Composite sheet for absorbent article

Abstract

Provided is a composite sheet for an absorbent article, the composite sheet having excellent durability while maintaining a good texture on the skin. A composite sheet (10A) for an absorbent article having a first direction (W), a second direction (L), and a thickness direction (T) that are orthogonal to each other, the composite sheet (10A) being provided with a first nonwoven fabric (11) and a second nonwoven fabric (14) in this order in the thickness direction (T), and also with a plurality of joining sections (18) that thermally join the first nonwoven fabric (11) and the second nonwoven fabric (14) to each other. The first non-woven fabric (11) has a first fiber layer (12) and a second fiber layer (13) disposed between the first fiber layer (12) and the second non-woven fabric (14), and the first fiber layer (12) contains composite fibers including, in a cross section, a polypropylene resin portion (20) containing a polypropylene resin and a polyethylene resin portion (22) containing a polyethylene resin. The second fiber layer (13) contains a single fiber comprising a polypropylene resin, and the second non-woven fabric (14) contains a polypropylene resin on the surface on the side in contact with the second fiber layer (13).

Description

Technical Field

[0001] The present invention relates to a composite sheet for absorbent articles. Background Art

[0002] In composite sheets for absorbent articles, research has been conducted to improve the goodness of skin touch. For example, Patent Document 1 discloses an absorbent article, which comprises: a main body having a liquid-permeable surface sheet, a liquid-impermeable back side sheet, and an absorbent body 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 non-woven fabrics, and the outermost non-woven fabric located on the outermost side has a torsion resistance of 3.8 gf·cm / cm or less. The following content is disclosed: The outermost non-woven fabric is composed of a single fiber of polypropylene and a core-sheath type composite fiber of polypropylene and polyethylene.

[0003] In addition, Patent Document 2 discloses an absorbent article having a longitudinal direction and a transverse direction, and having an absorbent body having an absorbent core, and a pair of waist parts. The waist parts have a skin side sheet portion disposed at a position closest to the skin side. In at least one of the pair of waist parts, the bending stiffness of the skin side sheet portion based on the KES method is 0.0096 N·m 2 / (m×10 -4 ) or less. An inner sheet portion is arranged at a position closer to the non-skin side than the skin side sheet portion. The bending stiffness of the inner sheet portion based on the KES method is higher than the bending stiffness of the skin side sheet portion. The inner sheet portion is arranged on the skin side of the absorbent body, straddling the edge of the waist side in the longitudinal direction of the absorbent body. It is disclosed that the above-mentioned skin side sheet portion mainly contains polyethylene.

[0004] Prior art literature

[0005] Patent Literature

[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] Problem that 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 hard, it is expected that the outer sheet composed of the outermost nonwoven fabric and other nonwoven fabrics as a whole has a limit in terms of the goodness of improving the skin touch. 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, the outer sheet formed by joining the outermost nonwoven fabric and other nonwoven fabrics formed of polypropylene has a large difference in melting points between polyethylene and polypropylene and lacks compatibility, so there is a problem that the bonding strength between the outermost nonwoven fabric composed of the composite fiber and the other nonwoven fabric is insufficient, and the outermost nonwoven fabric and the other nonwoven fabric will peel off from each other when used repeatedly.

[0010] The polyethylene mainly contained in the skin side sheet of Patent Document 2 is relatively soft, and therefore it is difficult to have a strength suitable for a composite sheet for absorbent articles, and there is a concern that it may be difficult to use repeatedly.

[0011] An object of the present invention is to provide a composite sheet for absorbent articles which has excellent durability while maintaining a good feel to the skin.

[0012] Solutions for solving problems

[0013] The present invention is a composite sheet for absorbent articles having a first direction, a second direction and a thickness direction which are orthogonal to each other, wherein the composite sheet comprises a first nonwoven fabric and a second nonwoven fabric in sequence in the thickness direction, and further comprises a plurality of joint portions for thermally joining the first nonwoven fabric and the second nonwoven fabric to each other, the first nonwoven fabric comprising a first fiber layer and a second fiber layer arranged between the first fiber layer and the second nonwoven fabric, the first fiber layer comprising composite fibers, the composite fibers comprising a polypropylene resin portion containing a polypropylene resin and a polyethylene resin portion containing a polyethylene resin in a cross section, the second fiber layer comprising a single fiber composed of a polypropylene resin, and the second nonwoven fabric comprising a polypropylene resin on a surface on a side in contact with the second fiber layer.

[0014] Effects of the Invention

[0015] The composite sheet for absorbent articles of the present invention has excellent durability while maintaining a good feel to the skin. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 2A It is a cross-sectional view schematically showing the state of the composite sheet according to the embodiment during expansion.

[0018] Figure 2B It is a cross-sectional view schematically showing a state of the composite sheet according to the embodiment during contraction.

[0019] Figure 3A It is a cross-sectional view of fibers of the first nonwoven fabric and the second nonwoven fabric according to the embodiment.

[0020] Figure 3B It is a cross-sectional view of fibers of a first nonwoven fabric and a second nonwoven fabric according to a modification of the embodiment.

[0021] Figure 4 This is a perspective view showing an absorbent article using the composite sheet according to the embodiment.

[0022] Figure 5 It is a top view of the composite sheet of modification (1).

[0023] Figure 6 This is a cross-sectional view schematically showing the state of the composite sheet of Modification (2) during expansion. DETAILED DESCRIPTION

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

[0025] [Method 1]

[0026] A composite sheet for an absorbent article having a first direction, a second direction and a thickness direction which are orthogonal to each other, wherein:

[0027] The composite sheet includes a first nonwoven fabric and a second nonwoven fabric in this order in the thickness direction.

[0028] The invention further comprises a plurality of joining parts for thermally joining the first nonwoven fabric and the second nonwoven fabric to each other,

[0029] The first nonwoven fabric comprises 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 includes composite fibers, wherein the composite fibers include a polypropylene resin portion containing a polypropylene resin and a polyethylene resin portion containing a polyethylene resin in a cross section.

[0031] The second fiber layer includes single fibers made of polypropylene resin.

[0032] The second nonwoven fabric contains a polypropylene-based resin on a surface of the side in contact with the second fiber layer.

[0033] Since the composite sheet includes the second fiber layer containing single fibers made of a polypropylene-based resin, it can have a strength suitable for a composite sheet for a waist portion of an absorbent article.

[0034] Since the first fiber layer includes composite fibers including a polypropylene resin portion including a polypropylene resin and a polyethylene resin portion including a polyethylene resin, the composite fiber is rich in softness derived from the polyethylene resin. Since the first fiber layer is disposed on the surface of the composite sheet, the composite sheet has an excellent skin touch.

[0035] The joining portion integrates the first fiber layer, the second fiber layer and the second nonwoven fabric by thermal bonding. Since the first fiber layer and the second fiber layer contain the same type of polypropylene resin, they are compatible and well bonded. Since the second nonwoven fabric contains the same type of resin as the single fiber contained in the second fiber layer, i.e., polypropylene resin, on the surface of the side in contact with the second fiber layer, it is easy to thermally bond with the second fiber layer. Since the second fiber layer and the second nonwoven fabric are well thermally bonded, the bonding strength between the first nonwoven fabric and the second nonwoven fabric is excellent for the composite sheet, and the peeling between the first nonwoven fabric and the second nonwoven fabric can be suppressed in the case of repeated use, and the durability is excellent.

[0036] Therefore, the composite sheet has excellent durability while maintaining good texture on the skin.

[0037] [Method 2]

[0038] In the composite sheet according to aspect 1, the second nonwoven fabric is an elastic nonwoven fabric that is stretchable in the first direction.

[0039] Since the composite sheet expands and contracts in the first direction, the composite sheet can be used as a composite sheet for the waist portion of an absorbent article, for example, by arranging the composite sheet in parallel with the first direction and the waist direction of the wearer.

[0040] Since the first nonwoven fabric includes the first fiber layer having high flexibility, it easily shrinks in accordance with the shrinkage of the elastic nonwoven fabric (second nonwoven fabric).

[0041] Since the elastic nonwoven fabric contains a polypropylene resin, which is the same type of resin as the single fibers contained in the second fiber layer, on the surface on the side in contact with the second fiber layer, the elastic nonwoven fabric is well thermally bonded to 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 is excellent in shrinkage and durability.

[0043] [Method 3]

[0044] The composite sheet according to aspect 2 includes a third nonwoven fabric on the side of the second nonwoven fabric opposite to the side in contact with the first nonwoven fabric.

[0045] In the composite sheet, a third nonwoven fabric matching the purpose is provided on the side opposite to the side of the second nonwoven fabric in contact with the first nonwoven fabric, thereby further expanding the selection range of providing the first nonwoven fabric on the skin side or the non-skin side. Furthermore, for the composite sheet, the mechanical strength of the composite sheet is increased by adding the third nonwoven fabric, so the durability is more excellent. Therefore, the composite sheet is more suitable for use as a composite sheet for the waist part of an absorbent article.

[0046] [Method 4]

[0047] The composite sheet according to aspect 1 includes elastic yarns that stretch in the first direction between the first nonwoven fabric and the second nonwoven fabric.

[0048] Since the composite sheet expands and contracts in the first direction, the composite sheet can be used as a composite sheet for the waist portion of an absorbent article, for example, by arranging the composite sheet in parallel with the first direction and the waist of the wearer.

[0049] Since the first nonwoven fabric includes the first fiber layer having high flexibility, it is easy to shrink in accordance with the shrinkage of the elastic yarn.

[0050] In the composite sheet, the second nonwoven fabric is arranged on the side opposite to the first nonwoven fabric with the elastic yarn sandwiched therebetween, and the second nonwoven fabric is thermally bonded well to the second fiber layer. That is, the second fiber layer and the second nonwoven fabric are thermally bonded well with the elastic yarn sandwiched therebetween. 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 is excellent in shrinkage and durability.

[0052] [Method 5]

[0053] The composite sheet according to any one of aspects 1 to 4, wherein

[0054] The polypropylene-based resin comprises a propylene·α-olefin random copolymer,

[0055] The polyethylene-based resin includes an ethylene-based polymer.

[0056] The difference in melting point between the propylene·α-olefin random copolymer and the polyethylene resin is smaller than the difference in melting point between polypropylene and polyethylene resin, and therefore the propylene·α-olefin random copolymer is easier to thermally bond with the polyethylene resin than polypropylene. Therefore, the fibers of the first fiber layer are thermally bonded to each other in a wider range at the bonding portion. Therefore, in the composite sheet, the fibers of the first fiber layer arranged on the surface are thermally bonded to each other in a wider range, so that fuzzing is reduced, and thus the composite sheet can be used for a long time.

[0057] [Method 6]

[0058] The composite sheet according to Embodiment 5, wherein:

[0059] The melting point of the propylene / α-olefin random copolymer is 155° C. or lower, and the melting point of the ethylene-based polymer is 95° C. or higher and 125° C. or lower.

[0060] By setting the melting points of the propylene·α-olefin random copolymer and the ethylene-based polymer to be within the above 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] In the composite sheet according to any one of aspects 1 to 6, the ratio of the polypropylene-based resin portion to the polyethylene-based resin portion is 70:30 to 10:90 (polypropylene-based resin portion: polyethylene-based resin portion) on a mass basis.

[0063] The first fiber layer contains composite fibers including a predetermined amount or more of a polyethylene resin portion, i.e., a polyethylene resin, so that the polyethylene resin can be easily disposed on the surface of the first fiber layer. Since the first fiber layer is disposed on the surface side of the composite sheet, the composite sheet has an excellent skin feel.

[0064] [Method 8]

[0065] In the composite sheet according to any one of aspects 1 to 7, the polyethylene-based resin portion is present on the fiber surface of the composite fiber.

[0066] There is a polyethylene resin part on the fiber surface of the composite fiber. For example, the composite fiber is an eccentric core-sheath type or a parallel type in which the polypropylene resin part is used as the core part and the polyethylene resin part is used as the sheath part, and a part of the polypropylene resin part is exposed from the polyethylene resin part. Since there is a polyethylene resin part on the fiber surface of the composite fiber, the composite fiber is rich in softness derived from the polyethylene resin. For the composite sheet, since the first fiber layer is arranged on the surface side of the composite sheet, the skin touch is excellent.

[0067] [Method 9]

[0068] In the composite sheet according to any one of aspects 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) on a mass basis.

[0069] The first nonwoven fabric includes a second fiber layer composed of a polypropylene resin in an amount greater than or equal to a predetermined amount. The second fiber layer is disposed at a position in contact with the second nonwoven fabric, and thus is more reliably thermally bonded to the second nonwoven fabric. Therefore, in the composite sheet, the bonding strength between the first nonwoven fabric and the second nonwoven fabric is excellent.

[0070] [Method 10]

[0071] In the composite sheet according to any one of aspects 1 to 9, the polypropylene-based resin of the first fiber layer and the polypropylene-based resin of the second fiber layer are the same propylene / α-olefin random copolymer.

[0072] The difference in melting point between the propylene·α-olefin random copolymer and the polyethylene resin is smaller than the difference in melting point between polypropylene and polyethylene resin, and therefore the propylene·α-olefin random copolymer is easier to thermally bond with the polyethylene resin than polypropylene. Therefore, the fibers of the first fiber layer are thermally bonded to each other in a wider range at the bonding portion. Therefore, in the composite sheet, the fibers of the first fiber layer arranged on the surface are thermally bonded to each other in a wider range, so that fuzzing is reduced, and thus the composite sheet can be used for a long time.

[0073] Since the polypropylene resin of the first fiber layer and the second fiber layer is the same propylene·α-olefin random copolymer, the compatibility is excellent, and the first fiber layer and the second fiber layer are easy to be thermally bonded in a wider range. Therefore, in the composite sheet, the bonding strength between the first fiber layer and the second fiber layer is excellent.

[0074] [Method 11]

[0075] The composite sheet according to any one of aspects 1 to 10, wherein:

[0076] The composite sheet has a plurality of embossed bonding portions on the surface of the first fiber layer, wherein the embossed bonding portions bond the first fiber layer and the second fiber layer but do not bond the second nonwoven fabric.

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

[0078] In the first nonwoven fabric, the total area of ​​the plurality of joints is smaller than the total area of ​​the plurality of embossed joints, so it is easy to separate from the second nonwoven fabric between the plurality of joints and deform in the thickness direction. Since the first nonwoven fabric is easy to deform in the thickness direction between the joints, when the composite sheet has an elastic member (elastic nonwoven fabric or stretch yarn), the second nonwoven fabric is not hindered by the first nonwoven fabric and is easy to shrink. Therefore, the composite sheet is easy to deform along the waist of the wearer, so the skin touch is excellent.

[0079] <Overall structure>

[0080] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In addition, the drawings schematically show an example of the embodiment, and the present invention is not limited to the illustrated form. Figure 1 It is a top view of the composite sheet of the embodiment.

[0081] Figure 2A It is a cross-sectional view schematically showing the state of the composite sheet according to the embodiment during expansion. Figure 2B It is a cross-sectional view schematically showing a state of the composite sheet according to the embodiment during contraction. Figure 3A It is a cross-sectional view of fibers of the first nonwoven fabric and the second nonwoven fabric according to the embodiment. Figure 1 The composite sheet 10A shown in FIG. 1 has a first direction W, a second direction L and a thickness direction T (in the direction of FIG. 1 ) which are orthogonal to each other. Figure 1 (not shown in the figure). Figure 2A and Figure 2B As shown, the composite sheet 10A has a first nonwoven fabric 11 and a second nonwoven fabric 14 in the thickness direction T. When the composite sheet 10A is used as a composite sheet for the waist portion of an absorbent article, the configuration is as follows: the first nonwoven fabric 11 is configured on the skin side, the second nonwoven fabric 14 is configured on the non-skin side, and the first direction W is roughly parallel to the waist of the wearer.

[0082] like Figure 1 As shown, the composite sheet 10A further includes a plurality of joints 18 for thermally bonding the first nonwoven fabric 11 and the second nonwoven fabric 14. Thermal bonding uses heat or ultrasonic waves to heat the first nonwoven fabric 11 and the second nonwoven fabric 14 until the melting point of the thermoplastic resin is exceeded, thereby bonding the first nonwoven fabric 11 and the second nonwoven fabric 14 to each other.

[0083] The shape of the plurality of joints 18 is a shape that is concave in the thickness direction T when viewed in cross section, but the shape when viewed from above is not particularly limited, and may be, for example, linear or dotted. At least one of the surface side and the other surface side of the composite sheet 10A of the plurality of joints 18 is concave in the thickness direction. Figure 1The shapes of the multiple joining portions 18 shown in the top view are dot-shaped. The shape, size, and distance between the multiple joining portions 18 are not particularly limited, and can be appropriately selected according to the size and thickness of the composite sheet 10A. For example, the shape of each joining portion 18 observed from the thickness direction T may be a circle or a polygon such as a triangle or a rectangle. As for the size of the joining portion 18, for example, in the case of a circle, the diameter can be set to be greater than 0.1 mm and less than 5.0 mm, and in the case of a rectangle, the length of one side can be set to be greater than 0.1 mm and less than 5.0 mm. The distance between the joining portions 18 can be set to be greater than 1 mm and less than 5 mm. Multiple joining portions 18 adjacent to each other in the first direction W can be offset along the second direction L. The distance between the multiple joining portions 18 adjacent to each other in the first direction W in the second direction L is preferably greater than 2.0 mm, and more preferably greater than 3.7 mm. As Figure 1 As shown, the joining parts 18 may be arranged alternately along the first direction W and the second direction L, respectively.

[0084] The composite sheet 10A may further include a third nonwoven fabric 16. The third nonwoven fabric 16 is provided on the side of the second nonwoven fabric 14 opposite to the side in contact with the first nonwoven fabric 11. The third nonwoven fabric 16 may be integrally thermally bonded to the first nonwoven fabric 11 and the second nonwoven fabric 14 at the bonding portion 18.

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

[0086] The bending rigidity of the composite sheet 10A in the CD direction in the second direction L by the KES method is preferably 0.02 (N·m 2 / (m×10 -4 )) and above and 0.38(N·m 2 / (m×10 -4 )) or less, preferably 0.02 (N·m 2 / (m×10 -4 )) and above and 0.32(N·m 2 / (m×10 -4 )) or less, more preferably 0.02 (N·m 2 / (m×10 -4 )) and above and 0.20(N·m 2 / (m×10 -4 By setting the bending rigidity in the second direction L based on the KES method to 0.38 (N·m 2 / (m×10 -4 )) or less, so that the composite sheet 10A is soft and has excellent skin touch.

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

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

[0089] (No. 1 nonwoven fabric)

[0090] The first nonwoven fabric 11 forms a surface on the skin side of a wearer when the absorbent article using the composite sheet 10A is worn. The first nonwoven fabric 11 includes a first fiber layer 12 having a surface on the skin side 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 by a spunbond method, a carding method, a meltblown method, an air-laid method, etc., and can be joined to each other by embossing. In addition to the above-mentioned plurality of joining portions 18 on the surface, the first nonwoven fabric 11 also has a plurality of embossed joining portions (not shown) that are recessed in the thickness direction T formed by embossing. At least one of the one surface and the other surface of the first nonwoven fabric 11 is recessed in the thickness direction. Preferably, the surface of the first fiber layer 12 side of the first nonwoven fabric 11 is recessed in the thickness direction. Preferably, the total area of ​​the plurality of joining portions 18 when viewed from above the surface of the first nonwoven fabric 11 is smaller than the total area of ​​the embossed joining portions when viewed from above the surface of the first nonwoven fabric 11. The embossed joining portion joins the first fiber layer 12 and the second fiber layer 13, but does not join the second nonwoven fabric 14. That is, the embossed joining portion does not join the first nonwoven fabric 11 and the second nonwoven fabric 14. When the embossed bonding portion is recessed in the thickness direction on the surface of the first fiber layer 12 side, it is preferred that, in the first nonwoven fabric 11, on the surface of the first fiber layer 12, the total area of ​​the plurality of bonding portions 18 when viewed from above is smaller than the total area of ​​the embossed bonding portions when viewed from above.

[0092] Preferably, when the total of the first fiber layer 12 and the second fiber layer 13 is 100 parts by mass, 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) on a mass basis. By making the ratio of the first fiber layer 12 to the second fiber layer 13 within the above range, there is a tendency to have an excellent balance between strength and flexibility.

[0093] (1st fiber layer)

[0094] The first fiber layer 12 includes composite fibers. The composite fibers include a polypropylene resin portion containing a polypropylene resin (hereinafter referred to as a "PP resin portion") and a polyethylene resin portion containing a polyethylene resin (hereinafter referred to as a "PE resin portion") in cross section. The composite fibers may be, for example, Figure 3A The core-sheath type composite fiber with the PP resin portion as the core 20 and the PE resin portion as the sheath 22 can also be Figure 3B The composite fiber is 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 may also be a side-by-side composite fiber including a PP resin portion and a PE resin portion.

[0095] Preferably, when the total of the PP resin portion and the PE resin portion is set to 100 parts by mass, the ratio of the PP resin portion to the PE resin portion is 70:30 to 10:90 (PP resin portion: PE resin portion) on a mass basis. The 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 the known nuclear magnetic resonance (NMR) based on the ratio of the integrated intensity of the hydrogen nuclei and carbon nuclei derived from the polyethylene resin to the integrated intensity of the hydrogen nuclei and carbon nuclei derived from the polypropylene resin. The ratio of the PP resin portion to the PE resin portion in the composite fiber can also be measured based on 13 The C-NMR spectrum was obtained by conventional methods.

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

[0097] The thickness and weight per unit area of ​​the first fiber layer 12 are not particularly limited as long as they do not hinder the effect of the present invention, and any thickness and weight per unit area can be adopted according to the desired use. The thickness of the first fiber layer 12 is preferably 0.03 mm or more and 2.00 mm or less, and 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 / m 2 ) and above 20(g / m 2 ) or less, more preferably 4 (g / m 2 ) and above and 16(g / m 2 ) or less, more preferably 5 (g / m 2 ) and above and 12(g / m 2 )the following.

[0098] (PP resin part)

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

[0100] The α-olefin in the propylene·α-olefin random copolymer is not particularly limited, as long as it is an α-olefin other than propylene. As the α-olefin, for example, 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, 4-methyl-1-hexene, etc. can be cited. Among them, from the viewpoint of further improving flexibility, as the α-olefin, ethylene is preferred.

[0101] The content of the 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, particularly preferably 99% by mass or more and 100% by mass or less.

[0102] Specific preferred examples of the propylene·α-olefin random copolymer include propylene·1-butene random copolymer, propylene·ethylene random copolymer, propylene·ethylene·1-butene random copolymer, etc. From the viewpoint of achieving both flexibility and strength, a random copolymer of propylene and ethylene is more preferred.

[0103] From the viewpoint of further improving the strength, the PP resin portion may further contain a propylene homopolymer or a plurality of types of propylene / α-olefin random copolymers.

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

[0105] The content of structural units derived from propylene in all resin components contained in the PP resin part is preferably 90 mass % to 99.5 mass %, more preferably 93 mass % to 99 mass %, further preferably 95 mass % to 98 mass %.

[0106] Preferably, the melting point of the propylene·α-olefin random copolymer is 155° C. or less. When the PP resin portion contains only the propylene·α-olefin random copolymer as a resin component, preferably, the melting point of the propylene·α-olefin random copolymer is 125° C. or more and 155° C. or less. The “melting point” in this specification is the “peak top temperature” when the endothermic behavior of changing from a solid state to a liquid state at a temperature increase rate of 10° C. / min is measured in a differential scanning calorimeter.

[0107] The melt flow rate (MFR; measurement conditions: 230°C, load 2.16 kg) of the propylene·α-olefin random copolymer measured by the method in accordance with ASTM standard D-1238 is preferably 10 (g / 10 minutes) or more and 100 (g / 10 minutes) or more, and more preferably 15 (g / 10 minutes) or more and 80 (g / 10 minutes) 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 / m 3 ) and above 945(kg / m 3 The density of the PE resin part is preferably 910 (kg / m 3 ) and above 940(kg / m 3 ) or less, more preferably 915 (kg / m 3 ) and above 940(kg / m 3 ) or less, more preferably 920 (kg / m 3 ) and above 940(kg / m 3 ) or less. If the density is within the above range, there is a tendency to have both excellent flexibility and strength. The density of the PE resin portion can be adjusted by changing the density of the resin constituting the PE resin portion. The melting point of the ethylene polymer is about 95°C or more and 125°C or less.

[0110] The content of the structural unit derived from ethylene in the ethylene polymer is more than 50 mass %, preferably more than 70 mass % and below 99.8 mass %, more preferably more than 90 mass % and below 99 mass %.The content of other structural units in the ethylene polymer is more than 0 mass % and below 50 mass %, preferably more than 0.2 mass % and below 30 mass %, more preferably more than 1 mass % and below 10 mass %.If the content of the structural unit derived from ethylene in the ethylene polymer and / or other structural units is in the above-mentioned scope, then there is the excellent tendency of taking into account both intensity and flexibility.

[0111] As monomers constituting other structural units, α-olefins can be mentioned. The α-olefin is not particularly limited as long as it is other than ethylene, and examples thereof 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, 4-methyl-1-hexene, etc. Among them, from the viewpoint of taking both flexibility and strength into consideration, 1-butene and 4-methyl-1-pentene are preferred as α-olefins.

[0112] Preferably, the ethylene polymer comprises an ethylene α-olefin copolymer. In addition, the ethylene α-olefin copolymer is preferably at least one selected from the group consisting of an ethylene 1-butene copolymer and an ethylene 4-methyl-1-pentene copolymer. If the ethylene polymer is in the above-mentioned form, it has a tendency to have both excellent strength and flexibility.

[0113] The melt flow rate (MFR) (ASTM D-1238, 190°C 2.16 kg load) of the ethylene polymer is preferably 10 (g / 10 minutes) or more and 100 (g / 10 minutes) or less, more preferably 15 (g / 10 minutes) or more and 60 (g / 10 minutes) or less, and further preferably 20 (g / 10 minutes) or more and 60 (g / 10 minutes) or less. If the melt flow rate (MFR) of the ethylene polymer is within the above range, there is a tendency to have excellent compatibility between strength and flexibility.

[0114] The content of the ethylene polymer 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, 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. If the content of the ethylene polymer in the PE resin portion is within the above range, there is a tendency to achieve excellent compatibility between strength and flexibility.

[0115] (Hydrophilic Agent)

[0116] It is preferred that the first fiber layer 12 has a high degree of hydrophilicity. When the composite fiber constituting the first fiber layer 12 is of an eccentric core-sheath type or a side-by-side type, it is preferred that a hydrophilic agent is mixed in the PP resin portion. In the case of an eccentric core-sheath type, a portion of the core portion 20, which is the PP resin portion mixed with a hydrophilic agent, is exposed from the sheath portion 22, so that the first fiber layer 12 has hydrophilicity.

[0117] The hydrophilic agent can be further classified into a penetrant and a wetting agent. The second nonwoven fabric 14 may contain both the penetrant and the wetting agent, or may contain the wetting agent instead of the penetrant. From the viewpoint of excellent hydrophilicity, it is preferred that the hydrophilic agent contain both the penetrant and the wetting agent.

[0118] Preferably, the hydrophilic agent contains at least one of a sulfonate and a sulfate ester salt as a penetrant. Examples of sulfonates include alkylbenzene sulfonates, alkylnaphthalene sulfonates, α-olefin sulfonates, alkyl sulfosuccinates, and the like. These sulfonates are preferably alkali metal salts. Examples of sulfate ester salts include higher alcohol sulfate ester salts, alkyl sulfate ester salts, and the like. These sulfate ester salts are preferably alkali metal salts. It is preferred that the hydrophilic agent contains a sulfonate as a penetrant, and it is more preferred that the hydrophilic agent contains an alkali metal salt of sulfonic acid as a penetrant.

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

[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 further preferably 0.1% by mass or more and 0.5% by mass or less. As a method of incorporating the hydrophilic agent into the raw material resin of the core-sheath type composite fiber, for example, a method of adding the above-mentioned hydrophilic agent to the raw material resin of the core portion 20 and then spinning to form fibers can be cited.

[0121] (Second fiber layer)

[0122] The second fiber layer 13 includes single fibers made of a polypropylene resin. The average fiber diameter of the single fibers is preferably 10 μm to 30 μm, more preferably 11 μm to 25 μm, and further preferably 12 μm to 20 μm.

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

[0124] The thickness and unit area weight of the second fiber layer 13 are not particularly limited as long as they do not hinder the effect of the present invention, and any thickness and unit area weight can be adopted according to the desired use. The thickness of the second fiber layer 13 is preferably 0.03 mm to 2.00 mm, and more preferably 0.05 mm to 1.00 mm. The unit area weight of the second fiber layer 13 is preferably 3 (g / m 2 ) and above 20(g / m 2 ) or less, more preferably 4 (g / m 2 ) and above and 16(g / m 2 ) or less, more preferably 5 (g / m 2 ) and above and 12(g / m 2 )the following.

[0125] The polypropylene-based resin of the second fiber layer 13 may include the above-mentioned propylene·α-olefin random copolymer constituting the first fiber layer 12 .

[0126] (No. 2 nonwoven fabric)

[0127] When the absorbent article using the composite sheet 10A is worn, the second nonwoven fabric 14 is disposed on the non-skin side of the wearer with respect to the first nonwoven fabric 11. The second nonwoven fabric 14 of the present embodiment is an elastic nonwoven fabric that stretches in the first direction W.

[0128] The second nonwoven fabric 14 can be any nonwoven fabric such as hot air nonwoven fabric, spunbond nonwoven fabric, point bonded nonwoven fabric, spunlace nonwoven fabric, needle punched nonwoven fabric, meltblown nonwoven fabric, and a combination of these nonwoven fabrics (such as SMS, etc.). The second nonwoven fabric 14 can be exemplified by a nonwoven fabric having thermoplastic elastomer fibers exhibiting substantial elasticity and thermoplastic resin fibers exhibiting substantial inelasticity subjected to appropriate stretching treatment such as gear stretching treatment. That is, if the substantially inelastic thermoplastic resin fibers contained in the nonwoven fabric are plastically deformed or the joining points between the fibers are destroyed by the stretching treatment, the nonwoven fabric can be made into a structure that is not easily hindered from the substantial elastic expansion and contraction deformation of the thermoplastic elastomer fibers. In this way, the elasticity of the nonwoven fabric can be exhibited, and the nonwoven fabric can be used as an elastic nonwoven fabric.

[0129] In addition, as substantially elastic thermoplastic elastomers, there can be exemplified polyurethane elastomers, polystyrene elastomers, polyolefin elastomers, polyamide elastomers, etc. In addition, as substantially inelastic thermoplastic resin fibers, polypropylene resins such as polypropylene (PP) are included, and polyethylene (PE) may also be included.

[0130] The polypropylene resin contained in the substantially 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, and can be, for example, 10 (g / m 2 ) and above 80(g / m 2 ) or less. The elongation ratio of the second nonwoven fabric 14 is not particularly limited, and can be set to, for example, 1.5 times or more and 3.5 times or less. The elongation ratio is the ratio of the length of the second nonwoven fabric 14 after elongation to the length of the second nonwoven fabric 14 when it is not elongated being 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 hinder the effect of the present invention, and any thickness and weight per unit area can be adopted according to the desired use. The thickness of the second nonwoven fabric 14 is preferably 0.05 mm or more and 2.00 mm or less, and 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 / m 2 ) and above 80(g / m 2 ) or less, more preferably 12 (g / m 2 ) and above 70(g / m 2 ) or less, more preferably 14 (g / m 2 ) and above and 60(g / m 2 )the following.

[0132] (No. 3 nonwoven fabric)

[0133] When the absorbent article using the 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 nonwoven fabric such as hot air nonwoven fabric, spunbond nonwoven fabric, point bonded nonwoven fabric, spunlace nonwoven fabric, needle punched nonwoven fabric, meltblown nonwoven fabric, and a combination of these nonwoven fabrics (such as SMS, etc.). The thickness and unit area weight of the third nonwoven fabric 16 are not particularly limited as long as they do not hinder the effect of the present invention, and any thickness and unit area weight corresponding to the desired use can be adopted. The thickness of the third nonwoven fabric 16 is preferably not less than 0.05 mm and not more than 2.00 mm, and more preferably not less than 0.10 mm and not more than 1.50 mm. The unit area weight of the third nonwoven fabric 16 is, for example, preferably 8 (g / m 2 ) and above and 30(g / m 2 ) or less, more preferably 10 (g / m 2 ) and above and 25(g / m 2 ) or less, more preferably 12 (g / m 2 ) and above 20(g / m 2The third nonwoven fabric 16 may be the same as the first nonwoven fabric 11 or may be a nonwoven fabric different from the first nonwoven fabric 11.

[0134] <Manufacturing method>

[0135] When manufacturing the composite sheet 10A, first, the first nonwoven fabric 11, the second nonwoven fabric 14, and the third nonwoven fabric 16 are prepared. The first nonwoven fabric 11 is formed by overlapping the first fiber layer 12 and the second fiber layer 13 in the thickness direction T and bonding them by embossing. A plurality of embossed bonding portions that are recessed in the thickness direction T are formed on the surface of the first nonwoven fabric 11 by embossing.

[0136] Next, the first nonwoven fabric 11, the second nonwoven fabric 14, and the third nonwoven fabric 16 are sequentially overlapped in 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 is implemented. The first nonwoven fabric 11 is arranged in a manner that the second fiber layer 13 is in contact with 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 be performed using, for example, an ultrasonic horn and an anvil roller. The ultrasonic horn generates ultrasonic vibrations on the outer peripheral surface. The anvil roller has a plurality of protrusions protruding outward in the radial direction on the outer peripheral surface. 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 horn and the anvil roller along the MD direction (W direction) as the conveying direction, and are sandwiched between the protrusions of the anvil roller and the ultrasonic horn, thereby forming a plurality of joints 18. The joining portion 18 has a shape recessed in the thickness direction T by ultrasonic compression bonding. The composite sheet 10A is formed as described above. The composite sheet 10A has the embossed joining portion and the joining portion 18 on the surface of the first nonwoven fabric 11 . The composite sheet 10A has the joining portion 18 on the surface of the third nonwoven fabric 16 .

[0137] <Function and Effect>

[0138] Since the composite sheet 10A expands and contracts along the first direction W, Figure 4As shown, by configuring the first direction W in parallel with the waist DW of the wearer, the composite sheet 10A can be applied to a composite sheet for the waist portion of an absorbent article. For example, a disposable diaper 1 as an absorbent article has a crotch portion 2 covering the crotch of the wearer and a waist portion 3 covering the waist of the wearer. The waist portion 3 is formed by the composite sheet 10A. The composite sheet 10A is configured as follows: the first non-woven fabric 11 is configured on the skin side, the second non-woven fabric 14 is configured on the non-skin side, and the first direction W is parallel to the waist DW of the wearer. When the composite sheet 10A is applied to the waist portion of the disposable diaper 1, it stretches along the waist direction DW and is pulled up to be worn on the wearer. The composite sheet 10A shrinks to match the length of the waist DW of the wearer when the first non-woven fabric 11 is in contact with the skin of the wearer.

[0139] Since the composite sheet 10A includes composite fibers including a PP resin portion and a PE resin portion, the composite sheet 10A has a first fiber layer 12 having high softness derived from the polyethylene resin on its surface. Therefore, the composite sheet 10A has excellent touch to the skin.

[0140] Since the composite sheet 10A includes the second fiber layer 13 containing single fibers made of polypropylene resin, it is possible to suppress the reduction in mechanical strength caused by the first fiber layer 12 containing polyethylene resin. The composite sheet 10A has a breaking strength in the CD direction (L direction) of 14 (N / 50 mm) or more, and thus, when the composite sheet 10A is used as a composite sheet for the waist portion of an absorbent article, it is possible to suppress the composite sheet 10A from breaking due to the force of pulling up the absorbent article when worn.

[0141] The second fiber layer 13 is in contact with the second nonwoven fabric 14 and is bonded to the second nonwoven fabric 14 by thermal bonding. Since the second fiber layer 13 includes a single fiber made of a polypropylene resin, and the second nonwoven fabric 14 includes a polypropylene resin on the surface of the side in contact with the second fiber layer 13, a joint 18 where polypropylene resins are bonded to each other can be formed. Since the bonding parts 18 where polypropylene resins are bonded to each other have high compatibility and there is no polyethylene resin between the bonding parts 18, they are well thermally bonded. Since the first nonwoven fabric 11 and the second nonwoven fabric 14 have the bonding parts 18 where the polypropylene resins are bonded to each other, the bonding strength is excellent. The peel strength of the composite sheet 10A is 1.0 (N / 25mm) or more, and thus, when the composite sheet 10A is applied to a composite sheet for the waist portion of an absorbent article, the first nonwoven fabric 11 can be prevented from peeling off from the second nonwoven fabric 14 due to repeated use. The second fiber layer 13 contains 60% by mass or more of single fibers composed of a polypropylene-based resin, and thus can more reliably form the joining portion 18 in which no polyethylene-based resin exists.

[0142] The composite sheet 10A has a first direction W, a second direction L and a thickness direction T which are orthogonal to each other, and comprises a first nonwoven fabric 11 and a second nonwoven fabric 14 in sequence in the thickness direction T, and also comprises a plurality of joints 18 for thermally joining the first nonwoven fabric 11 and the second nonwoven fabric 14 to each other, wherein the first nonwoven fabric 11 comprises a first fiber layer 12 and a second fiber layer 13 arranged between the first fiber layer 12 and the second nonwoven fabric 14, wherein the first fiber layer 12 comprises composite fibers, and the composite fibers comprise a polypropylene resin portion containing a polypropylene resin and a polyethylene resin portion containing a polyethylene resin in a cross section, the second fiber layer 13 comprises a single fiber composed of a polypropylene resin, and the second nonwoven fabric 14 comprises a polypropylene resin on a surface on a side in contact with the second fiber layer 13.

[0143] The joint portion 18 integrates the first fiber layer 12, the second fiber layer 13, and the second nonwoven fabric 14 by thermal bonding. Since the first fiber layer 12 and the second fiber layer 13 contain the same type of polypropylene resin, they are compatible and well bonded. Since the second nonwoven fabric 14 contains the same type of resin as the single fiber contained in the second fiber layer 13, i.e., polypropylene resin, on the surface of the side in contact with the second fiber layer 13, it is easy to thermally bond with the second fiber layer 13. Since the second fiber layer 13 and the second nonwoven fabric 14 are well thermally bonded, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 14 is excellent for the composite sheet 10A, and the peeling between the first nonwoven fabric 11 and the second nonwoven fabric 14 can be suppressed in the case of repeated use, and the durability is excellent. Therefore, the composite sheet 10A has excellent durability while maintaining good skin touch.

[0144] Preferably, the second nonwoven fabric 14 is an elastic nonwoven fabric that can be stretched along the first direction W. Since the composite sheet 10A stretches along the first direction W, the composite sheet 10A can be applied to the waist portion of an absorbent article, for example, by arranging the first direction W in parallel with the waist of the wearer. Since the first nonwoven fabric 11 includes the first fiber layer 12, which is rich in softness, it is easy to shrink in accordance with the shrinkage of the second nonwoven fabric 14 (elastic nonwoven fabric). Since 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, i.e., a polypropylene resin, on the surface of the side in contact with the second fiber layer 13, it is well thermally bonded to the second fiber layer 13. Therefore, in the composite sheet 10A, the bonding strength between the first nonwoven fabric 11 and the second nonwoven fabric 14 (elastic nonwoven fabric) is excellent. As a result, the composite sheet 10A has 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 that matches the purpose on the opposite side of the second nonwoven fabric 14 that contacts the first nonwoven fabric 11, the selection range of providing the first nonwoven fabric 11 on the skin side or the non-skin side is further expanded. Furthermore, for the composite sheet 10A, by adding the third nonwoven fabric 16, the mechanical strength of the composite sheet 10A is increased, so the durability is more excellent. Therefore, the composite sheet 10A is more suitable for use as a composite sheet for the waist portion of an absorbent article.

[0146] Preferably, the polypropylene resin includes a propylene·α-olefin random copolymer, and the polyethylene resin includes an ethylene polymer. The difference in melting point between the propylene·α-olefin random copolymer and the polyethylene resin is smaller than the difference in melting point between the polypropylene and polyethylene resins, and therefore, the propylene·α-olefin random copolymer is easier to thermally bond with the polyethylene resin than the polypropylene. Therefore, the fibers of the first fiber layer 12 are thermally bonded to each other in a larger range at the embossed bonding portion and the bonding portion 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 in a larger range, the fuzzing is reduced, and thus it can be used for a long time.

[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 making the melting points of the propylene α-olefin random copolymer and the ethylene polymer respectively within the above ranges, the fibers of the first fiber layer 12 can be more reliably thermally bonded to each other over a wider range.

[0148] Preferably, when the total of the PP resin part and the PE resin part is set to 100 parts by mass, the ratio of the PP resin part to the PE resin part is 70:30 to 10:90 (polypropylene resin part: polyethylene resin part) on a mass basis. The first fiber layer 12 includes composite fibers, and the composite fibers include a predetermined amount or more of the polyethylene resin part, that is, the polyethylene resin, so that the polyethylene resin is easily arranged on the surface of the first fiber layer 12. Since the first fiber layer 12 is arranged on the surface side of the composite sheet 10A, the composite sheet 10A has an excellent skin touch.

[0149] Preferably, the polyethylene resin portion is present on the fiber surface of the composite fiber. For example, the composite fiber is an eccentric core-sheath type or a parallel type in which the polypropylene resin portion is used as the core 20 and the polyethylene resin portion is used as the sheath 22, and a part of the polypropylene resin portion is exposed from the polyethylene resin portion. Since the polyethylene resin portion is present on the fiber surface of the composite fiber, the composite fiber is rich in softness derived from the polyethylene resin. Since the first fiber layer 12 is arranged on the surface side of the composite sheet 10A, the composite sheet 10A has an excellent skin touch.

[0150] Preferably, when the total of the first fiber layer 12 and the second fiber layer 13 is set to 100 parts by mass, 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) on a mass basis. The first nonwoven fabric 11 includes a predetermined amount or more of the second fiber layer 13 composed of a polypropylene resin. Since the second fiber layer 13 is arranged 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 melting point of the propylene·α-olefin random copolymer is lower, and the difference between the melting point of the propylene·α-olefin random copolymer and the polyethylene resin is smaller, so it is easier to thermally 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 thermally bonded to each other in a larger range. Therefore, for the composite sheet 10A, by thermally bonding the fibers of the first fiber layer 12 arranged on the surface of the composite sheet 10A to each other in a larger range, the fuzz is reduced, so that it can be used for a long time. Since the polypropylene resins of the first fiber layer 12 and the second fiber layer 13 are the same propylene·α-olefin random copolymer, they have excellent compatibility and the first fiber layer 12 and the second fiber layer 13 are easy to thermally bond in a larger range. 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 a plurality of embossed joints on the surface of the first fiber layer 12, the embossed joints join the first fiber layer 12 and the second fiber layer 13, but do not join the second nonwoven fabric 14, and the total area of ​​the plurality of joints 18 on the surface of the first fiber layer 12 is smaller than the total area of ​​the plurality of embossed joints on the surface of the first fiber layer 12. For the first nonwoven fabric 11, since the total area of ​​the plurality of joints 18 is smaller than the total area of ​​the plurality of embossed joints, it is easy to separate from the second nonwoven fabric 14 between the plurality of joints 18 and deform in the thickness direction T. Since the first nonwoven fabric 11 is easy to deform in the thickness direction T between the joints 18, the second nonwoven fabric 14 is not hindered by the first nonwoven fabric 11 and is easy to shrink. Therefore, the composite sheet 10A is easy to deform along the waist of the wearer, so the skin touch is excellent.

[0153] <Modification>

[0154] The present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within the scope of the present invention. For example, in the above-mentioned embodiment, the case where the dot-shaped joints 18 are arranged in a grid shape is described, but the present invention is not limited to this. Figure 1 The same structures are marked with the same reference numerals. Figure 5 Arranged in a grid pattern as shown. Figure 5 The bonding portions 18 adjacent to each other in the first direction W are offset from each other by about 0.2 mm in the second direction L. Figure 5 The composite sheet 10B having the dot-shaped joints 18 shown can obtain the same effects as those of the above-described embodiment.

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

[0156] The composite sheet 10C includes elastic yarns 24 that expand and contract along the first direction W between the first nonwoven fabric 11 and the second nonwoven fabric 26. Since the composite sheet 10C expands and contracts along the first direction W, by arranging the first direction W in parallel with the waist of the wearer, the composite sheet 10C can be applied to, for example, a composite sheet for the waist portion of the absorbent article 1. Since the first nonwoven fabric 11 includes the first fiber layer 12 that is rich in softness, it is easy to shrink in accordance with the shrinkage of the elastic yarns 24. The second nonwoven fabric 26 is arranged on the opposite side of the first nonwoven fabric 11 with the elastic yarns 24 sandwiched therebetween, and the second nonwoven fabric 26 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 in a state where the elastic yarns 24 are sandwiched therebetween. 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, the composite sheet 10C is excellent in shrinkage and durability.

[0157] <Measurement method>

[0158] Hereinafter, a method for measuring each numerical value described in the above embodiment will be described.

[0159] (Weight per unit area)

[0160] First, the composite sheet without stretching has a total area of ​​500 (cm 2 ) to cut out one or more test pieces as samples. Next, the total weight of the sample is measured using a direct reading balance (for example, an electronic balance HF-300 manufactured by Kensei Kogyo Co., Ltd.). Finally, the weight per unit area (g / m2) of the sample calculated from the measured total weight and the total area of ​​the sample is used as the weight of the sample. 2 ) is taken as the weight per unit area of ​​the composite sheet.

[0161] The weight per unit area of ​​the first nonwoven fabric, the second nonwoven fabric, and the third nonwoven fabric was determined as follows. First, after being separated from the composite sheet, each nonwoven fabric was subjected to a pleat stretching operation with a total area of ​​500 (cm 2 ) to cut out one or more sample pieces in the above manner. 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 ), as the weight per unit area of ​​each material.

[0162] (thickness)

[0163] The thickness was measured using a thickness gauge FS-60DS (diameter of the presser foot: 50.5 mm, measurement pressure: 0.3 KPa) manufactured by Daiei Kagaku Seiki Mfg. Co., Ltd.

[0164] (Bending stiffness based on KES method)

[0165] The bending rigidity according to the KES method was measured using a large bending tester KES-FB2-L manufactured by Kado Technology Co., Ltd. The composite sheet was cut into a size of 40 mm in length in the first direction and 60 mm in length in the second direction to prepare a sample.

[0166] The measurement conditions are as follows.

[0167] SENS: 4

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

[0169] Mode: One cycle

[0170] Bending curvature: 0.5cm -1

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

[0172] (Breaking Strength)

[0173] The breaking strength was measured using a universal testing machine AG-1 manufactured by Shimadzu Corporation. First, a composite sheet in an extended state without wrinkles was cut into a size of 50 mm in length in the first direction and 70 mm in length in the second direction as a sample. Next, the distance between the chucks was set to 50 mm and the breaking strength in the second direction of the composite sheet was measured at a tensile speed of 500 (mm / min). "N / 50mm" refers to the breaking strength (N) per 50 mm width.

[0174] (Average fiber diameter)

[0175] First, separate the first nonwoven fabric and the second nonwoven fabric from the composite sheet, cut out and prepare 10 mm × 10 mm samples of each nonwoven fabric, and place them on a glass slide. Next, drip an appropriate amount of glycerin onto each sample so that the entire sample is impregnated with glycerin, and place a cover glass on it. Next, use a known optical microscope (e.g., VHC-100 digital microscope VH-Z450 manufactured by Keyence Corporation) to observe the sample at a magnification of 1000 times, measure the fiber diameter of 50 fibers exposed on the surface of the sample, and take the average value as the average fiber diameter.

[0176] (Peel Strength)

[0177] (1) A portion including the joined portion (including the first nonwoven fabric and the second nonwoven fabric) of the composite sheet was cut out to a size of 70 mm in the stretching direction x 25 mm in the non-stretching direction to prepare a sample.

[0178] (2) Using a tester for peeling test, the first nonwoven fabric and the second nonwoven fabric of the cut sample are peeled off 20 mm in advance along the stretching direction L, and the end of the first nonwoven fabric and the end of the second nonwoven fabric are respectively held by two chucks provided in the tester. The distance between the chucks during holding (initial value) is preset to 30 mm.

[0179] (3) The two chucks are pulled at a constant speed (for example, 50 mm / min) using a tester so that the gap between the two chucks is enlarged, and the first nonwoven fabric and the second nonwoven fabric at the joint are peeled off in the 180° direction, while measuring the gap between the two chucks and the load F applied to the two chucks.

[0180] (4) The peel strength of the bonded portion 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 defined as the peel strength (N / 25 mm).

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

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

[0183] Example

[0184] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0185] (A) Sample

[0186] A composite sheet having a first nonwoven fabric, an elastic nonwoven fabric as a second nonwoven fabric, and a third nonwoven fabric is prepared. The first nonwoven fabric is formed by a spunbond method to form a first fiber layer composed of eccentric core-sheath type composite fibers and a second fiber layer composed of single fibers, respectively, and integrated by embossing. As a polypropylene resin, a propylene·α-olefin random copolymer (α-olefin: ethylene) is used, and as a polyethylene resin, an ethylene·α-olefin copolymer (α-olefin: 1-butene) is used. The elastic nonwoven fabric is a spunbond nonwoven fabric containing polyurethane and polypropylene, and a common material is used in all samples. The third nonwoven fabric is a spunbond nonwoven fabric having an eccentric core-sheath type composite fiber layer and a single fiber layer. The detailed structure of each nonwoven fabric is 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 parts by mass, the ratio of the first fiber layer to the second fiber layer is 67:33 in Examples 1 to 3 and is 33:67 in Examples 4 to 6.

[0187] The first nonwoven fabric, the elastic nonwoven fabric and the third nonwoven fabric were overlapped in the thickness direction and thermally bonded by ultrasonic wave. The thermal bonding by ultrasonic wave was performed using equipment manufactured by Herrmann Ultrasonics. The ultrasonic horn was set to: 161 mm in width × 2, frequency 20 KHz, and pressure 500 N. The speed of the anvil roll was set to 200 (m / min), the unwinding speed of the elastic nonwoven fabric was set to 80 (m / min), and the unwinding speed of the first nonwoven fabric and the third nonwoven fabric was set to 199 (m / min).

[0188] As reference examples, a composite sheet comprising a first nonwoven fabric being a spunbond nonwoven fabric composed of a single fiber, the above-mentioned elastic nonwoven fabric and a third nonwoven fabric being a spunbond nonwoven fabric composed of a single fiber (reference example 1), and a composite sheet comprising a first nonwoven fabric being a spunbond nonwoven fabric composed of eccentric core-sheath type composite fibers, the above-mentioned elastic nonwoven fabric and a third nonwoven fabric being a spunbond nonwoven fabric composed of eccentric core-sheath type composite fibers (reference examples 2 and 3) are prepared, and thermal bonding is performed using ultrasound under the same conditions as in the above-mentioned embodiment to obtain a composite sheet.

[0189] (B) Results

[0190] The composite sheets of the examples and reference examples were measured for the breaking strength in the CD direction, the bonding strength, and the bending rigidity in the CD direction. As shown in Table 1, in Examples 1 to 6, since the first fiber layer includes composite fibers containing a PP resin portion and a PE resin portion, the bending rigidity is 0.31 (N·m 2 / (m×10 -4 )) or less, because it has a second fiber layer containing single fibers formed of a polypropylene resin, the breaking strength is 17.39 (N / 50mm) or more. Furthermore, because the second fiber layer is thermally bonded to the elastic nonwoven fabric, a breaking strength of 1.47 (N / mm) or more is obtained.

[0191] In contrast, in Reference Example 1, since the first nonwoven fabric is composed of a single fiber of polypropylene, the breaking strength and the bonding strength in the CD direction are high, but the bending rigidity in the CD direction is also high. In Reference Examples 2 and 3, since the elastic nonwoven fabric and the first nonwoven fabric composed of composite fibers including a PP resin portion and a PE resin portion are thermally bonded, the bonding strength is low.

[0192] [Table 1]

[0193]

[0194] Description of Reference Numerals

[0195] 1. Absorbent article; 2. Crotch; 3. Waist; 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 an absorbent article having a first direction, a second direction and a thickness direction which are orthogonal to each other, wherein: The composite sheet includes a first nonwoven fabric and a second nonwoven fabric in this order in the thickness direction. The composite sheet further comprises a plurality of joining portions for thermally joining the first nonwoven fabric and the second nonwoven fabric to each other. The first nonwoven fabric comprises a first fiber layer and a second fiber layer disposed between the first fiber layer and the second nonwoven fabric. The first fiber layer includes composite fibers, wherein the composite fibers include a polypropylene resin portion containing a polypropylene resin and a polyethylene resin portion containing a polyethylene resin in a cross section. The second fiber layer includes single fibers made of polypropylene resin. The second nonwoven fabric contains a polypropylene-based resin on a surface of the side in contact with the second fiber layer.

2. The composite sheet according to claim 1, wherein: The second nonwoven fabric is an elastic nonwoven fabric that is stretchable in the first direction.

3. The composite sheet according to claim 2, wherein: The composite sheet includes a third nonwoven fabric on the side of the second nonwoven fabric opposite to the side in contact with 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 any one of claims 1 to 4, wherein The polypropylene-based resin comprises a propylene·α-olefin random copolymer, The polyethylene-based resin includes an ethylene-based polymer.

6. The composite sheet according to claim 5, wherein: The melting point of the propylene / α-olefin random copolymer is 155° C. or lower, and the melting point of the ethylene-based polymer is 95° C. or higher and 125° C. or lower.

7. The composite sheet according to any one of claims 1 to 6, wherein The ratio of the polypropylene resin portion to the polyethylene resin portion, that is, the polypropylene resin portion: the polyethylene resin portion, is 70:30 to 10:90 on a mass basis.

8. The composite sheet according to any one of claims 1 to 7, wherein The polyethylene-based resin portion exists on the fiber surface of the conjugate fiber.

9. The composite sheet according to any one of claims 1 to 8, wherein The ratio of the first fiber layer to the second fiber layer, that is, the first fiber layer: the second fiber layer, is 33:67 to 67:33 based on mass.

10. The composite sheet according to any one of claims 1 to 9, wherein The polypropylene-based resin of the first fiber layer and the polypropylene-based resin of the second fiber layer are the same propylene·α-olefin random copolymer.

11. The composite sheet according to any one of claims 1 to 10, wherein The composite sheet has a plurality of embossed bonding portions on the surface of the first fiber layer, and the embossed bonding portions bond the first fiber layer and the second fiber layer but do not bond the second nonwoven fabric. The total area of ​​the plurality of joining parts on the surface of the first fiber layer is smaller than the total area of ​​the plurality of embossed joining parts on the surface of the first fiber layer.

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