Nonwoven fabric and absorbent article

Abstract

To provide a nonwoven fabric for an absorbent article, which achieves soft touch and a high thickness recovering property.SOLUTION: A nonwoven fabric for an absorbent article has a film-forming polymer having siloxane skeleton on a surface of a fiber and uneven structure. An elastic modulus at 25°C of the film-forming polymer is 104 Pa or more and 109 Pa or less. The nonwoven fabric for the absorbent article has a plurality of fused bonding points at which fibers constituting the nonwoven fabric are fused and bonded to each other. A ratio of the siloxane skeleton in the film-forming polymer is preferably 40 mass% or more and 98 mass% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric suitable for use in an absorbent article, and to the absorbent article. [Background technology]

[0002] When absorbent articles such as sanitary napkins and diapers are shipped as products, a plurality of such products are generally packed so as to be compressed in the thickness direction. When such packing is performed, the bulk of the nonwoven fabric constituting the product is crushed, which may cause a problem that the texture of the nonwoven fabric is damaged when the product is used. As a technique for solving such a problem, it has been proposed to improve the thickness recovery of the nonwoven fabric after compression by blending a highly elastic resin binder into the nonwoven fabric.

[0003] For example, Patent Document 1 proposes a nonwoven fabric having fusion points between fibers and a binder present at the fiber intersections. It is described that the nonwoven fabric described in this document has high thickness recovery after compression due to the presence of the binder at the fiber intersections. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-166596 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a resin binder is blended into a nonwoven fabric, the nonwoven fabric may have roughness and stickiness due to the binder, which may deteriorate the feel of the nonwoven fabric against the skin. Therefore, there is a demand for a nonwoven fabric for absorbent articles that has high thickness recovery property and an improved feel against the skin.

[0006] Therefore, an object of the present invention is to provide a nonwoven fabric for absorbent articles which has both a smooth feel and high thickness recovery property. [Means for solving the problem]

[0007] The present invention relates to a nonwoven fabric for absorbent articles having a concave-convex structure and a film-forming polymer having a siloxane skeleton on the fiber surface. In one embodiment, the film-forming polymer has a modulus of elasticity of 10 at 25° C. 4 Pa or more 10 9 It is preferable that the pressure is 0.1 Pa or less. In one embodiment, the nonwoven fabric for absorbent articles preferably has a plurality of fusion points at which fibers constituting the nonwoven fabric are fused to each other. Effect of the Invention

[0008] According to the present invention, there is provided a nonwoven fabric which is smooth to the touch and has excellent thickness recovery properties. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating a nonwoven fabric according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view illustrating a nonwoven fabric according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a perspective view illustrating a nonwoven fabric according to another embodiment of the present invention. [Figure 4] 4(a) and 4(b) are perspective views that typically show other embodiments of the nonwoven fabric of the present invention. [Diagram 5] FIG. 5 is a perspective view that typically illustrates another embodiment of the nonwoven fabric of the present invention. [Figure 6] FIG. 6 is a perspective view that typically illustrates a nonwoven fabric according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will now be described based on preferred embodiments with reference to the drawings. The nonwoven fabric for absorbent articles of the present invention (hereinafter also referred to as "nonwoven fabric of the present invention") is a sheet-like material having a film-forming polymer on the surface of the fibers. Film-forming ability is the property of penetrating into a nonwoven fabric and covering the surface of the fibers constituting the nonwoven fabric in the form of a film. The present inventors have found that when a film-forming polymer forms a film on the surface of the fibers constituting the nonwoven fabric, the film has excellent elasticity, and therefore the thickness recovery of the nonwoven fabric is improved.

[0011] The film-forming polymer has a siloxane skeleton. The siloxane skeleton is a structure consisting of -O-Si-O-Si- bonds, and typically includes silicone. Since the polymer having a siloxane skeleton has a smooth texture, the nonwoven fabric of the present invention has a film-forming polymer on the surface of the fiber, so that the nonwoven fabric has a smoother texture. In addition, since the polymer having a siloxane skeleton is less sticky, the fibers are less likely to adhere to each other when the nonwoven fabric of the present invention is crushed, compared to the case where a conventional binder resin is used, and the thickness recovery of the nonwoven fabric is improved.

[0012] From the viewpoint of further enhancing the above-mentioned effects of the film-forming polymer, the ratio of the siloxane skeleton in the film-forming polymer is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 98% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less. The ratio of the siloxane skeleton in the film-forming polymer is the ratio of the total mass of the oxygen atoms and silicon atoms constituting the siloxane skeleton of the film-forming polymer, and the hydrogen atoms and carbon atoms constituting the hydrocarbon groups directly bonded to the oxygen atoms and silicon atoms, to the total mass of the atoms constituting the film-forming polymer. The ratio of the siloxane skeleton in the film-forming polymer can be determined, for example, by dissolving the film-forming polymer in deuterated chloroform and measuring the molecular weight using a nuclear magnetic resonance apparatus "Mercury 400" (manufactured by Varian). 1 It can be calculated by measuring the H-NMR spectrum.

[0013] From the viewpoint of achieving a balanced improvement in the feel and thickness recovery of the nonwoven fabric, the content of the film-forming polymer is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.5% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, relative to the mass of the nonwoven fabric to which the polymer is adhered. The amount of the film-forming polymer attached is the mass of the nonwoven fabric to which the polymer is attached minus the mass of the nonwoven fabric from which the polymer has been removed. The content of the film-forming polymer can be determined by calculating the ratio (mass %) of the amount of the polymer attached to the mass of the nonwoven fabric to which the polymer is attached.

[0014] In order to further improve the thickness recovery of the nonwoven fabric, the elastic modulus of the film-forming polymer at 25° C. is preferably 10 4 Pa or more, preferably 5×10 4 Pa or more, more preferably 10 5 From the viewpoint of maintaining the flexibility of the nonwoven fabric, the elastic modulus of the film-forming polymer at 25° C. is preferably 10 9 Pa or less, more preferably 5×10 8 Pa or less, more preferably 10 8 Pa or less. The elastic modulus of the film-forming polymer is measured at 25° C. using a viscoelasticity measuring device (RSA-G2: manufactured by TA instruments) for a polymer film obtained by casting the polymer solution in a petri dish and drying it.

[0015] The film-forming polymer preferably has an association site. The association site is an atom or atomic group that generates an attractive force between film-forming polymer molecules and promotes intermolecular association. When the film-forming polymer has an association site, the elastic modulus and film-forming property of the polymer are improved. Examples of such association sites include polar functional groups such as carbonyl groups and ionized sites such as ammonium. The film-forming polymer may have an association site in the main backbone or side chain of the film-forming polymer, but it is preferable to have the association site in the side chain from the viewpoint of improving the touch and thickness recovery of the nonwoven fabric in a well-balanced manner.

[0016] An example of a film-forming polymer having an association site is a silicone graft copolymer. The silicone graft copolymer may have a siloxane skeleton in the main skeleton (base material) or in the side chain (graft chain). When the main skeleton has a siloxane skeleton, the side chain contains at least one copolymer component selected from N-acylalkyleneimine, acrylic acid, salts of acrylic acid, acrylic acid esters, acrylamide, methacrylic acid, salts of methacrylic acid, methacrylic acid esters, and methacrylamides, and when the side chain has a siloxane skeleton, the main skeleton can contain the copolymer component.

[0017] An example of a silicone graft copolymer is poly(N-acylalkyleneimine)-modified silicone. Poly(N-acylalkyleneimine)-modified silicone is a silicone having one or more side chains represented by the following general formula (I). The side chains have cationic nitrogen atoms in addition to carbonyl groups, and therefore can increase the elastic modulus and film-forming properties of the film-forming polymer.

[0018] [ka]

[0019] In general formula (I), R 1 and R 2each independently represents a hydrogen atom, a saturated hydrocarbon group having from 1 to 5 carbon atoms, or an unsaturated hydrocarbon group having from 2 to 5 carbon atoms, A - represents a counter ion, l represents an integer between 0 and 5, m represents an integer of 1 to 5, n represents an integer between 1 and 1000, * represents a bond to a silicon atom constituting the siloxane skeleton.

[0020] In general formula (I), R 1 and R 2 Examples of the saturated hydrocarbon group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, a pentyl group, an isopentyl group, a neopentyl group, and a t-pentyl group.

[0021] In general formula (I), R 1 and R 2 Examples of the unsaturated hydrocarbon group having 2 to 5 carbon atoms, represented by the formula (1), include unsaturated hydrocarbon groups obtained by removing 2 or 4 hydrogen atoms from the above-mentioned examples of alkyl groups having 2 to 5 carbon atoms. Examples of such unsaturated hydrocarbon groups include vinyl groups, ethynyl groups, allyl groups, methallyl groups, 1-propenyl groups, prenyl groups, propargyl groups, and 2,4-pentadienyl groups.

[0022] In terms of the elastic modulus of the film-forming polymer, R 1 and R 2 are each independently preferably a saturated hydrocarbon group having 1 to 5 carbon atoms, more preferably a saturated hydrocarbon group having 1 to 3 carbon atoms, and even more preferably an ethyl group.

[0023] From the viewpoint of the elastic modulus of the film-forming polymer, in the general formula (I), A -Examples of the counter ion represented by the formula (I) include alkyl sulfate having 1 to 5 carbon atoms, chloride ion, iodide ion, sulfate ion, p-toluenesulfonate ion, and perchlorate ion. - is preferably an alkyl sulfate having from 1 to 5 carbon atoms, more preferably an alkyl sulfate having from 1 to 3 carbon atoms, and even more preferably ethyl sulfate.

[0024] From the viewpoint of the elastic modulus of the film-forming polymer, in general formula (I), 1 is preferably 1 or more and 4 or less, more preferably 2 or more and 4 or less, and even more preferably 3.

[0025] From the viewpoint of the elastic modulus of the film-forming polymer, in general formula (I), m is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and even more preferably 2. In this specification, the side chain represented by general formula (I) in which m is 2 is also referred to as a "polyoxazoline structure".

[0026] From the viewpoint of the elastic modulus of the film-forming polymer, n in formula (I) is preferably 1 or more and 500 or less, more preferably 2 or more and 300 or less, and even more preferably 3 or more and 100 or less. The weight average molecular weight of the side chain represented by general formula (I) is preferably 800 or more, more preferably 900 to 1000, and even more preferably 1000 to 5200. The weight average molecular weight of the side chain can be determined as a standard polystyrene equivalent value by, for example, gel permeation chromatography (GPC) (DP-8020) manufactured by Tosoh Corporation after hydrolyzing the film-forming polymer and removing the siloxane skeleton portion of the main chain from the side chain.

[0027] From the viewpoint of the elastic modulus of the film-forming polymer, the weight average molecular weight of the film-forming polymer is preferably 5,000 or more, more preferably 10,000 or more, even more preferably 20,000 or more, and preferably 500,000 or less, more preferably 300,000 or less, even more preferably 200,000 or less.

[0028] Another example of the silicone graft copolymer is a copolymer having acrylic acid or methacrylic acid in the main skeleton and a siloxane skeleton in the side chain (hereinafter referred to as "copolymer P"). Copolymer P is a copolymer containing, as constituent units, unit A represented by the following general formula (II), unit B represented by the following general formula (III), unit C represented by the following general formula (IV), and unit D represented by the following general formula (V). Copolymer P has a polyacrylate structure having multiple carbonyl groups in its main skeleton, and therefore has a high elastic modulus and film-forming properties. The copolymer P may be a block polymer or a random polymer.

[0029] [ka]

[0030] In the general formulas (II) to (V), R 3 is a hydrogen atom or a methyl group, and a plurality of R 3 may be the same as or different from each other.

[0031] In general formula (II), R 4 is a saturated hydrocarbon group having 5 to 10 carbon atoms, which may be linear or branched. Examples of such saturated hydrocarbon groups include a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a methylpentyl group, an ethylhexyl group, and an ethylheptyl group. R 4 is preferably a saturated hydrocarbon group having 6 to 9 carbon atoms, and more preferably an ethylhexyl group.

[0032] In general formula (III), R 5 is a saturated hydrocarbon group having 3 to 5 carbon atoms, which may be linear or branched. Examples of such saturated hydrocarbon groups include R 1 and R2 Among the examples of the saturated hydrocarbon group having 1 to 5 carbon atoms represented by the following formula, those having 3 to 5 carbon atoms can be mentioned. R 5 is preferably a saturated hydrocarbon group having 3 to 4 carbon atoms, more preferably a saturated hydrocarbon group having 4 carbon atoms, and even more preferably a butyl group.

[0033] In general formula (IV), R 6 is a methyl group or an ethyl group. R 6 is preferably a methyl group.

[0034] In formula (V), e represents an integer of 1 or more and 10 or less. e is preferably an integer of 2 or more and 8 or less, and more preferably an integer of 3 or more and 5 or less. In general formula (V), * represents a bond to a silicon atom constituting a siloxane skeleton represented by the following general formula (VI). [ka]

[0035] In formula (VI), * represents a bond. In formula (VI), n represents an integer of 50 or more and 62 or less. n is preferably 52 or more and 60 or less, more preferably 54 or more and 58 or less, and further preferably 56.

[0036] When the relative molar ratio (A:B:C:D) of the units A, B, C and D contained in the copolymer P is a:b:c:d and a+b+c+d=100, a+b is preferably 15 or more and 35 or less, more preferably 18 or more and 32 or less, even more preferably 20 or more and 28 or less, and particularly preferably 25. Furthermore, c is preferably 50 or more and 90 or less, more preferably 60 or more and 80 or less, further preferably 65 or more and 75 or less, and particularly preferably 70. Furthermore, d is preferably 1 or more and 10 or less, more preferably 2 or more and 9 or less, further preferably 3 or more and 8 or less, and particularly preferably 5. By setting the relative molar ratios a to d within the above-mentioned ranges, it becomes easier to control the elastic modulus of the film-forming polymer to a preferred value.

[0037] Copolymer P may contain structural units other than units A, B, C and D. However, from the viewpoint of appropriately controlling the elastic modulus of the film-forming polymer, it is preferable that copolymer P does not contain structural units other than units A, B, C and D. The weight average molecular weight of the copolymer P is preferably 5,000 or more, more preferably 10,000 to 100,000, and even more preferably 20,000 to 70,000. The weight average molecular weight can be determined, for example, by gel permeation chromatography (GPC) (DP-8020) manufactured by Tosoh Corporation, in terms of standard polystyrene.

[0038] As the film-forming polymer, those having a polyacrylate structure or a polyoxazoline structure can be particularly preferably used.

[0039] The silicone graft copolymer has a soft segment made of a siloxane skeleton and a hard segment made of a copolymerization component. The soft segment is a flexible portion that exhibits rubber elasticity, and the hard segment is a molecular restraint portion that acts as a crosslinking point that prevents plastic deformation. A silicone graft copolymer that has both portions is an elastomer that has both hardness and flexibility. By including such an elastomer in the nonwoven fabric, the thickness recovery of the nonwoven fabric can be effectively improved without impairing the cushioning properties of the nonwoven fabric. From this viewpoint, it is preferable to use a silicone graft copolymer as the film-forming polymer.

[0040] The fibers constituting the nonwoven fabric of the present invention maintain the form of a fiber sheet by fusion. Specifically, from the viewpoint of further improving the texture and breathability, the nonwoven fabric of the present invention has a plurality of fusion points where the fibers constituting the nonwoven fabric are fused to each other. Fusion refers to a state in which a plurality of fibers are melted by applying heat alone or heat and pressure to the fibers, making the boundaries between the fibers unclear. Examples of the nonwoven fabric of the present invention include air-through nonwoven fabrics, spunbond nonwoven fabrics, and meltblown nonwoven fabrics. Among the above-mentioned various nonwoven fabrics, air-through nonwoven fabrics are particularly suitable for use in absorbent articles because of their good texture due to their manufacturing method.

[0041] The fusion points between fibers are the sites from which distortion begins when the nonwoven fabric is compressed. Therefore, by increasing the elasticity of the fusion points, the thickness recovery of the nonwoven fabric can be effectively improved. From this viewpoint, it is preferable that at least a part of the fusion points between the fibers constituting the nonwoven fabric of the present invention is covered with a film-forming polymer. However, from the viewpoint of maximizing the thickness recovery of the nonwoven fabric by the film-forming polymer, it is more preferable that the film-forming polymer is also present in sites other than the fusion points between the fibers of the nonwoven fabric.

[0042] The fibers to which the film-forming polymer is applied may be present only in the interior of the nonwoven fabric in the thickness direction, or may be present only on the surface of the nonwoven fabric.Furthermore, the fibers to which the film-forming polymer is applied may be present both inside and on the surface of the nonwoven fabric.In contrast to the binder resins used in the past, the film-forming polymers having a siloxane skeleton have a good texture, so that even if the fibers to which the polymer is applied are present on the surface of the nonwoven fabric, i.e., on the surface that directly contacts the skin of the user, the smooth texture of the nonwoven fabric is not impaired. The fibers to which the film-forming polymer is applied may be present at any position in the planar direction of the nonwoven fabric.

[0043] There is no limitation on the method of applying the film-forming polymer to the fibers constituting the nonwoven fabric, and any conventional method can be used.For example, the film-forming polymer may be applied to the fibers before they are made into a nonwoven fabric, and then the fibers are made into a nonwoven fabric, or the film-forming polymer may be applied after the nonwoven fabric is formed.As a method of applying the film-forming polymer after the nonwoven fabric is formed, for example, a method of applying the film-forming polymer by spraying it onto one side of the nonwoven fabric using a spray or the like can be mentioned.

[0044] The type of fiber constituting the nonwoven fabric is not particularly limited, and fibers made of various thermoplastic resins having fiber forming ability can be used. Specifically, fibers made of polyolefin resins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers, fibers made of polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate, and fibers made of polyacrylic resins such as polyacrylic acid and polymethacrylic acid can be used. As the constituent fibers of the nonwoven fabric, multi-component fibers such as core-sheath type composite fibers and side-by-side type composite fibers containing the above-mentioned resins can also be used. The above fibers can be used alone or in combination of two or more. In particular, nonwoven fabrics containing core-sheath type composite fibers have a good texture and are therefore particularly suitable as constituent materials for absorbent articles. When using core-sheath type composite fibers as the constituent fibers of the nonwoven fabric, it is preferable that the core is made of PET. Core-sheath type composite fibers having a core made of PET have high elasticity and can improve the thickness recovery of the nonwoven fabric. From the viewpoint of further improving the feel of the nonwoven fabric, the sheath is preferably made of polyethylene.

[0045] From the viewpoint of the feel and thickness recovery of the nonwoven fabric, the fiber diameter of the constituent fibers of the nonwoven fabric is preferably 10 μm or more, more preferably 12 μm or more, even more preferably 14 μm or more, and preferably 30 μm or less, more preferably 25 μm or less, even more preferably 20 μm or less.

[0046] From the viewpoint of making the thickness suitable for use in absorbent articles, the thickness of the nonwoven fabric of the present invention is preferably 0.5 mm or more, more preferably 0.8 mm or more, even more preferably 1.0 mm or more, and preferably 3 mm or less, more preferably 2.8 mm or less, even more preferably 2.5 mm or less. The thickness of the nonwoven fabric is measured as follows. First, only a 12.5 g (diameter 55 mm) plate is placed on a laser displacement meter (LK-080: manufactured by Keyence Corporation) and the measured thickness is set to zero for zero point adjustment. Then, the plate is placed on the measurement sample and a pressure of 4.9 mN / cm is applied. 2 The thickness under the load is measured using a laser displacement meter, and this is taken as the thickness B (cm) of the measured sample.

[0047] The nonwoven fabric may be of a single layer structure or of a laminated structure of two or more layers. When the nonwoven fabric is of a laminated structure of two or more layers, the nonwoven fabric may have a low-density layer having a relatively low density and a high-density layer having a relatively high density along the thickness direction. In this case, from the viewpoint of increasing the thickness recovery of the nonwoven fabric, it is preferable that the film-forming polymer is present at least in the low-density layer.

[0048] The surface of the nonwoven fabric may be flat, may have an uneven shape, or may be raised, but from the viewpoint of making the nonwoven fabric smooth to the touch, it is preferable that the surface be uneven. Figures 1 to 6 show schematic diagrams of nonwoven fabrics having an uneven shape on at least one surface.

[0049] 1 has a first surface 10A and a second surface 10B located on the opposite side, and at least the first surface 10A has an uneven structure having a plurality of protrusions 13 protruding toward the first surface 10A and recesses 14 located between the protrusions 13. The second surface 10B is substantially flat. The nonwoven fabric 10 is composed of two layers, an upper layer 11A on the first surface 10A side and a lower layer 11B on the second surface 10B side. The upper layer 11A and the lower layer 11B are joined by embossing in the thickness direction. The embossed portions correspond to the recesses 14. The lower layer 11B is a layer in which the heat shrinkage of the heat shrinkable fiber is manifested. The upper layer 11A is a layer containing a non-heat shrinkable fiber. From the viewpoint of successfully forming a nonwoven fabric by applying heat, it is preferable that the non-heat shrinkable fiber is a non-heat shrinkable heat fusion fiber. Nonwoven fabric 10 can be manufactured using the materials and method described in, for example, JP 2002-187228 A. In this manufacturing method, for example, a laminate of upper layer 11A and lower layer 11B is embossed from the upper layer 11A side, and then heat is applied to heat-shrink the heat-shrinkable fibers contained in lower layer 11B. The shrinkage of the fibers causes deformation in which adjacent embossed sections are pulled together and the distance between them is reduced. This deformation causes the fibers contained in upper layer 11A to rise toward first surface 10A from the embossed sections as base points, forming protrusions 13. Therefore, lower layer 11B becomes a high-density layer, and upper layer 11A becomes a low-density layer with a lower density than lower layer 11B.

[0050] The nonwoven fabric 20 shown in FIG. 2 has a two-layer structure having a hollow portion 21. Both of the two layers constituting the nonwoven fabric 20 contain thermoplastic fibers. The nonwoven fabric 20 has a joint portion 22 where a first nonwoven fabric 20A and a second nonwoven fabric 20B are partially heat-fused together. In a non-joint portion surrounded by a plurality of joint portions 22 (four in FIG. 2), the first nonwoven fabric 20A protrudes in a direction away from the second nonwoven fabric 20B to form a convex portion 23 having a hollow portion 21 therein. The joint portion 22 is a recess located between adjacent convex portions 23, 23, and together with the convex portion 23, forms an uneven structure on the first nonwoven fabric 20A side. The nonwoven fabric 20 can be manufactured by the materials and method described in, for example, JP 2004-174234 A. In this method, a first nonwoven fabric 20A is shaped to have projections and recesses by engaging a pair of projection-recess rolls, and then the first nonwoven fabric 20A and a second nonwoven fabric 20B are bonded together. From the viewpoint of shaping the first nonwoven fabric 20A by engaging a pair of projection-recess rolls, it is preferable that both the first nonwoven fabric 20A and the second nonwoven fabric 20B contain non-thermally extensible, non-thermally shrinkable heat-fusible fibers.

[0051] 3 has a single-layer structure having an uneven structure on each surface thereof. In the nonwoven fabric 30, first protruding portions 31 protruding toward the first surface 30A and second protruding portions 32 protruding toward the second surface 30B are arranged alternately and continuously in two different directions that intersect when the nonwoven fabric 30 is viewed in a plan view. The first protruding portion 31 and the second protruding portion 32 each have an open internal space on the opposite surface side, and these portions form recesses 33, 34 on that surface. As a result, the first surface 30A has an uneven structure having the first protruding portion 31 and the recesses 34. The second surface 30B has an uneven structure having the second protruding portion 32 and the recesses 33. The nonwoven fabric 30 has a wall portion 35 that connects the first protruding portion 31 and the second protruding portion 32. The wall portion 35 forms a wall surface of the internal space of each of the first protruding portion 31 and the second protruding portion 32, and has a ring-shaped structure in the planar direction. The nonwoven fabric 30 can be manufactured by the material and method described in, for example, JP 2012-136790 A. In this method, the fiber web is supported on a support and subjected to an air-through process in which hot air is treated in multiple stages while controlling the hot air temperature and air speed, to impart irregularities to the fiber web. As the support for imparting irregularities to the fiber web, it is preferable to use one having solid protrusions and openings. For example, the support described in JP 2012-149370 A can be used.

[0052] The nonwoven fabric 40 shown in Fig. 4(a) has a single-layer structure containing thermoplastic fibers. The nonwoven fabric 40 has a shape on the first surface 40A side in which semi-cylindrical convex portions 41 and concave portions 42 arranged along the side edges of the convex portions 41 are alternately arranged. Under the concave portions 42, concave portion bottom portions 43 made of nonwoven fabric fibers are arranged. The concave portion bottom portions 43 have a lower fiber density than the convex portions 41. In the nonwoven fabric 40, another fiber layer 45 may be partially laminated on the convex portions 41 as shown in Fig. 4(b). The nonwoven fabric 40 can be formed by blowing a fluid such as hot air onto the portions of the fiber web that will become the recesses 42 to move the fibers. This makes it possible to make the fiber density at the bottoms 43 of the recesses lower than that of the surrounding areas.

[0053] The nonwoven fabric 50 shown in Fig. 5 has a single layer structure. The nonwoven fabric 50 has alternately arranged protruding streaks 51 and recessed streaks 52 that extend in one direction. The nonwoven fabric 50 has an uneven structure on both sides. The uneven structure on one side and the uneven structure on the other side have complementary shapes. The nonwoven fabric 50 may be used alone, or may be joined with a flat fiber layer to form a laminated nonwoven fabric, or may be laminated with a fiber layer having an uneven structure and integrated along the uneven structure to form a laminated nonwoven fabric.

[0054] The nonwoven fabric 60 shown in Fig. 6 has a single layer structure. The nonwoven fabric 60 is made from heat-extensible fibers and contains the heat-extensible fibers after stretching. A first surface 60A of the nonwoven fabric 60 has an uneven structure. A second surface 60B located on the opposite side to the first surface 60A is substantially flat or has a smaller unevenness than the first surface 60A. The first surface 60A of the nonwoven fabric 60 has a plurality of protruding portions 61 and linear recessed portions 62 surrounding the protruding portions 61. The recessed portions 62 have press-bonded portions where the constituent fibers of the nonwoven fabric 60 are pressed or bonded. In this state, the heat-extensible fibers contained in the nonwoven fabric are in an elongated state. The protruding portions 61 are portions where the heat-extensible fibers are thermally elongated and protrude toward the first surface 60A side. Therefore, the protruding portions 61 are portions with a lower fiber density and are bulkier than the recessed portions 62. The linear recesses 62 are arranged in a lattice pattern, and one protrusion 61 is arranged in one area defined by the lattice. The nonwoven fabric 60 may have a single layer structure as described above, but may also have a laminated structure of two or more layers. The nonwoven fabric 60 can be manufactured by the material and method described in, for example, JP 2010-168715 A. In this method, first, linear recesses 62 are formed in a fiber web by heat embossing. At this time, in the recesses 62, the heat-extensible fibers are compressed or fused and fixed in a state in which they are not thermally stretched. Next, hot air is blown by air-through processing to stretch the heat-extensible fibers present in the parts other than the recesses 62, thereby forming the protrusions 61.

[0055] The nonwoven fabric of the present invention is smooth to the touch and has high thickness recovery, and is therefore used as a constituent material for various absorbent articles, such as disposable diapers, sanitary napkins, incontinence pads, and panty liners.

[0056] The absorbent article generally has an elongated shape having a vertical direction corresponding to the direction extending from the wearer's abdomen through the crotch to the back, and a horizontal direction perpendicular to the vertical direction. The absorbent article has a crotch portion disposed in the wearer's crotch, and a ventral side portion and a back side portion extending in front and behind the crotch portion. The crotch portion has an excretory part facing portion disposed facing the excretory part of the wearer when the absorbent article is worn, and the excretory part facing portion is usually located in the vertical center of the absorbent article or in the vicinity thereof.

[0057] An absorbent article generally comprises a top sheet located on the wearer's skin-facing side, a back sheet located on the non-skin-facing side, and an absorbent interposed between the two sheets. The top sheet may be a liquid-permeable sheet, such as a nonwoven fabric or a perforated film. The top sheet may have an uneven surface on the skin-facing side. For example, a plurality of scattered convex portions may be formed on the skin-facing side of the top sheet. Alternatively, ridges and grooves extending in one direction may be alternately formed on the skin-facing side of the top sheet. For such a purpose, the top sheet may be formed using two or more sheets of nonwoven fabric.

[0058] On the other hand, the back sheet may be, for example, a liquid-impermeable film or a spunbond-meltblown-spunbond laminated nonwoven fabric. A liquid-impermeable film may be provided with a plurality of micropores to impart water vapor permeability to the film. In order to further improve the feel of the absorbent article, a sheet with a good texture such as a nonwoven fabric may be laminated on the outer surface of the back sheet.

[0059] The absorbent body has an absorbent core. The absorbent core is composed of, for example, a stack of hydrophilic fibers such as cellulose including pulp, a mixed stack of the hydrophilic fibers and an absorbent polymer, a stack of absorbent polymer, a laminated structure in which an absorbent polymer is supported between two absorbent sheets, or the like. At least the skin-facing surface of the absorbent core may be covered with a liquid-permeable core wrap sheet, or the entire surface including the skin-facing surface and the non-skin-facing surface may be covered with the core wrap sheet. As the core wrap sheet, for example, a tissue paper made of hydrophilic fibers or a liquid-permeable nonwoven fabric can be used.

[0060] In addition to the above-mentioned top sheet, back sheet and absorbent body, leakage-preventing cuffs extending in the vertical direction may be arranged on both sides of the skin-facing side along the vertical direction, depending on the specific use of the absorbent article. The leakage-preventing cuffs generally have a base end and a free end. The leakage-preventing cuffs have a base end on the skin-facing side of the absorbent article and stand up from the skin-facing side. The leakage-preventing cuffs are made of a liquid-resistant or water-repellent material and are breathable. An elastic member made of rubber thread or the like may be arranged in a stretched state at or near the free end of the leakage-preventing cuff. When the absorbent article is worn, the elastic member contracts, causing the leakage-preventing cuffs to stand up toward the wearer's body, effectively preventing liquid excreted on the top sheet from leaking outward in the lateral direction of the absorbent article along the top sheet.

[0061] The absorbent article may further have an adhesive layer on the non-skin-facing surface. The adhesive layer is used to fix the absorbent article to an undergarment or another absorbent article when the absorbent article is worn.

[0062] When the nonwoven fabric of the present invention is applied to an absorbent article, the nonwoven fabric is preferably used in a portion of the absorbent article that requires a smooth feel against the skin, such as the top sheet and back sheet of the absorbent article.

[0063] Although the present invention has been described based on the preferred embodiments, the present invention is not limited to the above-mentioned embodiments. For example, when the nonwoven fabric of the present invention has an uneven structure on its surface, the shape of the uneven structure is not limited to those shown in Figs. 1 to 6. The nonwoven fabric may contain additives other than the film-forming polymer, provided that the effects of the present invention are not impaired. EXAMPLES

[0064] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to such examples.

[0065] Example 1 A polymer having a siloxane skeleton and a polyoxazoline structure (hereinafter referred to as "Polymer CP1") was used as the film-forming polymer. Polymer CP1 was synthesized according to Synthesis Example 2 described in JP 2008-143820 A. Polymer CP1 is a poly(N-propionylethyleneimine) modified silicone, the counter ion is ethyl sulfate, and the ratio of the siloxane skeleton is 51 mass %. The nonwoven fabric used had an uneven surface structure as shown in FIG. 1. This nonwoven fabric had a thickness of 1.3 mm and a basis weight of 74 g / m 2 The air-through nonwoven fabric had an upper layer of PET / PE sheath-core composite fiber having a fiber diameter of 17 μm, and a lower layer of PP / PE sheath-core composite fiber having a fiber diameter of 17 μm. Furthermore, the lower layer of the nonwoven fabric had a density of 0.41 g / cm 3 The upper layer has a density of 0.02 g / cm 3 It was a low density layer. The ratio of the siloxane skeleton of the film-forming polymer was measured using a nuclear magnetic resonance apparatus "Mercury 400" (manufactured by Varian). 1 It was calculated by measuring the H-NMR spectrum. Polymer CP1 was sprayed onto the low density layer side of the air-through nonwoven fabric, and then dried for 2 hours at 60° C. to obtain a nonwoven fabric having polymer CP1 on the fiber surface. The amount of polymer CP1 attached was 0.7% by mass based on the mass of the air-through nonwoven fabric to which polymer CP1 was attached.

[0066] Example 2 A nonwoven fabric was obtained in the same manner as in Example 1, except that the amount of polymer CP1 attached was 5.8 mass % based on the mass of the air-through nonwoven fabric to which polymer CP1 was attached.

[0067] [Examples 3 and 4] A nonwoven fabric was obtained in the same manner as in Example 1, except that a polymer having a siloxane skeleton and a polyoxazoline structure (hereinafter referred to as "polymer CP2") was used as the film-forming polymer instead of polymer CP1. Polymer CP2 was synthesized according to Synthesis Example 1 described in JP-A-2008-143820. Polymer CP2 is a poly(N-propionylethyleneimine)-modified silicone, the counter ion is ethyl sulfate, and the ratio of the siloxane skeleton is 88 mass%.

[0068] [Examples 5 and 6] A nonwoven fabric was obtained in the same manner as in Example 1, except that a polymer having a siloxane skeleton and a polyacrylate structure (hereinafter referred to as "polymer CP3") was used as the film-forming polymer instead of polymer CP1. Polymer CP3 was synthesized by a method similar to that described in JP-A-3-91509. Polymer CP3 is a copolymer of acrylic acid ester and dimethylpolysiloxane, and the proportion of the siloxane skeleton is 63 mass%.

[0069] Comparative Example 1 A nonwoven fabric was obtained in the same manner as in Example 1, except that no film-forming polymer was used.

[0070] [Comparative Examples 2 and 3] A nonwoven fabric was obtained in the same manner as in Example 1, except that AB-886 (manufactured by DIC Corporation), which has a polyacrylate structure but no siloxane skeleton, was used instead of polymer CP1 as the film-forming polymer. AB-886 is an acrylic emulsion, and the proportion of the siloxane skeleton is 0% by mass.

[0071] Comparative Examples 4 and 5 A nonwoven fabric was obtained in the same manner as in Example 1, except that polymer CP1 was replaced with KF-96-100cs (manufactured by Shin-Etsu Chemical Co., Ltd.), a polymer having a siloxane skeleton but no film-forming ability. KF-96-100cs is a silicone that has no associative sites, and the proportion of the siloxane skeleton is 100% by mass.

[0072] 〔evaluation〕 For each of the Examples and Comparative Examples, the elastic modulus of the film-forming polymer at 25° C., the thickness recovery rate of the nonwoven fabric, and the sensory evaluation of KES friction and smoothness were evaluated by the following methods. The results are shown in Table 1.

[0073] [Elastic modulus of film-forming polymer] The elastic modulus of the film-forming polymer was measured by the following procedure. First, each polymer solution with a concentration of 30% by mass was cast into a petri dish and heated at 50°C for 13 hours to dry. Next, the elastic modulus of the resulting film was measured at room temperature (25°C) using a viscoelasticity measuring device (RSA-G2: manufactured by TA instruments). In Comparative Examples 4 and 5, since a polymer not capable of forming a film was used, the elastic modulus of the film could not be measured.

[0074] [Thickness recovery rate] The nonwoven fabric of each Example and Comparative Example was cut to prepare a test piece of 8 cm x 12.5 cm, and placed on an acrylic plate. Furthermore, another acrylic plate was placed on the nonwoven fabric, and the nonwoven fabric was sandwiched between the two acrylic plates. Next, a weight was placed on the upper acrylic plate, and the nonwoven fabric was compressed with a pressure of 20 kPa. After leaving the nonwoven fabric at room temperature for 13 hours with the weight placed on it, the thickness of the nonwoven fabric (thickness T1) was measured. Next, the nonwoven fabric was left at room temperature (25 ° C.) for 2 hours without the weight placed on it. After leaving the nonwoven fabric at room temperature for 2 hours, the nonwoven fabric was taken out and its thickness (thickness T2) was measured. The thickness ratio T2 / T1 was multiplied by 100 to calculate the thickness recovery rate (%).

[0075] [Average friction coefficient MIU and average deviation of friction coefficient MMD] The average friction coefficient MIU and the average deviation of the friction coefficient MMD on the low density layer side of the nonwoven fabric were measured using KES-FB4-AUTO-A (product name) manufactured by Kato Tech Co., Ltd. by the following method. First, the nonwoven fabric of each Example and Comparative Example was cut to prepare a 20 cm x 20 cm test piece. Next, the test piece was attached to a smooth metal test table. The contact surface of the contactor was pressed against the fiber aggregate surface of the test piece with a force of 49 cN, and the test piece was moved horizontally for 3 cm at a constant speed of 0.1 cm / sec. A uniaxial tension of 7.4 cN / cm was applied to the test piece. The contactor was made of 20 piano wires with a diameter of 0.5 mm arranged and bent into a U-shape with a width of 10 mm. The contactor was pressed against the test piece with a force of 49 cN using a weight. From this measurement, the average friction coefficient MIU and the average deviation of the friction coefficient MMD were calculated. The smaller the MIU, the more slippery the surface of the nonwoven fabric is, and the smaller the MMD, the smoother the surface of the nonwoven fabric is.

[0076] [Sensory evaluation of smoothness] Using the feel of the nonwoven fabric of Comparative Example 1 as the standard, the smoothness of the feel of the nonwoven fabrics of the Examples and Comparative Examples was evaluated according to the following criteria. 5: Smoother than the nonwoven fabric of Comparative Example 1. 4: Slightly smoother than the nonwoven fabric of Comparative Example 1. 3: Similar to the nonwoven fabric of Comparative Example 1. 2: Slightly less smooth than the nonwoven fabric of Comparative Example 1. 1: Less smooth than the nonwoven fabric of Comparative Example 1.

[0077] [Table 1]

[0078] As is clear from the results shown in Table 1, the nonwoven fabrics of each Example having a film-forming polymer having a siloxane skeleton on the fiber surface had a higher thickness recovery rate and a smoother texture than the nonwoven fabric of Comparative Example 1 having no polymer. On the other hand, the nonwoven fabrics of Comparative Examples 2 and 3 using AB-886 having no siloxane skeleton had a worse texture than the nonwoven fabric of Comparative Example 1. Furthermore, the nonwoven fabrics of Comparative Examples 4 and 5 using a polymer having no film-forming property did not show an improvement in thickness recovery rate compared to the nonwoven fabric of Comparative Example 1. [Explanation of symbols]

[0079] 10, 20, 30, 40, 50, 60 Nonwoven fabric 13, 23, 41, 61 Convex 14, 33, 34, 42, 62 Recess 31 1st protrusion 32 Second protrusion 51 Convex portion 52 Concave section

Claims

1. A nonwoven fabric for absorbent articles having a film-forming polymer having a siloxane skeleton on the surface of the fiber and having a concave-convex structure, The film-forming polymer has an elastic modulus of 10 at 25°C. ４ Pa or more 10 ９ Pa or less, The nonwoven fabric for absorbent articles has a plurality of fused points where fibers constituting the nonwoven fabric are fused to each other.

2. 2. The nonwoven fabric according to claim 1, wherein the film-forming polymer has a siloxane skeleton content of 40% by mass or more and 98% by mass or less.

3. 3. The nonwoven fabric according to claim 1, wherein the content of the film-forming polymer is 0.005% by mass or more and 15% by mass or less.

4. The nonwoven fabric according to claim 1 or 2, wherein at least a portion of the plurality of fusion-bonded points is covered with the film-forming polymer.

5. An absorbent article comprising the nonwoven fabric according to claim 1 or 2.

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