JP7490419B2 - Nonwoven fabric for absorbent article, top sheet for absorbent article, and absorbent article including same - Google Patents

Description

The present invention relates to a nonwoven fabric for absorbent articles, a top sheet for absorbent articles, and an absorbent article including the same.

Nonwoven fabrics with a two-layer structure have been proposed as top sheets for absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and panty liners.

For example, Patent Document 1 proposes a nonwoven fabric having at least a two-layer structure of a first fiber layer and a second fiber layer, in which both the first fiber layer and the second fiber layer each have a specific fineness, the fiber diameter of the first fiber layer is larger than the fiber diameter of the second fiber layer, both the first fiber layer and the second fiber layer have hydrophilicity that maintains a high degree of hydrophilicity even when contacted with water, and both the first fiber layer and the second fiber layer have the same hydrophilicity (see claim 1). Furthermore, Patent Document 1 proposes a top sheet for absorbent articles that includes the nonwoven fabric and is arranged so that the first fiber layer faces human skin, and an absorbent article that includes the top sheet and is arranged so that the first fiber layer faces human skin (see claims 6 and 7). Patent Document 1 states that at least one selected from texture, wetback amount, liquid absorption time, diffusion length, repeated durability, storage stability, etc. is improved (see [0014]).

Patent Document 2 proposes an absorbent article that receives excrement from a wearer, comprising an absorbent core containing 40% by weight or more of highly absorbent resin powder, a top sheet formed of a nonwoven fabric covering the main surface of the absorbent core facing the wearer, and a back sheet covering the other main surface of the absorbent core, the top sheet comprising a lower part of the top sheet that contacts the highly absorbent resin powder of the absorbent core and contains hydrophilic fibers that are natural and/or regenerated fibers, and an upper part of the top sheet that is disposed on the wearer side of the lower part of the top sheet and has a lower content of hydrophilic fibers than the lower part of the top sheet (see claim 1). Patent Document 2 describes that the absorbent article can be made thinner and the structure simplified, and that it can reliably absorb moisture from excrement and improve the feel of the absorbent article against the skin (see [0020]).

Patent Document 3 discloses an absorbent article in which an absorbent layer is interposed between a surface layer and a back layer, the surface layer contains hydrophobic fibers and hydrophilic fibers shorter than the hydrophobic fibers, the hydrophobic fibers are heat-fused to each other, at least a part of the hydrophilic fibers form an aggregate and are dispersed in the sheet, and at least a part of the hydrophilic fibers of the aggregate are fused to the surface of the hydrophobic fibers (see claim 1). Furthermore, Patent Document 3 discloses an absorbent article in which, when the surface layer is divided in the thickness direction, the liquid-receiving side is the surface portion and the absorbent layer side is the back portion, the aggregate of hydrophilic fibers is not provided on the surface portion but only on the back portion (see claim 4). Patent Document 3 describes that when a large amount of liquid is applied, the liquid quickly permeates the surface layer and is absorbed by the absorbent layer, and when a small amount of liquid or sweat is applied, moisture is retained by the aggregate of dispersed hydrophilic fibers, the surface of the surface layer can be kept dry, the wearer does not feel wet, and the wearing comfort is good (see [0064]).

WO2017/171017A1 JP 2009-327 A JP 2002-651 A

In recent years, there has been a demand for improved (enhanced) absorbency for soft stool, watery stool, and diarrheal stool (hereinafter simply referred to as "soft stool") while maintaining the liquid absorption performance and texture of absorbent articles. Soft stool is a highly viscous fluid that also contains water and oil. Because it contains oil, it is difficult for superabsorbent polymers (SAPs) to absorb it. Therefore, improvements are also needed for nonwoven fabrics used in top sheets, etc., to improve the absorbency of fluids such as soft stool. Patent Documents 1 to 3 are silent on this point, and there is still room for further improvement in the nonwoven fabrics described in Patent Documents 1 to 3, the top sheets containing them, and the absorbent articles containing those top sheets.

The present invention aims to provide a nonwoven fabric for absorbent articles, a top sheet containing the same, and an absorbent article containing the top sheet, which has improved (enhanced) absorbency for fluids such as loose stool while maintaining the liquid absorption performance and texture.

After extensive research, the inventors have discovered that a nonwoven fabric for absorbent articles containing a first fiber layer and a second fiber layer, in which the first fiber layer contains a specific composite fiber, the second fiber layer contains another specific composite fiber, and further contains a specific amount of cellulosic fiber, can be obtained that maintains its liquid absorption performance and texture while improving (enhancing) its ability to absorb fluids such as loose stool. They have also discovered that such a nonwoven fabric is suitable for use in top sheets and absorbent articles, and have completed the present invention.

That is, as one aspect of the present invention, there is provided a nonwoven fabric for absorbent articles, which comprises:
A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fiber layer includes a first sheath-core type composite fiber,
the second fiber layer includes a second sheath-core type composite fiber and a cellulosic fiber,
the first sheath-core type composite fiber has a smaller fineness than the second sheath-core type composite fiber,
The first core-sheath type composite fiber has a fineness of 1.0 to 2.8 dtex,
The fineness of the second core-sheath type composite fiber is 1.7 to 5.6 dtex,
The cellulosic fiber has a fineness of 1.2 to 6.0 dtex,
The second fibrous layer contains the cellulosic fibers in a proportion of 5% by mass to 40% by mass based on the total mass of the second fibrous layer.

Furthermore, in another aspect, the present invention provides a top sheet including the nonwoven fabric for absorbent articles, and an absorbent article including the top sheet.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can improve the absorbency of fluids such as loose stool while maintaining the liquid absorption performance and touch. Therefore, the nonwoven fabric for absorbent articles according to the embodiment of the present invention can be suitably used for manufacturing top sheets and absorbent articles.

The nonwoven fabric for absorbent articles according to an embodiment of the present invention is
The fiber optic cable includes a first fibrous layer and a second fibrous layer located on one major surface of the first fibrous layer.
The first fiber layer includes a first sheath-core type composite fiber,
The second fiber layer includes a second sheath-core type composite fiber and a cellulosic fiber.
The fineness of the first sheath-core type composite fiber is smaller than the fineness of the second sheath-core type composite fiber,
The first core-sheath type composite fiber has a fineness of 1.0 to 2.8 dtex,
The fineness of the second core-sheath type composite fiber is 1.7 to 5.6 dtex,
The fineness of the cellulosic fibers is 1.2 to 6.0 dtex.
The second fibrous layer contains the cellulosic fibers in a proportion of 5% by mass to 40% by mass based on the total mass of the second fibrous layer.

The first core-sheath type composite fiber is not particularly limited in terms of the core component, sheath component, and their mass ratio (core/sheath ratio), etc., as long as the nonwoven fabric for absorbent articles intended by the present invention can be obtained, and may be a concentric or eccentric core-sheath type composite fiber. It is preferable that the first core-sheath type composite fiber is a concentric core-sheath type composite fiber, since it does not make the thickness of the nonwoven fabric too large, provides an appropriate distance to the absorbent body, and exhibits good liquid absorption performance.

The first core-sheath type composite fiber is composed of a low melting point resin and a high melting point resin whose melting point is, for example, 10°C or more higher than the melting point of the low melting point resin (i.e., two types of resins that satisfy the relationship: melting point (°C) of the low melting point resin ≦ melting point of the high melting point resin - 10 (°C)), and the low melting point resin may form the sheath and the high melting point resin may form the core. The difference between the melting points of the low melting point resin and the high melting point resin is preferably 20 to 190°C, more preferably 70 to 170°C, and even more preferably 110 to 140°C.

The melting point of the low melting point resin is, for example, 100 to 170°C, preferably 110 to 150°C, and more preferably 120 to 140°C.
The melting point of the high melting point resin is, for example, 150 to 290°C, preferably 190 to 280°C, and more preferably 230 to 270°C.
In this specification, the melting point of a resin refers to a melting peak temperature determined from a DSC curve measured in accordance with JIS K 7121.

As the high melting point resin and the low melting point resin, one or more thermoplastic resins selected from the following may be appropriately used: polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polylactic acid, polybutylene succinate, and copolymers thereof; polyolefin resins such as polypropylene, polyethylene (including high density polyethylene, low density polyethylene, linear low density polyethylene, etc.), polybutene-1, propylene copolymers mainly composed of propylene (including propylene-ethylene copolymer, propylene-butene-1-ethylene copolymer), ethylene-vinyl alcohol copolymer, and ethylene-vinyl acetate copolymer; polyamide resins such as nylon 6, nylon 12, and nylon 66; acrylic resins; engineering plastics such as polycarbonate, polyacetal, polystyrene, and cyclic polyolefin, and elastomers thereof.

Examples of combinations of high melting point resin and low melting point resin (high melting point/low melting point) include, but are not limited to, polypropylene/high density polyethylene, polypropylene/low density polyethylene, polypropylene/linear low density polyethylene, polyethylene terephthalate/high density polyethylene, polyethylene terephthalate/low density polyethylene, polyethylene terephthalate/linear low density polyethylene, polyethylene terephthalate/copolymer polyester, polypropylene/ethylene-propylene copolymer, polyethylene terephthalate/ethylene-propylene copolymer, nylon 6/high density polyethylene, nylon 6/low density polyethylene, nylon 6/linear low density polyethylene, nylon 6/polypropylene, polylactic acid/polyethylene, polylactic acid/polybutylene succinate, and polylactic acid/polybutylene succinate adipate.

Preferred combinations of high-melting-point resin and low-melting-point resin are polyethylene terephthalate/high-density polyethylene, polyethylene terephthalate/low-density polyethylene, polyethylene terephthalate/linear low-density polyethylene, polypropylene/high-density polyethylene, polypropylene/low-density polyethylene, and polypropylene/linear low-density polyethylene, with polyethylene terephthalate/high-density polyethylene and polypropylene/high-density polyethylene being more preferable.

The mass ratio of the core component to the sheath component (core/sheath ratio) may be, for example, 80/20 to 40/60, preferably 70/30 to 50/50, and more preferably 65/35 to 55/45.

The fineness of the first sheath-core type conjugate fiber is, for example, 1.0 to 2.8 dtex, preferably 1.5 to 2.6 dtex, and more preferably 1.7 to 2.3 dtex. When the fineness of the first sheath-core type conjugate fiber is 1.0 to 2.8 dtex, an excellent effect of obtaining a smooth touch is obtained.
The fiber length of the first sheath-core type conjugate fiber is, for example, 10 to 100 mm, preferably 20 to 70 mm, more preferably 30 to 60 mm, and even more preferably 35 to 50 mm.

The second core-sheath type composite fiber is not particularly limited in terms of the core component, sheath component, and their mass ratio (core/sheath ratio), etc., as long as the nonwoven fabric for absorbent articles intended by the present invention can be obtained, and may be a concentric or eccentric core-sheath type composite fiber. It is preferable that the second core-sheath type composite fiber is a concentric core-sheath type composite fiber, since it does not make the thickness of the nonwoven fabric too large, provides an appropriate distance to the absorbent body, and exhibits good liquid absorption performance.

The second core-sheath composite fiber is composed of a low-melting-point resin and a high-melting-point resin whose melting point is, for example, 10°C or more higher than the melting point of the low-melting-point resin (i.e., two types of resins that satisfy the relationship: melting point (°C) of the low-melting-point resin ≦ melting point of the high-melting-point resin - 10 (°C)), and the low-melting-point resin may form the sheath and the high-melting-point resin may form the core. The difference between the melting points of the low-melting-point resin and the high-melting-point resin is preferably 20 to 190°C, more preferably 70 to 170°C, and even more preferably 110 to 140°C.

The melting point of the low melting point resin is, for example, 100 to 170°C, preferably 110 to 150°C, and more preferably 120 to 140°C.
The melting point of the high melting point resin is, for example, 150 to 290°C, preferably 190 to 280°C, and more preferably 230 to 270°C.

As the high melting point resin and the low melting point resin, the resins exemplified in the first sheath-core type composite fiber can be used appropriately. As the combination of the high melting point resin and the low melting point resin (high melting point/low melting point), the combinations exemplified in the first sheath-core type composite fiber can be used appropriately.
Preferred combinations of high-melting point resins and low-melting point resins are polyethylene terephthalate/high-density polyethylene, polyethylene terephthalate/low-density polyethylene, polyethylene terephthalate/linear low-density polyethylene, polypropylene/high-density polyethylene, polypropylene/low-density polyethylene, and polypropylene/linear low-density polyethylene, and more preferred are polyethylene terephthalate/high-density polyethylene and polypropylene/high-density polyethylene.

The mass ratio of the core component to the sheath component (core/sheath ratio) may be, for example, 80/20 to 40/60, preferably 70/30 to 50/50, and more preferably 65/35 to 55/45.

The fineness of the second sheath-core type composite fiber is, for example, 1.7 to 5.6 dtex, preferably 2.0 to 5.0 dtex, and more preferably 2.6 to 4.0 dtex. When the fineness of the second sheath-core type composite fiber is 1.7 to 5.6 dtex, an excellent effect of reducing the amount of wetback is achieved.
The fiber length of the second sheath-core type composite fiber is, for example, 10 to 100 mm, preferably 20 to 70 mm, more preferably 30 to 60 mm, and even more preferably 35 to 55 mm.

The fineness of the first sheath-core composite fiber is smaller than that of the second sheath-core composite fiber, and the difference between the fineness of the first sheath-core composite fiber and that of the second sheath-core composite fiber can be, for example, 0.5 to 4.0 dtex, preferably 0.7 to 3.0 dtex, and more preferably 1.0 to 2.0 dtex. When the fineness of the first sheath-core composite fiber is smaller than that of the second sheath-core composite fiber, it has the excellent effect of achieving both a smooth feel and a reduced amount of wetback.

The cellulosic fibers are not particularly limited in terms of type, etc., so long as the nonwoven fabric for absorbent articles that is the object of the present invention can be obtained.
Examples of cellulosic fibers include natural fibers such as cotton and hemp; and regenerated fibers such as viscose rayon, cupra, and solvent-spun cellulosic fibers (e.g., microwaved lyocell (registered trademark) and Tencel (registered trademark)). Cellulosic fibers have both hydrophilic and lipophilic properties, and it is presumed that the inclusion of cellulosic fibers in the second fiber layer has the effect of absorbing the fluid such as loose stool and preventing the fluid from returning to the surface of the first fiber layer of the nonwoven fabric when the fluid contains water and oil, such as loose stool, returns from the absorbent (wetback).

The cellulose-based fiber preferably contains at least one selected from cotton, viscose rayon, and solvent-spun cellulose fiber, and more preferably contains viscose rayon. When the cellulose-based fiber contains cotton, viscose rayon, and solvent-spun cellulose fiber, it has an excellent effect of providing a soft touch. Viscose rayon has a lower crystallinity and a larger amount of amorphous parts than cotton and solvent-spun cellulose fiber, so it has higher water absorption and oil absorption, and it is presumed that viscose rayon has a higher effect of absorbing the fluid such as loose stool and making it difficult for the fluid to return to the surface of the first fiber layer of the nonwoven fabric when the fluid containing water and oil such as loose stool returns from the absorbent. Therefore, when the cellulose-based fiber contains viscose rayon, it has good absorbency of loose stool and other fluids, and has an excellent effect of reducing the amount of wetback in particular.
Cotton is likely to form fiber agglomerates (fiber aggregates) inside the second fiber layer. When the second fiber layer contains fiber agglomerates, the thickness of the second fiber layer tends to be thicker, and the distance between the surface of the nonwoven fabric on the first fiber layer side and the absorbent body becomes longer, which may reduce the amount of liquid returning from the absorbent body. In addition, by forming fiber agglomerates, the number of contact points between the second core-sheath type composite fibers increases, which may make it easier to maintain the strength of the nonwoven fabric.
The solvent-spun cellulose fibers tend to increase the bending resistance of the nonwoven fabric, and the bulk of the second fiber layer is less likely to be crushed when a load is applied to the nonwoven fabric. If the bulk of the second fiber layer is less likely to be crushed when a load is applied, the distance between the surface of the nonwoven fabric facing the first fiber layer and the absorbent body becomes longer, which may reduce the amount of liquid returning from the absorbent body.

It is also preferable that the fiber contains cellulosic fibers with a chrysanthemum-shaped cross section, and it is particularly preferable that the fiber contains viscose rayon with a chrysanthemum-shaped cross section. In this case, the fiber has a larger surface area and has streaks in the fiber axis direction, which makes it easier to diffuse fluids such as loose stool in the second fiber layer and allows the absorbent to absorb fluids over a relatively large area in the absorbent, which has the excellent effect of making it easier to reduce the amount of wetback.

The fineness of the cellulose-based fiber is, for example, 1.2 to 6.0 dtex, preferably 1.5 to 5.0 dtex, and more preferably 2.0 to 4.0 dtex. When the fineness of the cellulose-based fiber is 1.2 to 6.0 dtex, an excellent effect of improving the absorbency of fluids such as loose stool is achieved.
The fiber length of the cellulosic fibers is, for example, 10 to 100 mm, preferably 15 to 80 mm, more preferably 20 to 60 mm, and even more preferably 30 to 55 mm.

The fineness or fiber length of the cellulose-based fiber is preferably uniform, since the cellulose-based fiber is less likely to form an aggregate (nep) in the second fiber layer. When the cellulose-based fiber forms an aggregate in the second fiber layer, the second core-sheath type composite fiber and the cellulose-based fiber contained in the second fiber layer are mixed relatively unevenly, and in the area where the aggregate does not exist, the number of adhesion points between the second core-sheath type composite fibers is relatively large, making it difficult for fluids such as loose stool to pass through the nonwoven fabric, and fluids such as loose stool are likely to remain at that area, reducing the absorbency, and in particular making it difficult to reduce the amount of wetback. Examples of cellulose-based fibers having a uniform fineness or fiber length include regenerated fibers, which are chemical fibers. It is more preferable that the fineness and fiber length of the cellulose-based fiber are uniform, respectively.
When the cellulosic fibers have a non-uniform fineness or fiber length, the cellulosic fibers are more likely to form fiber agglomerates (aggregates of fibers) in the second fiber layer. However, by forming fiber agglomerates, the number of points at which the second sheath-core composite fibers come into contact with each other increases, which may make it easier to maintain the strength of the nonwoven fabric.

The second fiber layer may contain the cellulosic fibers in a proportion (mixture ratio) of, for example, 5% by mass to 40% by mass, preferably 10% by mass to 30% by mass, more preferably 15% by mass to 25% by mass, and even more preferably 17% by mass to 23% by mass, based on the total mass of the second fiber layer. When the second fiber layer contains the cellulosic fibers in a proportion (mixture ratio) of 5% by mass to 40% by mass, based on the total mass of the second fiber layer, the second fiber layer exhibits excellent effects of improving the absorbency of fluids such as loose stool and improving the strength of the nonwoven fabric.
The second fiber layer may contain the second core-sheath type composite fiber in a proportion of, for example, 95% by mass to 60% by mass, preferably 90% by mass to 70% by mass, more preferably 85% by mass to 75% by mass, and even more preferably 83% by mass to 77% by mass, based on the total mass of the second fiber layer.

In the second fiber layer, the ratio of the number of fibers of the second sheath-core composite fiber to the number of fibers of the cellulosic fiber contained in the second fiber layer (number of fibers of the second sheath-core composite fiber/number of fibers of the cellulosic fiber) is preferably 0.6 to 10, more preferably 1.0 to 4.0, and even more preferably 1.2 to 3.0. When the value of the number of fibers of the second sheath-core composite fiber/number of fibers of the cellulosic fiber is 0.6 or more, there are more sufficient bonding points between the fibers by the second sheath-core composite fiber, so that the strength of the nonwoven fabric is more sufficient and the liquid absorption performance is more easily improved. When the value of the number of fibers of the second sheath-core composite fiber/number of fibers of the cellulosic fiber is 10 or less, the effect of improving the liquid absorption performance by including the cellulosic fiber is easily obtained.
The ratio R of the number of the second sheath-core composite fibers to the number of the cellulosic fibers in the second fiber layer (number of the second sheath-core composite fibers/number of the cellulosic fibers) is calculated by the following formula.
R = As × Dc × Lc / (Ds × Ls × Ac)
In the formula, As represents the mixing ratio (mass%) of the second sheath-core type composite fiber in the second fiber layer,
Ds represents the fineness (dtex) of the second core-sheath type composite fiber,
Ls represents the fiber length (mm) of the second core-sheath type composite fiber,
Ac represents the blend ratio (mass%) of cellulosic fibers in the second fiber layer,
Dc represents the fineness (dtex) of the cellulosic fiber,
Lc represents the fiber length (mm) of the cellulosic fiber.

The weight of the entire nonwoven fabric is preferably 10 to 80 g/ ^m2 , more preferably 15 to 50 g/ ^m2 , and even more preferably 17 to 40 g/ ^m2 .
In the case of disposable diapers, the weight per unit area of the entire nonwoven fabric is preferably as low as possible from the standpoint of cost, and in this case the weight per unit area is preferably 10 to 50 g/ ^m2 , and more preferably 15 to 40 g/ ^m2 .

The thickness of the nonwoven fabric is preferably 0.10 to 4.0 mm, more preferably 0.20 to 3.0 mm, and even more preferably 0.30 to 2.0 mm. In the case of disposable diapers, the thickness of the nonwoven fabric should be as low as possible from the standpoint of cost, and in that case the thickness is preferably 0.10 to 3.0 mm, and more preferably 0.30 to 2.0 mm. In the present invention, the thickness of the nonwoven fabric refers to the thickness measured when a load of 294 Pa is applied to the nonwoven fabric.

The specific volume of the nonwoven fabric is preferably 5 to 150 cm ³ /g, more preferably 7 to 120 cm ³ /g, and even more preferably 10 to 100 cm ³ /g. In the present invention, the specific volume of the nonwoven fabric refers to a value calculated from the basis weight and thickness described above.

The basis weight of the first fiber layer may be, for example, 3 to 40 g/ ^m2 , preferably 4 to 25 g/ ^m2 , and more preferably 5 to 15 g/ ^m2 .

The basis weight of the second fiber layer may be, for example, 3 to 40 g/ ^m2 , preferably 5 to 30 g/ ^m2 , and more preferably 8 to 20 g/ ^m2 .

The basis weight of the first fibrous layer is preferably smaller than the basis weight of the second fibrous layer.
The difference in basis weight between the first fiber layer and the second fiber layer may be, for example, 0 to 10 g/ ^m2 , preferably 1 to 8 g/ ^m2 , and even more preferably 2 to 6 g/ ^m2 .
When the basis weight of the first fibrous layer is smaller than the basis weight of the second fibrous layer, an excellent effect of reducing the amount of wetback is obtained.

The nonwoven fabric according to the embodiment of the present invention has a structure in which a first fiber layer and a second fiber layer are laminated. The fibers of the first fiber layer and the second fiber layer may be bonded to each other within each fiber layer, or the fibers of the first fiber layer and the second fiber layer may be bonded to each other between the first fiber layer and the second fiber layer.

The first and second fiber layers of the embodiments of the present invention can be manufactured using various fiber web manufacturing methods. There are no particular limitations on the manufacturing method as long as the nonwoven fabric for absorbent articles that is the object of the present invention can be obtained. Examples of such manufacturing methods include carding methods such as parallel webs, cross webs, criss-cross webs, semi-random webs, and random webs, and air laying methods.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can be manufactured by stacking and integrating a first fiber web and a second fiber web. As long as the nonwoven fabric for absorbent articles of the present invention can be obtained, the manufacturing method is not particularly limited. Examples of such manufacturing methods include the air-through method (hot air penetration type heat treatment method), hot air blowing type heat treatment method, heat roll method, infrared type heat treatment method, needle punch method, etc., and the air-through method (hot air penetration type heat treatment method) is preferred because it is easy to obtain a nonwoven fabric with good texture.
The fibers of the first fibrous layer and the fibers of the second fibrous layer of the integrated nonwoven fabric may be bonded.
The nonwoven fabric for absorbent articles according to the embodiment of the present invention may further have an additional layer that is usually included in nonwoven fabrics, if necessary. The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably has a two-layer structure consisting of a first fiber layer and a second fiber layer.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention may be subjected to additional processing such as embossing, if necessary, and may have such additional forms and shapes, etc.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably has a tensile strength in the MD (machine direction) of 10 to 45 N/5 cm, more preferably 15 to 40 N/5 cm, and even more preferably 20 to 35 N/5 cm.
When the tensile strength in the MD direction of the nonwoven fabric for absorbent articles according to the embodiment of the present invention is 10 to 45 N/5 cm, the fabric has a good feel to the touch and exhibits the excellent effect of suppressing width contraction of the nonwoven fabric during processing into absorbent articles.

The nonwoven fabric for absorbent articles according to an embodiment of the present invention has a tensile strength in the CD direction (direction perpendicular to the MD direction) of preferably 2 to 12 N/5 cm, more preferably 3 to 10 N/5 cm, and even more preferably 5 to 8 N/5 cm.
When the tensile strength in the CD direction of the nonwoven fabric for absorbent articles according to the embodiment of the present invention is 2 to 12 N/5 cm, the fabric has a good feel to the touch and exhibits the excellent effect of suppressing width contraction of the nonwoven fabric during processing into absorbent articles.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably has an elongation percentage in the MD direction of 20 to 80%, more preferably 30 to 70%, and even more preferably 40 to 60%.
The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably has an elongation in the CD direction of 20 to 130%, more preferably 40 to 110%, and even more preferably 60 to 90%.

The nonwoven fabric for absorbent articles according to an embodiment of the present invention preferably has a stress at 10% elongation in the MD direction of 1 to 20 N/5 cm, more preferably 2 to 10 N/5 cm, and even more preferably 3 to 7 N/5 cm.

The nonwoven fabric for absorbent articles according to an embodiment of the present invention preferably has a total bending resistance in the MD direction and the CD direction of 5 to 25 mN·cm, more preferably 6 to 20 mN·cm, and even more preferably 7 to 15 mN·cm.
When the sum of the bending resistance in the MD direction and the bending resistance in the CD direction of the nonwoven fabric for absorbent articles according to the embodiment of the present invention is 5 to 25 mN cm, the nonwoven fabric has a soft feel and is not easily torn when used as a member of an absorbent article. The bending resistance is measured according to the 41.5° cantilever method described in the examples.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can be used in various absorbent articles such as disposable diapers, sanitary napkins, incontinence pads, and panty liners. The nonwoven fabric for absorbent articles according to the embodiment of the present invention has an excellent feel and can be used in any component of various absorbent articles. The nonwoven fabric for absorbent articles according to the embodiment of the present invention has excellent feel and liquid absorption properties of a nonwoven fabric and can be suitably used for the top sheet or second sheet of an absorbent article, but it is particularly preferable to use it for the top sheet of an absorbent article that comes into contact with the wearer's skin and is the first to come into contact with urine, menstrual blood, and loose stool discharged from the wearer.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention preferably includes a nonwoven fabric for absorbent articles for absorbing fluids containing water and oil, more preferably a nonwoven fabric for absorbent articles for absorbing fluids containing water and oil, and more particularly preferably includes a nonwoven fabric for absorbent articles for absorbing loose stool, more preferably a nonwoven fabric for absorbent articles for absorbing loose stool. The nonwoven fabric for absorbent articles according to the embodiment of the present invention is particularly preferably a nonwoven fabric for disposable diapers, since it has good urine absorption performance and good absorbency for loose stool, and also has a good feel.

Furthermore, the present invention can provide various absorbent articles that include such nonwoven fabrics for absorbent articles. In particular, it is possible to provide an absorbent article that includes a top sheet for absorbent articles, in which the first fiber layer of the top sheet for absorbent articles of the embodiment of the present invention is disposed on the side closest to the skin of the user.

Furthermore, the present invention can provide various absorbent articles as described above. The absorbent articles of the embodiments of the present invention preferably include absorbent articles for absorbing fluids including water and oil, and more particularly preferably include absorbent articles for absorbing loose stools.

The present invention will be described in detail below with reference to examples and comparative examples. However, these examples are merely one aspect of the present invention, and the present invention is not limited to these examples in any way.

The fibers used to produce the nonwoven fabrics in the Examples and Comparative Examples are shown below.
First sheath-core composite fiber: a concentric sheath-core composite fiber having a core component made of polyethylene terephthalate resin (PET) with a melting point of 256°C, a sheath component made of high-density polyethylene (HDPE) resin with a melting point of 130°C, a core-sheath ratio (core/sheath mass ratio) which is the mass ratio of the core component to the sheath component in the fiber cross section, of 60/40, and a fineness of 2.0 dtex (fiber diameter 15 μm) and a fiber length of 45 mm (hereinafter also referred to as "composite fiber 1").
Second core-sheath type composite fiber: A concentric core-sheath type composite fiber having a core component made of polyethylene terephthalate resin (PET) having a melting point of 256°C, a sheath component made of high-density polyethylene (HDPE) resin having a melting point of 130°C, a core-sheath ratio (core/sheath mass ratio) which is the mass ratio of the core component to the sheath component in the fiber cross section, of 60/40, a fineness of 3.3 dtex (fiber diameter 19 μm) and a fiber length of 51 mm (hereinafter also referred to as "composite fiber 2").

Rayon fiber A: Viscose rayon having a fineness of 1.4 dtex and a fiber length of 44 mm (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.) (hereinafter also referred to as "Rayon A")
Rayon fiber B: Viscose rayon having a fineness of 1.7 dtex and a fiber length of 40 mm (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.) (hereinafter also referred to as "Rayon B")
Rayon fiber C: Viscose rayon having a fineness of 2.2 dtex and a fiber length of 51 mm (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.) (hereinafter also referred to as "Rayon C")
Rayon fiber D: Viscose rayon having a fineness of 3.3 dtex and a fiber length of 51 mm (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.) (hereinafter also referred to as "Rayon D")
Rayon fiber E: Viscose rayon having a fineness of 5.6 dtex and a fiber length of 51 mm (product name: Corona CD, manufactured by Daiwabo Rayon Co., Ltd.) (hereinafter also referred to as "Rayon E")
The fiber cross sections of the rayon fibers A to E all had irregular chrysanthemum-shaped cross sections.

Lyocell fiber: Solvent-spun cellulose fiber having a fineness of 1.7 dtex, a fiber length of 40 mm, and a circular cross section (Lyocell (product name) manufactured by Lenzing) (hereinafter also referred to as "Lyocell")
Cotton fiber: Cotton having a fineness of 1.0 to 5.0 dtex (average 2.5 dtex) and a fiber length of 10 to 60 mm (average fiber length 20 mm) (MSD (product name) manufactured by Marusan Sangyo Co., Ltd.) (hereinafter also referred to as "cotton")

[Example 1]
A first fiber web to be a first fiber layer was produced using the composite fiber 1 as the first core-sheath type composite fiber and a parallel carding machine. The basis weight of the first fiber web was about 8 g/ ^m2 .
The composite fiber 2 and the rayon B were weighed so that the composite fiber 2 was 90% by mass as the second core-sheath type composite fiber and the rayon B was 10% by mass as the cellulosic fiber, and these were thoroughly mixed, and then a second fiber web to be the second fiber layer was produced using a parallel carding machine. The basis weight of the second fiber web was about 12 g/ ^m2 .
The first and second fiber webs were overlapped and heat-treated by a hot air-penetrating heat treatment machine. When heat-treating, the first fiber web was placed on the conveyor net of the hot air-penetrating heat treatment machine so that it was in contact with the conveyor net. The heat treatment was performed by blowing hot air at 135°C from the second fiber web side, and the constituent fibers of each fiber web were thermally bonded to each other by the sheath components of the composite fiber 1 and the composite fiber 2, and the first and second fiber webs were thermally bonded to each other to integrate them, thereby obtaining a nonwoven fabric of Example 1. The basis weight of the nonwoven fabric of Example 1 was about 20 g/ ^m2 .

[Examples 2 to 10] and [Comparative Examples 1 to 3]
For Examples 2 to 10 and Comparative Examples 1 to 3, the fibers shown in Tables 1 to 3 were used to obtain the nonwoven fabrics of Examples 2 to 10 and Comparative Examples 1 to 3 using a method similar to that for producing the nonwoven fabric of Example 1 described above.

The nonwoven fabrics of the examples and comparative examples were measured and evaluated according to the methods shown below.

[Thickness and specific volume of nonwoven fabric]
The thickness of the nonwoven fabric (including the nonwoven fabric sample) was measured using a thickness gauge (manufactured by Daiei Scientific Instruments Co., Ltd., trade name: THICKNESS GAUGE, model CR-60A) with a load of 294 Pa applied to the nonwoven fabric.
The specific volume was calculated from the basis weight and thickness.

[Tensile strength, elongation, and stress at 10% elongation of nonwoven fabric]
According to JIS L 1913 (2010) 1096 6.312.1 A method (strip method), a constant-speed tension type tensile tester was used to perform a tensile test under the conditions of a sample width of 5 cm, a gripping distance of 10 cm, and a tensile speed of 30±2 cm/min, and the load value at break (tensile strength), elongation, and stress at 10% elongation were measured. The tensile test was performed in the MD direction (machine direction) and CD direction (direction perpendicular to the MD direction) of the nonwoven fabric as the tensile direction. For each value, measurements were taken on three samples, and the average values were shown.

[Bending resistance]
The bending resistance of the nonwoven fabric was measured in both the MD and CD directions according to the 41.5° cantilever method of JIS L 1913 (2010). Note that the measurement was performed with a release paper of the same size as the nonwoven fabric placed under the nonwoven fabric.

[Touch (smoothness, softness)]
A sensory evaluation was carried out by 12 panelists. Each panelist gave an evaluation according to the following 5-level criteria, and the average of the evaluations by the 12 panelists was calculated.
Sensory evaluation criteria for smoothness: 5: Very smooth 4: Smooth 3: Normal 2: Slightly rough 1: Rough Sensory evaluation criteria for softness: 5: Very soft 4: Soft 3: Normal 2: Slightly hard 1: Hard

The absorbency of the nonwoven fabrics of the Examples and Comparative Examples was evaluated by producing liquid-absorbent articles for evaluation.
[Manufacture of absorbent articles]
The top sheet was peeled off and removed from a commercially available disposable paper diaper (manufactured by Daio Paper Corporation under the trade name GOO.N (registered trademark)) whose crotch area is composed of a three-layer structure of a top sheet, a second sheet, and an absorbent body, and a leak-proof sheet that prevents moisture from leaking outward. The nonwoven fabrics of the above-mentioned Examples and Comparative Examples were laminated in place of the removed top sheet to prepare an absorbent article for evaluation. Note that, when laminating, the first fiber layer was arranged to face outward, and the second fiber layer was arranged to face the second sheet. Using this absorbent article for evaluation, the absorbency (absorption time, wetback, nonwoven surface diffusion length) of the nonwoven fabrics of the Examples and Comparative Examples was evaluated.

[Wet bag (saline solution)]
The wet bags of the nonwoven fabrics of the Examples and Comparative Examples were evaluated by the following methods.
(1) In order to measure the amount of wetback, the following items were prepared:
Absorbent articles for evaluation of the above-mentioned Examples and Comparative Examples Plate with injection tube (inner diameter of the tube bottom: 2.5 cm)
0.9% saline solution (colored with blue dye, viscosity at 37°C is 1.4 mPa·s)
Filter paper (Toyo Roshi Kaisha, Ltd., ADVANTEC (registered trademark) No. 2) 10 cm x 10 cm
Weight (5kg) 10cm x 10cm

(2) Method The amount of wetback was measured according to the following procedure.
(i) The absorbent article to be evaluated was placed with the nonwoven fabric (42 cm length x 21 cm width) facing upward, and a plate equipped with an injection tube was placed on top of it.
(ii) 50 ml of physiological saline solution warmed to about 37° C. was poured from the cylinder. The solution was left until the physiological saline solution was no longer visible on the surface of the nonwoven fabric (the physiological saline solution was no longer visible as a liquid).
(iii) The plate with the injection tube was removed and allowed to stand for 10 minutes.
(iv) The filter paper (30 sheets) whose mass had been measured in advance was placed on the nonwoven fabric, and a 5 kg weight was placed on top of the filter paper for 20 seconds. The mass of the filter paper was then measured. The difference between the mass of the filter paper before being placed on the nonwoven fabric and the mass of the filter paper after being placed on the nonwoven fabric and the weight was placed on top of the nonwoven fabric corresponds to the amount of wetback.
(v) Returning to (i) above, (i) to (iv) were repeated three times to perform the measurement, for a total of four evaluations of the wetback.
In addition, for Examples 11 to 19 and Comparative Examples 11 to 14, the evaluation was performed only twice in total, and the total amount described below was the total amount for the two evaluations.

Three samples were prepared for each specimen (nonwoven fabric), and the average value of the wetback amounts measured for each of the three samples was determined as the wetback amount of that specimen.
The results are shown in Table 1. The smaller the amount of moisture seeping out from the nonwoven fabric, the less sweaty the human skin becomes, so the smaller the wetback value is, the more preferable it is.
The wetback amount can also be evaluated by the total amount of the wetback amounts measured four times. It is considered that when the nonwoven fabric is actually used as a top sheet of an absorbent article such as a paper diaper or a sanitary napkin, even if the top sheet absorbs urine or menstrual blood multiple times, the amount of urine or menstrual blood returning to the nonwoven fabric surface on the first fiber layer side, i.e., the surface in contact with the skin, is small, which not only improves the comfort and feeling of use of the wearer, but also makes it less uncomfortable to wear the same absorbent article continuously.

[Absorption time (saline solution)]
In the measurement of the wetback, the liquid absorption time was measured at each of the first to fourth measurements. The liquid absorption time was measured as the time from injection of the saline solution until the saline solution became invisible from the surface of the nonwoven fabric (the saline solution was no longer visible as a liquid), and this was taken as the liquid absorption time.
The results are shown in Table 1. The shorter the absorption time (seconds), the less sweaty the human skin becomes, so the shorter the liquid absorption time (seconds) is.
The liquid absorption time is the time required for the nonwoven fabric to absorb liquid and for the liquid to disappear from the surface, and the shorter the liquid absorption time, the more preferable. When the obtained nonwoven fabric is used as a top sheet of an absorbent article, the top sheet quickly absorbs urine or menstrual blood, and the time until the liquid disappears on the surface in contact with the skin, i.e., the surface of the nonwoven fabric on the first fiber layer side, is shortened, improving the dry feeling of the nonwoven fabric and improving the comfort and usability of the wearer of the absorbent article.

[Wetback (milk)]
[Absorption time (milk)]
For the wet bag (physiological saline) and absorption time (physiological saline), measurements were carried out using 50 ml of milk (product name: Oishii Gyunyuu, manufactured by Meiji Co., Ltd., viscosity at 37°C is 1.7 mPa·s) warmed to approximately 37°C as a simulated soft stool instead of physiological saline.

[Nonwoven surface diffusion length (milk)]
After measuring the absorption time for the first to fourth times, the plate with the injection tube was removed and the length of the part of the nonwoven fabric in the vertical direction that had absorbed the milk in the examples and comparative examples was measured and used as the diffusion length for the first to fourth times, respectively.

[Spot absorbency (milk)]
For the nonwoven fabrics of Examples 5, 7, and 9, the first fiber layer was faced up, and a sheet of "Kimtowel (registered trademark)" manufactured by Nippon Paper Crecia Co., Ltd., folded in four (length 16.5 cm, width 19.0 cm) was placed under the nonwoven fabric, and a stainless steel plate (length 5 cm, width 22 cm, thickness 0.5 cm, mass 360 g, hole diameter 1.5 cm, center-to-center distance of holes 2.0 cm) with holes at equal intervals was placed on the nonwoven fabric, and milk warmed to about 37°C (product name: Oishii Gyunyuu, (Stock Company)) was poured onto the nonwoven fabric in the holes. One drop (approximately 0.03 g) of milk (manufactured by Meiji, viscosity at 37° C. of 1.7 mPa·s) was dropped using a pipette (manufactured by AS ONE Corporation, product name: 1-4655-01 Polydropper 1 mL) and observation was made as to whether it was absorbed into the nonwoven fabric. If the liquid was no longer present on the surface of the nonwoven fabric facing the first fiber layer one minute after the milk was dropped onto the nonwoven fabric at room temperature (20° C.), it was judged as "spot absorbency present," and if the liquid remained on the surface of the nonwoven fabric facing the first fiber layer, it was judged as "spot absorbency not present."

In Tables 1 to 3, Examples 1 to 3 and Comparative Examples 1 and 2 were manufactured and evaluated in the summer, and Examples 4 to 10 and Comparative Example 3 were manufactured and evaluated in the winter. There may be slight differences in the evaluation results, but the degree of difference does not affect the fact that Examples 1 to 10 are Examples and Comparative Examples 1 to 3 are Comparative Examples. In Tables 1 to 3, the liquid absorption performance was examined taking into account both the total of two runs and the total of four runs.

All of the nonwoven fabrics of Examples 1 to 10 are excellent in terms of saline absorption time and wet back, milk absorption time and wet back, and texture (smoothness and softness).

In contrast, Comparative Example 1 has a high cellulosic fiber content in the second fiber layer, and further improvement is required in terms of total wetback of saline solution.

In Comparative Examples 2 and 3, the second fiber layer does not contain cellulosic fibers, and further improvement in the texture (smoothness and softness) is required. In addition, the nonwoven fabrics of Examples 1 to 10 showed better results in terms of the amount of wetback of the first saline solution than the nonwoven fabrics of Comparative Examples 2 and 3. This is thought to be because the cellulosic fibers absorb the liquid that returns from the absorbent body to the surface of the nonwoven fabric, reducing the amount of wetback.

Comparing Examples 1 to 3 and Comparative Example 2, the total wetback of milk was good in Examples 1 to 3 in which the second fiber layer contained cellulosic fibers. Also, comparing Examples 4 to 10 and Comparative Example 3, the total wetback of milk was good in Examples 4 to 10 in which the second fiber layer contained cellulosic fibers. In Comparative Examples 2 and 3, the total absorption time of milk was short, and milk was transferred to the absorbent quickly, but fluids containing oil such as milk are difficult to absorb by the superabsorbent polymer (SAP) of the absorbent, and spread and accumulate at the top of the absorbent, which is thought to have appeared as a large amount of wetback. It is thought that by including cellulosic fibers in the second fiber layer as in Examples 1 to 3 and Examples 4 to 10, it was possible to control the absorption time and reduce the amount of wetback.

Next, the examples are compared with each other.
Focusing on the type of cellulosic fiber, Examples 5 and 9 are similar nonwoven fabrics except that the cellulosic fibers are rayon B (viscose rayon) and lyocell (solvent spun cellulose fiber), respectively. However, Example 5 showed better results in the total wetback of saline and the total wetback of milk.

The nonwoven surface diffusion length of milk was greater in Example 5, where the cellulosic fiber was rayon B (viscose rayon). This is thought to be because the fiber cross section of rayon B (viscose rayon) is chrysanthemum-shaped, has a large surface area, and has streaks in the fiber axis direction, which makes it easy for milk to flow, resulting in easy diffusion in the second fiber layer. And because the milk is absorbed over a wide area in the absorbent by being diffused, and because the second fiber layer contains cellulosic fibers as described above, the absorption time can be controlled, which is thought to have resulted in a reduction in the total wetback amount of milk in Example 5.

As for spot absorbency of milk, Examples 5 and 7, in which the cellulose fiber was rayon B or D (viscose rayon), had no spot absorbency, whereas Example 9, in which the cellulose fiber was lyocell (solvent spun cellulose fiber), had spot absorbency. However, it is believed that Example 9, which contains lyocell (solvent spun cellulose fiber), had spot absorbency, which made it prone to liquid return and resulted in a relatively large amount of wetback.

Furthermore, Examples 7 and 10 are similar nonwoven fabrics except that the cellulosic fibers are rayon D (viscose rayon) and cotton, respectively, and have slightly different finenesses. However, Example 7 showed better results in the total wet bag of saline and the total wet bag of milk. This is thought to be because viscose rayon has a more uniform fineness and fiber length than cotton, and therefore the viscose rayon and the second core-sheath type composite fiber are mixed relatively uniformly in the second fiber layer, making it relatively difficult for milk to remain in the second fiber layer.

Focusing on the fineness of the cellulosic fibers, Examples 4, 5, 6, 7, and 8 are similar nonwoven fabrics except for the difference in the fineness of the viscose rayon, which is a cellulosic fiber. However, in the total wet bag test for saline solution, Examples 5 to 8 showed better results.

Focusing on the blend ratio of cellulosic fibers, Examples 1 to 3 are similar nonwoven fabrics except for the blend ratio of viscose rayon, a cellulosic fiber, which is different, but Example 2 showed better results in the total wet bag test for milk.

[Examples 11 to 19] and [Comparative Examples 11 to 14]
For Examples 11 to 19 and Comparative Examples 11 to 14, the fibers shown in Tables 4 to 6 were used to obtain nonwoven fabrics of Examples 11 to 19 and Comparative Examples 11 to 14 in the same manner as in the nonwoven fabric manufacturing method of Example 1 described above.
Diapers were produced as absorbent articles according to the above-mentioned method for the nonwoven fabrics of Examples 11 to 19 and Comparative Examples 11 to 14, and measurements and evaluations were carried out. The results are shown in Tables 4 to 6.

In Examples 11 to 13 and Comparative Examples 11 to 12, rayon D of 3.3 dtex was used as the cellulose fiber, and the blending ratio was changed. In Example 13 (blend ratio of rayon D: 30%), the balance of wetback with saline and milk was better. It is presumed that Example 13 has a better balance of the number of fibers between the second sheath-core type composite fiber and the cellulose fiber, so that the number of bonding points between the second sheath-core type composite fibers is more appropriate, and liquid residue in the second fiber layer is less likely to occur, and that there are more appropriate bonding points between the second sheath-core type composite fiber and the cellulose fiber, and the bonding points peel off more appropriately during liquid absorption, making it less likely that liquid residue in the second fiber layer occurs.
The wetbacks of Examples 11 to 13 using physiological saline were equal to or better than Comparative Example 11 (100% second sheath-core composite fiber), and in particular, the first wetback of Examples 11 to 13 was better than Comparative Example 11. The wetbacks of Examples 11 to 13 using soft stools from milk were slightly improved compared to Comparative Example 11 (100% second sheath-core composite fiber). The nonwoven fabric surface diffusivity (total) of Examples 11 to 13 was equal to or better. As for the performance of napkins, as described below, the wetbacks of the Examples were greatly improved compared to the Comparative Example (100% second sheath-core composite fiber), and therefore it is understood that the Examples are more suitable for diapers (for newborns) and napkins that require performance under conditions of small amounts of liquid.
In Comparative Example 12 (blending ratio of rayon D: 50%), the processability in the production of the nonwoven fabric was insufficient, and the nonwoven fabric was too soft to be cut, so that fibers were likely to fall off from the cut surface, and delamination between the first and second fiber layers was likely to occur.

In Examples 14 to 16 and Comparative Example 13, cotton was used as the cellulose fiber, and the blend ratio was changed. In Example 14 (cotton blend ratio 10%), wetback with milk was better. Cotton is a fiber with non-uniform fiber length, so the number of fibers tends to be greater than that of rayon or lyocell. Therefore, it is presumed that in Example 14, the balance between the number of fibers of the second sheath-core composite fiber and the cellulose fiber was better, the number of bonding points between the second sheath-core composite fibers was more appropriate, and liquid residue in the second fiber layer was less likely to occur, and that there were more appropriate bonding points between the second sheath-core composite fiber and the cellulose fiber, and the bonding points peeled off more appropriately during liquid absorption, making it less likely that liquid residue in the second fiber layer occurred.
The wet bags for physiological saline in Examples 14 to 16 were equal to or better than Comparative Example 11 (100% second core-sheath type composite fiber), and in particular, the first wet bag was better in Examples 14 to 16 than Comparative Example 11. The wet bags for soft milk stool in Examples 14 to 16 were improved over Comparative Example 11 (100% second core-sheath type composite fiber). The nonwoven surface diffusivity (total) was equal to or better. It was found that the Examples are suitable for diapers for soft stool (especially for babies), and can also be used as napkins.
In Comparative Example 13 (cotton blend ratio 50%), the processability in the production of the nonwoven fabric was insufficient, and the nonwoven fabric was too soft to be cut, so that fibers were likely to fall off from the cut surface, and delamination between the first and second fiber layers was likely to occur.

In Examples 17 to 19 and Comparative Example 14, the blend ratio was changed by using lyocell (1.7 dtex) as the cellulose fiber. Example 19 (lyocell blend ratio 30%) had a better balance of wetback with saline and milk, but Example 18 (lyocell blend ratio 20%) was better in terms of processability in nonwoven fabric production and cutting processability of the nonwoven fabric, and overall Example 18 (lyocell blend ratio 20%) was better.
The wetbacks of Examples 17 to 19 using physiological saline were worse than those of Examples 11 to 16, but the wetbacks of physiological saline were equivalent to that of Comparative Example 11 (100% second sheath-core composite fiber), and the wetbacks of milk-derived soft stool were significantly improved over that of Comparative Example 11 (100% second sheath-core composite fiber), and the nonwoven fabric surface diffusivity (total) was equal to or better than that of Comparative Example 11. Therefore, it is considered that these are more effective as diapers for soft stool (especially for newborns). They can also be used as napkins.
In Comparative Example 14 (Lyocell content: 50%), the processability in the production of the nonwoven fabric was insufficient, and the nonwoven fabric was too soft to be cut, so that the fibers were likely to fall off from the cut surface. Also, delamination between the first and second fiber layers was likely to occur.

[Examples 21 to 29] and [Comparative Examples 21 to 24]
For Examples 21 to 29 and Comparative Examples 21 to 24, the fibers shown in Tables 7 to 9 were used to obtain nonwoven fabrics of Examples 21 to 29 and Comparative Examples 21 to 24 using a method similar to the method for producing the nonwoven fabric of Example 1 described above.
For the nonwoven fabrics of Examples 21 to 29 and Comparative Examples 21 to 24, napkins were manufactured as absorbent articles, and measurements and evaluations were carried out according to the methods described below. The results are shown in Tables 7 to 9.

The absorbency of the nonwoven fabrics of Examples 21 to 29 and Comparative Examples 21 to 24 was evaluated by producing napkins as absorbent articles for evaluation. The production method is described below.
[Manufacture of absorbent articles (napkins)]
The top sheet was peeled off and removed from a commercially available napkin (manufactured by Daio Paper Corporation, product name: Eris Megami, bare skin feeling, heavy day use, with wings, 23 cm) that is composed of a three-layer structure of a top sheet, a second sheet, and an absorbent body, and a leakproof sheet that prevents moisture from leaking outward. In place of the removed top sheet, the nonwoven fabrics (19 cm long x 8 cm wide) of Examples 21 to 29 and Comparative Examples 21 to 24 were laminated to prepare an absorbent article for evaluation. In addition, when laminating, the first fiber layer was arranged to face outward and the second fiber layer was arranged to face the second sheet. Using this absorbent article for evaluation, the absorbency (absorption time, wetback, nonwoven surface diffusion length) of the nonwoven fabrics of Examples 21 to 29 and Comparative Examples 21 to 24 was evaluated.

[Wetbag (artificial menstrual blood)]
The nonwoven fabric wet bags of Examples 21 to 29 and Comparative Examples 21 to 24 were evaluated by the following method.
(1) In order to measure the amount of wetback, the following items were prepared:
Absorbent articles for evaluation of the above-mentioned Examples and Comparative Examples Plate with injection tube (two-stage cylindrical shape with height 6.0 cm, inner diameter of upper tube 2.2 cm, inner diameter of lower tube 1.0 cm)
The artificial menstrual blood was adjusted to contain 100 ml of glycerin, 875 ml of ion-exchanged water, 4.6 g of CMC (sodium carboxymethylcellulose), 10 g of NaCl (sodium chloride), and 10.7 g of Na2CO3 (sodium carbonate) per liter, and was colored with a small amount of food blue No. 1. (Viscosity at 37°C is 8 mPa·s)
Filter paper (Toyo Roshi Kaisha, Ltd., ADVANTEC (registered trademark) No. 2) 10 cm x 10 cm
Weight (1kg) 10cm x 10cm

(2) Method The amount of wetback was measured according to the following procedure.
(i) The absorbent article to be evaluated was placed with the nonwoven fabric (19 cm length x 8 cm width) facing upwards, and a plate equipped with an injection tube was placed on top of it.
(ii) 5.0 ml of artificial menstrual blood warmed to about 37° C. was poured from the cylinder. The sample was left to stand until the artificial menstrual blood was no longer visible on the surface of the nonwoven fabric (the artificial menstrual blood was no longer visible as a liquid).
(iii) The plate with the injection tube was removed and allowed to stand for 10 minutes.
(iv) The mass of the filter paper (10 sheets) was measured in advance and placed on the nonwoven fabric, and a weight of 1 kg was placed on top of the filter paper for 20 seconds. The mass of the filter paper was then measured. The difference between the mass of the filter paper before being placed on the nonwoven fabric and the mass of the filter paper after being placed on the nonwoven fabric and the weight was placed on top of the nonwoven fabric corresponds to the amount of wetback.
(v) Returning to (i) above, steps (i) to (iv) were repeated to perform another measurement, for a total of two evaluations of the wetback.
Three samples were prepared for each specimen (nonwoven fabric), and the average value of the wetback amounts measured for each of the three samples was determined as the wetback amount of that specimen.

[Absorption time (artificial menstrual blood)]
In the measurement of the wet bag, the liquid absorption time was measured at the first and second measurements. The liquid absorption time was measured as the time from the injection of the artificial menstrual blood until the artificial menstrual blood became invisible from the surface of the nonwoven fabric (the artificial menstrual blood was no longer recognized as a liquid), and this was taken as the liquid absorption time.

Examples 21 to 29 correspond to Examples 11 to 19, respectively, and Comparative Examples 21 to 24 correspond to Comparative Examples 11 to 14, respectively. Examples 21 to 29 are napkins, and Examples 11 to 19 are diapers, so they are different absorbent articles, but Examples 21 to 29 showed similar trends to the above-mentioned Examples 11 to 19.

Among Examples 21 to 23, Example 23 (30% rayon D blend) had a better balance between the liquid absorption time and the wet back. Among Examples 24 to 26, Example 25 (20% cotton blend) had a better balance between the liquid absorption time and the wet back. Among Examples 27 to 29, Example 28 (20% lyocell blend) had a better balance between the liquid absorption time and the wet back. In Examples 23, 25, and 28, the balance between the number of fibers of the second sheath-core composite fiber and the cellulose fiber was better, so the number of bonding points between the second sheath-core composite fibers was more appropriate, making it less likely for liquid to remain in the second fiber layer, and there were more appropriate bonding points between the second sheath-core composite fiber and the cellulose fiber, so the bonding points peeled off more appropriately during liquid absorption, making it less likely for liquid to remain in the second fiber layer. In particular, since artificial menstrual blood has a high viscosity, it is thought that the impact of reducing the amount of residual liquid is large.

The nonwoven fabric for absorbent articles according to the embodiment of the present invention can improve the absorbency of fluids such as loose stool while maintaining the liquid absorption performance and touch. Therefore, the nonwoven fabric for absorbent articles according to the embodiment of the present invention can be suitably used for manufacturing top sheets and absorbent articles.

Claims (12)

A nonwoven fabric comprising a first fiber layer and a second fiber layer located on one main surface of the first fiber layer,
the first fiber layer includes a first sheath-core type composite fiber,
the second fiber layer includes a second sheath-core type composite fiber and a cellulosic fiber,
the first sheath-core type composite fiber has a smaller fineness than the second sheath-core type composite fiber,
The first core-sheath type composite fiber has a fineness of 1.0 to 2.8 dtex,
The fineness of the second core-sheath type composite fiber is 1.7 to 5.6 dtex,
The cellulosic fiber has a fineness of 1.2 to 6.0 dtex,
The second fiber layer contains the cellulosic fiber in a ratio of 5% by mass to 40% by mass based on the total mass of the second fiber layer,
A nonwoven fabric for a top sheet of an absorbent article, wherein the first fibrous layer is a layer that contacts the skin of a wearer . 2. The nonwoven fabric for a top sheet of an absorbent article according to claim 1, wherein a ratio of the number of fibers of the second sheath-core type composite fibers to the number of fibers of the cellulosic fibers is 0.6 to 4.0. 3. The nonwoven fabric for a top sheet of an absorbent article according to claim 1, wherein the fineness of the cellulosic fibers is 1.2 to 2.2 dtex. The nonwoven fabric for a top sheet of an absorbent article according to any one of claims 1 to 3 , wherein the second fiber layer contains the cellulosic fiber in a proportion of 15% by mass to 25% by mass, based on the total mass of the second fiber layer . The nonwoven fabric for a top sheet of an absorbent article according to claim 1 , wherein the cellulosic fiber comprises viscose rayon. The nonwoven fabric for a top sheet of an absorbent article according to any one of claims 1 to 5 , wherein the first fibrous layer has a smaller basis weight than the second fibrous layer. The nonwoven fabric for a top sheet of an absorbent article according to any one of claims 1 to 6 , wherein the absorbent article includes an absorbent article for absorbing fluids containing water and oil. The nonwoven fabric for a top sheet of an absorbent article according to claim 7 , wherein the fluid containing water and oil contains loose feces. A top sheet for absorbent articles, comprising the nonwoven fabric for top sheets for absorbent articles according to any one of claims 1 to 8 . An absorbent article comprising the top sheet for absorbent articles according to claim 9 , wherein the first fibrous layer of the top sheet for absorbent articles according to claim 9 is positioned on the side closest to the skin of a user. 11. The absorbent article of claim 10 , comprising an absorbent article for absorbing fluids, including water and oil. 12. The absorbent article of claim 11 , wherein the fluid containing water and oil comprises loose stool.