193]

[0194] Explanation of reference numerals in the attached figures

[0195] 1. Absorbent material; 2. Crotch area; 3. Waist area; 10A. Composite sheet; 10B. Composite sheet; 10C. Composite sheet; 11. First nonwoven fabric; 12. First fiber layer; 13. Second fiber layer; 14. 26. Second nonwoven fabric; 16. Third nonwoven fabric; 18. Joint; 20. Core; 22. Sheath; 24. Elastic yarn.

Claims

1. A composite sheet for use in absorbent articles having mutually orthogonal first, second, and thickness directions, wherein, The composite sheet comprises a first nonwoven fabric and a second nonwoven fabric in sequence in the thickness direction. The composite sheet also has multiple joints that thermally bond the first nonwoven fabric and the second nonwoven fabric together. The first nonwoven fabric has a first fiber layer and a second fiber layer disposed between the first fiber layer and the second nonwoven fabric and in contact with the second nonwoven fabric. The first fiber layer comprises composite fibers, which in cross-section include a polypropylene resin portion containing polypropylene resin and a polyethylene resin portion containing polyethylene resin. The second fiber layer comprises a single fiber made of polypropylene resin. The second nonwoven fabric contains polypropylene resin on the surface of the side that contacts the second fiber layer. The plurality of joints have a shape in which one surface of the composite sheet is recessed along the thickness direction. The composite sheet has multiple embossed joints on the surface of the first fiber layer, which join the first fiber layer and the second fiber layer without joining the second nonwoven fabric. The total area of ​​the plurality of joints on the surface of the first fiber layer is smaller than the total area of ​​the plurality of embossed joints on the surface of the first fiber layer.

2. The composite sheet according to claim 1, wherein, The second nonwoven fabric is an elastic nonwoven fabric capable of stretching along the first direction.

3. The composite sheet according to claim 2, wherein, The composite sheet has a third nonwoven fabric on the opposite side of the side of the second nonwoven fabric that contacts the first nonwoven fabric.

4. The composite sheet according to claim 1, wherein, The composite sheet includes elastic yarns that stretch along the first direction between the first nonwoven fabric and the second nonwoven fabric.

5. The composite sheet according to claim 1, wherein, The polypropylene resin comprises a propylene-α-olefin random copolymer. The polyethylene resins include ethylene polymers.

6. The composite sheet according to claim 5, wherein, The melting point of the propylene-α-olefin random copolymer is below 155°C, and the melting point of the ethylene polymer is above 95°C and below 125°C.

7. The composite sheet according to claim 1, wherein, The ratio of the polypropylene resin portion to the polyethylene resin portion, that is, the ratio of the polypropylene resin portion to the polyethylene resin portion by mass, is 70:30 to 10:

90.

8. The composite sheet according to claim 1, wherein, The polyethylene resin portion is present on the surface of the composite fiber.

9. The composite sheet according to claim 1, wherein, The ratio of the first fiber layer to the second fiber layer, i.e., the ratio of the first fiber layer to the second fiber layer by mass, is 33:67 to 67:

33.

10. The composite sheet according to claim 1, wherein, The polypropylene resin in the first fiber layer and the polypropylene resin in the second fiber layer are the same propylene-α-olefin random copolymer.

Images