Absorbent article
Patent Information
- Application Number
- JP2022126435
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-08-08
- Publication Date
- 2025-06-13
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to an absorbent article. [Background technology]
[0002] Since cellulose fibers generally have high wettability, when a nonwoven fabric containing cellulose fibers is used as a topsheet of an absorbent article, a hydrophobization treatment is required to enhance dryness in order to reduce liquid retention on the outermost surface of the topsheet. Cellulose fibers can be hydrophobized by using a hydrophobizing agent. However, when a nonwoven fabric manufactured by the spunlace method is used as a topsheet, the hydrophobizing agent falls off when a high-pressure water flow is applied to the fibers during the manufacturing process, so hydrophobization must be performed after the nonwoven fabric is manufactured.
[0003] When a hydrophobizing treatment is performed after the manufacture of a nonwoven fabric, the entire surface of the nonwoven fabric must be hydrophobized, and it is therefore not easy to impart a hydrophilicity gradient in the plane or thickness direction, which is adopted to achieve both high dryness and low runoff. Runoff is a phenomenon in which a liquid does not penetrate the top sheet and flows out along the surface of the top sheet. Patent Document 1 proposes a solution to this problem by using a nonwoven fabric that is a composite of cellulose fibers, from which the hydrophobizing agent is unlikely to fall off even when a high-pressure water flow is applied, and hydrophilic cellulose fibers. [Prior art documents] [Patent documents]
[0004] [Patent Document 1] Special Publication No. 2015-507977 Summary of the Invention [Problem to be solved by the invention]
[0005] It is possible to obtain a topsheet with a relatively high degree of dryness by using the nonwoven fabric described in Patent Document 1. However, there is a demand for reducing runoff while maintaining the dryness of the topsheet of an absorbent article. Therefore, an object of the present invention is to achieve both high dryness and low runoff in an absorbent article having a topsheet made of a nonwoven fabric using cellulose fibers. [Means for solving the problem]
[0006] The present invention provides an absorbent article comprising a liquid-permeable top sheet positioned on the wearer's skin-facing side, a back sheet positioned on the wearer's non-skin-facing side, and an absorbent body positioned between the two sheets, The top sheet has a first fiber layer located on the skin-facing side, the first fibrous layer comprises hydrophobized man-made cellulose fibers and hydrophilic cellulose fibers; The first fiber layer provides an absorbent article in which the presence rate of the hydrophobized artificial cellulose fibers differs between the skin-facing side and the non-skin-facing side. Effect of the Invention
[0007] According to the present invention, there is provided an absorbent article in which the dryness and run-off properties of the topsheet containing cellulose fibers are compatible. [Brief description of the drawings]
[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a top sheet provided in an absorbent article of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing another example of the top sheet provided in the absorbent article of the present invention. [Diagram 3] FIG. 3 is a perspective view showing yet another example of the top sheet provided in the absorbent article of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0009] The present invention will now be described based on its preferred embodiments. The absorbent article of the present invention generally has an elongated shape having a vertical direction corresponding to the direction extending from the wearer's abdomen through the crotch region to the back side, and a horizontal direction perpendicular to the vertical direction. The absorbent article has a crotch region located in the wearer's crotch region, and a ventral side region and a back side region extending in front and behind the crotch region. The crotch region has an excretory region facing portion that is disposed facing the excretory region of the wearer when the absorbent article is worn, and the excretory region facing portion is usually located in the vertical center of the absorbent article or in the vicinity thereof.
[0010] An absorbent article generally comprises a top sheet located on the wearer's skin-facing side, a back sheet located on the wearer's non-skin-facing side, and an absorbent body located between the two sheets. As the top sheet, a liquid-permeable sheet, such as a nonwoven fabric, can be used. The top sheet will be described in detail later. As shown in Figs. 1 to 3 described later, the top sheet may have an uneven shape on its skin-facing side. For example, a plurality of convex portions can be formed in a scattered manner on the skin-facing side of the top sheet. Alternatively, ridges and grooves extending in one direction can be formed alternately on the skin-facing side of the top sheet. For such a purpose, as described later, it is preferable to form the top sheet using two or more fiber layers. The uneven shape on the skin-facing side of the top sheet makes the top sheet plump, improving the feel of the absorbent article and reducing the contact area with the skin, thereby improving the dryness of the top sheet and creating an effect of blocking liquid flowing along the surface of the top sheet, thereby more efficiently reducing runoff.
[0011] On the other hand, the back sheet may be, for example, a liquid-impermeable or poorly liquid-permeable film or a spunbond, meltblown, or spunbond laminated nonwoven fabric. A poorly liquid-permeable film may be provided with water vapor permeability by providing a plurality of micropores or using a material with high water vapor solubility and diffusibility. 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] Examples of absorbent articles having the above-mentioned configuration include flat-type disposable diapers, pants-type disposable diapers, sanitary napkins, incontinence pads, etc., but are not limited to these.
[0016] The topsheet, which is one of the components of an absorbent article, can have a multi-layer structure in order to improve the dryness of the topsheet. For this purpose, the topsheet can have a second fibrous layer in addition to a first fibrous layer. The first fiber layer is located on the skin-facing side of the topsheet, and the surface of the first fiber layer forms one of the outer surfaces of the topsheet, i.e., the skin-facing surface, and therefore the outer surface of the first fiber layer is the surface that comes into direct contact with the wearer's skin when the absorbent article is worn by the wearer. On the other hand, when the second fiber layer is provided, the second fiber layer is located on the non-skin facing side of the topsheet, and the surface of the second fiber layer forms the other outer surface of the topsheet, i.e., the non-skin facing surface. Therefore, the outer surface of the second fiber layer faces the absorbent body. The first and second fibrous layers may be laminated directly to each other to form a multi-layer structure, in which case the top sheet is entirely made of fibers. The first fiber layer and the second fiber layer will be described below.
[0017] First, the first fiber layer will be described. The first fiber layer preferably contains at least hydrophobic artificial cellulose fibers and hydrophilic cellulose fibers. As described above, the outer surface of the first fiber layer is the surface that contacts the wearer's skin, so by forming the first fiber layer mainly from hydrophobic artificial cellulose fibers and hydrophilic cellulose fibers, it is possible to impart a good wearing feel reminiscent of cotton fabric. In addition, since the first fiber layer contains hydrophilic cellulose fibers, the absorption time of bodily fluids is shortened, and the runoff can be kept low, so that the wearer's wear of the absorbent article when absorbing bodily fluids is comfortable. In addition, since the first fiber layer contains hydrophobic artificial cellulose fibers, the hydrogen bonds between the fibers are weakened, the good texture of the cellulose fibers is further enhanced, and a sufficient dry feel can be imparted to the skin-facing surface of the top sheet. In this way, the inclusion of hydrophobic artificial cellulose fibers and hydrophilic cellulose fibers in the first fiber layer is very advantageous in terms of improving the wearer's wearer's wearer's dryness.
[0018] In this specification, hydrophilic fiber refers to a fiber whose surface exhibits hydrophilicity. The hydrophilicity of hydrophilic fiber refers to a fiber contact angle of 45° or less, as determined by the following method. When cellulose fiber is used as the fiber, the surface generally exhibits high hydrophilicity unless any treatment is applied, since the fiber has many hydroxyl groups due to its chemical structure. (Method of measuring fiber contact angle) A fiber is taken out from a predetermined portion of the nonwoven fabric, and the contact angle of water with the fiber is measured. An automatic contact angle meter MCA-J (product name) manufactured by Kyowa Interface Science Co., Ltd. is used as the measuring device. Distilled water is used for measuring the contact angle. The amount of liquid discharged from the inkjet water droplet discharge unit (CTC-25, a pulse injector with a 25 μm orifice diameter, manufactured by Cluster Technology Co., Ltd.) is set to 10 picoliters, and the water droplets are dropped directly onto the fiber. The dropping behavior is recorded on a high-speed recording device connected to a horizontally placed camera. From the viewpoint of later image analysis, a personal computer with a built-in high-speed capture device is preferable as the recording device. In this measurement, images are recorded every 17 msec. In the recorded video, the first image in which the water droplets land on the fiber taken out of the nonwoven fabric is analyzed using the attached software FAMAS (software version 2.6.2, analysis method is the droplet method, analysis method is the θ / 2 method, image processing algorithm is non-reflective, image processing image mode is frame, threshold level is 200, curvature correction is not performed), and the angle between the surface of the water droplet that is in contact with the air and the fiber is calculated, which is the contact angle. If the fiber taken out of the nonwoven fabric is 2 mm or longer, it is cut to a fiber length of 2 mm, and the fiber is placed on the sample stage of the contact angle meter and kept horizontal. The contact angles are measured at three different points for each fiber, and the average value (rounded off to the second decimal place) is defined as the fiber contact angle.
[0019] In this specification, hydrophobic fibers and hydrophobized fibers refer to fibers that exhibit hydrophobic properties. The hydrophobicity of hydrophobic fibers and hydrophobized fibers refers to the above-mentioned fiber contact angle of 70° or more.
[0020] In this specification, the term "artificial cellulose fibers" refers to cellulose fibers that are artificially produced using natural fibers such as pulp and cotton as raw materials. Specific examples will be described later.
[0021] The hydrophobized artificial cellulose fiber is obtained by subjecting the surface of a hydrophilic artificial cellulose fiber to a hydrophobic treatment to make the surface hydrophobic. There is no particular limitation on the method of hydrophobization, and a conventionally known method can be used. The hydrophobization is generally achieved by applying a hydrophobizing agent to the surface of the hydrophilic cellulose fiber. There is no particular limitation on the type of hydrophobizing agent, and a conventionally known hydrophobizing agent can be used. When the first fiber layer is produced by a method of applying a high-pressure water flow to a fiber web, such as the spunlace method, it is preferable to use a hydrophobizing agent that has the property of not being washed away by the high-pressure water flow. Examples of hydrophobizing agents having such properties include alkyl ketene dimers and alkenyl ketene dimers shown in the following formula (1).
[0022] [ka]
[0023] In the formula, R 1 and R 2 R are the same or different hydrocarbon groups having 8 to 40 carbon atoms. 1 and R 2 R may each independently be a saturated or unsaturated hydrocarbon group. 1 and R 2 may each independently be linear or branched.
[0024] Other preferred hydrophobizing agents include substituted cyclic dicarboxylic acid anhydrides, such as substituted succinic anhydrides and substituted glutaric anhydrides, and the like.
[0025] The preferred alkyl ketene dimers are prepared from acid chlorides, for example, by the method described by R. Adams, Org. Reactions Vol. III, p 129 John Wiley & Sons Inc. NY 1946 or JC Scanner; J. Am. Chem. Soc., Vol. 69, p. 2444 (1947).
[0026] An example of the artificial cellulose fiber that has been hydrophobized with a hydrophobizing agent made of an alkylketene dimer is VEOCEL (registered trademark) manufactured by Lenzing AG.
[0027] Other suitable hydrophobizing agents include DACC (di-alkyl-carbamoyl-chloride) or stearic acid amides, for example Leristan HEI / 42 from Zschimmer & Schwarz.
[0028] There is no particular limitation on the type of hydrophilic artificial cellulose fiber to which the above-mentioned various hydrophobizing agents are applied. As the artificial cellulose fiber, any artificial cellulose fiber used for various purposes including sanitary products can be used without particular limitation. These artificial cellulose fibers can be used alone or in combination of two or more kinds. Examples of artificial cellulose fibers include Lyocell (registered trademark), Tencel (registered trademark), cupra, viscose rayon, and Bemliese (registered trademark). The above-mentioned various man-made cellulose fibers may also be hydrophilic cellulose fibers to be used in combination with the hydrophobized man-made cellulose fibers in the present invention.
[0029] The hydrophobized artificial cellulose fibers and the hydrophilic cellulose fibers may each independently be long fibers (continuous filaments) or short fibers (staple fibers). The type of fiber to be used may be appropriately determined depending on the manufacturing method of the first fiber layer containing these fibers. For example, when the first fiber layer is manufactured by the spunlace method, the air-through method, the needle punch method, or the like, it is preferable to use short fibers as the hydrophobized artificial cellulose fibers and the hydrophilic cellulose fibers.
[0030] In addition to the above-mentioned hydrophobic artificial cellulose fibers and hydrophilic cellulose fibers, the first fiber layer may further contain thermoplastic fibers as necessary. The thermoplastic fibers are fibers made of a thermoplastic resin and are blended mainly for the purpose of improving the bond with the second fiber layer. Examples of thermoplastic fibers include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; poly(meth)acrylic acid alkyl esters, polyvinyl chloride, polyvinylidene chloride, etc. These thermoplastic fibers can be used alone or in combination of two or more. The thermoplastic fibers may be composite fibers such as core-sheath type or side-by-side type, split fibers, modified cross-section fibers, heat-shrinkable fibers, etc. The composite fibers may be composed of a plurality of resin components.
[0031] The thermoplastic fibers may be long fibers (continuous filaments) or short fibers (staple fibers). The type of fiber to be used may be appropriately determined depending on the method for producing the first fiber layer containing the thermoplastic fibers. For example, when the first fiber layer is produced by the spunlace method, the air-through method, the needle punch method, or the like, it is preferable to use short fibers as the thermoplastic fibers.
[0032] The hydrophobic artificial cellulose fibers and the hydrophilic cellulose fibers each preferably have a fiber diameter of 5 μm or more and 60 μm or less, from the viewpoint of achieving a good feel and high dryness of the topsheet, and more preferably have a fiber diameter of 7 μm or more and 30 μm or less, and even more preferably have a fiber diameter of 9 μm or more and 20 μm or less.
[0033] When the first fiber layer contains thermoplastic fibers, the fiber diameter of the thermoplastic fibers is preferably 5 μm or more and 60 μm or less from the viewpoints of achieving a good feel of the topsheet and good bonding with the second fiber layer described below. From this viewpoint, the fiber diameter of the thermoplastic fibers is more preferably 8 μm or more and 30 μm or less, and even more preferably 10 μm or more and 20 μm or less.
[0034] The total amount of the hydrophobized artificial cellulose fibers and the hydrophilic cellulose fibers is preferably 10% by mass or more and 100% by mass or less relative to the first fiber layer, from the viewpoint of achieving a good texture of the topsheet. From this viewpoint, the total amount of the hydrophobized artificial cellulose fibers and the hydrophilic cellulose fibers contained in the first fiber layer is more preferably 30% by mass or more and 100% by mass or less, and even more preferably 50% by mass or more and 100% by mass or less, relative to the first fiber layer.
[0035] When the first fiber layer contains thermoplastic fibers, the content of the thermoplastic fibers is preferably 1% by mass or more and 90% by mass or less relative to the first fiber layer, from the viewpoints of achieving a good feel of the topsheet and good bonding with the second fiber layer described below. From this viewpoint, the content of the thermoplastic fibers in the first fiber layer is more preferably 3% by mass or more and 70% by mass or less, and even more preferably 5% by mass or more and 50% by mass or less, relative to the first fiber layer.
[0036] From the viewpoint of achieving both high dryness and low runoff for the surface material, the water repellency R1 of the skin-facing surface of the first fiber layer is preferably 50° or more and 80° or less, more preferably 52° or more and 70° or less, and even more preferably 55° or more and 65° or less. In order to promote the transfer of excreted body fluid to the absorbent body and achieve an even lower runoff, when the water repellency of the non-skin-facing surface of the first fiber layer is R2, the value of R1-R2 is preferably 5° or more, more preferably 10° or more, and even more preferably 15° or more. The value of R1 is the average fiber contact angle of 50 fibers randomly selected from the skin-facing side of the first fiber layer, and the value of R2 is the average fiber contact angle of 50 fibers randomly selected from the non-skin-facing side of the first fiber layer. In this specification, the "water repellency of the fiber" refers to the water repellency taking into consideration all of the hydrophobized man-made cellulose fibers, the hydrophilic cellulose fibers, and the thermoplastic fibers (if contained).
[0037] In the first fiber layer, when the water repellency of the fiber differs between the skin-facing side and the non-skin-facing side, the water repellency of the fiber may decrease continuously from the skin-facing side to the non-skin-facing side, or may decrease in a step-like manner. In order to make the water repellency of the fibers on the skin-facing side and the non-skin-facing side of the first fiber layer different, for example, fiber webs having different blend ratios of hydrophobic artificial cellulose fibers, hydrophilic cellulose fibers, and thermoplastic fibers may be layered and integrated by spunlace processing.
[0038] In the first fiber layer, the fiber diameters of the hydrophobized artificial cellulose fibers, the hydrophilic cellulose fibers, and the thermoplastic fibers are preferably larger on the skin-facing side than on the non-skin-facing side. Such fiber diameters of the fibers can improve the transfer of liquid within the first fiber layer. From this viewpoint, when the fiber diameter of the fibers present on the skin-facing side of the first fiber layer is D1 and the fiber diameter of the fibers present on the non-skin-facing side is D2, the value of D1 / D2 is preferably 1.1 or more, more preferably 1.25 or more, and even more preferably 1.4 or more. The value of D1 is the average fiber diameter of 50 fibers randomly extracted from the skin-facing side of the first fiber layer, and the value of D2 is the average fiber diameter of 50 fibers randomly extracted from the non-skin-facing side of the first fiber layer. The fiber diameter is measured by observing the extracted fibers with a scanning electron microscope or the like, and if the cross section is not circular, the thickest part of the cross section is defined as the fiber diameter. In this specification, the "fiber diameter of the fibers" refers to the fiber diameter taking into consideration all of the hydrophobized man-made cellulose fibers, the hydrophilic cellulose fibers, and the thermoplastic fibers (if included).
[0039] In the first fiber layer, when the fiber diameter of the fibers differs between the skin-facing side and the non-skin-facing side, the fiber diameter of the fibers may decrease continuously from the skin-facing side to the non-skin-facing side, or may decrease in a step-like manner. In order to make the fiber diameter of the fibers in the first fiber layer different between the skin-facing side and the non-skin-facing side, for example, a multi-layer web may be formed by overlapping fiber webs each having a different blend ratio of fibers with different fiber diameters, and the multi-layer web may be subjected to, for example, a hydroentanglement treatment (spunlace treatment), a hot air penetration treatment (air-through treatment), or a needle punch treatment to produce the first fiber layer.
[0040] In the first fiber layer, the fiber diameter of the hydrophilic cellulose fiber is preferably larger on the skin-facing side than on the non-skin-facing side. Such a fiber diameter of the hydrophilic cellulose fiber can further improve the liquid transfer in the first fiber layer. From this viewpoint, when the fiber diameter of the hydrophilic cellulose fiber on the skin-facing side of the first fiber layer is d1 and the fiber diameter of the hydrophilic cellulose fiber on the non-skin-facing side is d2, the value of d1 / d2 is preferably 1.1 or more, more preferably 1.3 or more, and even more preferably 1.5 or more. When the hydrophilic cellulose fiber is not included in the skin-facing side, the value of d1 / d2 is defined as 10, and when the hydrophilic cellulose fiber is not included in the non-skin-facing side, the value of d1 / d2 is defined as 0. In the first fiber layer, the fiber diameter of the hydrophobized artificial cellulose fiber is preferably larger on the skin-facing side than on the non-skin-facing side. Such a fiber diameter of the hydrophobized artificial cellulose fiber can further improve the transfer of liquid within the first fiber layer. From this viewpoint, when the fiber diameter of the hydrophobized artificial cellulose fiber on the skin-facing side of the first fiber layer is d3 and the fiber diameter of the hydrophobized artificial cellulose fiber on the non-skin-facing side is d4, the value of d3 / d4 is preferably 1.1 or more, more preferably 1.3 or more, and even more preferably 1.5 or more. When the hydrophobized artificial cellulose fiber is not included on the skin-facing side, the value of d3 / d4 is defined as 0, and when the hydrophobized artificial cellulose fiber is not included on the non-skin-facing side, the value of d3 / d4 is defined as 10. The value of d1 is the average fiber diameter of 50 hydrophilic cellulose fibers randomly extracted from the skin-facing side of the first fiber layer, and the value of d2 is the average fiber diameter of 50 hydrophilic cellulose fibers randomly extracted from the non-skin-facing side of the first fiber layer. The value of d3 is the average fiber diameter of 50 hydrophobized artificial cellulose fibers randomly extracted from the skin-facing side of the first fiber layer, and the value of d4 is the average fiber diameter of 50 hydrophobized artificial cellulose fibers randomly extracted from the non-skin-facing side of the first fiber layer. The fiber diameter is measured by measuring the fiber contact angle of the extracted fibers in advance, separating them into hydrophobized artificial cellulose fibers and hydrophilic cellulose fibers, and observing them with a scanning electron microscope or the like. When the cross section is not circular, the thickest part of the cross section is defined as the fiber diameter.
[0041] In the first fiber layer, the presence rate of thermoplastic fibers is preferably higher on the non-skin facing side than on the skin facing side. When the thermoplastic fibers are present in such a state in the first fiber layer, good bonding to the second fiber layer described below can be achieved with a small thermoplastic fiber blending rate. From this viewpoint, when the proportion (mass%) of thermoplastic fibers contained in the entire first fiber layer is P1 and the proportion (mass%) of thermoplastic fibers present on the non-skin facing side is P2, the value of P1 / P2 is preferably 0.8 or less, more preferably 0.4 or less, and even more preferably 0.2 or less. The value of P1 is determined by the following method. First, a sample taken from the entire first fiber layer is weighed in advance. Then, only the cellulose fibers are selectively dissolved. For example, sulfuric acid can be used for selective dissolution. If the use of sulfuric acid causes dissolution of fibers other than cellulose fibers, other appropriate chemicals may be used instead of sulfuric acid. The mass of the fibers remaining after dissolving the cellulose fibers is measured, and this value is regarded as the mass of the thermoplastic fibers. P1 is calculated from the mass weighed in advance and the mass of the thermoplastic fibers. The value of P2 is calculated by dividing the first fiber layer into three equal parts along the thickness direction, and applying the same method as described above to the sample on the non-skin side.
[0042] In the first fiber layer, when the proportion of thermoplastic fibers differs between the skin-facing side and the non-skin-facing side, the proportion of thermoplastic fibers may decrease continuously or stepwise from the non-skin-facing side to the skin-facing side. In order to make the presence rate of thermoplastic fibers different between the skin-facing side and the non-skin-facing side in the first fiber layer, for example, a multilayer web can be formed by superposing a second web containing thermoplastic fibers, hydrophobized artificial cellulose fibers, and hydrophilic cellulose fibers, which has a lower thermoplastic fiber content than the first web, on a first web containing thermoplastic fibers, hydrophobized artificial cellulose fibers, and hydrophilic cellulose fibers, and then subjecting this multilayer web to, for example, hydroentanglement treatment (spunlace treatment), hot air penetration treatment (air-through treatment), needle punching treatment, or the like to produce the first fiber layer.
[0043] On the other hand, with regard to the presence of the hydrophobized artificial cellulose fiber in the first fiber layer, from the viewpoint of achieving both high dryness and low runoff of the surface material, the presence rate Q1 of the hydrophobized artificial cellulose fiber in the skin-facing surface of the first fiber layer is preferably 10% to 80%, more preferably 25% to 70%, and even more preferably 30% to 65%. In addition, in order to promote the transfer of excreted body fluids to the absorbent and achieve even lower runoff, it is preferable that the presence rate of the hydrophobized artificial cellulose fiber is higher on the skin-facing surface side than on the non-skin-facing surface side. From this viewpoint, when the proportion of the hydrophobized artificial cellulose fiber present on the non-skin-facing surface of the first fiber layer is Q2, the value of Q1-Q2 is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. The Q1 value is the ratio (%) of the number of hydrophobic artificial cellulose fibers to all cellulose fibers, which can be calculated by randomly extracting 30 cellulose fibers from the skin-facing side of the first fiber layer, measuring the fiber contact angle of each, and sorting them into hydrophilic cellulose fibers and hydrophobic artificial cellulose fibers.The Q2 value is the ratio (%) of the number of hydrophobic artificial cellulose fibers to all cellulose fibers, which can be calculated by randomly extracting 30 cellulose fibers from the non-skin-facing side of the first fiber layer, measuring the fiber contact angle of each, and sorting them into hydrophilic cellulose fibers and hydrophobic artificial cellulose fibers.
[0044] In the first fiber layer, when the proportion of hydrophobized artificial cellulose fibers differs between the skin-facing side and the non-skin-facing side, the proportion of hydrophobized artificial cellulose fibers may decrease continuously from the skin-facing side to the non-skin-facing side, or may decrease in a step-like manner. In order to make the presence rate of hydrophobic artificial cellulose fibers different between the skin-facing side and the non-skin-facing side in the first fiber layer, for example, a multilayer web can be formed by superposing a second web containing thermoplastic fibers, hydrophobic artificial cellulose fibers, and hydrophilic cellulose fibers on a first web containing thermoplastic fibers, hydrophobic artificial cellulose fibers, and hydrophilic cellulose fibers, and the second web containing a lower amount of hydrophobic artificial cellulose fibers than the first web, and then subjecting this multilayer web to, for example, a hydroentanglement treatment (spunlace treatment), a hot air penetration treatment (air-through treatment), or a needle punch treatment, etc., to produce the first fiber layer.
[0045] The first fibrous layer has a basis weight of 15 g / m 2 More than 50g / m 2 From the viewpoint of stabilizing the texture of the sheet and maintaining a uniform in-plane feel, it is preferable that the basis weight of the first fiber layer is 20 g / m or less. 2 More than 45g / m 2 More preferably, it is 25 g / m or less. 2 More than 40g / m 2 It is even more preferred that:
[0046] The first fiber layer can be manufactured by various nonwoven fabric manufacturing methods. For example, the spunlace method, the air-through method, the needle punch method, etc. can be used. However, the method is not limited to these. In particular, it is preferable that the first fiber layer is formed by intertwining at least hydrophobic artificial cellulose fibers and hydrophilic cellulose fibers by the spunlace method from the viewpoint of improving the wearing comfort and dryness of the absorbent article.
[0047] Next, the second fiber layer will be described. The second fiber layer may be composed of thermoplastic fibers and / or hydrophilic cellulose fibers. The presence of the second fiber layer can make the surface sheet softer and fluffier. The method of joining the first fiber layer and the second fiber layer is not limited, and can be thermal bonding using air-through or embossing, intertwining of fibers, or adhesives such as hot melt. However, by including thermoplastic fibers in both the first fiber layer and the second fiber layer, good thermal bonding can be achieved, and good bonding properties can be obtained. On the other hand, by including hydrophilic cellulose fibers in the second fiber layer, there is an advantage that the transfer of liquid from the first fiber layer to the second fiber layer proceeds smoothly. From this viewpoint, it is preferable that the hydrophilic cellulose fibers are present in the surface area of the second fiber layer facing the first fiber layer. The second fibrous layer may be composed only of thermoplastic fibers, may be composed only of hydrophilic cellulosic fibers, or may be composed of both thermoplastic fibers and hydrophilic cellulosic fibers. When the second fiber layer contains thermoplastic fibers, the proportion of the thermoplastic fibers is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of maintaining good bonding with the first fiber layer. On the other hand, when the second fiber layer contains hydrophilic cellulose fibers, the proportion of the hydrophilic cellulose fibers is preferably 20% by mass or more, more preferably 35% by mass or more, and even more preferably 45% by mass or more, provided that the proportion is higher than the proportion of the hydrophilic cellulose fibers contained in the first fiber layer, from the viewpoint of smoothly transferring liquid from the first fiber layer to the second fiber layer.
[0048] The thermoplastic fibers contained in the second fiber layer may be the same as those contained in the first fiber layer, in which case the type of thermoplastic fibers contained in the second fiber layer may be the same as or different from the type of thermoplastic fibers contained in the first fiber layer. Furthermore, the thickness of the thermoplastic fibers contained in the second fiber layer and the thickness of the thermoplastic fibers contained in the first fiber layer may be the same or different.
[0049] The hydrophilic cellulose fibers contained in the second fiber layer may be the same as the hydrophilic cellulose fibers contained in the first fiber layer, in which case the type of hydrophilic cellulose fibers contained in the second fiber layer may be the same as or different from the type of hydrophilic cellulose fibers contained in the first fiber layer. Furthermore, the thickness of the hydrophilic cellulose fibers contained in the second fibrous layer may be the same as or different from the thickness of the hydrophilic cellulose fibers contained in the first fibrous layer.
[0050] Regardless of the type of fiber constituting the second fiber layer, the basis weight of the second fiber layer is set to 10 g / m2 or less in consideration of the strength and shape retention of the top sheet. 2 It is preferable that the thickness is 20 g / m or more. 2 More preferably, it is 30 g / m or more. 2 It is more preferable that the surface sheet has a density of 70 g / m or more to prevent the surface sheet from retaining excessive liquid. 2 It is preferable that the thickness is less than 60 g / m 2 More preferably, it is 50 g / m or less. 2 It is even more preferable that:
[0051] The second fiber layer can be produced by various nonwoven fabric production methods, such as the spunlace method, the air-through method, the needle punch method, etc., but is not limited to these methods.
[0052] In the topsheet including the above-mentioned first and second fiber layers, it is preferable that the hydrophilicity of the topsheet gradually increases from the first surface to the second surface, from the viewpoint of smooth transfer of liquid to the absorbent. In order to control the hydrophilicity of the topsheet in this manner, the second fiber layer may be made more hydrophilic than the first fiber layer, for example, by incorporating a large amount of hydrophilic cellulose fibers or fibers having a hydrophilic oil agent attached thereto, or by incorporating fibers having a hydrophilic oil agent with a higher hydrophilicity.
[0053] An example of a topsheet used in the absorbent article of the present invention is shown in Figures 1 and 2. The topsheets 10A and 10B shown in these figures each have a two-layer structure consisting of a first fiber layer 11 and a second fiber layer 12. The topsheets 10A and 10B each have a first surface 10a which is a surface facing the skin, and a second surface 10b which is a non-skin facing surface facing the absorbent body (not shown).
[0054] The topsheets 10A and 10B have a plurality of convex portions 14 protruding toward the first surface 10a and a plurality of concave portions 15 located between adjacent convex portions 14. In detail, in the topsheets 10A and 10B, the first fiber layer 11 and the second fiber layer 12 are partially bonded to form a plurality of joints 13. The first fiber layer 11 protrudes in a direction away from the second fiber layer 12, i.e., toward the wearer's skin, in areas other than the joints 13. As a result, a plurality of convex portions 14 are formed in the topsheets 10A and 10B. In the topsheet 10A shown in FIG. 1, a closed space 16 defined by the first fiber layer 11 and the second fiber layer 12 is formed inside the convex portion 14. In other words, the inside of the convex portion 14 is hollow. On the other hand, in the topsheet 10B shown in FIG. 2, the inside of the convex portion 14 has a solid structure filled with fibers. Between adjacent protrusions 14, there is a recess 15, and the joints 13 are located in the recess 15. The thickness of the recess 15 is smaller than the thickness of the protrusions 14. As a result, the surface of the topsheets 10A, 10B facing the first fiber layer 11 has an uneven structure. On the other hand, the surface of the topsheets 10A, 10B facing the second fiber layer 12 is generally flat.
[0055] As shown in Fig. 1, the protrusions 14 of the topsheet 10A can be arranged in a scattered manner. In detail, in the topsheet 10A, the protrusions 14 and the recesses 15 are arranged alternately along one direction X in the plane of the topsheet 10A. At the same time, the protrusions 14 and the recesses 15 are arranged alternately along the Y direction perpendicular to the X direction. In other words, the protrusions 14 and the recesses 15 are arranged alternately and in rows in the X direction, with the rows being arranged in multiple rows, and the protrusions 14 and the recesses 15 are arranged alternately and in rows in the Y direction, with the rows being arranged in multiple rows. When focusing on any one of the recesses 15 in a row in the X direction and / or Y direction, it is preferable that the recess be surrounded by protrusions on the front, rear, left and right sides, in order to effectively prevent runoff of liquid. A nonwoven fabric with such a structure can be manufactured by, for example, the method described in JP 2004-174234 A. Although not shown, the protrusions 14 and recesses 15 in the topsheet 10B shown in Fig. 2 can also be arranged in a similar manner.
[0056] In the topsheet 10B shown in Fig. 2, the bonded areas 13 are formed by compressing and bonding the constituent fibers of the first fiber layer 11 and the second fiber layer 12. Methods for forming the bonded areas 13 include, for example, embossing with or without heat, ultrasonic embossing, etc. On the other hand, the protruding areas 14 are non-bonded areas.
[0057] In the topsheet 10B shown in Fig. 2, the convex portions 14 are preferably formed by heat shrinking the constituent fibers of the second fiber layer 12 between adjacent joints 13. In other words, the thermoplastic fibers contained in the second fiber layer 12 are preferably heat-shrinkable fibers that have been heat-shrunk. This makes it easier to make the convex portions 14 protrude in the topsheet 10B. Details of the method of forming the convex portions 14 by heat shrinking the heat-shrinkable fibers are described in, for example, JP 2002-187228 A.
[0058] In the topsheet 10B shown in Fig. 2, it is also preferred that the convex portions are formed by thermally stretching the constituent fibers of the first fiber layer between adjacent joints 13. In other words, it is preferred that the thermoplastic fibers contained in the first fiber layer 11 are thermally stretched heat-extensible fibers. This also makes it easier to make the convex portions 14 protrude in the topsheet 10B. Details of the method of forming the convex portions 14 by thermally stretching the heat-extensible fibers are described in, for example, JP 2011-137246 A.
[0059] In the topsheets 10A and 10B of the embodiment shown in Fig. 1 and Fig. 2, a plurality of openings may be formed from the first surface side to the second surface side, which may or may not penetrate the topsheet. The formation of the openings allows the liquid to move smoothly from the topsheet to the absorbent. In particular, when the openings are provided in the recesses 15 of the topsheets 10A and 10B, the liquid moves smoothly from the topsheet to the absorbent and the liquid does not easily return, which is preferable. When the openings are provided through the topsheets 10A and 10B, it is preferable that the openings are arranged so as to penetrate a part or the entire area of the absorbent in the thickness direction, in order to form a starting point for the liquid to enter the absorbent more effectively.
[0060] Fig. 3 shows the structure of another top sheet used in the absorbent article of the present invention. The top sheet 10C shown in the figure has a two-layer structure consisting of a first fiber layer 11 and a second fiber layer 12. The top sheet 10C has a first surface 10a which is a surface facing the skin, and a second surface 10b which is a non-skin facing surface facing the absorbent body (not shown).
[0061] The topsheet 10C has a plurality of protruding portions 14 protruding toward the first surface 10a in both the first fiber layer 11 and the second fiber layer 12. The topsheet 10C also has a plurality of recessed portions 15 located between adjacent protruding portions 14 and recessed toward the second surface 10b in both the first fiber layer 11 and the second fiber layer 12. The protrusions 14 extend in a first direction on the first surface 10a of the topsheet 10C and are provided at predetermined intervals in a second direction perpendicular to the first direction. On the other hand, the recesses 15 extend in the first direction and are provided between adjacent protrusions 14 in the second direction.
[0062] The first fiber layer 11 and the second fiber layer 12 are in close contact with each other over the entire area of their opposing surfaces, and no gaps exist between the layers 11 and 12. As a result, the topsheet 10C has an uneven structure on the surface facing the first fiber layer 11, and also has an uneven structure on the surface facing the second fiber layer 12. The protrusions 14 have voids 17 that face the second surface 10b of the topsheet 10C.
[0063] The recess 15 has a first recess 21 with a first bottom 22 located toward the absorbent body (not shown) from the position of the first surface 10a at the top 14a of the protrusion 14, and a plurality of second recesses 26 formed in a recessed shape that are discontinuously arranged in the longitudinal direction within this first recess 21 and open into the first bottom 22. The second recess 26 comprises a peripheral wall portion 27 extending from the first bottom portion 22 in the direction of the absorbent body 4, and a second bottom portion 28 having the highest fiber density in the top sheet 10C and provided at the end portion of the peripheral wall portion 27 on the absorbent body side so as to cover that end portion. The peripheral wall portion 27 includes a pair of first peripheral wall portions 29, 29 formed along the length direction of the topsheet 10C and a pair of second peripheral wall portions 30, 30 formed along the width direction of the topsheet 10C, the pair of first peripheral wall portions 29, 29 being disposed in positions facing each other, and the pair of second peripheral wall portions 30, 30 being disposed in positions facing each other. The first peripheral wall portions 29 may be provided with openings (not shown).
[0064] 1 to 3, the constituent fibers of the first fiber layer 11 and the constituent fibers of the second fiber layer 12 may be intertwined to integrate the two fiber layers. Alternatively, the thermoplastic fibers contained in the first fiber layer 11 and the thermoplastic fibers contained in the second fiber layer 12 may be heat-fused at the intersections of the fibers to integrate the two fiber layers. 1 to 3 have an uneven structure at least on the surface on the first fiber layer 11 side, but each surface of the topsheet may be flat instead. Even in this case, the constituent fibers of the first fiber layer 11 and the constituent fibers of the second fiber layer 12 may be intertwined to integrate the two fiber layers. Alternatively, the thermoplastic fibers contained in the first fiber layer 11 and the thermoplastic fibers contained in the second fiber layer 12 may be heat-fused at the intersections of the fibers to integrate the two fiber layers.
[0065] In absorbent articles equipped with topsheets that can be used in the present invention, including the topsheets 10A, 10B, and 10C shown in Figures 1 to 3, it is preferable that a compressed portion is provided that integrally consolidates the first surface side of the topsheet to the absorbent body. The capillary force of this compressed portion forms a starting point for the migration of liquid from the topsheet to the absorbent body. From this perspective, it is preferable that the compressed portion is formed so as to extend along the longitudinal direction or lateral direction of the absorbent article.
[0066] The topsheets 10A, 10B, and 10C shown in Fig. 1 to Fig. 3 have a two-layer structure of a first fiber layer and a second fiber layer, and the outer surface of the first fiber layer (i.e., the skin-facing surface) constituting the skin-facing surface has at least an uneven structure, but the present invention is not limited to these embodiments, and both the outer surface of the first fiber layer and the outer surface of the second fiber layer may be in a flat state. In this case, the topsheet may have a high fiber density region with a high fiber density on the skin-facing surface side, i.e., the skin-facing surface side of the first fiber layer, and a low fiber density region with a lower fiber density than the high fiber density region along the surface direction of the topsheet. In particular, it is preferable that both the high fiber density region and the low fiber density region form a visible macroscopic pattern, since runoff can be effectively suppressed. To form the high fiber density region and the low fiber density region, for example, when manufacturing a topsheet by the spunlace method, the web that is the raw material of the topsheet is placed on an aperture pattern net having a predetermined aperture pattern, and a water flow is sprayed onto the web. In this way, a high fiber density region is formed from the web located on the apertures, and a low fiber density region is formed from the web not located on the apertures. The method of forming the high fiber density region and the low fiber density region in this manner is well known in the art. The term "visible macroscopic pattern" refers to a pattern that is large enough that its presence can be confirmed with the naked eye. There is no particular limitation on the arrangement of the high fiber density regions and the low fiber density regions. For example, the high fiber density regions and the low fiber density regions may be arranged in multiple rows in one direction, with the rows being alternating high fiber density regions and low fiber density regions.
[0067] In the present invention, the top sheet may be composed of only the first fiber layer. In this case, the top sheet contains hydrophobized artificial cellulose fibers and hydrophilic cellulose fibers, and optionally contains thermoplastic fibers. The top sheet has a different abundance ratio of hydrophobized artificial cellulose fibers on the skin-facing side and the non-skin-facing side. With such a configuration, the above-mentioned effects of the present invention can be achieved.
[0068] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. For example, in the top sheet 10A shown in Fig. 1, the convex portions 14 and the concave portions 15 are alternately arranged in both the X direction and the Y direction perpendicular thereto, but the arrangement pattern of the convex portions 14 and the concave portions 15 is not limited to this. The same applies to the top sheet 10B shown in Fig. 2.
[0069] Furthermore, in the topsheet 10A shown in FIG. 1, the protrusions 14 and the recesses 15 each have one type of shape, but protrusions and / or recesses having two or more different shapes may be formed. EXAMPLES
[0070] 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 the description of such examples. The hydrophilic cellulose fibers and hydrophobic artificial cellulose fibers used in the following Examples and Comparative Examples both had a thickness of 1.7 dtex and a length of 38 mm. The fiber contact angle of the hydrophobic artificial cellulose fibers was 96°, and the fiber contact angle of the hydrophilic cellulose fibers was 41°.
[0071] Example 1 (1) First fiber layer and second fiber layer The first fibrous layer on the skin-facing side used Lyocell (registered trademark) as hydrophilic cellulose fiber and Lyocell (registered trademark) Dry as hydrophobic artificial cellulose fiber. The ratio of hydrophilic cellulose fiber was 60% by mass, and the ratio of hydrophobic artificial cellulose fiber was 40% by mass. The total basis weight of the hydrophilic cellulose fiber and the hydrophobic artificial cellulose fiber was 16 g / m 2 It was. The non-skin facing side of the first fibrous layer uses Lyocell (registered trademark) as a hydrophilic cellulose fiber as a constituent fiber. The basis weight is 16 g / m 2 It was. No second fibrous layer was used. (2) Manufacturing of surface sheets The top sheet was produced by the spunlace method, in which a web constituting the non-skin-facing surface of the first fibrous layer was overlaid on a web constituting the skin-facing surface of the first fibrous layer, and high-pressure water flow treatment was performed from the non-skin-facing surface side of the first fibrous layer. (3) Manufacturing of sanitary napkins 25g / m2 on the underside of the top sheet 2 A sublayer layer made of an air-through nonwoven fabric made of PET / PE fibers was placed, an absorbent body was placed under the sublayer layer, and a backsheet was placed under the absorbent body to manufacture a sanitary napkin. The topsheet and sublayer layer, and the sublayer layer and absorbent body were all made of 20 g / m 2 The absorbent and backsheet were made by deactivating the adhesive strength of the hot melt used to secure the topsheet from a Kao Corporation Laurier (registered trademark) Happy Skin Daytime Soft Type with Wings 22.5 cm (manufactured in 2022) using a cold spray, and then peeling off the topsheet.
[0072] Example 2 (1) First fiber layer and second fiber layer The same as in Example 1. The total basis weight of the hydrophilic cellulose fiber and the hydrophobic artificial cellulose fiber on the skin-facing side was 15 g / m 2 The basis weight of the hydrophilic cellulose fiber on the non-skin-facing side was 15 g / m 2 It was. (2) Manufacturing of surface sheets A topsheet was produced by a spunlace method in which a web constituting the non-skin facing surface of the first fiber layer was superimposed on a web constituting the skin facing surface of the first fiber layer, and high-pressure water flow was applied from the non-skin facing surface side of the first fiber layer. When performing the spunlace method, the web was placed on a stainless steel plate with openings. The openings of the stainless steel plate were arranged in a close-packed pattern of regular hexagonal openings. The line width of each side constituting the regular hexagon was 0.5 mm. The distance between two opposing sides of the regular hexagon was 6.5 mm. In the topsheet thus obtained, the area facing the openings of the stainless steel plate was a high fiber density area, and the area facing the non-openings of the stainless steel plate was a low fiber density area. In addition, both the high fiber density area and the low fiber density area were formed in a macroscopic pattern that was visible. (3) Manufacturing of sanitary napkins The same as in Example 1.
[0073] Comparative Example 1 (1) First fiber layer and second fiber layer The first fiber layer was made of hydrophilic cellulose fiber, Lyocell (registered trademark), and hydrophobic artificial cellulose fiber, Lyocell (registered trademark) Dry. The ratio of hydrophilic cellulose fiber was 60% by mass, and the ratio of hydrophobic artificial cellulose fiber was 40% by mass. The total basis weight of the hydrophilic cellulose fiber and the hydrophobic artificial cellulose fiber was 34 g / m 2 It was. No second fibrous layer was used. (2) Manufacturing of surface sheets A top sheet was produced by the spunlace method using a web containing hydrophilic cellulose fibers and hydrophobic artificial cellulose fibers. No open-hole pattern net was used in the spunlace method. (3) Manufacturing of sanitary napkins The same as in Example 1.
[0074] Comparative Example 2 In Comparative Example 1 (1), Lyocell (registered trademark) Dry, which is a hydrophobic artificial cellulose fiber, was used as the fiber constituting the first fiber layer. The total basis weight of the hydrophobic artificial cellulose fiber was 26 g / m 2 Other than this, a sanitary napkin was obtained in the same manner as in Example 1.
[0075] 〔evaluation〕 For the sanitary napkins obtained in the Examples and Comparative Examples, the amount of wetback, the liquid absorption time, and the runoff were measured by the following methods. The results are shown in Table 1 below.
[0076] [Liquid return amount / liquid absorption time] The sanitary napkins obtained in the examples and comparative examples were placed with the top sheet facing up. An acrylic plate having a through hole with an inner diameter of 1 cm was placed on the top sheet, and a load of 100 Pa was applied to the top sheet. Under such load, 3.0 g of horse blood was injected at once through the through hole of the acrylic plate. The time required for the injected horse blood to finish transferring to the absorbent through the top sheet was defined as the 3 g liquid absorption time (seconds). 50 seconds after the 3.0 g of horse blood finished transferring to the absorbent through the top sheet, the acrylic plate was removed, and 60 seconds after the same, a tissue paper (Kleenex (registered trademark)) folded to 9.5 cm x 5.5 cm was placed on the part of the nonwoven fabric where the horse blood was injected, and a weight was placed on the tissue paper, and a load of 500 Pa was applied. After the same 65 seconds, the weight and the tissue paper were removed, and the horse blood adhering to the surface of the removed acrylic plate in contact with the top sheet was wiped off. The weight of the tissue paper (W4) was measured, and the difference (W4-W3) between the weight of the tissue paper before it was placed on the surface of the nonwoven fabric and the weight of the tissue paper (W3) measured in advance was taken as the 3g liquid return amount (mg). 180 seconds after the first 3.0g of horse blood had completely transferred to the absorbent through the top sheet, the acrylic plate was placed on the top sheet again, and a load of 100 Pa was applied to the top sheet. Under this load, a second 3.0g (6.0g in total) of horse blood was injected at once through the through hole of the acrylic plate. The time required for the second injected horse blood to completely transfer to the absorbent through the top sheet was taken as the 6g liquid absorption time (seconds). 50 seconds after the second 3.0 g (total 6.0 g) of stripped horse blood had finished transferring through the top sheet to the absorbent, the acrylic plate was removed, and 60 seconds later, a piece of tissue paper (Kleenex (registered trademark)) folded to 9.5 cm x 5.5 cm was placed on the area of the nonwoven fabric where the stripped horse blood had been injected, and a weight was placed on top of the tissue paper to apply a load of 500 Pa.After the same 65 seconds had elapsed, the weight and the tissue paper were removed, and any horse blood adhering to the surface of the removed acrylic plate that came into contact with the top sheet was wiped off. The weight of the tissue paper (W6) was then measured, and the difference (W6-W5) between this and the weight (W5) of the tissue paper before it was placed on the surface of the nonwoven fabric, which had been measured in advance, was taken as the 6 g liquid return amount (mg). For both the 3g liquid absorption time and the 6g liquid absorption time, the smaller the value, the quicker the excreted menstrual blood is absorbed, reducing the risk of menstrual blood leakage. For both the 3g liquid return amount and the 6g liquid return amount, the smaller the value, the higher the dryness of the surface material. For the 3g liquid absorption time, 6g liquid absorption time, 3g liquid return amount, and 6g liquid return amount, the average value of three measurements was calculated and used for performance evaluation.
[0077] [Runoff] The test device used had a placement section where the surface on which the napkin was placed was inclined at 45° to the horizontal plane. The napkin was placed on this placement section so that the top sheet was facing upward. As the test liquid, horse defibrinated blood was dripped onto the napkin at a speed of 1 g / 10 sec for 5 seconds from a height 10 mm away vertically from the injection position into the napkin. The distance from the point where the top sheet first became wet to the point where the test liquid was absorbed into the absorbent and the droplets stopped falling was measured. The above operation was performed three times, and the average of the three measurements was taken as the runoff (mm). Runoff is an index of the amount of liquid that comes into contact with the wearer's skin without being absorbed by the sanitary napkin, and the shorter the runoff, the higher the evaluation.
[0078] The horse defibrinated blood used in the above measurements was manufactured by Japan Bio Test Laboratory Co., Ltd. When horse defibrinated blood is left to stand, the high viscosity parts (red blood cells, etc.) settle, while the low viscosity parts (plasma) remain as the supernatant. The high viscosity and low viscosity parts of the horse defibrinated blood were mixed, and the mixing ratio was adjusted so that the viscosity was 8.0 cP (25°C). A TVB10 viscometer (rotor name: L / Adp) manufactured by Toki Sangyo Co., Ltd. was used for the adjustment, and the condition was 30 rpm.
[0079] [Table 1]
[0080] As is clear from the results shown in Table 1, the sanitary napkins of each Example have a shorter liquid absorption time and a higher dryness of the topsheet than the sanitary napkin of Comparative Example 2. Furthermore, a comparison between Example 1 and Comparative Example 1 shows that the runoff value is reduced by making the non-skin-facing surface highly hydrophilic, and in particular, when high fiber density regions and low fiber density regions are formed in the topsheet as in Example 2, the runoff value is significantly reduced and dryness is further improved. [Explanation of symbols]
[0081] 10A, 10B, 10C Surface sheet 10a 1st page 10b 2nd side 11 First fiber layer 12 Second fiber layer 13 Joint 14 Convex part 15 Recess
Claims
1. An absorbent article comprising a liquid-permeable surface sheet positioned on the side facing the wearer's skin, a back sheet positioned on the side not facing the wearer's skin, and an absorber positioned between the two sheets, wherein the surface sheet has a first fiber layer positioned on the side facing the skin, the first fiber layer contains hydrophobized rayon fibers and hydrophilic cellulose fibers, and the absorbent article is such that the abundance ratio of the hydrophobized rayon fibers is different between the side facing the skin and the side not facing the skin.
2. The absorbent article according to claim 1, wherein the surface sheet has, along the plane direction of the surface sheet, a high fiber density region where the fiber presence density is high and a low fiber density region where the fiber presence density is lower than that of the high fiber density region, on the side facing the skin.
3. The absorbent article according to claim 2, wherein both the high fiber density region and the low fiber density region form a macroscopic pattern that is visible.
4. The absorbent article according to any one of claims 1 to 3, wherein the first fiber layer is formed by entangling the hydrophobized rayon fibers and the hydrophilic cellulose fibers by the spunlace method.
5. The absorbent article according to any one of claims 1 to 3, wherein the first fiber layer further contains thermoplastic fibers.
6. The absorbent article according to claim 5, wherein in the first fiber layer, the abundance ratio of the thermoplastic fibers is higher on the side not facing the skin than on the side facing the skin.
7. The surface sheet has a first surface that is the side facing the skin and a second surface that is the side not facing the skin and faces the absorber, and the absorbent article according to any one of claims 1 to 3, wherein the surface sheet includes a plurality of convex portions protruding in the direction of the first surface and a plurality of concave portions positioned between adjacent convex portions.
8. The absorbent article according to claim 7, wherein the inside of the convex portion is hollow.
9. The surface sheet further has a second fiber layer positioned on the side not facing the skin, and the absorbent article according to any one of claims 1 to 3, wherein the second fiber layer contains thermoplastic fibers or hydrophilic cellulose fibers.
10. The absorbent article according to claim 9, wherein the constituent fibers of the first fiber layer and the constituent fibers of the second fiber layer are entangled and the two fiber layers are integrated.
11. The first fiber layer further contains thermoplastic fibers, The absorbent article according to claim 9, wherein the thermoplastic fibers contained in the first fiber layer and the thermoplastic fibers contained in the second fiber layer are heat-sealed at the intersections of the fibers, and the two fiber layers are integrated.
12. The absorbent article according to claim 9, wherein the first fiber layer and the second fiber layer are partially joined to form a plurality of joined portions.
13. The surface sheet includes a plurality of convex portions protruding in the direction of the first surface and a plurality of concave portions located between adjacent convex portions. The absorbent article according to claim 12, wherein the convex portions are formed by the constituent fibers of the second fiber layer thermally contracting between adjacent joined portions.
14. The absorbent article according to claim 13, wherein the second fiber layer includes heat-shrinkable fibers that have shrunk.
15. The absorbent article according to claim 12, wherein the first fiber layer protrudes toward the wearer's skin side at portions other than the joined portions.
16. The surface sheet has a first surface that is the surface on the skin-facing side and a second surface that is the surface on the non-skin-facing side and faces the absorber. The surface sheet includes a plurality of convex portions protruding in the direction of the first surface and a plurality of convex portions located between adjacent convex portions and recessed in the direction of the second surface. The absorbent article according to any one of claims 1 to 3, wherein the convex portions have void portions facing the second surface.